Preparation and coking property of binder pitch: Effects of modification methods

Binder pitch is a crucial raw material for producing carbon/graphite electrodes and lithium-ion battery anodes. The quality and application of carbon/graphite products largely depend on properties of the binder pitch. High-quality binder pitch plays a key role in enhancing quality of the carbon/graphite materials. In this work, refined medium pitch was used as the raw material. Effect of various modification methods on properties of the binder pitch was examined, such as molecular structure, thermal stability, and optical microstructure, along with its coking properties including optical microstructure of pitch coke, carbon microcrystalline structure, and carbon surface morphology. The results indicate that a high-quality isotropic binder pitch (softening point: 144 °C, QI content: 0.46%, TI content: 26.74%, coking value: 51.53%, volatile matter: 56.65%) was achieved using a two-step oxidation polymerization and mild thermal polymerization method. In the first step, the refined pitch was oxidized at 280 °C for 3 h; in the second, it was rapidly heated to 360 °C and held for 1 h under nitrogen atmosphere. This process produced a binder pitch with a high degree of aromatic condensation and fewer small-molecule branched structures. Optical microstructure of the binder pitch coke, produced through thermal conversion and carbonization, comprised 83.92% leaflet and fibrous structures. Degree of disorder in the binder pitch coke was relatively low, resulting in a regular and orderly microcrystalline structure. The content of carbon microcrystals exhibited a high degree of regularity, reaching 90.89%, while the ideal graphite microcrystal content I_G/I_All was 18%.