High Specific Capacitance Research Articles

CVD-Synthesized Titanium Carbide Nanoflowers as High-Performance Anodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have emerged as promising candidates for energy storage applications due to the abundance and low cost of sodium. However, the larger radius of sodium ions limits their diffusion kinetics within electrode materials and contributes to electrode volume expansion. Here, we successfully synthesized porous titanium carbide (TiC) nanoflowers through chemical vapor deposition (CVD). The TiC nanoflowers exhibit exceptional electrochemical performance as SIB anodes, with their porous structure enhancing the conductivity, mechanical stability, and Na-ion diffusion. The TiC nanoflowers demonstrate a high reversible specific capacity of 73.5 mAh g-1 at 1 A g-1 after 2500 cycles, corresponding to an impressive capacity retention of 80.81%. Additionally, we developed a full sodium-ion cell utilizing TiC nanoflowers as the anode and Na3V2(PO4)3 as the cathode, which demonstrates a substantial reversible capacity and outstanding cycling stability. Our work presents a promising strategy for synthesizing nanostructured TiC materials as anode electrodes for SIBs.

Integration of 2D borophene into semiconducting N, P, S, and F-doped 1D carbon for energy storage and conversion devices

Innovative energy storage and high-performing conversion devices are urgently required to meet global energy issues. In this study, we synthesized and characterized a nitrogen, phosphorus, sulfur, and fluorine-doped one-dimensional carbon (NPSF@C) integrated with two-dimensional borophene (Bph) nanosheets, forming a nanocomposite (NPSF@C/Bph). The physicochemical and structural characterization confirmed borophene’s successful doping and integration into the NPSF@C matrix. Density Functional Theory (DFT) analysis indicated that the doping of heteroatoms and the integration of Bph increased the number of conduction bands in NPSF@C/Bph, effectively reducing the band gap of the material from 1.99 eV (MWCNT) and 1.43 eV (Bph) to 0.067 eV. This transformation was attributed to the introduction of localized states near the Fermi level and an enhanced density of states, resulting in a metal-like behavior for the NPSF@C/Bph composite. The NPSF@C/Bph composite demonstrated a specific surface area of 1962.78 m2/g and a pore volume of 1.2423 cm3/g, significantly enhancing its electrochemical performance. The composite showed a high specific capacitance of 837F/g at a current density of 1 A/g and retained 92.72 % of its initial capacitance after 10,000 cycles. It also exhibited a high energy density of 78.28 Wh/kg and a power density of 4545 W/kg in a symmetric supercapacitor device. Additionally, electrochemical tests revealed that the NPSF@C/Bph composite exhibited a lower overpotential and higher current density for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to its counterparts. Specifically, the overpotential for OER is 283 eV, and HER is 73 mV at a current density of 10 mA/cm2. The Tafel slopes were 63 mV/dec for OER and 67 mV/dec for HER, indicating superior reaction kinetics.

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.

Facile Preparation of Three-Dimensional Cubic MnSe2/CNTs and Their Application in Aqueous Copper Ion Batteries.

Transition metal sulfide compounds with high theoretical specific capacity and excellent electronic conductivity that can be used as cathode materials for secondary batteries attract great research interest in the field of electrochemical energy storage. Among these materials, MnSe2 garners significant interest from researchers due to its unique three-dimensional cubic structure and inherent stability. However, according to the relevant literature, the performance and cycle life of MnSe2 are not yet satisfactory. To address this issue, we synthesize MnSe2/CNTs composites via a straightforward hydrothermal method. MnSO4·H2O, Se, and N2H4·H2O are used as reactants, and CNTs are incorporated during the stirring process. The experimental outcomes indicate that the fabricated electrode demonstrates an initial discharge specific capacity that reaches 621 mAh g-1 at a current density of 0.1 A g-1. Moreover, it exhibits excellent rate capability, delivering a discharge specific capacity of 476 mAh g-1 at 10 A g-1. The electrode is able to maintain a high discharge specific capacity of 545 mAh g-1 after cycling for 1000 times at a current density of 2 A g-1. The exceptional electrochemical performance of the MnSe2/CNTs composites can be ascribed to their three-dimensional cubic architecture and the 3D CNT network. This research aids in the progression of aqueous Cu-ion cathode materials with significant potential, offering a viable route for their advancement.

