All solid-state battery

Abstract

The present invention relates to an all-solid-state battery. Specifically, one embodiment provides a sintered all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles that are the same or different from each other; the solid electrolyte layer comprises solid electrolyte particles; and the diameter (a) of the electrode active material particles and the diameter (b) of the solid electrolyte particles satisfy the relationship of Equation 1 below. [Mathematical Formula 1] 0.5≤(b / a)≤2.5

Description

Technology Field

[0001] The present disclosure relates to an all-solid-state battery. Background Technology

[0003] Lithium-ion batteries are widely used as power sources for small electronic devices such as mobile phones, laptops, and smartphones, and their applications are expanding to include power sources for electric vehicles and power storage for energy storage devices.

[0004] The most common type of lithium secondary battery is the 'lithium-ion battery,' which has problems associated with the use of a liquid electrolyte (e.g., potential risks such as leakage, ignition, and explosion).

[0005] Recently, "all-solid-state batteries," which replace the liquid electrolyte with a solid electrolyte, are gaining attention as a next-generation battery that solves the problems of the above-mentioned lithium-ion batteries. However, for the industrial mass production of all-solid-state batteries, lowering the interfacial resistance between the solid electrolyte layer and the electrode layer is a prerequisite.

[0006] Specifically, as a method for manufacturing an all-solid-state battery, a method for manufacturing a so-called 'sintered all-solid-state battery' is known, in which a solid electrolyte layer and an electrode layer (specifically, a positive electrode layer and a negative electrode layer) are stacked in an appropriate arrangement and then sintered in a high-temperature furnace. However, the generally known sintered all-solid-state battery has a problem of low capacity compared to lithium-ion batteries because the interfacial resistance between the solid electrolyte layer and the electrode layer is high. The problem to be solved

[0008] One embodiment aims to secure a high capacity of an all-solid-state battery by lowering the interfacial resistance between the solid electrolyte layer and the electrode layer. means of solving the problem

[0010] One embodiment provides a sintered all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles that are the same or different from each other; the solid electrolyte layer comprises solid electrolyte particles; and the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of Equation 1 below.

[0011] [Mathematical Formula 1] 0.5≤(b / a)≤2.5

[0012] The average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles can satisfy the relationship of Equation 1-1 below:

[0013] [Mathematical Formula 1] 1.1≤(b / a)≤1.4

[0014] The above electrode active material particles may include particles represented by the following chemical formula 1:

[0015] [Chemical Formula 1] Li x V 2-y M y (P04)3

[0016] In the above chemical formula 1, M is one or more selected from the group including Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr and Zr; 1≤x≤3; 0≤y<2; and 2≤z<3.

[0017] The average diameter (a) of the electrode active material particles may be 2 to 10 μm.

[0018] The above solid electrolyte particles may include particles represented by the following chemical formula 2:

[0019] [Chemical Formula 2] Li 1+y Al y Ti 2-y (PO4)3

[0020] In the above chemical formula 2, 0 <x≤0.6이다.

[0021] The average diameter (b) of the above solid electrolyte particles may be 2 to 10 μm.

[0022] The anode layer and the cathode layer may each independently include a current collector; and an electrode active material layer located on one or both sides of the current collector and comprising the electrode active material particles.

[0023] The above electrode active material layer may further include solid electrolyte particles that are identical or different from the solid electrolyte layer.

[0024] The electrode active material layer may include the electrode active material particles and the solid electrolyte particles in a weight ratio of 1:9 to 9:1.

[0025] The above electrode active material layer may further include a conductive material.

[0026] Of the total weight of the electrode active material layer, the solid electrolyte particles are included in an amount of 15 to 60 weight%, the conductive material is included in an amount of 1 to 5 weight%, and the electrode active material particles may be included as the remainder.

[0027] The thickness of the electrode active material layer may be 1.0 to 20 μm.

[0028] The above current collector may contain copper particles.

[0029] The average diameter of the copper particles may be 0.5 to 5 μm.

[0030] The thickness of the solid electrolyte layer may be 1.0 to 30 μm.

[0031] The above-described sintered all-solid-state battery may include a body comprising the above-described solid electrolyte layer and the above-described positive electrode layer and the above-described negative electrode layer alternately stacked with the above-described solid electrolyte layer in between.

[0032] The above-described sintered all-solid-state battery may further include a first external electrode and a second external electrode disposed on each side of the body.

[0034] Another embodiment may provide an all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles represented by the following chemical formula 1, either identically or differently; the solid electrolyte layer comprises solid electrolyte particles represented by the following chemical formula 2; and the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of the following mathematical formula 1.

[0035] [Chemical Formula 1] Li x V 2-y M y (P04)3

[0036] In the above chemical formula 1, M is one or more selected from the group comprising Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr, and Zr; 1≤x≤3; 0≤y<2; and 2≤z<3;

[0037] [Chemical Formula 2] Li 1+y Al y Ti 2-y (PO4)3

[0038] In the above chemical formula 2, 0 <x≤0.6이고;

[0039] [Mathematical Formula 1]

[0040] 0.5≤(b / a)≤2.5

[0041] The above all-solid-state battery may be a sintered all-solid-state battery. Effects of the invention

[0043] According to one embodiment, an all-solid-state battery can lower the interfacial resistance between the solid electrolyte layer and the electrode layer and secure a high capacity as a result of controlling the relationship between the average diameter of the electrode active material particles and the average diameter of the solid electrolyte particles as described above. Brief explanation of the drawing

[0045] FIG. 1 schematically illustrates a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention. Figure 2 is an enlarged view of area A of Figure 1. Figure 3 is an SEM image of the cross-section obtained when the all-solid-state battery of Example 4 is cut in the stacking direction. Specific details for implementing the invention

[0046] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0047] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0048] In this specification, "sintering" refers to the phenomenon in which powder bodies, pressure-molded into a suitable shape, adhere tightly to each other and solidify when heated.

