Positive electrode active material composite, positive electrode including composite, and lithium ion secondary battery including positive electrode

Abstract

The invention provides a positive electrode active material composite, a positive electrode comprising the positive electrode material composite, and a lithium ion secondary battery comprising the positive electrode. The positive electrode material composite comprises a positive electrode active material base material and a coating layer which is coated on the positive electrode active material base material and comprises a compound represented by the following formula 1. [Formula 1] Li Ti O < c-d > X < d >.

Description

[0001] This application claims priority from Korean Patent Application No. 10-2023-0106837, filed on August 16, 2023, and Korean Patent Application No. 10-2024-0109422, filed on August 14, 2024, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0002] The present invention relates to a positive electrode active material composite, a positive electrode comprising the positive electrode active material composite, and a lithium ion secondary battery comprising the positive electrode. Background Art

[0003] Compared with nickel-manganese dioxide or nickel-cadmium batteries, lithium-ion secondary batteries have the advantages of higher energy density, lower self-discharge rate and longer life, but their disadvantages include poor stability when overheated and low power output.

[0004] To overcome the problems of lithium-ion secondary batteries, all-solid-state batteries have been proposed as an alternative. All-solid-state batteries include an electrolyte layer containing a solid electrolyte, with positive and negative electrode layers containing solid electrolytes formed on both sides of the electrolyte layer, and each electrode having a structure coupled to a current collector.

[0005] Based on the raw materials of the solid electrolyte, all-solid-state batteries can be divided into oxide batteries, polymer batteries, and sulfide batteries. Sulfide all-solid-state batteries exhibit better lithium ion conductivity than other types of batteries. However, compared with conventional liquid electrolyte batteries, sulfide all-solid-state batteries have problems with low ion conductivity and high resistance between the positive electrode / negative electrode / solid electrolyte, which reduces the battery life and power output.

[0006] In other words, it is known that the cathode active material and the sulfide-based solid electrolyte react with each other at the interface to form a resistive material that interferes with the operation of the all-solid-state battery. The resistive material reduces the initial capacity of the all-solid-state battery and its efficiency.

[0007] To address these issues, various coatings are known to be formed on the surface of the positive electrode active material. For example, a technique is known to coat the surface of the positive electrode active material with lithium oxide Li-MO (wherein M is B, Al, Zr, P, Ti, Nb, W, etc.).

[0008] However, this type of coated cathode active material does not appear to be sufficiently effective for reducing the interfacial resistance between the cathode active material and the sulfide-based solid electrolyte and improving lithium ion conductivity.

[0009] [Prior art literature]

[0010] [Patent Document]

[0011] Korean Patent Publication No. 10-2018-0123369 Summary of the Invention

[0012] [Technical Issues]

[0013] The present invention aims to solve the above-mentioned problems in the prior art, and its purpose is to provide a positive electrode active material composite, a positive electrode comprising the positive electrode active material composite, and a lithium ion secondary battery comprising the positive electrode, wherein the positive electrode active material composite can improve the driving characteristics and life characteristics of the battery by reducing the interface resistance between the positive electrode active material and the solid electrolyte and improving the lithium ion conductivity.

[0014] [Technical solution]

[0015] To achieve the above object, the present invention provides a positive electrode active material composite comprising a positive electrode active material substrate and a coating layer comprising a compound represented by the following Formula 1 coated on the positive electrode active material substrate.

[0016] [Formula 1]

[0017] Li a Ti b O c-d X d

[0018] Where X is N, P or S, and

[0019] 1≤a≤6, 1≤b≤6, 3≤c≤15 and 0 <d≤1.5。

[0020] The present invention also provides a positive electrode comprising the positive electrode active material composite of the present invention.

[0021] The present invention also provides a lithium ion secondary battery comprising the positive electrode of the present invention, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0022] [Beneficial Effects]

[0023] The cathode active material composite of the present invention provides the following effects: reducing the interface resistance between the cathode active material and the solid electrolyte through the coating layer formed on the surface of the cathode active material, and improving lithium ion conductivity.

