LAUSR

Abstract Lithium ion battery electrodes with high rate capability are important for extreme fast charging (XFC) for electric vehicle applications. Making low-tortuous electrodes is one of the approaches to achieve XFC by enhancing ionic transport in the electrodes. In this study, we conducted directional freeze-drying of slurries cast on a copper foil to make graphite electrodes. Low-tortuous structure was created and verified by cross-sectional scanning electron microscope observations and tortuosity measurements. The out-of-plane alignment of graphite flakes, enhanced electrolyte wettability, and low tortuosity of the freeze-dried electrodes were confirmed by X-ray diffraction measurements, wettability tests, and electrochemical impedance measurements, respectively. Electrochemical measurements showed that the freeze-dried electrodes have higher capacity retention (over 8% higher after 90 cycles at C/5) and better rate capability (60% higher capacity at 1C) than the electrodes prepared by the conventional tape-casting method. These enhancements mainly arise from the improved ionic transport by the freeze-drying induced low-tortuous structure. This study provides a proof-of-concept example that tape-casting/freeze-drying can be an effective, low cost, and scalable method to reduce tortuosity and improve electrochemical performance of battery electrodes.