Name: in situ lithiated reference electrode: four electrode design for in-operando impedance spectroscopy
Uploaded: 2018-09-12T14:00:00.000+00:00
Duration: 9 min 36 s
Description: Watch this Scientific Journal Video about In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy at JoVE.com

The authors acknowledge financial support from the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy.

1. Stripping Copper/Tin Wires
<ol>
	<li>Heat commercially obtained stripping solution.
	<ol>
		<li>Pour commercial industrial grade stripping solution into a stainless steel beaker (7.6 cm in diameter and 8.5 cm in height) to a depth of about 5 mm from the bottom. Place the beaker on to a hot plate. Begin heating a slow rate of about 5 &#176;C/min.</li>
		<li>Immerse a portable thermocouple into the solution to closely monitor the temperature ramp of the solution and adjust the heating rate of the hot plate to maintain at the required heating rate.</li>
	</ol>
	</li>
	<li>Setting up of the Cu/Sn wire on the jig for preparing reference wires.
	<ol>
		<li>Wind a thick copper wire in the form of a jig (4 cm wide and 7 cm long). Mount the commercial Cu/Sn (or pure Cu) wire (25.4 &#181;m in diameter), plated with a thin layer of Sn and electronically insulated with a polyurethane coating) onto the jig as shown in Figure 1a. 
		NOTE: These wires are extremely delicate and may break if handled rough.</li>
	</ol>
	</li>
	<li>Stripping the polymer
	<ol>
		<li>Once the temperature of the stripping solution reads about 85 &#176;C on the thermocouple, stop heating the solution and immerse the wire mounted jig into the solution.</li>
		<li>Leave the jig inside the solution for 15 s and then rinse the jig in DI water for another 15 s to wash excess stripping solution adsorbed onto the wire.</li>
		<li>Check the wire for exposed Sn (appears as silvery white color) and repeat step 1.3.2 until the polymer is completely stripped. 
		CAUTION: Long term exposure of the wire to the stripping solution can etch away Sn coating and expose a reddish-brown Cu wire underneath. If the wires are being prepared for impedance spectroscopy analysis, the presence of Sn plating is essential.</li>
		<li>Rinse the jig in DI water and dry in air at room temperature (25 &#176;C).</li>
		<li>Cut the wires in the middle of the stripped regions to obtain wires with both ends with exposed Sn (or Cu over excess stripped wires). The size of each wire is approximately 10 cm.</li>
	</ol>
	</li>
</ol>
2. Reference Wire Preparation
<ol>
	<li>To make the reference wire contacts, connect the wires to an electrical wire and solder the junction.
	<ol>
		<li>From a roll of electrical circuit wires, cut pieces of 10 cm and strip the insulation cover from both the ends to expose about 2 cm of metal.</li>
		<li>Mount one end of the polymer stripped wire on to the end of the exposed electrical wire and solder the junction to form an electrical contact between the wires.</li>
		<li>Measure the resistance between the exposed Sn (or Cu) wire and the exposed electrical wire. 
		NOTE: The typical resistance values are between 6-8 &#8486;.</li>
		<li>Transfer one wire each with Sn exposed and with Cu exposed into an Argon filled glovebox for assembly into a cell.</li>
	</ol>
	</li>
	<li>Mount a pressed and flattened Li metal foil to the Cu exposed reference wire
	<ol>
		<li>Cut a small piece of Li metal (not more than 5 mm x 5 mm) from a large Li foil inside the glovebox. 
		NOTE: Use dedicated equipment for contact with Li metal and store inside the glovebox to prevent cross contamination and subsequent electrical micro-short.</li>
		<li>Using a roller covered with a polymer tape (to prevent sticking of the Li metal onto the metallic roller surface), roll the Li metal piece on a Teflon platform under Ar.</li>
		<li>Continue rolling to achieve a foil thickness of approximately 25 &#181;m. Check the thickness using a screw gauge.</li>
		<li>Upon obtaining the desired thickness of the Li metal foil, bend the foil at the center to form a U- shape. Place the Cu exposed wire in between the bend such that Cu is in contact with the Li metal and press the fold to encapsulate Cu wire between the two Li layers. 
		NOTE: Maintain extreme caution while encapsulating Cu wire so as to ensure covering all of the exposed tip. Cu is for electronic conductance only and contact of Cu to the electrolyte will result in reading a mixed surface potential generating erroneous voltage values in the data.</li>
	</ol>
	</li>
</ol>
3. Cell Assembly and Data Acquisition
<ol>
	<li>Place both the Li metal reference and the Sn reference wires in between the Li-ion cell assembly.
	<ol>
		<li>Place the negative electrode in the fixture such that the center of the electrode is slightly shifted from the center of the fixture. Add 400 &#181;L of the electrolyte (1.2M LiPF6 in Fluoroethylene Carbonate (FEC):Ethyl Methyl Carbonate EMC (5:95 w/w)) to wet the entire electrode.</li>
