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The combination of two different binders: styrene-butadiene rubber (SBR) and polyacrylic acid (PAA), in combination with carboxymethylcellulose (CMC) has been investigated for aqueous electrode preparation of LiNi0.83Co0.12Mn0.05O2 positive electrodes. The use of Ni-rich active materials in Li-ion batteries is becoming industry standard, however, such Ni-rich cathode materials are sensitive to water, which makes the aqueous electrode manufacturing especially challenging and based on industry-information even impossible. The preparation of aqueous Ni-rich electrodes with areal capacities of 2.7 mAh cm−2 and densities of up to 3.5 g cm−3 was investigated and optimized. The electrochemical evaluation in bi-layer pouch cells showed that the performance depends heavily on the individual combination of binders. Using PAA binders, the best electrode reached 80% capacity retention only after 470 cycles. In contrast, the best electrode with SBR binder performed very similar to the PVdF reference electrode in view of rate capability and a specific 1 C capacity with 177 mAh gCAM −1 compared to 179 mAh gCAM −1 of the PVdF reference electrode. In addition, this SBR-based electrode showed excellent cycling stability at 1 C/1 C with capacity retention of 84% after 1,000 cycles; therefore, matching typical requirements for such electrodes in electric vehicle batteries.

Water-based processing of positive Li-ion battery electrodes is becoming increasingly important to enable green and sustainable electrode production. Although already widely established for carbon-based anodes, the water-based coating process still poses challenges if applied to cathode materials containing high contents of nickel. Here, positive electrodes using Ni-rich cathode materials with areal capacities of 2.6 mAh/cm2 were prepared either with epoxy, a polyisocyanate-based (ICN) binder, or polyacrylic acid (PAA). All three binders can cross-link with Na-carboxymethyl cellulose used in the formulation. In bi-layer pouch-cells, such cathodes based on epoxy or ICN binders reach an excellent long-term 1 C charge/discharge capacity retention of 85% and 88% after 1000 cycles, whereas electrodes with PAA only reach 65%. Post-mortem analysis of cells after cycling suggests aging of the cathode electrode as the main source of deactivation. Scanning electron microscopy data shows that aqueous processing does not lead to a stronger cracking of the secondary CAM particles and no enhanced dissolution of transition metals was found on the anode side. However, a stronger increase in charge-transfer impedance is observed for the aged water-based cathodes. Thus, the formation of a blocking surface layer appears to be the major reason for performance deterioration with increasing cycle number.

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