WO2013176363A1 - Method for preparing nanocomposite comprising tin-based multiphase nanostructure and amorphous carbon, and cathode active material containing same - Google Patents

Abstract

The present invention relates to a tubular nanocomposite comprising: multiphase tin oxides having a zero-dimensional shape through a thermochemical reduction of a bacteria/tin oxide powder, obtained by directly binding tin oxide onto the surface of bacteria of the Bacillus genus, in an hydrogen atmosphere; and a complex of amorphous carbon derived from tin metals and bacteria. It is possible to resolve a low capacity and a low output (a low capacity at a high current density), and a large decrease in capacity with cycling due to a large change in volume during a reaction with lithium, which have been indicated as the shortcomings of a conventional cathode active material for a lithium secondary battery, by preparing a tubular nanocomposite comprising amorphous carbon/tin element-based multiphase low-dimensional nanostructures to be prepared by utilizing bacterial as a template, binding tin oxide capable of implementing a high capacity onto the surface of the bacteria, and thermochemically reducing the same. The thermochemical reduction of the present invention has a simple and economical preparation process, enables preparation of various shapes of a composite according to the shape of a bacteria template to be used, and facilitates low temperature synthesis, intermediate synthesis, and mass production. Thus, the present invention is expected to have practical applicability to the lithium secondary battery field and the electrical double-layer capacitor field.

Description

Method for preparing nanocomposite of tin-based polyphase nanostructure and amorphous carbon and anode active material comprising the same

The present invention relates to a method for producing a nanocomposite composed of polyphase nanostructures and amorphous carbon based on a tin element, and a negative electrode active material comprising the same.

In recent years, in response to the rapid development of the communication industry such as the electronics industry and various information and communication including mobile communication, in response to the demand for thin and short electronic devices, portable electronic products such as mobile phones, laptops, PDAs, digital cameras, camcorders, etc. are widely used. Therefore, interest in the development of a battery that is a driving power source for these devices is continuously increasing.

Particularly, according to the development of electric vehicles such as pure electric vehicles or hybrid vehicles, great attention has been focused on the development of batteries having high performance, large capacity, high density, high output and high stability, and also development of batteries having fast charge and discharge characteristics. It is a big issue.

Batteries, a device that converts chemical energy into electrical energy, are classified into primary cells, secondary batteries, fuel cells, and solar cells, depending on the types and characteristics of basic materials.

Among these, unlike the primary battery that can be used once, the secondary battery can be recharged and used several times when discharged. In the case of commonly used primary batteries, although they have large capacities such as alkali batteries, mercury batteries, and manganese batteries, they are limited in terms of primary batteries and are not recycled and thus not environmentally friendly. Recyclable secondary batteries such as cadmium batteries, nickel metal hybrid batteries, lithium metal batteries, and lithium ion batteries are not only energy efficient and environmentally friendly due to their higher voltage than primary batteries, but also have a low energy density and have many technical advantages. Unlike constraints, secondary batteries have high capacity and high energy density and are currently commercialized in various industrial fields.

To date, lithium ion secondary batteries among the various secondary batteries have attracted great attention in recent years due to applications ranging from small to medium and large.

The lithium ion secondary battery is largely composed of a positive electrode and a negative electrode, an electrolyte and a separator, and utilizes electrical energy generated by a redox reaction when lithium ions are inserted / desorbed between the positive electrode and the negative electrode. That is, based on the principle that lithium ions and electrons carrying charge reciprocate between the positive electrode and the negative electrode, during discharge, the lithium ions and electrons move to the positive electrode and are inserted into the negative electrode active material, and when charged, they are detached from the negative electrode active material. Thus, the process of being inserted into the positive electrode active material is repeated.

In recent years, as the utilization of the medium-large class using such a lithium ion secondary battery is accelerated, the high performance of a lithium ion secondary battery is required more than anything.

High performance of lithium-ion secondary batteries is closely related to the development of electrode active materials and improvement of physical properties, which are key factors.In particular, in the case of lithium ion secondary battery electrode active materials, innovative ideas and advanced nanotechnology are appropriate to avoid development of simple materials and process technologies. Fusion is necessary. That is, in order for a lithium ion battery to have a large capacity and excellent cycle stability, an anode and a cathode active material to be used must have an appropriate crystal structure and excellent electrical properties to react with lithium. In addition, there should be no side-reaction between the active material and the electrolyte, and the volume change of the active material lattice generated during charging and discharging should be small.

In particular, in the case of the negative electrode active material, the negative electrode active material based on the insertion / desorption reaction of the lithium ion of the carbon-based material is the core in the negative electrode material field of the lithium ion secondary battery technology. However, in the case of the carbon-based negative electrode active material, it is known that the capacity commercialized with a small theoretical capacity (372 mAh / g) is basically smaller than this. Therefore, in recent years, studies on new anode active materials to replace carbon-based materials and researches for improving performance of anode active materials having nanostructures have been actively conducted, and many research cases have been reported. Representatively CuO, which expresses its capacity through a reaction (alloying reaction) using Si, Ge, Sn, etc., which forms an alloy with lithium, or a conversion reaction between metal / metal oxides, rather than a conventional insertion / desorption process, Attention has been paid to transition metal oxides such as CoO, Fe ₂ O ₃ , NiO, MnO _2, etc. [WJ Weydanz et al., J. Power Sources 237 (1999) 81; P. Poizot et al., Nature 407 (2000) 496].

