KR20170085241A - Nano Sheet Containing Amorphous SiOx, Manufacturing Method Thereof and Secondary Battery Using the Same - Google Patents

Abstract

The present invention relates to a nanosheet containing amorphous silicon oxide, a method for producing the nanosheet, and a secondary battery including the amorphous silicon oxide. More particularly, the present invention relates to a nanosheet containing amorphous silicon oxide capable of minimizing volume change of silicon And also relates to a technique for applying the same to a secondary battery.
According to the present invention, amorphous silicon oxide can be realized in the form of a nano-sized sheet so as to minimize the change in the volume of silicon. Such a structure, when applied to a battery, shortens the diffusion distance of lithium, It is effective to improve the capacity, and further, it is possible to charge at a very high speed.

Description

TECHNICAL FIELD The present invention relates to a nanosheet containing amorphous silicon oxide, a method of manufacturing the nanosheet, and a secondary battery including the nanosheet,

The present invention relates to a nanosheet containing amorphous silicon oxide, a method for producing the nanosheet, and a secondary battery comprising the nanosheet. More particularly, the present invention relates to a nanosheet containing amorphous silicon oxide, To a method of manufacturing the same, and also to a technique for applying the same to a secondary battery.

In general, lithium secondary batteries are not only expanding the range from compact electronic device-driven power sources such as smart phones to large systems such as renewable energy storage systems, but also promoting human convenience such as medical robots and drones The role of robot as an energy storage source for robots that can work in extreme situations that can not be done by humans is emerging.

In particular, recently, interest in electric vehicles has been rapidly increasing, and a number of technologies have been developed in order to secure a mileage similar to that of an automobile employing an internal combustion engine in a single charge. However, 372 mAh / g), it is difficult to meet the market demands of current secondary batteries which require high capacity, high output and low cost.

Therefore, various negative electrode materials capable of exhibiting high capacity and high output characteristics are being developed. Among them, lithium (Al) is alloyed with silicon (Si) capable of releasing energy by storing energy and dealloying, (Sn), and germanium (Ge), have attracted great attention as next generation cathode materials.

Particularly, in the case of silicon, high energy density of the lithium secondary battery can be achieved by replacing graphite due to the highest theoretical capacity (Li3.75 Si, -3580 mAh / g) and relatively low operating voltage (-0.5 V) It is a viable alternative material.

However, these materials have a disadvantage in that the capacity of repeated charging and discharging is drastically reduced due to a serious change in volume during lithium and alloying and de-alloying reaction. In order to solve such a problem, studies using amorphous silicon oxide, which has a relatively small volume change and excellent lifetime maintenance characteristics, have been attracting attention. However, the electrode material using the silicon oxide has a spherical shape, (Patent Documents 1 and 2)

Accordingly, in the present invention, an electrode material having a nano-sized sheet shape other than a spherical shape is implemented to minimize the volume change of silicon oxide and significantly reduce the diffusion distance of lithium, and a method for manufacturing the same.

Patent Document 1. Korean Patent Publication No. 10-2015-0015086 Patent Document 2. Korean Patent Publication No. 10-2012-0010211

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a nanosheet containing amorphous silicon oxide having a nanosized sheet shape and a method of manufacturing the nanosheet, .

Another object of the present invention is to provide a secondary battery including the nanosheet to improve the output characteristics and the charge / discharge capacity, and further to charge at a very high speed.

In order to achieve the object of the present invention, the present invention provides a nanosheet comprising amorphous silicon oxide, wherein nanosized silicon particles are formed on the surface and inside of the nanosheet, do.

The silicon particles are characterized by a diameter of 1 to 20 nm.

Wherein the silicon oxide is SiOx (wherein x is a rational number of 0 < x < 2).

The present invention also provides a method for producing a nanosheet, which comprises (A) reacting a silicon precursor solution and (B) heat-treating the reactant.

The method further comprises (A-I) filtering and drying the reactant.

The silicon precursor is represented by the following general formula (1).

[Chemical Formula 1]

RSiH

(Wherein R is Cl ₃ or OR 'and R' is an alkenyl group having 1 to 3 carbon atoms).

The step (A) is characterized in that the silicon precursor is introduced into a solvent and reacted for 1 to 60 minutes.

