Batteries and performance. Batteries and performance

New High-Performance Solid-State Battery Surprises the Engineers Who Created It

Engineers created a new type of battery that weaves two promising battery sub-fields into a single battery. The battery uses both a solid-state electrolyte and an all-silicon anode, making it a silicon all-solid-state battery. The initial rounds of tests show that the new battery is safe, long-lasting, and energy-dense. It holds promise for a wide range of applications from grid storage to electric vehicles.

The battery technology is described in the September 24, 2021 issue of the journal Science. University of California San Diego nanoengineers led the research, in collaboration with researchers at LG Energy Solution.

Silicon anodes are famous for their energy density, which is 10 times greater than the graphite anodes most often used in today’s commercial lithium-ion batteries. On the other hand, silicon anodes are infamous for how they expand and contract as the battery charges and discharges, and for how they degrade with liquid electrolytes. These challenges have kept all-silicon anodes out of commercial lithium-ion batteries despite the tantalizing energy density. The new work published in Science provides a promising path forward for all-silicon-anodes, thanks to the right electrolyte.

1) The all solid-state battery consists of a cathode composite layer, a sulfide solid electrolyte layer, and a carbon free micro-silicon anode. 2) Before charging, discrete micro-scale Silicon particles make up the energy dense anode. During battery charging, positive Lithium ions move from the cathode to the anode, and a stable 2D interface is formed. 3) As more Lithium ions move into the anode, it reacts with micro-Silicon to form interconnected Lithium-Silicon alloy (Li-Si) particles. The reaction continues to propagate throughout the electrode. 4) The reaction causes expansion and densification of the micro-Silicon particles, forming a dense Li-Si alloy electrode. The mechanical properties of the Li-Si alloy and the solid electrolyte have a crucial role in maintaining the integrity and contact along the 2D interfacial plane. Credit: University of California San Diego

“With this battery configuration, we are opening a new territory for solid-state batteries using alloy anodes such as silicon,” said Darren H. S. Tan, the lead author on the paper. He recently completed his chemical engineering PhD at the UC San Diego Jacobs School of Engineering and co-founded a startup UNIGRID Battery that has licensed this technology.

Next-generation, solid-state batteries with high energy densities have always relied on metallic lithium as an anode. But that places restrictions on battery charge rates and the need for elevated temperature (usually 60 degrees Celsius or higher) during charging. The silicon anode overcomes these limitations, allowing much faster charge rates at room to low temperatures, while maintaining high energy densities.

The team demonstrated a laboratory scale full cell that delivers 500 charge and discharge cycles with 80% capacity retention at room temperature, which represents exciting progress for both the silicon anode and solid-state battery communities.

Silicon as an anode to replace graphite

Silicon anodes, of course, are not new. For decades, scientists and battery manufacturers have looked to silicon as an energy-dense material to mix into, or completely replace, conventional graphite anodes in lithium-ion batteries. Theoretically, silicon offers approximately 10 times the storage capacity of graphite. In practice however, lithium-ion batteries with silicon added to the anode to increase energy density typically suffer from real-world performance issues: in particular, the number of times the battery can be charged and discharged while maintaining performance is not high enough.

Much of the problem is caused by the interaction between silicon anodes and the liquid electrolytes they have been paired with. The situation is complicated by large volume expansion of silicon particles during charge and discharge. This results in severe capacity losses over time.

“As battery researchers, it’s vital to address the root problems in the system. For silicon anodes, we know that one of the big issues is the liquid electrolyte interface instability,” said UC San Diego nanoengineering professor Shirley Meng, the corresponding author on the Science paper, and director of the Institute for Materials Discovery and Design at UC San Diego. “We needed a totally different approach,” said Meng.

Indeed, the UC San Diego led team took a different approach: they eliminated the carbon and the binders that went with all-silicon anodes. In addition, the researchers used micro-silicon, which is less processed and less expensive than nano-silicon that is more often used.

An all solid-state solution

In addition to removing all carbon and binders from the anode, the team also removed the liquid electrolyte. Instead, they used a sulfide-based solid electrolyte. Their experiments showed this solid electrolyte is extremely stable in batteries with all-silicon anodes.

“This new work offers a promising solution to the silicon anode problem, though there is more work to do,” said professor Meng, “I see this project as a validation of our approach to battery research here at UC San Diego. We pair the most rigorous theoretical and experimental work with creativity and outside-the-box thinking. We also know how to interact with industry partners while pursuing tough fundamental challenges.”

