| Si,with advantages of high theoretical capacity,appropriate operating potential and high natural reserves,belongs to a new type of lithium ion battery cathode material.However,in practical applications,silicon produces distinct volume expansion when removing/embedding lithium,leading to a rapid decline in battery capacity,which hinders the commercialization of Si cathode.In view of the above problems,Si nanoparticles are compounded with a variety of carbon materials and Si/C anode materials are prepared in this paper.Through structural design,the electrode conductivity increases and the volume change level during charge and discharge reduces.The research contents and results of this paper are as follows:?1?The Si/C composite material?M-Si/C?is synthesized by one-step hydrothermal method.The outer layer of Si particles in the composite material has a structurally complete carbon coating.The carbon material could significantly reduces the internal stress of Si under the condition of volume expansion and avoids its contact with electrolyte.At the current density of 0.2A·g-1,the specific capacity is 510mAh·g-1 after100 cycles,and the capacity retention rate is above 80%after 200 cycles.?2?The composite structure of Si/C porous microspheres?P-Si/C?is obtained by one-step hydrothermal method,in which the Si nanoparticles are evenly embedded in the carbon spheres like pomegranate seeds.At the current density of 0.5A·g-1,the specific capacity is still 530mAh·g-1 after 100 cycles,with A capacity retention rate of 79.3%.Even if the current density increases to 1A·g-1,the reversible specific capacity could be reached to 420mAh·g-1.?3?Using filter paper as carbon skeleton,Si/C composites?F/G/Si?with three-dimensional structure are prepared by the polymerization of glucose.At the current density of 0.2A·g-1,the circulating capacity could reach 422mAh·g-1 embedded lithium capacity after 100 cycles,and the capacity could still be stable after 50 cycles. |
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