Abstract
Potassium ion hybrid capacitors (KICs) have drawn tremendous attention for large-scale energy storage applications because of their high energy and power densities and the abundance of potassium sources. However, achieving KICs with high capacity and long lifespan remains challenging because the large size of potassium ions causes sluggish kinetics and fast structural pulverization of electrodes. Here, we report a composite anode of VO2–V2O5 nanoheterostructures captured by a 3D N-doped carbon network (VO2–V2O5/NC) that exhibits a reversible capacity of 252 mAh g–1 at 1 A g–1 over 1600 cycles and a rate performance with 108 mAh g–1 at 10 A g–1. Quantitative kinetics analyses demonstrate that such great rate capability and cyclability are enabled by the capacitive-dominated potassium storage mechanism in the interfacial engineered VO2–V2O5 nanoheterostructures. The further fabricated full KIC cell consisting of a VO2–V2O5/NC anode and an active carbon cathode delivers a high operating voltage window of 4.0 V and energy and power densities up to 154 Wh kg–1 and 10 000 W kg–1, respectively, surpassing most state-of-the-art KICs.
Highlights
IntroductionLarge-scale and low-cost energy storage systems are becoming increasingly important in our society because of their ability to power industrial manufacturing and electric vehicles, store renewable energies (e.g., solar, wind, and hydropower energies), and balance power grids.[1]
Large-scale and low-cost energy storage systems are becoming increasingly important in our society because of their ability to power industrial manufacturing and electric vehicles, store renewable energies, and balance power grids.[1]
VO2−V2O5/N-doped carbon (NC) was synthesized via a self-template strategy (Figure S1)
Summary
Large-scale and low-cost energy storage systems are becoming increasingly important in our society because of their ability to power industrial manufacturing and electric vehicles, store renewable energies (e.g., solar, wind, and hydropower energies), and balance power grids.[1]. Potassium reserves in the Earth’s crust are nearly 1000 times greater than lithium sources. It features a low reduction potential of −2.93 V vs SHE, similar to the value of lithium (−3.04 V), promising for designing KICs with electrochemical performance comparable to LICs.[9,10] most of the reported KICs suffer from moderate energy density and electrochemical stability,[11−28] due to the large ionic radius of K+ (1.38 Å). As a result, developing electrode materials with high capacities and enhanced structural stability throughout long-term cycling is critical to the application of KICs.[29]
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