Ultrahigh Areal Capacitance Research Articles

Multicomponent hierarchical NiCo2O4@CoMoO4@Co3O4 arrayed structures for high areal energy density aqueous NiCo//Zn batteries

Directly growing nickel/cobalt-based cathode materials on current collectors as binder-free electrodes for rechargeable aqueous nickel/cobalt-Zn-based (NiCo//Zn) batteries have attracted tremendous attentions. However, most of the present binder-free cathodes suffer from low areal capacity and energy density, which severely restrict their practical applications. Herein, we demonstrate an efficient metal-organic framework (MOF)-involved strategy to rationally integration of the active NiCo2O4, CoMoO4 and Co3O4 cathode materials into one hierarchical arrayed structure that uniformly grown on nickel foam (NF) substrate (denoted as NF–NCO@CMO@CO) with a high mass loading of 9.6 ​mg ​cm−2. Such electrode design possesses favorable merits in the aspects of high electrical conductivity, robust arrayed architectures, abundant electrochemical active sites, rich redox reactions, facile ion diffusion and components’ synergetic effect. As a result, the aqueous NiCo//Zn battery based on NF–NCO@CMO@CO binder-free cathode exhibits an ultrahigh areal capacity of 2.51 ​mAh cm−2 at a current density of 2 ​mA ​cm−2, as well as good rate capability and long-term cycling stability. Impressively, the aqueous NF–NCO@CMO@CO//Zn battery shows a maximum areal energy density of 4.09 ​mWh cm−2 (corresponding to 424.5 ​Wh kg−1), which is superior to most of the previously reported aqueous NiCo//Zn batteries. Electrode reaction kinetics analysis reveals that both capacitive and diffusion-controlled behaviors are involved during the charge storage processes. Moreover, a quasi-solid-state NF–NCO@CMO@CO//Zn battery is also assembled by replacing the liquid electrolyte with gel electrolyte, suggesting the potential for practical applications. This work might shed light on the rational construction of advanced binder-free cathodes for high-performance aqueous NiCo//Zn batteries.

Polyaniline wrapped graphene functionalized textile with ultrahigh areal capacitance and energy density for high-performance all-solid-state supercapacitors for wearable electronics

Textile-based supercapacitors having intrinsically mechanical flexibility are regarded as hopeful power sources for wearable electronics. Herein, four PANI/graphene/textile electrodes are successfully synthesized using a simple ‘dipping and drying’ procedure followed by in-situ polymerization of aniline. The effects of the acidic dopants on the morphological, structural and capacitive characteristics of the resultant electrodes are systematically investigated. The PANI/graphene/textile-HCl (PANI/G/T-HCl) depicts a maximum areal specific capacitance of 1601 mF cm−2 at the current density of 1 mA cm−2, which is apparently higher than numerous textile-electrodes reported so far, and an attractive cycling stability with a capacitance retention more than 75% after 10,000 cycles at 10 mA cm−2. The constructed all-solid-state supercapacitor device affords an outstanding energy density of 755 mWh m−2 at a power density of 1448 mW m−2. The capacitive performance of this device remains stable under bending degrees from 0 to 180° and exhibits a high capacity retention of 77% over 600 bending cycles, verifying a superior mechanical flexibility and capacitive stability with extensive prospects for practical applications.

Freestanding agaric-like molybdenum carbide/graphene/N-doped carbon foam as effective polysulfide anchor and catalyst for high performance lithium sulfur batteries

Developing high energy density lithium-sulfur (Li–S) batteries mainly relies on the design of the electrode matrix which can accommodate high sulfur loading and still remain high utilization of active materials. Herein, a 3D hierarchical graphitic carbon foam supported graphene@Mo2C (GCF-G@Mo2C) heterostructure is introduced as a freestanding electrode for Li–S batteries with a facile and cost-effective method. The N-doped carbon foam wrapped by graphene sheets with agaric-like porous structure could promote fast electron and ion transport, meanwhile effectively anchor the polysulfides through physical confinement and chemical adsorption by strongly polar-polar interactions. More importantly, the Mo2C nanoparticles can act as the chemical anchoring center to provide strong polysulfide adsorption, as testified by experimental data and first-principle calculations. Moreover, the catalytic effect of Mo2C also accelerates the redox kinetics of polysulfide conversion, contributing to enhanced rate performance. As a result, the cell with GCF-G@Mo2C displays an initial capacity as high as 862 mAh g−1 and a retained capacity of 597 mAh g−1 after 600 cycles with only 0.051% capacity fade per cycle at 1C rate, presenting good cycling stability. In addition, the GCF-G@Mo2C substrate with high sulfur content (70 ​wt%) and sulfur loading (10.5 ​mg ​cm−2) achieves an ultra-high areal capacity of 12.6 mAh cm−2 at 0.1 ​C, offering a competitive cathode for high-performance Li–S batteries.

