Abstract
Sodium metal batteries are considered one of the most promising low-cost high-energy-density electrochemical energy storage systems. However, the growth of unfavourable Na metal deposition ...and the limited cell cycle life hamper the application of this battery system at a large scale. Here, we propose the use of polypropylene separator coated with a composite material comprising polydopamine and multilayer graphene to tackle these issues. The oxygen- and nitrogen- containing moieties as well as the nano- and meso- porous network of the coating allow cycling of Na metal electrodes in symmetric cell configuration for over 2000 h with a stable 4 mV overpotential at 1 mA cm
−2
. When tested in full Na || Na
3
V
2
(PO
4
)
3
coin cell, the coated separator enables the delivery of a stable capacity of about 100 mAh g
−1
for 500 cycles (90% capacity retention) at a specific current of 235 mA g
−1
and satisfactory rate capability performances (i.e., 75 mAh g
−1
at 3.5 A g
−1
).
Graphene and graphene oxide (GO), as wonder materials, have penetrated nearly every field of research. One of their most attractive features is the functionality and assembly of graphene or GO, in ...which they can be considered to be chemically functionalized building blocks for creating unconventional porous graphene materials (PGMs) that not only combine the merits of both porous materials and graphene, but also have major advantages over other porous carbons for specific applications. The chemistry and approaches for functionalizing graphene and GO are first introduced, and typical procedures for pore creation (e.g., in‐plane pores, 2D laminar pores, and 3D interconnected pore assemblies), self‐assembly, and tailoring mechanisms for PGMs to highlight the significance of precise control over the pore morphology and pore size are summarized. Because of their unique pore structures, with different morphologies and intriguing properties, PGMs serve as key components in a variety of applications such as energy storage, electrocatalysis, and molecular separation. Finally, the challenges relating to PGMs from the understanding of chemical self‐assembly to specific applications are discussed, and promising solutions on how to tackle them are presented. This provides an insightful outlook for the future development of the chemistry and applications of PGMs.
Recent advances in the chemistry of graphene and porous graphene materials, including surface chemistry, interface chemistry, assembly chemistry, and functionalization chemistry, and their potential applications are reviewed. Additionally, their porous structure‐performance relationships for energy storage and conversion, electrocatalysis, and molecular separation are summarized.
Scalable production of high-quality heteroatom-modified graphene is critical for microscale supercapacitors but remains a great challenge. Herein, we demonstrate a scalable, single-step ...electrochemical exfoliation of graphite into highly solution-processable fluorine-modified graphene (FG), achieved in an aqueous fluorine-containing neutral electrolyte, for flexible and high-energy-density ionogel-based microsupercapacitors (FG-MSCs). The electrochemically exfoliated FG nanosheets are characterized by atomic thinness, large lateral size (up to 12 μm), a high yield of >70% with ≤3 layers, and a fluorine doping of 3 at%, allowing for large-scale production of FG-MSCs. Our ionogel-based FG-MSCs deliver high energy density of 56 mWh cm–3, by far outperforming the most reported MSCs. Furthermore, the all-solid-state microdevices offer exceptional cyclability with ∼93% after 5000 cycles, robust mechanical flexibility with 100% of capacitance retention bended at 180°, and outstanding serial and parallel integration without the requirement of metal-based interconnects for high-voltage and high-capacitance output. Therefore, these FG-MSCs represent remarkable potential for electronics.
Heteroatom doping of nanocarbon films can efficiently boost the pseudocapacitance of micro-supercapacitors (MSCs); however, wafer-scale fabrication of sulfur-doped graphene films with a tailored ...thickness and homogeneous doping for MSCs remains a great challenge. Here we demonstrate the bottom-up fabrication of continuous, uniform, and ultrathin sulfur-doped graphene (SG) films, derived from the peripherical trisulfur-annulated hexa-peri-hexabenzocoronene (SHBC), for ultrahigh-rate MSCs (SG-MSCs) with landmark volumetric capacitance. The SG film was prepared by thermal annealing of the spray-coated SHBC-based film, with assistance of a thin Au protecting layer, at 800 °C for 30 min. SHBC with 12 phenylthio groups decorated at the periphery is critical as a precursor for the formation of the continuous and ultrathin SG film, with a uniform thickness of ∼10.0 nm. Notably, the as-produced all-solid-state planar SG-MSCs exhibited a highly stable pseudocapacitive behavior with a volumetric capacitance of ∼582 F cm–3 at 10 mV s–1, excellent rate capability with a remarkable capacitance of 8.1 F cm–3 even at an ultrahigh rate of 2000 V s–1, ultrafast frequency response with a short time constant of 0.26 ms, and ultrahigh power density of ∼1191 W cm–3. It is noteworthy that these values obtained are among the best values for carbon-based MSCs reported to date.
