KR20240077784A - Composite solid electrolyte, method for preparing the same and all solid state battery comprisign the same - Google Patents

Abstract

The present invention relates to a composite solid electrolyte, a method of manufacturing the same, and an all-solid-state battery containing the same. More specifically, the composite solid electrolyte has improved mechanical properties by reinforcing the sulfide-based solid electrolyte with polyester fiber and is in the form of a thin film. It can be manufactured with an improved ion conductance, which can improve the energy density of an all-solid-state battery.

Description

Composite solid electrolyte, manufacturing method thereof, and all-solid-state battery comprising the same {COMPOSITE SOLID ELECTROLYTE, METHOD FOR PREPARING THE SAME AND ALL SOLID STATE BATTERY COMPRISIGN THE SAME}

The present invention relates to a composite solid electrolyte, a method of manufacturing the same, and an all-solid-state battery containing the same.

Various batteries that can overcome the limitations of current lithium secondary batteries are being researched in terms of battery capacity, safety, output, large size, and ultra-miniaturization.

Representative examples include a metal-air battery with a very large theoretical capacity compared to lithium secondary batteries, an all-solid-state battery with no risk of explosion in terms of safety, and a super capacitor in terms of output. Continuous research is being conducted in academia and industry on supercapacitors, NaS batteries or RFBs (redox flow batteries) in terms of large size, and thin film batteries in terms of miniaturization.

An all-solid-state battery refers to a battery that replaces the liquid electrolyte used in existing lithium batteries with a solid one. It does not use flammable solvents in the battery, so there is no ignition or explosion caused by the decomposition reaction of the conventional electrolyte, so it is safe. It can be greatly improved. In addition, since Li metal or Li alloy can be used as the cathode material, there is an advantage in dramatically improving the energy density relative to the mass and volume of the battery.

The manufacture of an all-solid-state battery involves a dry compression process of preparing a solid electrolyte in powder form and then putting it into a predetermined molding machine and pressing it, or a process of mixing the solid electrolyte with a solvent and a binder to prepare a slurry, coating it, and then drying it. It is manufactured through

In order to secure high energy density in all-solid-state batteries, technology to make the solid electrolyte thin is needed.

However, among solid electrolytes, sulfide-based solid electrolytes are brittle when treated under pressure, making it difficult to manufacture them in thin thickness. Research has been conducted to improve this problem.

Chinese Patent Publication No. 14256499 relates to a method of manufacturing an all-solid-state battery including a sulfide solid electrolyte membrane. The sulfide solid electrolyte membrane is coated with a sulfide electrolyte slurry on the positive electrode by a coating method, and lithium powder is sprinkled on the surface of the sulfide electrolyte. It can be manufactured through a pressurized densification process. However, when a solvent is used when manufacturing the sulfide solid electrolyte membrane, the structure of the sulfide solid electrolyte is destroyed and ionic conductivity is reduced, which ultimately reduces cell performance.

Therefore, in order to secure high energy density of an all-solid-state battery, the sulfide-based solid electrolyte to be applied is manufactured thinly, while preventing the destruction of the structure of the sulfide-based solid electrolyte or a decrease in ionic conductivity. Development is needed.

Chinese Patent Publication No. 14256499

As a result of conducting various studies to solve the above problems, the present inventors confirmed that a thin film composite solid electrolyte can be manufactured without using a solvent by pressing sulfide-based solid electrolyte powder and polyester fiber at high temperature. .

Therefore, the purpose of the present invention is to provide a thin film composite solid electrolyte and a method for manufacturing the same.

Another object of the present invention is to provide an all-solid-state battery including a thin film composite solid electrolyte and a positive electrode integrated with the composite solid electrolyte.

In order to achieve the above object, the present invention provides a composite solid electrolyte including a sulfide-based solid electrolyte and polyester fiber.

The present invention also provides a composite solid electrolyte in which the polyester fiber is dispersed within the sulfide-based solid electrolyte.

The present invention also provides a composite solid electrolyte in which the sulfide-based solid electrolyte and the polyester fiber are bonded to each other.

The present invention also provides a composite solid electrolyte, wherein the composite solid electrolyte has a thickness of 20 ㎛ to 250 ㎛.

The present invention also provides a composite solid electrolyte, wherein the composite solid electrolyte is binder-free.

The present invention also provides that the sulfide-based solid electrolyte is Li ₆ PS ₅ Cl, Li ₁₀ GeP ₂ S ₁₂ , Li ₂ SP ₂ S ₅ , Li ₆ PS ₅ Cl _x Br _1-x (0≤x≤1) and Li It provides a composite solid electrolyte comprising at least one selected from the group consisting of ₃ PS ₄ .

The present invention also provides a composite solid electrolyte, wherein the polyester fiber is an aromatic polyester fiber:

The present invention also provides a composite solid electrolyte, wherein the aromatic polyester fiber is represented by the following formula (1):

<Formula 1>

In Formula 1, X is 0.5 ≤ X ≤ 0.9, and Y is 0.1 ≤ Y ≤ 0.5.

The present invention also provides a composite solid electrolyte, wherein the polyester fiber is contained in an amount of 10% by weight or less based on the total weight of the composite solid electrolyte.

The present invention also provides a composite solid electrolyte in which the hardness of the composite solid electrolyte is 250 MPa or more, and the hardness is measured by a nano indentation test method, and is measured by applying a force of 1 mN to the nano tip. Provides electrolytes.

The present invention also includes the steps of (S1) mixing sulfide-based solid electrolyte powder and polyester fiber; (S2) first pressurizing the mixture obtained in step (S1) at room temperature; and (S3) performing secondary pressurization at a high temperature after the primary pressurization.

The present invention also provides a method for producing a composite solid electrolyte, wherein the first pressurization is performed at a pressure of 200 MPa to 400 MPa.

The present invention also provides a method for producing a composite solid electrolyte, wherein the secondary pressurization is performed at a temperature of 100°C to 300°C and a pressure of 100 MPa to 350 MPa.

The present invention also provides the composite solid electrolyte; An anode formed on one side of the composite solid electrolyte; and a negative electrode formed on the other side of the composite solid electrolyte.

The present invention also provides an all-solid-state battery, wherein the positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

The present invention also provides an all-solid-state battery in which the composite solid electrolyte and the positive electrode are integrated.

The present invention also provides an all-solid-state battery, wherein the negative electrode includes lithium or a lithium alloy.

The composite solid electrolyte according to the present invention is manufactured by mixing polyester fibers with a sulfide-based solid electrolyte and then using a high-temperature pressing process, so that it has the form of a thin film and has the effect of improving mechanical properties.

In addition, the composite solid electrolyte has a thin film form and thus improves ion conductance, so when applied to an all-solid-state battery, energy density can be improved.

Additionally, since the composite solid electrolyte is manufactured through a dry process that does not use a solvent, ionic conductivity can be improved without destroying the internal structure of the electrolyte.

Additionally, since the composite solid electrolyte and the positive electrode are integrated through a high temperature and pressurization process, interfacial stability can be improved.

