Ion Transfer Rate Research Articles

Metal-organic framework/layered double hydroxide (MOF/LDH) hetero-nanosheet array for capacitive deionization

Achieving rational and precise tuning of the structure and composition of electrode materials represents a promising strategy for enhancing the performance of capacitive deionization (CDI). However, this endeavor encounters significant challenges. Herein, we present an elaborately designed hierarchical porous MOF/LDH Hetero-Nanosheet array (NiCoMn-HNA) which could be used as anode for the efficient Cl− capture. The unique hierarchical and permeable configuration of NiCoMn-HNA offers extensive accessibility to active sites and facilitates rapid electrolyte diffusion, thereby establishing a convenient pathway for efficient charge and ion transfer. Consequently, this enhances both the overall efficiency and respective rates. Furthermore, the synergistic effect between NiCo-ZIF-L and NiCoMn-LDH hollow pseudocapacitive materials significantly contributes to the enhancement of both electrochemical performance and desalination capabilities in NiCoMn-HNA. Accordingly, the NiCoMn-HNA electrode demonstrated larger electrochemical capacitym outstanding salt adsorption capacity (103.1 mg g−1), and remarkable cyclic desalination stability (90.47 % retention rate). Density functional theory (DFT) calculations confirmed that the hollow structure of NiCoMn-HNA promotes efficient the interfacial charge transfer from NiCo-ZIF-L and NiCoMn-LDH, leading to enhanced ion transfer rate and decreased energy required for ion migration. This research introduces a novel strategy for the purposeful design of high-performance electrode materials to advance CDI technology.

Flexible MXene/CuNWs/tartaric acid composite fabrics constructed by stacking assembly for electromagnetic interference shielding

With the rapid development of modern communication technology, the exploration of flexible wearable shielding fabrics with exceptional electromagnetic interference (EMI) shielding performance has emerged as an utmost priority to safeguard both human beings and electronic devices from the detrimental effects of electromagnetic radiation. Herein, a scalable multilayer stacking assembly method is proposed to prepare uniform MXene/CuNWs/Tartaric Acid (TA) composites-coated fabrics. MXene, as a new type of material, can achieve higher electron and ion transfer rates. However, it is prone to oxidation in air, leading to poor stability. Benefiting from the synergistic effect of tartaric acid, the MXene/CuNWs/TA-coated fabrics exhibit certain oxidation stability and corrosion resistance, while retaining the inherent flexibility and breathability of natural polymer textiles. Furthermore, the multilayer stacking structure works perfectly with the MXene/CuNWs conductive network, enabling multiple reflections and absorptions of electromagnetic waves internally, thus effectively diminishing energy transmission. The modified fabrics exhibit a low sheet resistance of 3.25 ± 0.12 Ω/sq and a good EMI shielding performance of 41.2 dB at X-band. Therefore, MXene/CuNWs/TA fabrics with high shielding performance are expected to reach their potential in wearable electronic products.

Microscale cephalosporin ion-selective amperometric/voltammetric sensors based on a micropipette-supported liquid/liquid interface: Multiple purposes of transmembrane studies and real-time determinations

The permeability of cephalosporins through cell membranes is crucial for their efficacy against gram-negative bacteria. To address this, a microsoft biphasic sensor utilizing the interface between two immiscible electrolyte solutions (ITIES) has been introduced for studying the ion transfer of cefotiam (CTM), ceftazidime (CAZ) and cefepime (CPM). The typical voltammograms of cephalosporin ion transfer can be further used to determine the formal ion transfer potentials (∆owφA′), ion transfer Gibbs free energies (∆owGA′), effective hydrophilicity (logPi), geometry of micro-ITIES, diffusion coefficient (Dw) and ion transfer rate constant (k0). In addition, the partitioning of CTM+, CAZ+, and CPM+ in two phases at different pH values was revealed by the corresponding ion partition diagrams (IPDs). The IPDs can further elucidate the mechanism of cephalosporin ion transfer across the ITIES at different pH values. Finally, the determination of CTM+, CAZ+ and CPM+ was achieved via real-time chronoamperometry. An excellent linear range for cephalosporin ions with a satisfactory limit of detection was obtained. The findings show the superb selectivity and anti-interferent ability of micro-ITIES sensors toward cephalosporins. The constructed micro-ITIES sensors for cephalosporin could contribute to medicinal design, single microorganism metabolism analysis, clinical diagnosis, and food safety inspection.

