Mechanistic study of the N-doping enhancement in thermal performance of MOF-based composite phase change material and its application in lithium-ion battery heat dissipation

Lithium-ion batteries may experience thermal runaway due to excessive temperature rise when operating at high discharge rates. By incorporating composite phase change materials (CPCMs) onto the battery surface, it is possible to effectively regulate the temperature, ensuring it stays below critical safety limits. In order to obtain CPCM with optimal stability and high thermal storage performance, this study proposes an N-doped metal-organic frameworks (MOFs) derived hierarchical porous carbon loading material. Specifically, g-C3N4 was utilized as a nitrogen source to dope MOF-199, leading to the synthesis of N-doped porous carbon (NC-X). Further treatment with concentrated nitric acid enriches the pore structure, yielding N-doped hierarchical porous carbon (NCN-X). After impregnation with lauric acid (LA), shape-stable CPCM (LA/NCN-X) was obtained. The results show that the performance characteristics of the CPCM vary with the amount of g-C3N4 incorporated. When the g-C3N4 content reaches 20 %, the CPCM exhibits peak values in effective loading ratio, crystallinity, and impregnation efficiency. The CPCM achieves a maximum loading ratio of 70.17 %, with a latent heat of 125.12 J·g−1, representing 94.01 % of its theoretical latent heat value, and a thermal storage efficiency of 99.16 %. Moreover, when the lithium-ion battery undergoes discharge at 3C, the surface temperature of the battery is reduced by 17.52 % for CPCM-G compared to BC-G, providing enhanced safety for the battery under high discharge rate conditions.