A molecular solution of an amphiphilic block copolymer may act as an oil phase by dispersing into an aqueous micellar system of small-molecular surfactant, forming oil-in-water (O/W) emulsion droplets. In this paper, an as-synthesized triblock copolymer poly(l-lactide)–polyoxyethylene–poly(l-lactide) (PLLA–PEO–PLLA) was dissolved in tetrahydrofuran (THF) and then added to an aqueous micellar solution of nonaethylene glycol monododecyl ether (AEO-9), forming initially coalescent O/W emulsion droplets in the size range of 35 nm–1.3 μm. Along with gradual volatilization of THF and simultaneous concentration of PLLA–PEO–PLLA molecules, the amphiphilic copolymer backbones themselves experience solution-based self-assembly, forming inverted core–corona aggregates within an oil-phase domain. Anisotropic coalescence of adjacent O/W emulsion droplets occurs, accompanied by further volatilization of THF. The hydrophilic block crystallization of core-forming PEOs and the hydrophobic chain stretch of corona-forming PLLAs together induce the intermediate formation of rod-like architectures with an average diameter of 300–800 nm, and this leads to a large-scale deposition of the triblock copolymer fibers with an average diameter of ∼2.0 μm. Consequently, this strategy could be of general interest in the self-assembly formation of amphiphilic block copolymer fibers and could also provide access to aqueous solution crystallization of hydrophilic segments of these copolymers.

•Commercial lignin can be facilely transferred into functional microporous carbon.•Both the subsurface micropores and surface oxygen-containing groups functionalize.•Sulfur-loading time greatly affects the electrochemical properties of C-S composite.•The effective utilization of elemental sulfur has been investigated systematically.In this paper, a framework of macro-/micro-porous carbon derived from commercial lignin is prepared by one-step carbonization/activation method and then utilized as sulfur-loading matrix to assay the effect of sulfur-loading time on the structural and electrochemical properties of carbon-sulfur composite (C-S-t, t defined as sulfur-loading time). As-prepared porous carbon possesses a high specific surface area of 1211.6 m2 g−1 and a pore volume of 0.59 cm3 g−1, acquires oxygen-containing functional groups on the surface of framework and functionalizes for the chemical adsorption of elemental sulfur. Under N2 atmosphere (flow rate ∼ 60 mL min−1) the longer is the sulfur-loading time, the lower value is the total sulfur content of carbon-sulfur composite and the higher percentage of sulfur embedded within the micropores. At a sulfur-loading time of ∼10 h, the resulting C-S-10 composites have a total sulfur content as low as 50.0 wt% (44.8% in micropores) but exhibit the better electrochemical performances than C-S-6 composites formed at 6 h (sulfur ∼ 58.8 wt%, 29.4% in micropores). Therefore, aside from the structural properties of porous carbon, an optimized sulfur-loading time, as well as the chemical binding between carbon host and sulfur, should be considered to develop high-performance cathode materials for liquid electrolyte lithium-sulfur (Li-S) batteries.Download high-res image (239KB)Download full-size image

As one of the most abundant natural aromatic polymers with plentiful oxygen-containing groups in molecular backbones, commercial lignin can be regarded as a sustainable precursor to develop porous carbonaceous frameworks for the encapsulation of elemental selenium. In this paper, an initial combined carbonization/activation of commercial alkaline lignin and subsequent selenium-loading are adopted to fabricate serial composites of lignin-derived porous carbon (LPC) and elemental selenium (i.e., serial Se/LPC composites) for high-performance lithium-selenium (Li-Se) batteries. The high specific surface area, large pore volume and good electron conductivity of each LPC scaffold facilitate the reversible electrochemical reaction of selenium towards metallic Li, and at 0.5 C a Se/LPC composite electrode exhibits a reversible capacity of 596.4 mAh g−1 in the 2nd cycle and a capacity retention of 453.1 mAh g−1 over 300 cycles with an average decay of 0.08% per cycle. The facilely obtained microporous features of LPC scaffold, as well as the high-rate performance of corresponding Se/LPC composites (e.g., 363.2 mAh g−1, 4 C), indicate that large-scale treatment of the biomass feedstock may find its potential application in renewable green energy sources.Download high-res image (266KB)Download full-size image

Interconnected nickel bicarbonate (Ni(HCO3)2) hollow spheres were produced and exploited for the first time as an anode of lithium ion batteries, delivering the 80th reversible capacity of 1442 mAh g–1 at a current rate of 100 mA g–1, which is 3.9 times the theoretical capacity of commercial anode graphite. The time-dependent study suggested a self-sacrificial templating formation mechanism that yielded intriguing interconnected hollow structures. X-ray photoelectron spectroscopy measurements on cycled electrodes indicated that both the deep oxidation of Ni2+ into Ni3+ and the reversible reactions in HCO3– accounted for the ultrahigh capacity of Ni(HCO3)2 in comparison to its generally accepted theoretical capacity of 297 mAh g–1. Morphological characterizations revealed that the interconnected hollow structures enabled the enhanced rate performance and cycling stability, compared to those of the solid counterpart, because of their larger contact areas with electrolyte and better buffering effect to accommodate the volume change.

