Thin Film Electrode Materials Research Articles

Understanding the Kinetics of Cation Insertion-Coupled Electron Transfer in Thin Film Electrodes from Cyclic Voltammetry

Cyclic voltammetry is a powerful technique for probing the electrochemical kinetics of energy storage materials. However, interpretation of the cyclic voltammetry kinetics of such materials has been limited by the application of analytical solutions initially developed for ion blocking electrodes, whereby mass transport is limited to semi-infinite diffusion in the electrolyte medium. Here, we utilize established numerical simulation models for finite diffusion coupled with experimental results of a model insertion electrode to demonstrate the relationship between solid-state diffusion and cyclic voltammetry current, peak potential, and capacity. This simulation is publicly available.1 We show that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained with finite diffusion. Specifically, we investigate the kinetic behavior of Li+ insertion-coupled electron transfer into thin films of orthorhombic Nb2O5. We observe a general trend in the b-value, a descriptive parameter derived from the relation ip=avb between peak current ip and scan rate v. We find that both in simulation and experiment, we can tune the b-value response between the theoretically limiting values of 0.5 and 1 based on the solid-state diffusion characteristics of the thin film and the experimental timescale. We also show that b-values below 0.5 are possible, and arise due to a combined effect of the potential window of the experiment and confined diffusion. Our findings show the power of a simple 1D finite-diffusion model for predicting the kinetic response of an electrode undergoing ion-coupled electron transfer, and help to inform on how the scan rate selection in voltammetry experiments affects the observed kinetic behavior. https://github.com/mchagnot/Numerical_CV_Sim_1D_Diffusion

Influence of Finite Diffusion on Cation Insertion-Coupled Electron Transfer Kinetics in Thin Film Electrodes

Materials that undergo ion-insertion coupled electron transfer are important for energy storage, energy conversion, and optoelectronics applications. Cyclic voltammetry is a powerful technique to understand electrochemical kinetics. However, the interpretation of the kinetic behavior of ion insertion electrodes with analytical solutions developed for ion blocking electrodes has led to confusion about their rate-limiting behavior. The purpose of this manuscript is to demonstrate that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained by well-established models for finite diffusion. To do this, we utilize an experimental and simulation approach to understand the kinetics of Li+ insertion-coupled electron transfer into a thin film material (Nb2O5). We demonstrate general trends for the peak current vs scan rate behavior, with the latter parameter elevated to an exponent between limiting values of 1 and 0.5, depending on the solid-state diffusion characteristics of the film (diffusion coefficient, film thickness) and the experiment timescale (scan rate). We also show that values < 0.5 are possible depending on the cathodic potential limit. Our results will be useful to fundamentally understand and guide the selection and design of intercalation materials for multiple applications.

Simulation and fabrication of titanium dioxide thin films for supercapacitor electrode applications

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO2 nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO2 nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm2 with oxidation and reduction peak currents of 6.18921×10[Formula: see text] A and −6.0320×10[Formula: see text] A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm2, which is improved to 12.8764 F/cm2 at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm2 and −0.105 mA/cm2, respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO2 nanotubes thin-film sample shows considerable similarity with the simulation results.

Mild synthesis of flower-like CuS modified MXene nanocomposites for high-performance supercapacitors and efficient microwave absorption

Benefiting from rich surface functional groups, two-dimensional transition metal carbides (MXene) exhibit excellent metallic conductivity, hydrophilicity and film-forming properties and are widely used in energy storage and microwave absorption. However, the agglomerate and stacking of MXene nanosheets during preparation are largely detrimental to the full realization of their merits at two-dimensional scale. Therefore, we developed an ultrasonic assisted and vacuum filtration method to obtain MXene/CuS thin film electrode material with a "sandwich" structure without destroying its inherent properties, which still maintains a good lamellar structure and exhibits excellent tensile properties. Due to the synergistic effect of MXene and CuS and their redox reaction, the MXene/CuS thin film electrode exhibits a specific capacitance of 491 F g−1 at a current density of 1 A g−1. It can be used directly as positive and negative electrodes to assemble a flexible supercapacitor with a capacitance retention of 89 % at current density of 2 A g−1 after 5000 cycles. In addition, the composite can achieve an effective absorption band width of 3.3 GHz (14.7–18 GHZ) at a thickness of 1 mm. The study shows that layer spacing modulation offers the possibility of large-scale applications of MXene in the field of flexible supercapacitors and microwave absorption, and provides new ideas for the development of multi-purpose materials to meet the needs of different applications.