[0049] In this specification, "average diameter of particles" or "average size of particles" refers to the average value obtained by averaging the major axis length and minor axis length of particles. Here, although the conditions for measuring the major axis length and minor axis length of particles are not specifically limited, scanning electron microscopy (SEM) of Carl Zeiss or similar company may be used to take SEM images of multiple particles at a magnification of 10,000x, and the major axis length and minor axis length of individual particles may be measured on the SEM images to obtain an average value, and then an average value may be obtained for all particles appearing on the SEM images. That is, the "average diameter of particles" or "average size of particles" can be calculated according to the following mathematical formula.

[0050] [Mathematical Formula]

[0051] [∑{(average of the major and minor axes of the first particle)+(average of the major and minor axes of the second particle)+… +(average of the major and minor axes of the nth particle)}] / n

[0052] In the above mathematical formula, n is an integer greater than or equal to 1, and its upper limit is not limited, but in the range of 100 or more, the larger the value, the higher the reliability of the "average diameter of the particle" or "average size of the particle".

[0053] Throughout the specification, the term "stacking direction" refers to the direction in which components are sequentially stacked; it may also be the "thickness direction" perpendicular to the broad surface (main surface) of the components on the sheet, and corresponds to the T-axis direction in the drawings. The term "lateral direction" refers to the direction extending parallel to the broad surface (main surface) from the edge of the component on the sheet, and may be the "planar direction," and corresponds to the L-axis direction in the drawings.

[0055] (First form)

[0056] One embodiment provides a sintered all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles that are the same or different from each other; the solid electrolyte layer comprises solid electrolyte particles; and the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of Equation 1 below.

[0057] [Mathematical Formula 1] 0.5≤(b / a)≤2.5

[0059] Since the above-mentioned first-type all-solid-state battery corresponds to a 'sintered all-solid-state battery,' even without specific mention, the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles each refer to the diameter 'after sintering.'

[0061] As previously pointed out, sintered all-solid-state batteries have a problem of lower capacity compared to lithium-ion batteries due to the high interfacial resistance between the solid electrolyte layer and the electrode layer. This is attributed to the relationship between the diameter of the electrode active material particles and the diameter of the solid electrolyte particles.

[0062] Specifically, if the difference between the average diameter (c) of the electrode active material particles before sintering and the average diameter (d) of the solid electrolyte particles before sintering is excessive, either the electrode active material layer or the solid electrolyte layer shrinks excessively during the sintering process.

[0063] For example, if the average diameter (c) of the electrode active material particles before sintering is excessively smaller than the average diameter (d) of the solid electrolyte particles before sintering, the electrode layer begins to shrink at a lower temperature than the solid electrolyte layer, so a sintered all-solid-state battery in which the electrode layer shrinks more than the solid electrolyte layer is obtained. Conversely, if the average diameter (d) of the solid electrolyte particles before sintering is excessively smaller than the average diameter (c) of the electrode active material particles before sintering, the solid electrolyte layer begins to shrink at a lower temperature than the electrode layer, so a sintered all-solid-state battery in which the solid electrolyte layer shrinks more than the electrode layer is obtained.

[0064] In this way, if either the electrode layer or the solid electrolyte layer shrinks excessively, the interfacial resistance between the electrode layer and the solid electrolyte layer increases, and consequently, the capacity of the sintered all-solid-state battery decreases.

[0066] On the other hand, if the difference between the average diameter (c) of the electrode active material particles before sintering and the average diameter (d) of the solid electrolyte particles before sintering is controlled within an appropriate range, the electrode layer and the solid electrolyte layer begin to shrink at similar temperatures, so a sintered all-solid-state battery with similar degrees of shrinkage of the electrode layer and the solid electrolyte layer will be obtained.

[0067] In fact, if the average diameter (d) of the solid electrolyte particles before sintering is controlled to be within 0.5 to 2.5 times the average diameter (c) of the electrode active material particles before sintering, the interfacial resistance between the solid electrolyte layer and the electrode layer is significantly lowered compared to cases where this range is not satisfied, and the capacity of the sintered all-solid-state battery is significantly increased. The average diameter (b) of the solid electrolyte particles after sintering is also controlled to be within 0.5 to 2.5 times the average diameter (a) of the electrode active material particles after sintering. This is supported by the evaluation examples described later.

[0069] Hereinafter, the sintered all-solid-state battery of the first type described above will be explained in detail.

