Improved solid electrolyte interphase and Li-storage performance of Si/graphite anode with ethylene sulfate as electrolyte additive

Silicon/graphite composite anodes have drawn extensive attention in the field of power Li-ion batteries for application in electric vehicles because of their much higher capacity than that of traditional graphite anodes. In this work, ethylene sulfate (1,3,2-dioxathiolane-2,2-dioxide, DTD) is investigated as an electrolyte additive to improve the Li-storage performance of silicon/graphite composite anode. The electrochemical behavior of silicon/graphite anode including cyclic voltammogram, discharge/charge performance at various current density and during long-term cycling, and electrochemical impedance is systematically studied by adding different amounts of DTD into electrolyte. The effects of DTD on the solid/electrolyte interphase (SEI) film are analyzed through scanning electron microscopy, X-ray photoelectron and Fourier transform infrared spectroscopy. It is found that DTD participates into the film-formation process through its reductive decomposition reactions on electrode surface, producing a thin, uniform and stable SEI. The Li-storage performance of silicon/graphite anode is improved at an optimized addition amount of DTD.

Optimising 3-phenyl-1,4,2-dioxazol-5-one as an electrolyte additive for Lithium-Ion cells

An effective method to reduce carbon dioxide emissions is to switch to renewables for energy generation and transportation. Since current sources of renewable energy, such as wind and solar, are intermittent, it is essential to find ways to store energy to match supply and demand. If vehicles are to be powered by renewable energy, they need portable energy storage. Currently, lithium-ion batteries are one of the most viable solutions for energy storage. Extending the lifespan of lithium-ion batteries is the goal of this research, carried out with Dr. David Hall of Dr. Jeff Dahn’s research group at Dalhousie University in late 2017. We developed and tested a chemical compound, 3-phenyl-1,4,2-dioxazol-5-one (PDO), which greatly improves the lifespan of lithium-ion batteries. One percent of this by weight in a cell’s electrolyte, along with two percent ethylene sulfate, will extend a battery’s lifespan more than three-fold over those containing conventional vinylene carbonate-containing electrolyte.

Synthesis of surfactants based on pentaerythritol. II. Anionic gemini surfactants

Efficient syntheses of three series of anionic gemini surfactants based on pentaerythritol are described. A series of disulfates was prepared by the double displacement of the two cyclic sulfates in the S4-symmetric compound pentaerythritol spirobicyclic sulfate (1) with linear alkoxides. A second series of disulfates was prepared by reaction of the dialkoxides of di-O-alkylpentaerythritols with ethylene sulfate. The di-O-alkylpentaerythritols can be prepared as previously reported by us or by the acid-catalyzed hydrolysis of the first series of disulfates. A series of disulfonates was prepared by reaction of the dialkoxides of di-O-alkylpentaerythritols with 1,3-propanesultone. This last set of reactions was complicated by the formation of oxetanes, which probably arose from initial reversible displacement on sulfur of the sultone alkoxide by the pentaerythritol alkoxide followed by a second intramolecular displacement of the resulting sulfonate. Changing the order of addition to keep the reaction medium from containing excess base as well as lowering the reaction temperature minimized the amounts of these byproducts. All three series had excellent surfactant properties.