Binder for positive electrode of all-solid-state battery, composite positive electrode comprising same, and all-solid-state battery

Abstract

The present invention relates to a binder for an all-solid-state battery positive electrode, a composite positive electrode comprising the binder, and an all-solid-state battery.

Description

Technical Field

[0001] The present invention relates to a binder for a positive electrode of an all-solid-state battery, a composite positive electrode including the binder, and an all-solid-state battery.

[0002] This application claims the priority benefits of Korean Patent Application No. 10-2023-0117967, filed on September 5, 2023, and Korean Patent Application No. 10-2024-0117383, filed on August 30, 2024, the disclosures of which are incorporated herein by reference in their entireties. Background Art

[0003] A secondary battery is a device that converts external electrical energy into chemical energy, stores it, and generates electricity when needed. A secondary battery is also called a rechargeable battery because it can be recharged multiple times. Common secondary batteries include lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (NiMH), and lithium secondary batteries. Compared with primary batteries that are discarded after one use, secondary batteries provide economic and environmental benefits.

[0004] On the other hand, as wireless communication technology becomes more and more advanced, the demand for lightweight, thin, and miniaturized portable devices and automotive accessories is increasing, and the demand for secondary batteries as the energy source for these devices is growing. In particular, as hybrid vehicles and electric vehicles become more practical in preventing environmental pollution, research is emerging to use secondary batteries in these next-generation automotive batteries to reduce manufacturing costs and weight while extending their service life. Among various secondary batteries, recently, lithium secondary batteries have received attention due to their light weight, high energy density, high operating potential, and long cycle life.

[0005] Generally, a lithium secondary battery is manufactured by installing an electrode assembly composed of a negative electrode, a positive electrode, and a separator in a cylindrical or rectangular metal can or an aluminum laminated pouch-shaped casing, and injecting an electrolyte into the electrode assembly.

[0006] Conventionally, a liquid electrolyte formed by dissolving a lithium salt in a non-aqueous organic solvent has been used in lithium secondary batteries. However, such a liquid electrolyte not only easily causes degradation of electrode materials and volatilization of organic solvents, but also causes combustion or explosion due to an increase in environmental temperature and the temperature of the battery itself, and is prone to leakage, making it difficult to realize various lithium secondary batteries with high safety.

[0007] On the other hand, an all-solid-state battery using a solid electrolyte has the advantage of eliminating organic solvents, which allows for a safe and simple electrode assembly.

[0008] However, in order to fabricate a positive electrode for all-solid-state batteries, a polymer binder that can effectively bind the positive electrode components is necessary, and widely known polymer binders include nitrile rubber-based binder materials. However, using nitrile rubber-based binders as polymer binders to fabricate all-solid-state batteries has problems of reducing the interfacial adhesion between the current collector and the electrode and decreasing the battery life.

[0009] Therefore, there is a need to develop a binder for the positive electrode that can improve the mechanical properties of the electrode and enhance its life retention.

[0010] [Prior Art Documents]

[0011] [Patent Documents]

[0012] (Patent Reference 1) Korean Patent Publication No. 10-2020-0063467

[0013] (Patent Reference 2) Korean Patent Publication No. 10-2020-0023308

[0014] [Non-Patent Documents]

[0015] (Non-Patent Reference 1) Journal of the Electrochemical Society 164, A2075 (2017)

[0016] (Non-Patent Reference 2) ACS Energy Letters 4, 94 (2018)

[0017] (Non-Patent Reference 3) Ecomat, 4(4), e12193 (2022) Summary of the Invention

[0018] [Technical Problem]

[0019] To solve the above problems, the inventors of the present invention conducted various studies and confirmed that using a terpolymer containing repeating units derived from ethylene, repeating units derived from methyl acrylate, and repeating units derived from glycidyl methacrylate as a positive electrode binder can improve the adhesion between the current collector and the electrode interface and the adhesion within the electrode, thereby fabricating a battery with improved life characteristics.

[0020] Therefore, the present invention aims to provide a positive electrode binder that improves the adhesion between the current collector and the electrode interface and the adhesion within the electrode.

[0021] Another object of the present invention is to provide a composite positive electrode having improved life characteristics containing the positive electrode binder, and an all-solid-state battery containing the composite positive electrode.

[0022] [Technical Solution]

[0023] In one aspect of the present invention, the composite positive electrode comprises a positive electrode active material, a conductive material, a solid electrolyte, and a polymer binder, wherein the polymer binder may be a terpolymer comprising repeating units derived from ethylene, repeating units derived from methyl acrylate, and repeating units derived from glycidyl methacrylate.

[0024] The polymer binder may comprise a terpolymer comprising repeating units represented by Formula 1, repeating units represented by Formula 2, and repeating units represented by Formula 3:

[0025] [Formula 1]

[0026]

[0027] [Formula 2]

[0028]

[0029] [Formula 3]

[0030]

[0031] In Formulas 1 to 3,

[0032] p, q, and r are each the number of moles of the repeating unit, and

[0033] p, q, and r are each independently an integer from 1 to 100.

[0034] The polymer binder may be a polymer comprising alternating repeating units represented by Formula 4:

[0035] [Formula 4]

[0036]

[0037] In Formula 4, A is the repeating unit represented by Formula 1 above, B is the repeating unit represented by Formula 2 above, and C is the repeating unit represented by Formula 3 above.

[0038] In Formula 4, for 1 mole of r, the molar ratio of p:q may be from 30 to 50:1 to 5.

[0039] In Formula 4, p:q:r may be 40:4:1.

[0040] In one aspect of the present invention, a composite positive electrode is provided, wherein, based on the total weight of the composite positive electrode, the content of the polymer binder is 3% by weight or less.

[0041] In one aspect of the present invention, a composite positive electrode is provided, wherein the positive electrode active material includes a lithium transition metal composite oxide, and wherein the transition metal includes at least one of Co, Mn, Ni, and Al.

