Boron-doped sodium layered oxide for reversible oxygen redox reaction in Na-ion battery cathodes

• Published in: Nature communications Vol. 12; no. 1; pp. 5267 - 11
• Main Authors: Guo, Yu-Jie, Wang, Peng-Fei, Niu, Yu-Bin, Zhang, Xu-Dong, Li, Qinghao, Yu, Xiqian, Fan, Min, Chen, Wan-Ping, Yu, Yang, Liu, Xiangfeng, Meng, Qinghai, Xin, Sen, Yin, Ya-Xia, Guo, Yu-Guo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.09.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/299/891; 639/4077/4079/891; 639/638/161/891; 639/638/298; Boron; Carbon; Cathodes; Cycles; Electrode materials; Energy; High voltage; High voltages; Humanities and Social Sciences; Laboratories; multidisciplinary; Oxidation; Oxygen; Oxygen atoms; Phase transitions; Rechargeable batteries; Redox reactions; Retention; Room temperature; Science; Science (multidisciplinary); Sodium; Sodium channels (voltage-gated); Sodium-ion batteries; Structural stability; Transition metals; Weight reduction
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-25610-7

Na-ion cathode materials operating at high voltage with a stable cycling behavior are needed to develop future high-energy Na-ion cells. However, the irreversible oxygen redox reaction at the high-voltage region in sodium layered cathode materials generates structural instability and poor capacity retention upon cycling. Here, we report a doping strategy by incorporating light-weight boron into the cathode active material lattice to decrease the irreversible oxygen oxidation at high voltages (i.e., >4.0 V vs. Na + /Na). The presence of covalent B–O bonds and the negative charges of the oxygen atoms ensures a robust ligand framework for the NaLi 1/9 Ni 2/9 Fe 2/9 Mn 4/9 O 2 cathode material while mitigating the excessive oxidation of oxygen for charge compensation and avoiding irreversible structural changes during cell operation. The B-doped cathode material promotes reversible transition metal redox reaction enabling a room-temperature capacity of 160.5 mAh g −1 at 25 mA g −1 and capacity retention of 82.8% after 200 cycles at 250 mA g −1 . A 71.28 mAh single-coated lab-scale Na-ion pouch cell comprising a pre-sodiated hard carbon-based anode and B-doped cathode material is also reported as proof of concept. The irreversible oxygen redox reaction during charging to the high-voltage region causes cathode structural degradation and Na-ion cell capacity fading. Here, the authors report a B-doped cathode active material to mitigate the irreversible oxygen oxidation and increase the cell capacity.