KR101929415B1 - Electrode active material-solid electrolyte composite, method for manufacturing the same, and all solid state rechargeable lithium battery including the same - Google Patents

Abstract

An electrode active material-solid electrolyte complex in the form of a solid electrolyte coating layer formed on the surface of an electrode active material particle, a method for producing the same, and a pre-solid battery including the same in an electrode layer are shown in embodiments of the present invention.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode active material-solid electrolyte composite, a method for producing the same, and a whole solid battery including the electrode active material-solid electrolyte complex,

Electrode active material-solid electrolyte complex, a method for producing the same, and an all-solid-state cell including the electrode active material-solid electrolyte complex.

The secondary battery has mainly been applied to a small-sized field such as a mobile device or a notebook computer. However, recently, the research direction has been expanded to middle and large-sized fields such as an energy storage system (ESS) and an electric vehicle .

In the case of such a large-sized secondary battery, unlike a small-sized battery, operating environment (for example, temperature, shock) is not only severe but also requires more batteries. There is a need.

However, most of the currently commercialized secondary batteries use an organic liquid electrolyte in which a metal salt is dissolved in a flammable organic solvent, which poses a potential risk of leakage, ignition, explosion, and the like.

Accordingly, the use of a solid electrolyte in place of the organic liquid electrolyte has attracted attention as an alternative to overcome the safety problem.

Specifically, a battery using a solid electrolyte, that is, a whole solid battery, can be classified into a thin film type and a thick film type. Among these, a thick-film type all-solid-state cell is a so-called composite-type all-solid-state cell, and in the currently commercialized secondary battery, the organic liquid electrolyte is simply replaced with a solid electrolyte.

In order to exhibit the performance of such a pre-solid battery, it is required that the solid electrolyte and the active material in the pre-solid battery have excellent contact properties between particles so that the theoretical capacity of the active material on which they are based can be fully expressed. Pharaoh is not meeting the demand.

On the other hand, most of the currently commercialized secondary batteries use lithium as a solid electrolyte material, but the distribution range of lithium is limited not only in the world but also in the reserves, which are disadvantageous in terms of price and continuous supply of materials. Accordingly, there is a movement to utilize sodium, which is widely distributed on the earth, as a solid electrolyte material. However, when sodium is used as a solid electrolyte material, ion conductivity lower than lithium is a problem.

In order to solve the above-mentioned problems, an embodiment of the present invention provides an electrode active material-solid electrolyte complex in the form of a solid electrolyte coating layer formed on the surface of electrode active material particles.

Another embodiment of the present invention provides a method for producing the electrode active material-solid electrolyte complex by preparing a sulfide-based solid electrolyte and then coating the surface of the electrode active material with the sulfide-based solid electrolyte.

According to still another embodiment of the present invention, there is provided an electrode including the electrode active material-solid electrolyte complex, and a pre-solid battery including the electrode.

In one embodiment of the present invention, electrode active material particles; And a solid electrolyte coating layer positioned on the surface of the electrode active material particle.

10^-4 S/cm 이상인 황화물계 화합물을 고체 전해질로 포함하는 것이다.Herein, the solid electrolyte coating layer is represented by the following general formula (1) or (2) and has an ionic conductivity of 1.0

And a sulfide-based compound of 10 < ^-4 > S / cm or more as a solid electrolyte.

Na _a M _b S _c X ¹ _d

Li _a M _b S _c X ¹ _d

In the above chemical formulas 1 and 2, M is at least one element selected from the group consisting of Sb, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Bi, Ti, , Co, Ni, Cu, Y , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, and Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, Or 0, 0 <a? 6, 0 <b? 6, 0 <c? 6, 0? D?

First, the chemical formula representing the sulfide compound will be described as follows.

In the formula 1 or 2, M is Sb, 0 < a? 3.5, 0 < b?

Specifically, the sulfide compound may be represented by the following formula (3).

???????? Na _{3 + x} SbS _{4 + y} ?????

(In the formula 3, -0.5 < x < 0.5 and -0.5 < y < 0.5)

10^-3 S/cm 이상일 수 있다.The sodium ion conductivity of the sulfide compound represented by the formula (3) is preferably 1.0

10 ^-3 S / cm or more.

The crystal structure of the sulfide compound will be described below.

The sulfide-based compound may be crystalline, and in this case, a Cu K? X-ray (X-r?) Is formed in at least one of the range of 2? In the range of 16 to 18, 29 to 32, ) May show a split peak of the XRD peak due to the X-ray diffraction.

At this time, the crystal structure of the sulfide-based compound is as follows. And may be tetragonal.

The electrode active material particles are described below.

The weight ratio of the solid electrolyte coating layer to the electrode active material particles may be 0.1: 99.9 to 50:50 (coating layer: electrode active material particles).

Wherein the electrode active material particle is at least one selected from the group consisting of NaCrO ₂ , Na _x M _y X _z, Li _x M _y X _z (where M = Ti, V, Cr, Mn, Fe, Co, Ni, = O, an _{S, F, Cl, PO 4} , P 2 O 7, SO 4, or SO ₄ F and, 0 <x <4, and, 0 <y <4, and, 0 <x <12), the carbon-based Material, or a combination thereof.

