Secondary batteries

Abstract

The present invention provides a secondary battery capable of more sufficiently prevent degradation of cycle characteristics relating to discharge capacity and electrode resistance. The present invention relates to a secondary battery comprising an electrode including an electrode active material and an electrically conductive material. At least part of the electrically conductive material is covered by a coating material, and the coating amount of the coating material is 0.0008 mmol / m2 to 0.06 mmol / m2 inclusive.

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] A secondary battery generally has a structure in which a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte are sealed in an outer casing. The positive electrode and the negative electrode, and particularly the positive electrode, contain positive electrode active material particles as an electrode active material.

[0003] For example, Patent Document 1 discloses that in a lithium ion secondary battery, a positive electrode active material and a portion of a conductive material contained in the positive electrode are coated with lithium ion conductive glass. It is shown that this coating can suppress oxidative decomposition of the electrolyte and suppress deterioration of battery performance such as gas generation and battery capacity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-173770 Summary of the Invention [Problem to be solved by the invention]

[0005] Research by the present inventors has revealed that conventional technologies do not provide sufficient cycle characteristics in terms of discharge capacity and electrode resistance, and that there is room for further improvement. Specifically, electrodes typically contain, in addition to an electrode active material, other electrode components, such as a conductive material. These other electrode components react with the electrolyte, etc., to generate gas and / or deposit by-products on their surfaces. As a result, charge-discharge cycling (i.e., repeated charge-discharge) reduces the discharge capacity and / or increases the electrode resistance, resulting in reduced cycle characteristics.

[0006] An object of the present invention is to provide a secondary battery that can more sufficiently prevent deterioration in cycle characteristics related to discharge capacity and electrode resistance. [Means for solving the problem]

[0007] The present invention provides an electrode including an electrode active material and a conductive material; At least a portion of the conductive material is covered with a coating material, The coating amount of the coating material is 0.0008 mmol / m 2 More than 0.06mmol / m 2 The following relates to a secondary battery. [Effects of the Invention]

[0008] The secondary battery of the present invention has sufficiently improved chemical stability, and as a result, deterioration in cycle characteristics related to discharge capacity and electrode resistance can be more sufficiently prevented. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Secondary battery] The secondary battery of the present invention includes a specific electrode (hereinafter, sometimes referred to as "the electrode of the present invention") containing an electrode active material and a conductive material. In this specification, "secondary battery" refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery according to one embodiment of the present invention is not limited to its name, and may also include electrochemical devices such as electricity storage devices.

[0010] The electrode of the present invention has a conductive material-coated structure in which at least a portion of the conductive material is covered with a coating material. This sufficiently improves the chemical stability of the secondary battery, more effectively prevents reactions between the conductive material and the electrolyte, and more effectively prevents the generation of gas and by-products. As a result, deterioration in cycle characteristics related to discharge capacity and electrode resistance is more effectively prevented.

[0011] In this specification, the cycle characteristics relating to discharge capacity refer to the characteristics that allow the discharge capacity to be more sufficiently maintained even through charge-discharge cycles (that is, repeated charge and discharge). The cycle characteristic regarding the electrode resistance refers to the characteristic that the increase in the electrode resistance is more sufficiently prevented even through charge / discharge cycles (that is, repeated charge / discharge). Hereinafter, the cycle characteristics relating to the discharge capacity and the cycle characteristics relating to the electrode resistance may be collectively referred to as "cycle characteristics."

[0012] In the present invention, the electrode having a conductive material coating structure may correspond to a positive electrode, a negative electrode, or both a positive electrode and a negative electrode. Specifically, only the positive electrode may have a conductive material coating structure, only the negative electrode may have a conductive material coating structure, or both the positive electrode and the negative electrode may have a conductive material coating structure. In the present invention, from the viewpoint of further improving cycle characteristics, the electrode having a conductive material coating structure preferably corresponds to at least a positive electrode, and may, for example, correspond to only a positive electrode or to both a positive electrode and a negative electrode.

[0013] The conductive material is a substance that can also be referred to as a "conductive assistant." The conductive material is not particularly limited, and examples thereof include at least one selected from 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. In a more preferred embodiment, the conductive material of the electrode (particularly the positive electrode) is carbon black (particularly ketjen black).

[0014] The average primary particle size of the conductive material is not particularly limited, and is, for example, 10 nm or more and 100 nm or less.

[0015] In this specification, the average primary particle size is the average value calculated by observing a conductive material under an electron microscope and measuring the lengths of 50 randomly selected particles. In the microscope image, a line is drawn from one end of each particle to the other, and the distance between the two points with the longest length is taken as the particle size.

