Electrode Structure Research Articles

Heterostructured ZnS/Co embedded in pinecone-like N/S-doped carbon for efficient sodium/lithium storage

Constructing heterogeneous electrodes to confront various electrochemical and structural requirements is demonstrated to be crucial for improving the sodium and lithium storage performances. Herein, a novel design of ZnS/Co heterostructures is expounded with abundant phase boundaries encapsulated in highly-conductive N/S-doped “pinecone”-like carbon framework (ZnS/Co@NSC-450) as a superior anode for sodium ion batteries (SIBs) and lithium-ion batteries (LIBs). In ZnS/Co@NSC-450, the ZnS/Co heterostructures can improve the electronic conductivity of material and stabilize the electrode structure integrity during cycling, while the N/S-doped “pinecone”-like carbon is beneficial for alleviating the volume expansion effect of active materials, providing additional active sites for sodium/lithium storage and ensuring the rapid electron/ion transfer across the electrode. Due to the synergistic effect of multiple components, both the SIBs and LIBs with ZnS/Co@NSC-450 anodes exhibit high-rate capability (476 mAh g−1 at 6.4 A g−1 for SIBs and 387 mAh g−1 at 12.8 A g−1 for LIBs) and outstanding long-term cycling stability (557 mAh g−1 at 2 A g−1 for SIBs after 1500 cycles and 767 mAh g−1 for LIBs after 1000 cycles). These results disclose the promising potential of ZnS/Co@NSC-450 toward high-performance SIBs and LIBs.

Tandem Acidic CO2 Electrolysis Coupled with Syngas Fermentation: A Two-Stage Process for Producing Medium-Chain Fatty Acids.

The tandem application of CO2 electrolysis with syngas fermentation holds promise for achieving heightened production rates and improved product quality. However, the significant impact of syngas composition on mixed culture-based microbial chain elongation remains unclear. Additionally, effective methods for generating syngas with an adjustable composition from acidic CO2 electrolysis are currently lacking. This study successfully demonstrated the production of medium-chain fatty acids from CO2 through tandem acidic electrolysis with syngas fermentation. CO could serve as the sole energy source or as the electron donor (when cofed with acetate) for caproate generation. Furthermore, the results of gas diffusion electrode structure engineering highlighted that the use of carbon black, either alone or in combination with graphite, enabled consistent syngas generation with an adjustable composition from acidic CO2 electrolysis (pH 1). The carbon black layer significantly improved the CO selectivity, increasing from 0% to 43.5% (0.05 M K+) and further to 92.4% (0.5 M K+). This enhancement in performance was attributed to the promotion of K+ accumulation, stabilizing catalytically active sites, rather than creating a localized alkaline environment for CO2-to-CO conversion. This research contributes to the advancement of hybrid technology for sustainable CO2 reduction and chemical production.

Efficient acidic CO2 electroreduction to formic acid by modulating electrode structure at industrial-level current

Acidic CO2 electroreduction has the potential to synthesize low carbon footprint chemicals using renewable electricity. However, proton-rich environments can lead to strong hydrogen evolution reaction (HER) and severe degradation of electrochemical CO2 reduction reaction (CO2RR) performance. Modulating electrode structure plays a critical role in improving the local microenvironment of CO2RR electrolytes. Here, by covering the catalyst layer with a hydrophobic silica aerosol layer, the surface of the catalyst is protected from corrosion, thereby increasing the efficiency and stability of the system. In the flow cell, the Sn-C/SiO2-3 catalyst has high formic acid (HCOOH) selectivity at high current density (∼90 % at −400 mA cm−2). Importantly, the Sn-C/SiO2-3 catalyst can operate stably for 45 h at −400 mA cm−2. Combined in situ infrared analysis reveals that hydrophobic SiO2 aerosol layer can engineer the local microenvironment over the Sn-C catalyst surface by increasing the coverage of *OCHO to improve the CO2RR, which ultimately promotes high-efficiency CO2 conversion to HCOOH in strong acidic media. This surface coating strategy for adjusting the interface microenvironment can also be used for other electrocatalytic reactions.

