Anode current collector comprising double coating layer and all solid state battery comprising the same

Abstract

The present invention relates to a negative electrode current collector comprising a double coating layer and an all-solid-state battery comprising the same.

Description

Technology Field

[0001] The present invention relates to a negative electrode current collector comprising a double coating layer and an all-solid-state battery comprising the same. Background Technology

[0002] To increase the energy density of all-solid-state batteries, a cathode-free system without a negative electrode material is required. A cathode-free system does not include a negative electrode active material layer and stores lithium ions from the positive electrode active material layer in the form of lithium metal at the interface between the negative electrode current collector and the solid electrolyte layer during charging. However, currently commercialized negative electrode current collectors, such as copper (Cu), nickel (Ni), and stainless steel (SUS), do not electrochemically react with lithium ions and therefore do not possess lithium affinity. In other words, it is difficult to store lithium ions uniformly on the surface of the negative electrode current collector during charging. Therefore, a negative electrode current collector with a surface coating of a metal having lithium affinity has been developed, and it has been reported that lithium can be uniformly deposited through this.

[0003] However, conventional technology cannot completely solve the problem of lithium dendrite formation during the charging and discharging process. This is because all lithium-affinity metals possess high electrical conductivity. Electrons moving freely through the metal act as a medium to transport electrons to the surface and interior of the solid electrolyte layer, and as charging and discharging continue, electrons continue to move into the solid electrolyte layer. As a result, efficiency per cycle decreases, and cell short circuits occur when operating for more than tens of cycles.

[0004] In addition, most metals react spontaneously with solid electrolytes due to their high chemical reactivity. Therefore, the formation of a lithium ion transport layer that can physically and chemically block the interface between the lithium-affinity metal and the solid electrolyte layer can improve the overall stability and performance of the all-solid-state battery. Prior art literature

[0005] Korean Patent Publication No. 10-2018-0091678 The problem to be solved

[0006] The present invention aims to provide an all-solid-state battery with excellent lifespan and charge / discharge efficiency.

[0007] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become more apparent from the following description and will be realized by the means and combinations thereof described in the claims. means of solving the problem

[0008] A negative electrode current collector for an all-solid-state battery according to one embodiment of the present invention may include: a current collector layer; a first coating layer located on one surface of the current collector layer and comprising a metal capable of forming an alloy with lithium; and a second coating layer located on the first coating layer and having lower electronic conductivity than the first coating layer.

[0009] The first coating layer may include at least one selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), magnesium (Mg), zinc (Zn), aluminum (Al), calcium (Ca), indium (In), bismuth (Bi), and combinations thereof.

[0010] The first coating layer may have a thickness of 10 nm to 10 µm.

[0011] The second coating layer may include a metal oxide having lithium ion conductivity.

[0012] The second coating layer may include at least one selected from the group consisting of titanium dioxide (TiO2), silicon dioxide (SiO2), aluminum oxide (Al2O3), cerium oxide (CeO2), magnesium oxide (MgO), calcium oxide (CaO), zirconium oxide (ZrO2), niobium oxide (Nb2O5), and combinations thereof.

[0013] The second coating layer may have a thickness of 10 nm to 100 nm.

[0014] A solid-state battery according to one embodiment of the present invention comprises: a negative electrode current collector; a solid electrolyte layer located on the negative electrode current collector; a positive electrode active material layer located on the solid electrolyte layer; and a positive electrode current collector located on the positive electrode active material layer; wherein a second coating layer of the negative electrode current collector may be in contact with the solid electrolyte layer.

[0015] When charging the above-mentioned all-solid-state battery, lithium ions can react with the first coating layer of the negative electrode current collector to form a lithium alloy layer. Effects of the invention

[0016] According to the present invention, an all-solid-state battery with excellent lifespan and charge / discharge efficiency can be obtained.

[0017] The effects of the present invention are not limited to those mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description. Brief explanation of the drawing

[0018] FIG. 1 illustrates an all-solid-state battery according to the present invention. Figure 2 illustrates a negative current collector according to the present invention. FIG. 3 illustrates a partial configuration of an all-solid-state battery according to the present invention when it is charged. Figure 4 is the result of TEM-EDS (Transmission electron microscopy-energy dispersive spectroscopy) analysis of the cathode current collector according to Example 1. Figure 5 is the result of TEM-EDS (Transmission electron microscopy-energy dispersive spectroscopy) analysis of the cathode current collector according to Example 2. Figure 6a shows the results for the first charge and discharge of each half-cell according to Example 1, Example 2 and Comparative Example. Figure 6b shows the results of evaluating the lifespan of half paper according to Example 1 and Comparative Example. Figure 6c shows the results of measuring the Coulomb efficiency per charge / discharge cycle of the half-battery according to Example 1 and the Comparative Example. Figure 7a shows the results of evaluating the lifespan of half paper according to Examples 3 and 4. Figure 7b shows the results of measuring the Coulomb efficiency per charge / discharge cycle of the half-battery according to Examples 3 and 4. Specific details for implementing the invention

