Composite anode active material layer for all-solid-state battery and manufacturing method thereof

Abstract

The invention relates to a composite anode active material layer for an all-solid-state battery and a manufacturing method thereof. A composite anode active material layer for an all-solid-state battery and a method for manufacturing the same at a temperature of 40 DEG C or less, the Young modulus ratio or the lithium ion conductivity ratio of the solid electrolyte in the anode active material layer to the solid electrolyte contained in the composite anode active material with the core-shell structure can be controlled within a certain range; thus, the occurrence of interface cracks caused by expansion and contraction behaviors of the anode during charging and discharging of the battery can be minimized, and durability and output characteristics of the battery can be improved.

Description

Technical Field

[0001] The invention relates to a composite anode active material layer for an all-solid-state battery and a method for manufacturing the same. Background Art

[0002] Recently, in order to solve the problem of carbon dioxide (CO 2 ) has been avoiding the use of fossil fuels, and therefore, the automobile industry related to transportation has shown great interest in electric vehicles using secondary batteries. Using currently developed lithium-ion batteries, vehicles can travel about 40km on a single charge, but problems such as instability at high temperatures and fire still exist. In order to solve these problems, many companies are competing to develop next-generation secondary batteries.

[0003] Compared with lithium-ion batteries using flammable organic solvents as electrolytes, all-solid-state batteries, which are attracting attention as next-generation secondary batteries, have advantages in lower fire and explosion risks and higher mechanical strength because all components of all-solid-state batteries are formed of solids. All-solid-state batteries generally include a cathode active material layer bonded to a cathode current collector, an anode active material layer bonded to an anode current collector, and a solid electrolyte layer located between the cathode active material layer and the anode active material layer.

[0004] The anode active material layer is generally used in the form of a composite of the anode active material and a solid electrolyte to ensure the lithium ion conductivity of the anode active material layer. The lithium ion conductivity varies depending on the degree and method of combining the anode active material and the solid electrolyte, and leads to differences in the output characteristics and durability characteristics of the battery.

[0005] Compared with lithium-ion batteries, all-solid-state batteries can use a variety of anode active materials, and recently, in order to achieve high energy density, research is being actively conducted on using high energy density materials such as silicon (about 3600 mAh / g) or lithium (about 3860 mAh / g) instead of existing graphite (about 375 mAh / g).

[0006] Among them, silicon has a volume change of nearly 400% during charging and discharging, and as the number of charging and discharging cycles increases, rapid capacity decay occurs due to the loss of contact surface between silicon and the solid electrolyte present in the form of a composite in the anode active material layer. Therefore, it is difficult to use silicon-based active materials alone.

[0007] The above information disclosed in this background technology is only used to deepen the understanding of the background technology of the present invention, and therefore, it may contain information that does not constitute the prior art that is already known, available or in use. Summary of the invention

[0008] The present invention relates to a composite anode active material layer for an all-solid-state battery and a method for manufacturing the same. More specifically, the present invention relates to a composite anode active material layer for an all-solid-state battery and a method for manufacturing the same, wherein the Young's modulus ratio or lithium ion conductivity ratio of a solid electrolyte in the anode active material layer and a solid electrolyte contained in a composite anode active material having a core-shell structure is controlled within a selected range or a predetermined range, so that the occurrence of interface cracks caused by the expansion and contraction behavior of the anode during the charge and discharge of the battery can be minimized, and the durability and output characteristics of the battery can be improved.

[0009] Some embodiments of the present invention may solve the above-mentioned problems and may improve the output and durability of a battery by coating the surface of a silicon-based active material with a solid electrolyte having high lithium ion conductivity.

[0010] Since the volume of the silicon-based active material can vary significantly according to the charge and discharge of the battery, when the charge and discharge of the battery are repeated, cracks or voids are formed at the interface between the solid electrolyte coated on the surface of the silicon-based active material and the solid electrolyte in the anode active material layer, and thus, the interface resistance may increase and the capacity expression rate may decrease. In addition, lithium may be irreversibly precipitated between the voids, and thus, the discharge capacity may decrease.

[0011] Some embodiments of the present invention can mitigate the impact of volume changes occurring during charge and discharge of a battery by controlling the ratio of the Young's modulus of a solid electrolyte included in the anode active material layer to the Young's modulus of a solid electrolyte coated on the surface of the anode active material within a specified range.

[0012] Some embodiments of the present invention can suppress an increase in interface resistance due to a difference in lithium ion conductivity by controlling the ratio of the lithium ion conductivity of a solid electrolyte included in the anode active material layer to the lithium ion conductivity of a solid electrolyte coated on the surface of the anode active material within a specified range.

[0013] The advantages of the present invention are not necessarily limited to the above advantages. Through the following description, the advantages provided by some embodiments of the present invention can become more clear, and they can be achieved according to the claims and their combinations.

[0014] In an embodiment of the present invention, the anode active material layer for an all-solid-state battery may include a composite anode active material having a core-shell structure and a first solid electrolyte, wherein the composite anode active material includes a core and an outer shell, the core includes a silicon-based active material, the outer shell is configured to coat at least a portion of the surface of the silicon-based active material, and includes a second solid electrolyte, wherein the Young's modulus E of the first solid electrolyte is 1and the Young's modulus E of the second solid electrolyte 2 The ratio E 1 / E 2 Satisfy 1.5≤E 1 / E 2 ≤3.0.

[0015] In an embodiment of the present invention, the lithium ion conductivity of the first solid electrolyte is 1 Lithium ion conductivity of the second solid electrolyte I 2 The ratio I 1 / I 2 Can satisfy 0.5≤I 1 / I 2 ≤2.0.

