In‐Situ Synthesized Gel Polymer Electrolyte Enable High Capacity and Long‐Cycle‐Life Lithium Metal Batteries

Abstract Solid‐state lithium‐metal batteries (SSLMBs) have attracted great attention due to their outstanding advantages in safety, electrochemical stability and interfacial compatibility. However, the low ionic conductivity and narrow electrochemical window restrict their practical application. Herein, in‐situ polymerization electrolytes (IPEs) crosslinked by acrylonitrile (AN) and ethylene glycol dimethacrylate (EGDMA) exhibit the superior ionic conductivity of 1.77×10−3 S cm−1 at 25 °C, the ultrahigh lithium transference number (tLi+) of 0.784 and the wider electrochemical stable window (ESW) of 5.65 V. The IPEs make the symmetrical Li||Li cells achieve the highly stable lithium stripping/plating cycling for over 3000 h at 0.1 mA cm−2. Meanwhile, IPE endows the solid‐state LiFePO4||Li batteries with an excellent long‐cycle performance over 700 cycles at 2.5 C with a capacity retention ratio over 95 %, as well as 1000 cycles at 1 C and superior capacity retention of 85 %. More importantly, the in‐situ polymerized electrolytes containing polyacrylonitrile (PAN) open up a new frontier to promote the practical application of solid‐state batteries with high safety and high energy density via in‐situ solidification technology.