Electrochemical properties of transition metal substituted calcium ferrite-type Lix(M0.1Mn0.9)2O4 (M = Ni, Ti)

Transition metal substituted CaFe2O4-type Lix(M0.1Mn0.9)2O4 (M = Ni, Ti) was synthesized by Na/Li ion exchange method from high-pressure synthesized CaFe2O4-type Na(M0.1Mn0.9)2O4 (M = Ni, Ti). The crystal structures were refined by Rietveld analysis using powder X-ray diffraction data. The electrochemical properties were measured. The initial discharge capacities of Lix(Ni0.1Mn0.9)2O4 and Lix(Ti0.1Mn0.9)2O4 were 119.3 and 122.0 mAh g−1 in the range of 4.8–3.0 V (vs Li/Li+). The capacities of substitutions were 5.29% and 7.68% increased than the value of Li0.81Mn2O4. After 50 charge–discharge cycles, the discharge capacities of Li0.81Mn2O4 and Lix(Ni0.1Mn0.9)2O4 were 5.78% and 11.1% decreased from the initial. The Ni substitution was effective for increasing the discharge voltage, although the effect was decreased with increasing cycle numbers.

► New crystal phase of calcium ferrite-type Lix(M0.1Mn0.9)2O4 (M = Ni, Ti) are synthesized.
► The crystal structures are revealed by X-ray powder diffraction data.
► The electrochemical properties show high energy densities and good cycle performances.
► Transition metals substitute the Mn sites selectively.
► Different substitution sites show different electrochemical properties.