New technologies enable safer and more efficient batteries
Your laptop, cell phone, electric lawn mowers, and most electric cars rely on lithium-ion batteries. Compared to traditional lead-acid batteries such as the ones used to start gasoline-powered vehicles, lithium-ion batteries are relatively small, rechargeable, and lightweight. As society moves towards electrification of more devices, lithium battery technology will need to improve to make the batteries safer and more efficient.
How Lithium-Ion Batteries Work
All batteries, including lithium-ion batteries, rely on chemical reactions to generate electricity. Lithium-ion batteries create electricity by harnessing the potential energy held in the attraction between electrons and lithium atoms. These batteries contain a cathode, the positive end of the battery, and an anode, the negative end. In many electronic devices, cathodes are usually made of lithium cobalt oxide, although lithium manganese oxide is often used for the cathodes of electric car batteries (4). Anodes are usually made of graphite which is a pure form of carbon (4). Batteries also require a liquid carrier of electrons, electrolytes, which is normally ether for lithium-ion batteries.
When the battery is in use, neutrally charged lithium releases an electron into the anode, shown on the right of the diagram. The anode carries the electron out of the battery to power the device, while the ionized lithium atom crosses a membrane to reach the cathode, shown on the left green part of the diagram. Once at the cathode, the lithium ion regains an electron and enters the structure of the cathode. This process happens easily because lithium’s electron configuration makes it more stable in its +1 form, meaning there is one fewer electron than the lithium has in its neutral form.
Lithium-ion batteries have very high energy density, meaning that lithium-ion batteries can provide more electricity than other types of batteries of the same size (4). The batteries can be recharged hundreds of times, making them more environmentally-sound than single-use batteries. Lithium-ion batteries are also relatively safe, although damaged or poorly constructed batteries may ignite. Researchers are working on several innovations to improve lithium-ion batteries with a focus on lowering cost, decreasing weight, increasing safety, and maximizing the ability to scale up production as more devices and vehicles rely on this technology.
The membranes used in today’s lithium-ion batteries to separate the anode and cathode are made of polymers, which are very large molecules, but researchers are now testing ceramic membranes (6). Regular polymer membranes do not allow many lithium atoms to pass through, which limits the amount of energy that can be produced. Polymer membranes are also unstable at high temperatures (275º F) and tend to break down over time. A study from 2016 determined that ceramic membranes allow a larger transfer of ions and are more stable at high temperatures but still break down eventually (8).
Earlier this year, researchers at Harvard University published a study on solid-state lithium-ion batteries (2). Solid-state batteries differ from regular lithium-ion batteries because the liquid electrolyte is replaced by a solid one, meaning that the battery is light, small, and stable, recharges quickly, and can sustain many more cycles of charging (3). Previously, solid-state batteries with lithium anodes were considered impractical because charging led to a build-up of crystals on the lithium-based electrode (2). These crystals would eventually break through the membrane between the anode and cathode, ruining the battery.
The new study, however, shows that the highly efficient lithium anode can successfully be used alongside an innovative layered membrane. The layered membrane developed in the study consists of two electrolytes: one that is more stable when exposed to lithium and is prone to destruction by crystals and another that is less stable when exposed to lithium and stops the growth of crystals (2). This layering system keeps the crystals from shorting the battery while maximizing its energy output. The use of a solid-state electrolyte makes lithium-ion batteries safer.
Silicon Anode Batteries
Instead of focusing on the electrolyte or the membrane, an Israeli company called StoreDot is seeking to redesign the anodes of lithium-ion batteries (5). StoreDot proposes using silicon instead of graphite in the anode. Silicon is isoelectronic to carbon, meaning that it interacts with other atoms in essentially the same way as carbon. However, silicon absorbs lithium ions better than graphite does (7). So far, an anode made of an alloy of carbon and a small amount of silicon has been successfully used to slightly increase the stored energy in batteries (1). Unfortunately, higher concentrations of silicon cannot be used without quickly degrading the battery’s performance over time. StoreDot continues to investigate this technology.
None of these battery technologies is yet ready for consumer use, but all three developments — ceramic membranes, solid-state batteries, and silicon anodes — show promise for improving lithium-ion batteries. Each of these technologies could lead to safer batteries with shorter charging times and longer battery life, but many testing steps remain before the technologies are commercially viable. These battery developments are laying the foundation for advances that will be essential to power the devices and electric cars of the future.
- Berdichevsky, G., & Yushin, G. (2020). The Future of Energy Storage Towards A Perfect Battery with Global Scale. Sila Nanotechnologies. Retrieved from https://silanano.com/wp-content/uploads/2020/09/The-Future-of-Energy-Storage.pdf
- Burrows, L. (2021, May 12). Researchers design long-lasting, solid-state lithium battery. Harvard Gazette. Retrieved from https://news.harvard.edu/gazette/story/2021/05/researchers-design-long-lasting-solid-state-lithium-battery/
- (2021). What is a Solid-State Battery for an Electric Car? J.D. Power. Retrieved from https://www.jdpower.com/cars/shopping-guides/what-is-a-solid-state-battery-for-an-electric-car
- (2020, September 25). Lithium-Ion Battery – Clean Energy Institute. Clean Energy Institute. Retrieved from https://www.cei.washington.edu/education/science-of-solar/battery-technology/
- Morris, J. (2021, September 4). This Company Has The Battery Technology To Beat Tesla. Forbes. Retrieved from https://www.forbes.com/sites/jamesmorris/2021/09/04/this-company-has-the-battery-technology-to-beat-tesla/?sh=f638e2748f3b
- (2021). Polymer. Encyclopædia Britannica. Retrieved from https://www.britannica.com/science/polymer
- (2021, June 29). StoreDot receives patent for anode active materials for lithium-ion devices. Stroredot. Retrieved from https://www.store-dot.com/post/storedot-receives-patent-for-anode-active-materials-for-lithium-ion-devices
- Suriyakumar, S., & Raja, M. (2016, September 19). A flexible zirconium oxide based-ceramic membrane as a separator for lithium-ion batteries. Royal Society of Chemistry Advances. Retrieved from https://www.researchgate.net/profile/Angulakshmi-Natarajan/publication/309062909_A_flexible_zirconium_oxide_based-ceramic_membrane_as_a_separator_for_lithium-ion_batteries/links/5e983b5a4585150839e09498/A-flexible-zirconium-oxide-based-ceramic-membrane-as-a-separator-for-lithium-ion-batteries.pdf
- (2021, May 17). This Solid-State Lithium-Ion Battery Recharges Fast, Protects Against Fire. IEEE Spectrum. Retrieved from https://spectrum.ieee.org/solidstate-lithiumion-battery-recharges-fire