[0042] In one aspect of the present invention, the lithium transition metal composite oxide provides a composite positive electrode including at least one of the compounds represented by Formula 5 below:

[0043] [Formula 5]

[0044] Li x Ni a CobMn c M z O y

[0045] Wherein, 0.5 ≤ x ≤ 1.5, 0 ≤ a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ z < 1, 1.5 < y < 5, wherein a + b + c + z is less than or equal to 1, and M includes at least one selected from Al.

[0046] In one aspect of the present invention, a composite positive electrode is provided, wherein the solid electrolyte is a sulfide-based solid electrolyte.

[0047] In one aspect of the present invention, a composite positive electrode is provided, wherein the sulfide-based solid electrolyte includes at least one selected from the group consisting of: Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 6 PS 5 I, Li 2 S-P 2 S 5 、Li 2 S-LiI-P 2 S 5 、Li 2 S-LiI-Li 2 O-P 2 S 5 、Li 2 S-LiBr-P 2 S 5 、Li 2 S-Li 2 O-P 2 S 5 、Li 2 S-Li 3 PO 4 -P 2 S 5 、Li 2 S-P2 S 5 -P 2 S 5 , Li 2 SP 2 S 5 -SiS 2 , Li 2 SP 2 S 5 -SnS、Li 2 SP 2 S 5 -Al 2 S 3 , Li 2 S-GeS 2 and Li 2 -GeS 2 -ZnS.

[0048] In one aspect of the present invention, an all-solid-state battery is provided, which comprises the composite positive electrode, a negative electrode and a solid electrolyte disposed therebetween.

[0049] [Beneficial Effects]

[0050] The present invention provides a terpolymer comprising repeating units derived from ethylene, repeating units derived from methyl acrylate and repeating units derived from glycidyl methacrylate as a polymer binder, which has the effect of increasing the bonding strength of the composite positive electrode, improving the adhesion between the current collector and the electrode interface and the adhesion inside the electrode.

[0051] In addition, inclusion of the ternary copolymer has the effect of improving the life characteristics of the all-solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of the manufacturing process of the composite positive electrode for all-solid-state batteries.

[0053] Figure 2 1 is a diagram showing X-ray powder diffraction (XRD) patterns of a solid electrolyte and a mixture of a solid electrolyte and a binder according to an example of the present invention.

[0054] Figure 3 It is a graph showing nanoindentation curves of composite positive electrodes according to one example of the present invention and a comparative example.

[0055] Figure 4 Schematic diagrams of SAICAS and measurement results of composite positive electrodes according to an example of the present invention and a comparative example are shown.

[0056] Figure 5It is a diagram showing a nano-scratch schematic diagram and measurement results of a composite positive electrode of an embodiment and a comparative example of the present invention.

[0057] Figure 6 It is a diagram showing the results of GITT analysis of a composite positive electrode of an embodiment and a comparative example of the present invention.

[0058] Figure 7 It is a diagram showing the ionic conductivity of a composite solid electrolyte of an embodiment and a comparative example of the present invention and an image of the composite solid electrolyte sheet.

[0059] Figure 8 It is a diagram showing the initial charge-discharge curve of a all-solid-state battery of an embodiment of the present invention.

[0060] Figure 9 It is a diagram showing the discharge capacity of a all-solid-state battery of an embodiment of the present invention in one cycle.

[0061] Figure 10 It is a schematic diagram showing the first charge and discharge curves of a all-solid-state battery of an embodiment and a comparative example of the present invention.

[0062] Figure 11 It is a diagram showing the CV electrochemical stability evaluation curve of a composite solid electrolyte sheet of an embodiment of the present invention.

[0063] Figure 12 It is a diagram showing the discharge capacity of a all-solid-state battery of an embodiment and a comparative example of the present invention in one cycle.

[0064] Figure 13 It is a diagram showing the discharge capacity of a all-solid-state battery of an embodiment and a comparative example of the present invention according to current.

[0065] Figure 14 It is an image depicting the cross-sections of a composite positive electrode of an embodiment and a comparative example of the present invention before and after cycling. Detailed Description of the Invention

[0066] Hereinafter, the present invention will be described in more detail.

[0067] The terms and words used in this specification and the claims should not be construed as their ordinary or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical idea of the present invention based on the principle that the inventor can define the terms in the way he deems most appropriate to best describe his invention.

[0068] The terms used in the present invention are only for describing certain examples and are not intended to limit the present invention. Unless otherwise clearly specified in the context, singular expressions include plurals. In the present invention, the terms "comprising" or "having" are intended to indicate the presence of the features, quantities, steps, actions, components, parts, or combinations thereof described in the specification, and should not be construed as excluding the possibility of the presence or addition of one or more other features, quantities, steps, actions, components, parts, or combinations thereof.

[0069] Although lithium secondary batteries have been used in small applications such as mobile phones and laptop computers, they have recently been extended to medium and large applications such as electric vehicles and energy storage devices. In this case, different from smaller applications, the operating environment is more severe and more batteries are required, so they need to have stability and good performance.

[0070] Currently, most commercially available lithium secondary batteries use liquid electrolytes formed by dissolving lithium salts in organic solvents, and the organic solvents contained in the liquid electrolytes are volatile and flammable, which brings potential risks of fire and explosion, and leakage may occur, resulting in a lack of long-term reliability.

[0071] In response, all-solid-state batteries that replace the liquid electrolyte in lithium secondary batteries with solid electrolytes are being developed. Since all-solid-state batteries do not contain volatile organic solvents, there is no risk of explosion or fire, and they are being paid attention to as a way to manufacture high-power batteries with excellent economy and productivity.

[0072] In order to achieve a high energy density of all-solid-state batteries, it is necessary to manufacture a polymer binder that can effectively bond the positive electrode components. Widely known nitrile rubber-based binder materials have been used as polymer binders for positive electrodes, but there are problems of reduced interfacial adhesion between the current collector and the electrode and reduced battery life.

[0073] Therefore, the present invention attempts to provide a positive electrode binder that can improve the mechanical properties of the electrode and increase its life retention.

[0074] Hereinafter, the composition and effectiveness of the present invention will be described in detail.

[0075] In one embodiment, the composite positive electrode includes a positive electrode active material, a conductive material, a solid electrolyte, and a polymer binder, wherein the polymer binder includes a terpolymer.