[0071] The relationship between b / a

[0072] As previously explained, by ensuring that the average diameter (b) of the solid electrolyte particles after sintering and the average diameter (a) of the electrode active material particles after sintering satisfy the relationship of Equation 1 below, the interfacial resistance between the solid electrolyte layer and the electrode layer can be lowered, and a high capacity of the sintered all-solid-state battery can be secured:

[0073] [Mathematical Formula 1] 0.5≤(b / a)≤2.5

[0074] Specifically, the lower limit of the above mathematical formula 1 can be controlled to 0.5, 0.7, 0.9, or 1.1; and the upper limit can be controlled to 2.5, 2.3, 2.1, 1.9, 1.7, 1.5, or 1.4.

[0075] For example, the average diameter (a) of the electrode active material particles after sintering and the average diameter (b) of the solid electrolyte particles after sintering may satisfy the relationship of Equation 1-1 below:

[0076] [Mathematical Equation 1-1] 1.1≤(b / a)≤1.4

[0077] In particular, when the average diameter (a) of the electrode active material particles after sintering and the average diameter (b) of the solid electrolyte particles after sintering are at a level similar enough to satisfy the relationship of Equation 1-1, the interfacial resistance between the solid electrolyte layer and the electrode layer is further significantly lowered, and the capacity of the sintered all-solid-state battery can also be further significantly increased:

[0079] Composition and average diameter of electrode active material particles after sintering (a)

[0080] The anode layer and the cathode layer include electrode active material particles that are the same or different from each other.

[0082] The electrode active material particles after sintering above may include LVP-based particles represented by the following chemical formula 1:

[0083] [Chemical Formula 1] Li x V 2-y M y (P04)3

[0084] In the above chemical formula 1, M is one or more selected from the group including Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr and Zr; 1≤x≤3; 0≤y<2; and 2≤z<3.

[0085] For example, the anode layer and the cathode layer may each include Li3V2(PO4)3 particles as the same electrode active material particles.

[0087] Meanwhile, during the above sintering process, primary particles of the electrode active material may aggregate with each other or combine with a solid electrolyte to form secondary particles, or secondary particles of the electrode active material may aggregate with each other to form larger secondary particles. Accordingly, the diameter (a) of the electrode active material particles after sintering may be larger than the diameter (c) of the electrode active material particles before sintering.

[0088] Specifically, the average diameter (a) of the electrode active material particles after sintering may be 2 to 5 μm. For example, the average diameter (a) of the electrode active material particles after sintering may be 2 μm or more, 2.2 μm or more, 2.4 μm or more, 2.6 μm or more, or 2.8 μm or more, and 5 μm or less, 4.8 μm or less, 4.6 μm or less, or 4.5 μm or less.

[0089] The average diameter (a) of the electrode active material particles after sintering can increase as the diameter (c) of the electrode active material particles before sintering increases and as the sintering temperature increases.

[0091] Composition and average diameter of solid electrolyte particles after sintering (b)

[0092] The above-mentioned solid electrolyte particles may include LATP-based particles represented by the following chemical formula 2:

[0093] [Chemical Formula 2]

[0094] Li 1+y Al y Ti 2-y (PO4)3

[0095] In the above chemical formula 2, 0 <x≤0.6이다.

[0096] For example, the above solid electrolyte particles are Li 1.3 Al 0.3 Ti 1.7 It may contain (PO4)3 particles.

[0098] Meanwhile, during the above sintering process, primary solid electrolyte particles may aggregate with each other or combine with the electrode active material to form secondary particles, or secondary solid electrolyte particles may aggregate with each other to form larger secondary particles. This means that during the above sintering process, primary solid electrolyte particles aggregate with each other to form secondary particles, or secondary solid electrolyte particles aggregate with each other to form larger secondary particles. Accordingly, the average diameter (b) of the solid electrolyte particles after sintering may be larger than the average diameter (d) of the solid electrolyte particles before sintering.

[0099] Specifically, the average diameter (b) of the solid electrolyte particles after sintering may be 2 to 10 μm. For example, the average diameter (b) of the solid electrolyte particles after sintering may be 2 μm or more, 2.5 μm or more, 3 μm or more, 3.5 μm or more, or 4 μm or more, and 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, or 6 μm or less.

[0100] The average diameter (b) of the solid electrolyte particles after sintering can increase as the average diameter (d) of the solid electrolyte particles before sintering increases, as the sintering temperature increases, and as the sintering time increases.

[0102] Electrode layers (anode layer and cathode layer) after sintering

[0103] The anode layer and the cathode layer may each independently include a current collector; and an electrode active material layer located on one or both sides of the current collector and comprising the electrode active material particles.

[0104] Specifically, when the electrode active material layer is located on both sides of the current collector, the capacity of the sintered all-solid-state battery can be higher compared to the case where it is located on one side of the current collector.

[0106] The electrode active material layer may further include solid electrolyte particles after sintering that are identical or different from the solid electrolyte layer. Specifically, the electrode active material layer may include solid electrolyte particles after sintering identical to the solid electrolyte layer, such as particles represented by Chemical Formula 2.

[0107] At this time, the electrode active material layer may include the electrode active material particles after sintering and the solid electrolyte particles after sintering in a weight ratio of 1:9 to 9:1, specifically 2:8 to 8:2, more specifically 3:7 to 7:3, for example 4:6 to 6:4 (electrode active material particles after sintering: solid electrolyte particles after sintering). Within this range, the ion-conducting network within the electrode active material layer may be improved.

