Electrochemical Characterization Research Articles

Synthesis of spherical LiFePO₄ microparticles with encapsulated carbon nanotubes for high-power lithium-ion batteries

Lithium ferrophosphate – LiFePO₄(LFP) – is one of the widely studied and used materials for lithium-ion batteries. However, one of the main drawbacks of LFP is its poor electrical conductivity. To address this issue, we propose an effective approach based on encapsulating carbon nanotubes within the volume of LFP particles in the volume of spherical LFP particles. Electrodes based on the obtained materials exhibit more aTₜᵣactive electrochemical characteristics than LFP obtained by the standard method: increased specific capacity (62 and 92 mAh g–1 at a current density of 20C for LFP and LFP/SWCNT, respectively), stability of cyclic characteristics (preservation of 98% capacity after 100 charge/discharge cycles for LFP/SWCNT and 96.5% for LFP), as well as reduced charge transfer resistance. Encapsulation of SWCNT into the structure of iron phosphate during deposition is an easy-to-implement approach to formation modified LFP-based cathodes with improved characteristics, which expands the possibilities of their practical application in high-power lithium-ion batteries.

In Situ Optical Observation of Lithium Dendrite Pattern in Solid Polymer Electrolytes.

Solid polymer electrolytes (SPEs) have been treated as a viable solution to build high-performance solid-state lithium metal batteries (SSLMBs) at the industrial level, bypassing the safety and energy density dilemmas experienced by today's lithium-ion battery technology. To promote a wider application of SPEs-based SSLMBs, the chemical and electrochemical characteristics of lithium metal (Li°) electrode in SPEs have to be clearly elucidated. In this work, the morphological evolution of Li° electrode in the SPEs-based SSLMBs is comprehensively investigated, via a customized electrochemical cell allowing optical microscopic analyses. The results demonstrate that differing from inorganic solid electrolytes, the elastic feature of SPEs eliminates the "memory effect" of the dendrite formation, in which the previously formed dendrites can be dissolved and the resulting space can be simultaneously occupied by electrolyte components, instead of leaving for a second-round growth of Li° dendrites. Furthermore, the largely increased electronic conductivities of the as-formed interphases between Li° electrode and SPEs are found to be responsible for the notoriously soft short-circuit behavior observed during cycling. These findings bring a fresh understanding of the formation and evolution of lithium dendrites in SPE-based cells, which are vital for improving the long-term stability of SSLMBs and other related high-energy battery systems.

Aluminium-doped vanadium nitride as cathode material for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are increasingly favored for their environmentally friendly and impressive energy storage performance. Vanadium nitride (VN) is receiving much attention as a cathode material for AZIBs due to its high electrical conductivity and controllable structure. However, the direct use of VN in AZIBs presents challenges such as sluggish kinetics, insufficient specific capacity and limited stability. Herein, a heteroatom doping strategy is utilized to improve the electrochemical energy storage performance of the VN by incorporating aluminium (Al) via a hydrothermal process and a subsequent calcination treatment. Electrochemical characterizations indicate that the as-synthesized aluminium-doped VN (Al-doped VN) exhibits an outstanding specific capacity of 544 mAh·g−1 at 1 A g−1 and retains a high rate capacity of 275.6 mAh·g−1 at 10 A g−1. Further studies show that the Al incorporation effectively modulates the electronic configuration of the VN, which accelerates the charge transfer kinetics and thus enhances the electrochemical storage performance of VN. The phase transformation mechanism of the Al-doped VN is also investigated and the results show that the VN undergoes partial conversion into Zn3(OH)2V2O7·2H2O during the charge/discharge process.

Tuning the Morphology of Transition Metal Disulfides: Advances in Electrocatalysts for Hydrogen Evolution Reaction

The hydrogen evolution reaction (HER) in the renewable energy system has gained a lot of attention from researchers as hydrogen is assumed to be a clean and renewable carrier. Transition metals and their compounds have been used as promising alternatives to precious noble metals for the HER, offering low cost, more availability, and high activity. In this work, we discussed the mechanisms of the HER and how morphology influenced the catalytic performance of transition metal disulfide (TMD), focusing on structures that range from zero-dimensional (0D) to three-dimensional (3D) TMD materials. Notably, two-dimensional (2D) TMDs, like nanosheets, exhibit the lowest overpotential and a very small Tafel slope, which can be ascribed to their inherent layered structure and large surface area. According to recent research reports, the efficacy and efficiency of the HER process are influenced by surface chemistry, electrochemical characteristics, and the existence of active sites.

