Large Specific Capacitance Research Articles

High-Na-Content Birnessite via P'3-Stacking with Tunable Active Facets for Advanced Aqueous Sodium-Ion Batteries.

Layered Na-birnessites are promising cathode materials for aqueous sodium-ion batteries due to their high theoretical capacity, low cost, and environmental benignity. However, the general O'3 Na-birnessites possess low Na content and dominant inactive {001} exposed facets, which compromise their Na storage capability and cycling stability. Herein, we develop a high-Na-content P'3-Na0.71MnO2·0.15H2O with highly enriched {010} active facets by a hydrothermal conversion method. In comparison with the O'3 Na-birnessite, the P'3 Na-birnessite with a high ratio of {010}/{001} exposed facets provides greatly increased open channels for Na+ diffusion, while the P'3 stacking affords a lower Na+ diffusion barrier, resulting in improved electrode kinetics with a large specific capacity of 176 mAh g-1 at 0.2 A g-1. More importantly, the P'3 Na-birnessite manifests solo Na+ intercalation/deintercalation with extraordinary cycling stability in an aqueous electrolyte, achieving 90.5% capacity retention after 60,000 cycles. When coupled with the NaTi2(PO4)3 anode, the P'3 Na-birnessite-based full cell delivers both high energy density and long cycle life, demonstrating the potential application in aqueous sodium-ion batteries. This study demonstrates an efficient method to prepare high-Na-content P'3 birnessite with tunable exposed facets and provides important insights into developing highly stable layered cathodes for sustainable aqueous sodium-ion batteries.

Enhanced bifunctional electrocatalysis of Co5.47N nanocrystals in porous carbon nanofibers for high-efficiency zinc-air batteries

As a promising energy conversion and storage device, recently, rechargeable zinc-air batteries (ZABs) have developed rapidly, and the exploitation of excellent electrode catalysts to improve the energy efficiency and long-term performance of ZABs has become a focus of current research. Herein, the Co5.47N nanocrystals embedded in porous carbon nanofibers (Co5.47N PCNFs) were designed to act as a bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and iodide oxidation reaction (IOR), which occur on the electrode in the charging-discharging process of ZABs. The electrochemistry results showed that the ORR activity of Co5.47N PCNFs is comparable to the commercial Pt/C electrocatalyst, and the IOR activity and stability are higher than those of the Pt/C electrocatalyst. Importantly, Co5.47N PCNFs electrocatalyst endows ZABs with a low charge–discharge voltage difference (0.49 V), a high round-trip energy efficiency (72.1 %), as well as a large specific capacity (791.5 mAh gZn−1), surpassing the performance of Pt/C electrocatalyst. Density functional theory calculation demonstrates that Co5.47N PCNFs have lower Gibbs free energy for the formation of IOR intermediate species, thereby displaying outstanding IOR catalytic performance compared to that of Pt/C electrocatalyst. These findings offer crucial insights into the rational design of cobalt nitride-based electrocatalysts for application in ZABs with high energy efficiency.

Efficient Synthesis of Flower-Ball Structured CuFeS2 as Advanced Anode Material for Lithium-Ion Batteries Across Wide Temperature Ranges.

Transition metal sulfides stand as potential anode candidates for lithium-ion batteries offering high capacity, redox reversibility, and safety. However, cycling-induced volume variations and slow kinetics hinder their application. Here, CuFeS2 with a flower-ball nanosheet structure is synthesized via a hydrothermal method, enhancing electrolyte infiltration, Li+ transport, and cycle life. CuFeS2 exhibits a large initial discharge specific capacity of 532.4 mAh g-1 at 500 mA g-1 with 95.7% initial Coulombic efficiency, retaining an impressive 90.5% (481.6 mAh g-1) of its initial capacity after 300 cycles. Remarkably, at 2000 mA g-1 for 700 cycles, it maintains a high specific capacity of 487.1 mAh g-1 with an 89.4% capacity retention rate. Moreover, it maintains excellent reversibility at both high temperature (60 °C) and low temperature (-25 °C) and demonstrates excellent electrochemical performance even under high loading conditions. Consequently, CuFeS2 holds immense promise as a lithium-ion battery anode material, offering fast charging, safety, high capacity, and long life.

