Rapid Ion Diffusion Research Articles

Selective extraction of uranium from seawater on amidoximated MXene/metal-organic framework architecture under an electric field

Seawater holds tremendous uranium resources, which can sustain the global nuclear industry for thousands of years. However, the existing technologies for uranium extraction from seawater (UES) are constrained by the ultra-low uranium concentration and high interference background. A three-dimensional amidoximated Ti3C2Tx/ZIF-67 architecture (TAZ) is fabricated for highly efficient uranium capture via electrosorption. Besides the excellent electrical conductivity of Ti3C2Tx, the introduction of amidoxime groups and ZIF-67 nanoparticles endows TAZ with porous structure and abundant active sites, which favors the rapid uranyl ions diffusion and enhanced electrosorption. TAZ displays a remarkable uranium extraction uptake of 2224.54 mg/g under an applied voltage of 1 V. Meanwhile, TAZ possesses prominent uranium selectivity resulting from amidoxime groups and imidazole N. TAZ also maintains a good reusability of 63.51% after 10 cycles. Furthermore, the bactericidal rates of TAZ against both Escherichia coli and Staphylococcus aureus achieve nearly 100%. The excellent properties have made TAZ apt for UES with a high uranium uptake of 11.40 mg/g in 24 h under an electric field, which is 5.3 times higher than the physicochemical adsorption. Our work provided a strategy to design high-performance nanomaterials for efficient uranium mining from seawater.

In situ synthesis of layered nickel organophosphonates for efficient aqueous nickel-zinc battery cathodes

Aqueous nickel-zinc (Ni-Zn) batteries have received increasing research interests because of their reliable safety and economical-friendliness. However, the retarded ionic diffusion, low capacity and limited stability of traditional Ni-based cathodes greatly impedes the practical application of Ni-Zn batteries. Herein, two metal organophosphonate materials of Ni methylphosphonate (Ni-MPA) and Ni phenylphosphonate (Ni-PPA) directly grown on Ni foam are constructed successfully through one step solvothermal technique. These two self-supported Ni organophosphonates featured hybrid two-dimensional (2D) structures consisting of alternating inorganic and organic layers, where the inorganic layers are formed by six-coordinated Ni2+ bridged by oxygen atoms and capped by organophosphonate groups, availing to provide rich open redox reaction sites, rapid ion diffusion and structural flexibility. The research results reveal that the organic groups in phosphonic acid ligands have important influence on their electrochemical properties. Consequently, the Ni-MPA electrode exhibits a higher specific capacity of 2.27 mAh/cm2 compared to that of the Ni-PPA electrode (1.1 mAh/cm2) at 3.0 mA/cm2; however, it demonstrates a more rapid transformation rate into Ni(OH)2 in an alkaline solution. Furthermore, the constructed Ni-MPA//Zn battery can deliver an impressive areal energy density of 2.95 mWh/cm2, good rate performance as well as a long-term cycling stability.

Cooperative regulation of hard template and emulsion self-assembly to the synthesis of N/O co-doped mesoporous hollow carbon nanospheres for supercapacitors

Hollow carbon nanospheres have attracted more and more attention as supercapacitor materials due to their excellent electrical conductivity, high theoretical surface area, high accumulation and rapid ion transfer and diffusion. In this work, we employed the Stöber method to create silica as a template, and then applied self-assembly and dopamine polymerization on the surface of the template to form SiO2@TMB-F127-PDA micelles. Then the nitrogen-doped mesoporous hollow carbon nanospheres (N-MHCNs) were prepared by carbonization and etching on the formed carbon precursors. The effect of dopamine amount on the structure and properties of N-MHCNs was systematically studied. Microstructural characterization results reveal that the morphology of N-MHCNs can be changed from sheet to sphere, and the particle size of N-MHCNs can be 33.8–225.7 nm, the specific surface area is distributed in the range of 175.9–430.1 m2 g−1. Due to the N,O heteroatomic co-doping and Porous spherical structure (with a small particle size of 33 nm, and a large specific surface area of 430.1 m2 g−1), typical sample N-MHCNS-2 shows excellent electrochemical performance in supercapacitors. And it has the highest specific capacitance (241 F g−1) at 0.5 A g−1 current density, excellent rate performance (capacity retention rate of 79 % when current density increases from 0.5 to 10 A g−1) and good cycling ability (capacity retention rate of 90.4 % after 3000 cycles), indicating that it shows great potential in energy storage. This approach provides new opportunities for the controllable synthesis of hollow mesoporous nanospheres and it can be extended to other systems such as hollow metals, metal oxide nanomaterials and carbon-based hybrids.

