Chen Keyi, Lei Meng, Yao Zhenguo, Zheng Yongjian, Hu Jiulin, Lai Chuanzhong, Li Chilin
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 585 He Shuo Road, Shanghai 201899, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Adv. 2021 Nov 5;7(45):eabj1491. doi: 10.1126/sciadv.abj1491. Epub 2021 Nov 3.
Conversion-type iron fluoride is a promising alternative cathode to intercalation oxides because of its higher energy density. However, its intrinsic solid-solid conversion is sluggish during repeated splitting and rebonding of metal-fluorine moieties. Here, we propose a solid-liquid conversion mechanism to activate the fluorine transport kinetics of iron oxyfluorides enabled by fluoride anion receptor of tris(pentafluorophenyl)borane (TPFPB). TPFPB promotes the dissociation of inert lithium fluoride and provides a facile fluorine transport channel at multiphase interfaces via the formation of solvated F intermediate therein. The construction of solid-liquid channel with fluorinated cathode electrolyte interface is the key for the achievement of FeOF and FeOF in terms of sustaining conversion reaction (with an energy efficiency approaching 80%) and high-rate performance (with reversible capacity of 320 mAh/g at 2 A/g). The cathode energy densities can reach 1100 Wh/kg for FeOF and 700 Wh/kg for FeOF under the power densities of 220 and 4300 W/kg, respectively.
转化型氟化铁因其较高的能量密度，是一种很有前景的层状氧化物阴极替代物。然而，在金属-氟部分的反复分裂和重新结合过程中，其固-固转化过程较为缓慢。在此，我们提出一种固-液转化机制，以激活由三（五氟苯基）硼烷（TPFPB）的氟阴离子受体实现的氟氧化亚铁的氟传输动力学。TPFPB促进惰性氟化锂的解离，并通过在其中形成溶剂化F中间体，在多相界面提供一个便捷的氟传输通道。就维持转化反应（能量效率接近80%）和高倍率性能（在2 A/g下可逆容量为320 mAh/g）而言，构建具有氟化阴极电解质界面的固-液通道是实现FeOF和FeOF的关键。在功率密度分别为220和4300 W/kg的情况下，FeOF的阴极能量密度可达到1100 Wh/kg，FeOF的阴极能量密度可达到700 Wh/kg。
