Directional guiding of mass and charge transfer via vertically aligned graphite nanosheets for high-rate and ultralong lifespan Dual-ion batteries

Abstract

Cathode materials based on graphite for dual-ion batteries (DIBs) demonstrate multifarious merits, such as abundant resources and high anion interaction potential etc. However, the traditional irregular spherical graphite cathodes suffer from uneven anion migration through the highly tortuous pathways and the inductive anisotropic electric fields, leading to mass transfer non-uniformity and sluggish reaction kinetics. Simultaneously, large-sized anions and solvent co-intercalation restrict the anion intercalation behavior and cause severe intercalation volume expansion. To address these challenges, the vertical graphite nanosheets (VGNs) were designed to guide the anion transport directionally for the first time. The perpendicular open structures of VGNs regulate the uniform ion gradient and electric field for rapid anion diffusion by the directional and shortened ion channels with low electrode tortuosity. Meanwhile, the ordered tunnels buffer the intercalation volume expansion, enhancing the structural stability. Consequently, the DIBs with the VGNs as cathodes deliver an impressive discharge specific capacity of ∼ 220 mAh/g at 300 mA g−1, superior rate capability of up to 2000 mA g−1, and excellent cycling stability without obvious degradation after 2000 cycles, which surpasses those of reported DIBs based on anion intercalation cathodes significantly. This investigation on vertically aligned graphite nanosheets provides insights for the development of highly efficient nanomaterials for energy storage systems.