Research On Overcharging Thermal Runaway Characteristic Of Lithium Iron Phosphate Energy Storage Battery

Lithium-iron phosphate battery has been widely used in grid energy storage field due to its advantages such as long cycle life and economy.In fact,MW class Lithium-iron phosphate energy storage power station is composed of battery clusters.The battery clusters are multiple battery modules in series and parallel,and the battery modules are multiple battery cells in series and parallel.The overcharging runaway of tightly packed energy storage batteries has become a serious threat to the safety accidents of the stations,because it has the characteristics of inherent heat generation.At present,the research object of thermal runaway of lithium-ion battery is mainly focused on the single lithium-ion battery,and the thermal runaway process and thermal diffusion law are rarely studied from the perspective of battery modules.Based on the experiment and simulation,this paper studies the phenomenon,temperature distribution and thermal diffusion law of overcharging runaway of lithium iron phosphate monomer batteries and battery modules.Then it further explores the characteristics of overcharging runaway of lithium iron phosphate monomer batteries and battery modules,and the protective measures of overcharging runaway are put forward in this paper.Firstly,we build an experimental platform for thermal runaway of the lithium iron phosphate energy storage battery and battery modules.The thermal runaway phenomenon and temperature change rule of the single battery and battery modules are studied under two different overcharging ratios of 0.4C and 0.5C.The experimental results show that when the overcharging ratios are 0.4C and 0.5C,the battery will bulge and produce gas.The higher the charging ratio,the earlier the time of thermal runaway.When the battery module is overcharged at 0.4C rate,it produces a large amount of flue gas.The maximum surface temperature of the module is 211~oC.When the battery module is overcharged at 0.5C,the combustion and explosion phenomenon will occur as soon as a large amount of flue gas generate.The maximum surface temperature of the module reaches 530~oC.Secondly,on the basis of experiment according to the lithium iron phosphate battery thermogenesis mechanism of thermal runaway reaction with Arrhenius formula,the paper establishes the lithium iron phosphate monomer battery overcharge thermal runaway simulation model.The simulation results show that the model can accurately predict the internal temperature distribution and the change of active material content of the battery.In addition,the thermal runaway of the surrounding cells will not be triggered when the overcharged thermal runaway occurs in the center of the module,from the study of the thermal runaway diffusion law of the single cell.Finally,the paper establishes the overcharging thermal field model of the lithium iron phosphate battery module.Then it studies the temperature characteristics at different overcharging rates and the thermal runaway diffusion law.The simulation results show that the thermal runaway of the surrounding battery modules will not be triggered when the battery module is overcharged at 0.4C rate.However,it will trigger the thermal runaway of the battery modules step by step upward when the overcharging rate is 0.5C.In addition,the design of heat diffusion protection with heat insulation plate is proposed,based on the overcharge of the battery module runaway diffusion phenomenon.The simulation results show that the protective effect of the heat insulation board is directly related to the thermal conductivity of the material.When the thermal conductivity of the heat insulation board is low enough,the thermal runaway diffusion of the module can be avoided.