Investigation of chemical-physical reaction mechanisms in solid-state and hydrothermal synthesis Li1.1Ni0.8Mn0.1Co0.1-La for energy storage of hybrid supercapacitor applications

The study explores the synthesis and electrochemical evaluation of La-doped LiNMC materials for hybrid supercapacitors using hydrothermal and solid-state methods. In the hydrothermal route, stoichiometric metal precursors and dopants were co-precipitated and treated in an autoclave, while solid-state synthesis involved mechanical mixing and ball milling of oxide powders. Electrodes were fabricated using NMP-based slurries coated on nickel foam, assembled in Swagelok cells with 6 M KOH electrolyte. FTIR and SEM analyses confirmed lattice vibrations and spherical morphology. Electrochemical Impedance Spectroscopy (EIS) revealed that La doping affects internal resistance, with optimal improvements seen at 0.6% doping. Galvanostatic charge-discharge (GCD) testing showed superior performance for hydrothermally synthesized 0.6% La-doped samples, achieving a specific capacitance of 86.58 F g −1 , energy density of 13.09 Wh kg −1 , and 90.02% retention after 500 cycles. The 0.9% La-doped variant showed slightly reduced capacitance but excellent stability (99.96% retention). Solid-state synthesis showed peak performance at 0.6% La with 175.20 F g −1 but lower power density. Overall, La doping notably enhances the capacitive behavior, energy storage, and stability of LiNMC-based supercapacitors, especially via hydrothermal synthesis.