Past efforts to commercialize silicon alloy anodes mainly FOCUS on silicon-graphite composites, or on combining nano-structured particles with polymeric binders. But they still struggle with poor stability.

By swapping out the liquid electrolyte for a solid electrolyte, and at the same time removing the carbon and binders from the silicon anode, the researchers avoided a series of related challenges that arise when anodes become soaked in the organic liquid electrolyte as the battery functions.

At the same time, by eliminating the carbon in the anode, the team significantly reduced the interfacial contact (and unwanted side reactions) with the solid electrolyte, avoiding continuous capacity loss that typically occurs with liquid-based electrolytes.

This two-part move allowed the researchers to fully reap the benefits of low cost, high energy and environmentally benign properties of silicon.

Impact Spin-off Commercialization

“The solid-state silicon approach overcomes many limitations in conventional batteries. It presents exciting opportunities for us to meet market demands for higher volumetric energy, lowered costs, and safer batteries especially for grid energy storage,” said Darren H. S. Tan, the first author on the Science paper.

Sulfide-based solid electrolytes were often believed to be highly unstable. However, this was based on traditional thermodynamic interpretations used in liquid electrolyte systems, which did not account for the excellent kinetic stability of solid electrolytes. The team saw an opportunity to utilize this counterintuitive property to create a highly stable anode.

Tan is the CEO and cofounder of a startup, UNIGRID Battery, that has licensed the technology for these silicon all solid-state batteries.

In parallel, related fundamental work will continue at UCSan Diego, including additional research collaboration with LG Energy Solution.

“LG Energy Solution is delighted that the latest research on battery technology with UC San Diego made it onto the journal of Science, a meaningful acknowledgment,” said Myung-hwan Kim, President and Chief Procurement Officer at LG Energy Solution. “With the latest finding, LG Energy Solution is much closer to realizing all-solid-state battery techniques, which would greatly diversify our battery product lineup.”

“As a leading battery manufacturer, LGES will continue its effort to foster state-of-the-art techniques in leading research of next-generation battery cells,” added Kim. LG Energy Solution said it plans to further expand its solid-state battery research collaboration with UC San Diego.

Reference: “Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes” by Darren H. S. Tan, Yu-Ting Chen, Hedi Yang, Wurigumula Bao, Bhagath Sreenarayanan, Jean-Marie Doux, Weikang Li, Bingyu Lu, So-Yeon Ham, Baharak Sayahpour, Jonathan Scharf, Erik A. Wu, Grayson Deysher, Hyea Eun Han, Hoe Jin Hah, Hyeri Jeong, Jeong Beom Lee, Zheng Chen and Ying Shirley Meng, 24 September 2021, Science.DOI: 10.1126/science.abg7217

The study had been supported by LG Energy Solution’s open innovation, a program that actively supports battery-related research. LGES has been working with researchers around the world to foster related techniques.

Authors: Darren H. S. Tan, Yu-Ting Chen, Hedi Yang, Wurigumula Bao, Bhagath Sreenarayanan, Jean-Marie Doux, Weikang Li, Bingyu Lu, So-Yeon Ham, Baharak Sayahpour, Jonathan Scharf, Erik A. Wu, Grayson Deysher, Zheng Chen and Ying Shirley Meng from the Department of NanoEngineering, Program of Chemical Engineering, and Sustainable Power Energy Center (SPEC) University of California San Diego Jacobs School of Engineering; Hyea Eun Han, Hoe Jin Hah, Hyeri Jeong, Jeong Beom Lee, from LG Energy Solution, Ltd.

Funding: This study was financially supported by the LG Energy Solution company through the Battery Innovation Contest (BIC) program. Z.C. acknowledges funding from the start-up fund support from the Jacob School of Engineering at University of California San Diego. Y.S.M. acknowledges funding support from Zable Endowed Chair Fund.

Batteries

Improving the batteries for electric drive vehicles, including hybrid electric (HEV) and plug-in electric vehicles (PEV). is key to improving vehicles’ economic, social, and environmental sustainability. In fact, transitioning to a light-duty fleet of HEVs and PEVs could reduce U.S. foreign oil dependence by 30-60% and greenhouse gas emissions by 30-45%, depending on the exact mix of technologies. For a general overview of electric drive vehicles, see the DOE’s Alternative Fuel Data Center’s pages on Hybrid and Plug-in Electric Vehicles and Vehicle Batteries.

