关键词: 锂离子电池, 热失控, 铜集流体, 催化, 电解液分解, 电池安全

Abstract: Lithium-ion batteries (LIBs) underpin modern portable electronics, electric transportation, and grid-scale energy storage, yet thermal runaway (TR) remains a critical safety barrier under the increasing demand for higher energy density. A major challenge in understanding TR is that its early-stage reactions are highly coupled: salt decomposition, solvent degradation, gas generation, interfacial reconstruction, and heat release typically occur simultaneously within a narrow temperature window. This complexity makes it difficult to identify which cell components initiate or accelerate thermal failure. In existing TR models, the copper current collector is generally regarded as an electrically conductive but chemically inert substrate. However, this assumption has rarely been experimentally verified under realistic thermal-abuse conditions, mainly because the chemical contribution of copper is easily masked by the intense reactions of lithiated anodes and electrolytes. Clarifying whether copper is merely a passive structural component or an active participant is therefore essential for improving the mechanistic accuracy of battery safety models. Here, we overturn the conventional view of copper as an inert current collector and demonstrate that it plays an active dual-function role-as both a catalyst and a reactant-in the early thermal failure of LIBs. By combining multi-scale thermal analysis, operando gas chromatography–mass spectrometry (GC-MS), and surface-sensitive spectroscopies, we show that copper surfaces markedly accelerate the conversion of LiPF₆ to PF₅. This process occurs at temperatures as low as 180 °C, nearly 100 °C earlier than in copper-free systems. This finding is significant because PF₅ is a highly reactive Lewis acid that can prematurely trigger electrolyte decomposition before the temperature reaches the conventionally recognized severe thermal-abuse regime. The prematurely generated PF₅ further initiates a catalytic cascade that promotes ring-opening decarboxylation of cyclic carbonate solvents, especially ethylene carbonate (EC) and fluoroethylene carbonate (FEC). Consequently, copper-containing systems exhibit substantially increased release of reductive gases, including CH₄ and C₂H₄, together with enhanced CO₂ evolution. Surface analysis further reveals the formation of fluorinated products on copper, confirming that copper is not only catalytically involved but also chemically consumed during electrolyte decomposition. The destabilizing effect of copper becomes more pronounced in the lithiated graphite anode–electrolyte system, where it increases the total heat release by 53.6%. These findings indicate that neglecting the chemical contribution of copper may lead to a systematic overestimation of the thermal stability of LIBs. By identifying copper–electrolyte interaction as a previously missing link in the TR chain, this work provides a mechanistic foundation for revising battery safety prediction models and opens a new materials-design direction for intrinsically safer current collectors.

Key words: Lithium-ion battery, Thermal runaway, Copper current collector, Catalysis, Electrolyte decomposition, Battery safety