Harnessing anisotropy of phase change composites for taming thermal runaway and fast charging of lithium-ion batteries

Regulating temperature uniformly below self-ignition point in lithium-ion battery (LIB) is paramount for optimal performance and to avert potential thermal runaways. Localized heat accumulations or hot spots underscore the need for effective thermal management, demanding a delicate balance between rapid heat expulsion to an external sink and limiting heat propagation between neighboring cells using interstitial sheets typically placed between cells. This study presents a novel strategy employing laminate composites with dual thermal conductivities (k): high k_In-plane for efficient heat expulsion and low k_Out-of-plane to curb heat spread. The approach exploits laminate anisotropy to passively address the challenges of managing hot spots during fast charging and preventing thermal runaway propagation. High k composites, while prompt in heat transfer, can inadvertently trigger thermal runaway by propagating heat to neighboring cells. Conversely, low k composite hinder dispersion, causing severe heat accumulation. The proposed dual k approach strikes a balance, optimizing heat dissipation to a sink while restricting heat propagation between the cells. Expanded graphite promotes the in-plane thermal conduction while air gap in between reduces the out-of-plane heat conduction. Our results suggest that interstitial composites with high anisotropy whose k_In-plane and k_Out-of-plane are 30 and 0.5 W·m⁻¹·K⁻¹, respectively, could mitigate thermal runaway propagation, maintaining the surface of adjacent cells below the self-ignition temperature of 200 °C. Our findings underscore the importance of customizing the thermal properties of interstitial materials to efficiently balance heat transfer in LIBs, especially under abuse conditions. This customization is vital for enhancing the thermal management and overall safety of these battery systems. The proposed approach contributes to the safe and reliable deployment of LIBs across diverse applications.