KR101308736B1 - Tin oxide embedded carbon nanofiber and method of manufacturing the same, and lithium secondary battery using the same - Google Patents

Abstract

The present invention relates to a method for producing carbon nanofibers in which tin (Sn) or tin oxide is dispersed in nano size, and specifically, tin oxide including an electrospinning of a tin precursor / carbon fiber precursor solution and a heat treatment process is converted into nano size. Provided is a method for producing dispersed carbon nanofibers, wherein the tin oxide-containing carbon nanofibers may be used as a negative electrode material of a secondary battery.
The secondary battery using the tin oxide-containing carbon nanofibers according to the present invention as a negative electrode material has a large capacity and maintains a discharge capacity of 649 mAh / g even after 100 cycles, thereby showing excellent cycle stability.

Description

TIN OXIDE EMBEDDED CARBON NANOFIBER AND METHOD OF MANUFACTURING THE SAME, AND LITHIUM SECONDARY BATTERY USING THE SAME}

The present invention relates to a method for producing carbon nanofibers in which nano-sized tin oxide is dispersed by spinning a fiber precursor composition containing a tin precursor in a carbon fiber precursor material.

At present, with the increase in the capacity of mobile devices and the development of battery vehicles, interest in lithium secondary batteries having high performance and high energy density is increasing. Accordingly, studies on non-graphite-based tin (Sn) and tin oxide (SnO, SnO ₂ ), etc., in which the theoretical capacity is much higher than that of the existing graphite material, are being actively conducted. Tin (Sn) is a typical anode material that is alloyed with lithium (Li) ions, and is 994mAh / due to the insertion (Li _x Sn (x <4.4))-deinsertion reaction of Sn and Li ions during charging and discharging. Although it has a very high theoretical capacity of g, the electrode material itself tends to break down or the electrical conductivity decreases rapidly due to the volume change generated during the insertion-deinsertion of Li ions. This phenomenon affects cycle characteristics and has a limit in showing excellent capacity and cycle characteristics. Tin oxide, which is a structure of tin and oxygen, also exhibits high theoretical capacities of SnO (875 mAh / g) and SnO ₂ (783 mAh / g), respectively, but expects excellent capacity and cycle characteristics due to volume changes occurring in tin (Sn). it's difficult.

SnO and SnO ₂ react mainly in the following two stages upon insertion of Li ions. In the first step, Li ions are inserted into SnO and SnO ₂ so that Li ₂ O is produced as in (1) or (1-1), respectively.

^{2 Li + + SnO + 2 e} - → Sn + Li 2 O (1)

_{^{4 Li + + SnO 2 + 4}} e - → Sn + 2Li 2 O (1-1)

^{x Li + + Sn + xe -} → Li x Sn (x ≤4.4) (2)

LiO ₂ generated in step (1) has been reported to play a role in alleviating the volume expansion caused by the alloy reaction of Li ions generated in the next step with Sn, but the formation of LiO ₂ is inherently highly irreversible in the first cycle Capacity. In addition, Li _x Sn formed during the insertion of Li ions in step (2) is the same as the reaction generated when Sn is used alone, and the volume change due to the insertion-deinsertion of Li ions is determined by the cycle characteristics. This leads to a significant reduction. To solve the above problems, tin oxide is made into porous structure or amorphous or thin film, and other surfactant-mediated method, sol-gel method, inverse micro- Attempts have been made to nanosize using reverse micro-emulsion and spray pyrolysis techniques. However, the above method is also inherently limited due to the low capacity and cycle characteristics that are far below theoretical capacity.

Electrospinning technique is an advantageous method for producing hundreds of nanometers to several tens of nanofibers using a polymer solution. Carbon nanofibers prepared using such electrospinning technique have high electrical conductivity, high specific surface area, Since carbon nanofibers containing oxides, porous materials, carbon nanotubes, and the like are easily manufactured, very high electrochemical activity can be expected when manufacturing secondary battery electrode materials.