Layered hydrated-titanium-oxide-laden reduced graphene oxide composite as a high-performance negative electrode for selective extraction of Li via membrane capacitive deionization

In this work, we initially prepared layered lithium titanate (Li2TiO3) using a solid-state reaction. Then Li+ of Li2TiO3 were acid-eluded with Hydrochloric acid to obtain hydrated titanium oxide (H2TiO3). Different weight percentages (50%, 60%, 70%, 80%, and 90%) of the as-prepared H2TiO3 were deposited on a conductive reduced graphene oxide (rGO) matrix to obtain a series of rGO/ H2TiO3 composites. Of the prepared composites, rGO/H2TiO3-60% showed excellent current density, high specific capacitance, and rapid ion diffusion. An asymmetric MCDI (membrane capacitive deionization) cell fabricated with activated carbon as the anode and rGO/H2TiO3-60% as the cathode displayed outstanding Li+ electrosorption capacity (13.67 mg g−1) with a mean removal rate of 0.40 mg g−1 min−1 in a 10 mM LiCl aqueous solution at 1.8 V. More importantly, the rGO/H2TiO3-60% composite electrode exhibited exceptional Li+ selectivity, superior cyclic stability up to 100,000 s, and a Li+ sorption capacity retention of 96.32% after 50 adsorption/desorption cycles. The excellent Li+ extraction obtained by MCDI using the rGO/H2TiO3-60% negative electrode was putatively attributed to: (i) ion exchange between Li+ and H+ of H2TiO3; (ii) the presence of narrow lattice spaces in H2TiO3 suitable for selective Li+ capture; (iii) capture of Li+ by isolated and hydrogen-bonded hydroxyl groups of H2TiO3; and (iv) enhanced interfacial contact and transfer of large numbers of Li+ ions from the electrolyte to H2TiO3 achieved by compositing H2TiO3 with a highly conductive rGO matrix.

Design of Co-doped hollow multi-channel carbon fibers for high performance lithium sulfur batteries

The low conductivity of active material and the detrimental shuttle effect of lithium polysulfides (LiPSs) intermediates in lithium sulfur batteries (LSBs) mainly limit their practical application. In this work, the well-designed “tube-in-fiber” structure is fabricated via confining carbon nanotubes (CNTs) in Co-doped hollow multi-channel carbon fibers (MCCFs-Co) as sulfur host material for LSBs. As a result, the MCCFs-Co/CNTs composite with hierarchically porous structure and high specific surface area demonstrate excellent electrolyte wettability and rapid Li ion diffusion rate. The addition of CNTs and Co nanoparticles improves the absorption capability and catalytic conversion activity of the composite towards LiPSs, thereby enhancing the redox kinetics and alleviating the shuttle effect. Consequently, the MCCFs-Co/CNTs/S cathode delivers remarkable cycling stability (843 mAh g−1 after 150 cycles at 0.5 C) and outstanding rate capability (698 mAh g−1 after 300 cycles at 2.0 C).

Hybridizing Ti3C2Tx Layers with Layered Double Hydroxide Nanosheets at the Molecular Level: A Smart Electrode Material for H2O2 Monitoring in Cancer Cells.

