Lowering the Interfacial Resistance in Li6.4La3Zr1.4Ta0.6O12|Poly(Ethylene Oxide) Composite Electrolytes

Abstract

Summary: Ceramic-polymer electrolytes are expected to improve safety, energy density, and power of next-generation battery technologies. The realization of this type of battery is, however, hindered by the high interfacial resistance across the ceramic-polymer interface. Here, we report a surface-modification strategy to lower the interfacial resistance by more than four orders of magnitude. For this purpose, we activate the surface-terminated oxygen of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles by plasma etching and functionalize them by immersing the LLZTO particles in a (3-glycidyloxypropyl)trimethoxysilane (Si-R) solution to form covalently bonded Si-R layers. The Si-Rs are terminated by an epoxy group that reacts with the hydroxyl group of the poly(ethylene oxide) (PEO) via a ring-opening reaction. The modifications improve the screening of the oxygen polarity of LLZTO particles and lower the free volume between both components, resulting in a LLZTO|PEO interface resistance of 500 Ω cm2 at 20°C, the lowest value reported so far to the best of our knowledge.

Keywords

• LLZTO
• PEO
• composite electrolyte
• solid electrolyte
• solid-state battery