Electrode material, electrode slurry, method for manufacturing electrode material, electrode, and method for manufacturing electrode

Abstract

An electrode material (1) for a secondary battery, which suppresses a decrease in electrode capacity and has excellent cycle characteristics, contains an electrode active material (10), and the entire surface or a part of the surface of the electrode active material (10) is coated in a shell form with a non-aqueous binder (20).

Description

TECHNICAL FIELD

[0001] The present application relates to an electrode material for a secondary battery, an electrode slurry, a method for manufacturing an electrode material, an electrode, and a method for manufacturing an electrode. BACKGROUND

[0002] An electrode constituting a secondary battery such as a lithium ion secondary battery is generally manufactured by coating a slurry in which an electrode active material, a binder, and a conductive aid are dispersed on a current collector and drying it.

[0003] Conventionally, as a binder for an electrode, polyvinylidene fluoride (PVDF) having excellent characteristics in mechanical strength, adhesiveness, oxidation resistance, and the like is widely used.

[0004] However, since PVDF is not soluble in water, a slurry in which PVDF is dissolved in an organic solvent such as N-methyl-pyrrolidone (NMP) needs to be manufactured, and thus there is a problem that environmental load increases with the use of the organic solvent. Therefore, in recent years, development of an aqueous binder capable of being dispersed in an aqueous solvent having small environmental load is desired.

[0005] As an aqueous binder for a negative electrode, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR) have been developed. However, in the case where these aqueous binders are directly used for a positive electrode, there is a problem that these aqueous binders are oxidatively deteriorated in a positive electrode environment.

[0006] In Patent Literature 1, as an aqueous binder for a positive electrode, a binder composed of an acrylic polymer is disclosed. This aqueous binder is not soluble in water, and a positive electrode slurry is manufactured by being dispersed as a suspended particle in an aqueous solvent. In the case where a positive electrode is manufactured by coating this positive electrode slurry on a current collector and drying it, the aqueous binder is agglomerated in a concave portion between positive electrode active materials in a particle shape.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Published Patent Publication No. 2017-91789 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The water-based binder disclosed in Patent Literature 1 is effective in terms of having oxidation resistance, but since the positive electrode active material contains lithium, when the water-based binder is dispersed in a water-based solvent together with the positive electrode active material and the conductive aid to produce a positive electrode slurry, lithium and the like transition metal in the positive electrode active material are eluted into the water-based solvent, and thus there is a problem that the capacity of the positive electrode decreases. Note that such a problem can also occur in the case where a material containing lithium is used as the negative electrode active material in the negative electrode.

[0012] In addition, the above water-based binder is only segregated in the recesses between the positive electrode active materials, and thus it is difficult to uniformly disperse the water-based binder within the positive electrode. Therefore, there is a problem that the adhesion between the positive electrode active materials and between the positive electrode active material and the current collector decreases, and the cycle characteristics of the secondary battery decrease. Note that such a problem can also occur in the case where the above water-based binder is used in the negative electrode.

[0013] The present application has been achieved in order to solve the above-described technical problems, and has an object to provide an electrode material for a secondary battery, an electrode slurry, a method for producing an electrode material, an electrode, and a method for producing an electrode, which suppresses a decrease in electrode capacity and have excellent cycle characteristics.

[0014] Technical Solution for Solving the Technical Problem

[0015] The electrode material according to the present application is an electrode material for a secondary battery, which includes an active material, and the entire surface of the active material is coated with a non-aqueous binder in a shell form.

[0016] In a preferred embodiment, a part of the surface of the electrode active material is coated with a metal oxide, and the non-aqueous binder coats the entire surface of the electrode active material in a shell form so as to cover the metal oxide.

[0017] The electrode slurry according to the present application is an electrode slurry including an electrode mixture, the electrode mixture including an active material and a conductive aid, the entire surface of the active material being coated with a non-aqueous binder in a shell form, and the electrode mixture being dispersed in a water-based solvent.

[0018] The method for producing an electrode material according to the present application is a method for producing an electrode material for a secondary battery, which includes the steps of dissolving a powder of a non-aqueous binder in a non-aqueous solvent, dispersing a powder of an electrode active material in the non-aqueous solvent, and evaporating the non-aqueous solvent to coat the entire surface of the electrode active material with the non-aqueous binder in a shell form.

[0019] The electrode according to the present application is an electrode for a secondary battery, and includes an electrode mixture formed on a current collector, the electrode mixture containing an electrode material and a conductive aid, the entire surface of an electrode active material of the electrode material being coated with a non-aqueous binder in a shell-like form, the electrode active material contained in the electrode material being dispersed in a state where the entire surface thereof is coated with the non-aqueous binder in a shell-like form, and when the total volume of the non-aqueous binder coating the entire surface of the electrode active material is set as VI and the total volume of the non-aqueous binder present in a region surrounded by the electrode active material coated with the non-aqueous binder is set as V2, VI > V2.

[0020] The electrode according to the present application is an electrode for a secondary battery, and includes an electrode mixture formed on a current collector, the electrode mixture containing an electrode material and a conductive aid, the entire surface of an electrode active material of the electrode material being coated with a non-aqueous binder in a shell-like form, the electrode active material contained in the electrode material being dispersed in a state where the entire surface thereof is coated with the non-aqueous binder in a shell-like form, and when the total volume of the non-aqueous binder coating the entire surface of the electrode active material is set as VI and the total volume of the non-aqueous binder present in a region surrounded by the electrode active material coated with the non-aqueous binder is set as V2, VI > V2.

[0021] The electrode according to the present application is an electrode for a secondary battery, and includes an electrode mixture formed on a current collector, the electrode mixture containing an electrode material and a conductive aid, the entire surface of an electrode active material of the electrode material being coated with a non-aqueous binder in a shell-like form, the electrode active material contained in the electrode material being dispersed in a state where the entire surface thereof is coated with the non-aqueous binder in a shell-like form, and when the total volume of the non-aqueous binder coating the entire surface of the electrode active material is set as VI and the total volume of the non-aqueous binder present in a region surrounded by the electrode active material coated with the non-aqueous binder is set as V2, VI > V2.

[0022] Effects of the Invention

[0023] According to the present application, it is possible to provide an electrode material for a secondary battery, an electrode slurry, a method for manufacturing an electrode material, an electrode, and a method for manufacturing an electrode, which suppresses a decrease in electrode capacity and have excellent cycle characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a diagram schematically showing the structure of a positive electrode material in an embodiment of the present application.

[0025] Figure 2 FIG. 2 is a diagram schematically showing the structure of a positive electrode plate produced using a positive electrode slurry containing the positive electrode material in the embodiment of the present application.

[0026] Figure 3 FIG. 2 is a diagram schematically showing the structure of a positive electrode plate produced using a positive electrode slurry containing the positive electrode material in the embodiment of the present application.