Abstract
Planar micro-supercapacitors are recognized as one of the most competitive on-chip power sources for integrated electronics. However, most reported symmetric micro-supercapacitors suffer ...from low energy density. Herein, we demonstrate the facile mask-assisted fabrication of new-type all-solid-state planar hybrid micro-supercapacitors with high energy density, based on interdigital patterned films of porous vanadium nitride nanosheets as negative electrode and Co(OH)
2
nanoflowers as positive electrode. The resultant planar hybrid micro-supercapacitors display high areal capacitance of 21 mF cm
−2
and volumetric capacitance of 39.7 F cm
−3
at 0.2 mA cm
−2
, and exhibit remarkable energy density of 12.4 mWh cm
−3
and power density of 1750 mW cm
−3
, based on the whole device, outperforming most reported planar hybrid micro-supercapacitors and planar asymmetric micro-supercapacitors. Moreover, all-solid-state planar hybrid micro-supercapacitors show excellent cyclability with 84% capacitance retention after 10000 cycles, and exceptionally mechanical flexibility. Therefore, our proposed strategy for the simplified construction of planar hybrid micro-supercapacitors will offer numerous opportunities of utilizing graphene and other 2D nanosheets for high-energy microscale supercapacitors for electronics.
Two-dimensional MXenes are key high-capacitance electrode materials for micro-supercapacitors (MSCs) catering to integrated microsystems. However, the narrow electrochemical voltage windows of ...conventional aqueous electrolytes (≤ 1.23 V) and symmetric MXene MSCs (typically ≤ 0.6 V) substantially limit their output voltage and energy density. Highly concentrated aqueous electrolytes exhibit lower water molecule activity, which inhibits water splitting and consequently widens the operating voltage window. Herein, we report ultrahigh-voltage aqueous planar asymmetric MSCs (AMSCs) based on a highly concentrated LiCl-gel quasi-solid-state electrolyte with MXene (Ti3C2Tx) as the negative electrode and MnO2 nanosheets as the positive electrode (MXene//MnO2-AMSCs). The MXene//MnO2-AMSCs exhibit a high voltage of up to 2.4 V, attaining an ultrahigh volumetric energy density of 53 mWh cm−3. Furthermore, the in-plane geometry and the quasi-solid-state electrolyte enabled excellent mechanical flexibility and performance uniformity in the serially/parallel connected packs of our AMSCs. Notably, the MXene//MnO2-AMSC-based integrated microsystem, in conjunction with solar cells and consumer electronics, could efficiently realize simultaneous energy harvesting, storage, and conversion. The findings of this study provide insights for constructing high-voltage aqueous MXene-based AMSCs as safe and self-sufficient micropower sources in smart integrated microsystems.
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Among typical energy storage devices, supercapacitors play a predominant role in industry and our life owing to their rapid charge/discharge rate, superior lifespan, high power density, low cost, and ...outstanding safety. However, their low energy density has severely hindered their further development. For active electrode materials, graphene-based mesoporous nanosheets (GMNs) can combine the advantages from graphene and mesoporous materials, which can be applied to significantly enhance the energy density of supercapacitors. Here, we review the recent advances in GMNs for supercapacitors, focusing on in-plane mesoporous graphene and sandwich-like graphene-based heterostructures. Firstly, the synthesis of in-plane mesoporous graphene with ordered and disordered mesopores for supercapacitors is introduced. Secondly, sandwich-like graphene-based heterostructures are classified into mesoporous carbon/graphene, mesoporous heteroatom-doped carbon/graphene, mesoporous conducting polymer/graphene, and mesoporous metal oxide/graphene, and their applications in supercapacitors are discussed in detail. Finally, the challenges and opportunities of GMNs for high-performance supercapacitors are proposed.