Regulating V2O5 Layer Spacing by a Polyaniline Molecule Chain to Improve Electrochemical Performance in Salinity Gradient Energy Conversion.

Salinity gradient energy is a chemical potential energy between two solutions with different ionic concentrations, which is also an ocean energy at the junction of rivers and seas. In our original work, the device "activated carbon//(0.083 M Na2SO4, 0.5 M Na2SO4)//vanadium pentoxide" for the conversion of salinity gradient energy was designed, and the conversion value of 6.29 J g-1 was obtained. However, the low specific surface area of the original V2O5 inevitably resulted in limited active sites and slow ionic transport rates, and the inherent lower conductivity and narrower layer spacing of the original V2O5 also resulted in poor electrode kinetic performance and cycle stability, hindering its practical application. To solve the above problems, the present work provides a strategy of using polyaniline (PANI) molecule chain intercalation to regulate the layer spacing of the original V2O5, and through the expansion and traction of the layer spacing, the composite PANI/V2O5 (PVO) with high specific surface area is prepared and used as an anode material for electrochemical conversion of salinity gradient energy application. The significantly increased layer spacing of the crystal plane (001) corresponding to the original V2O5 was confirmed with the PANI by the hydrogen bonding and the van der Waals force. The high specific surface area of the composite provides more electrochemical active sites to realize a fast Na+ migration rate and high specific capacitance. Meanwhile, the inserted PANI molecule chain, which acts not only as a pillar enlarging the Na+ diffusion channel but also as an anchor locking the gap between V2O5 bilayers, improves the structural stability of the V2O5 electrode during the electrochemical conversion process. The proposed insertion strategy for the conductive polymer PANI has created a new way to improve the cycle stability performance of the salinity gradient energy conversion device.

Dendrite Growth and Dead Lithium Formation in Lithium Metal Batteries and Mitigation Using a Protective Layer: A Phase-Field Study.

Lithium metal batteries (LMBs) are considered one of the most promising next-generation rechargeable batteries due to their high specific capacity. However, severe dendrite growth and subsequent formation of dead lithium (Li) during the battery cycling process impede its practical application. Although extensive experimental studies have been conducted to investigate the cycling process, and several theoretical models were developed to simulate the Li dendrite growth, there are limited theoretical studies on the dead Li formation, as well as the entire cycling process. Herein, we developed a phase-field model to simulate both electroplating and stripping process in a bare Li anode and Li anode covered with a protective layer. A step function is introduced in the stripping model to capture the dynamics of dead Li. Our simulation clearly shows the growth of dendrites from a bare Li anode during charging. These dendrites detach from the bulk anode during discharging, forming dead Li. Dendrite growth becomes more severe in subsequent cycles due to enhanced surface roughness of the Li anode, resulting in an increasing amount of dead Li. In addition, it is revealed that dendrites with smaller base diameters detach faster at the base and produce more dead lithium. Meanwhile, the Li anode covered with a protective layer cycles smoothly without forming Li dendrite and dead Li. However, if the protective layer is fractured, Li metal preferentially grows into the crack due to enhanced Li-ion (Li+) flux and forms a dendrite structure after penetration through the protective layer, which accelerates the dead Li formation in the subsequent stripping process. Our work thus provides a fundamental understanding of the mechanism of dead Li formation during the charging/discharging process and sheds light on the importance of the protective layer in the prevention of dead Li in LMBs.

