Crystal phase and morphology engineering of omega-Li3V2O5 nanospheres for high-rate lithium-ion capacitors

Lithium ion capacitors (LICs) as promising energy storage devices are receiving lots of attention recently. However, anodes with high rate performance are urgently needed to balance the thermodynamics and kinetics of the cathode and the anode. Here, we report a morphology structure strategy to enhance the rate properties of disordered rock-salt Li3V2O5 (DRS-LVO) based on crystal phase engineering. Li3V2O5 nanospheres (LVO-NSs) deliver a low average insertion voltage (similar to 0.6 V vs. Li+/Li), excellent rate capability, and outstanding cycling stability (more than 85% capacity is retained after 6000 cycles) in half-cell devices. The electrode kinetics study shows that the novel nanosphere morphology endows LVO-NSs with more capacitive capacity contribution and a rapid ion transport path. The first-principles calculations indicate the energy storage and transport mechanism of LVO-NSs, in which Li+ migrates into the lattice along the (110) plane with the lowest energy. A LIC with outstanding electrochemical performance is assembled by using LVO-NSs as the anode and active carbon as the cathode, delivering an energy density of 61.9 W h center dot kg(-1) at a power density of 12.75 kW center dot kg(-1). This electrode design strategy of synergistic morphology and crystal structure provides a new route for the development of high-power and long-life energy storage devices.