[0076] The terpolymer may include repeating units derived from ethylene, repeating units derived from methyl acrylate, and repeating units derived from glycidyl methacrylate.

[0077] The terpolymer can include repeating units represented by Formula 1, repeating units represented by Formula 2, and repeating units represented by Formula 3:

[0078] [Formula 1]

[0079]

[0080] [Formula 2]

[0081]

[0082] [Formula 3]

[0083]

[0084] In Formulas 1 to 3,

[0085] p, q, and r are each the molar number of repeating units, and

[0086] p, q, and r are each independently an integer from 1 to 100.

[0087] The terpolymer can be a polymer including alternating repeating units represented by Formula 4:

[0088] [Formula 4]

[0089]

[0090] In Formula 4, A is the repeating unit represented by Formula 1 above, B is the repeating unit represented by Formula 2 above, and C is the repeating unit represented by Formula 3 above.

[0091] In Formula 4, for 1 mole of r, the molar ratio of p:q can be from 30 to 50:1 to 5. For example, the molar ratio of p, q, and r can be 30:5:1, 40:5:1, 50:5:1, 30:4:1, 40:4:1, 50:4:1, 30:3:1, 40:3:1, 50:3:1, 30:2:1, 40:2:1, 50:2:1, 30:1:1, 40:1:1, 50:1:1, but not limited thereto.

[0092] For 1 mole of r, as the molar ratio of p decreases relative to the molar ratio of q, the flexibility imparted to the polymer binder decreases, thereby reducing the resistance of the positive electrode active material to volume fluctuations. This results in a decrease in the capacity retention rate during the cycle life assessment, and further reduces the formation cycle discharge capacity.

[0093] For 1 mole of r, as the molar ratio of r increases relative to the molar ratio of q, there is a problem that the relative molar ratio of q decreases, resulting in a decrease in the adhesive force. This means a decrease in the adhesion ability, resulting in a decrease in the formation cycle discharge capacity, and further reducing the cycle capacity retention rate.

[0094] For 1 mole of r, based on q with a molar ratio of 1 to 5, when the molar ratio of p is less than 30, the flexibility imparted to the polymer binder decreases, resulting in brittleness problems during electrode manufacturing. Additionally, based on q with a molar ratio of 1 to 5, when the molar ratio of p is less than 10, due to the relative increase in the molar ratio of q, the polarity of the polymer itself increases, and there is a problem of insolubility in low-polarity solvents during electrode manufacturing. The low-polarity solvent can be butyl butyrate.

[0095] For 1 mole of r, based on q with a molar ratio of 1 to 5, when the molar ratio of p is greater than 50, the adhesive force imparted to the polymer binder decreases, resulting in detachment between the current collector and the positive electrode composite.

[0096] Preferably, for 1 mole of r, based on q with a molar ratio of 1 to 5, the molar ratio of p is 30 to 50. More preferably, for 1 mole of r, the molar ratio of p:q can be 40:4.

[0097] In the molar ratios of p, q, and r, based on p with a molar ratio of 30 to 50, when the molar ratio of q is greater than 5, due to the relative increase in the molar ratio of q, the polarity of the polymer itself increases, and there is a problem of insolubility in low-polarity solvents during electrode manufacturing. The low-polarity solvent can be butyl butyrate.

[0098] In the ratio of p, q, and r, when r is 0, the flexibility imparted to the polymer binder decreases, and the adhesive force decreases, resulting in difficulties in battery manufacturing.

[0099] In one embodiment, based on the total weight of the composite positive electrode, the content of the polymer binder contained in the composite positive electrode is 3 wt% or less. Based on the total weight of the composite positive electrode, when the content of the polymer binder exceeds 3 wt%, the adhesion ability is improved, but the content of the solid electrolyte that serves as the traveling path for lithium-ion migration in the composite positive electrode decreases, which limits the smooth migration of lithium ions in the electrode and increases the resistance. In other words, based on the total weight of the composite positive electrode, when the content of the polymer binder exceeds 3 wt%, lithium ions cannot migrate smoothly within the electrode, resulting in a continuous decrease in charge and discharge capacity.

[0100] Specifically, based on the total weight of the composite positive electrode, the content of the polymer binder can be 3.0 wt% or less, 2.5 wt% or less, 2.0 wt% or less, 0.5 wt% or more, 1.0 wt% or more, 1.5 wt% or more.

[0101] In one embodiment, the solid electrolyte can include a sulfide-based solid electrolyte. The sulfide-based solid electrolyte can include a solid electrolyte containing sulfur (S) and having an ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table.

[0102] Sulfide solid electrolytes may include at least one selected from the group consisting of: Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 6 PS 5 I, Li 2 S-P 2 S 5 、Li 2 S-LiI-P 2 S 5 、Li 2 S-LiI-Li 2 O-P 2 S 5 、Li 2 S-LiBr-P 2 S 5 、Li 2 S-Li 2 O-P 2 S 5 、Li 2 S-Li 3 PO 4 -P 2 S 5 、Li 2 S-P 2 S 5 -P 2 S 5 、Li 2 S-P 2 S 5 -SiS 2 、Li 2 S-P 2 S 5 -SnS, Li 2 S-P 2 S 5 -Al 2 S 3 、Li 2 S-GeS 2 and Li 2 -GeS 2 -ZnS, but not limited thereto.

[0103] In one embodiment, the average particle size of the sulfide-based solid electrolyte can be adjusted to a range suitable for all-solid-state batteries. In a specific example of the present invention, the average particle size of the solid electrolyte can be from 0.1 μm to 10 μm. More specifically, the average particle size of the solid electrolyte is 0.1 μm or more, 0.5 μm or more, 1.0 μm or more, 1.5 μm or more, 2.0 μm or more, 2.5 μm or more, 3.0 μm or more, 3.5 μm or more, 4.0 μm or more, 4.5 μm or more, 5.0 μm or more, 10 μm or less, 9.5 μm or less, 9.0 μm or less, 8.5 μm or less, 8.0 μm or less, 7.5 μm or less, 7.0 μm or less, 6.5 μm or less, 6.0 μm or less, 5.5 μm or less, 5.0 μm or less, but not limited thereto.

