Tetra-arm Poly(ethylene glycol)-based Ion Gels with Controlled Polymer Network Defects: Application to Lithium-ion Battery Gel Electrolytes

We report network defect-controlled ion gels fabricated from two key materials: tetra-arm poly(ethylene glycol) (TetraPEG) prepolymers and a lithium (Li) salt/ionic liquid (IL) electrolyte. The resulting TetraPEG ion gels exhibited higher ionic conductivity than the corresponding IL solution, and the network defects in the gels strongly affected the electrode reaction (Li-ion insertion/desertion reaction at the graphite negative electrode). Specifically, the charge/discharge capacities increased linearly with the proportion of network defects. Three-dimensional polymer network ion gels were prepared from TetraPEG prepolymers. The network defects were quantitatively controlled to yield defect-controlled TetraPEG ion gels. The TetraPEG ion gels exhibited excellent ion-conducting properties, and their charge/discharge behaviors at a graphite electrode depended strongly on their network defects.