3D Printed Ordered Hierarchically‐Porous Electrodes for Developing High‐Performance Quasi‐Solid‐State Aqueous Nickel‐Iron Batteries

AbstractStructural engineering offers a viable and broadly applicable approach for further enhancing the energy density of aqueous nickel‐iron (Ni‐Fe) batteries without changing the fundamental battery chemistries. Herein, the synthesis of 3D printed low‐tortuosity and ultra‐thick ordered hierarchically porous reduced graphene oxide (rGO)‐based microlattice electrodes for high‐performance aqueous Ni‐Fe batteries through direct writing (DIW) 3D printing technology is presented. Significantly, the areal specific capacitance of the 3D printed electrodes scales positively with electrode thickness, whereas the gravimetric capacitance remains relatively constant, indicating that the capacitive performance is not constrained by ion diffusion and exhibits rapid kinetic behavior, even at elevated mass‐loading levels and in the context of ultra‐thick electrodes. Based on a 3 m KOH aqueous electrolyte, the 3D printed aqueous Ni‐Fe cell (thickness: ≈2 mm) exhibits high areal specific capacity (≈0.353 mAh cm−2), high volumetric energy/power density (≈1.15 mWh cm−2 at 48.00 mW cm−2), and excellent long‐term cycling performance (≈81.25% capacitance retained after 5000 cycles). As a micro‐battery device, 3D printed quasi‐solid‐state Ni‐Fe battery (3DP QSS Ni‐Fe) device with 4 mm thickness still exhibits a high areal capacity of 0.525 mAh cm−2, and excellent cycle stability with ≈81.1% capacity retention after 10000 cycles. The promising 3D printed strategy provides a novel avenue for the controllable assembly of higher‐dimensional architectures, thereby paving the way for the advancement of next‐generation materials and devices.

A versatile opened hollow carbon sphere with highly loaded antimony alloy for ultra-stable potassium-ion storage

Carbon materials meet the stringent practical requirements for anodes for potassium-ion batteries (PIBs) due to their abundance and chemical stability. The major issue of carbon-based anodes is the low specific capacity and poor cyclic stability. Equally importantly, scalable synthesis approaches for electrodes are highly desired for the future application in large-scale energy storage systems. Herein, we developed a novel composite of Sb encapsulated in N/P co-doped opened hollow carbon spheres (N/POHCs) with high Sb loading through a simple carbonization and subsequent impregnation process. Beneficial from the virtue of abundant pyridinic-N−P bonding and opened hollow spherical structure advantages, N/POHCs exhibit much lower diffusion barrier than that of pure carbon, prominent Sb carrier capability, as well as the extraordinary resistance to volume expansion. The resulting Sb@N/POHCs composite delivers a high specific capacity of 533.3 mAh g−1 at 0.1 A g−1 with an initial Coulombic efficiency of 83 %, and can maintain a specific capacity of 345 mAh g−1 at 1 A g−1 after 4000 cycles. This work provides rational structure design with universal carrier capability of active materials to achieve high-capacity and long cycle life anode for advanced PIBs accompanied by the potential for large-scale production.

Zinc-tin binary alloy interphase for zinc metal batteries

Aqueous zinc ion batteries are rapidly developing as the most propitious energy storage system due to their high security, high specific capacity and low cost, etc. However, zinc anodes suffered from dendrite growth and hydrogen evolution reactions during cycling, so it is of utmost importance to upgrade zinc anode properties. In this study, the homogeneous layer of ZnSn alloy interphase was formed by introducing metallic tin to the anode surface using an ion sputtering technique. ZnSn alloy can reduce the hydrogen evolution over-potential of anode and the corrosion current, inhibiting the occurrence of hydrogen evolution and corrosion reaction. Moreover, the ZnSn alloy anode can provide uniform nucleation sites and uniformize the electric field on the anode surface, promote the uniform deposition of Zn2+, thus inhibiting the formation of zinc dendrites. Notably, compared to the Zn foil//Zn foil cell (400 h), the ZnSn alloy symmetric cell showed excellent cycling performance by cycling for 1000 h at 0.5 mA cm−2. Furthermore, even at current density of 1 A/g, the capacity retention of the ZnSn alloy//MnO2 full cell was up to 89.5 % compared to only 32.3 % for Zn foil//MnO2 cell. The preparation of this ZnSn alloy anode may provide new ideas for future alloying strategies.