[0109] In addition, the electrode active material layer may further include a conductive material. Of course, the conductive material may also be in a form after sintering.

[0110] The above conductive material is used to impart conductivity to the electrode layer, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, furnace black, and activated carbon carbon fibers; metal-based materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0111] For example, the conductive material may be an amorphous carbon-based material, such as carbon black, acetylene black, Denka black, Ketjen black, furnace black, activated carbon, or a combination thereof. An example of the carbon black is Super P (Timcal).

[0112] Of the total weight of the electrode active material layer, the solid electrolyte particles are included in an amount of 15 to 60 weight%, the conductive material is included in an amount of 1 to 5 weight%, and the electrode active material particles may be included as the remainder.

[0114] The thickness of the electrode active material layer is not particularly limited, but may be 1.0 to 20 μm based on the time after sintering.

[0116] The above current collector may contain copper particles, and the average diameter of the copper particles may be 0.5 to 5 μm based on the time after sintering.

[0118] Solid electrolyte layer after sintering

[0119] The thickness of the above solid electrolyte layer is not particularly limited, but may be 1.0 to 30 μm based on the time after sintering.

[0121] Structure of a sintered all-solid-state battery

[0122] FIG. 1 schematically illustrates a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0123] The first type of sintered all-solid-state battery (100) may include a body comprising the solid electrolyte layer (130) and the positive electrode layer (120) and the negative electrode layer (140) that are alternately stacked with the solid electrolyte layer (130) in between.

[0124] In addition, the first type of sintered all-solid-state battery (100) may further include a first external electrode (112) and a second external electrode (114) disposed on each side of the body.

[0125] Specifically, the all-solid-state battery includes an electrode layer (120, 140) and a solid electrolyte layer (130) disposed adjacent to the electrode layer in a stacking direction. The electrode layer may basically include a current collector (123, 143) and an electrode active material layer (121, 122, 141, 142) coated on one or both sides of the current collector (125).

[0126] For example, the electrode layer located at the top based on the stacking direction may be formed by applying a negative active material layer (141) to one side of a negative current collector (143), and the electrode layer located at the bottom may be formed by applying a positive active material layer (121) to one side of a positive current collector (123). Also, the electrode layers located between the top and bottom may be formed by applying positive active material layers (121, 122) to both sides of a positive current collector (123) or by applying negative active material layers (141, 142) to both sides of a negative current collector (143).

[0127] A solid electrolyte layer (130) can be interposed and stacked between an anode layer (120) and a cathode layer (140). Accordingly, the solid electrolyte layer (130) can be arranged adjacently in the stacking direction between the positive active material layer (121, 122) of the anode layer (120) and the negative active material layer (141, 142) of the cathode layer (140). Thus, a plurality of anode layers (120) and cathode layers (140) can be alternately arranged within the all-solid-state battery (100), and a plurality of solid electrolyte layers (130) can be interposed and stacked between them.

[0128] An insulating layer (150) may be disposed along the edges of the positive and negative layers. The insulating layer (150) is located on the solid electrolyte layer (130) and may be formed laterally adjacent to the edges of the positive or negative layer. Thus, the insulating layer (150) may be located in the same layer as the positive layer and the negative layer, respectively. The insulating layer (150) may be constructed using the same material as the solid electrolyte layer (130). Therefore, in an all-solid-state battery, the insulating layer (150) and the solid electrolyte layer (130) may not have distinct boundaries and may be composed of a solid electrolyte layer (130) formed integrally.

[0130] A positive electrode layer (120), a solid electrolyte layer (130), a negative electrode layer (140), and an insulating layer (150) can be stacked as described above to form a cell stack of an all-solid-state battery (100). A protective layer (160) made of an insulating material can be formed on the top and bottom of the cell stack of the all-solid-state battery (100). Additionally, the terminals of a positive electrode current collector (123) and a negative electrode current collector (143) are exposed on both sides of the cell stack of the all-solid-state battery, and external electrodes (112, 114) can be connected to and combined with these exposed terminals. That is, the external electrodes (112, 114) can be configured to be connected to the terminal of the positive electrode current collector (123) to have a positive charge, and connected to the terminal of the negative electrode current collector (143) to have a negative charge. If the terminal of the positive electrode current collector (123) and the terminal of the negative electrode current collector (143) are configured to face in opposite directions, the external The electrodes (112, 114) can also be located on each side.

[0131] The positive electrode layer (120), the solid electrolyte layer (130), and the negative electrode layer (140) can be stacked to form a cell stack of an all-solid-state battery. A protective layer (160) made of an insulating material can be formed on the top and bottom of the cell stack of the all-solid-state battery, and this insulating material can also be made of the same material as the solid electrolyte layer (130).

[0133] Figure 2 is an enlarged view of area A of Figure 1.

[0134] As previously mentioned, the solid electrolyte layer (130), the anode layer (120), and the cathode layer (140) may each be one, and the structure may be such that the anode layer (120) is disposed on one side of the solid electrolyte layer (130) and the cathode layer (140) is disposed on the other side.

[0135] The anode layer (120) and the cathode layer (140) each contain electrode active material particles (124, 144) that are the same or different from each other; and the solid electrolyte layer (130) contains solid electrolyte particles (134). For convenience, the particle size included in each layer is exaggerated in FIG. 2.