[0104] In addition, in one embodiment, the ionic conductivity of the selected solid electrolyte is at least 1×10 -5 S / cm, preferably at least 1×10 -3 S / cm.

[0105] In one embodiment, the solid electrolyte layer can be prepared by, for example, the following method.

[0106] First, a solid electrolyte is prepared. The solid electrolyte can be prepared by obtaining a commercially available product or by preparing the solid electrolyte by any of the following methods. The solid electrolyte can be prepared as follows.

[0107] First, LiCl, Li 2 S and P 2 S 5 are mixed in stoichiometric amounts and ground in, for example, a planetary ball mill to obtain a homogeneous mixture. The mixture can be subjected to high-temperature heat treatment for a predetermined period of time to obtain the desired Li 6 PS 5 Cl solid electrolyte. The heat treatment can be carried out at about 550 °C, and the heat treatment time can be about 8 hours.

[0108] Next, a solid electrolyte material is added and dispersed in a predetermined organic solvent to prepare a slurry. Then, the slurry is coated on a current collector plate or the like, dried and formed into a sheet shape. If necessary, the obtained sheet-like product can be pressed to obtain a solid electrolyte layer.

[0109] In one embodiment, the positive electrode active material can include one or a mixture of two or more of the following: lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium manganese oxide (e.g., LiMn 1+x Mn 2-x O 4(where x ranges from 0 to 0.33, such as LiMn 2 O 4 )、LiMnO 3 、LiMn 2 O 3 and LiMnO 2 )、lithium copper oxide (Li 2 CuO 2 );vanadium oxides, such as LiV 3 O 8 、LiV 2 O 4 、V 2 O 5 or Cu 2 V 2 O 7 ;LiNi 1-x M x O 2 (where M is Co, Mn, Al, Cu, Fe, Mg, B or Ga, and 0 < x < 1) represents Ni-site lithium nickel oxide, such as LiNi 1-z (Co,Mn,Al) z O 2 (where 0 < z < 1);LiMn 2-x M x O 4 (where M is Co, Ni, Fe, Cr, Zn or Ta, and x ranges from 0.01 to 1, such as LiMn 1.5 Ni 0.5 O 4 ) or Li 2 Mn 3 MO 8 (where M is Fe, Co, Ni, Cu or Zn) represents lithium manganese composite oxide;LiMn 2 O 4 in which a part of Li in the chemical formula is replaced by alkaline earth metal ions;disulfide;or Fe 2 (MoO 4 ) 3 and lithium iron phosphate (LiFePO 4 ). In an example of the present invention, in lithium iron phosphate, all or at least a part of the surface of the active material particles may be coated with a carbon material to improve conductivity.

[0110] Preferably, the positive electrode active material may include at least one selected from the group consisting of: lithium nickel cobalt manganese oxide (for example, Li(Ni,Co,Mn)O 2 ,LiNi 1-z (Co,Mn,Al) z(where, 0 < z < 1)), lithium iron phosphate (e.g., LiFePO 4 / C), lithium nickel manganese spinel (e.g., LiNi 0.5 Mn 1.5 O 4 ), lithium nickel cobalt aluminum oxide (e.g., Li(Ni,Co,Al)O 2 ), lithium manganese oxide (e.g., LiMn 2 O 4 ), and lithium cobalt oxide (e.g., LiCoO 2 ).

[0111] In one embodiment, most preferably, the positive electrode active material includes a lithium transition metal composite oxide, wherein the transition metal may include at least one of Co, Mn, Ni, and Al.

[0112] In one embodiment, the lithium transition metal composite oxide may include at least one of the compounds represented by Formula 5 below.

[0113] <Formula 5>

[0114] Li x Ni a CobMn c M z O y

[0115] wherein, 0.5 ≤ x ≤ 1.5, 0 ≤ a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ z < 1, 1.5 < y < 5, wherein, a + b + c + z is less than or equal to 1, and M includes at least one selected from Al.

[0116] In one embodiment, the positive electrode conductive material may be any one or a mixture of two or more conductive materials selected from the group consisting of, for example, graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative. More specifically, it may be a mixture of one or two or more conductive materials selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide.

[0117] The current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver can be used.

[0118] In one embodiment, the solid electrolyte included in the positive electrode may include at least one selected from polymer solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes. In one example of the present invention, the positive electrode active material may preferably include the sulfide solid electrolyte as described above as the solid electrolyte.

[0119] In one embodiment, in the positive electrode, relative to 100% by weight of the positive electrode active material layer, the content of the positive electrode active material is preferably at least 70% by weight. Further, in the positive electrode, relative to 100% by weight of the positive electrode active material layer, the content of the solid electrolyte is preferably 10% to 30% by weight.

[0120] In one embodiment, the loading amount (relative to the electrode area) of the positive electrode may be 5 mAh / cm 2 or more, 6 mAh / cm 2 or more, or 10 mAh / cm 2 or more.

[0121] In one embodiment, even when such a high-loading positive electrode is applied, the battery can operate at an electrochemically stable level.

[0122] In one embodiment, the positive electrode active material layer can be obtained by preparing a slurry by adding a positive electrode active material, a conductive material, an adhesive resin, and a solid electrolyte to a suitable solvent, and casting the slurry.

[0123] [Examples of the Present Invention]

[0124] The present invention will now be further described with reference to the following examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention. The examples of the present invention are provided to more fully illustrate the present invention to those skilled in the art.

[0125] Production Example 1: Production of EMG Terpolymer Adhesive

[0126] The polymer adhesive of the present invention is prepared by preparing a terpolymer (hereinafter referred to as "EMG terpolymer") including repeating units derived from ethylene, repeating units derived from ethyl methacrylate, and repeating units derived from glycidyl methacrylate.

