高质量水系钠离子电池正极Fe4[Fe(CN)6]3的合成及其电化学性能

采用水热法合成高质量的Fe₄Fe(CN)₆]₃(HQ-FeHCF)纳米材料, 并对材料进行X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM)和热重分析测试(TGA)等表征。结果表明：Fe₄Fe(CN)₆]₃呈规则立方体, 颗粒大小约500 nm, 属面心立方结构。Fe₄Fe(CN)₆]₃在NaClO₄-H₂O-聚乙二醇电解液中1C、2C、5C、10C、20C、30C和40C的容量分别为124、118、105、94、83、74和64 mAh·g ^-1, 表现出优异的倍率性能; 以5C倍率循环500次, 容量保持率接近100%, 表现出极佳的循环稳定性。以Fe₄Fe(CN)₆]₃和磷酸钛钠分别为正负极的全电池工作电压高达1.9 V, 能量密度可达126 Wh·kg ^-1; 以5C倍率恒流充放电测试140次后全电池容量保持率为92%, 且库伦效率始终接近100%。

High-quality Fe4[Fe(CN)6]3 Nanocubes: Synthesis and Electrochemical Performance as Cathode Material for Aqueous Sodium-ion Battery

High-quality Fe₄Fe(CN)₆]₃ (HQ-FeHCF) nanocubes were synthesized by a simple hydrothermal method. Its structure, morphology and water content are characterized. Fe₄Fe(CN)₆]₃ exhibits regular cubic shape with a uniform size of ca. 500 nm, which belongs to the face-centered cubic phase. Fe₄Fe(CN)₆]₃ shows discharge capacities of 124, 118, 105, 94, 83, 74 and 64 mAh·g ^-1 at 1C, 2C, 5C, 10C, 20C, 30C and 40C rate, respectively, in the aqueous ternary electrolyte of NaClO₄-H₂O-Polyethylene glycol. Its capacity retention remains 100% after 500 charge/discharge cycles at the rate of 5C. The full battery with Fe₄Fe(CN)₆]₃ as cathode and NaTi₂(PO₄)₃ as anode was fabricated, which delivers a specific energy density of 126 Wh·kg ^-1 (based on the active electrode materials) with a voltage output of 1.9 V. Furthermore, 92% of its initial discharge capacity retains after 140 charge/discharge cycles at a rate of 5C, and its Coulomb efficiency is close to 100%.