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-Li_1.3Al_0.3Ti_1.7(PO₄)₃ (Si@LATP)/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 Si@LATP/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 LiNi_0.5Co_0.2Mn_0.3O₂||Li cells.