High-Power Na-Ion and K-Ion Hybrid Capacitors Exploiting Cointercalation in Graphite Negative Electrodes

Abstract

Enhanced solid-state ionic diffusion for high-power Na-ion and K-ion hybrid capacitors (SIHCs and PIHCs) is usually attained via tailoring anode materials to the nanoscale, which inevitably requires costly preactivation processes for practical applications. As an alternative to nanoscaling, herein, we propose SIHC and PIHC prototypes exploiting microsized graphite as the host anode material for cointercalation of diglyme-solvated Na+ or K+ and activated carbon as the capacitor-type cathode material. Despite the large grain size, the cointercalation of solvent–cation complexes in graphite is highly reversible and fast, endowing the devices with good cyclability (above 88% capacity retention after 5000 cycles) and power density (17 127 and 15 887 W kg–1 based on electrode materials for SIHCs and PIHCs, respectively) without any preactivation process. Furthermore, a calculation of the energy and power densities representative of the practical system was also performed, demonstrating the influence of the active electrolyte and emphasizing the importance of electrolytes and activated carbon in performance optimization.

Cucurbit[6]uril‐Derived Nitrogen‐Doped Hierarchical Porous Carbon Confined in Graphene Network for Potassium‐Ion Hybrid Capacitors

“…Both energy density and power density are comparable to or even exceed most of the reported lithium-/sodium-/PIHCs. [8,11,13,15,51,[54][55][56][57][58][59][60][61][62][63][64][65] In terms of cycling stability, the CBC@G//ACBC device delivers an extraordinary cycling stability with a capacity retention of 81.5% over 5000 cycles at 5 A g −1 , only 0.0037% capacity decay per cycle (Figure 5f and Figure S21, Supporting Information). In addition, a CBC@G//ACBC fully charged at 5 A g −1 can easily light up a "BUCT" panel welded by yellow light-emitting diodes (inset of Figure 5d).…”

“…Moreover, as shown in the radar map (Figure 5g), the comprehensive indexes of energy density, power density, and cycling stability of CBC@G//ACBC PIHCs are superior to most of the reported PIHCs. [8,11,13,15,51,[54][55][56][57][58]…”

Emerging Potassium‐ion Hybrid Capacitors

“…[48] Very recently, Passerini and co-workers reported the influence of electrolyte and ion co-intercalation in graphite on Na-ion and K-ion hybrid capacitors. [81] They assembled SICs and KICs with micro-sized graphite as the negative electrode and activated carbon cathode material by using 1 m NaPF 6 or KPF 6 in diglyme electrolyte (Figure 7a). Although K + and Na + have large ionic radius, the co-intercalation of diglyme-solvated Na + and K + in graphite is highly reversible and fast (Figure 7b, c).…”

“…The first KIC technology was assembled by using graphite as the anode and activated carbon cathode with outstanding rate capability and superior cycling stability as discussed above [48] . Very recently, Passerini and co‐workers reported the influence of electrolyte and ion co‐intercalation in graphite on Na‐ion and K‐ion hybrid capacitors [81] . They assembled SICs and KICs with micro‐sized graphite as the negative electrode and activated carbon cathode material by using 1 m NaPF 6 or KPF 6 in diglyme electrolyte (Figure 7a).…”

An Ultrastable Nonaqueous Potassium‐Ion Hybrid Capacitor

“…Hybrid capacitors (HCs), especially lithium ion hybrid capacitors (LIHCs), have been considered as a superior alternative to lithium-ion batteries (LIBs). [1][2][3] Unlike LIBs, the HCs composed of two electrodes with battery behavior and electrochemical capacitor behavior, respectively, [4,5] always possess the merits of high energy/power density and long cycling stability. [6][7][8] However, the rareness and uneven distribution of lithium resources restricts the further exploitation of LIHCs to a large extent.…”