Abstract: Cobalt was doped into the host spinel to produce cobalt-doped spinel material by a solution technique. The
end Co-doped materials have many advantages of narrowly distributed and well crystallized particles and small surface area. The determination of XRD patterns
shows that the peaks shift towards high angle and become sharp as the introduction of cobalt. The analysis of infrared (IR) spectroscopy illustrates that cobalt
doping can enhance the strength of Mn--O bonds and improve the structural stability of the materials. The presence of cobalt reduces the dissolution of
Mn into the electrolyte according to the investigation of ICP analysis results since Co-doped materials have more stable structure and smaller surface area.
Cobalt doping can enhance the bond Mn--O and weaken the bond Li--O in the spinel. As the result, the Li⁺ ion has easier diffusion in the spinel and the Co-doped
material has smaller charge-transfer resistant (R_ct). The measurement of electorchemical properties shows that the Co-doped material Li₁.₀₃Co_0.05Mn_1.92O₄
prepared in this technique has good cycling performance and high initial capacity.

Key words: lithium-ion batteries, LiMn₂O₄, cation doping, IR spectroscopy