Study of thermodynamic and kinetic behaviours of tin anode and its variation with state of charge, state of health and operating current rates of the battery

Abstract

Rechargeable lithium ion battery is strengthening its hold day by day on market of large range of products requiring different power usages together with other electrochemical properties. Open circuit potential (OCP), which is strongly related to thermodynamics, is one of the parameters which dictates the state of health of the battery. Apart from this, the diffusion coefficient of Li⁺ ions in the electrode material reveals a good picture of kinetics during charge–discharge process. Moreover, ohmic potential drop, electrode overpotential and ohmic resistance associated with various internal resistances, are crucial parameters, which need to be taken care of during the battery operation. Tin (Sn) has the potential to be used as an anode in lithium ion batteries (LIBs) due its high enough theoretical capacity (992mAh g⁻¹) and a suitable operating voltage. In this work, we have applied galvanostatic intermittent titration technique (GITT) to study the variations of diffusivity, thermodynamic factor, OCP, ohmic resistance and overpotential for Sn electrode with different states of charge (SoCs) and analysed the effect of ageing on those parameters. The effects of current rates on these parameters have also been analysed to check the performance and limitation of the battery at higher current rates. Few particular lithiated phases like LiSn, Li₇Sn₃ and Li₇Sn₂ hold the key for major alteration in the kinetic behaviour in terms of diffusivity. This is, in a way, related to the structural modifications and the extent of volume changes of the different lithiated phases formed during operation of the LIB.