Microstructure – twinning and hexad multiplet(s) in lithium-rich layered cathode materials for lithium-ion batteries

Abstract

Li-rich cathode materials synthesized through the solution combustion method essentially exhibits a super-lattice layered structure and appears to have an edge over conventional cathode materials in terms of a good capacity with fade control. The cobalt content in this Li-rich cathode material is vital in determining the morphology, microstructure, high reversible redox peak and stable charge–discharge cycling. A typical Li-rich cathode with a Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ composition exhibits strange microstructure features in the SAED pattern viz., the simultaneous occurrence of twinning, and the hexad multiplets patterns yielded a good discharge capacity of 231 mA h g⁻¹. Whilst it is the microstructure features, which have a profound dependence on the cobalt content appears to have control on the capacity. On the basis of these microstructural changes revealed in the SAED pattern and cation ordering in the superlattice structure, an attempt has been made to explain the dependence of cobalt content vs. capacity performance in Li-ion batteries.