锂离子电池电极结构参数对单体能量与功率的影响

Impact of electrode structure parameters on energy and power for lithium-ion cells

以模型化仿真技术为基础的电池正向设计方法可替代大量制样、实验选优的试错方法,从而显著缩短产品研发周期、降低物料与能源的成本消耗、提高产品创新能力。本文基于热-电化学耦合的三维跨尺度模型,在单体尺寸与容量不变的约束条件下探究了电极结构参数如电极涂层厚度、孔隙率等对单体主要性能参数如功率、能量、单位质量与体积比功率、单位质量与体积比能量的影响,并基于过电压分解方法揭示了其影响机理。结果表明,电池电极结构参数对电池多类性能存在不同的影响趋势,应重点权衡以下设计关系:第一,厚涂、少孔的电极结构提高了电池能量,但由于增大了液相传输阻力,使得电池功率降低;第二,薄涂、多孔的电极结构提高了电池功率,但由于可能增加电池总质量,反而诱发单位质量比功率下降;第三,薄涂、多孔设计方案对于功率性能改善的效用逐步递减,到达一定临界值后,其对液相传输的改善效用几乎消失,不再是设计改进的主要方向。

A simulation-based design method for batteries can replace the trial-and-error method,which is based on the repeated sampling and design of experiments,significantly shortening the product development cycle,reducing the cost of materials and energy,and improving the product innovation ability.In this work,the influence of the electrode structure parameters on the power,energy,specific power,and specific energy is investigated on the basis of a three-dimensional thermo-electrochemical coupling model.Further,the mechanism is revealed using the overpotential decomposition method with constant cell size and capacity.The results indicate that the electrode structure parameters have different effects on various performances.The following design relations should be considered:First,the electrode structure with considerable thickness and small porosity improves the battery energy but obstructs liquid phase transportation and affects the power.Conversely,the electrode structure with a small thickness and high porosity improves power performance but may increase the total mass of the battery and decrease the specific power.Finally,the effect of thin coating and porous design scheme on the improvement of power performance decreases gradually,and after a certain threshold,reducing the thickness and increasing the porosity will not improve the liquid phase transportation anymore.Other restrictions should be considered in this situation.