# Replacement of Cobalt in Lithium-Rich Layered Oxides by n-Doping: A DFT Study
## 3 Results
### Electronic Structure of the LRLOs  
The electronic structures in terms of density of states for LNMC12, LNMC08, LNMC04, and LNM are shown in Figure 4.  
First, we can observe a similar metallic character for all Co-containing compositions, whereas the LNM Co-free supercell shows a 0-bandgap character. This change in the electronic structure induced by the complete removal of cobalt from the LRDO lattice agrees with the enhancement of the electronic conductivity obtained by Co doping reported in the literature [61]. Second, a strong hybridization of Ni d states and Mn d states at the Fermi energy with the p-states of the oxygen anions is observed for all supercells, being that the energy distribution of the Ni states is highly distorted by the reduction in the cobalt content. The analysis of the magnetic moments of the metals allows us to shed light on the oxidation states in the lattices. The mean magnetic moments are:  
* Co sites: 0.00 \(\mu_{\text{B}}\), for LNMC12, LNMC08, and LNMC04;
* Ni sites of 1.649 \(\mu_{\text{B}}\), 1.609 \(\mu_{\text{B}}\), 1.521 \(\mu_{\text{B}}\), 1.489 \(\mu_{\text{B}}\) for LNMC12, LNMC08, LNMC04, and LNM respectively;
* Mn sites of 3.199 \(\mu_{\text{B}}\), 3.216 \(\mu_{\text{B}}\), 3.236 \(\mu_{\text{B}}\), 3.239 \(\mu_{\text{B}}\) for LNMC12, LNMC08, LNMC04, and LNM respectively. Magnetic moments confirm the qualitative results obtained by PDOS. The magnetic moments suggest that all Co ions are in 3+ oxidation state in low spin (LS) electronic configuration, \(t_{\text{2g}}{}^{6}\) (\(1\uparrow\downarrow\downarrow\uparrow\downarrow\uparrow\downarrow \downarrow\)) \(\text{e}_{\text{g}}{}^{0}\) ( \(1\mid 1\)) in all supercells. On the  
Figure 4: Atomic orbital projected density of states of LNMC12 (upper panel), LNMC08 (upper/middle panel), LNMC04 (middle/bottom panel), which presents a 0-bangap, and LNM (bottom panel). contrary, the monotonic reduction of the magnetic moments of Ni ions in parallel with the Co substitution suggests a decrease in the concentration of nickel ions in the 2+ oxidation states in the LS electronic configuration \(\text{t}_{\text{2g}}\)6 (\(1\uparrow\downarrow\downarrow\uparrow\downarrow\uparrow\downarrow 1\)) \(\text{e}_{\text{g}}^{\text{2}}\) (\(1\uparrow\downarrow\uparrow\downarrow\)), and an increase in the fraction of nickel ions in the 3+ oxidation state in the LS electronic configuration, \(\text{t}_{\text{2g}}\)6 (\(1\uparrow\downarrow\downarrow\uparrow\downarrow 1\)) \(\text{e}_{\text{g}}^{\text{2}}\) (\(1\uparrow\downarrow\uparrow\downarrow\)), and an increase in the fraction of nickel ions in the 3+ oxidation state in the LS electronic configuration, \(\text{t}_{\text{2g}}\)6 (\(1\uparrow\downarrow\uparrow\downarrow 1\)) \(\text{e}_{\text{g}}^{\text{2}}\) (\(1\uparrow\downarrow\) 1). In parallel, an analogue increase in the magnetic moment on Mn is the clue of the decrease in the concentration of manganese ions in the 4+ oxidation state in the HS electronic configuration, \(\text{t}_{\text{2g}}\)3 (\(1\uparrow\uparrow\uparrow\uparrow\downarrow\)) \(\text{e}_{\text{g}}^{\text{2}}\) (\(1\uparrow\downarrow\) 1), and an increase in the fraction of manganese ions in the 3+ oxidation state in the HS electronic configuration, \(\text{t}_{\text{2g}}\)3 (\(1\uparrow\uparrow\uparrow\uparrow\) 1) \(\text{e}_{\text{g}}^{\text{2}}\) (\(1\uparrow\downarrow\) 1). The molar fractions of 3+ ions are shown in the SI (Table S5) for all compositions. Previous experimental X-ray absorption analysis of the oxidation states of Mn and Ni for the same LMN Co-free composition agrees with our evaluations, thus confirming the contemporary presence of Ni3+, Ni2+, Mn3+, and Mn4+ in the structure [62]. This analysis is also confirmed by the computed Bader charges show in Figure S4 in the SI, that confirm the increase of the Ni3+ and Mn3+ concentrations in parallel with the Co substitution. Due to their electronic configurations, Ni3+ and Mn3+ are Jahn-Teller ions (JT) [60].