Enhanced electrochemical stability and ion transfer rate: A polymer/ceramic composite electrolyte for high-performance all-solid-state lithium-sulfur batteries

All-solid-state (ASS) lithium-sulfur (LiS) batteries utilizing composite polymer electrolytes (CPEs) represent a promising avenue in the domain of electric vehicles and large-scale energy storage systems, leveraging the combined benefits of polymer electrolytes (PEs) and ceramic electrolytes (CEs). However, the inherent weak interface compatibility between PEs and CEs often leads to phase separation, thereby impeding the transposition of Li+. In this study, the trimethoxy-[3-(2-methoxyethoxy)propyl]silane (TM-MES) is introduced as a chemical agent to form bonds with polyethylene oxide (PEO) and Li10GeP2S12 (LGPS), resulting in the development of a novel composite polymer electrolyte (CPETM-MES). This innovative approach mitigates phase separation between PEs and CEs while concurrently enhancing the protective capabilities of LGPS against decomposition at the interfaces of both the Li anode and sulfur cathode. Moreover, the CPETM-MES exhibits superior mechanical toughness, an expanded electrochemical window, and elevated ionic conductivity. In the symmetric cell, it demonstrates an extended operational lifespan exceeding 1800 h, and the current density can reach up to 1.05 mA/cm2. Furthermore, the initial discharge capacity of ASS LiS batteries utilizing CPETM-MES attains 1227 mAh/g and maintains a capacity of 904 mAh/g after 100 cycles. Notably, a high-energy-density of 2454 Wh/kg is achieved based on the sulfur cathode.

In-situ N, P co-doped porous carbon derived from biomass waste for supercapacitors

The development of heteroatom-doped porous carbon derived from biomass waste with high-performance electrodes for supercapacitors has been drawn extensive research. Herein, N, P co-doped porous carbon (NPC) was successfully synthesized using Chinese fir sawdust as a carbon source, NaOH as an activator, urea as a nitrogen source, and melamine phosphate as the phosphorus and nitrogen source by pretreatment with low-temperature NaOH/urea system. The low-temperature pretreatment and melamine phosphate greatly promoted the porous structure and uniform distributions of heteroatom about the NPC. The optimized NPC exhibits high specific surface area (1849 m2/g), hierarchical porous structure with high mesoporosity (87.3 %), appropriate heteroatom content (3.32 at% N, 0.36 at% P), and excellent wettability. This unique facilitates improved electrolyte diffusion efficiency and ion transfer rate. In the three-electrode system, the specific capacitance of the NPC electrode is as high as 260 F/g at 0.5 A/g and remains at 235 F/g at 10 A/g, and the charge transfer resistance is very low (0.08 Ω). In addition, the assembled symmetric supercapacitors deliver an energy density of 15.9 Wh/kg at a power density of 246 W/kg, a long cycling life with 90 % capacitance retention after 5000 cycles. The environment-friendly NPC has a broad development prospect for carbon-based high-performance electrodes for supercapacitors.

Extraordinary Hydrogen Evolution and Oxygen Evolution Reaction Activity From PPy@FeCo-LDH/NF Bifunctional Electrocatalyst in Alkaline Solution

Alkaline water electrolysis is a promising technique for the production of hydrogen and oxygen. Nevertheless, the development of low-cost, high-activity metal-based electrocatalysts that can effectively catalyze the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a significant challenge. Herein, we polymerized Polypyrrole (PPy) with FeCo layered double metal hydroxide grown in situ on nickel foam (NF) (FeCo-LDH/NF) by electrochemical polymerization to acquire composite material PPy@FeCo-LDH/NF. As a promising electrocatalyst with dual functionality for the HER and OER, the HER overpotential of PPy@FeCo-LDH/NF was 153 mV, and the OER overpotential was 245 mV at a current density of 10 mA·cm−2. It was because that PPy increased the number of active adsorption sites, which in turn regulated the ion transfer rate between the electrolyte and the prepared catalyst. At the same time, after 24 h of stability testing, the HER and OER capacitance retention rates were 96.7% and 97.1%, respectively.

