Cr-doped LiCoMnO4 cathode with high phase purity and promoted electrochemical performance

Summary To improve the electrochemical performances of high voltage LiCoMnO 4 spinel cathode material at 5.3 V, Cr doped LiCoMn 1-x Cr x O 4 ( x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one-step solid-state at 750°C. Rietveld refinement results showed that the phase purity of spinel is promoted with the increase in Cr concentration, which can be explained by the strong Cr  O bond that reduces oxygen deficiency and eliminates Li 2 MnO 3 impurity phase during the synthesis process. Such change in phase purity further causes the improvement in specific capacity, and the 5.0%Cr doped sample displays the best result with a value of 123.0 mAh/g at 0.1°C and 93.3 mAh/g at 10°C. For a comparison, the pristine sample only releases a capacity of 112.6 mAh/g at 0.1°C and 54.8 mAh/g at 10°C. Improved capacity retention, from 83.1% to 90.1% after 100 cycles at 1°C, is also observed due to the suppressed volume change during the redox process after the incorporation of Cr cations in the lattice. Promoted rate performance, attributed from the improved Li ion diffusion coefficient, is also confirmed in the experiment. The improvement of those electrochemical properties could be explained by high-phase purity and superior structural stability benefited from Cr-doping. Novelty statement LiCoMn 1-x Cr x O 4 ( x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one-step solid-state at 750°C, Chromium had been confirmed to reduce oxygen loss during LiCoMnO 4 synthesis due to high oxygen affinity of Cr, which improves phase purity. As a result, the specific capacity was increased. Cr-doping enhances the structural stability so that capacity retention was promoted due to higher bond energy of Cr  O than Mn  O; rate performance was also enhanced due to the improved diffusion coefficient.