Anode-free lithium metal batteries (AFLMBs) have attracted great attention owing to their higher energy density than conventional lithium metal batteries (LMBs). Unfortunately, the present AFLMBs still suffer from overall inferior Coulombic efficiencies (CEs) to those of LMBs due to the more severe dendrite growth and more unstable solid-electrolyte interface (SEI) formation at the anode side, which is an urgent issue to be solved. In this study, we explored the effect of increasing concentration and adding 0.1M LiNO3 additive on SEI layer and on Li plating/stripping efficiency using the low-concentration (0.4 M) tetraethylene glycol dimethyl ether (TEGDME)-based electrolyte in an AFLMB anode half-cell configuration. The influence of the oxidative subsequent SEI formation above 2.2 V vs. Li/Li+, called as “OSS”, was also discussed. It was found that Li plating/stripping stability was greatly improved by either blocking OSS or adding LiNO3, while increasing concentration to 2.0 M did not function well. The formation of the protective Li2O-based subsequent SEI layers when blocking reaction OSS is considered to guarantee the improved stability of Li plating/stripping, while LiNO3 additive helps sustaining the existence of Li2O even with the occurrence of OSS, therefore substantially improving the CE performance. Meanwhile, the effect of increasing concentration to 2.0 M in the existence of 0.1 M LiNO3 additive shifted the dominant SEI species from Li2O to LiF, further assuring the enhanced CE performance in the low-concentration TEGDME-based electrolytes.

中文翻译：

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揭示无阳极锂金属​​电池基于 TEGDME 的低浓度电解液的镀锂/脱锂效率的提高


无阳极锂金属​​电池（AFLMB）由于其比传统锂金属电池（LMB）更高的能量密度而引起了极大的关注。不幸的是，由于阳极侧更严重的枝晶生长和更不稳定的固体电解质界面（SEI）形成，目前的AFLMB总体库仑效率（CE）仍然低于LMB，这是一个亟待解决的问题。在本研究中，我们在 AFLMB 阳极中使用低浓度 (0.4 M) 四乙二醇二甲醚 (TEGDME) 电解液，探讨了增加浓度并添加 0.1M LiNO3 添加剂对 SEI 层以及锂沉积/剥离效率的影响半电池配置。还讨论了 2.2 V 以上相对于 Li/Li+ 的氧化随后 SEI 形成（称为“OSS”）的影响。研究发现，通过阻断 OSS 或添加 LiNO3，锂沉积/剥离稳定性得到极大改善，而将浓度增加至 2.0 M 效果不佳。当阻塞反应 OSS 时，基于 Li2O 的后续 SEI 层的形成被认为保证了锂沉积/剥离稳定性的提高，而 LiNO3 添加剂即使在 OSS 发生的情况下也有助于维持 Li2O 的存在，从而显着提高 CE 性能。同时，在 0.1 M LiNO3 添加剂存在下将浓度增加到 2.0 M 的效果将主要 SEI 物质从 Li2O 转移到 LiF，进一步确保了低浓度 TEGDME 电解液中 CE 性能的增强。