Lithium–sulfur (Li–S) battery is one of the most attractive candidates for the next-generation energy storage system. However, the intrinsic insulating nature of sulfur and the notorious polysulfide shuttle are the major obstacles, which hinder the commercial application of Li–S battery. Confining sulfur into conductive porous carbon matrices with designed polarized surfaces is regarded as a promising and effective strategy to overcome above issues. Herein, we propose to use microalgaes (Schizochytrium sp.) as low-cost, renewable carbon/nitrogen precursors and biological templates to synthesize N-doped porous carbon microspheres (NPCMs). These rational designed NPCMs can not only render the sulfur-loaded NPCMs (NPCSMs) composites with high electronic conductivity and sulfur content, but also greatly suppress the diffusion of polysulfides by strongly physical and chemical adsorptions. As a result, NPCSMs cathode demonstrates a superior reversible capacity (1030.7 mA h g–1) and remarkable capacity retention (91%) at 0.1 A g–1 after 100 cycles. Even at an extremely high current density of 5 A g–1, NPCSMs still can deliver a satisfactory discharge capacity of 692.3 mAh g–1. This work reveals a sustainable and effective biosynthetic strategy to fabricate N-doped porous carbon matrices for high performance sulfur cathode in Li–S battery, as well as offers a fascinating possibility to rationally design and synthesize novel carbon-based composites.Keywords: biotemplating method; lithium−sulfur batteries; microalgaes; nitrogen doping; porous carbon microspheres;

We report a novel synthesis of a mesoporous carbon–sulfur composite (MCSC) by electrodeposition of sulfur into the mesopores via a self-limiting process. With the merits of a high sulfur content (77%), uniform distribution and strong C–S bonds achieved by this method, the as-prepared materials demonstrate excellent performance in lithium–sulfur batteries. The electrode delivers high specific capacities at various C-rates (e.g. about 1160 and 590 mA h g−1 at current densities of 0.1 and 2.0 A g−1, respectively) and remarkable capacity retention, remaining above 857 mA h g−1 after 200 cycles at a high rate of 0.5 A g−1. This electrochemical strategy is industrially viable and scalable, and thus may pave a new way to push the commercialization of Li–S batteries.

•Fe3O4/C nanoparticles were successfully synthesized via a facile micro-tube method.•Easily available, carbon-rich kapok fibres play a dual role as the carbon source and the biotemplate.•As-prepared Fe3O4/C electrode exhibits notable cycle potential for anode material for LIBs.Kapok fibres were used as micro-tube biotemplate and bio-carbon source to synthesise Fe3O4/C composites, which were then utilised as anode materials. Fe3O4 nanoparticles were grown uniformly onto the external surface and internal channel of kapok carbon fibres. The flexibility, high specific surface area and electronic conduction of kapok fibres can buffer the volume expansion as well as inhibit the aggregation of Fe3O4 nanoparticles. Thus, the electrical integrity and structural of the Fe3O4/C composites electrode during lithiation/delithiation processes. The Fe3O4/C composites electrode delivers a high reversible capacity of 596 mA h g−1 after 100 cycles and an ultra-high coulombic efficiency approaching 100%. The high electrochemical performance of the Fe3O4/C composites can be caused by the synergistic effect of the Fe3O4 nanoparticles and the structure of kapok carbon fibres.Download high-res image (161KB)Download full-size image

Li2S is one of the most promising cathode materials for Li-ion batteries because of its high theoretical capacity and compatibility with Li-metal-free anode materials. However, the poor conductivity and electrochemical reactivity lead to low initial capacity and severe capacity decay. In this communication, a nitrogen and phosphorus codoped carbon (N,P–C) framework derived from phytic acid doped polyaniline hydrogel is designed to support Li2S nanoparticles as a binder-free cathode for Li–S battery. The porous 3D architecture of N and P codoped carbon provides continuous electron pathways and hierarchically porous channels for Li ion transport. Phosphorus doping can also suppress the shuttle effect through strong interaction between sulfur and the carbon framework, resulting in high Coulombic efficiency. Meanwhile, P doping in the carbon framework plays an important role in improving the reaction kinetics, as it may help catalyze the redox reactions of sulfur species to reduce electrochemical polarization, and enhance the ionic conductivity of Li2S. As a result, the Li2S/N,P–C composite electrode delivers a stable capacity of 700 mA h g−1 with average Coulombic efficiency of 99.4% over 100 cycles at 0.1C and an areal capacity as high as 2 mA h cm−2 at 0.5C.

•The effects of synthetic methods on Mn/Ce/TiW catalysts have been investigated.•C-Mn/Ce/TiW sample exhibits the highest SCR activity at low temperature.•The active species are highly dispersed on the surface of C-Mn/Ce/TiW sample.•High SCR activity is attributed to the enhanced redox ability and acid sites.In this work, Mn/Ce/TiW catalysts were prepared by various synthetic strategies including coprecipitation method (named as C-Mn/Ce/TiW), coprecipitation-mixing method (CM-Mn/Ce/TiW) and mixing method (M-Mn/Ce/TiW). As a result, C-Mn/Ce/TiW sample exhibited the highest NOx conversion of 90% and 99.4% at the low temperatures of 180 °C and 210 °C, respectively. This enhanced NOx conversion can be attributed to the increased surface active species served as active sites within the whole temperature range, such as Ce3+ (19.55%), Mn4+ (59.58%) and chemisorbed oxygen species (21.89%). These surface active species originated mainly from the highly dispersed CeOx and MnO2. The results revealed that the influences of the phase and texture property on catalytic activity were slight. And the gradually enhanced acidity and reducibility along with the dispersion degrees and the amount of surface active species were the main reasons for the improvement of SCR reaction. These fundamental findings will be helpful for the rational design of high-performance SCR catalysts at the low temperature.

•We report a novel hybrid nanoarchitecture of TiO2-nanotubes/graphene via a facile two-step hydrothermal route.•The TiO2 nanotubes show a net-like structure and high dispersion on the graphene host.•The TiO2-nanotubes/graphene exhibits high capacity, superior cycling stability and rate capability.A novel hybrid nanoarchitecture of TiO2 nanotubes/graphene was synthetized through a facile two-step hydrothermal route. The anatase TiO2 nanotubes with a diameter of about 20 nm show a net-like structure and high dispersion on the graphene nanosheets. The as-prepared sample (TOG2) exhibits a high average capacity of 410 mAh g−1 at 0.1 A g−1, superior cycling stability with negligible capacity fade over 300 cycles and rate capability of 192 mAh g−1 at 1 A g−1. The enhanced electrochemical properties can be attributed to its unique hybrid structure. One-dimensional hollow tubular structure of TiO2 provides numerous open channels for electrolyte to access and facilitate the ultrafast diffusion of lithium ions. In addition, the graphene sheets are favorable for the fast electron transport within the electrode, as well as keep the structural integrity during long-term cycling processes.Download high-res image (215KB)Download full-size image

•The electrochemical performance of SiO2 is strongly associated with ball milling.•Submicron silica show superior cycling performance for lithium storage.•Mechanism of electrochemical performance of SiO2 depended on milling was discussed.Submicron silica (SiO2) is prepared via directly milling bulk SiO2, which is the major constituent of the abundant sand on the earth. The electrochemical lithium storage performance of SiO2 is found to be strongly associated with the ball milling treatment. The reversible capacity of SiO2 gradually increases from 163 to 803 mAh g−1 as the milling time is extended from 0 to 72 h. For the SiO2 milled for 24 h, it exhibits excellent cycling performance with a discharge capacity of 602 mAh g−1 over 150 cycles, corresponding to the capacity retention of 99.8% relative to the 2nd cycle. The different particle sizes distribution and electrochemical activity of SiO2 are responsible for the effect of ball milling on its electrochemical lithium storage performance such as reversible capacity, cycling stability, electrode polarization and initial Coulombic efficiency.Download high-res image (116KB)Download full-size image