The composite of 3D carbon nanotube architecture and NiCo double hydroxide for high-performance supercapacitor

A three-dimensional porous architecture of multiwalled carbon nanotubes (MWCNT), denoted as 3D-MWCNT, was fabricated on Ni foam (NiF) via a simple hydrothermal method. The 3D-MWCNT, constructed with interlaced carbon nanotubes, is a highly porous network structure and is subsequently used as the electrical conductive platform for the fabrication of positive electrode of faradaic supercapacitor. The obtained positive electrode was denoted as NiCo-DH/3D-MWCNT/NiF, which was produced via the electrodeposition of NiCo double hydroxide (NiCo-DH) on 3D-MWCNT/NiF. The 3D-MWCNT platform not only endows NiCo-DH/3D-MWCNT/NiF large surface area but also enhanced electrical conductivity. NiCo-DH/3D-MWCNT/NiF displays an ultrahigh areal capacity of 6.142 C cm−2 at 60 mA cm−2 and 96.31% capacity retention after 2000 cycles at 60 mA cm−2. An asymmetrical supercapacitor (ASC) is also assembled with NiCo-DH/3D-MWCNT/NiF as the positive electrode and activated carbon (AC) as the negative electrode. The ASC exhibits a prominent specific energy of 30.99 Wh kg−1 at a high specific power of 427.46 W kg−1. It is especially worth noting that the ASC exhibited remarkable capacity retention of 84.7% even after 2000 galvanostatic charge–discharge cycles at a high current density of 30 mA cm−2.

Mesoporous carbon nanotube aerogel-sulfur cathodes: A strategy to achieve ultrahigh areal capacity for lithium-sulfur batteries via capillary action

A strategy to produce sulfur (S) cathodes with ultrahigh areal capacity for lithium-sulfur (Li–S) batteries is proposed. Porous carbon nanotube (CNT) aerogel@Li2S8 cathodes are obtained by dropping Li2S8 solution into the CNT aerogels that are prepared through a freeze-drying method. The three-dimensional (3D) porous structure of the CNT aerogel provides a complete electron transport network and rapid ion transport channels. Moreover, the rich mesoporous structure has an extreme capillary action on the electrolyte. Numerical simulation shows that in a surprisingly short time (2 μs), the electrolyte can be absorbed into the mesopores by capillary action and reach a stable state, limiting the “shuttle effect” of polysulfides. Based on these unique characteristics, the CNT aerogel@Li2S8 cathode exhibits excellent electrochemical performance. With an extremely high areal S loading of 20 mg cm−2, the cathode shows an ultrahigh areal specific capacity of 22.9 mAh cm−2. For the pouch cell with an areal S loading of 10 mg cm−2 and a low electrolyte/sulfur (E/S) ratio of 7.8 μL mg−1, the areal specific capacity reaches a high value of 10.4 mAh cm−2.

Realizing ultrahigh areal capacitance and cycle stability of polyaniline nanofiber network grown on graphene–modified carbon cloth with the addition of trivalent iron ions in electrolyte

