An ethylene carbonate/propylene carbonate electrolyte for improved cycle life and safety of silicon-graphite/NMC (Ni = 80–83 %) high-energy lithium-ion battery cells

High energy silicon-carbon electrodes have been paired with ‘high Nickel’ NMC cathodes and used to optimize a ‘linear alkyl carbonate-free’ electrolyte. The optimization was conducted via the screening of 23 electrolyte formulations using two sets of silicone carbon composite electrodes in coin cells. The best electrolyte formulation was then ‘validated’ in a setting closer to their final application, using single layer pouch cells and a commercial surfactant coated separator to solve the wetting issue met with this family of electrolytes with both conventional and ceramic coated separators. Despite its lower rate capability above 1C, this electrolyte allows a 45% increase of the capacity retention in pouch cell with a 9% Si-C-based anode and a NMC83 cathode. The safety of the electrolyte is also improved markedly. During cycling up to 4.3V and 5.0V, the total volume of hydrogen evolved was reduced more than 3.6 times over 3 cycles for the electrolyte free of linear carbonates. In fine, accelerating rate calorimetry shows that the use of these electrolytes improves the overall cell safety for this electrolyte, which shows that, for high energy applications, EC/PC electrolytes with the right additive combination can allow both longer cycle life and improved safety.