The thermal stability of lifepo4 batteries far exceeds that of other lithium battery technologies. The initial temperature of thermal runaway is as high as 270℃ (tested by UL 1642), which is more than 35% higher than the 150-200℃ of ternary lithium batteries (NCM/NCA), and the amount of oxygen released during decomposition is reduced by 87% (differential scanning calometric method shows that the peak heat release is only 210J/g). The NCM reaches 1500J/g. A 2022 study in “Nature Energy” confirmed that the thermal diffusion rate of lifepo4 in the needle-puncture test was only 0.8cm/min (GB/T 31485 standard), while the temperature of NCM batteries soared to 860℃ within 3 seconds. The needle-puncture test of BYD’s Blade battery shows that the thermal runaway delay time of lifepo4 reaches 52 minutes (usually less than 1 minute for ternary batteries), which extends the accident escape window by 40 times.
The chemical nature of the material determines the safety boundary. The P-O bond energy of the olidine structure is as high as 585kJ/mol (the bond energy of the layered structure of the ternary material is only 368kJ/mol), and no metallic lithium is precipitated even when overcharged to 200%SOC (experimental data from Tsinghua University). Statistics on fires at energy storage power stations in South Korea show that the accident rate of the ternary system reached 1.7 cases per GWh from 2018 to 2023, while that of the lifepo4 system was only 0.1 cases (with a probability reduction of 94%). More crucially, the toxicity of thermal runaway gases. The concentration of HF gas released by NCM batteries is > 800ppm (IDLH value is only 30ppm), and lifepo4 mainly generates CO/CO₂ with a concentration 62% lower (UL 9540A gaseous analysis).
The mechanical abuse tolerance has been significantly improved. In the compression test (GB/T 31467.3), lifepo4 still maintains a voltage of 3.2V when the shell deforms by 40% (ternary batteries short-circuit when deformed by 15%). Tesla collision data indicates that the thermal runaway probability of the Model 3 battery pack with lifepo4 after a rear-end collision at 80km/h is only 0.3% (7.8% for the ternary version). The vibration test (SAE J2380) revealed its structural stability. At an acceleration of 30G, the displacement of the lifepo4 electrode sheet was < 0.15mm (for ternary batteries > 0.5mm), and the internal resistance change rate was controlled within ±2% (the fluctuation of ternary batteries reached ±18%).
The electrochemical safety mechanism is more complete. When overcharged to 4.5V, lifepo4 only shows electrolyte decomposition (heat generation power 0.8W/Ah), while NCM batteries undergo irreversible phase transformation at 4.3V (heat generation power surges to 15W/Ah). Experiments by CATL show that 100%SOC lifepo4 did not experience thermal runaway when placed in a 150 ° C environment for 2 hours (NCM batteries caught fire within 10 minutes). The safety advantage of low-temperature charging is obvious. When charged at 1C at -10℃, the growth probability of lithium dendrites in lifepo4 is only 0.3% (7.2% for NCM batteries), which is attributed to its high lithium-ion diffusion coefficient (10⁻⁹cm²/s at 25℃ vs. 10⁻¹⁰cm²/s of NCM).
The risk of post-failure disposal has been significantly reduced. The UL 9540A test indicates that the minimum spacing required for the thermal runaway propagation of lifepo4 is only 25mm (300mm for ternary batteries), and the water consumption for fire extinguishing has decreased by 82% (only 18L per kWh). The recycling process is equally safe. In GEM’s wet recycling process, there is no risk of combustion or explosion for lifepo4, while the probability of fire when ternary batteries break is as high as 2.3%. The source tracing of the 2023 Munich Airport cargo fire shows that the lifepo4 battery packs during transportation self-extinguished for only 42 seconds after the external fire source was removed (ternary batteries continued to burn for 28 minutes).