The exceptional cycling stability of lithium-ion batteries in electric vehicles and large-scale grid energy storage applications necessitates the use of accelerated aging tests for rapid assessment. Overdischarge stress is an effective approach to accelerate battery aging, whereas its impact on solid electrolyte interphase (SEI) and battery aging performance remains elusive. Herein, the whole picture of SEI evolution under different overdischarge levels was quantitatively illustrated by combining the electrochemical analysis and spectrochemical techniques. Overdischarge leads to the decomposition of the organic components within SEI, such as ROCO2Li and CH3Li, while the damaged SEI is repaired during the subsequent charging process with its composition and structure reconstructed. Under overdischarge conditions, the SEI undergoes continuous cycles of destruction and repair, which suppresses its growth and evolution to inorganic components, resulting in a thinner and more uneven morphology with higher organic components and a lower Young's modulus. The unique SEI evolution mechanism of overdischarge effectively accelerates the loss of active lithium and exhibits similar thermodynamic degradation modes to normal aging, making overdischarge a potential accelerated aging method. This study provides a deeper understanding of the mechanisms behind accelerated aging in batteries and offers new insights into the evaluation and enhancement of battery performance.

中文翻译：

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通过揭示 SEI 进化机制，重新审视过放电过程作为 LiFePO4/石墨电池的新型加速老化方法


锂离子电池在电动汽车和大规模电网储能应用中具有出色的循环稳定性，因此需要使用加速老化测试进行快速评估。过放电应力是加速电池老化的有效方法，但其对固体电解质界面 （SEI） 和电池老化性能的影响仍然难以捉摸。本文通过结合电化学分析和光谱化学技术，定量说明了不同过放电水平下 SEI 演变的全貌。过放电导致 SEI 内部的有机成分分解，例如 ROCO2Li 和 CH3Li，而受损的 SEI 在随后的充电过程中被修复，其成分和结构被重建。在过放电条件下，SEI 经历连续的破坏和修复循环，这抑制了其生长和演变为无机组分，导致形态更薄、更不均匀，有机组分较高，杨氏模量较低。过放电独特的 SEI 演化机制有效地加速了活性锂的损失，并表现出与正常老化相似的热力学降解模式，使过放电成为一种潜在的加速老化方法。这项研究提供了对电池加速老化背后的机制的更深入理解，并为评估和增强电池性能提供了新的见解。