[0024] Furthermore, by the above-mentioned effects, there is also provided an effect of improving the driving characteristics and life characteristics of the battery.

[0025] By including the positive electrode active material, the lithium ion secondary battery of the present invention provides excellent driving characteristics and life characteristics. DETAILED DESCRIPTION

[0026] Hereinafter, the present invention will be described in more detail for better understanding of the present invention.

[0027] The terms and words used in this specification and claims should not be interpreted according to their conventional meaning or dictionary meaning, but should be interpreted based on the principle that the inventor can appropriately define the concept of the term to best describe his invention, with the meaning and concept consistent with the technical idea of the present invention. In addition, the terms used herein are only used to describe exemplary examples and are not intended to limit the present invention. Unless the context clearly indicates otherwise, expressions in the singular include the plural.

[0028] When a component is referred to as being “connected to, contained in, stacked on, or mounted on” another component, it should be understood that the component can be directly connected to or mounted on the other component, but other components may exist in between. On the other hand, when a component is referred to as being “directly connected to or mounted on” another component, it should be understood that there are no other components in between. Other expressions describing the relationship between components, such as “on” and “directly on,” or “between” and “directly between,” or “adjacent” and “directly adjacent,” should be interpreted in a similar manner.

[0029] As used herein, the term "combination" is inclusive of mixtures, alloys, reaction products, and the like, unless specifically indicated to the contrary.

[0030] The cathode active material composite of the present invention is characterized in that it includes: a cathode active material substrate; and a coating layer including a compound represented by the following Formula 1 coated on the cathode active material substrate.

[0031] [Formula 1]

[0032] Li a Ti b O c-d X d

[0033] Where X is N, P or S, and

[0034] 1≤a≤6, 1≤b≤6, 3≤c≤15 and 0 <d≤1.5。

[0035] The cathode active material composite of the present invention is characterized by reduced interfacial resistance between the cathode active material and the solid electrolyte due to the inclusion of a coating layer, and improved lithium ion conductivity due to the structure of the coating particles constituting the coating layer. Specifically, the coated particles forming the coating layer have a structure in which oxygen contained in LTO is replaced by a non-metallic element, X. As a result, the crystal distance between the coated particles is increased compared to conventional LTO-coated particles, thereby providing improved lithium ion conductivity.

[0036] In addition to the compound of Formula 1, the coating may also contain other coating substrates known in the art.

[0037] Preferably, in Formula 1, the ranges are 3 ≤ a ≤ 5, 4 ≤ b ≤ 6, 10 ≤ c ≤ 14, and 0 < d ≤ 1. More preferably, a can be 4, b can be 5, c can be 12, and d can be from 0.1 to 0.3.

[0038] The cathode active material substrate can be a compound represented by Formula 2 below.

[0039] [Formula 2]

[0040] Li a (Ni 1-x-y-z Co x M1 y M2 z )O2

[0041] Wherein, M1 is manganese (Mn), aluminum (Al), or a combination thereof;

[0042] M2 is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), aluminum (Al), or any combination of two or more thereof; and

[0043] 0.95 ≤ a ≤ 1.3, 0 < x < 1, 0 ≤ y < 1, and 0 ≤ z < 1.

[0044] However, the cathode active material substrate is not limited to the above compounds, and any cathode active material known in the art can be used or further included.

[0045] Specifically, at least one selected from the group consisting of NCM, NCMA, LFP, LCA, LCO, LMO, etc. can be used as the cathode active material substrate.

[0046] More specifically, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.75 Co 0.1 Mn 0.1 Al 0.05 O2, LiFePO4, etc. can be used.