1 is a schematic diagram of a method for manufacturing a composite solid electrolyte according to an embodiment of the present invention.
Figures 2a and 2b are schematic diagrams showing longitudinal cross-sections of an all-solid-state battery according to an embodiment of the present invention and an all-solid-state battery according to the prior art, respectively.
Figure 3 is a schematic diagram of a method for manufacturing an all-solid-state battery according to an embodiment of the present invention.
Figure 4 is a scanning electron microscope (SEM) photograph of an aromatic polyester fiber represented by Formula 1.
Figure 5 is a graph showing the thickness measurement results of the composite solid electrolyte prepared in Examples 1 to 3 and Comparative Example 1.
Figure 6 is a photograph showing the solid electrolyte prepared in Example 2 and Comparative Example 1 ((a) Comparative Example 1; (b) Example 2; and (c) Example 2 photograph of measuring the thickness of the composite solid electrolyte).
Figures 7a and 7b are graphs comparing ion conductivity and ion conductance when applying an ordinary pressure pressurization process and a high temperature pressurization process for the composite solid electrolytes of Examples 1 to 3 and Comparative Example 1.
Figure 8 is an XRD graph of the composite solid electrolyte prepared in Example 2.
Figure 9 shows a cross-sectional SEM image (a) and EDS mapping images ((b) to (d)) of the composite solid electrolyte prepared in Example 1.
Figures 10a and 10b show the results of measuring mechanical properties of the composite solid electrolytes of Example 2 and Comparative Example 1.
Figures 11a and 11b show voltage curves of a lithium-lithium symmetric cell using the composite solid electrolyte of Example 2 and Comparative Example 1.
Figure 12 is a chemical cycle charge/discharge curve for the all-solid-state battery manufactured in Example 2 and Comparative Example 1 (C rate: 0.05C, room temperature).
Figure 13 is a graph showing the discharge capacity according to cycle for the all-solid-state batteries manufactured in Example 2 and Comparative Example 1 (charge and discharge after two chemical cycles, C rate: 0.2C, room temperature).
Figure 14 is a graph showing the discharge capacity according to the change in current rate for the all-solid-state battery manufactured in Example 2 and Comparative Example 1 (C rate: 0.1C, 0.2C, 0.5C, 1.0C, 2.0C, and 0.1C) change to room temperature).
Figure 15 is a graph showing the discharge capacity according to cycle under a constant current rate for the all-solid-state battery manufactured in Comparative Example 2 (C rate: 0.2C, room temperature).
Figure 16 is a graph showing the electrochemical impedance measurement results of the composite solid electrolyte of Example 2 and Comparative Example 2.
Figures 17a and 17b show the results of measuring mechanical properties of the composite solid electrolytes of Example 2 and Comparative Example 2.
Figure 18 is a photograph showing the composite solid electrolyte containing aliphatic polyester fibers prepared in Example 4.

Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

Terms or words used in this specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

complex solid electrolyte

The present invention relates to composite solid electrolytes.

The composite solid electrolyte according to the present invention includes a sulfide-based solid electrolyte and polyester fiber.

In one embodiment of the present invention, the polyester fiber may be included in a dispersed form in the sulfide-based solid electrolyte.

The sulfide-based solid electrolyte is applied in powder form in the composite solid electrolyte manufacturing process, but in the final manufactured composite solid electrolyte by melting it through a high temperature and pressurization process, it can be formed in the form of a matrix forming the composite solid electrolyte. .

In addition, the polyester fibers can be uniformly dispersed within the matrix made of the sulfide-based solid electrolyte. As the dispersion is more uniform, the mechanical properties of the composite solid electrolyte improve, and at the same time, thinning can be easily achieved.

In one embodiment of the present invention, the interface between the sulfide-based solid electrolyte and the polyester fiber may be in a bonded state.

The polyester fibers are dispersed inside the sulfide-based solid electrolyte, but go through a process of pressurizing them at room temperature or high temperature during the manufacturing process, so their interface is strongly bonded, thereby further improving the mechanical strength of the composite solid electrolyte. It can be done and it can also be advantageous for thinning.

In one embodiment of the present invention, the thickness of the composite solid electrolyte may be 20 ㎛ to 250 ㎛.

Specifically, the thickness of the composite solid electrolyte may be 20 ㎛ or more, 50 ㎛ or more, or 100 ㎛ or more, and may be 230 ㎛ or less, 240 ㎛ or less, or 250 ㎛ or less. If the thickness of the composite solid electrolyte is less than 20 ㎛, durability may be reduced and may be easily damaged, and if it is more than 250 ㎛, the thickness may be so thick that it may act as resistance when applied to a battery.

In one embodiment of the present invention, the composite solid electrolyte may be binder-free.

The composite solid electrolyte uses a sulfide-based solid electrolyte and a polyester fiber as raw materials and undergoes only a primary pressurization process of pressurizing at room temperature and a secondary pressurization process of high-temperature pressurization, in which the polyester fibers are uniformly dispersed in the sulfide-based solid electrolyte. Since they can be manufactured in any form, no separate binder is needed to bind them together.

Therefore, when the composite solid electrolyte is manufactured without a binder, it can be superior in terms of processability compared to when a binder is used.

In one embodiment of the present invention, the sulfide-based solid electrolyte is Li ₆ PS ₅ Cl, Li ₁₀ GeP ₂ S ₁₂ , Li ₂ SP ₂ S ₅ , Li ₆ PS ₅ Cl _x Br _1-x (0≤x≤ 1) and Li ₃ PS ₄ and may include one or more selected from the group consisting of. However, the sulfide-based solid electrolyte is not limited to these, and sulfide-based solid electrolyte having physical properties that enable molding through room temperature and pressure can be widely used.

The sulfide-based solid electrolyte may be included in an amount of 90 to 98% by weight based on the total weight of the composite electrolyte. Specifically, the content of the sulfide-based solid electrolyte may be 90% by weight or more, 92% by weight or more, or 94% by weight or more, and may be 96% by weight or less, 97% by weight or less, or 98% by weight or less. If the content of the sulfide-based solid electrolyte is less than 90% by weight, the ion conductance of the composite solid electrolyte may decrease, and if it is more than 98% by weight, the content of polyester fibers is relatively reduced, making it difficult to manufacture a thin composite solid electrolyte. there is.

In one embodiment of the present invention, the polyester fiber may be an aromatic polyester fiber.

In one embodiment of the present invention, the aromatic polyester fiber may be an aromatic polyester fiber represented by the following formula (1):

<Formula 1>

In Formula 1, X is 0.5 ≤ X ≤ 0.9, and Y is 0.1 ≤ Y ≤ 0.5.

However, the polyester fiber is not limited to the aromatic polyester fiber and aliphatic polyester fiber can also be used. However, aromatic polyester fibers have relatively superior mechanical strength and heat resistance properties compared to aliphatic polyester, so aromatic polyester fibers may be more suitable for high-temperature pressing processes.

Additionally, the polyester fiber may be included in an amount of 10% by weight or less based on the total weight of the composite electrolyte. Specifically, the content of the polyester fiber may be 6% by weight or less, 8% by weight or less, or 10% by weight or less. If the polyester fiber content exceeds 10% by weight, resistance increases, making it difficult to secure appropriate ion conductance. The lower limit of the polyester fiber content range is not particularly limited, but may be more than 0% by weight, more than 1% by weight, or more than 2% by weight.

If the content of the polyester fiber is less than 2% by weight, the effect of improving the mechanical properties of the composite solid electrolyte may be minimal, making it difficult to manufacture a thin composite solid electrolyte. If the content of the polyester fiber is more than 10% by weight, the ion conductance of the composite solid electrolyte may decrease. .

