Single Particle Electrode Research Articles

The fabrication of SiOx single particle electrode and its electrochemo-mechanical study

In this study, deformation observation and rate performance of SiOx material in the particle scale are firstly conducted using the single particle electrode. Particle deformation is observed using an ex-situ method and the measured expansion ratio is close to the theoretical value. The rate performance of a SiOx particle at 25 °C is measured. For a single particle, the C-rate at which the capacity retention ratio retains above 80% is over 50 C while that of the porous electrode is only 7 C. A single particle model considering the electrochemo-mechanical interaction is derived to fit the results of rate performance and is used to analyze the spatial distribution of Li+ concentration and stress at different C-rates. According to simulation results, we find that the direction and value of stress are related to the difference between the localized concentration and the averaged concentration. By comparing the hydraulic stress at different positions with the yield strength, we find that the yield and failure may occur when the particle is delithiated at over 10 C. For battery use, it is suggested to improve the homogeneity of electrode structure to avoid large localized current density which may lead to diffusion-induced failure.

Characterization of electrochemical kinetics of SiOx using single-particle electrode technique: An impedance study

In this study, single-particle electrode technique is adopted to measure the impedance response of SiOx materials for the first time. The electrochemical impedance spectroscopies of two SiOx particles are measured at different insertion ratios and different temperatures. Two kinetic parameters, namely Li+ diffusivity and exchange current density, are obtained using our previously proposed impedance model which takes into account the stress effect on Li+ diffusion and surface reaction. The dependence of the two parameters on the Li+ insertion ratio and temperature is obtained. The fitted results are found to be strongly consistent with previous research. Lastly, through comparison with the results of earlier studies with the help of the single-particle electrode technique, we find that the kinetic performance of SiOx is much poorer than graphite, and smaller particles are recommended to use compared with graphite when applying SiOx as the anode material. The single-particle electrode can serve as an effective tool to evaluate the electrochemical kinetics of various materials and provides a new index for material evaluation.

The Fabrication of Siox Single Particle Electrode and its Electrochemo-Mechanical Study

The Fabrication of Siox Single Particle Electrode and its Electrochemo-Mechanical Study

A new single-particle model to evaluate the Li-ions diffusion coefficients of LiMn1−xFexPO4

It remains a challenge to evaluate the Li-ions diffusion coefficients of LiMn[Formula: see text]FexPO4 due to the presence of two voltage platforms upon charge/discharge. In this paper, a new single-particle model based on Butler–Volmer (BV) equation and one-dimensional diffusion equation is established. Using this model, the cyclic voltammogram curves of LiMn[Formula: see text]FexPO4 single-particle electrodes are successfully fitted and their Li-ion diffusion coefficients in organic electrolyte are obtained. Through analyzing the diffusion coefficients, it is found that the Li-ions diffusion coefficients for both Fe and Mn redox processes in LiMn[Formula: see text]FexPO4 reach the maximum when [Formula: see text]. In addition, the values for oxidation processes are much larger than those for reduction processes.

Bipolar Electrochemistry on a Nanopore-Supported Platinum Nanoparticle Electrode.

In this Technical Note, we describe a method to fabricate nanopore-supported Pt nanoparticle electrodes and their use in bipolar electrochemistry. A Pt nanoparticle is deposited on the orifice of a solid-state nanopore inside a focused-ion beam (FIB) system. Complete blockage of the nanopore with Pt metal forms a closed bipolar nanoparticle electrode whose size and shape can be tunable in one simple step. Nanoparticle electrodes and their arrays can be prepared on different substrates such as the tip of a glass pipet, a double-barrel pipet, and a freestanding silicon nitride membrane. Steady-state voltammetry can be performed on such nanoparticle electrodes via bipolar electrochemistry. Moreover, an array of Pt nanoparticles can be used for fluorescence-enabled electrochemical microscopy. Future use of highly advanced FIB systems may allow nanoparticles of <10 nm to be fabricated which may enable coupled electrochemical reactions of single redox molecules. Pipette-supported single particle electrodes may also find useful applications in high resolution imaging with nanoscale scanning electrochemical microscopy (SECM) and neurochemical analysis inside single cells.

