In July 2025, an electric vehicle (EV) in an underground parking garage in Guangzhou suddenly burst into flames during charging, with the fire spreading to adjacent parking spaces within 30 seconds. Investigations revealed that the accident was caused by the battery management system (BMS) failing to respond promptly to localized temperature anomalies in the battery pack-a single cell developed increased internal resistance due to poor contact and continued charging at 45°C, triggering a chain reaction of thermal runaway. This is not an isolated incident; globally, over 60% of lithium battery accidents are caused by temperature-related failures, affecting applications ranging from smartphones to energy storage systems, drones to electric aircraft. Temperature management has become a core challenge in the development of lithium battery technology.
I. High Temperatures: A Triple Blow from Gradual Degradation to Instantaneous Explosion
The ideal operating temperature range for lithium batteries is 0–40°C. When temperatures exceed 45°C, performance degradation accelerates by 3–5 times. High-temperature damage to lithium batteries is progressive but can culminate in catastrophic failure.
1. Electrolyte Decomposition: The Collapse of the Chemical System
The electrolyte serves as the "highway" for lithium-ion transport, composed of carbonate solvents and lithium salts. When temperatures exceed 60°C, solvents like ethylene carbonate (EC) begin to decompose, producing flammable gases such as carbon monoxide (CO) and methane (CH₄). Experimental data shows that in an 85°C environment, the gas volume generated by electrolyte decomposition in a certain NCM lithium battery can expand to three times its original volume within two hours, causing battery swelling or even leakage. More critically, the decomposition product lithium carbonate (Li₂CO₃) clogs electrode pores, increasing internal resistance by 30–50% and creating a vicious cycle.
2. Positive Electrode Material Collapse: Structural Disaster
Lithium cobalt oxide (LCO) undergoes lattice structure collapse at 60°C, reducing lithium-ion insertion channels and causing a 15% permanent capacity loss. Ternary materials (NCM) pose an even greater risk, as they release oxygen at high temperatures, reacting violently with the electrolyte. In a 2024 energy storage station accident, monitoring data revealed that oxygen release from an NCM811 cell reached 0.5% per second at 120°C, with the resulting reaction with the electrolyte raising temperatures to 300°C within 30 seconds and triggering an explosion.
3. SEI Film Uncontrolled Growth: The "Vampire" of Active Lithium
The solid electrolyte interphase (SEI) film on the graphite anode thickens abnormally at high temperatures. Scanning electron microscopy (SEM) observations show that after 100 cycles at 60°C, the SEI film thickness increases from 50 nm to 200 nm, consuming 15% of active lithium. This not only reduces available lithium ions but further impedes ion transport, creating a "capacity degradation → increased internal resistance → accelerated heat generation" death spiral.
4. Thermal Runaway: The Ultimate Form of Chain Reaction
When battery temperatures exceed 150°C, SEI film decomposition releases heat and generates flammable gases; at 130–180°C, separator melting causes positive-negative electrode short circuits; at 200–300°C, ternary material decomposition releases oxygen, forming a "flamethrower" effect with the electrolyte; at 180°C, carbonate solvent combustion requires only minimal external energy to ignite. A 2025 EV thermal runaway test showed that from SEI decomposition to complete battery pack combustion took just 187 seconds, releasing energy equivalent to 1.5 kg of TNT.
II. Low Temperatures: The Invisible Killer from Performance Degradation to Structural Damage
Lithium batteries face three critical issues below 0°C. While less visually dramatic than high-temperature failures, long-term impacts are more profound.
1. Impaired Lithium-Ion Migration: Electrolyte "Freezing"
Low temperatures increase electrolyte viscosity exponentially (10-fold increase at -20°C), reducing lithium-ion diffusion speed to 1/5 of room-temperature levels. Discharge tests on a lithium iron phosphate (LFP) battery at -10°C showed only 89% capacity retention with a voltage platform drop from 3.2 V to 2.8 V, rendering devices inoperable. More critically, during low-temperature charging, lithium ions plate onto the anode surface as lithium dendrites, with growth rates exponentially correlated with temperature-after 10 fast charges at -20°C, internal resistance increases by 30%, and the probability of dendrites puncturing the separator rises to 5%.
2. Active Material "Freezing": Electrode Material Failure
Electrolyte within electrode pores partially solidifies at low temperatures, blocking ion transport channels. X-ray diffraction (XRD) analysis reveals that at -30°C, lithium-ion diffusion coefficients in a ternary material electrode drop from 10⁻¹⁴ cm²/s to 10⁻¹⁶ cm²/s, causing "instantaneous battery collapse." This failure is irreversible, as electrode pore structures undergo permanent changes even after temperature recovery.
3. Anode Lithium Plating: Microscopic "Time Bombs"
During low-temperature charging, lithium-ion insertion speed into the anode lags behind reduction speed, causing metallic lithium to deposit directly on the graphite surface. Cryo-electron microscopy observations show that after charging at -10°C, lithium dendrite density on the anode reaches 10⁵ per square centimeter. These dendrites not only consume active lithium but also react with the electrolyte to form deposits that increase SEI film thickness by 50%, further degrading low-temperature performance.
III. Breaking Temperature Constraints: Dual Revolutions in Material Innovation and System Design
The industry is addressing temperature challenges through material, structural, and control innovations.
1. Material Innovation: High-Temperature Electrolytes and Solid-State Electrolytes
A company developed LiFSI-based electrolytes that maintain ionic conductivity at 120°C, with decomposition temperatures 40°C higher than traditional electrolytes. Solid-state electrolytes offer even greater improvements-an oxide solid-state battery operates stably at 200°C, while ceramic-coated separators raise thermal runaway initiation temperatures from 150°C to 220°C. By 2025, a aerospace project using sulfide solid-state batteries achieved a temperature range of -50°C to 120°C with an energy density of 450 Wh/kg.
2. Structural Optimization: Wide-Temperature Batteries and Thermal Management Technologies
A company's wide-temperature battery uses phase-change materials (PCMs) for packaging, maintaining over 85% capacity from -40°C to 70°C. Liquid cooling systems have become standard in EVs, with one model's battery pack maintaining module temperature differences within ±2°C using cold plates, extending battery life by 30%. Advanced thermal protection includes aerogel insulation layers (withstanding 800°C for 30 minutes) and distributed fiber-optic temperature sensing (±0.5°C accuracy), providing critical evacuation time during thermal runaway.
3. Intelligent Control: Multi-Parameter Collaborative BMS 3.0
Next-generation BMS systems integrate voltage gradients, gas composition (e.g., CO, H₂), and stress changes beyond traditional temperature sensors. A machine learning algorithm enables early warning during initial SEI decomposition (at 80°C), 5–8 minutes ahead of traditional methods. More aggressive solutions employ active fire suppression systems that automatically inject perfluorohexanone at 120°C to contain thermal runaway at its onset.