In one embodiment of the present invention, the hardness of the composite solid electrolyte is 250 MPa or more, and the hardness is measured by a nano indentation test method, and a 1 mN force is applied to the nano tip. It may be measured by applying it.

The composite solid electrolyte can be manufactured by a dry process using polyester fibers to enhance hardness.

Since the composite solid electrolyte as described above is manufactured using a sulfide-based solid electrolyte and polyester fiber as raw materials through a dry process without using a solvent, its mechanical properties are enhanced and it can be manufactured as a thin film.

In addition, since the polyester fiber is included in an appropriate amount, the ion conductance of the composite solid electrolyte is improved, making it suitable as a solid electrolyte for an all-solid-state battery.

Method for manufacturing composite solid electrolyte

The present invention also relates to a method for producing a composite solid electrolyte.

1 is a schematic diagram of a method for manufacturing a composite solid electrolyte according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a composite solid electrolyte according to the present invention includes (S1) mixing sulfide-based solid electrolyte powder and polyester fiber; (S2) first pressurizing the mixture obtained in step (S1) at room temperature; and (S3) performing secondary pressurization at a high temperature after the primary pressurization.

Hereinafter, the manufacturing method of the composite solid electrolyte will be described in more detail for each step.

In the present invention, in step (S1), sulfide-based solid electrolyte powder and polyester fiber may be mixed.

The type and weight of the sulfide-based solid electrolyte and polyester fiber are as described above.

However, the sulfide-based solid electrolyte used as a raw material may be in powder form. The particle size of the powder is not particularly limited, but considering the ease of mixing with the polyester fiber and fairness, the particle size (D50) of the powder may be 0.1 to 20 ㎛. If the particle diameter (D50) of the powder is less than 0.1 ㎛, it is difficult to economically manufacture a solid electrolyte and it may be difficult to secure sufficient ionic conductivity, and if it is more than 20 ㎛, it tends to be damaged during the pressurization process. Therefore, considering the aspect of carrying out the actual process, it may be desirable for the particle size of the powder to fall within the above range.

In the present invention, in step (S2), the mixture obtained in step (S1) may be first pressurized at room temperature. The first pressurization may be a room temperature pressurization process to facilitate molding. At this time, room temperature may be 25°C.

In one embodiment of the present invention, the first pressurization may be pressurization at a pressure of 200 MPa to 400 MPa at room temperature. Specifically, the pressure during the first pressurization may be 200 MPa or more, 250 MPa or more, or 280 MPa or more, and may be 320 MPa or less, 350 MPa or less, or 400 MPa or less. If the pressure during the first pressurization is less than 200 MPa, it may not be easy to mold the composite solid electrolyte, and if it is more than 400 MPa, the manufactured molded product may be damaged.

In the present invention, in step (S3), secondary pressurization may be performed at a high temperature after the primary pressurization. The secondary pressurization may be a high-temperature pressurization process to strengthen the bond between the sulfide-based solid electrolyte and the polyester fiber.

In one embodiment of the present invention, the secondary pressurization may be performed at a temperature of 100°C to 300°C and a pressure of 100 MPa to 350 MPa. Specifically, the temperature during the secondary pressurization may be 100°C or higher, 150°C or higher, or 180°C or higher, and may be 220°C or lower, 250°C or lower, or 300°C or lower. Additionally, the pressure during the secondary pressurization may be 100 MPa or more, 150 MPa or more, or 200 MPa or more, and may be 300 MPa or less, 320 MPa or less, or 350 MPa or less. If the temperature and/or pressure during the first pressurization is less than the above range, the bonding strength between the sulfide-based solid electrolyte and the polyester fiber may decrease, and if it exceeds the above range, the composite solid electrolyte may be deformed or damaged.

According to the manufacturing method of the composite solid electrolyte as described above, the composite solid electrolyte can be manufactured by using a sulfide-based solid electrolyte and polyester fiber as raw materials and pressurizing the composite solid electrolyte at high temperature.

Since a separate solvent is not used, it is possible to prevent the solvent from destroying the crystal structure of the sulfide-based solid electrolyte, thereby reducing ionic conductivity.

solid-state battery

The present invention also relates to an all-solid-state battery containing the above composite solid electrolyte.

The all-solid-state battery according to the present invention includes the above composite solid electrolyte; An anode formed on one side of the composite solid electrolyte; and a cathode formed on the other side of the composite solid electrolyte.

At this time, the composite solid electrolyte and the anode formed on one side of the composite solid electrolyte may be integrated. The term “integration” refers to a form in which individual layers are joined to the extent that there is no distinction between layers, unlike a form in which individual layers are simply stacked. In the all-solid-state battery manufacturing process, the composite solid electrolyte and the positive electrode can be bonded with minimized interfacial resistance through a high temperature and pressurization process. Among the manufacturing methods of all-solid-state batteries as described below, the interfacial resistance can be reduced through room temperature pressurization and high temperature pressurization. In particular, compared to the case where polyester fibers are not included, when polyester fibers are used, room temperature pressurization and After high-temperature pressurization, the ion conductance may be more than doubled, and in this case, it can be confirmed that the composite solid electrolyte and the positive electrode are integrated.

Figures 2a and 2b are schematic diagrams showing longitudinal cross-sections of an all-solid-state battery according to an embodiment of the present invention and an all-solid-state battery according to the prior art, respectively.

Referring to FIG. 2A, the all-solid-state battery according to an embodiment of the present invention has a structure in which a cathode 30, a composite solid electrolyte 10, and an anode 20 are sequentially stacked. The negative electrode 30 includes Cu, which is the negative electrode current collector 31, and a Li-In thin film of the negative electrode active material layer 32, and the positive electrode 20 includes Al, which is the positive electrode current collector 21, and the positive electrode active material layer 22. Includes.

The composite solid electrolyte 10 can be manufactured into a thin film by mixing polyester fibers with a sulfide-based solid electrolyte and using a high-temperature pressurizing process, so when applied to an all-solid-state battery, resistance can be reduced and energy density can be improved.

In addition, since the composite solid electrolyte 10 and the positive electrode 20 are bonded and integrated through a high-temperature pressurizing process, the contact property of the interface (I.F.) is improved and stabilization characteristics can be exhibited.

Referring to Figure 2b, the all-solid-state battery according to the prior art has a structure in which a cathode 30, a sulfide-based solid electrolyte 40, and an anode 20 are sequentially stacked. The negative electrode 30 includes Cu as the negative electrode current collector 31 and a Li-In thin film as the negative electrode active material layer 32, and the positive electrode 20 includes Al as the positive electrode current collector 21 and the positive electrode active material layer 22. It includes, and the sulfide-based solid electrolyte 40 may be Li ₆ PS ₅ Cl pellets.

When applying the sulfide-based solid electrolyte 40 to the all-solid-state battery 1, there is a limit to reducing the thickness, so it may be difficult to form it into a thin film.

In addition, the sulfide-based solid electrolyte 40 and the anode 20 included in the all-solid-state battery according to the prior art are bonded by a room temperature pressurization process, and in this case, a void (P) still exists at the interface (I.F.) Contact properties may be poor.

In one embodiment of the present invention, the positive electrode may include a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder. Since the anode contains a sulfide-based solid electrolyte, it may also be referred to as a composite anode.

In the present invention, the positive electrode included in the all-solid-state battery includes a positive electrode active material layer, and the positive active material layer may be formed on one side of the positive electrode current collector.

The positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

The sulfide-based solid electrolyte consists of Li ₆ PS ₅ Cl, Li ₁₀ GeP ₂ S ₁₂ , Li ₂ SP ₂ S ₅ , Li ₆ PS ₅ Cl _x Br _1-x (0≤x≤1) and Li ₃ PS _4. It may include one or more types selected from the group.

Additionally, the sulfide-based solid electrolyte may be included in an amount of 10 to 40% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 10 weight% or more, 15 weight% or more, or 20 weight% or more, and may be 30 weight% or less, 35 weight% or less, or 40 weight% or less. If the content of the sulfide-based solid electrolyte is less than 10% by weight, the ionic conductivity of the positive electrode active material layer may decrease, and if it is more than 40% by weight, the capacity that can be developed per unit mass or weight may decrease, resulting in a decrease in energy density. .

In addition, the positive electrode active material is not particularly limited as long as it is a material that can reversibly occlude and release lithium ions, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), Li[Ni _x Co _y Mn _z M _v ]O ₂ (NCM, in the above formula, M is any one or two or more elements selected from the group consisting of Al, Ga, and In; 0.3≤x<1.0, 0≤y, z≤ 0.5, 0≤v≤0.1, x+y+z+v=1), Li(Li _a M _ba-b' M'_b' )O _2-c A _c (in the above formula, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2; M is one or more selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, and Ti. M' is at least one selected from the group consisting of Al, Mg, and B, and A is at least one selected from the group consisting of P, F, S, and N.) or a layered compound such as 1 or Compounds substituted with more transition metals; Lithium manganese oxide with the formula Li _1+y Mn _2-y O ₄ (where y is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , etc.; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-y MyO ₂ (where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y is 0.01 to 0.3); Chemical formula LiMn _2-y M _y O ₂ (where M is Co, Ni, Fe, Cr, Zn or Ta and y is 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M is Fe, Co, Lithium manganese complex oxide expressed as Ni, Cu or Zn; LiMn ₂ O ₄ in which part of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. may be mentioned, but it is not limited to these alone. _{Preferably ,} the _positive electrode _active material is Li[ _Ni ; 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1).

Additionally, the positive electrode active material may be included in an amount of 60 to 85% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 60% by weight, 65% by weight or more, or 68% by weight or more, and may be 75% by weight or less, 80% by weight or less, or 85% by weight or less. If the content of the positive electrode active material is less than 60% by weight, battery performance may deteriorate, and if the content of the positive electrode active material is more than 85% by weight, mass transfer resistance may increase.

In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery and has excellent electrical conductivity without causing chemical changes in the battery. Representative examples include graphite or conductive carbon. For example, graphite such as natural graphite and artificial graphite; Carbon black, such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and thermal black; Carbon-based materials with a crystal structure of graphene or graphite; Conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; Metal powders such as aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; may be used alone or in a mixture of two or more types, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

The conductive material may typically be included in an amount of 1% to 5% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 1% by weight or more, 1.5% by weight or more, or 2% by weight or more, It may be 4% by weight or less, 4.5% by weight or less, or 5% by weight or less. If the content of the conductive material is too small (less than 1% by weight), it may be difficult to expect an improvement in electrical conductivity or the electrochemical properties of the battery may deteriorate, and if it is too large (more than 5% by weight), the amount of positive electrode active material is relatively small. Capacity and energy density may decrease. The method of including the conductive material in the positive electrode is not greatly limited, and conventional methods known in the art, such as mixing with the positive electrode active material and coating, can be used.

In addition, the binder is a component that assists the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, and includes styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, and nitrile. Butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene. , polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethyl cellulose. , hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, Consisting of polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly(vinylidene fluoride)-hexafluoropropene. It may include one or more types selected from the group. Preferably, the binder may include polytetrafluoroethylene (PTFE).

In addition, the binder may be included in an amount of 0.5% by weight to 4% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 0.5% by weight or more, 1% by weight or more, or 1.5% by weight or more. and may be 3% by weight or less, 3.5% by weight or less, or 4% by weight or less. If the content of the binder is less than 0.5% by weight, the adhesion between the positive electrode active material and the positive electrode current collector may decrease, and if it exceeds 4% by weight, the adhesion is improved, but the content of the positive electrode active material may decrease accordingly, lowering battery capacity.

Additionally, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, the positive electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. You can.

The positive electrode current collector may have a fine uneven structure on the surface of the positive electrode current collector or may adopt a three-dimensional porous structure to strengthen the bonding force with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as film, sheet, foil, mesh, net, porous material, foam, and non-woven fabric.

The above positive electrode can be manufactured according to a conventional method, and specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive active material, a conductive material, and a binder in a solvent is applied and dried on the positive electrode current collector, and optionally To improve electrode density, it can be manufactured by compression molding on a current collector. At this time, it is preferable to use a solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specifically, the solvent may be butyl butyrate, hexyl butyrate, xylene, ethyl acetate, dibromomethane, etc.

In the present invention, the negative electrode included in the all-solid-state battery includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one side of the negative electrode current collector.

The negative electrode active material is a material capable of reversibly intercalating or deintercalating lithium (Li ⁺ ), a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, lithium metal, or a lithium alloy. It can be included.

The material capable of reversibly inserting or de-inserting lithium ions (Li ⁺ ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material that can react with the lithium ion (Li ⁺ ) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy includes, for example, lithium (Li), indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), and magnesium ( It may be an alloy of a metal selected from the group consisting of Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

Preferably, the negative electrode active material may be lithium metal or lithium-indium alloy (Li-In), and specifically, may be in the form of lithium metal or lithium and a thin film or a lithium-indium alloy thin film or powder.

The negative electrode active material may be included in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% by weight or more or 50% by weight or more, and may be 70% by weight or less or 80% by weight or less. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if the content of the negative electrode active material is more than 80% by weight, mass transfer resistance may increase.

Additionally, the binder is the same as described above for the positive electrode active material layer.

Additionally, the conductive material is the same as described above for the positive electrode active material layer.

In addition, the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, the negative electrode current collector may include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and copper. Surface treatment of stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the negative electrode current collector may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics with fine irregularities formed on the surface.

The manufacturing method of the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film forming method commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, the case where a metallic lithium thin film is formed on a metal plate through initial charging after assembling a battery without a lithium thin film on the negative electrode current collector is also included in the negative electrode of the present invention.

Alternatively, the all-solid-state battery may be in an anodeless form.

Manufacturing method of all-solid-state battery

The present invention also relates to a method for manufacturing an all-solid-state battery.

Figure 3 is a schematic diagram of a method for manufacturing a composite solid electrolyte according to an embodiment of the present invention.

Referring to FIG. 3, the method for manufacturing an all-solid-state battery according to the present invention is (P1) placing a mixture for forming a positive electrode active material layer on one side of a composite solid electrolyte and applying high temperature and pressure to form a positive electrode on one side of the composite solid electrolyte. forming step; (P2) and placing a cathode on the other side of the composite solid material and pressing it (not shown).

In step (P1), the mixture for forming a positive electrode active material layer is placed on one side of the composite solid electrolyte and subjected to high temperature and pressure to form a positive electrode on one side of the composite solid electrolyte.

The mixture for forming the positive electrode active material layer may include a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder. Their specific types and weights are as described above. Additionally, after forming the positive electrode active material layer, a positive electrode may be manufactured by attaching a current collector.

