Influence of the Oil on the Structure and Electrochemical Performance of Emulsion-Templated Tin/Carbon Anodes for Lithium Ion Batteries.

Tin (Sn) is a useful anode material for lithium ion batteries (LIBs) because of its high theoretical capacity. We fabricated oil-in-water emulsion-templated tin nanoparticle/carbon black (SnNP/CB) anodes with octane, hexadecane, 1-chlorohexadecane, and 1-bromohexadecane as the oil phases. Emulsion creaming, the oil vapor pressure, and the emulsion droplet size distribution all affect drying and thus the morphology of the dried emulsion. This morphology has a direct impact on the electrochemical performance of the anode. SnNP/CB anodes prepared with hexadecane showed very few cracks and had the highest capacities and capacity retention. The combination of low vapor pressure, creaming, which forced the emulsion droplets into a close-packed arrangement on the surface of the continuous water phase, and the small droplets allowed for gentle evaporation of the liquids during drying. This led to lower differential stresses on the sample and reduced cracking. For octane, the vapor pressure was high, the droplet sizes were large for 1-cholorohexadecane, and there was no creaming for 1-bromohexadecane. All of these factors contributed to cracking of the anode surface during drying and reduced the electrochemical performance. Choosing an oil with balanced properties is important for obtaining the best cell performance for emulsion-templated anodes for LIBs.