All-solid-state battery having coating comprising layered carbon material and method of making same

Abstract

The present invention relates to an all-solid-state battery having a coating comprising a layered carbon material and a method for manufacturing the same. The all-solid-state battery has improved lifespan characteristics with repetition of charge and discharge cycles because lithium ions are readily diffused into the coating layer during charging.

Description

Technical Field

[0001] The present invention relates to an all-solid-state battery and a method for manufacturing the same, the all-solid-state battery having a coating layer containing a layered carbon material, and more particularly, the present invention relates to an all-solid-state battery having improved life characteristics in charge and discharge cycles due to easy diffusion of lithium ions into the coating layer during charging, and a method for manufacturing the same. Background Art

[0002] Lithium-ion batteries are widely used in various devices that require energy storage. Depending on the application field, they are required to have various battery characteristics such as high energy density, long cycle life, fast charge and discharge, and high / low temperature driving performance.

[0003] Recently, in order to solve the problem of carbon dioxide (CO 2 ) to avoid the use of fossil fuels to address environmental issues caused by the use of electric vehicles (EVs) in the automotive industry. Using currently developed lithium-ion batteries, EVs can travel about 400 km on a single charge, but there are still problems such as instability at high temperatures and fire. To solve these problems, many companies are racing to develop next-generation secondary batteries.

[0004] All-solid-state batteries have attracted much attention as next-generation secondary batteries, all of which include elements formed of solids, and have advantages such as low risk of fire and explosion and high mechanical strength compared to lithium-ion batteries using flammable organic solvents as electrolyte solutions. However, the negative electrode active material layer of the all-solid-state battery is formed by mixing the negative electrode active material and a solid electrolyte configured to ensure ionic conductivity, and the energy density of the above conventional all-solid-state batteries is low compared to lithium-ion batteries because the specific gravity of the solid electrolyte is greater than that of the liquid electrolyte.

[0005] To solve this problem, a type of energy storage-type anode-free all-solid-state battery is currently being studied, that is, the anode is omitted or a small amount of anode active material is used, and lithium is directly deposited on the anode current collector. When lithium ions are not stored in graphite, but deposited on the above-mentioned anode current collector in the form of lithium metal, due to the uneven deposition of lithium and the formation of lithium dendrites, irreversible reactions will gradually increase, thereby greatly reducing the life and durability of the anode-free all-solid-state battery.

[0006] The information contained in this Background of the invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0007] Various aspects of the present invention are directed to an all-solid-state battery having a coating layer including a carbon material on a negative electrode current collector to suppress uneven deposition of lithium and formation of lithium dendrites.

[0008] Here, the proportion, diameter, volume and surface area of ​​the pores can be varied depending on the structure of the carbon material, and the pores provide space for storing lithium ions in the form of lithium metal. Therefore, an object of the present invention is to provide an all-solid-state battery having a coating layer containing a carbon material capable of storing lithium metal during charging and migrating lithium ions to a solid electrolyte during discharging.

[0009] In addition, the various elements included in the all-solid-state battery are formed of solids, so it is more important to control the contact area of ​​the interface between the solid electrolyte and the negative electrode collector than when using a liquid electrolyte. Therefore, the manufacturing process of the all-solid-state battery is accompanied by a process of combining the positive electrode, solid electrolyte and negative electrode by applying high voltage.

[0010] Here, when such pressure applied to a conventional all-solid-state battery is also applied to an all-solid-state battery according to an exemplary embodiment of the present invention, the electrochemical characteristics of the all-solid-state battery may be deteriorated due to the shrinkage of pores included in the carbon material. Therefore, another object of the present invention is to provide a method for manufacturing an all-solid-state battery including a carbon material, applying optimal pressing conditions during the pressing process performed in manufacturing the all-solid-state battery.

[0011] In one aspect, the present invention provides an all-solid-state battery, comprising a negative electrode collector, a coating located on the negative electrode collector and comprising a layered carbon material, a solid electrolyte layer located on the coating, a positive electrode active material layer located on the solid electrolyte layer and comprising a positive electrode active material configured to achieve lithium ion insertion and deinsertion, and a positive electrode collector located on the positive electrode active material layer, wherein the layered carbon material comprises at least one pore.

[0012] In an exemplary embodiment of the present invention, the layered carbon material may include at least one selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and combinations thereof.

[0013] In another exemplary embodiment of the present invention, when the all-solid-state battery is charged, lithium ions may be stored in the form of lithium metal in at least one pore of the coating layer.

[0014] In yet another exemplary embodiment of the present invention, an average diameter D50 of at least one pore may be 30.08 nm to 33.13 nm.

[0015] In yet another exemplary embodiment of the present invention, the total pore volume of the coating may be 0.114 cm 3 g -1Up to 0.141cm 3 g -1 .

[0016] In yet another exemplary embodiment of the present invention, the coating may have a BET surface area of ​​15.03 m 2 g -1 Up to 17.15m 2 g -1 .

[0017] In another exemplary embodiment of the present invention, the difference between the thickness of the coating layer in the charged state of the all-solid-state battery and the thickness of the coating layer in the discharged state of the all-solid-state battery may be 5 μm or more.

[0018] In another exemplary embodiment of the present invention, in the charged state of the all-solid-state battery, the coating may not include sulfur (S), but may include at least one selected from bromine (Br), chlorine (Cl), iodine (I), and combinations thereof.

[0019] In another exemplary embodiment of the present invention, the upper portion of the coating adjacent to the solid electrolyte layer may include lithium (Li) and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof, and the lower portion of the coating adjacent to the negative electrode collector may include carbon (C), lithium (Li) and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof.

