Superior Specific Capacitance Research Articles

Boosted electrochemical performance of Na3V2(PO4)3 at low temperature through synergistical F substitution and construction of interconnected nitrogen-doped carbonaceous network

Benefitting from its unique NASICON-type framework, the Na3V2(PO4)3 (NVP) cathodes have aroused extensive interest and have been deemed as the promising cathode candidate for sodium-ion batteries (SIBs). Unfortunately, the poor electronic conductivity, combined with the undesirable volume variations, seriously hinders the practical application of NVP cathode, especially at low temperatures. Herein, a dual-strategy, F substitution accompanied by V vacancies and the construction of three-dimensional (3D) nitrogen-doped carbonaceous frameworks (NC), were employed for the NVP cathode (F-NVP/C@3DNC). The former can remarkably decrease the particle size and enhance Na+ migration capability, increasing the ionic conductivity. Meanwhile, the electronic connection and effective buffering can be obtained from the latter, strengthening the electrode integrity. Consequently, up to 100 cycles at 0.1 A g–1, a reversible capacity of 113.8 mAh g–1, approaching the theoretical value (117 mAh g–1), is demonstrated, accompanied by impressive capacity retentions at 1.0 (93.75% after 4800 cycles) and 20.0 A g–1 (92.7% after 1000 cycles). More importantly, even at –20 °C, a superior specific capacity (102.6 mAh g–1 after 100 cycles at 0.1 A g–1) and high capacity retention (86.6% at 20.0 A g–1 up to 1000 cycles) can still be obtained simultaneously. Significantly, the design of F-NVP/C@3DNC provides insights for the fabrication of polyanion cathodes for applications at low temperatures with modified structure stability and reaction kinetics.

Rational design of new, efficient, and suitable nickel phthalocyanine reinforced MXene electrodes for supercapacitors

2D transition metal carbides and nitrides (MXenes) are emerging as a novel class of pseudocapacitive materials. However, 2D MXene sheets usually easily restack and aggregate, which greatly hinder their practical application in high performance energy storage devices. Herein, the reinforced MXene electrode is rationally designed and constructed by inserting 18-π aromatic electron system of Phaseolus vulgaris-like MPc among MXene sheets, this system constitutes a new functionalization strategy through π-π interactions for stabilizing MXene. Further, in this study, MXenes/NiPc achieves a superior specific capacitance of 792 F g−1 at 1 A g−1, and the assembled ASC provides a high energy density of 84.58 Wh kg−1 at a power density of 749.97 W kg−1, while also produces the excellent cycling stability of 95.1 % retention over 5000 cycles. Notably, the assembled ASC can easily power the green LED light strip. Our research findings provide a novel strategy and paradigm to design high-performance MXene-based energy storage materials.

Sodium Super Ionic Conductor-Type Hybrid Electrolytes for High Performance Lithium Metal Batteries.

Composite solid electrolytes (CSEs), composed of sodium superionic conductor (NASICON)-type Li1+xAlxTi2-x(PO4)3 (LATP), poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), and lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) salt, are designed and fabricated for lithium-metal batteries. The effects of the key design parameters (i.e., LiTFSI/LATP ratio, CSE thickness, and carbon content) on the specific capacity, coulombic efficiency, and cyclic stability were systematically investigated. The optimal CSE configuration, superior specific capacity (~160 mAh g-1), low electrode polarization (~0.12 V), and remarkable cyclic stability (a capacity retention of 86.8%) were achieved during extended cycling (>200 cycles). In addition, with the optimal CSE structure, a high ionic conductivity (~2.83 × 10-4 S cm-1) was demonstrated at an ambient temperature. The CSE configuration demonstrated in this work can be employed for designing highly durable CSEs with enhanced ionic conductivity and significantly reduced interfacial electrolyte/electrode resistance.