Synthesis and characterization of WO3 based thin film electrode material for electrochromic device

Synthesis and characterization of WO3 based thin film electrode material for electrochromic device

All-Solid-State Thin Film Lithium/Lithium-Ion Microbatteries for Powering the Internet of Things.

As the world steps into the era of Internet of Things (IoT), numerous miniaturized electronic devices requiring autonomous micropower sources will be connected to the internet. All-solid-state thin-film lithium/lithium-ion microbatteries (TFBs) combining solid-state battery architecture and thin-film manufacturing are regarded as ideal on-chip power sources for IoT-enabled microelectronic devices. However, unlike commercialized lithium-ion batteries, TFBs are still in the immature state, and new advances in materials, manufacturing, and structure are required to improve their performance. In this review, the current status and existing challenges of TFBs for practical application in internet-connected devices for the IoT are discussed. Recent progress in thin-film deposition, electrode and electrolyte materials, interface modification, and 3D architecture design is comprehensively summarized and discussed, with emphasis on state-of-the-art strategies to improve the areal capacity and cycling stability of TFBs. Moreover, to be suitable power sources for IoT devices, the design of next-generation TFBs should consider multiple functionalities, including wide working temperature range, good flexibility, high transparency, and integration with energy-harvesting systems. Perspectives on designing practically accessible TFBs are provided, which may guide the future development of reliable power sources for IoT devices.

The regulation of resistivity for SiHfBCN thin films prepared by magnetron sputtering method

SiHfBCN ceramic is a kind of potential thin film electrode material applied in high temperature sensors. The ability to tune the resistivity is of primary importance for its further applications. Therefore, in this paper, the SiHfBCN film was prepared using magnetron sputtering method. The regulation means of resistivity were investigated through analyzing the relationship between microstructure and resistivity. The result shows that the resistivity of amorphous SiHfBCN film is mainly related to the overall electronegativity difference and contents of insulating chemical bonds. The resistivity of SiHfBCN films can be controlled over a broad range by changing their composition. In addition, the behavior of annealed SiHfBCN indicates a stable structure. • The SiHfBCN film, a potential high temperature electrode material, was prepared by magnetron sputtering method. • The relationship between resistivity and microstructure of SiHfBCN film was established to explain its conductive behavior. • The resistivity of SiHfBCN film is related to the “insulating” chemical bonds and overall electronegativity difference.

Chemical bath deposited Nickel oxide thin film as electrode material for pseudocapacitors

We have synthesized thin films of nickel oxide (NiO) on silver and glass substrates, at very low temperature of 60°C, by chemical bath deposition (CBD) method. The precursor used consists of nickel nitrate and aqueous ammonia. Structural characteristics were studied using x-ray diffraction (XRD) and morphological studies were done using scanning electron microscopy (SEM). Ultraviolet-visible (UV-Vis) spectroscopy was used for optical studies. To investigate electrochemical behaviour of thin film electrode materials, cyclic voltammetry (CV) measurements were conducted. For electrochemical studies the galvanostatic charge/discharge (GCD) tests were also conducted. The formation of face centred cubic NiO structure was confirmed using XRD. The scanning electron microscopy images show uniform distribution of worm-like porous morphology. CV measurements revealed the capacitive behaviour of the films.

Chlorophyll-a functionalised Zn-Cd-S thin film fabricated by SILAR technique for dye sensitised solar cells

Photoelectrochemical performance of DSSCs based on natural extracted chlorophyll-a dye sensitised Zn-Cd-S thin film semiconductor electrodes on Cr-plated stainless steel substrates as photoanodes are studied. Thin film electrode materials prepared by successive ionic layer adsorption and reaction (SILAR) method are characterised by using Powder X-ray diffraction (PXRD) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and UV–VIS spectroscopy. The prepared Zn-Cd-S thin films are found to be nanocrystalline with a crystal size of ≈ 6.6 nm. The optical band gap energy of the thin films found is to be ≈ 2.9 eV. Chlorophyll-a dye used as sensitizer for DSSC, is extracted from Marigold leaves using acetone as solvent. The optical to electrical energy conversion efficiency of the DSSC using 6 h chlorophyll-a dye loaded Zn-Cd-S thin film is estimated to be 0.988% with fill factor of 52%.

A Sustainable Approach for Preparing Porous Carbon Spheres Derived from Kraft Lignin and Sodium Hydroxide as Highly Packed Thin Film Electrode Materials.

