Influence of the Temperature of the Heat Treatment in a Nitrogen Atmosphere on the Physicochemical and Electrochemical Properties of Petroleum Coke

Abstract

Studies aimed at the development of cheap, safe, and effective carbon materials based on domestic resources for negative electrodes of lithium-ion and post-lithium-ion batteries are topical and have high practical significance. The paper summarizes the results of studying how the temperature of the heat treatment of petroleum coke in a nitrogen flow influences its physicochemical and electrochemical properties. Petroleum coke was kept for 5 h in a nitrogen flow at fixed temperatures of 450, 600, 800, 1000, and 1200°C. Heat treatment of petroleum coke leads to a significant decrease in the specific resistivity (from 4.8 × 10⁷ to 1 × 10^–2 Ω cm), to an increase in the specific surface area, and to a decrease in the pycnometric density (the temperature of 1200°C is an exception). Petroleum coke that has not been heat-treated or has been heat-treated at 450 °С exhibits no electrochemical activity. The carbon electrodes made of petroleum coke heat-treated at 600°C in a nitrogen atmosphere exhibit the maximal anodic capacity for lithium (340–350 mA h/g). However, carbon electrodes based on petroleum coke heat-treated at 600°С exhibit short cyclic duration and high irreversible capacity (58–60%). An increase in the petroleum coke heat treatment temperature to 1200°С leads to a decrease in the irreversible capacity to 40% and in the reversible anodic capacity to 220 mA h/g and to an increase in the cycling duration of the carbon electrodes. The petroleum coke heat-treated un a nitrogen atmosphere at 1000°C is the most promising material for negative electrodes of lithium-ion batteries from the viewpoint of the set of physicochemical and electrochemical properties.