[0020] In another aspect, the present invention provides a method for manufacturing an all-solid-state battery, the method comprising preparing a structure configured to stack a negative electrode collector, a coating, a solid electrolyte layer, a positive electrode active material layer and a positive electrode collector in sequence, and applying a processing pressure greater than 50 MPa but less than 200 MPa to the structure, wherein the coating comprises a layered carbon material, and the layered carbon material comprises at least one pore.

[0021] In an exemplary embodiment of the present invention, the layered carbon material may include at least one selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and combinations thereof.

[0022] In another exemplary embodiment of the present invention, when the all-solid-state battery is charged, lithium ions may be stored in the form of lithium metal in at least one pore of the coating layer.

[0023] In yet another exemplary embodiment of the present invention, an average diameter D50 of at least one pore may be 30.08 nm to 33.13 nm.

[0024] In yet another exemplary embodiment of the present invention, the total pore volume of the coating may be 0.114 cm 3 g-1 Up to 0.141cm 3 g -1 .

[0025] In yet another exemplary embodiment of the present invention, the BET surface area of ​​the coating may be 15.03 m 2 g -1 Up to 17.15m 2 g -1 .

[0026] In another exemplary embodiment of the present invention, the difference between the thickness of the coating layer in the charged state of the all-solid-state battery and the thickness of the coating layer in the discharged state of the all-solid-state battery may be 5 μm or more.

[0027] In another exemplary embodiment of the present invention, in the charged state of the all-solid-state battery, the coating may not include sulfur (S), but may include at least one selected from bromine (Br), chlorine (Cl), iodine (I), and combinations thereof.

[0028] In another exemplary embodiment of the present invention, the upper portion of the coating adjacent to the solid electrolyte layer may include lithium (Li) and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof, and the lower portion of the coating adjacent to the negative electrode collector may include carbon (C), lithium (Li) and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof.

[0029] Other aspects and exemplary embodiments of the invention are discussed below.

[0030] The above features and other features of the present invention are discussed below.

[0031] Other features and advantages of the method and apparatus of the present invention will become apparent or be described in more detail by the accompanying drawings incorporated herein and the following detailed description which, together with the accompanying drawings, serve to illustrate certain principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A shows a cross-sectional view of an all-solid-state battery in a discharged state according to an exemplary embodiment of the present invention;

[0033] Figure 1B shows a cross-sectional view of an all-solid-state battery in a charged state according to an exemplary embodiment of the present invention;

[0034] Figure 2 shows a scanning electron microscope (SEM) image of a half-cell manufactured according to an exemplary embodiment of the present invention in an uncharged state;

[0035] Figure 3Ashows a voltage curve graph of a half-cell manufactured according to an exemplary embodiment of the present invention in the first cycle;

[0036] Figure 3B , Figure 3C and Figure 3D The voltage curves of the half-cells manufactured according to Comparative Examples 1 to 3 in the first cycle are shown respectively;

[0037] Figure 4A A graph showing the coulombic efficiency and capacity of a half-cell manufactured according to an exemplary embodiment of the present invention as a function of repetition of charge and discharge cycles;

[0038] Figure 4B and Figure 4C Graphs showing the coulombic efficiency and capacity of half-cells manufactured according to Comparative Examples 1 and 2, respectively, as charge and discharge cycles are repeated;

[0039] Figure 5A A graph showing the results of analysis of the BET surface area, total pore volume, and average pore size of a coating included in a half-cell manufactured according to an exemplary embodiment of the present invention;

[0040] Figure 5B , Figure 5C and Figure 5D Graphs showing the analysis results of the BET surface area, the total pore volume, and the average pore size of each coating layer included in the half-cells manufactured according to Comparative Examples 1 to 3, respectively;

[0041] Figure 6 shows a pore distribution diagram of a half-cell according to an embodiment and a comparative embodiment;

[0042] Fig. 7A , Figure 7B , Figure 7C , Fig.7D and Fig. 7E 10 respectively show a SEM image and an energy dispersive X-ray spectroscopy (EDS) image of a half-cell manufactured according to Comparative Example 1;

[0043] Fig. 8A , Figure 8B , Figure 8C , Fig.8D and Fig. 8E The SEM image and EDS image of the half-cell manufactured according to Example 1 are shown respectively;

[0044] Fig.9A , Fig. 9B , Fig. 9C , Fig.9D and Fig.9E 10 show a SEM image and an EDS image of a half-cell manufactured according to Comparative Example 2, respectively; and

[0045] Fig.10 A SEM image of a half-cell fabricated according to Comparative Example 3 is shown.

[0046] It should be understood that the accompanying drawings are not necessarily drawn to scale, and they show various exemplary features of the basic principles of the invention that are simplified to some extent. The specific design features of the application disclosed herein (including, for example, specific dimensions, directions, locations, and shapes) will be determined in part by the specific target application and the environment of use.

[0047] In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0048] Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. Although the present invention will be described in conjunction with exemplary embodiments of the present invention, it should be understood that this specification is not intended to limit the present invention to those exemplary embodiments of the present invention. On the other hand, the present invention is intended to cover not only the exemplary embodiments of the present invention, but also various alternatives, variants, equivalents and other embodiments that may be included within the spirit and scope of the present invention.

[0049] The above-mentioned purpose, other purposes, advantages and features of the present invention will become apparent from the following description of the embodiments provided with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments included herein, but can be implemented in various different forms. The exemplary embodiments provided are intended to make the description of the present invention more thorough and to fully convey the scope of the present invention to those skilled in the art.