[0016] The conductive material may be composed of primary particles and / or secondary particles formed by aggregation of multiple primary particles. The phrase "at least a portion of the conductive material is covered with a coating material" means that in such a particulate conductive material, the coating material is present in partial or total contact with the surface of at least some of the primary particles. For example, the coating material of the conductive material may be present on at least a portion of the surface of the primary particles and / or at least a portion of the voids between the primary particles.

[0017] The coating material for the conductive material includes the following materials X and Y, or a mixture thereof. From the viewpoint of further improving cycle characteristics, the coating material preferably includes material X, and more preferably may consist of only material X.

[0018] Material X is a reactant containing at least a first metal alkoxide that does not contain a single metal atom-carbon atom bond in one molecule and a second metal alkoxide that contains one or more metal atom-carbon atom bonds in one molecule, and is also called an "organic-inorganic hybrid material."

[0019] In the present invention, material X is a reaction product containing at least a first metal alkoxide and a second metal alkoxide as monomer components. Specifically, in the present invention, material X as a coating material has a network structure (single-layer structure) consisting of a reaction product of a mixture of the above metal alkoxides, rather than a laminate of multiple layers formed from each of the above metal alkoxides. Material X has a moderately coarse network structure, resulting in sufficient flexibility. Material X also has sufficient adhesion to conductive materials. Therefore, material X has sufficient strength, which is believed to more effectively prevent peeling of the coating even with repeated charge / discharge cycles and improve cycle characteristics. If material X does not contain at least one of the first metal alkoxide and the second metal alkoxide, the material will lack sufficient flexibility and / or adhesion to conductive materials. Therefore, the material will lack sufficient strength and peel relatively easily with repeated charge / discharge cycles, resulting in poor cycle characteristics. Material X may also contain unreacted first metal alkoxide and second metal alkoxide.

[0020] The first metal alkoxide is a metal alkoxide that does not contain a single metal atom-carbon atom bond in one molecule, and all of the bonds on the metal are alkoxy groups (-OR 1 ) in the first metal alkoxide. In the first metal alkoxide, the metal atom-carbon atom bond is a direct covalent bond between a metal atom and a carbon atom. In the first metal alkoxide, the carbon atom that constitutes the metal atom-carbon atom bond is a carbon atom that constitutes a monovalent hydrocarbon group (e.g., an alkyl group or an alkenyl group) or a carbon atom that constitutes a divalent hydrocarbon group (e.g., an alkylene group). The first metal alkoxide does not have even one such metal atom-carbon atom bond in a single molecule. Therefore, the first metal alkoxide is relatively highly reactive, and at the interface between material X and the conductive material, it mainly fixes material X to the conductive material by a relatively strong bond.

[0021] Specifically, the first metal alkoxide is a compound represented by the following general formula (1).

[0022] [ka]

[0023] In formula (1), M 1 is a metal atom and is Si, Ti, Al or Zr, and from the viewpoint of further improving cycle characteristics, is preferably Si or Ti, more preferably Si. x is M 1 is the valence of M 1 When is Si, Ti or Zr, x is 4. 1 When is Al, x is 3. R 1 are each independently an alkyl group having 1 to 10 carbon atoms or a group of the general formula: -C(R 2 )=CH-CO-R 3 (wherein R 2 and R 3 is as described below), and from the viewpoint of further improving the cycle characteristics, it is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. 1 Examples of the alkyl group as R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. 1 About all R 1 may each independently be selected from the alkyl groups described above, or all of R 1 may be the same groups selected from the above alkyl groups. R 2 R is an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, it is preferably an alkyl group having 1 to 5 carbon atoms. 2 As the alkyl group, R 1Examples of the alkyl group include the same alkyl groups as those mentioned above. R 3 R is an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or an alkenyloxy group having 1 to 30 carbon atoms, and from the viewpoint of further improving the cycle characteristics, it is preferably an alkyl group having 1 to 20 carbon atoms (more preferably 1 to 10, and even more preferably 1 to 5), an alkyloxy group having 10 to 30 carbon atoms (particularly 14 to 24), or an alkenyloxy group having 10 to 30 carbon atoms (particularly 14 to 24). 3 Preferred alkyl groups as R 1 Examples of the alkyl group include the same alkyl groups as those in the alkyl group R, as well as undecyl, lauryl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, nonadecyl, and eicosyl groups. 3 Examples of the alkyloxy group as the formula: -OC p H 2p+1 (wherein p is an integer of 1 to 30). 3 Examples of the alkenyloxy group as the formula: -OC q H 2q-1 (wherein q is an integer of 1 to 30).

