•SnO2@C nanocomposites are synthesized by a new method in hydrogel system.•Ultrafine SnO2 nanoparticles are homogenously embedded in carbon networks.•The SnO2@C nanocomposites exhibit excellent cycling performance.SnO2@C nanocomposites are easily synthesized in a large scale by the hydrolysis of Sn4+ ions in a polyacrylic acid (PAA) hydrogel system, followed by the decomposition of Sn(OH)4 and carbonization of PAA by heat treatment in one-system. The SnO2@C nanocomposites contain uniform ultrafine SnO2 nanoparticles (≈4.3 nm) homogenously embedded in a three-dimensional carbon matrix. This unique structure efficiently suppresses the particle pulverization and aggregation of SnO2, thus maintaining the electrode integrity during long-term lithiation/delithiation process. The discharge capacity of SnO2@C nanocomposites is maintained at ∼597.3 mAh g−1 after 220 cycles. This scalable approach has great potential in the applications of high-capacity anodes in Li-ion batteries.

•LiMn0.6Fe0.4PO4/C)// LiV3O8 ARLBs in different aqueous solution were assembled.•Energy density of ARLB in different aqueous electrolyte at various rate was obtained.•LiMn0.6Fe0.4PO4/C)// LiV3O8 ARLB in LiNO3 aqueous solution showed better performance.The electrochemical performances of (LiMn0.6Fe0.4PO4/C)//LiV3O8 ARLB in different aqueous electrolyte, i.e. 0.5 M Li2SO4, 2 M Li2SO4, saturated Li2SO4 with pH value of 7, 2 M LiNO3, 5 M LiNO3, saturated LiNO3, saturated LiNO3 with pH value of 7, are studied. The results infer that (LiMn0.6Fe0.4PO4/C)//LiV3O8 ARLB in 5 M LiNO3 or saturated LiNO3 aqueous electrolyte with pH value of 7 has favorable specific capacity and rate performance. According to the energy density calculations, the electrochemical performance of (LiMn0.6Fe0.4PO4/C)//LiV3O8 ARLB in the saturated LiNO3 with pH value of 7 is better than that in 5 M LiNO3 solution.

A novel template synthesis route is developed to synthesize cobalt oxide hollow octahedra. The sodium chloride templates are formed in situ in the reaction system by controlling the supersaturation of sodium chloride in the N,N-dimethylformamide solution. Transmission electron microscopy indicates that the porous shells of hollow octahedra are composed of ultra small particles. Electrochemical tests show that the discharge capacity of the cobalt oxide hollow octahedra is about 965 mA h g−1 after 30 cycles at 0.2C.

Co(OH)2 nanosheets, which obtained from Polyvinyl Pyrrolidone (PVP) improved solution-phase synthesis, can be transformed to porous Co3O4 nanoplates by solid-state crystal reconstruction during heat treatment in air. Transmission electron microscopy (TEM) indicates that the transformation process and final crystal structure are strongly dependent on the temperature of heat treatment. When the temperature is increased to 500 °C, the mesoporous and single-crystal Co3O4 nanoplates with an average size of around 1 μm can be obtained by solid-state diffusion, coalescence and following orientational alignment. Electrochemical tests show that the lithium storage performance of porous Co3O4 nanoplates is associated more closely with its structural aspects than its morphology and size factors. The obtained plate-like Co3O4 mesocrystals exhibit low initial irreversible capacity and superior cycling performance due to its micrometer size, porous and robust single-crystal structure. Considering the improved electrochemical performance, simple and large scale synthesis, the obtained 2D Co3O4 mesocrystals should be suitable as anode materials for high performance lithium-ion batteries.Graphical abstractHighlights► We describe a facile and large-scale synthesis of Co3O4 anode materials. ► The Co3O4 mesocrystals are obtained through unconventional reconstruction mechanism. ► Micrometer size Co3O4 mesocrystals exhibit low initial irreversible capacities. ► Superior cycling performance is obtained due to its robust mesoporous 2D structure.

