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).