[0136] The diameter (a) of the electrode active material particles (124, 144) may be obtained by measuring the major axis length and minor axis length of individual particles and obtaining the average value. Specifically, the major axis length is a 11 and the short axis length is a 12 The diameter of the first electrode active material particle is (a 11 +a 12 It can be ) / 2.

[0137] To increase the reliability of the diameter (a) of the electrode active material particles (124, 144), an average value can be obtained for two or more electrode active material particle diameters. Specifically, the major axis length is a 11 and the short axis length is a 12 For the first electrode active material particle, the major axis length is a 21 and the short axis length is a 22 For the second electrode active material particle, the particle diameter can be calculated using [∑{(average value of the major axis length and minor axis length of the first electrode active material particle)+(average value of the major axis length and minor axis length of the second electrode active material particle)}] / 2.

[0139] The diameter (b) of the solid electrolyte particle (134) may also be obtained by measuring the major axis length and minor axis length of individual particles and obtaining an average value. Specifically, the major axis length is b 11 and the short axis length is b 12 The diameter of the first solid electrolyte particle is (b 11 +b 12 It can be ) / 2.

[0140] To increase the reliability of the diameter (a) of the solid electrolyte particle (134), an average value can be obtained for two or more solid electrolyte particle diameters. Specifically, the major axis length is b 11 and the short axis length is b 12 For the first solid electrolyte particle, the major axis length is b 21 and the short axis length is b 22For the second solid electrolyte particle, the particle diameter can be calculated using [∑{(average value of the major axis length and minor axis length of the first solid electrolyte particle)+(average value of the major axis length and minor axis length of the second solid electrolyte particle)}] / 2.

[0142] In fact, although the conditions for measuring the major axis length and minor axis length of the above particles are not specifically limited, scanning electron microscopy (SEM) of Carl Zeiss or others can be used to take SEM images of multiple particles at a magnification of 10,000 times, and the major axis length and minor axis length of individual particles can be measured on the SEM images to obtain an average value, and then an average value can be obtained for all particles appearing on the SEM images. That is, the "diameter of the particle" or "size of the particle" can be calculated according to the following mathematical formula.

[0143] [Mathematical Formula A]

[0144] [∑{(average of the major and minor axes of the first particle)+(average of the major and minor axes of the second particle)+… +(average of the major and minor axes of the nth particle)}] / n

[0145] In the above mathematical formula, n is an integer greater than or equal to 1, and its upper limit is not limited, but in the range of 100 or more, the larger the value, the higher the reliability of the "diameter of the particle" or "size of the particle".

[0147] (2nd form)

[0148] Another embodiment provides an all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles represented by the following chemical formula 1, either identically or differently; the solid electrolyte layer comprises solid electrolyte particles represented by the following chemical formula 2; and the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of the following mathematical formula 1.

[0149] [Chemical Formula 1] Li x V 2-y M y (P04)3

[0150] In the above chemical formula 1, M is one or more selected from the group comprising Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr, and Zr; 1≤x≤3; 0≤y<2; and 2≤z<3;

[0151] [Chemical Formula 2] Li 1+y Al y Ti 2-y (PO4)3

[0152] In the above chemical formula 2, 0 <x≤0.6이고;

[0153] [Mathematical Formula 1]

[0154] 0.5≤(b / a)≤2.5

[0156] The above-mentioned second type of all-solid-state battery may be a 'sintered all-solid-state battery,' and the description of the above-mentioned second type of all-solid-state battery may be the same as the description of the first type of all-solid-state battery.

[0158] (Third type of all-solid-state battery)

[0159] Another embodiment provides a sintered all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles that are the same or different from each other; the solid electrolyte layer comprises solid electrolyte particles; and the average diameter (c) of the electrode active material particles and the average diameter (d) of the solid electrolyte particles satisfy the relationship of Equation 1 below.

[0160] [Mathematical Formula 2] 0.5≤(d / c)≤2.5

[0161] The above-described third type of all-solid-state battery is an all-solid-state battery prior to sintering, and unless specifically mentioned otherwise, the diameter (d) of the electrode active material particle and the diameter (d) of the solid electrolyte particle each refer to the diameter 'before sintering'.

[0163] As a result of controlling the diameter (d) of the solid electrolyte particles before sintering to within 0.5 to 2.5 times the diameter (c) of the electrode active material particles before sintering, the interfacial resistance between the solid electrolyte layer and the electrode layer is significantly lowered compared to cases where this range is not satisfied, and the capacity of the sintered all-solid-state battery is significantly increased. This is as described above and is also supported by the evaluation examples described later.

[0165] The relationship between d / c

[0166] As explained above, by making the diameter (d) of the solid electrolyte particles before sintering satisfy the relationship (c) of the electrode active material particles before sintering as shown in Equation 2 below, the increase in interfacial resistance between the solid electrolyte layer and the electrode layer during the sintering process is suppressed, and a sintered all-solid-state battery with a high capacity can finally be obtained:

[0167] [Mathematical Formula 2] 0.5≤(d / c)≤2.5

[0168] Specifically, the lower limit of the above mathematical formula 2 can be controlled to 0.5, 0.7, 0.9, 1.1, or 1.3; and the upper limit can be controlled to 2.5, 2.4, or 2.3.

