Lithium and sodium ion binding in nanostructured carbon composites

ABSTRACT

High charge capacity in lithium and sodium-ion batteries can be achieved using anodes composed of nanostructured carbon composites. The tailoring of the nanostructure to achieve both high loading and low irreversible binding depends upon the binding mechanisms of the ion. In this work, reactive molecular dynamics simulations are performed on model carbon composite anodes to investigate and to compare the binding mechanisms of lithium and sodium ions. In composites composed of both crystalline and amorphous domains, lithium ions bind preferentially at the interface between the amorphous and crystalline domains, rather than via the standard intercalation mechanism observed in graphitic anodes. In these same composites, sodium ions bind preferentially in the crystalline domain, even though the intercalation of sodium in graphitic anodes is not a viable mechanism for charge storage. The difference in mechanisms is explained through a comparison of the binding energies in the carbon composite to the energies of the respective metals and metal hydrides.

KEYWORDS:

• Molecular dynamics
• ReaxFF
• lithium
• sodium
• carbon composite
• battery

Acknowledgments

This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. This work used the XSEDE COMET at the San Diego Supercomputer Center through allocations TG-DMR190050 and TG-DMR190098. This research was supported by a grant from the U.S. Department of Agriculture National Institute of Food and Agriculture Nanotechnology Program award number 2017-67021-26599. D.P. Harper acknowledges support from the USDA National Institute of Food and Agriculture, Hatch Project 1012359.AMR acknowledges support from the Center for Materials Processing at the University of Tennessee.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Institute of Food and Agriculture [grant number 2017-67021-26599].