钠离子电池红磷阳极的电化学-力学耦合理论和计算研究

Driven by the earth abundance and low cost of sodium, sodium-ion battery technology has the potential to become the next generation of environmentally-benign electrochemical energy storage system for grid-level applications. Red phosphorus represents most promising anode materials for sodium-ion batteries in view of its low cost and high theoretical capacity. This project aims at developing a coupled electro-chemo-mechanics model to investigate the stress generation and catastrophic mechanical failure during charging/discharging process of red phosphorus anodes in sodium-ion batteries. Specifically, Coupling among mechanical stresses, applied voltage and chemical reactions (sodiation and desodiation) will be considered in deriving the mathematical framework at continuum scale. Important model parameters, such as critical sodium concentration that initiates sodiation and mechanical properties of red phosphorus upon cycling, will be determined via atomic simulation at the nanoscale. Once developed, the model will be implemented into numerical method such as FEA commercial package ABAQUS to simulate the evolution of stresses and deformation of red phosphorus anodes in sodium-ion batteries during charging/discharging cycles. Possible mechanical failure modes such as fracture associated with large deformation during charging and discharging will be analyzed. Emerging from the analysis will be effective designs to enhance the mechanical integrity of the anode by tuning its geometry, composition, and structure. The results of the study will provide quantitative guidance for the material selection and structural optimization of red phosphorus anodes, which sheds lights on designs of sodium-ion batteries of improved capacity and cycling performance.

钠离子电池是未来电网级大规模储能技术最具潜力的发展方向。本项目将通过多场耦合建模方法建立红磷阳极充放电过程中的电化学-力学耦合的理论模型，并利用该模型改进红磷阳极的结构设计，提高钠离子电池的电容量和循环表现。在理论建模方面，分析红磷阳极充放电过程中机械应力、外加电压以及化学反应过程等因素之间的相互影响，基于连续介质力学理论建立描述红磷阳极充放电（钠化与去钠化）过程的电化学-力学耦合的本构模型。在计算仿真方面，利用第一性原理从原子尺度上计算本构模型中重要的材料参数，包括钠与磷反应所需要的钠离子浓度以及钠磷合金相的机械性能等；针对建立的本构模型开发相应的有限差分或有限元计算程序，求解红磷阳极在充放电过程中的变形与应力场，分析具有不同形状或结构的红磷阳极的机械失效模式。最终基于理论建模与计算仿真的结果，提出改进红磷阳极性能的设计方案，提高钠离子电池的电容量与循环表现。

在本项目（项目号：11802269）的直接资助下，项目负责人贾铮及课题组围绕钠离子电池红磷阳极充放电过程的大变形行为、电化学-力学耦合过程以及基于红磷的钠离子电池阳极结构力学设计开展理论建模和数值模拟工作。2018 至2021 年，已在《Journal of the Mechanics and Physics of Solids》、《Nature Communications》、《Extreme Mechanics Letters》、《Science China Technological Sciences》、《Journal of Power Sources》、《Energy Storage Materials》等期刊上发表SCI 论文6 篇（均已标注本项目资助）。负责人贾铮因发表在《Extreme Mechanics Letters》上的工作获得2019年度Extreme Mechanics Letters (EML) Young Investigator Award。. 项目期间项目负责人贾铮在包括中国力学大会2019、固体力学青年沙龙、第九届全国固体力学青年学者学术研讨会、中国力学学会第111次青年力学沙龙等学术会议做学术报告4 次。. 对照项目申请书的预期研究成果，项目完成情况如下：. 1..建立红磷阳极在充放电过程中的电化学-力学耦合的本构模型，准确预测红磷阳极的应力与变形场以及相应机械失效模式；该研究成果可用于提高钠离子电池性能。. 已完成，详见研究工作主要进展。. 2..力争在国际上有影响力的学术期刊发表高水平论文3-5篇，参加2-3次国际会议如IUTAM、SES等并作学术交流。. 已完成，详见研究成果目录。. 3..培养储能材料力学方向的博士研究生2名，硕士研究生一名。形成一支具有储能材料力学研究经验的科研队伍。. 已完成，详见人才培养情况。