Current Electrode Materials Research Articles

Soft Colloidal Electrode Enabled by Water Distribution Control for Ultra-Stable Aqueous Zn-I Batteries.

Designing effective electrode material is crucial for developing ultra-long lifetime batteries, thereby reducing daily battery costs. Current electrode materials are typically solid or liquid state, with an intermediate colloidal state offering the advantages of fixed redox-active species, akin to solid-state materials, and the absence of rigid atomic structure, akin to liquid-state materials, while avoiding the particle pulverization and uncontrolled migration. Herein, an aqueous Zn||Pluronic F127 (PF127)/ZnI2 colloid battery is developed utilizing the inherent water molecular control effect of ZnSO4. In this system, ZnSO4 in the electrolyte acts as a water molecular valve, regulating the water content within the PF127 polymer to form a PF127 colloid. The resulting aqueous Zn||PF127/ZnI2 colloid battery exhibits an ultra-long cycling lifetime and compatibility with various simulated and practical operating conditions, highlighting its potential for practical applications. Additionally, this battery design concept offers a platform for constructing ultra-stable aqueous batteries.

Calcium alginate/Polyaniline double network aerogel electrode for compressible and high electrochemical performance integrated supercapacitors

As a new type of energy storage device, supercapacitors have attracted more and more attention due to their excellent performance. However, the current electrode materials have limited specific surface area and cannot meet the needs of high energy storage. The aerogel material is a 3D network structure containing interconnected micro-nano structures, and also has hierarchical pores on the micro, meso and macro scales. The microporous and mesoporous structures can provide high specific surface area, while the macropores provide channels for the entry of active substances. In this study, calcium alginate (CA)/polyaniline (PANI)/reduced graphene oxide (RGO) aerogels based on double network structure with high mechanical property and excellent electrochemical performance are successfully constructed by sol-gel method. Due to the double network structure, the CA/PANI/RGO aerogel exhibits self-supported 3D porous network structures with high surface areas (330.3 m2/g). CA/PANI/RGO composite aerogel electrode shows high specific capacitance (908 F/g at 1 A/g) and excellent rate performance. The initial capacitance of more than 80 % can be maintained after 10,000 times of charge/discharge cycle test. Most importantly, the assembled flexible solid-state supercapacitor has high specific capacitance (885 F/g at 1 A/g) and mechanical flexibility (92.6 % of the capacitance retention after 1000 bending cycles).

Functionalized biobased carbon electrodes for selective phosphorus removal by capacitive deionization: Application and theory study

Capacitive deionization (CDI) emerges as a viable and efficient strategy for the removal and recovery of phosphorus from wastewater. However, the economic feasibility and complex synthesis of current electrode materials restrict its broader industrial application. To overcome the limitation, we fabricated aminated biobased electrode materials (MRSCN) from rice straw, forming active sites and hydrogen bonding interaction interfaces throughout the bulk phase by the nitrogen sites and peripheral amino groups in MRSCN, thereby enhancing the rapid enrichment and selective adsorption of phosphates. The phosphate adsorption capacity of MRSCN electrode reached up to 5.03 mg P/g at 1.2 V. In the presence of competing anions (Cl-, NO3– and SO42-), MRSCN exhibited markedly improved selective adsorption for phosphorus. Furthermore, density functional theory (DFT) calculations revealed that the incorporation of nitrogen active sites optimized the electronic structure of MRSCN. Meanwhile, H2PO4- and HPO42- anions served as hydrogen bond donors to the amino groups, leading to a more robust binding affinity between MRSCN and phosphates relative to other anions. The synergistic interaction between nitrogen sites and amino groups in facilitating selective phosphate removal was validated at the molecular scale. This study demonstrated the considerable potential of modified biobased carbon materials for the application in phosphate removal utilizing the CDI technique.

A new highly active and CO2-stable heterostructure cathode material for solid oxide fuel cells developed from bismuth ion-modified cation-deficient Nd0.9BaCo2O5+δ

Efficient oxygen reduction kinetics as well as excellent stability are the main goals of current electrode materials for solid oxide fuel cells (SOFCs). Here, we present the latest findings regarding the augmentation of performance in SOFC through utilization of a novel heterogeneous cathode, consisting of an excess cation-deficient double perovskite Nd0.9BaCo2O5+δ (NBC90) backbone and in situ exsolved BaCo1-yBiyO3-x nanoparticles modified by bismuth (NBC90+B). The anisotropic growth of such self-assembled nanoparticles and the formation of multiple heterointerfaces exhibit an extremely strong activation effect. The in situ formed BaCo1-yBiyO3-x nanoparticles and cation-deficient NBC90 parental perovskite significantly enhance the catalytic activity and durability of the cathode toward oxygen reduction. The structural stability and CO2 tolerance of the cathode are greatly enhanced, which is attributed to the penetration of the high acidic Bi ions in the separated phase and the synergistic effect of the two-phase interface. The results unequivocally demonstrate the exceptional stability and efficiency of the NBC90+B composite as a promising cathode candidate for SOFCs.