[0127] In order to initiate a reaction based on a nickel enolate catalyst during the polymerization process, a trifluoromethane ligand precursor (Sigma Aldrich) and Ni(COD) 2(Wherein, COD is 1,5 - cyclooctadiene) (Sigma Aldrich) was premixed in 30 ml of toluene solvent for 15 minutes to prepare a nickel enolate catalyst solution of 0.02 wt%. Then, (C) glycidyl methacrylate (Sigma Aldrich) was dissolved in toluene solvent at 1.6 M, (B) ethyl methacrylate (TCI) and (C) glycidyl methacrylate (Sigma Aldrich) were dissolved in toluene solvent at a molar ratio of 4:1 respectively, and then the nickel enolate catalyst solution and methylaluminoxane (Sigma Aldrich) cocatalyst prepared above were added. Then, (A) ethylene groups were injected into the polymer at a molar ratio of 40:1 relative to (C) glycidyl methacrylate (Sigma Aldrich) while controlling the ethylene gas flow rate to prepare the EMG terpolymer. The reaction was terminated by adding methanol to the reactor.

[0128] To increase the yield by fully activating the catalyst, the polymerization reaction was maintained at 55 °C using a water flow for temperature control between the inner jacket and the outer jacket of a Buchi autoclave (Buchiglas), and the internal pressure was maintained at about 4 atmospheres while supplying ethylene gas.

[0129] Production Example 2

[0130] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 30:4:1.

[0131] Production Example 3

[0132] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 50:4:1.

[0133] Comparative Example 1

[0134] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 10:4:1.

[0135] Comparative Example 2

[0136] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 60:4:1.

[0137] Comparative Example 3

[0138] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 5:4:1.

[0139] Comparative Example 4

[0140] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 40:4:0.

[0141] Comparative Example 5

[0142] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 40:20:1.

[0143] Comparative Example 6

[0144] The EMG terpolymer was prepared in the same manner as in Production Example 1, except that the molar ratio of ethylene group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) was 20:40:1.

[0145] Experimental Example 1: Comparison of electrode fabrication using the EMG terpolymer binder according to the molar ratio of repeating units

[0146] Relative to the EMG terpolymer of Production Example 1, the molar ratio of the ethylene group (A) in the copolymer of Comparative Example 1 was significantly reduced, and the copolymer exhibited reduced flexibility and brittle behavior during electrode fabrication. When the fabricated electrode was physically folded under stimulation, unlike an electrode with sufficient flexibility, the positive electrode composite was fractured and ruptured. Therefore, when the copolymer of Comparative Example 1 was included, it was difficult to fabricate the all-solid-state battery electrode.

[0147] In addition, relative to the EMG terpolymer of Production Example 1, the molar ratio of the ethylene group (A) in the copolymer of Comparative Example 2 was significantly increased, and the copolymer exhibited reduced adhesive force as a polymer binder, which led to detachment between the current collector and the positive electrode composite. Therefore, when the copolymer of Comparative Example 2 was included, due to the reduced adhesive force, it was difficult to fabricate the all-solid-state battery electrode.

[0148] In addition, in the case of the copolymers of Comparative Examples 3, 5, and 6, due to the increase in the molar ratio of ethyl methacrylate (B) relative to the ethylene group (A), the polarity of the polymer itself increased and it was insoluble in butyl butyrate (a low-polarity solvent for electrode preparation), resulting in difficulty in preparing the all-solid-state battery electrode.

[0149] In addition, in the case of the copolymer of Comparative Example 4, since it does not include glycidyl methacrylate (C), it was confirmed that when the electrode was blanked to manufacture the battery, the adhesion decreased due to the peeling of the composite at the electrode edge. It was also found that the surface of the composite was slightly rougher, which reduced the flexibility. Therefore, when the copolymer of Comparative Example 4 was included, it was difficult to manufacture the electrode of the all-solid-state battery.

[0150] Therefore, for the preparation of the composite positive electrode containing the EMG terpolymer and the all-solid-state battery containing the composite positive electrode, it was found that the most suitable was to prepare a copolymer with a molar ratio of vinyl group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) of 30 to 50:1 to 5:1.

[0151] Experimental Example 2: Comparison of electrode manufacturing using the EMG terpolymer binder according to the molar ratio of repeating units

[0152] In the EMG terpolymers of Production Examples 1 to 3, the formation cycle discharge capacity and capacity retention rate of the battery were evaluated according to the molar ratio of the vinyl group (A). The results of the discharge capacity and capacity retention rate are shown in Table 1 below.

[0153] [Table 1]

[0154]

[0155] As shown in Table 1, compared with the EMG terpolymer of Production Example 1, the molar ratio of the vinyl group (A) of the copolymer of Production Example 2 decreased, and as a result, it was confirmed that the flexibility of the polymer binder decreased, resulting in a decrease in the resistance to volume fluctuations of the active material, which led to a decrease in the capacity retention rate in the cycle life evaluation and also a decrease in the formation cycle discharge capacity compared with Production Example 1.

[0156] In addition, compared with the EMG terpolymer of Production Example 1, the molar ratio of the vinyl group (A) of the copolymer of Production Example 3 increased, and due to the relative decrease in the molar ratio of ethyl methacrylate (B) relative to the vinyl group (A), the adhesion decreased, the adhesion ability decreased, the formation cycle discharge capacity also decreased, and the cycle capacity retention rate also decreased compared with Production Example 1.

[0157] Therefore, when manufacturing a composite positive electrode containing an EMG terpolymer and an all-solid-state battery containing the composite positive electrode, it was found that the composite positive electrode containing a copolymer with a molar ratio of vinyl group (A), ethyl methacrylate (B), and glycidyl methacrylate (C) of 40:4:1 improved the mechanical properties of the electrode and had a high life retention.

