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fabricated freestanding cable-like CuO/carbon-nitride core-shell nanostructures which obviously improved energy/power densities of the whole electrode 12.

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prepared CuO nanoarrays by utilizing the ammonia solution to engrave the Cu foil as free standing anode 18. Furthermore, design and fabrication of freestanding and binder-free electrode composite could improve the conductivity and accommodation ability of volume expansions, which have been proved to be an effective strategy to enhance the electrochemical performance. It is found that the CuO microspheres exhibit a superior cycle stability of 429.0 mAh/g after 50 cycles 17. The morphology controlled copper oxides (porous microspheres, flower-like, and thorn-like CuO) were thoroughly investigated as anodes for LIBs. Facing these challenges, it is necessary to adopt new architecture design and material preparation processes. Although the conductive Cu appeared as one of the important lithiation products, it is hardly connected together to form an electrons transport way to the current collector, causing a low conductivity for the electrode composite. Nevertheless, similar with other transition metal oxides, it is still hindered by the morphological collapse caused by the volume fluctuation along with the lithiation/delithiation 13, 14, 15, 16. Therefore, freestanding and binder-free novel structures and materials are in demand and being developed 9, 10, 11, 12.Īmong various transition metal oxides, CuO is drawing great focus due to its merits such as high theoretical capacity of 674 mAh/g 13, low cost, environmental benignity and ease of production. In addition, the insulation essence of organic binder deteriorates the electrochemical performance. However, the weak bonding power between commonly used binders and anode materials are usually failed to meet the electrode volume expansions. Most of the nanoscale metal oxides or corresponding composite are fabricated into electrode by blending with organic binders. Another effective strategy is to integrating the transition metal oxides into conductive network such as carbon nanotubes, graphene and so on 9, 10, 11. To conquer these issues, tremendous efforts are devoted to fabricating nanoscale materials such as nanoparticles, nanowires, nanorods, nanotubes, nanosheets and their electrochemical performance have been improved to some extent 8.

Thus, metal oxide anodes have not yet been practical utilized. Unfortunately, the conversion reaction processes encountered with huge volume variation, pulverization and disconnected from the current collector during discharge/charge cycles. Transition metal oxides (M xO y where M can be Mn, Fe, Co, Ni, Cu and so on) exhibit super Li ions storage capability (600~1300 mAh/g) through a conversion reaction mechanism, which make them promising candidates for next generation LIBs anodes 5, 6, 7. Therefore, it is highly urgent to develop new anode materials with higher electrochemical performance and lower cost. The currently used graphite anode prohibited a higher specific capacity and energy density due to its relatively lower theoretical capacity of 372 mAh/g 3, 4. However, the rapid market growth requires better batteries in terms of capacity, durability and cost, which depends on the key electrode materials. Lithium ion battery (LIB) is one of the dominant choices due to its advantages such as high energy density, high operation potential and long cycle life since their commercialization 1, 2. The explosive growth of electronics market and electric vehicle industries raise stringent requirement for more reliable, cost-effective and high capacity energy storage devices. This novel strategy might open a new window to develop durable CuO based composite anodes for LIBs. The 3D CuO NWs network with a porous architecture simutaneously reduces the ion diffusion distances, promotes the electrolyte permeation and electronic conductivity.

By examining the surface morphology of the cycled samples, possible performance fading route is proposed. The reversible capacity remains 461.5 mAh/g after 100 repeated cycles at a current density of 100 mA/g, and a capacity of 150.6 mAh/g even at a high rate of 1000 mA/g. The porous and radial configuration of the hierarchical CuO NWs on the Cu foam substrate guarantees the remarkably improved electrochemical performance with durable cycle stability and excellent rate capability compared with CuO NWs on Cu foils. To remit capacity fading of lithium ion battery (LIB) anodes, freestanding yucca fern shaped CuO nanowires (NWs) on Cu foams are fabricated as anodes by combining facile and scalable anodization of copper foams followed by calcination.