Comparative Evaluation of Graphite Anode Structuring for Lithium‐Ion Batteries Using Laser Ablation and Mechanical Embossing

Lithium‐ion batteries inherently suffer from a target conflict between a high energy density and a high power density. The creation of microscopic holes in the electrodes alleviates the trade‐off by facilitating lithium‐ion diffusion. This study presents a novel concept for electrode structuring called structure calendering, combining mechanical embossing (MEC) and calendering. It is compared to the widely investigated laser ablation (LAS) process by structuring graphite anodes and examining their geometrical, mechanical, and electrochemical properties. It is shown that structure calendering results in wider and deeper holes of higher reproducibility than laser structuring. As a consequence of the different hole‐creation mechanisms, laser structuring induces a surface elevation around the holes while clogged pores are observed in the lateral walls of mechanically structured holes. In pull‐off tests, no pronounced impact of electrode structuring on the mechanical electrode properties is discerned. Structuring of electrodes using both methods yields significantly reduced electrode tortuosities and enhanced discharge rate performances. From a production engineering perspective, structure calendering has advantages over laser structuring in terms of material loss, processing rate, and investment costs, while the latter offers higher flexibility, precision, and presumably lower maintenance efforts. In conclusion, structure calendering represents an attractive process alternative to laser structuring.

Catalysis of hydrogen evolution reaction by nanocomposite electrodes composed of copper nanoparticles based on carbon quantum dots as highly efficient electrocatalyst

This study reports the synthesis, characterization, and electrochemical behavior of new non-platinum Cu-NPs/RCQDs/GCE nanocomposite. By investigating scanning electron microscopy images (SEM), the proposed and introduced nanocomposite shows spheres with an average size of less than 50 nm homogeneously dispersed on reduced carbon quantum dots (RCQDs) as an upper layer on glassy carbon electrode (GCE). Transmission electron microscopy image (TEM) of synthesized CQDs showed the small size of CQDs that was less than 20 nm. X-ray diffraction analysis (XRD) was used to investigate the crystallographic structures of electrodes. Also, the electrocatalytic treatment of catalysts toward hydrogen evolution reaction (HER) was studied in acidic media by some electrochemical techniques consisting of linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Results show that Cu-NPs/RCQDs/GCE nanocomposite with lower onset potential relative to Cu-NPs/GCE is a better electrocatalyst for reaction catalysis. Also, this proposed catalyst showed high stability and conductivity at special faradaic voltage.

H+/Cu2+ co-assisted corrosion synthesis of sustainable silicon dendrite anodes

Silicon (Si)-based materials have been identified as next-generation preferred anode materials owing to their ultra-high specific capacity, environmental friendliness and low price. However, the defects in Si-based materials (e.g., the large volume change with unstable solid electrolyte interface during repeated lithiation/delithiation processes and low intrinsic conductivity), will significantly destroy the integrity of electrode structure and get slow dynamic performance, resulting in a fast capacity fading. Herein, we prepared various silicon‑aluminum‑copper dendrites (named SCD-1/2/3) via a two-step displacement dealloying process, which was devoted to simultaneously improving structural instability, low ionic/electronic conductivity of Si crystals. Therefore, the SCD-2 anode possessed an initial Coulombic efficiency of 80 % and exhibited a superior capacity of 1851.7 mA h g−1 at 1 A g−1 after 100 cycles. This paper provides a simple method to gain the Si anodes with high initial Coulombic efficiency, relieved volume expansion and long cycling life.

