Lithium-ion battery technology plays a crucial role in realizing a sustainable energy future. With their high energy density, long service life, and fast charging capacity, lithium-ion batteries are essential for a wide range of applications, from electric vehicles to stationary energy storage systems. However, for the electrification of vehicles, there are still some challenges to overcome in terms of cost and driving range to keep up with the performance of combustion engines.
One way to reduce costs and increase gravimetric energy density is to optimize the amount of electrolyte in the battery. The main task of the electrolyte is to facilitate the charge transport of the lithium-ions between the anode and cathode. Further, the electrolyte is responsible for the formation of a stable solid electrolyte interphase to ensure a long service life. Hence, the electrolyte amount plays an important role on the electric performance of the lithium-ion battery.
To identify the most suitable electrolyte amount with regards to electric performance, eight distinct electrolyte amounts are investigated in the presented study. They range from very low electrolyte amounts, which roughly half-fill the pores of the electrodes and the separator in the jelly roll, to very high electrolyte amounts with completely filled pores and additional excess of electrolyte. The investigated cells have a cylindrical format of 4695. It is found that the energy and resistance remain constant as long as the pores are completely filled with electrolyte. As soon as electrolyte amount is not enough to completely fill the pores, the energy decreases, and the resistance increases with decreasing electrolyte amount.
If the exact electrolyte amount is unknown, it is difficult to identify its precise amount. Hence, a novel method based on moment of inertia measurements is presented to determine whether a cylindrical lithium-ion cell exhibits an excess of electrolyte or if the pores are not completely filled. Further, this method can be used to precisely determine the excess electrolyte amount generated by charging a lithium-ion cell from 0% state of charge to 100% state of charge.