Roll-to-roll manufacturing method of aqueous-processed thick LiNi0.5Mn0.3Co0.2O2 electrodes for lithium-ion batteries
Aqueous-based slurry media for cathode electrode production offers a cleaner and safer environment during the electrode manufacturing step compared with the conventional organic solvent-based method used in the lithium-ion battery industry. In this work, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and poly(ethylene oxide) (PEO) water-based binders are used to prepare LiNi0.5Mn0.3Co0.2O2 (NMC) cathode electrode. Detail electrochemical analysis reveals that the optimum mass ratio of CMC:SBR mixture is 1:2 when preparing an aqueous slurry for the NMC electrode. To mitigate particle cracking phenomenon during electrode drying step and obtain higher mass loading, a multi-layer coating technique is implemented. CMC-PEO binder mixture in aqueous media is also studied as an alternative aqueous processing method for NMC electrodes. The electrodes prepared with CMC-PEO mixture are demonstrated to be all crack-free, and electrochemical results indicate that the optimum mass loading of NMC electrode is between 15 and 18 mg cm−2. This method is further tested in pouch cell format using a roll-to-roll pilot-scale production line to show the feasibility for commercial applications. Remarkably, pouch cell results manifest that aqueous-processed NMC cathode against graphite anode maintains its 89% capacity at 1C even after 1000 cycles.