•Crystalline LMP with discontinuous distribution is decorated on the surface of LMCN.•LMP enhances the structural and cyclic stability of LMP-LMCN.•Voltage decay is suppressed by the surface modification of LMP.•An appropriate content of LMP improves the high-rate capacity of LMP-LMCN.Li-rich layered oxides with high specific capacity are considered as the next generation cathode materials for advanced Li-ion batteries. However, the large initial irreversible capacity loss, inferior cycling stability and fast voltage decay still remain to be overcome before large-scale practical applications. In this work, inspired by LiMnPO4 with superior thermal and chemical stabilities and high redox potential, we design and fabricate a series of LMnPO4-modified Li[Li0.2Mn0.534Co0.133Ni0.133]O2 composites. Among them, Li[Li0.2Mn0.534Co0.133Ni0.133]O2 modified with 5 wt.% LiMnPO4 (LMP5-LMCN) sample presents remarkable electrochemical properties with high initial discharge capacity of 292 mAh g−1 and good capacity retention of 78.65% after 100 cycles at current density of 30 mA g−1. The effects of LiMnPO4 as the surface modification layer on the electrochemical performance of Li[Li0.2Mn0.534Co0.133Ni0.133]O2 are systematically investigated. Our results demonstrate that the appropriate LiMnPO4 surface modification could not only enhance the structural stability, but also greatly suppress the voltage fading, which is beneficial to improve the cycling stability and rate capability of Li-rich layered oxides.

•Flexible electrothermal films with various content of SiO2 filler are investigated.•Non-conductive SiO2 filler can enhance the electrothermal reproducibility.•An intelligent thermochromic flexible electric heating film is developed.Carbon/polymer based flexible electrothermal films due to the excellent formability, flexibility, light weight and cost-effectiveness are recognized as a promising alternative material compared to traditional metal based materials. In this work, a series of flexible electrothermal films were synthesized by incorporating pyrolysis N991 and multi-walled carbon nanotubes (MWCNTs) in polyethylene oxide (PEO) matrix with adding non-conductive SiO2 filler. The influences of SiO2 on morphology, microstructure and electrothermal performance of electrothermal films were systematically investigated. SiO2 filler guarantees the homogeneous dispersion of N991 and MWCNTs in PEO polymer matrix, which could prevent the unceasing migration of N991 and MWCNTs during the repeating heating-cooling cycles. The result shows that adding 5 wt.% SiO2 can achieve a stable electrical resistivity and excellent electrothermal reproducibility. Bending tests were employed to evaluate its superior mechanical flexibility. A new application was further developed to fabricate a flexible electrothermal film with a reversible thermochromic temperature-indicating function.Electrothermal composites composed of PEO as polymer matrix, pyrolysis N991/MWCNTs as conductive filler and nano sized SiO2 particles as non-conductive filler were used to fabricate flexible electric heating films with thermochromic function.Download high-res image (168KB)Download full-size image

Lithium–sulfur batteries are considered as a promising candidate for high energy density storage applications. However, their specific capacity and cyclic stability are hindered by poor conductivity of sulfur and the dissolution of redox intermediates. Here, we design polypyrrole-MnO2 coaxial nanotubes to encapsulate sulfur, in which MnO2 restrains the shuttle effect of polysulfides greatly through chemisorption and polypyrrole serves as conductive frameworks. The polypyrrole-MnO2 nanotubes are synthesized through in situ polymerization of pyrrole using MnO2 nanowires as both template and oxidization initiator. A stable Coulombic efficiency of ∼98.6% and a decay rate of 0.07% per cycle along with 500 cycles at 1C-rate are achieved for S/PPy-MnO2 ternary electrodes with 70 wt % of S and 5 wt % of MnO2. The excellent trapping ability of MnO2 to polysulfides and tubular structure of polypyrrole with good flexibility and conductivity are responsible for the significantly improved cyclic stability and rate capability.Keywords: in situ polymerization; lithium−sulfur batteries; manganese dioxide; nanotubes; polypyrrole;

Pyrite FeS2 decorated sulfur-doped carbon (FeS2@S-C) fibers have been successfully synthesized by a facile bio-templating method and applied as the anode material for lithium ion batteries (LIBs). Cotton was used as both the carbon source and the template. SEM and TEM results showed that the FeS2 nanoparticles fabricated using 0.2 M FeSO4 were uniformly embedded in or attached on the surface of the carbon fibers. FeS2@S-C synthesized with 0.2 M FeSO4 showed the best cycle stability and rate capability, which retained a high reversible specific capacity of 689 mAh g−1 after 100 cycles. The specific capacities are about 1200, 900, 700, 550 and 400 mAh g−1 after every 10 cycles at 0.1, 0.2, 0.5, 1 and 2 A g−1. The excellent electrochemical performance can be ascribed to the highly conductive sulfur-doped carbon and the homogeneous distribution of FeS2 nanoparticles. It is believed that the S-doped carbon matrix acts as an effective buffer layer helping relieve the volume strain as well as a hinder preventing FeS2 from aggregating during cycling, which ensure the high electrochemical performance. This kind of low-cost anode with high specific capacity and improved cycling stability show potential application for high capacity lithium-ion batteries.

Silicon oxycarbide (Si–O–C) materials with high specific capacity are considered as a promising anodic material alternative to commercial graphite for advanced Li-ion batteries. However, the rapid capacity fading and poor rate performance are the main obstacles for practical application and still remain a large challenge. In this work, microalgae (Nannochloropsis) served as a biological template and carbon source to synthesize Si–O–C microspheres with the assistance of supercritical CO2 fluid. Compared to conventional artificial templates, microalgae is abundant, renewable and available, and can be regarded as a promising biological template. Meanwhile, supercritical CO2 fluid with high penetration, high diffusivity and high dissolving capacity can serve as a superior solvent to guarantee the efficient mass transfer and uniform dispersion of precursors. As anodic materials for Li-ion batteries, Si–O–C microspheres exhibit a high reversible specific capacity of 450 mA h g−1 at a current density of 0.1 A g−1 over 200 cycles, excellent rate cycling stability and high coulombic efficiency (100%). The discovery of this novel strategy to fabricate Si–O–C materials presents possibilities for energy storage applications.

Two-dimensional transition metal carbide materials called MXenes show potential application for energy storage due to their remarkable electrical conductivity and low Li+ diffusion barrier. However, the lower capacity of MXene anodes limits their further application in lithium-ion batteries. Herein, with inspiration from the unique metal ion uptake behavior of highly conductive Ti3C2 MXene, we overcome this impediment by fabricating Sn4+ ion decorated Ti3C2 nanocomposites (PVP-Sn(IV)@Ti3C2) via a facile polyvinylpyrrolidone (PVP)-assisted liquid-phase immersion process. An amorphous Sn(IV) nanocomplex, about 6–7 nm in lateral size, has been homogeneously anchored on the surface of alk-Ti3C2 matrix by ion-exchange and electrostatic interactions. In addition, XRD and TEM results demonstrate the successful insertion of Sn4+ into the interlamination of an alkalization-intercalated Ti3C2 (alk-Ti3C2) matrix. Due to the possible “pillar effect” of Sn between layers of alk-Ti3C2 and the synergistic effect between the alk-Ti3C2 matrix and Sn, the nanocomposites exhibit a superior reversible volumetric capacity of 1375 mAh cm–3 (635 mAh g–1) at 216.5 mA cm–3 (100 mA g–1), which is significantly higher than that of a graphite electrode (550 mAh cm–3), and show excellent cycling stability after 50 cycles. Even at a high current density of 6495 mA cm–3 (3 A g–1), these nanocomposites retain a stable specific capacity of 504.5 mAh cm–3 (233 mAh g–1). These results demonstrate that PVP-Sn(IV)@Ti3C2 nanocomposites offer fascinating potential for high-performance lithium-ion batteries.Keywords: lithium-ion battery; MXene; nanocomposites; Ti3C2;

Lithium–sulfur batteries show fascinating potential applications for rapid-growing electric vehicles and grid-level energy storage due to their low cost and high energy density. To date, various carbon hosts have been utilized to confine sulfur for improving Li–S battery performance. However, the adopted sulfur storage techniques are post-carbon-synthesis involving complex processes. It remains a great challenge to determine the ideal configuration of carbon–sulfur composites with uniform dispersion and high sulfur loading. Herein, we report a novel synthesis of graphene–sulfur composites by electrolytic exfoliation of graphite coupled with in situ sulfur electrodeposition. The sample delivers an initial discharge capacity of 1080 mA h g−1 at 0.1 A g−1 and retains above 900 mA h g−1 over 60 cycles. This strategy via electrochemical exfoliation/deposition synchronous reactions can provide strong sulfur chemical interactions with the graphene host, achieving advanced cathode materials for Li–S batteries.