		<li>Place one separator on top of the electrode and using a organophobic sweep, gently eliminate trapped air bubbles between the separator and the electrode. Adjust the placement of the separator to ensure concentricity with the fixture to completely insulate the base of the fixture from the positive electrode and avoid electric short inside the cell. 
		NOTE: Large electrodes tend to trap air pockets between the separator and the electrodes as they curl upon addition of the electrolyte. These air pockets need to be removed to ensure proper contact of the separator with the electrodes. The air bubbles increase the impedance of the cell and inhibit ion transfer.</li>
		<li>Add two drops (about 10 &#181;L) of electrolyte, one at 2 mm away from the cell sandwich and another one at the center of the electrode. Position the Sn exposed tip of the reference wire at the center of the electrode and the Li metal foil (encapsulated onto Cu wire) on the drop away from the electrode. The surface tension between the metals and the electrolyte drops hold the wires in position.</li>
		<li>Add one more drop (about 10 &#181;L) of electrolyte onto the Li metal after placing the wire in position.</li>
		<li>Remove additional air bubbles between the Li foil and the separator with the Teflon sweep. Add another 400 &#181;L of the electrolyte.</li>
		<li>Place a second separator aligned to the first separator such that both the reference wires are sandwiched between the two separators. Remove any additional air bubbles. 
		CAUTION: While placing the second separator, excessive tension can break the reference wires. Leave extra wire inside the cell to reduce tension in the wire.</li>
		<li>Wet the positive electrode with 400 &#181;L of the electrolyte. Place the electrode aligned with the negative electrode on top of the second separator.</li>
		<li>Place the stainless steel spacer onto the positive electrode carefully to not disturb the cell stack alignment. 
		NOTE: Misaligned electrodes result in inhomogeneous current distributions and reduced cell capacity due to reduced access of active cell area.</li>
		<li>Place two stainless steel wave springs on the puck to accommodate for cell volume changes and pressure build up which ensure proper electric contact between the electrodes and the fixture terminals. Close the fixture. Since the setup is not hermetically sealed, the tests are conducted inside the glove box in an inert atmosphere.</li>
	</ol>
	</li>
	<li>Record the data from the Li metal reference wire for individual electrode voltage profiles
	<ol>
		<li>Connect the auxiliary reference terminal of the cycler to the Li metal while the positive and negative electrode terminals of the cycler are connected to the respective electrodes. 
		NOTE: During the cycling of the cell, the cycler reads the potential difference between the positive terminal and the RE as Aux1 output and the negative electrode and the reference as Aux2. While the Li metal wire is connected, Aux1 and Aux2 are the potentials of individual electrodes with respect to Li metal.</li>
	</ol>
	</li>
	<li>Lithiate the Sn wire in situ to record electrochemical impedance spectroscopy (EIS).
	<ol>
		<li>Apply a constant current of 5 &#181;A for 6 h between the positive electrode and the Sn wire with an upper voltage cutoff of 4 V to electrochemically lithiate the Sn. The potential of Li/Sn alloy thus formed is close to that of the Li metal. Disconnect the terminals and allow the wire to equilibrate for 2 h. 
		NOTE: Ensure extremely low current (close to 0 A) in the circuit to confirm complete lithiation of the Sn wire.</li>
		<li>Alter cycler connections to Li metal to the auxiliary terminal of the cycler and Sn wire to the negative terminal of the cycler and ensure the reading of Aux2 close to 0 V. A lithiated phase of Sn is obtained, denoted as LixSn.</li>
		<li>Re-connect the positive and negative terminals of the cycler to the respective electrodes of the cell and the auxiliary terminal to LixSn wire.</li>
	</ol>
	</li>
	<li>Record EIS for (i) cathode vs.anode, (ii) cathode vs. lithiated Sn wire and (iii) anode vs. lithiated Sn wire. The impedance of (i) is the sum of the impedances obtained in (ii) and (iii). The potentiostat consists of two terminals to record the voltages and two for current outputs for each electrode.
	<ol>
		<li>To obtain the full cell spectra, connect voltage and current terminals to the respective positive and negative electrodes of the cell.</li>
		<li>For the positive electrode impedance, connect the voltage and current positive terminals (also known as working electrode, WE) to the positive electrode, and connect the negative terminals (also known as the counter electrode, CE) to the LixSn reference electrode.</li>
		<li>For the negative electrode impedance, connect the WE terminals to the negative electrode and connect the CE terminals to the LixSn reference electrode.</li>
		<li>To record the EIS, supply AC currents or varying frequencies to cycle the electrochemical couple between a small voltage amplitude (5 mV) and plot the impedance response as imaginary component vs. the real component.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