Exploration of experimentally feasible α-AsP as promising sulfur host material with superior electrochemic features for lithium-sulfur battery

Lithium-sulfur (Li-S) battery has become an ideal energy storage system due to high energy density and theoretical specific capacity. For the application of such a technique, a key is to find out a suitable sulfur host material. In this work, we, via examinations of 372 possible polysulfide@α-AsP configurations based on density functional theory (DFT), evaluated the potential of experimentally synthesized two-dimensional (2D) α-AsP structure as a promising sulfur host material of Li-S battery. Interestingly, we, revealed that polysulfides, that are caught on α-AsP substrate, can well maintain geometrical characteristics of isolated ones. Furthermore, some enthralling electrochemic features were revealed: (a) Adsorption energies of soluble polysulfides on α-AsP are lower than those on 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL), which enables α-AsP to exhibit a good anchoring ability for the suppression of shuttle effect; (b) In particular, low rate-limiting barrier of 0.50 eV of sulfur reduction reaction (SRR) and low Li2S decomposition barrier of 0.70 eV were demonstrated, which renders α-AsP to be a bifunctional catalyst for high conversion efficiencies; (c) In addition, we also observed that α-AsP can provide a platform for rapid Li ion diffusion with a low energy barrier of 0.15 eV, which further facilitates charging/discharging processes of Li-S battery. Our findings disclose a feasible sulfur host material with superior electrochemic features for high-performance Li-S battery.

Experimental investigations on strength and microstructural characteristics of air-cell impregnated light weight concrete

Concrete structures have high massive building materials than steel structures and possess very low thermal conductivity and high specific heat capacity. However, an efficient approach to reducing high production cost and structural weight of concrete elements without impacting their strength evolve as a growing necessity that leads to innovation in the Light weight concrete (LWC) fields such as aerated concrete and foamed concrete. Those large bubbles seem highly likely to get a break, move upwards through buoyancy and may get lost, while concrete has been mixed, transported, placed and vibrated. Hence to prevent increased bubble spacing, and air loss and to increase concrete durability, a sort of micron-sized air-cells could be generated in aerosol form, by passing out compressed air to dense form generating surfactants. Therefore to circumvent certain drawbacks of conventional LWC, the study delineated to bring out an innovative air-cell impregnated concrete (AIC) material, with homogenous mixing of cement, sand, water and uniformly distributed micron-sized air-cells wherein course-aggregates were replaced with air-cells. This uniform air-cell distribution creates durable concrete with unique feature characteristics since the micron-sized air-cells will be stable and does not collapse. The suitable surfactant towards contributing the strength and durability of proposed AIC structure are assessed, based on results.

Silicon-air batteries enabled by in-situ FeMn alloy-catalyzed nitrogen-doped carbon nanotube arrays as efficient air electrodes catalysts

Silicon-air batteries (SABs) have become promising candidates for energy conversion and storage devices due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, the slow kinetics of the 4e− transfer in the oxygen reduction reaction (ORR) at the cathode during discharge, coupled with severe polarization, reduces the battery’s capacity and hinders the development of silicon-air batteries. The cathodes of currently developed SABs primarily rely on commercial Pt/C and MnO2, with limited research on low-cost, efficient, and stable air cathodes for SABs. To address this issue, we synthesized nitrogen-doped carbon nanotubes containing FeMn alloy particles (FeMn@NCNTs) as cathode ORR catalysts using a simple high-temperature pyrolysis method combined with chemical vapor deposition. In an alkaline medium, the catalyst’s half-wave potential (E1/2) reached 0.83 V. Moreover, the FeMn@NCNTs air cathode exhibited excellent compatibility with the silicon anode, and the constructed aqueous silicon-air battery demonstrated a high specific capacity (165 Ah kg−1) and power density (3.69 mW cm−2). Additionally, the quasi-solid-state SABs constructed with FeMn@NCNTs showed stable operation over a wide temperature range, providing a new solution for the development of low-cost, efficient silicon-air batteries suitable for a wide range of applications.