In addition, the high-temperature pressurization process is intended to bond the composite solid electrolyte and the positive electrode, thereby reducing the interface resistance and integrating them, and may be performed at 70°C to 200°C and at a pressure of 300 MPa to 500 MPa. Specifically, the temperature of the high temperature pressing process may be 70°C or higher, 80°C or higher, or 90°C or higher, and may be 120°C or lower, 150°C or lower, or 200°C or lower. Additionally, the pressure of the high temperature pressing process may be 300 MPa or more, 350 MPa or more, or 400 MPa or more, and may be 450 MPa or less, 470 MPa or less, or 470 MPa or less. If the temperature and/or pressure of the high-temperature pressurizing process is less than the above range, the composite solid electrolyte and the positive electrode may not be integrated, and if it exceeds the above range, the composite solid electrolyte or the positive electrode may be deformed or damaged.

In step (P2), an all-solid-state battery can be manufactured by placing a negative electrode on the other side of the composite solid electrolyte and pressurizing it. The same as described above in the description of the cathode.

The pressure during pressurization may be 40 MPa to 80 MPa. Specifically, the pressure during pressurization may be 40 MPa or more, 45 MPa or more, or 50 MPa or more, and may be 70 MPa or less, 75 MPa or less, or 80 MPa or less. . If the pressure during pressurization is less than 40 MPa, the negative electrode may be separated from the composite solid electrolyte, and if it is more than 80 MPa, the composite solid electrolyte or the negative electrode may be deformed or damaged.

The all-solid-state battery manufactured in this way includes a thin composite solid electrolyte, so the manufacturing cost can be reduced and ion conductance and energy density can be improved.

Additionally, since the composite solid electrolyte and the positive electrode are integrated through a high temperature and pressurization process, interfacial stability can be improved.

battery module

The present invention also relates to a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

At this time, specific examples of the device include a power tool that is powered by an omni-electric motor and moves; Electric vehicles, including Electric Vehicle (EV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), etc.; Electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf cart; Examples include, but are not limited to, power storage systems. Preferred examples are presented below to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that changes and modifications fall within the scope of the attached patent claims.

Preferred examples are presented below to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that changes and modifications fall within the scope of the attached patent claims.

In the following examples and comparative examples, a composite solid electrolyte, a composite positive electrode, and an all-solid-state battery were manufactured according to the composition and process as shown in Table 1 below.

complex solid electrolyte anode Sulfide-based solid electrolyte polyester fiber Manufacture process Manufacture process structure content
(weight%) Example 1 Li ₆ PS ₅ Cl aromatic Formula 1
(X=0.73, Y=0.27) 2.5 deflation high temperature pressurization Example 2 Li ₆ PS ₅ Cl aromatic Formula 1 (X=0.73, Y=0.27) 5.0 deflation high temperature pressurization Example 3 Li ₆ PS ₅ Cl aromatic Formula 1 (X=0.73, Y=0.27) 7.5 deflation high temperature pressurization Example 4 Li ₆ PS ₅ Cl aliphatic PBA 5.0 deflation high temperature pressurization Comparative Example 1 Li ₆ PS ₅ Cl - - - deflation Pressurized at room temperature Comparative Example 2 Li ₆ PS ₅ Cl Use of binders and solvents for wet processes
-Binder: NBR (5.0% by weight)
-Solvent: Butyl butyrate wet high temperature pressurization

Reference example

In the following examples, aromatic polyester fiber (Vectran, Kuraray) represented by the following formula (1) or poly(butylene adipate) (PBA), an aliphatic polyester fiber, was used as the polyester fiber:

<Formula 1>

In Formula 1, X is 0.73 and Y is 0.27.

Figure 4 is a scanning electron microscope (SEM, Verios, ThermoFisher) photograph of an aromatic polyester fiber represented by Formula 1.

Referring to Figure 4, the structure of the aromatic polyester represented by Chemical Formula 1 can be confirmed, and it can be seen that the fibrous structure can be mixed with the sulfide-based solid electrolyte to complement the mechanical properties.

Example 1

(1) Preparation of composite solid electrolyte

The mixture obtained by mixing the aromatic polyester fiber with Li ₆ PS ₅ Cl powder, a sulfide-based solid electrolyte, was placed in a stainless steel (SUS) mold. The polyester fiber represented by Chemical Formula 1 in the Reference Example was used, and was adjusted to 2.5% by weight of the total weight of the composite solid electrolyte:

The mixture was first pressurized at room temperature and at a pressure of 300 MPa.

Afterwards, secondary pressure was applied at 200°C at a pressure of 240 MPa for 1 hour to prepare a composite solid electrolyte.

(2)Anode manufacturing

The mixture for forming a positive electrode active material layer was added to 11.0 mg/cm2 on the composite solid electrolyte, and then pressurized at 100°C at a pressure of 430 MPa for 30 minutes to form a positive electrode. At this time, the mixture for forming the positive electrode layer includes LiNi _0.7 Co _0.1 Mn _0.2 O ₂ as a positive electrode active material, Li ₆ PS ₅ Cl powder as the sulfide-based solid electrolyte, and vapor-grown carbon fiber (VGCF) as a conductive material. and polytetrafluoroethylene (PTFE), a binder, in a weight ratio of 70:25:3:2.

After pressure treatment, a positive electrode integrated with the composite solid electrolyte was manufactured.

(3) All-solid-state battery manufacturing

An all-solid-state battery was manufactured by placing a Li-In foil as a negative electrode on the surface opposite to the surface where the positive electrode was integrated in the composite solid electrolyte and then applying a pressure of 60 MPa. The Li-In foil contains Li and In at a molar ratio of 0.5:1.

Example 2

The same procedure as Example 1 was carried out, except that the content of the polyester fiber was 5% by weight of the total weight of the composite solid electrolyte.

Example 3

The same procedure as Example 1 was performed, except that the content of the polyester fiber was 7.5% by weight of the total weight of the composite solid electrolyte.

Example 4

The same procedure as Example 2 was carried out, except that the aliphatic polyester fiber (poly(butylene adipate)) of the Reference Example was used instead of the aromatic polyester fiber represented by Formula 1 of the Reference Example.

Comparative Example 1

(1) Preparation of composite solid electrolyte

100 mg of Li ₆ PS ₅ Cl powder was placed in a polyethyleneterephthalate (PET) mold and then pressed at room temperature at a pressure of 300 MPa to obtain Li ₆ PS ₅ Cl pellets.

(2) Manufacturing composite anode

The mixture for forming a composite anode layer was added to the composite solid electrolyte to a concentration of 11.0 mg/cm2, and then pressurized at room temperature at a pressure of 430 MPa for 30 minutes. At this time, the mixture for forming the composite positive electrode layer includes LiNi _0.7 Co _0.1 Mn _0.2 O ₂ as the positive electrode active material, Li ₆ PS ₅ Cl powder as the composite solid electrolyte, and vapor-grown carbon fiber (VGCF) as the conductive material. and polytetrafluoroethylene (PTFE), a binder, in a weight ratio of 70:25:3:2.

(3) All-solid-state battery manufacturing

An all-solid-state battery was manufactured by placing a Li-In foil as a negative electrode on the surface opposite to the surface where the composite anode was integrated in the composite solid electrolyte and then applying a pressure of 60 MPa. The Li-In foil contains Li and In at a molar ratio of 0.5:1.

