Heat Generation and Temperature Rise Characteristics of Single Overcharged Lithium-Ion Batteries

It’s critical to quantitatively investigate the thermal characteristics of single overcharged lithium-ion batteries to realize security alert before thermal runaway occurs. In this work, various (LiCoO 2 + LiMn 2 O 4 )/graphite soft pack cells overcharged under different cut-off voltages, temperatures and C-rates are tested electrochemically to calculate the heat generation rate and distinguish the dominating heat resource. The results show that overcharged cells with higher cut-off voltage, overcharge temperature and the lower overcharge C-rate exhibit higher heat generation and temperature rise rate as well as poorer state of healthy. Among nonexplosive tested cells, the cell overcharged to 4.8 V at 0.1 C rate and 40 °C exhibits the highest heat generation and temperature rise rates of 9.17 W·l −1 and 4.60 °C·h −1 during 1 C charging at 25 °C. For overcharged cells, lithium plating, increased resistance and gas generation are observed, which are the reason for the accelerated total heat generation rate compared to baseline cells. Comparing with reversible heat, the irreversible heat resulting from diffusion overpotential and the sum of ohmic and charge transfer overpotential is dominating for overcharged cells working under high current. It’s recommended to comprehensively monitor the temperature change of each cell of battery pack.