A composite anode based on intercalation and conversion mechanism for high-rate lithium-ion batteries

To increase the specific capacity and cycle stability of lithium-ion batteries at high current density, we have investigated the anode materials. Among them, black phosphorus has attracted attention because of its large theoretical specific capacity (2596 mA h/g). However, the moderate conductivity of black phosphorus itself makes it less effective. The addition of graphite to form P-C and P-O-C bonds with black phosphorus enhances the performance of the battery cell. Lithium ions are primarily stored in black phosphorus-graphite layered structural materials via an intercalation mechanism, which improves electrochemical performance at tiny current density but is inadequate for charge/discharge cycling at high current density. In addition, lithium ions also can undergo conversion mechanism with metal oxide materials (e.g. Tungsten trioxide). While this conversion mechanism enables more stable battery cycling at high current density, the specific capacity remains insufficiently high. Higher charge/discharge specific capacity and long cycle stability of lithium-ion batteries at high current density can be realized by the joint action of the two mechanisms. In this work, black phosphorus, graphite, and tungsten trioxide (BP/G/WO3) composites are prepared by ball milling method. A comprehensive series of electrochemical analyses reveals that the BP/G/WO3-532 electrode (BP, graphite, and WO3 mass ratio of 5:3:2) exhibits the most substantial enhancement in the cycling stability of lithium-ion batteries. The anode exhibits a high specific capacity of 1463.1 mA h/g at 6 A/g and presents a retention capacity of 1159.8 mA h/g after 300 charge/discharge cycles, indicating a high cycle stability and fast reaction kinetics. This result is mainly attributed to the joint action of two mechanisms of composites.

N, O and P co-doped hierarchically porous carbon fiber for high performance Zinc-ion hybrid capacitors

Multi-heteroatoms co-doped hierarchically porous carbon-based electrode is an effective strategy to solve the low energy density and poor cycle stability of Zn-ion hybrid capacitors (ZHCs). Herein, N/O/P co-doped porous carbon nanofiber (N-P-PCF) was prepared, which displays fibrous network hierarchically porous structure to fast electron/ Zn2+ transport and enhance Zn2+ adsorption sites. Meanwhile, rich N (9.47 at.%), O (11.29 at.%) and P (1.29 at.%) co-doping can be beneficial for the infiltration of electrode–electrolyte interface and provide an additional pseudocapacitance. The N-P-PCF based ZHCs can yield a large specific capacitance (205 mAh g−1 at 1 A g−1), high energy density (173 Wh kg−1 at 823 W kg−1) and excenllent cycle stability for 10,000 cycles (98.6 % capacity retention), which provides a reliable multi-heteroatoms co-doped porous carbon fiber for high-performance ZHCs.

One-Step Carbonization Synthesis of N, S Co-Doped Carbon Materials Derived from Agricultural Waste Peanut Shells for High-Performance Symmetric Supercapacitors.

Biomass carbon has the advantages of wide source, low cost and environmental protection, and has been widely used in the field of electrochemical energy storage. In this work, N and S co-doped carbon materials were prepared by using peanut shell as carbon source and thiourea as activator. When the peanut shell and activator were 2 g and 4 g, respectively, the prepared NSPC-4 had the largest specific surface area and special pore structure. Elemental analysis showed that the activator introduced more N, S and O atoms to the carbon material, and more heteroatoms helped to improve the surface structure of the carbon material and provide additional pseudocapacitance. In addition, NSPC-4 contains a short-range ordered graphite structure, which can provide excellent electrical conductivity. The electrochemical test results show that NSPC-4 has the largest specific capacitance. When the mass of the activator is higher than or below 4 g, the electrochemical performance of the carbon material will be reduced. The symmetric supercapacitor (SSC) assembled by NSPC-4 has an energy density of 8.3 Wh kg-1 when the power density is 350 W kg-1. The synthesis method is not only simple, green and economical, but also has important application value.

