In-situ measurements of resistance and structure of lithium intercalated pyrolytic polymer and the effect of 12 crown 4

The drastic changes of structure and resistance of a pyropolymer (graphite) prepared by pyrolysis at 2800°C have been investigated in an electrochemical cell with 1M LiClO4 in a 7:3 volumn mixture of propylene carbonate and 1,2-dimethoxyethane. Two characteristic X-ray diffraction peaks originated from the electrolyte decomposition in graphite bulk phase due to the cointercalation of solvent and lithium ions have been clearly observed in in-situ X-ray diffraction measurement during the 1st discharge. Upon addition of 12 crown 4 into the electrochemical cell, the excessive electrolyte decomposition responsible to the two diffraction peaks has been suppressed considerably and the reversibilities of changes in resistance and structure of the electrode material and also the capacity of the cell have been much improved.