# Replacement of Cobalt in Lithium-Rich Layered Oxides by n-Doping: A DFT Study
## 4 Conclusions  
In this work, we have investigated using firsts principles methods based on DFT, four TM oxide layered materials with a general stoichiometry Li\({}_{1.2}\)Ni\({}_{0.2-\chi/2}\)Mn\({}_{0.6-\chi/2}\)Co\({}_{\chi}\)O\({}_{2}\), considering different Co contents: LNMC12, LNMC08, LNMC04, and LNM with x = 0.12, 0.08, 0.04, and 0, respectively. We have addressed structural, electronic, and thermodynamic properties for each material to describe the impact of Co substitution by Mn/Ni and the parallel p-doping of the lattice. Our analysis describes in detail the structural features of all compositions, their relative stabilities, and their electronic properties, in terms of band gap, oxidation state of the transition metal and JT distortion. The obtained description of the bonding and structural properties of the modelled structures is in good agreement with the available experimental literature. Overall, reduction in the Co content in the LRLO lattice on the one hand leads to an expansion of the structures due to the greater electronic distortions. This structural effect can promote the mobility of lithium ions, thanks to the weaker coordination. However, the number of electronic states at the Fermi level decreases, possibly negatively impacting the electronic conductivity. These trends occur in parallel with the alteration of the thermodynamic stability of the lattices, while removing cobalt. In this view, the p-doping strategy provided by the Mn/Ni simultaneous incorporation appears as a balanced way to remove cobalt from the lattice without massively degrading the structural and electronic properties of the LRLO. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)]([https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)) 3390/app112210545/s1, Figure S1: Different Co distribution in different layers: diluted in which Co atoms are separated by two Li-layers and one TM-layer; intermediate, in which Co atoms are separated by one Li-layers; near, in which Co atoms are in same TM-layer. On the left a qualitative energy diagram of \(\Delta\)E between diluted, intermediate and near distribution. Figure S2: Different Co configuration for diluted and intermediate distribution, considering Co chemical environments. Table S1: Fractional Coordinate of LNMC04. Table S2: Fractional Coordinate of LNMC04. Table S3: Fractional Coordinate of LNMC08. Table S4: Fractional Coordinate of LNMC12. Figure S3: Pair Distribution Function (PDF) of LNMC12 (upper panel), LNMC08 (middle panel), LNMC04 (middle panel) and LNM (bottom panel) for Li-O bond distances. Table S5: Mole fraction of JT distortions with respect to: all TMs (\(\chi_{JT}\)), Ni ions (\(\chi_{Ni^{2}}\)-) and Mn ions (\(\chi_{Mn^{3+}}\)) for LNMC12, LNMC08, LNMC04 and LNM. Figure S4: Accumulative differences of Bader charges of Ni and Mn, considering the variation from LNMC12 to LNM; negative \(\Delta\)q implicates a reduction (Mn\({}^{4+}\rightarrow\) Mn\({}^{3+}\)), positive \(\Delta\)q implicates an oxidation (Ni\({}^{2+}\rightarrow\) Ni\({}^{3+}\)). Table S6: Gibbs energy of formation (\(\Delta_{\rm form}\)G\({}^{\circ}\)\({}_{298\rm K}\)/kJ mol at\({}^{-1}\)) of the LRLO as a function of the temperature. **Author Contributions:** Conceptualization, S.B., O.P., A.P. ; methodology, A.B.M.-G., M.P. ; investigation, M.T., L.M. ; writing--original draft preparation, S.B., M.T. ; writing--review and editing, A.B.M.-G., M.P., O.P., A.P. All authors have read and agreed to the published version of the manuscript. **Funding:** The authors would like to acknowledge the financial support from the European Union Horizon 2020 research and innovation program within the Si-DRIVE project; grant agreement No. 814464. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Data are available upon request to the corresponding author.