Ammonia controlled synthesis of NiO nanosheet arrays for high-performance electrochromic-supercapacitors

To optimize the synthesis process and improve the electrochromic and energy storage performance of NiO, in this paper, an ammonia hydrothermal method is used to prepare NiO nanosheet array electrodes with dual-functions of electrochromic and energy storage. When the concentration of ammonia reaches pH = 11.5, the prepared electrode exhibits optimal optical modulation capability (79.2 % at 620 nm). Additionally, this electrode also provides a large area specific capacitance (69.5 mF/cm² at 0.2 mA/cm²), good rate capability (maintaining 46.7 mF/cm² at 1.0 mA/cm²), and excellent capacitive stability (retaining 96 % of the initial capacitance after 5000 cycles). These excellent performances are mainly attributed to the hierarchical assembled nanosheets structure, which has a large active surface area and short ion transport paths. Furthermore, the uniform and interlinked self-assembled structure, as well as the preset seed layer significantly enhance the film's structural stability and the adhesion to the substrate. Notably, we also construct electrochromic-supercapacitors (ECSCs). During the charging process, two series-connected ECSCs turn dark brown and light up an LED lamp, while during the discharging process, the ECSCs gradually becomes colorless, and the LED lamp goes out. This study provides directions for the preparation of novel dual-functional visual energy storage materials and boosts the development of dual-functional electrochromic-energy storage devices.

Three-dimensional N,P co-doped graphene hydrogel cathode for zinc-ion hybrid capacitor with high specific capacitance and excellent rate performance

Zinc-ion hybrid capacitor (ZHSC) is recognized as a favorable energy storage device due to the combined advantages of battery-type anode and capacitor-type cathode. However, it still remains a huge challenge to achieve a high-specific-capacitance cathode without compromising the rate capability for high-performance ZHSC. Here, a three-dimensional hierarchical nitrogen and phosphorus co-doped reduced graphene oxide hydrogel (NPGH) is synthesized with small-sized graphene oxide precursors via one-step hydrothermal reduction and in-situ doping, which is firstly used as cathode for ZHSC without adding extra conductive additives and binders. In this case, small-sized graphene sheets can increase and shorten ions diffusion channels for the efficient utilization of active surface compared with commonly-used large-sized counterparts. Moreover, nitrogen and phosphorus co-doping can synergistically enhance the conductivity, provide additional active sites, and promote the adsorption of zinc ions, which is well demonstrated by electrochemical analysis, ex situ characterization and DFT theoretical calculation. Attributed to the synergy, NPGH-based ZHSC displays large specific capacitance (251.3 F g−1, 0.5 A g−1), outstanding rate performance (79 %, 50 A g−1) and excellent cycle stability. This work proposes a novel strategy of tailoring rGO cathode by simultaneous size effect and doping engineering, which shows a great promise of constructing high-performance rGO based ZHSC.

Synchronously Consolidating Li, Se, S, and C for Robust Li-SeS Batteries.

S-redox involving solvated polysulfides is accompanied by volumetric change and structural decay of the S-based cathodes. Here, we propose a synchronous construction strategy for consolidating Li, Se, S, and C elements within a composite cathode via a paradigm reaction of 8Li+2Se+CS2 = 2Li4SeS+C. The obtained composite features crystalline Li4SeS encapsulated in a carbon nanocage (Li4SeS@C), exhibiting ultrahigh electrical conductivity, ultralow activation barrier, and excellent structural integrity, accordingly enabling large specific capacity (615 mAh g-1) and high capacity retention (87.3% after 350 cycles) at 10 A g-1. TOF-SIMS demonstrates its superior volumetric efficiency to a similar derivative SeS@C (2Se+CS2 = 2SeS+C), and DFT reveals its lower activation barrier than Li2S@C and Li2Se@C. This consolidation design significantly improves the electrochemical performance of S-based cathodes, and the paradigm reaction guarantees structural diversity and flexibility. Moreover, employing a synchronous construction mechanism to maximize the synergistic effect between element consolidation and carbon encapsulation opens up a new approach for developing robust S or chalcogenide cathodes.