[0016] In an embodiment of the present invention, the first solid electrolyte may include a sulfide-based solid electrolyte. In addition, the second solid electrolyte may include a sulfide-based solid electrolyte.

[0017] In an embodiment of the present invention, the silicon-based active material may include at least one selected from the group consisting of silicon particles, silicon oxides, silicon alloys, and combinations thereof.

[0018] In an embodiment of the present invention, the silicon-based active material may include a carbon-based material.

[0019] In an embodiment of the present invention, a method for manufacturing an anode active material layer for an all-solid-state battery may include: synthesizing a composite anode active material by placing an anode active material and a second solid electrolyte into a mixer and then mixing the anode active material and the second solid electrolyte; preparing an anode active material slurry by mixing the composite anode active material and a first solid electrolyte; and forming an anode active material layer by applying the anode active material slurry to an anode collector and then drying the anode active material slurry.

[0020] In an embodiment of the present invention, the anode active material and the second solid electrolyte may be mixed for 2 minutes to 15 minutes. After mixing the anode active material and the second solid electrolyte, the temperature of the composite anode active material may be 40° C. or less.

[0021] In an embodiment of the present invention, the mixer may include a resonant acoustic mixer (RAM).

[0022] In an embodiment of the present invention, the anode active material and the second solid electrolyte may be put into the mixer in a weight ratio of 10:1 to 7:3. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above-mentioned and other features of the present invention will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are given by way of illustration only and therefore do not necessarily limit the present invention, in which:

[0024] Figure 1 A view schematically showing an anode active material layer according to an embodiment of the present invention;

[0025] Figure 2 A view schematically showing a composite anode active material and a first solid electrolyte surrounding the composite anode active material according to an embodiment of the present invention;

[0026] Figure 3 shows the Young's modulus measurement results of argyrodite-type sulfide-based solid electrolytes having various halogen contents according to an embodiment of the present invention;

[0027] Figure 4 A photograph of the composite anode active material according to Preparation Example 1 taken using a scanning electron microscope (SEM) according to an embodiment of the present invention;

[0028] Figure 5 Energy dispersive spectroscopy (EDS) is used to analyze the Figure 4 Results of analyzing sulfur (S) contained in the composite anode active material;

[0029] Figure 6 Energy dispersive spectroscopy (EDS) is used to analyze the Figure 4 Results of analyzing silicon (Si) contained in the composite anode active material;

[0030] Figure 7 A graph showing the results of durability evaluation conducted by charging and discharging compressed batteries according to Examples and Comparative Examples according to an embodiment of the present invention;

[0031] Figure 8 is a photograph of a cross section of the anode active material layer according to Example 1 taken using a scanning electron microscope (SEM) after durability evaluation according to an embodiment of the present invention;

[0032] Fig. 9 is a photograph of a cross section of the anode active material layer according to Comparative Example 4 taken using a scanning electron microscope (SEM) after durability evaluation according to an embodiment of the present invention; and

[0033] Fig.10A graph showing the results of charge / discharge evaluation of compressed batteries according to Example 1, Comparative Example 5, and Comparative Example 6 according to an embodiment of the present invention.

[0034] It is to be understood that the accompanying drawings are not necessarily drawn to scale, but may be slightly simplified to present various features of some embodiments of the invention. The specific design features of the embodiments of the invention disclosed herein (including, for example, specific dimensions, directions, positions and shapes) may be determined in part by specific intended applications and use environments.

[0035] In the drawings, reference numbers may refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0036] The above advantages and features of the present invention may become apparent through the description of the exemplary embodiments given below with reference to the accompanying drawings. However, the present invention is not necessarily limited to the exemplary embodiments disclosed herein, and may be implemented in various different forms and variations thereof. Exemplary embodiments are provided to make the description of the present invention thorough and to fully convey the scope of the present invention to those skilled in the art.

[0037] In the accompanying drawings, the size of the structure may be magnified compared to the actual size for a clearer description. In the following description, terms such as "first" and "second" may be used to describe the various elements, but these elements are not necessarily limited. Such terms may be used only to distinguish an element from other elements. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope and spirit of the present invention. Unless there is a significantly different contextual meaning, a singular expression may include a plural expression.

[0038] In the following description of the embodiments, terms such as "include", "comprising" and "having" may be interpreted as indicating the presence of features, values, steps, operations, elements or components or combinations thereof described in the specification, and do not exclude the presence of one or more other features, values, steps, operations, elements, components or combinations thereof, or the possibility of adding them. In addition, it is understood that when a part (such as a layer, film, region or plate) is referred to as being "on" another part, the part may be "directly on" the other part, or one or more other parts may be inserted between the two parts. In the same way, it is understood that when a part (such as a layer, film, region or plate) is referred to as being "under" another part, the part may be "directly under" the other part, or one or more other parts may be inserted between the two parts.

[0039] Unless otherwise stated, all numbers, values ​​and / or expressions used in this specification to represent the amount of components, reaction conditions, polymer ingredients and blends are approximate values, which reflect the various measurement uncertainties generated when obtaining these values ​​from essentially different things, so it is understood that it can be modified by the term "about". In addition, it is understood that if a numerical range is disclosed in the specification, unless otherwise stated, the range can include all continuous values ​​from the minimum value to the maximum value of the range. In addition, if the range involves integers, unless otherwise stated, the range can include all integers from the minimum integer to the maximum integer.

