The device, still in the prototype phase, is foldable and can be used for multiple applications, including vehicles, clothing, electronic devices, and even microsatellites
Measuring 5 cm2, the IPEN prototype is made using a carbon fabric impregnated with lead nanoparticles
Léo Ramos Chaves / Revista Pesquisa FAPESP
A research group from the Institute for Energy and Nuclear Research (IPEN) in São Paulo is betting on a new battery design that uses lead and carbon nanoparticles and features innovative architecture inspired by hydrogen fuel cells. The goal is to create an energy storage system that is lighter and more efficient than the conventional lead batteries used for automotive and industrial applications. The study’s results were published in the Journal of Energy Storage in March. A patent application for the device is expected to be submitted to the National Institute of Industrial Property (INPI).
“Our prototype replaces the traditional lead metal electrodes in conventional batteries with lead nanoparticles fixed on a flexible carbon fabric, which is much lighter and more conductive than metallic lead,” explains chemist Almir Oliveira Neto from the Fuel Cell and Hydrogen Center at IPEN, who led the project.
Another innovation is the use of a solid polymer electrolyte — a proton-conducting membrane — instead of the liquid electrolyte found in lead-acid batteries. In an automotive battery, the electrolyte (sulfuric acid diluted in water) plays the role of a conductor element, transporting electrical ions between the positive pole (cathode) and the negative pole (anode) when the battery is being charged or discharged.
“The polymer membrane gave flexibility to the system and reduced its weight,” says chemist Rodrigo Fernando Brambilla de Souza, the paper’s lead author. The advantage of solid electrolytes is that they are less prone to leaks and spills, increasing battery safety. The absence of liquids can also reduce internal corrosion and other types of degradation, extending the system’s lifespan.
The battery prototype, which was developed together with the Materials Science and Technology Center at IPEN, measures about 5 square centimeters and is 1.2 millimeters thick. It has a sandwich-like structure featuring two pieces of carbon fabric impregnated with hot-pressed lead nanoparticles with a proton-conducting membrane in the middle (see infographic). “The cell weighs just 0.73 grams (g) and, in laboratory tests, had the same energy efficiency as a traditional 15 g lead battery. It’s 20 times lighter and the size has been reduced by 90%,” says Souza, a postdoctoral researcher at IPEN.
Alexandre Affonso / Revista Pesquisa FAPESP
Another important aspect of the novel battery is its electrochemical stability, meaning its ability to charge and discharge, or cycle, in technical terms, without losing electrical voltage. In this case, the prototype operates at 2 volts. “The incorporation of carbon into the lead structure not only improved the stability of the nanoparticles but also resulted in highly stable battery performance over 100 cycles, with variations in discharge potential of less than 2%,” the authors noted in the Journal of Energy Storage article.
“The successful integration of PEM-FC architecture [proton-exchange membrane fuel cells] into CLAB [Carbon-Lead Acid Battery] technology opens avenues for innovative and flexible energy storage solutions,” the paper concludes. The team also includes researchers Édson Pereira Soares and Larissa Otubo from IPEN, nuclear technology doctoral candidate Victória Maia, and undergraduate research students Felipe Da Conceição from Osvaldo Cruz College and Gabriel Silvestrin of FMU University Center, both in São Paulo.
Technological advancement Lead-acid batteries (LAB) have been around for over 150 years and are still very relevant. “Various innovations have been made to improve the performance of this technology, which is still a low-cost, robust, reliable option in the rechargeable battery market today,” notes chemist Lucia Helena Mascaro Sales, a researcher at the Federal University of São Carlos (UFSCar) and the Center for Innovation in New Energies (CINE), supported by FAPESP. “Their disadvantage is that they’re heavy and take up a lot of space. Their current-collectors are lead grids, which account for 30% to 60% of the weight.” A traditional lead battery weighs on average 14 kilograms. “We estimate that an equivalent model of the device created by our group could weigh between one and two kilos,” says Souza.
Lead-carbon storage systems are an evolution of LAB technology that incorporates carbon materials into the electrodes. Carbon improves system performance by increasing cell stability and reducing sulfation — the growth of sulfate crystals on the electrodes — which degrades the battery. The result is a significant improvement in cycling and efficiency.
SOUZA, R. F. B. et al. Journal of Energy Storage. 2024
Physicist Hudson Zanin, an expert in energy storage systems from the School of Electrical and Computer Engineering at the University of Campinas (UNICAMP), who is not part of the IPEN team, observes that lead-carbon batteries have been commercially available for some time, with several manufacturers around the world. “Moura, for example, has an energy storage and management system called BEES, using lead-carbon technology,” the researcher says.
However, the solution proposed by IPEN is innovative in that in the near future these batteries could be made flexible, potentially resulting in a foldable device, adopting a design similar to fuel cells, where traditional metallic lead electrodes are replaced with carbon fabric impregnated with lead nanoparticles.
“IPEN proposes an innovative approach by combining conventional lead-acid battery technology with advanced fuel cell design elements,” observes Zanin. He observes that replacing conventional electrodes with lead nanoparticles fixed on a flexible carbon fabric makes the device more efficient because nanoparticles offer a significantly larger surface area for electrochemical reactions, which can generate denser electric current. “The fabric also has the advantage of absorbing mechanical stresses better than rigid metallic electrodes. This reduces the risk of structural damage during charge and discharge cycles,” the UNICAMP researcher adds.
Lucia Sales from UFSCar highlights that the battery’s flexibility will allow it to be twisted and shaped into different forms. “This could expand the technology’s use in modern applications, such as portable electronics, medical devices, wearable smart textiles, sensors, and other devices, in addition to more traditional uses in electronics, vehicles, and stationary energy storage systems,” she points out.
In laboratory tests, the prototype operated in the temperature range between -20 and 120 degrees Celsius with no efficiency loss. “If we can increase its performance to more than 2,000 cycles, even microsatellites could be a target for our solution,” suggests Souza. Lead batteries used in vehicles are normally rated at 500 cycles.
Alexandre Affonso / Revista Pesquisa FAPESP
Challenges to overcome Versatile and promising, the technology is still in its early stages, focused on proof of concept and the first phases of prototyping. “We are at TRL 3-4 and the next steps will be to reduce the cost of materials to enable production on a larger scale,” says Oliveira. Created by NASA, the TRL (Technology Readiness Level) scale ranges from Level 1 (basic research) to Level 9 (market product).
Mechanical engineer Giovani Grespan, a postdoctoral researcher at UFSCar and a specialist in lead-acid devices, considers the IPEN initiative positive but notes that battery development requires a long journey that involves various performance, safety, and validation tests. “There are issues to be resolved with this proposal. One of them concerns the solid polymer electrolytes, which can increase a battery’s internal resistance and reduce charging and discharging speeds,” he notes.
Reducing material and production process costs, especially for proton membranes and electrolytes, is another future challenge for the technology, Zanin adds, followed by the need to develop large-scale manufacturing processes that maintain the quality and consistency of advanced materials. It will also be necessary to demonstrate the prototype’s durability and reliability under real operating conditions over extended periods. “These improvements could position the technology as a viable and competitive alternative in the energy storage market,” the UNICAMP researcher says.
The story above was published with the title “Made of lead, yet light and flexible” in issue 342 of august/2024.
This article may be republished online under the CC-BY-NC-ND Creative Commons license. The Pesquisa FAPESP Digital Content Republishing Policy, specified here, must be followed. In summary, the text must not be edited and the author(s) and source (Pesquisa FAPESP) must be credited. Using the HTML button will ensure that these standards are followed. If reproducing only the text, please consult the Digital Republishing Policy.
