Structure Flexibility Enabled by Surface High-Concentration Titanium Doping for Durable Lithium-Ion Battery Cathodes
Jingxi Li, Gemeng Liang, Wei Zheng, Jinshuo Zou, Caoyu Wang, Jodie A. Yuwono, Yameng Fan, Bernt Johannessen, Lars Thomsen, Sijiang Hu, Lei Jiang, Zaiping Guo
Abstract
Ni-rich layered oxides have emerged as the most promising cathode materials for next-generation lithium-ion batteries due to their high energy densities. However, their strain-related instabilities, for example, microcracks and rock-salt phase formation, present a significant threat to battery performance. In this study, we successfully stabilize the structure of LiNi 0.8 Co 0.1 Mn 0.1 O 2 using flexible TiO 6 octahedron units through high-concentration surface Ti doping. The TiO 6 octahedron can tolerate Jahn–Teller distortions of other neighboring structural units due to the absence of d electrons in Ti 4+, allowing them to accommodate undesirable lattice distortions within the local domain and mitigate the lattice strain/changes. Compared with the conventional approach of increasing the rigidity of the layered structure, our strategy of using flexible TiO 6 structural units can fundamentally address the strain-related issues, contributing to significantly reduced lattice changes, especially along the c -direction (by 95.2%). This approach enables a high battery capacity (211.5 mAh g –1 at 0.1 C) and long battery durability of Ni-rich cathodes, surpassing most commercial products on the market. The strategy of surface optimization using flexible structural units to stabilize Ni-rich layered oxides can be broadly applied to other battery materials to address performance issues due to the similarities among layered-structured cathode materials.