Effect of Carbonization Temperature on the Structure of Pitch Carbon and Its Low-temperature Lithium Storage Properties

Abstract

Introduction: Lithium-ion batteries were one of the most promising battery systems for electric vehicles. Currently, lithium-ion batteries are required to have higher energy density and cycle stability. The traditional graphite negative electrode cannot meet the requirements. Pitch has many advantages such as wide source, low cost, high carbon residue rate and easy graphitization, as a carbon precursor has been widely used in lithium-ion battery anode and anode materials. Method: In this paper, pitch carbon was prepared by carbonization at different temperatures and studied. Result: The results showed that with the increase of carbonization temperature, the interlayer spacing decreased gradually, the degree of amorphousness decreases gradually, the specific surface area and pore volume also decrease gradually, the initial coulombic efficiency and capacity retention increased, and the discharge-specific capacity decreased. Galvanostatic Intermittent Titration Technique (GITT) tests show that there are two main mechanisms of lithium ions intercalation in the material, surface adsorption and interlayer intercalation. Conclusion: The difficulty of diffusion of lithium ions between pitch carbon layers at low temperatures is the main reason for the decrease of its capacity at low temperature. The carbon material obtained by carbonization of pitch at 800℃ has the best low temperature performance, with discharge specific capacities of 335, 272, 232 and 187mAh/g at 25, 0, -20 and -40℃, of which 55.8% of the discharge specific capacity at room temperature can be retained at -40℃. The amorphous carbon material has certain low temperature charge-discharge performance.