The solvent is characterized by being at least one selected from distilled water, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

The step (A-I) is characterized by drying at a temperature of 80 to 120 ° C for 5 to 20 hours.

The step (B) is performed at a temperature of 800 to 1200 ° C. for 1 to 5 hours.

And the rate of temperature increase for reaching the heat treatment temperature in the step (B) is 5 to 20 占 폚 / min.

Finally, the present invention provides a secondary battery comprising the nanosheet produced by the method.

According to the present invention, amorphous silicon oxide can be realized in the form of a nano-sized sheet so as to minimize the change in the volume of silicon. Such a structure, when applied to a battery, shortens the diffusion distance of lithium, It is effective to improve the capacity, and can be charged at super high speed.

1 is an image showing the result of observing the nanosheet of Example 1 with a scanning electron microscope (SEM).
2 (a) and 2 (b) are images showing the result of observing the nanosheet of Example 1 with naked eyes.
3 is a graph showing X-ray diffraction (XRD) results of the nanosheets of Examples 1 to 5.
Fig. 4 (a) is a schematic view showing the distribution of crystalline silicon particles formed on the surfaces of the nanosheets and inside of Examples 1, 2 and 5, (b) is a cross- And measuring the size of the crystalline silicon particles.
FIG. 5 is a graph showing the results of measurement of the charging capacity of the secondary batteries of Examples 6 to 10. FIG.
6 is a graph showing the first cycle charging / discharging curve for the secondary battery of Example 6 and Comparative Example 1. FIG.
7 is a graph showing the charge-discharge life characteristics of the secondary battery of Example 6 and Comparative Example 1. Fig.
8 is a graph showing the results of 100 cycle charge / discharge measurement of the secondary battery of Example 6. Fig.
FIG. 9 is an image showing a result of observation of a cross section of a secondary battery electrode according to Example 6 by a scanning electron microscope, in which (a) is before charging and discharging (Pristine), (b) c) is a graph showing the change in height of the electrode after 20 cycles of discharge, (d) after 50 cycles of discharge, and (e) of FIG.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

The present invention relates to a nanosheet containing amorphous silicon oxide, and a nanosheet having nano-sized silicon particles formed on the surface and inside of the nanosheet.

As shown in FIG. 1, the nanosheet according to the present invention has amorphous silicon oxide as a whole flat sheet shape. Such a sheet shape minimizes the volume change of silicon and significantly reduces the diffusion distance of lithium And is effective for improving the capacity and output characteristics of the battery.

Since the amorphous silicon oxide is not a crystalline single structure, the amorphous silicon oxide significantly reduces the expansion rate due to charging, thereby solving the structural degradation due to charge and discharge.

In addition, the nanosheets including crystalline silicon particles on the surface and inside of the nanosheet can further strengthen the structure of the nanosheet made of amorphous, and improve the strength of the nanosheet.

That is, the present invention realizes a high capacity and an improved output characteristic through the amorphous structural characteristic, and the physical properties of the nanosheet can be improved by impregnating the crystalline silicon particles into the inside and the outside.

The silicon oxide is SiOx, and x is preferably a rational number of 0 < x < 2.

The diameter of the silicon particles is preferably 1 to 20 nm, and if the diameter is less than 1 nm, the structural stability tends to deteriorate. If the diameter is more than 20 nm, the output characteristics of the battery may deteriorate. not.

As shown in FIG. 4 (a), the silicon particles are formed by bonding crystalline silicon particles to the surface of the amorphous silicon oxide.

The present invention also relates to a method for producing a nanosheet, which comprises (A) reacting a silicon precursor solution and (B) heat-treating the reactant.

It is more preferred that the method further comprises (A-I) filtering and drying the reactant produced in step (A).

In the step (A), the silicon precursor is dissolved in a solvent to induce a sol-gel reaction. Preferably, the silicon precursor is introduced into a solvent and reacted for 5 to 30 minutes.

The silicon precursor is represented by the following general formula (1).

[Chemical Formula 1]

RSiH

(Wherein R is Cl ₃ or OR 'and R' is an alkenyl group having 1 to 3 carbon atoms).

As shown in the above formula, in the present invention, by using a silane-based material, which is a silicon hydride, vaporized silicon hydride reacts at the surface of water using a high vapor pressure to form a flat sheet shape. Such a process is effective to make it possible to keep the sheet-like structure after the heat treatment process.