In particular, when the electrospinning technique is used, nano-sized metals or metal oxides can be uniformly dispersed in the carbon nanofibers, thereby producing metals or metal oxide-containing carbon nanofibers having excellent electrical conductivity and high electrochemically active areas. can do. However, metal / carbon nanofiber composites prepared by mixing metal precursors with carbon precursor polyacrylonitrile (PAN), which is a method currently used, are difficult to manufacture in a completely oxide state. In addition, carbon nanofibers have a problem in that the polyacrylonitrile and the metal precursors are poorly miscible due to agglomeration of metals.

In order to replace the graphite used as a negative electrode material of the lithium secondary battery as described above, extensive research has been conducted, and as a result, when using the highly dispersed tin oxide-containing carbon nanofibers according to the present invention, a higher capacity than the conventional negative electrode graphite The present invention was completed by recognizing the excellent cycle characteristics.

Therefore, in order to solve the above technical problem, the present invention is a negative electrode active material of a lithium secondary battery of the metal oxide, electrospinning the tin precursor / carbon fiber precursor solution in order to disperse the tin oxide in the carbon nanofibers in the nano-size and heat treatment, It provides a method for producing carbon nanofibers in which tin oxide is dispersed in nano size through a carbonization process.

The method for producing a tin oxide-containing carbon nanofiber according to the present invention includes the steps of preparing a fiber precursor composition by adding a tin precursor to a carbon fiber precursor material; Spinning the fiber precursor composition to produce fibers; And heat treating the fibers.

Specifically, the present invention relates to a method for producing a composite fiber web made of carbon nanofibers having a fiber diameter of 50 to 300 nm, an average diameter of 175 nm, and evenly dispersing tin oxide of 1 nm to 40 nm in and out of carbon nanofibers. will be. More specifically, the method for producing a composite fiber web made of the tin oxide-containing carbon nanofibers includes the following steps.

a) preparing a fiber precursor composition by adding a tin precursor to the carbon fiber precursor material, wherein the weight of the tin precursor is calculated and added so that the weight ratio of the residue of the final carbon nanofibers is 10 to 50;

b) preparing a composite fiber web from nanofibers prepared by electrospinning the fiber precursor composition into a syringe attached to a needle;

c) heating the fibrous web to 0.1 to 10 ° C./min from 220 to 300 ° C. at room temperature, and then heat treating the fiber web at a final temperature for 0.5 to 5 hours.

The method for producing the tin oxide-containing carbon nanofibers may further include carbonizing the heat treated fibrous web at 300 to 3000 ° C. in an inert atmosphere or in a vacuum state or activating the carbon web.

Hereinafter, the present invention will be described in more detail.

The fiber precursor composition, which is a starting material of the present invention, prepares a fiber precursor polymer solution by adding a tin precursor to a carbon fiber precursor material. In this case, the carbon fiber precursor material is polyacrylonitrile, polyperfuryl alcohol, cellulose, glucose, polyvinyl chloride, polyacrylic acid, polylactic acid, polyethylene oxide, polypyrrole, polyimide, polyimide, polyamideimide, polyaramid, It includes any one or a mixture of two or more selected from the group consisting of polybenzylimidazole, polyaniline, phenol resins and pitches, more preferably polyacrylonitrile resin.

In the present invention, the fiber precursor composition includes a mixture of a polyvinylpyrrolidone resin further dissolved in a solvent.

In this case, when using a mixture of a carbon fiber precursor material and a polyvinylpyrrolidone-based resin, the weight ratio of the two resins is preferably 80 to 20: 20 to 80% by weight, more preferably 50: 50% by weight It is good to mix with.

The carbon fiber precursor material used in the present invention may use a mixture of any conventional synthetic polymers and carbon precursors described above. In this case, when the polyacrylonitrile resin is used, if the weight average molecular weight is less than 50,000, the viscosity of the fiber precursor composition is low, and if it exceeds 500,000, the viscosity is high, which is not preferable.

The polyvinylpyrrolidone-based resin is a compound that interacts with the tin cation to maintain miscibility and donate oxygen to tin during heat treatment, and the polyvinylpyrrolidone-based resin may be any conventional synthetic polymer, The weight average molecular weight is preferably 40,000 to 1,500,000, more preferably 70,000 to 1,300,000. If the weight average molecular weight is less than 40,000, the viscosity of the fiber precursor composition is lowered, and if it exceeds 1,500,000, the viscosity is excessively increased, which is not preferable.

