负极补锂锂化裕度对电芯性能的影响及机理研究

Research on the impact and mechanism of the lithium replenishment degree of anode prelithiation on the performance of lithium-ion batteries

本工作以LiFePO_(4)为正极材料、以压延方式将金属锂片压延至石墨表面所得的Li/石墨为负极材料制作了软包锂离子电池,通过不同金属锂片的厚度设计了4种不同的软包电芯,研究了压延不同锂片厚度对电芯容量、首效、倍率、高低温放电、存储、循环寿命的影响。实验结果表明,相比于2.5μm、7.0μm金属锂片,4.0μm、5.0μm锂片锂化的石墨负极表现出更加优异的容量及循环性能,循环600周后,容量保持率均大于100%。其中,2.5μm压延的锂片厚度太薄库仑效率过低;7.0μm压延的锂片厚度太厚负极出现明显析锂,容量衰减过快。基于此本工作提出锂化裕度(DLRP)概念及其理论计算方法,用于评估压延预锂化法的最佳补锂范围。本研究有助于推动预锂化石墨负极的应用,为高比能量锂离子电池的研发提供实验依据。

In this work,a pouch-type lithium-ion battery was fabricated using LiFePO_(4)as the cathode.Moreover,Li/graphite obtained by calendering a lithium metal sheet onto the graphite surface was used as the anode material.Four pouch lithium-ion battery kinds were designed with different thicknesses of lithium metal sheet.The influences of different thicknesses of calendered lithium on cell capacity,first-cycle coulomb efficiency,rate discharge,high-and low-temperature discharge,storage,and cyclic life were investigated.The experimental results showed that compared with lithium metal sheets with 2.5 and 7.0μm thicknesses,the graphite anodes lithiated with 4.0 and 5.0μm lithium sheets showed better capacity and cyclic performance,and the capacity retention rate was greater than 100%after 600 cycles.Among them,the lithium sheet thickness of 2.5μm was too thin,leading to a low coulombic efficiency;the lithium sheet thickness of 7.0μm was too thick,and the anode had obvious lithium precipitation,and the capacity faded too quickly.Based on this work,the degree of lithium replenishment of anode prelithiation(DLRP)and its theoretical calculation method are proposed to evaluate the optimal prelithiation range of calendering pre-lithiation method.This study will help promote the application of prelithiated graphite anodes and provide an experimental basis for developing high-specific energy lithium-ion batteries.