Stabilized O3-Type Layered Sodium Oxides with Enhanced Rate Performance and Cycling Stability by Dual-Site Ti4+/K+ Substitution

• Published in: Advanced science 2023-11, Vol.10 (32), p.e2304067-e2304067
• Main Authors: Lin-Rong, Wu, Yu-Han, Zhang, Wu, Zhen, Tian, Jinlv, Wang, Haorui, Zhao, Haijun, Xu, Shoudong, Chen, Liang, Duan, Xiaochuan, Zhang, Ding, Guo, Huijuan, You, Ya, Zhu, Zhi
• Format: Article
• Language: English
• Subjects: Crystal structure; Electrolytes; Electrons; Energy; K/Ti co‐doping; NaNi0.5Mn0.5O2; O3‐oxide cathode; Particle size; Phase transitions; reversible phase transition; sodium‐ion batteries
• ISSN: 2198-3844
• DOI: 10.1002/advs.202304067

High-capacity O3-type layered sodium oxides are considered one of the most promising cathode materials for the next generation of Na-ion batteries (NIBs). However, these cathodes usually suffer from low high-rate capacity and poor cycling stability due to structure deformation, native air sensitivity, and interfacial side reactions. Herein, a multi-site substituted strategy is employed to enhance the stability of O3-type NaNi0.5Mn0.5O2. Simulations indicate that the Ti substitution decreases the charge density of Ni ions and improves the antioxidative capability of the material. In addition, the synergistic effect of K+ and Ti4+ significantly reduces the formation energy of Na+ vacancy and delivers an ultra-low lattice strain during the repeated Na+ extraction/insertion. In situ characterizations verify that the complicated phase transformation is mitigated during the charge/discharge process, resulting in greatly improved structure stability. The co-substituted cathode delivers a high-rate capacity of 97 mAh g−1 at 5 C and excellent capacity retention of 81% after 400 cycles at 0.5 C. The full cell paired with commercial hard carbon anode also exhibits high capacity and long cycling life. This dual-ion substitution strategy will provide a universal approach for the new rational design of high-capacity cathode materials for NIBs.