[0019] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0020] In describing each drawing, similar reference numerals have been used for similar components. In the attached drawings, the dimensions of the structures are depicted enlarged from their actual size for clarity of the invention. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0021] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0022] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0024] FIG. 1 illustrates an all-solid-state battery according to the present invention. Referring thereto, the all-solid-state battery may include a negative electrode current collector (10), a solid electrolyte layer (20) located on the negative electrode current collector (10), a positive electrode active material layer (30) located on the solid electrolyte layer (20), and a positive electrode current collector (40) located on the positive electrode active material layer (30).

[0025] FIG. 2 illustrates the above-mentioned negative current collector (10). The above-mentioned negative current collector (10) may include a current collecting layer (11), a first coating layer (12) located on one side of the current collecting layer (11), and a second coating layer (13) located on the first coating layer (12).

[0026] The current collecting layer (11) is a plate-shaped, sheet-shaped, or thin-shaped substrate composed of a conductive material. The material constituting the current collecting layer (11) is not particularly limited, but may include, for example, copper (Cu), nickel (Ni), stainless steel (SUS), etc.

[0027] The above current collection layer (11) may have a thickness of 0.1㎛ to 50㎛.

[0028] The first coating layer (12) is coated on one surface of the current collection layer (11) and is configured to react with lithium ions during charging of the all-solid-state battery so that the lithium ions can be uniformly deposited on the current collection layer (11) in the form of lithium metal or lithium alloy.

[0029] The first coating layer (12) may include a metal capable of forming an alloy with lithium. The metal capable of forming an alloy with lithium may include at least one selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), magnesium (Mg), zinc (Zn), aluminum (Al), calcium (Ca), indium (In), bismuth (Bi), and combinations thereof.

[0030] The first coating layer (12) may have a thickness of 10 nm to 10 µm.

[0031] The second coating layer (13) is coated on the first coating layer (12) to prevent the first coating layer (12) from physically coming into contact with the solid electrolyte layer (30) and to prevent electrons from moving to the solid electrolyte layer (30). Accordingly, the second coating layer (13) may be composed of an insulating material or a material with lower electron conductivity than the first coating layer (12).

[0032] Meanwhile, since the second coating layer (13) is located between the solid electrolyte layer (30) and the first coating layer (12), it must not hinder the movement of lithium ions. Therefore, the second coating layer (13) may be composed of a metal oxide that is lithium ion conductive.

[0033] Consequently, the second coating layer (13) may be composed of a material that has insulating or low electronic conductivity and is simultaneously lithium-ion conductive. The second coating layer (13) may include at least one selected from the group consisting of titanium dioxide (TiO2), silicon dioxide (SiO2), aluminum oxide (Al2O3), cerium oxide (CeO2), magnesium oxide (MgO), calcium oxide (CaO), zirconium oxide (ZrO2), niobium oxide (Nb2O5), and combinations thereof.

[0034] The above second coating layer (13) does not decompose even when it comes into contact with lithium ions. For example, when manganese oxide (MnO) comes into contact with lithium ions, MnO + Li + -> Electrochemical decomposition reactions occur as in Mn + Li2O. On the other hand, the above titanium dioxide (TiO2), etc., undergo TiO2 + Li + -> Li x The original MO bonds are maintained, as in TiO2.

[0035] The second coating layer (13) may have a thickness of 10 nm to 100 nm. If the thickness of the second coating layer (13) is less than 10 nm, it may be difficult to form, and it may be difficult to prevent contact between the solid electrolyte layer (30) and the first coating layer (12), and it may be difficult to prevent electrons from moving to the solid electrolyte layer (30). In addition, if the thickness of the second coating layer (13) exceeds 100 nm, it may be difficult for lithium ions to move to the first coating layer (12).

[0036] FIG. 3 illustrates a partial configuration of an all-solid-state battery according to the present invention when charged. Referring to the figure, when charging the all-solid-state battery, lithium ions pass through a solid electrolyte layer (20) and a second coating layer (13) that is lithium ion conductive, and react with a first coating layer (12) to form a lithium alloy layer (12'). Since the first coating layer (12) is made of a metal with lithium affinity, the lithium ions can be deposited uniformly.

[0037] Meanwhile, the second coating layer (13) prevents the lithium alloy layer (12') from physically contacting the solid electrolyte layer (20) so that they do not react with each other.

[0038] In addition, since the second coating layer (13) has insulating properties or low electronic conductivity, electrons move to the solid electrolyte layer (20), preventing lithium dendrites from forming on the surface of the solid electrolyte layer (20).