[0169] Within this range, the diameter (b) of the solid electrolyte particles after sintering and the diameter (a) of the electrode active material particles after sintering can be made to satisfy Equation 1.

[0171] Diameter (c) of electrode active material particles before sintering

[0172] The diameter (c) of the electrode active material particles before sintering may be 0.5 to 5 μm. For example, the diameter (c) of the electrode active material particles before sintering may be 0.5 μm or more, and 5 μm or less, 1.5 μm or less, 1.0 μm or less, 0.8 μm or less, or 0.6 μm or less.

[0174] Diameter (d) of solid electrolyte particles before sintering

[0175] The diameter (d) of the solid electrolyte particles before sintering may be 0.5 to 2 μm. For example, the diameter (d) of the solid electrolyte particles before sintering may be 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, or 0.8 μm or more, and 2 μm or less, 1.8 μm or less, 1.6 μm or less, or 1.4 μm or less.

[0177] Electrode layers (anode layer and cathode layer) before sintering

[0178] The thickness of the above electrode active material layer is not particularly limited, but may be 1.0 to 25 μm based on the pre-sintering standard.

[0180] The above current collector may include copper particles, and the diameter of the copper particles may be 0.5 to 8 μm based on the pre-sintering standard.

[0182] Solid electrolyte layer after sintering

[0184] The thickness of the above solid electrolyte layer is not particularly limited, but may be 1.0 to 35 μm based on the pre-sintering standard.

[0186] Except for the details described above, the description of the first type of sintered all-solid-state battery can be applied in the same way to the second type of all-solid-state battery.

[0188] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0190] Example 1

[0191] (1) Preparation of a solid electrolyte layer

[0192] Li as a solid electrolyte particle with a diameter of 0.8 μm 1.3 Al 0.3 Ti 1.7 A solid electrolyte slurry was prepared by mixing (PO4)3 particles, PVB as a binder, and a 1:1 (v:v) mixed solvent of toluene and ethanol as solvents in a weight ratio of 100:20:150 (solid electrolyte particles:binder:solvent).

[0193] After applying the solid electrolyte slurry onto the PET film, it was dried at a temperature range of 60 to 80°C. The thickness of the dried sheet was 20 μm. Thus, a film-shaped solid electrolyte layer attached to the PET film was formed.

[0194] (2) Preparation and lamination of the electrode layer

[0195] Li3V2(PO4)3 particles with a diameter of 0.6 μm as electrode active material particles, and Li with a diameter of 0.8 μm as solid electrolyte particles 1.3 Al 0.3 Ti 1.7 An electrode paste was prepared by mixing (PO4)3 particles, a carbon conductor as a conductive material, and PVB resin as a binder in a weight ratio of 59:40:1:10 (electrode active material particles: solid electrolyte particles: conductive material: binder).

[0196] Separately, a current collector paste was prepared by mixing copper (Cu) particles with a diameter of 2 μm and PVB resin as a binder in a weight ratio of 100:5 (copper:binder).

[0197] On the side of the solid electrolyte layer where the PET film is not attached, an electrode paste / current collector paste / electrode paste (3 layers) was continuously printed to form a first electrode layer. Specifically, the electrode paste was printed using a screen printing machine, dried at 60 to 80°C, the current collector paste was printed, and finally, the electrode paste was printed. In this way, the electrode paste / current collector paste / electrode paste (3 layers) was continuously printed.

[0198] The solid electrolyte with the electrode layer formed thereon is still attached to the PET film. The electrode paste / current collector paste / electrode paste (three layers) is printed continuously to form a second electrode layer. At this time, the method of forming the second electrode layer is the same as that of the first electrode layer.

[0199] Accordingly, a stacked body was obtained in which the first electrode layer, the solid electrolyte layer, and the second electrode layer were sequentially stacked, and after vacuum packaging in vinyl, ISO compression was performed under conditions of a temperature of 80°C, a pressure of 1000 kgf, and a maintenance time of 30 minutes.

[0200] (3) Cut

[0201] The above-mentioned compressed body was cut to a size of width * length = 10 mm * 10 mm. This can be viewed as the aforementioned second type of all-solid-state battery.

[0202] (4) Plasticization and sintering

[0203] The above-described cut body was plasticized for 42 hours in an air atmosphere of 450 to 500°C. Under the above conditions, all binders can be removed from the plasticized body.

[0204] The above-mentioned plasticized body was heated at a rate of 3 ℃ / min under a weak reducing and nitrogen atmosphere, reached 700 ℃, and then sintered under conditions of 10 hours and 0.5 MPa.

[0205] (5) External electrode formation

[0206] Ag paste was applied to both sides of the above-described sintered body and heat-cured at 150°C. This can be viewed as a sintered all-solid-state battery of the first type described above.

[0208] Examples 2 to 5 and Comparative Examples 1 to 4

[0209] A sintered all-solid-state battery was manufactured in the same manner as Example 1, except that the diameter of the solid electrolyte, the diameter of the electrode active material, and the sintering temperature were changed according to Table 1 below.

[0211] Comparative Example 5

[0212] A sintered all-solid-state battery was manufactured in the same manner as Example 1, except that the composition of the electrode active material was changed according to Table 1 below.

