Positive electrode for secondary batteries and method for manufacturing a positive electrode for secondary batteries

Abstract

To provide a positive electrode for a secondary battery that can improve the volumetric energy density while having a metal-organic structure. [Solution] A positive electrode for a secondary battery is provided, comprising a positive electrode current collector, a positive electrode composite layer provided on the main surface of the positive electrode current collector, and a metal-organic structure, wherein the positive electrode composite layer has a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles, and the metal-organic structure is located from the surface of the positive electrode composite layer to the gaps inside the positive electrode composite layer, with the main surface of the positive electrode current collector as the starting point, and the gaps extending to a thickness of 50% or less of the positive electrode composite layer.

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode for a secondary battery and a method for manufacturing a positive electrode for a secondary battery. [Background technology]

[0002] Rechargeable and rechargeable secondary batteries have long been used in a variety of applications. For example, secondary batteries are used as power sources for electronic devices such as smartphones and laptop computers.

[0003] A secondary battery has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes, and an electrolyte are housed in a housing. The positive electrode consists of a current collector and a positive electrode composite layer containing positive electrode active material provided on the current collector, and the negative electrode consists of a current collector and a negative electrode composite layer containing negative electrode active material provided on the current collector.

[0004] To achieve high energy density in batteries, attempts have been made to increase the voltage of the positive electrode. However, it is known that high voltages lead to oxidative decomposition of the electrolyte, resulting in a decrease in cycle characteristics. In this regard, Patent Document 1 describes how coating the positive electrode composite layer with a metal-organic framework (MOF) expands the potential window on the high-potential side of the electrolyte, thereby suppressing oxidative decomposition of the electrolyte near the positive electrode (see Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] A Liquid Electrolyte with De-Solvated Lithium Ions for Lithium-Metal Battery Zhi Chang, Haoshen Zhou et al., Joule 4, 1776 2020 [Overview of the project] [Problems that the invention aims to solve]

[0006] Here, the inventors of the present application newly found that in the aspect of coating the positive electrode composite material layer with a metal-organic structure, there are points to be improved in the following aspects. Specifically, in such an aspect, the volume including the positive electrode composite material layer and the metal-organic structure increases, resulting in a decrease in the volumetric energy density of the battery.

[0007] The present disclosure has been devised in view of such circumstances. Specifically, an object thereof is to provide a positive electrode for a secondary battery and a method for manufacturing the same capable of improving the volumetric energy density in a state having a metal-organic structure.

Means for Solving the Problems

[0008] In order to achieve the above object, in one embodiment of the present disclosure, a positive electrode current collector, a positive electrode composite material layer provided on a main surface of the positive electrode current collector, and a metal-organic structure are included, the positive electrode composite material layer has a plurality of positive electrode active material particles and a plurality of gap portions provided between the positive electrode active material particles inside, the metal-organic structure is located from the surface of the positive electrode composite material layer to the gap portions inside the positive electrode composite material layer that are 50% or less of the thickness of the positive electrode composite material layer based on the main surface of the positive electrode current collector, and a positive electrode for a secondary battery is provided.

[0009] In order to achieve the above object, in one embodiment of the present disclosure, a metal-containing material and a nitrogen-containing organic compound are prepared, and a positive electrode precursor having a positive electrode current collector and a positive electrode composite material layer provided on a main surface of the positive electrode current collector and having a plurality of positive electrode active material particles and a plurality of gap portions provided between the positive electrode active material particles inside is brought into contact with a solution having the metal-containing material and the nitrogen-containing organic compound, and a metal-organic structure is synthesized from the metal oxide and the nitrogen-containing organic compound in the gap portions of the positive electrode composite material layer A method for manufacturing a positive electrode for a secondary battery including the above is provided.

Effects of the Invention

[0010] According to the positive electrode for a secondary battery according to an embodiment of the present disclosure, it is possible to improve the volume energy density while having a metal organic structure.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing the configuration of the positive electrode for a secondary battery according to an embodiment of the present disclosure. [Figure 2] It is a graph showing the relationship (LSV) between potential and current when the electrode for a secondary battery of the present disclosure is used and when electrolytic solutions with different concentrations are used respectively. [Figure 3] It is a graph showing the Raman spectrum of the electrolytic solution in the metal organic structure. [Figure 4] It is an enlarged graph showing the Raman spectrum of the electrolytic solution in the metal organic structure. [Figure 5] It shows the Raman spectra of LiTFSI solutions with different concentrations using a DME / DOL mixed solvent as the solvent. [Figure 6] It is a graph showing the retention rates in Examples 1 to 3 and Comparative Example 1. [Figure 7] It is a graph showing the charge-discharge efficiencies in Examples 1 to 3 and Comparative Example 1. [Figure 8] It is a SEM image showing the configuration of the positive electrode for a secondary battery according to an embodiment of the present disclosure. [Figure 9] It is an enlarged SEM image showing the configuration of the positive electrode for a secondary battery according to an embodiment of the present disclosure. <00001…​​​​​​​​​​​​​​The following describes a positive electrode for a secondary battery according to one embodiment of the present disclosure with reference to the drawings. The various elements in the drawings are shown schematically and illustratively for the purpose of understanding the present disclosure, and their appearance, dimensional ratios, etc., may differ from those of the actual product.

[0013] As used herein, the term "secondary battery" refers to a battery that can be repeatedly charged and discharged. The term "secondary battery" is not overly restrictive and may also include, for example, "energy storage devices." As used herein, "cross-sectional view" refers to the state when viewed from a direction approximately perpendicular to the thickness direction of the electrode material constituting the secondary battery. As used directly or indirectly herein, "up and down direction" and "left and right direction" correspond to the up and down direction and left and right direction in the figures, respectively.

[0014] The various numerical ranges referred to herein are intended to include the lower and upper numerical values ​​themselves. That is, for example, a numerical range of 1 to 10 can be interpreted as including both the lower limit value of "1" and the upper limit value of "10".

[0015] [Basic configuration of a secondary battery] First, regarding the basic structure of a secondary battery, a secondary battery has a structure in which an electrode assembly and an electrolyte are housed and sealed inside a predetermined housing. The electrode assembly may include a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes.

[0016] (Positive electrode / Negative electrode) The positive electrode consists of at least a positive electrode composite layer and a positive electrode current collector. The positive electrode composite layer contains a positive electrode active material as an electrode active material. The positive electrode may have the positive electrode composite layer provided on at least one main surface of the positive electrode current collector.

[0017] The negative electrode consists of at least a negative electrode composite layer and a negative electrode current collector. The negative electrode composite layer contains a negative electrode active material as an electrode active material. The negative electrode may have the negative electrode composite layer provided on at least one main surface of the negative electrode current collector.

