Batteries commonly have two electrodes: anode and cathode. Ions travel through the separator to either electrode during the charge and discharge cycles and release energy in the process.
Battery test cells can be built to include a third electrode. This is known as the reference electrode (RE). The RE allows for greater analysis of battery performance as it decouples test results between anode and cathode.
When researching battery materials, the use of a reference electrode (RE) allows researchers to measure and differentiate the contribution of each component of the cell to its overall performance. Three-electrode experiments help identify which electrode (anode or cathode) limits the cell performance during long-term testing. It is important to identify how each electrode is contributing to cell degradation under various test conditions instead of blindly experimenting with one or both.
Why is this important?
Most all electrochemical experiments and battery tests provide greater understanding of the cell when the anode and cathode results can be decoupled through use of a reference electrode. This extends to what are traditionally considered “industrial” applications as well. The dynamic charge-discharge profiles and fast charge simulations associated with commercial devices and electric vehicles can draw unique performance from a battery compared to low-rate constant current cycling.
Three-electrode testing is also beneficial for evaluating battery safety. Minter and Juarez-Robles highlight how fast-charging, which is a highly sought characteristic for electric vehicles, creates a great need to detect and monitor lithium plating occurring on a cell anode. [Minter RD, Juarez-Robles D, et al 2018 J Vis Exp., (135):57735.] This can best be achieved using a three-electrode cell during testing.
One fundamental goal of battery research is to develop cells that are long-lasting. This is especially important for electric vehicle and grid storage applications where the commercial cells and battery packs must last thousands of cycles and up to 10 years. Three-electrode testing allows researchers to identify the limiting factor in their cell to focus attention where improvement is needed most.
How the reference electrode is used in different testing situations
- During HPPC test, which are common for electric vehicle applications, the use of a reference electrode reveals electrode polarization.
- Performing EIS shows the decoupled impedance from anode and cathode individually when a three-electrode cell is utilized.
- The individual contribution of anode and cathode is revealed when demonstrating lithium loss due to SEI growth as a dominant aging mechanism.
- Differential capacity analysis can reveal changes in the voltage profile of anode and cathode and how they individually contribute to cell degradation.
The obstacles in creating a stable and reliable three-electrode cell
Comparing results from a new three-electrode experiment to other published results needs to keep as many variables consistent as possible, such as electrode size, material amount, cell uniformity, etc., or else attempt to normalize results. This is a principal reason why traditional cell types are modified to incorporate a reference electrode as “homemade” cell, so results are easier to compare with minimal normalization. Researchers wish to demonstrate and compare their results to existing two-electrode data of the same cell type (cylindrical, pouch, coin). However, since most battery material work is conducted using coincells, this is the natural choice for three-electrode experiments to compare the new results with the vast amount of tradition two-electrode data in publication. The new experimental data will decouple the anode and cathode and provide new insights.
Other commercial three-electrode cells such as Swagelok-style or split cell designs are costly and not practical to implement and scale, and can sometimes to complicated to build and use. Test results from these types of cells must also be normalized when comparing with traditional battery formats (coin, cylindrical, pouch, etc.).
Arbin’s three-electrode test cell configuration and its benefits
The novel “3E” coincell has the same surface area as a traditional CR2032 coincell and makes it ideal for comparing results across all published coincell data. It provides users with the ability to rapidly prototype new materials by performing large-scale three electrode testing. Traditional methods have proven too expensive and provided inconsistent results. Arbin’s new 3E Coin Cell provides users with an affordable, easy to use three-electrode cell holder that allows for long-term cycling, and provides consistent results between samples. The low unit cost, disposable design, and easy-to-build coin cell structure allows users to quickly build a large number of cells for materials research testing. The 3E Coin Cell interfaces with Arbin’s 3E Coin Cell Holder, and connects directly with our MSTAT product series
The alternative solutions for decoupling test results between anode and cathode described in sections above exist because this data has the ability to expedite battery research and development and bring new battery chemistries to market faster.
Arbin’s latest generation of LBT and MSTAT high-precision battery test equipment has attracted attention from both academic and industry researchers due to its ability to also expedite the battery development process. 24-bit resolution, extreme precision, and state-of-the-art thermal management that are standard with Arbin produce more detailed and consistent results than other battery testers. This has led multiple industry partners to team up with Arbin on collaborative projects including ARPA-E grants. General Motors has permitted Arbin to license and commercialize a new three-electrode cell design that can further enhance and accelerate their battery testing program.