[0040] In the following description of exemplary embodiments, it is understood that when describing a variable range, the variable may include all numerical values ​​within the range (including the endpoints of the range). For example, it is understood that the range of "5 to 10" includes not only the values ​​of 5, 6, 7, 8, 9, and 10, but also includes any subrange (e.g., a subrange of 6 to 10, a subrange of 7 to 10, a subrange of 6 to 9, and a subrange of 7 to 9) and any value between integers effective within the range (e.g., 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9). In addition, for example, it is understood that the range of "10% to 30%" includes not only all integers (including values ​​of 10%, 11%, 12%, 13% ... 30%), but also includes any sub-ranges (for example, a sub-range of 10% to 15%, a sub-range of 12% to 18% and a sub-range of 20% to 30%) and any value between valid integers within the range (for example, 10.5%, 15.5% and 25.5%).

[0041] Anode active material layer for all-solid-state batteries

[0042] Figure 1 Schematic diagram of an anode active material layer 1 according to an embodiment of the present invention. Figure 1 , the anode active material layer 1 according to an embodiment of the present invention may include a composite anode active material 10 having a core-shell structure and a first solid electrolyte 20 .

[0043] When a conventional all-solid-state battery is charged, lithium ions (Li + ) is emitted from the cathode active material layer and migrates to the anode active material layer 1 along the solid electrolyte layer. The lithium ions (Li + ) can be stored in the anode active material or on the surface of the anode active material. When the anode active material layer 1 includes the first solid electrolyte 20 having high lithium ion conductivity as described in the present invention, lithium ions (Li +) can be easily moved and stored in the anode active material layer 1.

[0044] The first solid electrolyte 20 may be contained in the anode active material layer 1 , and may include a solid electrolyte having high lithium ion conductivity.

[0045] The first solid electrolyte 20 may include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, etc. In the embodiment, a sulfide-based solid electrolyte having high lithium ion conductivity may be used as the first solid electrolyte 20. For example, an argyrodite-type sulfide-based solid electrolyte may be used.

[0046] The sulfide-based solid electrolyte may include, for example, Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiI, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 -Li 2 O. Li 2 SP 2 S 5 -Li 2 O-LiI、Li 2 S-SiS 2 , Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 SB 2 S 3 , Li 2 SP 2 S 5 -Z m S n(m and n are positive numbers, and Z is one of Ge, Zn and Ga), Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li x MO y (x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 G 2 S 12 etc. without particular limitation.

[0047] If other conditions are the same, the Young's modulus of the sulfide-based solid electrolyte can decrease as the content of the halogen element in the sulfide-based solid electrolyte increases.

[0048] The oxide-based solid electrolyte may include, for example, a perovskite-type LLTO (Li 3x La 2 / 3-x TiO 3 ), phosphate NASICON type LATP (Li 1+x Al x Ti 2-x (PO 4 ) 3 )wait.

[0049] Figure 2 FIG. 2 is a view schematically showing a composite anode active material 10 and a first solid electrolyte 20 surrounding the composite anode active material 10 according to an embodiment of the present invention. Figure 2 In the figure, the first solid electrolyte 20 is shown in a suitably simplified manner. The composite anode active material 10 may include a core and a shell, wherein the core includes a silicon-based active material 11, and the shell is configured to coat at least a portion of the surface of the silicon-based active material 11 and includes a second solid electrolyte 12.

[0050] The silicon-based active material 11 may be any material as long as it has a higher theoretical capacity than conventional graphite-based anode active materials and contains silicon, without particular limitation. For example, the silicon-based active material 11 may contain at least one selected from silicon particles, silicon oxides, silicon alloys, and combinations thereof.

[0051] In addition, the silicon-based active material 11 may be a composite material containing a carbon-based material. For example, the silicon-based active material 11 may be a composite material formed by coating at least a portion of the surface of silicon particles, silicon oxides, or silicon alloys with a carbon-based material. Alternatively, the silicon-based active material 11 may be a composite material formed by coating at least a portion of the surface of a carbon-based material with silicon particles, silicon oxides, or silicon alloys. The silicon-based active material 11 may be a composite material in which primary particles formed of silicon particles, silicon oxides, or silicon alloys, respectively, are agglomerated with carbon-based materials to form secondary particles.

[0052] In the composite anode active material, the inner core may be formed of a silicon-based active material 11 to ensure a high theoretical capacity, and at least a portion of the surface of the silicon-based active material 11 may be coated with a second solid electrolyte 12 having high lithium ion conductivity, thereby promoting the storage and release of lithium ions when the battery is charged and discharged.

[0053] The second solid electrolyte 12 may coat at least a portion of the surface of the silicon-based active material 11 , and may include a solid electrolyte having high lithium ion conductivity.

[0054] The second solid electrolyte 12 may include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, etc. In the embodiment, a sulfide-based solid electrolyte having high lithium ion conductivity may be used as the second solid electrolyte 12. For example, an argyrodite-type sulfide-based solid electrolyte may be used.

[0055] The sulfide-based solid electrolyte may include, for example, Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiI, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 -Li 2 O. Li 2 SP 2 S 5 -Li 2 O-LiI、Li 2 S-SiS 2 , Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2-LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 SB 2 S 3 , Li 2 SP 2 S 5 -Z m S n (m and n are positive numbers, and Z is one of Ge, Zn and Ga), Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li x MO y (x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 G 2 S 12 etc. without particular limitation.

[0056] If other conditions are the same, the Young's modulus of the sulfide-based solid electrolyte can decrease as the content of the halogen element in the sulfide-based solid electrolyte increases.

[0057] The first solid electrolyte 20 and the second solid electrolyte 12 may be the same as or different from each other.

[0058] The anode active material layer 1 for an all-solid-state battery according to an embodiment of the present invention may be configured such that the Young's modulus E of the first solid electrolyte 20 is 1 and the Young's modulus E of the second solid electrolyte 12 2 The ratio E 1 / E 2 Can satisfy 1.5≤E 1 / E 2 ≤3.0.