[0047] The coating layer may contain 0.1 to 5% by weight, more preferably 0.5 to 2% by weight, and even more preferably 0.7 to 1.3% by weight, based on the total weight of the positive electrode active material composite. If the coating layer contains less than 0.1% by weight, the effects of reducing the interfacial resistance between the positive electrode active material and the solid electrolyte and improving lithium ion conductivity may be minimal, while if the coating layer contains more than 5% by weight, the interfacial resistance may actually increase due to the increased lithium ion migration distance between the active material and the solid electrolyte, which is undesirable.

[0048] Furthermore, the coating layer may have a thickness of 10 nm to 200 nm.

[0049] The molar ratio of Ti to X in the coating layer can be 1:0.01 to 0.2, preferably 1:0.01 to 0.1, and more preferably 1:0.02 to 0.06. If the molar ratio of X is less than 0.01, the oxygen content increases, reducing the distance between crystals, making it difficult to expect an effect of improving lithium ion conductivity. If the molar ratio of X exceeds 0.2, the content of non-metallic elements increases, disrupting the crystal structure of the existing lithium titanium oxide, making it impossible to form a uniform structure, which is undesirable.

[0050] The coating layer can be formed by dry mixing the positive electrode active material substrate and the coating layer substrate, but is not limited thereto and can also be formed by a wet process. The dry mixing can be high shear mixing.

[0051] The particle size (D50) of the positive active material substrate may be 10 nm to 10 μm, and the particle size (D50) of the coating substrate may be 10 nm to 200 nm.

[0052] In the present invention, the particle size can be measured using a particle size analyzer, for example, a Mastersizer 3000 (Malvern panalytical).

[0053] In one embodiment of the present invention, the positive electrode active material composite may further include a solid electrolyte. In this case, the solid electrolyte may include the same solid electrolyte as that in the positive electrode active material layer described below.

[0054] The present invention also relates to a positive electrode comprising the positive electrode active material composite.

[0055] The positive electrode is characterized in that it contains the positive electrode active material composite of the present invention. Since the description of the positive electrode active material composite is the same as that described above, it will be omitted.

[0056] The positive electrode of the present invention may be a self-standing positive electrode made of a positive electrode active material layer component, or may be in the form of a positive electrode active material layer stacked on a positive electrode current collector.

[0057] The positive electrode active material layer may further include positive electrode active materials known in the art in addition to the positive electrode active material composite.

[0058] Specific examples of positive electrode active materials known in the art include, but are not limited to, lithium cobaltate (hereinafter referred to as LCO), lithium nickelate, lithium nickel cobaltate, lithium nickel cobalt aluminumate (hereinafter referred to as NCA), lithium nickel cobalt manganate (hereinafter referred to as NCM), lithium salts (such as lithium manganate and lithium iron phosphate), and lithium sulfide.

[0059] The positive electrode active material layer may further include a solid electrolyte. As the solid electrolyte, any solid electrolyte known in the art may be used without limitation, for example, an oxide solid electrolyte, a polymer solid electrolyte, or a sulfide solid electrolyte may be used, and in particular, a sulfide solid electrolyte may be preferably used.

[0060] Sulfide solid electrolytes may include Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), 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, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (wherein p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In) or any combination thereof. The solid electrolyte may include one material selected from these sulfide-based solid electrolyte materials, or may include two or more materials selected therefrom.

[0061] The sulfide-based solid electrolyte may include a solid electrolyte represented by the following formula 3:

[0062] [Formula 3]

[0063] Li x M' y PS z A w

[0064] wherein x, y, z and w are independently 0 to 6, inclusive;

[0065] M' is at least one of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; and A is at least one of F, Cl, Br, or I.

[0066] As a solid electrolyte, a sulfide-based solid electrolyte material containing sulfur (S), phosphorus (P), and lithium (Li) can be used as a component. For example, a material containing Li2S-P2S5 can be used. When a material containing Li2S-P2S5 is used as a sulfide-based solid electrolyte material, the mixing molar ratio of Li2S and P2S5 can be selected within the range of, for example, 50:50 to 90:10.

[0067] The solid electrolyte may be included in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 10 to 20 wt %, based on the total weight of the positive electrode active material layer.

