Graphite materials have high chemical/physical stability and low resistance due to the structure in which graphene is stacked. These layered structures exchange electrons from the graphite surface through reactions with lithium ions in the organic electrolyte to provide a path by which lithium ions are stored. Lithium ions entering inside via the path accumulate between the graphite layers to form a lithium layer. Due to such lithium storage and transfer mechanisms, graphite has low fast charge-discharge performance. Also, it is difficult to manufacture good quality artificial graphite(or synthetic graphite) because high processing temperature(over 3000 ℃) is required.
In order to understand the disadvantage of graphite, carbon anode materials were produced according to the different temperatures, and the lithium intercalation-deintercalation mechanism was considered according to the structure of carbon. Based on this, we designed an artificial graphite anode material that composites small particles into secondary particles.
An artificial graphite anode material (10-15 ㎛) is produced using coke at two sizes (10-15 ㎛, 2-5 ㎛) and the electrochemical properties are compared and discussed. We produce and measure an artificial graphite anode material using coke with a particle size of 10-15 ㎛, limited lithium ion insertion-desorption pathways, increased migration pathways, and low-speed charge-discharge characteristics. When a block is manufactured using coke at a particle size of 2-5 ㎛ and an anode material is created with a particle size of 10 to 15 ㎛, voids capable of storing lithium ions between the coke particles form inside the anode material. These spaces are utilized and the capacity was measured. In addition, the lithium ion insertion-deintercalation path and lithium ion diffusion distance are controlled and the high-speed discharge properties were measured (78.3%) at low temperatures (5C / 0.1C, -10 ℃). At the same time, the high specific surface area due to the small size of the coke was controlled by the binder pitch used in the block, leading to excellent initial efficiency performance.
Elements used as additive to lower temperature the graphitic process include boron, phosphorus, and nitrogen. Boron is known as a graphitization additive, because it accelerates the homogeneous continuous graphitization process of the entire carbon without any formation of specific carbon components such as graphite. In this study, various amount of boron and PFO (pyrolysis fuel oil, carbon precursor) were used in an attempt to reveal the boron additive effect. Pitch was produced using a boric acid and pyrolysis fuel oil (PFO), and high-temperature carbonization was carried out at 2,600 ℃. As a result, synthetic graphite exhibiting high crystallinity at a relatively low temperature was produced. The electrochemical performance of several boron-doped and non-doped carbon materials with different structures as anodes in lithium ion batteries was investigated by a structure analysis.