[0059] Young's modulus E is a modulus that indicates how the relative length of an elastic object changes with respect to stress. The smaller the value of Young's modulus, the smaller the stiffness, and the larger the value of Young's modulus, the greater the stiffness.

[0060] Young's modulus is a generalization of the modulus of an elastic object in Hooke's law, but is generally independent of the processed shape of the object (for isotropic materials) and may be affected only by the inherent mechanical properties of the material constituting the object. Therefore, when measuring the Young's modulus of the first solid electrolyte 20 and the Young's modulus of the second solid electrolyte 12, it is not necessarily necessary to measure the respective values ​​of the Young's modulus of the first solid electrolyte 20 and the second solid electrolyte 12 after manufacturing the first solid electrolyte 20 and the second solid electrolyte 12 in the form of being contained in the anode active material 10 or the anode active material layer 1, and the Young's modulus of the first solid electrolyte 20 and the second solid electrolyte 12 may be measured after processing the first solid electrolyte 20 and the second solid electrolyte 12 into a sample form (whose Young's modulus is easy to measure).

[0061] The Young's modulus of a solid electrolyte can vary according to the type of halogen element doped with the solid electrolyte, the content of the halogen element, the crystallinity, etc. Specifically, the higher the content of the halogen element doped with the solid electrolyte, the smaller the Young's modulus. In addition, as the crystallinity of the solid electrolyte increases, its Young's modulus may increase. Typically, the crystallinity of a solid electrolyte can increase with the increase in the amount of heat applied to the raw material in the process of manufacturing the solid electrolyte (i.e., the firing temperature increases and the firing time is extended).

[0062] When the Young's modulus E of the first solid electrolyte 20 according to the embodiment of the present invention is 1 and the Young's modulus E of the second solid electrolyte 12 2 The ratio E 1 / E 2 Satisfy 1.5≤E 1 / E 2 ≤3.0, this may mean that the stiffness of the first solid electrolyte 20 is greater than the stiffness of the second solid electrolyte 12. Therefore, when the volume of the second solid electrolyte 12 increases or decreases as the volume of the silicon-based active material 11 changes, the first solid electrolyte 20 may suppress the expansion of the second solid electrolyte 12.

[0063] When the Young's modulus E of the first solid electrolyte 20 1 and the Young's modulus E of the second solid electrolyte 12 2 The ratio E 1 / E 2 When it is less than 1.5, this may indicate that the Young's modulus E of the first solid electrolyte 20 1 is higher, so the elasticity of the shell is lower, or the Young's modulus E of the second solid electrolyte 12 is 2Therefore, the mechanical properties of the composite anode active material 10 may not be sufficient to suppress its expansion, and when charging and discharging are repeated, cracks may occur at the interface of the first solid electrolyte 20 and the second solid electrolyte 12, and thus, the cycle life characteristics and output characteristics of the battery may deteriorate.

[0064] When the Young's modulus E of the first solid electrolyte 20 1 and the Young's modulus E of the second solid electrolyte 12 2 The ratio E 1 / E 2 When it exceeds 3, the difference in rigidity between the first solid electrolyte 20 and the second solid electrolyte 12 may be too large, so the degree of formation of the interface therebetween may be reduced, and the internal resistance may increase accordingly.

[0065] Since the Young's modulus E of the first solid electrolyte 20 1 and Young's modulus E of the second solid electrolyte 12 2 It may be affected not only by its composition but also by the crystal structure, crystal size, etc. Therefore, in order to satisfy the Young's modulus E of the first solid electrolyte 20 1 and the Young's modulus E of the second solid electrolyte 12 2 The above ratio E 1 / E 2 , the first solid electrolyte 20 and the second solid electrolyte 12 do not necessarily have to be different.

[0066] In the embodiment, the lithium ion conductivity of the first solid electrolyte 20 is 1 The lithium ion conductivity I of the second solid electrolyte 12 2 The ratio I 1 / I 2 Can satisfy 0.5≤I 1 / I 2 ≤2.0.

[0067] When the lithium ion conductivity of the first solid electrolyte 20 is 1 The lithium ion conductivity I of the second solid electrolyte 12 2 The ratio I 1 / I 2 Outside the above range, interface resistance may be generated between the first solid electrolyte 20 and the second solid electrolyte 12, and thus the effect of improving the output characteristics of the battery may be reduced.

[0068] In this regard, the lithium ion conductivity of the solid electrolyte may vary according to the composition of the solid electrolyte, the dopant, the crystal structure, the crystallinity, the lithium ion conduction path formed in the solid electrolyte, etc. For example, the lithium ion conductivity of the solid electrolyte may increase with the increase of the crystallinity of the solid electrolyte. Generally, the crystallinity of the solid electrolyte may increase with the increase of the amount of heat applied to the raw materials in the process of manufacturing the solid electrolyte (i.e., the sintering temperature increases and the sintering time is extended).

[0069] In the anode active material layer 1 for an all-solid-state battery according to an embodiment of the present invention, it is desirable that the Young's modulus E of the first solid electrolyte 20 is 1 and the Young's modulus E of the second solid electrolyte 12 2 The ratio E 1 / E 2 Satisfy 1.5≤E 1 / E 2 ≤3.0, and at the same time, the lithium ion conductivity I of the first solid electrolyte 20 1 The lithium ion conductivity I of the second solid electrolyte 12 2 The ratio I 1 / I 2 Satisfy 0.5≤I 1 / I 2 ≤2.0. Therefore, when the volume of the anode active material layer 1 changes due to charge and discharge of the battery, crack occurrence and increase in interface resistance at the interface between the first solid electrolyte 20 and the second solid electrolyte 12 can be suppressed, and the durability and output characteristics of the battery can be improved.

