Integration of flexibility, cyclability and high-capacity into one electrode for sodium-ion hybrid capacitors with low self-discharge rate

Advanced Energy Materials

et al. 2020

Self Cite

175

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.

Section: Synthesis Of Mose 2 @Hbcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In Situ Hard‐Template Synthesis of Hollow Bowl‐Like Carbon: A Potential Versatile Platform for Sodium and Zinc Ion Capacitors

Fei

Advanced Energy Materials

et al. 2020

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175

“…In addition, the conventional powder electrode is unsuitable for flexible cells. [ 16–19 ] Therefore, it is highly desirable to develop a facile and high‐yield synthesis methods toward carbon‐based composite hollow electrode materials, which are also freestanding and flexible.…”

Section: Introductionmentioning

confidence: 99%

Al₂O₃‐Assisted Confinement Synthesis of Oxide/Carbon Hollow Composite Nanofibers and Application in Metal‐Ion Capacitors

Mao

Chao

et al. 2020

Small

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Hollow micro-/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a "top-down" casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic-layerdeposition (ALD) Al 2 O 3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)-carbon composite hollow fibers after removal of Al 2 O 3. Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni-based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as-obtained hollow V 2 O 3-C fiber membrane is employed as a freestanding and flexible electrode for lithium-ion capacitor. The device shows an impressive energy density and a high power density.

“…It has been extensively demonstrated that the growth of 3D nanoarrays on highly conductive substrates is an effective method to achieve high rate capability and long‐term cyclability, because the ordered array configuration allows for mechanical stress release during ion insertion/de‐insertion processes. [ 3,32–35 ] Most of the reported high Na‐storage capacities of Na 2 Ti 3 O 7 are achieved at a rather low mass loading (usually <1 mg cm −2 ). In our recent work, Na 3 (VO) 2 (PO 4 ) 2 F cuboid arrays were uniformly grown on CNFs, and high sodium‐storage performance can be achieved at a high mass loading of 6.5 mg cm −2 .…”

Section: Introductionmentioning

confidence: 99%

“…In our recent work, Na 3 (VO) 2 (PO 4 ) 2 F cuboid arrays were uniformly grown on CNFs, and high sodium‐storage performance can be achieved at a high mass loading of 6.5 mg cm −2 . [ 34 ] We have also demonstrated that the capacity decay of some Na‐storage anode materials (such as MoS 2 , [ 33 ] VS 2 , [ 3 ] VO 2 , [ 32 ] and Nb 2 O 5 [ 36 ] ) can be efficiently restrained by integrating with the CNF membrane.…”

Section: Introductionmentioning

confidence: 99%

Aligned Arrays of Na₂Ti₃O₇ Nanobelts and Nanowires on Carbon Nanofiber as High‐Rate and Long‐Cycling Anodes for Sodium‐Ion Hybrid Capacitors

Qiu

et al. 2020

Small Structures

Self Cite

Sodium‐ion capacitors (SICs) have attracted extensive attentions due to their integration of high‐energy battery and high‐power capacitor as well as the naturally abundant sodium resource. A major challenge of current SICs is to achieve high rate performance and long‐cycle stability of the battery‐type anode. Herein, fast sodium storage is achieved from sodium titanate (Na2Ti3O7) arrays that are uniformly grown on highly conductive carbon nanofiber networks with a high mass loading of 5.6 mg cm−2. Nanowires and nanobelts of Na2Ti3O7 are both synthesized, and their Na‐ion storage properties are compared. Both arrays can be used as binder‐free and flexible electrodes, but the nanobelts exhibit higher specific capacity and better rate performance than the nanowires with similar mass loading. The difference between two types of nanostructures is ascribed to their different kinetics in ion/charge transport, according to the electrochemical impedance data. SIC full devices consisting of the Na2Ti3O7 nanobelt anode and biomass‐derived porous carbon cathode are constructed, which show pretty high specific energy and power performance.