[0018] The electrode active materials contained in the positive and negative electrodes, namely the positive electrode active material and the negative electrode active material, are substances directly involved in electron transfer in a secondary battery and are the main materials of the positive and negative electrodes that carry out charging and discharging, i.e., the battery reaction. More specifically, ions are brought into the electrolyte due to the "positive electrode active material contained in the positive electrode composite layer" and the "negative electrode active material contained in the negative electrode composite layer," and these ions move between the positive and negative electrodes to transfer electrons and perform charging and discharging. The positive electrode composite layer and the negative electrode composite layer may be layers that can intercept and deintercept lithium ions. In other words, the secondary battery may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive and negative electrodes via a non-aqueous electrolyte to perform charging and discharging of the battery. When lithium ions are involved in charging and discharging, the secondary battery according to this disclosure corresponds to a so-called "lithium-ion battery" and has layers that can intercept and deintercept lithium ions as the positive electrode and negative electrode.

[0019] In the context of lithium-ion batteries, the positive electrode active material may be a material that facilitates the intercalation and deintercalation of lithium ions. In other words, the positive electrode layer may contain one or more types of positive electrode materials capable of intercalating and deintercalating lithium. From this perspective, the positive electrode active material may be, for example, a lithium-containing compound. The type of lithium-containing compound is not particularly limited, but examples include lithium-containing composite oxides and lithium-containing phosphate compounds, because they easily provide high energy density.

[0020] Lithium-containing composite oxides are a general term for oxides that contain lithium and one or more other elements (elements other than lithium) as constituent elements, and may have one of the following crystal structures: layered rock salt type and spinel type. Lithium-containing phosphate compounds are a general term for phosphate compounds that contain lithium and one or more other elements as constituent elements, and may have one of the following crystal structures: olivine type. The types of other elements are not particularly limited as long as they are one or more of any elements. In particular, it is preferable that the other elements be one or more of the elements belonging to groups 2 to 15 of the long-period periodic table. More specifically, the other elements are, for example, nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe). This is because high voltages are easily obtained with these additive elements.

[0021] The positive electrode composite layer may contain a binder. Furthermore, the positive electrode composite layer may contain a positive electrode conductive agent to facilitate the transfer of electrons that drive the battery reaction. The positive electrode binder may contain one or more of the following: synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene-butadiene rubber, fluorine-based rubber, and ethylene-propylenediene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent may contain one or more of the following: carbon materials, for example. Examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black. However, the positive electrode conductive agent may also be any conductive material, such as metal materials and conductive polymers.

[0022] Similarly, the negative electrode active material in the negative electrode composite layer may be a material that facilitates the intercalation and deintercalation of lithium ions. In other words, the negative electrode layer may contain one or more negative electrode materials capable of intercalating and deintercalating lithium. From this perspective, the negative electrode active material may be, for example, various carbon materials, metallic materials, and / or other materials.

[0023] When carbon materials are used as the negative electrode active material, the change in crystal structure during lithium absorption and release is very small, making it easy to stably obtain a high energy density. In addition, since carbon materials also function as negative electrode conductive agents, the conductivity of the negative electrode layer is easily improved.

[0024] "Metallic materials" used as negative electrode active materials are a general term for materials that contain one or more metallic elements and metalloid elements as constituent elements. When carbon materials are used as negative electrode active materials, high energy density is easily obtained. Metallic materials may be elements, alloys, compounds, two or more of these, or materials that contain at least one or two or more of these phases in part.

[0025] In addition, the negative electrode material may be one or more of the following: metal oxides and polymer compounds. Examples of metal oxides include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of polymer compounds include polyacetylene, polyaniline, and polypyrrole.

[0026] The negative electrode composite layer may contain a binder. Furthermore, a negative electrode conductive agent may be included in the negative electrode composite layer to facilitate the transfer of electrons that drive the battery reaction. The binder that may be included in the negative electrode composite layer is not particularly limited, but at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resins, and polyamide-imide resins can be mentioned. The negative electrode conductive agent that may be included in the negative electrode composite layer is not particularly limited, but at least one selected from the group consisting of carbon black such as thermal black, furnace black, channel black, Ketjen black, and acetylene black; carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers; metal powders such as copper, nickel, aluminum, and silver; and polyphenylene derivatives can be mentioned. The negative electrode composite layer may also contain components resulting from the thickening agent components used during battery fabrication (e.g., carboxymethylcellulose).

[0027] The positive electrode current collector and the negative electrode current collector used in the positive and negative electrodes are components that help collect and supply electrons generated in the electrode active material due to the battery reaction. Such electrode current collectors may be sheet-shaped metal members. Furthermore, the electrode current collector may be single-layered or multi-layered. Moreover, the electrode current collector may have a porous or perforated form. For example, the current collector may be metal foil, perforated metal, mesh, or expanded metal. The positive electrode current collector used in the positive electrode may consist of metal foil containing at least one selected from the group consisting of aluminum, nickel, and stainless steel, for example. On the other hand, the negative electrode current collector used in the negative electrode may consist of metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, and stainless steel, for example.

[0028] (Separator) A separator, placed between the positive and negative electrodes, is a component provided to prevent short circuits caused by contact between the positive and negative electrodes and to maintain the electrolyte. In other words, the separator is a component that isolates the positive and negative electrodes, prevents short circuits of current caused by contact between the two electrodes, and allows ions (e.g., lithium ions) to pass through. For example, the separator may be a porous or microporous insulating material, and may have a film form due to its small thickness.

[0029] The separator may be one or more of the following porous membranes: synthetic resin and / or ceramic, or a laminated film of two or more porous membranes. Examples of synthetic resins used in the separator include polytetrafluoroethylene, polypropylene, and polyethylene.

[0030] (electrolyte) The electrolyte that can be used in the secondary battery of this disclosure may be a so-called “non-aqueous” electrolyte. Typically, the electrolyte solution comprises a solvent and an electrolyte salt. The electrolyte solution may further contain one or more of the other materials, such as additives. In one preferred embodiment, the separator may be impregnated with the electrolyte solution, and furthermore, the positive electrode and / or negative electrode may also be impregnated with the electrolyte solution.

