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Researchers Develop LiFePO4 Cathode Material with High Capacity and Long Cycle Life; New Process Applicable to Other Materials
29 August 2008
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| Capacity of the new olivine-structure LiFePO4 material. Click to enlarge. |
Researchers at the Institute of Energy Technology, National Institute of Advanced Industrial Science and Technology (AIST) in Japan have developed a new process to produce an optimized LiFePO4/carbon composite cathode material that offers high capacity and long cycling life.
The new lithium iron phosphate nanoparticles retain a capacity of 112 mAh/g and 90 mAh/g under high-rate charge/discharge of 30C and 60C, respectively. Capacity after 100% depth of discharge over 1,100 cycles is 165 mAh/g.
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| The new coating process, represented in (b) addresses issues of conductivity, according to the AIST team. Click to enlarge. |
The material contains a highly crystalline LiFePO4 core with a size of about 20-40 nm and a semi-graphitic carbon shell with a thickness of about 1-2 nm. The method devised to produce the material can be extended to the preparation of other electrode materials for lithium-ion batteries, such as Li4Ti5O12/carbon and Mn3O4/carbon composites.
A paper on the work is published online in the journal Angewandte Chemie International Edition.
Lithium-ion phosphate is an attractive cathode material because of its low raw material cost and stability. Its downside, however, it lower energy density and its poor electronic conductivity. (Earlier post.)
Capacity deterioration in olivine LiFePO4 is caused by the slow diffusion of Li-ion in active materials and low electron conductivity, according to the AIST researchers. High-temperature treatment to coat the LiFePO4 material with carbon to improve conductivity could result in overly large carbon particles, defeating the efforts to keep the coating to a nanometer order. Furthermore, aggregation could leave parts of the surface uncoated.
To address the problem, the group has been focused on the production of nanometer particles, and carbon-coating them using a new in-situ polymerization restriction process described in the paper.
Resources
Yonggang Wang, Yarong Wang, Eiji Hosono, Kaixue Wang, Haoshen Zhou (2008) The Design of a LiFePO4/Carbon Nanocomposite With a Core-Shell Structure and Its Synthesis by an In Situ Polymerization Restriction Method, Angewandte Chemie International Edition doi: 10.1002/anie.200802539
August 29, 2008 in Batteries | Permalink | Comments (7) | TrackBack (0)
Comments
Posted by: HarveyD | August 29, 2008 at 10:54 AM
This would be great for trash trucks aswell
Posted by: | August 29, 2008 at 02:54 PM
So much money is being spent on LiIon batteries they soon will have more capacity than ZEBRA batteries that now only have MES-DEA working on them. They will remain more environmentally robust. ..HG..
Posted by: Henry Gibson | August 29, 2008 at 09:14 PM
Good to see this line of research come to a success. We seem to have multiple viable formulations for PHEV type batteries.
Will we have PHEV cars by 2012 for under $30,000?
Posted by: Lulu | August 30, 2008 at 05:23 PM
A 20kWh ZEBRA battery could be mass produced now for about 2,000 per unit. This would get electric cars on the road.
This new LiFePO4 technology is very promising, but will take about 10 years to fully develop and get into production. Without a full market ready for the product, the needed investment will be tougher to find.
One thing, we see that battery cycle life issues will eventually be solved. 1000 cycles with an increase in power capacity is huge!
Now if production costs can be worked out, this is part of a winning product.
Posted by: | August 31, 2008 at 07:48 AM
BYD are already manufacturing LiFePO4 in large quantities for their F3 PHEV (which uses a 20 kWh battery pack). On sale this year in China.
Posted by: clett | September 01, 2008 at 01:29 AM
If BYD can incorporate these technology upgrades into its process, it will have a killer LiFePo4 battery pack for its EVs and hybrids.
BYD is a huge player in the Li battery field in general and will certainly become very successful with EVs if they manage to create a good pack for them.
Posted by: sola | September 02, 2008 at 02:44 AM
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Excellent resistance to multiple FULL discharge-charge cycles. This could lead to a smaller capacity battery pack.
Could be well suited for city cabs/buses (and others) HEVs and PHEVs with frequent high breaking power recouperation.
Wonder what would be the price per KWh when mass produced? Would have to under $300/Kwh for affordable PHEVs and BEVs.