Nanotechnology Boosts Efficiency of Lithium Ion Batteries
In 2009, the Recovery Grant Act made about $2.4 billion available for projects surrounding battery technology and electric vehicles. Lithium ion batteries continue to grow in popularity as an energy source, and manufacturers, engineers and OEMs continue in the quest for higher quality energy sources. Many factors impact the efficiency of a li-ion battery, and some begin early on in the manufacturing process. Nano World News had the opportunity to speak with John Hill, application and process advisor for NETZSCH Fine Particle Technology, about how nanotechnology is improving the quality of todayâ€™s li-ion batteries.
John Hill: Manufacturers are constantly striving for better batteries that offer improved conductivity, longer charge life and shorter recharge time. These elements are all critical to the evolution of li-ion batteries. Nanotechnology has shown to improve upon these features, enabling battery manufacturers to offer a better battery to OEMs producing a wide range of products, particularly consumer electronics. These advances are moving towards the possibility of widespread adoption of li-ions in electric vehicles.
NWN: For our readers who may not be entirely familiar with the science behind how lithium ion batteries work, can you walk us through the process?
JH: Â Within batteries, there are materials that operate as anodes and cathodes. During the charging process, the lithium ions move from the cathode into the anode. When a battery is discharging, that movement is reversed. Electrolytes conduct the lithium ions and serve as a carrier between the anode and the cathode when electric currents pass through an external circuit.
The materials selected as anodes and cathodes will affect a batteryâ€™s voltage, capacity and battery life. So will their quality â€” which is where nanotechnology comes into play.
NWN: What types of materials are typically used?
JH: Variations of carbon, typically graphite, primarily serve as anodes in todayâ€™s li-ion batteries.
NWN: And as cathodes?
JH: Manganese, cobalt and iron phosphate are common cathodes being used today. While lithium cobalt oxide and lithium manganese oxide batteries are commonly being used in consumer electronic products, the lithium iron phosphate (LFP) battery continues to gain popularity because of its improved safety and environmental advantages compared to the alternatives. Another major advantage is the longer cycle calendar life provided by LFP.
Iron and phosphate are also less expensive than other materials used in lithium ion battery production, and their high charge capacity makes them a good match for plug-in hybrid applications.
LFP battery cells do contain lower voltage and energy density levels than other li-ion batteries, but their slower rate of capacity loss helps LFP batteries maintain a higher energy density level than other li-ion batteries after a single year of use.
NWN: Where does nanotechnology fit into the production of li-ion batteries?
JH: Todayâ€™s nanotechnology manufacturing processes allow li-ion battery manufacturers to work with grinding media as small as 90 microns. (As a point of reference, a typical human hair is 10 microns wide.) This increased surface area of grinding particles not only leads to faster production time but to a more homogenous, consistent coating for use in the batteries.
Applying nanotechnology principles to the coating development process for both anodes and cathodes has proven to produce a better performing battery. At the most basic level, lithium ions penetrate the graphite anode faster and more easily when itâ€™s homogenous and consistent. Nothing achieves this better today than using nanotechnology.
NWN: What is the best way that manufacturers can introduce nanotechnology?
JH: Media milling â€“ or grinding â€“ is the most well-established manufacturing method for nanoparticle production. Stirred media mills are used in many different industries to reduce particle size. By preparing coatings using proper grinding techniques, lithium ion battery manufacturers are joining the ranks of those who are able to develop higher-quality products because of the equipment.
NWN: What are some key considerations during the coating development process?
JH: Consistent dispersions play an especially important role in the anode and cathode coatings. The particles must remain smooth and free from agglomerates or clustering. Micronized air bubbles within the mixture can also impact conductivity of coatings and, ultimately, a li-ion batteryâ€™s overall performance.
Before and during the grinding process, lithium and graphite particles require careful attention to ensure that no contamination occurs to the coating mixtures. Metal grinding equipment can slough off metal particles leading to accidental contamination, affecting the final quality of the coatings. Todayâ€™s ceramic and polyurethane mixing and grinding tools can prevent this contamination and ensure that the performance of the coatings isnâ€™t compromised.
NWN: How promising is the future for lithium ion batteries?
JH: Very promising. Right now, more resources than ever before are being funneled into the industry, and with the help of nanotechnology, the possibilities are endless. Itâ€™s hard to predict exactly what is ahead, but weâ€™ve come a long way since Sony released the first commercial lithium ion battery in 1991.