Graphene oxide (GO) possesses high electron conductivity and good chemical-binding ability and thus can be used as a multifunctional additive for the preparation and application of electrode materials. As for the hydrothermal crystallization of MnCO3 herein, the absence of GO causes the formation of MnCO3 flower-like architectures composed of secondary spindles, while the presence of GO induces the flower-to-petal structural conversion and results in MnCO3 spindle–GO composites. When applied as Li-ion battery anodes, the composite electrode delivers an initial coulombic efficiency (CE) of 71% and a reversible capacity of 1474 mA h g−1 in the 400th cycle, much higher than those of MnCO3 flowers (the initial CE ∼ 58%, the 400th capacity ∼ 1095 mA h g−1) operated under the same conditions. In particular, the combination of discharging behavior and its differential capacity profile has been successfully used to estimate the interfacial contribution fraction (42%) of the whole reversible capacity (i.e., 1474 mA h g−1) enhanced by the in situ mixing of 8.3 wt% GO.

Multicomponent composites with an integrated lattice structure can possess an atomic-scale distribution of different components within the crystallites and may express an enhanced synergistic effect compared to the mechanical mixture. In this paper, a series of cobaltous-ferrous carbonates CoxFe1−xCO3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) have been synthesized via a facile hydrothermal route with the assistance of ascorbic acid (AA). The four multicomponent CoxFe1−xCO3 composites exhibit hexagonal structures similar to those of the monocomponents FeCO3 and CoCO3, and the resulting rodlike crystallites give aspect ratios and unit-cell parameters linearly changed along with the increasing x value, indicating the successful synthesis of CoxFe1−xCO3 composites at an arbitrary Co/Fe molar ratio. When used as lithium ion battery anodes, the CoxFe1−xCO3 composites can well inherit both the high-conductivity characteristic of CoCO3 and the low-rate cycling stability of FeCO3. In particular, each composite presents better electrochemical properties than the corresponding xCoCO3 + (1 − x)FeCO3 mixture, mainly assigned to an inner atomic-scale synergistic effect within the formula CoxFe1−xCO3. Therefore, CoxFe1−xCO3 composites may serve as novel high-capacity LIB anode materials for practical application, and also a facile strategic approach is introduced for the full-molar-ratio synthesis of multicomponent composites.

The preparation of porous Mn2O3 boxes has been developed via a carbonate precursor route. As a Li-ion battery anode, it delivers a high reversible capacity of 1442 mA h g−1 over 600 cycles at 800 mA g−1, and 65% of the capacity originates from the gradually emerging interfacial storage contribution.

•CoCO3 dumbbells are hydrothermally synthesized in the presence of ascorbic acid.•The crystallization and aggregation of CoCO3 are greatly modified by ascorbic acid.•Ascorbic acid doped CoCO3 dumbbells exhibit enhanced electrochemical performances.•The 100th discharge capacity is as high as 1042 mAh g−1 at 200 mA g−1.Synthesis of materials with desirable nanostructures is a hot research topic owing to their enhanced performances in contrast to the bulk counterparts. Herein, dumbbell-shaped cobalt carbonate (CoCO3) nano architectures and the bulk counterpart of CoCO3 rhombohedra are prepared via a facile hydrothermal route in the presence and absence of ascorbic acid (AA), respectively. By comparison, it has been found that: the addition of AA in the hydrothermal crystallization system changes the shape of the building blocks from Co2CO3(OH)2 nanosheets to CoCO3 nanoparticles, and then further influences the final configuration of the products. When applied as anodes of lithium ion batteries, CoCO3 dumbbells deliver a 100th capacity of 1042 mAh g−1 at 200 mA g−1 and even exhibit a long-term value of 824 mAh g−1 over 500 cycles at 1000 mA g−1, which are much higher than the rhombohedral counterparts with corresponding 540 and 481 mAh g−1 respectively. The much higher capacity, better cycling stability and enhanced rate performance of CoCO3 dumbbells can be attributed to the higher specific surface area, smaller charge transport resistance and better structure stability resulting from the slight doping (∼4.6 wt%) of AA, and also relate with a novel lithium storage mechanism in CoCO3.

•Cupric-cobaltous oxalate hydrate and dehydrate are used as Li-ion battery anodes.•A jointly positive effectiveness of crystal water and FGO is investigated.•Cu1/3Co2/3C2O4·xH2O/FGO (x = 1.4) possesses high-rate electrochemical properties.•The 100th reversible capacity (Cu1/3Co2/3C2O4·xH2O/FGO) is 935.6 mAh g−1 at 2A g−1.The combination of co-precipitation and dehydration is used to prepare hydrated and dehydrated cupric-cobaltous oxalates (Cu1/3Co2/3C2O4·xH2O, x = 1.4; Cu1/3Co2/3C2O4). Then, the hydrothermal treatment of these binary oxalates with freshly prepared graphene oxide (GO) and then dehydration are subsequently adopted to combine the hydrated or dehydrated oxalate with functionalized graphene oxide (FGO), resulting in another two targets of Cu1/3Co2/3C2O4·xH2O/FGO and Cu1/3Co2/3C2O4/FGO composites. These facilitate the comparative studies on the lithium storage capability of cupric oxalate-containing anode materials enhanced by unavoidable crystal water. As a lithium-ion battery anode, Cu1/3Co2/3C2O4·xH2O possesses a reversible capacity of 565.0 mAh g−1 at 1000 mA g−1 over 200 discharge-charge cycles, higher than that of the dehydrated counterpart (246.1 mAh g−1) but lower than those of FGO-based composites (Cu1/3Co2/3C2O4/FGO ∼ 951.2 mAh g−1; Cu1/3Co2/3C2O4·xH2O/FGO ∼ 1134.9 mAh g−1) continuously cycled at the exactly same conditions. At an ultra-high current density of 2000 or 5000 mA g−1, anode Cu1/3Co2/3C2O4·xH2O/FGO delivers a constant discharge capacity of 935.6 mAh g−1 in the 100th cycle or 388.9 mAh g−1 in the 1000th cycle, indicating a jointly positive effect of crystal water and FGO on the high-rate electrochemical performance of cupric-cobaltous oxalate for the first time.