In another embodiment of the present invention, there is provided a process for producing a solid electrolyte, comprising the steps of: heat treating a mixture of a lithium or sodium raw material, a heterogeneous raw material, and a sulfur raw material to obtain a sulfide compound represented by the following formula 1 or 2 as a solid electrolyte; And coating the surface of the electrode active material particles with the solid electrolyte to obtain an electrode active material-solid electrolyte complex. The present invention also provides a method for producing an electrode active material-solid electrolyte complex.

Na _a M _b S _c X ¹ _d

Li _a M _b S _c X ¹ _d

In the above chemical formulas 1 and 2, M is at least one element selected from the group consisting of Sb, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Bi, Ti, , Co, Ni, Cu, Y , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, and Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, Or 0, 0 <a? 6, 0 <b? 6, 0 <c? 6, 0? D?

Specifically, the step of heat-treating the mixture to obtain the sulfide-based compound represented by Formula 1 or 2 as a solid electrolyte will now be described.

The heat treatment may be performed in a temperature range of more than 350 DEG C to 800 DEG C or less.

The hetero-element raw material may be an antimony (Sb) raw material.

Wherein the mixture of the lithium or sodium raw material, the heterogeneous element raw material and the sulfur raw material is selected from the group consisting of Na, Na ₂ S, Na _x Sn (0 <x <4), Sb, Sb ₂ S ₃ , Sb ₂ S ₅ , S, a heterogeneous elementary raw material, and a sulfur raw material may be mixed in the stoichiometric molar ratio of the above formula (1).

Subjecting the sulfide compound represented by Formula 1 or 2 to a solid electrolyte by the heat treatment; Thereafter, preparing a mixture comprising the solid electrolyte and the first solvent; Vaporizing a first solvent in the mixture comprising the solid electrolyte and the first solvent to obtain a dried material; And heat treating the dried material.

Wherein the first solvent is selected from the group consisting of water (H ₂ O), alcohol (C _n H _{2n + 1} OH, ₁ ≦ _n ≦ 20), formic acid and acetic acid, tetrahydrofuran, But are not limited to, dimethylformamide, acetonitrile, dimethyl sulfoxide, acetone, ethyl acetate, dimethoxy ethane, 1,3-dioxolane 1,3-dioxolane, N-methylpyrrolidinone, N-methylformamide, diethyl carbonate, ethylmethyl carbonate, and dimethyl carbonate dimethyl carbonate, or a mixture of two or more thereof.

The step of vaporizing the first solvent in the mixture comprising the solid electrolyte and the first solvent to obtain a dried material may be performed by a vacuum drying method or a thermal drying method.

In the vacuum drying method, a pressure of 0 torr to 1 torr may be applied in a temperature range of 20 to 40 ° C.

Independent thereto, the thermal drying method may be one in which the heat treatment is performed at a normal pressure at a temperature of not lower than the boiling point of the mixture at 40 ° C or higher.

Meanwhile, the step of heat-treating the dried material may be performed at a temperature ranging from 100 to 750 ° C.

Coating the solid electrolyte on the surface of the electrode active material particles to obtain an electrode active material-solid electrolyte complex, comprising the steps of: preparing a coating agent comprising the solid electrolyte and a second solvent; Preparing a mixture of the coating agent and the electrode active material particles; Forming a solid electrolyte coating layer on the surface of the electrode active material particles by vaporizing a second solvent in the mixture of the coating agent and the electrode active material particles; And heat treating the electrode active material particle having the solid electrolyte coating layer formed thereon.

The second solvent may be methanol, ehanol, or water (H ₂ O).

Wherein the solid electrolyte and the second solvent are contained in an amount of 0.1 to 50 wt% based on 100 wt% of the total amount of the coating agent, .

The step of heat-treating the electrode active material particles having the solid electrolyte coating layer may be performed at a temperature ranging from 100 to 450 ° C.

According to another embodiment of the present invention, there is provided an electrode for a pre-solid battery comprising the above-described electrode active material-solid electrolyte complex.

According to another embodiment of the present invention, cathode; And a solid electrolyte, wherein the electrode active material-solid electrolyte complex is contained in one of the positive electrode and the negative electrode.

The electrode active material-solid electrolyte composite according to an embodiment of the present invention is characterized in that the solid electrolyte coating layer is formed on the surface of the electrode active material particles, and the contact properties, ionic conductivity, and air stability of the solid electrolyte and the active material particles Can be excellently expressed.

Further, by the sulfide-based solid electrolyte contained in the electrode active material-solid electrolyte complex, lithium or sodium ion conductivity can be secured while having excellent safety as compared with the organic liquid electrolyte, and characteristics that are stably dissolved in a solvent are uniformly expressed .

According to another embodiment of the present invention, there is provided a method for producing a sulfide-based solid electrolyte, comprising the steps of: preparing a sulfide-based solid electrolyte by a solid phase method or wet-post-treating a material produced by a solid phase method, By coating the electrolyte wet, it is possible to produce a complex of the above excellent properties.

According to still another embodiment of the present invention, by providing the sulfide-based solid electrolyte in the electrode, it is possible to provide a pre-solid battery in which battery performance is stably exhibited while safety is secured as compared with a battery using the organic liquid electrolyte have.

