LAYERED COMPOSITE MATERIALS HAVING THE COMPOSITION: (1-x-y)LiNiO2(xLi2Mn03)(yLiCoO2), AND SURFACE COATINGS THEREFOR

摘要

A straightforward and scalable solid-state synthesis at 975° C. used to generate cathode materials in the system Li_(3+x)3Ni_(1-x-y)Co_yMn_2x/3O₂ {a combination of LiNiO₂, Li₂MnO₃, and LiCoO₂ as (1-x-y)LiNiO₂.xLi₂MnO₃.yLiCoO₂} is described. Coatings for improving the characteristics of the cathode material are also described. A ternary composition diagram was used to select sample points, and compositions for testing were initially chosen in an arrangement conducive to mathematical modeling. X-ray diffraction (XRD) characterization showed the formation of an α-NaFeO₂ structure, except in the region of compositions close to LiNiO₂. Electrochemical testing revealed a wide range of electrochemical capacities with the highest capacities found in a region of high Li₂MnO₃ content. The highest capacity composition identified was Li_1.222Mn_0.444Ni_0.167Co_0.167O₂ with a maximum initial discharge capacity of in the voltage range 4.6-2.0 V. Differential scanning calorimetry (DSC) testing on this material was promising as it showed an exothermic reaction of 0.2 W/g at 200° C. when tested up to 400° C. Cost for laboratory quantities of material yielded $1.49/Ah, which is significantly lower than the cost of LiCoO₂ due to the low cobalt content, and the straightforward synthesis. Li_1.222Mn_0.444Ni_0.167Co_0.167O₂ is thought to be near optimum composition for the specified synthesis conditions, and shows excellent capacity and safety characteristics while leaving room for optimization in composition, synthesis conditions, and surface treatment.