Recently, the lithium–oxygen (Li–O2) battery has attracted much interest due to its ultrahigh theoretical energy density. However, its potential application is limited by an unstable electrolyte system, low round-trip efficiency, and poor cyclic performance. In this study, we present a new electrolyte based on N,N′-dimethylpropyleneurea (DMPU) applied for the Li–O2 battery. This electrolyte possesses high ionic conductivity and achieves a low discharge/charge voltage gap of 0.6 V, which is mainly due to the possible one-electron charge transfer mechanism. The introduction of the antioxidant butylatedhydroxytoluene (BHT) as an additive stabilizes the superoxide radical by chemical adsorption and improves the cyclic performance remarkably. Thus, this new electrolyte system may be one of the candidates for Li–O2 batteries.

The detrimental shuttle effect of lithium polysulfides in ether-based liquid electrolytes upon cycling and their reduction/deposition on the lithium metal anode surface have severely restricted the practical application of rechargeable lithium–sulfur (Li–S) batteries. Much effort has been devoted to blocking the undesirable diffusion and shuttling of lithium polysulfides. In this review, recent developments of novel configurations for Li–S batteries, including hierarchical gradient cathodes, modified separators, solid-state electrolytes and lithium anode protection, are presented. It should be emphasized that the specific energy and cycling life are the most important parameters in the future production of Li–S batteries. Moreover, there are still enormous probabilities for the further development of novel configurations to improve the performance of the current Li–S batteries for portable devices and electric vehicles. Hence, these effective and reasonable configurations represent a significant step towards the commercialization of Li–S batteries.

•The NCM111 prepared by using PAALi as lithium source shows much better electrochemical performance than the one prepared by traditional method.•The in-situ polymerized PAALi will deliver lithium ion more efficiently, resulting in lower degree of cation mixing.•The PAALi can significantly limit the growth of the particle size under heat treatment.In this paper, a novel route using lithium polyacrylate (PAALi) as dual-functional lithium source was developed to produce layered oxide cathodes. The PAALi was in-situ polymerized on the surface of Ni1/3Co1/3Mn1/3(OH)2 precursor. By means of spray drying, spherical powders composed of PAALi wrapped around the precursor were prepared. The organic compound PAALi can function as a particle size control agent as well as the highly dispersed lithium source in the proposed route. It can transform to carbon coating layers during pre-heat treatment at 450 °C under inert atmosphere. Those carbon coating layers not only significantly reduce agglomeration of particles and limit growth of the particle size, but also provide enough inner voids and paths after the subsequent sintering at 900 °C. The produced layered cathodes can deliver capacity retention of 84.4% after 200 cycles at 1C and a capacity of 110.5 mA h g−1 at 10C. In comparison, the sample prepared with traditional lithium source only delivers capacity retention of 63.0% after 200 cycles at 1C and 70.9 mA h g−1 at 10C. The proposed route using PAALi as lithium source is potentially generalized to a broad application in the preparation of high-performance electrode materials.

Hexagonal close packed Cr2O3, fabricated by an electrospinning technique combined with a heating method, is adopted for the first time as a catalyst for non-aqueous lithium–oxygen (Li–O2) batteries. The synthesized highly mesoporous Cr2O3 nanotubes (Cr2O3-MNT) with a large surface area of 53.4 m2 g−1 are confirmed by field emission scanning electron microscopy (FESEM), field emission high-resolution transmission electron microscopy (TEM) and nitrogen adsorption/desorption isotherms (BET). By using the prepared Super P (SP) (60 wt%)/Cr2O3 (30 wt%)/polyvinylidenefluoride (PVDF) (10 wt%) composite as an oxygen electrode, the Li–O2 battery shows an astonishingly enhanced capacity of 8280 mA h g−1 at a current density of 50 mA g−1. More encouragingly, when the current densities are fixed at 25, 50, 100 and 200 mA g−1 with a limited capacity of 500 mA h g−1, the charging potentials are 3.47, 3.51, 3.78 and 4.01 V, respectively, which are among the lowest charge potentials reported to date. By using a capacity-controlled method (1000 mA h g−1) at a current density of 100 mA g−1, the cell shows excellent cyclic stability up to 50 cycles. The reversible formation and dissociation of Li2O2 are verified by X-ray diffusion (XRD) and SEM, indicating that the as-prepared Cr2O3 nanotubes are a promising catalyst for Li–O2 batteries.

