Introduction

Secondary lithium-ion batteries (LIBs) are rechargeable electrochemical energy storage devices which have grown in popularity with advantages over other types of battery chemistries such as high energy capacities, long lifespans, resistance to self-discharge, and higher voltage output (Velázquez-Martinez, et al., 2019; Li, et al., 2018). As a testament to this, the LIB market has grown from 500 million cells produced in 2000 (Mossali, et al., 2020) to 4.5 billion cells produced in 2011 (Bernhart, 2014) to an estimated 25 billion cells becoming waste in 2020 (Yu, et al., 2018). Table 1.1 presents the generic compositions of lithium-ion batteries reported by Velázquez-Martinez et al. (2019) and Mossali et al. (2020). A cell comprises of anode and cathode materials separated by a porous material and enclosed in a sealed case (Figure 1.1). The case is filled with an electrolyte mixture to enable the movement of lithium (Li) ions between the electrodes of the cell to allow charging and discharging of the cell (Li, et al., 2018). In the charging process, Li+ ions leave the cathode and move to the anode, where they intercalate between the graphite molecules (Sonoc, et al., 2015) as Li metal (Mossali, et al., 2020). The Li+ions are unstable on the anode, and as the battery discharges, they move to the cathode, which creates an electrical current (Al-Thyabat, et al., 2013). A lithium-ion cell can only operate between approximately 1.5 and 4.2 V. At lower voltages, the copper current collectors become degraded, and at higher voltages, lithium forms reactive dendrites. Both phenomena can be detrimental to the safe operation of the cells (Mossali, et al., 2020).
Table 1.1. Lithium-ion cell construction components and materials according to Velázquez-Martinez et al. (2019) and Mossali et al. (2020).