Maricite NaFePO₄ (m-NaFePO₄) was investigated as a positive electrode material for intermediate-temperature operation of sodium secondary batteries using ionic liquid electrolytes. Powdered m-NaFePO₄ was prepared by a conventional solid-state method at 873 K and subsequently fabricated in two different conditions; one is ball-milled in acetone and the other is re-calcined at 873 K after the ball-milling. Electrochemical properties of the electrodes prepared with the as-synthesized m-NaFePO₄, the ball-milled m-NaFePO₄, and the re-calcined m-NaFePO₄ were investigated in Na[FSA]-[C₂C₁im][FSA] (C₂C₁im⁺ = 1-ethyl-3-methylimidazolium, FSA⁻ = bis(fluorosulfonyl)amide) ionic liquid electrolytes at 298 K and 363 K to assess the effects of temperature and particle size on their electrochemical properties. A reversible charge-discharge capacity of 107 mAh g⁻¹ was achieved with a coulombic efficiency >98% from the 2nd cycle using the ball-milled m-NaFePO₄ electrode at a C–rate of 0.1 C and 363 K. Electrochemical impedance spectroscopy using m-NaFePO₄/m-NaFePO₄ symmetric cells indicated that inactive m-NaFePO₄ becomes an active material through ball-milling treatment and elevation of operating temperature. X-ray diffraction analysis of crystalline m-NaFePO₄ confirmed the lattice contraction and expansion upon charging and discharging, respectively. These results indicate that the desodiation-sodiation process in m-NaFePO₄ is reversible in the intermediate-temperature range.

研究了马氏体NaFePO ₄（m-NaFePO ₄）作为使用离子液体电解质的钠二次电池的中温操作的正极材料。通过常规的固态方法在873 K下制备粉末状的m-NaFePO ₄，随后在两种不同的条件下制备；一种在丙酮中球磨，另一种在球磨后于873 K重新煅烧。电极的电化学性质与所制备的合成后原样的M-型NaFePO ₄中，球磨间的NaFePO ₄，和重新煅烧的M-型NaFePO ₄中的Na进行了研究[FSA] - [C ₂ C ^ ₁ IM] [ FSA]（C ₂ C₁ IM ⁺  = 1-乙基-3-甲基咪唑鎓，FSA ^-  =双（氟磺酰基）酰胺）在298K和363 K下的离子液体的电解质，以评估温度和颗粒尺寸对它们的电化学性质的影响。使用球磨的m-NaFePO ₄电极，在0.1 C和363 K的C速率下，从第二个循环开始就获得了107 mAh g ^-1的可逆充电-放电容量，库伦效率> 98％。电化学阻抗谱使用m-NaFePO ₄ / m-NaFePO ₄对称电池表明无活性的m-NaFePO ₄通过球磨处理和升高工作温度成为一种活性材料。结晶的m-NaFePO _4的X射线衍射分析分别证实了充电和放电时的晶格收缩和膨胀。这些结果表明，在中间温度范围内，m-NaFePO ₄中的脱盐-碱化过程是可逆的。