1 shows XRD patterns of the solid electrolytes according to Production Examples 1 and 2 of the present invention.
2 shows Raman spectra of the solid electrolytes according to Production Examples 1 and 2 of the present invention.
Fig. 3 shows the results of TGA (thermogravimetric analysis) of the respective solid electrolytes according to Production Examples 1 and 2 of the present invention.
4 shows ion conductivity of each solid electrolyte according to Production Example 1 of the present invention.
5 shows the ion conductivity of each solid electrolyte according to Production Example 2 of the present invention.
Fig. 6 schematically shows the structure of each pre-solid battery according to Example 1 and Comparative Example 1 of the present invention.
7 shows the electrochemical characteristics of each of the all-solid-state cells according to Example 1 and Comparative Example 1 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Electrode Active Material - Solid Electrolyte Complex

In one embodiment of the present invention, electrode active material particles; And a solid electrolyte coating layer positioned on the surface of the electrode active material particle.

10^-4 S/cm 이상인 황화물계 화합물을 고체 전해질로 포함하는 것이다.Herein, the solid electrolyte coating layer is represented by the following general formula (1) or (2) and has an ionic conductivity of 1.0

And a sulfide-based compound of 10 &lt; ^-4 &gt; S / cm or more as a solid electrolyte.

Na _a M _b S _c X ¹ _d

Li _a M _b S _c X ¹ _d

In the above chemical formulas 1 and 2, M is at least one element selected from the group consisting of Sb, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Bi, Ti, , Co, Ni, Cu, Y , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, and Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, Or 0, 0 <a? 6, 0 <b? 6, 0 <c? 6, 0? D?

As mentioned above, in order to manifest the performance of the entire solid-state battery, it is required that the solid electrolyte and the electrode active material particles in the electrode layer are excellent in contact property so as to fully express the theoretical capacity of the active material on which the solid electrolyte is based.

However, in the case of an electrode layer of a generally known all-solid-state cell, since the electrode active material particles and the solid electrolyte are simply contained in the form of a mixture, there is a limit to the contact characteristics thereof and it is difficult to fully express the capacity of the electrode active material particles .

On the other hand, when the electrode active material-solid electrolyte composite is mixed with another solid electrolyte, the solid electrolyte coating layer and the other solid electrolyte are excellent .

Particularly, 1) the solid electrolyte included in one embodiment of the present invention is basically a sulfide-based solid electrolyte, so that it is superior in safety to the organic liquid electrolyte.

2) Furthermore, the solid electrolyte exhibits a function as an ion conductor superior in lithium or sodium ion conductivity than any generally known solid electrolyte. In this connection, when the compound represented by Formula 1 is included, it functions as a sodium ion conductor, and when the compound represented by Formula 2 is included, it can function as a lithium ion conductor.

10^-4 S/cm 이상의 이온 전도도를 발현할 수 있다. 이는 일반적으로 알려진 나트륨 이온 전도체에 비해 높은 이온 전도도의 범위이다. Particularly, in the case of a sodium ion conductor,

Ion conductivity of 10 ^-4 S / cm or more can be expressed. This is a range of ionic conductivities generally higher than known sodium ion conductors.

10^-3 S/cm )가 발현될 수 있으며, 이에 대해서는 후술하기로 한다.In addition, even in the range of the ionic conductivity, by appropriately controlling the production process thereof, a higher ionic conductivity (≥1.0

10 ^-3 S / cm) can be expressed, which will be described later.

3) At the same time, the solid electrolyte can be stably dissolved in a solvent, so that it is formed into the composite and is suitable for application as an electrode in a pre-solid battery.

In general, the solid electrolyte exhibits superior safety than the liquid electrolyte, and has superior ionic conductivity and solubility to the solvent than other known solid electrolytes.

In addition, the characteristics of the solid electrolyte may be synthesized by the solid phase method or may be caused by wet post-treatment of the material synthesized by the solid phase method, but the present invention is not limited thereto.

Hereinafter, each component of the electrode active material-solid electrolyte composite will be described in detail.

Sulfide compound

First, the sulfide-based compound contained in the solid electrolyte will be described.

Specifically, in the formula (1) or (2) representing the sulfide compound, M is Sb, 0 < a? 3.5, 0? B? 1, and 0? C?

More specifically, the sulfide compound may be represented by the following formula (3).

???????? Na _{3 + x} SbS _{4 + y} ?????

(In the formula 3, -0.5 < x < 0.5 and -0.5 < y < 0.5)

10^-3 S/cm 이상일 수 있다. The sodium ion conductivity of the sulfide compound represented by Formula 3 is preferably 1.0

10 ^-3 S / cm or more.

The sulfide compound represented by Formula 3 may be amorphous, crystalline, or a mixture thereof, and is not limited to the crystal structure thereof.

When the sulfide compound represented by the above-mentioned formula (3) is crystalline, it is preferable to use a Cu Kα X-ray (X-ra) in the range of 2θ in the range of 16 to 18 °, in the range of 29 to 32 °, A split peak of the XRD peak may appear.