[0070] Hereinafter, a method for manufacturing the anode active material layer 1 for an all-solid-state battery according to an embodiment of the present invention will be described in detail.

[0071] Method for manufacturing anode active material layer for all-solid-state battery

[0072] A method for manufacturing an anode active material layer 1 for an all-solid-state battery according to an embodiment of the present invention may include: synthesizing a composite anode active material 10 by placing an anode active material and a second solid electrolyte 12 into a mixer and then mixing them; preparing an anode active material slurry by mixing the composite anode active material 10 with a first solid electrolyte 20; and forming an anode active material layer 1 by applying the anode active material slurry to an anode collector and drying the anode active material slurry.

[0073] The anode active material may be substantially the same as the above-described anode active material, and may include a silicon-based active material, or may further include a carbon-based material.

[0074] Generally, the method of manufacturing a composite anode active material 10 having a core-shell structure by coating at least a portion of the surface of a silicon-based active material with a solid electrolyte can be divided into a wet method, in which a solution is prepared by dissolving a solid electrolyte in a solvent, and then the surface of the anode active material is coated with the solution, and a dry method, in which a paint shaker or a thinky mixer is used to pulverize the anode active material and the solid electrolyte raw material, and then the surface of the anode active material is coated with the solid electrolyte.

[0075] After coating the surface of the anode active material with a solid electrolyte, the wet method may require heat treatment at a high temperature of 300° C. or higher, and after synthesizing the composite anode active material 10 by a coating shaker, the temperature of the composite anode active material 10 may be increased to about 80° C. to 100° C. In addition, after synthesizing the composite anode active material 10 by a Thinky mixer, the temperature of the composite anode active material 10 may be increased to about 50° C. to 60° C.

[0076] However, when the composite anode active material 10 is synthesized by a wet process, or after mixing using a mixer (such as a paint shaker or a Thinky mixer), at a temperature exceeding 40° C., a side reaction between the carbon contained in the anode active material and the solid electrolyte may be promoted, and degradation of the anode active material may occur.

[0077] Therefore, as a mixer according to an embodiment of the present invention, a mixer that can reduce the temperature of the composite anode active material 10 to 40° C. or less after mixing can be used. For example, for process efficiency, a mixer that can manufacture the composite anode active material 10 by mixing for 2 to 15 minutes can be used.

[0078] In the manufacturing method according to the embodiment of the present invention, the composite anode active material 10 may be manufactured by putting the anode active material and the second solid electrolyte 12 into a resonant acoustic mixer (RAM) and then mixing them.

[0079] The resonant acoustic mixer is a device for dispersing, crushing or coating particles of a mixture by effectively transferring energy to the mixture using the resonance phenomenon. Specifically, the mixture is induced to an acoustic resonance state using a resonant acoustic frequency that can refine the size of particles constituting the mixture, at which time the acoustic energy including the resonant acoustic frequency can be accumulated in the particles constituting the mixture and the particles are inherently dispersed into a structure or a surrounding medium.

[0080] In the manufacturing method according to the embodiment of the present invention, a resonant acoustic mixer having better energy transfer efficiency than a conventional paint shaker or a Thinky mixer can be used, and therefore, the temperature of the composite anode active material 10 after mixing can become 25° C. to 40° C. In addition, mixing by the resonant acoustic mixer can be performed for 2 to 15 minutes, which can be much shorter than conventional wet and dry methods.

[0081] Furthermore, at least one of the steps of synthesizing the composite anode active material, preparing the anode active material slurry, and forming the anode active material layer may be performed at a temperature of 40° C. or less.

[0082] In the manufacturing method according to the embodiment of the present invention, the composite anode active material 10 can be manufactured at a lower temperature than other manufacturing methods using a resonant acoustic mixer, thereby being able to suppress the side reaction between the carbon contained in the silicon-based active material and the solid electrolyte. In addition, compared with other manufacturing methods, mixing can be performed for a shorter time, thereby being able to improve process efficiency.

[0083] Although the resonant acoustic mixer has been described as an example of the mixer used in the present invention, any mixer capable of lowering the temperature of the composite anode active material 10 to 40° C. or less after mixing may be used without particular limitation. For example, a mixer capable of preparing a composite anode active material by performing mixing for 2 to 15 minutes may be used.

[0084] In an embodiment, the anode active material and the second solid electrolyte 12 may be placed in the resonant acoustic mixer at a weight ratio of 10: 1 to 7: 3. When a larger amount of the anode active material exceeding the above range is placed in the resonant acoustic mixer, the lithium ion conductivity of the composite anode active material 10 may decrease, and when a larger amount of the second solid electrolyte 12 exceeding the above range is placed in the resonant acoustic mixer, the energy density of the battery may decrease.

[0085] The ball (for example, zirconium oxide (ZrO 2 ) balls) are added to the resonant acoustic mixer together with the anode active material and the second solid electrolyte 12. The anode active material and the second solid electrolyte 12 and the balls can be put into the resonant acoustic mixer in a weight ratio of 1:4 to 1:8. By adding the balls to the resonant acoustic mixer, the coating efficiency can be improved.

[0086] After synthesizing the composite anode active material 10, an anode active material slurry can be prepared by placing the composite anode active material 10 and the first solid electrolyte 20 in a solvent. Thereafter, an anode active material layer for an all-solid-state battery can be formed by applying the anode active material slurry to an anode current collector and then drying the anode active material slurry.

