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The lowdown on batteries: Lithium titanate

Posted: 02 Feb 2015 ?? ?Print Version ?Bookmark and Share

Keywords:lithium sulphur? battery? Lithium Titanate? charging? nanocrystals?

Several months 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 my previous article, we considered Lithium Sulfur (LiS) battery technology. Here we'll move on to consider batteries based on Lithium Titanate (Li4Ti5O12, which is referred to as LTO in the battery industry). Before we do so, however, today's tip is more about keeping informed and/or satisfying one's curiosity than it is a "tip" per se; none-the-less, here it is...

Tip No. 11: New battery developments
This is a continuation of Tip No. 10 from my previous column. If you have an interest in new energy developments, including batteries, you can keep in touch with what is happening at www.sdle.co.il (the website for Shmuel De-Leon Energy Ltd.). Of particular interest is the batteries subsection. Unfortunately, much of what is available in the line of marketing trends/research is available only for sale, but there are a few free things of interest if you dig around a little.

Now, on to the technical side...

The Lithium Titanate (LTO) battery
This technology is known for its very fast charging, low internal resistance/high charge and discharge-rate, very high cycle life, and excellent endurance/safety. It has found use mostly in electric vehicles and energy storage (Toshiba, YABO, and Altair Nanotechnologies), and wristwatches (Seiko). More recently, it is beginning to find use in mobile medical devices due to its high safety. One underlying reason for this technology's characteristics is that the chemistry uses nanocrystals on the anode instead of carbon, which provides much more effective surface area. Unfortunately, however, this battery has lower terminal voltages than other Lithium types.
???Specific energy: approximately 30-110Wh/kg
???Energy density: as high as 177 Wh/L
???Specific power: 3,000-5,100 W/kg (peak load)
???Discharge efficiency: approximately 85%; charge efficiency over 95% (low-rate)
???Energy/consumer-price: 0.5 Wh/dollar
???Service or shelf life: >10 years (some to 20 years)
???Self-discharge: 2-5 %/month
???Cycle durability: 6,000 cycles to 90% capacity (some models >10,000 cycles)
???Nominal cell voltage: 1.9 to 2.4V (Toshiba SCiB cells 1.5-2.7V operating; 2.3V nominal)
???Cut-off voltage: 1.5V typical (some at 1.7V)
???Temperature: -40 to +55C (extended models)
???Charging technique is using standard constant current, followed by constant voltage until the amps threshold is reached.

Chemistry (Li4Ti5O12 some companies are proprietary)
Li4Ti5O12 + 6LiCoO2 Li7Ti5O12 + 6Li0.5CoO2 (E=2.1V) (patented)

Additional information
Figures 1, 2, and 3 below are for Toshiba's SCiB 20Ah cells; figures 4 and 5 are for Altair Nano 50Ah cells.

Figure 1: Photo of one example type: A Toshiba SCiB cell.

Figure 2: State of charge percentage verses time.

Figure 3: Capacity recovery rate percentage vs. number of charge/discharge cycles.

Figure 3: Capacity recovery rate percentage vs. number of charge/discharge cycles.

Figure 4: Cell voltage verses cell capacity for three charging rates.

Figure 5: Cell voltage verses cell capacity for three discharge rates.

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.

About the author
Ivan Cowie is the Chief Engineer at MaxVision.





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