Thick LiCoO₂/Nickel Foam Cathode Prepared by an Adhesive and Water-Soluble PEG-Based Copolymer Binder

We report the first aqueous process fabrication of thick, flexible, and fully compressed lithium ion battery cathodes exceeding 200 μm in thickness using an adhesive, elastomeric, and ionically conductive PEG-based copolymer binder. The binder was synthesized through the statistical copolymerization of poly(ethylene glycol) methyl ether methacrylates (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) in optimal proportions. Using standard LiCoO2 as active material, dense and flexible cathode films can withhold active mass loadings over 30 mg/cm2 which deliver 4.53 mAh/cm 2 with 94% capacity retention at C/2-rate. Electrodes were fabricated by casting aqueous cathode slurries onto nickel foam, followed by drying and hard calendar compression at 10 tons/cm2. Coordinating the binder with lithium salt plays a crucial role in activating the cathode. © 2012 The Electrochemical Society.