Analysis of the effect of applying external mechanical pressure on next generation silicon alloy lithium-ion cells

Abstract This research will focus on characterising and analysing next generation batteries consisting of silicon-alloy/graphite blend anode combined with a nickel rich lithium nickel manganese cobalt oxide (NMC 622) as cathode. The study is performed on prototype pouch cells (1.4 Ah). Furthermore, the effect of applying external pressure on the pouch cell is investigated. The application of external pressure has a significant beneficial impact, more specifically a 19% increase in capacity combined with a significant decrease of 50% of the discharge ohmic resistance. To investigate and quantify the pressure variation over the state of charge (SoC) a dedicated set-up has been developed which allows to apply an external pressure while measuring the pressure variation. Up to 30 N of pressure variation is observed during static tests, while no pressure variation can be observed during short pulses, demonstrating its potential to use pressure as SoC estimator. Finally, a study on the effect of initial applied external pressure on the cells' lifetime has shown that the initial applied pressure, within the range of tested pressures, has little impact on the cells’ performance and lifetime.