A rough endoplasmic reticulum-like VSe/rGO anode for superior sodium-ion capacitors

Sodium ion capacitors (SICs) exhibit both high energy and power density, offering potential as a new type of energy device. However, the fabrication of highly effective SICs is limited by the sluggish kinetics and large-volume expansion of ion insertion/extraction in the anode materials. In this featured work inspired by the structure and function of the rough endoplasmic reticulum in living cells, layer-structured vanadium diselenide (VSe 2 ) was downsized and confined on both sides of reduced graphene oxide (rGO) sheets and further assembled into a porous 3-dimensional (3D) VSe 2 /rGO aerogel. The biomimetic-structured porous 3D rGO skeleton provides a stable host to fix VSe 2 , can accelerate the diffusion and adsorption of electrolyte in the electrode materials, and buffers the volume expansion of VSe 2 during long cycles. As the anode materials of SICs, the as-prepared VSe 2 /rGO aerogel delivered a far higher reversible capacity and superior long-life stability than those of pure VSe 2 . We further analyzed the VSe 2 /rGO charge and discharge mechanism by ex situ XRD. By pairing the VSe 2 /rGO anode with active carbon (AC) as the cathode, the as-assembled SIC displayed both high power density and high energy density (106 W h kg −1 at 125 W kg −1 , 68 W h kg −1 at 5000 W kg −1 ). Overall, the superior electrochemical performance and unique biomimetic-inspired architecture of the VSe 2 /rGO aerogel offer a promising platform for designing other ion insertion/extraction host electrode materials. A rough endoplasmic reticulum-like VSe 2 /rGO were designed to tackle the sluggish sodium ion storage and severe volume expansion in a sodium ion capacitor.