In recent years, the rapid development of new energy vehicles (NEVs) has been driven by global energy crises and carbon neutrality goals. As a core component, the EV power battery, particularly lithium-ion batteries, plays a critical role due to its high energy density and efficiency. However, thermal runaway incidents in China EV battery systems have led to frequent fire and explosion accidents, posing significant safety challenges. This article analyzes the mechanisms, hazards, and suppression technologies for thermal runaway-induced detonation in EV power batteries, with a focus on advancements in China. We incorporate tables and formulas to summarize key findings and provide insights into future research directions.
The safety of EV power batteries is paramount, as thermal runaway can be triggered by mechanical, electrical, or thermal abuse, leading to chain reactions that produce flammable gases and heat. For instance, in mechanical abuse, external forces cause internal short circuits, while overcharging in electrical abuse results in lithium deposition and gas generation. The energy release during thermal runaway can be modeled using the Arrhenius equation for reaction rates: $$ k = A e^{-E_a / RT} $$ where \( k \) is the rate constant, \( A \) is the pre-exponential factor, \( E_a \) is the activation energy, \( R \) is the gas constant, and \( T \) is temperature. This highlights the temperature dependence of exothermic reactions in China EV battery systems.
Statistical analysis of NEV accidents in 2023 reveals that 69% of fires involved ternary lithium batteries, while 21% used lithium iron phosphate batteries. Pure electric vehicles (EVs) accounted for 82% of incidents, compared to 14% for plug-in hybrid electric vehicles (PHEVs). Common scenarios included fires during driving (37%), non-charging parking (31%), and charging states (23%). The table below summarizes typical accident causes and consequences related to China EV battery failures:
| Battery Type | Incident Scenario | Primary Cause | Impact |
|---|---|---|---|
| Ternary Lithium | Collision or Overcharging | Internal Short Circuit | Fire and Explosion |
| Lithium Iron Phosphate | Thermal Abuse | Heat Accumulation | Smoke and Gas Release |
Thermal runaway in EV power batteries involves sequential reactions, such as SEI membrane decomposition at 80–120°C, electrolyte breakdown, and cathode material reactions, releasing gases like H₂ and CO₂. The pressure buildup inside the battery can be described by the ideal gas law: $$ PV = nRT $$ where \( P \) is pressure, \( V \) is volume, \( n \) is the number of moles of gas, \( R \) is the gas constant, and \( T \) is temperature. This equation underscores the risk of explosion when gas accumulation exceeds the structural limits of the China EV battery casing.
To mitigate detonation risks, various suppression technologies have been developed. Pressure relief valves are passive safety devices that vent gases when internal pressure exceeds a threshold. The mass flow rate through a valve can be expressed as: $$ \dot{m} = C_d A \sqrt{\frac{2 \gamma}{\gamma – 1} P_1 \rho_1 \left( \left( \frac{P_2}{P_1} \right)^{2/\gamma} – \left( \frac{P_2}{P_1} \right)^{(\gamma+1)/\gamma} \right)} $$ where \( \dot{m} \) is the mass flow rate, \( C_d \) is the discharge coefficient, \( A \) is the area, \( \gamma \) is the specific heat ratio, \( P_1 \) and \( P_2 \) are upstream and downstream pressures, and \( \rho_1 \) is density. However, current valves in EV power battery systems often lack adaptability to varying pressure rates, necessitating optimized designs for China EV battery applications.
Fire extinguishing agents, such as fine water mist, perfluorohexanone, and inert gases, are employed to suppress combustion. The cooling efficiency of water mist can be quantified by the heat absorption formula: $$ Q = m c_p \Delta T $$ where \( Q \) is heat absorbed, \( m \) is mass, \( c_p \) is specific heat capacity, and \( \Delta T \) is temperature change. The table below compares agents used in China EV battery fire suppression:
| Extinguishing Agent | Mechanism | Advantages | Limitations |
|---|---|---|---|
| Fine Water Mist | Cooling and Oxygen Dilution | Environmentally Friendly, Effective Cooling | Potential Short-Circuit Risk |
| Perfluorohexanone | Chemical Chain Inhibition | Rapid Fire Suppression | Toxic Byproducts |
| CO₂ | Oxygen Displacement | Non-Conductive | Ineffective Against Internal Reactions |
Thermal runaway propagation blocking techniques involve materials placed between battery modules to isolate heat. The heat transfer through a barrier can be modeled by Fourier’s law: $$ q = -k \frac{dT}{dx} $$ where \( q \) is heat flux, \( k \) is thermal conductivity, and \( \frac{dT}{dx} \) is temperature gradient. Aerogels and composite materials show promise in China EV battery systems due to low thermal conductivity (e.g., \( k < 0.02 \, \text{W/m·K} \)). However, these materials only delay propagation and require integration with other technologies for complete prevention.
In conclusion, the safety of EV power batteries hinges on advanced suppression strategies. Future research should focus on optimizing pressure relief valves, developing non-toxic extinguishing agents, and enhancing thermal barriers for China EV battery applications. Multidisciplinary approaches combining material science and thermal management will be crucial to reducing detonation risks and promoting the sustainable growth of NEVs.