 Uniform cathode films were prepared with a Li-rich solid-solution (Li[Li0.2Ni0.18Co0.03Mn0.58]O2) cathode material and a water-based hybrid polymer binder (TRD202A, JSR, Japan) composed of acrylic polymer and fluoropolymer, carboxymethyl cellulose, and conducting carbon additive. The films exhibited stable charge/discharge cycling performances (average discharge capacity: 260 mAh g−1) when cycled between 4.8 and 2.0 V for 80 cycles. After 80 cycles in the chemical environment of Li-ion cells, a cathode film prepared with the water-based hybrid polymer binder showed longer-term reliability as well as higher electrochemical resistance when compared with a cathode film using the conventional polyvinylidene difluoride binder. Additionally, even without electrochemical pretreatment, the Al2O3 coating on the cathode surfaces improved the cycling stability by preventing the cathode surface from making direct contact with H2O.