Low-Cost Production of Fe3O4/C Nanocomposite Anodes Derived from Banana Stem Waste Recycling for Sustainable Lithium-Ion Batteries

The development of lithium-ion batteries (LIBs) has become an important aspect of advanced technologies. Although LIBS have already outperformed other secondary batteries, they still require improvement in various aspects. Most crucially, graphite, the commercial anode, has a lower capacity than emerging materials. The goal of this research is to develop carbon-based materials from sustainable sources. Banana stem waste was employed as a precursor because of its xylem structure and large surface area. In addition, catalytic graphitization of biomass yields both graphitic carbon and metal oxides, which can be converted into higher-capacity Fe3O4/C nanocomposites. The nanocomposites consist of nanoparticles distributed on the surface of the carbon sheet. It was found that Fe3O4/C nanocomposites not only achieved a superior specific capacity (405.6 mAh/g at 0.1 A/g), but also had good stability in long-term cycling (1000 cycles). Interestingly, they had a significantly greater capacity than graphite at a high current density (2 A/g), 172.8 mAh/g compared to 63.9 mAh/g. For these reasons, the simple preparation approach, with its environmental friendliness and low cost, can be employed to produce Fe3O4/C nanocomposites with good electrochemical properties. Thus, this approach may be applicable to varied biomasses. These newly developed Fe3O4/C nanocomposites derived from banana waste recycling were found to be suitable to be used as anodes for sustainable LIBs.

A 3D nanocomposite of NiCo2S4/CuCo2S4 heterostructure synthesized by chemical precipitation for asymmetric supercapacitors

In recent years, transition metal sulfides have been regarded as a promising energy storage material for supercapacitors, due to their high theoretical specific capacity and conductivity compared with other similar metal oxides and hydroxides. However, the sluggish diffusion dynamics and low capacitance impede its practical implement application. Herein, an advanced 3D nanocomposite of NiCo2S4/CuCo2S4 heterostructure was designed via a time-saving, safe and efficient approach. The mass transfer kinetics of NiCo2S4/CuCo2S4 nanocomposite has been significantly promoted owing to this novel heterostructure. Therefore, the NiCo2S4/CuCo2S4 electrode materials reveal a superior specific capacitance (180.8 mAh g−1 at 2 A g−1) and excellent rate properties (84.7% capacitance retention from 2 to 20 A g−1). The asymmetric supercapacitor device assembled with NiCo2S4/CuCo2S4 and activated carbon has an energy density of 37.0 Wh kg−1 at 400 W kg−1 and outstanding cyclic stability (93.3% remained after 10,000 cycles at 10 A g−1). Density functional theory (DFT) calculation further proves the electronic structure and the charge transfer can be tuned by the heterostructure of NiCo2S4 and CuCo2S4. This work offers a new perspective to design a high-performance electrode material in the field of supercapacitors.

Developing Superior Hydrophobic 3D Hierarchical Electrocatalysts Embedding Abundant Catalytic Species for High Power Density Zn-Air Battery.

It is essential but still challenging to design and construct inexpensive, highly active bifunctional oxygen electrocatalysts for the development of high power density zinc-air batteries (ZABs). Herein, a CoFe-S@3D-S-NCNT electrocatalyst with a 3D hierarchical structure of carbon nanotubes growing on leaf-like carbon microplates is designed and prepared through chemical vapour deposition pyrolysis of CoFe-MOF and subsequent hydrothermal sulfurization. Its 3D hierarchical structure shows excellent hydrophobicity, which facilitates the diffusion of oxygen and thus accelerates the oxygen reduction reaction (ORR) kinetic process. Alloying and sulfurization strategies obviously enrich the catalytic species in the catalyst, including cobalt or cobalt ferroalloy sulfides, their heterojunction, core-shell structure, and S, N-doped carbon, which simultaneously improve the ORR/OER catalytic activity with a small potential gap (ΔE= 0.71V). Benefiting from these characteristics, the corresponding liquid ZABs show high peak power density (223mW cm-2 ), superior specific capacity (815mA h gZn -1 ), and excellent stability at 5mA cm-2 for ≈900 h. The quasi-solid-state ZABs also exhibit a very high peak power density of 490mW cm-2 and an excellent voltage round-trip efficiency of more than 64%. This work highlights that simultaneous composition optimization and microstructure design of catalysts can effectively improve the performance of ZABs.