[0158] Example 1: Composite Cathode Using EMG Terpolymer Adhesive and All-Solid-State Battery Containing the Composite Cathode

[0159] LiNi 0.9 Co 0.05 Mn 0.05 O 2 、Li 6 PS 5 Cl (LPSCl) powder (Posco JK solid solution), SuperC (Timcal), and the EMG terpolymer prepared in Preparation Example 1 were mixed in butyl butyrate solvent to prepare a slurry. The slurry was mixed with a Thinky mixer for 15 minutes and cast onto an aluminum current collector with a spatula to prepare a composite cathode. In the prepared composite cathode, the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder was 75:21.5:1.5:2. The loading amount of the prepared composite cathode was 15 mg / cm of the active material per unit area 2 。

[0160] 100 mg of Li 6 PS 5 Cl powder was placed into a PET mold and pressed at a pressure of 300 MPa at room temperature to prepare a Li 6 PS 5 Cl tablet, and then the above-prepared composite cathode was added and pressed at a pressure of 430 MPa. A lithium indium foil (lithium (Honjo), indium (Nilaco)) was placed on the other side of the Li 6 PS 5 Cl tablet and clamped at a pressure of 60 MPa to produce an all-solid-state battery.

[0161] Example 2

[0162] An all-solid-state battery was prepared in the same manner as in Example 1, except that in the composite cathode, the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder was 75:22.5:1.5:1.

[0163] Example 3

[0164] An all-solid-state battery was prepared in the same manner as in Example 1, except that in the composite cathode, the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder was 75:20.5:1.5:3.

[0165] Comparative Example 7

[0166] The all-solid-state battery was prepared in the same manner as in Example 1, except that in the composite cathode, the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder was 75:19.5:1.5:4.

[0167] Experimental Example 3: Comparison of electrode fabrication according to the content of the polymer binder

[0168] In the all-solid-state batteries of Example 1 and 3 and Comparative Example 7, the formation cycle discharge capacity and capacity retention rate of the batteries were evaluated according to the binder content in the composite cathode. The results of the discharge capacity and capacity retention rate are shown in Table 2 below.

[0169] [Table 2]

[0170]

[0171] As shown in Table 2, as the content of the polymer binder in the electrode increases, the amount of the solid electrolyte that serves as the traveling path for lithium ion migration decreases, which limits the smooth migration of lithium in the electrode and increases the resistance. Therefore, although the binding ability improves as the binder content increases, the migration of lithium ions within the composite cathode is hindered, and lithium ions cannot migrate smoothly within the electrode, and a continuous decrease in the charge and discharge capacity of the battery is observed.

[0172] Therefore, it was confirmed that the batteries of Example 1 and 3 with a polymer binder content of 3 wt% or less were superior to the battery of Comparative Example 7 with a polymer binder content greater than 3 wt% in terms of cycle discharge capacity and capacity retention rate.

[0173] Comparative Example 8: Composite cathode having nitrile rubber and all-solid-state battery including the same

[0174] LiNi 0.9 Co 0.05 Mn 0.05 O 2 、Li 6 PS 5 Cl (LPSCl) powder, Super C, and nitrile rubber (Kumho PetroChemical) were mixed in butyl butyrate solvent to prepare a slurry. The slurry was mixed for 15 minutes using a Thinky mixer (Thinky) and cast onto an aluminum current collector using a spatula to prepare a composite cathode. In the prepared composite cathode, the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder was 75:21.5:1.5:2. The loading amount of the prepared composite cathode was 15 mg / cm of the active material per unit area 2 .

[0175] 100 mg of Li 6 PS 5The Cl powder was placed into a PET mold and pressed at a pressure of 300 MPa at room temperature to prepare Li 6 PS 5 Cl tablets, and then the composite cathode prepared above was added and pressed at a pressure of 430 MPa. The lithium indium foil was placed on the other side of the Li 6 PS 5 Cl tablets and clamped at a pressure of 60 MPa to produce an all-solid-state battery.

[0176] Experimental Example 4: Evaluation of the Chemical Stability of the Composite Cathode Using an EMG Terpolymer Binder

[0177] To evaluate the chemical stability of the composite cathode prepared in Example 1, XRD evaluation was performed, and the results are shown in Figure 2 as follows.

[0178] For side reactions, as described below, the side reaction between the butyl butyrate solvent used to manufacture the composite cathode and the EMG terpolymer binder was tested.

[0179] First, the butyl butyrate solvent was added to the LPSCl solid electrolyte and reacted for 24 hours to prepare a solution, and the LPSCl solid electrolyte was mixed with the EMG terpolymer binder solution and reacted for 24 hours to prepare a solution. After drying these solutions in a vacuum oven, XRD evaluation was performed on the residual materials, as Figure 2 shown, confirming that the structural stability of the LPSCl solid electrolyte was well maintained in all compositions.

[0180] Experimental Example 5: Evaluation of the Mechanical Properties of the Composite Cathode Using an EMG Terpolymer Binder (Nanoindentation) - Hardness Measurement

[0181] The hardness of the composite cathodes of Example 1 and Comparative Example 8 was measured. Evaluation was performed using a nanoindentation instrument, and the results are shown in Figure 3 as follows.

[0182] Specifically, an electrode specimen was indented using a nanoindentation instrument (Anton Paar, NHT3) with a Vickers indenter (tip width of 0.5 μm) to measure the hardness. Specifically, the indenter was loaded onto the electrode specimen at a rate of 0.1 mN / s for 10 seconds to apply a force of up to 1 mN, allowed to creep for 10 seconds, and then the indenter was unloaded at a rate of 0.1 mN / s for 10 seconds, and the resulting indentation hardness was measured.

[0183] This hardness measurement showed that the composite cathode of Example 1 had a smaller penetration depth compared to the composite cathode of Comparative Example 1. Table 3 below shows the results of the hardness of the composite cathodes.

[0184] [Table 3]

[0185] Example 1 Comparative Example 8 Hardness (GPa) 0.0025 0.0012

[0186] As shown in Table 3 above, compared with the composite positive electrode of Comparative Example 8, the composite positive electrode of Example 1 containing the EMG terpolymer has a greater hardness.

[0187] Experimental Example 6: Evaluation of the mechanical properties of a composite positive electrode using an EMG terpolymer binder (SAICAS) - Measurement of interfacial adhesion

[0188] The interfacial adhesion of the composite positive electrodes of Example 1 and Comparative Example 8 was measured. Evaluation was carried out using a surface and interface cutting analysis system (SAICAS) instrument, and the results are shown in Figure 4 .

