Thermal Runaway Explained: Why Lithium-Ion Batteries Catch Fire and How to Prevent It
Thermal runaway in lithium-ion batteries has caused warehouse fires, EV recalls, and aviation incidents. Understanding the chain reaction — and the chemistry-level solutions that eliminate it entirely — is critical for anyone deploying energy storage at scale.
On September 4, 2024, a lithium-ion battery storage facility in Moss Landing, California — one of the world's largest — caught fire, burning for days and forcing evacuations across a two-mile radius. It was not an isolated incident. GM recalled 143,000 Bolt EVs due to battery fire risk. Samsung's Galaxy Note 7 was banned from flights after spontaneous combustion incidents. In South Korea, over 30 ESS (Energy Storage System) fires occurred between 2017 and 2019, temporarily halting the country's grid storage programme.
Thermal runaway is the root cause. It begins when an internal cell temperature exceeds approximately 150°C — triggered by manufacturing defects, external damage, overcharging, or internal short circuits. At this temperature, the solid electrolyte interface (SEI) layer on the anode decomposes exothermically, releasing heat that decomposes the cathode material, which releases oxygen. The oxygen reacts with the flammable organic electrolyte (typically ethylene carbonate or dimethyl carbonate), creating a self-sustaining fire that can exceed 800°C. Once thermal runaway begins in one cell, it propagates to adjacent cells through heat conduction.
The industry's response has focused on mitigation rather than elimination: better Battery Management Systems (BMS), thermal barriers between cells, fire suppression systems, and improved separator materials. These measures reduce the probability and consequences of thermal runaway but do not eliminate the fundamental vulnerability — a flammable electrolyte coexisting with a reactive cathode in a sealed container.
Chemistry-level solutions exist. Aluminium-graphene batteries developed by Nordische Energy Systems use ionic liquid electrolytes with flash points exceeding 300°C — compared to approximately 30°C for conventional organic electrolytes. In standardised nail penetration tests (where a steel nail is driven through a fully charged cell), aluminium-graphene cells show zero thermal runaway. No fire, no smoke, no cascading failure. The chemistry is inherently non-flammable.
For grid storage operators, this distinction is existential. A thermal runaway event at a utility-scale battery installation can cause millions in property damage, regulatory shutdowns, and community opposition that blocks future projects. Insurance premiums for lithium-ion BESS installations have doubled since 2020, reflecting the actuarial reality of fire risk. Non-flammable chemistries eliminate this risk category entirely, reducing insurance costs, siting restrictions, and fire suppression infrastructure requirements.
The battery industry's thermal runaway problem is not a software bug that can be patched with better monitoring. It is a chemistry problem that requires a chemistry solution. Until the industry moves beyond flammable electrolytes, thermal runaway will remain an inherent risk in every lithium-ion installation — from the phone in your pocket to the megawatt-scale battery behind the grid.