[0050] In the accompanying drawings, the same or similar elements are represented by the same reference numerals, even if they are described in different drawings. In the accompanying drawings, for the sake of clarity, the size of the structure may be enlarged than the actual size. In the following description of the embodiment, terms such as "first" and "second" can be used to describe various elements, but do not limit these elements. These terms are only used to distinguish one element from another element. For example, without departing from the scope and spirit of the present invention, the first element can be referred to as the second element, and similarly, the second element can also be referred to as the first element. Singular expressions can include plural expressions unless they have significantly different meanings in the context.

[0051] In the following description of the embodiments, terms such as "comprises", "includes", "having" are interpreted as indicating the presence of the features, values, steps, operations, elements, or parts or combinations thereof described in the description, and do not exclude the presence or possible addition of one or more other features, values, steps, operations, elements, parts or combinations thereof. In addition, it will be understood that when a component such as a layer, film, region or plate is referred to as being "above" another component, the component may be directly above the other component, or other components may be inserted between the two components. In the same manner, it will be understood that when a component such as a layer, film, region or plate is referred to as being "below" another component, the component may be directly below the other component, or other components may be inserted between the two components.

[0052] Unless otherwise stated, all numbers, values ​​and / or expressions used in the description to indicate the amount of components, reaction conditions, polymer compositions and blends are approximate values, which reflect the uncertainty of various measurements when these values ​​are obtained from essentially different things, and therefore should be understood as being modified by the term "about". In addition, it will be understood that if a numerical range is disclosed in the description, unless otherwise stated, the range includes all continuous values ​​from the minimum value to the maximum value of the range. In addition, if the range refers to an integer, unless otherwise stated, the range includes all integers from the minimum integer to the maximum integer.

[0053] In the following description of the embodiments, it will be understood that when a variable range is recorded, the variable includes all values ​​within the range, including the endpoints of the range. For example, it will be understood that the range of "5 to 10" includes not only the values ​​of 5, 6, 7, 8, 9 and 10, but also any sub-ranges, such as the sub-range of 6 to 10, the sub-range of 7 to 10, the sub-range of 6 to 9 and the sub-range of 7 to 9, and any values ​​between the valid integers in the range, such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9. In addition, for example, it will be understood that the range of "10% to 30%" includes not only all integers containing the values ​​of 10%, 11%, 12%, 13% ... 30%, but also any sub-ranges, such as the sub-range of 10% to 15%, the sub-range of 12% to 18% and the sub-range of 20% to 30%, and any values ​​between the valid integers in the range, such as 10.5%, 15.5% and 25.5%.

[0054] All-solid-state battery having a coating comprising a layered carbon material.

[0055] Figure 1A and Figure 1BThe all-solid-state battery according to an exemplary embodiment of the present invention is schematically shown in a discharge state and a charge state, respectively. Referring to these figures, the all-solid-state battery in a discharge state may include a negative electrode collector 11, a coating 12 located on the negative electrode collector 11 and including a layered carbon material, a solid electrolyte layer 30 located on the coating 12, a positive electrode active material layer 22 located on the solid electrolyte layer 30 and including a positive electrode active material configured to achieve lithium ion insertion and extraction, and a positive electrode collector 21 located on the positive electrode active material layer 22. Here, the layered carbon material may include at least one pore.

[0056] The negative electrode current collector 11 may be a plate-like substrate having conductivity. Specifically, the negative electrode current collector 11 may be provided in the form of a sheet, a film, or a foil. The negative electrode current collector 11 may be a high-density metal film having a porosity of less than about 1%. In addition, the thickness of the negative electrode current collector 11 may be 1 μm to 20 μm or 5 μm to 15 μm.

[0057] The negative electrode collector 11 may include a material that does not react with lithium. Specifically, the negative electrode collector 11 may include at least one selected from the group consisting of Ni, Cu, stainless steel (SUS), and a combination thereof.

[0058] The layered carbon material included in the coating 12 may include pores between one carbon material layer and another carbon material layer adjacent thereto. According to an exemplary embodiment of the present invention, the average pore size, total pore volume, and BET surface area of ​​the coating 12 using the layered carbon material may be increased compared to using the spherical carbon material. Therefore, a large amount of lithium can be stored.

[0059] The solid electrolyte layer 30 is located between the coating layer 12 and the positive electrode active material layer 22 and is responsible for the migration of lithium ions.

[0060] The solid electrolyte layer 30 may include a solid electrolyte having lithium ion conductivity.

[0061] The solid electrolyte may include at least one selected from an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer electrolyte, and a combination thereof. Preferably, a sulfide-based solid electrolyte having high lithium ion conductivity may be used.

[0062] The sulfide-based solid electrolyte may have an argyrodite-type crystal structure. The sulfide-based solid electrolyte having an argyrodite-type crystal structure may be represented by Li 6 PS 5 X (X is Cl, Br or I), and may include a selected from Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 6 PS5 At least one of I and a combination thereof.

[0063] Sulfide-based solid electrolytes can be 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, 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, M is one of P, Si, Ge, B, Al, Ga and In), Li 10 G 2 S 12 etc., but not limited to specific materials.

[0064] Oxide-based solid electrolytes may include perovskite-type LLTO (Li 3x La 2 / 3-x TiO 3 ), phosphate-based NASICON-type LATP (Li 1+x Al x Ti 2-x (PO 4 ) 3 )wait.

[0065] The polymer electrolyte may include a gel polymer electrolyte, a solid polymer electrolyte, and the like.

[0066] The solid electrolyte layer 30 may further include a binder, and the binder may include butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), and the like.

