High performance thick cathodes enabled by gradient porosity

Thick electrode with high areal loading is considered to be the most valid and practical strategy to improve the energy density of lithium ion batteries, however, its application is limited by serious electrochemical performance deterioration due to the sluggish Li+transportation. Here, LiNi0.8Co0.15Al0.05O2 (NCA) electrodes with areal loading of about 28 mg/cm2 and gradient porosity are constructed by two preparation methods, doctor-blade coating (DC) and electrostatic spinning (ES). It is revealed that the double-layered electrode (DE), whose bottom layer (close to the current collector) is made by DC and upper layer (closes to the separator) by ES, shows a high specific capacity of more than 150mAh/g under 0.5C rate, meantime it demonstrates preferable cycling stability and rate property compared to the other electrodes fabricated by diverse approaches. Experimental and simulation results indicate that the lithium concentration distribution and reaction kinetics of DE is preferable due to the reasonable porosity distribution in favor of electrolyte infiltration and polarization diminution. This finding proposes that the optimization of electrode architecture can improve the property of thick electrodes effectively, which is worth well for more attention in state-of-the-art battery manufacturing processes.