Atomically selective oxidation of (Ti,V) MXene to construct TiO2@TiVCTx heterojunction for high-performance Li-ion batteries

In situ derivation of TiO2 from Ti2CTx and Ti3C2Tx MXenes is a promising strategy to construct TiO2-based heterostructure. How to precisely control the conversion depth of MXene and well maintain its lamellar structure are the top priority. Herein, double transition metal (Ti, V) MXenes (Ti2−yVyCTx) act as precursors to engineer TiO2/MXene heterostructure as anode materials for lithium-ion batteries. Due to the different oxidation tendency, vanadium atoms with higher oxidative tolerance can maintain the 2D lamella morphology and high electronic conductivity while titanium atoms can be selectively oxidized to well-dispersed TiO2 nanoparticles. Moreover, the content and dispersity of derived TiO2 nanoparticles can be well controlled by adjusting the molar ratio of Ti/V in the Ti2−yVyCTx precursors. The intensive interfacial interaction between derived TiO2 and vanadium dominated MXene layers protects TiO2 nanoparticles from pulverization and detachment from 2D MXene as well as the restacking of MXene layers during charge/discharge cycles. Benefiting from the synergistic effects, the TiO2@TiVCTx anode delivers a superior specific capacity of 741.2 mAh g−1 at 0.1 A g−1, which shows prominent advantage in current MXene-derived anode materials. This work innovatively realizes atomically selective oxidation of double metal transition MXenes and regulate the derivatives for high performance anode materials.

Expanded mesocarbon microbead cathode for sodium-based dual-ion battery with superior specific capacity and long-term cycling stability

Expanded mesocarbon microbead cathode for sodium-based dual-ion battery with superior specific capacity and long-term cycling stability

MoWS2 Nanosheet Composite with MXene as Lithium-Sulfur Battery Cathode Material

Due to their superior theoretical specific capacity and energy density, lithium-sulfur (L‒S) batteries are gaining popularity in order to achieve the growing terms for more power generation. However, drawbacks such as low electrical conductivity of the active ingredient sulfur, severe volume expansion and shuttle effect of polysulfides, rapidly decaying battery capacity, and short battery life have hampered their development. A MoWS2@MXene@CNT composite material is used as the main cathode material for L-S batteries in this study. MoWS2 can improve the electrochemical reaction rate by accelerating polysulfide conversion, whereas MXene can suppress electrode volume expansion. Furthermore, the addition of carbon nanotubes (CNT) with high electrical conductivity improves the rate of the electrochemical reaction. Therefore, the MoWS2@MXene@CNT composites have good capacity and versatility as cathode materials and enhance the behavior of L-S batteries.

Multifunctional Antifreezing Organogel Polyelectrolyte for a Flexible Supercapacitor

A multifunctional antifreezing mechanically tough conductive organogel polyelectrolyte was designed and prepared by simultaneously introducing poly(vinyl alcohol), tripentaerythritol, and H2O/dimethyl sulfoxide (DMSO) binary solvent. Based on the outstanding freeze resistance of the H2O/DMSO binary solvent, this organogel showed good mechanical properties and long-term stability in the temperature range of −20 to 20 °C. Meanwhile, the as-prepared flexible supercapacitor exhibits superior electrode specific capacitance (140 F g–1), high ionic conductivity (18.9 mS cm–1), outstanding cycling stability (only 5% capacitance decay over 2000 cycles), and excellent durability (85% weight retention after storing for 10 days) even at a low temperature of −20 °C. In addition, the prepared organogel exhibits tunable optical performances in diverse polar solvents and could act as information storage installations for recording and wiping.

In-situ electrochemical oxidization of V2O3-C cathode for boosted zinc-ion storage performance