Figure 2a is the voltage profile of the full cell while Figure 2b and 2c show voltage profiles corresponding to the positive and the negative electrode vs Li/Li+ couple while the full cell is cycled between 3 and 4.4 V. It can be seen that as the full cell scans between 3 and 4.4 V, the positive electrode experiences voltages between 3.65 V and 4.45 V and the negative electrode between 0.65 V and 0.05 V vs. Li/Li+ ...

The demand for high energy densities from Li-ion batteries (LIBs) is driving research towards understanding fundamental factors that limit Li- ion cell performance1. High voltage operation of cells containing a new generation of layered transition metal oxide cathodes, graphite anodes and organic carbonate electrolytes is associated with several parasitic reactions2,3. Some of these reactions consume Li - ion inventory and often result in significant impedance rise of the cell4,5,6,7. Loss of Li- ion also results in a net shift of the surface potentials of electrodes. Monitoring of voltage changes on an individual electrode in a full cell versus a reference electrode (RE) can be performed in commercial 3-electrode cell designs8,9,10,11,12,13,14. Information pertaining to voltage profiles and the impedance changes on individual electrodes promotes a deeper understanding of the fundamental degradation mechanisms of a LIB. Conventional 3-electrode cells contain Li metal as a reference electrode, which facilitates a distinct understanding of the electrochemical processes at each electrode. Li-metal in contact with the organic electrolyte undergoes spontaneous surface modification and the contribution of this surface layer on Li cannot be quantified15. Several 3-electrode configurations such as (a) T-model, (b) a micro-RE positioned coaxial to both the working and the counter electrode, (c) a coin cell with an RE at the back of the counter electrode, etc. have been proposed earlier. Most of these cell configurations have the RE positioned away from the cell sandwich, generating significant drift in the impedance data due to low conductivity of the electrolyte. It has been proven that a RE with a stable potential throughout the measurement must be stationed in the center of the sandwich to ensure reliable impedance data.
In order to address these discrepancies, we have designed a cell setup involving a fourth RE16. An ultra-thin Sn plated Cu wire is sandwiched in between the electrodes of a battery that can be electrochemically lithiated in situ to form a LixSn alloy. As Sn undergoes lithiation, the voltage of the reference wire drops and a completely lithiated wire has a potential close to 0 V vs. Li+/Li17. The lithiated composition has a potential comparable to Li metal and the metastable alloys facilitate a stable potential during the time period of the measurement. A Li metal exposed to the electrolyte is prone to electrolyte decomposition products forming surface layers. An EIS measurement to probe the impedance of individual electrodes by collecting spectra between one of the electrodes and the Li metal reference as coupled have not been reliable due to the contribution of these layers on the impedance. Although electrolyte reduction is inevitable also on the Li-Sn surface, an in situ lithiated reference wire has the following advantages: (a) no constant electrolyte decomposition products as the voltage is always above the decomposition potential of the electrolyte unless lithiated ,implying no loss of Li inventory in the system to interfacial layers; (b) layers formed during lithiation of the Sn wire are over a very small area, providing negligible contribution to the EIS data; and (c) the formed products degrade as the Sn wire loses Li and the potential of the wire increases, resulting in lithiation of fresh Sn wire