High tap-density graphene cathode material for lithium-ion capacitors via a mass-scalable synthesis method

Abstract

Graphene-based Li-ion capacitors have attracted extensive attention in energy storage systems nowadays, due to their potential advantages: high energy density and power density. However, there are several limitations hindering their commercial production, including the low tap density and mass loading for the graphene cathode material, which severely limit the performance of Li-ion capacitors. Herein, to obtain high-density graphene cathode material with high efficiency, it reports a simple and mass-scalable method in which graphene-oxide is synergistically reacted with pretreated few-layer graphene via an in situ self-assembly hydrothermal process. Besides that, the rapid drying process for graphene-hydrogel is conducted at 90 °C in blast drying oven. After the ball-milling process, the acquired high tap density graphene (HTDG) powder can reach 0.7 kg L−1. The corresponding cathode with thickness of 120 μm exhibits a high mass loading up to 13.5 mg cm−2. Also, a reversible capacity up to 136.4 mAh g−1 is achieved based on HTDG material in a potential voltage range of 1.5–4.2 V (vs. Li/Li+) at a current density of 0.1 A g−1, and the capacity retention can reach 97% after 1500 cycles at 1 A g−1. The sample also possesses a good rate performance: the capacity can maintain about 68% at 100 C and 63% at 200 C.