[0027] Figure 4 is a view schematically showing a structure of a positive electrode plate produced using a positive electrode slurry containing the positive electrode material in another embodiment of the present application.

[0028] Figure 5 is a view schematically showing Modification 1 of the positive electrode material.

[0029] Figure 6 is a view schematically showing Modification 2 of the positive electrode material.

[0030] Figure 7 is a view schematically showing Modification 3 of the positive electrode material.

[0031] Figure 8A is a photograph taken with an SEM of a cross section of the positive electrode plate produced in Example 1.

[0032] Figure 8B is a photograph taken with an SEM of a cross section of the positive electrode plate after staining the fluorine component in the positive electrode plate.

[0033] Figure 9A is a photograph taken with an SEM of a cross section of the positive electrode plate produced in Comparative Example 1.

[0034] Figure 9B is a photograph taken with an SEM of a cross section of the positive electrode plate after staining the fluorine component in the positive electrode plate.

[0035] Figure 10A is a photograph taken with an SEM of a cross section of the positive electrode plate produced in Example 2.

[0036] Figure 10B is a photograph taken with an SEM of a cross section of the positive electrode plate after staining the fluorine component in the positive electrode plate.

[0037] Figure 11A is a photograph taken with an SEM of a cross section of the positive electrode plate produced in Comparative Example 2.

[0038] Figure 11B is a photograph taken with an SEM of a cross section of the positive electrode plate after staining the fluorine component in the positive electrode plate.

[0039] Figure 12A is a photograph taken with an SEM of a cross section of the positive electrode plate after resin embedding of the positive electrode plate produced in Example 1.

[0040] Figure 12B is a photograph showing a line drawing of a site in contact with the positive electrode active material in a region after staining the fluorine component in the positive electrode plate.

[0041] Figure 13A is a photograph obtained by taking a cross section of the positive electrode plate after resin embedding using SEM for the positive electrode plate produced in Comparative Example 1.

[0042] Figure 13B is a photograph showing a line drawing of a portion in contact with the positive electrode active material in a region after staining the fluorine component in the positive electrode plate.

[0043] Figure 14 is a graph showing measurement results of cycle characteristics of a lithium ion battery produced using the positive electrode material produced in Example 1.

[0044] Figure 15 is a graph showing measurement results of cycle characteristics of a lithium ion battery produced using the positive electrode material produced in Example 3. DETAILED DESCRIPTION

[0045] Hereinafter, an embodiment of the present application will be described in detail based on the drawings. Note that, in the following embodiment, as an electrode of a secondary battery, a positive electrode is exemplified and described, but the present application is not limited thereto, and can be applied to a negative electrode. That is, in the present specification, when "an electrode" is mentioned, a positive electrode and a negative electrode are included. For example, "an electrode material" includes a positive electrode material and a negative electrode material, "an electrode active material" includes a positive electrode active material and a negative electrode active material, "an electrode mixture" includes a positive electrode mixture and a negative electrode mixture, and "an electrode slurry" includes a positive electrode slurry and a negative electrode slurry.

[0046] The positive electrode material in the present embodiment is a positive electrode material for a secondary battery, and is a positive electrode material in which the entire surface of a positive electrode active material is coated with a non-aqueous binder in a shell form. Figure 1 As shown in the schematic view of FIG. 1, the positive electrode material 1 includes a positive electrode active material 10, and the entire surface of the positive electrode active material 10 is coated with a non-aqueous binder 20 in a shell form. Here, the non-aqueous binder 20 is composed of a fluorine-based resin that is insoluble in a water-based solvent such as water but can be dissolved in a non-aqueous solvent such as an organic solvent, and typically includes polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a fluorine-based rubber, or the like.

[0047] A secondary battery using the positive electrode material in the present embodiment includes a lithium ion secondary battery, a lithium-sulfur secondary battery, or the like. In the case of a lithium ion secondary battery, the positive electrode active material includes, for example, LiCoO2, LiNiO2, LiNi 0.8 Co 0.2 O2, LiMn2O4, LiFePO4, LiNiCoMnO2, or the like. In addition, the positive electrode active material is preferably composed of two or more kinds of positive electrode active materials having different particle diameters. The positive electrode active material having a small particle diameter can be formed, for example, using a fluxing agent method.

[0048] The positive electrode material 1 in the present embodiment can be manufactured by a process of dissolving a powder of the non-aqueous binder 20 in a non-aqueous solvent, a process of dispersing a powder of the positive electrode active material 10 in the non-aqueous solvent, and a process of evaporating the non-aqueous solvent by heating and coating the entire surface of the positive electrode active material 10 with the non-aqueous binder 20 in a shell form. Note that drying of the non-aqueous solvent can also be performed by vacuum drying at normal temperature without heating.

[0049] Here, the non-aqueous solvent is composed of a material capable of dissolving the powder of the non-aqueous binder 20, and includes an organic solvent such as N-methyl-2-pyrrolidone (NMP).

[0050] The amount of the non-aqueous binder 20 used in the process of manufacturing the positive electrode material 1 is appropriately determined within a range capable of coating the entire surface of the positive electrode active material 10 in a shell form, as long as the amount of the positive electrode active material 10.

[0051] The positive electrode slurry in the present embodiment contains a positive electrode mixture containing the above-described positive electrode material 1 and a conductive aid, and the positive electrode mixture is dispersed in an aqueous solvent. Note that the non-aqueous binder 20 coating the surface of the positive electrode active material 10 is not dissolved in the aqueous solvent.

[0052] Here, the aqueous solvent is composed of a material in which the powder of the non-aqueous binder 20 is not dissolved, and includes water or a dispersant such as polyvinylpyrrolidone (PVP). In addition, the conductive aid is not particularly limited, and preferably contains cellulose nanofiber. Since the viscosity of the aqueous solvent is low, by using cellulose nanofiber having high tackiness as the conductive aid, a positive electrode slurry having appropriate viscosity can be obtained.

[0053] In addition, the positive electrode plate in the present embodiment can be manufactured by coating the above-described positive electrode slurry on a current collector and drying the coated film. Note that drying of the coated film can also be performed by thermally joining the positive electrode slurry to the current collector using a roll or the like.

[0054] The positive electrode material 1 in the present embodiment, since the entire surface of the positive electrode active material 10 is coated with the non-aqueous binder 20 in a shell form, even if a positive electrode mixture containing the positive electrode material 1 and a conductive aid is dispersed in an aqueous solvent to produce a positive electrode slurry, lithium in the positive electrode active material 10 is not eluted into the aqueous solvent. As a result, reduction in the capacity of the positive electrode due to elution of lithium into the aqueous solvent can be suppressed.