However, in the case of such negative electrode active materials, there are still problems to be solved, such as hundreds of percent change in volume during charging and discharging, aggregation between particles, and low electrical conductivity.

Therefore, many studies have been made to solve the above problems, and there is a need for the production of a negative electrode active material having a high capacity but having a small change in volume between charge and discharge with lithium ions and which can give improved electrical conductivity. Such a negative electrode active material may be made by preparing a material having a nanostructure rather than a conventional micro-sized bulk material, which may react with lithium due to the high specific surface area, which is one of the biggest features of the nanostructure. This is because it can exhibit the characteristics as an improved negative electrode active material based on the advantage that the number of sites, the diffusion movement distance of lithium ions can be shortened. In particular, in recent years, attempts have been made to achieve high performance of lithium-ion secondary batteries using the advantages of each nanostructure by preparing nanocomposites through complexing of nanostructures, as well as simple application of a negative electrode active material using nanostructures.

As described above, the preparation of the negative electrode active material for the high performance of the lithium ion secondary battery is to improve the electrical conductivity through nano-structured or nano-composite material capable of realizing high capacity characteristics, small volume change between reaction with lithium, interparticle In order to solve the aggregation inhibition, etc., it is necessary to manufacture nanostructures of various compositions, as well as to manufacture various forms of nanostructures in a simple process. In particular, the preparation of a negative electrode active material through nanostructure of elements such as Sn, Ge, and Si, which realizes high capacity characteristics through an alloy reaction with lithium, is considered to be important as a negative electrode active material material capable of achieving high performance of a lithium ion secondary battery. Can be. However, as mentioned above, the problem of rapid capacity reduction due to large volume change, low electrical conductivity, and the like should be considered together, and the complexion with other nanomaterials of the nanostructure having the alloy reaction with lithium is also considered. Need to be.

In addition, since the nanostructures have a variety of properties depending on the shape produced, there is also a need for a manufacturing method that can easily control the shape of the nanostructures during synthesis.

The present inventors have developed a negative electrode active material consisting of nanocomposites composed of high carbon element-based nanostructures and amorphous carbons that can provide enhanced electrical conductivity through application of bacterial templates as a medium and through thermochemical reduction. .

In addition, the present invention is not only a simple manufacturing process in the production of the nanocomposite, but also easy to mass production of bacteria as a medium, the tube shape through a simple thermochemical reduction in the hydrogen atmosphere of the complex consisting of bacteria / tin oxide It is an object of the present invention to provide a method for producing a nanostructure consisting of a multi-phase tin element having a nanostructure and an amorphous carbon.

In addition, there is another object to provide a use of the prepared nanocomposites.

Other objects and advantages of the present invention will become apparent from the following detailed description, claims and drawings.

According to one aspect of the present invention,

1) preparing a bacterial dispersion solution by culturing bacteria having anion on the surface and adjusting the concentration of bacteria with deionized water;

2) Stirring at 20 to 30 ° C. for 0.5 to 2 hours while adding a tin precursor solution in which the transition metal precursor is dissolved in deionized water to the solution of 1) to uniformly disperse the Bacillus bacteria and the transition metal precursor. step;

3) refluxing while adding a solution of hydrazine (N ₂ H ₄ .H ₂ O) in deionized water to the solution of 2) to induce transition metal oxide to adhere evenly to the bacterial surface;

4) centrifuging and washing the reflux solution of 3) to obtain a precipitate;

5) vacuum drying the precipitate to obtain a bacterial / transition metal oxide composite powder; And

6) thermochemically reducing the obtained composite powder;

It provides a method for producing a nanostructure / amorphous carbon nanocomposite based transition metal element comprising a.

According to another aspect of the present invention, the present invention provides a tube-shaped nanocomposite composed of a transition-phase element-based multi-phase nanostructures and amorphous carbon derived from bacteria attached to the bacterial surface due to the thermochemical reduction of the nanocomposites. do.

According to another aspect of the invention, the present invention provides a negative electrode active material for a secondary battery comprising the nanocomposite.

According to another aspect of the invention, the present invention provides a secondary battery employing a negative electrode including the negative electrode active material.

The features and advantages of the present invention are summarized as follows.

(i) polyphase tin oxides and tin metals having a 0-dimensional shape by thermochemically reducing the powder of bacteria / tin oxides obtained by directly bonding tin oxides to the Bacillus bacterial surface of the present invention; Tube-shaped nanocomposites can be prepared that are complexed with amorphous carbon derived from bacteria.

(ii) The present invention can be easily obtained through simple thermochemical reduction and easy to mass production based on the bacteria / tin oxide complex which can be easily obtained at low temperature by applying bacteria as a template.

(iii) The manufacturing method of the present invention has the advantage of economical and time-saving effect because the manufacturing process is simple.

(iv) The production method of the present invention has the advantage of obtaining a tubular nanocomposite composed of a multiphase low-dimensional nanostructure and amorphous carbon in one manufacturing process.

(v) In terms of electrochemical properties, high volume characteristics of tin metals and polyphase tin oxides, high electroconductivity of amorphous carbon derived from bacteria, and large volume change in alloy reaction with lithium due to the tubular structure It has the characteristics of high power according to the advantage that can act as a buffer.

(vi) The nanocomposites composed of multiphase nanostructures and amorphous carbon based on the tin element presented in the present invention have a simple and economical manufacturing process and are easy to obtain a large amount of intermediate bacteria / tin oxides. With the advantage of being able to produce, various applications are possible across industries such as lithium secondary batteries, electric double layer super capacitors, and similar super capacitors.