Vertically stacked artificial 2D superlattice hybrids fabricated through molecular-level hybridization in a controlled fashion play a vital role in scientific and technological fields, but developing an alternate assembly of 2D atomic layers with strong electrostatic interactions could be much more challenging. In this study, we have constructed an alternately stacked self-assembled superlattice composite through integration of CuMgAl layered double hydroxide (LDH) nanosheets having positive charge with negatively charged Ti3C2Tx layers using well-controlled liquid-phase co-feeding protocol and electrostatic attraction and investigated its electrochemical performance in sensing early cancer biomarkers, i.e., hydrogen peroxide (H2O2). The molecular-level CuMgAl LDH/Ti3C2Tx superlattice self-assembly possesses superb conductivity and electrocatalytic properties, which are significant for obtaining a high electrochemical sensing aptitude. Electron penetration in Ti3C2Tx layers and rapid ion diffusion along 2D galleries have shortened the diffusion path and enhanced the charge transferring efficacy. The electrode modified with the CuMgAl LDH/Ti3C2Tx superlattice has demonstrated admirable electrocatalytic abilities in H2O2 detection with a wide linear concentration range and low real-time limit of detection (LOD) of 0.1 nM with signal/noise ratio (S/N) = 3. Practically, an electrochemical sensing podium based on the CuMgAl LDH/Ti3C2Tx superlattice has been effectively applied in real-time in vitro tracking of H2O2 effluxes excreted from different live cancer cells and normal cells after being encouraged by stimulation. The results exhibit that molecular-level heteroassembly holds great potential in electrochemical sensors to detect promising biomarkers.

Surface charge induced self-assembled nest-like Ni3S2/PNG composites for high-performance supercapacitors

The paper presents a self-assembly approach to synthesize Ni3S2/N, P co-doped graphene (PNG) composite electrode materials for supercapacitors with high energy storage performance and structural stability. Innovatively, the self-assembly approach is induced via the surface charge effect utilizing a two-step hydrothermal method. The doping of nitrogen (N) and phosphorus (P) atoms regulates the surface charge distribution on graphene nanosheets. Therefore, in the synthesized Ni3S2/PNG heterostructures, Ni3S2 nanowires are interwoven into nests and uniformly attached to PNG. The design of the electrode materials with such a special structure not only supports each other to improve the stability of the materials but also facilitates the rapid diffusion of electrolyte ions. Based on the advantages of composition and structure, Ni3S2/PNG has a high specific capacitance of 1117C g−1 at a current density of 1 A/g and excellent rate performance. The asymmetric supercapacitors (ASC) assembled with Ni3S2/PNG and PNG as positive and negative materials respectively have a high energy density of 62 Wh kg−1 at a power density of 158 W kg−1.

Synthesis of 3D flower-like zinc-chromium layered double hydroxides: A functional electrode material for furaltadone detection

Furaltadone (FLD) as an antibiotic has been widely used in animal husbandry to treat bacterial infection and promote animal growth. Its abnormal usage has threatened human health and the ecological system. The sensitive FLD detection is crucial for the protection of human health and eco-environment. In this study, unique 3D flower-like zinc-chromium layered double hydroxides (ZnCr-LDHs) are synthesized by a facile hydrothermal approach and further utilized as the electrode material for electrochemical FLD detection. The characteristics of 3D flower-like ZnCr-LDHs were systematically investigated by various microscopic and spectroscopic methods. This 3D-flower-like ZnCr-LDHs endows the electrocatalyst with rich electroactive sites, good conductivity, large surface area, and rapid ion diffusion to promote electrochemical activities. The ZnCr-LDHs modified glassy carbon electrode (GCE) shows superior electrochemical performance for the detection of FLD compared to the pristine GCE, including. wide linear ranges (0.01–60.8; 60.8–312.9 μM), low limit of detection (1.0 nM), low limit of quantitation (3.4 nM), high sensitivity (1.31 μA μM–1 cm–2), good reproducibility (4.75%), and anti-interfering ability (<±5%). The practicality of the fabricated ZnCr-LDHs/GCE was successfully confirmed by measuring FLD in the human-urine and river-water samples with acceptable recovery values (95–99%). This work opens a new perspective way for the design and preparation of novel electrode material with unique properties for boosting electrocatalysis toward electrochemical sensing applications.

Defect-rich hierarchical porous carbon prepared by homogeneous activation for high performance capacitive deionization