A battery intended for a smartwatch should be tested with a slow and steady discharge profile that mimics the watch’s energy use in actuality. Conversely, a battery intended for larger applications such as electric vehicles, should be tested with dynamic test profiles that simulate how a car is used and driven. Battery test equipment should be able to test cells in a way that can accurately examine the cell with regards to its intended application. For instance, Arbin’s Regenerative Battery Testing (RBT) series is designed specifically for high-power batteries used in applications such as electric vehicles, military and stationary grid storage.
All of Arbin’s equipment is designed around the principles of flexibility, safety, and dependability. Learn more about the key features of our RBT series below.
- Made for high-power applications
The RBT series is designed to test large battery packs. Providing wide voltage and current ranges and a high power range of up to 1MW.
The simulation control feature of the RBT allows the system to charge or discharge according to a dynamic test profile. For electric vehicles, this would mean importing a drive profile that mimics how energy and power demand changes during a drive. In an application such as grid storage, the test profile could mimic how the grid would collect and release energy throughout a certain period of time. The ability to conduct tests in this way is important to see how the switching between charging and discharging or the fluctuations in power requirements would affect the battery pack. Making use of true bipolar circuitry, there is no switching time between charging and discharging, meaning that more accurate simulations can be achieved. Each system is also built to run continuously at maximum power so there is no fear of overpowering the system if tests need to be run at high power for long periods of time.
- Easy to program and collect data
Testing systems come with a PC equipped with MITS Pro, Arbin’s software package. The software is completely user-friendly and programming dynamic test profiles is simple. A text profile of time-vs-power or time-vs-current data in .xlsx, .csv, or .txt formats can be directly uploaded to the system. The system can safely handle thousands of data points to run your desired simulation.
Test profiles are completely customizable and easily programmed using dropdown menus. Parameters for different experiment controls such as current, voltage, power, load, and many others can be input directly into the system. All testing channels are completely independent but can also be combined to operate in parallel.
Data can be logged based on changes in Time, Current, or Voltage; data analysis and plotting tools are based in accessible programs such as Data Watcher and Microsoft Excel.
The goal of Arbin’s software is to simplify and streamline the testing process so users can get the most accurate and precise results.
- The system has built-in safety features
Accidents or mishaps in battery testing can be dangerous. Circuit overloads, overheating, overcharging or over-discharging are problems that can occur during testing. MITS Pro also allows users to program safety limits for current, voltage, total power and more. Once a channel reaches the set limit, the system enters a rest state for a period of time, or halts the test altogether.
The system is also equipped with an emergency stop button and multiple levels of fusing to protect it from unintentional misuse. The equipment has onboard microcontrollers that will stop tests if there is a failure that poses a risk. These features are crucial in halting any problems as they arise, ensuring a safe testing environment.
- An economical and efficient solution
One special feature of the RBT system is its use of regenerative circuitry to discharge power back to the grid. The system is able to send power back to the grid with >95% efficiency, making it a more economical solution by decreasing the net energy consumption of the system. This also helps facilitate the overall cooling process by reducing heat dissipation.
The discharge power is also cleaner than before with the total harmonic distortion as low as 3%.
- Customizable to meet your needs
There are multiple auxiliary options that can be added to the RBT system to fit your testing needs. Extra options would allow users to better monitor individual cells within a pack. Temperature measurement channels and temperature chamber interfaces are available, which would give users more flexibility in measuring and controlling temperature during testing. CAN-bus communication is an option to test battery packs with integrated Battery Management Systems, which can help communicate valuable messages to the MITS Pro software. Digital or analog input/output modules can further help control testing procedures.
A comprehensive system that provides easy to use features greatly facilitates the testing process. High-power dynamic applications especially require strong and power-efficient equipment to conduct meticulous and rigorous testing and ensure safe procedures.
Using a reference electrode, or RE, is critical in the research of battery materials. It allows researchers to measure and differentiate the contribution of each component in the cell to the cell’s overall performance, providing a clearer picture of the cell.
To find which electrode, either the anode or cathode, limits the cell performance during long-term testing, three-electrode experiments are particularly useful, preventing wasted time and resources blindly testing one electrode or the other under various conditions to find a meaningful result.
To that end, coincells are the more common format for early materials development. Faster development can be achieved by decoupling test results between positive and negative electrodes, since each can be evaluated simultaneously in the context of the full cell.
Arbin’s Three-Electrode Coincell Test Solution
Arbin has developed its MSTAT with 3-Electrode Package to make this critical process as easy as possible.
