Structure Design And Preparation Of High Specific Capacity Silicon-based And Znic Oxide-based Anode Materials

Silicon and zinc oxide anode are expected to be the next generation of anode materials for lithium-ion batteries due to the high specific capacities.However,the huge volume change during lithium ion insertion/extraction and the inherent poor conductivity of silicon and zinc oxide seriously influence the cycling stability and the coulombic efficiency of electrode materials.In order to further improve the electrochemical performance of the two electrode materials,we design and prepare three different carbon coated composites in our study,and construct the high-performance lithium ion batteries using the prepared anode materials.At the same time,the relationship between the microstructure characteristics of the materials and the electrochemical performance is studied,thus achieving the goal of satisfying the actual needs by adjusting the materials structureFor the silicon anode materials,firstly,we synthesize the Si/C composite with polyvinylidene fluoride pyrolysis coating on the nano silicon,and the effect on the electrochemical performance is also studied.The results show that the Si/C composite has a good core-shell structure,which is beneficial to realize the the double functions of volume expansion mitigation and SEI stabilization.When used as the anode materials,the first coulombic efficiency of the Si/C composite is 69%,and the capacity retention is 72%after 50 cycles at the current density of 0.2 A/g.In order to develop practical high specific capacity lithium-ion batteries,we design and propose the preparation of Si/C microspheres with unique structure by spray drying and high temperature pyrolysis using kerf loss waste silicon and biomass lignin as raw materials.The preparation method here has the advantages of simple,green and large-scale implementation,and the obtained Si/C microspheres not only have the porous structure and conductive network,which are helpful to lithium ion diffusion and electron migration,respectively;but also the controllable micron scale of the secondary particles and the high tap density are also beneficial to the preparation of electrode slurry and the improvement of battery volumetric specific energy.At the same time,we confirm the mechanism of the material controllable structure to stabilize the silicon anode through different electrochemical characterizations and performance texts.The results show that the Si/C-5:5-800 anode has high capacity and stable cycle life.At the current density of 0.5 A/g,the specific capacity is 1418 mAh/g after 200 cycles with 83%capacity retention,which is higher than the reported silicon-based anode.In addition,the composite anode has high rate performance,and the discharge capacity is 988.8 mAh/g when the current density is 5 A/g,which is helpful to obtain a high specific energy and high specific power battery.In view of the low cost,green and nontoxic zinc oxide anode,ZnO@G composite is prepared by high energy ball milling zinc oxide and graphene under the high energy impact and friction energy.Due to the excellent conductive network and mechanical stability of graphene,the ZnO@G composite shows excellent electrochemical properties.Based on the above half battery research,the prepared anode is matched with commercial lithium cobalt oxide(LiCoO2)and nickel cobalt manganese ternary materials(NCM811)respectively,obtaining high energy density full batteries,which verify the feasibility of zinc oxide materials for high specific energy lithium ion batteries...