[0055] In addition, when a positive electrode plate is produced using a positive electrode slurry containing the positive electrode material 1 in the present embodiment, since the non-aqueous binder 20 is not dissolved in the aqueous solvent, as Figure 2As shown in the schematic view, the positive electrode active material 10 is uniformly dispersed in a state in which the entire surface is coated with the non-aqueous binder 20 in a shell-like form. Therefore, the non-aqueous binder 20 is also uniformly dispersed, and the positive electrode active material 10 can be uniformly bonded to each other and to the current collector by the non-aqueous binder 20 throughout the positive electrode, and thus a secondary battery with excellent cycle characteristics can be achieved.

[0056] In particular, in the case where the positive electrode active material 10 includes two or more kinds of positive electrode active materials 10 having different particle diameters, the positive electrode active material 10 is more uniformly dispersed, and thus the adhesion between the positive electrode active material 10 and the current collector and between the positive electrode active materials 10 via the non-aqueous binder 20 becomes higher, and as a result, further improvement in cycle characteristics can be achieved.

[0057] Note that the positive electrode material 1 in the present embodiment has a structure in which the entire surface of the positive electrode active material 10 is coated with the non-aqueous binder 20 in a shell-like form, but also includes a positive electrode material 1 having a structure in which only a part of the surface of the positive electrode active material 10 is coated with the non-aqueous binder 20.

[0058] In the case of the conventional production of a positive electrode slurry by dispersing a positive electrode mixture including a non-aqueous binder 20 such as PVDF in an organic solvent, the conductive aid such as carbon black contained in the positive electrode mixture is not dissolved in the organic solvent, and a nano-sized small hole can suck in the organic solvent, and thus the amount of the used organic solvent increases.

[0059] On the other hand, an organic solvent (non-aqueous solvent) is also used in the production of the positive electrode material 1 in the present embodiment, but only the positive electrode active material 10 and the non-aqueous binder 20 dissolved in the organic solvent are contained in the organic solvent, and thus the amount of the non-aqueous solvent used can be greatly reduced compared to the case of the conventional production of a positive electrode slurry by dispersing a positive electrode mixture including a non-aqueous binder 20 such as PVDF in an organic solvent. As a result, the positive electrode in the present embodiment is produced using a positive electrode slurry in which a positive electrode mixture including the positive electrode material 1 and a conductive aid is dispersed in an aqueous solvent, and thus the amount of the non-aqueous solvent used in the production of a secondary battery can be greatly reduced.

[0060] In addition, the positive electrode material 1 in the present embodiment is coated with the non-aqueous binder 20 in a shell-like form over the entire surface of the positive electrode active material 10, and thus it is possible to obtain an effect of suppressing a decrease in the positive electrode capacity and improving the cycle characteristics. Therefore, in order to obtain such an effect, the amount of the non-aqueous binder 20 used in the process of manufacturing the positive electrode material 1 can be within a range in which the positive electrode active material 10 can be coated with the non-aqueous binder 20 in a shell-like form, as long as the amount is in accordance with the amount of the positive electrode active material 10. Generally, a minimum amount of the non-aqueous binder 20 including a margin is used, taking into account a variation in the size of the positive electrode active material 10, a variation in the manufacturing process of the positive electrode material 1, and the like.

[0061] As described above, when a positive electrode plate is manufactured using a positive electrode slurry containing the positive electrode material 1 in the present embodiment, the non-aqueous binder 20 is present in a shell-like form over the entire surface of the positive electrode active material 10, as shown in a schematic view of FIG. 6. At this time, since only a minimum amount of the non-aqueous binder 20 is used, there is only an excess amount of the non-aqueous binder 40 in a region 50 surrounded by the positive electrode active material 10 coated with the non-aqueous binder 20, and most of the region 50 is in a void state. Figure 3

[0062] Therefore, when the sum of the volumes of the non-aqueous binder 20 covering the entire surface of the positive electrode active material 10 is set to VI, and the sum of the volumes of the non-aqueous binder 40 present in the region 50 surrounded by the positive electrode active material 10 coated with the non-aqueous binder 20 is set to V2, the relationship VI > V2 is satisfied. In addition, when the sum of the volumes of the region 50 surrounded by the positive electrode active material 10 coated with the non-aqueous binder 20 is set to V3, the relationship V3 > V2 is satisfied.

[0063] Note that, when the positive electrode mixture formed on the current collector is observed from a cross section perpendicular to the film thickness direction, the sum of the areas of the non-aqueous binder 20 covering the entire surface of the positive electrode active material 10 is set to Al, and the sum of the areas of the non-aqueous binder 40 present in the region 50 surrounded by the positive electrode active material 10 coated with the non-aqueous binder 20 is set to A2, Al > A2. In addition, when the sum of the areas of the region 50 surrounded by the positive electrode active material 10 coated with the non-aqueous binder 20 is set to A3, A3 > A2.

[0064] However, the positive electrode material 1 in the present embodiment is coated with the non-aqueous binder 20 in a shell-like form over the entire surface of the positive electrode active material 10, and thus even when a positive electrode slurry is manufactured by dispersing a positive electrode mixture containing the positive electrode material 1 and a conductive aid in an aqueous solvent, lithium in the positive electrode active material 10 is not eluted into the aqueous solvent, and thus it is possible to suppress a decrease in the positive electrode capacity. ​

[0065] In addition, when a positive electrode plate is produced using a positive electrode slurry containing the positive electrode material 1 in the present embodiment, the non-aqueous binder 20 is not dissolved in the aqueous solvent, and thus the positive electrode active material 10 is uniformly dispersed in a state in which the entire surface is covered with the non-aqueous binder 20 in a shell-like form. Therefore, the non-aqueous binder 20 is also uniformly dispersed, and in the entire positive electrode, the positive electrode active material 10 can be uniformly bonded to each other and to the current collector by the non-aqueous binder 20, and thus a secondary battery having excellent cycle characteristics can be achieved.

[0066] Such an effect is obtained by covering the surface of the positive electrode active material 10 with the non-aqueous binder 20 in a shell-like form, and thus the entire surface of the positive electrode active material 10 can not necessarily be completely covered with the non-aqueous binder 20 in a shell-like form, and such an effect can be obtained even when a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form.

[0067] For example, two cases in which a positive electrode plate is produced using the same amount of non-aqueous binder 20 are compared, one of which is a case in which, in the present embodiment, the positive electrode mixture contains the positive electrode material 1 in which a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, and the positive electrode plate is produced using a positive electrode slurry in which the positive electrode mixture is dispersed in an aqueous solvent, and the other of which is a case in which, in the conventional method, the positive electrode mixture contains the non-aqueous binder 20, and the positive electrode plate is produced using a positive electrode slurry in which the positive electrode mixture is dispersed in an organic solvent. Through the comparison, it is confirmed that the secondary battery produced by the present embodiment has more excellent characteristics in terms of the positive electrode capacity and the cycle characteristics compared to the secondary battery produced by the conventional method.