Although lithium–sulfur (Li–S) batteries deliver high specific energy densities, lots of intrinsic and fatal obstacles still restrict their practical application. Electrospun carbon nanofibers (CNFs) decorated with ultrafine TiO2 nanoparticles (CNF-T) were prepared and used as a multifunctional interlayer to suppress the volume expansion and shuttle effect of Li–S battery. With this strategy, the CNF network with abundant space and superior conductivity can accommodate and recycle the dissolved polysulfides for the bare sulfur cathode. Meanwhile, the ultrafine TiO2 nanoparticles on CNFs work as anchoring points to capture the polysulfides with the strong interaction, making the battery perform with remarkable and stable electrochemical properties. As a result, the Li–S battery with the CNF-T interlayer delivers an initial reversible capacity of 935 mA h g–1 at 1 C with a capacity retention of 74.2% after 500 cycles. It is believed that this simple, low-cost and scalable method will definitely bring a novel perspective on the practical utilization of Li–S batteries.Keywords: carbon nanofibers; electrochemical properties; interlayer; lithium−sulfur batteries; TiO2

•An ideal material-tin oxide quantum dots is proposed for gas sensing.•The quantum dots with size of 5–10 nm are synthesized in 0.5 min by microwave.•Oleic acid, oleylamine and water are vital during fast microwave-assisted synthesis.•The sensor response towards 1000 ppm ethanol vapor is 215.Tin oxide (SnO2) quantum dots (QDs) have been prepared by microwave-assisted method. Firstly, through microwave-assisted method, organic component-wrapped SnO2 QDs with size of ca. 2–4 nm can be synthesized in only 0.5 min at 160 °C. Then, SnO2 of very good crystallinity and ca. 5–10 nm can be obtained by annealing the organic component-wrapped SnO2 QDs in air at 400 °C for 4 h. The annealed SnO2 QDs exhibit excellent gas sensitivity towards ethanol vapor. Typically, the relative resistance, i.e., ratio of resistance of sample in air to that in tested gases, of sensors towards 300 ppm of ethanol vapor is 215.

Core–shell silicon/carbon (Si/C) fibers with an internal honeycomb-like carbon framework are prepared based on the coaxial electrospinning technique. For this hierarchical structure, the fiber's core is composed of a porous carbon framework and embedded Si nanoparticles, which is further wrapped by a compact carbon shell. The well-defined Si/C composite anode shows high specific capacities, good capacity retention, and high accessibility of Si in lithium-ion batteries. An initial reversible capacity of 997 mA h g−1 and a capacity retention of 71% after 150 cycles are demonstrated with a current density of 0.2 A g−1. At a higher current density of 0.5 A g−1, a reversible capacity of 603 mA h g−1 can be maintained after 300 cycles. The accessibility of Si in the Si/C anode is up to 3612 mA h g−1 in the 1st cycle. The excellent electrochemical properties are attributed to the hierarchical structure of Si/C fibers. The porous carbon framework in the core region could not only accommodate the volume expansion of Si, but also enhance the conductivity inside these fibers. The compact carbon shell is able to prevent the electrolyte from permeating into the core section, therefore a stable solid-electrolyte interphase can be formed on the fiber surface.

This study presents a method to optimize the mass transport and electron transfer of metal oxides in electrochemical processes by using a three-dimensional (3D) porous graphene macroassembly (GM) as a framework. A simple method, pressurized infiltration, is reported to realize uniform dispersion of metal oxide nanoparticles on the graphene skeleton in the GM. The obtained GM–NiO hybrid shows significantly improved performance in electrochemical catalytic processes and energy storage applications. When used as the active material in nonenzymic sensors, it shows a low detection limit towards glucose while maintaining high sensitivity. It also shows a high capacitance of about 727 F g−1 and maintains high rate performance when used as the electrode material for supercapacitors. More importantly, this method may be sufficiently versatile for the hybridization of different kinds of noncarbon materials with GM to promote their practical applications.

