Fadila El Kouihen, Synthesis and Characterization of Novel Nickel-Rich Cathode Materials for Conventional Lithium-Ion and All-Solid-State Batteries, PhD thesis, Mohammed VI Polytechnic University (UM6P, LIMSET), supervised by Abdessamad Faik and Mohamed Chakir, defence on 4 November 2026. Read here from the revised manuscript of 17 October 2026 (258 pp.); page numbers are its printed ones.
Nickel-rich layered oxides, \(\mathrm{LiNi_{1-x-y}M_xM'_yO_2}\) in the \(\alpha\)-\(\mathrm{NaFeO_{2}}\) structure (\(R\bar{3}m\)), give high capacity, and cobalt is the costly, scarce element that keeps them ordered. The thesis asks how far cobalt can be reduced (NCA with Mn for Co) or removed (NMA, \(\mathrm{LiNi_{0.8}Mn_{0.15}Al_{0.05}O_2}\)), and whether dopants and co-dopants can give back the stability: Fe/Sb, Mg, Y, La, Sc, Na. Their common target is the cation mixing of Ni\(^{2}\)⁺ into the lithium layer, which blocks lithium diffusion and degrades cycling (§I.10, pp. 28–35).
Co-precipitation of the transition-metal hydroxides from nitrates (NaOH, \(\mathrm{NH_{4}OH}\) as chelating agent, pH 11.5, 55 °C for NCA; 85 °C for NMA), dopant salts added to the same solution, drying, mixing with LiOH·\(\mathrm{H_{2}O}\), and calcination under oxygen: 500 °C for 12 h then 750 °C for 24 h (NCA), 750 °C for 24 h at 2 °C min\(^{-1}\) (NMA) (§II.4, pp. 54–59).
| Technique | On what | What it gave |
|---|---|---|
| X-ray powder diffraction, Rietveld | calcined powders | cells (a, c, c/a, V); I(003)/I(104) for every material; Li–O distances (Tables II.5, II.9); a refined Li/Ni antisite for NMA and La–NMA only. Instrument Bruker D6 (Annex A); range, step, software, refined parameters and zero-shift treatment not stated. |
| ICP-OES | powders | metal ratios for all; lithium for the Co-reduction line (Table II.4) |
| SEM–EDS, particle size | powders | morphology, agglomerate size, element maps |
| FTIR, TGA, DSC | lithiated powders | M–O bands; mass loss on heating |
| Electrochemistry | coin cells against Li; solid-state cells | capacity, Coulombic efficiency, rate, cycling to 200 cycles, CV, EIS and DLi |
| DFT (Annex C) | NCA and doped models | structural, electronic and migration properties |
Not measured: any oxidation state (no XANES; XPS not reported in the results), the site of any dopant, the bulk lithium separately from surface species, the structure of any electrode after cycling, the coating's structure.
Co reduction. Mn enters with small shifts of the cell; ICP confirms the metal ratios and shows Li 0.6–0.9 wt% below nominal. NMA has a lower peak intensity, read as lower crystallinity or more mixing (p. 61).
Fe/Sb co-doping. I(003)/I(104) rises from 1.05 to 1.30 (NCA) and from 1.20 to 1.35 (NMA), read as less mixing; capacity and efficiency improve; Fe/Sb–NMA keeps 96.7 % after 200 cycles (pp. 77–81, 106–109, 146).
Substitution and single-site doping. Mg, Y and La raise the ratio to 1.28, 1.35 and 1.40, and the refined antisite falls from 3.5 % (NMA) to 2.2 % (La–NMA); Sc and Na raise it to 1.32 and 1.45, with c growing by 2 % for Na. Y–NMA gives the highest capacity (182 mAh g\(^{-1}\)), La–NMA the best retention of the line (96.3 %) (pp. 88–101, 136).
Solid state. The \(\mathrm{LiNbO_{3}}\) coating improves the NMA | \(\mathrm{Li_{6}PS_{5}Cl}\) cell: 73.8 % of capacity after 50 cycles against 60.1 % (§IV.3.2).
"Additional experimental tools such as operando X-ray diffraction, in situ Raman spectroscopy, or synchrotron-based techniques would allow direct observation of structural evolution during cycling. Even limited access to such techniques would significantly enhance the understanding of phase transitions, oxygen activity, and interfacial reactions in Ni-rich layered oxides" (Perspectives, p. 183). This project is that access, with neutrons added for what only they see.
Next: the crystallography in detail, and the fact base.