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

Abstract

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. The low-tortuous thick electrode with straight lithium-ion transport channels is prepared by freezing drying strategy. Low-tortuous electrodes can not only accelerate lithium-ion transport kinetics and reduce the concentration polarization, but also possess a stable cathode electrolyte interface, enabling superior rate capability and cyclability. The rate determining step of the low-tortuous electrode changes to concentration polarization at bigger critical thickness. • The low tortuous LiFePO 4 thick electrode was prepared by the freeze-drying route. • Low tortuous electrode structure is beneficial for the transport of lithium-ions. • Low tortuous LiFePO 4 electrode shows superior rate capability and cyclability.