Phase-engineering modulation of Mn-based oxide cathode for constructing super-stable sodium storage

Abstract

The Mn-based oxide cathode with enriched crystal phase structure and component diversity can provide the excellent chemistry structure for Na-ion batteries. Nevertheless, the broad application prospect is obstructed by the sluggish Na⁺ kinetics and the phase transitions upon cycling. Herein, we establish the thermodynamically stable phase diagram of various Mn-based oxide composites precisely controlled by sodium content tailoring strategy coupling with co-doping and solid-state reaction. The chemical environment of the P2/P'3 and P2/P3 biphasic composites indicate that the charge compensation mechanism stems from the cooperative contribution of anions and cations. Benefiting from the no phase transition to scavenge the structure strain, P2/P'3 electrode can deliver long cycling stability (capacity retention of 73.8 % after 1000 cycles at 10 C) and outstanding rate properties (the discharge capacity of 84.08 mA h g⁻¹ at 20 C) than P2/P3 electrode. Furthermore, the DFT calculation demonstrates that the introducing novel P'3 phase can significantly regulate the Na⁺ reaction dynamics and modify the local electron configuration of Mn. The effective phase engineering can provide a reference for designing other high-performance electrode materials for Na-ion batteries.