In-situ electrochemical activation can bring about unexpected improvement for electrode materials, while the nature behind the structural evolution during this activation remains unclear, which to a great extent limits the applications in searching for efficient cathodes for rechargeable zinc-ion battery (ZIB) with outstanding rate performance. Herein, we report on in-situ electrochemical oxidation of V2O3-C cathode for boosted zinc-ion storage performance. A solvothermal method is implemented to directly synthesize V2O3 nanoparticles coated with a carbon layer. Detailed characterizations reveal that due to co-embedding of H2O and Zn2+, tunnel-like V2O3 undergoes an in-situ electrochemical oxidation to generate layered V5O12·6H2O upon initial cycling. The intercalation of H2O molecules results in an expansion of layer spacing, accelerating the Zn2+ diffusion kinetics. As a consequence, a symmetric cell equipped with activated V2O3-C electrode delivers a high-rate capability (349 mA h g−1 at 1000 mA g−1) and superior specific capacity (260 mA h g−1 at 100 mA g−1 after 100 cycles). The strategy of in-situ electrochemical oxidation delivers the guidance to tunnel-like materials as cathode for rechargeable ZIBs.

Intercalative pseudocapacitive anhydrous NiC2O4 quantum dot electrode for the fabrication of supercapacitor using aqueous KOH and neutral Na2SO4 electrolyte

The energy storage capacity of a material depends on the active-ion arrangement and electron transfer rate at the electrode−electrolyte interface. Overcoming the low power density issues of batteries, the pseudocapacitive electrode can be an excellent alternative to improve the power density of the full cell in Asymmetric Supercapacitors (ASCs) mode to make grid-scale energy storage and delivery feasible. Quantum dots (QDs) is another class of nanomaterial that exhibits unique optical and electrical properties due to the quantum confinement effect and shows high mobility of diffused ions due to nanoscale dimension resulting in a very high surface area. Anhydrous NiC2O4 QDs are envisaged here as a potential energy storage material partly because of the presence of planer oxalates anions (C2O42−) resulting in a quasi-zero 2d arrangement. Superior specific capacity equivalent to 227.5mAh/g (capacitance:1638 F/g) at 1A/g in the potential window of 0.5 V was observed for Anhydrous NiC2O4 QDs electrodes in an aqueous 2 M KOH electrolyte. The battery-type intercalative pseudocapacitance mechanism seems to operate behind the high charge storage capacity of anhydrous NiC2O4 QDs. Almost 22 % (surface controlled) and 78 % (diffusion-controlled intercalative) storage was observed for anhydrous NiC2O4 QDs electrodes. Further, in a full cell, asymmetric supercapacitors (ASCs) mode in which porous anhydrous NiC2O4 QDs are made as the positive electrode and Activated Carbon (AC) as the negative electrode, operating potential window 1.6 V, the highest specific energy of 292 Wh/kg at a specific power of ~772 W/kg and Even at a high power density of 2884 W/kg− at an energy density equivalence of 87 Wh/kg was obtained with high cyclic stability in aqueous 2 M KOH electrolyte. Even in neutral 1 M aqueous Na2SO4 electrolyte, and in the operating potential window 1.6 V, The highest specific energy of 126 Wh/kg and specific power of ~480 W/kg at 1 A/g current density was observed in 1 M Na2SO4 was obtained with high cyclic stability for NiC2O4 QDs full cell in ASCs mode.

NiCoSe4@CFF with excellent properties prepared by microwave method for flexible supercapacitors and oxygen evolution reaction

NiCoSe4 nanoflowers were synthesized on carbon fiber felt (CFF) by microwave method, and the effects of microwave time and microwave power on the morphology, physical phase and performance of NiCoSe4@CFF were explored. The results display that the nanostructured NiCoSe4 prepared under the microwave irradiation of 1000 W for 120 s is uniformly loaded on the CFF. The NiCoSe4@CFF electrode exhibits a superior specific capacity of 1653.6F g−1 at 1A/g and maintains a superior cycling performance of 87.05 % of the initial capacitance over 150,000 cycles. In addition, the flexible supercapacitor fabricated with NiCoSe4@CFF as the cathode exhibits excellent flexibility and flexural strength. As an effective catalyst for oxygen evolution reaction (OER), NiCoSe4@CFF demonstrates a low overpotential of 0.358 V, a relatively small Tafel slope of 115.93 mV dec−1 and an excellent lifetime at 10 mA cm−2.

Electrochemical analysis of asymmetric supercapacitors based on BiCoO3@g-C3N4 nanocomposites.