[0039] As a result, by applying the second coating layer (13) above, the lifespan and cell performance can be realized as an all-solid-state battery. In addition, compared to conventional anode-free all-solid-state batteries, the storage capacity of lithium ions can be increased, so an all-solid-state battery with a high energy density of 1,000 Wh / L or more can be realized.

[0040] The method of forming the first coating layer (12) and the second coating layer (13) on the current collection layer (11) is not particularly limited. For example, they can be formed by various methods such as sputtering, spray coating, or slurry coating. In addition, the first coating layer (12) and the second coating layer (13) can be formed by different methods. They can be formed by appropriate methods considering the purpose of introduction, material, thickness, etc. of each component.

[0041] The solid electrolyte layer (20) is positioned between the positive electrode active material layer (30) and the negative electrode current collector (10) to allow lithium ions to move between the two components.

[0042] The above solid electrolyte layer (20) may include an oxide-based solid electrolyte or a sulfide-based solid electrolyte. However, it may be preferable to use a sulfide-based solid electrolyte with high lithium ion conductivity. The above sulfide-based solid electrolyte is not particularly limited, but includes Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, or In), Li 10 GeP2S 12 It may include the back.

[0043] The above positive active material layer (30) may include a positive active material, a solid electrolyte, a conductive material, a binder, etc.

[0044] The above positive active material may be an oxide active material or a sulfide active material.

[0045] The above oxide active materials are LiCoO2, LiMnO2, LiNiO2, LiVO2, Li1 + x Ni1 / 3Co1 / 3Mn1 / Rock salt layer type active materials such as 3O2, LiMn2O4, Li(Ni 0.5 Mn 1.5 Spinel-type active materials such as )O4, inverse spinel-type active materials such as LiNiVO4 and LiCoVO4, olivine-type active materials such as LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, silicon-containing active materials such as Li2FeSiO4 and Li2MnSiO4, LiNiO . 8Co (0.2-x) Al x A salt-layered active material in which a portion of the transition metal is replaced with a heterogeneous metal, such as O2 (0<x<0.2), Li 1+x Mn 2-x-y M y Spinel-type active material in which a portion of the transition metal is replaced with a heterogeneous metal, such as O4 (M is at least one of Al, Mg, Co, Fe, Ni, Zn and 0 < x+y < 2), Li4Ti5O 12 It may be lithium titanate.

[0046] The above sulfide active material may be copper chevrell, iron sulfide, cobalt sulfide, nickel sulfide, etc.

[0047] The above solid electrolyte may be an oxide solid electrolyte or a sulfide solid electrolyte. However, it may be preferable to use a sulfide-based solid electrolyte with high lithium ion conductivity. The above sulfide-based solid electrolyte is not particularly limited, but includes Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, or In), Li 10 GeP2S 12 It may include the back.

[0048] The above conductive material may be carbon black, conducting graphite, ethylene black, graphene, etc.

[0049] The above binder may be BR (Butadiene rubber), NBR (Nitrile butadiene rubber), HNBR (Hydrogenated nitrile butadiene rubber), PVDF (polyvinylidene difluoride), PTFE (polytetrafluoroethylene), CMC (carboxymethylcellulose), etc.

[0050] The above positive current collector (40) is a plate-shaped, sheet-shaped, or thin-shaped substrate made of a conductive material. The above positive current collector (40) may include aluminum (Al), stainless steel (SUS), etc.

[0052] Other forms of the present invention will be described in more detail through the following examples. The following examples are merely illustrative to aid in understanding the present invention and do not limit the scope of the present invention.

[0054] Example 1

[0055] A negative electrode current collector according to Example 1 was prepared as follows. A magnesium thin plate was prepared as the current collector. A first coating layer was formed by depositing magnesium (Mg), a metal capable of forming an alloy with lithium, to a thickness of approximately 300 nm on the current collector. A second coating layer was formed by depositing titanium dioxide (TiO2) to a thickness of approximately 10 nm on the first coating layer via sputtering. Figure 4 shows the results of TEM-EDS (Transmission electron microscopy-energy dispersive spectroscopy) analysis of the negative electrode current collector according to Example 1. Referring to this, it is determined that the second coating layer was properly formed as the titanium element is evenly distributed.

[0057] Example 2

[0058] A negative current collector was manufactured in the same manner as in Example 1, except that a second coating layer was formed using silicon dioxide (SiO2). Figure 5 shows the results of TEM-EDS (Transmission electron microscopy-energy dispersive spectroscopy) analysis of the negative current collector according to Example 2. Referring to this, it can be seen that the first coating layer and the second coating layer are both uniformly formed, as magnesium, silicon, and oxygen elements are all evenly distributed.