Self-grown carbon nanotubes supported fluorine-free Mo2CTx conductive layers for efficient potassium storage

Mo2CTx is relatively less studied among MXenes family, especially for rechargeable alkali metal ion batteries. Herein, a systematic investigation has been conducted to unlock its potential as electrode materials in potassium-ion battery (PIBs), including innovative fluorine-free synthesis strategy, construction of heterostructure, and exploration of suitable electrolyte systems. Firstly, Cetyltriethylammnonium bromide (CTAB)-assisted etching route was provided to fabricate high-quality multilayer Mo2CTx with expanded interlayer space (C-Mo2CTx). The as-obtained C-Mo2CTx demonstrates a large specific capacity of 200 mAh g−1over 300 cycles in potassium-ion battery, surpassing the HF etched counterparts (F-Mo2CTx) by about 300 %. Afterwards, Zeolitic Imidazolate Frameworks (ZIF-67) derived Co, N-codoped carbon nanotubes (Co@NCNTs) were homogenously grown on the surface of Mo2CTx, working as embedding spacer to open the stacked Mo2CTx conductive layers (Mo2CTx-Co@NCNTs). Mo2CTx-Co@NCNTs electrode represents stable reversible capacity of 280 mA h g−1 over 300 cycles. The highly conductive matrix constructed by the strong bond between CNTs arrays and Mo2CTx conductive layer could provide numerous K-ion-diffusion pathways, and buffer volume strain and facilitate electron transfer. The present work proves the potential of Mo2CTx in PIBs and gives the systematic research methodologies on Mo2CTx-based materials in alkali metal ion storage.

Selective electro-capacitive deionization of Yb(III) by nanospherical N-doped carbon supported nickel‑iron bimetallic oxide, nitride and phosphide

The separation of rare earth elements from the mining waste water is highly important but still facing challenge. In this study, three different porous composite electrode materials were well-designed by decorating the nickel‑iron bimetallic oxide, nitride or phosphide onto nitrogen-doped carbon nanosphere, respectively (termed as NiFeO@NC, NiFeN@NC and NiFeP@NC), and utilized in capacitive deionization device for electrosorption of Yb(III) from water under the low-voltage electric field. The characterization and electrochemical results indicated that the incorporation of N or P atom lead to the reduced specific surface area and the enhanced electrochemical properties (i.e., larger specific capacitance, lower charge transfer resistance). In addition, NiFeN@NC and NiFeP@NC exhibited the excellent electrosorption capacities of Yb(III) with 105.24 mg·g−1 and 90.31 mg·g−1, respectively, under conditions of a flow rate of 20 mL·min−1, a voltage of 1.2 V, and pH of 5.0, which was extremely higher than NiFeO@NC (i.e., 50.7 mg·g−1). Moreover, all these three materials also demonstrated the remarkable electrosorption selectivity of Yb(III) from the mixed solution, and the robust durability with over 90 % of initial capacities after ten consecutive electrosorption-desorption cycles. Furthermore, the XPS characterizations and electrosorption results revealed that the electrosorption mechanism mainly depended on the synergistic effects of intrinsic Faraday redox reaction, electric double layer capacitance and active binding sites. Therefore, this work provided a feasible strategy for the separation of rare earth elements from aqueous solution, and the prospective applications related to the recovery of rare earth elements from mining wastes or spent permanent magnets in future life.

One-pot fabrication of hydrophobic, superelastic, harakeke-derived nanocellulose aerogels with excellent shape recovery for oil adsorption and water-in-oil emulsion separation