[0068] In the case of the positive electrode material 1 in which a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, the amount of the non-aqueous binder 20 used in the manufacturing process of the positive electrode material 1 is only required to be set within a range in which a part of the surface of the positive electrode active material 10 can be covered in a shell-like form.

[0069] Note that, in the case where a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, in order to exert the effect of the present application, it is preferable that 50% or more of the surface of the positive electrode active material 10 be covered with the non-aqueous binder 20, and it is more preferable that 70% or more of the surface of the positive electrode active material 10 be covered with the non-aqueous binder 20.

[0070] In the case where a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, in order to exert the effect of the present application, it is preferable that 50% or more of the surface of the positive electrode active material 10 be covered with the non-aqueous binder 20, and it is more preferable that 70% or more of the surface of the positive electrode active material 10 be covered with the non-aqueous binder 20. Figure 4As shown in a schematic view, the positive electrode active material 10 is uniformly dispersed in a state where a part of the surface is covered with the non-aqueous binder 20 in a shell-like form. At this time, compared with a case where the entire surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, the non-aqueous binder 20 used is less, and thus, in the region 50 surrounded by the positive electrode active material 10 covered with the non-aqueous binder 20, the non-aqueous binder 40 is almost absent, but is in a void state.

[0071] Therefore, as in the case where the entire surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, when the sum of the volumes of the non-aqueous binder 20 covering a part of the surface of the positive electrode active material 10 is set to VI, and the sum of the volumes of the non-aqueous binder 40 present in the region 50 surrounded by the positive electrode active material 10 covered with the non-aqueous binder 20 is set to V2, the relation of VI > V2 is satisfied. In addition, when the sum of the volumes of the region 50 surrounded by the positive electrode active material 10 covered with the non-aqueous binder 20 is set to V3, the relation of V3 > V2 is satisfied.

[0072] Note that, when the positive electrode mixture formed on the current collector is observed from a cross section perpendicular to the film thickness direction, the sum of the areas of the non-aqueous binder 20 covering a part of the surface of the positive electrode active material 10 is set to Al, and the sum of the areas of the non-aqueous binder 40 present in the region 50 surrounded by the positive electrode active material 10 covered with the non-aqueous binder 20 is set to A2, Al > A2. In addition, when the sum of the areas of the region 50 surrounded by the positive electrode active material 10 covered with the non-aqueous binder 20 is set to A3, A3 > A2.

[0073] <Modification Example>

[0074] In the above embodiment, the positive electrode material 1 is provided with a structure in which the entire surface or a part of the surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, but if the thickness of the non-aqueous binder 20 to be covered is too thick, the electric resistance of the surface of the positive electrode active material 10 increases, which can cause a decrease in the capacity of the battery. In the present modification example, a structure of the positive electrode material 1 capable of suppressing a decrease in the capacity of the battery due to an increase in the thickness of the non-aqueous binder 20 is shown.

[0075] Figure 5is a view schematically showing Modification 1 of the positive electrode material 1, a part of the surface of the positive electrode active material 10 is coated with the metal oxide 30, and the non-aqueous binder 20 forms a structure in which the entire surface of the positive electrode active material 10 is coated in a shell-like form in a manner so as to cover the metal oxide 30. With such a structure, an increase in the electric resistance of the surface of the positive electrode active material 10 can be suppressed, and thus, a decrease in the battery capacity can be suppressed while maintaining the effect of the improvement in the adhesion by the non-aqueous binder 20 (improvement in the cycle characteristics).

[0076] The positive electrode material 1 in the present modification 1 can be manufactured by performing a process of causing the metal oxide 30 to adhere to a part of the surface of the positive electrode active material 10 before performing a process of coating the entire surface of the positive electrode active material 10 in a shell-like form with the non-aqueous binder 20. Thereby, the entire surface of the positive electrode active material 10 can be coated in a shell-like form with the non-aqueous binder 20 in a manner so as to cover the metal oxide 30.

[0077] The metal oxide 30 that covers the surface of the positive electrode active material 10 is not particularly limited as long as it is a material having a low electric resistance, and for example, titanium oxide, niobium oxide, titanium-containing oxide, or the like can be used. In addition, the coating of the surface of the positive electrode active material 10 with the metal oxide 30 can be performed, for example, by mixing the positive electrode active material 10 and the metal oxide 30 and then sintering or firing them.

[0078] Figure 6 is a view schematically showing Modification 2 of the positive electrode material 1, and forms a structure in which the entire surface of the positive electrode active material 10 is coated in a shell-like form in a manner such that a part of the surface of the positive electrode active material 10 is coated with the non-aqueous binder 20 and the remaining part of the surface of the positive electrode active material 10 is coated with the metal oxide 30.

[0079] Figure 7 is a view schematically showing Modification 3 of the positive electrode material 1, and forms a structure in which the entire surface of the positive electrode active material 10 is coated in a shell-like form with the metal oxide 30, and a part of the surface of the metal oxide 30 is coated with the non-aqueous binder 20.

[0080] Figure 6 and Figure 7 The positive electrode material 1 shown in the structure is not such that the entire surface of the positive electrode active material 10 is coated with the non-aqueous binder 20, but since a part of the surface or the entire surface of the positive electrode active material 10 is coated with the metal oxide 30, a decrease in the battery capacity can be suppressed while maintaining the effect of the improvement in the adhesion by the non-aqueous binder 20.

[0081] Figure 6 and Figure 7The positive electrode material 1 of the illustrated structure can be manufactured by the following procedures: a procedure of attaching the metal oxide 30 to a part of the surface or the entire surface of the positive electrode active material 10; a procedure of dissolving the powder of the non-aqueous binder 20 in a non-aqueous solvent, and dispersing the powder of the positive electrode active material 10 having the metal oxide 30 attached to the surface in the non-aqueous solvent; and a procedure of evaporating the non-aqueous solvent.

[0082] The amount of the metal oxide 30 used in the procedure of manufacturing the positive electrode material 1 can be appropriately determined within a range capable of covering a part of the surface or the entire surface of the positive electrode active material 10, as long as the amount is in accordance with the amount of the positive electrode active material 10.

[0083]

EXAMPLE

[0084] Hereinafter, the present application will be described in more detail by citing examples, but the present application is not limited to the following examples.

[0085] [Example 1]

[0086] <Manufacture of Positive Electrode Material>

[0087] The powder of 0.05 g of the non-aqueous binder (PVDF) was dissolved in 0.45 g of the non-aqueous solvent (NMP solvent), and the powder of 0.95 g of the positive electrode active material (lithium iron phosphate (LiFeP04)) was dispersed in the non-aqueous solvent. Then, the non-aqueous solvent was heated at 100°C for two minutes to evaporate it. Thus, the positive electrode material 1 in which the positive electrode active material 10 was coated with the non-aqueous binder in a shell form was manufactured.