Enhanced construction of 3D carbon skeleton through molten salt coupling activation effect for high efficiency capacitive deionization of lead (II) ions removal in wastewater

Efficiently eliminating of highly toxic ultra-dilute lead ions (Pb2+) from wastewater is a challenging task. Capacitive deionization (CDI) technology, based on the electrochemical capacitance mechanism, has emerged as a pivotal approach to address this challenge. In this work, a KNO3-mediated molten salt-coupled activation strategy was proposed to prepare nitrogen-doped hierarchical porous biomass carbon electrode material (3DCF-650-0.2) with a three-dimensional carbon skeleton, which was integrated into a symmetrical CDI device for Pb2+ removal. The 3DCF-650-0.2 electrode exhibited a high specific capacitance of 330.3 F g-1 at a current density of 1 A g-1, with a capacity retention rate of 98.45% after 10,000 cycles at 10 A g-1. Furthermore, the electrochemical adsorption capacity of the CDI device for Pb2+ reached 72.86 mg g-1 (1.2 V, 50 mg L-1), and the CDI device retained a high adsorption capacity of 91.14% after twenty adsorption/desorption cycles. These excellent adsorption properties are attributed to the in-situ activation and gas foaming of KNO3, which favors the production of reasonable pore structure (electric double-layer capacitance) and an appropriate pyrrolic nitrogen doping amount (selective adsorption) in the carbon materials. This work provides insight into the mechanism of the molten salt-coupled activation strategy, offering new ideas for the targeted design of high-performance CDI biomass carbon materials.

Electrolyte-triggered in-situ polymerization of multi-site organic cathodes for superior-longevity cation-anion co-storage secondary batteries

Organic electrodes are promising as next-generation energy storage materials owing to their diverse structures, low mass, and environmental friendliness. Nevertheless, the dissolution and degradation of organic active species in electrolytes are remaining obstacles to their authentic commercialization. Herein, we report an instantaneous in-situ upgrading strategy to convert multi-site organic cathode materials, e.g., 1-aminoanthraquinone (1-AAQ) and 1,5-diaminoanthraquinone (1,5-DAAQ), into poly(1-aminoanthraquinone) (PAAQ) and poly(1,5-diaminoanthraquinone) (PDAAQ) simply by dropping the electrolyte during battery assembly without extra operations. The remarkable chemistry is essentially a chemical polymerization process of redox-active organic monomers triggered by the electrolyte containing magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) as an initiator. Notably, due to the π-conjugated polymer chain with inhibited dissolution, high conductivity, and improved stability, the as-obtained PDAAQ cathode delivered a high specific capacity (254 mAh/g at 100 mA/g), superior rate performance (83 mAh/g at 2000 mA/g), and excellent cycling stability for over 8000 cycles accompanied by an average capacity decay of only 0.0026 % per cycle. Detailed characterizations further explore the kinetic behaviors and verify a reversible hybrid cation–anion co-redox mechanism of PDDAQ cathode, which involves reversible Mg2+ cation insertion/extraction on AQ units and anion doping/de-doping reactions on the PANI backbones. Density functional theory (DFT) computations demonstrate the optimized structure of the discharged products and indicate that Mg2+ preferably interact with two carbonyls oxygen atoms and nitrogen atom for both PAAQ and PDAAQ. This study demonstrates an intriguing in-situ chemical-polymerization synthetic approach for preparing multi-site organic electrode materials that compromise structure optimization and synthetic efforts, offering great promise for high-performance and sustainable secondary batteries.