One kind of polyaniline (PANi)–based flexible electrodes for all–solid–state supercapacitor with ultrahigh areal capacitance and cycle stability is fabricated through electrochemical polymerization. The oriented growth of PANi nanofibers is efficiently promoted when graphene shell is firstly coated on carbon fiber. Then ferric sulfate is introduced into the electrolytes for further enhancing the pseudocapacitance contribution, and the best charge storage ability of the composite electrode is achieved at 15 mol. % Fe3+ ion content. The assembled supercapacitor possesses a maximum areal capacitance of 1.90 F cm−2 at the current density of 5 mA cm−2. At 30 mA cm−2, the device retained 74.7% of the maximum capacitance. It showed a maximum energy density of 264 μWh cm−2 at a power density of 2.5 mW cm−2 and a capacitance retention of up to 93.1% after 3000 cycles at 10 mA cm−2. These results can be attributed to high efficient pathway for ion diffusion and electron transport constructed between PANi nanofiber array and graphene shell on the CC, as well as the redox reaction in electrolyte and metal ion–doping effects of PANi caused by trivalent iron ions. Such device with the desirable characteristics has a promising application prospect in wearable power supply system.

High Areal Capacity Dendrite‐Free Li Anode Enabled by Metal–Organic Framework‐Derived Nanorod Array Modified Carbon Cloth for Solid State Li Metal Batteries

AbstractLi metal is one of the most promising anode materials for high energy density batteries. However, uncontrollable Li dendrite growth and infinite volume change during the charge/discharge process lead to safety issues and capacity decay. Herein, a carbonized metal–organic framework (MOF) nanorod arrays modified carbon cloth (NRA‐CC) is developed for uniform Li plating/stripping. The carbonized MOF NRAs effectively convert the CC from lithiophobic to lithiophilic, decreasing the polarization and ensuring homogenous Li nucleation. The 3D interconnected hierarchal CC provides adequate Li nucleation sites for reducing the local current density to avoid Li dendrite growth, and broadens internal space for buffering the volume change during Li plating/stripping. These characteristics afford a stable cycling of the NRA‐CC electrode with ultrahigh Coulombic efficiencies of 96.7% after 1000 h cycling at 2 mA cm−2 and a prolonged lifespan of 200 h in the symmetrical cell under ultrahigh areal capacity (12 mAh cm−2) and current (12 mA cm−2). The solid‐state batteries assembled with the composite Li anode, high‐voltage cathode (LiNi0.5Co0.2Mn0.3O2), and composite solid‐state electrolyte also deliver excellent cyclic and rate performance at 25 °C. This work sheds fresh insights on the design principles of a dendrite‐free Li metal anode for safe solid‐state Li metal batteries.

Electrode Design with Integration of High Tortuosity and Sulfur-Philicity for High-Performance Lithium-Sulfur Battery

Summary Practical applications of Li-S batteries are hindered by the dissolution/diffusion loss of sulfur-related active materials in cathode and dendrite growth in Li metal anode. Here we present an integrated sulfur cathode design on tortuosity and sulfur-binding affinity parameters for mitigating diffusion loss of sulfur-based active materials. The high sulfur-philicity property (from oxygen functional groups, 16% in concentration) in reduced graphene oxide (rGO) host favors bonding with sulfur species to mitigate their diffusion/dissolution loss, while the high tortuosity (13.24, from horizontal arrangement of rGO sheets) can localize the soluble active materials within the host rather than outward diffusion loss with subsequent uneven redeposition. With this integrated concept, we achieved ultrahigh cathode areal capacities of 21 mAh cm−2 with 98.1% retention after 160 cycles, surpassing those electrodes with lower tortuosity and sulfur-philicity. In addition, same rGO host suppresses dendrite growth in Li anode, enabling 278% prolonged cycle life in the full cell.

An ultrahigh-areal-capacity SiOx negative electrode for lithium ion batteries

Constructing a stable microstructure is highly crucial in promoting the practical applications of Si-based negative electrodes, addressing the issues of huge volume change and unstable solid electrolyte interface (SEI). Herein, an integrated electrode structure is developed based on micro-sized SiOx particles by bilayers coating of carbon and poly(3,4-ethylene dioxythiophene) (PEDOT) with carbon nanotube/Super P conductive network in-situ embedded (SiOx@C@P_CS). The as-prepared SiOx@C@P_CS negative electrode exhibits high Coulombic efficiency reaching 99.9% and capacity retentions of 86.7% (1019 mAh g−1) after 1000 cycles at 750 mA g−1 and 98.4% (973 mAh g−1) after 400 cycles at 1500 mA g−1 (with a commercial-level areal capacity of 2.57 mAh cm−2). The excellent long cycling capability is further evidenced both in half cell with ultrahigh areal capacity up to 11.75 mAh cm−2 at the mass loading of 8.66 mg cm−2 and Li[Ni0.8Co0.1Mn0.1]O2 (NCM811)||SiOx@C@P_CS full cell with commercial loading. The improved electrochemical performance is attributed to the synergistic effects of the bilayers. This study offers a facile solution to the challenges facing alloying-type negative electrode materials with huge volume changes by confining volume change, enhancing electric conductivity, and isolating the growth of SEI to promote their practical uses.

