Addition of Na3PO4 for Enhanced Positive Electrode Performance in All-Solid-State Sodium Batteries (Supporting Information)

All-solid-state sodium secondary batteries have attracted attention as next-generation batteries owing to their balanced performances in terms of energy density, battery life, abundant availability of sodium resources, and resulting cost reduction. For the positive electrode materials, NaFe0.5Mn0.5O2 is promising because it consists of abundant elements. However, its application in all-solid-state batteries with sulfide solid electrolytes are hindered by side reactions with the solid electrolytes, which lower the operating voltage. In this study, the electrode performances of all-solid-state sodium batteries were enhanced by mixing Na3PO4 with NaFe0.5Mn0.5O2 particles. Subsequent heat treatment further improved the electrode performance, resulting in an increased discharge voltage and a reversible capacity of 140 mAh g−1.

全固态钠二次电池因其能量密度、电池寿命的平衡性能、钠资源的丰富供应以及由此带来的成本降低，而受到广泛关注，被视为下一代电池。在正极材料方面，NaFe0.5Mn0.5O2因其组成元素丰富而具有巨大潜力。然而，由于其与硫化物固态电解质的副反应，限制了其在全固态电池中的应用，并降低了工作电压。本研究通过将Na3PO4与NaFe0.5Mn0.5O2颗粒混合，提升了全固态钠电池的电极性能。后续的热处理进一步优化了电极性能，导致放电电压提升，并实现了140 mAh g−1的可逆容量。