[0031] The solvent may contain one or more non-aqueous solvents, such as organic solvents. An electrolyte containing a non-aqueous solvent can be a so-called non-aqueous electrolyte. Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, lactones, linear carboxylic acid esters, and / or nitriles (e.g., mononitriles). This makes it easier to obtain better battery capacity, cycle characteristics, and / or storage characteristics. Examples of cyclic carbonate esters include ethylene carbonate, propylene carbonate, and / or butylene carbonate. Examples of linear carbonate esters include dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, and / or methylpropyl carbonate. Examples of lactones include γ-butyrolactone and / or γ-valerolactone. Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and / or trimethylethyl acetate. The nitrile may be, for example, acetonitrile, methoxyacetonitrile and / or 3-methoxypropionitrile. In addition, the non-aqueous solvent may be, for example, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate and / or dimethyl sulfoxide.

[0032] The electrolyte solution may contain one or more types of salts, such as lithium salts. Examples of lithium salts include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl), and / or lithium bromide (LiBr). This is because it makes it easier to obtain better battery capacity, cycle characteristics, and / or storage characteristics.

[0033] The following describes the key features of this disclosure. This disclosure relates to the positive electrode for a secondary battery, which is one of the components of the secondary battery described above.

[0034] Figure 1 is a schematic cross-sectional view showing the configuration of a positive electrode for a secondary battery according to one embodiment of the present disclosure. Figure 2 is a graph showing the relationship between potential and current (LSV) when using the secondary battery electrode of the present disclosure and when using electrolytes of different concentrations. Figure 3 is a graph showing the Raman spectrum of the electrolyte in the metal-organic structure. Figure 4 is an enlarged graph showing the Raman spectrum of the electrolyte in the metal-organic structure.

[0035] As shown in Figure 1, a positive electrode 10 for a secondary battery according to one embodiment of the present disclosure includes a positive electrode current collector 1, a positive electrode composite material layer 2 provided on the main surface of the positive electrode current collector 1, and a metal organic framework 3 (MOF). The positive electrode composite material layer 2 has a plurality of positive electrode active material particles 2X and a plurality of gaps 2Y provided between the positive electrode active material particles 2X. The main surface of the positive electrode current collector 1 faces the positive electrode composite material layer 2.

[0036] As shown in Figure 1, the positive electrode composite layer 2 according to one embodiment of the present disclosure includes a first region 2I on the side in contact with the positive electrode current collector 1 and a second region 2II on the side in contact with the separator. The first region 2I is the region from the dividing line (corresponding to the dotted line in Figure 1) that divides the positive electrode composite layer 2 in the longitudinal direction to the interface 4 between the positive electrode composite layer 2 and the positive electrode current collector 1. The second region 2II is the region from the dividing line that divides the positive electrode composite layer 2 in the longitudinal direction to the interface between the positive electrode composite layer 2 and the separator. The gap portion 2Y inside the positive electrode composite layer 2 includes the gap portion 2Y1 inside the first region 2I and the gap portion 2Y2 inside the second region 2II.

[0037] Furthermore, the present disclosure is characterized in that the metal-organic structure 3 is located from the surface 5 of the positive electrode composite layer 2 (corresponding to the interface between the positive electrode composite layer 2 and the separator) to the gap 2Y inside the positive electrode composite layer 2, which is 50% or less of the thickness of the positive electrode composite layer 2, with the main surface of the positive electrode current collector 1 as the starting point. In other words, the present disclosure is characterized in that the metal-organic structure 3 is located in the gap 2Y1 inside the first region 2I of the positive electrode composite layer 2 and in the gap 2Y2 inside the second region 2II of the positive electrode composite layer 2.

[0038] The metal-organic structure described above may have a central metal atom and an organic ligand. This central metal atom and the organic ligand form a coordination bond, and as a whole, the metal-organic structure may have a structure with multiple pores inside. These pores can serve as spaces for receiving the electrolyte within the positive electrode 10. These pores may include mesopores or micropores as pore types. The average pore width of these pores is between 0.3 nm and 1.5 nm. By appropriately selecting the metal-organic structure, the pore type, pore width, or pore diameter of the metal-organic structure can be optimized. The particle size of the metal-organic structure 3 is between 30 nm and 270 nm (see Figures 10 and 11). Furthermore, the thickness of the metal-organic structure 3, which can be formed as a film on the positive electrode active material particles 2X, is between 60 nm and 420 nm (see Figure 12).

[0039] The central metal atom described above can be selected from the group consisting of V, Cr, Fe, Cu, Mg, Zr, Ti, Mn, Al, Zn, Co, and Ni, with at least one element selected. For example, the central metal atom can be selected from the group consisting of atoms contained in the positive electrode active material and the group consisting of atoms with the same period as the atoms contained in the positive electrode active material. For example, Zn, Co, or Ni can be selected as the central metal atom. The organic ligand is a nitrogen-containing organic compound. Specifically, the organic ligand is an organic compound having an azole skeleton. From another perspective, the organic ligand is an organic compound having two or more nucleophilic sites relative to the central metal atom.

[0040] As an example, an organic ligand may have one of the following skeletons: imidazole skeleton, triazole skeleton, benzimidazole skeleton, or purine skeleton. [Chemical Formula 1] Imidazole skeleton JPEG2026061941000002.jpg34138 (In the formula, R1 to R3 are hydrogen groups, methyl groups, ethyl groups, nitro groups, etc.) [Chemical Formula 2] Triazole skeleton JPEG2026061941000003.jpg23137 (In the formula, R4~R5 are hydrogen groups, methyl groups, etc.) [Chemical Formula 3] Benzimidazole skeleton JPEG2026061941000004.jpg37142 (In the formula, R6~R9 are hydrogen groups, methyl groups (Cl), Br groups, nitro groups, etc.) [Chemical Formula 4] Purine skeleton JPEG2026061941000005.jpg28147 (In the formula, R10 to R12 are hydrogen groups, methyl groups, etc.)

[0041] For example, possible organic ligands include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, imidazole-4-carbonitride, 4,5-dichloroimidazole, imidazole-2-carboxyaldehyde, 4-azabenzimidazole, benzimidazole, 5-chlorobenzimidazole, 5,6-dimethylbenzimidazole, 5-methylbenzimidazole, 5-bromobenzimidazole, 5-nitrobenzimidazole, imidazo[4,5-c]pyridine, 1,2,3-triazole, 1,2,4-triazole, purine, etc. The organic ligand can coordinate to the central metal atom and exist as anion. Two or more organic ligands may be selected.

[0042] For example, TIF-4, ZIF-8, ZIF-7, ZIF-9, ZIF-22, MMOF, SIM-1, ZIF-90, ZIF95, ZIF78, ZIF-71, ZIF-73, ZIF-69, MIL-96, MIL-100, MIL-53, HKUST-1 (Cu-BTC), MOF-5 (IRMOF-1), MIL-47, UiO-66, ZSM-5, etc. can be used as the metal-organic structure 3. In one embodiment of this disclosure, ZIF (zeolitic imidazolate framework) is used as the metal-organic structure 3. More specifically, ZIF-8 (2-methylimidazole zinc salt) is used.

