Electrolyte decomposition constitutes an outstanding challenge to long-life Li-ion batteries (LIBs) as well as emergent energy storage technologies, contributing to protection via solid electrolyte interphase (SEI) formation and irreversible capacity loss over a battery's life. Major strides have been made to understand the breakdown of common LIB solvents; however, salt decomposition mechanisms remain elusive. In this work, we use density functional theory to explain the decomposition of lithium hexafluorophosphate (LiPF6) salt under SEI formation conditions. Our results suggest that LiPF6 forms POF3 primarily through rapid chemical reactions with Li2CO3, while hydrolysis should be kinetically limited at moderate temperatures. We further identify selectivity in the proposed autocatalysis of POF3, finding that POF3 preferentially reacts with highly anionic oxygens. These results provide a means of interphase design in LIBs, indicating that LiPF6 reactivity may be controlled by varying the abundance or distribution of inorganic carbonate species or by limiting the transport of PF6- through the SEI.

中文翻译：

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六氟磷酸锂在电池电解质和相间的基本分解机制

电解质分解对长寿命锂离子电池 (LIB) 和新兴储能技术构成了一个突出的挑战，通过固态电解质界面 (SEI) 的形成和电池寿命期间不可逆的容量损失来提供保护。在了解常见 LIB 溶剂的分解方面取得了重大进展；然而，盐分解机制仍然难以捉摸。在这项工作中，我们使用密度泛函理论来解释六氟磷酸锂 (LiPF6) 盐在 SEI 形成条件下的分解。我们的结果表明，LiPF6 主要通过与 Li2CO3 的快速化学反应形成 POF3，而水解应在中等温度下受到动力学限制。我们进一步确定了所提出的 POF3 自催化的选择性，发现 POF3 优先与高阴离子氧反应。这些结果提供了 LIB 相间设计的一种方法，表明 LiPF6 反应性可以通过改变无机碳酸盐物种的丰度或分布或通过限制 PF6- 通过 SEI 的传输来控制。