during every lithiation and thus formation of very thin interfacial layers every time instead of increased thickness of these layers. Spectra recorded with these alloys as reference provide more accurate and reliable data of the electrode impedance. We conducted tests with standard 2032-type coin cells and 4-electrode RE cells to validate our design. Results from these tests and our interpretation of the data will be used as a representative result to explain the efficacy of our protocol. The 3-4.4 V cycling followed a standard protocol, which included formation cycles, aging cycles, and periodic AC impedance measurements during the cycling. The coin cell measurements provide valuable information on the parameters such as cycle life, capacity retention, AC impedance changes, etc. RE cells enable monitoring voltage changes and impedance rise on individual electrodes. Our mechanistic understanding into the capacity fade and impedance rise can provide guidelines for the development of electrolyte systems and understand contributions for capacity loss from each electrode during high-voltage cell operation.
Our cells contained Li1.03 (Ni0.5Co0.2Mn0.3)0.97O2 (denoted here as NMC532)-based positive electrodes, graphite-based negative electrodes (denoted here as Gr) and a 1.2 M solution of LiPF6 in Fluoroethylene Carbonate (FEC):Ethyl Methyl Carbonate (EMC) (5:95 w/w) as the electrolyte. The electrodes used in this study are standard electrodes fabricated at the Cell Analysis, Modeling and Prototyping (CAMP) Facility at Argonne National Laboratory. The positive electrode consists of NMC532, conductive carbon additive (C-45) and polyvinylidene fluoride (PVdF) binder in a weight ratio of 90:5:5 on a 20 &#181;m thick Al current collector. The negative electrode consists of graphite, mixed with C-45, and PVdF binder in a weight ratio of 92:2:6 on a 10 &#181;m thick Cu current collector. Circular discs of 5.08 cm diameter were punched from the electrode laminates and the separators were punched with a 7.62 cm die for use in fixtures with 7.62 cm inner diameter. These electrodes were dried at 120 &#176;C and the separators at 75 &#176;C in a vacuum oven for at least 12 h prior to the cell assembly. A schematic representation of the fixture design is represented in Figure 1. Large fixtures and electrodes ensure minimum inhomogeneities in current distributions per unit area, thus, providing the least distortions in the impedance spectra. The 3-4.4 V cycling followed a standard protocol, which included two formation cycles at a C/20 rate, 100 ageing cycles at a C/3 rate and two diagnostic cycles at C/20. All battery tests were conducted at 30 &#176;C. Electrochemical cycling data was measured using a battery cycler and the electrochemical impedance spectroscopy (EIS) is performed using a potentiostat system.

<table><tbody><tr><td>Insulstrip 220</td><td>Ambion Corporation</td><td>081607-1</td><td></td></tr><tr><td>Sodium Hydroxide (23 wt%)</td><td>Ambion Corporation</td><td>1310-73-2</td><td>Contents of Insulstrip 220</td></tr><tr><td>Furfuryl Alcohol (10 wt%)</td><td>Ambion Corporation</td><td>98-00-0</td><td>Contents of Insulstrip 220</td></tr><tr><td>NCM523</td><td>TODA America</td><td>NM4100</td><td></td></tr><tr><td>C-45&amp;nbsp;</td><td>Timcal Inc.</td><td></td><td></td></tr><tr><td>polyvinylidene fluoride (PVdF)</td><td>Sigma Aldrich</td><td>427152</td><td></td></tr><tr><td>Sn over Cu wire</td><td>Kanthal</td><td>MELT # 24633</td><td>Custom ordered</td></tr><tr><td>Battery cycler</td><td>Maccor USA</td><td>Series 2300&amp;nbsp;</td><td></td></tr><tr><td>Potentiostat</td><td>Solartron Analytical</td><td>1470 E</td><td></td></tr></tbody></table>

in situ lithiated reference electrode: four electrode design for in-operando impedance spectroscopy

