The formation process of lithium‐ion batteries commonly uses low current densities, which is time‐consuming and costly. Experimental studies have already shown that slow formation may neither be necessary nor beneficial for cell lifetime and performance. This work combines an experimental formation variation with physicochemical cell and solid electrolyte interphase (SEI) modeling to reveal formation‐induced changes within the cells. Formation at C/2 without full discharge compared to a standard C/10 formation at 20◦C notably improves the discharge and charge capacities at 2C by up to 41% and 63%, respectively, while reducing the formation time by over 80%. Model‐based cell diagnostics reveal that these performance gains are driven by improved transport in the anode electrolyte phase, which is affected by SEI formation, and by enhanced transport on the cathode side. Hence, the focus on the dense SEI layer is insufficient for a comprehensive understanding and, ultimately, optimization of cell formation. All formation procedures were also tested at temperatures of 35◦C and 50◦C. Despite often surpassing the 2C discharge capacity of the standard formation at 20◦C, these cells showed comparable or lower 2C charge capacities. This suggests a pivotal role of local temperature in the formation of large‐format cells.

中文翻译：

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快速化成后锂离子电池性能提高的根源

锂离子电池的化成过程通常采用低电流密度，耗时且成本高。实验研究已经表明，缓慢形成对于细胞寿命和性能来说既不必要也不有益。这项工作将实验形成变化与物理化学细胞和固体电解质界面（SEI）模型相结合，以揭示细胞内形成引起的变化。与 20°C 下的标准 C/10 化成相比，在没有完全放电的情况下以 C/2 化成可显着提高 2C 下的放电和充电容量，分别高达 41% 和 63%，同时将化成时间缩短 80% 以上。基于模型的电池诊断表明，这些性能提升是由于阳极电解质相传输的改善（受 SEI 形成的影响）以及阴极侧传输的增强所驱动。因此，对致密 SEI 层的关注不足以全面理解并最终优化细胞形成。所有形成过程也在 35°C 和 50°C 的温度下进行了测试。尽管在 20°C 时，这些电池的 2C 放电容量经常超过标准电池的 2C 放电容量，但这些电池却表现出相当或更低的 2C 充电容量。这表明局部温度在大型细胞的形成中起着关键作用。