Positive electrode particles, positive electrode containing the same, and all-solid-state battery

Abstract

The present disclosure relates to positive electrode particles including a positive electrode active material layer containing positive electrode active material particles and a solid electrolyte layer surrounding the positive electrode active material layer and containing solid electrolyte particles, wherein the average size of the solid electrolyte particles is 10 to 20% of the average size of the positive electrode active material particles.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0134725 dated October 19, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present disclosure relates to a positive electrode particle, a positive electrode including the same, and an all-solid-state battery. More particularly, the present disclosure relates to a positive electrode particle manufactured by adjusting the sizes of positive electrode active material particles and solid electrolyte particles included in the positive electrode particle, and a positive electrode and an all-solid-state battery including the same. [Background technology]

[0003] Currently, various batteries that can overcome the limitations of lithium secondary batteries are being researched from the viewpoints of battery capacity, safety, output, size increase, miniaturization, etc.

[0004] Research is being continuously conducted in both academia and industry on metal-air batteries, which have a much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries, which are safe and do not pose a risk of explosion, supercapacitors, NaS batteries or RFBs (redox flow batteries), which are large-scale batteries, and thin film batteries, which are ultra-miniaturized batteries.

[0005] Among these, all-solid-state batteries are batteries that replace the liquid electrolyte used in conventional lithium secondary batteries with a solid, and by not using flammable solvents inside the battery, there is absolutely no risk of fire or explosion due to the decomposition reaction of conventional electrolytes, thereby significantly improving safety. In addition, because lithium metal or lithium alloys can be used as the anode material, there is the advantage that the energy density relative to the mass and volume of the battery can be dramatically improved.

[0006] In particular, inorganic solid electrolytes for solid-state batteries can be divided into sulfide-based and oxide-based types. Of these, sulfide-based solid electrolytes are the type that are currently undergoing the most technological development, and sulfide-based solid electrolyte materials with ionic conductivity close to that of organic electrolytes have even been developed.

[0007] On the other hand, unlike conventional lithium secondary batteries which use liquid electrolytes, all-solid-state batteries use a solid electrolyte, which makes it difficult for the solid electrolyte to easily penetrate into the pores in the electrode active material layer, making it difficult to achieve physical contact between the electrode active material and the solid electrolyte.

[0008] In the manufacturing process of cathodes for solid-state batteries, a solvent drying process is required after slurry coating. Solvents are used in large quantities to dissolve powder materials such as binders, thickeners, and dispersants. During the drying process, the mobility of the binder dissolved in the solvent is expressed, causing the binder to migrate within the electrode. This binder migration phenomenon is particularly noticeable in high-loading electrodes. Binder migration in high-loading electrodes reduces the electrode's adhesive strength, leading to electrode non-uniformity and affecting battery performance.

[0009] In addition, the particle density increases during the manufacturing process of the cathode of an all-solid-state battery, resulting in densely packed areas, which can lead to a decrease in battery performance. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Korean Patent Publication No. 2018-0036631 (2021.04.27) Summary of the Invention [Problem to be solved by the invention]

[0011] The present disclosure has been proposed to solve the above problems, and an object of the present disclosure is to provide positive electrode particles manufactured by adjusting the size ratio of positive electrode active material particles and solid electrolyte particles. [Means for solving the problem]

[0012] In one embodiment of the present disclosure, a positive electrode particle includes a positive electrode active material layer including positive electrode active material particles, and a solid electrolyte layer surrounding the positive electrode active material layer and including solid electrolyte particles, and the average size of the solid electrolyte particles may be 10 to 20% of the average size of the positive electrode active material particles.

[0013] In one embodiment, the solid electrolyte particles may be sulfide-based solid electrolyte particles.

[0014] In one embodiment, the value A calculated from the following [Equation 1] may be 0.25 / μm or less.

[0015] [Formula 1] A=Span / D50 Here, the span is (D90-D10) / (D50), and the units of D10, D50 and D90 are each μm.

[0016] In one embodiment, when the surface of the positive electrode particle is observed in an image measured at 5,000 times magnification using a scanning electron microscope (SEM), the area forming a plane may be 20% or more, and the plane may be a portion where no unevenness is formed in the image.

[0017] In one embodiment, the surface has an area of ​​0.2 cm 2 It can be defined as the above part.

[0018] In one embodiment, the positive electrode active material particles may have an average particle size of 4 to 6 μm, and the solid electrolyte particles may have an average particle size of 0.4 to 1.2 μm.

