Efficient method for synthesizing graphene materials applied in lithium-ion capacitors with high performance

To solve the problem of extremely low washing efficiency of graphite oxide (GO), an efficient method is successfully developed to prepare few-layer graphene powder, which is a key raw material for the preparation of high tap-density graphene (HTDG) anode materials. HTDG anode powder with the tap density of 0.68 kg L −1 can be obtained. The characterization results demonstrate that this efficient method is feasible for synthesizing the few-layer graphene and HTDG anode materials. The results of electrochemical measurements show that the HTDG anode materials display satisfactory electrochemical performance. The reversible capacity up to 326.3 mAh g −1 and excellent cyclic and rate performance, which are all better than those of commercial hard carbon materials, are achieved based on HTDG anode materials in a potential range of 0–1.5 V (vs. Li/Li + ). Additionally, the acquired HTDG anode materials are also applied in soft-packaged Li-ion capacitors (LICs). The capacity retention of the LICs with operating voltage of 1.5–4.2 V can reach 90.4% after 1500 cycles at 1 C rate. The devices also possess the good rate performance: the capacity can maintain about 90% at 10 C, 86% at 15 C, 84% at 20 C, 79% at 40 C, 75% at 60 C, 70% at 80 C, and 56% at 100 C.