Enhanced Li capacity at high lithiation potentials in graphene oxide

TL;DR

This study uses first principles calculations to show how controlling oxygen coverage in graphene oxide can optimize lithiation potentials and capacities, potentially surpassing graphite and avoiding SEI formation.

Contribution

It demonstrates that tuning oxygen coverage in graphene oxide enhances lithiation potentials and capacities, offering a pathway for improved lithium-ion battery anodes.

Findings

Lithiation potentials above SEI formation threshold at certain oxygen coverages.

Capacities comparable or larger than graphite in specific GO configurations.

High lithiation potentials at graphene nanoribbon edges prevent SEI formation.

Abstract

We have studied lithiation of graphene oxide (GO) as a function of oxygen coverage using first principles calculations. Our results show that the lithiation potentials and capacities in GO can be tuned by controlling the oxygen coverage, or the degree of reduction. We find a range of coverages where the lithiation potentials are above the solid electrolyte interface (SEI) formation threshold, but with capacities comparable to, or larger than graphite. We observe that in highly oxidized and mildly reduced sheets, lithiation occurs through the formation of Li-O bonds, whereas at low coverages that are typical of reduced-GO (rGO) (O:C - 12.5 %), both Li-O bonds and LiC6 configurations are observed. The covalent Li-O bond is much stronger than the bonds formed in the LiC6 ring and the lithiation potentials for epoxides at high and medium coverages are generally large (> 1 eV). For these congifurations, as in the case of Li4Ti5O12 anodes, there will be no formation of SEI, but with the additional advantage of having higher lithium storage capacity than Li4Ti5O12. In reduced GO sheets, the presence of residual oxygen atoms allows for formation of covalent Li-O bonds that lead to storage capacities and lithiation potentials higher than that of graphite. Finally, our calculations show high lithiation potentials for the edges of graphene nanoribbons, which will impede the formation of SEI and hence lead to large reversible capacity.