[0019] A positive electrode according to an embodiment of the present disclosure may include the positive electrode particles.

[0020] An all-solid-state battery according to an embodiment of the present disclosure may include a positive electrode, a negative electrode including negative electrode particles, and the solid electrolyte particles disposed between the positive electrode and the negative electrode. [Effects of the Invention]

[0021] An effect of the present disclosure is to improve the performance of a battery including positive electrode particles, by manufacturing the positive electrode particles including a positive electrode active material layer including positive electrode active material particles and a solid electrolyte layer including solid electrolyte particles such that the size ratio between the positive electrode active material particles and the solid electrolyte particles is within a certain range. [Brief explanation of the drawings]

[0022] [Figure 1] 1 shows an image of a cathode particle fabricated according to an embodiment of the present disclosure, observed under a scanning electron microscope (SEM), with a magnification of ×5,000. [Figure 2] FIG. 2 shows the surfaced area from the image of FIG. 1. The image magnification is ×5,000. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present disclosure will be described in detail below. However, the following description should be understood as an example to facilitate understanding of the present disclosure, and should not be understood as restricting or limiting the present disclosure. Furthermore, it goes without saying that the present disclosure is not limited to the accompanying drawings. A person skilled in the art will be able to embody the present disclosure in various forms without departing from the technical spirit of the present disclosure by referring to the following description and the accompanying drawings.

[0024] negative electrode The negative electrode may include negative electrode particles. For example, the negative electrode may include lithium metal. The negative electrode may be made of pure lithium metal or a lithium alloy, or may be made by coating and drying a negative electrode active material on the lithium metal.

[0025] The lithium metal may include at least one of pure lithium, a lithium alloy, and a lithium metal composite oxide. The lithium alloy may include a metal selected from the group consisting of Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, and Zn. The lithium metal composite oxide may include lithium and any one metal (Me) oxide (MeO) selected from the group consisting of Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe. x ) and as an example, Li x Fe2O3(0<0≦1) or Li x WO2(0 <x≦1)であってもよい。

[0026] The lithium metal battery according to the present disclosure may have a protective layer, as in the case of conventional lithium metal batteries that contain an electrolyte. The protective layer may include any material that has lithium ion conductivity, does not interfere with the operation of the battery, and does not react with lithium. Examples of such a material include a garnet-type ceramic protective layer, a protective layer made of lithium-substituted polyacrylic acid, and a molybdenum disulfide-based protective layer. Any protective layer that improves the stability of the lithium metal may be used.

[0027] The lithium metal is generally prepared to a thickness of 3 μm to 500 μm. The lithium metal may have fine irregularities on its surface to strengthen the bonding force between the lithium metal and the negative electrode active material or the solid electrolyte, and may be used in various forms such as a film, sheet, foil, net, porous body, foaming agent, or nonwoven fabric.

[0028] Examples of the negative electrode active material include carbon such as non-graphitizable carbon and graphite-based carbon:Li x Fe2O3(0<0≦1), Lix WO₂(0 < x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO₂, PbO, PbO₂, Pb₂O₃, Pb₃O₄, Sb₂O₃, Sb₂O₄, Sb₂O₅, GeO, GeO₂, Bi₂O₃, Bi₂O₄, and Bi₂O₅; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. can be used.

[0029] solid electrolyte The solid electrolyte can contain solid electrolyte particles. The solid electrolyte particles may contain at least one or more of sulfide-based solid electrolyte particles, oxide-based solid electrolyte particles, and organic solid electrolyte particles. The solid electrolyte according to the present disclosure can use particles whose surfaces are coated or modified. Sulfide-based solid electrolytes have advantages in terms of ionic conductivity and production cost compared to other solid electrolytes. Therefore, the present disclosure will proceed with the description of examples where sulfide-based solid electrolytes are used.

[0030] Sulfide-based solid electrolytes have the advantages of high lithium ion conductivity of 10 -2 ~10 -3 S / cm, being easy to form a contact interface between the electrode and the electrolyte, and having good mechanical strength and mechanical flexibility. The sulfide-based solid electrolyte powder contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and can include Li-P-S-based glass and Li-P-S-based glass ceramics. The sulfide-based solid electrolyte is not particularly limited in the present disclosure, and all known sulfide-based substances used in the field of lithium batteries can be used. As an example, the sulfide-based solid electrolyte is Li₆PS₅Cl (LPSCl), Li₆PS₅Br (LPSClBr), Thio-LISICON (Li 3.25 Ge 0.25 P0.75 S4), Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiILi3PO4-P2S5, Li2S-P2S5, Li3PS4, Li7P3S 11 , LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, Li 10 GeP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li7P3S 11 etc.