[0068] The positive electrode current collector may be in the form of a plate or foil. For example, the positive electrode current collector may be a metal or an alloy of two or more metals selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium.

[0069] Furthermore, the positive electrode active material layer may further contain a conductive agent and a binder, and may further contain additives such as a filler, a dispersant, or an ion conduction aid.

[0070] Conductive materials are used to impart conductivity to electrodes. As long as they have electronic conductivity and do not cause chemical changes, they can be used in the battery being manufactured without particular limitation. Specific examples include: graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fibers, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. One or a mixture of two or more of these materials can also be used.

[0071] The conductive material may be included in an amount of 0.01 to 10 wt %, preferably 0.1 to 5 wt %, and more preferably 0.1 to 2 wt %, based on the total weight of the positive active material layer.

[0072] Binders are used to improve the bonding force between the positive electrode active material particles and the bonding force between the positive electrode active material and the positive electrode current collector. Specific examples may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber or various copolymers thereof, and a mixture of one or more selected therefrom may be used.

[0073] The binder may be included in an amount of 0.5 to 20 wt %, preferably 1 to 10 wt %, and more preferably 1 to 5 wt %, based on the total weight of the positive electrode active material layer.

[0074] As the filler, dispersant, or ion-conducting aid, any known material conventionally used for lithium-ion secondary battery electrodes can be used.

[0075] The positive electrode active material layer of the present invention may contain 50% to 90% by weight of a positive electrode active material composite, 1% to 30% by weight of a solid electrolyte, 0.1% to 5% by weight of a conductive material and 0.5% to 20% by weight of a binder; preferably, it may contain 75% to 85% by weight of a positive electrode active material composite, 10% to 20% by weight of a solid electrolyte, 0.1% to 2% by weight of a conductive material and 0.5% to 3% by weight of a binder.

[0076] The present invention also relates to a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0077] Lithium-ion secondary batteries can be all-solid-state batteries, which are defined as batteries that include not only solid-state electrolytes but also electrolytes obtained by adding some liquid electrolytes to solid-state electrolytes.

[0078] Hereinafter, an example of a lithium ion secondary battery will be described.

[0079] A lithium secondary battery includes a positive electrode, a negative electrode located opposite the positive electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode, and optionally includes a separator.

[0080] (1) Positive electrode

[0081] The lithium ion secondary battery of the present invention is characterized in that it includes the positive electrode of the present invention described above. Therefore, the description of the positive electrode is omitted.

[0082] (2) Negative electrode

[0083] The negative electrode includes a self-standing negative electrode type and a negative electrode type in which a negative electrode active material layer is stacked on a negative electrode current collector. The negative electrode in the lithium ion secondary battery is not particularly limited, and any negative electrode known in the art can be used without limitation.

[0084] The negative electrode current collector is not particularly limited, as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloys can be used. The thickness of the negative electrode current collector can generally be 3 to 500 μm. As with the positive electrode current collector, microscopic irregularities can be formed on the current collector surface to enhance the adhesion of the negative electrode active material. The negative electrode current collector can be in various forms, such as films, sheets, foils, meshes, porous materials, foams, non-woven fabrics, etc.

[0085] The negative electrode active material layer contains a negative electrode active material, which may optionally further contain a binder and a conductive material, and may further contain a solid electrolyte.

[0086] As the negative electrode active material, a compound that can reversibly intercalate and deintercalate lithium can be used. Specific examples include carbon materials such as artificial graphite, natural graphite, graphitized carbon fibers, amorphous carbon, etc.; metal substances that can alloy with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides that can be doped and dedoped with lithium, such as SiO β (where 0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, etc.; or a complex comprising a metal substance and a carbonaceous material, such as an Ag-C complex, a Si-C complex or a Sn-C complex, and a mixture of one or more selected therefrom can be used.

[0087] In addition, metallic lithium thin films can be used as the negative electrode active material, while anode-free batteries do not contain a separate negative electrode active material.

