电流密度对微米硅电极断裂行为的影响

张兴玉

doi:10.7498/aps.69.20200915

摘要

高容量硅电极在脱/嵌锂过程中所发生的大体积变形、断裂行为会引起严重的力学衰减, 并导致电极的电化学性能退化. 这严重制约着硅电极材料在商业锂离子电池中的应用. 目前, 硅电极断裂行为的一些细节还未被彻底研究清楚. 为了进一步研究微米硅电极的断裂行为, 本文利用光学显微镜观测了单晶硅电极的形貌演化, 分析了不同电流密度下硅电极的断裂行为, 并重点研究了在不同电流密度下裂纹形成时硅电极的相对嵌锂深度. 结果表明, 电流密度越大, 硅电极断裂越严重. 但是在三种不同电流密度下, 裂纹形成时硅电极相对嵌锂深度差异不大(18%—22%). 这可能是由于微米硅电极各向异性变形所引起的局部应力集中在主导着断裂行为. 这些实验结果与有限元模型预测结果一致. 结合裂纹形成时锂化硅和晶体硅的界面位置以及力学模型, 讨论了裂纹形成时锂化硅层内部应力分布状态. 这些结果深化了对硅电极断裂行为的认识, 并为硅电极的设计和合适的脱/嵌锂速率选择提供一定的指导.

关键词:

Abstract

The large volume change during lithiation/delithiation leads the silicon electrodes in lithium-ion batteries to severely degrade the mechanical performance and the silicon electrodes in lithium-ion batteries to further deteriorate electrochemical properties, which limits the commercial applications of silicon electrodes. After several year’s studies, the whole process of fracture for crystalline silicon anodes has been almost understood. However, the relationship between fracture behaviors and the lithiation depth has not been sufficiently studied. In this work, the in-situ observations of morphological changes (e.g., volume expansion, crack initiation, propagation, and debonding of lithiated silicon) during lithiation at the different current densities are reported for silicon micropillars fabricated by standard photolithography and a deep reactive ion etching process. Also, this work focuses on the relative depth of lithiation of silicon electrodes at the moment of crack initiation, which is one of the crucial parameters representing the utilization of active materials with no crack. The results show that the silicon micropillars are broken faster (i.e., crack initiation and pulverization in a shorter lithiation time) and more seriously at a large current density, exhibiting more prominent symmetry of morphology. However, the relative depths of lithiation at the different current densities have just a slight difference (i.e., 18%–22%), when cracks are initiated. Here in this work, a silicon micropillar fracture is confirmed by the optical observation, while the relative depth of lithiation is calculated according to the capacity data recorded by the charge/discharge battery test system. The small fluctuation of the relative depth of lithiation with the large wave of current density can be ascribed to the dominant role of local stress concentration caused by anisotropic volume change in fracture behavior, which is validated by the results obtained by the finite element model (i.e., the depth of lithiation predicted by numerical simulations is ～ 22.6%). Therefore, the relationship between fracture behavior and the lithiation kinetics is established, providing an effective strategy for estimating the utilization of active materials under crack-free operation. With the help of the theoretical mechanics model considering both volume change and concurrent movement of reaction front, the stress state in the lithiated silicon at the moment of crack initiation is given, showing the tensile hoop stress near the reaction front. Consequently, these results suggest that the fracture behaviors depend on the current density, but the position of crack initiation (i.e., the depth of lithiation with no crack) is unrelated to current density (at least in a relatively broad range) for large micron-sized crystalline silicon electrodes, thereby shedding light on the fracture mechanisms and the design of alloy anodes (e.g., size and structure) in lithium-ion batteries.

Keywords:

作者及机构信息

张兴玉

南京航空航天大学航空学院, 航空航天交叉研究院, 机械结构力学及控制国家重点实验室, 南京　210016

通信作者: 张兴玉, xingyuzhang@nuaa.edu.cn

基金项目: 国家自然科学基金(批准号: 11902149)、江苏省自然科学基金(批准号: BK20190380)和江苏高校优势学科建设工程资助的课题

Authors and contacts

Zhang Xing-Yu

State Key Laboratory of Mechanics and Control of Mechanical Structures, Interdisciplinary Research Institute of Aeronautics and Astronautics, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Corresponding author: Zhang Xing-Yu, xingyuzhang@nuaa.edu.cn

Funds: Project supported by the National Natural Science Foundation of China (Grant No. 11902149), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20190380), and the Priority Academic Program Development of Higher Education Institutions of Jiangsu Province, China.

