Making Lithium-ion Battery Energy Storage Systems: A Primer

Summary: Various lithium-ion battery chemistries, when combined into a battery energy storage system (BESS), create powerful energy solutions that have a multitude of applications in stationary as well as e-mobility markets. Herein a basic discussion on the components, the risks and what to look out for for those interested in understanding better this key piece of the energy storage revolution.

About the author: Carlos St. James is a board member of Austin, Texas-based CleanTX, a non-profit that promotes advancement of clean energy solutions across the state of Texas, and is a board member of the Washington, D.C.-based Latin American & Caribbean Council on Renewable Energy (LAC-CORE). In the last decade he has spoken in over three dozen countries across five continents on clean energy issues at international conferences, and publishes the Clean Energy Review to help generate debate on the industry’s issues. This is his 45th article in five years. He works at Voltabox of Texas, Inc., which manufactures lithium-ion energy storage solutions.

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Understanding lithium-ion batteries requires a quick glance at the periodic table first.

Lithium (top left of the periodic table, atomic number 3 in the image below) is the lightest of all metals, has the greatest electrochemical potential and provides the largest energy density for its weight. That’s why it’s preferred for batteries. But because lithium batteries cannot be recharged (lithium batteries are the ones typically sized and shaped like coins), lithium-ions are used, where electron transference takes place. The moving of electrons from cathode to anode and back is what causes discharge and recharge of a battery.

Lithium-ion batteries are rechargeable and made in combination with several different elements, creating cell chemistries such as nickel manganese cobalt (known as NMC); lithium iron phosphate (LFP); nickel cobalt aluminum (NCA); lithium cobalt oxide (LCO); and many more. Lithium-ion combines very well with the first row of the Transition Metals to create the most viable batteries. These are circled in blue above. Specifically, iron (Fe), cobalt (Co) and nickel (Ni) are known as the “Iron Triad”: they can create a large magnetic pole due to their unpaired electrons and can engage with lithium-ions productively and powerfully -- but each giving the combo slightly different traits. Understanding those traits and putting them to optimal use is the job of a battery energy storage system (“BESS”) designer-manufacturer.

Cell chemistries

Much is made of cell chemistries and their different performance attributes. Check out the image below, which uses a spider graph to compare in basic terms NMC, LMO, NCA, and others in attributes such as energy, discharge power, cost, longevity, safety, etc. This graph suggests that, for example, lithium-ion NCA battery chemistry has among the best Discharge Power but is also expensive (relative to the others). Do you love Tesla’s impressive Ludicrous Mode acceleration? Give thanks in part to their use of NCA batteries.

That’s all well and good -- but it is also an over-simplification. Battery cell performance is actually affected by at least five key factors:

1. cell chemistry
2. cell geometry: round, prismatic or pouch are the most common options
3. quality of cell manufacturing
4. matching of the chemistry and geometry to its application
5. the overall integration of the system (a.k.a., the Battery Energy Storage System, “BESS”, sometimes shortened to just “ESS”)

The manufacturing process: where quality begins

The starting point for a BESS are the cells. In your search for a BESS designer-manufacturer to help you incorporate energy storage into your business model, seek out those that are “chemistry agnostic”, i.e., do not manufacture the battery cells in addition to the BESS. Otherwise you run the risk of unwittingly having excess inventory shoved down your throat -- to your detriment. It is also important that your BESS manufacturer have employees that travel to battery cell manufacturing facilities to participate in quality audits and know the processes of all battery cell suppliers.

"... seek out [BESS designer-manufacturers] that are 'chemistry agnostic'. Otherwise you run the risk of unwittingly having excess inventory shoved down your throat -- to your detriment."

Battery manufacturing is comprised of four major steps:

• Electrode production (anode and cathode): Are raw materials of the right purity and humidity levels acceptable? Is equipment well calibrated? Are the foils used for cathodes and anodes (aluminum foil used for cathodes and copper for anodes) of consistent thickness?
• Cell stack assembly: How well are the two foils separated, and were they all properly assembled?
• Drying and electrolyte filling: How long are the cells baked to eliminate humidity? Here is where cells are graded and defective cells are (ideally) eliminated
• Assembling the cells: How well have they been tested and what is their quality control process?

Matching cell uses to their applications

This is the area where much of the initial creativity takes place, where engineers become alchemists yet use software programs to delineate boundaries. I’ve worked with them upon receiving requests to help convert research submarines to battery-powered; to have stationary storage placed high in the Andes mountains at temperatures that challenge a BESS; to create systems with sufficient thrust to launch airplanes; to convert gantry cranes at seaports and amusement park rides to lithium-ion; to create storage solutions to take advantage of electricity price arbitrage opportunities; and to similarly convert tow tractors, mining equipment, locomotives and ferries to lithium-ion.