Optimization of oxygen electrode combined with soluble catalyst to enhance the performance of lithium–oxygen battery

Lithium-air batteries possess a high theoretical energy density among the current battery technologies, and are expected to become the driving power for electric vehicles. However, the practical application of lithium air batteries is handicapped by their poor cycle life, high over-charge potential and low energy efficiency. Numerous studies have performed to improve the kinetics of the electrochemical reaction. Making a good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalyst system is under intense scrutiny. In this work, we report a rational design of air electrode, which derives from biomass and presents a three-dimensional porous carbon architecture with high specific surface and large volume expansion coefficient. Combining with a soluble catalyst, this oxygen electrode presents an ultrahigh areal specific capacity of 7.95 mAh/cm2 and a long cycling life up to 1000 cycles with suppressed polarization (about 0.46 ​V). The greatly improved overall performance is due to the synergetic effect of the novel designed oxygen electrode capable of mediating the redox mediators to trigger the ORR and OER process.

Covalent Selenium Embedded in Hierarchical Carbon Nanofibers for Ultra-High Areal Capacity Li-Se Batteries.

SummaryLithium selenium (Li-Se) batteries have attracted increasing interest for its high theoretical volumetric capacities up to 3,253 Ah L−1. However, current studies are largely limited to electrodes with rather low mass loading and low areal capacity, resulting in low volumetric performance. Herein, we report a design of covalent selenium embedded in hierarchical nitrogen-doped carbon nanofibers (CSe@HNCNFs) for ultra-high areal capacity Li-Se batteries. The CSe@HNCNFs provide excellent ion and electron transport performance, whereas effectively retard polyselenides diffusion during cycling. We show that the Li-Se battery with mass loading of 1.87 mg cm−2 displays a specific capacity of 762 mAh g−1 after 2,500 cycles, with almost no capacity fading. Furthermore, by increasing the mass loading to 37.31 mg cm−2, ultra-high areal capacities of 7.30 mAh cm−2 is achieved, which greatly exceeds those reported previously for Li-Se batteries.

Surface engineered carbon-cloth with broadening voltage window for boosted energy density aqueous supercapacitors

An efficient strategy of surface engineering is developed to extraordinarily boost the energy density of multiscale porous carbon cloth for aqueous symmetric supercapacitors by optimizing the oxygen-containing functional groups. The operating voltage with neutral electrolyte is remarkably broadened from 1.3 to 1.8 V for electrochemical oxidized active carbon cloth (EOACC), enabling its ultrahigh areal capacitance (1548 mF cm−2) and extraordinary energy density (239.25 μWh cm−2). More importantly, engineering such a functionalized electrode with improved operating potential window is critically hinged on the fundamental understanding of the underlying electrochemical mechanism. The outstanding performance can be attributed to the enlarged ions-accessible specific surface area and created electrochemical active CO quinone-type groups, contributing to the combination of electrical double-layer capacitance and pseudo-capacitance, respectively. More significantly, the broadened potential window is originated from the increase of the onset overpotential for oxygen evolution reaction, induced by the physical barrier of adsorbed Na+ and the kinetic limitations of fast faradic redox reactions. This strategy sheds a light on the understanding of the electrochemical mechanism for broadened potential range, which provides a promising way for designing and engineering carbon-based aqueous supercapacitors with boosted energy density.

