A mass transfer based variable porosity model with particle radius change for a Lithium-ion battery

T.R Ashwin,A Mcgordon,P.A Jennings

doi:10.1016/j.electacta.2017.02.129

Abstract

Micro pore-clogging in the electrodes due to SEI growth and other side reactions can cause adverse effects on the performance of a Lithium-ion battery. The fundamental problem of volume fraction variation and particle radius change during the charge-discharge process in a lithium-ion battery is modelled in this paper with the help of mass transfer based formulation and demonstrated on a battery with LiCoO2 chemistry. The model can handle the volume fraction change due to intercalation reaction, solvent reduction side reaction and the electrolyte density change due to side reaction contamination in the battery. The entire calculation presented in this paper models particle radius and volume fraction together and therefore gives greater accuracy in calculating the volume-specific-area of the reacting particles which is an important parameter controlling the Butler-Volmer kinetics. The mass deposit on the electrode (or loss of lithium) gives an indication of the amount of pre-lithiation required to maintain cell performance while the amount of mass deposited on the SEI helps to decide the safe operating condition for which the clogging of pores and capacity fade will be minimal. Moreover the model presented in this paper has wide applicability in analysing the stress development inside the battery due to irreversible porous filling.

Highlights

A Pseudo Two Dimensional (P2D) model offers flexibility in solving the interlinked chemical governing equations of a Lithium-ion battery based on concentrated solution theory [1,2]
Fact that excessive heat generation accelerates the Solid Electrolyte Interphase (SEI) growth has been already proven by researchers and this effect can lead to accelerated power fade and capacity fade.Parametric studies with different heat transfer coefficient and the resulting SEI growth can be found in Ashwin et al [7] for a single cell battery and for a battery pack in Ashwin et al [8]
A novel mass balance based model has been developed to predict the particle radius change and volume fraction variation due to Lithium deposition. This manuscript quantifies the radius change and volume fraction change from fundamental electrochemical equations using the framework of a P2D model

Summary

Introduction

A Pseudo Two Dimensional (P2D) model offers flexibility in solving the interlinked chemical governing equations of a Lithium-ion battery based on concentrated solution theory [1,2]. The volume fraction change during charging and discharging, and the Solid Electrolyte Interphase (SEI) grows over the particles forming a porous film, which is responsible for the lithium loss and voltage drop [3]. SEI build up increases the internal resistance of the battery leading to excessive heat generation while charging and discharging. The intercalation and other side reactions need to be captured accurately to model the volume fraction change. The motivation for this paper is to develop a more fundamental model which predicts the mass transfer across the anode-separator-cathode boundaries by measuring the Li+ concentration in the electrolyte within the framework of a P2D model

Methods

Results

Conclusion