In situ fabrication of lithium polymer battery basing on a novel electro-polymerization technique

Electro-polymerization technology is proposed for the in situ fabrication of polymer lithium secondary battery and exciting results have been obtained. The polymerization starts from a common used electrolyte of 1 M LiTFSI in DOL/DME (2:1 by weight) with no initiator addition through a routine charge–discharge treatment under some appointed current rate. It is found that once an appropriate current is applied in the charging–discharging of Li/1 M LiTFSI in DOL + DME/LiCoO2 cell, the original liquid electrolyte polymerizes readily during the first several cycles in an irreversible mode, and thus the desired polymer electrolyte obtained. SEM observation indicates that unlike previous report, the designed electro-polymerization does not result in destructive local break and then turnoff of the circuit, just the reverse, it helps to the formation of a smooth polymer layer, which can effectively protect the lithium substrate from corrosion and dendrite growth. Detailed examination shows that the in situ electro-polymerization does not disturb the electrochemical behavior of the cell, the cycleabilty, internal resistance are all comparable to that of a normal Li/LiCoO2 liquid secondary battery.