Ultralow Charge Voltage Triggering Exceptional Post-Charging Antibacterial Capability of Co3 O4 /MnOOH Nanoneedles for Skin Infection Treatment.

The post-charging antibacterial therapy is highly promising for treatment of Gram-negative bacterial wound infections. However, the therapeutic efficacy of the current electrode materials is yet unsatisfactory due to their low charge storage capacity and limited reactive oxygen species (ROS) yields. Herein, the design of MnOOH decorated Co3 O4 nanoneedles (MCO) with exceptional post-charging antibacterial effect against Gram-negative bacteria at a low charge voltage and their implementation as a robust antibacterial electrode for skin wound treatment are reported. Taking advantaging of the increased active sites and enhanced OH- adsorption capability, the charge storage capacity and ROS production of the MCO electrode are remarkably boosted. As a result, the MCO electrode after charging at an ultralow voltage of 1.4V gives a 5.49 log and 5.82 log bacterial reduction inEscherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa)within an incubation time of only 5min, respectively. More importantly, the antibacterial efficiency of the MCO electrode against multi-drug resistant (MDR) bacteria including Klebsiella pneumoniae (K. pneumoniae)and Acinetobacter baumannii (A. baumannii)also reaches 99.999%. In addition, the MCO electrode exhibits excellent reusability, and the role of extracellular ROS in enhancing post-charging antibacterial activity is also unraveled.

Fabrication and Characterization of Free-Standing and Flexible Polyaniline Membranes: Role of Graphene Nanoscrolls

Wearable technologies can contribute to the early and accurate detection of chronic diseases which can be achieved by the integration of biosensors into wearable technologies. However, the challenges associated with the performance of current electrode materials—i.e., flexibility, conductivity, and mechanical stability, made from conducting polymers are preventing their widespread usage. Herein, we report a freestanding and flexible electrode synthesized from polyaniline (PANI) and graphene nanoscrolls (GNS). The PANI-GNS nanohybrid membranes were synthesized via chemical oxidative polymerization and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and four-point probe techniques. FTIR results showed an increase in conjugation length of the PANI after the addition of GNS into the mixture which can be indicative of an enhancement of electrical properties. Nanoindentation studies showed an elastic modulus and hardness of 2.6 GPa and 0.17 GPa, respectively, for PANI-GNS-5 nanocomposite, compared to 1.9 GPa and 0.08 GPa, for pure PANI. This was later confirmed by the four-point probe technique as the addition of GNS increased the conductivity of electrodes up to 9 S/cm at a 5% weight ratio. Moreover, SEM results of the PANI-GNS showed an open porous morphology of the polymer matrix in comparison with pure PANI samples which would readily translate into higher amounts of enzyme immobilization on the surface.

Research progress on the cathode and anode of aqueous zinc ion battry

Electrochemical energy storage problems become a worldwide research direction. Now Lithium-ion batteries (LIBs) are the most common battery product. However, LIBs still has many shortcomings such as, safety problems, a scarcity of lithium, and high price. Rechargeable aqueous-based zinc ion batteries (AZIBs) with lower costs, fewer safety risks as well as abundant zinc reserves have attracted extensive research interest. For the current electrode materials of AZIBs, for example, Mn-based materials, V-based materials and metallic zinc, scientists have done in-depth research to develop the performance of the materials, but complex processes are still inevitable. As a result, sustainable and scalable manufacturing technology and electrode materials with high capacity and the longer service life is the research direction.

Few-Layer Siloxene as an Electrode for Superior High-Rate Zinc Ion Hybrid Capacitors

Zinc ion hybrid capacitors have emerged as promising energy storage devices due to the attributes of high energy density and superb power output. The current electrode materials applied to zinc ion hybrid capacitors are mainly various carbon and MXenes. Therefore, there are great demands for developing electrode materials for zinc ion hybrid capacitors. Considering the boom of silicon semiconductor technology, the integration of silicon-based materials into zinc ion hybrid capacitors is desirable and appreciable. Few-layer siloxene is reported here in the development of the cathode of a zinc ion hybrid capacitor, which has a maximum specific capacitance of 6.86 mF cm–2, a maximum power density of 4.50 mW cm–2, and a maximum energy density of 10.66 mJ cm–2, surpassing those of silicon-based supercapacitors. In addition, this hybrid capacitor retains a capacitance retention of 94.3% over 16000 cycles. These results highlight the promising possibility of siloxene as an electrode material for future energy storage applications.

