Unveiling low-tortuous effect on electrochemical performance toward ultrathick LiFePO4 electrode with 100 mg cm−2 area loading

Thickening electrodes can significantly increase the energy density and reduce the cost of batteries. However, the electrochemical performance of thick electrodes is limited by the kinetics of lithium-ion transport, resulting in severe polarization and poor electrochemical performance. Here, we investigate the electrochemical behavior of low-tortuous thick electrodes constructed by freeze-drying method. It is shown that low tortuosity can accelerate the transport of lithium-ions and mainly reduce the concentration polarization, leading to improved rate capability. Due to the fast lithium-ions transport kinetics, the electrochemical performance of low tortuous thick electrode is not dominantly determined by concentration polarization until a thickness of 125 μm, much higher than a thickness of 46 μm for the high tortuosity electrode. Thick electrodes with low tortuosity possess a stable cathode electrolyte interface, leading to superior cyclability. Area capacities of low tortuous thick electrodes increase linearly with active material loadings, indicating the independence of specific capacity and electrode thickness. Even at an ultrahigh area loading of 99.56 mg cm−2, this low-tortuous thick electrode delivers an area capacity of 14.8 mAh cm−2. This work reveals the electrochemical behavior of low tortuous thick electrode, providing guidance for applicable thick electrodes in high-performance lithium batteries.