EFFECT OF SURFACE MODIFICATION USING VARIOUS ACIDS ON ELECTRODEPOSITION OF LITHIUM

Surface modification of lithium was carried out using the chemical reaction of the native film with acids (HF, H3PO4, HI, HCl) dissolved in propylene carbonate (PC). The chemical composition change of the lithium surface was detected using X-ray photoelectron spectroscopy. The electrodeposition of lithium on the as-received lithium or the modified lithium was conducted in PC containing 1.0 mol dm(-3) LiClO4 or LiPF6 under galvanostatic conditions. The morphology of electrodeposited lithium particles was observed with scanning electron microscopy. The lithium dendrites were observed when lithium was deposited on the as-received lithium in both electrolytes. Moreover the dendrites were also formed on the lithium surface modified with H3PO4, HI, Or HCl. On the other hand, spherical lithium particles were produced, when lithium was electrodeposited in PC containing 1.0 mol dm(-3) LiPF6 on the lithium surface modified with HF. However spherical lithium particles were not obtained, when PC containing 1.0 mol dm(-3) LiClO4 was used as the electrolyte. The lithium surface modified by H3PO4, HI, Or HCl was covered with a thick film consisting of Li3PO4, Li2CO3, LIOH, or Li2O. The lithium surface modified with HF was covered with a thin bilayer structure film consisting of LIF and Li2O. These results clearly show that the surface film having the thin bilayer structure (LIF and Li2O) and the use of PC containing 1.0 mol dm(-3) LIPF(6) enhance the suppression of dendrite formation of lithium.