The MSTAT features 4-64 channels, a -5 to 5V range, a 5A max current, and optional EIS and multi-chamber functionality.
Each channel is an independent potentiostat/galvanostat, giving you full control of test profiles and data logging. In this way, Arbin’s solution delivers unmatched flexibility and agility.
In addition, the MSTAT features holders that plug directly into the unit, an overall compact and easy-to-use design, cells that include case, cap and gasket, SS316 stainless steel construction, and optional nickel coating.
The Arbin complete three-electrode test solution includes the MSTAT, patented thee-electrode kits, the MZTC Multi-Chamber and integrated EIS.
Primary applications for Arbin’s solution include life-cycle testing, dQ/dV and Coulombic Efficiency measurements, PITT/GITT, symmetric-cell testing, cyclic and linear sweep voltammetry, chronoamperometry, and more.
Offering higher resolution, improved software algorithms, new methods of temperature management, a patented shunt design, new time-keeping methods and improved materials, Arbin’s solutions offer precision that’s critical for long-term battery testing and projections.
Arbin’s Solution Delivers Results
By leveraging Arbin’s complete three-electrode testing solution, you can get clear, accurate and efficient results.
Utilizing the aforementioned decoupling of test results for anode and cathode, you can immediately reveal which one is the limiting factor in your cell, delivering an actionable insight you can use to move forward.
In short, Arbin’s Three-Electrode Coincell Kits and Holders are a major time-saver for material development, combining performance and functionality you can count on with speed that leads to more optimal results.
In the following graphs, you can see results for CC-CV Cycling testing delivered by the Arbin MSTAT:
These graphs highlight results delivered by Arbin’s three-electrode kits regarding electrode performance:
With the Abrin MZTC Multi-Chamber, you can monitor temperature and test time of the equipment:
And, finally, integrated EIS solutions provide thorough insights through galvanostatic testing:
Ready to learn more about Arbin’s solutions for materials research and how they can improve your operations? Visit arbin.com/products/materials-research/ today, call 979-690-2751 or reach out to email@example.com.
Test equipment should facilitate rather than frustrate the testing process. Good equipment allows researchers to pick up the smallest of changes during the experiment. Durable and reliable equipment have a mixture of qualities that work together for an accurate and efficient testing process. Outlined below are 5 key features of good battery testing equipment.
- High resolution Resolution refers to the smallest change in measurement that can be detected by the equipment’s sense and control circuitry. Higher resolution allows for higher clarity in the data. For instance, Arbin’s equipment has 24-bit resolution, compared with the industry standard of 16-bit. This allows the slightest changes in voltage and current to be visible to a greater number of digits. This is crucial as significant changes and patterns in measurement would be missed with lower resolution equipment.
- High Precision High precision equipment means that there is less noise/fluctuation in the equipment’s measurement. Precision also indicates the consistency and repeatability of the instrument’s measurement circuitry. Miniscule changes in the data are lost when there is too much noise. The lack of precision also prevents consistent and repeatable results from experiments. This makes it extremely difficult to see trends early in the cycle life, and see the differences between early cell degradation.
- Accuracy Accuracy refers to the trueness of the test equipment measurement. In other words, the closeness of the average sample to its true value. Good accuracy is best evaluated when the equipment also has high resolution and precision. Without the clarity and clean readings, the accuracy specification alone is much less meaningful.
- Minimal temperature fluctuations The temperature of the test equipment will inevitably affect its measurement. Good equipment minimizes this impact. Temperature stabilization is achieved through the design of the equipment. For example, Arbin’s equipment makes use of shunt designs and high quality materials that are resistant to temperature fluctuations. Internal thermal control mechanisms also isolate sensitive components and tightly regulate temperature. Since temperature is a component that greatly affects the functioning of a battery, these features that regulate temperature are essential in maintaining control over the testing process. Temperature fluctuations are easily visible with high resolution and high precision equipment, allowing researchers to catch these changes.
- Robust Materials As with any research equipment, ones made with quality material and quality construction stand the test of time. Reliable battery test equipment is resistant to corrosion and temperature and can hold calibration well. Since battery-testing can be quite long-term, reliable equipment should be able to stay consistent throughout the entire testing process. Equipment that fails or breaks down in the middle of the testing cycle will greatly hinder the research and development process.