Specifically, peaks that are divided into two in each of the above ranges may appear, which may mean a tetragonal crystal structure. This is because the generally known crystalline compounds are distinguished from those having a cubic crystal structure.

However, with respect to the production method described later, when synthesized by the solid phase method, it is possible to clearly identify two split peaks, but when the material synthesized by the solid phase method is wet post-treated, two split peaks are observed unclearly .

That is, even when the sulfide compound represented by Formula 3 is crystalline, the split peak of the XRD peak due to the Cu K? X-ray (X-r?) Ranges from 29 to 32 And a range of 34 to 36 DEG, and may appear indefinitely in the remaining range.

In this regard, the sulfide-based compound used in the examples described below is Na ₃ SnS ₄ .

Electrode active material particle

The weight ratio of the solid electrolyte coating layer to the electrode active material particles may be 0.1: 99.9 to 50:50 (coating layer: electrode active material particles). The thickness of the solid electrolyte coating layer may be 0.05 to 0.5 탆 on the surface of the electrode active material particle having a diameter of 5 to 30 탆 when the weight ratio is satisfied, and the solid electrolyte coating layer may be formed by ion- Path can be provided.

As the electrode active material particles, a compound capable of reversible intercalation and deintercalation of sodium or lithium (a lithiated intercalation compound) can be used.

Specifically, the electrode active material particle may include one or more of a metal of cobalt, manganese, nickel, or a combination thereof, and a composite of sodium and lithium, a carbonaceous material, or a combination thereof.

Examples of the composite electrode active material particles include NaCrO ₂ , Na _x M _y X _{z, and} Li _x M _y X _z (where M = Ti, V, Cr, Mn, Fe, X is O, S is O, S is F, Cl, PO ₄ , P ₂ O ₇ , SO ₄ or SO ₄ F, 0 <x <4, 0 <y < ), Carbon-based materials, and the like, but are not limited thereto.

Method for producing electrode active material-solid electrolyte complex

In another embodiment of the present invention, there is provided a process for producing a solid electrolyte, comprising the steps of: heat treating a mixture of a lithium or sodium raw material, a heterogeneous raw material, and a sulfur raw material to obtain a sulfide compound represented by the following formula 1 or 2 as a solid electrolyte; And coating the surface of the electrode active material particles with the solid electrolyte to obtain an electrode active material-solid electrolyte complex. The present invention also provides a method for producing an electrode active material-solid electrolyte complex.

Na _a M _b S _c X ¹ _d

Li _a M _b S _c X ¹ _d

In the above chemical formulas 1 and 2, M is at least one element selected from the group consisting of Sb, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Bi, Ti, , Co, Ni, Cu, Y , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, and Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, Or 0, 0 <a? 6, 0 <b? 6, 0 <c? 6, 0? D?

In other words, the method for producing the electrode active material-solid electrolyte composite may be such that the sulfide compound represented by Formula 1 or 2 is obtained as a solid electrolyte and then coated on the surface of the electrode active material particles to form an electrode active material- &Lt; / RTI &gt;

At this time, the electrode active material-solid electrolyte composite has a composite structure in which a solid electrolyte coating layer is formed on the surface of the electrode active material particle, and may be the same as the material described in the embodiment of the present invention.

On the other hand, although the sulfide compound produced by the heat treatment as described above can be used as the solid electrolyte (solid phase method), the material obtained by subjecting the material prepared by the solid phase method to a wet post- It may also be used as a solid electrolyte.

The material obtained by the wet post-treatment may further include the sulfide-based compound represented by the above formula (1) or (2), as will be described later in detail.

In addition, when the synthesis conditions by the solid phase method are controlled and the wet post-treatment is carried out, a solid electrolyte having excellent lithium or sodium ion conductivity as compared with a generally known solid electrolyte can be produced by appropriately controlling the conditions.

Hereinafter, each step of the production method will be described in detail.

Process for the production of solid electrolyte by the solid phase method

The step of heat treating the mixture to obtain the sulfide compound represented by Formula 1 or 2 as a solid electrolyte will now be described.

The heat treatment may be performed in a temperature range of more than 350 DEG C to 800 DEG C or less.

When the synthesis conditions by the solid phase method are below 350 ° C, the synthesized material has a low ionic conductivity and is therefore unsuitable as a solid electrolyte. Alternatively, when the synthesis conditions according to the solid phase method are controlled to a temperature higher than 350 ° C and lower than 800 ° C, a material exhibiting an appropriate ion conductivity can be synthesized.

Specifically, when the temperature is higher than 350 ° C and less than 750 ° C, a general solid phase reaction is performed. When the temperature is controlled to be not lower than 750 ° C and not higher than 800 ° C, the raw material mixture is solidified after being melted as a liquid. have. Therefore, as the heat treatment is carried out at a temperature as high as possible close to the upper limit within the temperature range of above 350 ° C to 800 ° C, there is an advantage in terms of ion conductivity.

However, from the viewpoint of solubility in solvents, there is no large difference within the temperature range of 350 ° C to 800 ° C.

Therefore, the synthesis conditions according to the solid phase method can be controlled by suitably taking into account the ionic conductivity of the synthesized material, ease of process control, easiness to the solvent, and the like.