Figure 1 is a schematic diagram showing a tube-shaped nanocomposite manufacturing process consisting of amorphous carbon / tin element-based multi-phase nanostructures prepared through the use of the bacterial template and tin precursor presented in the present invention.

2 is a field emission scanning electron microscope (FESEM) photograph of a complex composed of bacteria / tin oxide (SnO 2) prepared as an intermediate medium in the present invention [(a) low magnification photograph, (b High magnification pictures]

Figure 3 is a transmission electron microscopy (TEM) picture of the composite consisting of bacteria / tin oxide (SnO2) prepared by the intermediate medium in the present invention ((a) transmission electron micrograph, (b) high resolution Transmission electron micrograph].

Figure 4 is an X-ray Diffraction patterns (XRD) of the composite consisting of bacteria / tin oxide (SnO2) prepared in the intermediate medium in the present invention.

FIG. 5 is a result of a thermogravimetry analyzer (TGA) of a complex composed of bacteria / tin oxide (SnO 2) prepared as an intermediate medium in the present invention.

Figure 6 is a field emission scanning electron micrograph showing the shape of the tube-shaped nanocomposite consisting of the amorphous carbon / tin element-based multiphase nanostructures of the present invention.

7 is a transmission electron micrograph showing a shape of a tube-shaped nanocomposite composed of the amorphous carbon / tin element-based multiphase nanostructure of the present invention, a high resolution transmission electron micrograph, and a selected area electron diffraction (SAED) pattern photograph. .

8 is an X-ray powder diffraction pattern of a tube-shaped nanocomposite composed of the amorphous carbon / tin element based multiphase nanostructures of the present invention.

9 is a scanning electron micrograph showing the shape of the nanocomposite prepared according to Examples 2 to 4 of the present invention ((a) Example 2, (b) Example 3, (c) Example 4).

10 is a field emission scanning electron micrograph showing the shape of the nanocomposite prepared according to Example 5 of the present invention.

11 are X-ray powder diffraction patterns of nanocomposites prepared according to Examples 6 to 9 of the present invention.

12 is a field emission scanning electron microscope, a transmission electron microscope, and a high resolution transmission electron micrograph of a nanocomposite shape prepared according to Example 8 of the present invention ((a) field emission scanning electron micrograph, (b) transmission electron Micrograph, (c) high resolution transmission electron micrograph].

13 is a scanning electron micrograph showing the shape of the nanocomposite prepared according to Example 10 of the present invention.

14 is a cycle-shaped nanocomposite composed of amorphous carbon / tin element-based multi-phase nanostructures prepared in the present invention and various current density changes of the negative electrode active materials prepared using the powders of Example 8 and Comparative Example 1 This is a result of comparing the measured dose change curves.

According to one aspect of the present invention,

1) preparing a bacterial dispersion solution by culturing bacteria having anion on the surface and adjusting the concentration of bacteria with deionized water;

2) Stirring at 20 to 30 ° C. for 0.5 to 2 hours while adding a tin precursor solution in which the transition metal precursor is dissolved in deionized water to the solution of 1) to uniformly disperse the Bacillus bacteria and the transition metal precursor. step;

3) refluxing while adding a solution of hydrazine (N ₂ H ₄ .H ₂ O) in deionized water to the solution of 2) to induce transition metal oxide to adhere evenly to the bacterial surface;

4) centrifuging and washing the reflux solution of 3) to obtain a precipitate;

5) vacuum drying the precipitate to obtain a bacterial / transition metal oxide composite powder; And

6) thermochemically reducing the obtained composite powder;

It provides a method for producing a nanostructure / amorphous carbon nanocomposite based transition metal element comprising a.

According to another aspect of the present invention, the present invention provides a tube-shaped nanocomposite composed of a transition-phase element-based multi-phase nanostructures and amorphous carbon derived from bacteria attached to the bacterial surface due to the thermochemical reduction of the nanocomposites. do.

According to another aspect of the invention, the present invention provides a negative electrode active material for a secondary battery comprising the nanocomposite.

According to another aspect of the invention, the present invention provides a secondary battery employing a negative electrode including the negative electrode active material.

The present invention will be described in more detail as follows.

According to one aspect of the present invention,

1) preparing a bacterial dispersion solution by culturing bacteria having anion on the surface and adjusting the concentration of bacteria with deionized water;

2) Stirring at 20 to 30 ° C. for 0.5 to 2 hours while adding a tin precursor solution in which the transition metal precursor is dissolved in deionized water to the solution of 1) to uniformly disperse the Bacillus bacteria and the transition metal precursor. step;

3) refluxing while adding a solution of hydrazine (N ₂ H ₄ .H ₂ O) in deionized water to the solution of 2) to induce transition metal oxide to adhere evenly to the bacterial surface;

4) centrifuging and washing the reflux solution of 3) to obtain a precipitate;

5) vacuum drying the precipitate to obtain a bacterial / transition metal oxide composite powder; And

6) thermochemically reducing the obtained composite powder;

It provides a method for producing a transition metal-based nanostructure / amorphous carbon nanocomposite comprising a.

The transition metal used in the present invention is not particularly limited, and Cu, Co, Fe, Ni, Mn, Ti, which are the four periodic elements on the periodic table, and Y, Zr, Nb, Mo, Tc, Ru, and Rh, which are the five periodic elements on the periodic table. , Pd, Ag, Cd, In, Sn, Sb, Te and the like can be used. More preferably, it is a 5 period element, Most preferably, it is Sn.