•Composite Zn0.5Mn0.5CO3 microspheres are facilely co-precipitated.•Porous ZnMnO3 spherulites can be used as a lithium-ion battery anode.•Porous ZnMnO3 spherulites show superior electrochemical properties.•A synergistic effect of Zn-O and Mn-O components in cubic ZnMnO3 is proposed.In this paper, pure-phase ZnMnO3 porous spherulites are uniquely synthesized through the thermal decomposition of Zn-Mn binary carbonate precursors facilely co-precipitated at room temperature, possessing an average diameter of 1.2 ± 0.3 μm and acquiring porosity with a specific surface area of 24.3 m2 g−1. When tentatively applied as lithium-ion battery anodes for the first time, these porous spherulites deliver an initial discharge capacity of 1294 mAh g−1 at 500 mA g−1 and retain an reversible value of 879 mAh g−1 over 150 cycles. By comparison, the equimolar powder mixture of nano-sized ZnO and MnO2 synergistically shows a higher lithium storage capability than the two unary transition metal oxides, but lower than anode material ZnMnO3. Aside from its nanostructured characteristics, an inner atomic synergistic effect within the cubic lattices may account for the superior electrochemical performance of well-crystallized ZnMnO3.Porous ZnMnO3 spherulites show an enhanced high lithium storage capability when potentially applied as a lithium-ion battery anode for the first time.

A two-step process of initial oxalate co-precipitation and subsequent thermal decomposition facilitates the formation of hydrated oxalate precursors with hollow quadrangular prism shapes, and then confers a porous nature for the prismatic shells of synthetic hematite (α-Fe2O3) and its Mn-doped derivative. When applied as lithium-ion battery anodes, Mn-doped α-Fe2O3 exhibits an improved electrochemical performance compared with undoped α-Fe2O3. At a current density of 200 mA g−1, the pure α-Fe2O3 electrode gives an initial discharge capacity of ∼1280 mA h g−1 with a low retention ratio of 13.9% (i.e., capacity ∼ 178 mA h g−1) over 80 cycles, while the Mn-doped product, rhombohedral Fe1.7Mn0.3O3, delivers a relatively low initial value of ∼1190 mA h g−1 and retains an 80th cycle reversible capacity of ∼1000 mA h g−1 (i.e., retention ratio ∼ 84.0%). These, together with the better high-rate capability and the lower charge-transfer resistance of the Mn-doped α-Fe2O3 anode, simultaneously demonstrate a successful mass production of hollow porous configurations and an effective doping with elemental Mn for potential application.

To visualize the one-dimensional (1D) migration of Li+ ions along the ⟨010⟩ direction, two kinds of (010)-defective LiFePO4 platelets with different hollow interiors are prepared using the polyethylene glycol (PEG)-assisted hydrothermal reaction of LiOH, FeSO4, and H3PO4 at the molar ratio of 3:1:1. Owing to the acidic and viscous reaction circumstance in the presence of polymeric PEG, the relatively high concentration of PEG induces the formation of (010)-defective LiFePO4 platelets with a small average length and a small hollow interior. As a Li-ion battery cathode, (010)-defective crystallites with a small hollow interior exhibit higher reversible capacity at each charge–discharge cycle, smaller concentration polarization and charge transfer resistance, and bigger Coulombic efficiency and Li-ion diffusion coefficient than (010)-defective LiFePO4 platelets with a large hollow interior. Furthermore, (010)-manifested LiFePO4 microrhombohedra and their surface-etched derivatives could be treated as a comparative couple to prove the probable formation mechanism of (010)-defective LiFePO4 platelets and to visualize their sluggish charge transfers along the ⟨010⟩ direction.

Crystalline vaterite is the most thermodynamically unstable polymorph of anhydrous calcium carbonate (CaCO3), and various morphologies can be controlled in the presence of organic additives. Constructing vaterite with minimal defects, determining its distinctive properties, and understanding the formation mechanism behind a biomimetic process are the main challenges in this field. In this paper, a unique single-crystal-like vaterite hexagonal bifrustum with two hexagonal and 12 trapezoidal faces has been fabricated through a catanionic surfactant-assisted mineralization approach for the first time. Compared with the polycrystalline vaterite aggregates, these bifrustums clearly present a doublet for Raman v1 symmetric stretching mode, a low depolarizaiton ratio for carbonate molecular symmetry, and a high structural stability. These indicate a dominant position of hexagonal phase in each crystallite and confirm the Raman v1 doublet characteristics of synthetic and biomineral-based vaterites. Our finding may provide evidence to distinguish vaterite with different structures and shed light on a possible formation mechanism of vaterite single crystals.

