方壳磷酸铁锂锂离子电池热失控不同阶段产热产气机理OA

Lithium-ion batteries have become the most widely used energy storage medium due to their high energy density and long cycle life.However,these systems'intricate physicochemical processes introduce safety concerns related to thermal runaway,which cannot be disregarded.In order to enhance the safety and reliability of battery energy storage systems and establish early warning thresholds for energy storage safety monitoring systems,it is essential to investigate the behavioral characteristics of critical parameters.These parameters include temperature,voltage,gas evolution,and safety valve activation during battery thermal runaway.Furthermore,a mechanistic analysis of the various gases produced during this process is necessary.This study investigates the heat and gas generation characteristics of a 22 Ah lithium iron phosphate hard-case battery during thermal runaway under external heating and typical SOC conditions(0%,25%,50%,75%,100%).A multifunctional experimental platform for studying battery thermal runaway was established.The findings of the study indicate that as the battery's state of charge(SOC)increases from 25%to 100%,the onset time of thermal runaway advances by 47 s,29 s,and 207 s,respectively,with an escalating severity of runaway and a maximum temperature increase of 20.4℃,32.6℃,and 66.8℃,respectively.The temporal interval between the activation of the safety valve and the onset of battery thermal runaway gradually diminishes.Furthermore,the analysis of multiple gas samples collected during the experiment revealed an increase in total gas concentration from 3879.22 μL/L(25%SOC)to 39260.14 μL/L(100%SOC),representing a 912.06%increase.Concurrently,the proportion of H2 decreased as thermal runaway progressed,while the proportions of CO2,CO,and hydrocarbons increased.During the thermal runaway phase,as the SOC increased from 25%to 75%,a significant increase in the H2 proportion was observed,accompanied by a corresponding decrease in the CO2 proportion.Furthermore,batteries undergoing thermal runaway at elevated SOC levels exhibited a substantially greater production of combustible gases in comparison to those operating at lower SOC levels.This study offers a valuable reference for the safety design of energy storage systems and provides guidance for enhancing their safety and reliability.