NaV3O8 nanobelts, nanorods and microrods have been successfully synthesized using a facile, one-step solid-state sintering method. The morphology, crystallinity and purity of NaV3O8 can be easily controlled by the calcination temperature. As a cathode material for Li-ion batteries, NaV3O8 nanorods synthesized at 450 °C show a relatively higher specific discharge capacity of 226 mA h g−1 at 30 mA g−1 and a good cycling performance without considerable capacity loss over 100 cycles at 100 and 300 mA g−1. In situ TEM characterization confirmed that the intercalation/deintercalation of Li+ ions in NaV3O8 is a single-phase reaction process with small lattice change, which can result in obvious cracks and fractures. The SEM characterizations of the electrodes after cycling reveal that the structure destruction is the main reason for the capacity fading of NaV3O8.

The further development of electrode materials with high capacity and excellent rate capability presents a great challenge for advanced lithium-ion batteries. Herein, we demonstrate a battery-capacitive synchronous lithium storage mechanism based on a scrupulous design of TiC/NiO core/shell nanoarchitecture, in which the TiC nanowire core exhibits a typical double-layer capacitive behavior, and the NiO nanosheet shell acts as active materials for Li+ storage. The as-constructed TiC/NiO (32 wt % NiO) core/shell nanoarchitecture offers high overall capacity and excellent cycling ability, retaining above 507.5 mAh g–1 throughout 60 cycles at a current density of 200 mA g–1 (much higher than theoretical value of the TiC/NiO composite). Most importantly, the high rate capability is far superior to that of NiO or other metal oxide electrode materials, owing to its double-layer capacitive characteristics of TiC nanowire and intrinsic high electrical conductivity for facile electron transport during Li+ storage process. Our work offers a promising approach via a rational hybridization of two electrochemical energy storage materials for harvesting high capacity and good rate performance.Keywords: core/shell nanoarchitecture; lithium storage mechanism; lithium-ion batteries; metal oxides; titanium carbide;

In this work, porous MnO/C composites were successfully synthesized via a new ammonia diffusion method, in which the MnO nanoparticles were tightly embedded into a porous carbon matrix. Kapok fibers (KFs) were used as both the bio-template and the renewable carbon source. The KFs-templated MnO/C electrodes exhibited a high reversible specific capacity of 1454 mAh g−1 with a high coulombic efficiency, up to 98%, at a current density of 200 mA g−1 over 150 cycles. The high reversible capacity of the MnO/C composites could be ascribed to the synergetic effects of several factors including the unique porous microstructure, the small MnO nanoparticle size and the high defective carbon matrix. Due to the small MnO nanoparticles size and a moderate amount of carbon (13.3 wt%), the electrodes showed a small voltage polarization (about 0.89 V).The porous MnO/C composites were successfully synthesized via a new ammonia diffusion method, using Kapok fibers as both the bio-template and the renewable carbon source. The porous MnO/C composites possess high electrical conductivity, structural stability, and high reversible capacities.

•Li3V2−xSnx(PO4)3/C composites were synthesized via a sol–gel method.•Sn-doping expanded the unit cell volume, but did not alter the lattice structure.•Electronic and ionic conductivity can be enhanced by doping Sn.•Li3V1.85Sn0.15(PO4)3/C exhibited enhanced cycling stability and rate performance.A series of Sn-doped Li3V2−xSnx(PO4)3/C (x = 0, 0.1, 0.15, 0.2) samples were synthesized via a citric acid assisted sol–gel method. XRD patterns indicated that all the Li3V2−xSnx(PO4)3/C samples were pure single phase with a monoclinic structure (space group P21/n) and well crystallized. The structural refinement results and HRTEM analysis both indicated that Sn-doping did not alter the lattice structure of Li3V2(PO4)3, but increased the unit cell volume. SEM images revealed that Sn-doping has no obvious effects on the morphology and particle size of Li3V2(PO4)3. HRTEM, XRF and Raman results demonstrated that a thin carbon layer was coated on the surface of Li3V2−xSnx(PO4)3/C samples with a similar carbon content and good quality. The electrochemical performance was evaluated using coin-type half cells. Among the samples synthesized in this work, Li3V1.85Sn0.15(PO4)3/C exhibited the electrochemical performance in terms of specific capacity, rate capability, cycling performance. CV and EIS results implied that optimizing Sn-doping contents with x = 0.15 could greatly enhance the structural stability of Li3V2(PO4)3 during the charge–discharge processes, as well as increase electrical conductivity with a lower charge transfer resistance and a higher Li+ diffusion coefficient.

•Rutile TiO2/rGO composite was fabricated by a hydrothermal route.•TiO2 nanoneedles have a uniform dispersion on the interlayer of rGO nanosheets.•TiO2/rGO composite exhibited enhanced cycling stability and rate performance.•rGO promoted Li+ mobility and kept the structural integrity of electrode.In this paper, rutile TiO2 nanoneedle/graphene composites with a unique one dimensional/two dimensional (1D/2D) hybrid nanostructure were prepared via a facile hydrothermal route. These obtained rutile TiO2 nanoneedles with the length of ~ 500 nm have a homogeneous dispersion on the interlayers of graphene nanosheets. As the anodic materials, the as-prepared sample exhibited the superior Li storage capability with good cycling stability (over 94% capacity retention) and remarkable rate performance (149 mA h g− 1 at a 5 C rate). The improved electrochemical performance can be attributed to the unique microstructure. On the one hand, 1D rutile TiO2 nanoneedles shorten the length of Li+ transport paths to achieve a higher Li+ diffusion rate. On the other hand, 2D graphene sheets provide good electronic contacts to reduce the contact resistance, as well as keep the structural integrity of the electrode materials.

Lithium–sulfur batteries show fascinating potential for advanced energy storage systems due to their high specific capacity, low-cost, and environmental benignity. However, the shuttle effect and the uncontrollable deposition of lithium sulfide species result in poor cycling performance and low Coulombic efficiency. Despite the recent success in trapping soluble polysulfides via porous matrix and chemical binding, the important mechanism of such controllable deposition of sulfur species has not been well understood. Herein, we discovered that conductive Magnéli phase Ti4O7 is highly effective matrix to bind with sulfur species. Compared with the TiO2–S, the Ti4O7–S cathodes exhibit higher reversible capacity and improved cycling performance. It delivers high specific capacities at various C-rates (1342, 1044, and 623 mAh g–1 at 0.02, 0.1, and 0.5 C, respectively) and remarkable capacity retention of 99% (100 cycles at 0.1 C). The superior properties of Ti4O7–S are attributed to the strong adsorption of sulfur species on the low-coordinated Ti sites of Ti4O7 as revealed by density functional theory calculations and confirmed through experimental characterizations. Our study demonstrates the importance of surface coordination environment for strongly influencing the S-species binding. These findings can be also applicable to numerous other metal oxide materials.

Developing Pt eletrocatalysts with high activity and long-term durability remains a great challenge in commercializing fuel cells. Herein, we report a new kind of bark-structured TiC nanowire (NW) as an efficient support for Pt electrocatalysts, which exhibits a higher electrochemically active surface area (ECSA), much improved electrocatalytic activity and long-term durability toward a methanol oxidation reaction (MOR) when compared with commercial Pt/C (Vulcan XC-72) catalysts. The TiC NWs were synthesized via a simple biotemplating method using natural nanoporous cotton fibers as both the carbon source and the template. Their typical size is in the range of 50–150 nm in width and up to several micrometers in length. The Pt nanoparticles deposited onto the TiC NWs by a urea-assisted ethylene glycol reduction method are small (ca. 3 nm), narrowly distributed and well crystallized. The unique one-dimensional (1D) nanostructure of the TiC NWs provides fast transport and a short diffusion path for electroactive species, and a high utilization of catalysts. Moreover, the merits of TiC NWs, such as high electrical conductivity and excellent chemical/electrochemical stability also contribute to enhancing their electrocatalytic properties. The carbide support reported here will promote broader interest in the further development of Pt electrocatalysts in the fields of fuel cells and related electrocatalytic applications.

