Mn<sup>4+</sup>-Substituted Li-Rich Li<sub>1.2</sub>Mn<sub>0.4</sub><sup>3+</sup>Mn<i><sub>x</sub></i><sup>4+</sup>Ti<sub>0.4–<i>x</i></sub>O<sub>2</sub> Materials with High Energy Density
Shiyao Zheng, Ke Zhou, Feng Zheng, Haodong Liu, Guiming Zhong, Wenhua Zuo, Ningbo Xu, Gang Zhao, Mingzeng Luo, Jue Wu, Chunyang Zhang, Zhongru Zhang, Shunqing Wu, Yong Yang
Abstract
In this work, Li-rich Li 1.2 Mn 0.4 3+ Mn x 4+ Ti 0.4– x O 2 (LMM x TO, 0 ≤ x ≤ 0.4) oxides have been studied for the first time. X-ray diffraction (XRD) patterns show a cation-disordered rocksalt structure when x ranges from 0 to 0.2. After Mn 4+ substitution, LMM 0.2 TO delivers a high specific capacity of 322 mAh g –1 at room temperature (30 °C, 30 mA g –1 ) and even 352 mAh g –1 (45 °C, 30 mA g –1 ) with an energy density of 1041 Wh kg –1 . The reason for such a high capacity of LMM 0.2 TO is ascribed to the increase of both cationic (Mn) and anionic (O) redox after Mn 4+ substitution, which is proved by d Q /d V curves, X-ray absorption near edge structure, DFT calculations, and in situ XRD results. In addition, the roles of Mn 3+ and Ti 4+ in LMM 0.2 TO are also discussed in detail. A ternary phase diagram is established to comprehend and further optimize the earth-abundant Mn 3+ –Mn 4+ –Ti 4+ system. This work gives an innovative strategy to improve the energy density, broadening the ideas of designing Li-rich materials with better performance.