Multiscale modelling of mechanical deterioration in lithium-ion batteries

寻找廉价而有效的方法来储存清洁电能是实现低碳经济道路上必须克服的关键障碍之一。其中一个重要组成部分是开发用于电动汽车的具有商业吸引力的电池组;目前这些汽车总成本的一半左右是电池。最近的立法禁止在未来几十年内在世界大部分地区销售内燃机，这意味着必须紧急实现这一目标。锂离子电池是目前满足这些需求的最佳候选人。它们都是能量和功率密集的，只有在不使用时才会慢慢失去电荷。虽然它们的寿命在相对温和的应用中已经是合理的，例如它们可以使用超过1000次循环的消费电子产品，但它们在电动汽车中常见的滥用高电流状态中受到相当快的退化的困扰。电池寿命缩短直接导致消费者成本上涨，因此延长电池的可循环性对于实现锂离子技术的健康市场至关重要。电池退化的主要原因是内部电极微结构在使用时因组成材料的膨胀/收缩而粉碎。这种机械降解又可以加速电池的化学降解。为了解决这一问题，必须确定新的材料和架构，以减轻这种损害的来源。通过一个连贯的建模框架，可以有效地指导对改进设计的搜索，该框架可用于（i）对新设计进行基准测试，而无需构建和测试它们，以及（ii）为制造商确定目标的最佳配置。这种工具的开发是基于克服一些重大的数学挑战，这些数学挑战与解决描述各种不同材料（液体电解质和几种不同固体）在非常不同的相关长度尺度（从微米到厘米）上的相互作用的精确模型方程有关。该工作计划将通过应用系统的数学方法来克服这些挑战，并提供一种工具来解决准确建模电池内部组件在其寿命期间所承受的损坏演变的任务。这将大大加快更强大电池的开发，并为实现可持续发展的未来铺平道路。

Identifying cheap and efficient methods to store clean electrical energy is one of the key hurdles that must be overcome on the path to achieving a low carbon economy. An important component of this is developing commercially attractive battery packs for use in electric vehicles; around one half of the total cost of these vehicles is currently the battery. Recent legislation to ban the sale of combustion engines across large parts of the world over the next few decades means that this goal must be achieved as a matter of urgency.Lithium-ion batteries are currently the best candidates to meet these demands. They are both energy and power dense, and only slowly lose their charge when not in use. Although their lifetime is already reasonable in relatively mild applications, such as consumer electronics where they can be used for upwards of 1000 cycles, they are plagued by rather more rapid degradation in the abusive high-current regimes that are common in electric vehicles. Reduced longevity is directly responsible for inflated consumer cost, and so extending battery cyclability is of paramount importance in realizing a healthy market for lithium-ion technology.The root cause of a significant portion of battery degradation is the pulverisation of the internal electrode microstructure by the swelling/contraction of constituent material when the device is in use. This mechanical degradation can in turn accelerate chemical degradation of the cell. To combat this, new materials and architectures must be identified to mitigate this source of damage. The search for improved design can be effectively guided by a coherent modelling framework that can be used to (i) benchmark novel designs without the need to construct and test them, and (ii) identify optimal configurations for manufacturers to target. The development of such a tool is predicated on overcoming some significant mathematical challenges related to resolving the accurate model equations describing the interaction of the variety of different materials (a liquid electrolyte and several different solids) over the vastly differing relevant lengthscales (from microns to centimeters). This program of work will overcome these challenges by applying systematic mathematical methods and deliver a tool to tackle the task of accurately modelling the evolution of the damage sustained by the internal components of a battery over its lifetime. This will significantly accelerate the development of more robust batteries and pave the way to realizing a sustainable future.