关键词: 固态锂电池, 正极/电解质界面, 密度泛函模拟, 锂离子迁移

Abstract:

The rapidly expanding application of lithium ion batteries stimulates research interest on energy storage devices with higher energy density, better safety and faster charge/discharge speed. All-solid-state lithium batteries have been considered as promising candidates because of their fewer side reactions and better safety compared with conventional lithium-ion batteries with organic liquid electrolytes. Looking for well-matched electrode/electrolyte interfaces is one of the keys to ensuring good comprehensive performance of solid-state lithium batteries. In this report, with the aid of first-principles simulations, the local structure and lithium ions transportation properties of electrolyte surfaces and cathode/electrolyte interfaces are investigated. The β-Li₃PS₄ (010)/LiCoO₂ (104) and Li₄GeS₄(010)/LiCoO₂(104) interfaces are adopted as model systems to understand the bonding interaction and Li+ migration barriers at interfaces. The ability of Li+ motion is improved in partial delithiated state for both systems, due to that Co atoms at the interface in high oxidized state oxidize the S atoms nearby and weaken the P/Ge-S bond resulting in less constrains on Li ions in neighbor and promoting the exchange of Li ions across the interface. It provides information for cathode/electrolyte interface optimization, and may help us discover appropriate techniques for solid-state lithium batteries.

Key words: solid state lithium batteries, cathode/electrolyte interface, density functional theory calculations, lithium migration