Defect engineering has emerged as an effective approach for modulating the electronic structure and physicochemical properties of carbon materials. Porous carbon materials with abundant defects are regarded as prospective electrode materials for capacitive deionization. Nevertheless, constructing defect-rich carbon materials and revealing the relationship between desalination capacity and intrinsic defects remains a daunting challenge. Herein, the defect-rich interconnected hierarchical porous carbon (IHPC) was fabricated via sol-gel method to form a supramolecular hydrogel containing highly dispersed K+ using coal, polyvinylpyrrolidone, and KOH as raw materials, followed by homogeneous activation. The spectroscopic studies coupled with density functional theory calculations demonstrate that the introduction of intrinsic defects can optimize the distribution of electron density to promote charge transfer, thereby enhancing saline ions adsorption. The plentiful adsorption sites, robust charge transfer kinetics and rapid ion diffusion derived from the multiple advantageous characteristics of IHPC facilitate a high desalination capacity of 31.25 mg g−1 in 800 mg L−1 NaCl solution. Meanwhile, it also presented excellent desalination performances in KCl (31.42 mg g−1), CaCl2 (29.55 mg g−1), and MgCl2 (26.65 mg g−1) solutions. The higher desalination capacity, rapid salt adsorption rate as well as outstanding cycling stability rank the IHPC as a potential candidate for capacitive deionization applications.

Spotting Interface Structuring during Na‐Insertion into the NaSICON Na3V2(PO4)3 by EQCM and Operando Fiber Optic Infrared Spectroscopy

AbstractReliable operation of Na‐ion batteries requires a mastering of the interfacial processes governing intercalation kinetics. Ion desolvation, amongst others, is a crucial phenomenon as far as power applications are envisioned. Studying the intricacies of interfacial processes faces experimental challenges. Here the complementary use of electrochemical quartz crystal microbalance (EQCM) and operando infrared fiber evanescent wave spectroscopy (IR‐FEWS) combined with molecular dynamics (MD) simulations is reported to investigate the electrode/electrolyte interface of polyanionic Na‐insertion compounds Na3V2(PO4)3 (NVP) and Na3V2(PO4)2F3 (NVPF). Through screening of various electrolytes that differ in their solvation energy and viscosity, the existence of an unusual mass uptake/depletion signal is demonstrated at the NVP interfaces only, indicative of a dissimilarity in migration kinetics of solvent molecules between NVP and NVPF interfaces as supported by IR‐FEWS. This finding is rationalized by positing that sodium depletion is caused by the unusually rapid ion diffusion within NVP mediated by an intermediate metastable phase, which leads to opposite Na+ concentration and free solvent molecule gradients at the interface that causes the unusual and anomalous feature observed on EQCM frequency profiles. This feature does not appear with NVPF showing lower ionic diffusion. Altogether, this fundamental study provides valuable fundamental insights into the interface structuring of insertion compounds depending upon their Na+ mobility.

In-situ etching activation towards flexible carbonized paper-supported electrode with transition-metal oxides embedded into carbonized cellulose fibers

Cellulose paper is considered to be a promising substrate of energy materials for energy storage device due to its flexible, porous, renewable, degradable, and environmental-friendly feature. However, the large weight and low conductivity of cellulose fibers limit the specific capacitance and energy density of the paper electrodes. Converting cellulose fibers into conductive carbon fibers (CCF) by high temperature carbonization is an effective strategy for improving the electrochemical performance of paper electrodes. But the brittleness of carbonized paper limits its application in flexible supercapacitors. In addition, stable loading of energy materials on CCF is another challenge. Here, KNO3 in-situ etching activation method is used to construct the embedded structure of transition-metal oxides (TMOs) on CCF. And the embedding degree of TMOs on CCF can be adjusted by controlling the amount of KNO3. The embedded structure releases the mechanical stress from bending of CCF, endowing good flexibility for carbonized paper. In addition, embedded structure can anchor TMOs into CCF, and increase the porosity and specific surface area of CCF, promoting a rapid ion diffusion and electron transport for high capacitance contributions. The KNO3-etched Co3O4@CCF paper as an electrode exhibits a high volume specific capacitance of 72.3 F cm−3 at current density of 0.5 mA cm−2 (more than three times higher than that of Co3O4/CCF paper) and shows good rate capability (capacitance retention of 83.3% with 10 times current density) and long lifetime (charge-discharge stability of 94.8% after 10000 cycles). Even in bending state, the composite paper still maintains stable electrochemical performances, which can broaden potential application in flexible supercapacitors.