Comparative Example 2

Unlike Example 2, where the composite solid electrolyte was manufactured through a dry process without using a solvent, the composite solid electrolyte was manufactured through a wet process using a solvent.

For the wet process, nitrile butadiene rubber (NBR) was used as a binder instead of the polyester fiber of Example 2, and the solvent was butyl butyrate, which can minimize structural destruction of the sulfide-based solid electrolyte. A solvent was used.

A solution of NBR (AN (Acrylonitrile) content) polymer dissolved in a butyl butyrate solvent at a concentration of 5% by weight was prepared and mixed with Li ₆ PS ₅ Cl powder, a sulfide-based solid electrolyte, to form a slurry. The same procedure as Example 2 was performed, except that the slurry was cast on a substrate using a doctor blade and then dried to remove the solvent to prepare a composite solid electrolyte.

Experimental Example 1: Measurement of thickness of composite solid electrolyte

In order to confirm the correlation between the polyester fiber content and thinning of the composite solid electrolyte, the thickness of the composite solid electrolyte was measured.

In addition to the polyester fiber content, the thickness measurement object was the solid electrolyte of Examples 1 to 3 and Comparative Example 1 prepared under the same conditions.

The thickness measurement method was to measure the thickness of the composite solid electrolyte in the form of a pellet using a micrometer (547-401, Mitutoyo).

Figure 5 is a graph showing the thickness measurement results of the composite solid electrolyte prepared in Examples 1 to 3 and Comparative Example 1.

Referring to FIG. 5, it was found that the thickness of the composite solid electrolyte of Examples 1 to 3 was thinner than that of the solid electrolyte of Comparative Example 1. From this, it was confirmed that it was possible to thin the composite solid electrolyte reinforced with polyester fibers.

In addition, it was confirmed that when the polyester fiber content was 5% by weight, the thickness of the composite solid electrolyte tended to decrease in inverse proportion to the increase in the content, but when the content was 5% by weight or more, the thickness tended to be maintained.

From this, it can be seen that the appropriate content of polyester fibers that can thin the thickness of the composite solid electrolyte is 5% by weight.

Figure 6 is a photograph showing the solid electrolyte prepared in Example 2 and Comparative Example 1 ((a) Comparative Example 1; (b) Example 2; and (c) Example 2 photograph of measuring the thickness of the composite solid electrolyte).

Referring to FIG. 6, it was confirmed that the solid electrolyte of Comparative Example 1 was broken when pressed to a thickness of 400 ㎛ during the manufacturing process. On the other hand, it was confirmed that the composite solid electrolyte was manufactured without damage even when pressed to a thickness of 98 ㎛ during the manufacturing process of Example 2.

Accordingly, it was found that the composite solid electrolyte of Example 2 had enhanced physical properties as it contained 5% by weight of polyester fiber, and was able to be thinned by withstanding the pressurizing conditions applied to manufacture it in a thin film.

Experimental Example 2: Measurement of ion conduction properties of composite solid electrolyte

In order to confirm the correlation between the polyester fiber content and temperature conditions during pressurization and the ion conduction characteristics of the composite solid electrolyte, the ionic conductivity and ion conductance of the composite solid electrolyte were measured.

In addition to the polyester fiber content, the object of thickness measurement was the composite solid electrolyte of Examples 1 to 3 and Comparative Example 1 prepared under the same conditions.

(1) Ion conductivity measurement

To measure the ionic conductivity of the composite solid electrolyte prepared in Examples and Comparative Examples, the composite solid electrolyte was formed in a pressure cell mold of 0.8167 cm ² in size, and then stainless steel was used as an inert electrode (blocking electrode) to conduct ions. A pressure cell was manufactured for measuring conductivity.

After measuring the resistance using an electrochemical impedance spectrometer (Impedance analyzer, CH Instrument) at 25°C with an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, the ions of the solid electrolyte were calculated using Equation 1 below. Conductivity was calculated.

[Equation 1]

In Equation 1, σi is the ionic conductivity of the solid electrolyte (mS/cm), R is the resistance of the solid electrolyte (Ω) measured with the electrochemical impedance spectrometer, L is the thickness of the solid electrolyte (㎛), and A means the area of the solid electrolyte (cm ² ). For the solid electrolyte sample, L was the thickness measured in FIG. 5 and A = 0.8167cm ² was used.

(2) Ion conductance measurement

The ion conductance of the solid electrolyte was calculated using Equation 2:

<Equation 2>

In Equation 2, IC is the ion conductance (mS) of the solid electrolyte, and R is the resistance (Ω) of the solid electrolyte measured with the electrochemical impedance spectrometer. The σi is the ionic conductivity of the solid electrolyte (mS/cm) calculated by Equation 1 above, L is the thickness of the solid electrolyte (㎛), and A is the area of the solid electrolyte (cm ² ). For the solid electrolyte sample, L was the thickness measured in FIG. 5 and A = 0.8167cm ² was used.

Figures 7a and 7b are graphs comparing ion conductivity and ion conductance when applying an ordinary pressure pressurization process and a high temperature pressurization process for the composite solid electrolytes of Examples 1 to 3 and Comparative Example 1. In Examples 1 to 3, CP-CE is a composite solid electrolyte after primary pressurization, which is a room temperature pressurization process, and HP-CE is a composite solid electrolyte after secondary pressurization, which is a high temperature pressurization process. In addition, in Comparative Example 1, CP-CE is a composite solid electrolyte after the room temperature pressing process described in Comparative Example 1, and HP-CE is a composite solid electrolyte after performing a high temperature pressing process under the secondary pressing conditions of Example 1 after the room temperature pressing process. It is a solid electrolyte.

Referring to Figure 7a, it can be seen that the ionic conductivity of the composite solid electrolyte tends to decrease as the polyester fiber content increases in the room temperature pressing process (CP-CE) and the high temperature pressing process (HP-CE). . These results are due to the fact that polyester fiber, a polymer fiber, acts as an ion resistor.

In addition, it was confirmed that the ionic conductivity was higher when the composite solid electrolyte was manufactured through the high-temperature pressurization process compared to the room temperature pressurization process. This result is due to the fact that when a high temperature pressurization process is performed, the pores in the composite solid electrolyte are reduced due to the application of high temperature, thereby forming an ion conduction path.

Referring to Figure 7b, the ion conductance of the solid electrolyte increases as the polyester fiber content increases up to 5% by weight in the room temperature pressing process (CP-CE) and the high temperature pressing process (HP-CE). First, it can be seen that when the polyester fiber content is 7.5% by weight, the ion conductance of the solid electrolyte decreases.

In an all-solid-state battery, as the ionic conductance of the composite solid electrolyte increases, the resistance of the solid electrolyte decreases, so the ionic conductance is evaluated as a more important factor than the ionic conductance of the composite solid electrolyte.

As the content of polyester fiber increases, the thickness of the composite solid electrolyte decreases (Figure 5) and the ionic conductivity also decreases (Figure 7a), but when the content of polyester fiber is more than 5% by weight, the thickness of the composite solid electrolyte no longer decreases. Since it does not show a tendency (Figure 5), the ion conductance no longer increases but decreases.

From this, it was confirmed that in order to obtain high ionic conductance of the composite solid electrolyte, the high temperature pressing process must be performed with the appropriate content of polyester fibers at 5% by weight.

Experimental Example 3: Evaluation of chemical stability of composite solid electrolyte

An analysis was conducted to evaluate the chemical stability of the composite solid electrolyte.