Meanwhile, among the raw materials used in the solid phase method, the heterogeneous element raw material may be an antimony (Sb) raw material. Accordingly, in the above formula (1) or (2), a sulfide compound in which M is Sb can be obtained.

More specifically, the mixture of the lithium or sodium raw material, the heterogeneous element raw material and the sulfur raw material is selected from the group consisting of Na, Na ₂ S, Na _x Sn (0 <x <4), Sb, Sb ₂ S ₃ , Sb ₂ S ₅ , and S may be mixed in the stoichiometric molar ratio of the above formula (1), but the present invention is not limited thereto.

According to the solid phase method, a sulfide compound represented by the following general formula (3) can be obtained. The sodium ion conductivity at 30 ° C is 1.0 × 0 ^-4 S / cm or more, specifically 1.0 × 10 ^-3 S / cm or more .

???????? Na _{3 + x} SbS _{4 + y} ?????

(In the formula 3, -0.5 < x < 0.5 and -0.5 < y < 0.5)

At this time, the sulfide-based compound may be amorphous, crystalline, or a mixture thereof, and is not limited to the crystal structure thereof. However, when the sulfide compound is crystalline, it may have a tetragonal crystal structure.

Wet post-treatment process of solid electrolyte

When the material synthesized by the solid phase method (that is, the sulfide-based compound represented by the above formula (1), (2) or (3)) is subjected to wet post-treatment, the conditions are as follows.

The wet post-treatment step is a step of mixing the material synthesized by the solid-phase method with the first solvent, vaporizing the solvent to obtain a dried material, and then heat-treating the material.

The type and amount of the first solvent used in the wet post-treatment process and the solvent treatment time are not particularly limited as long as they can sufficiently dissolve the material synthesized by the solid phase method.

For example, the first solvent may be water (H ₂ O), alcohol (C _n H _{2n + 1} OH, _{1? N?} 20), formic acid, and acetic acid, tetrahydrofuran tetrahydrofuran, dimethylformamide, acetonitrile, dimethyl sulfoxide, acetone, ethyl acetate, dimethoxy ethane, 1,3- But are not limited to, 1,3-dioxolane, N-methylpyrrolidinone, N-methylformamide, diethyl carbonate, ethylmethyl carbonate, And dimethyl carbonate, or a mixture of two or more thereof.

However, depending on the type of the first solvent, the wet post-treatment temperature can be appropriately controlled. For example, when methanol is used, wet treatment can be performed at a lower temperature than when water is used.

Meanwhile, the step of vaporizing the first solvent in the mixture containing the sulfide compound and the first solvent to obtain a dried material may be carried out by a vacuum drying method or a thermal drying method.

For example, the vacuum drying method may be performed by applying a pressure of 0 torr to 1 torr in a temperature range of 20 to 40 ° C. The heat drying method may be a heat treatment at a temperature of 40 ° C or higher and a boiling point or lower of the mixture at normal pressure.

Finally, heat treating the dried material may be performed at a temperature ranging from 100 to 750 ° C.

However, when the dried material is heat-treated at a temperature of less than 100 ° C, the drying is not completed. When the material is heat-treated at a temperature exceeding 750 ° C, the solid electrolyte is melted to lower the processability.

Process of coating solid electrolyte on the surface of electrode active material particles

Coating the solid electrolyte on the surface of the electrode active material particles to obtain an electrode active material-solid electrolyte complex, comprising the steps of: preparing a coating agent comprising the solid electrolyte and a second solvent; Preparing a mixture of the coating agent and the electrode active material particles; Forming a solid electrolyte coating layer on the surface of the electrode active material particles by vaporizing a second solvent in the mixture of the coating agent and the electrode active material particles; And heat treating the electrode active material particle having the solid electrolyte coating layer formed thereon.

That is, when the electrode active material is dissolved in a mixture containing the sulfide compound and the first solvent and the first solvent is vaporized, a dried powder is obtained in which a coating layer is formed on the surface of the electrode active material particles, The above-described electrode active material-solid electrolyte complex can be obtained by a series of steps of heat-treating the dried powder.

The second solvent is not particularly limited to a protic solvent or an aprotic solvent. Specific examples of the protic solvent include water (H ₂ O), alcohols having 1 to 20 carbon atoms (C _n H _{2n + 1} OH, _{1? N?} 20), formic acid, acetic acid acetic acid and the like.

Specific examples of the aprotic solvent include tetrahydrofuran, dimethylformamide, acetonitrile, dimethyl sulfoxide, acetone, ethyl acetate, and the like. ethyl acetate, dimethoxy ethane, 1,3-dioxolane, N-methylpyrrolidinone, N-methylformamide, Diethyl carbonate, ethylmethyl carbonate, dimethyl carbonate, and the like.

Specifically, methanol, ethanol (ehanol), or water (H ₂ O), which is low in toxicity and low in protic solvent, can be selected as the second solvent. This can be a process advantage, as compared to using a toxic solvent such as NMF or THF in a generally known wet process.

Wherein the solid electrolyte and the second solvent are contained in an amount of 0.1 to 50 wt% based on 100 wt% of the total amount of the coating agent, , But is not limited thereto.

