Polymer electrolytes based on PEO and lithium tetraalkoxyborate salts with ionic liquid properties for lithium-based batteries

Abstract The development of lithium-ion batteries (LIBs) with improved safety features is crucial due to the inherent risks associated with liquid electrolytes, such as fires, explosions, and leakage. This study explores the potential of solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO) and lithium tetraalkoxyborate salts (LiTAB) with ionic liquid properties as a safer alternative. Ionic liquids (ILs) are examined for their high ionic conductivity, wide electrochemical window, and excellent thermal stability, despite their high synthesis costs and viscosity challenges. The study proposes the use of a novel LiTAB salt with an oligomeric star-shaped anion structure that reduces mobility, enhancing lithium ion transference numbers. This IL serves as both a lithium salt and an active plasticizer in PEO-based SPEs, offering potential for 3D printing applications. Experimental results demonstrate that these electrolytes exhibit favorable rheological properties, high ionic conductivities, and significant lithium ion transference numbers, addressing the key limitations of conventional PEO-based electrolytes. The findings suggest that incorporating these LiTAB salts in SPEs could significantly enhance the safety and performance of LIBs, particularly for applications in miniaturized consumer electronics and electronic implants.