In order to improve the cycling performance of LiMn₂O₄ based cathode materials, we have synthesized a new composition, LiNi_0.4M_0.1Mn_1.5O₄ (𝑀 = Al, Bi), by the sol–gel method. The formation of solid solutions is confirmed by structural characterization using TG/DTA, XRD, FT–IR, EPR, SEM and EPR. A.c.-impedance (Nyquist plot) showed a high frequency semicircle and a sloping line in the low-frequency region. The semicircle is ascribed to the Li-ion migration through the interface from the surface layer of the particles to the electrolyte. Cyclic voltammogram (between 3.5 and 4.9 V) for these materials using CR2032 coin-type cell shows two pairs of redox peaks corresponding to two-step reversible intercalation process, wherein Li-ions occupy two different tetragonal 8a sites in spinel Li_𝑥Mn₂O₄ (𝑥 < 1) lattice. The galvanostatic charge/discharge curves for 𝑀 = Al (77 mAh g^-1) showed reasonably good capacity retention than that of 𝑀 = Bi (11 mAh g^-1) at the end of 17th cycle.