Influence of Fluoroethylene Carbonate Additive Concentration on Silicon/Graphene Composite Anode
Electrode morphology and surface chemistry of SEI was investigated with various FEC concentrations (3, 5, 10, 20 wt%) in 1.2M LiPF6 at EC/EMC (3/7, by wt) electrolyte. Electrodes were prepared by blending Si/graphene active material (XG sciences), graphene and poly acrylic acid (PAA) and casting the slurry on copper foil. In the presence of FEC additive, the better capacity retention with cycling, as shown in Figure 1, was obtained, which is consistent to previous report because of thinner and stable SEI film formation (5). FEC concentration effect on cycle performance of silicon electrodes can also be observed from Figure 1. Initially, cell containing 3wt% FEC has higher reversible capacity only until 20th cycle. The cells with other FEC concentration (5-20% FEC) have better capacity retention up to 69thcycles. Lower FEC concentration in Si/graphene electrode may not lead to enough SEI layer formation due to lack of the additive for longer cyclic life. In order to find out the FEC concentration related SEI properties, we conducted electrochemical impedance spectroscopy (EIS). Other surface analysis, such as SEM, EDX and Raman, will be reported. Optimum amount of FEC additive concentration will be discussed.
The silicon material is provided by XG sciences. The validation was conducted under Cell Analysis, Modeling, and Prototyping (CAMP) Facility at ANL. Support from David Howell and Peter Faguy of the U.S. Department of Energy’s Office of Vehicle Technologies is gratefully acknowledged.
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