Influence of Electrolyte Additives on the Degradation of Li2VO2F Li-Rich Cathodes
Influence of Electrolyte Additives on the Degradation of Li2VO2F Li-Rich Cathodes
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DOI：
10.1021/acs.jpcc.0c02840
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发表时间：
2020-06-18
影响因子：
3.7
通讯作者：
Hahlin, Maria
中科院分区：
文献类型：
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作者：
Kallquist, Ida;Martin, Jean-Frederic;Hahlin, Maria
丰富的无序岩盐结构由于其较高的理论容量，作为一类很有前途的电池正极材料，受到了人们的广泛关注。然而，到目前为止，这些材料的循环稳定性并不令人满意。在这里，我们介绍了三种不同的成膜电解液添加剂：双(草酸)硼酸锂(LiBOB)、二氟(草酸)硼酸锂(LiODFB)和乙交酯，它们都改善了高容量富锂无序岩盐材料Li2VO2F的循环性能。性能最好的添加剂LiODFB在20次循环后容量保持率提高了12.5%。循环性能的改善是通过在电极表面形成保护性阴极界面来解释的。光电子能谱表明，表面层是由电解液、盐和添加剂共盐的降解形成的。阴极界面可以缓解活性物质的氧化和后续降解，从而在20次循环后仍能保持较高程度的氧化还原活性钒。
rich disordered rock-salt structures have, because of their high theoretical capacity, gained a lot of attention as a promising class of cathode materials for battery applications. However, the cycling stability of these materials has so far been less satisfactory. Here, we present three different film-forming electrolyte additives: lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), and glycolide, which all improve the cycling performance of the high-capacity Li-rich disordered rock-salt material Li2VO2F. The best performing additive, LiODFB, shows a 12.5% increase of capacity retention after 20 cycles. The improved cycling performance is explained by the formation of a protective cathode interphase on the electrode surface. Photoelectron spectroscopy is used to show that the surface layer is created from degradation of the electrolyte salt and additive cosalts. The cathode interphase can mitigate oxidation and following degradation of the active material, and thereby a higher degree of redox-active vanadium can be maintained after 20 cycles.