in LIBs are mostly organic and harmful, which inevitably enhance the difficulty and the cost of battery fabrication and also bring about some environmental impact. [3] As an alternative, rechargeable aqueous zinc-ion batteries (ZIBs) have shown great promise because of low toxicity, low cost, and the abundant distribution of zinc resources. [4] More importantly, zinc possesses a low redox potential (−0.762 V vs. standard hydrogen electrode) and a high theoretical capacity (819 mAh g −1 , 5851 mAh mL −1 ). [4d] Furthermore, zinc is stable in water, which can reduce the production cost and improve the safety. [5] Despite these advantages, it is a large challenge to develop a high-performance cathode material for aqueous ZIBs that provides high and stable capacities and keeps the structure integrity in Zn 2+ uptake, which is mainly due to heavy mass and high polarization of divalent Zn 2+ . Among various reported cathode materials (such as α, β, γ, and δ-MnO 2 , [4c,6] Prussian blue analogs, [7] Na 3 V 2 (PO 4 ) 3 , [8] and vanadium-based materials [9] ), vanadium pentoxide (V 2 O 5 ) is of particular interest owing to its high Zn 2+ ion storage capacity (≈590 mAh g −1 according to the two-electron redox center of vanadium) in its layered structure consisting of VO 5 units. [10] Unfortunately, V 2 O 5 cathodes exhibit rapid capacity decline during (de)intercalation of Zn 2+ due to the low ion diffusion coefficient, poor conductivity, elements dissolution, and selfaggregation. [11] To overcome this drawback, it has been reported that intercalation of H 2 O molecules into the interlayers of V 2 O 5 could effectively enlarge and maintain the layered configuration of V 2 O 5 -based materials, which offered high Zn 2+ ion storage capability and stable cycling performance. [5c,12] Also, by inserting other metallic ions such as Ca 2+ , [9a] Zn 2+ , [9e] Na + , [13] or Li + , [14] the formation of metal vanadium oxide bronzes has been demonstrated to enhance Zn 2+ storage performances. The typical structure of these metal vanadates is that the V-O layers expand along the c-axis while the intercalated metal ions and H 2 O molecules stay in the interlayer space. [15] Despite significant progress, further boosting the Zn 2+ storage ability of V 2 O 5 -based cathodes through other strategies is still urgently required, particularly at large rates.As a highly conductive and extremely stable polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) has been reported to not only effectively improve the electronic conductivity of Aqueous zinc-ion batteries (ZIBs) have become research focus because of their cost-effectiveness, high safety, and eco-friendliness. Unfortunately, sluggish Zn 2+ diffusion kinetics and the poor cycling stability in cathode materials impede their large-scale application. Herein, V 2 O 5 @poly(3,4ethylenedioxythiophene) (PEDOT) hybrid nanosheet arrays are uniformly deposited on carbon cloth (CC) as a superior ZIB cathode. The as-fabricated V 2 O 5 @PEDOT/CC electrode displays a maximum capacity of 360 mAh ...

storage device, lithium ion batteries can provide high energy but usually suffer from a low power rate and short life span. To overcome these drawbacks, researchers propose the so-called metal-ion capacitors, or hybrid batteries, which combine a battery anode and a capacitor electrode in order to achieve tradeoff between conventional battery and supercapacitor. [6][7][8] It is expected that such hybrid system delivers a capacitor-like fast charge/ discharge rate and battery-like high capacity. Since the first introduction in 2001, great progress has been achieved in the field of hybrid lithium-ion capacitors (LICs) through better understanding of the charge storage mechanism and the development of highperformance nanostructured materials. In a LIC, the capacitive cathode is typically a carbonaceous material that enables fast charge− discharge processes, while the reported battery-type anode includes Li 4 Ti 5 O 12 , [9,10] graphite, [11] TiO 2 , [12] MnO, [13] and LiVO 3 . [14] Sodium-ion batteries are becoming one of most promising battery technologies for the foreseeable grid-scale applications, because of more earth-abundant sodium source and their similar chemistry to that of the existing lithium-ion batteries. [15][16][17][18][19][20][21][22] Despite the potential low-cost, constructing hybrid sodium ion capacitors (NICs) faces more challenge because most Na host materials have a rather sluggish kinetic due to the large Na ion sizes. Research on NICs began in early 2012, [23] and was focused on improving the power capability of the anode in order to match the fast kinetics of the capacitive cathode. Strategies to increase sodium ion (Na + ) and electron (e − ) transport kinetics of NIC electrodes reported so far include: (1) developing new electrode materials (such as 2D MXene Ti 2 C, [24] V 2 C), [25] (2) constructing more conductive electrode structures by hybridizing with carbon (such as NaTi 2 (PO 4 ) 3 /rGO, [26] C@NVP, [27] Nb 2 O 5 @C/rGO, [28] TiO 2 mesocages@rGO, [29] and (3) shortening the ion diffusion and electron transport lengths by rational designing nanostructures (such as TiO 2 nanospheres, [30] Ti(O,N) nanowires, [31] Na 2 Ti 3 O 7 nanosheets [32] ). Despite these efforts, these reported anodes of NIC still have relatively limited rate performance and especially low Na-ion storage capacity. Among other reasons, most of these electrode materials are powder samples, which require substantial amount of conductive additives (such as super P, 10-20 wt%) and binder in order to make compact films. This not only weakens the electron transport but also unable to meet the flexibility requirement.Achieving high-performance Na-ion capacitors (NICs) has the particular challenge of matching both capacity and kinetics between the anode and cathode. Here a high-power NIC full device constructed from 2D metal-organic framework (MOFs) array is reported as the reactive template. The MOF array is converted to N-doped mesoporous carbon nanosheets (mp-CNSs), which are then uniformly encapsulated with VO 2 and Na...

Metal‐ion capacitors are being widely studied to reach a balance between power and energy output by combining the merits of conventional batteries and capacitors. The main challenge for Na‐ion capacitors is that the battery‐type anode usually has unsatisfactory power density and long‐term stability since most Na host materials have a poor kinetic and structural stability. Herein, asymmetric hollow bowl‐like carbon (HBC) materials are rationally designed and fabricated through an in situ hard‐template approach. The formation originates from a subtle control of capillary force and the mechanical strength of the carbon shell. The HBCs possess abundant mesopores, high volumes of accessible surface area as well as an open macropore network. As a 3D host, MoSe2 nanocrystals are anchored onto the HBC matrix by a solid‐phase reaction. The obtained MoSe2@HBC nanobowl electrode exhibits pseudocapacitive sodium storage with fast kinetics, improved capacity at high currents, and cycle stability, which is also supported by DFT calculations. Sodium ion capacitor full cells are fabricated using the two bowl‐like architectures (MoSe2@HBC as the anode and HBC as the cathode), which deliver high energy and power densities, long cycle life, and a comparably low self‐discharge rate. Moreover, application of the HBC in a zinc‐ion capacitor (ZIC) is also demonstrated.

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