Functionalization of PTFE substrates with quaternary ammonium groups – An approach towards anion conducting properties

Hydrogen produced by electrolysis using renewable energy sources offers a zero-emission alternative to fossil-based sources providing high efficiencies in all energy sectors. Anion Exchange Membrane Water Electrolysis (AEM-WE) combines the advantages of the established technologies, alkaline (AEL) and proton exchange membrane (PEM) water electrolysis. However, AEM-WE still requires optimization, especially with regard to the membrane, catalysts and electrode structure. In this contribution we focus on the improvement of PTFE-based binders for AEM-WE membranes, which provide high chemical stability but lack the required ion conductivity. Thus, the functionalization of PTFE towards quaternary ammonium moieties (QAS) was investigated employing two approaches: (i) NH3-plasma treatment and (ii) O2-plasma with subsequent coupling of aminosilanes. Finally, the surface coupled amino groups were converted into QAS via alkylation with iodomethane (CH3-I), introducing ion conductivity. Successful functionalization was proved by X-ray photoelectron spectroscopy (XPS), displaying changes in the surface composition of PTFE surfaces such as the introduction of amino groups at the expense of fluorine, and the increase in surface carbon content upon alkylation. Furthermore, contact angle measurements revealed increased wettability with water due to the introduction of the polar surface functionalities, while zeta potential measurements confirmed the increase of positive surface charges along the modification processes.

In Situ Transmission Electron Microscopy for Sodium Batteries

AbstractSodium batteries, encompassing sodium‐ion batteries (SIBs) and sodium metal batteries (SMBs), have emerged as a significant trend in the advancement of secondary batteries owing to the natural abundance and economical characteristics of sodium. Despite significant strides in enhancing the electrochemical performance of sodium batteries, understanding their sodium storage mechanism and the factors contributing to capacity degradation remains a challenge. The utilization of in situ transmission electron microscopy (TEM) enables direct observation and a comprehensive investigation of the structure and chemical evolution of electrodes and interfaces during dynamic electrochemical processes. This review first systematically explores the fundamental mechanism of in situ TEM in the context of rechargeable batteries. Then, recent advancements in applying in situ TEM to sodium batteries including SIBs and SMBs are detailed. Finally, this review emphasizes potential opportunities and challenges for the future development of in situ TEM in the realm of sodium batteries, highlighting its significance in unraveling crucial aspects of their operation and guiding further advancements in the field.

Cellulose-based high-loading flexible electrode for lithium-ion battery with high volumetric energy density

Thick electrodes with high loading are attractive for high-energy storage devices, but they face major challenges of slow ion transfer and poor mechanical stability. Carbon templates such as reduced graphene oxide and carbon nanotube can promote the electrons transfer of thick electrodes and enhance their strength, but they still exhibit a complex producing process, slow Li+ transfer and high cost. Herein, a nanofiber network with double fast Li+ and electrons transfer pathways by the self-assembly of carbon nanoparticles on the negatively charged natural cellulose fibers was designed. The abundant oxygen-containing functional groups from the cellulose fibers enabled the electrode with abundant negative charge which can adsorb the neutral particles with strong electrostatic interaction. And the Density Functional Theory calculation demonstrates that oxygen-containing functional groups also has stronger adsorption energy for PF6− anions in electrolyte which can promote the desolvation of the solvated Li salts, thus promote Li+ transfer. After integration with lithium iron phosphate, this network achieves a robust high-loaded electrode with good electrical conductivity and shortened ion transfer pathways without traditional current collector and binder. Based on the robust electrode structure and fast transfer kinetics of electrons and Li+, the batteries exhibit excellent cycle stability with capacity retention of 98 % after long 400 cycles and high volumetric energy density of 740 Wh/L, which greatly surpass the conventional batteries with coating LiFePO4 (LFP) cathode. Given the low-cost raw materials and convenient operation, the design of self-standing flexible electrodes with high loading will offer a promising and effective strategy for other storage devices with high energy.

