Preparation, Modification Of Activated Carbon And Application In The Lithium-sulfur Battery

Activated carbon has been widely applied in various industries for several years. It shows high specific surface area, developed microporous structure and perfect adsorption capacity, and has been used in electrode material, catalyst carrier, chemical, environmental protection and food and pharmaceutical industrial etc. To meet the ever-increased demand of the production and living and the development of the science, high surface area activated carbon, which shows its specific surface area higher than3000m2/g, attract an increasing number of people pay attention on it, becoming a research hotspot in the field of energy storage and environment protection.In this paper, activated carbon with high specific surface area was synthesized by chemical activated method, coconut shell of Hainan as a raw material, and nitrogen was used as a protective gas. The effect factors, such as the activation agent selection, the ratio of the carbon and alkali, the carbonization temperature, the carbonization time, the activation temperature, the activation time etc, had been studied to the pore structure of activated carbon during the preparation though orthogonal experiment and single factor experiment. And we finally confirmed the optimization experiment process and process conditions. Microporous activated carbon was determined by iodine adsorption, and by the method of BET (low temperature nitrogen adsorption method) on the activated carbon, surface area and pore structure was determined. The prepared activated carbon, through certain process assembled into a lithium battery, was used as an electrode material for lithium battery. Through the charge and discharge performance of the lithium battery, we study the effect of the pore structure and surface area of the activated carbon to the lithium-sulfur battery performance.Obtained result showed that the optimal process a condition for preparation of coconut activated carbon was firstly pyrolyzed at500℃(carbonization temperature) for2h(carbonization time), and nitrogen (N2) was used as a protective gas, with a heating rate of10℃/min. Then, mix the carbonization with potassium hydrate in a weight ratio as4. These mixtures were heated to300℃(per activation temperature) for30min (per activation time), then to800℃(activation temperature) and held at this temperature for2h (activation time) in a nitrogen purged reactor tube in the pipe furnace with a heating rate of10℃/min. Iodine adsorption value was2718.613mg/g. The specific surface area and pore volume of the prepared activated carbon were3125m/g and1.691cm/g, respectively. BJH adsorption average pore width was2.176nm.The oil adsorption performance of the modified activated carbon, which was modified by ammonia water and Hydrogen peroxide solution, was studied. Through the activated carbon modified by ammonia water, the adsorption capacity of diesel is1.81times of the original; and hydrogen peroxide modified activated carbon, the adsorption capacity of diesel down to87.98%of the unmodified activated carbon.The electrochemical performance of the production as cathode materials was studied by the galvanostatic method with the condition of1.5-2.8V,0.1mA. The sulfur/activated carbon composite with a mass ratio of7:3deliver the initial charge and discharge specific capacity up to944.792mAh/g and1301.042mAh/g, respectively. The charge specific capacity was lower than the discharge one356.350mAh/g. It shows that the capacitance performance of the obtained lithium-sulfur battery, which has the activated carbon and sulfur as cathode, is closely related to its specific area and rises along with its specific area.