The present invention binds tin element-based oxide nanostructures capable of realizing high capacity properties to the Bacillus bacterial surface and thermochemically reduces the obtained bacteria / tin oxide complexes under hydrogen atmosphere, thereby removing from bacteria with high capacity properties. The present invention relates to a method of manufacturing a nanocomposite that can mitigate volume change during reaction with lithium through a tube shape by providing high electrical conductivity by induced amorphous carbon.

Specifically, the present invention provides a method for preparing a bacterial / tin oxide complex which is an intermediate step; And obtaining a final nanocomposite through thermochemical reduction of the obtained composite. The bacterium / tin oxide composite obtained in the intermediate step has the advantage of increasing the yield of tin oxide nanostructures that are combined with the simple synthesis, low temperature, and increase of bacteria used as a template. This gives the possibility of mass production of the nanocomposites finally obtained. Such a process for synthesizing a bacterial / tin oxide complex is similarly made by the inventors, focusing on incorporating a transition metal oxide on the surface of the Bacillus bacterium, which has been previously patented [Korean Patent Application, Application No. 10-2009-0011628]. Can lose.

In detail, step 1 of culturing Bacillus bacteria to control the concentration of bacteria with deionized water to prepare a bacterial dispersion solution;

Adding a tin precursor solution in which tin precursor is dissolved in deionized water to the solution of step 1 and stiring at 20 to 30 ° C. for 0.5 to 2 hours to uniformly disperse bacteria and tin precursors;

Adding a solution in which hydrazine (N ₂ H ₄ .H ₂ O) is dissolved in deionized water to reflux while adding to the solution in step 2 to induce tin oxide to adhere evenly to the bacterial surface;

Centrifuging and washing the reflux solution to obtain a precipitate;

Vacuum drying the precipitate to prepare a bacterial / tin oxide complex; And

6 steps of thermally reducing the obtained composite powder in a hydrogen atmosphere at 400 ° C. for 12 hours;

It relates to a method for producing a nanocomposite consisting of a multi-phase nanostructure / amorphous carbon based on a tin element comprising a.

The tin precursor used in the present invention is not particularly limited according to the number of divalent and tetravalent oxidized numbers, and examples thereof include nitrate, chloride, acetate, and the like.

Synthesis of the bacterial / tin oxide complex, an intermediate step presented in the present invention, is carried out by hydrazine (N ₂ H ₄ ㆍ H ₂ O) using tin ions of cations attached to the bacterial surface as a reducing agent through electrostatic attraction in solution. It can be obtained on the basis of a liquid phase synthesis method, which is used to reduce and simultaneously oxidize. In general, the liquid phase synthesis method is not excellent in crystallinity, but the crystalline material can be obtained at a low temperature according to the synthesis method, and there is an advantage that particles of uniform and small size can be obtained.

In addition, the synthesis process of the bacterial / tin oxide composite presented in the present invention is a simple process, it is possible to obtain a nano powder consisting of uniformly sized tin oxide nanostructures with crystallinity at room temperature (20 ~ 30 ℃) It has the advantage that mass production is possible.

A series of synthesis methods used to prepare the nano-composite composed of the tin phase-based polyphase nanostructure and amorphous carbon according to the present invention is well illustrated in FIG. 1, and a detailed description based on FIG. 1 is as follows.

First, in order to prepare Bacillus bacteria to be used as a template, a portion of the preservation of the frozen Bacillus bacteria is collected and subjected to subculture in an Erlenmeyer flask containing 10-12 hours of initial culture and liquid medium. Thereafter, centrifugation and washing are carried out, while deionized water is added to adjust the proper concentration of the dilute solution in which bacteria are dispersed, and sterling is performed at room temperature. In collecting the bacteria through the centrifugation, if the centrifugation is performed in a state of less than 5 hours after subculture, the amount of bacteria to be collected is small, and thus the amount of bacteria / tin oxide complex obtained in an intermediate step is reduced. Centrifugation is preferably performed after passage for at least 5 hours. This is when the bacterial growth curve reaches the end of the growth phase.

In addition, the concentration control of the bacterial template solution may be performed through the optical absorbance (Optical Density, OD) measured at 600 nm wavelength using an UV spectrometer, the concentration of the bacterial template applied in the present invention is 600 nm It is preferable to use the thing of the range whose optical absorbance is 1.0-2.0 in wavelength.

While maintaining the bacteria dispersion solution in the proper concentration range while stirring at room temperature, the tin precursor is added to deionized water to prepare a tin chloride precursor in the range of 10 to 100 mM, and dissolve so that the tin precursor is sufficiently dispersed during the stirring process. After that, the tin precursor solution, which has been dissolved, is slowly added to the bacterial dispersion solution that is being stirred at room temperature while the stirring is maintained. At this time, when the tin precursor solution is rapidly added, the transition metal precursor of the cation may not be adhered evenly to the surface of the dispersed bacteria, and thereafter, it may be reduced or reduced in the aqueous solution by the reducing agent of hydrazine. Partial reflux in the course of spontaneous oxidation at may make it difficult to achieve agglomerate and a well-shaped single rod shape between the bacteria, so it is preferable to add slowly using a burette if possible.

Then, a sufficient sterling time of 0.5 to 2 hours is maintained at 20 to 30 ° C. to allow sufficient adhesion and even distribution and dispersion between the tin precursor of the cation and the bacteria.