In addition, the present invention may include a compound having an oxygen atom as a donor atom that can replace the polyvinylpyrrolidone-based resin. Compounds having an oxygen atom as the donor atom are -RO-, -C = O-, -CO-, -SO-, -OR-CO-, -ORO-, -OC-R-CO-, -NH in the molecule. It may be replaced with a compound comprising any one or two or more functional groups selected from -R-CO- and -NH-RO- and containing oleic acid or glycerides. R is a C1-C20 alkyl group, a C6-C20 aryl group or a substituted aryl group.

In the present invention, further comprising a polyvinylpyrrolidone-based resin may be preferably used as a dispersant for metal oxides in carbon nanofibers for non-toxicity and cost reduction.

The mixing ratio of the polyvinylpyrrolidone-based resin is suitably added in the range of 20 to 80% by weight, preferably 20 to 50% by weight, and in the case of the polyvinylpyrrolidone-based resin, the tin precursor cannot be easily dissolved, or more. Is not preferable because the carbon yield is low.

The tin precursor may be at least one selected from tin nitrate, tin chloride, tin acetate, tin alkoxide or mixtures thereof, and particularly preferably tin acetate may be used.

Solvents that can be used in the present invention is a polar solvent other than water in which the resin can be dissolved, dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), gamma Butyrolactone, N-methylpyrrolidone, chloroform, toluene, acetone or mixtures thereof may be used. Preferably, one or more may be selected from dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF).

The fiber precursor polymer solution is preferably 95 to 70% by weight solvent and 5 to 30% by weight polymer. Using a polymer having a solid content within the above range can prevent a decrease in physical properties due to uniform dispersion. In addition, the tin precursor is added so that the content of tin oxide is 10 to 50 parts by weight of the amount of carbon in consideration of the final carbon nanofiber yield and the amount of carbon remaining after burn-off.

In a preferred embodiment, the polyacrylonitrile polymer and the polyvinylpyrrolidone-based resin are quantified in an amount of 80 to 20: 20 to 80 parts by weight, and then about 5 to 30% by weight, preferably 6 to 10% by weight, of the polymer resin in the solvent. Dissolve to Thereafter, a temperature of 100 to 150 ° C. is added to completely dissolve the polymer solution, and the solution is cooled to room temperature and then tin precursor is added. At this time, the amount of tin precursor is calculated by considering the yield of carbon after the final burn-off (total 50 to 90%) and the amount of tin oxide as 10 to 50%.

The most important factor in the preparation of nanofibers using electrospinning is the proper viscosity of the composition. When the tin precursor is added to the solution of the mixed polymer, the viscosity tends to increase. When prepared, the composition has a low viscosity, and when it exceeds 30 parts by weight, it is not suitable for spinning because of its high viscosity.

The composition thus prepared was subjected to temperature homogenization, and then placed in a syringe with a needle, and electrospun by applying a voltage of 10 to 50 kV, preferably 20 to 30 kV to prepare a fiber, and prepared in the above manner. The fiber is heated to 220 ~ 300 ℃, and heat treated for 0.5 to 10 hours in an air atmosphere.

The heat treatment process is a process of oxidizing the fibers from the surface in order to convert the thermoplastic resin into a thermosetting resin to prevent the fusion and thermal melting of the fibers in subsequent high temperature carbonization and activation processes. In general, thermoplastic resins are melted when carbonized and activated at high temperatures, or fusion between fibers occurs. To prevent this, thermoplastic resins are converted into thermosetting resins through heat treatment, which is an oxidation stabilization process. If carbonization or activation is performed directly without performing the heat treatment process, exothermic reactions such as ring opening and dehydrogenation proceed rapidly and are burned rather than carbonized. Therefore, the heat treatment process of the present invention forms a crosslinking of oxygen or strong hydrogen bonds, thereby reducing volatile matter in the subsequent high temperature carbonization or activation process, and solid phase carbonization reaction occurs, thereby maintaining the dimensions and structure of the fiber even in the carbonization process.

The carbonization process in the present invention is subjected to a heat treatment process, which is a stabilization process to maintain the dimensions and structure of the fiber, and then by heating the raw material at a high temperature under special conditions to remove volatile non-carbon components or increase the surface area again. Is performed. Specifically, the heat-treated fiber was carbonized at 300 to 3000 ° C. in an inert atmosphere or in a vacuum state, thereby preparing carbon nanofibers containing nano-size tin oxide.

