Pseudocapacitive lithium-rich disordered rock salt vanadium oxide with 3D lithium-ion transport pathways for high-performance lithium-ion capacitor

Pseudocapacitive materials with high-rate behavior of lithium-ion charge storage offer a pathway to narrow the kinetics gap with capacitive porous carbon cathode toward lithium-ion capacitors both with high energy and high power densities. However, most of pseudocapacitive materials are subject to their relatively high redox potential, thus resulting in an undesirable decrease in energy density. Here, we demonstrate that lithium-rich disordered rock salt vanadium oxide (DRX-Li3V2O5), electrochemically transformed from V2O5 bulk, exhibits typical pseudocapacitive behaviors within a low working potential range between 0.1 and 2.0 V (vs. Li/Li+). The pseudocapacitive behaviors of DRX-Li3V2O5 mainly arise upon a percolating network that offers three-dimensional Li + transport pathways confirmed by Monte Carlo simulations. When the V2O5 bulk precursor is replaced by V2O5 nanosheets, as-obtained DRX-Li3V2O5 electrode displays a nearly symmetrical cyclic voltammetry curve, suggesting an ideal pseudocapacitive behavior. A lithium-ion capacitor further assembled by this pseudocapacitive DRX-Li3V2O5 anode, yields a cell voltage of 4.0 V, a maximum energy density of 186 Wh kg−1 and a maximum power density of 51,680 W kg−1 as well as long-term cycling life over 30,000 cycles, which are higher than or comparable to that of the state-of-art lithium-ion capacitors based on graphite and other pseudocapacitive materials.