## 1 Introduction  
The technological advance from single use alkaline batteries to rechargeable Li-ion batteries is beneficial in terms of sustainability [1; 2]. The cathodes used in Li-ion batteries are typically made from complex metal oxides (CMOs). The prototypical cathode material is LiCoO\({}_{2}\) (LCO) of the delafossite structure type, and is found in a wide range of electrical devices, including cellphones, computers and cars [3]. Recently, there has been a surge in the production of electronic devices, resulting in an increased amount of cathode material being generated [3]. While the Li-ion battery lasts for multiple charge cycles, eventually the material degrades and loses function. Unfortunately, there are not sufficient incentives in place to dispose of these materials properly, nor are there cost-effective ways to enable recycling [4]. Thus, the spent and disposed LCO (and related CMO cathode materials) can ultimately be exposed to the environment [3]. One additional concern is the that average life expectancy of newer electronic devices has decreased over the years and this contributes to the amount of disposed cathode material [3]. The sustainability of LCO can be viewed through two considerations. Firstly, cobalt is not Earth abundant, which makes it a very expensive transition metal (that also happens to be sourced in countries of political instability) [5]. Secondly, when exposed to aqueous settings, Co can leach out of LCO to form aqueous cations that have been shown to be toxic to aquatic organisms [6; 7]. This has led to research investigating new transition metal compositions that reduce the amount of cobalt needed for a functional cathode in Li-ion battery technology. The development of Li(Ni\({}_{1/3}\)Mn\({}_{1/3}\)Co\({}_{1/3}\))O\({}_{2}\) (NMC) is an improvedcathode material where Ni and Mn are more abundant, reducing the cost to make this material. Another benefit of this composition is that charge cycling is improved, allowing the material to last longer [1,8]. As with LCO, NMC also undergoes partial dissolution in aqueous conditions. It has been shown that equistoichiometric NMC releases metal cations in amounts ranking Ni > Co > Mn. The released cobalt poses the most significant adverse biological impact, as its release from the NMC is shown to kill the model organisms daphnid and schwenella [6,9]. In our previous work, a combined computational chemistry and thermodynamics methodology was established, capturing the salient trends of the experimental studies and used to investigate Ni-rich and Mn-rich compositions of NMC. This work found that the oxidation state of transition metals plays key role on metal release [10, 11, 12, 13]. When equal amounts of Ni, Mn, and Co are present in NMC, the charge balance dictates the nominal oxidation states to be 2+, 3+, and 4+, respectively. In the case of Ni-rich NMC, Ni is taking the place of Co\({}^{3+}\) and Mn\({}^{4+}\), as verified through electronic structure calculations. As a result, some of the Ni in Ni-rich NMC oxidizes to maintain a charge balanced structure. Ni then forms stronger bonds with lattice oxygen, increasing the stability of Ni in the CMO and hindering metal release in water. The opposite effect was seen for Mn-rich compositions where some of the Mn (present and particularly stable as Mn\({}^{4+}\) in the octahedral environment of equistoichiometric NMC) reduced to form Mn\({}^{2+}\). In another work, this dissolution model examined different sized supercells of LiCoO\({}_{2}\) to determine the threshold of metal release under given pH conditions, providing a better understanding of why these materials do not fully dissolve [13]. This model also examined metal release trends influenced by the strength of anions present in the lattice and metal connectivity, gaining further insights into the features governing release favorability [14].