Copper-substituted Na0.67Ni0.3−xCuxMn0.7O2 cathode materials for sodium-ion batteries with suppressed P2–O2 phase transition

In situ XRD resolves the structural evolution of the Na–Cu/Ni/Mn–O system during the Na intercalation/deintercalation processes. The introduction of Cu²⁺ into the transition metal lattice is an strategy to prevent P2–O2 phase transitions.