Structural Analysis of NaCuO₂ Cathode at Various Charged/Discharged Stages and Its Reaction Mechanism

抄録

We investigated NaCuO₂ as a positive electrode material for sodium-ion energy storage batteries. Its charge/discharge properties in a Na/NaCuO₂ cell were evaluated in voltage ranges of 0.75–3.0, 1.7–4.2, and 0.75–4.2 V. It was found that the charge/discharge properties and cycling-induced new products depended on the voltage range. In the range of 0.75–4.2 V, NaCuO₂ showed a reversible capacity of 190 mAh/g after ten cycles, with an average voltage of 2.5 V versus Na/Na⁺. The results of an ex-situ XRD analysis of NaCuO₂ electrode at various charged/discharged stages revealed that NaCuO₂ is converted to NaCuO after the second cycle, and then, reversible structural changes occur between NaCuO and CuO.