[0088] <Manufacture of Positive Electrode Plate>

[0089] The positive electrode material 1 manufactured by the above-described method, the conductive aid (containing cellulose nanofiber), and the dispersant were mixed in a mass ratio of 95:4:1 in an aqueous solvent (pure water) to manufacture a positive electrode slurry.

[0090] The positive electrode slurry was coated on a positive electrode current collector (aluminum foil), and after drying by heating at 100°C for six minutes, the positive electrode plate was manufactured by pressing together with the aluminum foil.

[0091] [Example 2]

[0092] Except that a material of a ternary system (LiNiCoMn02) was used as the positive electrode active material, the positive electrode plate was manufactured in the same manner as in Example 1.

[0093] [Comparative Example 1]

[0094] According to the conventional method, the positive electrode active material (lithium iron phosphate), the conductive additive (acetylene black), and the binder (PVDF) were mixed in an organic solvent (NMP) at a mass ratio of 90:5:5 to form a positive electrode slurry, and a positive electrode plate was produced by the same method as in Example 1.

[0095] [Comparative Example 2]

[0096] A positive electrode plate was produced in the same manner as in Comparative Example 1 except that a ternary material (LiNiCoMnO2) was used as the positive electrode active material.

[0097] <Evaluation of the Dispersion State of the Non-aqueous Binder in the Positive Electrode Plate>

[0098] Figure 8A This is a photograph of a cross section of the positive electrode plate produced in Example 1, taken using a SEM (scanning electron microscope). Figure 8B In this photograph, a cross section at the same position of the positive electrode plate was photographed using EDS (Energy Dispersive X-ray Spectroscopy), and the area where the fluorine component was detected by the EDS was dyed to emphasize the fluorine component (PVDF) in the positive electrode plate.

[0099] It should be noted that the SEM cross-sectional photographs were obtained by processing a cross section of the fabricated positive electrode sample plate using a focused ion beam (FIB), and then photographing the cross section after conductive treatment at an acceleration voltage of 15 kV and a magnification of 2000.

[0100] like Figure 8B As shown, it can be confirmed that many areas on the surface of the positive electrode active material 10 are covered with the non-aqueous binder (PVDF) 20 in a shell-like form. In addition, it can be confirmed that the amount of binder (PVDF) 20 present in the gaps formed between the positive electrode active materials 10 is relatively small.

[0101] That is, it was confirmed that when the total volume of the binder (PVDF) 20 covering the surface of the positive electrode active material 10 is defined as V1 and the total volume of the binder (PVDF) 20 present in the region enclosed by the positive electrode active material 10 covered by the binder (PVDF) 20 is defined as V2, the relationship V1>V2 is satisfied. Furthermore, it was confirmed that when the total volume of the region enclosed by the positive electrode active material 10 covered by the binder (PVDF) 20 is defined as V3, the relationship V3>V2 is satisfied.

[0102] Furthermore, it was confirmed that, in the cross section of the positive electrode mixture, when the sum of the areas of the binder (PVDF) 20 covering the surface of the positive electrode active material 10 is defined as A1, and the sum of the areas of the binder (PVDF) 20 present in the region enclosed by the positive electrode active material 10 covered by the binder (PVDF) 20 is defined as A2, the relationship A1>A2 is satisfied. Furthermore, it was confirmed that when the sum of the areas of the region enclosed by the positive electrode active material 10 covered by the binder (PVDF) 20 is defined as A3, the relationship A3>A2 is satisfied.

[0103] on the other hand, Figure 9A This is a photograph of a cross section of the positive electrode plate produced in Comparative Example 1 taken with an SEM. Figure 9B This photograph shows a cross-section of the positive electrode plate at the same location using EDS (energy dispersive X-ray spectroscopy). The area where fluorine was detected by EDS was stained to emphasize the fluorine component (PVDF) in the positive electrode plate. Note that the SEM cross-sectional photograph was obtained under the same conditions as in Example 1.

[0104] like Figure 9B As shown, in the positive electrode plate produced in Comparative Example 1, it can be confirmed that the binder (PVDF) 20 is dispersed between the positive electrode active materials 10, but on the surface of the positive electrode active material 10, there is almost no area covered by the binder (PVDF) in a shell-like form. In other words, in the positive electrode plate produced in Comparative Example 1, it can be confirmed that the binder (PVDF) exists in a state of being pressed into the gaps formed between the positive electrode active materials 10. In other words, it can be confirmed that around the positive electrode active material 10, the binder (PVDF) does not exist in a state of covering the positive electrode active material 10 in a thin film-like shell-like form as in Example 1, but exists in a manner of filling the gaps formed between the positive electrode active materials 10.

[0105] Figure 10A This is a photograph of a cross section of the positive electrode plate produced in Example 2 taken with an SEM. The particle size of the positive electrode active material (LiNiCoMnO2) used in Example 2 is smaller than that of the positive electrode active material (LiFePO4) used in Example 1. Figure 10B This photograph shows a cross-section of the positive electrode plate at the same location using EDS (energy dispersive X-ray spectroscopy). The area where fluorine was detected by EDS was stained to emphasize the fluorine component (PVDF) in the positive electrode plate. Note that the SEM cross-sectional photograph was obtained under the same conditions as in Example 1.

[0106] like Figure 10BAs shown, in the positive electrode plate produced in Example 2, as in Example 1, it was confirmed that many regions of the surface of the positive electrode active material 10 were coated in a shell-like form by the non-aqueous binder (PVDF) 20. In addition, it was confirmed that the amount of the binder (PVDF) 20 present in the gaps formed between the positive electrode active materials 10 was small.

[0107] That is, it was confirmed that when the sum of the volumes of the binder (PVDF) 20 covering the surface of the positive electrode active material 10 was set as VI, the sum of the volumes of the binder (PVDF) 20 present in the region surrounded by the positive electrode active material 10 coated by the binder (PVDF) 20 was set as V2, the relationship VI > V2 was satisfied. In addition, it was confirmed that when the sum of the volumes of the region surrounded by the positive electrode active material 10 coated by the binder (PVDF) 20 was set as V3, the relationship V3 > V2 was satisfied.

[0108] In addition, it was confirmed that in the cross section of the positive electrode mixture, when the sum of the areas of the binder (PVDF) 20 covering the surface of the positive electrode active material 10 was set as Al, the sum of the areas of the binder (PVDF) 20 present in the region surrounded by the positive electrode active material 10 coated by the binder (PVDF) 20 was set as A2, the relationship Al > A2 was satisfied. In addition, it was confirmed that when the sum of the areas of the region surrounded by the positive electrode active material 10 coated by the binder (PVDF) 20 was set as A3, the relationship A3 > A2 was satisfied.

