Abstract The ability of fast and safe charging is critical for the further success of lithium ion batteries in automotive applications. In state-of-the-art lithium ion batteries, the charging rate is limited by the onset of lithium plating on the graphite anode. Despite its high importance, so far no analytical technique has been available for directly measuring lithium plating during battery charge. Herein, we introduce operando electron paramagnetic resonance (EPR) spectroscopy as the first technique capable of time-resolved and quantitative detection of lithium metal plating in lithium ion batteries. In an exemplary study, the C-rate dependence of lithium metal plating during low-temperature charging at −20 °C is investigated. It is possible to quantify the amount of ‘dead lithium’ and observe the chemical reintercalation of plated lithium metal. In this way, it is possible to deconvolute the coulombic inefficiency of the lithium plating/stripping process and quantify the contributions of both dead lithium and active lithium loss due to solid electrolyte interphase (SEI) formation. The time-resolved and quantitative information accessible with operando EPR spectroscopy will be very useful for the optimization of fast charging procedures, testing of electrolyte additives, and model validation.

中文翻译：

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锂离子电池石墨负极锂镀层的定量和时间分辨检测

摘要 快速安全充电的能力对于锂离子电池在汽车应用中的进一步成功至关重要。在最先进的锂离子电池中，充电速率受到石墨阳极上开始镀锂的限制。尽管它非常重要，但迄今为止还没有可用于在电池充电期间直接测量锂电镀的分析技术。在此，我们介绍了操作电子顺磁共振 (EPR) 光谱作为第一种能够对锂离子电池中的锂金属镀层进行时间分辨和定量检测的技术。在示例性研究中，研究了锂金属镀层在 -20 °C 低温充电期间的 C 速率依赖性。可以量化“死锂”的数量并观察镀锂金属的化学再嵌入。通过这种方式，可以消除锂电镀/剥离过程的库仑效率低下的问题，并量化由于固体电解质中间相 (SEI) 形成造成的死锂和活性锂损失的贡献。可通过操作 EPR 光谱获得的时间分辨和定量信息对于快速充电程序的优化、电解质添加剂的测试和模型验证非常有用。