Shuttling Induced Starvation of Redox Mediators in High Areal Capacity Rechargeable Lithium-Oxygen Batteries

Redox mediators (RMs) for lithium-oxygen batteries (LOBs) are electrochemically active soluble molecules or ions that can chemically oxidize insoluble discharge products to improve the battery rechargeability. Most LOBs investigated so far in research laboratories were of low cyclable areal capacities (0.5 mAh cm−2 or less). In future practical LOBs, ultrahigh areal capacities beyond 10 mAh cm−2 may be needed. It is known that RMs may be subjected to various side reactions in LOBs, such as shuttling toward the Li anode. However, because the amount of RMs in the electrolyte solution in the low areal capacity research batteries were often in large excess, the implications of inevitable RM depletion during cycling toward practical LOBs have rarely been discussed. Here we report the use of a RM in LOBs of high areal capacities up to 10 mAh cm−2 enabled by using our recently developed high mass loading air cathode system based on holey graphene scaffold. With lithium iodide (LiI) as a model RM, the cycling performance, the catalytic capacity, and the parasitic shuttling kinetics were studied in detail. The understanding of these phenomena is a crucial step toward effective solutions with regard to RM applications for practical LOBs with ultrahigh areal capacities.

MOF-assisted construction of a Co9S8@Ni3S2/ZnS microplate array with ultrahigh areal specific capacity for advanced supercapattery.

Transition metal sulfides are important candidates of battery-type electrode materials for advanced supercapatteries due to their high electric conductivity and electrochemical activity. The Co9S8@Ni3S2/ZnS composite microplate array was prepared by a metal-organic framework-assisted strategy because the electrochemical properties of composite arrays are governed by the synergistic effects of their diverse structures and compositions. As a battery-type material, the Co9S8@Ni3S2/ZnS electrode expressed an ultrahigh areal specific capacity of 8192 C cm-2 at the current density of 2 mA cm-2, and excellent cycling stability of 79.7% capacitance retention after 4000 cycles. An assembled supercapattery device using the Co9S8@Ni3S2/ZnS microplate array as a positive electrode and active carbon as the negative electrode delivered a high energy density of 0.377 mW h cm-2 at a high power density of 1.517 mW cm-2, and outstanding retention of 95.2% after 5000 cycles. As a result, the obtained Co9S8@Ni3S2/ZnS shows potential for applications in high-performance supercapattery.

Jahn-Teller distortions boost the ultrahigh areal capacity and cycling robustness of holey NiMn-hydroxide nanosheets for flexible energy storage devices.

Flexible energy storage devices with ultrahigh areal capacity and excellent cycling stability are highly desired for portable and wearable electronics. Bimetal hydroxides with low crystallinity are preferred as electrode materials due to their advantageous features of high electrochemical performance, rapid ion diffusion and high structure stability enabled by lattice disorder. Herein, holey NiMn-hydroxide (NiMn-OH) nanosheets with abundant lattice disorder induced by Jahn-Teller distortion are grown vertically on carbon cloth and their loading level reaches as high as 3.27 mg cm-2. The obtained NiMn-OH nanosheets demonstrate a superior capacity of 881 μAh cm-2 at 3 mA cm-2 and outstanding rate capability (66.4% capacity retained at 30 mA cm-2). The flexible all-solid hybrid device (NiMn-OH//Fe2O3) delivers a high energy density of 573.8 μW h cm-2 at a power density of 2.4 mW cm-2 and more importantly exhibits good cycling stability with 90.1% retained after 10 000 cycles and mechanical robustness. This proof-of-principle investigation is opening up a viable way to develop high performance electrodes for flexible energy storage devices.

Cobalt-doping in hierarchical Ni3S2 nanorod arrays enables high areal capacitance

Cobalt-doped Ni3S2 nanorod arrays have been prepared via a hydrothermal method. As a free-standing electrode, the Co-Ni3S2 demonstrates ultrahigh areal capacitance, affording the Co-Ni3S2//FeOOH hybrid supercapacitor a high energy density.

3D nanoflower-like MoSe2 encapsulated with hierarchically anisotropic carbon architecture: a new and free-standing anode with ultra-high areal capacitance for asymmetric supercapacitors.

A novel anode material with a delicate composite structure, which is assembled by growing 3D MoSe2 nanoflowers onto the hierarchically anisotropic carbon architecture, is designed for the first time. The structural superiority and synergistic effects from EDLC and pseudocapacitance endow the free-standing anode with an ultra-high areal capacitance of 1043 mF cm-2 at 1 mA cm-2 and high cycling stability. Moreover, an asymmetric supercapacitor device consisting of this anode and a common MnO2-based cathode yields a quite large energy density of 147 μW h cm-2 at the power density of 2 mW cm-2, which is higher than or comparable to that of some Li-ion batteries. These results verify the huge application potential of this new anode for supercapacitors.

