Dual Modification of P3-Type Layered Cathodes to Achieve High Capacity and Long Cyclability for Sodium-Ion Batteries.

Abstract

Sodium-ion batteries (SIBs) have garnered extensive attentions in recent years as a low-cost alternative to lithium-ion batteries. However, achieving both high capacity and long cyclability in cathode materials remains a challenge for SIB commercialization. P3-type Na0.67Ni0.33Mn0.67O2 cathodes exhibit high capacity and prominent Na+ diffusion kinetics but suffer from serious capacity decay and structural deterioration due to stress accumulation and phase transformations upon cycling. In this work, a dual modification strategy with both morphology control and element doping is applied to modify the structure and optimize the properties of the P3-type Na0.67Ni0.33Mn0.67O2 cathode. The modified Na0.67Ni0.26Cu0.07Mn0.67O2 layered cathode with hollow porous microrod structure exhibits an excellent reversible capacity of 167.5 mAh g-1 at 150 mA g-1 and maintains a capacity above 95 mAh g-1 after 300 cycles at 750 mA g-1. For one thing, the specific morphology shortens the Na+ diffusion pathway and releases stress during cycling, leading to excellent rate performance and high cyclability. For another, Cu doping at the Ni site reduces the Na+ diffusion energy barrier and mitigates unfavorable phase transitions. This work demonstrates that the electrochemical performance of P3-type cathodes can be significantly improved by applying a dual modification strategy, resulting in reduced stress accumulation and optimized Na+ migration behavior for high-performance SIBs.