Electrochemical Studies of the LiFePO[sub 4] Thin Films Prepared with Pulsed Laser Deposition

Abstract

Thin films of have been prepared on stainless steel substrates with pulsed laser deposition utilizing an Ar atmosphere. Raman spectral analysis revealed the presence of carbon in the films, even though the targets contained less than a few percent residual carbon. The Raman spectra also suggest the presence of iron oxide species on the surface of the film. Though the film morphology became rough with cycling and thicker films were cleaved; the films showed good stability on cycling. The -thick film prepared with a carbon-containing target showed a reversible cycling of more than for . The use of the low-carbon , green-colored target significantly lowered the carbon content of the film. The low-carbon films cycled stable at moderate current density but with lower capacities such as 80 and for the 75 and films, respectively. Film capacity and crystallinity improved significantly when the pulsed-laser-deposited target-substrate distance was reduced to less than . The -thick film produced in this way showed a layered texture in surface morphology and delivered more than , keeping its particle morphology on cycling. The excellent capacity retention, despite low-carbon content, can be attributed in part to the enhanced conductivity derived from the excellent adherence between pulsed-laser-deposited film and the substrate.