The subject of chemical stability evaluation was the composite solid electrolyte of Example 2, which showed the highest ion inductance among the examples.

The chemical stability evaluation method was conducted using X-ray diffraction (XRD).

Figure 8 is an XRD graph of the composite solid electrolyte prepared in Example 2.

Referring to FIG. 8, it can be seen that in the composite solid electrolyte (HP-CE) prepared in Example 2, the crystal peaks of Li ₆ PS ₅ Cl and polyester fiber are well maintained in the composite solid electrolyte. You can. CP-CE is a composite solid electrolyte after primary pressurization, which is a room temperature pressurization process, and HP-CE is a composite solid electrolyte after secondary pressurization, which is a high temperature pressurization process.

From this, it was confirmed that Li ₆ PS ₅ Cl and polyester fiber were chemically stable without side reactions in the composite solid electrolyte.

In addition, when manufacturing the composite solid electrolyte, it was confirmed that both the composite solid electrolyte produced by the room temperature pressurization process (CP-CE) and the high temperature pressurization process (HP-CE) were chemically stable.

Experimental Example 4: Morphology analysis of composite solid electrolyte

In order to confirm the dispersibility of polyester fibers within the composite solid electrolyte, the shape of the composite solid electrolyte was analyzed.

The object of morphological analysis was the composite solid electrolyte of Example 2, which showed the highest ion inductance among the examples.

The morphological analysis method was to check the cross section of the composite solid electrolyte using a scanning electron microscope (FE-SEM, Verio, ThermoFisher) and conduct energy dispersive spectrometer (EDS) analysis. .

Figure 9 shows a cross-sectional SEM image (a) and EDS mapping images ((b) to (d)) of the composite solid electrolyte prepared in Example 2.

Referring to FIG. 9, it can be seen from the SEM image (a) that the interfacial contact between Li ₆ PS ₅ Cl and polyester fiber is well established and that it is densely composited without empty spaces or defects. In addition, (b) In the EDS mapping images from (d) to (d), the distribution of the C element of the polyester fiber and the P and Cl elements of Li ₆ PS ₅ Cl can be confirmed ((b) distribution of the C element; (c) distribution of the P element; and (d) Distribution of Cl element).

Experimental Example 5: Evaluation of mechanical properties of composite solid electrolyte

The mechanical properties of the composite solid electrolyte were evaluated.

The subject of mechanical property evaluation was the composite solid electrolyte of Example 2 containing 5% by weight of polyester fiber. In addition, the mechanical properties of Comparative Example 1, which did not contain polyester fibers, were also evaluated and the mechanical properties were compared depending on the presence or absence of polyester fibers.

The method for evaluating mechanical properties was to use nano indentation testing. In the nano-indentation experiment, the depth at which the nano-tip was inserted was measured by applying a force of 1 mN, and it was determined that the smaller the depth at which the nano-tip was inserted, the better the mechanical properties.

Figures 10a and 10b show the results of measuring mechanical properties of the composite solid electrolyte of Example 2 and Comparative Example 1.

Referring to Figure 10a, as a result of the nano-indentation experiment, it can be seen that the depth of the nanotip inserted into the composite solid electrolyte of Example 2 is smaller than that of Comparative Example 1 when a load of up to 1 mN is applied. .

From this, it was confirmed that the composite solid electrolyte of Example 2 containing polyester fibers had enhanced mechanical properties due to the polyester fibers.

Referring to Figure 10b, as a result of hardness measurement, the composite electrolyte of Example 2 was found to be 258.8 MPa, confirming that the actual mechanical properties were strengthened by the polyester fiber.

Experimental Example 6: Lithium-lithium symmetric cell performance evaluation

Cell performance evaluation of a lithium-lithium symmetric cell incorporating a composite solid electrolyte was conducted.

The composite solid electrolyte used to evaluate the performance of the lithium-lithium symmetric cell was the composite solid electrolyte of Example 2 containing 5% by weight of polyester fiber. In addition, cell performance was evaluated in the same manner for Comparative Example 1, which did not contain polyester fibers, to compare cell performance with and without polyester fibers.

The lithium-lithium symmetric cell performance evaluation method is to manufacture a lithium-composite solid electrolyte-lithium symmetric cell, then increase the current density to 0.1, 0.2, and 0.4 mA/cm2 (charge: 0.1, 0.2, and 0.4 mAh/cm2) The purpose was to evaluate charge and discharge characteristics.

Figures 11a and 11b show voltage curves of a lithium-lithium symmetric cell using the composite solid electrolyte of Example 2 and Comparative Example 1.

Referring to FIGS. 11A and 11B, it can be seen that both lithium-lithium symmetric cells using the composite solid electrolyte of Example 2 and Comparative Example 1 showed stable cycle characteristics without short circuit.

This is because the composite solid electrolyte of Example 2 effectively inhibits the growth of lithium dendrites due to its excellent mechanical properties despite its thin thickness.

In particular, the lithium-lithium symmetric cell using the composite solid electrolyte of Example 2 shows a lower overvoltage, and this is because the composite solid electrolyte is thin and has high ion conductance.

Experimental Example 7: Evaluation of cycle characteristics of all-solid-state battery

The cycle characteristics of an all-solid-state battery incorporating a composite solid electrolyte were evaluated.

The all-solid-state battery used to evaluate the cycle characteristics of the all-solid-state battery was the all-solid-state battery manufactured in Example 2, which was an all-solid-state battery containing a composite solid electrolyte containing 5% by weight of polyester fiber. In addition, cycle characteristics were evaluated in the same manner for the all-solid-state battery of Comparative Example 1 that did not contain polyester fibers, and the performance of the battery with and without polyester fibers was compared.

The method for evaluating the cycle characteristics of an all-solid-state battery is to charge and discharge at a constant current rate (C rate) at room temperature, or charge and discharge while changing the current rate at room temperature to evaluate the discharge capacity, capacity retention rate, or cycle characteristics. .

Figure 12 is a chemical cycle charge/discharge curve for the all-solid-state battery manufactured in Example 2 and Comparative Example 1 (C rate: 0.05C, room temperature).

Referring to FIG. 12, the all-solid-state batteries of Example 2 and Comparative Example 1 have discharge capacities of 185.7 mAhg ^-1 and 180.2 mAhg ^-1 , respectively, based on the positive electrode active material, and the discharge of the all-solid-state batteries manufactured in Example 2 It can be seen that the capacity is higher.

Figure 13 is a graph showing the discharge capacity according to cycle for the all-solid-state batteries manufactured in Example 2 and Comparative Example 1 (charge and discharge after two chemical cycles, C rate: 0.2C, room temperature).

Referring to FIG. 13, the all-solid-state batteries of Example 2 and Comparative Example 1 had initial discharge capacities of 161.9 mAhg ^-1 and 155.1 mAhg ^-1 , respectively, and capacity retention rates of 70.8% and 65.0% at 300 cycles, respectively. It can be seen that the all-solid-state battery of Example 2 has better cycle characteristics.

Figure 14 is a graph showing the discharge capacity according to the change in current rate for the all-solid-state battery manufactured in Example 2 and Comparative Example 1 (C rate: 0.1C, 0.2C, 0.5C, 1.0C, 2.0C, and 0.1C) change to room temperature).

