Biomass-derived fluorinated corn starch emulsion as binder for silicon and silicon oxide based anodes in lithium-ion batteries

In this work, an in situ crosslinked network is prepared as the binder of silicon (Si), Si-graphite and silicon oxide (SiO)-graphite anodes. Fluorinated hydrolyzed corn starch synthesized by emulsifier-free polymerization is mixed with equal corn starch and 0.1 mg mL−1 dopamine, consequently form reversible interactions with electrode particles and copper foil, which plays a vital role in maintaining electrode structural integrity. It is found that the electrochemical performances of Si electrodes are heavily influenced by fluorinated carbon atoms and space linker groups of perfluoroalkyl side chains in polymeric binder. Binder with poly(N-methylperfluorobutane-1-sulfonamide ethyl acrylate) side chains (SSC4SA) exhibits the best performance, which realizes an initial discharge capacity of 3801 mAh g−1 and 88.0% capacity retention at 1 A g−1 after 100 cycles. Si-graphite and SiO–graphite composite electrodes with the mass ratio of 15:73 are prepared applying SSC4SA binder. The capacity retention of composite electrodes are 58.7% and 95.6% after 200 and 500 cycles respectively, which are far superior to commercial carboxyl methyl cellulose-styrene butadiene rubber (CMC-SBR) binder based electrodes. Such simply preparation method and the understanding of design principles for silicon anode binders in molecular-level are useful for further fundamental researches and practical applications.