In addition, the resulting carbon nanofibers containing tin oxide according to the present invention had a diameter of 50 to 300 nm, an average diameter of 175 nm, and uniformly dispersed 1 to 40 nm of tin oxide inside and outside the carbon nanofibers. .

The produced carbon nanofibers are very high at a discharge capacity of 649 mAh / g after 100 cycles when used as a negative electrode of a lithium secondary battery, and the tin oxide according to the present invention is maintained at 90% or more of the initial capacity for 100 cycles. Containing carbon nanofibers showed very good electrochemical properties compared to conventional tin oxide-containing anode materials.

The present invention can easily produce tin oxide of the nano-nano inside the carbon nanofibers, it is possible to appropriately control the content of the tin oxide, the diameter of the fiber and the size of the tin oxide.

In addition, the tin oxide-containing carbon nanofiber of the present invention has a discharge capacity of 649 mAh / g after 100 cycles when used as a negative electrode of a lithium secondary battery, and its capacity is very high compared to graphite, which is a commercially available negative electrode material, and 100 cycles. Over 90% of the initial dose.

In addition, compared to the conventional case using the particulate form, since the production of the fibrous web, the electron transfer is very fast by itself, does not require an active material, a binder and a conductive agent, other solvents, auxiliary facilities, and the like to prepare a slurry It has the advantage that there is no need to coating process. In addition, since the handling is easy, the negative electrode material to replace the graphite later, the expected effect is very high. Therefore, the tin oxide-containing carbon nanofibers according to the present invention may be replaced as a negative electrode material of a secondary battery, and may be widely applied to electrode materials and catalysts such as other solar cells, fuel cells, and secondary batteries. do.

Figure 1a is a scanning micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-700 ℃) prepared at 700 ℃.
Figure 1b is a scanning micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-800 ℃) prepared at 800 ℃.
Figure 1c is a scanning micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-900 ℃) prepared at 900 ℃.
Figure 2a is a transmission micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-700 ℃) prepared at 700 ℃.
Figure 2b is a transmission micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-800 ℃) prepared at 800 ℃.
Figure 2c is a transmission micrograph of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-900 ℃) prepared at 900 ℃.
Figure 3a is a graph of crystallinity according to the temperature of the tin oxide containing carbon nanofibers prepared in Example 1.
Figure 3b is a microstructure analysis graph according to the temperature of the tin oxide containing carbon nanofibers prepared in Example 1.
Figure 4a is a charge and discharge results of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-700 ℃) prepared in Example 1 at 700 ℃.
Figure 4b is the charge and discharge results at 800 ℃ of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-800 ℃) prepared in Example 1.
Figure 4c is the charge and discharge results at 900 ℃ of the tin oxide containing carbon nanofibers (SnO _x -PANPVP-900 ℃) prepared in Example 1.
5 is a cycle characteristic result according to the temperature of the tin oxide-containing carbon nanofibers prepared in Example 1.
6 is a Coulomb efficiency characteristic results according to the temperature of the tin oxide-containing carbon nanofibers prepared in Example 1.
7 is a scanning micrograph of the composite carbon nanofibers (SnO _x -PAN-800 ℃) prepared in Example 2.
8 is a transmission micrograph of the tin composite carbon nanofibers (SnO _x -PAN-800 ℃) prepared in Example 2.
Figure 9 shows the results of charge and discharge cycles when using the tin composite carbon nanofibers (SnO _x -PAN-800 ℃) prepared in Example 2 as an electrode.
10 is a cycle characteristic results when using the tin composite carbon nanofibers (SnO _x -PAN-800 ℃) prepared in Example 2 as a cathode.

The following will be described by way of example for the detailed description of the invention. However, the present invention is not limited to the following examples.

Physical property measurement method used in the following Examples are as follows.

Diameter distribution and surface images were measured using a scanning microscope (FE-SEM, S-4700 Hitachi, Japan).

-The dispersion degree of metal oxide was measured by transmission microscope (FE-TEM, a JEM-2000 FXII JEOL, USA).