Electrochemical study of an enhanced platform by electrochemical synthesis of three-dimensional polyaniline nanofibers/reduced graphene oxide thin films for diverse applications

This work reports the electrochemical fabrication of thin films comprising polyaniline nanofibers (PANI) in conjunction with graphene oxide (GO) and reduced graphene oxide (rGO) on ITO substrate, along with examining the electrochemical properties, with a focus on the influence of the substrate and electrolyte in the electrodeposition methods. The study explores the electrochemical characteristics of these thin films and establishes a flexible framework for their application in diverse sectors such as sensors, supercapacitors, and electronic devices. It analyzes the impact of the substrate and electrolyte in electrodeposition techniques. The effects were studied using techniques such as cyclic voltammetry and chronoamperometry. The fabrication process of PANI/GO and PANI/rGO thin films involved the integration of rGO within PANI via electropolymerization, conducted under sulfuric acid. GO was synthesized by modifying the well-known Hummers’ method and characterized by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). SEM showed the diameters of the formed PANI were between 40 and 150 nm, which helped to intertwine the rGO nanosheets with PANI nanofibers to form thin films. The electrochemical behavior of the PANI/rGO thin films was examined using cyclic voltammetry (CV) and chronoamperometry in different electrolytes, including sulfuric acid (H₂SO₄) and potassium nitrate (KNO₃). The CV profiles exhibited distinct oxidation and reduction peaks, with variations in the voltammogram morphology attributed to the nature of the electrolyte and the substrate employed during the electrodeposition process. These results highlight the critical role of both the substrate and electrolyte in governing the electrochemical performance of PANI/rGO thin films. The findings from this study demonstrate a versatile approach for the fabrication of PANI/graphene-based thin films with tunable electrochemical properties, and such a strategy has great application to fabricating other thin film composites for supercapacitors or other control source frameworks requiring enhanced charge storage and electrochemical responsiveness.

Enhancing the electrochemical characteristics of P2-Na0.7Mn0.6Cu0.3Cr0.1O2 cathode materials through morphological manipulation: assessment of rate capability and coulombic efficiency

Abstract Manganese-based layered oxides are regarded as an excellent cathode material for Na-ion batteries. These materials are susceptible to phase transitions, which result in structural instability and constrain their reversible capacity. Layered self-assembled microsphere-type cathodes Na0.7Mn0.6Cu0.3Cr0.1O2 were developed to modify the efficiency of sodium-ion batteries through a technique focused on controlling morphology. The incorporation of organic compounds such as benzoic acid employs molecular design techniques to modify intermolecular interactions and increase the spacing between layers. The self-assembled layered spherical architecture enhances the interface between the cathode and electrolyte, thereby markedly boosting the transport efficiency of sodium ions. Based on the cathode for batteries, it demonstrates a substantial initial capacity of 200.26 mAh g-1 at a current density of 26 mA g-1 within the voltage amount of 1.5-4.1 V, with a capacity retention of 82.69% after 100 cycles.

Effects of ultrasonic treatment and current pulse frequency on properties of micro-arc oxidation coating on Mg alloy LAZ931

To enhance corrosion resistance of magnesium-lithium (Mg-Li) alloy LAZ931 in corrosive environments, a micro-arc oxidation (MAO) based surface treatment was carried out under a unipolar pulsed power supply. Effects of ultrasonic treatment and current pulse frequency on the performance of MAO coatings were investigated using scanning electron microscopy, electrochemical characterization, and friction wear tests. Results demonstrate that ultrasonic treatment greatly reduced the number density of micro-defects in the resulting MAO coatings and improved their overall performance. Corrosion and wear resistance of the MAO coating increased when current pulse frequency increased from 400 to 2000 Hz. Those findings are beneficial for improving the performance of MAO on Mg-Li alloys through optimizing the processing parameters.

