Pechini Synthesis of Nanostructured Li_1.05M_0.02Mn_1.98O₄ (M = Al³⁺ or Ga³⁺)

Doped Li_1.05M_0.02Mn_1.98O₄ (M = Ga³⁺ or Al³⁺) were prepared by Pechini synthesis using lithium and manganese acetates, citric acid, ethylene glycol, and the respective oxide or acetate of the doping ions in molar ratios of 2.00 (Mn_1.98 + M_0.02) to 1.05 Li. The TGA/DTA of the precursor gels showed weight loss/energy relative to crystallization below 450 ºC. From the XRD, a single cubic phase (F_d3m) was identified for the all-doped or undoped oxides after only 2 h calcination. The unit cell parameters a for both aluminum- and gallium-doped oxides calcined at 750 °C for 2 h (8.212 Å and 8.210 Å, respectively) were higher than that for the undoped oxide (8.199 Å). The crystallite sizes ranged from ~ 20 nm to 70 nm, conferring nanometric character. The specific capacities decreased in order: C_discharge (Li_1.05Mn₂O₄) >C_discharge (Li_1.05Ga_0.02Mn_1.98O₄) >C_discharge (Li_1.05Al_0.02Mn_1.98O₄), but with increasing capacity retention for the doped samples.

Keywords:
doped spinel; LiMn₂O₄; Jahn Teller effect; lithium-ion battery; Pechini method; nanostructured oxide