[0024] In formula (1), multiple R 1 Among them, the two adjacent R 1 When the two R are alkyl groups, they are bonded to each other. 1 and the oxygen atom to which the oxygen atom is bonded, 1 Two adjacent R 1 Examples of the ring formed by bonding together include a 6-membered ring represented by general formula (1X).

[0025] [ka]

[0026] In formula (1X), R 4, R 5 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 4 , R 5 and R 6 The total number of carbon atoms in R is usually 0 to 12, and from the viewpoint of further improving cycle characteristics, it is preferably 2 to 8. 4 , R 5 and R 6 As the alkyl group, R 1 Examples of the alkyl group include the same alkyl groups as those mentioned above.

[0027] Examples of the first metal alkoxide include compounds represented by the following general formulas (1A), (1B), (1B'), (1C), and (1D). From the viewpoint of further improving cycle characteristics, the first metal alkoxide is preferably a compound represented by general formula (1A), (1B), (1C), or (1D) or a mixture thereof, more preferably a compound represented by general formula (1A) or (1B) or a mixture thereof, and even more preferably a compound represented by general formula (1A) or a mixture thereof.

[0028] [ka]

[0029] In formula (1A), R 1 are each independently R in formula (1). 1 Similar to R 1 R 1 are each independently an alkyl group preferably having 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, from the viewpoint of further improving cycle characteristics.

[0030] Specific examples of the compound (1A) represented by such a general formula are shown in the table below. [Table 1]

[0031] [ka]

[0032] In formula (1B), R 1 are each independently R in formula (1). 1 Similar to R 1 R 1 From the viewpoint of further improving cycle characteristics, each of the groups independently represents preferably an alkyl group having 1 to 10 carbon atoms or a group represented by the general formula: -C(R 2 )=CH-CO-R 3 (wherein R 2 and R 3 are R explained in the general formula (1), 2 and R 3 The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms (particularly 1 to 5 carbon atoms). In formula (1B), R 2 and R 3 From the viewpoint of further improving cycle characteristics, R is preferably the following group: 2 is an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. 2 As the alkyl group, R 1 The alkyl groups are the same as those of the alkyl groups mentioned above. 3 R is an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms (more preferably 1 to 10, and even more preferably 1 to 5). 3 Preferred alkyl groups as R 1 Examples of the alkyl group include the same alkyl groups as those in the above, as well as undecyl, lauryl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, nonadecyl, and eicosyl groups.

[0033] Specific examples of the compound (1B) represented by such a general formula are shown in the table below. [Table 2]

[0034] [ka]

[0035] In formula (1B'), Ra 1 , Ra 2 , Ra 3 , Ra 4 , Ra 5 and Ra 6 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably alkyl groups having 1 to 5 carbon atoms. 1 , Ra 2 , Ra 3 , Ra 4 , Ra 5 and Ra 6 The alkyl group as R 1 The alkyl group is the same as the alkyl group.

[0036] Specific examples of the compound (1B') represented by such a general formula are shown in the table below. [Table 3]

[0037] [ka]

[0038] In formula (1C), R 1 are each independently R in formula (1). 1 Similar to R 1 R 1 and each independently represent, from the viewpoint of further improving the cycle characteristics, packing property, and load characteristics of the positive electrode active material, preferably an alkyl group having 1 to 10 carbon atoms or a group represented by the general formula: -C(R 2 )=CH-CO-R3 (wherein R 2 and R 3 are R explained in the general formula (1), 2 and R 3 The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms (particularly 1 to 5 carbon atoms). In formula (1C), R 2 and R 3 From the viewpoint of further improving cycle characteristics, R is preferably the following group: 2 is an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. 2 As the alkyl group, R 1 The alkyl groups are the same as those of the alkyl groups mentioned above. 3 R is an alkyloxy group having 1 to 30 carbon atoms or an alkenyloxy group having 1 to 30 carbon atoms, preferably an alkyloxy group having 10 to 30 (particularly 14 to 24) carbon atoms or an alkenyloxy group having 10 to 30 (particularly 14 to 24) carbon atoms. 3 Examples of the alkyloxy group as the formula: -OC p H 2p+1 (wherein p is an integer of 1 to 30). 3 Examples of the alkenyloxy group as the formula: -OC q H 2q-1 (wherein q is an integer of 1 to 30).

[0039] Specific examples of the compound (1C) represented by such a general formula are shown in the table below.