[0031] The thickness of the solid electrolyte can be selected differently depending on the desired battery characteristics. For example, the thickness after being pressed and densified can be preferably about 0.1 μm to 1000 μm, more preferably about 1 μm to 100 μm, and even more preferably about 10 μm to 50 μm.

[0032] positive electrode The positive electrode may include a plurality of positive electrode particles. The positive electrode may be manufactured by, for example, applying a positive electrode mixture to a positive electrode current collector, the positive electrode mixture including a positive electrode active material layer including positive electrode active material particles, a solid electrolyte layer including solid electrolyte particles surrounding the positive electrode active material layer, a conductive material, and a binder. If necessary, a filler may be further added to the positive electrode mixture.

[0033] The positive electrode current collector is generally manufactured to a thickness of about 3 μm to 500 μm, and is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity, and can be made of, for example, stainless steel, aluminum, nickel, titanium, or aluminum or stainless steel surface-treated with carbon, nickel titanium, or silver, and more particularly, aluminum. The current collector can have fine irregularities on its surface to increase the adhesive strength of the positive electrode active material, and can be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0034] The positive electrode active material may include, in addition to the positive electrode active material particles, a layered compound such as lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; +x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and Ni-site lithium nickel oxides represented by the chemical formula LiNi1-xMxO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3). Lithium manganese composite oxides represented by the chemical formula LiMn2-xMxO2 (where M=Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or Li2Mn3MO8 (where M=Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc., but are not limited to these. For example, the positive electrode active material can be NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2).

[0035] The conductive material can typically be added in an amount of 0.1 to 30 wt % based on the total weight of the mixture containing the positive electrode active material. There are no particular limitations on the conductive material, so long as it does not cause chemical changes in the battery and is conductive. Examples of such conductive materials include graphite, such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers, such as carbon fiber and metal fiber; metal powders, such as carbon fluoride, aluminum, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives. For example, the conductive material can also be carbon nanofiber (CNF).

[0036] The binder contained in the positive electrode is a component that aids in binding the active material with the conductive material and the current collector, and is usually added in an amount of 0.1 to 30 wt % based on the total weight of the mixture including the positive electrode active material. The addition of the binder can also increase the binding strength between the positive electrode and the solid electrolyte.

[0037] The binder is not particularly limited in the present disclosure, and known methods can be used. The binder may be any one selected from the group consisting of polyamide-imide (PAI), polyimide (PI), polyamide (PA), polyamic acid (polyamic acid), polyethylene oxide (PEO), polystyrene (PS), PEP-MNB (poly(ethylene-copropylene-co-5-methylene-2-norbornene)), VDF (polyvinylidene fluoride), PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)), PS-NBR (polystyrene nitrile-butadiene rubber), PMMANBR (poly(methacrylate)nitrile-butadiene rubber), and mixtures thereof, or a mixture of two or more thereof.

[0038] The surface of the positive electrode active material layer may be coated with a material such as LiNbO to form a buffer layer. The buffer layer may be formed with a thickness of 10 nm or less, thereby reducing the interfacial resistance between the positive electrode and the solid electrolyte.

[0039] The sizes of the positive electrode active material particles and the solid electrolyte particles present in the positive electrode may vary, but in the present disclosure, the sizes of the positive electrode active material particles and the solid electrolyte particles may be controlled to obtain a positive electrode in which the positive electrode active material particles and the solid electrolyte particles are highly densely and uniformly arranged.

[0040] For example, the average size of the solid electrolyte particles may be about 10 to 20% of the average size of the positive electrode active material particles. In this case, the average size of the positive electrode active material particles may be about 4 μm to 6 μm, and the average size of the solid electrolyte particles may be about 0.4 μm to 1.2 μm. The average size defined above refers to the average diameter, which is the average particle size defined as D50.

[0041] FIG. 1 shows an image of a cathode particle produced according to one embodiment of the present disclosure, observed with a scanning electron microscope (SEM). The image magnification is ×5,000. FIG. 2 shows a diagram of a surface-formed region from the image of FIG. 1. The image magnification is ×5,000.

