A copper phosphide/carbon (CuP₂/C) composite was synthesized by using a two‐step ball‐milling process from copper metal and red phosphorous and investigated as a negative electrode for a sodium secondary battery using Na[FSA]−[C₃C₁pyrr][FSA] [FSA=bis(fluorosulfonyl)amide anion and C₃C₁pyrr=N‐methyl‐N‐propylpyrrolidinium cation] ionic liquid as the electrolyte. Operation at an intermediate temperature of 363 K revealed that the aforementioned composite showed a large reversible capacity of 595 mAh g⁻¹ at 100 mA g⁻¹ and a high rate capability with a capacity retention of 65 % (366 mAh g⁻¹) at a high current density of 8000 mA g⁻¹. Cyclability tests confirmed that 71.0 % of the initial capacity was retained at the 200th cycle with 99.5 % coulombic efficiency at 500 mA g⁻¹. The CuP₂/C composite forms a solid‐electrolyte interphase layer during the initial charging step and becomes amorphous after the initial charge‐discharge cycle at 363 K.

中文翻译：

---

使用离子液体电解质在室温至中温下运行的钠二次电池用CuP2 / C复合负极

采用两步球磨工艺，由铜金属和红磷合成了磷化碳/碳（CuP ₂ / C）复合材料，并使用Na [FSA]-[C ₃作为钠二次电池的负极进行了研究。C ₁ pyrr] [FSA] [FSA =双（氟磺酰基）酰胺阴离子和C ₃ C ₁ pyrr = N-甲基-N-丙基吡咯烷鎓阳离子]离子液体作为电解质。在363 K的中间温度下操作表明，上述复合材料在100 mA g ^-1下显示出595 mAh g ^-1的大可逆容量，在容量保持率达65％（366 mAh g ^{-1）的情况下显示}出高倍率容量。）在8000 mA g ^-1的高电流密度下。循环性测试证实，在500mA g ^-1时，第200次循环可保留71.0％的初始容量，而库仑效率为99.5％。CuP ₂ / C复合材料在初始充电步骤期间形成固体电解质中间相层，并在363 K的初始充放电循环后变为非晶态。