[0043] Here, the electrolyte located within the metal-organic structure 3 is Li + The coordination state changes, and two or more Li atoms are added to the opposing anion. + It can primarily take the form of an aggregate (AGG) in which the anions are coordinated. The counteranion is contained in the electrolyte, and for example, an anion contained in the electrolyte salt can become the counteranion. For example, when LiTFSI is used as the electrolyte, TFSI -The (bis(trifluoromethanesulfonyl)imide anion) can act as a counter anion. When the electrolyte exists in the AGG state within the metal-organic structure 3, the electrolyte can adopt a solvation structure similar to that of a high-salt concentration electrolyte. This makes it possible to expand the potential window on the high-potential side of the electrolyte (see Figures 2 to 4). As a result, oxidative decomposition of the electrolyte near the positive electrode can be suitably suppressed, and the cycle characteristics of the secondary battery can be improved.

[0044] For example, as shown in Figure 2, if an ether-based electrolyte containing an electrolyte (e.g., LiTFSI) is used, increasing the battery potential above a certain level can cause current to flow through the ether-based electrolyte containing the electrolyte (e.g., LiTFSI). This current generation indicates that oxidative decomposition of the electrolyte has occurred, leading to a decrease in the battery's cycle characteristics.

[0045] In this regard, the configuration in which a metal-organic structure (ZIF-8) is incorporated into the positive electrode composite layer 2 and a low-salt concentration (1M) electrolyte is used, and the configuration in which a high-salt concentration (4M) electrolyte is used, exhibit similar behavior (LSV) (see Figure 2). That is, it suggests that the electrolyte state is similar to that of a high-salt concentration electrolyte. This can also be understood from the Raman spectra shown in Figures 3 and 4, in which the intensity of the electrolyte at a predetermined wavenumber is high when a low-salt concentration (1M) electrolyte is applied to the metal-organic structure (ZIF-8).

[0046] Here, Figure 5 shows the Raman spectra of LiTFSI solutions of different concentrations using a DME / DOL mixed solvent. + In terms of existence states, there is the anti-anion and Li + The form of an aggregate (SSIP / Solvent Separated Ion Pair) in which a solvent molecule is interposed between the two anions, with one Li for each counter-anion. + The form of a coordinated aggregate (CIP / Contact Ion Pair), or two or more Li for each pair anion. +can take the form of an aggregate (AGG / Aggregate) in which it is coordinated. Li + When the state of existence of is in the form of SSIP, in the Raman spectrum, 735 cm -1 or more and 745 cm -1 or less, for example, a peak is detected around 740 cm -1 . When the state of existence of Li + is in the form of CIP, in the Raman spectrum, 740 cm -1 or more and 750 cm -1 or less, for example, a peak is detected around 746 cm -1 . When the state of existence of Li[[ID=1​​​​​​​​​​​​​​​​​​​​​​​​​​In other words, the metal-organic structure 3 is positioned from the surface side of the positive electrode composite layer 2 to the interface side between the positive electrode composite layer 2 and the positive electrode current collector 1. Preferably, the metal-organic structure 3 can come into contact with the positive electrode current collector 1. To put it simply, the metal-organic structure 3 penetrates into the back of the positive electrode composite layer 2 in the thickness direction so as to fill the gap 2Y within the positive electrode composite layer 2.

[0050] By adopting this configuration, in the positive electrode 10, compared to the conventional embodiment in which the metal-organic structure is coated on the positive electrode composite layer, the metal-organic structure 3 penetrates deeper into the interior of the positive electrode composite layer 2, resulting in a relatively lower coverage rate of the metal-organic structure 3 on the positive electrode composite layer 2. Therefore, compared to the embodiment in which the metal-organic structure is coated on the positive electrode composite layer, the volume including the positive electrode composite layer 2 and the metal-organic structure 3 can be reduced.

[0051] Based on the above, the positive electrode for secondary batteries of this disclosure makes it possible to improve the volumetric energy density in a secondary battery while suppressing oxidative decomposition of the electrolyte near the positive electrode.

[0052] Furthermore, as described above, by arranging the metal-organic structure 3 within the positive electrode composite layer 2, the electrolyte can adopt a solvation structure similar to that of a high-salt concentration electrolyte, which suppresses the decomposition of the electrolyte near the positive electrode. This expands the range of application for electrolytes in which the solvent is ether (ether-based electrolytes), which have been understood to be less prone to decomposition on the negative electrode side but more prone to oxidative decomposition on the positive electrode side. For example, electrolytes with an electrolyte salt concentration of 3M or less can be used.

[0053] Furthermore, while the use of a high-salt concentration electrolyte can be considered to suppress oxidative decomposition of the electrolyte on the positive electrode side at high voltage, it is not necessarily an appropriate solution because it leads to increased viscosity of the electrolyte within the battery.

[0054] In this regard, as described above, the combination of a metal-organic structure and a low-salt concentration electrolyte in the positive electrode composite layer 2 exhibits the same behavior (LSV) as the combination using a high-salt concentration electrolyte, and a low-salt concentration electrolyte can be selected. Therefore, the problem of high viscosity of the electrolyte within the battery can be avoided.

[0055] Furthermore, in the positive electrode composite layer 2, the ligands of the metal-organic structure 3 located between the positive electrode active material particles 2X can coordinate bond with the metal of the positive electrode active material particles 2X adjacent to the metal-organic structure 3. Through such coordination bonding, the metal-organic structure 3 can assume a stable position in the gap 2Y of the positive electrode composite layer 2.

[0056] According to this disclosure, it is possible to provide a state in which at least one positive electrode active material particle 2X is in contact with an adjacent positive electrode active material particle 2X and the metal-organic structure 3. In other words, the surface of at least one positive electrode active material particle 2X is in partial contact with the metal-organic structure.

[0057] With this configuration, compared to the case where the entire surface of the positive electrode active material particles 2X is surrounded by the metal-organic structure 3, interruptions in the conductive path are avoided, and smooth electron movement within the positive electrode 10 during battery charging and discharging can be ensured.

[0058] The following describes the method for manufacturing the positive electrode for secondary batteries according to this disclosure.

[0059] First, a method for manufacturing a positive electrode for a secondary battery according to one embodiment of the present disclosure is as follows: Prepare a metal-containing material and a nitrogen-containing organic compound. A method for manufacturing a positive electrode for a secondary battery is provided, which includes synthesizing a metal-organic structure by contacting a positive electrode precursor with a solution containing a metal-containing material and a nitrogen-containing organic compound.

