Continuum and atomistic scale computational mechanics for structures with small length scales. With on-demand call to molecular dynamics simulations and scale up to continuum level constitute models, where predictions can be made for laboratory accessible time and length scales.

Material systems including: crystal plasticity in singly/poly crystalline metals, interfacial/grain-boundary mechanics in nanostructured materials, amorphous solids, nanowires, soft materials.

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电极材料的力-电-化耦合的本构模型研究新进展

       硅基、锡基等电极材料由于其高的电容量密度成为锂离子电池的理想电极材料。但力学上这一类材料在充放电过程中往往伴随着大的体积变形,导致高的应力状态,并引发电极结构的断裂破坏等问题,严重影响到锂离子电池的使用寿命。 

  为了合理地设计电极结构,规避结构可能产生的力学破坏问题,需要建立电极材料在充放电过程中的力-电-化学耦合本构关系。通常的做法是通过原位的测量实验及Stoney公式获得的电极材料充放电过程中的应力演化。然而该方法必须依赖于薄膜的厚度远小于基底的厚度、薄膜的厚度变化在变形过程可以忽略不计、薄膜与基底之间粘接良好等三个假设,时间高性能电池通常难以满足这些条件。 

  为了解决这个问题,力学所非线性力学国家重点实验室的科研团队基于力-电-化学耦合理论,发展了一套有限元计算方法,可准确刻画电极材料在充放电过程中的弹塑性大变形及内在的应力演化。并采用该方法进行有限元模拟,阐述了由电极薄膜的弹塑性大变形引起的Stoney公式的误差分析,电极薄膜的大变形、弹塑性本构关系和界面材料性质对应力-充放电状态曲线的影响,以及电极材料参数与应力-充放电状态曲线特征之间的对应关系。该工作为研究电极材料在充放电过程中的力-电-化学耦合本构关系提供了帮助。 

  相关的研究成果已发表于国际权威期刊Journal of power sources(Wen,J.,Wei,Y.,Cheng,Y.T.,2018.Examining the validity of Stoney-equation for in-situ stress measurements in thin film electrodes using a large-deformation finite-element procedure. J.Power Sources,387,126-134.)和Journal of the Mechanics and Physics of Solids(Wen,J.,Wei,Y.,Cheng,Y.T.,2018.Stress evolution in elastic-plastic electrodes during electrochemical processes: A numerical method and its applications.J.Mech.Phys.Solids,116,403-415.)。该研究获得了国家自然科学基金委,中科院B类先导项目,以及美国国家科学基金的支持。 

 

图:典型层状电池结构及其变形。(a)电极薄膜-粘接剂-基底结构;(b)数值模型与实验结果的对照,展示充放电过程时电极膜中的应力变化;(c)电极材料的弹塑性与界面破坏情况下的薄膜内部剪切应力分布图。

Recent Publications

[1] Yanglizhi Li, Luzhao Sun, Zhenghua Chang, ..., Yujie Wei*, Hailin Peng*, Li Lin*, Zhongfan Liu*. Large Single‐Crystal Cu Foils with High‐Index Facets by Strain‐Engineered Anomalous Grain Growth. Advanced Materials, 2020, 32, 2002034.
[2] Shenyou Peng, Yujie Wei*, Huajian Gao*. Nanoscale precipitates as sustainable dislocation sources for enhanced ductility and high strength. PNAS, 2020, 117(10).
[3] Zhenghua Chang, Ronggui Yang*, Yujie Wei*. The linear-dependence of adhesion strength and adhesion range on temperature in soft membranes. Journal of the Mechanics and Physics of Solids, 2019, 132: 103697.
[4] Shenyou Peng, Yujie Wei*, Zhaohui jin,Wei Yang. Supersonic Screw Dislocations Gliding at the Shear Wave Speed. Physical Review Letters, 2019, 122(4).
[5] Zeng XG,Yujie Wei*. The effective fracture strength and fracture toughness of solids with energy dissipation confined to localized strips. International Journal of Plasticity,2019,120:47-63.
[6] Chengqi Sun, Qingyuan Song, Lingling Zhou, Jialong Liu, Yao Wang, Xiaolei Wu, Yujie Wei*. The formation of discontinuous gradient regimes during crack initiation in high strength steels under very high cycle fatigue. International Journal of Fatigue, 2019, 124: 483-492.
[7] Chao Wang, Jici Wen, Fei Luo, Baogang Quan, Hong Li, Yujie Wei*, Changzhi Gu, Junjie Li. Anisotropic expansion and size-dependent fracture of silicon nanotubes during lithiation. Journal of Materials Chemistry A, 2019.
[8] Yujie Wei*, Ronggui Yang*. Nanomechanics of graphene. National Science Review, Volume 6, Issue 2, March 2019, Pages 324–348.
[9] Xiaokun Gu, Yujie Wei*, Xiaobo Yin, Baowen Li*, Ronggui Yang*. Colloquium: Phononic thermal properties of two-dimensional materials. Reviews of Modern Physics, 2018, 90(4): 041002.
[10] Yue Qi, Yunyu Wang, Zhenqian Pang, ..., Yujie Wei*, Jinmin Li*, Zhongfan Liu*. Fast Growth of strain-free AlN on graphene-buffered sapphire. Journal of the American Chemical Society, 2018, 140(38): 11935-11941.

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