High energy density layered-spinel hybrid cathodes for lithium ion rechargeable batteries

摘要

High energy density Li_2MnO_3 (layered)-LiMn_(1.5)Ni_(0.5)O_4 (spinel) composite cathodes have been synthesized using auto-combustion route. Rietveld refinements together with the analyses of high resolution transmission electron micrographs confirm the structural integration of Li_2MnO_3 nano-domains into the LiMn_(1.5)Ni_(0.5)O_4 matrix of the composite cathodes. The discharge capacity of the composite cathodes are due to the intercalation of Li~+ ion in the tetrahedral (8a) and octahedral (16c) sites of the spinel component and also the insertion of Li~+ in the freshly prepared MnO_2 lattice, formed after Li_2O extraction from the Li_2MnO_3 domains. The capacity fading of the composite cathodes are explained to be due to the layered to spinel transition of the Li_2MnO_3 component and Li~+ insertion into the octahedral site of the spinel lattices which trigger cubic to tetragonal phase transition resulting volume expansion which eventually retard the Li~+intercalation with cycling.