In this paper, a citric acid-assisted sol–gel route has been successfully used for the nanofabrication of serial solid solutions in a chemical formula of Li1.2Ni0.13+xCo0.13Mn0.54–xO2 at the x value of −0.06, −0.03, 0, 0.03, or 0.06. Powdered X-ray diffraction (XRD) results indicate that all the solid solutions possess the well-established structural characteristics for a homogeneous solid solution of Li2MnO3 and LiNi1/3+xCo1/3Mn1/3–xO2 components with an increasing Li2MnO3 content along with the decrease of x value. Scanning electron microscope (SEM) observation and elemental analyses show that these samples are composed of polyhedral nanoparticles with a chemical composition similar to that of the corresponding raw materials. Applied as lithium-ion battery cathodes, the initial Coulombic efficiency, cycling stability, and rate capability of solid solutions are determined by their chemical compositions, giving an optimal x value within the range of −0.03 and 0.03. That is, the variation of x value in the formula Li1.2Ni0.13+xCo0.13Mn0.54–xO2 should exert a great influence on the electrochemical performances of these cathodes. Anyways, these suggest an effective strategy to understand the relationship between the Mn–Ni content-dependent crystal structures and electrochemical behaviors of solid solutions.Keywords: cathode materials; crystal structure; electrochemical behaviors; lithium-ion batteries; solid solution;

•FeCO3 micro-rhombohedra are uniquely obtained via a hydrothermal route.•Synthetic siderite can serve as a high-capacity lithium ion battery anode.•The 120th discharge capacity is as high as 1018 mAh g−1 at 200 mA g−1.•The excellent lithium storage capability of FeCO3 has been investigated.Natural siderite is a valuable iron mineral composed of ferrous carbonate (FeCO3), which is commonly found in hydrothermal veins and contains no sulfur or phosphorus. In this paper, micro-sized FeCO3 crystallites are synthesized via a facile hydrothermal route, and almost all of them possess a rhombohedral shape similar to that of natural products. When applied as an anode material for lithium ion batteries, the synthetic siderite can deliver an initial specific discharge capacity of ∼1587 mAh g−1 with a coulombic efficiency of 68% at 200 mA g−1, remaining a reversible value of 1018 mAh g−1 over 120 cycles. Even at a high current density of 1000 mA g−1, after 120 cycles the residual specific capacity (812 mAh g−1) is still higher than the theoretical capacity of FeCO3 (463 mAh g−1). Moreover, a novel reversible conversion mechanism accounts for the excellent electrochemical performances of rhombohedral FeCO3 to a great extent, implying the potential applicability of synthetic siderite as lithium ion battery anodes.

Lithium-rich manganese-based oxide Li1.2Ni0.13Co0.13Mn0.54O2 nanorods and polyhedrons have been successfully prepared using precursor β-MnO2 nanorods as sacrificial templates at a calcination temperature of 750, 800, 850 or 900 °C. X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements show that the elevated calcination temperatures help to improve the layered structure and average particle size of the target products. Rod-like Li1.2Ni0.13Co0.13Mn0.54O2 can be obtained at low calcination temperatures (i.e., 750 and 800 °C), which becomes polyhedral at 850 or 900 °C. As lithium ion battery cathodes, the Li1.2Ni0.13Co0.13Mn0.54O2 obtained at 850 °C shows the highest discharge capacity of 239.2 mA h g−1 at 20 mA g−1, and a stable discharge capacity of 92.8 mA h g−1 at 1000 mA g−1. The good electrochemical performances of the 850 °C sample should be attributed to the better crystal structure and/or the more appropriate particle size compared with those of other samples.

•AMn2O4 (A = Zn, Zn0.5Co0.5, Co) are prepared by carbonate template route.•The AMn2O4 shows porous microspheres structures.•The lithium storage performances of AMn2O4 are comparatively studied.•The ZnMn2O4 retains a discharge capacity of 698.8 mAh g− 1 after 50 cycles.Porous AMn2O4 (A = Zn, Zn0.5Co0.5, Co) microspheres have been prepared through a carbonate co-precipitation and subsequent heat treatment at 600 °C. X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images reveal that, the porous AMn2O4 microspheres with hausmannite (Mn3O4) structure are composed of well-defined primary nanoparticles, and these nanoparticles have the size of 30–100 nm. As lithium-ion battery anodes, the electrochemical properties of porous AMn2O4 microspheres are determined by their chemical compositions. The porous ZnMn2O4 microspheres can retain a discharge capacity of 698.8 mAh g− 1 after 50 charge–discharge cycles, which is much better than the other two oxides. The CoMn2O4 shows the highest discharge potential among three samples. Interestingly, the Zn0.5Co0.5Mn2O4 inherits the shortage of CoMn2O4 and ZnMn2O4, and its cycling stability is the worst.The electrochemical properties of porous AMn2O4 (A = Zn, Zn0.5Co0.5, Co) microspheres are determined by their chemical compositions.