Interfacial Approach toward Benzene‐Bridged Polypyrrole Film–Based Micro‐Supercapacitors with Ultrahigh Volumetric Power Density

Abstract2D soft nanomaterials are an emerging research field due to their versatile chemical structures, easily tunable properties, and broad application potential. In this study, a benzene‐bridged polypyrrole film with a large area, up to a few square centimeters, is synthesized through an interfacial polymerization approach. As‐prepared semiconductive films exhibit a bandgap of ≈2 eV and a carrier mobility of ≈1.5 cm2 V−1 s−1, inferred from time‐resolved terahertz spectroscopy. The samples are employed to fabricate in‐plane micro‐supercapacitors (MSCs) by laser scribing and exhibit an ultrahigh areal capacitance of 0.95 mF cm−2, using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]) as an electrolyte. Importantly, the maximum energy and power densities of the developed MSCs reach values up to 50.7 mWh cm−3 and 9.6 kW cm−3, respectively; the performance surpassing most of the 2D material‐based MSCs is reported to date.

Hierarchical Bimetallic Hydroxides Built by Porous Nanowire‐Lapped Bundles with Ultrahigh Areal Capacity for Stable Hybrid Solid‐State Supercapacitors

AbstractExploring advanced electrode materials with superb energy/power densities and long lifetime as well as low cost is the recent focus of hybrid solid‐state supercapacitor (HSSC). This study reports a novel hierarchical bimetallic hydroxide (Ni1Co1‐OH) built by nanowire‐lapped bonfire‐like bundles through a facile and scalable method, and provides thorough insights into possible formation mechanism and structural merits of the interesting hierarchical architecture. Benefiting from multistep redox reactions, high accessible surface area and fast kinetics contributed by the unique structure, Ni1Co1‐OH using 2 m KOH electrolyte can achieve highly improved gravimetric capacity/capacitance of 876.8 C g−1/1753.6 F g−1 at active mass loading of 3 mg cm−2 at 1 A g−1, and especially deliver a record‐high areal capacity of 7.6 C cm−2 at 1 A g−1 under a commercial loading of 15 mg cm−2. 1.5 V Ni1Co1‐OH based HSSC with the poly(vinyl alcohol)/KOH gel electrolyte verifies the intriguing performance including high energy/power densities of 27.9 Wh kg−1/13812.9 W kg−1, a long life over 10 000 cycles, and a low self‐discharge rate with a voltage decline of 20% after 24 h. The findings identify the scalable production of high‐performance bimetal compounds, which will boost the development of highly demanding HSSC devices.

Ultrahigh areal capacity of self-combusted nanoporous NiCuMn/Cu flexible anode for Li-ion battery

Nanostructured transition metal oxides (TMOs) have shown extraordinary promise as anode materials for Lithium ion battery but still been challenging for practical applications due to their low conductivity and activity with high loading mass. Herein, we prepare an integrated high-loading-mass TMOs based anode with 3D nanoporous structure and metallurgical bonding interface between oxide and current collector by self-combustion and subsequently mild annealing of the nanoporous NiCuMn (np-NiCuMn). Self-combustion, caused by the high surface energy of np-NiCuMn, induces ligament coarsening and deep surface oxidation of the alloy, which consumes all the energy quickly and form metal core and oxide shell structure with loading mass up to 7.3 mg cm−2. Mild annealing in H2 at 250 °C creates robust vacancies in oxide layers (6.9 mg cm−2 of oxide retention) with some precipitated Cu doping, which not only provides more Li+ storage sites but also further enhance the electron/ion transportation in the anode. Consequently, the flexible integrated electrode demonstrates an ultrahigh area capacity of up to 9.48 mAh cm−2 at a current density of 0.5 mA cm−2, as well as excellent rate performance and cycle stability. This work is expected to open a cost-effective and large-scale route to prepare high-capacity electrodes for next-generation energy storage devices.