Reversible anion redox in Mn-based layered oxide via Ce-doping for stable Na-ion storage

Sodium-ion batteries (SIBs) have garnered significant interest due to their cost-effectiveness and operational similarities to lithium-ion batteries. Amongst the various components, the cathode plays a pivotal role in determining the energy density of these batteries. Mn-based layered oxides stand out as promising cathode materials, owing to their abundance and non-toxicity. However, these oxides tend to suffer from structural instability during high-voltage cycling, leading to a decline in capacity. In this work, we have designed Ce-doped Na 0.6 Li 0.2 Mn 0.79 Ce 0.01 O 2 cathodes through a solid-state reaction process. This innovation aims to inhibit undesirable phase transitions and enhance the electrochemical performance of the electrodes. By integrating electrochemical testing with a suite of characterization techniques, we have shown that 1 mol% Ce doping effectively suppresses the formation of birnessite and the irreversible oxygen redox reactions in the high-voltage region. Moreover, our findings indicate that the detrimental phase transitions can be significantly mitigated throughout the electrochemical cycling process, thereby bolstering structural stability. Notably, the capacity of the Ce-doping cathode after 20 cycles substantially exceeds its initial discharge specific capacity, reaching 169.3 mAh g –1 . This research introduces a strategy for stabilizing the cathode structure of P2-type Mn-based layered oxides through Ce-doping, offering valuable insights for the advancement of next-generation SIBs.