The step of heat-treating the electrode active material particles having the solid electrolyte coating layer may be performed at a temperature ranging from 100 to 450 ° C.

In this temperature range, the solid electrolyte in the coating layer can be crystalline.

Electrodes and all solid-state cells

In another embodiment of the present invention, there is provided an electrode for a pre-solid battery comprising the above-described electrode active material-solid electrolyte complex.

In another embodiment of the present invention, cathode; And a solid electrolyte which is the same as or different from the solid electrolyte in the electrode active material-solid electrolyte composite, wherein the electrode active material-solid electrolyte complex is contained in any one of the positive electrode and the negative electrode .

By including the electrode active material-solid electrolyte composite having the above excellent characteristics in the electrode layer, the performance of the entire solid battery can be improved without including a separate solid electrolyte unlike a general pre-solid battery, and the improved performance can be stably Can be maintained.

As mentioned above, the solid electrolyte in the battery can be selected from commonly used solid electrolytes. For example, _x Li ₂ S- _(100-x) P ₂ S ₅ (50 <x <90), LiGe ₂ P ₅ S ₁₂ , Li ₆ PS ₅ X (X = Cl, Br, Or I), Li ₄ SnS ₄ and _x LiI- _(1-x) Li ₄ SnS ₄ (0 <x <0.5).

Other components may be used, which are generally known in the art.

Hereinafter, preferred embodiments of the present invention, comparative examples thereof, and evaluation examples thereof will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

I. Solid electrolyte (Production example)

Prior to the presentation of the preferred embodiments of the present invention, the solid electrolytes used in the examples and the comparative solid electrolytes used in the comparative examples were prepared, and their properties were compared and evaluated .

Production Example 1: Solid phase method

Na ₂ S, Sb ₂ S ₃ , and S were uniformly mixed so as to satisfy the stoichiometric molar ratio of Na ₃ SbS ₄ , and then heat-treated in a vacuum state for 24 hours to obtain a solid electrolyte of Production Example 1. At this time, the heat treatment temperature was 550 캜 or 750 캜.

Production Example 2: Wet post-treatment of a substance synthesized by solid phase method

 The solid electrolyte obtained in Production Example 1 was subjected to wet post-treatment to obtain the solid electrolyte of Production Example 2.

Specifically, the product obtained by heat-treating at 550 ° C in Production Example 1 was used and dissolved in a solvent to prepare a mixture. The solvent used here was water or methanol, and the weight ratio of the solute to the solvent was 50:50, and the mixture was maintained for 4 hours.

The mixture was subjected to a vacuum condition at a pressure of 1 torr or less at room temperature around 25 캜 for about 10 hours to vaporize the solvent in the mixture to obtain a dried material.

The dried material was heat treated for 6 hours to finally obtain a solid electrolyte. At this time, the heat treatment temperature of the dried material was set to 200 ° C or 300 ° C.

Manufacturing Comparative Example 1:

A solid electrolyte of Production Comparative Example 1 was obtained by using the solid phase method of Production Example 1, and the heat treatment temperature was 350 占 폚.

Manufacturing Evaluation Example 1: XRD

XRD analysis was performed on each of the solid electrolytes of Preparation Examples 1 and 2 and Comparative Preparation Example 1, and the results are shown in Fig.

In FIG. 1, the solid electrolytes of Production Example 1, NAS MeOH 200 ° C and water 200 ° C synthesized at the temperatures indicated at 550 ° C and 750 ° C are shown in Table 1, respectively. Electrolyte, and NAS 350 [deg.] C is Comparative Production Example 1.

Ref. Shows calculated values of XRD appearing in Na ₃ SbS ₄ of a cubic structure, and it is possible to grasp respective crystal structures by comparing XRD of each solid electrolyte of Production Examples 1 and 2.

Ref., Production Example 1 and each of the solid electrolyte 2 is, 2θ is shown that each peak (peak) in the 16 to 18 ° in the range, 29 to 32 ° in the range, 34 to 36 ° range, the same composition (Na ₃ SbS ₄ ). However, peaks were not separated in Ref., But peaks of each solid electrolyte in Production Examples 1 and 2 were observed.

Specifically, in Production Examples 1 and 2, two peaks were observed at the same positions as in Ref., And it can be seen that the crystals have different crystal structures, specifically tetragonal structures, from Ref.

However, in the case of the synthesis by the solid phase method (Production Example 1), clearly two peaks were confirmed, but when the material synthesized by the solid phase method was subjected to wet post-treatment (Production Example 2), the two divided peaks were indefinite .

From this, it can be seen that, although the solid electrolyte of Production Example 2 was subjected to a process of dissolving the solid electrolyte of Production Example 1 in a solvent, after the heat treatment after drying, the original crystal structure was almost recovered without impurities. This is an advantage in the solid electrolyte production process.

Manufacturing Evaluation Example 2: Raman spectroscopic analysis

Raman spectroscopy was performed on each of the solid electrolytes of Preparation Examples 1 and 2 and Comparative Preparation Example 1, and the results are shown in Fig.

