Optimization of electrolyte volume in lithium-ion pouch-type cells

Continued improvements in Li-ion battery (LIB) technology are needed to increase consumer adoption of electric vehicles. One opportunity to increase the specific energy while decreasing the price of LIBs is to reduce the volume of liquid electrolyte contained within the cell. Sufficient electrolyte is needed to wet all the electrode material surfaces within the cell and allow for sufficient ion transport during charge and discharge; however, excess electrolyte increases both cell weight and manufacturing cost. Herein we evaluate a series of ratios of electrolyte volume to total pore volume of separators and electrodes in single-layer pouch cells utilizing a graphite negative electrode and LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) positive electrode under charge rates ranging from 0.5 to 6C. The electrolyte volume:pore volume ratio of 1.5 demonstrated high capacity retention and low resistance after 200 cycles, while also maximizing cell specific energy. Graphical abstract: [Figure not available: see fulltext.].