Electrochemical Properties of Powdery LiNi_1/3Mn_1/3Co_1/3O₂ Electrodes with Styrene-Acrylic-Rubber-Based Latex Binders at High Voltage

Efforts to improve the energy density and cycling stability of lithium-ion batteries have focused on replacing LiCoO₂ in cathodes with LiNi_<i>x</i>Mn_<i>y</i>Co_1-<i>x</i>-<i>_y</i>O₂. However, reliance on polyvinylidene fluoride (PVdF) as the binder limits the application of the LiNi_<i>x</i>Mn_<i>y</i>Co_1-<i>x</i>-<i>_y</i>O₂ composite electrode for lithium-ion batteries. Here, we evaluate the electrochemical properties of a LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) powder electrode formed using a waterborne-styrene-acrylic-rubber (SAR) latex binder combined with sodium carboxymethylcellulose. The composite electrodes prepared with the SAR-based binder copolymerized with the butyl acrylate monomer and styrene exhibited high adhesive strength and excellent cyclability and rate capability. The results of surface analysis via X-ray photoelectron spectroscopy suggested that the electrode with the SAR-based binder is more resistant to electrolyte decomposition during charge and discharge cycling compared with the NMC111 electrode comprising the conventional PVdF binder. The SAR-derived passivation resulted in enhanced capacity retention during long-term cycling tests of both half- and full-cells (NMC111//graphite). An electrode with a higher Ni content, LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622), fabricated using the SAR-based binder, retained 87.1% of its capacity after 50 cycles at 4.6 V and exhibited excellent cycling stability.