Biowaste-derived oxygen-self-doped three-dimensional interconnected porous carbon for electrochemical supercapacitor applications

ABSTRACT Biowaste for producing a biomaterial is an inexpensive, profuse, widely available, and viable natural source and has been extensively investigated and applied in a wide range of research fields. In this work, jackfruit leaf waste as a biowaste source was utilized to prepare a three-dimensional (3D) interconnected porous carbon framework self-doped with oxygen by KOH impregnation, carbonization, and activation under a CO2 atmosphere. The as-prepared porous carbon has a 3D interconnected porous framework with a rich oxygen content of 36.82%, and high BET surface area of 455.687 m2 g−1 with a pore volume of 0.522 cm3 g−1. The 3D interconnected porous framework exhibits a high specific capacitance of 199 F g−1 with a maximum energy density of 27.64 Wh kg−1 at a power density of 99.60 W kg−1 at a sweep rate of 1 mV s−1 in a two-electrode setup. The correlation between structure and great performance of electrode materials is deeply studied. The great capacitive performance of porous carbon materials can be assigned to its 3D interconnected porous framework, high specific surface area, suitable pore size distributions, and advantageous heteroatom-doping, resulting in the rapid ion diffusion and sufficient charge storage along with the contributed pseudocapacitance behavior. Hence, the exciting results reveal an efficient, cost-effective, time-saving, and facile method to prepare 3D interconnected porous carbon frameworks self-doped with oxygen derived from natural biowaste sources for developing supercapacitor devices.

Structural design and fabrication of metal vanadate hydrates for wearable electronic applications

The structural design of electroactive materials including rich profits of high capacitance/capacity and exalted durability is of considerable importance in the development of high-performance wearable energy storage technologies. Herein, a simple and single-step hydrothermal approach is demonstrated to design hierarchical feathers-like microsheet arrays for asymmetric supercapacitors (ASCs) with stable cycling performance. The preparation is carried out at low temperatures without any annealing process, and the as-designed nickel/cobalt vanadate hydrates supported on conductive carbon cloth textile are endowed with the unique architecture of feathers-like microsheets, which allows for the effective contact of active materials, rapid ion diffusion, easy electrolyte penetration, and fast electron transfer. Considering these merits in amalgamation, the Ni0.33Co0.67 vanadate hydrate active material shows a superior areal/specific capacity value of 373.9 µAh cm−2/140 mAh g−1 with outstanding cycling performance (100,000 cycles) than those in the design of mono NiV and CoV hydrates as well as the other fabricated electrode (Ni:Co ratio) materials. Furthermore, the Ni0.33Co0.67 vanadate hydrate active material, when employed as a positive electrode for ASCs, demonstrates excellent electrochemical performance. The assembled ASC exhibits high energy and power density values of 0.19 mWh cm−2 and 2.04 mW cm−2, respectively along with remarkable cycling retention of 82.2% after the completion of 100,000 cycles. Also, the as-assembled device was tested by powering different wearable electronics. This work creates a new pathway for the fabrication of single-step Ni-Co vanadate hydrates for durable electrochemical energy storage applications.

Recent Advances and Prospects of FeOOH-Based Electrode Materials for Supercapacitors

Supercapacitors (SCs) offer a potential replacement for traditional lithium-based batteries in energy-storage devices thanks to the increased power density and stable charge–discharge cycles, as well as negligible environmental impact. Given this, a vast array of materials has been explored for SCs devices. Among the materials, iron oxyhydroxide (FeOOH) has gained significant attention in SC devices, owing to its superior specific capacitance, stability, eco-friendliness, abundance, and affordability. However, FeOOH has certain limitations that impact its energy storage capabilities and thus implicate the need for optimizing its structural, crystal, electrical, and chemical properties. This review delves into the latest advancements in FeOOH-based materials for SCs, exploring factors that impact their electrochemical performance. To address the limitations of FeOOH’s materials, several strategies have been developed, which enhance the surface area and facilitate rapid electron transfer and ion diffusion. In this review, composite materials are also examined for their synergistic effects on supercapacitive performance. It investigates binary, ternary, and quaternary Fe-based hydroxides, as well as layered double hydroxides (LDHs). Promising results have been achieved with binder-free Fe-based binary LDH composites featuring unique architectures. Furthermore, the analysis of the asymmetric cell performance of FeOOH-based materials is discussed, demonstrating their potential exploitation for high energy-density SCs that could potentially provide an effective pathway in fabricating efficient, cost-effective, and practical energy storage systems for future exploitations in devices. This review provides up-to-date progress studies of novel FeOOH’s based electrodes for SCs applications.

