Preparation And Modification Of Soybean Shell Carbon Materials And Ternary Cathode Materials For Lithium Ion Batteries

In order to alleviate the energy crisis,the development,storage and utilization of new energy materials have become a research hotspot.In lithium-ion batteries,positive and negative anode materials are indispensable,which are related to the capacity,energy storage density,cycle life and safety of the battery.Biomass-based porous carbon is a potential energy material with low cost,light weight,non-toxic,surface chemical inertia,good electrical conductivity and large specific surface area,etc.It is attracting more and more attention in the field of lithium ion batteries.In addition,higher energy density,safer,lower cost has always been the core goal of the development of lithium battery,which also puts forward higher requirements for one of its components—cathode material synthesis technology.Li-rich terpolymer cathode material has become a hot topic of cathode material research due to its advantages of high specific capacity,low cost and better safety performance.Therefore,this paper mainly studies the preparation,characterization andlithium storage proparties of soybeen shell porous carbon cathode materials and ternary cathode materials,the specific work is as follows:（1）The structure and lithium storage properties of porous carbon materials（abbreviated as DK-proportion-activator）prepared under different process conditions（activator type and mass ratio of raw material to activator）were studied by hydrothermal carbonization with soybean shell as raw material.The process conditions were optimized and applied to lithium ion batteries.The results show that each material is porous carbon with certain graphitized lamellar structure.DK-4-KOH has micropores,mesopores and narrow fissure pores.When the current density is 185.0 m A/g and the voltage range is 0-3.0 V,the initial charge-discharge capacity of DK-4-KOH is307.5/986.7 m Ah/g.After 200 cycles,the discharge specific capacity retains to 317.2m Ah/g and the energy density is stable at 177.0 Wh/kg,indicating that DK-4-KOH material has good cycling performance and high specific capacity.The optimal process conditions were obtained:the activator was KOH,and the mass ratio of raw material to activator was 1:4.（2）The precursor of MCO₃microspheres（abbreviated as NS-MCO₃）was prepared by hydrothermal method with nickel-cobalt-manganese acetate as raw material at different urea ratios,and Li_1.1Mn_0.55Ni_0.3Co_0.05O₂（abbreviated as LMRO）was prepared by high-temperature calcination and used in lithium ion batteries.The results show that 0.015NS-MCO₃,0.025NS-MCO₃and 0.035NS-MCO₃are all solid solutions of Ni CO₃,Co CO₃and Mn CO₃.All 0.015NS-LMRO,0.025NS-LMRO and0.035NS-LMRO contain R-3m and C2/m space groups.When the voltage range is2.0-4.8 V,the initial charge-discharge capacity of 0.025NS-LMRO at 15.85 m A/g current density is 179.1 m Ah/g and the initial charge-discharge capacity of0.025NS-LMRO at 158.5 m A/g current density is 179.6/104.3 m Ah/g.The electrochemical performance of 0.025NS-LMRO is best,because when the molar ratio of urea to metal salt is 0.025:1,the nucleation rate and growth rate of the crystal tend to balance,the distribution of primary particles is uniform,and the sphericity of secondary particles is the best.（3）CuS with different coating amounts were used to modify the structure stability of Li_1.1Mn_0.55Ni_0.3Co_0.05O₂.When the voltage range is 2.0-4.8 V,the initial discharge specific capacity of CuS-2%at 15.85 m A/g current density is 216.4 m Ah/g and the initial charge-discharge capacity of CuS-2%at 158.5 m A/g current density is215.4/149.3 m Ah/g.CuS coated can isolate the contact between Li_1.1Mn_0.55Ni_0.3Co_0.05O₂and HF in the electrolyte,reduce the occurrence of electrode side reaction,shorten the migration path of lithium ions,and improve the cycling performance and Coulomb efficiency of the material.There are 40 figures,12 tables and 182 references.