Overcharge is considered to be one of the most severity safety problems for large format lithium ion battery (LIB), understanding of correlation between overcharge states and associated degradations is still a challenging issue. Here overcharge features of 51Ah prismatic LIBs were studied by charging the LIBs to various state of charge (SOC). When the SOC reaches up to 125%, lithium plating and lithium involved side reactions have taken place accompanied by capacity fade, internal resistance increase and LIB swelling. Meanwhile, the interlayer spacing of graphite anode is enlarged as indicated by shift of (002) diffraction peak to lower angle. When the SOC reaches up to 140%, additional to above reactions aggravation, structural damage of cathode materials was found. With further increase of SOC, internal side reactions became more violent as indicated by obvious self-heating at 146% SOC. Moreover, effects of charging current and initial temperature on overcharge behaviors were also discussed. Large charging current (4C) can lead to more severity thermal runaway as supported by higher maximum surface temperature of 413.34 °C compared to that of 187.90 °C at 1C. LIB overcharged at initial low temperature shows quick temperature rise but lower maximum surface temperature of 143.15 °C at 160% SOC compared to that of 187.90 °C at 159% SOC for LIB overcharged under ambient temperature

对于大型锂离子电池（LIB），过充电被认为是最严重的安全问题之一，因此了解过充电状态与相关退化之间的相关性仍然是一个具有挑战性的问题。在此，通过将LIB充电至各种电荷状态（SOC），研究了51Ah棱柱形LIB的过充电特性。当SOC达到125％时，会发生锂电镀和涉及锂的副反应，并伴有容量下降，内部电阻增加和LIB膨胀。同时，如（002）衍射峰向较低角度的移动所示，石墨阳极的层间间隔增大。当SOC达到140％时，除了上述反应加剧之外，还发现阴极材料的结构损坏。随着SOC的进一步增加，内部不良反应变得更加剧烈，如在146％SOC时明显自热所表明。此外，还讨论了充电电流和初始温度对过充电行为的影响。较大的充电电流（4C）可导致更高的严酷热失控，这是由413.34°C的最高最高表面温度（相比于1C的187.90°C）所支持的。在初始低温下过充的LIB表现出快速的升温，但在环境温度下过充的LIB的最大表面温度在SOC为159％时为143.15°C，而在SOC为159％时为187.90°C 较大的充电电流（4C）可以导致更大的热失控，这是由413.34°C的最高最高表面温度（相比于1C的187.90°C）所支持的。在初始低温下过充的LIB表现出快速的升温，但在环境温度下过充的LIB的最高表面温度在160％SOC时为143.15°C，而在159％SOC时为187.90°C 大的充电电流（4C）可以导致更高的严酷热失控，这是由413.34°C的最高最高表面温度（相比于1C的187.90°C）所支持的。在初始低温下过充的LIB表现出快速的升温，但在环境温度下过充的LIB的最大表面温度在SOC为159％时为143.15°C，而在SOC为159％时则为187.90°C