Lithium and niobium dual-mediated P2-layered cathode for low-temperature and ultralong lifespan sodium-ion batteries

P2-type manganese-based cathode materials are notable for their high theoretical capacity and open prismatic channels. However, rapid capacity decay caused by harmful irreversible phase transformations (P2-O2) and oxygen release in the high-voltage region (>4.2 V) limits their commercial application. Here, a co-doping strategy with lithium and niobium is proposed to enhance the structural stability at both room-temperature (RT) and low-temperature (LT) over extended cycles. The X-ray absorption near-edge spectra and firstprinciples calculations reveal that Li doping elevates the valence states of transition metals, thereby enhancing the reversibility of anionic redox reactions. Additionally, Nb doping leads to the formation of a rocksalt-like phase on the surface, which improves the stability of the electrode/electrolyte interface. In situ X-ray diffraction and differential electrochemical mass spectrometry show that Li and Nb co-doping prevents the P2-O2 phase transition, suppresses gas release, and enhances long-cycle stability. The P2-Na0.67Ni0.24Mn0.64Li0.1Nb0.02O2(NNMLNb) exhibits a reversible specific capacity of 127.4 mAh g-1 and 101.5 mAh g-1 at -20 degrees C and -30 degrees C, respectively. Remarkably, the sample cycles stably for 1200 cycles with a discharge capacity of 85 mAh g-1, corresponding 90 % capacity retention. This work provides a novel strategy to improve the cycling life of sodiumion batteries at both RT and LT.