While the mixed solution of the bacterial template and the tin precursor is stirred at 20 to 30 ° C. for 0.5 to 2 hours, hydrazine, which can act as a reducing agent, is added to deionized water to prepare a hydrazine solution in the range of 10 to 1000 mM and the sterling process is performed. Dissolve to ensure sufficient dispersion. Thereafter, the hydrazine solution, which has been dissolved, is slowly added to the mixed solution being stirred at room temperature in the state where the sterling is maintained. At this time, the amount of about 10 ml per minute is added using a burette as in the case of adding the tin precursor solution.

It is then desirable to maintain sufficient sterling so that evenly dispersing the hydrazine in the solution distributes the tin precursor of the cation attached to the bacterial surface evenly as tin oxide.

The mixed solution added to the reducing agent hydrazine is refluxed for 10 to 15 hours while continuously stirring at 20 ℃ to 30 ℃, after which the supernatant and the precipitate is separated by centrifugation, the supernatant is removed and The precipitate is washed with deionized water and acetone (acetone). At this time, the precipitate is a state in which the tin oxide is evenly distributed and attached to the bacterial surface. Thereafter, the obtained precipitate is subjected to a drying process in a vacuum oven.

The vacuum drying proceeded in the present invention was carried out at a temperature of 60 ~ 70 ℃, pressure range of 10 ^-2 to 10 ^-3 torr for 6 to 8 hours.

The shape of the bacteria / tin oxide composite powder obtained after the vacuum drying is 500 ~ 800 nm in diameter, 1 ~ 2 ㎛ Bacillus bacteria surface of 2 ~ 5 nm evenly surrounded by tin oxide nanostructures, oxide nanostructures Has a very uniform and fine particle size distribution.

As an intermediate step of the present invention, the shape of the prepared bacterial / tin oxide complex can be observed through field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). 2, 3]. In addition, the phase type and crystal structure of the synthesis result of the prepared bacterial / tin oxide complex can be confirmed using X-ray diffraction patterns (XRD) [FIG. 4]. According to FIG. 4, the synthesized bacterial / tin oxide composite powder shows the same X-ray diffraction pattern as SnO ₂ (JCPDS card No. 41-1445). In addition, Figure 5 shows the quantitative characteristics of the tin oxide bound to the bacterial / tin oxide complex synthesized by thermal gravimetric analysis (TGA).

Next, the synthesized bacteria / tin oxide complex is prepared through the thermochemical reduction under a hydrogen atmosphere to prepare a tubular nanocomposite consisting of tin-based multi-phase nanostructures and amorphous carbon derived from bacteria. In addition, the advanced thermochemical reduction process is maintained for 12 hours after reaching 400 ℃ at a temperature rising rate of 10 ℃ per minute under a hydrogen atmosphere, if the conditions of the gas atmosphere, temperature, time does not satisfy the desired tin base Since it is impossible to obtain a tube-shaped nanocomposite composed of polyphase nanostructures and amorphous carbon, it is preferable to comply with the conditions.

The shape of the final powder obtained after the thermochemical reduction process can be observed through field emission scanning electron microscopy and transmission electron microscopy, and it can be seen that the diameter is reduced by 100 to 200 nm compared to the bacterial / tin oxide composite shown after vacuum drying. 6 and 7. Moreover, according to FIG. 7, it can be seen through the high resolution transmission electron micrograph that after the thermochemical reduction, multiphase nanostructures based on tin elements were formed. In addition, according to FIG. 8, the phase and crystal structures of the resultant obtained after thermodynamic reduction were confirmed by using an X-ray diffraction pattern [FIG. 8].

On the other hand, as a medium of such intermediate stages, tube-shaped nanocomposites composed of microstructured nanostructures and amorphous carbon based on tin element through bacteria / tin oxides and thermochemical reduction are electrochemical devices, more specifically lithium-ion in the art. It can be used for secondary batteries, electric double layer super capacitors and the like.

Therefore, the present invention provides a nanocomposite powder composed of a multi-phase tin element-based nanostructure / amorphous carbon in a tubular shape obtained through thermochemical reduction, as well as the intermediate complex composed of the bacteria / tin oxide. In order to determine the potential as a negative electrode active material, an electrode for a lithium battery was separately prepared and a half cell was constructed to evaluate electrochemical properties. The lithium ion secondary battery exhibits better electrochemical performance as the number of lithium charges that can react per unit molecular weight of the negative electrode active material used, and the particle aggregation phenomenon during charging and discharging are limited.

First, the inert powder and the conductive additive and binder composed of the bacteria / tin oxide prepared as the intermediate step or the tubular tin element based polyphase nanostructure / amorphous carbon obtained after thermochemical reduction are finally obtained. After dissolving in organic solvent, mix uniformly by sonication and mechanical mixing. Thereafter, the mixture is thinly coated on a copper current collector in a slurry state to prepare an electrode.

Lithium metal is used as a negative electrode, and the prepared electrode is used as an anode. An electrolyte and a separator are inserted between two electrodes to complete a half cell. The manufactured battery was evaluated for charging and discharging cycles while varying the current density flowing in the voltage range of 0.01 to 3.0V.

Among the powders prepared above, electrochemical characteristics were measured only for powders subjected to thermochemical reduction at 400 ° C., and electrochemical characteristics were also obtained for bacteria / tin oxides prepared in an intermediate step as a control and powders subjected to thermochemical reduction at 500 ° C. Were measured and compared with each other.

As a result of manufacturing the electrode and measuring the properties according to the above-described sequence, the powder of the tin element-based multiphase nanostructure / amorphous carbon proposed in the present invention exhibits a higher capacity than the measured results of the controls, and has a high current. Higher capacity also showed better stability in density.

