Homologous Nitrogen‐Doped Hierarchical Carbon Architectures Enabling Compatible Anode and Cathode for Potassium‐Ion Hybrid Capacitors

Abstract

practical application of PIHCs is greatly impeded by the sluggish kinetics of potassiation/depotassiation within electrodes due to the large ionic size of K + . Moreover, the imbalance of charge storage mechanism between the anode and cathode would inevitably affect the cycle stability of PIHCs. Exploring compatible anode and cathode materials is still an unmet challenge.To date, many types of anode candidates, such as MoSe 2 , [19] FeSe 2 /N-C, [20] K 2 Ti 6 O 13 , [21] NbSe 2 , [22] Ca 0.5 Ti 2 (PO 4 ) 3 @C [23] and carbon-based architectures have been tested in PIHCs. [24][25][26][27][28][29][30][31][32][33] Typically, inexpensive carbonaceous materials have been envisioned as one of the ideal candidates owing to their conspicuous cycling stability, high electrical conductivity, and environmental friendliness. Nevertheless, it has remained a tough mission to deal with their low specific capacity and volume expansion issue. Two optimization strategies have therefore been proposed to boost the capacity and cyclic stability: i) Heteroatom (N, B, P, and S) incorporation to create active sites for the potassium adsorption and enlarge the interlayer spacing of the carbon skeleton for accommodating ions; ii) Nanostructure design to alleviate the volume change and promote the contact between electrolyte and electrode material. As for the cathode, commercial activated carbon (AC) is generally employed, normally delivering limited capacity values and inferior electrochemical performance due to the incompatibility with the anode. In this regard, homologous strategy with material simplicity and cost-effectiveness affords an effective avenue to offset the kinetic imbalance between anode/cathode and improve the overall energy density of PIHCs. For example, Xu et al. synthesized S-doped multi-channel carbon fiber as an anode and activated multi-channel carbon fiber as a cathode by electrospinning. Benefiting from the advantage of a single precursor, the thus-constructed PIHCs exhibited a favorable cycling stability (a 90% capacity retention over 7000 cycles). [29] Oiu et al. used cucurbit uril as the homologous precursor to respectively derive graphene-confined nitrogen-doped carbon as the anode and KOH-activated nitrogen-doped carbon as the cathode, accordingly harvesting a high energy/power density output (172 Wh kg −1 /22 kW kg −1 ) for PIHCs. [31] Although the homology strategy has improved the performance of PIHCs, a large number of side reactions are still inevitable because of the high activity of potassium. Meanwhile, ionic conductivity is a Potassium-ion hybrid capacitors (PIHCs) have been considered as an emerging device to render grid-scale energy storage. Nevertheless, the sluggish kinetics at the anode side and limited capacity output at the cathode side remain daunting challenges for the overall performances of PIHCs. Herein, an exquisite "homologous strategy" to devise multi-dimensional N-doped carbon nanopolyhedron@nanosheet anode and activated N-doped hierarchical carbon cathode targeting high-performance PI...

Rationally Tailoring Superstructured Hexahedron Composed of Defective Graphitic Nanosheets and Macropores: Realizing Durable and Fast Potassium Storage

“…The b value usually is employed as an indicator to reflect capacitive behavior ( b = 1) or diffusion process ( b = 0.5), and it can be extracted by the slope of the log( i ) versus log( v ) plot. [ 41,42 ] As shown in Figure 5b, the calculated b values are 0.71, 0.75, and 0.72, respectively, suggesting a more dominant capacitive process in DGN‐900. Moreover, capacitive contribution to total capacity can be further quantified based on the formula of i = k 1 v + k 2 v 1/2 , [ 43,44 ] where k 1 v stands for the capacitive reaction.…”

Dimensional engineering of anode materials for high performance potassium ion hybrid capacitor—A review

“…Second, 3D frame with stable structure gives PIHC anode material strong self‐support ability, which can adapt to the volume expansion of active substance in the process of potassiation and depotassiation, reduce the influence of electrode material pulverization caused by structural collapse, and enhance the cycling stability of PIHCs 108 …”

“…Heteroatomic doping can enhance intercalation dynamics, change the electronic structure, and promote the improvement of electrochemical performance 38,108,124 . Wang et al prepared a N‐doped carbonaceous layered nanostructure (c‐SnNC‐HNA 0.75/800 ) by one‐pot method, in which tin clusters can be incorporated (Figure 6J,K).…”

“…52 Second, 3D frame with stable structure gives PIHC anode material strong self-support ability, which can adapt to the volume expansion of active substance in the process of potassiation and depotassiation, reduce the influence of electrode material pulverization caused by structural collapse, and enhance the cycling stability of PIHCs. 108 In addition, 3D nanostructured materials provide an excellent platform for a variety of active substances because of their high specific surface area and excellent electrochemical stability. Through doping and isomerization engineering treatment, a good catalytic and adsorption site for potassium ion is provided in the battery side anode in PIHC, and the utilization rate of active substances is improved.…”

“…38 Heteroatom doping 3D PIHC anode materials Heteroatomic doping can enhance intercalation dynamics, change the electronic structure, and promote the improvement of electrochemical performance. 38,108,124 Wang et al prepared a N-doped carbonaceous layered nanostructure (c-SnNC-HNA 0.75/800 ) by one-pot method, in which tin clusters can be incorporated (Figure 6J,K). The synergistic effect of the two provides a significant specific capacity increase and excellent cycling performance for the electrode material (14.47 Wh kg À1 at 7369.0 W kg À1 ) (Figure 6L,M).…”