A spin-injected ferroelectric tunnel junction based on spin-dependent screening theory

In this work, spin transport in ferroelectric tunnel junctions with composite barriers and magnetic electrodes is investigated theoretically using spin-dependent screening theory. The shape of the insulator barrier and the electronic structure of the ferromagnetic electrode inevitably affect the spin transport properties. Interestingly, we find that when the Fermi level approaches the bottom of the minority-spin band of the electrode, an approximately ±100% bidirectional spin-filtering effect can be realized due to the included exchange potential with an appropriate electronic band structure of electrodes. Additionally, electrically induced magnetic reconstruction would occur on the electrode surface due to spin-dependent band bending. Our study significantly deepens the current understanding of spin-dependent screening on metal surfaces and at metal/ferroelectric interfaces and provides a feasible method for achieving the interface magnetoelectric effect.

Biomass-derived porous carbon with single-atomic cobalt toward high-performance aqueous zinc-sulfur batteries at room temperature

Aqueous zinc-sulfur batteries at room temperature hold great potential for next-generation energy storage technology due to their low cost, safety and high energy density. However, slow reaction kinetics and high activation energy at the sulfur cathode pose great challenges for the practical applications. Herein, biomass-derived carbon with single-atomic cobalt sites (MMPC-Co) is synthesized as the cathode in Zn-S batteries. The catalysis of single-atom Co sites greatly promotes the transform of cathode electrolyte interface (CEI) on the cathode surface, while offering accelerated charge transfer rate for high conversion reversibility and large electrochemical surface area (ECSA) for high electrocatalytic current. Furthermore, the rich pore structure not only physically limits sulfur loss, but also accelerates the transport of zinc ions. In addition, the large pore volume of MMPC-Co is able to relieve the stress effect caused by the volume expansion of ZnS during charge/discharge cycles, thereby maintaining the stability of electrode structure. Consequently, the sulfur cathode maintains a high specific capacity of 729.96 mA h g−1 after 500 cycles at 4 A g−1, which is much better than most cathode materials reported in the literature. This work provides new insights into the design and development of room-temperature aqueous Zn-S batteries.

A groovy laser processing route to achieving high power and energy lithium-ion batteries

3D-structured NMC622 with precisely controlled electrolyte channels were manufactured by incorporating femtosecond laser processing with conventional slurry casting. Demonstrated in a full cell for the first time, the 3D electrode structures mitigate plating and dendrite growth at the graphite electrode and lead to improved cycling performance, 75 % capacity retention vs 58 % after 500 cycles. 3D-structured NMC622 with a high areal capacity, 5.5 mAh cm−2, exhibits an areal capacity retention of ∼70 % and volumetric capacity exceeding 250 mAh cm−3 at ∼1.15C, three times and twice that of a conventional slurry-casted NMC622, respectively. The improved rate performance is attributed to the enhanced ionic transport and reduced charge transfer resistance facilitated by the 3D electrode structure, as shown through galvanostatic titration measurements. A finite element method-based 3D model illustrated the improved uniform distribution of Li-ion concentration and state of charge within the 3D-structured electrode. Additionally, the 3D electrode structure proved beneficial for wettability and accelerated electrolyte absorption, leading to improved manufacturing efficiency.

A novel improvement strategy and a comprehensive mechanism insight for α‐MnO2 energy storage in rechargeable aqueous zinc‐ion batteries

AbstractAqueous zinc‐ion batteries have been regarded as the most potential candidate to substitute lithium‐ion batteries. However, many serious challenges such as suppressing zinc dendrite growth and undesirable reactions, and achieving fully accepted mechanism also have not been solved. Herein, the commensal composite microspheres with α‐MnO2 nano‐wires and carbon nanotubes were achieved and could effectively suppress ZnSO4·3Zn(OH)2·nH2O rampant crystallization. The electrode assembled with the microspheres delivered a high initial capacity at a current density of 0.05 A g−1 and maintained a significantly prominent capacity retention of 88% over 2500 cycles. Furthermore, a novel energy‐storage mechanism, in which multivalent manganese oxides play a synergistic effect, was comprehensively investigated by the quantitative and qualitative analysis for ZnSO4·3Zn(OH)2·nH2O. The capacity contribution of multivalent manganese oxides and the crystal structure dissection in the transformed processes were completely identified. Therefore, our research could provide a novel strategy for designing improved electrode structure and a comprehensive understanding of the energy storage mechanism of α‐MnO2 cathodes.

