Constructing 3D Li+-percolated transport network in composite polymer electrolytes for rechargeable quasi-solid-state lithium batteries

Rational design of solid electrolyte is of great significance to meet the criterion for high-performance lithium batteries. Herein, a solid electrolyte containing Li+-percolated conduction network has been constructed through the in-situ polymerization of nonflammable polymer electrolyte inside silane modified-Li1.3Al0.3Ti1.7(PO4)3 ([email protected])/poly (vinylidene fluoride) (PVDF) composite nanofiber membrane. Notably, the silane functionalization fully exposes the Lewis-acid sites of LATP, and the -NH3+ in polysiloxanes further enhances the anion adsorption ability of LATP based on electrostatic interaction. Characterizations and Density Function Theory (DFT) calculations suggest that the 3D [email protected]/PVDF composite fiber network functions as an ion-regulative skeleton and facilitates the generation of continuous rapid Li+ conducting pathways. The resulting composite electrolyte integrates the features of superior ionic conductivity (1.06 mS cm-1 at 25℃), near single-ion conducting characteristic (Li+ transference number=0.82), nanofiber backbone-reinforced interpenetrating polymer framework (tensile strength=15.3 MPa) and high-voltage endurance (4.86 V). Based on this mechanically robust composite electrolyte with regulated Li+ flux, symmetric Li cells exhibit outstanding Li stripping/plating reversibility. Benefitting from the in-situ solidification technique, continuous ionic conduction channels inside electrode and integrated electrode/electrolyte interface are guaranteed, rendering remarkable cycling performances for quasi-solid-state LiFePO4||Li cells (capacity retention of 99.9% after 200 cycles at 0.5C) and LiNi0.5Co0.2Mn0.3O2||Li cells.