[0042] Referring to FIGS. 1 and 2, when observing an image of a positive electrode particle taken at 5,000x magnification using a scanning electron microscope, it can be seen that the area forming the surface (see the dotted circle in FIG. 2) accounts for approximately 20% or more of the entire image. Here, the area forming the surface refers to a surface that is formed smoothly in the image. The smooth surface is defined as a surface on the image that does not have any irregularities or protrusions. That is, it is a portion of the image where no protrusions exist. The surface can be defined as a surface that is flattened by applying pressure to the solid electrolyte particles during the preparation of the positive electrode particles. When the positive electrode active material particles and the solid electrolyte are mixed and dispersed, the positive electrode particles can be prepared so that the solid electrolyte surrounds the surfaces of the positive electrode active material particles, and the flat surface can be formed by applying pressure. The presence of many flat surfaces in the positive electrode particles means that there are many areas where pressure is appropriately applied, which can indicate that the positive electrode particles are densely packed and ion paths are well formed in the positive electrode particles. The surface has an area of ​​0.2 cm 2 A surface can be defined only if the above conditions are satisfied.

[0043] If the area forming the surface is less than 20% of the entire image, the packing density of the positive electrode particles will be low and ion passages may not be formed to the desired extent. The area forming the surface must be 20% or more, preferably 30% or more, and more preferably 35% or more of the entire image.

[0044] The area forming the surface is preferably 80% or less of the entire image, more preferably 75% or less, and even more preferably 70% or less. As described above, the surface is the area where the solid electrolyte is flattened under pressure. However, in order for the particulate cathode active material particles to flatten more than 80% of the surface of the cathode particles, a small amount of the cathode active material particles must be used. Therefore, to prevent a decrease in the performance of the cathode particles, the surface is preferably 80% or less of the entire image.

[0045] In the embodiment of the present disclosure, the area of ​​the area forming the surface in the image is preferably 20% or more of the total area. 2 The area forming the surface is 9.10 cm 2 In Fig. 2, the area ratio of the area forming the surface corresponds to 45.5% of the total area, which satisfies the embodiment of the present disclosure.

[0046] The positive electrode particles are preferably manufactured to have a value represented by the following [Equation 1].

[0047] [Formula 1] 0.03 / μm ≦ Span / D50 ≦ 0.25 / μm Here, the Span value can be defined as the average size of the positive electrode particles, for example, as the average diameter. Specifically, the Span value is defined as (D90-D10) / D50, and has a value less than 1.

[0048] If the Span / D50 value exceeds 0.25 / μm, the Span value is large, the diameter (D50) of the positive electrode particles is small, the fine particles increase, and the packing density of the electrode may decrease. If the Span / D50 value is less than 0.03 / μm, the Span value of the positive electrode particles is small, the diameter (D50) of the positive electrode particles is large, and high-rate discharge may be poor. Here, the units of D10, D50, and D90 are all μm.

[0049] Positive electrode particles according to one embodiment of the present disclosure are manufactured by mixing solid electrolyte particles having an average size that is 10 to 20% of the average size of the positive electrode active material particles, thereby obtaining positive electrode particles with uniformity and improved density. When a solid electrolyte having an average size smaller than the average size of the positive electrode active material is used, the specific surface area of ​​the solid electrolyte that can adhere to the periphery of the positive electrode active material increases, thereby improving the structure and cell performance of the positive electrode particles. However, if the particle size difference between the positive electrode active material and the solid electrolyte becomes too large, dispersion becomes difficult, and there is a limit to how small the solid electrolyte particle size can be.

[0050] The description of each component included in the electrode for an all-solid-state battery according to an embodiment of the present disclosure is applicable in the same manner as that described in detail in the description of the manufacturing method for an electrode for an all-solid-state battery according to an embodiment of the present disclosure, and therefore detailed description thereof will be omitted.

[0051] Preferred examples are shown below to aid in understanding the present disclosure, but the following examples are provided to aid in understanding the present disclosure, and the present disclosure is not limited to the following examples.

[0052] Example 1 In Example 1, an electrode active material (NCM811), an electrolyte (LPSCl), and a conductive material (CNF) were mixed in a weight ratio of 60 wt %:35 wt %:5 wt % (electrode active material:electrolyte:conductive material), and positive electrode particles were produced in which the average size of the solid electrolyte particles was 12% of the average size of the electrode active material particles.

[0053] Comparative Example 1 In Comparative Example 1, an electrode active material (NCM811), an electrolyte (LPSCl), and a conductive material (CNF) were mixed in a weight ratio of 60 wt %:35 wt %:5 wt % (electrode active material: electrolyte: conductive material), and positive electrode particles were produced in which the average size of the solid electrolyte particles was 32% of the average size of the electrode active material particles.

