Carbon-coated nanophase CaMoO4 as anode material for Li ion batteries.

Abstract

Pure and carbon (C)-coated CaMoO4 were synthesized by solution precipitation and solgel

methods, and their electrochemical properties were studied vs Li by galvanostatic cycling

and cyclic voltammetry (CV). Combined X-ray diffraction, SEM, and TEM results revealed

the formation of nanocrystalline particles with the scheelite structure, the morphology being

a function of the synthetic procedure. TEM of 10% C-coated CaMoO4 shows the amorphous

nature of carbon on the crystalline particles with a thickness of 8-12 nm. Galvanostatic

data in the voltage range of 0.005-2.5 V up to 50 cycles at a rate of 60 mA/g revealed that

the 10% C-coated CaMoO4 gave the highest reversible capacities. At the 20th discharge cycle,

the capacity values (mA h/g) are as follows: solution precipitated, 190; sol-gel, 268; 5%

C-coated, 401; and 10% C-coated, 508. The latter value corresponds to 3.8 mol of recyclable

Li. The improvement in the interparticle electronic conductivity imparted by the C-coating

led to superior performance. The Coulombic efficiency for all the compositions is >98%.

Galvanostatic cycling results are supplemented by the CV data. A plausible mechanism for

charge-discharge cycling has been proposed.