Negative Lattice Expansion in an O3-Type Transition-Metal Oxide Cathode for Highly Stable Sodium-Ion Batteries

The sodium extraction/insertion in layered transition-metal oxide (TMO) cathode materials are typically accompanied by slab sliding and lattice changes, leading to microstructure destruction and capacity decay. Herein, negative lattice expansion is observed in an O3 type Ni-based layered cathode of Na0.9Ni0.32Zn0.08Fe0.1Mn0.3Ti0.2O2 upon Na+ extraction. It is attributed to the weak Zn2+-O2- orbital hybridization and increased electron density of the surrounding oxygen for reinforced interlayer O-O repulsive force. This enables gliding of TMO slabs for the intergrowth phase transition of P3 -> OP2 to alleviate lattice strain with moderate lattice shrinkage, which exhibits general interslab spacings and volume changes as low as 2.4 % and 1.9 %, respectively. The strong Ti-O bonds accommodate the internal distortion of TMO6 octahedra due to the flexibility of TiO6 octahedra during cycling. These endow a high specific capacity of 144.9 mAh g-1 and excellent cycling performance of pouch-type sodium-ion batteries with 93 % capacity retention after 3600 cycles. An O3-type Ni-based layered oxide cathode material is designed to regulate the electron density of surrounding oxygen and trigger the intergrowth phase transition P3 -> OP2 for negative lattice expansion. It favors to alleviate the volume change and mitigate cracks generation, and hence renders excellent cycling performance in pouch-type sodium-ion batteries.image