A strategy to build high-performance thick electrodes for lithium-ion batteries with enhanced compressive modulus and regulated tortuosity in the phase-inversion process

Abstract

Building low-tortuosity thick electrodes, which is a practical strategy to boost the energy density of lithium-ion batteries (LIBs) by improving ion transport, has been investigated widely. As one of the effective and low-cost methods to form vertically aligned porous architectures, phase-inversion has been explored to enhance the performance of electrodes. Despite the achievement of electrodes with high mass loading and brilliant electrochemical performance via the phase-inversion process, the poor mechanical properties of electrodes impede their application in large-scale devices, such as electric vehicles (EVs). Herein, we developed a method to upgrade the compressive strength of LiFePO₄ (LFP) electrodes by tuning the composition of in the non-solvent used in the non-solvent induced phase-inversion based electrode fabrication. With the introduction of ethanol in the non-solvent bath, the compressive modulus of the low-tortuosity LFP electrode with a loading of 40 mg cm⁻² reaches up to 18.1 MPa, around four times higher than that of the electrodes processed in only water with the same mass loading. Additionally, the low-tortuosity LFP electrode produced with a mixture of water and ethanol exhibits superior rate capability (73.3 mA h g⁻¹ at 2C) and cycling stability (89.3% capacity retention after 100 cycles at 0.5C). Furthermore, electrodes with different mass loadings (20 and 30 mg cm⁻²) but similar tortuosity were obtained by adjusting the duration of immersion during the phase-inversion process with the same non-solvent bath. This report provides a novel approach to enhance the mechanical robustness of high-performance thick electrodes produced through phase-inversion as well as more precise control of the microstructures.