[0040] [Table 4]

[0041] [ka]

[0042] In formula (1D), R1 are each independently R in formula (1). 1 Similar to R 1 R 1 are each independently an alkyl group preferably having 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, from the viewpoint of further improving cycle characteristics.

[0043] Specific examples of the compound (1D) represented by such a general formula are shown in the table below.

[0044] [Table 5]

[0045] The compound (1) represented by the general formula (1) can be obtained as a commercial product or can be produced by a known method. For example, compound (1A) is available as a commercially available product, tetraethyl orthosilicate (manufactured by Tokyo Chemical Industry Co., Ltd.). Furthermore, for example, compound (1B) is available as a commercially available product such as tetrabutyl orthotitanate (manufactured by Tokyo Chemical Industry Co., Ltd.) or T-50 (manufactured by Nippon Soda Co., Ltd.). Furthermore, for example, compound (1B') is available as a commercially available product TOG (manufactured by Nippon Soda Co., Ltd.). Furthermore, for example, compound (1C) is available as a commercially available product, aluminum triisopropoxide (manufactured by Kanto Chemical Co., Ltd.). Furthermore, for example, compound (1D) can be obtained as a commercially available product, zirconium (IV) tetrabutoxide (trade name TBZR, manufactured by Nippon Soda Co., Ltd.), ZR-181 (manufactured by Nippon Soda Co., Ltd.).

[0046] The content of the first metal alkoxide in material X is typically 1 wt % to 99 wt % of its total weight (e.g., the total weight of the first metal alkoxide and the second metal alkoxide), and from the viewpoint of further improving cycle characteristics, is preferably 5 wt % to 95 wt %. Material X may contain two or more types of first metal alkoxides, in which case the total amount thereof may be within the above range. The content of the first metal alkoxide in material X may be the ratio of the amount of the first metal alkoxide to the total amount of the first metal alkoxide and the second metal alkoxide.

[0047] The second metal alkoxide is a metal alkoxide containing one or more (particularly two or more, for example, two or more to 20 or less, particularly two or more to 12 or less) metal atom-carbon atom bonds per molecule. In the second metal alkoxide, the carbon atoms constituting one or more (particularly two or more) metal atom-carbon atom bonds are carbon atoms constituting monovalent hydrocarbon groups (e.g., alkyl groups and alkenyl groups) and / or carbon atoms constituting divalent hydrocarbon groups (e.g., alkylene groups). In the second metal alkoxide, the carbon atoms constituting all of the one or more (particularly two or more) metal atom-carbon atom bonds are preferably carbon atoms constituting divalent hydrocarbon groups (e.g., alkylene groups) from the viewpoint of further improving cycle characteristics. The metal atom of the second metal alkoxide is preferably silicon from the viewpoint of further improving cycle characteristics. The second metal alkoxide contains one or more (particularly two or more) such metal atom-carbon atom bonds per molecule. Therefore, the second metal alkoxide prevents the formation of a dense network structure, and material X forms a flexible, moderately coarse network structure. Specifically, for example, when the carbon atom constituting the metal atom-carbon atom bond in the second metal alkoxide is a carbon atom constituting a divalent hydrocarbon group (e.g., an alkylene group), the "flexibility" and "moderate coarseness" of material X are preferably based on the divalent hydrocarbon group 30 possessed by the second metal alkoxide, from the viewpoint of further improving cycle characteristics. As a result, the conductive material in the present invention is considered to have sufficiently improved ionic conductivity when ions (especially lithium ions) responsible for transferring electrons pass through material X. If material X does not contain the second metal alkoxide, material X will have a relatively dense network structure, resulting in poor cycle characteristics.

[0048] When the carbon atom constituting the metal atom-carbon atom bond in the second metal alkoxide is a carbon atom constituting a divalent hydrocarbon group, the second metal alkoxide is preferably a compound having two or more trialkoxysilyl groups represented by the following general formula (2) in one molecule:

[0049] [ka]

[0050] In formula (2), R 21 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Examples of such alkyl groups include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. 21 About all R 21 may each independently be selected from the alkyl groups described above, or all of R 21 may be the same groups selected from the above alkyl groups.

[0051] The trialkoxysilyl groups in the second metal alkoxide may be independently selected from the trialkoxysilyl groups of the general formula (2) above, or may be the same group.

[0052] Specific examples of such trialkoxysilyl groups represented by general formula (2) are shown in the table below.