Hereinafter, the present invention will be described in detail with reference to Examples, but the following Examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following Examples.

Example

(1) Example 1

5 μl were taken from the stock solution of Bacillus subtilis, which was stored frozen, and then inoculated into a test tube containing 5 ml LB liquid medium (Luria-Bertani, LB broth) and rotating at 200 rpm at 37 ° C. Were initially cultured in an incubator. After 10 to 12 hours from the initial incubation, 500 μl was collected from the culture solution and passaged in 5 Erlenmeyer flasks each containing 200 ml of liquid medium. Bacteria culture 5 hours after subculture were centrifuged at 12,000 rpm for 20 minutes to separate bacteria and supernatant. The sunk bacteria separated from the supernatant were washed twice with deionized water and centrifuged. Thereafter, the concentration of bacteria was adjusted to 1.0 (= 1 × 10 ⁸ cells / ml) by optical absorbance measurement at 600 nm wavelength using an ultraviolet spectrometer while adding 1 L or more of deionized water. While the solution in which the bacteria were dispersed was stirred at room temperature, the molar concentration of SnCl ₄ ㆍ 5H ₂ O, one of the metal chloride materials used, was measured to be 10 mM each, and each was dissolved in 400 ml of deionized water, and then stored at room temperature. Stir for 30 minutes. The solution was stirred for 30 minutes and then added to the solution at which the stirring was maintained at room temperature and bacteria were dispersed (at a rate of about 10 ml per minute). Thereafter, sterling was maintained at room temperature for 1 hour so that the tin precursor and bacteria were evenly dispersed. While maintaining the mixture, the molar concentration of N ₂ H ₄ .H ₂ O used as a reducing agent was weighed to 10 mM each, and each was dissolved in 200 ml of deionized water and then stirred at room temperature for 30 minutes.

To the mixture, which had been dispersed for 1 hour at room temperature, 200 ml of the N2H4.H2O-terminated solution for 30 minutes was slowly added thereto. Thereafter, the mixture was refluxed at 25 ° C. for 12 hours, after which the supernatant and the precipitate were separated by centrifugation at 10,000 rpm for 20 minutes, and then the supernatant was removed and the precipitate at the bottom was deionized water and acetone. 3 to 4 washes were performed. At this time, the precipitate is deposited in the state that the tin oxide is evenly distributed on the surface of the Bacillus bacteria, the synthesized precipitate was vacuum dried for 6 hours under the temperature of 60 ℃, pressure condition of 10 ^-2 torr, intermediate step Bacteria / tin oxide complexes were prepared.

Subsequently, the prepared bacteria / tin oxide composite was subjected to thermochemical reduction under a hydrogen atmosphere. First, 0.2 to 0.3 g of the prepared bacteria / tin oxide composite powder was weighed and subjected to thermochemical reduction in a tubular high temperature electric furnace. Was implemented. In order to proceed with heat treatment in a fully reducing atmosphere before performing heat treatment of the tubular high temperature electric furnace, a purge process is performed by flowing argon gas at a flow rate of 100 sccm for 30 minutes while the vacuum pump is operated. Thereafter, hydrogen gas was flowed at a flow rate of 40 sccm for 30 minutes to create a reducing atmosphere. Thereafter, a thermochemical reduction process was performed at 400 ° C. for 12 hours. At this time, the vacuum pump was not operated, and only hydrogen gas was continuously flowed at a flow rate of 40 sccm. The temperature rising rate was 10 ° C. / Proceed to min. After 12 hours of thermochemical reduction, a nanocomposite powder consisting of the nanotubes based on tin element based multiphase nanostructures and amorphous carbon derived from bacteria was obtained.

(2) Examples 2-4

Synthesis method is the same as in Example 1, but after fixing the concentration of the tin chloride precursor in Table 1 to 10 mM, to change the concentration of N ₂ H ₄ · H ₂ O reducing agent to 100, 500, 1000 mM, respectively The bacterial / tin oxide complexes thus obtained as intermediate steps of the present invention were prepared. 9 shows scanning electron micrographs of the bacterial / tin oxide complexes prepared according to the conditions of Examples 2, 3, and 4, respectively.

(3) Example 5

Synthesis method is the same as in Example 1, but obtained by the intermediate step of the present invention with the concentration of the tin chloride precursors shown in Table 1 to 100 mM, the concentration of the N ₂ H ₄ · H ₂ O reducing agent to 100 mM The resulting bacterial / tin oxide complex was prepared. Field emission scanning electron micrographs of the bacterial / tin oxide complexes prepared according to Example 5 are shown in FIG. 10.

As can be expected from Examples 2 to 5 above, when the intermediate compound of the present invention, the bacterial / tin oxide complex, does not retain the rod shape of the bacterial template and no tin oxide is formed, subsequent thermochemical Nanocomposites consisting of amorphous carbon and multiphase nanostructures based on tin elements with final tube shapes obtained through reduction cannot be prepared. Therefore, suitable forms of bacterial / tin oxide composite intermediate stage mediators should be prepared through the above examples.

(4) Examples 6-9

It was carried out by the same synthesis method as Example 1, but the final element of the present invention, the tin element-based polyphase of the final product of the present invention, while varying the treatment temperature or the heat treatment atmosphere to argon as shown in Table 1 between the final thermochemical reduction treatment process To prepare a nanocomposite consisting of nanostructures and amorphous carbon.