Sustainable hybrid nanocomposites of Au nanoparticles modified carboxylated nanographene oxide: Electrochemical characterisation and estrone detection

Sustainable hybrid nanocomposites of Au nanoparticles modified carboxylated nanographene oxide: Electrochemical characterisation and estrone detection

An Antibiofouling Electrochemical Sensor Consisting of Amphiphilic Copolymer on CNT-COOH Electrodes for Point-of-Care Monitoring of Propofol Blood Concentration in Surgical Patients

The monitoring of propofol (PPF) blood concentration is vital for the safety of intravenous anesthesia. Electrochemical sensors represent a powerful tool for the detection of PPF. Our previous research has demonstrated that CNT-COOH electrodes exhibit advantages in resisting electrochemical fouling from PPF oxidation products. Nevertheless, biofouling remains a critical challenge hindering the clinical transformation of PPF electrochemical sensors. To address this issue, we employed in-situ electrodeposition to deposit zwitterionic sulfobetaine methacrylate (SBMA) and overoxidation polydopamine (OPDA) onto CNT-COOH screen-printed electrodes (SPEs) and proposed an innovative CNT-COOH/OPDA-SBMA (CNT-COOH/OPS) amphiphilic antifouling biosensor. This amphiphilic electrode, featuring both hydrophilic and hydrophobic properties, demonstrated excellent antifouling performance through electrochemical characterization in ex-vivo blood assays, coupled with commendable sensitivity, stability, and selectivity. CNT-COOH/OPS SPEs were also applied in point-of-care monitoring of the PPF blood concentrations in animals and clinical surgical patients and exhibited good accuracy and linearity (Ipa=0.0084c+0.4458, R2=0.995) with a limit of detection of 2.948μM. Further, the electrodes demonstrated a high recovery and the blood concentrations determined by electrochemical detection had robust negative correlation with the depth of anesthesia. Therefore, CNT-COOH/OPS SPEs hold promise as a significant tool in point-of-care monitoring of PPF, offering patients safer and more personalized medical care.

"Synergistic Hybridization of Mn-MOF@rGO and Ti3C2 for High-Performance Supercapattery Devices and Hydrogen Evolution Reaction"

The burgeoning interest in two-dimensional (2D) materials stems from their heightened storage capacity and superior conductivity. Here, we synthesized a metal-organic framework of manganese (Mn-MOF) and introduced reduced graphene oxide (rGO) doping into this heterostructure using a hydrothermal method. Subsequently, Ti3C2Tx MXene was prepared via a template method. The Mn-MOF@rGO was then combined with Ti3C2Tx MXene in a 50/50 wt% ratio using hydrothermal techniques, and their structural and electrochemical characteristics were evaluated. In 3-electrode measurements, the MnMOF@rGO/Ti3C2Tx composite conductor exhibited a precise capacity of 2645 C/g (5.29 C/cm3) at 1.8 A/g. Furthermore, a hybrid device termed a supercapattery was fabricated employing MnMOF@rGO/Ti3C2Tx along with activated carbon (AC) composite electrodes, demonstrating remarkable energy density of 67 Wh/kg and an impressive power density of 880 W/kg. After 8,000 cycles, the electrode exhibited 84% capacity retention and maintained 92% columbic efficiency. In the hydrogen evolution reaction (HER), the MnMOF@rGO/Ti3C2Tx composite displayed a minimal Tafel slope of 54.65 mV/dec. These two-dimensional composite electrodes offer novel avenues for the advancement of high-performance energy device.

High-strength polyvinyl alcohol/gelatin/LiCl dual-network conductive hydrogel for multifunctional sensors and supercapacitors

The synthesis of conductive hydrogels with high mechanical strength, toughness, optimal fracture growth rate and the capability to detect diverse human body movements poses a significant challenge in the realm of flexible electronics. In this study, a one-pot technique utilized effectively to fabricate conductive materials by doping LiCl into a mixture of polyvinyl alcohol (PVA) and gelatin. The PVA/gelatin/LiCl0.3(PGL) conductive hydrogel demonstrates exceptional robustness, flexibility, and resistance to deformation, enabling the monitoring of various physiological signals such as temperature and humidity. Additionally, the PGL demonstrates exceptional elongation properties (up to 1111.32 %), high lifting capacity (up to 25 kg), resistance to deformation, and sustained stability of peak signals even after 300 cycles at 50 % strain. The hydrogel electrolyte exhibits a conductivity of 2.114 S/m at 25 °C and a specific capacitance of up to 48.75 F/g, along with favorable mechanical and electrochemical characteristics. These findings suggest that the PVA/gelatin/LiCl0.3 hydrogel supercapacitor (PGLSC) conductive hydrogel shows significant potential for integration into flexible electronics and wearable technology devices.

