From Atomistic to Continuum Models of Interfaces in Lithium-Ion Batteries

锂离子电池界面从原子模型到连续体模型

• 批准号: 2119790
• 金额: --
• 依托单位: University of Bath
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2119790
• 关键词: Atomistic; Continuum; Models; Interfaces; Lithium

Modelling Li transport through Li-ion solid-state electrolytes is important for predicting their performances. These materials are often polycrystalline and have interfaces which significantly affect Li transport through the material. Therefore, it is vital to be able to model the effect of these grain batteries in order to fully explore potential new materials to be used in Li-ion batteries.The conventional method of modelling ionic transport across grain boundaries involves solving the Poisson-Boltzmann equation to find the equilibrium distri- bution of point defects (e.g. Li interstitials and vacancies) in a 1D continuum model. This approach assumes defects interact only through mean-field electro- statics, and corresponds to modelling the dilute limit of defect concentrations. Where here, structural defects include ion vacancies and dopant ions. In bat- tery materials, where defect concentrations can be high, interactions between these defects are more complex than the dilute limit mean-field description. To develop accurate models of the effects of grain boundaries on lithium-ion trans- port in these materials, it is therefore necessary to go beyond the dilute limit approximation.The project will involve investigating the thermodynamics of the problem in order to try to incorporate an additional concentration dependent term to the chemical potential. Attempts of producing a model that incorporates the inter- actions between structural defects in solid state electrolytes have been made, however these methods are not widely accepted at the present time, due to the lack of a method for calculating the key parameters for these models [1]. After the form of this additional term is determined, methods of calculating coefficients for such a term for individual grain boundaries and materials will be required. This will require investigating the fundamental thermodynamics of the problem further and determining which calculations are required in order to obtain the values of these parameters a priori. An alternative approach whereby chemical activities are used in order to minimise the free energy of the entire system will also be explored.Throughout the project, the existing code (written and developed by the pre- vious PhD candidate, Georgina Wellock) will be improved and altered to meet the requirements of the new thermodynamics of the problem or to improve efficiency.References[1] Mebane D. S. and De Souza R. A.; Energy Environ. Sci. 2015, 8, 2935-2940.

模拟锂离子固态电解质中锂的输运对于预测其性能具有重要意义。这些材料通常是多晶的，并且具有显著影响Li通过材料的传输的界面。因此，能够模拟这些颗粒电池的效应对于充分探索锂离子电池中潜在的新材料至关重要。模拟离子在晶界上传输的传统方法包括求解Poisson-Boltzmann方程，以在一维连续介质模型中找到点缺陷（例如Li晶体和空位）的平衡分布。这种方法假设缺陷仅通过平均场静电相互作用，并且对应于对缺陷浓度的稀释极限进行建模。在此，结构缺陷包括离子空位和掺杂剂离子。在电池材料中，缺陷浓度可能很高，这些缺陷之间的相互作用比稀释极限平均场描述更复杂。为了建立这些材料中晶界对锂离子输运影响的精确模型，因此有必要超越稀释极限近似。该项目将涉及研究问题的热力学，以便尝试将额外的浓度依赖项纳入化学势。已经尝试产生结合固态电解质中的结构缺陷之间的相互作用的模型，然而，由于缺乏用于计算这些模型的关键参数的方法，这些方法目前没有被广泛接受[1]。在确定了这一附加项的形式之后，将需要计算单个晶界和材料的这一项的系数的方法。这将需要进一步研究问题的基本热力学，并确定需要进行哪些计算，以便先验地获得这些参数的值。此外，还将探索另一种方法，即使用化学活性来最小化整个系统的自由能。在整个项目中，现有的代码（由先前的博士候选人Georgina Wellock编写和开发）将得到改进和修改，以满足问题的新热力学要求或提高效率。参考文献[1] Mebane D. S.和De Souza R.一、能源环境。Sci. 2015，8，2935-2940中。