Cathode‐Driven Aluminothermic Fronts Amplify Thermal Runaway in Lithium‐Ion Batteries

Thermal runaway in lithium-ion batteries often develops from a local failure into a spatially propagating high-temperature front. Here, we show that oxygen-bearing cathode materials and metallic aluminium can form self-sustained, glowing, cathode-driven aluminothermic fronts in inert gas as a heat-amplification pathway relevant to severe thermal runaway. Using a mesoscale platform based on semi-1D composite bars, we isolate this interfacial redox chemistry from gas-phase combustion, internal short-circuit heating, and other coupled cell-failure processes. Nickel-rich layered oxide/aluminium bars sustain aluminothermic-front propagation in argon, with velocities of the same order of magnitude as reported thermal-runaway fronts. By varying aluminium loading, reaction atmosphere and cathode chemistry, we show that front propagation depends on aluminium fuel supply, the oxygen-donor capability of the cathode, and access to oxygen gas. Crystalline phase and chemical-state analyses reveal Li-Al-O/Al-O products together with reduced or reconstructed transition-metal species, supporting cathode-to-aluminium oxygen transfer as the underlying redox pathway. For a representative 2-Ah cell, energy-audit calculations indicate that the aluminium-cathode reaction gives a potential heat scale equivalent to about half of the stored electrical energy. These findings identify cathode-Al redox chemistry as an internal heat-amplification mechanism that should be considered in battery hazard assessment and high-energy-cell safety design.