Learning from biological materials with complex, optimized and hierarchical morphologies and microstructures has become one of the hottest subjects in material design. Herein, we report a bio-inspired fabrication of fish scale-like carbon nanotiles, which were synthesized by a facile carbonization and grind procedure using kapok fibers (KFs) as green carbon source. Kapok fiber derived carbon nanotiles (KFCNTs) were used as the host of sulfur to construct KFCNTs/S cathodes for Li–S batteries. KFCNTs with scale-like microstructure are important for retarding the shuttling of soluble polysulfides, rendering S particles electrically conducting, and accommodating volume variation of S during the Li+ insertion/extraction. Owing to their unique microstructure, the resulting KFCNTs/S (93.2 wt%) electrodes exhibit a high and stable volumetric capacity of 504 mA h cm−3 (calculated from the whole electrode, the corresponding gravimetric capacity is 524 mA h g−1) with a superior capacity retention up to 95.4% after 90 cycles at 0.4 A g−1, representing a promising cathode material for rechargeable Li–S batteries. KFCNTs may also find potential applications in catalysis, electronics, sensors and separation technology. The bionic strategy outlined here can be generalized to other advanced electrode materials.

Biotemplating is an effective strategy to obtain morphology-controllable materials with structural specificity, complexity, and corresponding unique functions. Different from traditional biotemplating strategies replicating the morphology and using biogenic elements of biomaterials (e.g., C, Si, N, Fe, P, S), we take advantage of the unique heavy-metal-ion biosorption behavior of microalgae to fabricate tin-decorated carbon (Sn@C) anode materials for lithium-ion batteries. Microalgae Spirulina platensis is used as the biotemplate, the renewable carbon source, and the biosorbent. After a facile one-step heat treatment, Sn@C with tin particles (20–30 nm) dispersing into the porous carbon matrix can be obtained. Fourier transform infrared spectra reveal that metal-ion biosorption results from the complexation reactions between Sn4+ ions and the hydroxyl groups associated with alginate. The Sn@C anode shows a discharge capacity of 520 mAh g–1 after 100 cycles, as well as excellent cycle stability and high coulombic efficiency (approximately 100%), exhibiting fascinating electrochemical performance. This facile, green, and economical strategy not only will extend the scope of biotemplating synthesis of functional materials but also will provide reference for environmental protection and water purification.Keywords: anode; biotemplate; lithium-ion batteries; microalgae; tin;

•Facile synthesis of mesoporous CoO NRs/rGO composite by a hydrothermal method.•The composite has an unique 1D porous nanorods/2D sheets hybrid nanostructure.•The CoO NRs/rGO composite shows excellent electrochemical performance as anode materials for Li-ion batteries.Graphene-based hybrid nanostructures could offer many opportunities for improved lithium storage performance. Herein, we report a facile synthesis of mesoporous CoO nanorods (CoO NRs) on a reduced graphene oxide (rGO) substrate by hydrothermal and calcination treatment. Transmission electron microscopy (TEM) investigation reveals that the CoO NRs with a diameter of 20–60 nm are tightly anchored on the surface of rGO sheets. Compared to pure CoO NRs, the CoO NRs/rGO composite shows higher lithium storage capacity and superior rate capability as anode materials for Li-ion batteries. The CoO NRs/rGO composite delivers an initial discharge capacity of 1452 mAh g−1, and it can still remains 960 mAh g−1 after 50 cycles at 0.1 A g−1. After each 10 cycles at 0.1, 0.2, 0.5, and 1 A g−1, the specific capacities of the composite are about 1096, 1049, 934 and 513 mAh g−1, respectively. The enhanced electrochemical performance of the composite is closely related to its unique structure, such as 1D mesoporous morphology of CoO NRs and its tightly-contacting with rGO nanosheets, which could shorten the transport pathway for both electrons and ions, enhance the electrical conductivity and accommodate the volume expansion during prolonged cycling.

Graphene-based hybrid nanostructures could offer many opportunities for improved lithium storage performance. Herein, we report a novel synthesis of the Mn3O4–reduced graphene oxide (Mn3O4–r-GO) composite based on a microexplosion mechanism and reduction treatment. It is found that the well-dispersed ultrafine Mn3O4 particles with a size of about 20 nm are closely anchored onto the surface of r-GO sheets. Compared to pure Mn3O4, the Mn3O4–r-GO composite delivers higher lithium storage capacity and superior rate capability as a promising anode material for Li-ion batteries. The enhanced electrochemical performance of the Mn3O4–r-GO composite can be attributed to the buffering, confining and conducting effects of the r-GO sheets, as well as the small and uniform particle size of Mn3O4.

In this work, mesoporous Fe3O4@C submicrospheres with a diameter of 500 nm were successfully synthesized via a template-free hydrothermal method. Time-dependent experiments revealed that this unique microstructure evolved by a novel self-corrosion mechanism. As the anodic materials for lithium-ion batteries, these mesoporous Fe3O4@C submicrospheres exhibited enhanced cycling performance (930 mA h g−1 at a current density of 100 mA g−1 after 50 cycles) and high rate capabilities (910, 884, 770 and 710 mA h g−1 at current densities of 100, 200, 500 and 1000 mA g−1, respectively). This outstanding electrochemical behavior was ascribed to the enhanced structural stability and increased electrical conductivity arising from the porosity and carbon coating layers of the Fe3O4@C submicrospheres.

•The hierarchically porous TiO2–B nanoflowers are constructed by many ultrathin nanosheets, presenting ultrahigh specific surface area as high as 214.6 m2 g−1.•The TiO2–B electrode delivers high reversible capacity of 285 mA h g−1 at 1 C, and decreases from 196 to 181 mAh g−1 at 10 C rate during 100 cycles.•The excellent electrochemical properties of TiO2–B are attributed to the ultrahigh surface area, pseudocapacitive mechanism and scrupulous nanoarchitecture.In this work, hierarchically porous TiO2–B nanoflowers have been successfully synthesized via a facile solvothermal method followed by calcination treatment. The TiO2–B nanoflowers are constructed by thin nanosheets, presenting ultrahigh specific surface area, up to 214.6 m2 g−1. As anode materials for Li-ion batteries, the TiO2–B sample shows high reversible capacity, excellent cycling performance and superior rate capability. The specific capacity of TiO2–B could remain over 285 mA h g−1 at 1 C and 181 mA h g−1 at 10 C rate after 100 cycles. We believe that the pseudocapacitive mechanism, ultrahigh surface area and scrupulous nanoarchitecture of the TiO2–B are responsible for the enhancement of electrochemical properties.

Hollow α-Fe2O3 microcubes were fabricated by a facile hydrothermal method in an ethanol–water co-solvent system. The as-synthesized microcubes have a uniform size with an edge length of about 1.5 μm. Time and solvent proportion dependent experiments reveal that the ethanol adsorption and surface-protected etching mechanisms play key roles in the formation hollow cubic structures. Compared with their solid counterparts, hollow α-Fe2O3 microcubes show an enhanced electrochemical performance in terms of long-term cycling (458 mA h g−1 at a current density of 100 mA g−1 after 100 cycles) and high rate capability (859, 855, 688 and 460 mA h g−1 at current densities of 100, 200, 500 and 1000 mA g−1, respectively). These remarkable electrochemical properties can be attributed to the unique hollow microstructure, which could retain structural stability, relieve stress and increase reaction areas.