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate multiple processes responsible for long-term performance decay. Given the complexity of physical processes occurring inside the cell, it is often challenging to achieve a full understanding of the root causes of this performance degradation. This difficulty arises in part from the fact that any electrochemical measurement of a battery will return the combined contributions of all components in the cell. Incorporation of a reference electrode can solve part of the problem, as it allows the electrochemical reactions of the cathode and the anode to be individually probed. A variation in the voltage range experienced by the cathode, for example, can indicate alterations in the pool of cyclable lithium ions in the full-cell. The structural evolution of the many interphases existing in the battery can also be monitored, by measuring the contributions of each electrode to the overall cell impedance. Such wealth of information amplifies the reach of diagnostic analysis in Li-ion batteries and provides valuable input to the optimization of individual cell components. In this work, we introduce the design of a test cell able to accommodate multiple reference electrodes, and present reference electrodes that are appropriate for each specific type of measurement, detailing the assembly process in order to maximize the accuracy of the experimental results.

Figure 2 is a representative profile of the voltages of individual electrodes with 1.2M LiPF6 in (FEC):EMC (5:95 w/w) as the electrolyte during the first and second cycles of formation. Figure 3 shows the EIS spectra of the cell after three formation cycles and at the end of the cycle life ageing protocol. The ability to re-lithiate the RE to obtain EIS data aids in precise tracking of the impedance changes in individu...

Watch this Scientific Journal Video about In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy at JoVE.com

In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy

The incorporation of reference electrodes in a Li-ion battery provides valuable information to elucidate degradation mechanisms at high voltages. In this article, we present a cell design that accommodates multiple reference electrodes, along with the assembly steps to assure maximum accuracy of the data obtained in electrochemical measurements.

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate ...

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Research

JoVE Journal

Chemistry

8.7K Views.  Argonne National Laboratory. The incorporation of reference electrodes in a Li-ion battery provides valuable information to elucidate degradation mechanisms at high voltages. In this article, we present a cell design that accommodates multiple reference electrodes, along with the assembly steps to assure maximum accuracy of the data obtained in electrochemical measurements.

Video: In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Engineering

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries.
We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the &#8216;roll-over&#8217; cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

We describe the design and construction of an electrochemical cell for the examination of electrode materials using in situ neutron powder diffraction (NPD). We briefly comment on alternate in situ NPD cell designs and discuss methods for the analysis of the corresponding in situ NPD data produced using this cell.

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended solvent window, low background currents, corrosion resistance, etc., arise from the catalytically inert nature of the surface. However, if during the growth process, non-diamond-carbon (NDC) becomes incorporated into the electrode matrix, the electrochemical properties will change as the surface becomes more catalytically active. As such it is important that the electrochemist is aware of the quality and resulting key electrochemical properties of the BDD electrode prior to use. This paper describes a series of characterization steps, including Raman microscopy, capacitance, solvent window and redox electrochemistry, to ascertain whether the BDD electrode contains negligible NDC i.e. negligible sp2 carbon. One application is highlighted which takes advantage of the catalytically inert and corrosion resistant nature of an NDC-free surface i.e. stable and quantifiable local proton and hydroxide production due to water electrolysis at a BDD electrode. An approach to measuring the local pH change induced by water electrolysis using iridium oxide coated BDD electrodes is also described in detail.

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

A protocol is described for the characterization of the key electrochemical parameters of a boron doped diamond (BDD) electrode and subsequent application for in situ pH generation experiments.

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended ...

Voltage Biasing, Cyclic Voltammetry, &amp; Electrical Impedance Spectroscopy for Neural Interfaces

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays.

Voltage Biasing, Cyclic Voltammetry, & Electrical Impedance Spectroscopy for Neural Interfaces

The electrode-tissue interface of neural recording electrodes can be characterized with electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Application of voltage biasing changes the electrochemical properties of the electrode-tissue interface and can improve recording capability. Voltage biasing, EIS, CV, and neural recordings are complementary.

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive ...