[0088] Conductive materials are used to impart conductivity to electrodes. As long as they have electronic conductivity and do not cause chemical changes, they can be used in the battery being manufactured without particular limitation. Specific examples include: graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fibers, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. One or a mixture of two or more of these materials can be used.

[0089] The content of the conductive material may generally be 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the negative electrode active material layer.

[0090] The binder is used to enhance the bonding force between the negative electrode active material particles and the bonding force between the negative electrode active material and the negative electrode current collector. Specific examples include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber or various copolymers thereof, and one or a mixture of two or more selected therefrom can be used.

[0091] The binder may be included in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the negative active material layer.

[0092] As the solid electrolyte, any solid electrolyte known in the art can be used without limitation, for example, an oxide-based solid electrolyte, a polymer-based solid electrolyte, or a sulfide-based solid electrolyte can be used, and in particular, a sulfide-based solid electrolyte can be preferably used. As the sulfide-based solid electrolyte, any sulfide-based solid electrolyte described previously can be used.

[0093] The solid electrolyte may be contained in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 10 to 20 wt %, based on the total weight of the negative electrode active material layer.

[0094] The negative electrode active material layer may be prepared by coating and drying a negative electrode slurry, or may be prepared by casting the negative electrode slurry onto a separate support and then laminating the film obtained by peeling off the support onto a negative electrode current collector.

[0095] (3) Solid electrolyte layer

[0096] The solid electrolyte layer contains a solid electrolyte capable of ion migration. As the solid electrolyte, any solid electrolyte known in the art can be used without limitation. For example, an oxide-based solid electrolyte, a polymer-based solid electrolyte, or a sulfide-based solid electrolyte can be used. In particular, a sulfide-based solid electrolyte can be preferably used. As the sulfide-based solid electrolyte, any sulfide-based solid electrolyte described previously can be used.

[0097] The solid electrolyte can be in an amorphous or crystalline state, or a mixture of amorphous and crystalline states.

[0098] The solid electrolyte layer may further include a binder. For example, the binder material may be a resin such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyacrylic acid, etc. The binder may be the same material as or different from the binder in the positive electrode active material layer and the negative electrode active material layer.

[0099] In the lithium ion secondary battery of the present invention, as for configurations other than the above-mentioned positive electrode active material composite, configurations known in the art can be applied without limitation. Therefore, a more detailed description will be omitted.

[0100] Example

[0101] Hereinafter, the present invention will be described with reference to Examples to illustrate the present invention in detail. However, the embodiments of the present invention can be modified in many other ways, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more fully illustrate the present invention to those skilled in the art.

[0102] Example 1: Fabrication of a positive electrode active material composite

[0103] (1) Manufacturing positive electrode active material substrate

[0104] Li2CO3 and Ni 0.8 Co 0.1 Mn 0.1 (OH)2 was mixed in a mixer at a weight ratio of 1.1:1 to form a reaction mixture, and then the reaction mixture was placed in a crucible made of stainless steel and subjected to a first heat treatment at 600°C in an ambient atmosphere for 5 hours to form a plasticized mixture, which was then cooled. Subsequently, it was quenched and sieved, and the crushed plasticized mixture was placed in an aluminum crucible and subjected to a second heat treatment at 800°C in an ambient atmosphere for 10 hours to prepare LiNi with a particle size (D50) of 5 μm. 0.8 Co 0.1 Mn 0.1 O2.

[0105] (2) Manufacturing coating substrate

[0106] Li2CO3, TiO2 and melamine (C3N3(NH2)3) were added in a stoichiometric ratio and mixed in a mortar for 4 hours. Then, the mixture was placed in a tube furnace with an inner diameter of 50 mm and a length of 1000 mm and heat-treated at 700 ° C for 12 hours to prepare Li4Ti5O 11.8 N 0.2 .