[0067] The positive electrode collector 21 may be a plate-shaped substrate having conductivity. Specifically, the positive electrode collector 21 may be provided in the form of a sheet or a film. The positive electrode collector 21 may include at least one selected from indium (In), copper (Cu), magnesium (Mg), aluminum (Al), stainless steel, iron, and combinations thereof. Specifically, the positive electrode collector 21 may include aluminum foil.

[0068] The positive electrode active material layer 22 may be configured to reversibly intercalate and deintercalate lithium ions therein, and may include a positive electrode active material, a conductive material, a binder, etc. In addition, a solid electrolyte may be partially mixed with the positive electrode active material layer 22 .

[0069] The positive electrode active material may be an oxide active material or a sulfide active material.

[0070] The oxide active material can be a rock salt layer type active material, such as LiCoO 2 、LiMnO 2 、LiNiO 2 、LiVO 2 or Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 ; Spinel active materials, such as LiMn 2 O 4 Or Li(Ni 0.5 Mn1.5 )O 4 ; Spinel - type active materials, such as LiNiVO 4 or LiCoVO 4 ; Olivine - type active materials, such as LiFePO 4 , LiMnPO 4 , LiCoPO 4 or LiNiPO 4 ; Silicon - containing active materials, such as Li 2 FeSiO 4 or Li 2 MnSiO 4 ; Rock - salt - type active materials in which part of the transition metals are replaced by different metals, such as LiNi 0.8 Co (0.2-x) Al x O 2 (0 < x < 0.2), Spinel - type active materials in which part of the transition metals are replaced by different metals, such as Li 1+x Mn 2-x-y M y O 4 (M is at least one selected from Al, Mg, Co, Fe, Ni, and Zn, 0 < x + y < 2); Lithium titanate, such as Li 4 Ti 5 O 12 .

[0071] Sulfide active materials can be Chevrel copper, iron sulfide, cobalt sulfide, nickel sulfide, etc.

[0072] The solid electrolyte mixed with the positive - electrode active - material layer 22 can be substantially the same as the solid electrolyte included in the solid - electrolyte layer 30.

[0073] The conductive material can be carbon black, conductive graphite, acetylene black, carbon fiber, graphene, etc.

[0074] The binder can include butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), etc.

[0075] In an exemplary embodiment of the present invention, the layered carbon material can include at least one selected from graphene, graphene oxide, reduced graphene oxide, carbon nanotubes (CNT), and combinations thereof.

[0076] Graphene is a material in which carbon atoms are located at the vertices of a hexagonal lattice to form a two-dimensional plane. It is a representative layered carbon material. Carbon nanotubes (CNTs) are tubes formed by rolling up graphene, with a diameter of nanometers, that is, a few nanometers to tens of nanometers. According to the number of carbon nanotube walls, carbon nanotubes (CNTs) can be divided into single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanotube ropes.

[0077] refer to Figure 1B , when the all-solid-state battery is charged, lithium ions can be stored in the pores of the coating 12 ′ in the form of lithium metal.

[0078] When the all-solid-state battery is charged, lithium ions are extracted from the positive electrode active material layer 22, and the lithium ions can migrate to the negative electrode collector 11 through the solid electrolyte layer 30. The lithium ions reaching the coating layer 12' can migrate to the inside of the coating layer 12' by diffusion. Specifically, the diffusion can be diffusion creep.

[0079] Creep is the continuous deformation of a material over time when a stress of yield strength or less is applied to the material. Creep due to diffusion as atoms and pores in a material exchange positions is called diffusion creep.

[0080] Diffusion creep can be divided into Nabarro-Herring creep (atoms move along the interior of grains) and Coble creep (atoms move along boundaries such as grain boundaries, interfaces and surfaces).

[0081] During the charge and discharge process, the yield strength or less operating pressure may be applied to the all-solid-state battery according to the exemplary embodiment of the present invention. Therefore, the lithium ions adjacent to the solid electrolyte layer 30 and the coating 12' may move to the inside of the coating 12' by diffusion creep. Depending on the position of the lithium ions, the lithium ions may diffuse to the inside of the coating 12' by Nabarro-Herring creep and Coble creep.

[0082] Lithium ions can preferentially move into the pores of layered carbon materials through Coble creep and be stored as lithium metal. Compared with Nabarro-Herring creep, Coble creep occurs at low temperatures and can therefore be beneficial for low-temperature driving of all-solid-state batteries.

[0083] In an exemplary embodiment of the present invention, in a charged state of the all-solid-state battery, the coating layer 12 ′ may not include sulfur (S), and may include at least one selected from bromine (Br), chlorine (Cl), iodine (I), and combinations thereof.

[0084] Specifically, the upper portion of the coating 12' adjacent to the solid electrolyte layer 30 may include lithium (Li); and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof, while the lower portion of the coating 12' adjacent to the negative electrode collector 11 may include carbon (C); lithium (Li); and at least one selected from bromine (Br), chlorine (Cl), iodine (I) and a combination thereof.

[0085] In the charged state of the all-solid-state battery, carbon (C) or lithium (Li) included in the coating 12' may react with bromine (Br), chlorine (Cl) and iodine (I) to form a composite material, but does not react with sulfur (S) to form a composite material.

[0086] In an exemplary embodiment of the present invention, the average diameter D50 of the pores may be 30.08 nm to 33.13 nm. When the average diameter D50 of the pores is less than 30.08 nm, the space configured to receive and store lithium ions in the form of lithium metal in the coating layer 12 may be insufficient.

