| With the development of social economy, energy shortages and environmental pollution problems have become more and more serious. It is highly urgent to develop clean energy storage systems. Large-scale use of clean energy is highly dependent on high-energy, high-power and low-cost energy storage devices. Among the existing energy storage devices, lithium ion batteries (LIBs) have great potential in portable electronic devices, electric vehicles and renewable energy systems supplied by intermittent energy sources (e.g. wind and solar power, etc.), due to their high operating voltage, high energy density, high power density and long cycle life, etc. Currently commercialized lithium ion battery mainly uses graphite as a negative electrode active material. However, the specific capacity of commercial graphite is relatively low and can not meet the demand for high-capacity battery, and thus it is significant to develop new anode materials with high capacity and stability.Sodium is the second lightest metal among the alkali metals after lithium, and its abundance is 4-5 orders of magnitude higher than that of lithium. Thus, sodium may meet the requirements of sustainable development and have great commercial when it is applied in the battery field (Na ion batteries, NIBs) as an alternative energy storage technology to LIBs.Dealloying method, known as a representative method selectively etching active components from an alloy, has many advantages, such as no surfactant assistance, mild conditions, convenience and rapid fabrication, so the prepared materials can be used without tedious post-processing. Herein, by employing dealloying method, we prepared a series of nanomaterials as anodes for LIBs and NIBs as follows:(1) We have synthesized petal-like MnO2 microspheres through dealloying Mn5Al95 followed by a calcination step. The MnO2 microspheres show as hierarchical flowers-like micro/nano structures with a diameter of 1-2μm, which are composed of numerous nanosheets (thickness of ～20 nm). As the anode material for LIBs, MnO2 exhibits high capacities of 1012.4 and 488.8 mAh g-1 after 100 cycles at 200 and 2000 mA g-1, respectively. As the anode material for NIBs, MnO2 delivers a capacity of 52.7 mAh g-1 after 100 cycles at 200 mA g-1. The enhanced electrochemical performance of MnO2 is due to the unique micro/nano structure which can provide many active sites for Li/Na storage and transfer, shorten Li+/Na+diffusion distance, as well as supply the high accommodation ability towards the volume expansion.(2) We also investigated the influence of reaction time on the products through dealloying Cu17Sn7Al76 and prepared 3 kinds of nanoporous CuSn alloy materials (CuSn-12, CuSn-24 and CuSn-48), whose pore diameters are approximately 70,30 and 20 nm. As the anode materials for LIBs, the reversible capacities of CuSn-12, CuSn-24 and CuSn-48 are 135.9,335.5 and 243.7 mAh g-1 after 100 cycles at the current density of 200 mA g-1, respectively. When using as the anode materials for NIBs, the capacities of the 100th cycle of CuSn-12, CuSn-24 and CuSn-48 are 27.8, 41.7 and 60.3 mAh g-1, respectively. On the one hand, nanoporous structures with high specific surface area can provide many active sites for Li/Na insertion/extraction. On the other hand, there exists much Cu not involved in the formation of the alloy in CuSn-24 and CuSn-48, which can effectively increase the conductivity of the electrode materials. In addition, the nanoporous structures can buffer the volume expansion during the discharge/charge process. So it is reasonable that CuSn-24 and CuSn-48 exhibit excellent electrochemical performance. |
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