Zinc bis(2–ethylhexanoate), a homogeneous and bifunctional additive, to improve conductivity and lithium deposition for poly (ethylene oxide) based all-solid-state lithium metal battery

Poly (ethylene oxide) based solid polymer electrolytes are suitable candidates for constructing all-solid-state lithium metal batteries . However, the low ionic conductivities , poor mechanical strength and incompetence to suppress the penetration of Li dendrites hinder their practical application. Herein, we introduce Zinc bis(2-ethylhexanoate) (Zn (BEH) 2 ) as a homogeneous and bifunctional additive into PEO network by a simple solution casting method to achieve improvements of ionic conductivity and uniformity of lithium deposition. It is shown that the Lewis acid–base interactions between Zn (BEH) 2 and PEO chains suppress the polymer crystallization and weaken the O–Li + interaction, resulting in a good ionic conductivity of 1.1 × 10 −5  S cm −1  at 30 °C, 2.7 × 10 −4  S cm −1  at 60 °C and an improved lithium ion transfer number of 0.5 at 60 °C. Furthermore, a LiZn alloy layer is formed in-situ on lithium metal anode via the reaction between Zn (BEH) 2 and Li, which effectively prevents dendrite growth. Based on PEO–Zn (BEH) 2 polymer electrolyte, a Li/Li symmetric cell exhibits a steady cycling over 500 h with a low polarization potential of 150 mV. This strategy will illuminate new design strategy to advance polymer electrolytes towards high performance solid-state lithium batteries .