Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity
Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity
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DOI：
10.1038/ncomms2705
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发表时间：
2013-04-01
影响因子：
16.6
通讯作者：
Li, Lain-Jong
中科院分区：
文献类型：
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作者：
Hu, Lung-Hao;Wu, Feng-Yu;Li, Lain-Jong
商用正极碳包覆磷酸铁锂的比容量通常为120-160mAhg(-1)，低于理论值170mAhg(-1)。用2wt%的电化学剥离石墨烯对碳包覆的磷酸铁锂进行表面修饰后，其比容量可达208mAhg(-1)。容量过剩的原因是电解液中的锂离子与剥落的石墨烯发生了可逆的还原-氧化反应，其中石墨烯的容量大于2000mAhg(-1)。高导电性的石墨烯薄片包裹在碳包覆的磷酸铁锂上，也有助于充放电过程中的电子迁移，降低了第一次循环的不可逆容量，并导致在不同的C速率下保持接近100%的库仑效率。这种简单且可扩展的方法也可以应用于其他正极系统，提高各种锂电池的容量。
The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160 mAh g(-1), which is lower than the theoretical value 170 mAhg(-1). Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208 m Ah g(-1) in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000 m Ah g(-1). The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to similar to 100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.