Research on High-Temperature Safety Performance of Lithium Batteries

Lithium-ion batteries are prone to safety risks under high-temperature conditions, making research on their high-temperature safety performance critical for advancing their application in demanding environments such as electric vehicles, aerospace, and industrial energy storage. High temperatures (above 60°C) can accelerate chemical reactions within the battery, leading to thermal runaway—a cascading exothermic process involving electrolyte decomposition, electrode material breakdown, and gas release, which may result in fire or explosion. Understanding the mechanisms, evaluating safety metrics, and developing mitigation strategies are key focuses of this research.

The primary mechanism driving high-temperature hazards is thermal runaway, triggered by internal or external heat sources. Internally, factors such as overcharging, short circuits, or cell imbalance can generate excessive heat. For example, overcharging a lithium cobalt oxide (LCO) battery beyond 4.5V causes lithium plating on the anode, which reacts with the electrolyte to produce heat and gas. Externally, ambient high temperatures (e.g., in desert climates or near engine compartments) reduce the thermal runaway threshold, making the battery more susceptible to triggering. Research using accelerating rate calorimetry (ARC) shows that Li-ion batteries can reach self-heating rates exceeding 100°C per minute once thermal runaway is initiated, with gas emissions including flammable hydrocarbons (e.g., ethylene) and toxic compounds (e.g., HF).

Evaluating high-temperature safety involves standardized and advanced testing methods. The UN 38.3 test, required for battery transportation, includes a "high-temperature storage" test where batteries are held at 72°C for 12 hours to check for leakage or explosion. More rigorous tests, such as the thermal abuse test, heat the battery from room temperature to 200°C at a controlled rate (5°C/min) while monitoring temperature, pressure, and gas release. Differential scanning calorimetry (DSC) analyzes the exothermic reactions of electrode materials and electrolytes, identifying critical temperatures where decomposition begins (e.g., cathode materials like NCM [nickel-cobalt-manganese] start decomposing above 210°C). These tests help quantify safety margins and compare performance across battery chemistries—for instance, LFP (lithium iron phosphate) batteries exhibit higher thermal stability than LCO, with thermal runaway initiation temperatures around 270°C vs. 150°C.

Mitigation strategies to enhance high-temperature safety include material modification, thermal management systems, and BMS improvements. Material innovations focus on developing heat-resistant electrolytes (e.g., adding flame retardants like phosphazenes) and stable electrode coatings (e.g., Al₂O₃ or TiO₂ layers on cathodes to prevent direct contact with electrolytes). Thermal management systems, such as liquid cooling in EV batteries, maintain temperatures within 25–40°C by dissipating excess heat. Advanced BMS algorithms predict thermal risks using temperature and resistance data, triggering cooling or shutdown before dangerous conditions arise. For example, some EV BMS systems use machine learning to forecast cell temperatures based on driving patterns, pre-emptively adjusting cooling flow.

Another research direction is the development of intrinsic safety designs, such as solid-state batteries, which replace flammable liquid electrolytes with solid electrolytes (e.g., sulfides or oxides). Solid electrolytes are non-flammable and exhibit higher thermal stability, reducing the risk of thermal runaway even at high temperatures. However, challenges like low ionic conductivity at room temperature and high manufacturing costs remain, requiring further material optimization.

 research on high-temperature safety performance of lithium batteries is multifaceted, encompassing mechanism analysis, testing standards, and mitigation technologies. Advances in this field are crucial for enabling the safe deployment of lithium-ion batteries in high-temperature environments, supporting the growth of electric mobility and renewable energy storage.

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