Fine Structure Regulation Of Fluorinated Carbon Nanotube Arrays And Study Of Lithium Primary Battery

Lithium/fluorocarbon（Li/CF_x）batteries are widely used in military equipment,aerospace and other fields due to their significant advantages in service temperature range,storage life and theoretical energy density.However,on account of the strong covalency of C-F bond,CF_x materials have the problems of low conductivity and low electrolyte wettability.Therefore,when CF_x is used in lithium primary batteries,it is often accompanied by the phenomenon of voltage delay and polarization in the initial discharge period,which limits the application of Li/CF_x batteries in the scenario where high-rate discharge is required.Conventional CF_x precursors are generally disordered and cannot be adequately dispersed in organic solvents,thus hindering the performance of the active substance.Based on the above background,in this thesis,two aspects of the composition proportion regulation and precursor structure design of CF_x cathode were studiedFirst of all,the disordered commercial fluorinated carbon nanotubes（FCNTs）were used as the active substances in the CF_x cathode,the dispersibility in organic solution as well as the relationship between the proportion of components in the CF_x cathode and the discharge performance of Li/CF_x batteries were studied.The experimental results showed that after standing for 6 h,FCNTs precipitated obviously,and the dispersion effect was not satisfactory.As the amount of conductive additives augmented,the discharge performance of Li/CF_x battery increases first and then decreases.When the mass ratio of active substance,conductive additive and binder in CF_x cathode was 8:1:1,FCNTs contributed a specific capacity of 816.09 m Ah·g^-1 and an energy density of 1976.9 Wh·kg^-1 at 0.01 C.The discharge results of Li/CF_x batteries demonstrate that the appropriate cathode component ratio can not only enhance the polarization phenomenon,but also maximize the role of active substances,resulting in the increase of discharge performance of Li/CF_x batteries.Secondly,a new type of CF_x precursor of ordered carbon nanotube arrays（CNTAs）was prepared by catalytic chemical vapor deposition（CCVD）method,and then fluorinated carbon nanotube arrays（FCNTAs）were synthesized to investigate the effect of fluorination temperature on the structure,pore size,conductivity,F/C ratio and battery performance of FCNTAs.The experimental results show that the pore size and F/C ratio of FCNTAs are proportional to the fluorination temperature,and the conductivity is inversely proportional to it.The specific capacity and energy density of FCNTAs-500 at0.01 C are 840.3 m Ah·g^-1 and 1996.4 Wh·kg^-1,respectively,when the fluorination temperature was 500℃.The large pore size,suitable F/C ratio（1.51）and half-ion C-F bond content（33.4%）of FCNTAs-500 together promote the improvement of the discharge performance of Li/CF_x cells.In conclusion,this thesis verified the dispersibility of disordered FCNTs and explored the optimal component ratio in CF_x cathode,and further improved the discharge performance of Li/CF_x battery through the design of CF_x precursor and the regulation of fluorination temperature,which provided a new type of ordered CF_x precursor material for the cathode material research of Li/CF_x battery.