Engineering electronic structure of graphene to boost Lithium-Storage performances.

Organic functionalization of graphene framework was an effective means used to boost the storage performances of lithium, but it lacked a universal strategic guideline for introducing functional groups (electron-withdrawing and electron-donating modules are overall classified). It mainly entailed designing and synthesizing graphene derivatives, in which the interference functional groups were necessarily excluded. To this end, a unique synthetic methodology based on graphite reduction cascaded by electrophilic reaction was developed. The electron-withdrawing-type groups (Br; trifluoroacetyl: TFAc) and electron-donating-type counterparts (butyl: Bu; 4-methoxyphenyl: 4-MeOPh) were readily attached to graphene sheets at a comparable functionalization degree. As the electron density of carbon skeleton was enriched by electron-donating modules, particularly for Bu units, the lithium-storage capacity, rate capability and cyclability were appreciably boosted. For example, they had 512 and 286 mA h g at 0.5C and 2C, respectively; and 88 % of capacity retention after 500 cycles at 1C.