Experimental investigation of aging effects on thermal behavior of lithium-ion batteries during charging process

Thermal runaway generated by lithium-ion batteries is considered as one of the major hazards that exhibits great thermal risk during operation. The aging behavior, as an inevitable phenomenon after long-term cycling, largely contributes to the deterioration of thermal characteristics. In this paper, comparative experiments were conducted to investigate the aging cell thermal performance during the charging process. The results indicate that the aging cell with a high charging rate presents a higher thermal risk. With the decrease of SOH, the anode structure was destroyed and side reactions reduced the thermal stability. The thermal runaway onset temperature decreased from 274.8 +/- 9.1 degrees C for fresh to 238 +/- 1.2 degrees C for aging cells, and the corresponding critical time shortened by approximately 1 min. In addition, the maximum heat release rate increased by 37.5 %-45.5 % for aging cells under high charging conditions, manifesting that aging cells are more prone to trigger fire accidents. Finally, a modified risk assessment method was established. This study contributes to comprehending the coupling effects of aging behavior and charging rate thermal runaway mechanisms, and provides valuable guidance for thermal runaway detection during the whole life.