Fabrication of an electrochemical sensor based on Zinc Vanadate anchored with multi-walled carbon nanotubes modified glassy carbon electrode for the determination of Carbendazim

The detection of Carbendazim (CBZ) insecticides has prompted concerns regarding their potential impacts on both human health and the environment. To address this issue, a novel nanocomposite comprising Zinc Vanadate (ZVO) was prepared using a common hydrothermal technique and incorporated with multi-walled carbon nanotube (MWCNT) to form ZVO/MWCNT nanocomposite. Thus, a glassy carbon electrode (GCE) has been modified using this ZVO/MWCNT nanocomposite, which offering a simple and affordable platform for the electrochemcial detection of CBZ. The structure and composition of the nanomaterial were confirmed through various microscopic and spectroscopic techniques, while its electrochemical characteristics were investigated using electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) techniques. The GCE/ZVO/MWCNT modified electrode exhibited a broad linear response ranging from 0.05 to 110μM, with a low detection limit of 0.005μM and high sensitivity (2.93 μA μM−1 cm−2), with recoveries ranging from 98% to 99.93%, respectively. Moreover, GCE/ZVO/MWCNT electrode demonstrated excellent stability, repeatability, and practical utility for CBZ detection. Based on electrochemical studies that indicate the formation of oxidized products consistent with a 2-electron transfer process. Therefore, this innovative GCE/ZVO/MWCNT modified electrode offers promising prospects for sensitive and selective CBZ determination, with potential applications in environmental monitoring and health protection.

DFT and AIMD studies of SnFe2O4 as a promising anode for Li-ion batteries

Tin ferrite (SnFe2O4) is considered as a perspective lithium ion battery anode, owing to its low cost, large theoretical capacity, low toxicity, structural stability, and easy synthesis method. Prior research has been done on the performance of lithium storage in SnFe2O4. However, the electrochemical processes that take place during the lithiation-delithiation cycle of LIBs have not been explained in depth yet. In order to understand the discharge mechanism in the LixSnFe2O4 anode (x = 0 to 2), we systematically investigated its electrochemical characteristics, structural and electronic properties, average formation energies, open-circuit voltages, diffusion coefficient, and volume expansion using density functional theory. According to our calculations, an increase in Li concentration x up to 1.125 leads to enhanced stability of the LixSnFe2O4 systems. During this process, Li+ ions prefer to be intercalated at the octahedral 16c sites, inducing the displacement of Sn2+ ions from tetrahedral sites 8a to 16c and 48f sites. However, for 1.125 < x < 2, lithium ions tend to occupy the less stable sites 48f , which reduces the stability of LixSnFe2O4 systems.Additionally, the calculated lithium intercalation voltage for full lithiation Li1.125SnFe2O4 is equal to 1.5 V, and the distortion of the LixSnFe2O4 system occurs at a voltage of 0.75 V, which is in well agreement with experimental results. The Li-coefficient diffusion on SnFe2O4 at 300 K is calculated by ab initio molecular dynamic simulation and equal to 8.22 × 10−8 cm2/s, which indicates the excellent mobility of Li ions in SnFe2O4. Considering all these results, we can suggest SnFe2O4 as a promising negative electrode material for lithium-ion batteries.

