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U. Alberta team developing new high power and energy lithium-carbon battery system using induced fluorination; dual storage mechanism
18 August 2014
|Ragone plot, comparing Li-CNT-F batteries with other batteries in terms of weight of cathode materials. The highest energy density for Li-CNT-F batteries, 4,113 Wh kgcarbon−1 is presented as a red star. Cui et al. Click to enlarge.|
Researchers at the University of Alberta are developing, and, via their spin-out AdvEn Solutions working to commercialize, a new high power- and -energy density battery system: lithium-carbon-fluorine (Li-C-F). Their system is based on a lithium-carbon battery configuration, but with a different approach.
In a paper in Nature’s open access journal Scientific Reports, the team reported that a rechargeable Li-C-F battery (in this case, a Li-CNT-F battery given their use of carbon nanotubes) demonstrated a maximum discharging capacity of 2174 mAh gcarbon−1 and a specific energy of 4113 Wh kgcarbon−1 with good cycling performance.
Reaching beyond the horizon of LIBs [lithium-ion batteries] requires the exploration of new electrochemistry and/or new materials. The recent popular attempts are Li-sulfur (Li-S) and Li-air (Li-O2) batteries. However, there are some formidable challenges for Li-S and Li-O2 batteries, e.g., dissolution of discharging products, poor cathode electrical conductivity, and large volume expansion upon lithiation.
Li-CFx batteries have the highest energy density among all primary lithium batteries with a theoretical specific energy of 2180 Wh kg(Li+CF)−1. A high capacity of 615 mAh gCFx−1 was also reported for the pre-synthesized CFx cathodes. It is well known that defluorination of carbon fluorides can be achieved with the assistance of lithium cations during discharging in Li-CFx batteries. However, Li-CFx batteries have attracted limited interest because of their strictly non-rechargeable nature and the non-environmental-friendly synthesis process for carbon fluorides, e.g., the use of F2 gas and/or catalysts under extreme temperature conditions.
In a departure from previous approaches, we adopted the lithium-carbon battery configuration. Instead of using carbon materials as the surface provider for lithium-ion adsorption and desorption, we realized induced fluorination of carbon nanotube array (CNTA) paper cathodes, with the source of fluoride ions from electrolytes, by an in-situ electrochemical induction process. The induced fluorination of CNTA papers activates the reversible fluorination/defluorination reactions and lithium-ion storage/release at the CNTA paper cathodes, resulting in a dual-storage mechanism. It is the first time that the reversible fluorination/defluorination reactions were realized at pure carbon and non-fluoride materials. … After the battery cells were assembled, CNTA paper cathodes with no binding materials and no conductive additives were in-situ fluorinated by induction charging for a number of cycles, which enables Li-CNT-F batteries with high energy density and high reversibility.—Cui et al.
AdvEn Solutions hopes to have a prototype by the end of 2014 and aims to develop three versions of the battery to serve different goals. One battery would have a high power output and a long life cycle, the second would have high energy for quick charging, and the third a super-high energy storage.
AdvEn is a growing company housed within the Department of Chemical and Materials Engineering at the U of A. It aims to expand by taking on new researchers and gaining more funding. The company recently secured a partnership with the US-based aerospace company Lockheed Martin to develop an advanced anode for AdvEn’s high-performance carbon cathode.
Xinwei Cui, Jian Chen, Tianfei Wang & Weixing Chen (2014) “Rechargeable Batteries with High Energy Storage Activated by In-situ Induced Fluorination of Carbon Nanotube Cathode” Scientific Reports 4, Article number: 5310 doi: 10.1038/srep05310
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