Single‐Particle Performances and Properties of LiFePO4 Nanocrystals for Li‐Ion Batteries

It has been recently reported that the solution diffusion, efficiency porosity, and electrode thickness can dominate the high rate performance in the 3D‐printed and traditional LiMn0.21Fe0.79PO4 electrodes for Li‐ions batteries. Here, the intrinsic properties and performances of the single‐particle (SP) of LiFePO4 are investigated by developing the SP electrode and creating the SP‐model, which will share deep insight on how to further improve the performance of the electrode and related materials. The SP electrode is generated by fully scattering and distributing LiFePO4 nanoparticles to contact with the conductive network of carbon nanotube or conductive carbon to demonstrate the sharpest cyclic voltammetry peak and related SP‐model is developed, by which it is found that the interfacial rate constant in aqueous electrolyte is one order of magnitude higher, accounting for the excellent rate performance in aqueous electrolyte for LiFePO4. For the first time it has been proposed that the insight of pre‐exponential factor of interface kinetic Arrhenius equation is related to desolvation/solvation process. Thus, this much higher interfacial rate constant in aqueous electrolyte shall be attributed to the much larger pre‐exponential factor of interface kinetic Arrhenius equation, because the desolvation process is much easier for Li‐ions jumping from aqueous electrolyte to the Janus solid–liquid interface of LiFePO4.

Facet dependent SEI formation on the LiNi(0.5)Mn(1.5)O4 cathode identified by in situ single particle atomic force microscopy.

A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM. The SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.

Quasi-random assembled single particle electrode and instinct electrochemical performance of LiFePO4 in wide temperature scope

In this paper, we report a kind of quasi-random assembled single particle LiFePO4 electrode (QRASPE). The result of the SEM indicated that all of the LiFePO4 particles, separated completely by a sufficient amount of super-P conductor, form an assembled model of LiFePO4 particle micro-electrodes. Our results indicate that the interaction among LiFePO4 particles, overlapping the outer diffusion field around each LiFePO4 particle and shielding effect, affects accurate exhibition of instinct performance of LiFePO4. Results of cyclic voltammograms of QRASPE can exhibit integrated redox performance of LiFePO4 even at a high rate and wide temperature scope (233–313K) owing to no interaction among LiFePO4 particles. Larger DLi+ values and lower apparent diffusion activation energy of Li+ in LiFePO4/FePO4 solid phases are also revealed by QRASPE because of the merits of a single-particle microelectrode technique shown on QRASPE felicitously. Our investigation also explains the reason for the difference among the results of classical plate, single-particle electrode and theoretical simulation.

Evaluation of real performance of LiFePO4 by using single particle technique

Single particle technique was employed to investigate the intrinsic electrochemical properties of LiFePO4. A micro-size LiFePO4 single particle composed of a plurality of primary particles was contacted with a micro Pt electrode in an electrolyte solution using a micromanipulator under optical microscope observation, and then galvanostatic charge/discharge tests were performed. The specific capacity of the particle with a diameter of 24μm was estimated to be 1.5nAh in the potential rage of 2.0–4.2V vs. Li/Li+. The particle had a good reversibility for charge/discharge processes, and also showed excellent rate performance, for example, that more than 50% of the full capacity was maintained even when the discharge current was as high as 750nA corresponding to 4s discharge (900C rate). From the dependency of over-potential in the single particle electrode on discharge current density, it was expected that the discharge reaction was controlled at the discharge current densities higher than 2.56mAcm−2 by Li+ diffusion step in the particle accompanied with the phase conversion from FePO4 to LiFePO4. According to this assumption, Li+ diffusion coefficient in the particle was estimated as 2.7×10−9cm2s−1.

Design and optimization of single particle electrodes for the kinetic analysis of hydrogen evolution and absorption on hydrogen storage alloys

In the literature, there is a large discrepancy between reported values of electrochemical, kinetic and transport parameters of hydrogen storage alloys. These discrepancies arise, because in most cases, electrodes are prepared with the powdered alloy supported within a porous matrix, constituted by carbon and additive binders such as PTFE. The main drawback, of this preparation technique, for the identification of kinetic parameters, is the uncertainty in the specific active area value, where the hydrogen evolution and absorption processes take place. To overcome the disadvantages described, a new type of electrode, was designed, using a single particle of AB5 and AB2 hydride forming alloys. The data obtained from electrochemical impedance measurements were adjusted in terms of a physicochemical model that takes into account the processes of hydrogen evolution and absorption coupled to hydrogen diffusion. From the study it can be concluded that the differences in the behavior of the AB5 and AB2 alloys, presenting the first best performance during the activation and operation at high discharge currents, are mainly due to higher values of the exchange current density and the diffusion coefficient of H for the AB5 alloy.

