Potassium ion batteries (KIB) have become a compelling energy‐storage system owing to their cost effectiveness and the high abundance of potassium in comparison with lithium. However, its practical applications have been thwarted by a series of challenges, including marked volume expansion and sluggish reaction kinetics caused by the large radius of potassium ions. In line with this, the exploration of reliable anode materials affording high electrical conductivity, sufficient active sites, and structural robustness is the key. The synthesis of ZIF‐8@ZIF‐67 derived nitrogen‐doped porous carbon confined CoP polyhedron architectures (NC@CoP/NC) to function as innovative KIB anode materials is reported. Such composites enable an outstanding rate performance to harvest a capacity of ≈200 mAh g−1 at 2000 mA g−1. Additionally, a high cycling stability can be gained by maintaining a high capacity retention of 93% after 100 cycles at 100 mA g−1. Furthermore, the potassium ion storage mechanism of the NC@CoP/NC anode is systematically probed through theoretical simulations and experimental characterization. This contribution may offer an innovative and feasible route of emerging anode design toward high performance KIBs.

Graphdiyne (GDY), an emerging type of carbon allotropes, possesses fascinating electrical, chemical, and mechanical properties to readily spark energy applications in the realm of Li‐ion and Na‐ion batteries. Nevertheless, rational design of GDY architectures targeting advanced K‐ion storage has rarely been reported to date. Herein, the first example of synthesizing GDY frameworks in a scalable fashion to realize superb potassium storage for high‐performance K‐ion battery (KIB) anodes is showcased. To begin with, first principles calculations provide theoretical guidances for analyzing the intrinsic potassium storage capability of GDY. Meanwhile, the specific capacity is predicted to be as high as 620 mAh g−1, which is considerably augmented as compared with graphite (278 mAh g−1). Experimental tests then reveal that prepared GDY framework indeed harvests excellent electrochemical performance as a KIB anode, achieving high specific capacity (≈505 mAh g−1 at 50 mA g−1), outstanding rate performance (150 mAh g−1 at 5000 mA g−1) and favorable cycling stability (a high capacity retention of over 90% after 2000 cycles at 1000 mA g−1). Furthermore, kinetic analysis reveals that capacitive effect mainly accounts for the K‐ion storage, with operando Raman spectroscopy/ex situ X‐ray photoelectron spectroscopy identifying good electrochemical reversibility of GDY.

Nitrogen doping has readily emerged as an efficient solution to boost potassium‐ion storage of carbonaceous materials. Nevertheless, the capacity and lifespan enhancement of derived electrodes is still plagued by the incompetent in coordinating the dopant configurations. In the realm of emerging potassium‐ion hybrid capacitor (PIHC) device, dictating nitrogen doping to enhance pseudocapacitive behavior and improve K+ diffusion kinetics of carbonaceous anodes is scarcely demonstrated. Herein, we report the design of hierarchical N‐doped carbon nanopolyhedron@nanosheet composite via a salt‐confined synthetic strategy with tunable doping configurations toward advanced PIHC anode. A harmonized edge‐ to graphitic‐nitrogen ratio in such dual‐carbon materials enables outstanding rate capability (130 mAh g−1 at 10.0 A g−1) and cyclic performance (with a capacity retention of 80% after 2000 cycles at 5.0 A g−1) in half‐cell tests. As expected, the thus‐assembled PIHC full device with a working voltage of 4.2 V presents a high energy/power density (146 Wh kg−1/8000 W kg−1) and favorable cyclicability. This work is anticipated to offer an innovative insight into the coordination of nitrogen doping configurations in heteroatom‐doped carbon anode targeting high‐performance PIHC applications.

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...

N‐doped carbon nanopolyhedron@nanosheet composite produced by a salt‐confined route harnesses 3D porous framework, dual‐carbon architecture and harmonized nitrogen content, accordingly enabling excellent potassium ion storage toward the construction of high‐performance potassium‐ion hybrid capacitor device. (DOI: 10.1002/inf2.12225) image

No abstract