Developing an abnormal high-Na-content P2-type layered oxide cathode with near-zero-strain for high-performance sodium-ion batteries

• Published in: Chemical science (Cambridge) Vol. 15; no. 14; pp. 5192 - 52
• Main Authors: Hu, Hai-Yan, Li, Jia-Yang, Liu, Yi-Feng, Zhu, Yan-Fang, Li, Hong-Wei, Jia, Xin-Bei, Jian, Zhuang-Chun, Liu, Han-Xiao, Kong, Ling-Yi, Li, Zhi-Qi, Dong, Hang-Hang, Zhang, Meng-Ke, Qiu, Lang, Wang, Jing-Qiang, Chen, Shuang-Qiang, Wu, Xiong-Wei, Guo, Xiao-Dong, Xiao, Yao
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 03.04.2024; The Royal Society of Chemistry
• Subjects: Cathodes; Chemistry; Crystal structure; Electrochemical analysis; Electrode materials; Ion currents; Phase transitions; Sodium; Sodium-ion batteries; Solid solutions; Transition metal oxides
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d3sc06878a

Layered transition metal oxides (Na x TMO 2 ) possess attractive features such as large specific capacity, high ionic conductivity, and a scalable synthesis process, making them a promising cathode candidate for sodium-ion batteries (SIBs). However, Na x TMO 2 suffer from multiple phase transitions and Na + /vacancy ordering upon Na + insertion/extraction, which is detrimental to their electrochemical performance. Herein, we developed a novel cathode material that exhibits an abnormal P2-type structure at a stoichiometric content of Na up to 1. The cathode material delivers a reversible capacity of 108 mA h g −1 at 0.2C and 97 mA h g −1 at 2C, retaining a capacity retention of 76.15% after 200 cycles within 2.0-4.3 V. In situ diffraction studies demonstrated that this material exhibits an absolute solid-solution reaction with a low volume change of 0.8% during cycling. This near-zero-strain characteristic enables a highly stabilized crystal structure for Na + storage, contributing to a significant improvement in battery performance. Overall, this work presents a simple yet effective approach to realizing high Na content in P2-type layered oxides, offering new opportunities for high-performance SIB cathode materials. A Mg-substituted abnormal P2-Na x TMO 2 cathode material with a stoichiometric content of Na up to 1 was developed. Such ultrahigh Na content in the P2-type structure enables an absolute solid-solution reaction with near-zero-strain characteristics.