In order to optimise the thermal treatment of PPP at 700 degrees C, we report on the electrochemical studies using solid polymer electrolytes composed of polyethylene oxide (PEO) and LiClO4 of the insertion of lithium ions into PPP pyrolyzed at 700 degrees C in argon atmosphere during increasing pyrolysis times (0.5; 1, 2 and 6 hours). The electrochemical measurements reveal that two parameters are necessary to improve the affinity of these materials for lithium : i) the density of crosslinking (or the lateral extension of the graphene sheets for the longest pyrolysis times) must be large, ii) a high molar ratio H/C.