[0087] When the average diameter D50 of the pores exceeds 33.13 nm, lithium ions may be deposited and stored between the coating 12 and the negative electrode collector 11 instead of in the coating 12. When lithium ions are deposited between the coating 12 and the negative electrode collector 11, lithium may be unevenly deposited or lithium dendrites may be formed due to repetition of charge and discharge cycles, and irreversible reactions gradually increase, which may reduce the life characteristics of the all-solid-state battery.

[0088] In an exemplary embodiment of the present invention, the total pore volume of the coating 12 may be 0.114 cm 3 g -1 Specifically, the total pore volume of the coating 12 may be 0.114 cm 3 g -1 Up to 0.141cm 3 g -1 .

[0089] When the total pore volume of the coating 12 is less than 0.114 cm 3 g -1 When the coating 12 is filled with lithium ions, the space configured to receive and store lithium ions in the form of lithium metal may be insufficient, and thus the capacity of the all-solid-state battery may be reduced.

[0090] Furthermore, lithium ions that are not stored in the coating layer 12 may be deposited between the coating layer 12 and the solid electrolyte layer 30 , and thus the life characteristics of the all-solid-state battery may be degraded.

[0091] In an exemplary embodiment of the present invention, the BET surface area of ​​the coating 12 may be 15.03 m 2 g -1Specifically, the BET surface area of ​​the coating 12 may be 115.03 m 2 g -1 Up to 17.15m 2 g -1 .

[0092] When the BET surface area of ​​the coating 12 is less than 15.03 m 2 g -1 When the coating 12 is filled with lithium ions, the pores configured to receive and store lithium ions in the form of lithium metal may be insufficient, and thus the capacity of the all-solid-state battery may be reduced.

[0093] Furthermore, lithium ions that are not stored in the coating layer 12 may be deposited between the coating layer 12 and the solid electrolyte layer 30 , and thus the life characteristics of the all-solid-state battery may be degraded.

[0094] In an exemplary embodiment of the present invention, the thickness of the coating 12 may be 10 μm to 30 μm in the discharge state of the all-solid-state battery. When the thickness of the coating 12 is less than 10 μm in the discharge state of the all-solid-state battery, it is difficult to store a sufficient amount of lithium, and when the thickness of the coating 12 exceeds 30 μm in the discharge state of the all-solid-state battery, the energy density of the all-solid-state battery may be reduced.

[0095] In an exemplary embodiment of the present invention, the difference between the thickness of the coating 12' in the charged state of the all-solid-state battery and the thickness of the coating 12 in the discharged state of the all-solid-state battery may be 5 μm or more. The upper limit of the difference between the thickness of the coating 12' and the thickness of the coating 12 is not limited to a specific value, and for example, may be 30 μm or less, 20 μm or less, or 10 μm or less.

[0096] When the difference between the thickness of the coating 12' in the all-solid-state battery in the charged state and the thickness of the coating 12 in the all-solid-state battery in the discharged state is less than 5 μm, it can be determined that a sufficient amount of lithium metal is not stored in the coating 12. In addition, it can also be determined that the lithium not stored in the coating 12 is deposited between the coating 12 and the negative electrode collector 11, or a separate lithium metal layer is formed between the coating 12 and the solid electrolyte layer 30.

[0097] A method for making an all-solid-state battery having a coating layer comprising a layered carbon material.

[0098] The method for manufacturing an all-solid-state battery according to an exemplary embodiment of the present invention may include preparing a structure in which a negative electrode collector 11, a coating layer 12, a solid electrolyte layer 30, a positive electrode active material layer 22, and a positive electrode collector 21 are sequentially stacked, and pressing the structure.

[0099] The processing pressure for pressing the structure may be greater than 50 MPa, but less than 200 MPa. The processing pressure may preferably be 85 MPa to 150 MPa, and may more preferably be about 100 MPa.

[0100] The manufacturing method of the all-solid-state battery is accompanied by a process of bonding the negative electrode, the solid electrolyte and the positive electrode together by applying high pressure (hereinafter referred to as "processing pressure"). Generally, a processing pressure of 500 MPa or more is applied to the stacked structure. When the same processing pressure as the conventionally applied processing pressure is applied to the all-solid-state battery according to the exemplary embodiment of the invention, the electrochemical characteristics and life characteristics of the all-solid-state battery may be reduced due to the reduction of pores included in the layered carbon material.

[0101] When the processing pressure is 50 MPa or less, the adhesion between the solid electrolyte layer 30 and the coating layer 12 may be reduced, and the interface resistance may be increased, so that the electrochemical characteristics and life characteristics of the all-solid-state battery may be reduced.

[0102] When the processing pressure is in the range of 85 MPa to 150 MPa, the electrochemical characteristics and life characteristics of the all-solid-state battery can be improved, especially when the processing pressure is about 100 MPa, the electrochemical characteristics and life characteristics of the all-solid-state battery can be greatly improved.

[0103] During the charge and discharge process of an all-solid-state battery, heat loss of electrical energy may occur due to the interface resistance between the layers of the all-solid-state battery. Therefore, the charge and discharge voltage of the all-solid-state battery should be higher than the voltage calculated by thermodynamics. The difference between the voltage required in theory and the voltage required for actual driving is called overvoltage. The closer the overvoltage is to zero, the smaller the difference between the theoretical driving voltage and the actual driving voltage of the all-solid-state battery will be, and the efficiency of the all-solid-state battery may increase.

[0104] When the processing pressure is 50 MPa or less, the interface resistance between the solid electrolyte layer 30 and the coating layer 12 may increase, the overvoltage may increase, and the efficiency of the all-solid-state battery may decrease.