[0107] (3) Manufacturing positive electrode active material composites

[0108] 99 g of the positive electrode active material substrate LiNi prepared in the above (1) with a particle size (D50) of 5 μm was added. 0.8 Co 0.1 Mn 0.1 O2 powder and 1g of Li4Ti5O prepared in (2) above 11.8 N 0.2 The powder was placed in a container and mixed at 5000 rpm for 1 minute using a Lab Blender (manufactured by Waring) without using any solvent. The mixture was then subjected to high shear mixing (NOB-130, Hosokawa Micron) at 3000 rpm for 10 minutes to prepare a LiNi 0.8 Co 0.1 Mn 0.1 Li4Ti5O is formed on the O2 substrate 11.8 N 0.2 Coated positive electrode active material composite.

[0109] Example 2: Fabrication of a positive electrode active material composite

[0110] Li2CO3, TiO2 and NH4H2PO4 were added in a stoichiometric ratio and mixed in a mortar for 4 hours. Then, the mixture was placed in a tube furnace with an inner diameter of 50 mm and a length of 1000 mm and heat-treated at 800 ° C for 6 hours to produce Li4Ti5O 11.8 P 0.2 .

[0111] The same method as in Example 1 was used except that the Li4Ti5O 11.8 P 0.2 Instead of Li4Ti5O in Example 1 11.8 N 0.2 , prepared in LiNi 0.8 Co 0.1 Mn 0.1 O2 substrate coated with Li4Ti5O 11.8 P 0.2 positive electrode active material composite.

[0112] Example 3: Fabrication of a positive electrode active material composite

[0113] Titanium (IV) isopropoxide (Ti(OC3H7)4), lithium hydroxide (LiOH), and thioacetamide (C2H5NS) were dissolved in a stoichiometric ratio in a mixture of ethanol and distilled water (3:1 by weight) and mixed for about 2 hours to prepare a solution.

[0114] The LiNi prepared by the same method as in Example 10.8 Co 0.1 Mn 0.1 O2 was added to the solution prepared above, and then dried under vacuum at 80 °C.

[0115] Finally, it was placed in a tube furnace with an inner diameter of 50 mm and a length of 1000 mm and heat treated at 600 ° C for 10 hours to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 substrate coated with Li4Ti5O 11.8 S 0.2 Composite composite of positive electrode active materials.

[0116] Comparative Example 1: Preparation of a positive electrode active material composite

[0117] Li2CO3 and TiO2 were added in a weight ratio of 1:2.5, mixed in a mortar for four hours, and then loaded into a tube furnace with an inner diameter of 50 mm and a length of 1000 mm and heat treated at 800 ° C for 12 hours to prepare Li4Ti5O 12 .

[0118] The same method as in Example 1 was used except that the Li4Ti5O 12 Instead of Li4Ti5O in Example 1 11.8 N 0.2 , prepared in LiNi 0.8 Co 0.1 Mn 0.1 O2 substrate coated with Li4Ti5O 12 positive electrode active material composite.

[0119] Examples 4 to 6 and Comparative Example 2: Manufacturing of All-Solid-State Lithium-Ion Secondary Batteries

[0120] (1) Manufacturing the positive electrode

[0121] 81.9 wt % of each positive electrode active material composite prepared in Examples 1 to 3 and Comparative Example 1, 15.6 wt % of solid electrolyte LPS (Li6PS5Cl), 1.5 wt % of carbon black powder and 1 wt % of binder PTFE were mixed at 5000 rpm for 1 minute (primary mixing) using a laboratory blender (Waring) without a solvent. Then, high shear mixing (using PBV-0.1L, Irie Shokai) was performed by applying a shear force of 100 N to the mixture to prepare a dough (secondary mixing). Next, a double-roll mill MR-3 (Inoue) was used to make a positive electrode layer with a free-standing structure from the dough.

[0122] This electrode layer was placed on one side of an aluminum current collector having a thickness of 15 μm and pressed to produce each positive electrode.