The possibilities are endless. Each of these has unique demands, often unusual space constraints, sometimes rapid charge/discharge needs, all of which require a lot of creativity to determine ideal solutions, the necessary standards, and addressing thermal concerns. A good BESS designer-manufacturer will ask as many questions as possible in the early stages to allow for the selection of the best possible solution and because often the clients themselves aren’t clear on their own needs. And of course, there’s usually a target price point (typically set in dollars per kilowatt-hour) to meet.

The battery energy storage system (BESS)

A BESS is comprised of various components:

1. The right battery cells for the application
2. A bi-directional power conversion system (i.e., an inverter) if supplying AC power
3. An intelligent electronic control system, which informs the inverter on charge and discharge and incorporates safety features and triggers
4. The thermal management system (TMS), which keeps the BESS within approved temperature ranges; and
5. An enclosure to house all of this in a shape in accordance with the application’s constraints and with the appropriate ingress protection from dust, accidental contact and humidity.

Manufacturing and assembling a BESS is all about precision. When looking for a BESS manufacturer to provide you with a complete storage solution, the more automation involved the better. Why? Because the slightest variation can lead to weaknesses in the BESS and increase chances of a thermal event. The ideal BESS manufacturers use robotics to assemble battery cells into modules so they are each done with the greatest consistency possible. Repeatability is the watchword. Using automated laser welding equipment further ensures consistency and quality. The last thing you want is to have this done by hand, where a welder’s mood, weariness and a host of other variables all but ensure lower quality and increase risk. Some companies in low-cost labor countries still use this method.

Regarding Thermal Management Systems (TMS)

Batteries are a form of concentrated energy. The speed with which batteries get discharged (or re-charged) can cause rapid increases in their temperature, which in turn is a function of several other variables including the battery chemistry, the quality of the cells, etc. TMS options include the simpler air cooling to the more complex liquid cooling, and coupled with this are fire suppression mechanisms for further protection. Within each of these there are numerous options. Each cell chemistry has its own optimal temperature range limits that must be adhered to, and the application itself informs the type of TMS required.

Regarding enclosures

What the BESS will be used for determines the enclosure needed. Plastic, aluminum and steel are common. Standardized ratings for solid and water ingress have been established. For example, if the storage solution will be used in the desert adjacent to a solar power plant to create hybrid solar power, you may need to seek a solution rated to IP51 standard (see image below): very well protected from dust (the number 5) but with minimal protection against water (the number 1).

With respect to shock and vibration compliance, your requirements will be very different if it’ll be a stationary application in the desert like the example above, or used in underground mining to power giant drills -- or if it’ll have military applications where it needs to be used off-road and be literally bullet- and shrapnel-proof. (I mention these because in the last year alone we’ve had these requests.) There are at least three commonly used tests along these lines for battery systems: UN 38.3; ISO 12405-1, and SA J2380. Make sure you get the one you need.

Conclusion

My employer, Voltabox of Texas, Inc., is a German-owned designer-manufacturer of battery energy storage systems (BESS’s) tailored to clients’ needs. Given how young the storage industry still is and its rapid evolution, we spend a lot of time educating clients. It is rare to find one that is very clear on what they need. Our job is to help them figure it out and then design and manufacture the best solution at a specific target price.

Voltabox is chemistry agnostic, meaning that we aren’t beholden to any cell manufacturer. Our manufacturing facilities are fully automated and a pleasure to show off: robots and laser welders everywhere, ensuring consistent high quality throughout. We also have operations in China and staff that travels to audit and review quality processes at battery cell manufacturers – which are usually in Asia. Our Chief Technology Officer brings a wealth of experience and a keen sense of what the storage future looks like. We have German (read: strict on safety and procedures) parentage, are led by executives with an abundance of international energy experience, and have young engineers on staff well-schooled on the latest storage technologies and practices. Our employees take pride in knowing the reduction in global CO2 emissions resulting from our products. I welcome requests for information; please contact me at carlos.stjames@voltabox.com.

? Clean Energy Review 2020

This report has been prepared by Carlos St. James for the Clean Energy Review. The views expressed on this site are his own and do not necessarily reflect the views of Voltabox of Texas, Inc., its affiliates or business partners, nor of CleanTX, its affiliates or members. This report has no regard to the specific investment objectives, financial situation or particular needs of any specific recipient. It is published solely for informational purposes and is not to be construed as a solicitation or an offer to buy or sell any securities or related financial instruments. The report is based on information obtained from sources believed to be reliable but is not guaranteed as being accurate, nor is it a complete statement or summary of the securities, markets or developments referred to in the report. The report should not be regarded by recipients as a substitute for the exercise of their own judgment. Any opinions expressed herewith are subject to change without notice and the Clean Energy Review is not under any obligation to update or keep current the information contained herein. The Clean Energy Review accepts no liability whatsoever for any loss or damage of any kind arising out of the use of all or any part of this report. Additional information will be made available upon request.