While a number of electric drive vehicles are available on the market, further improvements in batteries could make them more affordable and convenient to consumers. In addition to light-duty vehicles, some heavy-duty manufacturers are also pursuing hybridization of medium and heavy-duty vehicles to improve fuel economy and reduce idling.

The Vehicle Technologies Office’s Contribution

The Vehicle Technologies Office focuses on reducing the cost, volume, and weight of batteries, while simultaneously improving the vehicle batteries’ performance (power, energy, and durability) and ability to tolerate abuse conditions. Reaching the Office’s goals in these areas and commercializing advanced energy storage technologies will allow more people to purchase and use electric drive vehicles.

The Vehicle Technologies Office pursues three major areas of research in batteries:

• Exploratory Battery Materials Research: Addresses fundamental issues of materials and electrochemical interactions associated with lithium and beyond-lithium batteries. This research attempts to develop new and promising materials, use advanced material models to predict the modes in which batteries fail, and employ scientific diagnostic tools and techniques to gain insight into why materials and systems fail. Building on these findings, it works to develop ways to mitigate those failures.
• Applied Battery Research: Focuses on optimizing next generation, high-energy lithium ion electrochemistries that incorporate new battery materials. The activity emphasizes identifying, diagnosing, and mitigating issues that negatively impact the performance and life of cells using advanced materials.
• Advanced Battery Development, System Analysis, and Testing: Focuses on the development of robust battery cells and modules to significantly reduce battery cost, increase life, and improve performance. This research aims to ensure these systems meet specific goals for particular vehicle applications.

These research and development activities are described at the Annual Merit Review and Progress Reports.

This research builds upon decades of work that the Department of Energy has conducted in batteries and energy storage. Research supported by the Vehicle Technologies Office led to today’s modern nickel metal hydride batteries, which nearly all first generation hybrid electric vehicles used. Similarly, the Office’s research also helped develop the lithium-ion battery technology used in the Chevrolet Volt, the first commercially available plug-in hybrid electric vehicle. This technology is now being used in a variety of hybrid and plug-in electric vehicles coming on the market now and in the next few years, including the Ford Focus EV.

Partnerships

The batteries subprogram works extensively with a number of different organizations, including national laboratories and universities. Within the Department, the office collaborates with the Office of Science and ARPA-e (Advanced Research Projects Agency-Energy). Across the federal government, the subprogram works with:

• The Interagency Advanced Power Group
• The Environmental Protection Agency
• The National Aeronautics and Space Administration
• The National Science Foundation
• The National Highway Traffic Safety Administration (Department of Transportation)
• The U.S. Army Tank, Automotive Research and Development and Engineering Center (Department of Defense)

They also collaborate on international research with:

• International Energy Agency’s Hybrid Electric Vehicle Technology Collaboration Programme
• The Clean Energy Ministerial’s Electric Vehicle Initiative
• The Clean Energy Research Center bilateral agreement between the US and China.

Much of the subprogram’s research is conducted in sync with industry partners through:

• The U.S. DRIVE Partnership focusing on light-duty vehicles
• The 21st Century Truck Partnership, focusing on heavy-duty vehicles
• The United States Advanced Battery Consortium (USABC), a partnership between the U.S. Department of Energy (DOE), Chrysler, Ford, and General Motors to develop and demonstrate advanced battery technologies for hybrid and electric vehicles, as well as benchmark test emerging technologies.

Goals

VTO’s Batteries and Energy Storage subprogram aims to research new battery chemistry and cell technologies that can:

• Reduce the cost of electric vehicle batteries to less than 100/kWh—ultimately 80/kWh
• Increase range of electric vehicles to 300 miles
• Decrease charge time to 15 minutes or less.

For more information on the Vehicle Technologies Office’s research on batteries, contact Brian Cunningham on the batteries team.

Battery performance. influencing factor detailed analysis

Battery performance mainly includes battery cycle performance, voltage, internal resistance and high temperature storage performance. This article analyzes the effects of lithium battery formation process, battery aging and battery internal resistance on the lithium battery performance.

Effect of battery formation process on lithium battery performance

A key factor affecting the lithium-ion battery performance is the solid electrolyte film (SEI) formed by the decomposition of the electrolyte on the surface of the anode in lithium-ion batteries. The SEI film is formed by charging and discharging for the first time during the battery formation process.