Hereinafter, the crystalline phases of the powders finally obtained according to the conditions of Examples 6 to 9 were confirmed by X-ray diffraction analysis, which are shown in comparison with FIG. 11.

According to FIG. 11, in the case of the final powder prepared under the conditions of Examples 6 to 9, tin phase-based multiphase nanostructures were not synthesized, as in the X-ray diffraction analysis obtained through Example 1, but a single phase It can be seen that it is made of tin oxide (SnO ₂ ) or tin metal (metallic tin, Sn). Therefore, in order to produce a nanocomposite having a tube shape which is the final form of the present invention between the thermochemical reduction processes through the above embodiments, and consisting of polyphase nanostructures and amorphous carbon on the basis of tin element, the temperature between the thermochemical reduction processes, Conditions such as time and mood must be adequately set. In particular, the shape of the nanocomposite prepared in Example 8 is shown in FIG. 12 using a field emission scanning electron microscope, a transmission electron microscope, and a high resolution transmission electron microscope. As shown in FIG. 12, the nanostructures based on amorphous carbon and tin elements derived from bacteria after the thermochemical reduction process are not evenly distributed, but a recrystallized reduction to tin metal due to a high reduction temperature is achieved. It can be seen that the increase significantly. These results later showed lower capacity characteristics in composites with tin-based multiphase nanostructures in secondary battery tests with lithium.

(5) Example 10

The synthesis was carried out in the same manner as in Example 1, except that the precipitate in the intermediate step was obtained without using a bacterial template as described in Table 1 below. In addition, a scanning micrograph of the obtained precipitate is shown in FIG. 13, and when the bacterial template identified in FIG. 13 is not applied, it is not formed on a template of tin oxide obtained in an intermediate step, and thus a desired rod shape cannot be obtained. This means that the nanocomposite consisting of amorphous carbon and multiphase nanostructures based on tin element having the final tube shape of the present invention cannot be produced.

Table 1

2. Comparative Example 1

In order to compare and analyze the secondary battery characteristics of the tubular nanocomposite consisting of the tin element-based polyphase nanostructure and amorphous carbon prepared in Example 1, the same synthesis as in Example 1 as a control as shown in Table 2 below. Secondary battery characteristics were compared by using the nanopowder prepared in Example 8 and the intermediate bacteria / tin oxide complex which was performed by the method but did not undergo the thermochemical reduction process.

TABLE 2

3. Test Example 1

The negative electrode active material of the anode active material of the tube-shaped nanocomposite composed of the tin element-based polyphase nanostructure and amorphous carbon prepared in Example 1 and the nanopowder prepared in Comparative Example 1 and the powder prepared in Example 8 In order to compare and evaluate as an active material, the capacity of the half battery was measured after producing an electrode.

(a) Electrode manufacturing

0.5 to 1 mg of the nano-powder negative electrode active material prepared in Example 1 was weighed to have a mass ratio of 70: 15: 15 and graphite (MMM Cabon) and a binder, Kynar 2801 (PVdF-HFP), and then inert. It was prepared in the form of a slurry by dissolving in N-methyl- pitolidon (NMP), an organic solvent. Thereafter, the slurry was applied to a copper foil as a current collector, dried in a vacuum oven at 100 ° C. for 4 hours to volatilize an organic solvent, and then pressed into a circular shape having a diameter of 1 cm.

In addition, as a control, the nano powders prepared in Comparative Examples 1 and 8 were also weighed 0.5 to 1 mg as a negative electrode active material, and the mass ratio of graphite as a conductive agent and Kynar 2801 as a binder was 70:15:15, and then inert. It was dissolved in organic solvent to form a slurry. The subsequent process is the same as the manufacturing process of the electrode presented through the sample of Example 1.

(b) Fabrication and measurement of half cell for evaluation of electrochemical properties

In order to examine the electrochemical properties of the nanostructures of the tube-shaped nanocomposites composed of the tin-based multiphase nanostructures and amorphous carbon prepared in the present invention, the electrodes prepared in (a) as lithium metal ions as the cathode and the anode An electrolyte and a separator (Celgard 2400) were inserted between the two, and a half cell of a Swagelok type was configured. The electrolyte used was a material in which LiPF6 was dissolved in a solution in which a volume ratio of ethylene carbonate (EC) and dimethyl carbonate (dimethyl carbonate, DMC) was 1: 1. All procedures of the half cell preparation presented above were carried out in a glove box filled with argon, an inert gas.

The manufactured half-slave type half cell uses a charge / discharge cycler (WBCS 3000, WonA Tech., Korea) to change the voltage to 0.03 ㎷ / sec between 0.01 and 3.0 V voltages and is in a positive static mode. The current density was 78 mA / g, 157 mA / g, 235 mA / g, 392 mA / g, and the current density was changed to galvanostatic mode. The electrochemical characteristics were evaluated by changing the current density while performing 10 cycle charge / discharge tests.

The graph analyzed according to the constant current method is shown in FIG. 14. In the case of the anode active material prepared from the tin element-based polyphase nanostructure and amorphous carbon composite tubular nanocomposites presented in the present invention, the bacteria / tin oxide (SnO 2) obtained in the intermediate step of the present invention. Compared to the composite consisting of or nanocomposites made of amorphous carbon / single-phase tin metal (Sn) (metallic tin, Sn) prepared through Example 8, it is found that exhibits excellent cycle characteristics while achieving high capacity characteristics even at high current density Can be.

