Application of Modified Styrene-Acrylic-Rubber-based Latex Binder to LiCoO₂ Composite Electrodes for Lithium-ion Batteries

Abstract

A new combination of styrene acrylic rubber (SAR) and sodium carboxymethylcellulose was developed as a water-borne binder for LiCoO 2 composite electrodes operating at high voltages. Four novel SAR-based latex binders were synthesized with butyl acrylate or 2-ethylhexyl acrylate monomer and styrene via copolymerization with low and high crosslinking degrees. Composite electrodes prepared using lower-crosslinking-degree SAR binders became more stretchable and flexible. Surface analysis using electron microscopy and X-ray photoelectron spectroscopy revealed that the cycled LiCoO 2 electrode was covered with approximately 10-nanometer-thick decomposition products when a conventional poly(vinylidene fluoride) binder was used. The electrodes with SAR-based binders with low crosslinkage formed a stable passivation surface during the initial cycle, and further continuous electrolyte decomposition was successfully suppressed. This passivation improved the cycle stability of LiCoO 2 electrode up to 4.5 V, i.e., 87.1 % capacity retention, even after 100 cycles and suppressed self-discharge performance at 45 °C.

Versatile Composite Binder with Fast Lithium-Ion Transport for LiCoO2 Cathodes

“…However, PEO2M and PVDF are unable to accommodate the volume changes induced by lithiation and delithiation during the cycling process, resulting in the destruction of the lattice structure and rapid capacity decay of the LiCoO 2 electrode. 49 In addition, the O5F5-LCO electrode also shows an excellent rate performance (Figure 2d). At the different cycle rates, the discharge-specific capacities of the O5F5-LCO electrode are superior to those of the PEO2M-LCO and PVDF-LCO electrodes.…”

“…The O5F5-LCO electrode maintains a higher capacity throughout the cycling process. However, PEO2M and PVDF are unable to accommodate the volume changes induced by lithiation and delithiation during the cycling process, resulting in the destruction of the lattice structure and rapid capacity decay of the LiCoO 2 electrode . In addition, the O5F5-LCO electrode also shows an excellent rate performance (Figure d).…”