The increasing demand for portable, wearable, and miniaturized electronics has substantially promoted the immense development of planar microsupercapacitors (MSCs) built on a single substrate. ...Atomically thin two-dimensional (2D) nanosheets, by virtue of their intrinsically unique structure and fascinating electrochemical properties, provide a new material platform for the creation of high performance planar MSCs in which the electrolyte ions can completely utilize flat architecture and ultrathin thickness of 2D nanosheets, parallel to the direction of ionic diffusion along the plane of 2D nanosheets. Herein, we present an overview and perspective on diverse 2D materials for planar MSCs. First, an introduction is presented to highlight the advances of MSCs, the uniqueness of 2D materials in the assembly of planar MSCs with three different configurations, i.e., stacked, interdigital, and 3D planar geometries, and the progress of microfabrication techniques for microelectrodes of MSCs. Second, the state-of-the-art 2D materials to manufacture planar MSCs, including graphene, transition metal oxides/hydroxides, transition metal dichalcogenides, metal carbides, metal nitrides, phosphorene, boron nitride, metal-organic frameworks, and covalent-organic frameworks, are systemically discussed in detail. Special emphasis is given to the multiple roles of 2D materials for functional components as active materials, current collectors, additives/binders, and separators for planar MSCs. Finally, the existing challenges and prospective solutions of 2D materials for planar MSCs with high performance and various innovative form factors are proposed.
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A simple process to synthesize polyglycerol modified polysiloxane surfactants has been carried out applying a “grafting-to” approach. After formation of allyl polyglycerol ether ...(APGE) from diglycerol (DGY) and allyl glycidyl ether (AGE), polysiloxane modified by designed number of polyglycerol groups (PHMS-APGE) were obtained by connecting the APGE structure to different SiH functionalized polyhydromethyl siloxane (PHMS). The synthesized APGE-PHMS were characterized by IR and 1H NMR. Solubility measurements showed that the solubility of the as-prepared polymers increased in polar solvents with the increasing of the amount of hydrophilic APGE groups. Furthermore, the surface activity, surface adsorption, aggregation and spreading behaviors of APGE-PHMS were investigated utilizing surface tension measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM) and contact angle measurements. The results showed that critical aggregation concentration (CAC) and the time needed to reach adsorption equilibrium on water surface decrease systematically with the increase in the number of APGE groups. These polymers in aqueous solutions could aggregate to form spherical assemblies. Moreover, the spreading behavior of these polymers on low energy surface was found to be influenced by the number of hydrophilic APGE groups.
With the relentless development of smart and miniaturized electronics, the worldwide thirst for microscale electrochemical energy storage devices with form factors is launching a new era of ...competition. Herein, the first prototype planar sodium‐ion microcapacitors (NIMCs) are constructed based on the interdigital microelectrodes of urchin‐like sodium titanate as faradaic anode and nanoporous activated graphene as non‐faradaic cathode along with high‐voltage ionogel electrolyte on a single flexible substrate. By effectively coupling with battery‐type anode and capacitor‐type cathode, the resultant all‐solid‐state NIMCs working at 3.5 V exhibit a high volumetric energy density of 37.1 mWh cm−3 and an ultralow self‐discharge rate of 44 h from Vmax to 0.6 Vmax, both of which surpass most reported hybrid micro‐supercapacitors. Through tuning graphene layer covered on the top surface of interdigital microelectrodes, the NIMCs unveil remarkably enhanced power density, owing to the establishment of favorable multidirectional fast ion diffusion pathways that significantly reduce the charge transfer resistance. Meanwhile, the as‐fabricated NIMCs present excellent mechanical flexibility without capacitance fade under repeated deformation, and electrochemical stability at a high temperature of 80 °C because of using nonflammable ionogel electrolyte and in‐plane geometry. Therefore, these flexible planar NIMCs with multidirectional ion diffusion pathways hold tremendous potential for microelectronics.
All‐solid‐state planar sodium‐ion microcapacitors are constructed on a single substrate based on faradaic sodium titanate as anode and non‐faradaic activated graphene as cathode along with nonflammable high‐voltage ionogel electrolyte. The resultant microcapacitors possess the merit of multidirectional fast ion diffusion pathways and show high volumetric performance, remarkable flexibility, and high‐temperature stability.
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