A composite electrolyte with homogeneous heat and ion transfer for high-safety solid-state lithium batteries

Abstract

Realizing homogeneous heat and ion transfer in solid-state electrolytes is critical but remains challenging. Herein, we revealed that localized temperature hotspots in polyvinylidene fluoride electrolyte trigger side reactions and Li dendrite growth. We rationally designed a composite electrolyte by coupling modified boron nitride nanosheets (M-BNNS), enabling high in-plane (0.735 W m -1 K -1 ) and out-of-plane (0.173 W m -1 K -1 ) thermal conductivities for temperature homogenization. Moreover, the grafted functional hydroxyl and amino groups on M-BNNS can regulate Li⁺ flux through hydrogen-bonding-induced ligand adsorption, delivering a high ionic conductivity (6.43×10 -4 S cm -1 ), while tailoring the Li⁺ coordination to generate inorganic-rich interphases. Consequently, a record critical current density of 4.2 mA cm -2 was achieved. The Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells show robust cyclability under high rate (1000 cycles at 5C), highloading cathodes (15 mg cm -2 ), and high temperature (550 cycles at 60°C). The four-layer pouch cells maintain thermal stability under abusive overcharge (10 V) conditions. This work provides a promising strategy to design intrinsically safe electrolytes for solid-state batteries.