Background & Technology:
ARL’s Sensors and Electronic Devices Directorate has developed an improved lithium iron phosphate (LiFePO4) material that offers a lower-cost, more environmentally friendly alternative to commercial lithium cobalt oxide (LiCoO2) for cathodes found in rechargeable batteries. Compared to standard LiFePO4 cathodes, this innovation provides greater conductivity, as well as higher average capacity and charge-discharge rate, yielding a greater range of applications with negligible additional materials or fabrication cost.
LiFePO4 has advantages over transition metal oxide cathode materials such as LiCoO2, common in rechargeable batteries, especially with respect to abuse tolerance. However, low conductivity constrains use as a practical battery component. Fixes such as particle size engineering and applying conductive carbon coatings improve conductivity but lower energy density.
ARL synthesized lithium-doped cathodes, where iron ions in the LiFePO4 material are substituted with lithium ions. This substitution improves conductivity by more than 1,000,000 times as compared to non-doped LiFePO4, making it comparable to LiCoO2, an industry standard. Moreover, the ARL approach increases bulk electronic conductivity, which minimizes loss of energy density. This approach is also attractive in that no foreign atoms are introduced into the material that may be unstable in the electrochemical environment.
The ARL lithium-doped LiFePO4 cathode material also maintains advantages of non-doped LiFePO4, such as
high thermal stability and low reactivity with common electrolytes. Based upon iron, it is also less expensive, more abundant, and environmentally more acceptable than cobalt metal-based cathode material. Fabrication of the new ARL material can be accomplished using existing process lines and materials.
- Less expensive and more environmentally acceptable than cobalt cathodes
- Conductive as cobalt and more abuse tolerant
- Superior conductivity and capacitance as compared to standard LiFePO4
Status and Opportunity:
Issued US Patent No. 7,629,080 is available for license
Supplemental Technical Information:
- LI1+XFE1-XPO4 : ELECTRONICALLY CONDUCTIVE LITHIUM IRON PHOSPHO-OLIVINES WITH IMPROVED ELECTROCHEMICAL PERFORMANCE – Article
- Synthesis and electronic properties of Li doped LiFePO4 – Article
- Electronic Properties of LiFePO4 and Li doped LiFePO4 – Article
- Li1+xFe1-xPO4: Electronically Conductive Lithium Iron Phospho-olivines with Improved Electrochemical Performance – Presentation
For more information, contact:
Dan Swanson, CLP (406) 994-7736, email@example.com
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