Correlation between Battery Performance and Lithium Ion Diffusion in Glyme–Lithium Bis(trifluoromethanesulfonyl)amide Equimolar Complexes

Li+ cation diffusion processes during electrochemical reactions in molten glyme–Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl) amide) equimolar complexes were explored in detail. The correlation between the Li+ limiting current density under one-dimensional finite-diffusion conditions and rate capability of [Li metal foil | electrolyte | porous LiCoO2 cathode sheet] electrochemical cells was explored. The diffusion processes in the vicinity of LiCoO2 single particles were also studied using a microelectrode technique. Electrochemical properties of the particles in the electrolytes were characterized by using micrometer-sized particles in contact with a metal microfilament encapsulated in a glass capillary, under conditions where the Li+ cations around the particles could have spherical diffusion profiles. A comparison of the electrochemical behaviors of the LiCoO2 sheet and the single-particle electrode in a typical organic electrolyte (LiClO4 dissolved in propylene carbonate), in a binary ionic liquid (Li[TFSA] dissolved in N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)amide), and in the molten complex ([Li(glyme)1][TFSA]) clearly revealed that the Li+ cation flux in the electrolytes dominates the rate capability of the cells using the porous LiCoO2 cathode sheet.

Implementing Realistic Geometry and Measured Diffusion Coefficients into Single Particle Electrode Modeling Based on Experiments with Single LiMn2O4 Spinel Particles

Realistic geometry and diffusion coefficients were measured from a single particle LiMn2O4 electrode and implemented into a three-dimensional multiphysics simulation of a single particle, in order to demonstrate a novel approach to electrode material study. Dispersed particles were used, and electrochemical techniques and atomic force microscopy were performed on isolated single particles. Diffusion coefficients measured from both cyclic voltammetry and the potentiostatic intermittent titration technique ranged between 3.2 × 10−12 and 1.2 × 10−11 cm2/s, which was similar to values measured from thin film LiMn2O4 electrodes. The trend of diffusivity change over potential (versus lithium counter electrode) was similar to those observed from both composite cells and thin film electrodes. The measured diffusion coefficients were then used in simulation of discharge of the irregular particle, by importing the particle morphology into a finite element simulation, in order to simulate intercalation-induced stress generation. Simulation results showed a higher maximum stress generation due to altering diffusivity around the peak current potentials and high local stress concentration on the sharply indented surface area, suggesting that particle irregularities are important in studying both electrochemical performance and local failure mechanisms in cathode materials.

High-Rate Lithium Deintercalation from Lithiated Graphite Single-Particle Electrode

The electrochemical behavior of a lithiated graphite single-particle electrode during high-rate Li deintercalation in an organic electrolyte was investigated using a microelectrode technique. A Ni-plated metal filament (diameter: 10 μm) was attached to a mesocarbon microbead (MCMB) in the electrolyte under optical microscope observation, and galvanostatic charge−discharge tests were carried out. The discharge capacity of a lithiated MCMB particle (diameter: 18 μm) was 2.02 nA h in the potential range of 0.005−2.5 V vs Li/Li+. The fully lithiated MCMB particle showed an extremely high rate capability and released more than 98% of the accommodated Li at a constant discharge current of 1000 nA within 10 s. At discharge currents lower than 200 nA, the charge transfer process at the interface controlled the reaction of the single-particle electrode, and the Li diffusion process in the MCMB particle did not significantly affect the Li deintercalation rate. The charge transfer resistance for Li intercalation/dei...

Characterization of Metal Alloy Powder Materials for Metal-Hydride Anodes Using Thin-Layer Electrode Approach

A type of small electrode for basic studies on metal alloy powder materials for metal-hydride anodes has been proposed. The electrode holds a few milligrams of the active material and contains no inert binder material admixed to the active material. The electrode is prepared simply in a laboratory mechanical press. It was shown using cyclic voltammetry and electrochemical impedance spectroscopy that the electrode exhibits features of single-particle electrodes. Thus, it is suitable for a direct determination of performance parameters characteristic of the active particles without the need to resort to a complicated porous-electrode modeling.