[0189] Specifically, a SAICAS device (SAICAS EN-EX (Daipla Wintes, Japan)) was used to measure the interfacial adhesion. While obliquely cutting the positive electrode in the depth direction with a diamond microblade, the horizontal force was measured by the force on the blade, and the horizontal force is a measure of the force applied horizontally to the microblade to maintain a constant cutting speed.

[0190] In the composite positive electrodes of Example 1 and Comparative Example 8, the internal adhesion between the composite positive electrode materials was measured by the constant speed mode, and the interfacial adhesion between the composite positive electrode and the current collector was measured by the constant load mode (rake angle: 20°, clearance angle: 10°). Figure 4 (a) and (b) of are diagrams showing the internal adhesion between the composite positive electrode materials, and Figure 4 (c) and (d) of are diagrams showing the interfacial adhesion between the composite positive electrode and the current collector.

[0191] The greater the value of the horizontal force required to maintain the set cutting speed, the harder and more difficult the material is to cut, that is, the material has excellent adhesion. Therefore, compared with the composite positive electrode of Comparative Example 8, it was found that the composite positive electrode of Example 1 has excellent adhesion at the interface and internally.

[0192] Experimental Example 7: Evaluation of the mechanical properties of a composite positive electrode using an EMG terpolymer binder (nano-scratch) - Hardness measurement

[0193] The hardness of the composite positive electrodes of Example 1 and Comparative Example 8 was measured. Evaluation was carried out using a nano-scratch instrument, and the results are shown in Figure 5 .

[0194] Specifically, the hardness was measured using a nano-scratch instrument (Anton Paar). During the initial process, while maintaining a constant speed in the horizontal direction and a constant load in the vertical direction (scanning speed = 10 μm / s, scratch load = 200 mN), the blade was moved approximately 50 μm within the electrode to measure the penetration depth of the blade into the positive electrode. Figure 5 (a) of Figure 5 is a schematic diagram of nano-scratching.

[0195] When the same load value is set, a harder material results in a smaller penetration depth of the blade, and it is confirmed that the composite positive electrode of Example 1 exhibits a shallower penetration depth compared to the composite positive electrode of Comparative Example 8. Figure 5 (b) of Figure 5 shows a graph of the measurement results of the penetration depth. This confirms that the hardness of the composite positive electrode of Example 1 is better than that of the composite positive electrode of Comparative Example 8.

[0196] Experimental Example 8: Measurement of surface activation of the composite positive electrode active material using an EMG terpolymer binder

[0197] The surface activation of the positive electrode active materials distributed in the composite positive electrodes of Example 1 and Comparative Example 8 was compared. The results of galvanostatic intermittent titration technique (GITT) analysis are shown in Figure 6

[0198] The all-solid-state batteries of Example 1 and Comparative Example 8 were prepared by charging and discharging at a current of 0.05C, and then prepared in a charged state at a current rate of 0.05C. Then a current of 0.2C was applied for 1 minute. Subsequently, it was left standing for 2 hours to compare the surface activation of the positive electrode active materials.

[0199] Compared with the all-solid-state battery of Comparative Example 8, lower polarization was observed in the all-solid-state battery of Example 1, and the final discharge capacity was 181.0 mAh / g in Comparative Example 8 and 189.8 mAh / g in Example 1, confirming that the surface activation of the positive electrode active material is better in Example 1.

[0200] Experimental Example 9: Measurement of ionic conductivity of the composite solid electrolyte using an EMG terpolymer binder

[0201] The ionic conductivity of the composite solid electrolyte applied to the all-solid-state batteries of Example 1 and Comparative Example 8 was measured. The LPSCl solid electrolyte and the binder were mixed at a weight ratio of 95:5 to prepare a solid electrolyte sheet. Figure 7 (b) is a diagram showing the solid electrolyte sheet prepared as described above.

[0202] The ionic conductivity of the individual LPSCl was 2.41 mS / cm, while the compositions with binders had similar values: 0.44 mS / cm in the case of containing nitrile rubber and 0.45 mS / cm in the case of containing the EMG terpolymer. Figure 7 (a) of Figure 7 is a graph showing the ionic conductivity of the composite solid electrolyte of the all-solid-state batteries applied to Comparative Example 8 and Example 1. This confirms that the EMG terpolymer binder exhibits properties similar to those of the nitrile rubber binder in terms of ionic conductivity.

[0203] Experimental Example 10: Evaluation of the cycle life characteristics of all-solid-state batteries based on composite cathodes with different contents of EMG terpolymer binder

[0204] Before evaluating the all-solid-state batteries prepared in Examples 1 to 3, the content of the EMG terpolymer was changed to find the optimal binder composition.

[0205] Figure 8 are the charge and discharge curves of the formation cycles obtained by charging and discharging at a current rate of 0.05C. Table 4 below shows the discharge capacities of the all-solid-state battery cathode active materials according to the EMG terpolymer binder containing 1 wt%, 2 wt%, and 3 wt%.

[0206] [Table 4]

[0207] Example 1 Example 2 Example 3 Discharge capacity (mAh / g) 199.1 196.8 194.6

[0208] Figure 9 shows the cycle discharge capacity obtained by charging and discharging at a current rate of 0.2C after two formation cycles. Table 5 below shows the initial discharge capacity and the capacity retention rate at 20 cycles at a current rate of 0.2C.

[0209] [Table 5]

[0210] Example 1 Example 2 Example 3 Discharge capacity (mAh / g) 158.9 155.3 153.5 Capacity retention rate (%) 95.6 92.6 90.1

[0211] As shown in Table 5 above, the all-solid-state battery of Example 1 with 2 wt% of the EMG terpolymer binder exhibited the best cycle characteristics. Therefore, it can be seen that the optimal content of the EMG terpolymer binder is 2 wt%.

[0212] Experimental Example 11: Evaluation of the cycle life characteristics and high-rate characteristics of all-solid-state batteries based on composite cathodes using EMG terpolymer binder

[0213] Figure 10The charge and discharge curves of the formation cycles obtained by charging and discharging the all-solid-state batteries prepared in Comparative Example 8 and Example 1 at a rate of 0.05C are shown. The all-solid-state batteries of Comparative Example 8 and Example 1 exhibited discharge capacities according to the positive electrode active material as shown in Table 6 below.

