Mn4+-Substituted Li-Rich Li1.2Mn0.43+Mn x4+Ti0.4- xO2 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

doi:10.1021/acsami.0c11544

Mn⁴⁺-Substituted Li-Rich Li_1.2Mn_0.4³⁺Mn _x⁴⁺Ti_{0.4- x}O₂ Materials with High Energy Density

ACS Appl Mater Interfaces. 2020 Sep 9;12(36):40347-40354. doi: 10.1021/acsami.0c11544. Epub 2020 Aug 25.

Authors

Shiyao Zheng¹, Ke Zhou¹, Feng Zheng², Haodong Liu³, Guiming Zhong⁴, Wenhua Zuo¹, Ningbo Xu¹, Gang Zhao⁵, Mingzeng Luo¹, Jue Wu¹, Chunyang Zhang⁶, Zhongru Zhang¹, Shunqing Wu², Yong Yang^{1

5}

Affiliations

¹ State Key Laboratory for Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
² Department of Physics, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Key Laboratory of Low Dimensional Condensed Matter Physics (Department of Education of Fujian Province), and Jiujiang Research Institute, Xiamen University, Xiamen 361005, China.
³ Department of NanoEngineering, University of California San Diego, La Jolla, California 92093, United States.
⁴ Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China.
⁵ School of Energy, Xiamen University, Xiamen 361005, China.
⁶ Laboratory of Photonics and Interfaces, Department of Chemistry and Chemical Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.

PMID: 32805881
DOI: 10.1021/acsami.0c11544

Abstract

In this work, Li-rich Li_1.2Mn_0.4³⁺Mn_x⁴⁺Ti_0.4-xO₂ (LMM_xTO, 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 Mn⁴⁺ substitution, LMM_0.2TO 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_0.2TO is ascribed to the increase of both cationic (Mn) and anionic (O) redox after Mn⁴⁺ substitution, which is proved by dQ/dV curves, X-ray absorption near edge structure, DFT calculations, and in situ XRD results. In addition, the roles of Mn³⁺ and Ti⁴⁺ in LMM_0.2TO are also discussed in detail. A ternary phase diagram is established to comprehend and further optimize the earth-abundant Mn³⁺-Mn⁴⁺-Ti⁴⁺ system. This work gives an innovative strategy to improve the energy density, broadening the ideas of designing Li-rich materials with better performance.

Keywords: Li-rich; cathode; cation-disordered materials; high energy density; oxygen redox.