WITHDRAWN: Recent advances on the metal oxides and nanocomposites based on quantum dots and metal oxides for supercapacitor applications: A mini-review

Considering the limited resources of fossil fuels and the environmental pollution caused by their use, the need for alternative technology has become a global challenge. As a candidate for replacing fossil fuels, batteries have limitations such as the lack of sodium and lithium sources. Supercapacitors are a suitable alternative technology due to the availability of electrode materials. In this study, our team reviewed the supercapacitor performance of metal oxides and nanocomposites based on metal oxides and quantum dots to overcome the limitations of metal oxide electrode materials. In this study, by investigating the supercapacitor performance of nanocomposites based on metal oxide and quantum dots in three categories of carbon quantum dot, graphene quantum dot, and polymer dot, the performance of each quantum dot in improving the supercapacitor behavior of metal oxides was discussed. The results confirmed that the synergistic effect of quantum dots and metal oxides is improving the supercapacitor performance of nanocomposites. Also, the functional groups on the surface of the quantum dots accelerate the rate of penetration of ions and the rate of ion transfer. The results of this study confirmed that polymer dots have better performance among quantum dots with polymer properties and quantum dots properties at the same time which provides research opportunities for researchers in the field of supercapacitors.

Hierarchical heterostructures of MXene and mesoporous hollow carbon sphere for improved ion accessibility and rate performance

The development of electrode materials with a hierarchically porous structure and good electrical connection is key to improving the charging-discharging rate and energy density of supercapacitors. However, the restacking issue of two-dimensional nanomaterials, such as MXene, seriously hinders the diffusion of electrolyte ions. Different from the extensively used sacrificing template method, a hierarchical heterostructure of electrically conducting mesoporous hollow carbon spheres (MHCS) and MXene composite electrode is designed and achieved through simple vacuum filtration without further template removing procedures. This direct preparation strategy not only effectively improves the specific surface area of the electrode but also enhances the abundant surface pores and good conductivity of MHCS, improving the penetration of the electrolyte solution and shortening the ion transport path, leading to a pronounced improvement in specific capacitance and rate performance of the electrodes. Additionally, the influence of sheath thickness of MHCSs on ion transfer rate is deeply discussed. The introduction of carbon nanotubes (CNTs) further improves conductivity and stability while maintaining good flexibility. Consequently, the MXene/MHCS/CNT film delivers a high specific capacitance (395F g−1 at 2 mV s−1), outstanding rate performance (70.9 % at 1000 mV s−1), and excellent cycling stability (98.3 % capacity retention after 10,000 cycles). Furthermore, the assembled symmetric supercapacitor provides a maximum energy density of 14.48 Wh kg−1. This work provides a quick and effective approach for constructing high performance 3D MXene architectures for fast ion transfer electrodes.

Hierarchical Ni3V2O8@N-Doped Carbon Hollow Double-Shell Microspheres for High-Performance Lithium-Ion Storage.

Transition metal oxides (TMOs) are highly dense in energy and considered as promising anode materials for a new generation of alkaline ion batteries. However, their electrode structure is disrupted due to significant volume changes during charging and discharging, resulting in the short cycle life of batteries. In this paper, the hierarchical Ni3V2O8@N-doped carbon (Ni3V2O8@NC) hollow double-shell microspheres were prepared and used as electrode materials for lithium-ion batteries (LIBs). The utilization efficiency and ion transfer rate of Ni3V2O8 were improved by the hollow microsphere structure formed through nanoparticle self-assembly. Furthermore, the uniform N-doped carbon layer not only enhanced the structural stability of Ni3V2O8, but also improved the overall electrical conductivity of the composite. The Ni3V2O8@NC electrode has an initial discharge capacity of up to 1167.3 mAh g-1 at a current density of 0.3 A g-1, a reversible capacity of up to 726.5 mAh g-1 after 200 cycles, and still has a capacity of 567.6 mAh g-1 after 500 cycles at a current density of 1 A g-1, indicating that the material has good cycle stability and high-rate capability. This work presents new findings on the design and fabrication of complex porous double-shell nanostructures.