Supercapacitors are gaining popularity these days because of their good cycle stability, superior specific capacitance, high power density, and energy density. Herein, we report the synthesis of bismuth cobalt oxide (BiCoO3) combined with graphitic carbon nitride (g-C3N4) by the hydrothermal method. The BiCoO3@g-C3N4 nanocomposite was well characterized using XRD, FE-SEM, FT-IR, and DRS-UV techniques. The supercapacitor properties of the BiCoO3@g-C3N4 nanocomposite were then studied using cyclic voltammetry, galvanic charging-discharging, and impedance spectroscopy techniques. Due to the synergistic effect, BiCoO3@g-C3N4 showed a high specific capacitance value of 341 F g-1 at a current density of 1 A g-1 and excellent retention of specific capacitance (98.82%) after 1000 cycles and a high power density of 1125 W kg-1. Using the impedance spectroscopy technique, the charge transfer resistance of BiCoO3, g-C3N4, and BiCoO3@g-C3N4 was measured. BiCoO3@g-C3N4 showed a low charge transfer resistance compared with BiCoO3 and g-C3N4. The asymmetric supercapacitor (ASC) device was prepared using activated carbon (negative side) and BiCoO3@g-C3N4 (positive side) electrodes. It showed a specific capacitance of 129 F g-1 at 1 A g-1, power density 2800 W kg-1 and energy density 35 W h kg-1. Finally, we conclude that, due to the high specific capacitance, good cycle retention, fast redox activity, and low charge transfer resistance BiCoO3@g-C3N4 is a good electrode material for energy storage applications.

Mg-doped NiCoP microflower grown on Ni foam for high-capacity supercapacitor electrode

In this work, a binder-free electrode Mg-doped NiCoP/Ni foam (MNCP-x/NF) was prepared via hydrothermal and phosphorization process, in which echinoid microflower-like MNCP-xwas densely loaded on the NF skeleton. By regulating the Mg2+doping amount, remarkable enhancements in the morphology, mass-loading of MNCP, electrode conductivity and overall electrochemical capacitive properties of MNCP-x/NF have been achieved. Particularly, moderate doped MNCP-0.5/NF exhibits the best energy storage performances with a superior specific capacity (4461 mC cm−2@ 2 mA cm−2), acceptable rate capability (retaining 50.1% @ 50 mA cm−2), and striking cyclability (retaining 83% over 5000 cycles). Moreover, a solid-state asymmetric supercapacitor constructed with MNCP-0.5/NF as cathode, graphene hydrogel/NF (GH/NF) as anode, PVA/KOH gel as electrolyte, outputs the notable energy density of 39.8 Wh kg−1(1.8 mWh cm−3) and power density of 16674 W kg−1(750 mW cm−3), companied by a superior cyclability (retaining 87% over 5000 cycles).

Hybrid CuSn nanosphere-functionalized Cu/Sn co-doped hollow carbon nanofibers as anode materials for sodium-ion batteries.

To strengthen the electrochemical performance of anode materials for sodium-ion batteries, Cu/Sn co-doped hollow carbon nanofibers functionalized by hybrid CuSn nanospheres (CuSn/C@MCNF) were prepared by a simple electrospinning method. The microstructural characteristics of CuSn/C@MCNF confirmed the same doped elements and strong interactions in hybrid CuSn nanospheres and the hollow carbon nanofiber substrate. CuSn/C@MCNF has superior specific capacity, excellent conductivity and high cycling stability. In particular, the doped hollow carbon nanofiber substrate can facilitate Na+ transport and alleviate volume expansion during the process of sodium storage. When applied as an anode material for sodium-ion batteries, CuSn/C@MCNF can deliver a reversible capacity of 340.1 mA h g-1 at a large current density of 1 A g-1 for 1000 cycles and a high-rate capacity of 202.5 mA h g-1 at 4.0 A g-1, all superior to the corresponding Sn-SnOx@MCNF- and MCNF-based electrodes. This work provides a basic idea for future anode materials in high-performance sodium-ion batteries.

Modified preparation of Si@C@TiO2 porous microspheres as anodes for high-performance lithium-ion batteries.

