Gel Polymer Electrolytes Based on an Interconnected Porous Matrix Functionalized with Poly(ethylene glycol) Brushes Showing High Lithium Transference Numbers for High Charging-Rate Lithium Ion Batteries

:gel polymer electrolytes (GPEs) with a high ionicconductivity and a high lithium transference number (tLi+) arehighly expected for lithium ion batteries to exhibit high lithium ionconduction efficiency and depression on lithium dendriteformation. In this work, a 3-dimensional interconnected porouspoly(vinylidene difluoride) (PVDF) membrane grafted with brush-like poly(ethylene glycol) (PEG) segments on pore walls has beenprepared and utilized as the porous polymer matrix for GPEs. Theinterconnected porous structure and grafted PEG segments formconduction channels and interfacial transport pathways for ions,contributing to high ionic conductivities. The brush-like PEGstructure obstructs the anion motion in the ion-conductionchannels, bringing hightLi+values to the resulting GPEs. Theprepared GPEs exhibit an ionic conductivity and atLi+value of 2.39 mS cm-1and 0.82, respectively. Consequently, the batteriesemploying the GPEs exhibit noteworthy cell performance including a capacity of 95 mAh g-1under 15C, an initial capacity retentionabove 72.5%, and a Coulombic efficiency of 99.2% after a 400-cycle test at 2C. Moreover, the cells could stably work for more than600 h at a constant current density of 0.2 mA cm-2with overpotential values lower than 15 mV. The result indicates the extremestability and subtle voltage polarization without short circuiting contributed from the restriction of lithium dendrite growth. Astructure design concept for high performance GPEs has been demonstrated.