Grinding And Shaping Processes Of Calcined Coke And Its Electrochemical Properties For Lithium-ion Batteries

In recent years,lithium-ion batteries have been used more and more widely,and the development of high-performance and low-cost anode materials has become an important research direction.The factors influencing the properties of negative electrode materials are material,particle size,morphology and other factors.The purpose of this paper is to investigate the influences of grinding and shaping conditions and graphitization to a kind of cheap,wide source,high carbon content of petroleum coke on the particle size,morphology and electrochemical performance.The results of this research have important guiding significance for the actual production and application of anode materials of lithium-ion batteries.In this paper,a kind of shaping machine was used to study the influences of the grinding process conditions on the particle size and morphology of calcined petroleum coke by particle size measurement,morphology characterization,and tap density analysis,the research results showed that:(1)shaping machine can effectively control the sample size distribution;(2)In the process of grinding,main frequency decreases or classifier frequency decreases or fan frequency increasing can effectively increase the grain size of the sample,and the frequency of classifier has the greatest impact;(3)In shaping process,if main frequency increases,the sample shows the smaller grain size and more irregular morphology.If the frequency of classifier increases,fine powder in the sample will reduce,and the sample size will also change.The classifier frequency is too large or too small is negative on the morphology of the samples;(4)After the 1st-shaping,there still has some fine powders in sample,it needs the 2nd-shaping;(5)2nd-shaping can effectively reduce the fine powder content in the sample;(6)The big particles can be effectively reduced by vibrating;(7)The optimum technological conditions are as follows:in griding process,the main frequency is 45 Hz,the frequency of the classifier is 15 Hz,and the frequency of the draft fan is 25 Hz;in shaping process,the main frequency is 35 Hz,the frequency of the classifier is 18 Hz,and the frequency of the draft fan is 30 Hz.The size of the coke powder obtained at this time is about 20 um,and the morphology of the powder is regular and similar to potato.The effects of particle size,morphology and graphitization of the calcined coke on the electrochemical properties were investigated.The results show that(1)the particle size D50 of calcined coke is at 5?26 m.With the increase of particle size,its initial discharge capacity(Li-insertion)shows the tendency of firstly increase and then decrease.When the D50 is 18?m,the initial maximum discharge capacity of 364.3 mAh/g can be obtained,with the reversible specific capacity of 264.2 mAh/g;(2)the first coulombic efficiency with the increase of particle size,increases from 66.8%to 72.5%;(3)the first coulombic efficiency of 2nd-shaping calcined coke improves about 10%,and vibrated and classified calcined coke shows about 15%higher than the 1st-shaping calcined coke;(4)needle coke has higher crystallinity than calcined coke,but the first charge and discharge specific capacity and cycle performance is relatively low than those of the calcined coke.The first coulombic efficiency of needle coke is 82%,while for the calcined coke just 72%;(5)Graphitized coke exhibits coulombic efficiency with about 87%and excellent cycling performance,the first reversible capacity of petroleum coke has reached 343.8 mAh/g.