Electrolyte optimization, such as using fluoride-bearing electrolytes, is regarded as an effective way to improve the cycle performance of lithium metal batteries (LMBs), but the promotion mechanisms of the electrolytes are in controversy due to the lack of quantitative understanding of the reaction products during cycling. Here, taking several fluorinated electrolytes as models, we use mass spectrometry titration (MST) and solid state nuclear magnetic resonance (NMR) techniques to quantify the evolution of dead Li metal, solid electrolyte interphases (SEI) and lithium hydride (LiH) during cycling. Our quantitative results clearly disclose that lithium difluoro(oxalato)borate (LiODFB) is able to inhibit the formation of SEI and LiH while fluoroethylene carbonate (FEC) mainly inhibits the formation of dead Li metal. Furthermore, we surprisingly observe a linear correlation between LiH and SEI formation, whereas the commonly mentioned lithium fluoride (LiF) shows a weak correlation with either dead Li metal or SEI. Guided by the clear failure mechanism, we can provide a reasonable explanation for the synergistic effect with the combination of LiODFB and FEC from a quantitative perspective. We believe that a quantitative insight of electrolytes on the failure mechanism of LMBs will guide us to explore the functional electrolytes to achieve the practical application of LMBs.

中文翻译：

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量化非活性锂/氢化锂的演变及其在可充电无阳极锂电池中的相关性

电解质优化，例如使用含氟电解质，被认为是提高锂金属电池（LMBs）循环性能的有效途径，但由于缺乏对反应的定量理解，电解质的促进机制存在争议骑自行车时的产品。在这里，以几种氟化电解质为模型，我们使用质谱滴定 (MST) 和固态核磁共振 (NMR) 技术来量化死锂金属、固体电解质界面 (SEI) 和氢化锂 (LiH) 在循环过程中的演变. 我们的定量结果清楚地表明，二氟（草酸根）硼酸锂（LiODFB）能够抑制 SEI 和 LiH 的形成，而氟代碳酸亚乙酯（FEC）主要抑制死锂金属的形成。此外，我们惊奇地观察到 LiH 和 SEI 形成之间的线性相关性，而通常提到的氟化锂 (LiF) 与死锂金属或 SEI 的相关性较弱。在明确的失效机制的指导下，我们可以从定量的角度对 LiODFB 和 FEC 组合的协同效应提供合理的解释。我们相信，电解质对 LMBs 失效机制的定量洞察将指导我们探索功能性电解质以实现 LMBs 的实际应用。我们可以从定量的角度为 LiODFB 和 FEC 组合的协同效应提供合理的解释。我们相信，电解质对 LMBs 失效机制的定量洞察将指导我们探索功能性电解质以实现 LMBs 的实际应用。我们可以从定量的角度为 LiODFB 和 FEC 组合的协同效应提供合理的解释。我们相信，电解质对 LMBs 失效机制的定量洞察将指导我们探索功能性电解质以实现 LMBs 的实际应用。