[0054] Comparative Example 2 In Comparative Example 2, an electrode active material (NCM811), an electrolyte (LPSCl), and a conductive material (CNF) were mixed in a weight ratio of 60 wt %:35 wt %:5 wt % (electrode active material:electrolyte:conductive material), and positive electrode particles were produced in which the average size of the solid electrolyte particles was 6.7% of the average size of the electrode active material particles.

[0055] Comparative Example 3 In Comparative Example 3, an electrode active material (NCM811), an electrolyte (LPSCl), and a conductive material (CNF) were mixed in a weight ratio of 60 wt %:35 wt %:5 wt % (electrode active material: electrolyte: conductive material), and positive electrode particles were produced in which the average size of the solid electrolyte particles was 20% of the average size of the electrode active material particles.

[0056] Experimental example 1: Measuring the area that forms a surface The performance of the positive electrode particles according to the above-mentioned Examples and Comparative Examples is as shown in Table 1.

[0057] [Table 1]

[0058] Referring to Table 1, the ratio of the average size of the positive electrode active material particles to the average size of the solid electrolyte particles of the positive electrode particles in the comparative example is outside the range of the present disclosure. The ratio of the average size of the solid electrolyte particles to the average size of the electrode active material particles in Example 1 is 12%, which is within the range of the present disclosure, and it can be seen that the performance of the positive electrode particles is superior to that of the comparative example.

[0059] In Comparative Example 3, the average size of the solid electrolyte was 20% of the average size of the cathode active material, but the Span value exceeded 1, and it was confirmed that the charge / discharge efficiency and rate-limiting property were lower than those of Example 1.

[0060] Although one embodiment and specific examples of the present disclosure have been described above as illustrative, they should be understood to be for the purpose of aiding understanding of the present disclosure and should not be understood as limiting the embodiments of the present disclosure. Those skilled in the art will be able to appropriately modify one embodiment and example of the present disclosure, such as by omitting, changing, or replacing all or part of the configuration of one embodiment and example of the present disclosure, or by adding other configurations, without departing from the technical spirit of the present disclosure, by referring to this specification and the accompanying drawings. Therefore, the scope of protection of the present disclosure should be interpreted by the scope of the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of rights of the present disclosure.

[0061] Unless otherwise defined, all terms and expressions used in this specification should be understood in a manner that is commonly understood by a person having ordinary skill in the art to which this disclosure pertains. Furthermore, the terms and expressions used in this specification should be interpreted broadly and not in a restrictive sense.

[0062] In this specification, the word "comprises" does not exclude the presence or addition of one or more other components other than those mentioned.

[0063] Furthermore, in this specification, the singular form includes the plural form unless the context clearly indicates otherwise.

[0064] In this specification, the embodiments described as examples can be combined with each other, and unless contradictory, the content described in a particular example can be applied to other embodiments in the same manner, even if it is not described in other embodiments.

Claims

1. a positive electrode active material layer containing positive electrode active material particles; and a solid electrolyte layer disposed around the positive electrode active material layer and including solid electrolyte particles; The positive electrode particles, wherein the average size of the solid electrolyte particles is 10% or more and 20% or less of the average size of the positive electrode active material particles.

2. The positive electrode particles according to claim 1 , wherein the solid electrolyte particles are sulfide-based solid electrolyte particles.

3. The positive electrode particles according to claim 1, wherein the value A calculated from the following formula 1 is 0.25 / µm or less. [Formula 1] A=Span / D50 Here, the Span is (D90-D10) / (D50), and the units of D10, D50 and D90 are each μm.

4. When the surface of the positive electrode particle is observed in an image measured at 5,000 times magnification using a scanning electron microscope (SEM), the area forming the surface is 20% or more of the entire image, The positive electrode particles according to claim 1 , wherein the surface is a portion of the image where no unevenness is formed.

5. The surface has an area of ​​0.2 cm ２ 5. The cathode particles according to claim 4, characterized in that they are defined as the above moieties.

6. the average size of the positive electrode active material particles is 4 μm or more and 6 μm or less in terms of average particle size; The positive electrode particles according to claim 1 , wherein the solid electrolyte particles have an average particle size of 0.4 μm or more and 1.2 μm or less.

7. A positive electrode comprising the positive electrode particles according to any one of claims 1 to 6.

8. The positive electrode according to claim 7 ; a negative electrode comprising negative electrode particles; and an all-solid-state battery comprising the solid electrolyte particles disposed between the positive electrode and the negative electrode;

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