Study Of SiO And Spherical Graphite Composite Material Preparation And Performance

The silicon monoxide and spherical graphite and its composite material are studied in this topic. Because silicon monoxide material has high theoretical capacity volume with poor cycling performance, and spherical graphite is on the contray, so the separate research on two kinds of materials is needed. With improving the performance of silicon monoxide by disproportionation, ball mill, carbon coating method and so on,and improving the performance of spherical graphite materials by alkali etching method, we can combine the two methods to find out the best proportion of composite materials, so that the composite material has good reversible capacity as well as good cycling performance. Using XRD, SEM and other testing methods for characterizing the material, the use of cyclic voltammograms test, ac impedance, constant current charge-discharge test to study the electrochemical properties of materials.With the disproportionation of the Si O material at 700℃, 800℃, 900℃, 1000℃,1100℃, the best disproportionation temperature is 1000℃. The disproportionation material under 0.1C cycle 100 times, still can keep the reversible capacity of about93.6m Ah/g. Disproportionation for the Si O is limited to improve the performance of the material and is not fundamentally solve the problem of diminishing the Si O based anode materials capacity. Ball mill and carbon coating to a certain extent, improved the material circulation capacity, but neither can change the Si O based anode materials circulation stability problems. So, it is necessary to further improve the electrochemical performance of the Si O based anode materials, so that they can be applied for the commercial purpose.Mixing respectively by the suction filter and wet mixed alkali etching two methods of spherical graphite materials for etching process. Mixing the best condition of the suction filter alkali etching in alkali carbon quality ratio 10:1~20:1, under 0.1C and 0.2C, alkali carbon ratio 10:1 processing the good performance of spherical graphite anode materials, the reversible specific capacity in 350 m Ah/g and 345 m Ah/g,is better than that of spherical graphite as 332 m Ah/g and 312 m Ah/g, cycle stability is better also, 0.1C ratio in circulation after 40 times, reversible capacity keep341.6m Ah/g. But when large current charge and discharge, alkali carbon ratio 20:1processing materials reversible capacity is slightly better and alkali carbon ratio 10:1processing material stability is better. The best condition of wet mixing alkali etching process in alkali carbon ratio is about 3:1, 0.1C and 0.2C conditions, with the reversible specific capacity being 345 m Ah/g and 320 m Ah/g respectively, so thatcycling is relatively stable, and the reversible capacity is about 348.7m Ah/g in 0.1C ratio in circulation after 60 times. 1C ratio in circulation after 200 times the reversible capacity is about 280.3m Ah/g, and the reversible capacity of spherical graphite material is obviously better than the 180.6m Ah/g.Preparation of etching processing spherical graphite and disproportionation of the Si O composite materials by means of mechanical mixing.The performance of two alkali etching spherical graphite/disproportionation the Si O is getting worse gradually with the increase of the Si O content, and the best performance is the material containing 5% of the Si O composite materials. The Stirred suction filter alkali etching spherical graphite/disproportionation Si O composite material under 0.1C cycling 40 times, keeps the reversible capacity of 413.8m Ah/g, and the reversible capacity can also reach 396 m Ah/g under the cycle of 0.2C.t The reversible capacity of wet mixed alkali etching spherical graphite/disproportionation the Si O composite material under0.1 Cand 0.2 Cratio is 403 m Ah/g and 397 m Ah/g respectively, wit cycling stability being better too. It can retain the reversible capacity of 399.4m Ah/g after 50 times cycle in the 0.1C.