Research On Modification And Application Of The Silicon/graphite/carbon Anode Material For Lithium Ion Batteries

Due to natural advantages of silicon’s high capacity, it can effectively improve thelithium ion battery energy density and be very good to adapt to today’s market demandfor high capacity lithium ion battery when used as lithium ion battery anode materials.But the serious volume effect can make the material capacity fade quickly in the processof circulation, which makes the silicon material difficult to be applied in practicalproduction. In order to effectively limit the volume effect of silicon material, this articleis based on the silicon carbon composite material modification, preparation technologyof electrode and the preparation technology of full batteries was optimized at the sametime. Therefore the silicon material application can be promoted in practical process.The Si/graphite/carbon including different types of graphite was studied and theresult showed that the Si/graphite/carbon including Cl-A graphite had the bestperformance, the first delithiation capacity can reach1003mAh/g, and capacityretention of82.6%after50times circulation; The effect of silicon source’s particle sizeon the properties of materials was invested,the silicon source particle size less than1μm micron grade was used to prepare silicon/carbon/graphite composite material,thefirst delithiation capacity is799mAh/g, and the capacity retention of85.7%after50times circulation; Besides,the composite electrode coated twice by pitch pyrolyticcarbon effectively improve the cycle stability.On the research of electrode preparation of silicon/carbon/graphite compositematerial, it can be found that the first delithiation capacity is998mAh/g, and the160cycles capacity retention of70.6%after the electrode was heated under200℃for sixhours, ammonium bicarbonate is added to the electrode to form pores which can leavethe expansion reserved space for embedded lithium. When ammonium bicarbonateaddition amount was2%, the first delithiation capacity is959mAh/g, and the40cyclescapacity remain at a rate of85.3%.When the ammonium bicarbonate addition amount is5%, the efficiency is86.2%for the first time, and the first delithiation capacity is907mAh/g, while the capacity of40cycles is at a rate of82.9%. At the same time, to limitcapacity in charge and discharge process can alleviate the volume effect, especiallywhen the capacity is controlled at740mAh/g, the charge&discharge capacity was notfade after97times.Considering the formation process of SEI layer on anode materials,Si/Graphite/carbon-LiCoO₂full batteries have higher capacity retention ration. Theoptimized schemes were researched; the capacity retention ration was improved from85.5%to88%.