The benefits of high quality battery test equipment High quality test equipment is needed to accelerate the battery development process. Industries like the Electrical Vehicle (EV) industry benefit greatly from high precision test equipment like Arbin’s that can detect the smallest differences between cells and materials early in the cycle life. EV batteries are projected to last 8-10 years, but a long test cycle slows down the development process. EV batteries can then fall behind the development speed of the other parts of the vehicle. Reliable, high-precision test equipment allow researchers and manufacturers to accelerate the testing and development process, and allow them to advance faster with materials research and battery development.
High quality test equipment accelerates development by providing reliable and precise data for the research process. All the above features are complementary and work best together. For more in depth information on how to evaluate battery test equipment click here.
Why researching Electric Vehicles batteries has never been safer
Advancement in battery testing equipment has made the process of battery testing safer. With more [precise and accurate testing equipment], the smallest changes in a battery can be detected before it becomes a critical issue. Improved equipment also allows for a more stable and controlled testing environment, making the [research and development process] much more efficient.
The safety concerns with EV batteries
While electric vehicles (EV) have been on the road for a while, questions regarding the battery’s stability and safety still come up. A few of the major, key issues with EV batteries are flammability, gases, and trauma to the battery cell.
As with any device that uses lithium-ion batteries, flammability is a huge concern with EV batteries. There have been cases where EVs have experienced thermal runaway events with catastrophic failures. Battery fires require special equipment to extinguish, and if one’s not careful, the batteries can reignite even after the fire is put out.
Common electrolytes found in batteries are mixtures of carbonates and a dissolved salt. In the event of a thermal runaway, decomposing electrolytes lead to a formation of gases within the cell, increasing pressure within the battery, leading to the release of toxic gas.
Trauma and impact to the battery pack can also greatly affect its capabilities and compromise its stability and safety. EVs have been reported to spontaneously combust days after being in an accident, showing how the risks are real if batteries are not properly monitored. This is equally true during testing; even in a lab environment.
How Arbin’s equipment is designed to test EV batteries
Arbin’s equipment allows batteries to be tested using dynamic cycling. Traditional batteries are mainly tested with constant current charge/discharge profiles. On the other hand, EV batteries need to charge and discharge dynamically, based on the car’s action.
Arbin’s systems make putting the battery through a dynamic cycle easy. Using [Arbin’s software], standardized test profiles, such as USACB's FUDS profile can be easily uploaded into the testing system, allowing batteries to be safely and efficiently tested according to regional, national, and international standards just by uploading a text file of time-vs-power or time-vs-current data to simulate the drive cycle. [LEARN MORE] High quality and precise testing equipment detect the slightest change in the battery, allowing researchers to detect any issues early on in the testing process and know better what materials and situations affect battery health and life. Researchers can catch these changes and make appropriate adjustments to the battery before it becomes a critical issue. It also allows manufacturers to create comprehensive safety guidelines for use of the battery. Battery test equipment from other manufacturers has been shown to significantly average the output of a dynamic drive profile and fails to accurately reproduce the real-world requirements.
It is also possible to have the EV battery pack’s battery management system (BMS) fully control the Arbin tester charge/discharge via [CANBus protocol]. This software is not limited to cutoff limits or safety conditions like other brands of test equipment, but can also be used as dynamic control values.
Temperature stability is also key in testing EV batteries. As mentioned before, overheating batteries is a serious safety hazard. Creating a stable thermal environment in which batteries can be tested is crucial to safe testing. It is also imperative to contain any problems in the event of a thermal runaway or cascade failure so as not to affect other batteries within the test chamber.
[Arbin’s multi-chamber equipment] isolates each battery cell or pairs of cells during testing, creating a safer and contained test environment that maintains temperature stability. Each chamber is thermally isolated and can have its own unique temperature set point so as to keep batteries from affecting each other during testing. This is a safer and more accurate testing method to see how temperature affects batteries.
Batteries are a critical component of the increasing global need for energy storage, including electric vehicles. Thus, testing processes must be able to meet the demands of the research needed for the technology to develop. Better testing equipment not only accelerates the testing process, allowing manufacturers to innovate and improve at a greater speed, but also makes testing and the creation of batteries safer overall.
A recent [Nature] publication from researchers at Stanford University, MIT, and Toyota describes how machine learning models can be used to predict the useful life of advanced lithium-ion and any future "next-generation" battery chemistry. [News Article from Stanford] The research team used Arbin battery test equipment over the past two years for the on-going study.
