New Lithium Iron Pyrophosphate as Li-ion Cathode Material; Highest Voltage Among Known Iron-based Phosphate Cathodes
12 September 2010
A team from the University of Tokyo and the Tokyo Institute of Technology has synthesized a new pyrophosphate compound (Li2FeP2O7) by a conventional solid-state reaction for use as a cathode material in Li-ion batteries. Reversible electrode operation at ca. 3.5 V vs. Li was identified with the capacity of a one-electron theoretical value of 110 mAh g-1 even for ca. 1 µm particles without any special efforts such as nanosizing or carbon coating.
The new pyrophosphate Li2FeP2O7 thus offers the highest voltage among the known Fe-based phosphate cathodes, they noted in a Communication in the Journal of the American Chemical Society.
The material showed steady capacity retention upon cycling. However, they found, the initial charge curve showed a different shape from that of subsequent cycles, possibly due to the irreversible structural change. About 40% of the initial capacity can be delivered in 1 h (1C rate), and about 20% even in 6 min (10C rate), suggesting that such electrodes could sustain respectable rate capabilities, they observed.
Li2FeP2O7 and its derivatives should provide a new platform for related lithium battery electrode research and could be potential competitors to commercial olivine LiFePO4, which has been recognized as the most promising positive cathode for a lithium-ion battery system for large-scale applications, such as plug-in hybrid electric vehicles.
—Nishimura et al.
Resources
Shin-ichi Nishimura, Megumi Nakamura, Ryuichi Natsui, and Atsuo Yamada (2010) New Lithium Iron Pyrophosphate as 3.5 V Class Cathode Material for Lithium Ion Battery. J. Am. Chem. Soc., Article ASAP doi: 10.1021/ja106297a
Wow, 385Wh/kg and capable of handling 10C....that would be quite a step forward in energy density for the Lithium Phosphate family.
Posted by: DaveD | 12 September 2010 at 10:49 AM
"About 40% of the initial capacity can be delivered in 1 h (1C rate)"
It sounds good at first, until you read the rest...
"However, they found the initial charge curve showed a different shape from that of subsequent cycles, possibly due to the irreversible structural change."
There is quite often a "however".
Posted by: SJC | 12 September 2010 at 12:28 PM
Frankly, I couldn't tell what they were saying about the capacity rate and the number of cycles.
First they say it's great, then they say it is only great on the first time, then they add the last sentence in the same paragraph "suggesting that such electrodes could sustain respectable rate capabilities, they observed."... and now I don't know how the hell to interpret the whole thing.
Either poor writing or a bad quote from one of the researchers. I guess you can interpret whatever you want from this one. LOL
Posted by: DaveD | 13 September 2010 at 07:45 AM
It sounds like there is work to be done. It seems various chemistries have their pluses and minuses. I am encouraged that there is so much development being done, that can bring about more advancement sooner.
Posted by: SJC | 13 September 2010 at 11:55 AM
Exactly. The more advancements the better. Some of them can even work together and have an additive effect on the overall state of the art.
I'm just encouraged at the amount of work across the board and all the small breakthroughs that will add up quickly.
I think by 2015, we will have a very different battery available. I'm betting that it will be around 400Wh/kg at a cost of around $350 per kWh for large volumes.
Posted by: DaveD | 13 September 2010 at 12:52 PM