High-performance composite solid-state electrolyte combining NASICON-type Li1.5Al0.5Ti1.5(PO4)3 with ionic liquid and polymeric binders

Abstract

The use of composite solid-state electrolytes (CSEs) in Li-ion batteries presents a promising future for a new generation of solid-state battery technology. These composites address current limitations like poor room temperature ionic conductivity, low mechanical strength, and unstable interfaces. In this study, a NASICON-type Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) ceramic was prepared using a cold sintering process (CSP), incorporating LATP, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). This three-component CSE demonstrated reduced sintering temperature, energy, time, and operational costs compared to traditional methods. The LATP-based pellet achieved high density and a prismatic structure without impurities. The addition of a polymeric binder and an ionic liquid improved the nanostructuration, dispersion, mechanical properties, and relative density of the CSEs. Small-angle neutron scattering revealed nanostructuration changes, decreasing air pore size. Notably, room temperature ionic conductivities between 10^-4 – 10^-3 S cm^-1 were achieved, with a maximum conductivity of 7.02 × 10^-3 S cm^-1 and lithium-transference number of 0.35 for the sample with 99 wt.% LATP and 1 wt.% polymeric binder. Additionally, a room temperature discharge capacity of 141 mAh.g^-1 at C/10 rate was attained after 50 cycles, validating this three-component structure as a promising platform for high-performance CSEs in solid-state batteries.