Enhancing Electron/Ion Transport in SnO2 Quantum Dots Decorated Polyaniline/Graphene Hybrid Fibers for Wearable Supercapacitors with High Energy Density.

Fiber-based supercapacitors are the potential power sources in the field of wearable electronics and energy storage textiles due to their unique advantages of electrochemical properties and mechanical flexibility, but achieving high energy density and practical energy supply still presents some challenges. In this study, we reported an approach of microfluidic assisted wet-spinning to fabricate SnO2 quantum dots encapsulated polyaniline/graphene hybrid fibers (SnO2 QDs@PGF) by incorporating uniformly polyaniline into graphene fibers and covalently bridging SnO2 quantum dots. The assembled SnO2 QDs@PGF fiber-typed flexible supercapacitors exhibit an ultralarge specific areal capacitance of 925 mF cm-2 in PVA/H2SO4, superior rate capabilities, and capacitance retention of 88% after 8000 cycles, indicating that the SnO2 QDs@PGF possess near-ideal capacitance properties, efficient ion transfer rate, and good cycling stability. In the EMITFSI/PVDF-HFP electrolyte system, SnO2 QDs@PGF realize a wide operating potential window of 2.5 V, a specific areal capacitance of 678.4 mF cm-2, and an energy density of 147.2 μWh cm-2 at 500 μW cm-2, which can be utilized to power an alarm clock, an electronic timer, and a desk lamp with a requirement of a 3 V battery. The exceptional performance of the SnO2 QDs@PGF can be attributed to the molecular-level homogeneous composite of granular polyaniline and graphene nanosheets and the interfacial C-O-Sn covalent coupling strategy employed between SnO2 QDs and PGF. These avenues not only effectively prevent the undesirable restacking of graphene nanosheets but also increase the interlayer electroactive sites, ordered ion diffusion channels, and strong interfacial charge transfer.

Enhanced electrochromic performance of WO3/PEDOT by π-electron conjugation system

Tungsten oxide (WO3) is one of the most extensively studied electrochromic materials and regarded as a promising candidate for commercial application. However, its slow response time and poor coloring efficiency limit its practical applications. Here, tungsten oxide and poly(3,4-ethyldioxythiophene) (PEDOT) hybrid nanorod array are prepared by hydrothermal method and in situ electro-polymerization. The WO3/PEDOT hybrid nanorod array exhibits shorter response time (22.4 s coloring and 26.0 s bleaching) compared to WO3 film (27.2 s coloring and 30.0 s bleaching) and a rapid Li+ diffusion rate (3.65 × 10−12 cm2/s). Within the range of λ = 700 nm, the optical contrast of the composite film increases from 42.8 % (WO3) to 68.2 % (WO3/PEDOT). The coloring efficiency and stability of WO3/PEDOT composite film are also improved compared to individual components (WO3 or PEDOT). The improvement of the electrochromic performance can be attributed to the highly ordered nanorod structure of WO3/PEDOT composite film which provides a larger surface area and a faster charge transport path. The special 1D structure of the nanorod can also increase the length of the PEDOT conjugate chain, which in turn facilitate the π-electrons transfer and accelerate the rate of electron and ion transfer, resulting in the decrease of the response time. The novel structure of WO3/PEDOT combines the best advantages of WO3 and PEDOT, making it an ideal electrochromic material.

Interfacial salt effect induced by competitive adsorption of coexisting ions: A new understanding of the mass transfer selectivity in the near-interface boundary layer

