In situ XRD and electrochemical investigation on a new intercalation-type anode for high-rate lithium ion capacitor

A new intercalation-type anode material is reported herein to improve the lithium storage kinetics for high-rate lithium ion capacitors. The crystal structure of orthorhombic NaNbO3 indicates two possible tunnels for lithium ions insertion into NaNbO3 host along the <101> and <141> directions. Moreover, in situ XRD is conducted to investigate the lithium storage mechanism and structural evolution of the NaNbO3 anode, demonstrating its intercalation behavior through (101) and (141) planes. Furthermore, the rGO nanosheets are introduced to facilitate the charge transfer, which also effectively prevent the aggregation of NaNbO3 nanocubes. As expected, the NaNbO3/rGO nanocomposites possess remarkable reversible capacity (465 mA h g−1 at 0.1 A g−1), superior rate capability (325 mA h g−1 at 1.0 A g−1) and cycling stability, attributed to their synergistic effect and high Li+ diffusion coefficient DLi [D(NaNbO3/rGO)/D(NaNbO3) ≈ 31.54]. Remarkably, the NaNbO3/rGO-based LIC delivers a high energy density of 166.7 W h kg−1 at 112.4 W kg−1 and remains 24.1 W h kg−1 at an ultrahigh power density of 26621.2 W kg−1, with an outstanding cycling durability (90% retention over 3000 cycles at 1.0 A g−1). This study provides new insights on novel intercalation-type anode material to enrich the materials system of LICs.