TiO2(B) is considered as a new kind of anode material, and an alternative to graphite, for high-power lithium ion batteries (LIBs) due to its characteristic pseudocapacitive energy storage mechanism. Herein, we firstly report the synthesis of one-dimensional (1D) mesoporous TiO2(B) nanobelts by hydrothermal treatment of commercial TiO2 (P25) powders in NaOH medium. The as-prepared TiO2(B) nanobelts, with typical sizes of 50–100 nm in width and several micrometers in length, have mesopore channels in the range of 10–30 nm. Moreover, we demonstrate the use of graphene as an excellent mini-current collector to in situ construct unique hybrid sheet–belt nanostructures (G–TiO2(B)) to optimize the performance. Such a 1D mesoporous TiO2(B) structure can provide numerous open channels for the electrolyte to access and facilitate the ultrafast diffusion of lithium ions. In addition, the introduced graphene layers will both be favorable for the fast electron transport in the electrode and make a great contribution to the specific capacity. As a consequence, this G–TiO2(B) hybrid can deliver an ultrahigh reversible capacity (over 430 mA h g−1 at a low current density of 0.15 A g−1), and present a superior rate capability (210 mA h g−1 at 3 A g−1).

Highly mesoporous carbon foam (MCF) with a high specific surface area has been successfully synthesized via a facile, cost-effective and template-free Pechini method. The as-prepared MCF exhibits a high specific surface area of 1478.55 m2 g−1 and a commendable pore size distribution for impregnating sulfur. After sulfur loaded in MCF, the relationship between pore size distribution of mesoporous carbon foam/sulfur nanocomposite (MCF/S) and the content of loaded sulfur is investigated in detail, which impacts on subtle variation of lithium storage performance. MCF/S (57.22 wt%) delivers an initial discharge of 1285 mA h g−1 and retains 878 mA h g−1 after 50 cycles. Compared with pristine sulfur, MCF/S cathodes display enhanced electrochemical performances, which can be attributed to the cross-linked hierarchical structure of MCF conductive matrix. Based on the advantages of the template-free Pechini method such as low cost, relative simplicity and atomic-scaled mixing, the MCF with hierarchical porous structure can be generalized to other practical applications including electrochemical double-layer capacitors, adsorption, separation, catalyst supports, etc. In addition, we believe that this modified Pechini method is general and can be extended to the fabrication of other types of mesoporous carbon by changing metal salts and organic reagents.

Porous Pt nanostructure decorated sulfur microparticles (Pt@S) are fabricated using sulfur as the template. The Pt@S electrode shows a higher volumetric specific capacity of 520 mA h cm−3 and improved cyclability with only 15% capacity fading after 80 cycles at 0.1 C (167.5 mA g−1).

•Boron carbide nanoflakes were successfully synthesized via a bamboo-based carbon thermal reduction method.•A fluoride-assisted VLS nucleation and VS growth mechanism were proposed.•We studied the resistivity of boron carbide nanoflakes via in situ TEM techniques for the first time.Boron carbide nanoflakes have been successfully synthesized by a facile and cost-effective bamboo-based carbon thermal reduction method. The majority of the boron carbide products exhibited a flake-like morphology with lateral dimensions of 0.5–50 μm in width and more than 50 μm in length, while the thickness was less than 150 nm. The structural, morphological, and elemental analyses demonstrated that these nanoflakes grew via the fluoride-assisted vapor–liquid–solid combined with vapor–solid growth mechanism. The corresponding growth model was proposed. In addition, the electrical property of individual boron carbide nanoflake was investigated by an in situ two point method inside a transmission electron microscope. The resistivity of boron carbide nanoflakes was measured to be 0.14 MΩ cm.Graphical abstractB4C nanoflakes were synthesized via a facile and cost-effective bamboo-based carbon thermal reduction method.

Hollow porous micro/nanostructures with high surface area and shell permeability have attracted tremendous attention. Particularly, the synthesis and structural tailoring of diverse hollow porous materials is regarded as a crucial step toward the realization of high-performance electrode materials, which has several advantages including a large contact area with electrolyte, a superior structural stability, and a short transport path for Li+ ions. Meanwhile, owing to the inexpensive, abundant, environmentally benign, and renewable biological resources provided by nature, great efforts have been devoted to understand and practice the biotemplating technology, which has been considered as an effective strategy to achieve morphology-controllable materials with structural specialty, complexity, and related unique properties. Herein, we are inspired by the natural microalgae with its special features (easy availability, biological activity, and carbon sources) to develop a green and facile biotemplating method to fabricate monodisperse MnO/C microspheres for lithium-ion batteries. Due to the unique hollow porous structure in which MnO nanoparticles were tightly embedded into a porous carbon matrix and form a penetrative shell, MnO/C microspheres exhibited high reversible specific capacity of 700 mAh g–1 at 0.1 A g–1, excellent cycling stability with 94% capacity retention, and enhanced rate performance of 230 mAh g–1 at 3 A g–1. This green, sustainable, and economical strategy will extend the scope of biotemplating synthesis for exploring other functional materials in various structure-dependent applications such as catalysis, gas sensing, and energy storage.Keywords: biotemplate; hollow; lithium-ion batteries; microalgae; MnO/C; porous structure

In this work, hierarchically porous NiO/C microspheres were successfully synthesized via a facile biotemplating method using natural porous lotus pollen grains as both the carbon source and the template. The as-prepared hierarchically porous NiO/C microspheres exhibited a large specific surface area and multiple pore size distribution, which could effectively increase the electrochemical reaction area and allow better penetration of the electrolyte. The Raman results also confirmed that the pollen grains have been well carbonized, which could provide good electronic conductivity. The specific capacities of the porous NiO/C microspheres after every 10 cycles at 0.1, 0.5, 1, and 3 A g−1 are about 698, 608, 454 and 352 mAh g−1. As an anode material in a Li ion half-cell, these unique hybrid hierarchically porous NiO/C microspheres exhibited fascinating electrochemical performance.

In this communication, we report a facile and novel molten salt electrolysis method to prepare high-quality graphene sheets. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirmed that the final products exfoliated from the electrolysis of graphite cathode in the molten LiOH medium are mainly graphene sheets (approx. 80 wt% conversion efficiency). Raman spectroscopy revealed that the as-formed graphene sheets have significantly low density of defects. Based on these observations, the exfoliation mechanism of graphite cathode into graphene sheets through lithium intercalation–expansion–microexplosion processes was proposed. The discovery of a molten salt electrolysis method presents us with the possibility for large scale and continuous production of graphene.

In this paper, one-dimensional (1D) mesoporous single-crystalline Co3O4 nanobelts are synthesized by a facile hydrothermal method followed by calcination treatment. The as-prepared nanobelts have unique mesoporous structures, which are constructed by many interconnected nanocrystals with sizes of about 20–30 nm. And typical size of the nanobelts is in the range of 100–300 nm in width and up to several micrometers in length. The BET surface area of Co3O4 nanobelts is determined to be about 36.5 m2 g–1 with dominant pore diameter of 29.2 nm. Because of the 1D structure, mesoporous morphologies and scrupulous nanoarchitectures, the Co3O4 nanobelts show excellent electrochemical performances such as high storage capacity and superior rate capability. The specific capacity of Co3O4 nanobelts could remains over 614 mA h g–1 at a current density of 1 A g–1 after 60 cycles. Even at a high current density of 3 A g–1, these Co3O4 nanobelts still could deliver a remarkable discharge capacity of 605 mA h g–1 with good cycling stability.Keywords: Co3O4; hydrothermal synthesis; lithium-ion batteries; mesoporous nanobelts; single-crystalline;

Unique amorphous FePO4 with particle size ranging from 20 to 80 nm has been successfully synthesized by a new cost-effective electrochemical method. This FePO4 possesses a mesoporous structure with specific surface area of 65.2 m2 g−1 and dominant pore diameter of 23.6 nm. The basic formation mechanism has been discussed. These amorphous mesoporous FePO4 nanoparticles can be used as precursors to prepare LiFePO4/C nanocrystals with porous structure. The obtained LiFePO4/C cathode materials exhibit excellent cycling performances. At a 0.5 C rate, the discharge capability is above 140.0 mA h g−1 and the capacity retention rate is higher than 98% after 50 cycles. The microstructural and electrochemical analyses reveal that these amorphous mesoporous FePO4 nanoparticles are the perfect precursors to prepare LiFePO4/C composite. Furthermore, this facile, cost-effective and green electrochemical strategy can be easily scaled up for commercialization, and also could open avenues towards synthesizing other mesoporous phosphate materials.Graphical abstractThe schematic diagram of formation mechanism for mesoporous FePO4 nanoparticles.Highlights► We synthesize amorphous mesoporous FePO4 via a new electrochemical method. ► The specific surface area is 65.2 m2 g−1, the dominant pore diameter is 23.6 nm. ► The LiFePO4/C prepared from FePO4 exhibits excellent electrochemical performance.