A silver vanadium oxide (SVO) material with an interlaced structure was prepared using graphene as a two-dimensional substrate that directs the crystal growth in the hydrothermal process. The obtained SVO–graphene hybrid showed high structural stability, and lithium ion batteries (LIBs) using the hybrid as the cathode showed excellent cycling stability and rate performance.

Graphene is used as a barrier film to suppress the “shuttle effect” and to improve the performance of activated carbon-sulphur hybrid cathode materials in a lithium-sulphur battery by forming a core-shell structure. Graphene wraps around the activated carbon-sulphur hybrid to form a core-shell structure, in which the porous carbon framework stores most of the sulphur and the graphene layer suppresses the movement of the soluble polysulfide in the electrolyte during charge-discharge, resulting in an improvement of capacity and cyclic stability during long-term cycling. Such a core-shell structure is formed by changing the hydrophilicity of graphene oxide during reduction, in which the hydrophobic graphene closely wraps around the hydrophobic carbon surface.

A novel LiFePO4/C composite with 3D carbon network was prepared using Cetyltrimethyl Ammonium Bromid (CTAB) and starch as carbon sources via a facile method. The 3D carbon network structure was composed of a full and uniform carbon coating and a continuous carbon film framework. Good conductive paths enhancing electrons transfer efficiency and porous structure facilitating diffusion of lithium ions have been constructed by the 3D conductive network structure, which contributes the high ionic and electrical conductivities. As a result, the LiFePO4/C composite possesses an excellent electrochemical performance especially the high-rate cyclic performance. It delivers a capacity of 95 mAh g−1 at current density of 3.4 A g−1 (20 C). After 1200 cycles, the discharge capacity of 74 mAh g−1 can still be obtained, almost reaching a retention of 80%, which is higher than the best cyclic performance in previous investigations.

Sliced orange-shaped ZnCo2O4 (SOS-ZCO) constructed by radically aligned subunit nanoparticles is solvothermally synthesized for the first time. When used as lithium-ion battery (LIB) anode, SOS-ZCO demonstrates excellent electrochemical performances benefiting from its advantageous structural features. It shows a high reversible capacity of 890 mA h g−1 at 0.2 A g−1 and good rate capability with capacity retention of 47% at 5 A g−1. Moreover, it displays a superior cycling stability with 96.5% capacity retention over 130 cycles at 0.2 A g−1 and 92.3% capacity retention over 300 cycles at 1 A g−1. It is noteworthy that during high-rate cycling, SOS-ZCO anode does not show common pulverization phenomenon to form irregular morphology, but experiences regular morphology transformation. In the first 100 high-rate cycles, SOS-ZCO anode transforms into a network of randomly arranged nanowires with high firmness, leading to negligible capacity fading in the following 200 cycles. Therefore, novel SOS-ZCO micro-/nanostructure exhibits great potential for high-performance LIB anode.Sliced orange-shaped ZnCo2O4 (SOS-ZCO) constructed by radially aligned nanoparticles has been prepared for the first time. As-prepared SOS-ZCO anode shows excellent lithium storage properties, and transforms into a robust network of randomly arranged nanowires during high rate cycling.Download high-res image (249KB)Download full-size image

The detrimental shuttle effect of lithium polysulfides in ether-based liquid electrolytes upon cycling and their reduction/deposition on the lithium metal anode surface have severely restricted the practical application of rechargeable lithium–sulfur (Li–S) batteries. Much effort has been devoted to blocking the undesirable diffusion and shuttling of lithium polysulfides. In this review, recent developments of novel configurations for Li–S batteries, including hierarchical gradient cathodes, modified separators, solid-state electrolytes and lithium anode protection, are presented. It should be emphasized that the specific energy and cycling life are the most important parameters in the future production of Li–S batteries. Moreover, there are still enormous probabilities for the further development of novel configurations to improve the performance of the current Li–S batteries for portable devices and electric vehicles. Hence, these effective and reasonable configurations represent a significant step towards the commercialization of Li–S batteries.

