Fully Coupled Simulation of Lithium Ion Battery Cell Performance

Abstract

Lithium-ion battery particle-scale (non-porous electrode) simulations applied to resolved electrode geometries predict localized phenomena and can lead to better informed decisions on electrode design and manufacturing. This work develops and implements a fully-coupled finite volume methodology for the simulation of the electrochemical equations in a lithium-ion battery cell. The model implementation is used to investigate 3D battery electrode architectures that offer potential energy density and power density improvements over traditional layer-by-layer particle bed battery geometries. Advancement of micro-scale additive manufacturing techniques has made it possible to fabricate these 3D electrode microarchitectures. A variety of 3D battery electrode geometries are simulated and compared across various battery discharge rates and length scales in order to quantify performance trends and investigate geometrical factors that improve battery p erformance. T he energy d ensity a nd power density of t he 3D battery microstructures are compared in several ways, including a uniform surface area to volume ratio comparison as well as a comparison requiring a minimum manufacturable feature size. Significant performance improvements over traditional particle bed electrode designs are observed, and electrode microarchitectures derived from minimal surfaces are shown to be superior. A reduced-order volume-averaged porous electrode theory f ormulation for these unique 3D batteries is also developed, allowing simulations on the full-battery scale. Electrode concentration gradients are modeled using the diffusion length method, and results for plate and cylinder electrode geometries are compared to particle-scale simulation results. Additionally, effective diffusion lengths that minimize error with respect to particle-scale results for gyroid and Schwarz P electrode microstructures are determined. INTRODUCTION: Motivation and Battery Background Research in lithium-ion batteries has proliferated during the last decade as a result of their recognition as a viable green alternative to energy transport and storage [1] [2]. Though welldeveloped for portable electronics applications, there are numerous challenges to be overcome for their use in heavy duty applications like electric vehicles or grid storage [3] [4] [5] [6] [7]. Modeling and simulation of these battery systems play a critical role in their effective and safe commercialization for such high energy density applications [8] [9] [10].