SOC gradient-based passive safety design: a chessboard-inspired structural configuration for mitigating thermal runaway propagation in lithium-ion battery packs

Abstract

In conventional lithium-ion battery packs, adjacent cells are interconnected through series-parallel arrangements, where thermal runaway in a single cell can trigger cascading thermal propagation, leading to catastrophic thermal events. To address this issue, we propose a novel chessboard-inspired battery pack featuring two interdigitated cell groups with alternating state-of-charge (SOC) distribution. During operation, the sequential discharge of these groups creates spatial SOC differentiation. Each high-SOC cell is strategically surrounded by lower-SOC neighbors that serve as inherent thermal buffers. A comparative safety analysis was conducted between conventional and chessboard-inspired pack configurations using a validated thermal runaway propagation model. Simulation results reveal that only the chessboard architecture successfully inhibits the thermal runaway propagation in the 75 %-SOC battery pack. The 50 %-SOC cells surrounding thermal failed cell unit increase the thermal propagation threshold by 22 °C compared to conventional packs with 75 %-SOC cells. In addition, energy flow analysis indicates that the specialized tab design redirects approximately 10 % of the energy released during thermal runaway to non-adjacent cells. This redistribution further increases the required energy release from the initial thermal runaway cell to trigger propagation. Through the integration of geometric layout and operational strategies, the chessboard-inspired configuration demonstrates strong potential for practical applications in electric vehicles and energy storage systems, offering a promising pathway for advancing passive safety technologies in battery system design.