文章全文

参考文献

[1]	Kim U H, Ryu H H, Kim J H, Mücke R, Kaghazchi P, Yoon C S, Sun Y K 2019 Adv. Energy Mater. 9 1803902 Google Scholar
[2]	Uxa D, Jerliu B, Hüger E, Dörrer L, Horisberger M, Stahn J, Schmidt H 2019 J. Phys. Chem. C 123 22027 Google Scholar
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施引文献

图 1 在锂化过程中(111)单晶硅电极的衰减机制

Fig. 1. Degradation mechanism of (111) single-crystalline silicon electrodes during lithiation.

下载: 全尺寸图片幻灯片

图 2 (a) 自制电池装置示意图; (b) 光学观测平台

Fig. 2. (a) Schematic diagram of a home-made battery cell; (b) experimental platform for the optical observation.

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图 3 硅柱典型形貌FE-SEM图, 标尺为10 μm

Fig. 3. Typical FE-SEM images of a micron-sized silicon pillar. Here, the scale bars are 10 μm.

下载: 全尺寸图片幻灯片

图 4 在以(a)−(d) 72.9 μA/cm²^[10]、(e)−(h) 193.3 μA/cm²和(i)−(l) 465.3 μA/cm²的电流密度嵌锂过程中硅电极截面的形貌演化, 标尺为5 μm

Fig. 4. Morphological changes during lithiation for silicon electrodes at (a)−(d) 72.9 μA/cm²^[10], (e)−(h) 193.3 μA/cm² and (i)−(l) 465.3 μA/cm². Here, the scale bars are 5 μm.

下载: 全尺寸图片幻灯片

图 5 不同电流密度下硅电极裂纹形成时对应的锂化时间和电压, 标尺为5 μm

Fig. 5. Profile of voltage and lithiation time for crack initiation of silicon electrodes at different current density. Here, the scale bars are 5 μm.

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图 6 (a) 不同电流密度下硅电极起裂时相对嵌锂深度; (b) 有限元模拟所得的应力云图; (c) 不同相边界移动速度下不同r/R (红色箭头标示)处径向应力分布

Fig. 6. (a) Relative lithiation depth for crack initiation of silicon electrodes at different current density; (b) hoop stress contour of Si micropillars obtained by finite element method; (c) hoop stress along the radial direction at different moving velocity of phase interfaces.

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图 7 硅基底锂化后形貌, 标尺为500 nm

Fig. 7. Morphology of the silicon substrate after lithiation. Here, the scale bar is 500 nm.

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图 8 (a) 锂化前硅柱圆截面示意图; (b) 锂化过程中硅柱圆界面示意图

Fig. 8. Cross-section of a silicon micropillar: (a) Before lithiation; (b) during lithiation.

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图 9 裂纹形成时硅电极在全锂化区域的受力示意图

Fig. 9. Schematic diagram of stress state at the moment of crack initiation.