Li1.2Ni0.13Co0.13Mn0.54O2 powders have been prepared through co-precipitation of metal oxalate precursor and subsequent solid state reaction with lithium carbonate. X-ray diffraction pattern shows that the massive rock-like structure has a good layered structure and solid solution characteristic. Scanning electron microscope and transition electron microscope images reveal that the Li1.2Ni0.13Co0.13Mn0.54O2 composed of nanoparticles have the size of 1–2 μm. As a lithium ion battery positive electrode, the Li1.2Ni0.13Co0.13Mn0.54O2 has an initial discharge capacity of 285.2 mAh g−1 at 0.1 C within 2.0–4.8 V. When the cutoff voltage is decreased to 4.6 V, the cycling stability of product can be greatly improved, and a discharge capacity of 178.5 mAh g−1 could be retained at 0.5 C after 100 cycles. At a high charge–discharge rate of 5 C (1,000 mAh g−1), a stable discharge capacity of 121.4 mAh g−1 also can be reached. As the experimental results, the Li1.2Ni0.13Co0.13Mn0.54O2 prepared from oxalate precursor route is suitable as lithium ion battery positive electrode.

A facile two-step approach has been used for the synthesis of porous SnO2 rods: the initial room-temperature precipitation of precursor SnC2O4 and its subsequent thermal decomposition at 550 °C. Both the as-obtained porous SnO2 microrods (length ∼10.0 ± 3.5 μm, diameter ∼1.1 ± 0.4 μm) and submicrorods (length ∼5.8 ± 1.9 μm, diameter ∼0.4 ± 0.1 μm) are the crystalline mixtures of major tetragonal and minor orthorhombic crystal phases, showing a tetragonal fraction of 84.7 and 87.0 %, respectively. When applied as a lithium-ion battery anode, the porous submicrorods (specific surface area ∼13.6 m2 g−1) can deliver an initial discharge capacity of 1,730.7 mAh g−1 with a high coulombic efficiency of 61.6 % and show the 50th discharge capacity of 662.8 mAh g−1 at 160 mA g−1 within a narrow potential range of 10.0 mV to 2.0 V. Similarly, even the anode of porous microrods (specific surface area ∼11.8 m2 g−1) can still exhibit an initial discharge capacity of 1,661.1 mAh g−1 at 160 mA g−1 with a coulombic efficiency of 60.9 %. Regardless of the polymorphic nature, the acquired porosity may only alleviate the huge volume change of anodes for the first cycle; thus, the structural parameters of average size and specific surface area can be feasibly associated with the enhanced lithium storage capability. Anyway, these indicate a facile oxalate precursor method for the controlling synthesis and high performance of rodlike SnO2 for lithium-ion batteries.

In this work, a facile hydrothermal method has been used to prepare hierarchical flower-like SnO2 nanostructures without the assistance of any templates or surfactants. The obtained three-dimensional (3D) nanostructures are composed of two-dimensional (2D) nanosheets with smooth surfaces, which are endowed with a specific surface area of 46.7 m2 g−1. As lithium ion battery anodes, hierarchical flower-like SnO2 can interestingly present a high initial coulombic efficiency of 63.4 % and give the 40th reversible discharge capacity of 771.9 mAh g−1 at a current density of 160 mA g−1. Therefore, the 180 °C heat-treatment of aqueous mixture of tin dichloride and sodium hydroxide facilitates the mass production of nanostructured SnO2 for its potential application as lithium ion battery anodes.

•CuC2O4·xH2O nanostructures are facilely obtained in the absence of additives.•Structural properties of CuC2O4·xH2O depend upon the polarity of reaction medium.•A novel lithium storage mechanism of CuC2O4·xH2O has been investigated.•Crystal water induces an uptrend of CuC2O4·xH2O reversible capacity on cycling.•The 100th discharge capacity of CuC2O4·xH2O reaches 970 mAh g−1 at 200 mA g−1.In a hydrothermal and solvothermal system at 120 °C, cylinder-like and rod-like nanostructures of hydrate copper oxalate (CuC2O4·xH2O) can be thoroughly synthesized in the absence of any shape-controlling additives, respectively. The self-assembly of primary nanocrystals has been investigated considering the polarity of reaction medium, and in the chemical formula of CuC2O4·xH2O the average x value of crystal water is estimated to discuss the superior lithium storage capability of hydrate products. The results show that cylinder-like aggregate of CuC2O4·xH2O (x ∼ 0.14) possesses an initial discharge capacity of 920.3 mAh g−1 with a residual capacity of 970.0 mAh g−1 at 200 mA g−1 over 100 discharge–charge cycles, while rod-like aggregate with a x value of ∼0.53 per chemical formula exhibits a higher initial capacity of 1211.3 mAh g−1 and a lower retention of 849.3 mAh g−1 under the same conditions. Furthermore, time-dependent measurements present a novel crystal-to-amorphous transformation of active substances, suggesting a positive effect of unavoidable crystal water on the superior lithium storage capability of nanostructured CuC2O4·xH2O.

Temporarily stabilized iron oxychloride (FeOCl) nanospindles have been collected for the first time shortly after the forced hydrolysis of iron(III) chloride (FeCl3) in the reaction medium of glycerol and water (1:7, v/v) at 145 °C. In this paper, a novel chemical composition evolution of orthorhombic FeOCl to tetragonal akaganeite (β-FeOOH) and then to cubic magnetite (Fe3O4) has been successfully used for the shape-controlled synthesis of Fe3O4–C spindle-like nanocomposites. During this evolution process, the crystal structures of spindle-like intermediates have been investigated, along with the random doping of amorphous carbon into the final products. As a lithium ion battery anode, Fe3O4–C composite nanospindles can give a significantly high initial coulombic efficiency (80.6%), a reversible discharge capacity of 1029 mA h g−1 at 200 mA g−1 over 100 cycles, and the 100th retention value of 711.6 mA h g−1 at a high current rate of 1000 mA g−1. Therefore, a combination of the fine nanofabrication of Fe3O4 crystals with a spindle-like shape and the random doping of amorphous carbon may offer an effective approach to the development of transition metal oxide-based anode materials for high-energy lithium ion batteries.