-Crystallization degree and microstructure analysis of metal oxides using X-ray diffraction analysis (XRD, D / MAX Uitima III, Rigaku, Japan) and X-ray Absorption Fine Structure (EXAFS), Pohang Accelerator Laboratory, Korea) It was measured by.

-As a negative electrode of a lithium secondary battery, a charge and discharge capacity and cycle characteristics are prepared by using a coin cell composed of lithium (Li) metal / separator / tin oxide-containing carbon nanofibers, and LiPF ₆ 1: 1 vol% EC: DMC liquid electrolyte. Investigate.

-The charging and discharging experiment was conducted using the charging and discharging for the coin cell.

Example 1

0.4 g of polyacrylonitrile resin (weight average molecular weight 150,000) and 0.4 g of polypyrrolidone resin (molecular weight 1,700,000) were added to 9 g of dimethylformamide (N, N-dimethylforamide) solvent and dissolved at 120 ° C for 5 hours. (A) was prepared. 0.1097 g of tin acetate (molecular weight: 236.78) was added to the polymer solution (A) at room temperature, and then stirred at 120 ° C. for 5 hours.

The homogenized tin acetate / polyacrylonitrile / polyvinylpyrrolidone solution was electrospun using an electrospinner. At this time, the spinning condition was electrospinned by applying the fiber precursor solution to a 10 ml syringe attached to a 0.5 mm needle and applying a voltage of 20 kV. At this time, the distance between the needle and the current collector was maintained at 17 cm, and the dissolution rate of the fiber precursor solution was 1 ml / h. When the fibers were accumulated in the current collector, the nonwoven fabric was separated and separated.

The fibrous web consisting of the separated tin acetate / polyacrylonitrile / polyvinylpyrrolidone was heat-treated at 280 ° C. for 5 hours under an air atmosphere. At this time, the temperature was increased by 1 ℃ / min, and maintained for 5 hours at 280 ℃. Thereafter, a carbonization process was performed at 700 ° C., 800 ° C., and 900 ° C. for 1 hour.

Scanning micrographs of the tin oxide-containing carbon nanofibers prepared for each temperature as described above are shown in FIG. 1 (1a, 1b, 1c). In addition, the transmission micrograph of the prepared tin oxide-containing carbon nanofibers are shown in Figure 2, the crystallinity of the tin oxide-containing carbon nanofibers are shown in Figure 3a and the microstructure analysis is shown in Figure 3b. When the tin oxide-containing carbon nanofibers were used as electrodes in FIGS. 4 (4a, 4b and 4c), the charge and discharge results of the electrodes were shown. In addition, Figure 5 shows the cycle characteristics when used as a cathode, Figure 6 shows the Coulomb efficiency.

[Example 2]

0.8 g of polyacrylonitrile resin (weight average molecular weight 150,000) was added to 9 g of 9 g of dimethylformamide (N, N-dimethylforamide) solvent and dissolved at 120 ° C. for 5 hours to prepare a polymer solution (B). 0.2188 g of tin acetate was added to the polymer solution (B) at room temperature, and then stirred at 120 ° C. for 5 hours.

The homogenized tin acetate / polyacrylonitrile polymer solution was electrospun using an electrospinner. Hereinafter, the electrospinning conditions are the same as in Example 1.

The fibrous web consisting of the separated tin acetate / polyacrylonitrile was heat treated at 280 ° C. for 5 hours under an air atmosphere. At this time, the temperature was increased by 1 ℃ / min, and maintained for 5 hours at 280 ℃.

After the heat treatment process, the carbonization process was performed for 1 hour at 800 ℃.

Scanning micrographs of the prepared tin composite carbon nanofibers (SnO _x -PAN-800 ^o C) are shown in FIG. 7. In addition, the transmission micrograph of the prepared tin composite carbon nanofibers are shown in FIG. 8, the crystallinity of the tin composite carbon nanofibers is shown in FIG. 9, and when the tin composite carbon nanofibers are used in FIG. Charge and discharge cycle characteristics are shown. In addition, Figure 11 shows the cycle characteristics when used as a negative electrode, Figure 12 shows the Coulomb efficiency.

