▎ 摘　　要

The mixture of citric acid and histidine was used as the carbon source for the preparation of histidine-functionalized graphene quantum dots via a high temperature pyrolysis (CH-GQD). The as-prepared CH-GQD is composed of graphene sheets with an average size of 3.5 nm. The edge of graphene sheets contains the rich of hydrophilic groups. The product is very soluble in water and displays strong and stable fluorescence emission. CH-GQD was coated on the surface of silica nanoparticles to obtain graphene quantum dots-silicon composite. Then, the lithium ion battery was assembled and its electrochemical performance was investigated, in which the composite electrode and metal lithium plate were used as the anode and the cathode, respectively. The results show that the introduction of CH-GQD leads to decrease of the electron transfer impedance of the silicon cathode by more than 14.7 times, increase of the lithium ion diffusion coefficient between the electrode and the electrolyte by 310 times, and reduce of storage lithium capacity fading caused by the side reactions of the silicon atoms with the electrolyte molecules. The first discharge capacity of CH-GQD@Si cell reaches 3325 mAh.g(-1) at the current density of 50 mA.g(-1) and 1119 mAh.g(-1) at the current density of 1000 The discharge capacity can remain 1454.4 mAh.g(-1) at least after 100 cycles at the current density of 100 mA.g(-1). The battery performance of CH-GQD@Si composite electrode is obviously better than that of pristine silicon anode and the modified silicon anode with the graphene quantum dots (CA-GQD), which was produced by the pyrolysis of citric acid and alanine. Because the difference in the structure between CH-GQD and CA-GQD only is the imidazole groups on the edge of their graphene sheets, the above result also proves that the imidazole group plays important roles to improve the electrochemical performance of the composite electrode.