Graphene-Sandwiched LiNi_0.5Mn_1.5O₄Cathode Composites for Enhanced High Voltage Performance in Li Ion Batteries

Graphene was used to form efficient conducting networks and to suppress the formation of a solid-electrolyte interface layer, in a sandwiched composite with LiNi 0.5 Mn 1.5 O 4 (LNMO), which resulted in an improvement in rate capability and coulombic efficiency, respectively. The interaction between the LNMO particles and the residual oxygen functionalities on the basal plane of graphene in solution spontaneously produced LNMO particles that were sandwiched by the graphene. This configuration provided LNMO with less polarization due to higher electronic conductivity, which contributed to an increased rate capability. The graphene-sandwiched LNMO also enhanced a coulombic efficiency due to the suppression of continuous electrolyte decomposition, which eventually resulted in improved capacity retention. Unlike this graphene-sandwiched LNMO, a simple mixture of LNMO with graphene did not show noticeable improvements in rate capability due to a lack of efficient conducting network. A LiMn 2 O 4 /graphene composite prepared using the same procedure showed no improvement in coulombic efficiency and, thus, capacity retention was similar to graphene-free LiMn 2 O 4 , indicating that the graphene-sandwiching is an effective strategy for high-voltage cathode materials.