Preparation Of Cobalt-Based Compound And Application In Anode Electrode Of Lithium Ion Battery

Lithium ion batteries are considered to be one of the most promising energy storage devices for portable electronic devices and new energy vehicles due to their high energy density,long cycle life,and environmental friendliness.The negative electrode material is an indispensable part of the lithium ion battery,and its lithium storage capacity also directly determines the capacity of the entire battery.The anode material of commercial lithium ion batteries is mainly graphite carbon material.Although the cost is low,the conductivity and safety are relatively good,but the theoretical capacity is only 372 mAh g-1,which is difficult to meet the requirements of modern society for high energy density.Therefore,it is imperative to actively develop new anode materials for lithium ion batteries with large lithium storage capacity and good safety stability,and to solve the key scientific problems that exist.The transition metal compound(such as oxide,sulfide,selenide,etc.)material has a relatively high theoretical capacity,natural abundance and environmental eco-friendliness,is a promising anode material for lithium-ion batteries.However,due to relatively poor conductivity and volume changes during charging and discharging,the electrode material has a capacity that decays too quickly during cycling.Therefore,this paper designs and synthesizes a series of porous fiber-structured cobalt-based composites for the above two drawbacks,and explores its lithium storage performance.The specific research contents are as follows:(1)Co3O4/C porous nanofiber composites were prepared by electrospinning technology and subsequent heat treatment using polyacrylonitrile(PAN)and cobalt nitrate(Co(NO3)2.6H2O)as raw materials.The study found that Co3O4/C composite materials showed superior electrochemical performance when used as anode materials for lithium ion batteries.The first specific capacity of Co3O4/C electrode at current density of 0.1 A g-1 was as high as 1375 mAh g-1.The specific discharge capacities of 1142;1107,1016,863,570,and 336 mAh g-1 were shown at current densities of 0.1,0.2,0.5,1.0,2.0,and 5.0 A g-1.In addition,the reversible capacity of the Co3O4/C electrode after 100 cycles at a current density of 0.1 A g-1 remains 1115 mAh g-1,and the capacity retention rate is 97.9%.It shows that Co3O4/C material has better rate performance.cycle stability and reversibility.(2)Using polyacrylonitrile(PAN)and cobalt nitrate(Co(N03)2·6H2O)as raw materials,Co3O4/C porous nanofiber material was prepared by electrospinning technology and subsequent heat treatment,and then vulcanized to obtain blood vessel CoS2/C nanofiber material.Experiments show that,compared with granular CoS2 materials,CoS2/C composite fiber materials have higher reversible capacity,more stable cycle performance and more excellent rate performance.The specific discharge capacity of the CoS2/C electrode at a current density of 0.1 A g-1 was as high as 1215 mAh g-1.In addition,the CoS2/C electrode has a reversible capacity of 904 mAh g-1 after 100 cycles at a current density of 0.1 A g-1,and the capacity retention rate is 96%.The excellent cycle stability and rate performance of CoS2/C electrode materials may come from the carbon-nitrogen co-doped vascular porous fiber structure,which not only helps to improve its electrical conductivity and electronic conductivity,but more importantly,the doped carbon It can also adsorb polysulfide intermediates produced on the electrode surface.(3)Using polyacrylonitrile(PAN)and cobalt nitrate(Co(NO3)2·6H2O)as raw materials,the intermediate product Co/C fiber material was prepared by electrostatic spinning technology and subsequent heat treatment,and then SeSe was obtained to obtain CoSe2/C porous composite nanofiber material.The electrochemical tests show that CoSe2/C composite fiber materials exhibit excellent rate performance and cycle performance.The specific discharge capacity of the CoSe2/C electrode at a current density of 0.1 A g-1 was as high as 1149 mAh g-1.In addition,the CoSe2/C electrode has a reversible capacity of 795 mAh g-1 after 100 cycles at a current density of 0.1 A g-1.CoSe2/C electrode material composite Li+has improved storage performance due to the composite carbon fiber matrix.It acts as a carrier for CoSe2,which not only improves the electrical conductivity and conductivity of the material,but also relieves volume expansion during charge and discharge.In summary,this paper aims at the poor conductivity of the cobalt-based metal compound electrode material and the volume expansion problem during cycling.A series of cobalt-based compound and porous carbon fiber composite materials have been designed and prepared using electrospinning technology to help improve the conductivity of the electrode material compound particles are embedded in the porous carbon fiber,which can effectively suppress the volume change of the electrode material,thereby obtaining a high-performance cobalt-based compound negative electrode.