Abstract
The effect of calendar aging on the thermal safety of 4.6 Ah pouch cells with a LiMn2O4 (LMO) cathode was investigated by a battery test calorimeter (BTC) that can be used to determine the heat evolved during an uncontrolled exothermic runaway reaction. Cells were stored at 55 °C and 100% state of charge (SOC) for accelerated aging, and they were taken out after 10, 20, 40, 68, and 90 days of storage to obtain different aging states. Those cells were then put into the BTC for thermal safety tests. The results show the cell thermal safety improves after aging: (1) the self-heating temperature increases; (2) the thermal runaway temperature increases; and (3) the exothermal rate during the process of thermal runaway decreases. The cell voltage drops to zero about 40 °C earlier than the thermal runaway, indicating the voltage can be used as a signal for cell safety monitoring.
Highlights
Lithium-ion cells have become one of the most attractive energy sources due to their excellent performance, including high power and energy density [1,2]
Jiang and Dahn [16] compared the safety of different solvents and concluded that ethylene carbonate (EC) was better in protecting the lithiated carbon compared with dimethyl carbonate (DMC) and diethyl carbonate (DEC)
The results show that the 3 displays thedecreases cell capacity fadethe during thedays storing process.while
Summary
Lithium-ion cells have become one of the most attractive energy sources due to their excellent performance, including high power and energy density [1,2]. Jiang and Dahn [16] compared the safety of different solvents and concluded that ethylene carbonate (EC) was better in protecting the lithiated carbon compared with dimethyl carbonate (DMC) and diethyl carbonate (DEC) Based on those results, cells with higher safety have been designed, but, in the meantime, other performances such as energy density might be compromised. Most of the studies current address studies the thermal safety issue of fresh cells, hardly considering the cell in aged states [20,21,22]. Fleischhammer et al [22] investigated the safety of lithium-ion cells after and low-temperature Their results indicated that cells indicated cycled at high ratescycled show only slightly aging at high-rate andcycling.
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