High rate discharge capability of single particle electrode of LiCoO 2

The electrochemical properties of a single particle of LiCoO 2 (8 μm in diameter) in an organic electrolyte were characterized using a microelectrode technique, and the high rate capability of commercially available micron-sized LiCoO 2 was examined in this study. A Pt microfilament (10 μm in diameter) was attached to the single LiCoO 2 particle in the electrolyte during optical microscope observation, and galvanostatic charge-discharge tests were carried out. The discharge capacity of the single LiCoO 2 particle (8 μm diameter) was 0.157 nA h in the potential range of 3.0–4.2 V vs. Li/Li +, which was close to the theoretical capacity. The discharge rate capability of the single LiCoO 2 particle was excellent, and the particle exhibited its full-discharge capacity up to a high rate of 30 C (5 nA). The discharge reaction of the single particle was not controlled by the solid-state diffusion of Li +, but by the charge transfer process at a rate lower than 30 C. The discharge capacity of the particle measured at a high rate of 300 C (50 nA) was 0.12 nA h, which was more than 75% of the full capacity of a single particle.

A study of Faradaic phenomena in activated carbon by means of macroelectrodes and single particle electrodes

The electrochemical behaviour of a chemically activated carbon with oxygen-containing surface groups was studied using a conventional macroelectrode configuration with disc electrodes and the single particle microelectrode technique. The results of both experimental set-ups were compare taking into account the visible peaks of the surface groups, capacitance and Faradaic currents. Galvanostatic cycling and cyclic voltammetry performed at different potential windows clearly indicated that the microelectrode configuration was more sensitive to Faradic phenomena (i.e. oxygenated functional groups). The incorporation of mainly CO 2-evolving groups after positive polarization may cause the degradation of the carbon material, leading to a distortion in its capacitive behaviour as a result of a restriction of the available surface area.

Single‐Walled Carbon Nanotubes as Templates and Interconnects for Nanoelectrodes

A bottom-up approach for metal nanoelectrode fabrication is described involving the electrodeposition of a noble-metal nanoparticle at the exposed end of a single-walled carbon nanotube (see figure). The nanotube end serves as a template for nanoparticle electrodeposition, while the tube itself interfaces the deposited nanoparticle with macroscopic leads. The fabrication method is general and can easily be adapted to generate single-particle electrodes or arrays.

Single-Particle Electrode Microbatteries Studied

Single-Particle Electrode Microbatteries Studied

Cyclic Voltammetry and AC Impedance of MmNi3.55Co0.75Mn0.4Al0.3 Alloy Single-Particle Electrode for Rechargeable Ni/MH Battery

Voltammetry and ac impedance techniques were run on a single particle of alloy electrode with the aim of refining the investigating of the kinetics of the hydrogen adsorption-absorption processes into mischmetal alloys. The experimental impedance spectra for the hydrogen adsorption/absorption are similar in shape and in accordance with the theoretical predictions. Data were analyzed using an equivalent circuit based on the knowledge of the different processes taking place in the metal hydride electrodes. The model fitted the experimental data remarkably well. The equivalent circuit considers the charge-transfer reaction, the hydrogen transition between the adsorbed and absorbed states, and the impedance of finite hydrogen diffusion into the metal hydride electrode particle with spherical symmetry. The values of the obtained diffusion coefficient of hydrogen in the solid phase were and for the hydrogenation and dehydrogenation processes, respectively. © 2002 The Electrochemical Society. All rights reserved.

Electrochemical impedance study of Li-ion insertion into mesocarbon microbead single particle electrode: Part II. Disordered carbon

Electrochemical impedance spectroscopy (EIS) was applied for a single mesocarbon microbead (heat-treated at 1000 °C) of 30 μm diameter during Li-ion insertion and extraction using a stainless tip-microelectrode in the electrolyte of 1 M LiClO 4/propylene carbonate+ethylene carbonate. Obtained spectra were analyzed with an equivalent circuit model. Kinetic parameters such as the charge transfer resistance, and the apparent chemical diffusion coefficient of Li-ion in the particle were evaluated without interference of organic binders. The charge transfer resistance decreased and chemical diffusion coefficient of Li-ion increased as the electrode potential was made more negative. The chemical diffusion coefficient varied within 10 −12–10 −6 cm 2 s −1.