Coral reef-inspired hierarchical channel electrolyte: LATP framework-ZrO₂ triggering activation of amorphous fast-ion channels in PVDF-HFP.

Abstract

To cope with the demand for high-safe lithium-ion batteries, this study developed a new PVDF-HFP/LiTFSI/LATP/ZrO₂ (PHLZ) composite solid electrolyte with coral reef-type hierarchical channel structure. This electrolyte integrates the advantages of the NASICON fast ion conductor Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃ (LATP) framework and the multifunctional inducer ZrO₂ through a dual-filler synergistic strategy. LATP large particles construct a continuous three-dimensional lithium ion rapid transmission main channel and promote LiTFSI dissociation through the surface Lewis acid site. ZrO₂ nanoparticles effectively passivate the LATP surface to inhibit reduction and improve their dispersion, and form hydrogen bonds with the -CF₂-group of PVDF-HFP through the surface hydroxyl group, trigger activation of the fast ion channel in the amorphous region of the polymer and inhibit crystallization. The PHLZ-2 electrolyte with an optimized ratio (LATP:ZrO₂ = 2:1) exhibits excellent comprehensive performance, with ion conductivity up to 1.76 × 10^-3 S cm^-1 at 60 °C, lithium ion migration number up to 0.76, wide electrochemical window (>4.74 V vs. Li⁺/Li), significantly improved thermal stability and flame retardant (3 s self-extinguishing), and excellent lithium deposition/peel stability. When applied to Fe₃O₄/phosphorus doped graphene oxide (FPG) anode system, the FPG//PHLZ-2//Li half-cell showed high rate performance (1101.65 mAh g^-1 at 3 A/g) and long cycle life (1225.19 mAh g^-1 after 300 times at 1.10 mA cm^-2); the assembled FPG//PHLZ-2//LFP full battery also showed high capacity and excellent cycle stability. This research provides new ideas for designing high-performance and safe composite solid electrolytes.