Building Efficient Ion Pathway in Highly Densified Thick Electrodes with High Gravimetric and Volumetric Energy Densities

A common practice in thick electrode design is to increase porosity to boost charge transport kinetics. However, a high porosity offsets the advantages of thick electrodes in both gravimetric and volumetric energy densities. Here we design a freestanding thick electrode composed of highly densified active material regions connected by continuous electrolyte-buffering voids. By wet calendering of the phase-inversion electrode, the continuous compact active material region and continuous ion transport network are controllably formed. Rate capabilities and cycling stability at high LiFePO4 loading of 126 mg cm–2 were achieved for the densified cathode with porosity as low as 38%. The decreased porosity and efficient void utilization enable high gravimetric/volumetric energy densities of 330 Wh kg–1 and 614 Wh L–1, as well as improved power densities. The versatility of this method and the industrial compatible “roll-to-roll” fabrication demonstrate an important step toward the practical application of thick electrodes.