Initiated Chemical Vapor Deposition of Copolymer Based Electrolytes for 3D Microbatteries

Reliable fabrication of nanoscale, solid-state polymer electrolytes (SPEs) with conformal 3D coating capability and good ionic conductivity is one major challenge toward fully assembled 3D microbatteries. Here we utilize initiated chemical vapor deposition (iCVD) to produce sub-micron copolymer thin films comprised of hydroxyethyl methacrylate (HEMA) and ethylene glycol diacrylate (EGDA). These copolymer films are subsequently converted into SPEs via solution-based lithium salt doping and demonstrate ionic conductivity of (6.1±2.7)×10^-6 S cm^-1 at room temperature, the highest value reported to date for nanoscale SPEs. An investigation of copolymer composition, crosslinking density, polarity, structural relaxation is presented to explain the ion conduction.