Consecutive metal oxides with self-supported nanoarchitecture achieves highly stable and enhanced photoelectrocatalytic oxidation for water purification

Owing to its low cost and plentiful different semiconductor configurations resources, photoelectrocatalysis (PEC) has come into the spotlight in large-scale water purification systems. However, the insufficiency of photoelectrocatalytic performance and the issues of long-term durability of current electrode materials are the main bottlenecks for future latent applications. Here, we reported that the multidimensional Ti/SnO2-Sb/PbO2/ZnO nanoarchitecture (PbO2 nanotrees grown on Sb-doped SnO2 nanowires, then ZnO nanowall embedded into PbO2 nanotrees’ skeleton) significantly boosts the PEC properties in terms of the organic contaminated water treatment (i.e., reactive brilliant blue KN-R). Benefiting from the synergistic effects of ZnO and PbO2 (the ZnO can be used as the supply station of water, promptly transferring water molecules to adjacent PbO2 to yield hydroxyl radicals), Ti/SnO2-Sb/PbO2/ZnO electrode manifests an unprecedented removal rate of dye, large electroactive areas, noticeable wettability, and high separation efficiency of induced carriers, better stability, which represents a type of promising material in the applications of water purification.

Understanding the Mechanism of High Capacitance in Nickel Hexaaminobenzene-Based Conductive Metal-Organic Frameworks in Aqueous Electrolytes.

Recently, intrinsically conductive metal-organic frameworks (MOFs) have demonstrated promising performance in fast-charging energy storage applications and may outperform some current electrode materials (e.g., porous carbons) for supercapacitors in terms of both gravimetric and volumetric capacitance. In this report, we examine the mechanism of high capacitance in a nickel hexaaminobenzene-based MOF (NiHAB). Using a combination of in situ Raman and X-ray absorption spectroscopies, as well as detailed electrochemical studies in a series of aqueous electrolytes, we demonstrate that the charge storage mechanism is, in fact, a pH-dependent surface pseudocapacitance, and unlike typical inorganic systems, where transition metals change oxidation state during charge/discharge cycles, NiHAB redox activity is ligand-centered.

Sucrose-assisted rapid synthesis of multifunctional CrVO4 nanoparticles: a new high-performance cathode material for lithium ion batteries

The search of new multifunctional cathode materials, with new crystal structures and compositions, for lithium ion battery is extremely important to mitigate the drawbacks associated with the current electrode materials used in rechargeable lithium ion batteries. In this paper, orthovanadate family CrVO4 has been identified and investigated as a new cathode material for high-rate and high-capacity lithium ion battery for the first time. A solution-based effective and versatile synthetic protocol has been proposed to synthesize CrVO4 nanoparticles. Physical characterizations reveal that the prepared CrVO4 consists of uniform and discreet nanoparticles of crystallite size ~ 19 nm with widespread pore diameter, enhanced conductivity and surface area. The prepared CrVO4 nanoparticles have been evaluated as a potential cathode material for lithium ion batteries, wherein the experimental results demonstrate enhanced lithium storage with high rate-capability and cyclability. The experimental results reveal that the proposed CrVO4 is working through a partial conversion reaction mechanism.

Interface Engineering between the Metal-Organic Framework Nanocrystal and Graphene toward Ultrahigh Potassium-Ion Storage Performance.

The potassium-ion battery (PIB) has been recognized as a promising low-cost and high-energy battery; however, it suffers from a relatively low capacity and inferior cycling performance compared with current electrode materials. Herein, we report an effective interface engineering strategy to prepare metal-organic framework (MOF) nanocrystals tightly encapsulated by reduced graphene oxide (rGO) via strong chemical interaction as a free-standing anode for PIB. Based on experimental analysis and theoretical calculations, we systematically investigated the effect of the chemical-bonded interface between MOF nanocrystals and conductive rGO and revealed that the strong chemical interface can substantially enhance the adsorption energy and ion transport kinetics of the potassium ion within the MOF nanocrystals compared to the physical mixture of MOF and rGO with almost the same microscopic morphologies. As a result, such an MOF-rGO hybrid with strong interfacial chemical couplings delivered an ultrahigh reversible capacity of 422 mAh g-1 at 0.1 A g-1, superior rate performance (202 mAh g-1 at 5 A g-1), and outstanding long-term cycling performance (an ultralow decay rate of 0.013% per cycle after 2000 cycles at 2 A g-1), which are not only significantly better than those of the physical mixture of MOF/rGO but also among the best for anodes for PIB reported thus far.

Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction: Applications in Microbial Fuel Cells

Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a revolutionary answer to the global environmental challenges. Yet, one key factor that limits the implementation of larger scale MFCs is the high cost and low durability of current electrode materials, owing to the use of platinum at the cathode side. To address this issue, the scientific community has devoted its research efforts for identifying innovative and low cost materials and components to assemble lab-scale MFC prototypes, fed with wastewaters of different nature. This review work summarizes the state-of the-art of developing platinum group metal-free (PGM-free) catalysts for applications at the cathode side of MFCs. We address how different catalyst families boost oxygen reduction reaction (ORR) in neutral pH, as result of an interplay between surface chemistry and morphology on the efficiency of ORR active sites. We particularly review the properties, performance, and applicability of metal-free carbon-based materials, molecular catalysts based on metal macrocycles supported on carbon nanostructures, M-N-C catalysts activated via pyrolysis, metal oxide-based catalysts, and enzyme catalysts. We finally discuss recent progress on MFC cathode design, providing a guidance for improving cathode activity and stability under MFC operating conditions.

Transcranial Electrical Stimulation and Recording of Brain Activity using Freestanding Plant‐Based Conducting Polymer Hydrogel Composites

AbstractTranscranial electrical stimulation is a noninvasive neurostimulation technique with a wide range of therapeutic applications. However, current electrode materials are typically not optimized for this abiotic/biotic interface which requires high charge capacity, operational stability, and conformability. Here, a plant‐based composite electrode material based on the combination of aloe vera (AV) hydrogel and a conducting polymer (CP; poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS) is reported. This material system is fabricated into films and provides biocompatibility, conformability, and stability, while offering desirable electrical properties of the PEDOT:PSS. AVCP films are also molded onto the rough surface of the skull leading to a mechanically stable and robust interface. The in vivo efficacy of the AVCP films is verified to function as stimulating and recording electrodes by placing them on the skull of a rat and concomitantly inducing focal seizures and acquiring the evoked neural activity. AVCP films pave the way for high‐quality biological interfaces that are broadly applicable and can facilitate advances in closed‐loop responsive stimulation devices.

Highly Multifunctional Dopamine-Functionalized Reduced Graphene Oxide Supercapacitors

Summary Batteries and supercapacitors that possess the mechanical properties of structural composites are desirable for electric vehicles and aerospace applications, as energy may be stored within structural panels to realize significant mass and volume savings. However, current electrode materials suffer from poor mechanical performance, as described by a low multifunctional efficiency parameter (

Multiple templates fabrication of hierarchical porous carbon for enhanced rate capability in potassium-ion batteries

Potassium-ion batteries (PIBs) are attracting more and more attention as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage owing to the abundance and low price of potassium. However, it is still challenging to achieve high capacity and rate capability for the current electrode materials in view of the sluggish potassiation kinetics. In this study, a simple multiple templates strategy is applied to obtain the hierarchical porous carbon (HPC) material as a novel anode for PIBs after the pyrolysis and washing of polyacrylate (PAA) composed of NaCl crystals and Zn nanoparticles. The resulting HPC possesses a hierarchical porous construction with a typical hard carbon feature, abundant structural defects, a high Brunauer-Emmett-Teller (BET) surface area (604.4 m2 g−1), and an enlarged interlayer distance (0.395 nm). These characteristics can augment potassium ion storage, exhibiting a moderate charge capacity of 211.5 mA h g−1 after 50 cycles at 50 mA g−1 with excellent rate capability of 76.7 mA h g−1 at 10 A g−1. To investigate the crucial effect of hierarchical porosity, cyclic voltammogram measurements are conducted to verify the contributions of surface-dominated K-storage and the apparent diffusion coefficient. The potassium storage mechanism during the intercalation process of potassium ions is also investigated by ex situ SEM, XRD and HRTEM characterizations. Regarding the cost-effectiveness and sustainability, this work shows a promising development of anode materials for PIBs.

Highly nitrogen doped carbon nanofibers with superior rate capability and cyclability for potassium ion batteries

Potassium-ion batteries are a promising alternative to lithium-ion batteries. However, it is challenging to achieve fast charging/discharging and long cycle life with the current electrode materials because of the sluggish potassiation kinetics. Here we report a soft carbon anode, namely highly nitrogen-doped carbon nanofibers, with superior rate capability and cyclability. The anode delivers reversible capacities of 248 mAh g–1 at 25 mA g–1 and 101 mAh g–1 at 20 A g–1, and retains 146 mAh g–1 at 2 A g–1 after 4000 cycles. Surface-dominated K-storage is verified by quantitative kinetics analysis and theoretical investigation. A full cell coupling the anode and Prussian blue cathode delivers a reversible capacity of 195 mAh g–1 at 0.2 A g–1. Considering the cost-effectiveness and material sustainability, our work may shed some light on searching for K-storage materials with high performance.