[0214] [Table 6]

[0215] Example 1 Comparative Example 8 Discharge capacity (mAh / g) 199.1 196.0

[0216] As shown in Table 6 above, it can be seen that the all-solid-state battery of Example 1 has a higher initial capacity compared to the all-solid-state battery of Comparative Example 8. Table 7 below shows the efficiency of the initial formation cycle (discharge capacity / charge capacity × 100%).

[0217] [Table 7]

[0218] Example 1 Comparative Example 8 Efficiency (%) 87.4 83.1

[0219] To verify this efficiency, cyclic voltammetry (CV) analysis was performed, and the results are shown in Figure 11 . The nitrile rubber and EMG terpolymer electrolyte sheets used in the analysis were solid electrolyte sheets with an adhesive weight ratio of 5% applied in Experimental Example 9. The voltage range was from 1.0V to 3.7V (vs. Li-In), and the evaluation was performed using a scan rate of 0.5 mV / s. More side reactions were observed in Comparative Example 8 during the initial voltage increase, which can explain the difference in the efficiency of the early formation cycles in the battery life evaluation. The cycle discharge capacity obtained by charging and discharging at a current rate of 0.2C after two formation cycles is shown in Figure 12 . The initial discharge capacity and capacity retention rate of the all-solid-state batteries of Comparative Example 8 and Example 1 at a current rate of 0.2C are shown in Table 8.

[0220] [Table 8]

[0221] Example 1 Comparative Example 8 Discharge capacity (mAh / g) 158.9 150.7 Capacity retention rate (%) 88.5 81.3

[0222] As shown in Table 8 above, it can be seen that the all-solid-state battery of Example 1 using the EMG terpolymer binder exhibits better cycle characteristics. The discharge capacities of the all-solid-state batteries prepared in Comparative Example 8 and Example 1 according to the change in current rate are shown in Figure 13 . At a current rate of 1.0C, the discharge capacity is shown in Table 9 below.

[0223] [Table 9]

[0224] Example 1 Comparative Example 8 Discharge capacity (mAh / g) 87.4 68.4

[0225] As shown in Table 9 above, compared to Comparative Example 8, the all-solid-state battery of Example 1 exhibits better high-rate characteristics.

[0226] Experimental Example 12: Cross-sectional Image Analysis of Composite Cathode with EMG Terpolymer Binder

[0227] The cross-section of the composite cathode was analyzed by field emission scanning electron microscopy (FE-SEM, Hitachi) to compare the cross-sections of the composite cathodes of all-solid-state batteries before and after cycling according to the type of polymer binder applied, and the results are shown in Figure 14 as follows.

[0228] Figure 14 (a) of is an image depicting the cross-section before cycling of the composite cathode of the all-solid-state battery prepared in Comparative Example 8, Figure 14 (b) of is an image depicting the cross-section before cycling of the composite cathode of the all-solid-state battery prepared in Example 1. In the cross-section before cycling, no cracks were observed in the positive electrode active material for both Comparative Example 8 using nitrile rubber binder and Example 1 using EMG terpolymer binder.

[0229] Figure 14 (c) of is an image showing the cross-sectional view of the composite cathode of the all-solid-state battery prepared in Comparative Example 8 after 100 cycles, Figure 14 (d) of is an image showing the cross-sectional view of the composite cathode of the all-solid-state battery prepared in Example 1 after 100 cycles. After 100 evaluation cycles, it was found that in Comparative Example 8, there were a large number of cracks in the active material, while in Example 1, the morphology of the active material remained mostly intact, and the interface between the active material and the solid electrolyte remained stable.

Claims

1. A composite positive electrode, comprising: a positive electrode active material, a conductive material, a solid electrolyte, and a polymer binder, in, The polymer binder is a terpolymer comprising repeating units derived from ethylene, repeating units derived from methyl acrylate, and repeating units derived from glycidyl methacrylate.

2. The composite positive electrode according to claim 1, wherein The polymer binder is a terpolymer comprising repeating units represented by Formula 1, repeating units represented by Formula 2, and repeating units represented by Formula 3: [Formula 1] [Formula 2] [Formula 3] In Formulas 1 to 3, p, q, and r are the number of moles of the repeating units, respectively, and p, q, and r are each independently an integer from 1 to 100.

3. The composite positive electrode according to claim 2, wherein: The polymer binder is a polymer comprising alternating repeating units represented by Formula 4: [Formula 4] Wherein, A is the repeating unit represented by the above Formula 1, B is the repeating unit represented by the above Formula 2, and C is the repeating unit represented by the above Formula 3.

4. The composite positive electrode according to claim 3, wherein: In Formula 4, for 1 mole of r, the molar ratio of p:q is 30 to 50:1 to 5.

5. The composite positive electrode according to claim 3, wherein: p:q:r is 40:4:

1.

6. The composite positive electrode according to claim 1, wherein: Based on the total weight of the composite positive electrode, the content of the polymer binder is 3 wt% or less.

7. The composite positive electrode according to claim 1, in, The positive electrode active material includes a lithium transition metal composite oxide, Wherein, the transition metal includes at least one of Co, Mn, Ni, and Al.

8. The composite positive electrode according to claim 7, wherein: The lithium transition metal composite oxide includes at least one of the compounds represented by Formula 5: [Formula 5] Li x Ni a CobMn c M z About y Wherein, 0.5 ≤ x ≤ 1.5, 0 ≤ a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ z < 1, 1.5 < y < 5, wherein, a + b + c + z is less than or equal to 1, and M includes Al.

9. The composite positive electrode according to claim 1, wherein: The solid electrolyte is a sulfide-based solid electrolyte.

10. The composite positive electrode according to claim 9, wherein: The sulfide-based solid electrolyte includes at least one selected from the group consisting of: Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2-GeS2-ZnS.

11. A all-solid-state battery, comprising: The composite positive electrode according to any one of claims 1 to 10; A negative electrode; and A solid electrolyte disposed therebetween.

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