The solvent is preferably at least one selected from distilled water, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, but is not limited thereto.

The step (A-I) is a step of filtering and drying the reactant. The solution is filtered, the filtered precipitate is washed with distilled water several times, and the precipitate is dried at 80 to 120 ° C for 5 to 20 hours, .

The step (B) is a step of heat-treating the dried powder through the step (A-I), and the heat treatment is preferably performed at a temperature of 800 to 1200 ° C for 1 to 5 hours.

The crystalline silicon particle size can be controlled according to the heat treatment temperature. If the temperature is lower than 800 ° C, silicon particles are not formed well. On the other hand, when the temperature exceeds 1200 ° C, crystalline silicon particles may be formed to a large extent, but at the same time, the content of lithium and inactive SiO ₂ may increase, and charging and discharging can not be performed.

The rate of temperature rise to reach the heat treatment temperature is preferably 5 to 20 ° C / min, which is more effective in forming uniformly crystalline silicon particles.

The present invention also provides a secondary battery comprising the nanosheet produced by the method.

Hereinafter, the present invention will be described in detail with reference to examples.

Example  1: Production of nanosheet (heat treatment at 1000 占 폚)

A beaker containing Trichlorosilane (Cl ₃ SiH, 99.8%) was kept in a closed container containing distilled water at a temperature of 0-20 ° C for about 20 minutes. The solution was filtered to wash the precipitated product with distilled water several times, Dry at 100 ° C for about 10 hours to remove any remaining moisture. The dried powder was placed in an electric furnace and heat-treated in a 4 to 10% H ₂ / Ar atmosphere at a temperature of 1000 ° C for 2 hours to prepare a nanosheet containing amorphous silicon oxide.

(However, the heating rate of the heat treatment temperature was 10 ° C / min.)

Example  2: Production of nanosheet (heat treatment at 800 ° C)

The same procedure as in Example 1 was carried out except that the heat treatment was performed at 800 占 폚 instead of 1000 占 폚.

Example  3: Production of nanosheet (heat treatment at 900 占 폚)

The same procedure as in Example 1 was carried out except that the heat treatment was conducted at 900 占 폚 instead of 1000 占 폚.

Example  4: Production of nanosheet (heat treatment at 1100 占 폚)

The same procedure as in Example 1 was carried out except that the heat treatment was performed at 1100 占 폚 instead of 1000 占 폚.

Example  5: Production of nanosheet (heat treatment at 1200 占 폚)

The same procedure as in Example 1 was carried out except that the heat treatment was performed at 1200 占 폚 instead of 1000 占 폚.

Example 6: Manufacture of secondary battery comprising nanosheet

The nanosheets of Example 1 and carbon black (Super-P, Ensaco) and polyacrylic acid (PAA, Sigma-Aldrich) were added to distilled water at a weight ratio of 7: 1: 2 and dispersed and then applied to Cu foil And vacuum dried at a temperature of 120 캜 to prepare an electrode.

The electrolyte used was 1.0 M LiPF ₆ and ethylene carbonate: ethyl methyl carbonate (1: 2, vol.%). The electrolyte was prepared by assembling a coin cell (2032 size) using the electrode, lithium metal and polyolefin separator. )to be.

Examples 7 to 10: Preparation of secondary battery including nanosheet

Except that the nanosheets prepared in Examples 2 to 5 were used in place of those in Example 1, respectively.

Comparative Example 1: Manufacture of secondary battery without nanosheet

A secondary battery was produced in the same manner as in Example 6 except that amorphous silicon oxide (SiO _1.5 ), which is not a sheet, was used instead of the first embodiment.

FIG. 1 is an image showing a result of observation of a nanosheet of Example 1 by a scanning electron microscope (SEM), and it is confirmed that the nanosheet shows a very flat shape including several nanosized silicon particles .

2 (a) and 2 (b) are images showing the result of visual observation of the nanosheet of Example 1, and the structure of the sheet shape can be confirmed visually.

FIG. 3 is a graph showing the results of X-ray diffraction (XRD) of the nanosheets of Examples 1 to 5, and the change of the crystal structure according to the heat treatment temperature can be confirmed. In the case of Examples 4 and 5, it can be seen that the effective peak is observed more clearly in the vicinity of 30 DEG because the crystalline silicon particle size is formed larger as the heat treatment temperature is raised.