About the Battery Research Project
Batteries were tested to end-of-life and then machine learning was used to analyze the Arbin data and develop algorithms to predict battery life based on early cycles. Charge-discharge cycling to end-of-life can take months or years for advanced chemistry batteries comprising many thousands of cycles. It is a slow and costly phase of the battery research and development process. Expediting this process by identifying key metrics and indicators in the data during early cycles (<100) is critical to reduce the time required for battery development. Beyond material development and cell-grading, these evaluation testing techniques can also be used to evaluate fast-charge protocols, which is the next phase of the research project.
The joint team has published data that is available publicly [https://data.matr.io/1/].
Arbin [LBT test equipment] and [cell holders] were used along with temperature chambers.
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Why Arbin is Most Suitable for This Level of Battery Research
Previous research has been done using coulombic efficiency as the primary metric to predict battery end-of-life [Source]. Arbin was involved in a 3-year [ARPA-E project] from 2012 through 2015 with Ford Motors and Sandia National Lab to develop a new generation of high-precision battery test systems that are capable of performing meaningful coulombic efficiency calculations on high-current cells. This technology has been implemented across [Arbin’s cyclers] and is available to researchers worldwide.
The new findings from the team at Stanford, MIT, and Toyota is another breakthrough that has utilized Arbin’s 24-bit resolution and superior measurement precision. Arbin has also recently developed a new [cell-isolating thermal safety chamber], "MZTC," that has 8 independently controlled mini-chambers in 1. It allows greater temperature uniformity by isolating individual or small sets of cells that can reduce the error calculation and further improve the machine learning algorithms to evaluate battery life. It also provides a safer environment when testing cells at high c-rates.
Arbin is committed to providing the best test equipment as a tool for researchers because we understand the import role energy storage plays in our everyday life and future. Battery test equipment is available for [materials research applications], up to [commercial cell testing at high c-rates]. [Arbin’s cell-isolating thermal safety chamber] also provides a greater temperature stability and uniformity than a traditional large chamber can provide.
Arbin is expanding in 2019 to increase production line testing capability. Dozens of new input power lines have already been installed in our 65,000 sqft. headquarters in Texas.
There has been extreme demand for our high-power battery testing systems and we are working hard to keep up.
Batteries are a critical component of many products, and energy storage plays a very active role in our lives even outside of the research/industry setting. Therefore, selecting the right battery test equipment is an important decision for companies and the individual researchers who are responsible for producing results, whether they are starting small, or at massive scale.
The expert engineers at Arbin have been advancing the benchmark of “state-of-the-art” battery test equipment for over 27 years. We are defined by innovation, from being the first to apply multiple current ranges on a single test channel to more recently being the only company to offer true high-precision testing for high current applications, and supporting “Turbo Mode” with smart battery modules. We continue to learn from our industry partners and work with them on key technology breakthroughs.
The following report shares some of this knowledge using plain terminology and illustrations. Here are five key topics to consider when choosing battery test equipment:
1. Hardware - Specifications & Quality of Materials [Continue Report Preview]
2. Software - Usability and Features
3. Data - Logging, Management, and Analysis
4. Options - Auxiliary Features and Accessories
5. Support - Product Safety and Support
All battery test equipment requires software to operate the instrument. The software interface can be one of the main differentiating points besides hardware performance. It is important to confirm the software communicates using a modern high-speed standard such as TCP/IP (Ethernet) protocol and whether high-performance microcontrollers are used internally. This helps future-proof the system as well as meet the bandwidth necessary for fast data logging.
A software user interface should use familiar commands and follow a logical process to create tests, but also needs the flexibility to control advanced test protocols. The best software will not restrict the researcher to pre-defined test parameters, but will give full authority over the equipment’s voltage and current control. The following questions will help identify a complete feature-set:
Are capacity and energy calculations made at the micro-controller level or post-processed data?
- Is there a limit on the number of steps per test?
- How can an EV drive profile be performed?
- Do tests utilize branching and looping conditions?
- Can tests utilize multiple condition like this for each step and combine logical functions?
- Can tests use mathematical functions?
- Can the software use meta-variables instead of numeric values only, such as stopping a test based on
“80% discharge capacity” instead of only a numeric value?
- How many of these meta-variables are offered?
- Can tests be controlled using C-rate values instead of amperage if the cells under test vary in capacity?
- Can channels be connected in parallel to increase the current capability? If yes, then how many?
Arbin allows all these methods and more to apply dynamic and complete control of voltage, current, power, & load, and offers user-defined variables in addition to the 90+ standard meta-variables.