Specific ion effects are known to influence the interfacial behavior of ions in the aqueous phase and thus affect their extraction and separation. There are many studies on enhanced extraction and separation of the target ions based on the specific ion effects. A microscopic level understanding of the competitive mass transfer and selectivity of ions at the interface between heterogeneous phases is crucial importance for the precise control of numerous chemical reaction and separation processes. The conventional salt effect (i.e., background coexisting ions promoting the mass transfer of the target ions) are only observed at higher coexisting ion concentrations. However, the present work reveals an interesting phenomenon: the adsorption enrichment and competitive hydration of coexisting salt cations at the liquid–liquid interface can significantly influence the mass transfer rate of the target rare earth ions in the near-interface boundary layer. Notably, such a distinct interfacial salt effect can promote the separation between coexisting and target ions at lower coexisting ion concentrations, and it cannot be explained by the traditional theory for the salt effect. A thin-layer organic oil film extraction system was employed here as a simplified model experiment to investigate this new interfacial salt effect on the non-equilibrium extraction and separation of target rare earth ions. The results demonstrated that the diffusion rate of the target ions (Er3+) is subject to the local concentration gradient of coexisting salt cations (Mg2+) in the near-interface boundary layer. At the lower bulk concentrations, the Mg2+ ions enriched at the interface would compete for water molecules around the hydration shell of target Er3+ ions, resulting in the dehydration of Er3+ ions. Therefore, an enhanced diffusion rate of Er3+ ions and their adsorption affinity towards the interface were observed. However, at a higher bulk concentration of Mg2+ ions, the diffusion resistance of Er3+ ions increased due to the competitive adsorption and hydration of Mg2+ ions at the interface. The thickness of the organic oil film layer also plays an important role in the diffusion of Er3+ ions. In particular, a thinner oil layer makes it easier to perceive the interfacial salt effect, which enhances the separation between Er3+ and Mg2+ compared to the case of a thicker oil layer. A quantitative correlation between the diffusion rate of Er3+ ions and the concentration of coexisting Mg2+ ions was established to describe the interfacial salt effect. This work highlights the microscopic nature of the salt effect induced by the competitive adsorption kinetics of coexisting ions in the near-interface boundary layer on promoting the extraction and separation of target metal ions. The results will help the development of new approaches to control the separation selectivity and enhance the mass transfer of target metal ions in practical applications.

Effect of ITZ on chloride ion transport in recycled aggregate concrete: Analytical and numerical studies

The weaker ITZ is one of the significant differences between recycled concrete and ordinary concrete. How the weaker ITZ between recycled aggregate and mortar in recycled concrete affects the transport mechanism of chloride ions has become the main obstacle to the large-scale promotion and recycling of demolished building waste. To tackle this issue, a novel equivalent single-phase analytical method was proposed and a series of numerical simulations with different ITZ distributions and characteristics were carried out. The research results indicated that the transport of chloride ions in recycled aggregate concrete was primarily controlled by the diffusion coefficient, volume, and distribution of the ITZ (mainly affected by recycled aggregates). The current analytical methods effectively described the aggregate blocking effect and ITZ effect. The research results revealed that the addition of recycled aggregate within a certain range had little effect on chloride ion transport (the difference in the effect of 30 % and 35 % recycled aggregates addition on chloride ion transport was within 5 %). However, once the volume fraction of aggregates exceeded the threshold, the transfer rate of chloride ions increased sharply. Furthermore, the uniform mixing of recycled aggregates was crucial. As the ITZ non-uniformity coefficient increased, the ITZ diffusion coefficient increased. The weaker ITZ of recycled concrete amplified the impact of concrete cracks, ITZ-crack channels of chloride ions were formed even if minor cracks developed. Current research provided technical support for the durability design of recycled concrete structures.

Interface engineering of N, P and S-doped hollow/porous Co3O4@Co3V2O8 heterostructure nanocube for high-activity supercapacitor and oxygen evolution reaction

Cobalt-based materials exhibit high theoretical specific capacitance and desirable electrocatalytic activity. However, their practical specific capacitance and electrocatalytic activity are significantly constrained by a lack of active sites and limited conductivity. Herein, N, P and S-doped hollow Co3O4@Co3V2O8 heterostructure nanocube is reasonably constructed via in-situ ion exchange method combined with calcination strategy. Besides, the relationship of heterogeneous interface and heteroatom doping on electrochemical performance is explored. The heterogeneous interface provides rich active sites and accelerates electron transfer. Additionally, N, P, and S-doping regulate the internal electronic structures, boost ion transfer rates, and increase active sites. The hollow structure accelerates the adsorption and desorption processes due to the increased electrochemical reaction sites. Benefiting from internal electronic structure and structural advantages, N, P, S-Co3O4@Co3V2O8 exhibits low overpotentials (561 mV and 649 mV at the current density of 50 mA/cm2 and 100 mA/cm2), low Tafel slopes (100.9 mV/dec), prospective specific capacitance (550.2 F/g) and outstanding charge/discharge behavior with remarkable life span. N, P, S-Co3O4@Co3V2O8 based device delivers favorable energy density (21.3 Wh/kg at 802.3 W/kg), which surpasses most of the latest cobalt-based materials. Overall, this work provides novel insights into the development of highly active and durable bifunctional electrode materials.

A precisely Assembled Wall-Like Architecture for High Lithium/Sodium Storage.

MXene nanosheets and ordered porous carbons both have their own advantages and disadvantages. Assembling and combining the advantages of the two will be a good choice for battery electrode hosts of active materials. In this work, an electrostatic separation-adsorption strategy is proposed to realize the ordered alternating self-assembly of MXene nanosheets and ordered porous carbon (MPOC), obtaining a unique wall-like porous material with a high conductivity and interconnected porous nanostructure, which strengthens the transfer rate of electrons and ions simultaneously. Meanwhile, the introduction of N-doping from porous carbon into MPOC prolongs the cycle life. When use red phosphorus (RP) as active materials, the MPOC@RP anode exhibited high-capacity output (2454.3 and 2408.1 mAh g-1 in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) at 0.1 C) and long cycle life (the decay rates per cycle of 0.028% and 0.036% after 1500 and 1200 cycles at 2 C in LIBs and SIBs respectively). The successful application in RP anodes displays great potential in other electrode materials such as silicon, sulfur, selenium, and so on. Meanwhile, this strategy is also effective to design other composites materials like MXene and carbon nanotubes, MXene and Graphene, and so on.

Fe3O4/Fe/FeS Tri‐Heterojunction Node Spawning N‐Carbon Nanotube Scaffold Structure for High‐Performance Sodium‐Ion Battery

The Fe‐based anode of sodium‐ion batteries attracts much attention due to the abundant source, low‐cost, and high specific capacity. However, the low electron and ion transfer rate, poor structural stability, and shuttle effect of NaS2 intermediate restrain its further development. Herein, the Fe3O4/Fe/FeS tri‐heterojunction node spawned N‐carbon nanotube scaffold structure (FHNCS) was designed using the modified MIL‐88B(Fe) as a template followed by catalytic growth and sulfidation process. During catalytic growth process, the reduced Fe monomers catalyze the growth of N‐doped carbon nanotubes to connect the Fe3O4/Fe/FeS tri‐heterojunction node, forming a 3D scaffold structure. Wherein the N‐doped carbon promotes the transfer of electrons between Fe3O4/Fe/FeS particles, and the tri‐heterojunction facilitates the diffusion of electrons at the interface, to organize a 3D conductive network. The unique scaffold structure provides more active sites and shortens the Na+ diffusion path. Meanwhile, the structure exhibits excellent mechanical stability to alleviate the volume expansion during circulation. Furthermore, the Fe in Fe3O4/Fe heterojunction can adjust the d‐band center of Fe in Fe3O4 to enhance the adsorption between Fe3O4 and Na2S intermediate, which restrains the shuttle effect. Therefore, the FHNCS demonstrates a high specific capacity of 436 mAh g−1 at 0.5 A g−1, 84.7% and 73.4% of the initial capacities are maintained after 100 cycles at 0.5 A g−1 and 1000 cycles at 1.0 A g−1. We believe that this strategy gives an inspiration for constructing Fe‐based anode with excellent rate capability and cycling stability.