[0214] Comparative Example 6

[0215] A sintered all-solid-state battery was manufactured in the same manner as Example 1, except that the composition of the solid electrolyte was changed according to Table 1 below.

[0217] Comparative Example 7

[0218] According to Table 1 below, the composition of the electrode active material and the composition of the solid electrolyte were changed, and an all-solid-state battery was manufactured by proceeding only up to the cutting process in Example 1.

[0220] Electrode active material particles (raw material) Solid electrolyte particles (raw material) d / c Sintering temperature (°C) furtherance Diameter (c) furtherance Diameter (d) Example 1 Li3V2(PO4)3 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.8 1.3 700 Example 2 Li3V2(PO4)3 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.8 1.3 750 Example 3 Li3V2(PO4)3 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.8 1.3 800 Example 4 Li3V2(PO4)3 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.4 2.3 700 Example 5 Li3V2(PO4)3 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.4 2.3 750 Comparative Example 1 Li3V2(PO4)3 0.4 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.4 3.5 700 Comparative Example 2 Li3V2(PO4)3 0.4 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.4 3.5 750 Comparative Example 3 Li3V2(PO4)3 2.5 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.6 0.2 700 Comparative Example 4 Li3V2(PO4)3 2.5 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.6 0.2 750 Comparative Example 5 Li3V2(PO4)3 0.6 Li2S-P2S5 0.6 1.3 700 Comparative Example 6 LiCoO2 0.6 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 0.8 1.3 700 Comparative Example 7 LiCoO2 0.6 Li2S-P2S5 0.6 1.3 750

[0222] Evaluation Example 1: SEM

[0223] The sintered all-solid-state battery of Example 4 above was cut in the stacking direction, and an SEM image (Fig. 3) was taken of the cut surface at a magnification of 10,000x using a scanning electron microscope from Carl Zeiss.

[0224] For convenience, a dotted line distinguishing the electrode layer and the solid electrolyte layer is shown in Fig. 3.

[0225] In the above SEM image, the major axis length and minor axis length of individual particles constituting each layer can be measured to obtain an average value, and then an average value can be obtained for all particles appearing in the above SEM image. That is, the "diameter of the particle" or "size of the particle" can be calculated according to the following mathematical formula.

[0226] [Mathematical Formula]

[0227] [∑{(average of the major and minor axes of the first particle)+(average of the major and minor axes of the second particle)+… +(average of the major and minor axes of the nth particle)}] / n

[0228] The same operation was performed for all examples and comparative examples as well as Example 4 above, and the results are shown in Table 2 below.

[0230] Electrode active material particles (final) Solid electrolyte particles (final) b / a Sintering temperature (°C) furtherance Diameter (a) furtherance Diameter (b) Example 1 Li3V2(PO4)3 2.8 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 4 1.4 700 Example 2 Li3V2(PO4)3 3.7 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 5 1.4 750 Example 3 Li3V2(PO4)3 4.5 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 6 1.3 800 Example 4 Li3V2(PO4)3 3.7 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 4.5 1.2 700 Example 5 Li3V2(PO4)3 4.5 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 5 1.1 750 Comparative Example 1 Li3V2(PO4)3 1.8 Li 1.3 Al 0.3 Ti3 1.7 (PO4)3 5 2.8 700 Comparative Example 2 Li3V2(PO4)3 1.9 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 6 3.2 750 Comparative Example 3 Li3V2(PO4)3 5.4 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.8 0.3 700 Comparative Example 4 Li3V2(PO4)3 5.9 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 1.2 0.2 750 Comparative Example 5 Li3V2(PO4)3 3.0 Li2S-P2S5 3.2 1.0 700 Comparative Example 6 LiCoO2 2.4 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 3.5 1.4 700 Comparative Example 7 LiCoO2 3.2 Li2S-P2S5 4.8 1.5 750

[0232] In Table 2 above, the diameter (a) of the electrode active material particle after sintering tends to increase as the diameter (c) of the electrode active material particle before sintering increases and as the sintering temperature increases. Additionally, the diameter (b) of the solid electrolyte particle after sintering tends to increase as the diameter (d) of the solid electrolyte particle before sintering increases and as the sintering temperature increases.

[0234] Evaluation Example 2: Interface Resistance and Discharge Capacity

[0235] The sintered all-solid-state batteries of Examples 1 to 5, the sintered all-solid-state batteries of Comparative Examples 1 to 6, and the all-solid-state battery of Comparative Example 7 were evaluated in the following manner, and the results are listed in Table 3 below.

[0236] (1) Electrode layer-solid electrolyte layer interface resistance: 1.6 V, 5 mA (cut-off condition) CC / CV charging and 1.5 V, 0.1 mA CC discharging were repeated 3 times. Afterwards, the voltage drop that occurred when the fully charged cell was discharged at a current of 0.1 mA for 30 minutes was recorded, and the DC-resistance value was calculated using R=V / I (Ohm's law).

[0237] (2) Discharge capacity: 0.1C charging, 0.1C discharge once, 0.33C charging once, and 0.1C charging and 1C discharge once were performed in a constant temperature chamber at 25 ℃, and then 0.33C charging was performed, and then the 0.33C discharge capacity was measured.

