The differences in safety between lithium iron phosphate batteries and ternary lithium batteries mainly lie in multiple aspects, including material characteristics, thermal runaway risk, chemical stability, physical structure, protection design, and actual test performance. These differences directly determine their safety and reliability in different application scenarios.
From a material characteristics perspective, the cathode material of a lithium iron phosphate battery uses an olivine structure with extremely high Fe-O and P-O bond energies. This structure remains stable at high temperatures and is not prone to decomposition or oxygen release. In contrast, the cathode material of a ternary lithium battery (such as nickel-cobalt-manganese or nickel-cobalt-aluminum) has a layered structure. The higher the nickel content, the worse the high-temperature stability, and it begins to decompose at 200°C to 250°C. The released oxygen, upon contact with the electrolyte, easily triggers a violent oxidation reaction, leading to thermal runaway.
Thermal runaway risk is a core indicator for measuring battery safety. The thermal runaway initiation temperature of a lithium iron phosphate battery is as high as 500°C to 600°C. Even in the event of a short circuit or overheating, the battery management system has sufficient time to activate protective measures to prevent the spread of fire. Ternary lithium batteries have a thermal runaway temperature of only 200°C to 300°C. Under abnormal operating conditions, they are highly susceptible to triggering chain reactions, resulting in rapid thermal runaway propagation, difficulty in timely intervention by the battery management system (BMS), and significant challenges in fire control.
Regarding chemical stability, lithium iron phosphate batteries have lower electrode material activity, resulting in fewer side reactions with the electrolyte during charging and discharging, and less gas and heat accumulation. In contrast, ternary lithium batteries, due to their high nickel content and strong chemical activity, are prone to electrolyte decomposition and transition metal dissolution under high temperatures or overcharge conditions, leading to capacity decay and the generation of large amounts of heat and gas, increasing internal pressure and threatening battery safety.
Physical structural stability is also an advantage of lithium iron phosphate batteries. Their stable P-O bonds prevent lattice collapse even under high voltage or overcharge conditions, effectively reducing the risk of structural collapse. In contrast, ternary lithium batteries may undergo irreversible phase transitions in the positive electrode material during overcharge, releasing oxygen, while the electrolyte decomposes to produce flammable gases, leading to a sharp increase in internal pressure, causing bulging, fire, or even explosion.
In terms of protective design, lithium iron phosphate batteries have a greater advantage due to the inherent safety of their materials. During thermal runaway, they decompose slowly, releasing less heat and gas. Combined with designs such as directional venting and heat-insulating, flame-retardant materials, they can effectively suppress the spread of thermal runaway. Ternary lithium batteries, on the other hand, require more complex protective structures, such as enhanced battery pack strength and optimized thermal management systems, to compensate for the material's lack of stability.
Practical testing further validates the safety of lithium iron phosphate batteries. In nail penetration tests, ternary lithium batteries reach a peak temperature of 400°C to 600°C within approximately 10 seconds of being punctured, accompanied by a violent reaction; while the peak temperature of lithium iron phosphate batteries is only about 300°C, and it takes about 2 minutes to reach the peak, with a smoother reaction. Furthermore, lithium iron phosphate batteries exhibit higher tolerance in extreme tests such as overcharging, short circuits, and compression, and are less prone to combustion or explosion.
Lithium iron phosphate batteries, with their unique material system, excellent thermal stability, good chemical stability, and outstanding performance in practical tests, significantly outperform ternary lithium batteries in terms of safety. This characteristic makes them widely used in energy storage systems, household electricity, public transportation, and other fields with extremely high safety requirements, becoming an important force in promoting the safe development of the new energy industry.
