Integration of Cointercalation and Adsorption Enabling Superior Rate Performance of Carbon Anodes for Symmetric Sodium-Ion Capacitors

Carbonmaterials have been the most common anodes for sodium-ionstorage. However, it is well-known that most carbon materials cannotobtain a satisfactory rate performance because of the sluggish kineticsof large-sized sodium-ion intercalation in ordered carbon layers.Here, we propose an integration of co-intercalation and adsorptioninstead of conventional simplex-intercalation and adsorption to promotethe rate capability of sodium-ion storage in carbon materials. Theexperiment was demonstrated by using a typical carbon material, reducedgraphite oxide (RGO400) in an ether-solvent electrolyte. The orderedand disordered carbon layers efficiently store solvated sodium ionsand simplex sodium ions, which endows RGO400 with enhanced reversiblecapacity (403 mA h g(-1) at 50 mA g(-1) after 100 cycles) and superior rate performance (166 mA h g(-1) at 20 A g(-1)). Furthermore, a symmetricsodium-ion capacitor was demonstrated by employing RGO400 as boththe anode and cathode. It exhibits a high energy density of 48 W hg(-1) at a very high power density of 10,896 W kg(-1). This work updates the sodium-ion storage mechanismand provides a rational strategy to realize high rate capability forcarbon electrode materials.

Automated summary

Researchers propose an integration of co-intercalation and adsorption to enhance the rate capability of sodium-ion storage in carbon materials. Through experiments, it is found that this approach improves the reversible capacity and rate performance of carbon materials, and can be applied to create sodium-ion capacitors with high energy density.