Efficient Preparation And Research Of Fluorinated Carbon Cathode Materials For High-rate Performance Lithium Primary Battery

As one of the most promising lithium primary batteries,lithium/fluorinated carbon(Li/CF_x)batteries are irreplaceable in military,aerospace,medical,and other markets due to their advantages such as the high energy density,long shelf life,and wide operating temperature range.However,their applications in high-power devices are limited because of the low intrinsic conductivity of CF_x materials due to the high fluorine content and strong covalent C-F bond.A novel plasma enhanced fluorination method(PEF)was developed to prepare CF_x cathode materials with high energy density and high power density.Furthermore,the effect on the fluorination from the thermal field in PEF process,fluorination time and the selection of carbon source were studied systematically.Firstly,the underling fluorination mechanism was analyzed by combining with the plasma diagnostic tool of optic emission spectroscopy(OES).The effect of coupled thermal field on PEF process was studied.And a series of plasma fluorinated multi-walled carbon nanotubes under various temperatures(i.e.,PFCNT-x,x=300,330,or 360℃)were designed to study the coupled thermal effect within PEF process on the structure and chemical bonds of PFCNTs.Low fluorination temperature(300℃)and short fluorination time(110 min)enable carbon nanotubes to maintain their intact morphology and tubular structure with superior conductive chemical bonds.PFCNT-300 coin cell displays a specific capacity of 819.3 m Ah/g at a current density of 0.1 A/g,and a power density of 58,206.0 W/kg at an excessively high current density of 30 A/g.Secondly,the influence of fluorination time on the PEF process was also experimentally studied.And a series of plasma fluorinated multi-walled carbon nanotubes(i.e.,PFCNT-y,y=70,90,110,or 150 min)were designed to study the time effect within PEF process.SEM,XPS,EIS and electrochemical tests were utilized to evaluate the properties of the series of fluorinated carbon nanotubes materials.The results showed that conductive tube structure of PECNT-110 can be completely preserved when the fluorination time was 110 min.Meanwhile,the fluorine content of the CF_x material was appropriate with more conductive chemical bonds.Finally,as an important factor affecting the properties of CF_x materials,the properties of carbon sources on PEF process have also been systematically studied.Three types of carbon nanotubes(i.e.,SCNT,MCNT1,MCNT2)with different tube diameter,carbon layer number and specific surface area were selected as the precursor carbon to be fluorinated.The microstructure,composition of elements,chemical bonds and distribution of lattice in these fluorinated carbon nanotubes were intensively analyzed by using SEM,TEM,XPS,XRD and Raman etc.A certain thickness of carbon layers(～5nm)is retained in F-MCNT2.The maximum energy density of F-MCNT2 is 2050.8Wh/kg,with a maximum power density of 69618.46 W/kg.In summary,this paper developed a novel and efficient plasma enhanced fluorination method and successfully prepared CF_x materials(270℃,110 min here)with both high capacity and high rate,providing a new idea for the high quality CF_xcathode materials preparation.