[0109] On the other hand, Figure 11A is a photograph taken with an SEM of the cross section of the positive electrode plate produced in Comparative Example 2, Figure 11B is a photograph taken with an EDS (energy dispersive X-ray spectroscopy) of the cross section at the same position of the positive electrode plate, and the region in which the fluorine component was detected with the EDS was colored to emphasize the fluorine component (PVDF) in the positive electrode plate. Note that the cross section photograph of the SEM was obtained under the same conditions as in Example 1.

[0110] As Figure 11BAs shown, in the positive electrode plate produced in Comparative Example 2, as in Comparative Example 1, it was confirmed that the binder (PVDF) 20 was dispersed among the positive electrode active materials 10, but on the surface of the positive electrode active material 10, a region coated with the binder (PVDF) in a shell-like form could hardly be confirmed. That is, in the positive electrode plate produced in Comparative Example 2, it was confirmed that the binder (PVDF) existed in a state of being pressed into the gap formed among the positive electrode active materials 10. That is, it was confirmed that, around the positive electrode active material 10, the binder (PVDF) did not exist in a state of covering the positive electrode active material 10 in a shell-like form in a film-like manner as in Example 1, but existed in a manner of being filled in the gap formed among the positive electrode active materials 10.

[0111] <Measurement of Coating Rate>

[0112] Based on the SEM photograph of Example 1 and the SEM photograph of Comparative Example 1, the coating rate C (%) defined by the following formula (1) was measured in the cross section of the positive electrode mixture formed on the positive electrode current collector. Figure 8B Figure 9B C = (C2 ÷ CI) x 100 (1)

[0113] In formula (1), CI represents the circumference of the positive electrode active material 10, and C2 represents the total length of the contact portion of the binder (PVDF) in contact with the periphery of the positive electrode active material 10.

[0114] As a result, in the positive electrode plate produced in Example 1, the coating rate was 60%, and, in contrast, in the positive electrode plate produced in Comparative Example 1, the coating rate was 23%.

[0115] However, in the case of observing the cross section of the positive electrode plate using SEM, the binder (PVDF) present on the inner side of the cross section can also be photographed to exist on the same plane as the cross section. Therefore, in order to avoid such an influence, after the positive electrode plates produced in Example 1 and Comparative Example 1 were embedded in resin, the cross section of the positive electrode plate after resin embedding was processed using a BIB (Broad Ion Beam) method, and then the cross section after the conductive treatment was photographed under the conditions of an acceleration voltage of 15 kV and a magnification of 3000 times, whereby the cross section photograph of SEM was obtained.

[0116] is a photograph obtained by photographing the cross section of the positive electrode plate after resin embedding using SEM with respect to the positive electrode plate produced in Example 1,

[0117] Figure 12A is a photograph obtained by photographing the cross section of the positive electrode plate after resin embedding using SEM with respect to the positive electrode plate produced in Comparative Example 1, Figure 12B ​is a photograph showing the fluorine component (PVDF) in the positive electrode plate, which is taken by photographing the cross section at the same position of the positive electrode plate with EDS (Energy Dispersive X-ray Spectrometry), dyeing the region where the fluorine component is detected by the EDS, and line graphing the part 20 in contact with the positive electrode active material 10 in the dyed region.

[0118] Likewise, Figure 13A is a photograph taken by photographing the cross section of the positive electrode plate after resin embedding with SEM, Figure 13B is a photograph showing the fluorine component (PVDF) in the positive electrode plate, which is taken by photographing the cross section at the same position of the positive electrode plate with EDS (Energy Dispersive X-ray Spectrometry), dyeing the region where the fluorine component is detected by the EDS, and line graphing the part 20 in contact with the positive electrode active material 10 in the dyed region.

[0119] Based on Figure 12B the SEM photograph of Example 1 and Figure 13B the SEM photograph of Comparative Example 1, the coating rate C (%) defined by the above formula (1) was measured in the cross section of the positive electrode mixture formed on the positive electrode current collector. As a result, the coating rate was 37% in the positive electrode plate produced in Example 1, and, in contrast, the coating rate was 10% in the positive electrode plate produced in Comparative Example 1.

[0120] Note that the reason why the coating rate C of the positive electrode plate after resin embedding is smaller than the coating rate C of the positive electrode plate which is not subjected to resin embedding can be considered as follows: in the case where the positive electrode plate is subjected to resin embedding, a part of the binder (PVDF), particularly the thinner part, is peeled off from the surface of the positive electrode active material 10 due to the difference in expansion rate between the positive electrode active material and the resin, or the like, when the resin is solidified by heating after the positive electrode plate is embedded in the resin.

[0121] According to the above results, the coating rate C of the positive electrode plate after resin embedding is preferably 30% or more in the cross section of the positive electrode mixture formed on the positive electrode current collector.

[0122] Evaluation of Cycle Characteristics of Lithium Ion Secondary Battery

[0123] A lithium ion secondary battery was produced by winding the positive electrode plate and the negative electrode plate (lithium metal foil) produced in Example 1 with a separator, and by housing the electrode body together with a nonaqueous electrolyte in a battery case.

[0124] The produced lithium ion secondary battery was repeatedly subjected to charge and discharge at a charge and discharge rate of 1C, and the change in discharge capacity [mAh / g] was measured, whereby the cycle characteristics were measured.

[0125] Figure 14is a graph showing the measurement results of the cycle characteristics, the curve indicated by an arrow A shows the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Example 1, and the curve indicated by an arrow B shows the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Comparative Example 1.

[0126] As shown in Figure 14 , it is known that the number of cycles until the discharge capacity decreases to 1 / 3 of the initial capacity is increased by about two times for the lithium ion secondary battery produced using the positive electrode material of Example 1, as compared with the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Comparative Example 1. It is considered that this is because the positive electrode active material 10 is uniformly dispersed in a state where the entire surface is covered with the non-aqueous binder 20 in a shell-like form, and thus the non-aqueous binder 20 is also uniformly dispersed, and the positive electrode active material 10 and the current collector are uniformly adhered with the non-aqueous binder 20 in the entire positive electrode.

[0127] As shown in Figure 14 , the initial capacity of the lithium ion secondary battery produced using the positive electrode material of Example 1 is slightly lower than that of the lithium ion secondary battery produced using the positive electrode material of Comparative Example 1. It is considered that this is because the entire surface of the positive electrode active material 10 is covered with the non-aqueous binder 20 in a shell-like form, and thus the resistance of the surface of the positive electrode active material 10 is increased.

[0128] [Example 3]

[0129] <Production of Positive Electrode Material>

[0130] The powder of the positive electrode active material (lithium iron phosphate) and the powder of the metal oxide (titanium oxide and niobium oxide) were mixed at a mass ratio of 99.8:0.2, and the mixture was sintered at a temperature of 800°C for 180 minutes, so that the metal oxide 30 was attached to the surface of the positive electrode active material 10.