Enhanced rate performance and high potential as well as decreased strain of LiNi0.6Co0.2Mn0.2O2 by facile fluorine modification

Fluorine is interesting for improving the electrochemical performance of current electrode materials, but the preparation process faces challenges because of the difficult homogeneous mixing of powders. A facile novel strategy of surface fluorine modification using polytetrafluoroethylene (PTFE) emulsion at low temperature, where the powders are easy to be homogeneously mixed and evenly covered by fluorine polymer, has been proposed to enhance the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 material. Though the initial discharge capacities of LiNi0.6Co0.2Mn0.2O2-yFy (y = 0.02, 0.05, 0.08) are slightly decreased at 0.1C, the capacity retention ratios at higher current densities, higher potential and elevated temperatures are improved compared to that of the pristine one. Among the samples with different fluorine contents, LiNi0.6Co0.2Mn0.2O1.95F0.05 exhibits the best performance, and the average discharge capacity fade rate in one cycle and the residual stress after 50 cycles at 1.0 C, as well as the discharge capacity after 10 cycles at 4.0 C are respectively about 0.03%, 10.3 MPa, 129.5 mAh g−1, while the corresponding values of the pristine samples are around 0.12%, 29.4 MPa, and 99.7 mAh g−1, respectively. After 50 cycles at 1.0 C between 2.8 and 4.7 V, LiNi0.6Co0.2Mn0.2O1.95F0.05 improves the capacity retention ratio and the discharge capacity of the pristine sample from 80.0% to 90.4%, and from 156.7 to 176.3 mAh g−1, respectively. The electrode reaction process and fluorine modification mechanisms have been discussed using various techniques. This method is easily achievable and may be used to modify other powder materials via a simple solid-solution mixing and an in-situ surface modification.

(Invited) The Bright Future for Electrode Materials─Highly Conductive Porous Na-Embedded Carbon Nanowalls for Energy Conversion and Storage

Although doping alkali metals into carbon materials was demonstrated to create highly conductive carbon materials in 1991, the dopants were located on the carbon surface and could be easily oxidized, leading to a great loss in conductivity. As an ideal material, alkali metal atoms must be completely surrounded by carbon atoms to form alkali-metal-embedded carbon material. Such a hypothetical material is totally different from widely used intercalation carbon compounds, in which alkali ions are inserted into spaces between graphite layers. However, the alkali-metal-embedded carbon material has not yet been successfully synthesized for 25 years. In this presentation, I will talk about our recent success of synthesizing highly-conductive porous Na-embedded carbon nano-wall materials (with large accessible surface areas) using an original reaction between liquid Na and CO gas. The novel materials solve the critical issue “the contradiction between high electrical conductivity and large accessible surface area” in current electrode materials. Furthermore, the synthesized materials were tested as electrodes for (1) dye-sensitized solar cells (DSSCs), energy devices, leading to high power conversion efficiency up to 11.03% and (2) supercapacitors, resulting in ultrahigh areal capacitance of 1.14 F/cm2 and a wide operating temperature range.

An Ideal Electrode Material, 3D Surface-Microporous Graphene for Supercapacitors with Ultrahigh Areal Capacitance.

The efficient charge accumulation of an ideal supercapacitor electrode requires abundant micropores and its fast electrolyte-ions transport prefers meso/macropores. However, current electrode materials cannot meet both requirements, resulting in poor performance. Herein, we creatively constructed three-dimensional cabbage-coral-like graphene as an ideal electrode material, in which meso/macro channels are formed by graphene walls and rich micropores are incorporated in the surface layer of the graphene walls. The unique 3D graphene material can achieve a high gravimetric capacitance of 200 F/g with aqueous electrolyte, 3 times larger than that of commercially used activated carbon (70.8 F/g). Furthermore, it can reach an ultrahigh areal capacitance of 1.28 F/cm2 and excellent rate capability (83.5% from 0.5 to 10 A/g) as well as high cycling stability (86.2% retention after 5000 cycles). The excellent electric double-layer performance of the 3D graphene electrode can be attributed to the fast electrolyte ion transport in the meso/macro channels and the rapid and reversible charge adsorption with negligible transport distance in the surface micropores.