Cellulose-based aerogels have attracted significant attention for oil/water separation due to their high porosity, large specific surface area and high adsorption capacity. However, their intrinsic hydrophilicity, and inadequate mechanical properties have often limited their practical applications. Traditional freeze-dried cellulose aerogels exhibit unsatisfactory elasticity and require a separate surface modification process to adjust the surface wettability. In this study, we present a novel one-pot fabrication strategy which simultaneously achieves the crosslinking of individual cellulose nanofibers and the hydrophobic modification of the surface wettability. Following directional freeze-drying, hydrophobic, superelastic, and anisotropic cellulose-based aerogel was prepared from the 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibers, isolated from harakeke (New Zealand native flax). The resulting aerogel exhibits a high water contact angle of 142°, good compressive recovery performance (85 % recovery of the original height after 100 compression cycles at 70 % strain), and outstanding adsorption capacity for various types of oil and organic solvents (80–105 g/g). Furthermore, the aerogel could also be used as a filter to separate surfactant stabilized water-in-oil emulsions with a high flux (782 L m−2 h−1) and a high separation efficiency (98.7–99.2 %). The novel aerogel prepared in this study is expected to have great potential for practical applications in oily wastewater remediation.

Ligand-tuning of coordination compound for improved oxygen evolution

Controllable regulation of the reconstruction process for the pre-catalysts towards oxygen evolution remains as a great challenge. In this study, we report a bi-ligand strategy to facilitate the structural transformation of coordination compounds to metal oxyhydroxides during oxygen evolution with enhanced activity. A coordination compound consisting of 1,1′-ferrocene acid (Fc) and Ni2+ was synthesized, in which terephthalic acid was introduced. The second ligand of terephthalic acid facilitates the reconstruction process, inducing an enhanced catalytic activity. In 1 mol·L−1 KOH aqueous solution, the optimized catalyst can drive a current density of 10 mA·cm–2 under a lower overpotential of 220 mV. Using this catalyst, zinc-air batteries can be prepared. The obtained zinc-air battery presents a large specific capacity of 718 mA·h·g−1 with excellent cycling stability for over 100 h far exceeding that of Pt/C+RuO2 battery fabricated with commercial catalysts. The excellent performance and low cost of this catalyst will open up broad prospects for the development of advanced systems for water electrolysis and zinc air batteries.

Waste Plastic‐Derived FeMo@MgO/CNTs Nanocomposites for High‐Performance Supercapacitor Applications

AbstractMultiwalled carbon nanotubes (MWCNTs) were prepared from low‐density polyethylene (LDPE) plastic waste using FeMo(x)@MgO catalysts with several FeMo contents (x=10, 30, and 50 %). Pyrolysis of waste LDPE and growth of CNTs over FeMo/MgO catalysts were performed at 450 and 750 °C, respectively. The results indicated that FeMoO4, Fe2(MoO4)3, MgFe2O4, MgMoO4, and Mg2Mo3O11 species were the main components of the calcined catalyst containing 50 %FeMo. However, free monometallic iron oxides and bimetallic oxides (MgFe2O4, and MgMoO4) were the components of the calcined catalyst containing 10 %FeMo. The FeMo content was found to correlate with the yield and quality of the carbon product. TEM images of the spent catalysts proved the formation of MWCNTs at all FeMo contents. The FeMo(30)/MgO catalyst was the most active in CNT production. Raman spectroscopy results proved the generation of the best quality MWCNTs at 30 %FeMo content. XRD analysis of the spent catalysts demonstrated that nanocomposite of Fe3C, Mo2C, MgO, and MWCNTs (FeMoC(x)@MgO/CNTs) was successfully synthesized. The electrochemical performance of FeMoC(x)@MgO/CNTs composites was evaluated as low‐cost supercapacitor nanoelectrodes. Large specific capacity values of 806, 978, and 1180 F g were achieved at the current density of 0.1 A g using nanocomposites with 10, 30, and 50 %FeMo contents, respectively.

Magnesiothermic reduction SiO coated with vertical carbon layer as high-performance anode for lithium-ion batteries

