The storage performances of 0% SOC and 100%SOC lithium iron phosphate (LFP) batteries are investigated. 0%SOC batteries exhibit higher swelling rate than 100%SOC batteries. In order to find out the source of battery swelling, cathode and anode electrodes obtained from 0%SOC battery are evaluated separately. By analyzing the results, the anode is identified as the main source of battery swelling. The 0%SOC anodes are then stored with different solvents of electrolyte and gas chromatography is utilized to analyze the main components of the gas products. Moreover, different types of anodes are also investigated. A three-electrode system is designed to study the voltage change during charging and discharging process. The results confirm that the battery swelling is related to the voltage state of the anode. The anode is unstable at high voltage which may cause the decomposition of SEI during storage process. After SEI decomposes, the fresh anode surface will be exposed to the electrolyte, and the new SEI will be formed to generate large amount of gas which can cause the battery swelling. Finally, different SOCs of LFP batteries are investigated. It is found that the swelling rate tends to be stable at 30% SOC.

研究了0％SOC和100％SOC磷酸铁锂（LFP）电池的存储性能。0％SOC电池比100％SOC电池具有更高的溶胀率。为了找出电池膨胀的根源，分别评估从0％SOC电池获得的阴极和阳极。通过分析结果，可以确定阳极是电池膨胀的主要来源。然后将0％SOC阳极与不同的电解质溶剂一起储存，并利用气相色谱法分析气体产物的主要成分。此外，还研究了不同类型的阳极。设计了一个三电极系统来研究充电和放电过程中的电压变化。结果证实电池膨胀与阳极的电压状态有关。阳极在高压下不稳定，这可能会导致SEI在存储过程中分解。SEI分解后，新的阳极表面将暴露于电解质中，新的SEI将形成以产生大量气体，从而导致电池膨胀。最后，研究了LFP电池的不同SOC。发现溶胀率趋于在30％SOC下稳定。