Realizing Complete Solid‐Solution Reaction in High Sodium Content P2‐Type Cathode for High‐Performance Sodium‐Ion Batteries
Ting Jin, Pengfei Wang, Qinchao Wang, Kunjie Zhu, Tao Deng, Jiaxun Zhang, Wei Zhang, Xiao‐Qing Yang, Lifang Jiao, Chunsheng Wang
Abstract
Abstract P2‐type layered oxides suffer from an ordered Na + /vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na + extraction/insertion. The deficient sodium in the P2‐type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na + de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2‐type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau‐free P2‐type cathode‐Na 0.85 Li 0.12 Ni 0.22 Mn 0.66 O 2 (P2‐NLNMO) was developed. The complete solid‐solution reaction over a wide voltage range ensures both fast Na + mobility (10 −11 to 10 −10 cm 2 s −1 ) and small volume variation (1.7 %). The high sodium content P2‐NLNMO exhibits a higher reversible capacity of 123.4 mA h g −1 , superior rate capability of 79.3 mA h g −1 at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid‐solution reaction are critical to realizing high‐performance P2‐type cathodes for sodium‐ion batteries.