[0105] When the processing pressure is 200 MPa or more, excessive pressure is applied to the coating 12, so that the pore volume, pore size, and BET surface area of ​​the coating 12 may be reduced. That is, the pores formed in the coating 12 may be insufficient. Therefore, the capacity of the all-solid-state battery may be reduced.

[0106] The present invention will be described in more detail below by the following examples and comparative examples. The following examples and comparative examples are only used to exemplarily describe the present invention and are not intended to limit the scope and spirit of the present invention.

[0107] Manufacturing Example 1. Manufacturing of negative electrode

[0108] The prepared graphene is used as a layered carbon material, polyvinylidene fluoride (PVDF) is used as a binder, and is placed in N-methyl-2-pyrrolidone (NMP) as a solvent to make a slurry. The slurry is applied to a nickel film as a negative electrode collector, and then the slurry is dried to form a coating 12. A negative electrode including a negative electrode collector and a coating 12 is obtained by the above method.

[0109] Manufacturing Example 2. Manufacturing of solid electrolyte

[0110] The raw materials are mixed with lithium sulfide (Li 2 S) powder (produced by Sigma-Aldrich), phosphorus pentasulfide (P 2 S 5 ) powder (produced by Sigma-Aldrich), lithium chloride (LiCl) powder (produced by Sigma-Aldrich) and lithium bromide (LiBr) powder. A precursor solution was prepared by dissolving the raw materials in acetonitrile as a solvent. The precursor solution was stirred at room temperature (25° C.) until all the raw materials were dissolved in the solvent.

[0111] The solvent was completely removed by vacuum drying the precursor solution at a temperature of about 200° C. for about 12 hours. A precursor powder was thereby obtained. The precursor powder was heat-treated at a temperature of about 550° C. for about 5 hours to obtain a sulfide-based solid electrolyte having an argyrodite-type crystal structure including Br and Cl.

[0112] Example 1

[0113] A half-cell was manufactured, the half-cell including the negative electrode manufactured according to Manufacturing Example 1 and the solid electrolyte manufactured according to Manufacturing Example 2. The manufacturing method of the half-cell was as follows.

[0114] A solid electrolyte layer was manufactured, the solid electrolyte layer being formed of the sulfide-based solid electrolyte according to Manufacturing Example 2 and having a specified size and thickness.

[0115] The negative electrode according to Manufacturing Example 1 was placed on one surface of the solid electrolyte layer and pressed on the surface of the solid electrolyte layer by applying a processing pressure of 100 MPa thereto. A half-cell was prepared by adhering a lithium foil (produced by Honjo Chemical Co., Ltd.) having a thickness of 200 μm to the other surface of the solid electrolyte layer. An operating pressure of 5 MPa was applied to the half-cell by a spring.

[0116] Comparative Example 1

[0117] The half-cell was manufactured in the same manner as in Example 1, except that the processing pressure applied to the solid electrolyte and the negative electrode was adjusted to 50 MPa.

[0118] Comparative Example 2

[0119] The half-cell was manufactured in the same manner as in Example 1, except that the processing pressure applied to the solid electrolyte and the negative electrode was adjusted to 200 MPa.

[0120] Comparative Example 3

[0121] The half-cell was manufactured in the same manner as in Example 1, except that the processing pressure applied to the solid electrolyte and the negative electrode was adjusted to 400 MPa.

[0122] Test Example 1: SEM analysis before charging

[0123] Figure 2 is a scanning electron microscope (SEM) image of a half-cell in an uncharged state manufactured according to Example 1. Prior to SEM, the negative electrode current collector was removed.

[0124] refer to Figure 2 , a coating layer 12 including a layered carbon material is formed on the solid electrolyte layer 30, and the thickness of the coating layer 12 is about 10 μm.

[0125] Test Example 2: Voltage Curve and Life Characteristics

[0126] Under the predetermined conditions (i.e., operating temperature of 30°C, current density of 0.666 mA·cm -2 , deposition capacity is 2.0 mAh cm -2 ) When the charge and discharge cycles were repeated, the voltage curves and life characteristics of the half-cells manufactured according to Example 1 and Comparative Examples 1 to 3 were evaluated.

[0127] Figure 3A is a graph showing the voltage curve of the half-cell manufactured according to Example 1 in the first cycle. Figure 3B , Figure 3C and Figure 3D is a graph showing voltage curves of half cells manufactured according to Comparative Examples 1 to 3 in the first cycle.

[0128] refer to Figure 3A , Figure 3B , Figure 3C and Figure 3D , the half-cell manufactured according to Example 1 by applying a processing pressure of 100 MPa showed the lowest overvoltage.

[0129] Furthermore, the overvoltage of the half-cell manufactured by applying a processing pressure of 400 MPa according to Comparative Example 3 could not be normally measured due to the short circuit.

[0130] Figure 4Ais a graph showing the coulombic efficiency and capacity of a half-cell manufactured according to an exemplary embodiment of the present invention as the charge and discharge cycles are repeated. Figure 4B and Figure 4C is a graph showing changes in coulombic efficiency and capacity with repetition of charge and discharge cycles of half-cells manufactured according to Comparative Examples 1 and 2. In the case of the half-cell according to Comparative Example 3, the charge and discharge cycles could not be repeated due to short circuit.

[0131] refer to Figure 4A , Figure 4B and Figure 4C , according to Example 1, the half-cell manufactured by applying a processing pressure of 100 MPa exhibited uniform coulombic efficiency and life characteristics, and the cycle life of the half-cell was 75 cycles.