In Fig. 2, c-NAS is the solid electrolyte of Production Example 1 synthesized at 550 캜, and NAS MeOH 200 캜 and water 200 캜 are the solid electrolytes of Production Example 2 after wet treatment after the respective solvents and heat treatment conditions.

Particularly, although the solid electrolyte of Production Example 2 has undergone the process of dissolving the solid electrolyte of Production Example 1 in a solvent, the local structure of the solid electrolyte is maintained even after heat treatment after drying.

Manufacturing Evaluation Example 3: Thermogravimetric analysis (TGA)

For each of the solid electrolytes of Production Examples 1 and 2 and Manufacturing Comparative Example 1, Thermogravimetric analysis (TGA) was performed, and the results are shown in FIG.

In Fig. 3, NAS-750 占 폚 is the solid electrolyte of Production Example 1 synthesized at 750 占 폚, and NAS MeOH-200 占 폚 is the solid electrolyte of Production Example 2 after wet treatment with the indicated solvent and heat treatment conditions.

Particularly, the solid electrolyte of Production Example 2 has a mass change rate of less than 2% from 50 占 폚 to 400 占 폚 and has a comparatively small variation range.

Generally, in the TGA results, the lower the mass change width according to the temperature change, the smaller the residual solvent. The solid electrolyte of Production Example 2 of Production Example 2, although having undergone the process of dissolving the solid electrolyte of Production Example 1 in a solvent After drying and heat treatment, the remaining solvent is removed.

Manufacturing Evaluation Example 4: Evaluation of ionic conductivity and activation energy

(1) Production Example 1

For each of the solid electrolytes of Production Example 1 and Comparative Example 1, The ion conductivity and the activation energy were analyzed, and the results are shown in FIG. 4 and Table 1.

10^-3S/cm 미만인 반면, 550 ℃에서 합성된 제조예 1은 1.3x10^-3 S/cm, 750 ℃에서 합성된 1.9x10-3 S/cm의 이온 전도도를 각각 가지는 것이다.4, it can be confirmed that the solid electrolytes of Production Example 1 synthesized at 550 ° C and 750 ° C, respectively, are higher than those of Comparative Comparative Example 1 synthesized at 350 ° C. Specifically, at 30 占 폚, the ionic conductivity of Comparative Preparation Example 1 was 1.0

10 ^-3 S / cm, while Production Example 1 synthesized at 550 ° C has 1.3 × 10 ^-3 S / cm and ion conductivity of 1.9 × 10 ^-3 S / cm synthesized at 750 ° C.

It is also seen that, in Production Example 1, when the synthesis temperature is high, it is advantageous in terms of ion conductivity.

(2) Production example 2

For each solid electrolyte of Production Example 2, The ion conductivity and the activation energy were analyzed, and the results are shown in FIG. 5 and Table 1.

10^-4S/cm 이상의 이온 전도도를 나타냄을 알 수 있다.In FIG. 5, MeOH 200 ° C, H ₂ O 200 ° C and 300 ° C were wet post-treated with the respective solvents and heat treatment conditions, and the ionic conductivity was slightly lowered by wet post-treatment. Nonetheless, it is believed that 1.0, which is higher than the sodium solid ion conductor known so far

^10-4 we can be seen to represent the more S / cm ion conductivity.

In Table 1, the activation energy of Preparation Example 1 is lower than that of Preparation Comparative Example 1, and it seems that it slightly increased in Preparation Example 2.

Generally, as the temperature rises, the ion conductivity of the solid electrolyte rises exponentially, and the slope of the log plot corresponds to the activation energy, so that the lower the activation energy is, Ion diffusion is easy.

In this connection, it can be seen that the activation energy of Preparation Example 1 is lower than that of Comparative Production Example 1, and ion diffusion in the solid electrolyte is relatively easy. On the other hand, although the activation energy of Production Example 2 was low and the degree of ion diffusion was slightly lowered, there was a process advantage that can be taken according to the wet post-treatment as described above.

menstruum Final heat treatment temperature ( ^o C) Conductivity at 30 ° C (S / cm) Activation energy (kJ / mol) Manufacturing Comparative Example 1 350 3.1x10 ^-4 18.6 Production Example 1 550 1.3 x 10 ^-3 17.2 Production Example 1 750 1.9x10 ^-3 17.6 Production Example 2
(Solvent: water) 200 1.8 x 10 ^-4 27.2 Production Example 2
(Solvent: water) 300 2.3x10-4 27.2 Production Example 2
(Solvent: methanol) 200 1.4x10-4 35.8

Note) The final heat treatment temperatures in Comparative Manufacturing Example 1 and Manufacturing Example 1 refer to the synthesis temperature by the solid phase method, respectively, and the final heat treatment temperature in Production Example 2 means the wet post treatment temperature

II. Electrode Active Material-Solid Electrolyte Complex (Example)

Using the solid electrolytes of the preparation examples and comparative production examples described above, a composite of each electrode active material-solid electrolyte was prepared and applied to the electrodes to prepare all solid batteries.

