Preparation And Research Of Three-dimensional Porous Conductive Paper On New Energy Field

With the development of society,a series of environmental pollution and energy crisis have been triggered.This stimulated a research hotspot to clean energy sources in various countries.Lithiumion battery?LIB?,as a new type of green secondary charging energy,show a broad application prospect in the field of transportation,national defenseand electronic equipment.Tin oxide?SnO₂?is considered as a promising lithium ion battery anode material,for the advantages of the high theoretical lithium storage capacity?782 mAh g-1?,low cost,easy synthesis,and lower lithium insertion potential.However,practical applications of tin oxide lithium-ion batteries have been limited by their own characteristic.The large volume change?about 300%?during the charge-discharge process leads to particle pulverization,agglomeration and even peeling from the base material,resulted in a rapid decrease in battery capacity and poor cycle performance.Therefore,there is an urgent need to develop an insertable flexible porous current collector to cushioning the volume effects.Carbon nanotubes?CNTs?has a unique graphitized layer structure,a large aspect ratio,good electrical conductivity,and mechanical properties.In this paper,carbon nanotubes and flexible paper fibers are combined to fabricate a three-dimensional conductive porous structure,a rough surface,good conductivity,and an internal porous bulky flexible current collector.A large conductive contact and high degree of adhesion was between the current collector and the active material,and the active material is not easily peeled off from the current collector during charge and discharge.Thus,it retaina better cycle stability.The high temperature graphitization was taken to increase the purity and crystallinity of the carbon nanotubes.At the same time,the preparation of carbon nanotube conductive paper,carbon nanotube conductive paper as the current collector on the electrochemical performance of Tin oxide lithium-ion battery,carbon nanotube carbon conductive paper as current collector for the Tin oxide lithium-ion battery and the impact of chemical properties was studied in depth.The results identify as follows:?1?The hightemperature graphitization process eliminates the impurities attached to the surface of the carbon nanotubes during the production process by evaporation,which is favorable for increasing the purity of the carbon nanotubes.At the same time,hightemperature graphitization causes the anisotropy of the graphite layer structure to expand,resulting in a huge internal stress,dislocations and defects in the structure are eliminated,crystallites are rearranged,and the disordered graphite layer structure tends to a three-dimensionally ordered stable structure,greatly improves the crystallinity and graphitization degree of carbon nanotubes,and can effectively improve the electrical and thermal conductivity of carbon nanotubes.?2?High-temperature graphitized carbon nanotubes and paper cellulose are respectively prepared into a suspension,and the two are mixed uniformly and then high-speed sheared,and a carbon nanotube conductive paper is successfully prepared by vacuum filtration.This kind of flexible three-dimensional porous material has the characteristics of low density,good conductivity,surface roughness and internal loose and porous,and is an ideal current collector material for lithium ion batteries.?3?Carbon nanotube conductive paper instead of copper foil current collector loaded SnO₂/MWCNTs active material.The carbon nanotube conductive paper with a three-dimensional conductive network structure can effectively alleviate the powdering,agglomeration and cracking during charge and discharge of SnO₂,ensure the microscopic integrity of the electrode material,increase the utilization efficiency of the active material,and improve the negative electrode of the SnO₂ lithium ion battery.The material's cycle stability and Coulomb efficiency increase its rate performance.In particular,it is worth noting that,comparing a tin oxide lithium-ion battery in which a copper foil is a current collector,the flexible conductive paper as a current collector is circulated,the electrochemical impedance does not increase,which indicates that the current collector is effective.Relieve the volume effect of tin oxide active materials.It can be maintained above 500 mAhg^-1 after 100 cycles at a current density of200 mAg^-1.?4?carbon nanotubes conductive paper carbonization,carbonized carbon nanotube conductive paper has more excellent conductivity,lower density,its three-dimensional conductive network provides more charge transfer pathway interface,enhance lithium intercalation/off Lithium kinetics reduce ohmic polarization.The two current collectors can provide a certain specific capacity in addition to the load carrier for the tin oxide active material,which helps to increase the energy density of the lithium ion battery.After cycling 100 times at a current density of 200 mAg^-1,the reversible capacity of the current-carrying SnO₂/MWCNTs electrode remained at 897 mAhg^-1 after carbonization,and the Coulomb efficiency reached 98%,which was comparable to that of the non-carbonized current collector-supported SnO₂ active material.The capacity has increased by 41.2%and shows good electrochemical performance.