The following Table 3 shows the discharge capacity when 10 charge and discharge cycle tests were performed at each current density in the secondary battery characteristics evaluation of the powders prepared in Examples 1, 9 and Comparative Example 1. .

TABLE 3

Table 3 is a negative electrode using the powders prepared in Example 8 and Comparative Example 1 is the negative electrode active material of the tube-shaped nanocomposite composed of the amorphous carbon / tin element-based multi-phase nanostructures prepared in Example 1 of the present invention It has much higher capacity characteristics than active materials, and shows cycle stability with high capacity characteristics even at high current densities. From this, the material of the tube-shaped nanocomposite composed of amorphous carbon / tin element-based multiphase nanostructures raised in the present invention can achieve high capacity due to low dimensional nanostructures composed of polyphase tin elements. In addition, due to the fact that it can give improved electrical conductivity through complexing with amorphous carbon derived from bacteria, it realizes relatively high capacity even at high current density, and has a tubular characteristic, It can be seen that small volume changes can maintain high capacity and also improve cycle stability.

The present invention is directed to polyphase tin oxides having a 0-dimensional shape and tin metal and bacteria by thermochemically reducing the powder of bacteria / tin oxide obtained by directly binding tin oxide to the Bacillus bacterial surface in a hydrogen atmosphere. The present invention relates to a tube-shaped nanocomposite complexed with amorphous carbon.

Bacteria are used as a template for low capacity and low output (low capacity for high current density), which have been pointed out as a disadvantage in the conventional negative electrode active material for lithium secondary batteries, and the capacity greatly decreases due to large volume change when reacting with lithium. In addition, it is possible to solve the problem by manufacturing a tubular nanocomposite composed of amorphous carbon / tin element based multi-dimensional low dimensional nanostructures, which are manufactured through thermochemical reduction by combining tin oxide, which can realize high capacity, with the bacterial surface. Do.

In the present invention, the thermochemical reduction process is simple, economical, and it is possible not only to obtain various types of complexes depending on the shape of the bacterium template used, but also to facilitate low-temperature synthesis and synthesis of intermediate media. Because of the ease of production, it is expected to be practically applicable not only to lithium secondary batteries but also to electric double layer super capacitors.

Claims (16)

1) preparing a bacterial dispersion solution by culturing bacteria having anion on the surface and adjusting the concentration of bacteria with deionized water;

2) Stirring at 20 to 30 ° C. for 0.5 to 2 hours while adding a tin precursor solution in which the transition metal precursor is dissolved in deionized water to the solution of 1) to uniformly disperse the Bacillus bacteria and the transition metal precursor. step;

3) refluxing while adding a solution of hydrazine (N ₂ H ₄ .H ₂ O) in deionized water to the solution of 2) to induce transition metal oxide to adhere evenly to the bacterial surface;

4) centrifuging and washing the reflux solution of 3) to obtain a precipitate;

5) vacuum drying the precipitate to obtain a bacterial / transition metal oxide composite powder; And

6) thermochemically reducing the obtained composite powder;

Method for producing a transition metal based nanostructure / amorphous carbon nanocomposite comprising a.

The method of claim 1, wherein the bacterium that exhibits a negative charge on the surface is Bacillus subtilis.

The method according to claim 1, wherein the bacteria concentration of step 1) is a method for producing a nanostructure / amorphous carbon nanocomposite, characterized in that the optical absorbance of 1.0-2.0 at 600 nm wavelength through an ultraviolet spectrometer measurement.

The method according to claim 1, wherein the transition metal precursor is a method for producing a nanostructure / amorphous carbon nanocomposite, characterized in that the tin.

The method of claim 4, wherein the tin is at a concentration of 1-200 mM.

The method of claim 1, wherein the hydrazine is at a concentration of 10-1000 mM.

The method of claim 1, wherein the reflux is performed at 20 30 ° C. for 10-15 hours.

The method according to claim 1, wherein the vacuum-dried at a temperature of 60 70 ℃, 10 ^-2 - production method characterized in that it carried out in the 10 ^-3 torr pressure.

The method according to claim 1, wherein the thermochemical reduction step of step 6) is maintained for 5 to 24 hours in a hydrogen atmosphere at a temperature of 350-500 ℃.

The process according to claim 9, wherein the temperature is 400 ° C., characterized in that it is reached at a temperature increase rate of 10 ° C. per minute and the thermochemical reduction step is carried out for 10-15 hours.

2. The tin oxide nanostructure of 2-5 nm according to claim 1, wherein the bacteria / transition metal (tin) oxide composite powder is vacuum-dried in step 5) on a bacterial surface having a diameter of 500 to 800 nm and a length of 1 to 2 μm. Is bonded to a manufacturing method.

A transition metal based nanostructure / amorphous carbon nanocomposite prepared by the method of any one of claims 1 to 11.

The nanocomposite of claim 12, wherein the transition metal is tin.

The tube of claim 12, wherein the transition metal-based nanostructure / amorphous carbon nanocomposite is a tube composed of microcrystalline nanostructures based on tin element attached to the surface of bacteria and amorphous carbon derived from bacteria due to thermochemical reduction of the nanocomposite. Nanocomposite, characterized in that the nanocomposite of the shape.

The negative electrode active material of a lithium secondary battery comprising the transition metal-based nanostructure / amorphous carbon nanocomposite of claim 12.

A lithium secondary battery comprising a negative electrode active material of a lithium secondary battery comprising a transition metal-based nanostructure / amorphous carbon nanocomposite of claim 15.

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