Pr6O11 modification effectively enhancing sodium storage for Na3V2(PO4)3 batteries

Na3V2(PO4)3 (NVP) is one of the most promising cathode materials for sodium-ion batteries (SIBs) due to its robust three-dimensional framework, high tunability, and relatively high Na+ intercalation potentials. However, its utility is generally constrained by low conductivity, inefficient charge transfer, and subpar interface kinetics. This work presents an efficient and simple method to address these issues. We innovatively modified the NVP surface with Pr6O11 nanoparticles, a negative temperature coefficient (NTC) thermosensitive material, to enhance interface compatibility with electrolytes and improve conductivity. This modification significantly enhances the overall sodium-ion storage performance. Specifically, the optimized NVP-2 %Pr6O11 electrode exhibits excellent electrochemical properties with the aid of an optimized conductivity network compared to the unmodified NVP. Cycled at an 8C current density, the NVP-2 %Pr6O11 electrode achieves high specific capacities of 102.6 mAh·g−1 at 27 °C and 95.6 mAh·g−1 at 45 °C. After 1000 cycles, the capacity retention rates are 81.18 % and 78.97 %, respectively, significantly higher than the 20.59 % and 14.99 % of pure NVP. In coin full-battery testing, the NVP-2 %Pr6O11 electrode retains 89.76 % capacity after 500 cycles at 8C. In addition, the assembled The NVP-2 %Pr6O11//HC pouch full battery exhibits better sodium-ion storage and thermal safety performance compared to the NVP-SP//HC battery. This simple modification strategy provides an effective insight into the application of NVP electrodes in energy storage.

Electrospun mesoporous Ni0.5Zn0.5Fe2O4 - CNT - hollow carbon ternary composite nanofibers as high performance electrodes for advanced symmetric supercapacitors.

Despite being potential electrode materials for supercapacitors, Spinel ferrites suffer from poor electronic conductivity and low specific capacity. We have addressed this limitation by synthesizing composite hollow carbon nanofibers (HCNF) embedded with nanostructured Nickel Zinc Ferrite (NZF) and Multiwalled carbon nanotubes (CNT), through coaxial electrospinning. These ternary composite nanofibers NZF-CNT-HCNF have a high specific capacity of 833 C g-1at a current density of 1 A g-1and have a capacity retention of 90% after 3000 cycles. This is much better than that of pure NZF fibers (180 C g-1) or hollow carbon nanofibers (96 C g-1), suggesting synergy between various constituents of the composite. A symmetric supercapacitor fabricated from NZF-CNT-HCNF composite nanofibers (30% NZF) has a high specific capacity of 302 C g-1(302 A g-1) at a current density of 1 A g-1and has a capacity retention of 95% after 5000 cycles. At the same current density, the device has a high energy density of 39 Whkg-1and power density of 1000 Wkg-1at a current density of 1 A g-1. This performance can be attributed to high specific surface area (776 m2g-1), mesoporosity (pore size ~ 4 nm) and high electrical conductivity of CNTs..

Breaking the Lithiation Barrier via Tailored-Design Facile Kinetic Pathways in TiO2(B) Realizing 50C Ultrafast Charging.

As a promising anode material for fast charging lithium-ion batteries, bronze-phase titanium dioxide (TiO2(B)) still faces the challenge of sluggish Li+ diffusion kinetics in the solid phase during lithiation/delithiation processes. Herein, a facile synthetic strategy has been proposed to optimize the microstructure of TiO2(B), which enables facilitated lithiation and therefore significantly improved rate performance. The rice-granular nanoparticles with precisely controlled aspect ratios (AR) can be obtained via manipulating the ligand concentrations that affect nucleation and oriented attachment processes, as well as adjusting the calcination temperatures to control the Oswald ripening process. As a result, the smaller ab plane in rice-granular TiO2(B) enhances Li+ diffusion efficiency on C' site and inhibits the inhomogeneity of Li+ between inter and inside particles. Benefiting from breaking the Li+ diffusion kinetics, the rice-granular TiO2(B) maintains a high specific capacity of 159.5 mAh g-1 at 50C, with an excellent capacity retention ratio of 93.67% after 5000 cycles at 10C. This work provides an efficient and simple strategy to minimize the challenging lithiation paths in TiO2(B) anode, and offers new opportunities for high rate battery design.