[0087] Any solvent generally used in a process of preparing an anode active material slurry may be applied, such as N-methyl-2-pyrrolidone (NMP).

[0088] The anode current collector is a component that transmits current to or receives current from the anode active material during charge and discharge, and may be a conductive plate-like substrate. Specifically, the anode current collector may be in the form of a sheet, a film, or a foil.

[0089] The anode current collector may include a material that does not react with lithium. Specifically, the anode current collector may include, for example, at least one selected from nickel (Ni), copper (Cu), stainless steel, and a combination thereof.

[0090] The thickness of the anode current collector is not particularly limited, and may be, for example, 1 μm to 500 μm.

[0091] Hereinafter, exemplary embodiments of the present invention will be described in more detail through the following examples and comparative examples. The following examples and comparative examples are only used to describe the present invention and are not intended to necessarily limit the scope and spirit of the present invention.

[0092] Test Example 1

[0093] Figure 3 The Young's modulus measurements of argyrodite-type sulfide-based solid electrolytes with different halogen contents are shown. Specifically, the pressed composition is Li 6 PS 5 A solid electrolyte powder of X (X is Br or Br+Cl) is prepared and processed into a rectangular specimen with a specified thickness, and then the specimen is mounted on a tensile strength tester to measure its Young's modulus.

[0094] refer to Figure 3 , confirming that the Young's modulus decreases with the decrease in the content of halogen elements doped in the argyrodite-type sulfide-based solid electrolyte.

[0095] Manufacturing Example 1

[0096] (a) Preparation of Si / C composite materials as anode active materials. Preparation of Young's modulus E 1 is 12.8 GPa and the lithium ion conductivity is I 1 A sulfide-based solid electrolyte with a Young's modulus E of 8.8 mS / cm was prepared as the first solid electrolyte. 2 is 8.3 GPa and the lithium ion conductivity is I 2 A sulfide-based solid electrolyte with a concentration of 5.3 mS / cm was used as the second solid electrolyte.

[0097] (b) The anode active material and the second solid electrolyte prepared in powder form were weighed in a weight ratio of 10:1 and placed in a resonant acoustic mixer (LabRAM1, Resodyn Acoustic Mixers). In addition, zirconium oxide (ZrO 2 ) balls are added to the resonant acoustic mixer so that the anode active material and the second solid electrolyte in powder form are mixed with zirconium oxide (ZrO 2 )The weight ratio of the balls is 1:4.

[0098] Thereafter, the anode active material and the second solid electrolyte were mixed with zirconium oxide (ZrO 2 ) for 5 minutes to obtain a composite anode active material having a core-shell structure, the composite anode active material comprising a silicon-based anode active material as a core and a second solid electrolyte configured to coat at least a portion of the silicon-based anode active material. The measured temperature of the composite anode active material was about 30° C.

[0099] (c) preparing an anode active material slurry by placing the composite anode active material and the prepared first solid electrolyte into N-methyl-2-pyrrolidone (NMP) as an organic solvent and mixing them. Thereafter, forming an anode active material layer by applying the anode active material slurry to a Ni foil as an anode current collector and drying the anode active material slurry, thereby obtaining an anode comprising an anode current collector and an anode active material layer stacked on the anode current collector.

[0100] Manufacturing Example 2

[0101] The anode was obtained by the same method as in Manufacturing Example 1, except that: the Young's modulus E 1 is 26.9 GPa and the lithium ion conductivity is I 1 A sulfide-based solid electrolyte with a Young's modulus E of 3.9 mS / cm was used as the first solid electrolyte. 2 is 11.0 GPa and the lithium ion conductivity is I 2 A sulfide-based solid electrolyte with a concentration of 5.2 mS / cm was used as the second solid electrolyte.

[0102] Comparative Manufacturing Example 1

[0103] An anode was obtained by the same method as that of Manufacturing Example 1, except that the second solid electrolyte was not put into the resonant acoustic mixer in step (b) of Manufacturing Example 1.

[0104] Comparative Manufacturing Example 2

[0105] The anode was obtained by the same method as in Manufacturing Example 1, except that: the Young's modulus E 2 is 26.9 GPa and the lithium ion conductivity is I 2 A sulfide-based solid electrolyte with a concentration of 3.9 mS / cm was used as the second solid electrolyte.

[0106] Comparative Manufacturing Example 3

[0107] The anode was obtained by the same method as in Manufacturing Example 2, except that: the Young's modulus E 2 is 8.3 GPa and the lithium ion conductivity is I 2 A sulfide-based solid electrolyte with a concentration of 5.3 mS / cm was used as the second solid electrolyte.

[0108] Comparative Manufacturing Example 4

[0109] The anode was obtained by the same method as in Manufacturing Example 2, except that: the Young's modulus E 2 is 16.5 GPa and the lithium ion conductivity is I 2 A sulfide-based solid electrolyte with a concentration of 9.1 mS / cm was used as the second solid electrolyte.

[0110] Comparative Manufacturing Example 5

[0111] In order to study the effect of the type of mixer on the electrochemical properties of the composite anode active material, a paint shaker was used instead of a resonant acoustic mixer to manufacture the composite anode active material and an anode including the composite anode active material.

[0112] Specifically, (b) the anode active material and the second solid electrolyte prepared in powder form were weighed at a weight ratio of 10:1 and placed in a paint shaker (YJ-2A02, SH Sigma). 2 ) balls are added to the paint shaker so that the anode active material and the second solid electrolyte in powder form are mixed with zirconium oxide (ZrO 2 )The weight ratio of the balls is 1:4.