Mechanism of electrical performance deterioration in a-Si:H TFTs caused by source/drain Decap treatment

During the fabrication process of the display industry, the Decap treatment is usually employed as a means to reuse semiconductor materials of thin film transistors (TFTs), but the influence and mechanism of Decap process on the properties of the decapped samples is unknown. To elucidate this occurrence, the electrical characteristics of the channel layer, as well as the microstructure and components at the interface between the Source/Drain (S/D) and the channel layer were examined. It reveals that the infiltration of impurity ion (O and Mo) has significant impact on the deterioration of device performance for a-Si:H TFTs with a Mo/Al/Mo stacked S/D electrode structure. More specifically, oxygen's intrusion leads to the formation of SiOX and the alterations of the surface energy levels and charge distribution of Si, thus introduces an interface trap states between channel layer and S/D electrodes to scatter and capture of interface carriers. And Mo's intrusion may induce the come into being of MoSi or MoP chemical states, causing the decrease of the doping efficiency of phosphorus and the reduction of carrier concentration (from 5.52 × 1016 cm−3 to 4.44 × 1016 cm−3) of a-Si:H channel layer. The combined effect of these two factors results in the decline of electrical performance of S/D decapped a-Si:H TFTs.

Cobalt Ion-Stabilized VO2 for Aqueous Ammonium Ion Hybrid Supercapacitors.

Aqueous ammonium ion hybrid supercapacitor (A-HSC) is an efficient energy storage device based on nonmetallic ion carriers (NH4+), which combines advantages such as low cost, safety, and sustainability. However, unstable electrode structures are prone to structural collapse in aqueous electrolytes, leading to fast capacitance decay, especially in host materials represented by vanadium-based oxidation. Here, the Co2+ preintercalation strategy is used to stabilize the VO2 tunnel structure and improve the electrochemical stability of the fast NH4+ storage process. In addition, the understanding of the NH4+ storage mechanism has been deepened through ex situ structural characterization and electrochemical analysis. The results indicate that Co2+ preintercalation effectively enhances the conductivity and structural stability of VO2, and inhibits the dissolution of V in aqueous electrolytes. In addition, the charge storage mechanisms of NH4+ intercalation/deintercalation and the reversible formation/fracture of hydrogen bonds were revealed.

Inorganic/organic composite binder with self-healing property for silicon anode in lithium-ion battery

Silicon (Si) has garnered significant attention as a high-capacity anode material in high-energy density lithium-ion batteries (LIBs). Nevertheless, the huge volume variation of Si (>300%) during cycling results in rapid capacity deterioration, thereby impeding its commercial application. To confront this challenge, inorganic binder has been identified as a highly promising solution for Si anode due to its high bonding strength. Despite its effectiveness, the inorganic binder's limited elasticity hinders the rejuvenation of the impaired electrode structure. Hence, we devised an elasticity and self-healing composite binder, incorporating both inorganic and organic binders. The inorganic lithium metasilicate not only offers ample adhesion sites to Si but also establishes a protective coating layer on SiNPs. Simultaneously, the organic poly (vinyl alcohol) featuring a low glass transition temperature (72 °C) furnishes elasticity and a self-healing framework. Consequently, the Si anode shows exemplary cycling and rate performances. Additionally, the Si||NCM811 full cell attains a reversible capacity of 1.86 mAh/cm2 with a capacity retention of 67% after 50 cycles, indicating the commercial application potential of the composite binder. This study thus explores design strategies for composite binders, paving the way for high-performance Si anode.

