Univ. of Western Ontario researchers develop graphene nanosheet electrodes with high energy capacity for non-aqueous Li-air batteries
|Discharge–charge performance of lithium-oxygen batteries with (a) GNSs, (b) BP-2000, and (c) Vulcan XC-72 cathodes at a current density of 75 mA g-1. Li et al. Click to enlarge.|
Researchers from the Nanomaterials and Energy Group at the University of Western Ontario, Canada, report the development of graphene nanosheet (GNS) cathode materials for non-aqueous lithium-oxygen (Li-air) batteries that show a capacity of 8,705.9 mAh g-1—the highest capacity of any carbon-based materials in lithium-oxygen batteries reported so far, according to the team. Their paper appears in the RSC journal Chemical Communications.
Non-aqueous Li-air batteries are one of the promising systems being explored for “beyond Li-ion” energy storage solutions for electric vehicles (EVs) because of their extremely high theoretical energy density. The porosity of the air electrode is one of the critical factors in Li-air battery performance, because insoluble products are deposited in the electrode, which block O2 from diffusing to the reaction sites.
Other work, notes the team, also shows that the oxygen reduction reaction (ORR) in the carbon electrode signficantly affects performance.
Therefore, it is important to develop new carbon electrodes to improve the kinetics and enhance the energy capacity. Graphene nanosheets (GNSs) have attracted great attention for energy storage applications. Especially, they have been widely used as catalyst supports or non-noble catalysts for fuel cells.
Recently, Yoo and Zhou examined the GNSs as air electrodes in lithium-air batteries with a hybrid electrolyte and found that GNSs showed good electrocatalytic activity for ORR in an aqueous electrolyte, resulting in high performance. They also developed an idea of applying a graphene-like thin film on a ceramic state electrolyte in a lithium-air battery.
However, to the best of our knowledge, no research on GNSs as a cathode for nonaqueous lithium-oxygen batteries has been reported. Herein, for the first time, we employed GNSs as cathode active materials in nonaqueous lithium-oxygen batteries and found that GNSs delivered an extremely high discharge capacity.—Li et al.
The research team, led by Professor Xueliang (Andy) Sun, believes that the superior capacity is due to the unique structures of the synthesized GNSs, which provides ideal porosity suitable for the electrolyte wetting and O2 diffusion, thereby significantly improving the discharge capacity.
The team also pointed out that the edge sites of the GNSs which contained a large amount of unsaturated atoms were highly active in reaction with oxygen and form oxygen-containing groups, contributing to the battery performance.
Although the detailed mechanism for the oxygen reduction reaction on GNSs in a nonaqueous electrolyte is unclear, it has [been] revealed that GNSs can deliver an extremely high discharge capacity, showing promising applications in lithium-oxygen batteries—Xueliang Sun
The research was supported by Natural Sciences and Engineering Research Council of Canada, Canada Research Chair Program, Canada Foundation for Innovation, Ontario Early Researcher Award and the University of Western Ontario.
Yongliang Li, Jiajun Wang, Xifei Li, Dongsheng Geng, Ruying Li and Xueling Sun (2011) Superior energy capacity of graphene nanosheets for a nonaqueous lithium-oxygen battery. Chem. Commun., 47, 9438–9440 doi: 10.1039/c1cc13464g