In this article, we focus on lithium sulfur (LiS) batteries, including their advantages, disadvantages, and chemistry.
Some time ago, Max Maxfield roped me into his ongoing robot project. This led to my writing this series of articles on the various battery technologies available to us.
In part 10, we considered lithium sulfur dioxide (LiSO2) battery technology. In keeping with the lithium and sulfur theme, let's continue with the lithium-sulfur variant, which boasts some impressive new developments. Before we do, and at the risk of my being labeled American-biased, today's tip is more about keeping informed and/or satisfying one's curiosity than it is a tip per se. Nonetheless, here it is.
Tip No. 10: New battery developments
Those who have an interest in new battery developments can follow along with what is happening in North America at the National Alliance for Advanced Technology Batteries site, NAATBatt.org. Here is some information from that site:
The National Alliance for Advanced Technology Batteries ("NAATBatt") is a not-for-profit trade association of foreign and domestic corporations, associations and research institutions focused on the manufacture of large format advanced batteries for use in transportation and large scale energy storage applications in the United States. Members include advanced battery and electrode manufacturers, materials suppliers, vehicle makers, electric utilities, equipment vendors, service providers, universities and national laboratories.
NAATBatt's core missions are to grow the North American market for products incorporating advanced energy storage technology and to reduce the cost of those products to U.S. consumers. The two missions are intimately related. NAATBatt believes that the high cost of electrochemical energy storage, compared to competing technologies, is the principal barrier to widespread adoption of large format advanced battery technology. NAATBatt supports the adoption of public policies and the development of new technologies and industrial standards that will reduce the price to consumers of large format advanced batteries and the products that use them.
By the way, to go against the North American grain a bit technology-wise, in my opinion, the more impressive advancements in battery technology in the last few years have not actually come from America. If you disagree, I would be more than happy to be proved wrong, and I welcome and thank you in advance for sharing your thoughts on this topic. Now, on to the technical side.
The LiS battery
This technology is known for its potentially very high mechanical robustness and safety (shock, crush, puncture, and thermal stability), very high energy density and specific energy, and very high depth of discharge. It's also known for being maintenance free, lightweight, and eco-friendly. This technology helped the Zephyr set the record for the highest-altitude and longest solar/battery-powered flight in 2008.
Given the very high theoretical energy limit that LiS technology could produce, there are now multiple chemistries in wide variations as companies scramble to develop products and compete with one another. As a side note, as the technology develops, interesting features are also becoming available, such as Oxis Energy's claim of having a version that can be safely discharged to 100% depth of discharge and cannot be damaged by overdischarge.
- Specific energy: as high as 160-300 Wh/kg
- Energy density: approximately 140-270 Wh/L
- Specific power: 590-1,300 W/kg (peak load)
- Discharge efficiency: approximately 50-95% (C/5)
- Energy/consumer-price: predicted to be lower than Li-ion in Wh/dollar
- Service or shelf life: >10 years (selected types)
- Self-discharge: 0.002%/month (some types have negligible loss)
- Cycle durability: 110-1,000 (future models >2,000)
- Nominal cell voltage: 2 V (varies by manufacturer)
- Open-circuit voltage: 2.4 V (varies by manufacturer)
- Cutoff voltage: 1.5 V (varies by manufacturer and use)
- Temperature: -20 to +60°C (selected versions to +85°C)
Charging (polymers of sulfur form at the cathode):
Li2S → Li2S2 → Li2S3 → Li2S4 → Li2S6 → Li2S8 → S8
S8 → Li2S8 → Li2S6 → Li2S4 → Li2S3
This chemistry is now finding use in military systems, urban electric vehicles, electric scooters, marine propulsion, UAVs, and grid storage. Here's a photo of one example taking some abuse.
The following figures show various attributes of the LiS technology.
One example of the functional construction of an LiS cell.
(Image: Oxis Energy)
Dependence of temperature at 3C rate of discharge.
(Image: Sion Power Corp.)
Charging: The top three curves are constant current; the bottom three curves are constant voltage with taper.
(Image: Sion Power Corp.)
Comparison of some common battery chemistries highlighting Oxis's version of LiS.
In my next column, we'll look at some more tips and tricks, and we will consider another battery technology. In the meantime, as always, I welcome any questions or comments.
- All About Batteries, Part 1: Introduction
- All About Batteries, Part 2: Specifications & Terminology
- All About Batteries, Part 3: Lead-Acid Batteries
- All About Batteries, Part 4: Alkaline Batteries
- All About Batteries, Part 5: Carbon Zinc Batteries
- All About Batteries, Part 6: Zinc-Air
- All About Batteries, Part 7: Lithium Thionyl Chloride
- All About Batteries, Part 8: Zinc/Silver-Oxide
- All About Batteries, Part 9: Sodium Sulfur (NaS)
- All About Batteries, Part 10: Lithium Sulfur Dioxide (LiSO2)