[0131] Then, the entire surface of the positive electrode active material 10 was covered with the non-aqueous binder (PVDF) in a shell-like form in a manner of covering the metal oxide by the same method as in Example 1, and the positive electrode material 1 having the structure shown in Figure 5 was produced.

[0132] <Evaluation of Cycle Characteristics of Lithium Ion Secondary Battery>

[0133] The lithium ion secondary battery was produced by the same method as in Example 1 using the positive electrode material 1 produced in Example 3, and the cycle characteristics were measured.

[0134] Figure 15is a graph showing the measurement results of the cycle characteristics, the curve indicated by an arrow A shows the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Example 1, the curve indicated by an arrow B shows the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Comparative Example 1, and the curve indicated by an arrow C shows the cycle characteristics of the lithium ion secondary battery produced using the positive electrode material of Example 3.

[0135] As shown in Figure 15 , it is known that the initial capacity of the lithium ion secondary battery produced using the positive electrode material of Example 3 is improved compared to the initial capacity of the lithium ion secondary battery produced using the positive electrode material of Example 1. It is considered that this is due to the fact that the increase in the resistance of the surface of the positive electrode active material 10 is suppressed by attaching the metal oxide 30 having a small resistance to the surface of the positive electrode active material 10. Note that the improvement in the cycle characteristics brought about by the fact that the entire surface of the positive electrode active material 10 is coated with the non-aqueous binder 20 in the form of a shell is maintained.

[0136] The present application has been described above through preferred embodiments, but these descriptions are not limiting matters, and various changes can of course be made.

[0137] For example, in the above-described embodiments, as the method of producing the positive electrode material 1, the method of dissolving the powder of the non-aqueous binder 20 in a non-aqueous solvent, dispersing the powder of the positive electrode active material 10 in the non-aqueous solvent, and then evaporating the non-aqueous solvent, thereby coating the entire surface of the positive electrode active material 10 with the non-aqueous binder 20 in the form of a shell, is described, but it is not limited thereto, and for example, as long as the average particle diameter of the non-aqueous binder 20 is less than or equal to about half the average particle diameter of the positive electrode active material 10, the powder of the positive electrode active material 10 and the powder of the non-aqueous binder 20 after being micronized can be mixed and heated without using a water-based solvent such as water, a non-aqueous solvent such as an organic solvent, thereby producing the positive electrode material 1. In this case, the average particle diameter of the positive electrode active material 10 is preferably in the range of 1 μm to 10 μm.

[0138] In addition, in the above-described embodiments, as the electrode of the secondary battery, the positive electrode is described as an example, but even in the case where a lithium-containing negative electrode active material such as lithium titanate (Li4Ti5O 12 ) is used for the negative electrode, the lithium in the negative electrode active material does not dissolve into the water-based solvent, and thus the decrease in the capacity of the negative electrode can be suppressed. In addition, even in the case where a negative electrode active material such as graphite or silicon is used for the negative electrode, since the negative electrode active materials are bonded to each other and to the current collector by the uniformly dispersed non-aqueous binder, a secondary battery having excellent cycle characteristics can be realized.

[0139] Symbol explanation

[0140] 1 positive electrode material (electrode material)

[0141] 10 positive electrode active material (electrode active material)

[0142] 20, 40 non-aqueous binder

[0143] 30 metal oxide

[0144] 50 area surrounded by positive electrode active material coated with non-aqueous binder

Claims

1. An electrode material for a secondary battery, characterized by: the electrode material comprising an electrode active material, the entire surface of the electrode active material being coated in a shell-like form with a non-aqueous binder.

2. The electrode material of claim 1, wherein: a part of the surface of the electrode active material being coated with a metal oxide, the non-aqueous binder coating the entire surface of the electrode active material in a shell-like form so as to cover the metal oxide.

3. An electrode material for a secondary battery, characterized by: the electrode material comprising an electrode active material, the entire surface of the electrode active material being coated in a shell-like form in such a manner that a part of the surface of the electrode active material is coated with a non-aqueous binder and the remaining part of the surface of the electrode active material is coated with a metal oxide.

4. An electrode material for a secondary battery, characterized by: the electrode material comprising an electrode active material, the entire surface of the electrode active material being coated in a shell-like form with a metal oxide, a part of the surface of the metal oxide being coated with a non-aqueous binder.

5. The electrode material of any one of claims 1 to 4, wherein: the non-aqueous binder comprising a fluorine-based resin.

6. The electrode material of any one of claims 1 to 4, wherein: the electrode active material consisting of a positive electrode active material.

7. The electrode material of any one of claims 1 to 4, wherein: the electrode active material consisting of a lithium-containing complex oxide.

8. An electrode slurry comprising an electrode mixture, characterized by: the electrode mixture comprising the electrode material according to any one of claims 1 to 4 and a conductive aid, the electrode mixture being dispersed in an aqueous solvent.

9. The electrode paste of claim 8, wherein: the non-aqueous binder coating the surface of the electrode active material is insoluble in the aqueous solvent.

10. The electrode paste of claim 8, wherein: the conductive aid comprising cellulose nanofiber.

11. A method for producing an electrode material for a secondary battery, characterized by: the method for producing the electrode material comprising the following two steps: a step of dissolving a powder of a non-aqueous binder in a non-aqueous solvent and dispersing a powder of an electrode active material in the non-aqueous solvent; and a step of evaporating the non-aqueous solvent and coating the entire surface of the electrode active material in a shell-like form with the non-aqueous binder.

12. The method of producing an electrode material according to claim 11, characterized by: the method for producing the electrode material further comprising, before the two steps, a step of attaching a metal oxide to a part of the surface of the electrode active material, the entire surface of the electrode active material being coated in a shell-like form with the non-aqueous binder so as to cover the metal oxide.

13. A method for producing an electrode material for a secondary battery, characterized by: the method for producing the electrode material comprising the following steps: a step of attaching a metal oxide to a part of the surface of an electrode active material; a step of dissolving a powder of a non-aqueous binder in a non-aqueous solvent and dispersing a powder of the electrode active material having the metal oxide attached to the surface in the non-aqueous solvent; and a step of evaporating the non-aqueous solvent, the method for producing the electrode material further comprising, before the two steps, a step of attaching a metal oxide to a part of the surface of the electrode active material, the entire surface of the electrode active material being coated in a shell-like form with the non-aqueous binder so as to cover the metal oxide. In the process of evaporating the non-aqueous solvent, the entire surface of the electrode active material is coated in a shell-like form with the non-aqueous binder coating a part of the surface of the electrode active material and the metal oxide coating the remaining part of the surface of the electrode active material.