Crystallization and oriented attachment of monohydrocalcite (MHC) for the self-organization of dumbbell-like superstructures in the absence of any additives, as well as the crystalline phase transformation of MHC to anhydrous calcium carbonate (CaCO3), have been systematically described in this paper. In Mg2+-containing artificial seawater at 4 °C, the dissolution of initially formed amorphous calcium carbonate (abbreviated as ACC) cannot be detected prior to the crystallization of MHC, and the detected inter-particle hydrogen bonds probably induce the oriented attachment of nanocrystalline MHC building blocks with a protective Mg-rich layer. As for the crystalline phase transformation of MHC to an anhydrous CaCO3 (i.e., vaterite, aragonite or calcite), two novel aspects have been highlighted: (i) the unexpected detection of unstable vaterite for the calcination of solid-state MHC, (ii) the unique product of cube-shaped or dumbbell-like superstructures of tiny calcite rhombohedrons from Mg2+-free artificial seawater at 30 °C. In particular, the effect of Mg2+-chelators (organic acetylacetone or inorganic sodium hydroxide) on the abnormal solution-mediated transformation of MHC to calcite may be potentially applied for biomimetic synthesis purposes.

Hydro- and/or solvo-thermal nanocrystallization of lithium iron phosphate (LiFePO4) has been well recognized as an effective pathway to improve its electrochemical performances. Herein, it is reported that high-performance LiFePO4 single-crystalline nanoparticles have been successfully prepared by the additive-free solvothermal reaction and subsequent glucose-assisted calcination. In comparison with the similar hydrothermal reaction, the presence of ethylene glycol can unexpectedly induce the formation of gel-like intermediates at the time interval of 0.5 h, resulting in LiFePO4 nanoparticles with a three-dimensional (3D) lattice structure and an amorphous nanocoating for a reaction time of 2 h. Interestingly, the lattice structure of growing LiFePO4 crystals can be thoroughly damaged under the irradiation of an electron beam. Furthermore, after the continuous crystal growth and subsequent heat-treatment, nanocrystalline LiFePO4 can achieve a discharge capacity of ∼165 mAh g−1 at 0.1 C in assembled LiFePO4/Li half-cells, proving a successful nanocrystal-forming engineering of LiFePO4 for a lithium-ion battery cathode.

Hollow cylindrical multi-walled hybrid nanotubes go through dynamic growth and subsequent disappearance during the biomimetic fabrication of hexagonal calcite platelets, simulating the in vivo purpose-driven self-assembly of tubular plasma-membrane calcium-ion channels for biomaterials to adapt, respond and repair.

Chemical reaction occurring between an insoluble solid and a saltwater solution relates to an exchange of ionic components and is therefore referred to as ion-exchange reaction. In this paper, we used the ion-exchange reaction of solid-state barium carbonate (BaCO3) and aqueous sodium sulfate (Na2SO4) for the crystal design of barium sulfate (BaSO4). This anionic ion-exchange, driven by the solubility discrepancy between BaCO3 and BaSO4, was rate-limited chemical transformation owing to the slow release of barium ions, resulting in the unusual BaSO4 crystallite with the bounded (200), (002), and (210) faces. Therein, cationic surfactant of cetyltrimethylammonium bromide (CTAB) exerted almost no influence on the morphological control of crystalline products. In a striking contrast to this, the similar cationic surfactant of CTAOH (i.e., cetyltrimethylammonium hydroxide) promoted the crystal growth along the [020] direction. Surprisingly, the addition of anionic sodium dodecyl sulfate (SDS) enhanced the surface etching phenomenon of BaSO4 crystals along the [002] direction at 120 °C. The Fajans rule of common-ion adsorption and the layer-like arrangement of pendent surfactant hydrocarbon chains accounted for the formation of BaSO4 secondary architectures of trigonal bipyramids or nanorods at a relatively high concentration of SDS. In a word, through the rate-controlled chemical reaction assisted by ionic surfactants, we found a successful ion-exchange approach to the crystal design of BaSO4, suggesting a potential application of solid-state BaCO3 in the removal of aqueous sulfate ions from industrial wastewaters.