As shown in Fig. 1 (1a, 1b, 1c), the diameter of the fiber is 200nm at 700 ℃, it can be seen that the fiber diameter becomes smaller with increasing temperature. The average diameter of the tin oxide-containing carbon nanofibers prepared by the method of the present invention was about 175 nm or less, and the fiber diameter ranged from 50 nm to 300 nm. It is known that the fiber made from melt spinning and gel spinning, which is a common fiber manufacturing method, has a diameter of about 10 μm, but is about 50 times thinner and thinner than the carbon nanofibers that are monospun polyacrylonitrile. Can be. In addition, the tin oxide structure was not well developed inside the carbon nanofiber at 700 ° C, but it was found that the tin oxide was developed in nano size at the fiber surface at 800 ° C. In addition, it was found that the tin oxide dispersed in the nano-sized at 900 ℃.

2A shows a transmission micrograph of the tin oxide-containing carbon nanofibers prepared at 700 ° C., and it can be seen that tin oxide is finely dispersed to 2 nm or less in the carbon nanofibers. 2b and 2c show transmission micrographs of the tin oxide-containing carbon nanofibers prepared at 800 ° C. and 900 ^° C., respectively. As can be seen in FIGS. 2b and 2c, the sizes of the tin oxides are very low at 4 nm and 40 nm, respectively. Small and very good dispersion. Therefore, in order to properly disperse the tin oxide particles in the carbon fiber it was found that the appropriate temperature should be added. To date, active researches are being made on nano-scale or thin-film manufacturing of Sn, Si, Ag, Bi, SnOx, Cu ₂ O, Fe ₂ O ₃ , Co ₃ O _4, etc. However, there is no example of highly dispersing tin oxide inside the carbon nanofibers by the manufacturing method according to the present invention. In addition, the use of lithium secondary battery as an anode material completely overcomes the problems of tin oxide.

As shown in Figure 3a, it can be seen that the degree of crystallinity increases with temperature and the degree of crystallinity increases with increasing temperature. In addition, the peak size indicating the degree of crystallization of tin oxide-containing carbon nanofibers is very small compared to pure tin oxide (SnO ₂ ), and it can be seen that carbon nanofibers play a role of preventing agglomeration of tin oxide. . However, because X-ray diffraction analysis provides only crystallization information, in order to know the precise structure of tin oxide dispersed in carbon nanofibers, fine structure analysis using X-ray diffraction analysis and X-ray diffraction spectroscopy are performed. need. X-ray absorption fine structure analysis of tin oxide containing In the case of carbon nanofibers was a tin oxide of the non-uniform (disordered) inside the carbon nanofiber formation, six oxygen around tin (Sn ^IV) atom in 800 ℃ prepared in 700 ℃ ( O ₂ ^-) it was confirmed that the development of a non-uniform (disordered) type structure forming the octahedral atoms. In addition, it was confirmed that the tin oxide-containing carbon nanofibers prepared at 900 ° C. reduced the degree of disordered, thereby becoming almost similar to the structure of pure tin oxide.

4 and 5 show charge and discharge results and cycle characteristics when the tin oxide-containing carbon nanofibers prepared at each temperature are used as a negative electrode of a secondary battery. As can be seen from the charge and discharge results, the tin oxide-containing carbon nanofibers prepared at 800 ° C. showed the smallest irreversible capacity for 100 cycles of charge and discharge. This is because the particle distribution of tin oxide is small and carbon nanofibers maintain the conductivity and show the best cycle characteristics despite the generation of LiO ₂ produced during the insetion of the tin oxide of Li ions.

6 shows the coulomb efficiency and the coulomb efficiency also showed the best characteristics of the metal oxide-containing carbon nanofibers prepared at 800 ° C. in the first cycle, as described above.

FIG. 7 shows scanning micrographs of tin or tin oxide-containing carbon nanofibers (SnOx-PAN-800oC) prepared by electrospinning a tin acetate / polyacrylonitrile solution, followed by heat treatment and carbonization at 800 ° C. FIG. In this case, the diameter of the prepared tin or tin oxide-containing carbon nanofibers was 250 nm, and it was confirmed that the diameter was larger than that of the sample spun by adding polyvinylpyrrolidone.