[0132] The coulombic efficiency and life characteristics of the half-cell manufactured according to Comparative Example 1 dropped sharply from about the 20th cycle, and the cycle life of the half-cell was 36 cycles. The coulombic efficiency and life characteristics of the half-cell manufactured according to Comparative Example 2 deviated from the charge and discharge cycles, and the cycle life of the half-cell was 35 cycles.

[0133] Test Example 3: Measurement of Porosity

[0134] The BET surface area, total pore volume, and average pore size of the coating 12 included in the half-cells manufactured according to Example 1 and Comparative Examples 1 to 3 were analyzed and are shown in FIG. Figure 5A , Figure 5B , Figure 5C and Figure 5D , and are listed in Table 1. Figure 6 The pore distribution of the half cells manufactured according to Example 1 and Comparative Examples 1 to 3 is shown. Here, the BET surface area, total pore volume and average pore size were measured using the BET method, and the pore distribution was measured using the Barrett-Joyner-Halenda (BJH) method.

[0135] [Table 1]

[0136]

[0137] As shown in Table 1, it can be seen that as the processing pressure applied during the half-cell manufacturing process increases, all BET surface areas, total pore volumes, and average pore sizes of the coatings included in the half-cell decrease.

[0138] In addition, reference Figure 6, it can be confirmed that during the fabrication of the half-cell, when the applied processing pressure increases, the proportion of pores with a size less than 20 nm is uniform, but the proportion of pores with a size of 20 nm or more decreases with increasing processing pressure.

[0139] Test Example 5: SEM and EDS measurement results in a fully charged state

[0140] SEM images and energy dispersive X-ray spectroscopy (EDS) images of the half-cells manufactured according to Example 1 and Comparative Examples 1 to 3 were obtained to confirm that the storage position of lithium depends on the pressing conditions. Here, the SEM images and EDS images were obtained by tilting the side portions of each electrode at a specified angle.

[0141] Fig. 7A is a SEM image of a half-cell manufactured according to Comparative Example 1. FIG. 7B to FIG. 7E They are respectively EDS images of carbon (C), sulfur (S), bromine (Br), and chlorine (Cl) included in the half-cell manufactured according to Comparative Example 1. Here, the images are obtained after the solid electrolyte layer 30 located on the coating layer 12 is removed.

[0142] refer to Fig. 7A , it was confirmed that the thickness of the coating 12 was about 10 μm and the thickness of the lithium metal layer was about 8 μm, and the lithium metal layer was observed to be located between the negative electrode current collector 11 and the coating 12. Bromine (Br) and chlorine (Cl) were detected from the lithium metal layer. It is predicted that the lithium metal layer is formed between the coating 12 and the negative electrode current collector 11, rather than in the coating 12, as shown in FIG. 7A to 7E As shown, the reason is that when the half-cell is manufactured under relatively low pressure conditions according to Comparative Example 1, lithium easily penetrates into the coating layer 12 with a relatively high porosity.

[0143] Furthermore, it is predicted that the detection of sulfur (S) on the surface of the coating layer 12 is due to the sulfur (S) remaining on the surface of the coating layer 12 after the solid electrolyte layer 30 is removed from the coating layer 12 .

[0144] Fig. 8A is a SEM image of a half-cell manufactured according to Example 1. FIG. 8B to FIG. 8E They are respectively EDS images of carbon (C), sulfur (S), bromine (Br), and chlorine (Cl) included in the half-cell manufactured according to Example 1. Here, the SEM and EDS images are obtained after removing the negative electrode collector.

[0145] refer to Fig. 8A It was confirmed that the thickness of the coating 12' was about 20 μm, and no Fig. 7AA separate lithium metal layer different from the coating layer 12' is shown in FIG. Bromine (Br) and chlorine (Cl) were detected from the coating layer 12', but sulfur (S) was not detected, confirming that lithium was uniformly stored in the coating layer 12'.

[0146] The reason for these results is that lithium included in the coating layer 12' reacts with bromine (Br) and chlorine (Cl) to form a composite material, but does not react with sulfur (S) and thus does not form a composite material.

[0147] In addition, bromine (Br) and chlorine (Cl) were observed in the upper portion of the coating 12' adjacent to the solid electrolyte layer 30, but carbon (C) and sulfur (S) were not observed; carbon (C), bromine (Br) and chlorine (Cl) were observed on the surface of the coating 12' adjacent to the negative electrode collector 11 (i.e., the lower portion of the coating 12'), but sulfur (S) was not observed.

[0148] Fig.9A is a SEM image of a half-cell manufactured according to Comparative Example 2. FIG. 9B to FIG. 9E 1 and 2 are EDS images of carbon (C), sulfur (S), bromine (Br), and chlorine (Cl) included in the half-cell manufactured according to Comparative Example 2, respectively.

[0149] refer to Fig.9A , it was confirmed that the thickness of the coating 12 was about 14 μm and the thickness of the lithium metal layer separated from the coating 12 was about 25 μm, and the lithium metal layer was observed to be located between the coating 12 and the solid electrolyte layer 30. Bromine (Br) and chlorine (Cl) were detected from the lithium metal layer, but sulfur (S) was not detected from the lithium metal layer. In addition, it was also confirmed that bromine (Br) and chlorine (Cl) were not detected from the coating 12.

[0150] It is expected that the lithium metal layer is formed between the coating layer 12 and the solid electrolyte layer body 30, rather than being formed in the coating layer 12, as shown in FIG. 9A to 9E As shown, the reason is that when the half-cell is manufactured under relatively high pressure conditions according to Comparative Example 2, it is difficult for lithium to penetrate into the coating layer 12 with a lower porosity.

[0151] Fig.10 is a SEM image of a half-cell manufactured according to Comparative Example 3. Here, the SEM image is obtained after removing the negative electrode collector.

