The Preparation Of Calcium Carbide-derived-carbon And Its Application In The Surpercapacitor

The supercapacitor is a new type of electrochemical energy storage devices, which also called electrochemical capacitor （EC） or electrical double layer capacitor （EDLC）. The capacitance of supercapacitor can reach the order of Farad （F） even ten thousand Farads （F）. At the same time its specific energy density is 20-200 times of traditional capacitor. Environment-friendly Supercapacitor can work in wide temperature range of -20℃-60℃. Besides, it has much higher power density, much longer cycle life. Supercapacitor has begun filling the niche between electrochemical batteries and dielectric capacitors. Because of their wide application foreground, it’s of great importance to conduct a series of experimental studies on electrode materials and electrolytes for the application of supercapacitor, which can promote the development in the the civil and military field.In this study, a new type of one-step preparation technique for the calcium carbide-derived- carbon （CCDC） was developed. CCDC was synthesized from CaC₂ in a freshly prepared chlorine environment in the temperature range of 100-600℃. The structure and morphology of CCDCs were studied by x-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results showed that CCDCs were amorphous nanoscaled materials, which pores were interlaced. XRD indicated they consisted of two broad peaks and the CCDCs structures depended on the synthesis temperature. When reaction temperature was at 600℃, the （002） diffraction peak of CCDCs became more narrow, which was due to the beginning of graphitization tendency. Porosity measurements demonstrated that the CCDCs had narrow pore size distribution （1.4-17 nm） and specific surface area close to 800 m²g^-1 at a synthesized temperature of 100℃. The average pore size increased from1.9 nm to 3.8 nm with reaction temperature increasing from 100℃to 600℃.Coin cell supercapacitors were assembled by CCDCs as electrode materials and 6 molL^-1 KOH as electrolyte. The coin cells were studied by a series of electrochemical measurements. The results showed that the CCDCs electrodes exhibitated good electrochemical performances, high reversibility and high charge-discharge efficiency in KOH electrolyte. The specific capacitance of electrode with the CDCC prepared at 400℃had maximum capacitance of 174.6 Fg^-1. The coin cell was cycled for 10000 cycles, and specific capacitance had only a decrease of 5%.Activation is a good method to improve the electrochemical performances of electrode materials. The CCDCs synthesized at 200°C, 400°C, 600°C were treated in nitric acid （HNO₃） at 70°C. Oxygenous functions on the surface of CCDCs were studied by infrared spectrometer （IR）. The capacitive properties of treated CCDCs were studied by a series of electrochemical tests. It was found that the moderate content of oxygenous functions on the surface of CDCCs could result in a higher specific capacitance.