[0113] Thereafter, the anode active material and the second solid electrolyte were mixed with zirconium oxide (ZrO 2 ) balls for 30 minutes to obtain a composite anode active material having a core-shell structure, the composite anode active material comprising a silicon-based anode active material as a core and a second solid electrolyte configured to coat at least a portion of the silicon-based anode active material. The anode was manufactured by the same method as in Manufacturing Example 1, except that the temperature of the composite anode active material measured was about 90°C.

[0114] Comparative Manufacturing Example 6

[0115] In order to study the effect of the type of mixer on the electrochemical properties of the composite anode active material, a Thinky mixer was used instead of a resonant acoustic mixer to manufacture the composite anode active material and an anode including the composite anode active material.

[0116] Specifically, (b) the anode active material and the second solid electrolyte prepared in powder form were weighed at a weight ratio of 10:1 and placed in a Thinky mixer (ARE-500, THINKY). 2 ) balls are added to the Thinky mixer so that the anode active material and the second solid electrolyte in powder form are mixed with zirconium oxide (ZrO 2 )The weight ratio of the balls is 1:4.

[0117] Thereafter, the anode active material and the second solid electrolyte were mixed with zirconium oxide (ZrO 2 ) balls for 10 minutes to obtain a composite anode active material having a core-shell structure, the composite anode active material comprising a silicon-based anode active material as a core and a second solid electrolyte configured to coat at least a portion of the silicon-based anode active material. The anode was manufactured by the same method as in Manufacturing Example 1, except that the temperature of the composite anode active material measured was about 55°C.

[0118] The conditions of the composite anode active material used in the method of obtaining the anode according to the above-mentioned Manufacturing Example and Comparative Manufacturing Example are listed in Table 1 below.

[0119] [Table 1]

[0120]

[0121] Test Example 2 - SEM and EDS analysis of composite anode active material

[0122] In the method for manufacturing the anode according to Manufacturing Example 1, the composite anode active material synthesized by step (b) is photographed using a scanning electron microscope (SEM), and the photograph of the composite anode active material is shown in Figure 4 In addition, energy dispersive spectroscopy (EDS) was used to scan sulfur (S) and silicon (Si) in the same composite anode active material, and the analysis results are shown in Figure 5 and Figure 6 middle.

[0123] refer to Figure 5 and Figure 6, sulfur (S) and silicon (Si) were observed in the synthesized composite anode active material, thereby confirming that at least a portion of the surface of the silicon-based anode active material was appropriately coated with the second solid electrolyte.

[0124] Example 1

[0125] (a) Preparation of the anode according to Manufacturing Example 1, Li 6 PS 5 Cl (which is a sulfide-based solid electrolyte with an argyrodite-type crystal structure) and a lithium (Li) thin film.

[0126] (b) By sequentially stacking anodes, Li 6 PS 5 A solid electrolyte layer of Cl (i.e., a sulfide-based solid electrolyte having an argyrodite-type crystal structure) and a lithium (Li) thin film are then pressed to manufacture a compressed battery, which is an all-solid-state battery.

[0127] Example 2

[0128] A compressed battery was manufactured by the same method as in Example 1, except that the anode according to Manufacturing Example 2 was used.

[0129] Comparative Example 1

[0130] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 1 was used.

[0131] Comparative Example 2

[0132] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 2 was used.

[0133] Comparative Example 3

[0134] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 3 was used.

[0135] Comparative Example 4

[0136] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 4 was used.

[0137] Comparative Example 5

[0138] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 5 was used.

[0139] Comparative Example 6

[0140] A compressed battery was manufactured by the same method as Example 1, except that the anode according to Comparative Manufacturing Example 6 was used.

[0141] Test Example 3 - Output Evaluation and Durability Evaluation of Compressed Battery

[0142] In order to measure the durability of the compressed batteries manufactured according to the above embodiments and comparative examples, the output evaluation of the compressed batteries manufactured according to the above embodiments and comparative examples was performed by charging and discharging the compressed batteries twice under the conditions listed in Table 2 below, and the durability evaluation of the compressed batteries manufactured according to the above embodiments and comparative examples was performed by charging and discharging the compressed batteries 50 times under the conditions listed in Table 2 below.

[0143] The results are shown in Table 2 and Figure 7 middle.

[0144] [Table 2]

[0145]

[0146] Referring to Table 2, it is confirmed that the compressed batteries according to Examples 1 and 2 (wherein the Young's modulus E 1 and the Young's modulus E of the second solid electrolyte 2 The ratio E 1 / E 2 Satisfy 1.5≤E 1 / E 2 ≤3.0, and the lithium ion conductivity of the first solid electrolyte I 1 Lithium ion conductivity of the second solid electrolyte I 2 The ratio I 1 / I 2 Satisfy 0.5≤I 1 / I 2 ≤2.0) are better than those of the compressed battery according to the comparative example.

[0147] Test Example 4 - Structural Evaluation of Anode Active Material Layer after Durability Evaluation

[0148] After durability evaluation according to Test Example 3, the anode was separated from the compressed batteries of Example 1 and Comparative Example 4, and then photographed using a scanning electron microscope (SEM). The obtained photographs are shown in Figure 8 and Fig. 9 middle.

[0149] refer to Figure 8 and Fig. 9In the anode of Example 1 including the anode active material layer according to the present invention, no obvious cracks or voids were observed between the composite anode active material and the first solid electrolyte. On the other hand, in the case of the anode of Comparative Example 4, it was confirmed that cracks were formed at the interface between the composite anode active material and the first solid electrolyte. Thus, it can be predicted that the anode of Comparative Example 4 has a high interface resistance.