Example 1

(1) Preparation of complex (electrode active material - solid electrolyte complex)

After the Preparation Example 1, the Na ₃ SbS made of a high commercial law of ₄ (heat treatment temperature is represented by 550 ℃, below NAS-550, 20 mg), and a positive electrode active material of NaCrO ₂ (80 mg) was mixed with 1 mL methanol, The methanol solvent was removed under a vacuum condition at room temperature for 10 hours (wet post-treatment) and then heat-treated at 200 ° C for 6 hours to obtain a cathode active material-solid electrolyte complex.

The composite may comprise: The solid electrolyte of Production Example 2 is coated with NaCrO ₂ .

(2) Preparation of all solid-state batteries

A total solid battery having the structure shown in Fig. 6 was fabricated.

Specifically, the pre-solid battery shown in Fig. 6 has a structure in which an electrode layer, a solid electrolyte layer, and a Na-Sn based alloy layer are sequentially stacked. Here, the solid electrolyte of Production Example 1 synthesized at 550 캜 was applied to a solid electrolyte layer, and the composite was applied to an electrode layer.

More specifically, 50 mg of a Na ₃ Sn alloy, 150 mg of the solid electrolyte of Production Example 1, and 10 mg of the complex were laminated in this order on a cylindrical frame of f 13 mm in this order, and then a pressure of 370 MPa was applied to the pellet, .

Comparative Example 1 (mixture)

Unlike Example 1, Na ₃ SbS ₄ (NAS-550) and NaCrO ₂ were dry-mixed at a weight ratio of 20:80 (NAS-550: NaCrO ₂ ) using a mortar and a pestle This mixture was then applied to the electrode layer. The manufacturing method (lamination) of this external solid-state cell was the same as that of Example 1.

Evaluation Example 1: Performance evaluation of all solid batteries

Charge and discharge were carried out for each cell of Example 1 and Comparative Example 1 by applying a constant current of 50 μA / cm ² at a drive voltage of 1.2 to 4.0 V (vs. Na / Na ⁺ ), 7. In both cases, it was confirmed that all the solid batteries to which the sodium ion conductor was applied exhibited considerable performance.

However, when the mixture is applied to the electrode layer, it exhibits a discharge capacity of 5 mAh / g. However, when the composite is applied, it exhibits a discharge capacity of 110 mAh / g which is close to the theoretical capacity.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (13)

Electrode active material particles; And
And a solid electrolyte coating layer disposed on a surface of the electrode active material particle,
Wherein the solid electrolyte coating layer comprises a solid electrolyte,
The solid electrolyte is represented by the following formula 1 or 2, and has an ionic conductivity of 1.0

10 ^-4 S / cm or higher,
Wherein the electrode active material particles
_{NaCrO 2, Na x M y X} z, ( where, M = Ti, V, Cr , and Mn, Fe, Co, Ni, or Al, X = O, S, F, Cl, PO 4, P 2 O 7 , SO ₄ , or SO ₄ F, where 0 <x <4, 0 <y <4, 0 <z <12,
Electrode Active Material - Solid Electrolyte Complex.
[Chemical Formula 1]
Na _a M _b S _c X ¹ _d
(2)
Li _a M _b S _c X ¹ _d
In the above chemical formulas 1 and 2, M is at least one element selected from the group consisting of Sb, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Bi, Ti, , Co, Ni, Cu, Y , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, and Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, Or 0, 0 <a? 6, 0 <b? 6, 0 <c? 6, 0? D?
The method according to claim 1,
In the above formula (1) or (2)
M is Sb.
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
In the above formula (1) or (2)
0 &lt; a < / = 3.5.
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
In the above formula (1) or (2)
0 &lt; b < 1,
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
In the above formula (1) or (2)
0 &lt; c < / = 4.5.
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
The sulfide-
Wherein R < 1 &gt;
Electrode Active Material - Solid Electrolyte Complex.
(3)
Na _{3 + x} SbS _{4 + y}
(In the formula 3, -0.5 < x < 0.5 and -0.5 &lt; y &lt; 0.5)
The method according to claim 6,
The sodium ion conductivity of the sulfide-
1.0 at &lt; RTI ID =

10 &lt; ^-3 &gt; S / cm or more,
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
The sulfide-
Lt; / RTI &gt;
Electrode Active Material - Solid Electrolyte Complex.
9. The method of claim 8,
The sulfide-
The split peak of the XRD peak due to the Cu K? X-ray (X-r?) In the range of 2? In the range of 16 to 18 °, in the range of 29 to 32 °, and in the range of 34 to 36 ° That is,
Electrode Active Material - Solid Electrolyte Complex.
10. The method of claim 9,
The sulfide-
The crystal structure of the sulfide compound is as follows.
Is tetragonal. &Lt; RTI ID = 0.0 &gt;
Electrode Active Material - Solid Electrolyte Complex.
The method according to claim 1,
The weight ratio of the solid electrolyte coating layer to the electrode active material particles,
0.1: 99.9 to 50:50 (coating layer: electrode active material particle),
Electrode Active Material - Solid Electrolyte Complex.
11. An electrode active material-solid electrolyte composite according to any one of claims 1 to 11,
Electrodes for all solid state batteries.
anode;
cathode; And
A solid electrolyte,
Wherein one of the positive electrode and the negative electrode comprises the electrode active material-solid electrolyte complex according to any one of claims 1 to 11,
All solid state batteries.

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