2D coordination unsaturated Ni-MOFs hierarchical nanosheets with internal electric fields for high-performance hybrid supercapacitors

The poor intrinsic electronic conductivity and low-exposure electroactive sites of MOFs limit their practical application in energy storage. Herein, the coordination unsaturated nickel-based metal organic frameworks (Ni-MOFs) were prepared by one-step solvothermal method via adjusting the molar ratio of metal salts to organic ligands (RM/L). The coordination unsaturated degree and morphology of the materials can be controlled by adjusting RM/L. When the RM/L is 2, the obtained Ni-MOF 2:1 is a two-dimensional (2D) hierarchical nanosheets made of interwoven ultra-thin nanoribbons. The 2D hierarchical nanosheets structure of Ni-MOF 2:1 can not only expose more electroactive sites, but also promote ions diffusion. The density functional theory (DFT) simulations reveal that the coordination unsaturated centers can narrow the band gap, thus resetting the internal electric field and improving the conductivity of Ni-MOF 2:1. Benefit from abundant electroactive sites, rapid ions diffusion and improved electrical conductivity, the Ni-MOF 2:1 shows a high specific capacity of 746 C g−1 at 1 A g−1 and excellent cycling stability of 89.7 % capacity retention after 10,000 cycles at 10 A g−1. The hybrid supercapacitor (HSC) assembled with Ni-MOF 2:1 as cathode and activated carbon (AC) as anode has a maximum energy density of 53.1 Wh Kg−1 at 799.9 W Kg−1. This work provides a promising strategy for the rational design of MOFs-based electrode materials for high performance HSC. Moreover, compared with the studies using MOFs derivatives as electrode materials, the direct use of Ni-MOFs as electrode materials in this study is of great significance to avoid energy waste and maintain the inherent advantages of MOFs.

Preparation of sulfur vacancy modified NiCo2S4@NiCoS2 core-shell electrode material and its application in asymmetric supercapacitors

Nickel-cobalt based bimetallic sulfide has attracted much attention as positive electrode materials for supercapacitors due to its microstructure designability. However, charge storage occurs mostly on the surface of the material, which limits the full utilization of the active material inside. Here, rich sulfur vacancies modified NiCo2S4@NiCoS2 (Vs-NiCo2S4@NiCoS2) core-shell structures are grown tightly on a nickel foam substrate and prepared as positive material for supercapacitors. The rich sulfur vacancies in the Vs-NiCo2S4 "core" increase the electrochemical active sites and electron transport rates, while the amorphous NiCoS2 "shell" facilitates the rapid diffusion of ions. The results show that Vs-NiCo2S4@NiCoS2 core-shell structure has a specific capacitance of 3200 F g−1, achieving the effect of "1 + 1>2". The excellent electrochemical performance is attributed to the surface/interface modification of rich sulfur vacancies and the synergistic effect induced by heterogeneous core-shell boundaries. Moreover, the asymmetric supercapacitor Vs-NiCo2S4@NiCoS2//AC exhibits an energy density of 46.3 Wh kg−1 and a power density of 799.8 W kg−1, as well as excellent cyclic stability (nearly 80% capacity retention after 10,000 cycles). This work provides a new idea and strategy for core-shell structure design of nickel-cobalt sulfide electrode materials combined with surface/interface modification.

Oxygen vacancies and heterointerface co-boosted Zn2+ (De)intercalation kinetics in VO2 for ultra-efficient aqueous zinc-ion batteries

In this study, we demonstrated the co-modification of oxygen vacancies and heterojunctions in VO2(B) (VO–VO2/MXene) as a cathode material for zinc-ion batteries (ZIBs). VO2 nanobelts are uniformly distributed on MXene nanosheets, which providing complete electron transport channels during the insertion or de-insertion of Zn2+. The formation of oxygen vacancies provides additional active sites and enhances the conductivity of VO2. Density functional theory calculations reveal that the oxygen vacancies effectively facilitate reversible intercalation/deintercalation process, which results in rapid intra-crystal zinc ion diffusion. The combination of VO–VO2 with MXene introduces an interfacial electric field, ultimately leading to synergistic enhancement in electrochemical activity. The VO–VO2/MXene composite exhibits the highest specific capacity (287 mAh g−1) at 10 A g−1 and excellent cycling lifespan (253 mAh g−1 after 3000 cycles) for ZIBs. This work provides a reliable strategy for the co-modification of metal oxide electrodes with oxygen vacancies and heterostructures.

