| Graphite is one of the most widely used anode materials for lithium ion batteries because of its high capacity, low cost and low working voltage platform. However, it also has some bad defects such as the bad compatibility with electrolyte and the poor cycling performance, and needs to be modified to improve the electrochemical performance. Carbon coating is one of the commonly used way to modify graphite. In this paper, the crushed aggregates of artificial graphite was researched and modified with amorphous carbon layer through liquid carbon coating method. Besides, the electrochemical performance of carbon-coated graphite was also tested. In this work, the crushed aggregates of artificial graphite was coated bycarbon using pitch as precursor, and we obtained a better way to prepare the carbon-coated graphite. Moreover, we evaluated the performance of composite materials which were coated different amount of carbon. The tests showed that the first charge/discharge performance was best when 6% pitch was coated and carbonized on graphite, the first reversible capacity and charge-discharge efficiency were 350.5 mAh·g-1 and 91.5% at 30 mA·g-1. The reversible capacity can improve 40 mAh·g-1 than raw materials at 60 mA·g-1 after 50 cycles.We also used straw lignin as carbon precursor to coat artificial graphite and obtained an aqueous carbon coating method to prepare carbon-coated graphite. In addition, two kinds of lignin were used as carbon precursor to prepare different composite materials, it reveals that the materials which were coated by lignin with different molecular weight have the same electrochemical performance. Furthermore, the lignin was heated at 250℃ to improve its carbon yield, and then coated on graphite to prepare carbon-coated graphite. The tests showed the first reversible capacity and charge-discharge efficiency were 350.1 mAh·g-1 and 90.6% at 30 mA·g-1. Compared with raw materials, the reversible capacity can improve more than 30 mAh·g-1 at 60mA·g-1 after 50 cycles. |
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