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map

[1]	Kim U H, Ryu H H, Kim J H, Mücke R, Kaghazchi P, Yoon C S, Sun Y K 2019 Adv. Energy Mater. 9 1803902 Google Scholar
[2]	Uxa D, Jerliu B, Hüger E, Dörrer L, Horisberger M, Stahn J, Schmidt H 2019 J. Phys. Chem. C 123 22027 Google Scholar
[3]	Ryu J, Bok T, Kim S, Park S 2018 ChemNanoMat 4 319 Google Scholar
[4]	Mukanova A, Jetybayeva A, Myung S, Kim S, Bakenov Z 2018 Mater. Today Energy 9 49 Google Scholar
[5]	Li P, Zhao G, Zheng X, Xu X, Yao C, Sun W, Dou S X 2018 Energy Storage Mater. 15 422 Google Scholar
[6]	Franco Gonzalez A, Yang N, Liu R 2017 J. Phys. Chem. C 121 27775 Google Scholar
[7]	Zhang S 2017 npj Comput. Mater. 3 7 Google Scholar
[8]	Jin Y, Zhu B, Lu Z, Liu N, Zhu J 2017 Adv. Energy Mater. 7 1700715 Google Scholar
[9]	He Y, Yu X, Li G, Wang R, Li H, Wang Y, Gao H, Huang X 2012 J. Power Sources 216 131 Google Scholar
[10]	Zhang X, Song W, Liu Z, Chen H, Li T, Wei Y, Fang D 2017 J. Mater. Chem. A 5 12793 Google Scholar
[11]	Shi F, Song Z, Ross P N, Somorjai G A, Ritchie R O, Komvopoulos K 2016 Nat. Commun. 7 11886 Google Scholar
[12]	Lee S W, Lee H, Ryu I, Nix W D, Gao H, Cui Y 2015 Nat. Commun. 6 7533 Google Scholar
[13]	Lee S W, McDowell M T, Berla L A, Nix W D, Cui Y 2012 Proc. Natl. Acad. Sci. U.S.A. 109 4080 Google Scholar
[14]	Pharr M, Zhao K, Wang X, Suo Z, Vlassak J J 2012 Nano Lett. 12 5039 Google Scholar
[15]	McDowell M T, Ryu I, Lee S W, Wang C, Nix W D, Cui Y 2012 Adv. Mater. 24 6034 Google Scholar
[16]	Ryu I, Choi J W, Cui Y, Nix W D 2011 J. Mech. Phys. Solids 59 1717 Google Scholar
[17]	Lee S W, McDowell M T, Choi J W, Cui Y 2011 Nano Lett. 11 3034 Google Scholar
[18]	Goldman J L, Long B R, Gewirth A A, Nuzzo R G 2011 Adv. Funct. Mater. 21 2412 Google Scholar
[19]	Jia Z, Li T 2015 J. Power Sources 275 866 Google Scholar
[20]	Zhao K, Pharr M, Wan Q, Wang W L, Kaxiras E, Vlassak J J, Suo Z 2012 J. Electrochem. Soc. 159 A238 Google Scholar
[21]	Cui Z, Gao F, Qu J 2012 J. Mech. Phys. Solids 60 1280 Google Scholar
[22]	Di Leo C V, Rejovitzky E, Anand L 2015 Int. J. Solids Struct. 67-68 283 Google Scholar
[23]	孙凤楠, 冯露, 卜家贺, 张静, 李林安, 王世斌 2019 68 120201 Google Scholar Sun F N, Feng L, Bu J H, Zhang J, Li L A, Wang S B 2019 Acta Phys. Sin. 68 120201 Google Scholar
[24]	彭劼扬, 王家海, 沈斌, 张静, 李浩亮, 孙昊明 2019 68 090202 Google Scholar Peng J Y, Wang J H, Shen B, Zhang J, Li H L, Sun H M 2019 Acta Phys. Sin. 68 090202 Google Scholar
[25]	An Y, Wood B C, Ye J, Chiang Y, Wang Y M, Tang M, Jiang H 2015 Phys. Chem. Chem. Phys. 17 17718 Google Scholar
[26]	Ryu I, Lee S W, Gao H, Cui Y, Nix W D 2014 J. Power Sources 255 274 Google Scholar
[27]	Ye J C, An Y H, Heo T W, Biener M M, Nikolic R J, Tang M, Jiang H, Wang Y M 2014 J. Power Sources 248 447 Google Scholar
[28]	Yang H, Fan F, Liang W, Guo X, Zhu T, Zhang S 2014 J. Mech. Phys. Solids 70 349 Google Scholar
[29]	Tian R, Park S, King P J, Cunningham G, Coelho J, Nicolosi V, Coleman J N 2019 Nat. Commun. 10 1933 Google Scholar
[30]	Pharr M, Suo Z, Vlassak J J 2014 J. Power Sources 270 569 Google Scholar
[31]	Soni S K, Sheldon B W, Xiao X, Bower A F, Verbrugge M W 2012 J. Electrochem. Soc. 159 A1520 Google Scholar
[32]	Boles S T, Thompson C V, Kraft O, Mönig R 2013 Appl. Phys. Lett. 103 263906 Google Scholar
[33]	Berla L A, Lee S W, Cui Y, Nix W D 2015 J. Power Sources 273 41 Google Scholar
[34]	Jia Z, Liu W K 2016 Appl. Phys. Lett. 109 163903 Google Scholar

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电流密度对微米硅电极断裂行为的影响