A visible-light photocatalytic, mesoporous, hierarchical spirulina/TiO2 composite with dye-sensitized surface was fabricated through a one-step hydrothermal process. The microstructure, mesoporous characteristics, surface morphology, as well as the visible-light photocatalytic activities are studied. The spirulina/TiO2 had an anatase phase and an enhanced harvesting of visible light. It was found that the spirulina/TiO2 composite exhibited higher specific surface area with narrow distributed mesopores. The photocatalytic activity of spirulina/TiO2 was evaluated by decolorizing methyl orange aqueous solutions under visible light irradiation. As a bio-template, spirulina prevents TiO2 from further aggregating and provides photosynthesis pigments as in situ dye-sensitizing source. The enlarged specific surface area and dye-sensitized surface improved the visible-light photocatalytic activity of spirulina/TiO2.

Here, we report a new biotemplating method to synthesize hierarchical LiFePO4/C microstructures using native spirulina as both the carbon source and the template. Owing to its unique hierarchical microstructure, spirulina-templated LiFePO4/C exhibits remarkable electrochemical performance as cathode materials for lithium ion batteries. This facile strategy may open avenues towards replicating specific biological structures for phosphate materials in other potential applications.

Finding a general procedure to produce a whole class of materials in a similar way is a desired goal of materials chemistry. In this work, we report a new bamboo-based carbothermal method to prepare nanowires of covalent carbides (SiC and B4C) and interstitial carbides (TiC, TaC, NbC, TixNb1−xC, and TaxNb1−xC). The use of natural nanoporous bamboo as both the renewable carbon source and the template for the formation of catalyst particles greatly simplifies the synthesis process. Based on the structural, morphological and elemental analysis, volatile oxides or halides assisted vapour–liquid–solid growth mechanism was proposed. This bamboo based carbothermal method can be generalized to other carbide systems, providing a general, one-pot, convenient, low-cost, nontoxic, mass production, and innovative strategy for the synthesis of carbide nanostructures.

Self-assembled mesoporous LiFePO4 (LFP) with hierarchical spindle-like architectures has been successfully synthesized via the hydrothermal method. Time dependent X-ray diffraction, scanning electron microscopy, and cross section high resolution transmission electron microscopy are used to investigate the detailed growth mechanism of these unique architectures. Reaction time and pH value play multifold roles in controlling the microstructures of LFP. The LFP particles are uniform mesoporous spindles, which are comprised of numerous single-crystal LFP nanocrystals. As the cathode material for lithium batteries, LFP exhibits high initial discharge capacity (163 mAh g−1, 0.1 C), excellent high-rate discharge capability (111 mAh g−1, 5 C), and cycling stability. These enhanced electrochemical properties can be attributed to this unique microstructure, which will remain structural stability for long-term cycling. Furthermore, nanosizing of LFP nanocrystals can increase the electrochemical reaction surface, enhance the electronic conductivity, and promote lithium ion diffusion.Graphical abstractHighlights► A growth model of hierarchical spindle-like LiFePO4 has been proposed. ► The mesoporous structure remains the structural stability for long-term cycling. ► Nanocrystals achieve higher surface area and shorter Li+ diffusion length.

Highly porous nickel oxide (NiO) thin films were prepared on ITO glass by chemical bath deposition (CBD) method. SEM results show that the as-deposited NiO film is constructed by many interconnected nanoflakes with a thickness of about 20 nm. The electrochromic properties of the NiO film were investigated in a nonaqueous LiClO4–PC electrolyte by means of optical transmittance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The NiO film exhibits a noticeable electrochromic performance with a variation of transmittance up to 38.6% at 550 nm. The CV and EIS measurements reveal that the NiO film has high electrochemical reaction activity and reversibility due to its highly porous structure. The electrochromic (EC) window based on complementary WO3/NiO structure shows an optical modulation of 83.7% at 550 nm, much higher than that of single WO3 film (65.5% at 550 nm). The response time of the EC widow is found to be about 1.76 s for coloration and 1.54 s for bleaching, respectively. These advantages such as large optical modulation, fast switch speed and excellent cycle durability make it attractive for a practical application.Research highlights► The highly porous NiO film is constructed by many interconnected nanoflakes. ► The NiO film exhibits good electrochemical kinetics for injection/extraction of Li+ due to its porous structure. ► The NiO film has a noticeable electrochromism related to the annealing temperature. ► The assembled WO3/NiO window shows large optical modulation, fast switch speed and excellent cycle durability.

In this work, single-crystalline TiC nanorods (NRs) were successfully synthesized via a simple, convenient, and cost-effective biotemplate method. Use of natural nanoporous cotton fibers as both the carbon source and the template for formation of catalyst particles significantly simplifies the synthesis process of TiC NRs. On the basis of the structural, morphological, and elemental analyses, a chloride-assisted vapor–liquid–solid growth mechanism and the corresponding growth model were proposed. The activation energy for the TiC NRs was calculated to be 259 kJ/mol. From in situ nanoscale three-point bending measurements, we also determined the Young’s modulus of TiC NRs, which is an important parameter for practical applications. The measured Young’s modulus of TiC NRs is in the range from 394 to 468 GPa with an average value of 432 ± 22 GPa.

Li3V2−xNbx(PO4)3/C cathode materials were synthesized by a sol–gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li3V2(PO4)3, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li3V2−xNbx(PO4)3/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li3V1.85Nb0.15(PO4)3/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li3V2−xNbx(PO4)3/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li3V2(PO4)3 system by enhancing structural stability and electrical conductivity.

Spherical LiFePO4/C powders were synthesized by the conventional solid-state reaction method via Ni doping. Low-cost asphalt was used as both the reduction agent and the carbon source. An Ni-doped spherical LiFePO4/C composite exhibited better electrochemical performances compared to an un-doped one. It presented an initial discharge capacity of 161 mAhg−1 at 0.1 C rate (the theoretical capacity of LiFePO4 with 5 wt% carbon is about 161 mAhg−1). After 50 cycles at 0.5 C rate, its capacity remained 137 mAhg−1 (100% of the initial capacity) compared to 115 mAhg−1 (92% of the initial capacity) for an un-doped one. The electrochemical impedance spectroscopy analysis and cyclic voltammograms results revealed that Ni doping could decrease the resistance of LiFePO4/C composite electrode drastically and improve its reversibility.

A high-yield of carbon nanotubes filled with β-Sn nanowires has been produced by the thermal pyrolysis of acetylene over SnO2 catalysts. Electron beam irradiation (EBI) induced melting and flow of Sn in the nanotubes and this could be controlled by changing the electron beam current density. The mass flow rate of the Sn ranged from 0.9 to 8.2 fg/s. The melting of the nanowires is a result of the temperature rise caused by the EBI. Many factors, including temperature variation, charging, and EBI induced deformation of the carbon shells, contribute to the flow of Sn.

A new kind of TiO2 nanotube array/Ni(OH)2 (TiO2/Ni(OH)2) composite electrode with the storage ability of light energy was prepared by the deposition of Ni(OH)2 on the TiO2 nanotube array, which was synthesized by anodizing Ti foils in an HF aqueous solution. SEM and XRD results showed that Ni(OH)2 particles were well distributed on high density, well-ordered and uniform TiO2 nanotube arrays. The photoelectrochemical properties of the TiO2/Ni(OH)2 electrode were investigated in NaHCO3/NaOH buffer solution (pH 10) by means of UV–vis absorption spectra, cyclic voltammogram (CV) and photocurrent measurements. It was found that the TiO2/Ni(OH)2 electrode was highly sensitive to light and exhibited excellent photoelectrochromic properties. Upon UV irradiation, the photogenerated holes by TiO2 nanotube arrays can oxidize Ni(OH)2 to NiOOH, and thus the TiO2/Ni(OH)2 electrode can be photo-charged by light.

