Improving the electrochemical performance of an anionic redox P3-type layered oxide cathode by the synergistic effect by sodium metaborate coating and boron doping

Abstract

The lattice oxygen redox (LOR) reaction, known for its potential to augment the capacity of layered transition metal oxides in sodium-ion batteries (SIBs), has attracted widespread attention. However, the utilization of the LOR reaction often leads to irreversible release of lattice oxygen, causing damage to the crystal structure and deterioration in electrochemical performance, thereby impeding its practical application. Here, we demonstrate a method to significantly enhance the electrochemical performance of P3-type Na_0.6Li_0.2Mn_0.8O₂ cathodes by concurrently applying surface NaBO₂ coatings and boron doping. We reveal that the NaBO₂ coating efficiently mitigates electrolyte corrosion and side reactions on the electrode surface. In addition, boron doping enhances the involvement of manganese in the redox process, thereby boosting capacity, while inhibiting the irreversible Li migration, thereby stabilizing the crystal structure of the material. The synergistic effect of surface NaBO₂ coating and bulk phase boron doping enables 6%B-NLMO to exhibit improved electrochemical performance, achieving a discharge capacity of 98.7 mA h g⁻¹ and 95.8% retention after 100 cycles at 20 mA g⁻¹. This synergistic strategy, employing multiple modification techniques, offers a potential way to improve the performance of anion redox cathode materials.