Lithium-ion pre-doping of graphite electrodes using lithium naphthalenide derivatives with electron-donating substituents

We evaluated the effect of the molecular structure of lithium naphthalenide derivatives on the lithium doping depth, for a simple pre-doping method for natural graphite electrodes by immersing in 2-methyltetrahydrofuran (2-MeTHF) solution of lithium naphthalenide derivatives. To increase the reducing ability of lithium naphthalenide, multiple kinds of naphthalene derivatives having electron-donating substituents on the aromatic ring were examined. As a result, it was found that when a radical anion solution prepared from a 1 mol kg-1 solution of 1,5-dimethylnaphthalene in 2-MeTHF and an excess amount of lithium metal was used, the doping depth of 88 mAh g-1 could be achieved by immersion for 1 hour at room temperature. This method may be potentially applied as a pre-doping method for the negative electrodes for electrochemical energy storage devices.