[0060] (1) Preparation of metal-containing materials and nitrogen-containing organic compounds First, a metal oxide or metal salt containing at least one metal atom selected from the group consisting of Zn, Co, and Ni is prepared as the metal-containing material. As an example, Zn(NO3)2·6H2O can be used as the metal oxide.

[0061] Furthermore, as nitrogen-containing organic compounds, organic compounds having two or more nucleophilic sites relative to the above-mentioned metal atoms, such as organic compounds having an azole skeleton, are prepared. For example, at least one can be selected from the group consisting of imidazole, benzimidazole, triazole, and purine as the nitrogen-containing organic compound. As an example, 2-methylimidazole can be used as the nitrogen-containing organic compound. The molar ratio of the above-mentioned metal-containing material to the nitrogen-containing organic compound should be 1:4 to 1:2.

[0062] (2) Contact of a cathode precursor with a solution containing the above-mentioned metal-containing material and a nitrogen-containing organic compound, and synthesis of a metal-organic structure. Next, the positive electrode precursor is brought into contact with a solution containing the metal-containing material and a nitrogen-containing organic compound. For example, a first solution containing either the metal-containing material or the nitrogen-containing organic compound is prepared, the positive electrode precursor is immersed in the first solution, and while the positive electrode precursor is immersed in the first solution, a second solution containing the other of the metal-containing material or the nitrogen-containing organic compound is added dropwise.

[0063] As a positive electrode precursor, one is used that has a positive electrode current collector and a positive electrode composite material layer provided on the main surface of the positive electrode current collector. This positive electrode composite material layer has a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles inside.

[0064] For example, as a positive electrode precursor, the positive electrode current collector (SUS foil) contains NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) or NCM (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A positive electrode composite layer such as O2 can be used. In this specification, the finished product produced by the final step (7) below is described as the positive electrode, and the material used during the manufacturing process is described as the positive electrode precursor.

[0065] In this case, for example, the cathode precursor is immersed in a solution containing a metal-containing material and a nitrogen-containing organic compound, and ultrasonic treatment is performed for a predetermined time. Specifically, ultrasonic treatment is performed for a period of 5 minutes to 15 minutes, for example, 10 minutes.

[0066] In another example, the positive electrode precursor is immersed in the above solution and subjected to a heat treatment for a predetermined time. Specifically, this heat treatment is performed at a temperature of 50°C to 70°C, for example, 60°C for 1 hour. As a result, the metal-containing material and the nitrogen-containing organic compound react in the gaps of the positive electrode composite layer to synthesize a metal-organic structure. That is, the metal-organic structure is synthesized in the liquid phase.

[0067] (3) Primary drying process of the cathode precursor Next, the cathode precursor containing the synthesized metal-organic structure is removed from the solution containing the metal-containing material and the nitrogen-containing organic compound, and temporarily air-dried in the atmosphere for a predetermined time, for example, 1 minute.

[0068] (4) Washing process of the positive electrode precursor Next, the cathode precursor, which has been air-dried, is immersed in ethanol once and left to soak for a day to wash it.

[0069] (5) Reduced pressure and secondary drying process of the cathode precursor Next, the washed cathode precursor is subjected to reduced pressure (to approximately 0.1 MPa) and secondarily dried for a predetermined time (for example, about 10 hours) at a temperature between 120°C and 180°C (for example, 150°C) using a drying apparatus (manufactured by Yamato Scientific Co., Ltd.).

[0070] (6) Pressurization of the cathode precursor Finally, the positive electrode precursor is pressurized with a pressure of approximately 10 MPa using a RIKEN hydraulic press. Through this process, the positive electrode for secondary batteries according to this disclosure can be manufactured. [Examples]

[0071] The following describes examples of the positive electrode for secondary batteries of this disclosure.

[0072] Example 1 [Manufacturing Procedure] First, the positive electrode for the secondary battery was manufactured through the following process. (1) Preparation of metal-containing materials and nitrogen-containing organic compounds First, 10 ml of 0.1 mol / l Zn(NO3)2·6H2O (Aldrich, product code: 228737) was prepared as the metal-containing material. In addition, 10 ml of 0.4 mol / l 2-methylimidazole (Tokyo Chemical Industries, Ltd., product code: M0345) was prepared as the nitrogen-containing organic compound.

[0073] (2) Contact of a cathode precursor with a solution containing the above-mentioned metal-containing material and a nitrogen-containing organic compound, and synthesis of a metal-organic structure. Next, the solution containing the above metal-containing material and nitrogen-containing organic compound is added to the positive electrode precursor (SUS foil current collector NCA (LiNi 0.8 Co 0.15 Al 0.05 A positive electrode composite layer of O2 (so-called NCA electrode) was brought into contact with the electrode.

[0074] Specifically, a first solution of 0.4 mol / l 2-methylimidazole (a nitrogen-containing organic compound) was prepared, the cathode precursor was immersed in the first solution, and while the cathode precursor was still immersed in the first solution, a second solution of 0.1 mol / l Zn(NO3)2·6H2O (a metal-containing material) was added dropwise.

[0075] In this process, a first ultrasonic treatment was performed for 5 minutes at 20% output (80W) using a Hielscher UP400S (400W, 24kHz) ultrasonic device to fill the cathode precursor with the first solution. Subsequently, the second solution was added dropwise, and the second ultrasonic treatment described above was performed for 10 minutes. As a result, a metal-organic structure (ZIF-8) was synthesized in the liquid phase by reacting 2-methylimidazole (a nitrogen-containing organic compound) and Zn(NO3)2·6H2O (a metal-containing material) in the gaps of the cathode composite layer.

[0076] (3) Primary drying process of the cathode precursor Next, a cathode precursor containing a metal-organic structure (ZIF-8) was extracted from the mixed solution of the first and second solutions and air-dried for 1 minute.

[0077] (4) Washing process of the positive electrode precursor Next, the cathode precursor, which had been air-dried, was immersed in ethanol once and left to soak for a day to wash it.

[0078] (5) Reduced pressure and secondary drying process of the cathode precursor Next, the washed cathode precursor was secondarily dried under reduced pressure at 150 degrees Celsius for 10 hours using a drying apparatus (manufactured by Yamato Scientific Co., Ltd.).

[0079] (6) Pressurization of the cathode precursor Finally, the positive electrode precursor was pressurized with a pressure of approximately 10 MPa using a RIKEN hydraulic press. Through this process, a positive electrode for a secondary battery was manufactured.