[0152] refer to Fig.10 , the coating is completely integrated with the solid electrolyte layer, so it is difficult to observe the coating and the solid electrolyte layer separately. In the SEM image, only the boundary where the coating is buried in the electrolyte layer can be observed.

[0153] As apparent from the above description, the present invention provides an all-solid-state battery having improved lifespan characteristics by including a coating layer of a layered carbon material including at least one pore.

[0154] In addition, the all-solid-state battery is manufactured by pressing the negative electrode, solid electrolyte and positive electrode within a pressure range of greater than 50MPa but less than 200MPa, which can have improved life characteristics and reduce overvoltage during the charge and discharge process of the all-solid-state battery.

[0155] In this specification, a singular expression includes a plural expression unless the context clearly indicates otherwise.

[0156] In an exemplary embodiment of the present invention, it should be understood that terms such as "include" or "have" are intended to specify the presence of features, numbers, steps, operations, elements, parts, or a combination thereof described in the specification, but do not exclude the possibility of adding or existing one or more other features, numbers, steps, operations, elements, parts, or a combination thereof.

[0157] The foregoing descriptions of specific exemplary embodiments of the present invention are presented for purposes of illustration and description. These descriptions are not intended to be exhaustive or to limit the invention to the precise form disclosed, and it is apparent that many variations and modifications are possible in light of the above teachings. The exemplary embodiments are selected and described in order to explain the specific principles of the invention and its practical application, so that other persons skilled in the art can realize and utilize the various exemplary embodiments of the present disclosure and its different selected forms and modified forms.

Claims

1. An all-solid-state battery, comprising: A negative electrode current collector; a coating layer on the negative electrode current collector and comprising a layered carbon material; a solid electrolyte layer disposed on the coating; a positive electrode active material layer disposed on the solid electrolyte layer and comprising a positive electrode active material configured to enable intercalation and deintercalation of lithium ions; and a positive electrode current collector located on the positive electrode active material layer, Wherein, the layered carbon material includes at least one pore.

2. The all-solid-state battery according to claim 1, wherein: The layered carbon material includes at least one selected from graphene, graphene oxide, reduced graphene oxide, carbon nanotubes and combinations thereof.

3. The all-solid-state battery according to claim 1, wherein: When the all-solid-state battery is in a charged state, lithium ions are stored in the form of lithium metal in at least one pore of the coating.

4. The all-solid-state battery according to claim 1, wherein: The average diameter D50 of the at least one pore is 30.08 nm to 33.13 nm.

5. The all-solid-state battery according to claim 1, wherein: The total pore volume of the coating is 0.114 cm 3 g -1 Up to 0.141cm 3 g -1 .

6. The all-solid-state battery according to claim 1, wherein: The Brewer-Emmett-Teller surface area of ​​the coating is 15.03 m 2 g -1 Up to 17.15m 2 g -1 .

7. The all-solid-state battery according to claim 1, wherein: The difference between the thickness of the coating of the all-solid-state battery in a charged state and the thickness of the coating of the all-solid-state battery in a discharged state is equal to or greater than 5 μm.

8. The all-solid-state battery according to claim 1, wherein: In the charged state of the all-solid-state battery, the coating does not include sulfur but includes at least one selected from bromine, chlorine, iodine and combinations thereof.

9. The all-solid-state battery according to claim 8, in, an upper portion of the coating layer adjacent to the solid electrolyte layer comprises lithium and at least one selected from bromine, chlorine, iodine, and combinations thereof, and The lower portion of the coating layer adjacent to the negative electrode current collector includes carbon, lithium, and at least one selected from bromine, chlorine, iodine, and combinations thereof.

10. A method for manufacturing an all-solid-state battery, the method comprising: preparing a structure configured to sequentially stack a negative electrode current collector, a coating layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector; as well as applying a processing pressure greater than 50 MPa but less than 200 MPa to the structure, Wherein, the coating comprises a layered carbon material, and the layered carbon material comprises at least one pore.

11. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The processing pressure applied to the structure is 85 MPa to 150 MPa.

12. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The layered carbon material includes at least one selected from graphene, graphene oxide, reduced graphene oxide, carbon nanotubes and combinations thereof.

13. The method for manufacturing an all-solid-state battery according to claim 10, wherein: When the all-solid-state battery is in a charged state, lithium ions are stored in the form of lithium metal in at least one pore of the coating.

14. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The average diameter D50 of the at least one pore is 30.08 nm to 33.13 nm.

15. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The total pore volume of the coating is 0.114 cm 3 g -1 Up to 0.141cm 3 g -1 .

16. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The Brewer-Emmett-Teller surface area of ​​the coating is 15.03 m 2 g -1 Up to 17.15m 2 g -1 .

17. The method for manufacturing an all-solid-state battery according to claim 10, wherein: The difference between the thickness of the coating of the all-solid-state battery in a charged state and the thickness of the coating of the all-solid-state battery in a discharged state is equal to or greater than 5 μm.

18. The method for manufacturing an all-solid-state battery according to claim 10, wherein: In the charged state of the all-solid-state battery, the coating does not include sulfur but includes at least one selected from bromine, chlorine, iodine and combinations thereof.

19. The method for manufacturing an all-solid-state battery according to claim 18, in, an upper portion of the coating layer adjacent to the solid electrolyte layer comprises lithium and at least one selected from bromine, chlorine, iodine, and combinations thereof, and The lower portion of the coating layer adjacent to the negative electrode current collector includes carbon, lithium, and at least one selected from bromine, chlorine, iodine, and combinations thereof.

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