S. K. Sharma, T. Majumder, M. Dewan and S. Ram* Pages 23 - 38 ( 16 )
Background: Olivine structured LiMnPO4 is a pioneering energy-storage material of Li+-ion batteries. Its synthesis in a shape of small plates (large free-surfaces) bonding over a C-sp2 surface layer is demanded in harvesting its functional properties.Objective: In situ synthesis of grafted LiMnPO4 of nanopaltes with a C-sp2 surface layer, with tailored impedance properties. Method: A simple hydrothermal reaction is explored in a solution LiOH·H2O, MnSO4·H2O and H3PO4 with sodium dodecyl sulphate (a surfactant) to synthesize LiMnPO4 of small plates. A phase pure LiMnPO4 is obtained in 8-12 h heating a precursor solution at 150°C in an autoclave, and then washing a recovered powder in hot water. Results: The sample LiMnPO4 contains nanoplates of a Pmnb orthorhombic crystal structure, 20-40 m2/g surface area, 30-40 nm thickness, and self-assemblies. The lattice parameters a = 0.6104 nm, b = 1.0468 nm and c = 0.4758 nm describe a marked 0.43 % lattice expansion over the bulk phase, with an enhanced aspect ratio c/a = 0.7795 above the bulk value 0.7777, which likely promotes the charge-carrier dynamics. In the HRTEM images, the LiMnPO4 plates wear a GO-surface layer of a conductive 2D-network with sp2-C electrons. Uniquely, a cell made of the sample yields largely enhanced (i) conductivity of Li+ ions and electrons at a 10-6 S-cm-1 scale and (ii) Li+ diffusion coefficient 3.291x10-14 cm2s-1 at room temperature. Conclusion: The results describe LiMnPO4 nanoplates with an inbuilt surface C-sp2 layer extend fast charge diffusion kinetics useful for powerful Li+- ion batteries.
Energy storage materials, hybrid electric vehicles, hydrothermal synthesis, nanoplates, selfassemblies, solid electrolytes.
Materials Science Centre, Materials Science Centre, Materials Science Centre, Materials Science Centre and School of Nanoscience and Technology, Indian Institute of Technology, Kharagpur -721 302