A green synthetic strategy to design biomass-derived porous carbon electrode materials with precisely tailored structure and morphology has always been a challenging goal because these materials can fulfill the demands of next-generation supercapacitors and other electrochemical devices. Potassium hydroxide (KOH) is extensively utilized as an activator since it can produce porous carbon with high specific surface area and well-developed porous channels. The exploitation of sodium hydroxide (NaOH) as an activating agent is less referenced in the literature, although it offers some advantages over KOH in terms of low cost, less corrosiveness, and simple handling procedure, all of which are appealing particularly from an industrial viewpoint. The motivation for this present study is to fabricate porous carbon spheres in a sustainable manner via a spray drying approach followed by a carbonization process, using Kraft lignin as the carbon precursor and NaOH as an alternative activation agent instead of the high-cost and high-corrosive KOH for the first time. The structure of carbon particles can be accurately transitioned from a compact to hollow structure, and the surface textural properties can be easily tuned by altering the NaOH concentration. The obtained porous carbon spheres were applied as highly packed thin film electrode materials for supercapacitor devices. The specific capacitance value of porous carbon spheres with a highly compact structure (high packing density) is 66.5 F g-1, which is higher than that of commercial activated carbon and other biomass-derived carbon. This work provides a green processing for producing low-cost and environment-friendly porous carbon spheres from abundant Kraft lignin and important insight for selecting NaOH as an activator to tailor the morphology and structure, which represents an economical and sustainable approach for energy storage devices.

Feasible preparation of Cu6Sn5 alloy thin-film anode materials for lithium-ion batteries from waste printed circuit boards by electrodeposition

Homogeneous and three-dimensional structural Cu6Sn5 alloy thin-film composite materials are successfully fabricated by efficiently electrodepositing the acidic leaching solution of waste printed circuit boards with the pH value adjusted to 10 at different current densities, which are confirmed by inductive coupled plasma-optical emission spectrometer, scanning electron microscope, and X-ray diffraction. When the Cu6Sn5 alloy thin-film composite materials electrodeposited at 5 mA/cm2 are employed as anode materials for lithium-ions batteries, the assembled coin cells can deliver initial discharge and charge specific capacity of about 617 and 502 mAh/g at 100 mA/g, respectively, and can retain a discharge specific capacity of 448 mAh/g after 25 cycles. Moreover, the cells assembled with Cu6Sn5 alloy anodes can exhibit an enhanced lithium-ion diffusion coefficient of 5.045 × 10−16 cm2/s with a lower transfer resistance of 63.43 Ω. Those results may provide an effective strategy for the resource utilization of low-value wastes into copper‑tin alloy thin-film electrode materials.

A high-performance covalently bonded self-doped polyaniline–graphene assembly film with superior stability for supercapacitors

In this study, a robust high-performance polyaniline-modified graphene electrode is successfully used to assemble a supercapacitor. Graphene is covalently bonded to self-doped polyaniline (SPANI) and used in supercapacitors, and 4-aminobenzoic acid-modified graphene (ABF-G) sheet materials are first bonded to an aniline functional group at graphene edges. Then, aniline, o-aminobenzene sulfonic acid monomers, and an oxidising agent are added into the ABF-G aqueous dispersion to achieve polymerisation on the surface of ABF-G. This covalently bonded SPANI-modified ABF-G (SPANI-ABF-G) thin-film electrode material is then used for fabricating supercapacitors. A Raman spectrometer, a scanning electron microscope, a secondary ion mass spectrometer, an X-ray electron photon spectrometer, and a specific surface area analyser are used to characterise this film. The supercapacitor with the proposed SPANI-ABF-G electrodes exhibits a high specific capacitance value of 642.6 F/g for charging and discharging at a current density of 1 A/g. After 5000 cycle-life testing, this supercapacitor exhibits a charging and discharging capacitance retention of 100% and 98.13% at a current density of 1 and 2 A/g, respectively. These capacitance retentions are higher than those of supercapacitors with conductive polymers electrodes. The results prove that electrode materials prepared using covalently bonded graphene and PANI can considerably improve supercapacitor performance.