This paper describes a new synthesis and lithium ion charge–discharge property of tin dioxide (SnO2) hollow nanocubes. SnO2 is one of the best-known anode materials for lithium-ion battery application because of its high lithiation-delithiation capacity. Hollow nanostructures with high surface area are preferred, because they accommodate large volume changes and maintain the structural stability of electrode materials during charge–discharge cycles. The SnO2 hollow cubes made in this study had a discharge capacity of up to 1783 mA h g–1 for the initial cycle and 546 mA h g–1 after 30 cycles at a current density of 0.2 C between 0.02 and 2.0 V (vs Li/Li+).Keywords: hollow structure; lithium ion battery; nanocubes; tin dioxide;

Hierarchical Co3O4 nanostructure is synthesized via a self-assembled process in molten hydroxides. The morphologies, crystal structures and the phase transformation processes are analyzed by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. As an anode material for lithium ion batteries, the hierarchical Co3O4 exhibit an initial capacity of 1336 mAh g−1 and a stable capacity of 680 mAh g−1 over 50 cycles. More importantly, high rate capability is obtained at different current densities between 140 and 1120 mA g−1. The improved electrochemical performance of Co3O4 could be attributed to the unique hierarchical nanostructure.Highlights► Composite-hydroxide-mediated synthesis of hierarchical Co3O4 nanostructure. ► Hierarchical Co3O4 nanostructure is assembled by extremely thin nanosheets. ► Hierarchical Co3O4 anode exhibits good cycle performance and high rate capability.

Various CuO nanostructures with different morphologies, such as nanosheets, nanowires and nanobundles have been synthesized via a composite-hydroxide-mediated approach. The morphologies can be easily tailored by adjusting the concentration of precursor and the possible morphology transformation process is proposed. Scanning electron microscopy, X-ray diffraction and galvanostatical charge–discharge test are employed to characterize the morphology, structure and electrochemical properties of the CuO nanostructures, respectively. It is found that different morphologies of CuO result in different electrochemical performances. Compared to others, CuO nanosheets exhibit not only high reversible capacity but also good cycling stability. The improved electrochemical performance is attributed to the novel 3D hierarchical nanostructure, which could relieve the stress caused by the drastic volume change and ensure good capacity retention.Graphical AbstractThe concentration and pH value will affect the crystal growth mechanism in aqueous solution and various nanostructures with different morphologies are obtained.Highlights► Composite-hydroxide-mediated synthesis of CuO nanostructures. ► Morphology can be easily tailored by adjusting the concentration of precursor. ► Extremely thin CuO nanosheets shows improved electrochemical performance.

Porous SnO2 micro-tubes were synthesized by the thermal decomposition of SnC2O4 precursor. The morphology of SnC2O4 could be preserved after the controlled heat treatment and a lot of mesopores left due to the release of gases. The mesoporous nature with a range of 3–50 nm was characterized by BET method. SEM images showed that the obtained SnO2 samples were rhombic tube-like with swallow-tailed nozzles. When the porous SnO2 micro-tubes were used as anode materials for lithium-ion battery, they exhibited high lithium storage capacity and coulomb efficiency. In addition, CV results demonstrated that the formation of Li2O at high voltage was partially reversible reactions.

Nano-sized SnSbCux alloy anode materials are prepared by reductive co-precipitation method combining with the aging treatment in water bath at 80 °C. The microstructure, morphology and electrochemical properties of synthesized SnSbCux alloy powders are evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and galvanostatical cycling tests. The results indicate that the average particle size is reduced and the Cu6Sn5, Cu2Sb phases appear successively along with the increase of Cu content in the SnSbCux alloy. The reduction of average particle size, the existence of inactive element Cu and the complex multi-step reaction mechanism in SnSbCux alloy anodes are propitious to improve the structure stability and thus improve the cycling performance. When cycled at a constant current density of 0.1 mA cm−2 between 0.02 and 1.50 V, the coulomb efficiency of first cycle exceeds 74% and the reversible capacity of 20th cycle attains to 490 mAh g−1 in SnSbCu0.5 alloy anode.