Li₁.₂Mn₀.₅₄Ni₀.₁₃Co₀.₁₃O₂ (LMNCO) is known a promising high-capacity cathode material for next-generation lithiumion batteries (LIBs), leveraging both transition-metal and oxygen redox reactions. However, challenges such as oxygen loss, structural degradation, and voltage fading hinder their practical application. To address these issues, we synthesized LMNCO cathode via solid-state methods and systematically investigated the effects of indium (In) or tin (Sn) dopant on its structural and electrochemical properties. X-ray diffraction (XRD) spectroscopy with Rietveld refinement confirmed the retention of the α-NaFeO₂ structure (R-3 m symmetry) in all samples with Sn or In doping inducing lattice expansion. Characterization tests revealed minimal morphological changes but altered surface chemistry and metal–oxygen bonding. Electrochemically, doped cathodes exhibited enhanced Li⁺ diffusion kinetics and reduced charge-transfer resistance. Compared to undoped and In-doped cathodes, the one doped with Sn delivered better electrochemical performance where it delivered discharge capacity of 308.9 mAh/g after 10 cycles 0.1 C, attributing to facilitated Li⁺ transport and lowered impedance. This study demonstrates that strategic doping with Sn or In can significantly stabilize Li-rich cathodes, offering a viable route toward high-energy, durable lithium-ion batteries.

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