A phase inversion strategy for low-tortuosity and ultrahigh-mass-loading nickel-rich layered oxide electrodes

Abstract

Increasing the electrode thickness, thereby reducing the proportion of inactive cell components, is one way to achieve higher-energy-density lithium-ion batteries. This, however, results in higher electronic and ionic overpotentials and/or mechanical failure induced by binder migration. Here, we report ethanol-induced phase inversion as an effective method for making high-mass-loading nickel-rich, layered oxide (LiNi0.8Mn0.1Co0.1O2 [NMC811]) electrodes. The ethanol-induced phase inversion electrodes significantly outperform their conventionally processed counterparts with similar loading (35 mg/cm2) and porosity (30%) in Li/NMC half-cells (131.7 mAh/g vs. 56.7 mAh/g) at 1C (7 mA/cm2) discharge. The binder structure induced by the nonsolvent improves the pore connectivity and results in lower tortuosity factors. The rapid solvent removal reduces the binder migration during drying, enabling ultrahigh active mass loadings up to 60 mg/cm2 (12 mAh/cm2). Further, the compatibility of the phase inversion process with current roll-to-roll coating setups makes this a processing technique with high industrial feasibility.