Effect of Organic Functional Groups on Poly(ethylene oxide) Electrolytes for High-Performance Solid-State Lithium-Metal Batteries

Solid polymer electrolytes are anticipated to enhance safety in high-energy lithium (Li)-metal batteries, but their further application is hindered by low ionic conductivity and uncontrollable Li dendrite growth. Herein, we propose novel fillers consisting of organic hard particles, such as chitin, chitosan, and carboxylated chitosan, to investigate the effect of functional groups on poly(ethylene oxide)-based electrolytes. Specifically, organic fillers containing amino groups (−NH2) can greatly improve the ionic conductivity with decreased activation energy, elevate the Li-ion transference number, and broaden the electrochemical window, without causing additional parasitic reactions at the interface. Consequently, it achieved stable cycling for 1000 h at 0.2 mA cm–2 and a maximum endurable current density up to 1 mA cm–2 in symmetric Li/Li cells, along with homogeneous Li deposition and a stable interface. Furthermore, it shows superior C-rate performances and long-term cycling coupled with a LiFePO4 cathode, delivering a high specific capacity of 138.8 mAh cm–2 after 400 cycles with 89.7% retention at 1C. Owing to environmental friendliness and abundant resources, organic fillers with amino functional groups have practical prospects for the design of composite polymer electrolytes.