Ultra-uniform interfacial matrix via high-temperature thermal shock for long-cycle stability cathodes of sodium-ion batteries†

Abstract

NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM333) is a promising cobalt-free, high-capacity cathode material for sodium-ion batteries, but suffers from poor cycling stability when prepared by the conventional tube furnace method due to electroactive metal migration, leading to a passive surface layer. To address this challenge, a high-temperature shock (HTS) method was employed. Compared to the tube furnace method, HTS offers a rapid heating process that contributes to a more compact and ultra-uniform NaCaPO₄ (NCP) coating, leading to enhanced structural integrity and coating quality. The HTS method first enables the formation of a compact and ultra-uniform NCP coating, which prevents nickel migration more effectively compared to tube furnace-prepared NFM333 (Tu-NFM333). By preventing nickel migration, the surface residual alkalinity is reduced, enhancing air stability and improving electrochemical performance. As a result, HTS-treated NFM333 demonstrated 80% capacity retention after 1000 cycles at a 1C rate, while a pouch cell retained 70% capacity after 700 cycles. The stabilization of NFM333 through HTS highlights a promising approach for developing durable sodium-ion batteries.