Unlocking Electrode Performance of Disordered Rocksalt Oxides Through Structural Defect Engineering and Surface Stabilization with Concentrated Electrolyte

• Published in: Advanced energy materials 2024-06, Vol.14 (23), p.n/a
• Main Authors: Zhang, Yanjia, Ugata, Yosuke, Campéon, BenoîtDenis Louis, Yabuuchi, Naoaki
• Format: Article
• Language: English
• Subjects: anionic redox; Chemical Sciences; concentrated electrolyte solution; Defects; disordered rocksalt; Electrodes; Electrolytes; Electron transport; Ion migration; Li‐excess oxide; Oxides; Percolation; Rechargeable batteries; Stabilization; structural defects; Transition metals; Transport properties
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202304074

Li‐excess cation‐disordered rocksalt oxides can boost the energy density of rechargeable batteries by using anionic redox, but the inferior reversibility of anionic redox hinders its use for practical applications. Herein, a binary system of Li3NbO4–LiMnO2 is targeted and the systematic study on factors affecting electrode reversibility, i.e., percolation probability, electronic conductivity, defect concentrations, and electrolyte solutions, is conducted. A Mn‐rich sample, Li1.1Nb0.1Mn0.8O2, delivers a smaller reversible capacity compared with a Li‐rich sample, Li1.3Nb0.3Mn0.4O2, because of the limitation of ionic migration associated with insufficient percolation probability for disordered oxides. Nevertheless, a larger reversible capacity of Li1.3Nb0.3Mn0.4O2 originates from excessive activation of anionic redox, leading to the degradation of electrode reversibility. The superior performance of Li1.1Nb0.1Mn0.8O2, including Li ion migration kinetics and electronic transport properties, is unlocked by the enrichment of structural defects for nanosized oxides. Moreover, electrode reversibility is further improved by using a highly concentrated electrolyte solution with LiN(SO2F)2 through the surface stabilization on high‐voltage exposure. Superior capacity retention, >100 cycles, is achieved for nanosized Li1.1Nb0.1Mn0.8O2. The electrolyte decomposition and surface stabilization mechanisms are also carefully examined, and it is revealed that the use of highly concentrated electrolyte solution can effectively prevent lattice oxygen being further oxidized and transition metal ion dissolution. Li‐excess cation‐disordered rocksalt oxides are synthesized and the systematic study on factors affecting electrode reversibility is conducted. The superior performance of Li1.1Nb0.1Mn0.8O2 is unlocked for nanosized oxides by the enrichment of structural defects. Moreover, electrode reversibility is further improved by using a highly concentrated electrolyte solution through the surface stabilization on high‐voltage exposure, and superior capacity retention is achieved.