In addition, in the case of tin or tin oxide-containing carbon nanofibers as shown in the transmission micrograph of FIG. 8, it can be seen that the particles of the oxide are present inside and outside the carbon nanofibers, which is added to the polyvinylpyrrolidone of the present invention. It can be seen that the sample prepared more uniformly disperses the tin oxide particles in the carbon nanofibers.

9 shows charge and discharge cycle characteristics of tin or tin oxide-containing carbon nanofibers prepared by mixing tin acetate and polyacrylonitrile. 9 and 10, carbon nanofibers prepared by mixing only polyacrylonitrile contain tin oxide prepared by adding polyvinylpyrrolidone when used as a negative electrode because tin or tin oxide particles are relatively large. It can be seen that the cycle characteristics are lower than that of carbon nanofibers. As described above, the high dispersion of tin oxide increases the electrochemically active site, and despite the formation of LiO ₂ generated during charging and discharging, carbon nanofibers maintain electrical conductivity and buffer the aggregation of tin oxide particles. It is believed that the electrochemical properties are very good by buffering.

Therefore, in one embodiment of the embodiment, the addition of a compound having an oxygen atom as a donor atom such as polyvinylpyrrolidone, the carbon precursor material during electrospinning and the content of the compound, the content of the tin precursor is controlled by the lithium secondary battery It can be seen that a tin oxide-containing carbon nanofiber composite having an electrochemically superior property as a negative electrode can be manufactured as a negative electrode.

Claims (12)

The fiber is added to the carbon fiber precursor material by adding a tin precursor compound selected from tin nitrate, tin chloride, tin acetate, tin alkoxide and mixtures thereof and a polyvinylpyrrolidone resin having a weight average molecular weight of 40,000 to 1,500,000. Preparing a precursor composition;
Spinning the fiber precursor composition to produce fibers;
Heating the fiber at an ambient temperature of 220 ° C. to 300 ° C. at a temperature of 0.1 ° C. to 10 ° C./min, and then performing a heat treatment for 0.5 to 5 hours at a final temperature;
Carbonizing the heat treated fiber at 600 to 800 ° C; And
Activating the carbonized fiber; method of manufacturing a tin oxide-containing carbon nanofibers for a lithium secondary battery negative electrode comprising a. delete delete The method of claim 1,
The fiber precursor composition is a method of producing a tin oxide-containing carbon nanofibers for a lithium secondary battery negative electrode further comprising a compound having an oxygen atom as a donor atom. 5. The method of claim 4,
The compound having an oxygen atom as the donor atom is -RO-, -C = O-, -CO-, -SO-, -OR-CO-, -ORO-, -OC-R-CO-, -NH-R -CO- and -NH-RO-, wherein R is C1 to C20 alkyl group, C6 to C20 aryl group or substituted aryl group, characterized in that it comprises any one or two or more functional groups selected from Method for producing carbon nanofibers containing tin oxide for a lithium secondary battery negative electrode. The method of claim 1,
The carbon fiber precursor material is polyacrylonitrile, polyperfuryl alcohol, cellulose, glucose, polyvinyl chloride, polyacrylic acid, polylactic acid, polyethylene oxide, polypyrrole, polyimide, polyamideimide, polyaramid, polybenzylimidazole , Polyaniline, a phenol resin and a pitch, any one or a mixture of two or more selected from the group consisting of a tin oxide-containing carbon nanofibers for a negative electrode. delete The method of claim 1,
The fiber precursor composition is a method for producing a tin oxide-containing carbon nanofibers for lithium secondary battery negative electrode, characterized in that the solid content of 5 to 30% by weight. delete The method of claim 1,
The fiber precursor composition is N, N-dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), gamma butyrolactone, N-methylpyrrolidone, chloroform And toluene and acetone, any one or a mixture of two or more selected from the group consisting of a method for producing a tin oxide-containing carbon nanofibers for a lithium secondary battery negative electrode. A tin oxide-containing carbon nanofiber for a lithium secondary battery negative electrode manufactured by the manufacturing method according to any one of claims 1, 4, 5, 6, 8 and 10. Lithium using a composite fiber web made of tin oxide-containing carbon nanofibers prepared by the manufacturing method according to any one of claims 1, 4, 5, 6, 8 and 10 Secondary battery negative electrode material.

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