Graphene-based Electrode Leads to Highest Capacity Lithium-Air Batteries

New approach to molecular self-assembly produces porous, thin films of carbon (aka graphene), enabling high-capacity electrodes for lithium-air batteries.

Hierarchically porous electrode made of self-assembled functionalized graphene sheets. — Image courtesy of PNNL

The Science

Functionalized graphene sheets are self-assembled in oil-water emulsions to produce a novel, high-capacity electrode material with a unique, hierarchical arrangement of pore structures and a high number of reactive sites.

The Impact

This study developed a new self-assembly approach to obtain 3-dimensional (3D) graphene architectures and verified, for the first time, that defects within the graphene structures are the active sites for electrochemical reactions, an important understanding for Lithium-air battery function. It also led to an exceptionally high capacity electrode—15,000mAh/g—which is the highest value reported to date for Lithium-air batteries.

Summary

Graphene, a molecularly thin sheet of carbon, is among the most interesting new materials being developed to achieve revolutionary, high-performance batteries needed for the electrical grid, electric cars, and other types of energy storage. In research at Pacific Northwest National Laboratory and Princeton University, a new way to control the 3D porous architecture and reactive surfaces of graphene has been discovered. By employing self-assembly at the oil-water interface in oil-water emulsions, an unusual hierarchical arrangement of functionalized graphene sheets has been achieved. This material when used as an air electrode delivers an exceptionally high capacity of 15,000 mAh/g in lithium-air batteries, the highest value ever reported. This excellent performance is shown to be due to the presence of two types of pore structures in the electrode material—micron scale pores for facilitating rapid air (oxygen) diffusion and nanoscale pores with a high density of reactive sites for lithium-oxygen reactions. The hierarchically ordered porous structure also enables high storage capacity by promoting accessibility to most graphene sheets in the structure, and a patent application has been filed.

Contact

Jun Liu
Pacific Northwest National Laboratory
jun.liu@pnnl.gov

Funding

Basic Research: DOE Office of Science, Office of Basic Energy Sciences supported the modeling and understanding of the structure of the materials.

Microscopy utilized the Environmental Molecular Sciences Laboratory, a user facility supported by DOE, Office of Science, Office of Biological and Environmental Research; Computations used the National Energy Research Supercomputing Center, a user facility supported by DOE’s Office of Science, Office of Advanced Scientific Computing Research.

Publications

Jie Xiao, et al. “Hierarchically Porous Graphene as a Lithium-Air Battery Electrode”, Nano Letters, 2011, 11, 5071-5078; Doi/10.1021/nl203332e http://pubs.acs.org/doi/abs/10.1021/nl203332e.