Air‐Stable Copper‐Based P2‐Na_7/9Cu_2/9Fe_1/9Mn_2/3O₂ as a New Positive Electrode Material for Sodium‐Ion Batteries

Abstract

<b>An air-stable copper-based P2-Na_7/9Cu_2/9Fe_1/9Mn_2/3O₂</b> is designed and synthesized by a simple solid-state method and investigated as a positive electrode material for sodium-ion batteries. The attractive long cycling stability is demonstrated by the capacity retention of 85% after 150 cycles at 1 C rate without phase transformation. The reversible Cu²⁺/Cu³⁺ redox couple in P2 phase oxides is proved for the first time.