新能源汽车快速发展对动力电池的能量密度和安全性提出了更高的要求,刀片电池构型显著提高了动力电池体积利用率,弥补现有磷酸铁锂(Lithium iron phosphate batteries,LFP)电池材料体系能量密度低的缺点.通过搭建刀片电池1D电化学+3D热耦合模型,进行如下三方面的探究:第一,探究环境温度、充电倍率和换热系数三类变量对不同长度刀片电池的容量、内阻等电化学性能的影响,通过直流阻抗分解法(Directive current resistance,DCR)溯源影响性能的原因并定位了对应的物理化学过程;第二,探究上述三种变量对长/短刀电池温升过程和充电末期电池最大温差的影响,通过产热分解法(Heat production decomposition,HPD)揭示电池各部件的产热程度;第三,探究电池尺寸和换热系数对电池温度均一性的影响.结果表明:①刀片电池长短对电化学性能的影响源于集流体电阻,其电阻随电池长度增加而增大;刀片电池长短对热性能影响由电池产热、传热和表面散热三者共同决定,长度增加增大集流体产热,降低电池各向均温性能:②环境温度和换热系数对电化学性能和热性能影响较小,倍率增大使过电势增加造成电池容量下降;电极产热随倍率增加均有所增大.换热系数增强提高长度方向均温性能,L400,L800,L1200计算结果表明,控制电池长度和提高材料热导率亦有利于增强电池各向均温性能.
Comparative Study of Long/Short Blade Lithium-ion Batteries Based on Electrochemical-thermal Coupling Model
With the rapid development of battery electric vehicles,there has been a higher demand for increased energy density and safety in power batteries.The blade battery has significantly enhanced space utilization and addressed the issue of low energy density in conventional Lithium iron phosphate batteries(LFP).A model combining 1D electrochemical with a 3D thermal model is developed to investigate the following three aspects.Firstly,the effect of environmental temperature,charge rate,and heat transfer coefficient on the electrochemical properties of blade batteries with varying lengths is studied.Through the use of the DC impedance decomposition method(DCR),the primary physicochemical process that affects the electrochemical performance of the long/short blade battery is identified and traced.Secondly,the influence of the above three variables on temperature distribution and temperature rise process at the end of charging of the long/short blade batteries is investigated.Furthermore,a heat production decomposition(HPD)study is carried out to demonstrate the heat production of each component.Thirdly,the influence of battery size and heat transfer coefficient on battery temperature uniformity is explored,and several helpful proposals that benefit to temperature uniformity are suggested.The main results are as follows ① The effect of blade battery length on electrochemical performance is attributed to the different collector resistance,and the resistance increases as the length of the battery increases.Additionally,the thermal performance is affected by the length of the blade battery,which is dependent on internal heat production,conduction,and surface dissipation.According to the results,as the length increases,there will be a corresponding increase in heat production and temperature difference of the battery.② The three factors mentioned above displayed varying effects on electrochemical and thermal properties.On the one hand,the environmental temperature and heat transfer coefficient have little influence on electrochemical properties and heat production constitution.On the other hand,as the charging rate increases,the capacity declines noticeably because of the rise in overpotential,and heat production increases considerably both reversible heat and irreversible heat.Additionally,the temperature uniformity improves in length direction with the increasing heat transfer coefficient.Moreover,improving thermal conductivity is proven another effective way to temperature uniformity.According to the simulations,the L400 shows the best temperature consistency among the three different battery sizes,containing the L400,L800,and L1200.In summary,decreasing the length of the battery and improving the thermal conductivity of the material are effective methods to enhance temperature uniformity in each direction of the batteries.
blade batteriesmultiscale electrochemical-thermal coupling modeldirect current impedance decompositionheat production analysistemperature field design
万方数据
维普