N-doped TiO2 film was synthesized on indium–tin oxide (ITO) conducting glass substrate by the hydrolysis method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Then high porous NiO was deposited onto the TiO2−xNx layer by chemical bath deposition (CBD) to prepare a double-layer TiO2−xNx/NiO electrode. The photoelectrochromic properties of the TiO2−xNx/NiO electrode were discussed through the results of UV–vis transmittance spectra, cyclic voltammogram and photocurrent transient measurements. It was found that the TiO2−xNx/NiO electrode was sensitive to light and exhibited a noticeable photoelectrochromism. The NiO film changed its color from colorless to brown, and the transmittance varied from 86.8% to 14.5% at 500 nm after 1 h irradiation.

A novel process via sintering of a precursor from the solution of metal acetates by spray-drying technology was used to synthesize Co-substituted LiCo1/6Mn11/6O4 material for lithium ion batteries. The as-prepared particles were identified as single-phase spinel structure without any impurities in the XRD pattern. The SEM image showed that the particles had good cubic shapes and uniform size distribution with sizes of about 100–200 nm. An ex situ XRD technique was used to characterize the first charge process of the LiCo1/6Mn11/6O4 electrode. The result suggested that the material configuration maintained invariability. The electrochemical properties of the synthesized cathode material were investigated using Li-ion model cells at room and elevated temperature, respectively. In the charge/discharge potential of 3.5–4.4 V at 1/10 C rate, the LiCo1/6Mn11/6O4 electrode delivered high initial capacities of 123 and 127 mAh g−1 at 25 and 55 °C, respectively. Electrochemical cycling tests revealed that the capacity fading occurred mainly in the high-voltage region of 4.08–4.40 V, and the fading rate was 0.107% and 0.302% per cycle at 25 and 55 °C, respectively. The excellent cycling stability and low material cost make it an attractive cathode for high-temperature lithium ion batteries.

A novel ZnO/conductive-ceramic nanocomposite was prepared by a homogeneous precipitation between Zn(NO3)2 and CO(NH2)2 with conductive ceramic powders as the nucleation sites. The conductive ceramic powders contained zinc oxide, bismuth oxide, cobalt oxide and rare earth oxide, and the nominal chemical composition (mole fraction) was represented by (ZnO)0.92(Bi2O3)0.054(Co2O3)0.025(Nb2O5)0.00075(Y2O3)0.00025. The phase composition and surface morphology of the as-synthesized materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). ZnO nanorods with the length of about 200 nm were dispersed homogeneously on the surface of the conductive ceramic, and identified as a well-defined single-phase hexagonal structure. The electrochemical properties of the ZnO/conductive-ceramic nanocomposite as anode material of Ni/Zn battery were investigated by charge/discharge cycling test, slow rate cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with pure nanosized ZnO, the ZnO/conductive-ceramic nanocomposite showed better cycling stability, higher discharge capacity and utilization ratio. The initial discharge capacity of ZnO/conductive-ceramic nanocomposite reached about 644 mAh g−1. The discharge capacity hardly declined over 50 cycling tests, and the average utilization ratio could reach 99.5%. EIS revealed that the charge-transfer resistance was lower than that of pure nanosized ZnO.

Co-substituted LiCo1/6Mn11/6O4 powders were prepared by a spray-drying method for positive electrodes of lithium ion batteries. The heat treating process, crystal structure and electrochemical properties of the synthesized materials were investigated by TG/DTG, DSC, XRD, SEM, slow rate cyclic voltammetry (CV) and galvanostatic charge/discharge cycling tests. The final powders were identified as single-phase spinel LiCo1/6Mn11/6O4 with high degree of crystallization and uniform particle size distribution. In the charge/discharge potential (versus Li/Li+) ranging from 2.0 to 4.4 V, the LiCo1/6Mn11/6O4 electrode delivered high initial discharge capacity of 242 mAh g−1 at 1/10 C rate at 25 °C. In the potential range of 3.5–4.4 V, it showed high discharge capacity and excellent cycling performance at 1/5, 1/2, 1 C rate at 25 °C and 55 °C. The improvement in cycling performance might be contributed by the stabilization of spinel structure by smaller lattice constant when manganese ion was partially substituted by Co3+ ion. The spray-drying method is an effective method to prepare co-substituted lithium manganese oxide within very short production time, and thus is promising for commercial application.

•Facile embedding of titanium carbide particles into CMK-3 mesoporous carbon with the assistance of supercritical CO2 fluid.•TiC/C host shows high surface area, large mesoporous volume and interfacial affinity for sulfur.•TiC/C-S composite shows attractive electrochemical performance as cathode materials for Li-S batteries.Because of high theoretical energy density, low-cost and environmental benignity, lithium-sulfur battery is recognized as a prospective candidate for replacing conventional lithium-ion batteries. However, its large scale commercialization is limited by inherent defects of sulfur cathode such as poor electronic conductivity and polysulfide shuttle effect. Herein, we report that titanium carbide particles embedded in CMK-3 mesoporous carbon (TiC/C) with the assistance of supercritical CO2 fluid is highly effective sulfur host to improve cycling capability and rate performance. Compared with TiO2/C-S and CMK-3-S, the TiC/C-S cathode exhibits higher reversible capacity and better cycling performance. It delivers high specific capacities at various C-rates (866, 622, and 438 mAh g−1 at 0.1, 0.5, and 2 A g−1, respectively) and remarkable capacity retention of 73% (200 cycles at 0.2 A g−1). The excellent electrochemical properties of TiC/C-S can be attributed to the polar nature and high conductivity of TiC particles. The present work provides a novel strategy in synthesizing cathode materials for high performance Li-S battery.

Finding a general procedure to produce a whole class of materials in a similar way is a desired goal of materials chemistry. In this work, we report a new bamboo-based carbothermal method to prepare nanowires of covalent carbides (SiC and B4C) and interstitial carbides (TiC, TaC, NbC, TixNb1−xC, and TaxNb1−xC). The use of natural nanoporous bamboo as both the renewable carbon source and the template for the formation of catalyst particles greatly simplifies the synthesis process. Based on the structural, morphological and elemental analysis, volatile oxides or halides assisted vapour–liquid–solid growth mechanism was proposed. This bamboo based carbothermal method can be generalized to other carbide systems, providing a general, one-pot, convenient, low-cost, nontoxic, mass production, and innovative strategy for the synthesis of carbide nanostructures.

Developing Pt eletrocatalysts with high activity and long-term durability remains a great challenge in commercializing fuel cells. Herein, we report a new kind of bark-structured TiC nanowire (NW) as an efficient support for Pt electrocatalysts, which exhibits a higher electrochemically active surface area (ECSA), much improved electrocatalytic activity and long-term durability toward a methanol oxidation reaction (MOR) when compared with commercial Pt/C (Vulcan XC-72) catalysts. The TiC NWs were synthesized via a simple biotemplating method using natural nanoporous cotton fibers as both the carbon source and the template. Their typical size is in the range of 50–150 nm in width and up to several micrometers in length. The Pt nanoparticles deposited onto the TiC NWs by a urea-assisted ethylene glycol reduction method are small (ca. 3 nm), narrowly distributed and well crystallized. The unique one-dimensional (1D) nanostructure of the TiC NWs provides fast transport and a short diffusion path for electroactive species, and a high utilization of catalysts. Moreover, the merits of TiC NWs, such as high electrical conductivity and excellent chemical/electrochemical stability also contribute to enhancing their electrocatalytic properties. The carbide support reported here will promote broader interest in the further development of Pt electrocatalysts in the fields of fuel cells and related electrocatalytic applications.

