In recent years, the lithium iron phosphate battery (LIB) has been widely used in energy storage and power transformation systems because of its advantages of good stability and high reliability. With the purpose of investigating the fire risk of LIB with large capacity, the thermal abuse test of the 228 A·h LIB is conducted through the fire test platform. The combustion process and heat generation law of the LIB were systematically studied, as well the fire characteristics of the battery with different state of charge (SOCs) were compared and analyzed. The result indicates that the combustion behavior of the battery can be roughly divided into several stages: the first jet flame, stable combustion, multiple jet lame and extinguishing stages. Further, the combustion behavior will further accelerate the temperature rise, and the internal short circuit for the battery with higher SOC will cause the rapid temperature rise. The battery with high SOC shows intense combustion behavior while the corresponding burning time will be shorter, which is specifically reflected in the higher temperature, heat release rate (HRR) and heat of combustion. In addition, the venting time is earlier than the voltage drops although the high temperature will result in the slight attenuation of the battery. The results in this work can provide theoretical and technical support for the safety design and fire prevention and control technology of lithium-ion battery systems in the fields of energy storage and transformer substation system.

Keywords： lithium-ion battery safety ; thermal runaway ; fire risk ; heat release rate ; state of charge