Stability and Li+ extraction/adsorption properties of LiMxMn2−xO4 (M = Ni, Al, Ti; 0 ≤ x ≤ 1) in aqueous solution

Series spinels LiMxMn2−xO4 (M = Ni, Al, Ti; 0 ≤ x ≤ 1) were synthesized and a study of their stability and Li+ extraction and adsorption properties in aqueous solution was carried out. XRD analysis shows that pure cation-substituted spinels were obtained for x ≤ 0.5, impurity or cation disordering occurred when x ≥ 0.7. Ni and Al are incorporated into the spinel structures with cell contractions; but the incorporated Ti has an opposite effect. All the three cation-substituted spinels LiM0.5Mn1.5O4 (M = Ni, Al, Ti) maintain the spinel structures and morphologies after acid treatment, but their stability and Li+ extraction and adsorption behaviors differ from each other. LiAl0.5Mn1.5O4 shows a relatively high Li extraction ratio and relatively low Mn and Al extraction ratios during acid treatment, and in the subsequent adsorption experiment it shows a better Li+ adsorption performance which fits Langmuir isotherm. LiNi0.5Mn1.5O4 and LiTi0.5Mn1.5O4 do not show satisfying Li+ extraction and adsorption properties because of the significant cell contraction or expansion.