[0239] Interface resistance (kΩ) Discharge capacity (μA) Example 1 111 3.4 Example 2 85 4.6 Example 3 62 5.2 Example 4 72 4.8 Example 5 48 6.3 Comparative Example 1 258 0.7 Comparative Example 2 198 1.2 Comparative Example 3 350 0.8 Comparative Example 4 221 0.9 Comparative Example 5 115 2.4 Comparative Example 6 99 3.1 Comparative Example 7 121 4.2

[0241] In Table 3 above, it can be seen that the interfacial resistance of Examples 1 to 5 is significantly lower and the discharge capacity is significantly higher compared to Comparative Examples 1 to 7.

[0242] If the diameter (d) of the solid electrolyte particles before sintering is controlled to be within 0.5 to 2.5 times the diameter (c) of the electrode active material particles before sintering, the interfacial resistance between the solid electrolyte layer and the electrode layer is significantly lowered in preparation for cases where this range is not satisfied, and the capacity of the sintered all-solid-state battery is significantly increased. The diameter (b) of the solid electrolyte particles after sintering is also controlled to be within 0.5 to 2.5 times the diameter (a) of the electrode active material particles after sintering.

[0244] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention. Explanation of the symbols

[0246] 100: All-solid-state battery 112, 114: First and second external electrodes 120: Anode layer 121, 122: Anode active material layer 123: Positive current collector 124: Positive active material particles 130: Solid electrolyte layer 134: Solid electrolyte particles 140: Cathode layer 141, 142: Cathode active material layer 143: Cathode current collector 144: Cathode active material particles 150: Insulating layer 160: Protection layer

Claims

Claim 1 A sintered all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles that are the same or different from each other; wherein the solid electrolyte layer comprises solid electrolyte particles; wherein the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of the following Equation 1, and the electrode active material particles comprise particles represented by the following Chemical Formula 1: [Equation 1] 1.1 ≤ (b / a) ≤ 1.4 [Chemical Formula 1] Li x V 2-y M y (P04)3 In the above chemical formula 1, M is one or more selected from the group including Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr and Zr; 1≤x≤3 and 0≤y<2. Claim 2 delete Claim 3 delete Claim 4 An all-solid-state battery according to claim 1, wherein the diameter (a) of the electrode active material particles is 2 to 10 μm. Claim 5 In claim 1, the solid electrolyte particles comprise particles represented by the following chemical formula 2 in an all-solid-state battery: [Chemical Formula 2]Li 1+y Al y Ti 2-y (PO4)3 in the above chemical formula 2, 0 <y≤0.6이다. Claim 6 An all-solid-state battery according to claim 1, wherein the diameter (b) of the solid electrolyte particles is 2 to 10 μm. Claim 7 A solid-state battery according to claim 1, wherein the positive electrode layer and the negative electrode layer each independently comprise a current collector; and an electrode active material layer located on one or both sides of the current collector and comprising the electrode active material particles. Claim 8 In claim 7, the electrode active material layer further comprises solid electrolyte particles identical or different from the solid electrolyte layer, in an all-solid-state battery. Claim 9 In claim 7, the electrode active material layer comprises the electrode active material particles and the solid electrolyte particles in a weight ratio of 1:9 to 9:1, for an all-solid-state battery. Claim 10 In claim 9, the electrode active material layer further comprises a conductive material in an all-solid-state battery. Claim 11 An all-solid-state battery according to claim 10, wherein, among the total weight of the electrode active material layer, the solid electrolyte particles are included in an amount of 15 to 60 weight%, the conductive material is included in an amount of 1 to 5 weight%, and the electrode active material particles are included as the remainder. Claim 12 In claim 7, an all-solid-state battery having a thickness of 1.0 to 20 μm of the electrode active material layer. Claim 13 In claim 7, the current collector is an all-solid-state battery containing copper particles. Claim 14 In claim 13, an all-solid-state battery in which the diameter of the copper particles is 0.5 to 5 μm. Claim 15 An all-solid-state battery according to claim 1, wherein the thickness of the solid electrolyte layer is 1.0 to 30 μm. Claim 16 In claim 1, the sintered all-solid-state battery is an all-solid-state battery comprising a body including the solid electrolyte layer and the positive electrode layer and the negative electrode layer alternately stacked with the solid electrolyte layer in between. Claim 17 In claim 16, the sintered all-solid-state battery further comprises a first external electrode and a second external electrode disposed on each side of the body. Claim 18 An all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; wherein the positive electrode layer and the negative electrode layer comprise electrode active material particles represented by the following Chemical Formula 1, either identically or differently; wherein the solid electrolyte layer comprises solid electrolyte particles represented by the following Chemical Formula 2; and wherein the average diameter (a) of the electrode active material particles and the average diameter (b) of the solid electrolyte particles satisfy the relationship of the following Chemical Formula 1: [Chemical Formula 1]Li x V 2-y M y (P04)3 In the above Formula 1, M is one or more selected from the group comprising Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr and Zr; 1≤x≤3 and 0≤y<2 and [Formula 2]Li 1+y Al y Ti 2-y (PO4)3 in the above chemical formula 2, 0 <y≤0.6이고;[수학식 1]1.1≤(b / a)≤1.4 Claim 19 In paragraph 18, the above-mentioned all-solid-state battery is an all-solid-state battery that is a sintered all-solid-state battery.

Images