[0080] (7) Manufacturing process of secondary batteries Subsequently, a lithium electrode was prepared as the counter electrode, and a 1M LiTFSI DME (1,2-dimethoxyethane) / DOL (1,3-dioxolane) ether-based electrolyte was prepared as the electrolyte. The DME / DOL mixed solvent was used at a ratio of 1 / 1 (vol%). Then, the positive and negative electrodes were stacked via a separator (specifically, F20BHE manufactured by Toray Industries, Inc.) to form an electrode assembly. Next, the electrode assembly was placed inside the outer casing, and the electrolyte was injected into the outer casing to impregnate the electrode assembly with the electrolyte. In this way, the specified secondary battery was prepared.

[0081] Example 2 Example 2 differs from Example 1 in that, instead of the second ultrasonic treatment, the positive electrode precursor is immersed in or in contact with the above solution, and a heat treatment is performed for a predetermined time. Note that, in the following examples from Example 2 onward, the explanation of steps that overlap with those performed in Example 1 will be omitted.

[0082] Specifically, in step (2) of Example 1 described above, a first solution of 0.4 mol / l 2-methylimidazole (nitrogen-containing organic compound) was prepared, the cathode precursor was immersed in the first solution, and the first ultrasonic treatment was performed in the same manner as in Example 1. Then, with the cathode precursor still immersed in the first solution, a second solution of 0.1 mol / l Zn(NO3)2·6H2O (metal-containing material) was added dropwise. Subsequently, using a heating device (manufactured by Yamato Scientific Co., Ltd., model number: DP-33), the cathode precursor was heated at 60 degrees Celsius for 1 hour while immersed in the mixed solution of the first and second solutions.

[0083] As described above, a metal-organic structure (ZIF-8) was synthesized in the liquid phase by reacting 2-methylimidazole (a nitrogen-containing organic compound) with Zn(NO3)2·6H2O (a metal-containing material) in the gaps of the positive electrode composite layer. Subsequently, a positive electrode for a secondary battery was manufactured through the same process as in Example 1.

[0084] The conditions in Example 2 are as follows: • Thickness of the cathode precursor before contact with the solution containing the metal-containing material and nitrogen-containing organic compound: 19 μm • Positive electrode thickness of the positive electrode for secondary batteries after the pressurization process of the positive electrode precursor: 19 μm • Volume of electrode composite layer (including ZIF-8): 3.4 × 10⁻⁶ -4 cm 3 ·Battery capacity 1.2mAh

[0085] Example 3 In Example 3, the process differed from Example 2 in that, in the preparation steps for the metal-containing material and nitrogen-containing organic compound, 10 ml of 0.1 mol / l Zn(NO3)2·6H2O (Aldrich, product code: 228737) was prepared as the metal-containing material, while 10 ml of 0.2 mol / l 2-methylimidazole (Tokyo Chemical Industries, Ltd., product code: M0345) was prepared as the nitrogen-containing organic compound. Subsequently, a positive electrode for a secondary battery was manufactured through the same process as in Example 2.

[0086] Comparative Example 1 Comparative Example 1 differs from Example 1 in that it simply uses an NCA electrode as the positive electrode, without synthesizing a metal-organic structure within the positive electrode. In addition, as the electrolyte, a 1M LiTFSI DME / DOL ether-based electrolyte, a 3M LiTFSI DME / DOL ether-based electrolyte, and a 4M LiTFSI DME / DOL ether-based electrolyte were prepared. Then, the positive and negative electrodes were stacked via a separator, and the electrode assembly and electrolyte were placed inside the outer casing to prepare a secondary battery.

[0087] Comparative Example 2 Comparative Example 2 differs from Example 2 in that a metal-organic structure (ZIF-8) is pressed and coated onto the positive electrode composite layer (see Patent Document 1). The conditions are as follows: • Thickness of the cathode precursor before contact with the solution containing the metal-containing material and nitrogen-containing organic compound: 19 μm • Positive electrode thickness of the positive electrode for secondary batteries after the pressurization process of the positive electrode precursor: 26 μm • Volume of electrode composite layer (with ZIF-8): 4.6 × 10 -4cm 3 ·Battery capacity 1.2mAh Subsequently, a positive electrode for a secondary battery was manufactured by pressurizing the positive electrode precursor (same as in Example 1), and then a secondary battery was manufactured by following the secondary battery manufacturing process, similar to Example 1.

[0088] [evaluation] The retention rate and charge / discharge efficiency of the secondary batteries prepared for each of Examples 1-3 and Comparative Example 1 were measured (see Figures 6 and 7). Specifically, the maintenance rate and charge / discharge efficiency were measured based on the following formulas. Maintenance rate (%): ((discharge capacity at the nth discharge) / (discharge capacity at the first discharge)) × 100 • Charge / discharge efficiency: ((Discharge capacity) / (Charge capacity)) × 100 Charging was performed in constant current / constant voltage mode, with a current equivalent to 0.2C, and termination was reached when the voltage dropped to 1 / 40C after reaching 4.1V. Discharging was performed in constant current mode, with a current equivalent to 0.2C, and termination was reached when the voltage reached 2V. Furthermore, the relationship between potential and current (LSV) was measured for a secondary battery prepared using the positive electrode for secondary batteries obtained in Example 1 and for a secondary battery prepared using electrolytes of different concentrations in Comparative Example 1 (see Figure 2).

[0089] These measurement results are shown in Figures 2, 6, and 7. From the measurement results in Figures 6 and 7, it was found that, compared to Comparative Example 1, Examples 1 to 3 (when using a positive electrode for a secondary battery having a metal-organic structure inside the positive electrode composite layer) showed improved maintenance rate and charge / discharge efficiency, as well as improved cycle characteristics for the secondary battery.

[0090] Figures 8 and 9 show SEM images and magnified images, respectively, of the positive electrode for a secondary battery having a metal-organic structure inside the positive electrode composite layer in Example 1. From these images, it was found that the metal-organic structure is located near the current collector foil. From this, it was found that, with the main surface of the positive electrode current collector 1 as the starting point, the structure is located from the surface of the positive electrode composite layer to the gap inside the positive electrode composite layer 2, which is less than 50% of the thickness of the positive electrode composite layer.

[0091] Furthermore, the results in Figure 2 show that the secondary battery prepared using the positive electrode for secondary batteries obtained in Example 1 and the secondary battery prepared using electrolytes of different concentrations in Comparative Example 1 exhibited similar behavior (LSV) to the configuration of Example 1 and the configuration using a high-salt concentration (4M) electrolyte. In other words, the examples suggest an electrolyte state similar to that of a high-salt concentration electrolyte.

