Regulating Surface and Local Chemistry in High Na-content P2-type Cathode to Achieve Ultrahigh Power and Low Temperature Sodium Storage

Abstract Application of sodium ion batteries in grid-scale energy storage demands electrode materials that facilitate fast and stable charge storage from room-temperature to sub-zero temperature range. The key issues that hinder P2-type layered oxides from achieving such goals are their unsatisfied charge transfer kinetics and unavoidable surface fading. Herein, we report a P2-type Na0.78Ni0.31Mn0.67Nb0.02O2 whereby the trace Nb substitution simultaneously reduces the electronic band gap and ionic diffusion energy barrier, thus enables fast electron and Na+ mobility (~10-9 cm s-1 at -40 °C). While the Nb induced atomic-scale surface pre-construction efficiently prevents the electrolyte penetration and surface metal dissolution. The material demonstrates a record high rate capability (50 C), unprecedented low temperature performance and ultrahigh cycling stability (98% capacity retention at -40 °C with 76% capacity remaining after 1800 cycles). Different from literatures, this work shows that complete solid-solution is not always critical for high rate performance.