# Ab initio study of sodium cointercalation with diglyme molecule into graphite

## TL;DR

This study uses ab initio calculations to understand sodium cointercalation with diglyme molecules into graphite, revealing structural, energetic, and electronic properties relevant for sodium-ion battery anodes.

## Contribution

It provides detailed atomistic insights into sodium-diglyme cointercalation mechanisms and properties, advancing the development of improved anode materials.

## Key findings

- Na(digl)$_2$C$_n$ has lowest intercalation energy at n≈21
- Solvated Na(digl)$_2$ diffuses rapidly in graphite layers
- Electronic conductance of cointercalated compounds is enhanced

## Abstract

The cointercalation of sodium with the solvent organic molecule into graphite can resolve difficulty of forming the stage-I Na-graphite intercalation compound, which is a predominant anode of Na-ion battery. To clarify the mechanism of such cointercalation, we investigate the atomistic structure, energetics, electrochemical properties, ion and electron conductance, and charge transferring upon de/intercalation of the solvated Na-diglyme ion into graphite with {\it ab initio} calculations. It is found that the Na(digl)$_2$C$_n$ compound has the negatively lowest intercalation energy at $n\approx$21, the solvated Na(digl)$_2$ ion diffuses fast in the interlayer space, and their electronic conductance can be enhanced compared to graphite. The calculations reveal that the diglyme molecules as well as Na atom donates electrons to the graphene layer, resulting in the formation of ionic bonding between the graphene layer and the moiety of diglyme molecule. This work will contribute to the development of innovative anode materials for alkali-ion battery applications.