[0092] This is because Li contained in the electrolyte located within the metal-organic structure. + The coordination state changes, and two or more Li atoms are added to the opposing anion. + It is understood that by primarily adopting the form of coordinated aggregates (AGG), the electrolyte located within the metal-organic structure adopts a solvation structure similar to that of a high-salt concentration electrolyte. This makes it possible to expand the potential window on the high-potential side of the electrolyte, and it has been found that oxidative decomposition of the electrolyte near the positive electrode can be suppressed.

[0093] Furthermore, comparing Example 1 with Examples 2 and 3, it was found that Example 1, which underwent the second ultrasonic treatment, showed improved retention rate and charge / discharge efficiency, as well as improved cycle characteristics. This indicates that ultrasonic treatment is effective during the synthesis of metal-organic structures.

[0094] Although not bound by any particular theory, it is understood that ultrasonic treatment, by applying vibrations, can reduce the diameter of the particles constituting the synthesized metal-organic structure, making it easier to fill the gaps within the positive electrode composite layer. This difference in particle size can be seen from Figure 10 (Example 1) and Figure 11 (Example 2), which show SEM images of the particles of the metal-organic structure.

[0095] Furthermore, comparing Example 2 with Comparative Example 2, the volumetric energy density of Comparative Example 2 is 261.3 mAh / cm³. 3 In contrast, the volumetric energy density of Example 2 was 357.5 mAh / cm³. 3 That was the case. From the above, it was found that in Comparative Example 2 (a configuration in which a metal-organic structure is coated on the positive electrode composite layer), the volume including the positive electrode composite layer and the metal-organic structure increases, resulting in a decrease in the volumetric energy density of the battery. In contrast, in the embodiment, the volume increase is less likely to occur, making it possible to improve the volumetric energy density even with the metal-organic structure present.

[0096] Furthermore, the above-described embodiment of the present disclosure includes the following preferred embodiments. <1> It includes a positive electrode current collector, a positive electrode composite material layer provided on the main surface of the positive electrode current collector, and a metal-organic structure. The positive electrode composite layer has a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles inside, The metal-organic structure is located from the surface of the positive electrode composite layer, extending from the main surface of the positive electrode current collector to the gap inside the positive electrode composite layer, with a thickness of 50% or less of the positive electrode composite layer. This is a positive electrode for a secondary battery. <2> The metal-organic structure is positioned from the surface side of the positive electrode composite layer to the gap inside the positive electrode composite layer on the interface side between the positive electrode composite layer and the positive electrode current collector. <1> The positive electrode for secondary batteries as described above. <3> At least one of the positive electrode active material particles is in contact with an adjacent positive electrode active material particle and the metal-organic structure. <1> or <2> The positive electrode for secondary batteries as described above. <4> The metal-organic structure is in contact with the positive electrode current collector. <1> ~ <3> A positive electrode for a secondary battery as described in any of the following. <5> The aforementioned metal-organic structure has a central metal atom and an organic ligand, The central metal atom is selected from the group consisting of Zn, Co, and Ni, and the organic ligand is a nitrogen-containing organic compound. <1> ~ <4> A positive electrode for a secondary battery as described in any of the following. <6> The aforementioned metal-organic structure is ZIF. <1> ~ <5> A positive electrode for a secondary battery as described in any of the following. <7> The aforementioned organic ligand is an organic compound having an azole skeleton. <5> or <6> The positive electrode for secondary batteries as described above. <8> The organic ligand has one of the following skeletons: an imidazole skeleton, a benzimidazole skeleton, a triazole skeleton, and a purine skeleton. <5> ~ <7> A positive electrode for a secondary battery as described in any of the following. <9> The aforementioned metal-organic structure is ZIF-8 (2-methylimidazole zinc salt). <1> ~ <8> A positive electrode for a secondary battery as described in any of the following. <10> The battery comprises a positive electrode for secondary batteries, a negative electrode, and an electrolyte solution containing an electrolyte salt. The electrolyte contains an ether-based solvent. <1> ~ <9> A secondary battery as described in any of the following. <11> The battery comprises the positive electrode for the secondary battery, the negative electrode, and an electrolyte containing the electrolyte salt. The concentration of the electrolyte salt is 3M or less. <1> ~ <10> A secondary battery as described in any of the following. <12> The battery comprises the positive electrode for the secondary battery, the negative electrode, and an electrolyte containing the electrolyte salt. The electrolyte within the aforementioned metal-organic structure has a Raman spectrum of 745 cm⁻¹. -1 755cm or more -1 Peaks are detected in the following region: <1> ~ <11> A secondary battery as described in any of the following. <13> Prepare a metal-containing material and a nitrogen-containing organic compound, and A positive electrode precursor having a positive electrode current collector and a positive electrode composite layer provided on the main surface of the positive electrode current collector and having a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles is brought into contact with a solution having the metal-containing material and the nitrogen-containing organic compound to synthesize a metal-organic structure from the metal oxide and the nitrogen-containing organic compound in the gaps of the positive electrode composite layer. Includes, The aforementioned metal material includes a metal oxide or a metal salt, and the method for manufacturing a positive electrode for a secondary battery. <14> Prepare a first solution containing either the metal-containing material or the nitrogen-containing organic compound. Immersing the positive electrode precursor in the first solution, and With the positive electrode precursor immersed in the first solution, a second solution containing the metal material or the other of the nitrogen-containing organic compound is added dropwise to synthesize the metal-organic structure. including, <13> A method for manufacturing a positive electrode for a secondary battery, as described above. <15> The ultrasonic treatment is performed in both the state in which the positive electrode precursor is immersed in the first solution and the state in which the second solution is added dropwise. <14> A method for manufacturing a positive electrode for a secondary battery, as described above. <16> The positive electrode precursor is immersed in the solution, and then the heat treatment is carried out. <13> A method for manufacturing a positive electrode for a secondary battery, as described above. <17> The metal-containing material comprises at least one metal atom selected from the group consisting of Zn, Co, and Ni, and the nitrogen-containing organic compound is an organic compound having an azole skeleton. <13> ~ <16> A method for manufacturing a positive electrode for a secondary battery as described in any of the following. <18> The metal-containing material is Zn(NO3)2·6H2O, and the nitrogen-containing organic compound is 2-methylimidazole. <13> ~ <17> A method for manufacturing a positive electrode for a secondary battery as described in any of the following. <19> The molar ratio of the metal-containing material to the nitrogen-containing organic compound is 1:4 to 1:2. <13> ~ <18> A method for manufacturing a positive electrode for a secondary battery as described in any of the following. <20> The synthesized metal-organic structure is positioned from the surface of the positive electrode composite layer, extending from the main surface of the positive electrode current collector to the gap within the positive electrode composite layer, with a thickness of 50% or less of the positive electrode composite layer, and at least one of the positive electrode active material particles is in contact with an adjacent positive electrode active material particle and the metal-organic structure. <13> ~ <19> A method for manufacturing a positive electrode for a secondary battery as described in any of the following. [Industrial applicability]