Referring to FIG. 14, the discharge capacities of Example 2 and Comparative Example 1 at a current rate of 2.0C are 103.8 mAhg ^-1 and 72.3 mAhg ^-1 , respectively, showing that the all-solid-state battery of Example 2 exhibits better high-rate characteristics. Able to know. This is because the composite solid electrolyte of Example 2 had reduced cell internal resistance due to an increase in ion conductance.

Figure 15 is a graph showing the discharge capacity according to cycle under a constant current rate for the all-solid-state battery manufactured in Comparative Example 2 (C rate: 0.2C, room temperature).

Referring to FIG. 15, it can be seen that the all-solid-state battery of Comparative Example 2 had an initial discharge capacity of 150.5 mAhg ^-1 and a capacity maintenance rate of 22.4% at 100 cycles. This is because the interfacial contact between the composite solid electrolyte and the composite anode decreases when pressurized at room temperature.

Experimental Example 8: Comparison of physical properties of composite solid electrolyte depending on whether solvent was used during production

In order to compare physical properties depending on whether or not a solvent was used when manufacturing a composite solid electrolyte, an experiment was conducted to measure thickness, electrochemical impedance, and mechanical properties.

The test subject was the composite solid electrolyte of Example 2, which did not use a solvent, and Comparative Example 2, which used a solvent.

In terms of the experimental method, the thickness was conducted in the same manner as in Experimental Example 1, and the electrochemical impedance was conducted in the same manner as in Experimental Example 2. In addition, the mechanical properties were tested using a nano-indentation test in the same manner as in Experimental Example 5.

The measurement results of thickness and electrochemical impedance are shown in Table 2 and Figure 16 below.

thickness
(㎛) resistance
(ohms) ionic conductivity
(mS/cm) Example 2 98 4.26 2.9 Comparative Example 2 112 15.3 0.9

As shown in Table 2, it can be seen that the composite solid electrolyte of Comparative Example 2 manufactured by a wet process using a solvent was thicker than the composite solid electrolyte of Example 2 manufactured by a solvent-free dry process.

In addition, the ionic conductivity of the composite solid electrolyte of Comparative Example 2 was lower than that of Example 2, which was due to the structure of the sulfide-based solid electrolyte being destroyed by the solvent. Butyl butyrate solvent was used to minimize structural destruction of the sulfide-based solid electrolyte due to the solvent, but ionic conductivity was lower than that of Example 2, which was a solvent-free dry process.

Figure 16 is a graph showing the electrochemical impedance measurement results of the composite solid electrolyte of Example 2 and Comparative Example 2.

Referring to Figure 16, it can be seen that the resistance of Comparative Example 2 is high.

Figures 17a and 17b show the results of measuring mechanical properties of the composite solid electrolytes of Example 2 and Comparative Example 2.

Referring to Figure 17a, as a result of the nano-indentation experiment, it can be seen that the depth of the nanotip inserted into the composite solid electrolyte of Example 2 is smaller than that of Comparative Example 2 when a load of up to 1 mN is applied. .

From this, it can be seen that when manufacturing a composite solid electrolyte, performing a dry process without using a solvent as in Example 2 is advantageous in strengthening mechanical properties compared to a wet process using a solvent as in Comparative Example 2.

Referring to FIG. 17b, as a result of hardness measurement, the composite solid electrolyte of Example 2 was found to be 258.8 MPa, which is higher than the composite solid electrolyte of Comparative Example 2, which was 247.5 MPa. Therefore, the hardness was measured by the wet process and polyester fiber. It was confirmed that the actual mechanical properties were strengthened.

Experimental Example 9: Comparison of physical properties of composite solid electrolyte according to polyester fiber type

The mechanical properties of the composite solid electrolyte were compared according to the type of polyester fiber used in manufacturing the composite solid electrolyte.

The objects of physical property measurement were the composite solid electrolytes of Examples 2 and 4, each containing equal amounts of aromatic polyester fibers and aliphatic polyester fibers.

As shown in the above experimental examples, the composite solid electrolyte of Example 2 was reinforced with aromatic polyester fibers and was found to have excellent mechanical properties.

Figure 18 is a photograph showing the composite solid electrolyte containing aliphatic polyester fibers prepared in Example 4.

Referring to Figure 18, it can be seen that the composite solid electrolyte of Example 4 was pressed and adhered to the mold after high-temperature pressurization, from which it was confirmed that the mechanical strength was poor. These results are due to the use of aliphatic polyester fibers instead of aromatic polyester fibers.

Although the present invention has been described above with limited examples and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following description will be provided by those skilled in the art in the technical field to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalence of the patent claims.

1: All-solid-state battery
10: Composite solid electrolyte
20: anode
21: negative electrode current collector, 22: positive electrode active material layer
30: cathode
31: negative electrode current collector, 32: negative electrode active material layer
40: Sulfide-based solid electrolyte
IF: interface
P: void

Claims (17)

A composite solid electrolyte comprising a sulfide-based solid electrolyte and polyester fiber. According to paragraph 1,
The polyester fiber is dispersed within the sulfide-based solid electrolyte. According to paragraph 1,
A composite solid electrolyte wherein the sulfide-based solid electrolyte and the polyester fiber are bonded to each other. According to paragraph 1,
The composite solid electrolyte has a thickness of 20 ㎛ to 250 ㎛. According to paragraph 1,
The composite solid electrolyte is binder-free. According to paragraph 1,
The sulfide-based solid electrolyte consists of Li ₆ PS ₅ Cl, Li ₁₀ GeP ₂ S ₁₂ , Li ₂ SP ₂ S ₅ , Li ₆ PS ₅ Cl _x Br _1-x (0≤x≤1) and Li ₃ PS _4. A composite solid electrolyte comprising one or more selected from the group. According to paragraph 1,
A composite solid electrolyte wherein the polyester fiber is an aromatic polyester fiber. According to paragraph 1,
The aromatic polyester fiber is a composite solid electrolyte represented by the following formula (1):
<Formula 1>

In Formula 1, X is 0.5 ≤ X ≤ 0.9, and Y is 0.1 ≤ Y ≤ 0.5. According to paragraph 1,
The polyester fiber is contained in an amount of 10% by weight or less based on the total weight of the composite solid electrolyte. According to paragraph 1,
The hardness of the composite solid electrolyte is 250 MPa or more,
The hardness is measured by a nano indentation test method, and is measured by applying a 1 mN force to the nano tip. (S1) mixing sulfide-based solid electrolyte powder and polyester fiber;
(S2) first pressurizing the mixture obtained in step (S1) at room temperature; and
(S3) After the first pressurization, a second pressurization step is performed at a high temperature;
Method for producing a composite solid electrolyte comprising. According to clause 11,
A method of producing a composite solid electrolyte, wherein the first pressurization is performed at a pressure of 200 MPa to 400 MPa. According to clause 11,
A method of producing a composite solid electrolyte, wherein the secondary pressurization is performed at a temperature of 100°C to 300°C and a pressure of 100 MPa to 350 MPa. The composite solid electrolyte of claim 1;
An anode formed on one side of the composite solid electrolyte; and
An all-solid-state battery comprising a negative electrode formed on the other side of the composite solid electrolyte. According to clause 14,
The positive electrode includes a positive electrode active material layer,
An all-solid-state battery, wherein the positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder. According to clause 14,
An all-solid-state battery, wherein the composite solid electrolyte and the positive electrode are integrated. According to clause 14,
An all-solid-state battery, wherein the negative electrode contains lithium or a lithium alloy.