电化-力耦合作用下硅基电极微结构演化原位实验与多孔电极理论模型研究

Next-generation silicon-based electrodes with the extensive commercial prospect and high energy density, suffer from prominent electrochemo-mechanical coupled degradation, which leads to fast capacity loss and short cycle life. Based on the electronic imaging and X-ray computed tomography methods, this project will characterize the microstructure evolution, and discover the electrochemo-mechanical coupled degradation mechanisms for silicon-based electrodes with different composition ratios. The electrochemo-mechanical porous electrode theory of silicon-based negative electrodes will be established that takes into account the porosity variation and volume change of electrodes, by which the electrochemo-mechanical coupled behaviors will be predicted for silicon-based Li-ion batteries. Based on the coupled mechanisms between electrode deformation and electrochemical performance and combined with the developed electrochemo-mechanical porous electrode model, the graded porosity design for silicon-based electrodes will be proposed to migrate the electrochemo-mechanical degradation. This project will provide the feasible characterization methods, precise prediction models and novel structure design method for the electrochemo-mechanical degradation of silicon-based electrodes, and put forth efforts to solve the key issues of silicon-based electrodes to promote the sustainable development of Li-ion battery industry, and facilitate the convergence and development of knowledge systems of this novel electrochemo-mechanical interdisciplinary science.

具有商业应用前景、高能量密度的下一代硅基电极面临着突出的电化-力耦合性能衰减问题，这导致硅基锂离子电池较快的容量损失和较短的循环寿命。本项目拟利用电子成像技术和X射线断层扫描技术表征不同组分比例硅基电极的微观结构演化，揭示硅基电极电化-力衰减机理。拟建立考虑孔隙率变化及体积变形影响的硅基电极电化-力耦合多孔电极理论模型，预测硅基锂离子电池的电化-力耦合行为。基于电极变形与电化学性能耦合机理，并结合所建立的电化-力耦合多孔电极理论模型，提出基于孔隙率的硅基电极梯度结构设计方法，缓解硅基电极电化-力耦合衰减行为。本项目的研究将为硅基电极的电化-力耦合衰减行为提供可行的表征方法、准确的预测模型和新颖的结构设计方法，着力解决阻碍硅基电极应用的关键性基础问题，推动锂离子电池产业的持续发展；同时促进这一新兴的电化学-力学交叉方向知识体系进一步融通发展。

作为最具商业化前景的高容量锂离子电池负极材料之一，硅基电极面临着诸如容量衰减、循环寿命较差等挑战，这些问题都和其在充放电过程中发生的电化-力耦合衰减过程紧密相关。本项目利用在位光学表征、电子成像技术等表征了有无约束情况下硅电极的变形、破坏行为及硅基电池厚度演化，确立了起裂行为和嵌锂深度的对应关系，揭示了非均匀外部条件引起的非均匀损伤行为，发现外部约束可以缓解硅电极的断裂行为；建立了考虑外部约束和表面应力影响的单颗粒模型，发现外部约束施加的压应力阻碍了锂离子的扩散，使得锂离子更多的集聚在纳米电极颗粒的表面，引起电极容量降低；发展了考虑变形影响的多孔硅基电极模型，基于最大变形和最小孔隙率限制给出了孔隙率和硅组分含量的设计空间，并探讨了硅基电极结构变化对评估硅基电极电化学性能的影响。本项目的顺利开展，加深了对硅基电极电化-力耦合衰减机制的认识，促进了硅基电极的开发和性能预测，推动了高容量锂离子电池的发展。