Richo wrote: ↑
Thu, 04 Apr 2019, 13:10
Just remember that the shelf life of the [LTO] battery won't be much better than any other battery.
Hi Richo. Can you tell us why you think that?
I've been searching, and I can find precious little about the calendar life of LTOs.
It just seemed to me that since they are considered to withstand higher temperatures, that might translate to longer life at ordinary temperatures. And I kept finding stuff about how the calendar ageing of non-LTO lithiums is dominated by growth of the SEI layer on their graphite anodes. This not only increases internal resistance as it gets thicker, but also reduces capacity by locking up lithium. And I read that the titanate anode does not have an SEI layer at all. Sure it would still have cathode ageing, but apparently that's slower.
I finally found this, a Chem Eng Degree project by one Joakim Andersson, 2017-06-13.
http://www.diva-portal.org/smash/get/di ... TEXT01.pdf
Search on "titanate" and "LTO" within the above document. Here are the important quotes about LTO calendar ageing:
Page 12: "The great disadvantages of LTO are the low electron conductivity along with the rather extensive release of gas by-products, predominately H2, CO and CO2, during operation at high temperatures . These issues have limited the use of LTO cells for large-scale applications . Researchers have been trying to improve the material properties in these regards through doping or protective coatings ."
Page 19: "Lastly, it is worth mentioning that the main aging mechanisms are quite different for LTO-based anodes. First and foremost, no SEI formation will occur on LTO anodes due to their higher potential vs. Li/Li+ compared to graphitic anodes. For the same reason, no lithium or manganese plating will occur either. ... The main concern of LTO anode aging is instead the quite substantial production of gas at high temperatures. Still, it is commonly so that aging processes occurring at the cathode will dominate the overall aging behavior of cells with an LTO anode [53, 82, 83]."
Page 24: "As SEI formation on the anode appears to at least be the dominating aging mechanism during storage, cells with titanate-based anodes should see relatively little calendar aging as no SEI is formed on these electrodes."
"The work done on calendar aging of cells featuring LTO-based anodes suggests that these materials will vastly outperform those with graphite based anodes in terms of capacity and internal resistance retention over time."
Page 25: See the graph at the top of the page.
Page 27: "It has also been seen that aging characteristics are dependent on cell chemistry, especially so for different anode materials. LTO-based cells display superior calendar-and cycle aging compared to those featuring a graphite anode. In addition, the main aging mechanisms are very different for LTO-based cells as no SEI formation and hardly any electrolyte oxidation will occur in cells with these anodes."
Keep in mind that this is not a peer reviewed paper, but a student project. But it may be useful to try to obtain some of the LTO papers it references.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).