Crystalline materials with a well-defined morphology and/or a narrow size distribution might exhibit a specific shape- and/or size-dependent performances. In the first instance, the catanionic surfactants of anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium hydroxide (CTAOH) were added as crystal modifiers into the 60 °C reaction systems of copper chloride and sodium hydroxide for the syntheses of cuprous oxide (Cu2O). Then, the reversible reaction activity of crystalline Cu2O with metal lithium was conducted to investigate its electrochemical performance as rechargeable lithium ion battery anodes. The presence of SDS-rich catanionic surfactants could induce the formation of polyhedral Cu2O structures with 8 triangular {111}, 6 square {100}, and 12 rectangular {110} faces outside, while the presence of CTAOH-rich catanionic surfactants, especially the doping methanol in CTAOH, led to the generation of hexapod-shaped Cu2O mesostructures with tiny nanoparticles on these symmetrical branches. At a discharge–charge cycling current of 80 mA g−1, the 26-faceted Cu2O crystals with rough {110} faces displayed an initial capacity of 756 mA h g−1 and a reversible capacity of 280 mA h g−1 at the first cycling. In comparison with the electrochemical performance of Cu2O hexapod-shaped mesocrystals at the same cycling current, the 26-faceted crystals of Cu2O could be capable of remaining a relatively high capacity (∼145 mA h g−1) and keeping an excellent Coulombic efficiency (∼100%) over 50 discharge–charge cycles. As a whole, the catanionic surfactants at different anionic/cationic molar ratios were used as additives to highlight the secondary nucleation and growth mechanism for the formation of Cu2O, then, the resulting 26-faceted crystallites and hexapod-shaped mesoparticles were separately used as active materials in the assembled Cu2O/Li half-cells to study their shape-dependent electrochemical performances.

Pseudohexagonal and single-crystal-like aragonite tablets, found in nacre, could be uniformly fabricated through a temperature-varying approach for the first time, indicating the triplet twinning nature and implying a potential significance in biomineralization.

Hydrogels of calcium alginate are the cross-linked networks containing a large fraction of water, which were used as the precursors of calcium carbonate (CaCO3) mineralization for the first time. The well-defined geometry, the permeability, and the ion-exchange property of these pregels favored the facile fabrication of calcite superstructures through the slow inpouring of ammonia and carbon dioxide gases. When calcium alginate hydrogels sponged up a relatively high amount of liquid, the resulting products with the outside calcite sequences transcribed the spongelike pregel beads with the outside nucleation sites of carboxyl groups. The inner characteristic of these CaCO3 superstructures showed the endocentric growth trends of calcite, indicating the permeability of hydrogel beads and the diffusing directions of permeated gases. In the presence of low liquid content, the pregels favored the formation of calcite superstructures with relatively smooth surfaces, demonstrating the inside lamellar array of calcite nanoparticles. This strategic approach indicated to a great extent the biologically controlled mineralization mechanism, dealing with (1) the preadsorption of calcium ions by the functional groups of biomolecules, (2) the confined crystallization within the three-dimensional networks, and (3) the proper arrangement of nanosized calcites by association with the organic architectures. Surprisingly, even the apparently “single-crystalline” CaCO3 was proven to comprise tiny calcite rhombohedrons. Furthermore, these building blocks coaligned each other with respect to the polymers’ conjugated backbones. Therefore, these suggest a novel pathway of multivalent metal pregelation phases for the biomimetic fabrication of functional materials.

In this paper, the synthesized surfactant of copper dodecyl sulfate (Cu(DS)2) was used as a special metal-ion source for the morphological control of copper oxide (CuO) architectures. During the fabrication processes, the ribbon-shaped intermediates of basic copper salt with lamellar structures were observed at 60.0 °C for the first time. In the absence or presence of dodecanol (DOH), Cu(DS)2 could react with sodium hydroxide to form dumbbell-like architectures of CuO nanoparticles. The incorporation of DOH molecules into the adsorption monolayers of surfactant ions could greatly enlarge the dumbbell size in length, probably depending upon the formation of the DOH−DS complex. These indicated that the template effectiveness of the intermediate ribbons, together with the hydrophobic interactions of adsorbed hydrocarbon chains, should account for the formation process of CuO dumbbells. Interestingly, the addition of sodium chloride into the reaction systems could induce the morphological change of CuO dumbbells to the twin-anchors and then to the twin-spheres with two holes in the center. This further suggests that the hydrophobic interaction of pendent hydrocarbon chains provides an important approach for material fabrication purposes.

The oriented attachment of inorganic nanocrystals controlled by adsorbed surfactants can lead to the formation of hollow nanoarchitectures with various well-defined morphologies. In this paper, Mg(OH)2 hollow nanospheres and the “encapsulated” catanionic vesicles could be simultaneously constructed by using the cationic surfactant of cetyltrimethylammonium hydroxide (CTAOH) and the anionic surfactant of magnesium dodecyl sulfate (Mg(DS)2) as reactants at pH 11.0. Therein, the driven forces for the oriented attachment of Mg(OH)2 particles should involve hydrophobic interactions among pendent surfactants. Similarly, the secondary architectures derived from catanionic surfactant−Mg(OH)2 hollow nanospheres could also be encountered under nonequilibrium conditions. Interestingly, the coating of Mg(OH)2 particles facilitated the direct observation of nanosized surfactant self-assemblies and the membrane fusion without using general staining methods. After the crystalline fusion of coating particles, Mg(OH)2 hollow nanospheres and the correspondingly shell-fused superstructures were obtained, implying a simple and versatile method for the study of lipid membranes and the fabrication of M(OH)2 (M = divalent metal ions) hollow architectures.

