Advanced Pre‐Diagnosis Method of Biomass Intermediates Toward High Energy Dual‐Carbon Potassium‐Ion Capacitor

Abstract Potassium ion capacitors (PICs) have the potential to combine the advantages of capacitors and batteries, making them promising energy storage substitutes for existing systems. Biomass‐based‐electrodes are very promising materials for potassium storage, however, at present, the acquisition of biomass‐based‐electrodes is mainly dependent on high temperature calcination, which makes the efficient utilization of biomass materials quite challenging. Herein, in accordance with ex‐situ 13 C NMR and Raman, a universally directional selection strategy of biomass precursors through an advanced pre‐diagnosis method for calcination intermediates and a sulfur engineering strategy are initially proposed, proving that the carbon materials derived from precursors with fewer aliphatic chains and more aromatic carbons show a higher yield and can be have more K ions inserted. In addition, the evolution mechanism of in‐plane/interlayered CS bonds is thoroughly evaluated. Notably, PICs assembled by such carbon materials as the battery‐type anode, deliver a high energy density of 151 Wh kg ‐1 and an ultrahigh power output of 10 kW kg ‐1 , closing to state‐of‐the‐art values for PICs. This breakthrough opens up a new avenue for targeted design of biomass materials and offers in‐depth insights into the evolution of S‐C bonds, promoting the energy/power density of PICs devices to a higher level.