Silicon monoxide (SiO), as one of the most competitive anode materials for lithium-ion batteries (LIBs), has received considerable attention. Nevertheless, poor initial Coulombic efficiency (ICE) and larger volume change are the main obstacles to the application of SiO. Here, we suggest a controllable route for the modification of micro-sized SiO via magnesiothermic reduction. To prevent the excessive growth of Si grains caused by the overheating reaction, the solid-state thermal reaction between Mg and SiO is achieved by mixing a certain proportion of NaCl at a suitable temperature, resulting in a loose surface and porous structure of SiO particles, which is conducive to the transportation of lithium ions and electrons. Combined with chemical vapor deposition (CVD), the carbon-coated SiOx composites (M-SiOx@C-R, where R is the molar ratio for Mg and SiO) exhibit unique morphology structure and remarkable electrochemical characteristics. As expected, the vertical carbon network improves the conductivity and alleviates the volume expansion of SiOx. Notably, the M-SiOx@C-0.75 electrode offers a large initial specific capacity of 2283.17 mAh g−1 with a higher ICE of 86.03 % at 100 mA g−1. Furthermore, the full cells using M-SiOx@C-0.75 composite as the negative electrode and LiNi0.8Co0.1Mn0.1O2 (NCM811) as the positive electrode were assembled. After 150 cycles, the full cell still delivers a high specific capacity of 72.22 mAh g−1 (with a retention rate of 47 %). This work provides a feasible route for the fabrication of applicable SiO-based anode materials.

Enhancing electrochemical performance of graphene oxide/polyaniline composite through plasma-assisted chemical cross-linking and surface modification

The composite of graphene oxide (GO) and polyaniline (PANI) is a promising electrode material for supercapacitors. A high loading of PANI can provide large specific capacitance, but it is a pervasive challenge to reconcile long-term cycling stability and high-rate discharge. Herein, we focus on a GO/PANI composite with low PANI content (∼25 wt%), developing a stable network of GO with an even distribution of PANI. Moreover, significantly enhanced electrochemical performance is achieved by utilizing plasma technology. The specific capacitance increases by 99 % to 433 F g−1 at 1.5 A g−1 after Argon (Ar) plasma treatment. Even at 15 A g−1, a capacitance retention rate of 91 % is obtained. After 15,000 cycles, the capacitance retention rate is 93 %, surpassing most previously reported GO/PANI composite electrodes. The further assembled all-solid-state supercapacitors can deliver a high energy density of 13.6 Wh kg−1 and exceptional cycling stability. According to results of characterization, it is demonstrated that Ar plasma imparts GO/PANI better surface morphology and achieves etching, reduction of GO, and cross-linking of GO and PANI, thereby activating the electrochemical activities of GO and PANI while ensuring stability. In this regard, the synergistic effects of cross-linking, reduction, and etching, and the mechanism are theoretically illustrated by dynamic differential equations. This work presents plasma processing unique charm for designing graphene-based materials via a customized strategy, exploiting an effectual approach to drive the applications of graphene-based materials in energy storage.

Tailoring Single‐Atom Coordination Environments in Carbon Nanofibers via Flash Heating for Highly Efficient Bifunctional Oxygen Electrocatalysis

The rational design of carbon‐supported transition metal single‐atom catalysts necessitates precise atomic positioning within the precursor. However, structural collapse during pyrolysis can occlude single atoms, posing significant challenges in controlling both their utilization and coordination environment. Herein, we present a surface atom adsorption‐flash heating (FH) strategy, which ensures that the pre‐designed carbon nanofiber structure remains intact during heating, preventing unforeseen collapse effects and enabling the formation of metal atoms in nano‐environments with either tetra‐nitrogen or penta‐nitrogen coordination at different flash heating temperatures. Theoretical calculations and in situ Raman spectroscopy reveal that penta‐nitrogen coordinated cobalt atoms (Co‐N5) promote a lower energy pathway for oxygen reduction and oxygen evolution reactions compared to the commonly formed Co‐N4 sites. This strategy ensures that Co‐N5 sites are fully exposed on the surface, achieving exceptionally high atomic utilization. The turnover frequency (65.33 s‐1) is 47.4 times higher than that of 20% Pt/C under alkaline conditions. The porous, flexible carbon nanofibers significantly enhance zinc‐air battery performance, with a high peak power density (273.8 mW cm‐2), large specific capacity (784.2 mA h g‐1), and long‐term cycling stability over 600 h. Additionally, the flexible fiber‐shaped zinc‐air battery can power wearable devices, demonstrating significant potential in flexible electronics applications.

Enhancing Rapid Li+/Na+ Storage Performance via Interface Engineering of Reduced Graphene Oxide-Wrapped Bimetallic Sulfide Nanocages.

