基于原位参比的氧化亚硅--石墨复合负极循环衰减机制  

Degradation mechanisms of SiO_(x)-C composite anode based on in situ reference electrode

作　　者：宋缙华 张兴浩 丰震河[1] 程广玉[1] 顾洪汇[1] 顾海涛[1] 王可[1] SONG Jinhua;ZHANG Xinghao;FENG Zhenhe;CHENG Guangyu;GU Honghui;GU Haitao;WANG Ke(Shanghai Institute of Space Power Sources,Shanghai 200245,China)

机构地区：[1]上海空间电源研究所,上海200245

出　　处：《储能科学与技术》2023年第4期1059-1065,共7页Energy Storage Science and Technology

摘　　要：为了研究氧化亚硅和石墨在复合应用时的循环衰减机制,本工作通过在循环过程中增加小电流可逆容量标定,消除了电压极化对衰减行为的影响。通过在软包装电池内部预先埋入参比电极,对比不同循环次数时正极和负极的电化学特征变化,利用负极微分曲线解析氧化亚硅和石墨的去锂化容量演变过程和衰减程度。同时,结合交流阻抗谱(EIS)、扫描电子显微技术(SEM)、元素能谱(EDS)和等离子体发射光谱(ICP)等测试。结果表明,造成电池循环衰减的主要原因是活性锂损失和氧化亚硅衰减,两者造成的容量损失分别为0.45 Ah和0.36 Ah。负极衰减速率明显快于正极,循环600次后,负极中石墨和氧化亚硅的衰减程度分别为2.2%和30.3%。电池在循环过程中产生了新的界面阻抗,所有动力学阻抗参数呈逐渐增大的趋势。拆解电池发现,循环后负极发生了严重的体积膨胀和副反应,导致锂损失在负极并失活,引起界面阻抗的增长和电池容量的衰减。本研究可以无损定量识别氧化亚硅和石墨在循环过程中的衰减程度,为含硅复合负极的工程化应用提供了研究基础。In this study,a capacity calibration method at low current was introduced during cycling to eliminate the influence of polarization voltage and to better understand the degradation mechanisms of the composites containing silicon oxide and graphite.The electrochemical characteristics of the cathode and the anode at different cycles were compared by pre-embedding a reference electrode in the pouch battery.The evolution process and attenuation degree of silicon oxide and graphite were analyzed using the negative differential curves.In addition,AC impedance spectroscopy,scanning electron microscopy,energy dispersive spectroscopy,and plasma emission spectroscopy were discussed.The results demonstrate that capacity attenuation was caused due to the loss of active lithium and the decay of silicon oxide,and the resultant capacity loss was 0.45 Ah and 0.36 Ah,respectively.Moreover,the degradation rate of the anode was found to be faster than that of the cathode,while the attenuation of the graphite and the silicon oxide in the negative electrode was 2.2%and 30.3%,respectively,after 600 cycles.During cycling,a new interface impedance was generated,and all kinetic impedance parameters increased gradually.Serious volume expansion and side reactions occurred in the aged anode on disassembling the cycled battery,leading to lithium inactivation in the anode,thickening of the solid electrolyte interphase layer,and capacity degradation.The quantitative evaluation of the decay degree of silicon oxide and graphite during cycling is helpful for engineering applications of silicon-graphite composite electrode.

关 键 词：氧化亚硅 参比电极 循环衰减 锂离子电池 

分 类 号：TM912.9[电气工程—电力电子与电力传动]