A silver vanadium oxide (SVO) material with an interlaced structure was prepared using graphene as a two-dimensional substrate that directs the crystal growth in the hydrothermal process. The obtained SVO–graphene hybrid showed high structural stability, and lithium ion batteries (LIBs) using the hybrid as the cathode showed excellent cycling stability and rate performance.

Hexagonal close packed Cr2O3, fabricated by an electrospinning technique combined with a heating method, is adopted for the first time as a catalyst for non-aqueous lithium–oxygen (Li–O2) batteries. The synthesized highly mesoporous Cr2O3 nanotubes (Cr2O3-MNT) with a large surface area of 53.4 m2 g−1 are confirmed by field emission scanning electron microscopy (FESEM), field emission high-resolution transmission electron microscopy (TEM) and nitrogen adsorption/desorption isotherms (BET). By using the prepared Super P (SP) (60 wt%)/Cr2O3 (30 wt%)/polyvinylidenefluoride (PVDF) (10 wt%) composite as an oxygen electrode, the Li–O2 battery shows an astonishingly enhanced capacity of 8280 mA h g−1 at a current density of 50 mA g−1. More encouragingly, when the current densities are fixed at 25, 50, 100 and 200 mA g−1 with a limited capacity of 500 mA h g−1, the charging potentials are 3.47, 3.51, 3.78 and 4.01 V, respectively, which are among the lowest charge potentials reported to date. By using a capacity-controlled method (1000 mA h g−1) at a current density of 100 mA g−1, the cell shows excellent cyclic stability up to 50 cycles. The reversible formation and dissociation of Li2O2 are verified by X-ray diffusion (XRD) and SEM, indicating that the as-prepared Cr2O3 nanotubes are a promising catalyst for Li–O2 batteries.

This study presents a method to optimize the mass transport and electron transfer of metal oxides in electrochemical processes by using a three-dimensional (3D) porous graphene macroassembly (GM) as a framework. A simple method, pressurized infiltration, is reported to realize uniform dispersion of metal oxide nanoparticles on the graphene skeleton in the GM. The obtained GM–NiO hybrid shows significantly improved performance in electrochemical catalytic processes and energy storage applications. When used as the active material in nonenzymic sensors, it shows a low detection limit towards glucose while maintaining high sensitivity. It also shows a high capacitance of about 727 F g−1 and maintains high rate performance when used as the electrode material for supercapacitors. More importantly, this method may be sufficiently versatile for the hybridization of different kinds of noncarbon materials with GM to promote their practical applications.

Core–shell silicon/carbon (Si/C) fibers with an internal honeycomb-like carbon framework are prepared based on the coaxial electrospinning technique. For this hierarchical structure, the fiber's core is composed of a porous carbon framework and embedded Si nanoparticles, which is further wrapped by a compact carbon shell. The well-defined Si/C composite anode shows high specific capacities, good capacity retention, and high accessibility of Si in lithium-ion batteries. An initial reversible capacity of 997 mA h g−1 and a capacity retention of 71% after 150 cycles are demonstrated with a current density of 0.2 A g−1. At a higher current density of 0.5 A g−1, a reversible capacity of 603 mA h g−1 can be maintained after 300 cycles. The accessibility of Si in the Si/C anode is up to 3612 mA h g−1 in the 1st cycle. The excellent electrochemical properties are attributed to the hierarchical structure of Si/C fibers. The porous carbon framework in the core region could not only accommodate the volume expansion of Si, but also enhance the conductivity inside these fibers. The compact carbon shell is able to prevent the electrolyte from permeating into the core section, therefore a stable solid-electrolyte interphase can be formed on the fiber surface.