[0123] (2) Manufacturing all-solid-state lithium-ion secondary batteries

[0124] A lithium metal with a thickness of 40 μm was used as the negative electrode, and a Li6PS5Cl solid electrolyte membrane with a thickness of 50 μm was arranged between each positive electrode and negative electrode, and then pressurized at a pressure of 500 MPa to prepare the clamp battery cells of Examples 4 to 6 and Comparative Example 2 with a driving pressure of 3 MPa and a capacity of 5 mAh.

[0125] Experimental Example 1: Evaluating Battery Characteristics

[0126] (1) Evaluating the initial discharge capacity and efficiency of all-solid-state batteries

[0127] The fixture cells prepared in Examples 4 to 6 and Comparative Example 2 were charged at a rate of 0.1C (C-rate) until the voltage reached 4.25V (relative to Li), and then the charge was cut off at a rate of 0.05C while maintaining 4.25V (relative to Li). They were then discharged at a rate of 0.1C (C-rate) to a discharge voltage of 3.0V (relative to Li) (1st cycle). The initial efficiency was calculated as follows: discharge capacity / charge capacity × 100 (%). The experimental results are shown in Table 1 below.

[0128] (2) Evaluating the lifespan characteristics of all-solid-state batteries

[0129] The fixture cells prepared in Examples 4 to 6 and Comparative Example 2 were charged at a rate of 0.33C (C-rate) until the voltage reached 4.25V (relative to Li), and then the charge was cut off at a rate of 0.1C while maintaining 4.25V (relative to Li). They were then discharged at a rate of 0.33C (C-rate) to a discharge voltage of 3.0V (relative to Li) (1st cycle). The charge and discharge test was repeated for 50 cycles, and the capacity retention rate of the discharge capacity was determined. The experimental results are shown in Table 1 below.

[0130] [Table 1]

[0131]

Claims

1. A positive electrode active material composite, comprising a positive electrode active material substrate and a coating coated on the positive electrode active material substrate and containing a compound represented by Formula 1, [Formula 1] Li a You b ON c-d X d where X is N, P or S; and 1 ≤ a ≤ 6, 1 ≤ b ≤ 6, 3 ≤ c ≤ 15 and 0 < d ≤ 1.

5.

2. The positive electrode active material composite according to claim 1, in, a is 4, b is 5, c is 12, and d is 0.1 to 0.

3.

3. The positive electrode active material composite according to claim 1, in, where the positive electrode active material substrate is a compound represented by Formula 2, [Formula 2] The a (Nor 1-x-y-z Co x M1 y M2 z )O2 where M1 is manganese (Mn), aluminum (Al) or a combination thereof; M2 is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), aluminum (Al) or any combination of two or more thereof; and 0.95 ≤ a ≤ 1.3, 0 < x < 1, 0 ≤ y < 1, and 0 ≤ z < 1.

4. The positive electrode active material composite according to claim 1, in, Based on the total weight of the positive electrode active material composite, the content of the coating is 0.1% by weight to 5% by weight.

5. The positive electrode active material composite according to claim 1, in, The thickness of the coating is 10 nm to 200 nm.

6. The positive electrode active material composite according to claim 1, in, The molar ratio of Ti to X in the coating is 1:0.01 to 0.

2.

7. The positive electrode active material composite according to claim 1, in, The coating is formed by dry-mixing the positive electrode active material substrate and the coating substrate.

8. A positive electrode, comprising the positive electrode active material composite according to claim 1.

9. The positive electrode according to claim 8, further comprising a sulfide-based solid electrolyte.

10. The positive electrode according to claim 9, wherein The sulfide-based solid electrolyte is a compound represented by Formula 3, [Formula 3] Li x M' y P.S. z A w where x, y, z and w are independently 0 to 6, including 0 and 6; M' is at least one of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta; and A is at least one of F, Cl, Br or I. [[ID=二十七]]11. A lithium-ion secondary battery, comprising the positive electrode according to claim 8, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

12. The lithium ion secondary battery according to claim 11, wherein The lithium-ion secondary battery is a sulfide-based all-solid-state battery.

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