Fabricating ultrathick, dense electrodes for compact rechargeable batteries with ultrahigh areal and volumetric capacity

Thick electrode engineering greatly enhances the areal loading of electroactive materials and gravimetric energy density of batteries , but it brings sluggish electron/ion diffusion kinetics and fluffy structure (high porosity) owing to its prolonged electronic/ionic diffusion length . Herein, we develop a general soft chemical strategy to fabricate a series of ultrathick yet dense electrodes with high conductivity, which achieves high utilization of electroactive materials, ultrahigh areal and volumetric capacities. Specifically, the ultrathick dense graphene-encapsulated Na 3 V 2 (PO 4 ) 3 electrode (loading: 120 mg cm −2 , thickness: 492 μm) and graphene-encapsulated LiFePO 4 (HD-LFP@G) electrode (loading: 152 mg cm −2 , thickness: 623 μm) achieve the utilization ratios of 73 and 90%, and the ultrahigh areal capacities of 9.3 and 21 mAh cm −2 , respectively. Importantly, the ultrathick and dense HD-LFP@G//graphene-encapsulated graphite (HD-graphite@G) full batteries also displayed a high areal capacity of 9.4 mAh cm −2 . Detailed mechanism analysis revealed that such superior electrochemical performance stems from its 3D high-conductivity and network-like graphene-encapsulated structure, which maintains good electronic/ionic diffusion kinetics and structural stability, while the dense structure endows high volumetric performance in the ultrathick dense electrodes. This work provides an universal strategy to design ultrathick, dense electrodes towards compact energy storage with high volumetric and gravimetric energy density in practical applications.