Pseudocapacitance multiporous vanadyl phosphate/graphene thin film electrode for high performance electrochemical capacitors

Supercapacitors are being considered as promising electricity storage devices with green sustainable energy conversion. To efficiently develop and optimize pseudocapacitive material of vanadyl phosphate, herein, multiporous vanadyl phosphate/graphene (denoted as MP-VOPO4@rGO) is fabricated for the first time with phytic acid as a phosphorus source by extremely simple sol-gel and drop coating methods, and used as the free binder thin film electrode of supercapacitors. The smart combination of honeycomb-like architecture and graphene incorporation results in more active sites and low internal resistance, significantly improving energy storage performance. The effect of introducting polystyrene (denoted as PS) template and rGO on the performance of the nanocomposite is systematically analyzed by comparing the performance of the corresponding thin film electrodes. The MP-VOPO4@rGO thin film electrode delivers superior pseudocapacitive performance of 672 F g−1 at 1 A g−1 as well as a remarkable rate capability of 552 F g−1 at 5 A g−1, and it presents a remarkable longterm cycling stability, with a capacitance retention of 83.5% after 5000 cycles. Very interestingly, the results of surface capacitance contribution dominance clearly demonstrates its rapid capacitive response. In addition, based on MP-VOPO4@rGO thin film as positive and negative electrodes, the corresponding assembled symmetric supercapacitors exihibits outstanding energy density of 26.3 Wh kg−1 at power density of 249.9 W kg−1. This investigation can not only provide a versatile strategy to design other thin film electrode materials but also open up a new insight into the development of polyanion phosphate composites for next-generation high performance energy storage systems.

Development of Novel 3d Printable Graphene-based Composite Towards Fabrication of Thin Film Electrode Material

Graphene/polymer composite thin film electrodes have many important applications, but the fabrication of these electrodes is often difficult because of poor processability of graphene. This paper presents the primary results on using 3D printing technique for thin film electrode preparation from graphene-based composite ink. The printing ink was synthesized from graphene oxide (GO), polyvinyl alcohol (PVA) as a binder and stabilizer, and ascorbic acid (AA) as a reducing agent. The measured zeta potential value showed that PVA can make GO ink more stable, the absolute value of zeta potential increased from 10.1 mV (without PVA) to 31.4 mV (with 12 wt. % PVA). The thin film electrodes can be easily printed using GO/PVA/AA composite ink, and obtained voltammograms recorded on the surface of these electrodes in 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] solution clearly indicated the GO reduction by AA. The best electrochemical properties of printed electrodes were founded in the case of composite ink with wt/wt ratio GO:PVA:AA = 80:12:8. The cyclic voltammetric results demonstrated the linear dependence of the anodic and cathodic signals of redox couple [Fe(CN)6]4-/K3[Fe(CN)6]3- with the square root of scan rate, indicating a reversible redox reaction on the electrode surface. The thin films printed from GO/PVA/AA composite ink can be used as electrode material for diverse applications in electrochemistry.

Syntheses and characterizations of GO/Mn3O4 nanocomposite film electrode materials for supercapacitor applications

We have, in this study; used simple, in-expensive and environmentally-friendly successive ionic layer adsorption and reactions (SILAR) deposition procedure to successfully grow GO/Mn3O4 thin film electrode materials. The deposited films were examined for their surface morphology using scanning electron microscopy (SEM) while its morphology and structure was confirmed using transmission electron microscopy (TEM) and selected area electron diffractometry (SAED) respectively. X-ray diffraction (XRD) was used to study their structural properties while their supercapacitive studies were obtained using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. All deposited films were scanned in 1 M solution of Na2SO4 electrolyte. The SEM images of the deposited films revealed highly porous interconnected morphology with Mn3O4 densely dispersed among graphene oxide (GO). Individual peaks of Mn3O4 and GO compounds indicating uniform spread of Mn3O4 inside the porous matrix of GO were observed from the XRD. Mn3O4 nanograins well-dispersed on the surface were further confirmed through the TEM images while bright concentric rings confirming the polycrystalline nature of the films were observed from SAED images. The film deposited at 40 cycles yielded the maximum specific capacitance of 532.54 Fg−1at 5 mVs−1 scan rate. The results of the electrochemical studies show that the GO/Mn3O4 composite films synthesized by SILAR could be a promising material for supercapacitors.

Thin-film coating technologies on porous materials for chemical current sources

This paper investigates the technologies for the formation of the thin-film electrode material of the chemical current sources. To get the high specific energy density of the electrode we used the grinding of chemically active material (LiCoO2), which the most widely used for cathode materials of chemical current sources to deposit on the materialized carbon-based electrode materials. The tested results show that the specific energy density of the electrode reaches to 210 mAh/g, which is more than thick-film technologies can reach (150 mAh/g).