[0150] Test Example 5 - Changes in electrochemical properties depending on the type of mixer

[0151] In order to find out the changes in electrochemical properties according to the type of mixer, electrochemical evaluation was performed by initially charging and discharging the compressed batteries manufactured according to Example 1, Comparative Example 5 and Comparative Example 6. The results are shown in Fig.10 middle.

[0152] refer to Fig.10 , it was confirmed that the compressed battery of Example 1 (in which mixing was performed using a resonant acoustic mixer for about 5 minutes) exhibited the best initial charge and discharge characteristics. On the other hand, it was confirmed that the compressed battery manufactured using a paint shaker (which required a longer composite treatment time and a higher temperature of the anode active material after mixing) exhibited significantly lower initial charge and discharge capacities.

[0153] This is expected because when the temperature of the anode active material exceeds 40° C. during mixing, a side reaction may occur between the carbon in the anode active material and the solid electrolyte, thereby causing the anode active material to deteriorate.

[0154] As is apparent from the above description, the anode active material layer according to the present invention is a layer having a Young's modulus E of the first solid electrolyte. 1 and the Young's modulus E of the second solid electrolyte 2 The ratio E 1 / E 2 Controlled at 1.5≤E 1 / E 2 ≤3.0, and thus an increase in the interface resistance between the first solid electrolyte and the second solid electrolyte due to the volume change of the silicon-based anode active material can be suppressed.

[0155] In addition, the anode active material layer according to the present invention increases the lithium ion conductivity of the first solid electrolyte to 1 Lithium ion conductivity of the second solid electrolyte I 2 The ratio I 1 / I 2 Controlled at 0.5≤I 1 / I 2≤2.0, and thus an increase in interface resistance between the first solid electrolyte and the second solid electrolyte due to the difference in lithium ion conductivity therebetween can be suppressed.

[0156] Furthermore, in the method for manufacturing a composite anode active material layer according to an embodiment of the present invention, the composite anode active material can be prepared at a low temperature using a resonant acoustic mixer, and thus a side reaction between the anode active material and the solid electrolyte can be suppressed.

[0157] The advantages of the embodiments of the present invention are not limited to the above advantages. The advantages of the present invention can be understood to include all advantages that can be inferred from the above description.

[0158] The present invention has been described in detail with reference to exemplary embodiments. However, it will be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the present invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. An anode active material layer for an all-solid-state battery, the anode active material layer comprising: a first solid electrolyte; and A composite anode active material having a core-shell structure, wherein the composite anode active material comprises: a core comprising a silicon-based active material, and a shell configured to coat at least a portion of a surface of the core, and comprising a second solid electrolyte, Wherein, a ratio E1 / E2 of a first Young's modulus E1 of the first solid electrolyte to a second Young's modulus E2 of the second solid electrolyte satisfies 1.5≤E1 / E2≤3.

0.

2. The anode active material layer for an all-solid-state battery according to claim 1, wherein: A ratio I1 / I2 of a first lithium ion conductivity I1 of the first solid electrolyte to a second lithium ion conductivity I2 of the second solid electrolyte satisfies 0.5≤I1 / I2≤2.

0.

3. The anode active material layer for an all-solid-state battery according to claim 1, wherein: The first solid electrolyte includes a sulfide-based solid electrolyte.

4. The anode active material layer for an all-solid-state battery according to claim 1, wherein: The second solid electrolyte includes a sulfide-based solid electrolyte.

5. The anode active material layer for an all-solid-state battery according to claim 1, wherein: The silicon-based active material comprises one selected from silicon particles, silicon oxides, silicon alloys and combinations thereof.

6. The anode active material layer for an all-solid-state battery according to claim 1, wherein: The silicon-based active material includes a carbon-based material.

7. A method for manufacturing an anode active material layer for an all-solid-state battery, the method comprising: synthesizing a composite anode active material by placing the anode active material and a second solid electrolyte into a mixer and then mixing the anode active material and the second solid electrolyte; preparing an anode active material slurry by mixing a composite anode active material and a first solid electrolyte; and forming an anode active material layer by applying an anode active material slurry to an anode current collector and then drying the anode active material slurry, Wherein, after mixing the anode active material and the second solid electrolyte, the temperature of the composite anode active material is 40° C. or less.

8. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 7, wherein: The mixer includes a resonant acoustic mixer.

9. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 7, wherein: The anode active material and the second solid electrolyte are mixed for 2 minutes to 15 minutes.

10. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 7, wherein: The anode active material and the second solid electrolyte are put into the mixer at a weight ratio of 10:1 to 7:

3.

11. A method for manufacturing an anode active material layer for an all-solid-state battery, the method comprising: synthesizing a composite anode active material by placing an anode active material and a second solid electrolyte into a mixer and then mixing the anode active material and the second solid electrolyte at a mixing temperature of 40° C. or less; preparing an anode active material slurry by mixing a composite anode active material and a first solid electrolyte; and The anode active material layer is formed by applying an anode active material slurry onto an anode current collector and then drying the anode active material slurry.

12. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 11, wherein: The mixer includes a resonant acoustic mixer.

13. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 11, wherein: The anode active material and the second solid electrolyte are mixed for 2 minutes to 15 minutes.

14. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 11, wherein: The anode active material and the second solid electrolyte are put into the mixer at a weight ratio of 10:1 to 7:

3.

15. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 11, wherein: The preparation of the anode active material slurry is performed at a preparation temperature of 40° C. or lower.

16. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 15, wherein: Applying the anode active material slurry to the anode current collector is performed at an application temperature of 40° C. or lower.

17. The method for manufacturing an anode active material layer for an all-solid-state battery according to claim 16, wherein: Drying the anode active material slurry is performed at a drying temperature of 40° C. or lower.

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