A stable SEI film can protect the anode from being consumed during the subsequent decomposition of the electrolyte and prevent graphite from falling off, so the formation process is an important process in the manufacturing process of lithium-ion batteries. The state of the SEI film formed by different formation processes is different, and different SEI film states have different effects on battery performance. Therefore, different formation processes have different effects on the lithium-ion battery performance.

① Effect of formation charge and discharge current on battery performance

The formation charge and discharge current mainly includes the first part of the open charging current, the second part of the closed charging current and the fourth part of the closed discharge current. The first part of the opening formation is mainly small current charging, the purpose is to form a stable and dense SEI film, so that the gas generated by the additive reaction in the electrolyte can be discharged, and the impact on battery performance such as battery cycle performance and rate performance can be reduced. over, the type and quantity of the electrolyte additive, the reaction potential and the time are different, and the charging rate required for the reaction is different.

Therefore, the charging at this stage mainly chooses the ladder charging mode, that is, the first step is low-current charging, and the subsequent steps increase current charging on the basis of the previous step. The second part of closed formation is mainly to increase the charging current on the basis of the first part. In the first part, part of the additives in the electrolyte has reacted and a dense SEI film has been formed. However, excessive density of the SEI film will affect the transport of lithium ions during the reaction, so it is necessary to gradually increase the current to make the formed SEI film satisfy the transition from dense to loose.

In addition, increasing the charging current will also shorten the battery charging time and improve production efficiency. However, if the charging current is too large, the temperature of the batteries will rise, the SEI film will be destroyed, and it will be dissolved and reorganized. Battery capacity attenuation, poor cycle performance, and even cause safety accidents. The fourth part of closed discharge is to discharge the fully charged battery for the first time, so as to complete the entire activation process of the battery.

Before discharging, the SEI film on the surface of the anode has been basically formed, so the discharge current of this part can be equal to or slightly greater than the charging current of the second part, but the current should not be too large, which will lead to serious polarization of the batteries and Rapid temperature rise of the batteries. In addition, in order to ensure the consistency of the battery, a part of small current discharge should be performed after high current discharge.

② Influence of formation charging and discharging time on battery performance

The formation charging and discharging time mainly includes the above-mentioned first part of the opening charging time, the second part of the closing charging time and the fourth part of the closing discharging time. The first part of the open charging time is the low current charging time, which should not be too long, because long-term low current charging will increase the impedance of the formed SEI film and increase the internal resistance of the batteries. The second part is the closed charging time.

If there is no voltage limit, charging for a long time will cause the batteries to overcharge, and charging for a short time will cause the active material of the electrode inside the batteries to not be fully activated, and the SEI film will not be dense and incomplete, which will affect the battery performance. Therefore, this part of the charging time should be controlled jointly with the charging cut-off voltage. The fourth part is that the closed discharge time is related to the discharge depth of the battery. Without the limit of the discharge cut-off voltage, the longer the battery discharge time, the deeper the battery discharge depth will lead to over-discharge of the battery and shorten the life of the battery, thus affecting the battery performance.

Effect of aging time and temperature on battery performance

The aging time is the interval between the first charge and the first discharge. After the lithium-ion battery is fully charged for the first time, it needs a certain period of rest to remove the internal polarization of the battery, which will have a significant impact on the capacity and impedance of the battery. The impact of temperature on battery performance is mainly reflected in the increase of temperature, the acceleration of electrolyte and additive decomposition, the thickening of SEI film on the surface of anode, and the increase of battery internal resistance.

LiPF6 is the main component of the lithium ion battery electrolyte. LiPF6 will be thermally decomposed at too high a temperature to generate PF5. PF5 will further hydrolyze with the water in the electrolyte to generate HF. HF is an important reason for the dissolution of metallic iron in cathode materials.

Influence of lithium battery internal resistance on battery performance

Internal resistance is one of the key characteristics of lithium batteries. Generally speaking, battery internal resistance is divided into ohmic internal resistance and polarization internal resistance, which affect the power and charge and discharge efficiency of the battery. In short, all factors that hinder the movement of lithium ions and electrons in the lithium battery from one pole to the other constitute the internal resistance of the lithium battery.

The smaller the internal resistance of the battery, the better, because high internal resistance will increase its own heat loss, and it will not be able to discharge with a large current. In addition, when the internal resistance is large, the battery will heat up during use. If the temperature is too high, the working voltage of the battery will be reduced, and the discharge time will be shortened, which will seriously affect the battery performance and battery life, and even cause the risk of spontaneous combustion.