Fig. 4 (a) is a schematic view showing the distribution of crystalline silicon particles formed on the surfaces of the nanosheets and inside of Examples 1, 2 and 5, (b) is a cross- And measuring the size of the crystalline silicon particles.

Referring to FIG. 4, it can be seen that as the annealing temperature is increased, the size of the crystalline silicon particles increases. However, in the case of Example 5, it can be seen that the tendency is lowered in terms of distribution. In other words, it can be seen that Embodiment 1 is most suitable when the size and distribution of silicon particles are considered in combination.

FIG. 5 is a graph showing the results of measurement of the charging capacity for the secondary batteries of Examples 6 to 10. In the case of Example 10, the charging / discharging capacity could not be measured.

FIG. 6 is a graph showing the first cycle charging / discharging curve of the secondary battery of Example 6 and Comparative Example 1. In the case of Example 6, it is confirmed that the secondary battery has improved initial capacity and efficiency as compared with Comparative Example 1.

That is, Example 6 exhibits a sheet-like structure, and the diffusion path of lithium ions is shortened due to the structural characteristics thereof, and the area of the interface contacting the electrolyte is increased, and the electrochemical activity is greatly improved.

FIG. 7 is a graph showing charge / discharge life characteristics of the secondary battery of Example 6 and Comparative Example 1. In Example 6, the life characteristics of the secondary battery are better than those of the Comparative Example. These results indicate that the sheet-like amorphous silicon oxide This is because the volume change due to repeated charging and discharging was efficiently controlled.

FIG. 8 is a graph showing the results of 100 cycle charge / discharge measurement of the secondary battery of Example 6, and it can be realized at a level similar to the capacity value in 0.5 to 20 cycles even after 50 cycles of charging or discharging in 1 hour. And a capacity of about 450 mAh / g even after 100 cycles, indicating high output characteristics.

FIG. 9 is an image showing a result of observation of a cross section of a secondary battery electrode according to Example 6 by a scanning electron microscope, in which (a) is before charging and discharging (Pristine), (b) c) is a graph showing the change in height of the electrode after 20 cycles of discharge, (d) after 50 cycles of discharge, and (e) of FIG. As shown in FIG. 9, it can be seen that the height of the electrode is maintained without changing the degree of volume expansion even after 50 cycles.

Therefore, according to the present invention, amorphous silicon oxide can be realized in the form of a nano-sized sheet so as to minimize the volume change of silicon. Such a structure can reduce the diffusion distance of lithium when applied to a battery, It is effective to improve the charging / discharging capacity, and it is possible to charge at a very high speed.

Claims (12)

In a nanosheet containing amorphous silicon oxide,
Wherein nanosized silicon particles are formed on the surface and inside of the nanosheet.
The method according to claim 1,
Wherein the silicon particles have a diameter of 1 to 20 nm.
The method according to claim 1,
Wherein the silicon oxide is SiOx.
(Wherein x is a rational number of 0 < x < 2)
(A) reacting a silicon precursor solution; And
(B) heat treating the reactant. &Lt; RTI ID = 0.0 &gt; 21. &lt; / RTI &gt;
5. The method of claim 4,
Wherein the silicon precursor is represented by the following formula (1).
[Chemical Formula 1]
RSiH
(Wherein R is Cl ₃ or OR 'and R' is an alkenyl group having 1 to 3 carbon atoms).
5. The method of claim 4,
Wherein the step (A) comprises introducing the silicon precursor into a solvent and reacting the mixture for 1 to 60 minutes.
The method according to claim 6,
Wherein the solvent is at least one selected from distilled water, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
5. The method of claim 4,
Wherein the step (B) is performed at a temperature of 800 to 1200 ° C for 1 to 5 hours.
5. The method of claim 4,
Wherein the rate of temperature increase for reaching the heat treatment temperature in the step (B) is 5 to 20 占 폚 / min.
5. The method of claim 4,
The method according to claim 1, further comprising (A-I) filtering and drying the reactant.
11. The method of claim 10,
Wherein the step (A-I) is performed at a temperature of 80 to 120 ° C for 5 to 20 hours.
A secondary battery comprising a nanosheet produced according to any one of claims 4 to 11.

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