Learning from biological materials with complex, optimized and hierarchical morphologies and microstructures has become one of the hottest subjects in material design. Herein, we report a bio-inspired fabrication of fish scale-like carbon nanotiles, which were synthesized by a facile carbonization and grind procedure using kapok fibers (KFs) as green carbon source. Kapok fiber derived carbon nanotiles (KFCNTs) were used as the host of sulfur to construct KFCNTs/S cathodes for Li–S batteries. KFCNTs with scale-like microstructure are important for retarding the shuttling of soluble polysulfides, rendering S particles electrically conducting, and accommodating volume variation of S during the Li+ insertion/extraction. Owing to their unique microstructure, the resulting KFCNTs/S (93.2 wt%) electrodes exhibit a high and stable volumetric capacity of 504 mA h cm−3 (calculated from the whole electrode, the corresponding gravimetric capacity is 524 mA h g−1) with a superior capacity retention up to 95.4% after 90 cycles at 0.4 A g−1, representing a promising cathode material for rechargeable Li–S batteries. KFCNTs may also find potential applications in catalysis, electronics, sensors and separation technology. The bionic strategy outlined here can be generalized to other advanced electrode materials.

Lithium–sulfur batteries show fascinating potential applications for rapid-growing electric vehicles and grid-level energy storage due to their low cost and high energy density. To date, various carbon hosts have been utilized to confine sulfur for improving Li–S battery performance. However, the adopted sulfur storage techniques are post-carbon-synthesis involving complex processes. It remains a great challenge to determine the ideal configuration of carbon–sulfur composites with uniform dispersion and high sulfur loading. Herein, we report a novel synthesis of graphene–sulfur composites by electrolytic exfoliation of graphite coupled with in situ sulfur electrodeposition. The sample delivers an initial discharge capacity of 1080 mA h g−1 at 0.1 A g−1 and retains above 900 mA h g−1 over 60 cycles. This strategy via electrochemical exfoliation/deposition synchronous reactions can provide strong sulfur chemical interactions with the graphene host, achieving advanced cathode materials for Li–S batteries.

NaV3O8 nanobelts, nanorods and microrods have been successfully synthesized using a facile, one-step solid-state sintering method. The morphology, crystallinity and purity of NaV3O8 can be easily controlled by the calcination temperature. As a cathode material for Li-ion batteries, NaV3O8 nanorods synthesized at 450 °C show a relatively higher specific discharge capacity of 226 mA h g−1 at 30 mA g−1 and a good cycling performance without considerable capacity loss over 100 cycles at 100 and 300 mA g−1. In situ TEM characterization confirmed that the intercalation/deintercalation of Li+ ions in NaV3O8 is a single-phase reaction process with small lattice change, which can result in obvious cracks and fractures. The SEM characterizations of the electrodes after cycling reveal that the structure destruction is the main reason for the capacity fading of NaV3O8.

Porous Pt nanostructure decorated sulfur microparticles (Pt@S) are fabricated using sulfur as the template. The Pt@S electrode shows a higher volumetric specific capacity of 520 mA h cm−3 and improved cyclability with only 15% capacity fading after 80 cycles at 0.1 C (167.5 mA g−1).

We report a novel synthesis of a mesoporous carbon–sulfur composite (MCSC) by electrodeposition of sulfur into the mesopores via a self-limiting process. With the merits of a high sulfur content (77%), uniform distribution and strong C–S bonds achieved by this method, the as-prepared materials demonstrate excellent performance in lithium–sulfur batteries. The electrode delivers high specific capacities at various C-rates (e.g. about 1160 and 590 mA h g−1 at current densities of 0.1 and 2.0 A g−1, respectively) and remarkable capacity retention, remaining above 857 mA h g−1 after 200 cycles at a high rate of 0.5 A g−1. This electrochemical strategy is industrially viable and scalable, and thus may pave a new way to push the commercialization of Li–S batteries.

Highly mesoporous carbon foam (MCF) with a high specific surface area has been successfully synthesized via a facile, cost-effective and template-free Pechini method. The as-prepared MCF exhibits a high specific surface area of 1478.55 m2 g−1 and a commendable pore size distribution for impregnating sulfur. After sulfur loaded in MCF, the relationship between pore size distribution of mesoporous carbon foam/sulfur nanocomposite (MCF/S) and the content of loaded sulfur is investigated in detail, which impacts on subtle variation of lithium storage performance. MCF/S (57.22 wt%) delivers an initial discharge of 1285 mA h g−1 and retains 878 mA h g−1 after 50 cycles. Compared with pristine sulfur, MCF/S cathodes display enhanced electrochemical performances, which can be attributed to the cross-linked hierarchical structure of MCF conductive matrix. Based on the advantages of the template-free Pechini method such as low cost, relative simplicity and atomic-scaled mixing, the MCF with hierarchical porous structure can be generalized to other practical applications including electrochemical double-layer capacitors, adsorption, separation, catalyst supports, etc. In addition, we believe that this modified Pechini method is general and can be extended to the fabrication of other types of mesoporous carbon by changing metal salts and organic reagents.

Hollow α-Fe2O3 microcubes were fabricated by a facile hydrothermal method in an ethanol–water co-solvent system. The as-synthesized microcubes have a uniform size with an edge length of about 1.5 μm. Time and solvent proportion dependent experiments reveal that the ethanol adsorption and surface-protected etching mechanisms play key roles in the formation hollow cubic structures. Compared with their solid counterparts, hollow α-Fe2O3 microcubes show an enhanced electrochemical performance in terms of long-term cycling (458 mA h g−1 at a current density of 100 mA g−1 after 100 cycles) and high rate capability (859, 855, 688 and 460 mA h g−1 at current densities of 100, 200, 500 and 1000 mA g−1, respectively). These remarkable electrochemical properties can be attributed to the unique hollow microstructure, which could retain structural stability, relieve stress and increase reaction areas.

TiO2(B) is considered as a new kind of anode material, and an alternative to graphite, for high-power lithium ion batteries (LIBs) due to its characteristic pseudocapacitive energy storage mechanism. Herein, we firstly report the synthesis of one-dimensional (1D) mesoporous TiO2(B) nanobelts by hydrothermal treatment of commercial TiO2 (P25) powders in NaOH medium. The as-prepared TiO2(B) nanobelts, with typical sizes of 50–100 nm in width and several micrometers in length, have mesopore channels in the range of 10–30 nm. Moreover, we demonstrate the use of graphene as an excellent mini-current collector to in situ construct unique hybrid sheet–belt nanostructures (G–TiO2(B)) to optimize the performance. Such a 1D mesoporous TiO2(B) structure can provide numerous open channels for the electrolyte to access and facilitate the ultrafast diffusion of lithium ions. In addition, the introduced graphene layers will both be favorable for the fast electron transport in the electrode and make a great contribution to the specific capacity. As a consequence, this G–TiO2(B) hybrid can deliver an ultrahigh reversible capacity (over 430 mA h g−1 at a low current density of 0.15 A g−1), and present a superior rate capability (210 mA h g−1 at 3 A g−1).

In this work, hierarchically porous NiO/C microspheres were successfully synthesized via a facile biotemplating method using natural porous lotus pollen grains as both the carbon source and the template. The as-prepared hierarchically porous NiO/C microspheres exhibited a large specific surface area and multiple pore size distribution, which could effectively increase the electrochemical reaction area and allow better penetration of the electrolyte. The Raman results also confirmed that the pollen grains have been well carbonized, which could provide good electronic conductivity. The specific capacities of the porous NiO/C microspheres after every 10 cycles at 0.1, 0.5, 1, and 3 A g−1 are about 698, 608, 454 and 352 mAh g−1. As an anode material in a Li ion half-cell, these unique hybrid hierarchically porous NiO/C microspheres exhibited fascinating electrochemical performance.

Here, we report a new biotemplating method to synthesize hierarchical LiFePO4/C microstructures using native spirulina as both the carbon source and the template. Owing to its unique hierarchical microstructure, spirulina-templated LiFePO4/C exhibits remarkable electrochemical performance as cathode materials for lithium ion batteries. This facile strategy may open avenues towards replicating specific biological structures for phosphate materials in other potential applications.