Electrochemical intercalation of lithium into different varieties of carbon in solid polymer electrolyte

The electrochemical intercalation of lithium into different varieties of carbon was carried out using a solid polymer electrolyte. The faradaic efficiency obtained in the first cycle is relatively low compared with those obtained with a liquid electrolyte. The specific capacity exhibited by graphite materials is greater than that displayed with coke. A discharge capacity of 290 mAh/g after 15 cycles is encountered with a synthetic graphite, for which the variation in impedance before and after cycling was less significant. For natural graphite, a decrease in discharge capacity was found to be associated with an increase in impedance. This probably involves an irreversible reduction of the electrolyte which is more likely to occur on natural graphite presenting a greater BET surface area. Analysis by electron energy loss spectroscopy shows that the graphite surface was covered with carbonates.