Turbostratic Lattice and Electronegativity Modification Jointly Enabled an Ultra-High-Rate and Long-Lived Carbon Anode for Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are considered as a promising technology alternative to lithium-ion batteries due to more abundance of potassium than lithium and a lower redox potential of K/K+ than that of Na/Na+. The critical limitation in PIBs is the electrode with poor rate capability and cycling stability induced by the sluggish reaction kinetics and large volume change during potassiation and depotassiation. In this work, we report a turbostratic lattice iodine-doped carbon (TLIC) nanosheet as an advanced innovative anode for PIBs displaying fast charge/discharge and electrode stability. The turbostratic lattice caused by doping of large-sized iodine and the unique charge transfer between iodine/carbon atoms creates more active sites and a shorter transport distance for K ions, improves the electrochemical activity, promotes rapid ion diffusion, and enhances pseudocapacitive behavior. The TLIC exhibits a high capacity of 433.5 mAh g-1 at 50 mA g-1, an ultrahigh rate capability of 162.1 mAh g-1 at 20 A g-1, and an excellent capacity retention of ∼96% (206 mAh g-1) after 4000 cycles. The combination of turbostratic lattice and pseudocapactive storage is an effective approach to designing carbon electrodes with the transformational performance of high capacity, rate performance, and long lifetime for practical applications of PIBs.

Energy storage enhancement of LixMn1.8Ti0.2O4@N-doped graphene oxide in organic and ionic liquid electrolytes

Spinel-type Li1-xMn2O4 material is a promising positive electrode material for lithium-ion batteries. This material presents 3D diffusion channels through the structure, allowing for the rapid diffusion of lithium ions during charge/discharge processes. Given its relevant properties, such as a theoretical specific capacity of 149 mA h g−1 and high working potential, we propose LixMn1.8Ti0.2O4@N-doped graphene oxide (x ≤ 1) as a superior positive electrode material for lithium-ion battery applications. In organic media, the spinel showed excellent Li storage performance due to the incorporation of a conductive carbonaceous matrix (using 1,10 phenanthroline as a graphene precursor). We obtained a specific capacity of 139 mA h g–1, which represented 81% charge retention after 70 cycles. Furthermore, taking advantage of the high working potential of this material, we studied the Li storage capacity using ionic liquids as electrolyte solvents. High rate cycling at high temperatures is essential for their practical applications in extreme environments. In this work, we performed rate capability experiments at different temperatures, obtaining the best response at 40 °C with a specific capacity of 117 mA h g–1 at an applied current density of 1 C.

An environment-friendly strategy to prepare oxygen-nitrogen-sulfur doped mesopore-dominant porous carbons for symmetric supercapacitors

We report an environment-friendly method of particular mesopore-dominant oxygen-nitrogen-sulfur co-doped porous carbons from biomass-derived carbon materials (BCMs) using methylene blue (MB) as self-doping media for high performance supercapacitors. The as-prepared BCMs possess a high specific surface area of 1734.58 m2/g, large pore volume of 1.80 cm3/g, high oxygen (8.08 %), nitrogen (3.13 %) contents, and ultra-strong MB adsorption capacity (1337.83 mg/g). This unique architecture provides ion shuttle back and forth pore size to enhance double layer capacitance, and rapid diffusion of electrolyte ions. Besides, after adsorption with methylene blue, N/S elements (4.22/1.17 wt%) co-doped into BSMs led to multiple synergistic effects, improve surface wettability and supply additional pseudo-capacitance. The as-obtained co-doped BCMs exhibited the highest specific capacitance of 208 F/g at 1 A/g in a three-electrode system, and the symmetric supercapacitor showed superior cycling stability with high retention of 100 % at 5 A/g over 20,000 cycles. The symmetric supercapacitor showed a high energy density of 6.89 Wh/kg at a power density of 5272.23 W/kg in a 1 M Et4NBF4/PC electrolyte. The high energy density and high power density of as-obtained carbon materials can approach commercial porous carbon YP-50, demonstrating the good potential for practical application. Overall, this study is valuable for the multifunctional applications of BCMs in dye wastewater treatment and capacitive energy storage, and builds a bridge to the future between environment and capacitive energy storage.