Ball milling-derived nanostructured Li3VO4 anode with enhanced surface-confined capacitive contribution for lithium ion capacitors

To balance the kinetics gap between anode/cathode of lithium ion capacitors (LICs), we developed a straightforward ball milling method to tune the electrochemical performance of Li3VO4 (LVO) particles. After the mechanical crushing, the particle size of the pristine LVO with a densely bulky structure is reduced significantly; furthermore, a partial transition from V5+ to V4+ may induce the oxygen vacancy, resulting into the shortened Li+ diffusion path and low diffusion barrier. More active sites are exposed, and the long-range ordering of the structure is disturbed, leading to a fast Li+ transport on the surface or subsurface. The calculated capacitive contribution ratio achieves 49.6% at the lowest scan rate. The LICs deliver high energy and power densities (max. 108.5 Wh kg−1 at 114.5 W kg−1, 1180 W kg−1 at 21 Wh kg−1), revealing the efficiency of ball milling to facilitate the surface-induced capacitive contribution toward high-performance LICs.