14. A method for manufacturing an electrode material, which is a method for manufacturing an electrode material for a secondary battery, characterized by comprising the following processes: the method for manufacturing the electrode material comprises the following processes: a process of causing a metal oxide to adhere to the entire surface of an electrode active material; a process of dissolving a powder of a non-aqueous binder in a non-aqueous solvent and dispersing a powder of the electrode active material having the entire surface to which the metal oxide adheres in the non-aqueous solvent; and a process of evaporating the non-aqueous solvent, in the process of evaporating the non-aqueous solvent, a part of the surface of the metal oxide is coated with the non-aqueous binder.

15. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized by: the electrode mixture comprises the electrode material according to any one of claims 1 to 4, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which the entire surface is coated in a shell-like form with the non-aqueous binder, when the total of the volumes of the non-aqueous binder coating the entire surface of the electrode active material is set as VI and the total of the volumes of the non-aqueous binder present in the region surrounded by the electrode active material coated with the non-aqueous binder is set as V2, VI > V2.

16. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized by: the electrode mixture comprises the electrode material according to any one of claims 1 to 4, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which the entire surface is coated in a shell-like form with the non-aqueous binder, when the total of the areas of the non-aqueous binder coating the entire surface of the electrode active material is set as Al and the total of the areas of the non-aqueous binder present in the region surrounded by the electrode active material coated with the non-aqueous binder is set as A2, Al > A2.

17. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized by: the electrode mixture comprises the electrode material according to any one of claims 1 to 4, and a conductive aid, the electrode active material contained in the electrode material is uniformly dispersed in a state in which the entire surface is coated in a shell-like form with the non-aqueous binder, when the total of the volumes of the region surrounded by the electrode active material coated with the non-aqueous binder is set as V3 and the total of the volumes of the non-aqueous binder present in the region surrounded by the electrode active material coated with the non-aqueous binder is set as V2, V3 > V2.

18. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized by: The electrode mixture comprises the electrode material according to any one of claims 1 to 4, and a conductive additive. The electrode active material contained in the electrode material is uniformly dispersed in a state where the entire surface is covered with a non-aqueous binder in a shell-like form. In the cross-section of the electrode mixture, when the sum of the areas of the regions enclosed by the electrode active material coated by the non-aqueous binder is set to A3, and the sum of the areas of the non-aqueous binder present in the regions enclosed by the electrode active material coated by the non-aqueous binder is set to A2, A3>A2.

19. A method for manufacturing an electrode for a secondary battery, characterized in that: The manufacturing method of the electrode comprises the following steps: A step of forming an electrode material in which the entire surface of the electrode active material is coated with a non-aqueous binder in a shell-like form by the method according to any one of claims 11 to 14; a step of dispersing an electrode mixture comprising the electrode material and a conductive additive in an aqueous solvent to form an electrode slurry; and The process of drying the coating film after coating the electrode slurry on the current collector.

20. An electrode material for a secondary battery, characterized in that: The electrode material comprises an electrode active substance, A portion of the surface of the electrode active material is covered with a non-aqueous binder in a shell-like form.

21. The electrode material of claim 20, wherein: More than 50% of the surface of the electrode active material is covered with the non-aqueous binder.

22. The electrode material of claim 20, wherein: The non-aqueous binder includes a fluorine-based resin.

23. The electrode material of claim 20, wherein: The electrode active material is composed of a positive electrode active material.

24. The electrode material of claim 20, wherein: The electrode active material is composed of a lithium-containing composite oxide.

25. An electrode slurry comprising an electrode mixture, characterized in that: The electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive additive. The electrode mixture is dispersed in an aqueous solvent.

26. The electrode slurry of claim 25, wherein: The non-aqueous binder covering the surface of the electrode active material is insoluble in the aqueous solvent.

27. The electrode slurry of claim 25, wherein: The conductive aid comprises cellulose nanofibers.

28. A method for producing an electrode material for a secondary battery, characterized in that: The manufacturing method of the electrode material comprises the following steps: a step of dissolving a powder of a non-aqueous binder in a non-aqueous solvent and dispersing a powder of an electrode active material in the non-aqueous solvent; and The non-aqueous solvent is evaporated, and a portion of the surface of the electrode active material is covered with the non-aqueous binder in a shell-like form.

29. An electrode for a secondary battery, comprising an electrode mixture formed on a current collector, characterized in that: The electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive additive. The electrode active material contained in the electrode material is dispersed in a state where a portion of the surface is covered with a non-aqueous binder in a shell-like form. V1 > V2, when the sum of the volumes of the nonaqueous binder covering a part of the surface of the electrode active material is set as V1, and the sum of the volumes of the nonaqueous binder present in the region surrounded by the electrode active material covered with the nonaqueous binder is set as V2.

30. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized in that: the electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which a part of the surface is covered with the nonaqueous binder in a shell-like form, in a cross section of the electrode mixture, the sum of the areas of the nonaqueous binder covering a part of the surface of the electrode active material is set as Al, and the sum of the areas of the nonaqueous binder present in the region surrounded by the electrode active material covered with the nonaqueous binder is set as A2, Al > A2.

31. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized in that: the electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which a part of the surface is covered with the nonaqueous binder in a shell-like form, the sum of the volumes of the region surrounded by the electrode active material covered with the nonaqueous binder is set as V3, and the sum of the volumes of the nonaqueous binder present in the region surrounded by the electrode active material covered with the nonaqueous binder is set as V2, V3 > V2.

32. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized in that: the electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which a part of the surface is covered with the nonaqueous binder in a shell-like form, in a cross section of the electrode mixture, the sum of the areas of the region surrounded by the electrode active material covered with the nonaqueous binder is set as A3, and the sum of the areas of the nonaqueous binder present in the region surrounded by the electrode active material covered with the nonaqueous binder is set as A2, A3 > A2.

33. An electrode, which is an electrode for a secondary battery, the electrode comprising an electrode mixture formed on a current collector, characterized in that: the electrode mixture comprises the electrode material according to any one of claims 20 to 24, and a conductive aid, the electrode active material contained in the electrode material is dispersed in a state in which a part of the surface is covered with the nonaqueous binder in a shell-like form, in a cross section of the electrode mixture, the covering ratio C defined by the following formula (1) is 30% or more, C = (C2 ÷ Cl) x 100... (1) In formula (1), C1 represents the circumference of the electrode active material, and C2 represents the total length of the contact portions of the non-aqueous binder in contact with the circumference of the electrode active material.

34. A method for manufacturing an electrode, which is a method for manufacturing an electrode for a secondary battery, characterized by: The method for manufacturing an electrode comprises the following steps: The step of forming an electrode material in which a part of the surface of an electrode active material is coated with a non-aqueous binder in a shell-like form by the method according to claim 28; The step of dispersing an electrode mixture containing the electrode material and a conductive aid in an aqueous solvent to form an electrode slurry; and The step of drying the coated film after the electrode slurry is applied to the current collector.

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