Implementing Binder Gradients in Thick Water-Based NMC811 Cathodes via Multi-Layer Coating

Abstract

Multi-layer coating of electrodes with different material compositions helps unlock the full potential of high-loaded electrodes. Within this work, LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes with an areal capacity of >8.5 mA h cm−2 and tuned binder concentrations were fabricated by using an industrially relevant roll-to-roll process. Rate capability tests revealed an increase in practical specific discharge capacity independent from the C-rate for cathodes with reduced binder concentration in the top layer. At high current densities (C-rate of 1C) an improved performance of up to 27% was achieved. Additionally, at lower C-rates, binder gradients perpendicular to the current collector have beneficial effects on thick electrodes. However, surface analysis and electrochemical impedance spectroscopy revealed that without an adequate connection between the active material particles through a carbon-binder domain, charge transfer resistance limits cycling performance at high current densities.