One-step potentiostatic electrodeposition of cross-linked bimetallic sulfide nanosheet thin film for supercapacitors

The structural design of electrode material plays a vital role in the development of supercapacitor. Here we propose a binder-free bimetallic sulfide (NiCo2S4) nanosheet thin-film electrode with the cross-linked structure synthesized via a robust one-step potentiostatic electrodeposition. The microstructure and morphology are optimized by adjusting the deposition potential (vs Ag/AgCl). Particularly, the 3D cross-linked NiCo2S4 nanosheet thin-film electrode prepared at − 0.9 V delivers the best electrochemical performance, demonstrating a specific capacitance of 1410 F g−1 at 1 A g−1, and high capacitance retention of 98.02% after 2000 cycles at 5 A g−1. The excellent capacitance retention of the electrode from 1 to 10 A g−1 confirms the good rate capability of the prepared sample. This study reveals that the one-step potentiostatic electrodeposition is an effective route for designing and preparing 3D structured thin-film electrode materials by electrodeposition.

Enhanced energy density of flexible asymmetric solid state supercapacitor device fabricated with amorphous thin film electrode materials

Supercapacitors have recently received immense interest in scientific community, as a complementary technology to batteries, to meet the various requirements for energy usage in practice. Amorphous MnO2 and CuS thin films are prepared on stainless steel-304 (SS) substrate by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) methods, respectively. Asymmetric flexible solid state supercapacitor fabricated with configuration of SS/A-MnO2/Polyvinyl acetate (PVA)-Na2SO4/A-CuS/SS delivered an impressive specific energy of 57.4 Wh kg−1 at specific power 317 W kg−1 and excellent cycling stability over 10,000 cycles with capacitive retention of 84%. Moreover, series configuration of two asymmetric devices shows the capability of powering 211 red LEDs for ~150 s after charging for 30 s.

Electrochemical energy storage of silver and silver oxide thin films in an aqueous NaCl electrolyte

We present an investigation into the pseudo-capacitive energy storage potential of silver (Ag) and silver oxide (Ag2O) thin film electrode materials prepared by reactive magnetron sputtering. The growth mode and morphology of the prepared films were investigated using the scanning electron microscope (SEM), which reveals columnar growth structure and microporous sites.The stoichiometry and oxidation states of the silver oxide films were monitored with X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). The XRD results reveal the nano-crystalline nature of the silver and silver oxide thin films with peak intensities indexed at (111) planes.Static and dynamic Contact angle measurements were used to probe the penetration of the aqueous NaCl electrolyte into the pores in the prepared silver and silver oxide films, with surface wettability of all (Ag) and (Ag2O) thin films hydrophilic in nature, which is vital for a good electrochemical performance.The Faradaic redox reactions, capacitance and the charge discharge of the films when exposed to the NaCl electrolyte, were monitored with cyclic voltammetry and chronopotentiometry charge-discharge. Results show that Silver and silver oxide possess specific capacitance of 240.52 F/g and 275.50 F/g at 2 mV/s respectively, which is promising for electrochemical energy storage application.

Structural and Electrochemical Evaluation of Three- and Two-Dimensional Organohalide Perovskites and Their Influence on the Reversibility of Lithium Intercalation.

Organic-inorganic hybrid perovskite materials have recently been investigated in a variety of applications, including solar cells, light emitting devices (LEDs), and lasers because of their impressive semiconductor properties. Nevertheless, the perovskite structure has the ability to host extrinsic elements, making its application in the battery field possible. During the present study, we fabricated and investigated the electrochemical properties of three-dimensional (3D) methylammonium lead mixed-halide CH3NH3PbI3- xBr x and two-dimensional (2D) propylammonium-methlylammonium lead bromide (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 hybrid perovskite thin films as electrode materials for Li-ion batteries. These electrodes were obtained by solution processing at 100 °C. CH3NH3PbBr3 achieved high discharge/charge capacities of ∼500 mA h g-1 /160 mA h g-1 that could account also for other processes taking place during the Li intercalation. It was also found that bromine plays an important role for lithium intercalation, while the new 2D (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 with a layered structure allowed reversibility of the lithium insertion-extraction of 100% with capacities of ∼375 mA h g-1 in the form of a thin film. Results suggest that tuning the composition of these materials can be used to improve intercalation capacities, while modification from 3D to 2D layered structures contributes to improving lithium extraction. The mechanism of the lithium insertion-extraction may consist of an intercalation mechanism in the hybrid material accompanying the alloying-dealloying process of the Li xPb intermetallic compounds. This work contributes to revealing the relevance of both composition and structure of potential hybrid perovskite materials as future thin film electrode materials with high capacity and compositional versatility.