Boosting the synergistic activation of δ-MnO2 as cathode for aqueous zinc-ion batteries through Ni, Co co-doping

Layered δ-MnO2 is regarded as a promising cathode material for high-performance aqueous zinc-ion batteries (AZIBs) due to the sufficient interlayer spacing for the accommodation and migration of charge carriers. However, the sluggish activation process limits the reversible capacity, thus prevent their application. In this study, Ni-Co co-doped layered δ-MnO2 was designed to enhance ion diffusion capability and cycling stability. The influencing mechanism of Ni and Co on the long activation process are proposed by a comparative analysis between single doping and co-doping approaches. Specifically, the optimized co-doped δ-MnO2 maintained a high specific capacity of 200.2 mAh·g−1 with a capacity retention of 97.40 % after 700 cycles at 1 A·g−1. The co-doping approach exhibited a synergistic effect in suppressing Mn dissolution and enhancing ion diffusion capability. These findings provide new directions on boosting the synergistic activation process of manganese oxide and shed lights on the rational design of low-cost and high-safe batteries.

Insights into the electrochemical performance of manganese dioxide coated metallic foils as potential electrodes for supercapacitors

AbstractManganese dioxide (MnO2) is a promising electrode material for supercapacitors due to its high theoretical specific capacitance. In this study, MnO2 particles were synthesized using a simple hydrothermal method and subsequently coated onto silver, nickel, and aluminum foils via dip coating. The structural, morphological, and functional properties of the resulting MnO2 nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT–IR). Electrochemical impedance spectroscopy (EIS), galvanostatic charge–discharge (GCD), and cyclic voltammetry (CV) were employed to investigate the electrochemical performance of the coated metallic foils. The results demonstrated that MnO2/Ag foils exhibited the highest specific capacitance of 198 F g–1 at a scan rate of 0.25 A g−1, accompanied by excellent cycle stability (89% capacitance retention). This performance surpassed that of MnO2/Ni and MnO2/Al foils, which exhibited maximum specific capacitances of 150 and 101 F g−1, respectively. Additionally, MnO2/Ag foils displayed the highest charge storage capacity, as evidenced by EIS analysis, reaching 4000 Ω, nearly double that of MnO2/Ni and MnO2/Al foils. These findings highlight the potential of cost-effective and high-performance MnO2/Ag foils for widespread applications in energy storage devices such as electrochemical capacitors. Graphical Abstract

Bimetallic NiCo@C with a Hollow Sea Urchin Structure Enables Li-S Batteries to Hasten the Reaction Kinetics and Effectively Inhibit the Shuttling of Polysulfides.

The "shuttle effect" and several issues related to it are seen as "obstacles" to the study and development of lithium-sulfur batteries (LSBs). This work aims at finding how to fully expose bimetallic sites and quicken the battery reaction kinetics. Here, a bimetallic NiCo-MOF and its derivative NiCo@C with a hollow sea urchin structure are produced. The obtained NiCo@C possesses a micromesoporous structure and fully disclosed bimetallic active sites because of its distinctive structure. The experimental findings demonstrate that fully exposed bimetallic active sites take on chemical adsorbents and collaborate with micromesopores as physical constraints to effectively suppress the "shuttle effect". Furthermore, the hollow sea urchin structure of NiCo@C enables a highly conductive grid, which provides channels to facilitate the movement of solvated Li+. Thanks to these advantages, the NiCo@C-based sulfur cathode offers a high initial discharge specific capacity of 924.41 mAh g-1 at 0.1 C and sustains 390.35 mAh g-1 discharge specific capacity after 100 cycles. The quick transfer of solvated lithium ions (DLi+ = 1.81 × 10-8 cm2 s-1) enables the battery to still contribute a discharge specific capacity of 367.54 mAh g-1 at 1 C. This work provides a new understanding for the structural design of positive electrodes in LSBs.