[0060] Comparative example

[0061] A negative current collector was manufactured in the same manner as in Example 1, except that a second coating layer was not formed.

[0063] Experimental Example 1

[0064] Half-cells including negative current collectors according to the above Examples 1, 2, and Comparative Example were each prepared. Each half-cell had a current density of 1.175 mA / cm² 2 , deposition capacity 3.52mAh / cm² 2 It was charged and discharged, and its performance was evaluated at a temperature of about 30°C.

[0065] FIG. 6a shows the results of the first charge and discharge of each half-cell according to Example 1, Example 2 and Comparative Example. In light of the fact that the half-cells of Example 1 and Example 2 are properly charged and discharged, it can be seen that lithium ions can pass through the second coating layer.

[0066] FIG. 6b shows the results of evaluating the lifespan of half batteries according to Example 1 and the Comparative Example. Referring to this, both half batteries are stably charged and discharged up to 30 times, but the half battery of the Comparative Example exhibits a short circuit phenomenon from the 33rd cycle, in which lithium detachment occurs more than lithium deposition. The half battery of Example 1 is stably charged and discharged even after 30 cycles.

[0067] FIG. 6c shows the results of measuring the Coulomb efficiency per charge-discharge cycle of the half-battery according to Example 1 and the Comparative Example. Referring to this, it can be seen that, unlike the Comparative Example, the half-battery of Example 1 maintains substantially the same Coulomb efficiency as at the beginning of the charge-discharge cycle even after the charge-discharge cycle exceeds 30.

[0069] Example 3

[0070] A negative current collector was manufactured in the same manner as in Example 1, except that the thickness of the second coating layer was adjusted to 50 nm.

[0072] Example 4

[0073] A negative current collector was manufactured in the same manner as in Example 1, except that the thickness of the second coating layer was adjusted to 100 nm.

[0075] Experimental Example 2

[0076] Half-cells including the negative current collectors according to Examples 3 and 4 above were each prepared. Each half-cell had a current density of 1.175 mA / cm² 2 , deposition capacity 3.52mAh / cm² 2 It was charged and discharged, and its performance was evaluated at a temperature of about 30°C.

[0077] FIG. 7a shows the results of evaluating the lifespan of half batteries according to the above Examples 3 and 4. It can be seen that both half batteries are capable of more than 100 charge-discharge cycles.

[0078] FIG. 7b shows the results of measuring the Coulomb efficiency per charge-discharge cycle of half batteries according to Examples 3 and 4 above. It can be seen that both half batteries maintain their initial Coulomb efficiency until the charge-discharge cycle exceeds 100.

[0080] As embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to the aforementioned embodiments, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention. Explanation of the symbols

[0081] 10: Cathode current collector 11: Current collector layer 12: First coating layer 13: Second coating layer 20: Solid electrolyte layer 30: Positive electrode active material layer 40: Positive electrode current collector

Claims

Claim 1 A negative electrode current collector for an all-solid-state battery comprising: a current collector layer; a first coating layer that is directly laminated on one surface of the current collector layer and comprises a metal capable of forming an alloy with lithium; and a second coating layer located on the first coating layer and having lower electronic conductivity than the first coating layer. Claim 2 A negative current collector for an all-solid-state battery according to claim 1, wherein the first coating layer comprises at least one selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), magnesium (Mg), zinc (Zn), aluminum (Al), calcium (Ca), indium (In), bismuth (Bi), and combinations thereof. Claim 3 In claim 1, the first coating layer is a negative current collector for an all-solid-state battery having a thickness of 10 nm to 10 μm. Claim 4 In claim 1, the second coating layer comprises a lithium-ion conductive metal oxide, forming a negative current collector for an all-solid-state battery. Claim 5 A negative current collector for an all-solid-state battery according to claim 1, wherein the second coating layer comprises at least one selected from the group consisting of titanium dioxide (TiO2), silicon dioxide (SiO2), aluminum oxide (Al2O3), cerium oxide (CeO2), magnesium oxide (MgO), calcium oxide (CaO), zirconium oxide (ZrO2), niobium oxide (Nb2O5), and combinations thereof. Claim 6 In claim 1, the second coating layer is a negative current collector for an all-solid-state battery having a thickness of 10 nm to 100 nm. Claim 7 An all-solid-state battery comprising: a negative electrode current collector according to any one of claims 1 to 6; a solid electrolyte layer located on the negative electrode current collector; a positive electrode active material layer located on the solid electrolyte layer; and a positive electrode current collector located on the positive electrode active material layer, wherein a second coating layer of the negative electrode current collector is in contact with the solid electrolyte layer. Claim 8 In claim 7, the all-solid-state battery in which, during charging, lithium ions react with the first coating layer of the negative electrode current collector to form a lithium alloy layer.

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