Improvement of specific capacity of lithium iron phosphate battery by increasing the surface area and electrical conductivity of cathode electrode using graphene foam

Lithium iron phosphate (LFP) is widely used as an active material in a cathode electrode for lithium-ion batteries (LIBs). LFP has many remarkable properties such as high working voltage and excellent thermal stability. However, it suffers with slow ion diffusion and low electrical conductivity. Graphene foam has many outstanding properties such as large surface area and great electrical conductivity. These properties are suitable for improving the cathode electrode. In this work, the graphene foam was synthesized by chemical vapor deposition. The cathode electrode was prepared by dropping the LFP on the graphene foam. We found that the specific capacity of battery which contained the LFP between the anode and the graphene foam (LFP/GF) was 23.1 mAh⸳g-1 at 3C, while the specific capacity of battery which contained the graphene foam between the anode and the LFP (GF/LFP) was 112.6 mAh⸳g-1 at 3C. The diffusion coefficients of Li+ of GF/LFP was 9.1 times higher than that of LFP/GF. The specific capacity of GF/LFP was higher than that of LFP/GF at high current density due to the high ion transfer rate which arises from the graphene foam.

Construction of 3D N-doped Ti3C2/TiO2 hollow sphere structure with superior electrochemical performance for supercapacitor

Herein, the 3D N-doped Ti3C2/TiO2 sphere structure is constructed via an innovative three-step method including the preparation of 3D Ti3C2 microspheres with PMMA as templates, the situ-growth of TiO2 nanoparticles on Ti3C2 and the subsequent annealing treatment in NH3. N element is doped in composite after annealing in NH3 to improve the transfer rate of ions and electrons, and N-doped Ti3C2/TiO2 hollow composite provides an abundant active surface for the sufficient contact between electrodes and electrolytes to enhance charge transport and electrolyte diffusion. Benefiting the unique structure feature and the synergistic effects of active materials, the N-doped Ti3C2/TiO2 electrode exhibits a high specific capacitance of 572 F g−1 at a current density of 1 A g−1 and a superior cyclic stability of 99.6% of its initial value for 9500 cycles at 10 A g−1. Based on this, a symmetric supercapacitor (SSC) based on N-doped Ti3C2/TiO2 electrode is further assembled. The SSC shows a competitive capacitance of 157 F g−1 at 1 A g−1. More importantly, the comparable energy density of 17.7 Wh kg−1 is achieved at the power density of 450 W kg−1. This work will give promising guidance for designing and fabricating the durable electrodes with excellent electrochemical behavior for practical application in future.

Phase-field simulation of interface growth of magnesium metal anodes during electrodeposition

Mg-metal has abundant reserves and extremely high-volume capacity, making it an excellent choice as the negative electrode for low-cost, high-volume energy-density batteries. More and more studies have shown that there is still a problem of dendritic growth in Mg-metal. Here, we use the open-source MOOSE software package to establish a phase-field model for Mg-electrodeposition and study the dynamic morphological evolution of the growth of Mg-metal anode interfaces under different overpotentials in two dimensions. By studying the temporal-spatial distributions of ion concentration, chemical potential, and electric potential, we analyze the growth processes of Mg-metal anode interfaces under different applied overpotentials in detail. The results show that the Mg-metal anode interfaces only grow dendrites under applied overpotentials ranging from −0.24 to −0.30 V because the interface electrochemical reactions rate is greater than the interface ion transfer rate.

ZIF-90 derived carbon-coated kerf-loss silicon for enhanced lithium storage

The utilization of kerf-loss silicon (KL-Si) waste as anode materials in lithium-ion batteries (LIBs) faces limitations of the rapid structural degradation during repeated charging/discharging. To overcome this limitation, 3D carbon-coated Si is constructed to buffer the Si volume expansion caused by the lithiation, while simultaneously forming a robust conductive network. Meanwhile, the well-dispersed porous carbon (C) shell, doped with suitable heteroatoms, plays a pivotal role in facilitating rapid ion transfer rates. In addition, a cobalt (Co) and nitrogen (N)-doped C shell is employed to encapsulate KL-Si, aimed at enhancing its lithium (Li) storage performances. The electrochemical performance of KL-Si@C-ZIF/N/Co composites, synthesized through the encapsulation of KL-Si with a metal-organic framework (MOF) structure (ZIF-90) followed by heat treatment. The resulting composites exhibit an outstanding reversible capacity of 981 mAh g−1 and an impressive capacity retention of 81.9% at 2 A g−1 even after 350 cycles. This paper presents a promising method for maximizing the value-added utilization of KL-Si and reveals the advantages of MOF-derived porous C shell in accommodating the inherent volume expansion of Si-based anodes.