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LiMnPO4 Nanoplates with In-Situ Growth of a sp2-Carbon Surface Layer from a Liquid Precursor, Phase Stability, and Tailored Impedance Properties

[ Vol. 7 , Issue. 1 ]

Author(s):

S. K. Sharma, T. Majumder, M. Dewan and S. Ram   Pages 23 - 38 ( 16 )

Abstract:


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.

Keywords:

Energy storage materials, hybrid electric vehicles, hydrothermal synthesis, nanoplates, selfassemblies, solid electrolytes.

Affiliation:

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

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