[0097] The secondary battery described herein can be used in applications where the utilization of electrical energy is typically required. For example, the secondary battery described herein can be used in various fields where energy storage is anticipated. While these are merely examples, the batteries of this disclosure can be used in the electrical, information, and communication fields where electrical and electronic equipment is used (e.g., the electrical and electronic equipment field or mobile device field, including mobile phones, smartphones, laptops and digital cameras, activity trackers, ARM computers, electronic paper, wearable devices, and small electronic devices such as RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (e.g., power tools, golf carts, household, caregiving, and industrial robots), large industrial applications (e.g., forklifts, elevators, and port cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (e.g., various power generation systems, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT applications and space and deep-sea applications (e.g., space probes, submersible research vessels, etc.). [Explanation of Symbols]

[0098] 10 positive electrode 1 Positive electrode current collector 2. Positive electrode composite layer 2I First region of the positive electrode composite layer 2II Second region of the positive electrode composite layer 2X positive electrode active material particles 2Y gap 2Y1 Gap inside the first region 2Y2 Gap inside the second region 3 Metal-organic framework 4. Interface between the positive electrode composite layer and the positive electrode current collector 5. Surface of the positive electrode composite layer 2 (corresponding to the interface between the positive electrode composite layer and the separator)

Claims

1. It includes a positive electrode current collector, a positive electrode composite material layer provided on the main surface of the positive electrode current collector, and a metal-organic structure. The positive electrode composite layer has a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles inside, The metal-organic structure is located from the surface of the positive electrode composite layer, extending from the main surface of the positive electrode current collector to the gap inside the positive electrode composite layer, with a thickness of 50% or less of the positive electrode composite layer. This is a positive electrode for a secondary battery.

2. The positive electrode for a secondary battery according to claim 1, wherein the metal-organic structure is located from the surface side of the positive electrode composite layer to the gap inside the positive electrode composite layer on the interface side between the positive electrode composite layer and the positive electrode current collector.

3. The positive electrode for a secondary battery according to claim 1, wherein at least one of the positive electrode active material particles is in contact with an adjacent positive electrode active material particle and the metal-organic structure.

4. The positive electrode for a secondary battery according to claim 1, wherein the metal-organic structure is in contact with the positive electrode current collector.

5. The aforementioned metal-organic structure has a central metal atom and an organic ligand, The positive electrode for a secondary battery according to claim 1, wherein the central metal atom is selected from the group consisting of Zn, Co, and Ni, and the organic ligand is a nitrogen-containing organic compound.

6. The positive electrode for a secondary battery according to claim 1, wherein the metal-organic structure is ZIF.

7. The positive electrode for a secondary battery according to claim 5, wherein the organic ligand is an organic compound having an azole skeleton.

8. The positive electrode for a secondary battery according to claim 5, wherein the organic ligand has one of the following skeletons: an imidazole skeleton, a benzimidazole skeleton, a triazole skeleton, and a purine skeleton.

9. The positive electrode for a secondary battery according to claim 6, wherein the metal-organic structure is ZIF-8 (2-methylimidazole zinc salt).

10. The battery comprises a positive electrode for secondary batteries, a negative electrode, and an electrolyte solution containing an electrolyte salt. The secondary battery according to claim 1, wherein the electrolyte contains an ether-based solvent.

11. The battery comprises the positive electrode for the secondary battery, the negative electrode, and an electrolyte containing the electrolyte salt. The secondary battery according to claim 1, wherein the concentration of the electrolyte salt is 3 M or less.

12. The battery comprises the positive electrode for the secondary battery, the negative electrode, and an electrolyte containing the electrolyte salt. The electrolyte within the aforementioned metal-organic structure has a Raman spectrum of 745 cm⁻¹. －１ 755cm or more －１ The secondary battery according to claim 1, wherein a peak is detected in the following region.

13. Prepare a metal-containing material and a nitrogen-containing organic compound, and A positive electrode precursor having a positive electrode current collector and a positive electrode composite layer provided on the main surface of the positive electrode current collector and having a plurality of positive electrode active material particles and a plurality of gaps provided between the positive electrode active material particles is brought into contact with a solution having the metal-containing material and the nitrogen-containing organic compound to synthesize a metal-organic structure from the metal oxide and the nitrogen-containing organic compound in the gaps of the positive electrode composite layer. Includes, The aforementioned metal material includes a metal oxide or a metal salt, and the method for manufacturing a positive electrode for a secondary battery.

14. Prepare a first solution containing either the metal-containing material or the nitrogen-containing organic compound. Immersing the positive electrode precursor in the first solution, and With the positive electrode precursor immersed in the first solution, a second solution containing the metal material or the other of the nitrogen-containing organic compound is added dropwise to synthesize the metal-organic structure. A method for manufacturing a positive electrode for a secondary battery according to claim 13, including the method described in claim 13.

15. A method for manufacturing a positive electrode for a secondary battery according to claim 14, wherein ultrasonic treatment is performed in both the state in which the positive electrode precursor is immersed in the first solution and the state in which the second solution is dropped onto it.

16. A method for manufacturing a positive electrode for a secondary battery according to claim 13, wherein the positive electrode precursor is immersed in the solution and a heat treatment is performed.

17. The method for producing a positive electrode for a secondary battery according to claim 13, wherein the metal-containing material comprises at least one metal atom selected from the group consisting of Zn, Co, and Ni, and the nitrogen-containing organic compound is an organic compound having an azole skeleton.

18. The aforementioned metal-containing material is Zn(NO ３ ) ２ 6H ２ The method for producing a positive electrode for a secondary battery according to claim 13, wherein the nitrogen-containing organic compound is 2-methylimidazole.

19. A method for manufacturing a positive electrode for a secondary battery according to claim 13, wherein the molar ratio of the metal-containing material to the nitrogen-containing organic compound is 1:4 to 1:

2.

20. A method for manufacturing a positive electrode for a secondary battery according to claim 13 or 14, wherein the synthesized metal-organic structure is located from the surface of the positive electrode composite layer, extending from the main surface of the positive electrode current collector to the gap portion inside the positive electrode composite layer, with a thickness of 50% or less of the positive electrode composite layer, and at least one positive electrode active material particle is in contact with an adjacent positive electrode active material particle and the metal-organic structure.

Images