Carbon-Coated Na3.32Fe2.34( P2O7)2 Cathode Material for High-Rate and Long-Life Sodium-Ion Batteries
Carbon-Coated Na3.32Fe2.34( P2O7)2 Cathode Material for High-Rate and Long-Life Sodium-Ion Batteries
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碳包覆Na3.32Fe2.34(P2O7)(2)高倍率长寿命钠离子电池正极材料
DOI：
10.1002/adma.201605535
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发表时间：
2017-06-06
影响因子：
29.4
通讯作者：
Dou, Shi-Xue
中科院分区：
文献类型：
--
作者：
Chen, Mingzhe;Chen, Lingna;Dou, Shi-Xue
由于锂资源有限，可充电钠离子电池消耗快，因此被认为是锂电池最合适的替代品。由于其安全性的提高，聚阴离子框架化合物最近作为潜在的候选物受到了关注。均匀碳包覆Na3.32Fe2.34(P2O7)(2)/C复合材料是一种很有前途的钠离子电池替代材料。电化学结果表明，制备的Na3.32Fe2.34(P2O7)(2)/C复合材料在0.1 C条件下（1 C = 120 mA g(-1)）的容量接近100 mA h g(-1)，在0.5 C条件下循环300次后容量保持率为92.3%。在电解质中加入氟碳酸乙烯添加剂后，即使在5℃下循环1100次后，仍能保持89.6%的初始容量。通过原位同步加速器x射线衍射和密度泛函理论计算系统地研究了电化学机理。结果表明：钠化和解钠化过程为单相转变过程，具有双一维钠通道，有利于离子的快速扩散；体积变化小，第一循环库仑效率接近100%，赝电容也有贡献。这项研究表明，这种新化合物可能成为其他铁基阴极电极在大规模钠可充电电池中应用的潜在竞争者。
Rechargeable sodium-ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth-abundant element Fe being the redox center, the uniform carboncoated Na3.32Fe2.34(P2O7)(2)/C composite represents a promising alternative for sodium-ion batteries. The electrochemical results show that the as-prepared Na3.32Fe2.34(P2O7)(2)/C composite can deliver capacity of approximate to 100 mA h g(-1) at 0.1 C (1 C = 120 mA g(-1)), with capacity retention of 92.3% at 0.5 C after 300 cycles. After adding fluoroethylene carbonate additive to the electrolyte, 89.6% of the initial capacity is maintained, even after 1100 cycles at 5 C. The electrochemical mechanism is systematically investigated via both in situ synchrotron X-ray diffraction and density functional theory calculations. The results show that the sodiation and desodiation are single-phase-transition processes with two 1D sodium paths, which facilitates fast ionic diffusion. A small volume change, nearly 100% first-cycle Coulombic efficiency, and a pseudocapacitance contribution are also demonstrated. This research indicates that this new compound could be a potential competitor for other iron-based cathode electrodes for application in large-scale Na rechargeable batteries.