Local oxygen transport resistance in polymer electrolyte fuel cells: origin, dependencies and mitigation

Next-generation polymer electrolyte fuel cells (PEFCs) require an integral design of the porous structure of electrodes at different scales to improve performance and enlarge durability while reducing cost. One of today’s biggest challenges is the stable, high-performance operation at low Pt loading due to the detrimental effect of the local oxygen transport resistance caused by ionomer around catalyst sites. Hindered local oxygen transport arises from sluggish kinetics at the local reaction environment, that comprises adsorption at (wet) ionomer and Pt interfaces, and diffusivity of gas species in ionomer and water. Diverse factors affect oxygen transport, including operating conditions (relative humidity, temperature, and pressure), ionomer content and morphology, ionomer heterogeneity, porosity of carbon support, catalyst dispersity, and flooding. To attain performance and durability targets, it is essential to maximize the oxygen utilization of the catalyst layer by implementing enhanced membrane electrode assembly architectures. This involves employing advanced catalyst layer preparation techniques, including electrospraying, to generate optimized highly porous morphologies. Furthermore, achieving these targets necessitates the development of new materials with tailored properties, such as high permeability and porous ionomers, among other innovative strategies.

Machinability of different cutting tool materials for electric discharge machining: A review and future prospects

Electric Discharge Machining (EDM) is essential for shaping and cutting tool steel. EDM’s precision in machining difficult materials and tool steel characteristics are well known. EDM efficiency requires reliable performance measurement parameters. The physical shape and mobility of the electrode tool are critical in EDM research. Layer machining is an advanced method that removes material in a sequential manner to produce intricate 3D shapes in tool steel and several other materials. The improvement in layer machining methods with precise toolpath algorithms, adaptive layer thickness management, and real-time monitoring systems is required to maximize precision and efficiency. Response surface methodology, the artificial neural network, and other techniques are necessary to optimize EDM operations and maximize performance. Many researchers experimented with electrode shapes and movement patterns to enhance the removal of material and the quality of surfaces. Investigation of complex electrode structures and innovative tool path strategies has been performed in previous studies. It was very difficult to consider various factors during the EDM operation; hence, the present review summarizes the positive outcomes of previous research. The review emphasizes optimizing pulse duration and discharge current to improve EDM efficiency. The present comprehensive review discusses research on EDM in three main areas: electrode tool geometry and motion, tool steel layer processing, and factors for measuring EDM performance. The objective of the present review is to focus on measuring material removal rates, surface roughness, tool wear, and energy usage. The present review concludes that EDM is crucial to machining tool steel and cutting tool materials. Integrating and hybrid machining technologies can improve performance, and improved optimization techniques are crucial. It also recognizes knowledge gaps and explores new frontiers in this dynamic field.

Simulation and Design of LiNbO$_{3}$ Modulators With Switched Segmented Electrode Structure for High Bandwidth and Low Half-Wave Voltage

Simulation and Design of LiNbO$_{3}$ Modulators With Switched Segmented Electrode Structure for High Bandwidth and Low Half-Wave Voltage

Application of Multistage Drying Profiles for Accelerated Production of Li‐Ion Battery Anodes Using Infrared Radiation: Validation with Electrochemical Performance and Structural Properties

The drying of solvent‐processed electrodes is a critical process step in the manufacturing of lithium‐ion batteries. The technology used to introduce the energy required for drying into the material, combined with the specified process parameters, significantly influences the resulting electrode properties. A major challenge is to counteract binder migration effects that may occur during drying of the porous electrode structure, causing a decrease in adhesion and electrochemical performance, especially for high drying rates. From this motivation, investigations on the influence of process design during near‐infrared drying of aqueous‐processed graphite anodes are carried out. A multistage drying design with varying parameters in specific drying sections with energy input by radiation is applied. The results show that the specific application of a three‐stage drying profile in combination with energy input by radiation enables a significant decrease in drying time by at least 60% while the electrode properties can be preserved. These findings indicate a beneficial development of binder distribution as a consequence of multistage NIR drying, evidenced by adhesion and electrochemical performance. Finally, the application of the multistage drying profile is theoretically transferred to an industrial‐scale roll‐to‐roll dryer, whereby the necessary dryer length can be reduced by 53%.