Fast Li+ Transport Kinetics Enabled by TiN Nanofiber in Hybrid Polymer-based Electrolyte for Long-life Li Metal Batteries

Abstract

Polymer-based solid-state electrolytes exhibit superior advantages in flexibility, lightweight, and large-scale processability, rendering them promising for high-performance solid-state lithium metal batteries (SSLMBs) with enhanced safety. However, challenges like poor structural uniformity, sluggish Li+ transport kinetics, and inferior interface compatibility hinder their practical applications. Herein, a hybrid quasi-solid-state electrolyte (PHLT) composed of titanium nitride (TiN) fibrous nanofiller and poly(vinylidene fluoride-co-hexafluoropropylene)/lithium bis(trifluoromethanesulfonyl)imide (PVDF-HFP/LiTFSI) matrix was developed. The inorganic filler could decrease the crystallinity of PVDF-HFP, propel the polar transformation of the polymer, as well as adsorb and immobile the TFSI− anions, significantly enhancing Li-ion transport kinetics. Further, the in-situ generated fast Li-ion conductor, i.e., LixTiN, derived from lithiated TiN, along with a smooth but dense LiF interphase, effectively bridges the electrolyte|electrode interface and suppresses Li dendrite growth. Consequently, the as-fabricated Li|PHLT|LiFePO4 cells achieve exceptional cycling stability over 3000 cycles at 2 C with superior average Coulombic efficiency of 99.8%. Notably, this strategy also enables great compatibility with matching high-loading cathodes (9.5 mg cm−2), moreover, delivers impressive performance in large areal pouch cells as well as bilayer stacking cells. This work provides an innovative approach to constructing solid-state electrolyte with enhanced diffusion kinetics and interface compatibility, paving the way for practical SSLMB applications.