Microscale porous silicon materials have shown great application potential as anodes for next-generation lithium-ion batteries (LIBs); however, they face significant challenges, including mechanical structure instability, low intrinsic conductivity, and uncontrollable processing. In this study, a modified etching strategy combined with a facile sol-gel method is demonstrated to prepare microscale porous Si microspheres encapsulated by an inner amorphous carbon shell (≈10 nm) and an outer rigid anatase titanium oxide (TiO2) shell (≈20 nm) (PSi@C@TiO2), with the intact porous framework and core-shell-shell spherical structure. The interconnected pores can sufficiently accommodate the expansion of the Si core during lithiation. Moreover, the double shells can not only enhance the kinetic behavior of the PSi@C@TiO2 microspheres, but can act as a compact fence to force the Si core to expand toward the internal pores during lithiation, ensuring the integrity of the porous spherical structure. As a result, the PSi@C@TiO2 anodes show greatly superior high specific capacity, excellent rate capability, stable solid-electrolyte interphase (SEI) films and steady mechanical structure. It delivers a high reversible capacity of 1004 mA h g-1 after 250 cycles at 0.5 A g-1. This study provides a modified method to prepare microscale porous Si anodes with a stable mechanical structure and long cycle life for LIBs.

Recycling Used-Coffee Grounds into Hierarchical Nanostructured Carbon for Supercapacitor Application

Hierarchical nanostructured activated carbon electrode material was prepared from the used-coffee grounds to fabricate a cost-effective, scalable and high-performance symmetric supercapacitor. The interconnected, disordered and microporous material was synthesized in a simple two-stage method of chemical activation with zinc chloride followed by direct pyrolysis of the coffee grounds at 900 ºC in nitrogen atmosphere. The N2 adsorption and desorption analysis showed that the prepared material had an extraordinary surface area of ~1178 m2 g-1. The fabricated symmetric supercapacitor device in non-aqueous tetraethylammonium tetrafluoroborate (TEABF4) electrolyte exhibited 2.7 V cell voltage with superior specific capacitance, energy and power density of 129 F g–1, 56.4 Wh kg–1 and 797.9 W kg–1, respectively. Besides, it also had a high specific capacitance retention of 99% even after 10,000 cycles. This work demonstrated an effective approach to transform coffee grounds into high performance electrode material for renewable energy devices. The observed electrochemical performance evidently showed that the materials derived from waste coffee grounds could be recycled into potential electrode material for supercapacitors. The cost-effectiveness and abundance of waste coffee grounds combined with the simple activation process and high performance of the synthesized material increased its feasibility for commercial applications in energy storage devices.

Nonporous, conducting bimetallic coordination polymers with an advantageous electronic structure for boosted faradaic capacitance.

Conductive coordination polymers (c-CPs) are promising electrode materials for supercapacitors (SCs) owing to their excellent conductivity, designable structures and dense redox sites. However, despite their high intrinsic density and outstanding electrical properties, nonporous c-CPs have largely been overlooked in SCs because of their low specific surface areas and deficient ion-diffusion channels. Herein, we demonstrate that the nonporous c-CPs Ag5BHT (BHT = benzenehexathiolate) and CuAg4BHT are both battery-type capacitor materials with high specific capacitances and a large potential window. Notably, nonporous CuAg4BHT with bimetallic bis(dithiolene) units exhibits superior specific capacitance (372 F g-1 at 0.5 A g-1) and better rate capability than isostructural Ag5BHT. Structural and electrochemical studies showed that the enhanced charge transfer between different metal sites is responsible for its outstanding capacitive performance. Additionally, the assembled CuAg4BHT//AC SC device displays a favorable energy density of 17.1 W h kg-1 at a power density of 446.1 W kg-1 and an excellent cycling stability (90% capacitance retention after 5000 cycles). This work demonstrates the potential applications of such nonporous redox-active c-CPs in SCs and highlights the roles of bimetallic redox sites in capacitive performance, which hold promise for the future development of c-CP-based energy storage technologies.

Flower-like manganese and phosphorus co-doped MoS2with high 1T phase content as a supercapacitor electrode material

Flower-like MnP–MoS2was fabricated using manganese chloride and sodium hypophosphite as dopants, which exhibited superior specific capacitance and rate capability.