Transition-metal sulfide is considered to be an admirable transformational electrode material due to low cost, large specific capacity, and good reversibility in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, the reduced graphene oxide-wrapped open bimetallic sulfide (NiS2-Co3S4@rGO) nanocage, derived from nickel-cobalt Prussian blue, was obtained by two-step calcination. There are luxuriant pore structures in the nanocage composite with a specific surface area of 85.28 m2 g-1, which provides plentiful paths for rapid transmission of Li+/Na+ and alleviates the volume stress caused by insertion and extraction of alkali metal ions. The excellent interface combination of bimetallic sulfide wrapped in reduced graphene oxide improves the conductivity and overall performance of the battery. Thanks to the special interface engineering, the open NiS2-Co3S4@rGO nanocage composite displays rapid lithium storage properties with an average diffusion coefficient of 8.5 × 10-13 cm2 s-1. Moreover, after 300 cycles, the reversible capacity of the composite is 1113.2 mAh g-1 at 1 A g-1. In SIBs, the capacity of the open NiS2-Co3S4@rGO composite is 487.9 mAh g-1 when the current density is 5 A g-1. These preeminent performances demonstrate the enormous development prospects of bimetallic sulfide nanocage as anode material in LIBs and SIBs.

Tailoring Single-Atom Coordination Environments in Carbon Nanofibers via Flash Heating for Highly Efficient Bifunctional Oxygen Electrocatalysis.

The rational design of carbon-supported transition metal single-atom catalysts necessitates precise atomic positioning within the precursor. However, structural collapse during pyrolysis can occlude single atoms, posing significant challenges in controlling both their utilization and coordination environment. Herein, we present a surface atom adsorption-flash heating (FH) strategy, which ensures that the pre-designed carbon nanofiber structure remains intact during heating, preventing unforeseen collapse effects and enabling the formation of metal atoms in nano-environments with either tetra-nitrogen or penta-nitrogen coordination at different flash heating temperatures. Theoretical calculations and in situ Raman spectroscopy reveal that penta-nitrogen coordinated cobalt atoms (Co-N5) promote a lower energy pathway for oxygen reduction and oxygen evolution reactions compared to the commonly formed Co-N4 sites. This strategy ensures that Co-N5 sites are fully exposed on the surface, achieving exceptionally high atomic utilization. The turnover frequency (65.33 s-1) is 47.4 times higher than that of 20 % Pt/C under alkaline conditions. The porous, flexible carbon nanofibers significantly enhance zinc-air battery performance, with a high peak power density (273.8 mW cm-2), large specific capacity (784.2 mAh g-1), and long-term cycling stability over 600 h. Additionally, the flexible fiber-shaped zinc-air battery can power wearable devices, demonstrating significant potential in flexible electronics applications.

Efficient microwave induction to modify surface for high-rate lithium/fluorinated carbon battery with ultra-high power density

The practical application of high-rate lithium/fluorinated carbon (Li/CFx) primary batteries faces challenge of relatively slow electrode reaction kinetics limited by inert C-F bond and strong polarity. Herein, an effective microwave-induction strategy was developed to regulate C-F bond for 80C high-rate Li/CFx battery with suppressed polarization. The as-mentioned microwave method was carried out in the alcohol-based solvent for uniformly modify CFx, including precise defluorination, C-F bond regulation, surface functional groups and carbon quantum dots. Precise defluorination contains the conversion of C-F bond to semi-ionic C-F bond while preserving C-F2 and C-F3. During the process of C-F bond regulation, hydroxyl groups is grafted onto the surface of CFx to increase the wettability and electronegativity of the electrode. Compared with raw CFx, the Li/CFx batteries using microwave-modified CFx achieved high discharge rate of 80C possessing a high power density of 134.091 kW/kg. In addition, the optimal Li/CFx battery possesses a large specific capacity increase ratio of 142.6 % at 50C. This microwave-induction approach for modifying CFx in ethanol-based solvent provides a facile and effective pathway to design high-rate Li/CFx battery.