Lyotropic liquid crystalline phases have immediate relevance in biology because of the prevalence of organized lipid structures in living systems. The incorporation of hydrophilic reagents in water domains with well-defined nanoscale geometry favors the construction of nanostructured materials of inorganics, and/or the inorganic−organic hybrids. In this paper, the lamellar mesophases composed of calcium dodecyl sulfate (CDS), n-pentanol, and ammonia (5 wt% NH3·H2O in water) were constructed and used as the precipitation media of calcium carbonate (CaCO3). Under the atmosphere of carbon dioxide gas, the occurring solid−liquid−gas reaction resulted only in rhombohedral calcite particles at the beginning, then ultimately in layer-cake aggregates of calcite and stick-bundle aggregates of aragonite. Furthermore, the aragonite content increased with the proceeding time interval of the three-phase reaction, indicating a special crystallization habit of CaCO3 in the lamellar mesophases of CDS. Aside from these, the influence of the structure of CDS lamellar mesophases on the formation of CaCO3 crystals is also discussed. These imply an effective biomimetic approach for the simultaneous fabrication of metastable aragonite and thermodynamically stable calcite under mild conditions.

Alkaline agents have an appeal for enhanced oil recovery because of their low cost and favorable performance. In this paper, sodium carbonate (Na2CO3) and sodium hydroxide (NaOH) are used as the alkaline chemicals, at the same Na2O content, to investigate the oil/water interfacial reactions between the Daqing crude oil and the alkaline solutions. Moreover, oleic acid or the mixture of ethyl acetate and phthalic acid diethyl ester were added into the crude oil, respectively, to facilitate the direct observation of the interfacial reactions and to compare the functional effectiveness of alkalis. The results showed that: Na2CO3 reacted slowly and partly with the acid components in crude oil, while NaOH did it very fast and completely. Interestingly, Na2CO3 is better than NaOH in lowering the oil/water interfacial tension (IFT), due to its buffer effect. These help the optimum formulation design of flooding alkali, which should also be of great importance for tertiary oil recovery.

The crystallization of calcium carbonate was conducted by the reaction of sodium carbonate with calcium chloride in the presence of polyvinylpyrrolidone (PVP), sodium dodecylbenzene sulfonate (SDBS), or the mixture of PVP and SDBS, respectively. The morphology and polymorphism of these CaCO3 crystals were characterized with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The results showed that the organic additives and their self-assemblies turn out to be important factors to affect the crystallization habit of CaCO3. In particular, the controlling effect on the morphology depends upon not only the total concentration of PVP and SDBS, but also the relative concentration ratio of PVP to SDBS.

The preparation of porous Mn2O3 boxes has been developed via a carbonate precursor route. As a Li-ion battery anode, it delivers a high reversible capacity of 1442 mA h g−1 over 600 cycles at 800 mA g−1, and 65% of the capacity originates from the gradually emerging interfacial storage contribution.

Pseudohexagonal and single-crystal-like aragonite tablets, found in nacre, could be uniformly fabricated through a temperature-varying approach for the first time, indicating the triplet twinning nature and implying a potential significance in biomineralization.

Hollow cylindrical multi-walled hybrid nanotubes go through dynamic growth and subsequent disappearance during the biomimetic fabrication of hexagonal calcite platelets, simulating the in vivo purpose-driven self-assembly of tubular plasma-membrane calcium-ion channels for biomaterials to adapt, respond and repair.

Graphene oxide (GO) possesses high electron conductivity and good chemical-binding ability and thus can be used as a multifunctional additive for the preparation and application of electrode materials. As for the hydrothermal crystallization of MnCO3 herein, the absence of GO causes the formation of MnCO3 flower-like architectures composed of secondary spindles, while the presence of GO induces the flower-to-petal structural conversion and results in MnCO3 spindle–GO composites. When applied as Li-ion battery anodes, the composite electrode delivers an initial coulombic efficiency (CE) of 71% and a reversible capacity of 1474 mA h g−1 in the 400th cycle, much higher than those of MnCO3 flowers (the initial CE ∼ 58%, the 400th capacity ∼ 1095 mA h g−1) operated under the same conditions. In particular, the combination of discharging behavior and its differential capacity profile has been successfully used to estimate the interfacial contribution fraction (42%) of the whole reversible capacity (i.e., 1474 mA h g−1) enhanced by the in situ mixing of 8.3 wt% GO.

Multicomponent composites with an integrated lattice structure can possess an atomic-scale distribution of different components within the crystallites and may express an enhanced synergistic effect compared to the mechanical mixture. In this paper, a series of cobaltous-ferrous carbonates CoxFe1−xCO3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) have been synthesized via a facile hydrothermal route with the assistance of ascorbic acid (AA). The four multicomponent CoxFe1−xCO3 composites exhibit hexagonal structures similar to those of the monocomponents FeCO3 and CoCO3, and the resulting rodlike crystallites give aspect ratios and unit-cell parameters linearly changed along with the increasing x value, indicating the successful synthesis of CoxFe1−xCO3 composites at an arbitrary Co/Fe molar ratio. When used as lithium ion battery anodes, the CoxFe1−xCO3 composites can well inherit both the high-conductivity characteristic of CoCO3 and the low-rate cycling stability of FeCO3. In particular, each composite presents better electrochemical properties than the corresponding xCoCO3 + (1 − x)FeCO3 mixture, mainly assigned to an inner atomic-scale synergistic effect within the formula CoxFe1−xCO3. Therefore, CoxFe1−xCO3 composites may serve as novel high-capacity LIB anode materials for practical application, and also a facile strategic approach is introduced for the full-molar-ratio synthesis of multicomponent composites.