Study on the influence of high-rate charge/discharge cycle numbers and spacing on thermal runaway propagation in lithium-ion batteries

This study examines the effects of high-rate cycling and inter-battery spacing on thermal runaway propagation (TRP) in lithium-ion batteries through thermal abuse tests. Experiments were conducted under a 3C charge/discharge rate with cycle numbers of 30, 50, 70, and 100, and inter-battery spacings of 0 cm, 1 cm, 1.5 cm, and 2 cm. The results reveal that increasing spacing significantly delays the onset of TRP, with no TR occurring at a spacing of 2 cm and a maximum temperature of 72 °C, establishing 2 cm as the critical spacing for TRP. 100 charge/discharge cycles at a 3C rate resulted in a 21.3 % decrease in state of health (SOH), a 317-s advancement in thermal runaway (TR) onset time, and a 17.2 % reduction in peak temperature compared to 30 charge/discharge cycles. Declining SOH led to greater instability, shortening the time to trigger TR and reducing the peak temperature. The mass loss during TR was directly proportional to SOH. Thermal analysis showed that, at a 1 cm spacing, the second battery experienced TR with minimal heat absorption, whereas increasing spacing to 1.5 cm or 2 cm improved heat dissipation and extended TRP time, preventing TR despite increased surface temperatures. Additionally, at a 1 cm spacing, fewer charge/discharge cycles required greater heat absorption for the second battery to reach TR. Changes in electrode morphology after charge/discharge cycling were also examined. This research provides insights into TRP mechanisms in high-rate charge/discharge cycling, offering theoretical guidance for TR suppression and enhancing battery safety and energy storage technology.