Synergistic effect of NASICON Na3V2(PO4)2F3 and 2D MXene for high-performance symmetric Sodium-ion batteries

Sodium fluorophosphate-based Na3V2(PO4)2F3 (NVPF) cathode materials have been widely analyzed in Sodium-ion batteries (SIB) owing to their high energy density and high working voltage. However, the low electronic conductivity of NVPF is a factor hindering their efficient use. To enhance the electronic conductivity of NVPF, in this work, a porous Na3V2(PO4)2F3 and a 2D Ti3C2-based MXene nanocomposite was synthesized using a facile sol-gel method. The NVPF, with the presence of two active redox couples, is a suitable choice for symmetric batteries. The NVPF + 2D MXene nanocomposite was analyzed for its structural and thermal characteristics, and a symmetric cell prepared from them was investigated for its electrochemical characteristics. Structural analysis of the materials developed indicates that the MXene addition has not altered the crystal structure of the NVPF. A remarkable improvement in the electrochemical performance of NVPF in the sodium symmetric cell is noticed, as indicated by its high specific discharge capacity of 92mAhg-1 at 1C for the MXene-incorporated composite structures. This improvement in electrochemical behaviour is confirmed in the rate capability curves, GCD curves, and GITT curves. The diffusion coefficient values obtained from GITT analysis showed improved kinetics in the synthesized material due to the MXene incorporation. The calculated values of the diffusion coefficient of Na+confirms the accelerated kinetics of Na+ ion migration during the intercalation/de-intercalation process in the MXene 5wt% nanocomposites, with a value of 9.57 × 10–9 cm2s-1 when compared to 4. 14 × 10–9 cm2s-1 for the pristine sample.

Evaluation of 14-(p-tolyl)-14H-dibenzo[a,j]xanthene as a Highly Efficient Organic Corrosion Inhibitor for Mild Steel in 1 M HCl: Electrochemical, Theoretical, and Surface Characterization

Corrosion of mild steel, particularly in acidic environments such as hydrochloric acid (HCl), remains a critical issue due to its impact on material durability, economic costs, and safety concerns. This study introduces 14-(p-tolyl)-14H-dibenzo[a,j]xanthene (ZM5), a novel and highly effective organic corrosion inhibitor, to mitigate this challenge. Employing advanced electrochemical techniques: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), we evaluated ZM5’s performance in a 1M HCl solution, revealing an impressive inhibition efficiency of 94.7%. Surface characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) further confirmed the formation of a robust protective film on the steel surface, shedding light on ZM5’s adsorption mechanisms. Complementing the experimental findings, Density Functional Theory (DFT) simulations provided theoretical insights into the anti-corrosion mechanism of ZM5, aligning well with observed results. These findings underscore ZM5's potential as a highly promising corrosion inhibitor for industrial applications, effectively enhancing the corrosion resistance of mild steel in aggressive environments.

Preparation and application of ZnO-Ecoflex composite sensors for lactate detection during physical training

This study presents the development of a flexible ZnO-Ecoflex composite sensor for noninvasive lactate detection during physical training. ZnO nanostructures with an average diameter of 50 nm were synthesized and incorporated into an Ecoflex matrix. The optimized sensor, featuring 15 wt% ZnO loading, demonstrated high sensitivity (22.7 μA·mM⁻¹·cm⁻²) and a low detection limit (2.3 μM). The composite displayed impressive mechanical characteristics, showcasing a tensile strength of 1.3 MPa and an elongation at fracture of 390%. Electrochemical characterization revealed a diffusion-controlled electron transfer process and rapid response time of 5 seconds. The sensor showed minimal interference from common sweat components (&lt;3.2% relative response) and maintained consistent performance under various bending conditions (RSD 3.2%). Real-time monitoring during a 30-minute jogging session demonstrated the sensor's ability to capture dynamic changes in sweat lactate levels. This research contributes to the development of wearable biosensors for continuous lactate monitoring in sports and exercise science, offering potential for personalized training optimization.

Potential application of room temperature synthesized MIL-100(Fe) in enhancing methane production in microbial electrolysis Cells-Anaerobic digestion treating Protein-Rich wastewater

