A hydro-stable and phase-transition-free P2-type cathode with superior cycling stability for high-voltage sodium-ion batteries
Jun Xiao, Hong Gao, Yang Xiao, Shijian Wang, Cheng Gong, Zefu Huang, Bing Sun, Chung‐Li Dong, Xin Guo, Hao Liu, Guoxiu Wang
Abstract
• Cu 2+ and Mg 2+ ions mitigate the Jahn-Teller effect of Mn 3+ and suppress unfavorable phase transitions. • Mg 2+ ions with strong electronegativity enhance ion diffusion kinetics, enabling excellent rate capacity. • Mg 2+ “pillars” stabilize the crystal structure by reducing electrostatic repulsion and forming strong Mg-O bonds. • Dual-site substitution modulation significantly improves the moisture stability of the cathode material. A dual-site substitution strategy was applied to enhance the electrochemical performance of sodium-ion batteries, leading to the development of the Na 0.80 Mg 0.03 Li 0.18 Mn 0.67 Cu 0.15 O 2 cathode material. By introducing Mg and Cu ions at multiple sites, the local chemical environment was optimized, resulting in improved ion diffusion kinetics and charge transfer dynamics, which accelerate the overall electrochemical reactions. Mg ions substituted at Na sites act as “pillars” effectively mitigating detrimental O 2− –O 2− electrostatic repulsion and enabling stable anion redox activity. This novel cathode demonstrates a high specific capacity of 162 mAh/g, excellent rate capability with 114 mAh/g at 1000 mA g −1 (8C), and superior cycling stability with 80.3 % capacity retention after 300 cycles. Furthermore, the dual-site substitution minimizes volume variation to just 1.3 % during electrochemical processes and significantly enhances moisture resistance, offering promising potential for practical sodium-ion battery applications.