Effect of electrode pores on potassium-ion storage of α-Fe2O3

At electrode level, the contact between active material particles would inevitably form pores, which had critical impact on battery performance. In this study, urchin-shaped alpha-Fe2O3 particles were used to generate such pores. By controlling the grinding time of electrode slurry, multiple pores, including micropores, mesopores and macropores, were obtained on the electrode. It was found that the longer the grinding time, the larger the pore size on the electrode. The influence of pore topology on potassium-ion storage was further investigated by conducting cycle performance test, rate capability test, cyclic voltammetry test as well as electrochemical impedance test. The results showed that the electrode with the richest pore types delivered the highest initial Coulombic efficiency and the largest capacity of potassium-ion storage after long-term cycling. In addition, the electrode with macroporous topology exhibited the most stable cyclability at high current densities until 14 A g(-1). Further, the mechanism study indicated that the potassium-ion storage process of the electrode with micropores and mesopores varied from capacitance-dominant type to diffusion-controlled type upon cycling, whereas the opposite was true for macropores-laden electrode. This study provides a broader vision into effective pore design for potassium-ion batteries. In application scenarios, it is not only necessary to design the pores of the energy storage material itself, but also to design the pores of the whole electrode material to gain exceptional potassium-ion storage performance.