Therefore, the development of low internal resistance batteries can effectively improve the battery performance and prolong the service life of the battery. The industry mainly reduces the internal resistance of the battery by improving the adhesion and adhesion of the active material and the current collector, reducing polarization, and protecting the current collector.

How to Improve EV Battery Performance in Cold Weather

As fleet companies are investing more into electrification, they’re learning how to deal with external factors that can impact electric vehicle (EV) range. For example, one big question many fleets have is whether cold will impact an EV’s performance. And, in research cold weather has been shown to make an impact. In 2019, AAA tested the range effects on EVs and found that 20-degree weather could reduce range by 10-12%. The study also found that when there is up to 95-degree weather outside and air conditioning is used inside the vehicle, ranges can decrease by 17%.

Minimizing Cold Weather Battery Concerns

Cold weather has proven to impact an EV’s battery performance, and fleets are looking to lessen the blow of low temperatures. Understanding how an EV battery works best is important to minimize these concerns. Ramesh Natarajan, business unit engineering manager of Webasto Group, cited low charging performance, potential lithium plating, potentially permanent damage to electrochemistry, time-consuming charging loops, and additional heat energy required to heat the system as the main cold-weather concerns.

• Keep speeds moderate. Higher speeds use more energy.
• Use “Eco” or “L” drive modes to increase regenerative braking to help recover more energy from the battery.
• Avoid harsh acceleration and braking to help maximize battery range.
• Keep doors and Windows closed when running the heat (or air conditioning) to conserve energy.
• If driving a long distance, fast charging when the vehicle drops below 80% state of charge will heat up the battery, increasing available energy for the next leg of the trip.
• If the vehicle is covered with snow, start it remotely or schedule preconditioning to melt snow, and brush off any remaining snow before driving to eliminate extra weight and drag.

Park in a garage whenever possible to shield EVs from colder temperatures, according to Walker.

“They also should be plugged in when parked,” Walker said. “In cold temperatures, the vehicle uses power from the charger to heat the battery. Keeping it plugged in can ensure the battery remains charged.”

Checking the Outside Temperature for EV Battery Performance

Batteries work best between 40 to 80 degrees F (5-30 degrees C), according to Natarajan.

“Anything below 40-degrees F over a prolonged time would mean reduced performance,” he said. “The underlying physics is that the batteries have higher internal resistance in colder temperatures. The most concern is below 5 degrees, where the possibility of formation of lithium-plating is higher. Again, this is cell chemistry dependent.”

One of the ways to address this is to heat the batteries. Megan Soule, director of Chevrolet Trucks Full-size SUV Communications, outlined how General Motors tests its EV batteries. Chevrolet has hot and cold chambers in its Estes battery systems lab to test its batteries in both conditions.

“The lab can simulate minus 68 degrees C to 85 degrees C and 5-95% relative humidity environments for battery pack testing and minus 73 degrees C to 190 degrees C and 5-95% humidity for cell testing,” Soule said.

The solution for minimizing cold weather damage to battery performance is to choose the right size and chemistry for the applications.

Pursuing EV Initiatives that Matter to Work Truck Fleets

Recognizing the issue is one part, but fleet companies are also taking action to reduce cold weather concerns.

“We are constantly working toward optimizing battery performance,” Soule said. “Last month, GM announced a feature standard in its Ultium-based EVs that captures and repurposes waste energy from the battery and heat from inside and outside the vehicle.”

To address applications in colder regions, Webasto has an off-the-shelf product eBTM (Battery Thermal Management) which is a system with a:

• Water pump.
• Reservoir.
• Chiller.
• Radiator.
• Expansion.
• Valves
• Heater.

“This system was designed, developed, and tested from day one for our battery packs,” Natarajan said. “Understanding the application’s use case is still key to ensuring the sizing and power demands correlate.”

Ford is investing 50 billion through 2026 as part of its plan to lead electrification in several areas and electrify its products, according to Walker.

Ford said it plans to build more than 2 million EVs by late 2026.

From advice to initiatives, fleet companies are adapting to ensure the battery performance of their EVs is not severely impacted by factors like cold weather. Check out these tips to improve your EV battery performance in cold weather.

And cold impacts more than just electric cars and trucks. driver injuries increase during winter months due to icy walk ways and accidents are more frequent, too. Be sure to protect your trucks and your drivers during the colder winter months.