Jun
22
Its How You Make Things That Makes the Difference
June 22, 2010 | 3 Comments
The Tokyo University of Agriculture and Technology Graduate School has announced electrode materials made by adding lithium iron phosphate (positive-electrode material, LiFePO4) and tin oxide (negative-electrode material, SnO2), respectively, inside carbon.
The new process drastically improves the performance of the materials in lithium-ion (Li-ion) rechargeable batteries by using an ultracentrifugal processing technology to add an active material inside carbon.
The ultracentrifugal processing technology was developed by K&W, a venture firm spun off from the university. It is a kind of mechanochemical processing and makes materials in a centrifugal force field by using a ‘sol-gel’ method. The actual working of the technology seems a bit, understandably, hush, hush.
Kenji Tamamitsu, chief of the Functionality Materials Lab at the Basic Research Headquarters of Nippon Chemi-Con said, “We found that the ultracentrifugal processing technology enables adding a variety of active materials inside carbon and enhance the performance. We would like to utilize it for battery materials in the future.”
The research was conducted at the university’s Naoi Laboratory by the participants of the “Capacitor Technology Lecture,” a project funded by Nippon Chemi-Con Corp, at the university. Nippon Chemi-Con is saying that it plans to discuss the commercialization of the high-performance Li-ion battery using the new electrode materials at an early date. The company has various options including providing high-performance materials and directly selling batteries.
Ultra Centrifugal Cherry Type Lithium Iron Phosphate. Click image for the largest view.
The announcement brings some interesting construction ideas up for a look. On the positive anode side the university scientists made two positive-electrode materials. One is the “ground cherry type,” in which LiFePO4 is included in hollow carbon shell. The other is the “podded pea type,” in which LiFePO4 is included in carbon nanofibers. Both of the materials ensure high outputs because conductive networks are formed by adding LiFePO4, which has a low conductivity. Got to love those Japanese descriptions.
Ultra Centrifugal Podded Pea Type Lithium Iron Phosphate. Click image for the largest view.
In a discharge of 60 seconds, the specific capacities of the ground cherry type and the podded pea type are 131mAh/g and 113mAh/g, respectively. The advantage of the ground cherry type is that it has a high performance at a high output and it can be made by using commercially available carbon black. The podded pea type, on the other hand, has a high specific gravity, making it easy to enhance the energy density.
On the negative side the electrode material, SnO2 was included in the carbon. SnO2 enables increasing the capacity. But when carbon is used alone its volume significantly changes due to charging and discharging, and its charge/discharge cycle life has been short.
Ultra Centrifugal Tin Oxide Included in Carbon. Click image for the largest view.
Katsuhiko Naoi, professor at the graduate school said, “The ratio of tin oxide and carbon is important. When this ratio was within a certain range, no sign of degradation such as cracking was seen on tin oxide.” The specific capacity per mass of SnO2 is about 80% of the theoretical capacity.
When a cell was made using the new negative-electrode and positive-electrode materials using lithium cobalt oxide (LiCoO2), its specific capacity was 693mAh/g after 800 cycles, showing no sign of capacity degradation.
This is impressive work. Leave it to the Japanese to miniaturize and you’ll get great results. The battery electrodes seem to be made of relatively common materials – a source of great relief. One has to wonder what the amount of lithium is compared to other construction designs. If it’s significantly less, the design merits wide acclaim beyond the announced capacity and cycle life.
With the mineral discoveries last week in Afghanistan there might be some price pressure someday in the major metal elements market. But in the meantime innovation is going to matter a great deal and the Tokyo University results are, one hopes, just the beginning. There could come a day when a top of the line battery’s life is measured in tens of thousands of cycles or more.
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Wow this is clever, looks a bit complex but is very interesting, keep up the good work!
cheers, adam
I still have not read whether this also reduces the recharge time significantly. Being able to deplete a battery faster is good. Being able to recharge faster is better.
Sitting here in Charlotte, within 30 miles of the largest proven reserves of Lithium in the USA. And, only one mine running. Why?
Terrific work! This is the type of information that should be shared around the web. Shame on the search engines for not positioning this post higher!