Microbial electrolysis cell-anaerobic digestion (MEC-AD) is an emerging technology for methane production. However, low substrate degradation efficiency remains a challenge when processing protein substrates. This study developed a MIL-100(Fe) carbon cloth anode to enhance methane production and substrate degradation in MEC-AD. The effects of MIL-100(Fe) prepared under hydrothermal (H-MIL-100(Fe)) and room temperature conditions (R-MIL-100(Fe)) were compared. Results indicated that H-MIL-100(Fe) and R-MIL-100(Fe) increased cumulative methane production by 16.01% and 14.99%, respectively compared to normal cloth, each influencing methane production through distinct mechanisms. Electrochemical characterization showed that H-MIL-100(Fe) enhanced the electrochemical performance more significantly due to the enrichment of Geotalea, with the oxidation current improved by 7.39-fold (R-MIL-100(Fe) increased it by only 2.95-fold) to promote growth of Methanobacterium. Metagenomic analysis revealed that R-MIL-100(Fe) tended to metabolize amino acids into methane rather than support cellular life activities, indicating its practicality under limited substrate concentration. In summary, R-MIL-100(Fe) shows greater potential for application due to its mild synthesis conditions and advantages in treating complex substrates.

Six element high-entropy Prussian blue analogue cathode enabling high cycle stability for sodium-ion batteries

Prussian blue analogues (PBA) are promising cathode materials for sodium-ion batteries. However, the cycle life of PBA is limited due to its structure instability during cycling. Here, we successfully introduce six transition metals into N coordination site to increase the configurational entropy, significantly improving the structure stability and cycle life of PBA cathode materials. Electrochemical characterization methods are used to compare the behavior of hexa-, penta-, quadr-, and tri-metal PBA, exhibiting the characteristic of performance increasing with entropy. Time-resolved in situ X-ray diffraction confirms the “quasi-zero-strain” structure of H-PBA during desodiation/sodiation process. X-ray absorption spectroscopy and density functional theory calculations reveal that Mn, Fe, Co and Cu contribute the high capacity of H-PBA, while Ni and Zn stabilize the structure. The strategy will inspire new ideas in designing long life cathode materials with high capacity for sodium-ion batteries.

Unraveling the Complex Temperature-Dependent Performance and Degradation of Li-Ion Batteries with Silicon-Graphite Composite Anodes

Competing effects of graphite and Si result in a complex temperature dependent performance and degradation of Li-ion batteries with Si-graphite composite anodes. This study examines the influence of varying the Si content (0 to 20.8 wt%) in Si-graphite composite anodes with consistent areal capacity and N/P ratio in full cells containing NMC622 cathodes. One hundred pilot-scale double-layer pouch cells were built and cycle aged in the temperature range from −10 to 55 °C. Electrochemical characterization demonstrated that increasing Si contents enhance capacity and mitigate internal resistance at low temperatures. On the other hand, high Si contents decrease charge-discharge energy efficiency and cycle life, particularly at elevated temperatures. Post-mortem analysis of aged electrodes, including physico-chemical characterization (scanning electron microscopy, energy-dispersive X-ray analysis, thickness measurements) and cell reconstruction revealed significant solid electrolyte interphase growth and increased loss of active material in anodes with high Si content. The optimum temperature for longest cycle life as derived from Arrhenius plots decreased from 30 °C for graphite anodes to 10 °C for cells with moderate Si content up to 5.8 wt%. These findings allow the design of optimized cells by balancing the Si content versus operating temperature in order to achieve lowest cell aging.

Facile fabrication of FeSe/MnSe composite for improved electrochemical characterization by hydrothermal route

Globally, researchers are primarily focused on creating new electrode materials with high energy and power density (Pd) to develop the efficiency of energy storage devices. This work demonstrates significant advancements in use of transition metal selenide as electrode material for supercapacitors (SCs). FeSe/MnSe composite was produced by a hydrothermal approach and the findings indicated a notable improvement in electrochemical characteristics due to the combined effect of FeSe and MnSe materials. The exceptional electrochemical performance of FeSe/MnSe composite electrode attributed to its inherent features, including crystal structure, excellent electrical conductivity with varying oxidation states, distinct morphology and large surface area. Moreover, FeSe/MnSe composite demonstrated specific capacitances (Csp) of 1533.23 F/g at current density of 1.0 A g−1 with notable energy density (68.70 Wh kg−1) and Pd (284 W kg−1). Furthermore, the FeSe/MnSe composite electrode demonstrates remarkable cyclability, sustaining its effectiveness reliably for more than 5000 cycles while also exhibiting low-impedance features with a Rct of 0.09 Ω. This study delves into a new approach for creating unique FeSe/MnSe electrodes that show potential as a reliable option with extended cycling durability and increased energy capacity for use in energy storage devices.