The Impact of Vinylene Carbonate and Fluoroethylene Carbonate Mixtures in Lithium-Ion Pouch Cells with Chemically Synthesized Silicon-Carbon Containing Graphite Composite Negative Electrodes

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Abstract
Silicon-containing lithium-ion cells provide higher energy density than cells with only graphite in the negative electrode. This paper investigated the impact of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) on the performance of lithium-ion pouch cells with NMC-type positive electrodes (Ni83-type and Ni65-type) and 20 % chemical silicon-carbon (chemical SiC) in their negative electrode. The additive blends consisted of 2 wt. % VC with either 0, 4, or 10 wt. % FEC. Insitu volume measurements were carried out to study the impact of additives on gas volume produced during the formation step. Long-term cycling tests at 40 °C and 55 °C, and storage experiments at 60 °C, were conducted to investigate the effect of the additives on cell performance. Post-cycle analyses were conducted on cells using impedance spectroscopy (EIS) and gas chromatography-mass spectrometry (GC-MS). The results demonstrate that 2 wt % VC is an effective additive to improve cell performance in both Ni83-type and Ni65-type pouch cells with 20 % chemical SiC. The additive blend, 2 wt % with 4 wt % FEC, shows a positive impact, however, addition of 10 wt % FEC produces minimal additional impact.