Cao Yuge, Xiao Meijing, Dong Wujie, Cai Tianxun, Gao Yusha, Bi Hui, Huang Fuqiang
State Key Laboratory of High-Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China.
Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China.
ACS Appl Mater Interfaces. 2023 Aug 30;15(34):40469-40477. doi: 10.1021/acsami.3c06928. Epub 2023 Aug 16.
Sodium-ion batteries, as an attractive option for large-scale energy storage, still face the problems of low energy density and unsatisfactory rate performance. Among various cathodes, the tunnel-type NaMnO with large S-shaped Na transport tunnels is one of the promising cathode materials for fast and robust sodium-ion storage, yet suffering from Mn dissolution and structural collapse. Herein, a Na-rich layered oxide NaTiO is first constructed as a multifunctional coating layer on the surface of the NaMnO nanorod. NaTiO not only acts as an Na reservoir, but also serves as a protective layer to prevent NaMnO from electrolyte etching. Besides, the derived Ti-doped NaMnO transition layer supplies additional Na diffusion pathways along the radial direction of the nanorod with a short migration distance. The optimized 3 wt % NaTiO-coated NaMnO exhibits enhanced an initial capacity of 127 mAh g at 2-4.5 V. In addition, it shows an ultra-high capacitive-like capacity ratio of 96.7%, hence delivering an excellent rate performance of 80.2 mAh g at 20C. Long-term cycling tests indicate splendid stability against high voltage, achieving 97.7% capacity retention at 20C after 900 cycles. This work provides an effective strategy to improve the rate performance and high-voltage stability of NaMnO for high energy and power density batteries.
钠离子电池作为大规模储能的一个有吸引力的选择，仍然面临着能量密度低和倍率性能不理想的问题。在各种阴极材料中，具有大S形钠传输隧道的隧道型NaMnO是用于快速且稳定的钠离子存储的有前景的阴极材料之一，但存在锰溶解和结构坍塌的问题。在此，首次构建了富钠层状氧化物NaTiO作为NaMnO纳米棒表面的多功能涂层。NaTiO不仅作为钠储存库，还作为保护层防止NaMnO被电解质侵蚀。此外，衍生的Ti掺杂NaMnO过渡层沿纳米棒径向提供了额外的钠扩散途径，迁移距离短。优化后的3 wt% NaTiO包覆的NaMnO在2-4.5 V时表现出增强的初始容量127 mAh g。此外，它显示出96.7%的超高电容式容量比，因此在20C时具有80.2 mAh g的优异倍率性能。长期循环测试表明其在高压下具有出色的稳定性，在20C下900次循环后容量保持率达到97.7%。这项工作为提高用于高能量和功率密度电池的NaMnO的倍率性能和高压稳定性提供了一种有效策略。