Neuroscience

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Three-electrode cells are useful in studying the electrochemistry of lithium-ion batteries. Such an electrochemical setup allows the phenomena associated with the cathode and anode to be decoupled and examined independently. Here, we present a guide for construction and use of a three-electrode coin cell with emphasis on lithium plating analytics.

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and ...

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries of the metal. Using this method, a crack free, thin-film macroelectrode surface with up to 40 times increase in active surface area was obtained. The roughening is easy to do in a standard electrochemical characterization laboratory and incudes the application of voltage pulses followed by extended application of a reductive voltage in a perchloric acid solution. The protocol includes the chemical and electrochemical preparation of both a macroscale (1.2 mm diameter) and microscale (20 &#181;m diameter) platinum disc electrode surface, roughening the electrode surface and characterizing the effects of surface roughening on electrode active surface area. This electrochemical characterization includes cyclic voltammetry and impedance spectroscopy and is demonstrated for both the macroelectrodes and the microelectrodes. Roughening increases electrode active surface area, decreases electrode impedance, increases platinum charge injection limits to those of titanium nitride electrodes of same geometry and improves substrates for adhesion of electrochemically deposited films.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries ...

A Method for Systematic Electrochemical and Electrophysiological Evaluation of Neural Recording Electrodes

New materials and designs for neural implants are typically tested separately, with a demonstration of performance but without reference to other implant characteristics.&#160;This precludes a rational selection of a particular implant as optimal for a particular application and the development of new materials based on the most critical performance parameters.&#160;This article develops a protocol for in vitro and in vivo testing of neural recording electrodes.&#160;Recommended parameters for electrochemical and electrophysiological testing are documented with the key steps and potential issues discussed.&#160;This method eliminates or reduces the impact of many systematic errors present in simpler in vivo testing paradigms, especially variations in electrode/neuron distance and between animal models.&#160;The result is a strong correlation between the critical in vitro and in vivo responses, such as impedance and signal-to-noise ratio.&#160;This protocol can easily be adapted to test other electrode materials and designs.&#160;The in vitro techniques can be expanded to any other nondestructive method to determine further important performance indicators.&#160;The principles used for the surgical approach in the auditory pathway can also be modified to other neural regions or tissue.

Different electrode coatings affect neural recording performance through changes to electrochemical, chemical and mechanical properties. Comparison of electrodes in vitro is relatively simple, however comparison of in vivo response is typically complicated by variations in electrode/neuron distance and between animals. This article provides a robust method to compare neural recording electrodes.

New materials and designs for neural implants are typically tested separately, with a demonstration of performance but without reference to other implant ...

A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed by rinsing and supercritical drying steps, often resulting in mechanically fragile materials. Here, a method to synthesize nanostructured porous platinum-based macrotubes and macrobeams with a square cross section from insoluble salt needle templates is presented. The combination of oppositely charged platinum, palladium, and copper square planar ions results in the rapid formation of insoluble salt needles. Depending on the stoichiometric ratio of metal ions present in the salt-template and the choice of chemical reducing agent, either macrotubes or macrobeams form with a porous nanostructure comprised of either fused nanoparticles or nanofibrils. Elemental composition of the macrotubes and macrobeams, determined with x-ray diffractometry and x-ray photoelectron spectroscopy, is controlled by the stoichiometric ratio of metal ions present in the salt-template. Macrotubes and macrobeams may be pressed into free standing films, and the electrochemically active surface area is determined with electrochemical impedance spectroscopy and cyclic voltammetry. This synthesis method demonstrates a simple, relatively fast approach to achieve high-surface area platinum-based macrotubes and macrobeams with tunable nanostructure and elemental composition that may be pressed into free-standing films with no required binding materials.

A synthesis method to obtain porous platinum-based macrotubes and macrobeams with a square cross section through chemical reduction of insoluble salt-needle templates is presented.

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed ...

In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy

Summary

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Chapters in this video

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

Voltage Biasing, Cyclic Voltammetry, & Electrical Impedance Spectroscopy for Neural Interfaces

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

A Method for Systematic Electrochemical and Electrophysiological Evaluation of Neural Recording Electrodes

A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes