Chemistry and electrochemistry of concentric ring cathode Li1.42Ni0.25Mn0.75O2+γ for lithium batteries

Abstract

A co-precipitation method in a continuous stirred tank reactor was developed to synthesize the carbonate precursor Ni_0.25Mn_0.75CO₃ for the cathode material Li_1.42Ni_0.25Mn_0.75O_2+γ. Both the precursor and the cathode materials were studied by a variety of characterization methods in order to establish a link between the compositions, structures, and physical properties of these compounds and the electrochemical properties of the Li_1.42Ni_0.25Mn_0.75O_2+γ cathode. The precursor particles were found to have concentric ring architectures during the co-precipitation reaction, resulting in spherical particles composed of 20 μm bulky cores around which several shells/layers formed. The variation in the number of layers grown on each precursor particle led to a wide size distribution for both the precursor and cathode compounds. Cathode particles whose sizes were above 20 μm yielded lower specific capacities due to the diminished lithium ion diffusion across the voids that separate the subsequent shells. The ring architecture of the particles can be destroyed by soft ball milling, which improves the overall electrochemical performance of the cathode.