[0053] [Table 6]

[0054] In the case where all of the carbon atoms constituting two or more metal atom-carbon atom bonds in the second metal alkoxide are carbon atoms constituting a divalent hydrocarbon group, the second metal alkoxide may be, for example, a compound represented by the following general formula (2A), (2B), (2C), (2E), or (2F), or a mixture thereof. Among these, from the viewpoint of further improving cycle characteristics, the second metal alkoxide is preferably a compound represented by general formula (2A), (2B), or (2C), or a mixture thereof, more preferably a compound represented by general formula (2A) or (2B), or a mixture thereof, and even more preferably a compound represented by general formula (2A).

[0055] When all of the carbon atoms constituting two or more metal atom-carbon atom bonds in the second metal alkoxide are carbon atoms constituting a monovalent hydrocarbon group, the second metal alkoxide may be, for example, a compound represented by the following general formula (2D) or a mixture thereof.

[0056] [ka]

[0057] In formula (2A), R 211 and R 212 are each independently R in formula (2). 21 In detail, the three R 211 and the three R's 212 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 211 and the three R's 212 are each independently R in the general formula (2) 21 or may be the same group as each other. R 31is a divalent hydrocarbon group having 1 to 20 carbon atoms, and from the viewpoint of further improving cycle characteristics, is preferably a divalent hydrocarbon group having 1 to 10 carbon atoms, and more preferably a divalent hydrocarbon group having 2 to 8 carbon atoms. 31 The divalent hydrocarbon group as R may be a divalent saturated aliphatic hydrocarbon group (e.g., an alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g., an alkenylene group). 31 From the viewpoint of further improving cycle characteristics, the divalent hydrocarbon group as R is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group). 31 As a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group), for example, -(CH2) p - (wherein p is an integer of 1 to 10, more preferably 2 to 8), and the like.

[0058] Specific examples of the compound (2A) represented by such a general formula are shown in the table below.

[0059] [Table 7]

[0060] [ka]

[0061] In formula (2B), R 211 , R 212 , R 213 and R 214 is R in Equation (2) 21 In detail, the three R 211 ,The Three Rs 212 ,The Three Rs 213 and the three R's 214 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 211 ,The Three Rs 212 , The Three Rs213 and the three R's 214 are each independently R in the general formula (2) 21 or may be the same group as each other. R 32 are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably divalent hydrocarbon groups having 1 to 10 carbon atoms, and more preferably divalent hydrocarbon groups having 6 to 10 carbon atoms. 32 The divalent hydrocarbon group as R may be a divalent saturated aliphatic hydrocarbon group (e.g., an alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g., an alkenylene group). 32 From the viewpoint of further improving cycle characteristics, the divalent hydrocarbon group as R is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group). 32 As a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group), for example, -(CH2) q - (wherein q is an integer of 1 to 10, more preferably 6 to 10). 32 are each independently 32 or may be the same group as each other. R 33 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably a monovalent hydrocarbon group having 1 to 5 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms. 33 The monovalent hydrocarbon group as R may be a saturated aliphatic hydrocarbon group (e.g., an alkyl group) or an unsaturated aliphatic hydrocarbon group (e.g., an alkenyl group). 33 From the viewpoint of further improving cycle characteristics, the monovalent hydrocarbon group as R is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group). 33Examples of the monovalent saturated aliphatic hydrocarbon group (particularly an alkyl group) as R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. 33 are each independently 33 or may be the same group as each other.

[0062] Specific examples of the compound (2B) represented by such a general formula are shown in the table below.

[0063] [Table 8]

[0064] [ka]

[0065] In formula (2C), R 211 and R 212 is R in Equation (2) 21 In detail, the three R 211 , and the three R's 212 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 211 and the three R's 212 are each independently R in the general formula (2) 21 or may be the same group as each other. R 34 , R 35 , and R 36 are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably divalent hydrocarbon groups having 1 to 5 carbon atoms. 34 , R 35 , and R36 The divalent hydrocarbon group as R may be a divalent saturated aliphatic hydrocarbon group (e.g., an alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g., an alkenylene group). 34 , R 35 , and R 36 From the viewpoint of further improving cycle characteristics, the divalent hydrocarbon group as R is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group). 34 , R 35 , and R 36 As a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group), for example, -(CH2) r - (wherein r is an integer of 1 to 10, more preferably 1 to 5). 34 , R 35 , and R 36 may be independently selected from the divalent hydrocarbon groups described above, or may be the same group as each other. 34 , R 35 , and R 36 The total number of carbon atoms is preferably 3 to 20, and more preferably 6 to 10, from the viewpoint of further improving cycle characteristics.

[0066] Specific examples of the compound (2C) represented by such a general formula are shown in the table below.

[0067] [Table 9]

[0068] [ka]

[0069] In formula (2D), R 211 and R 212 are each independently R in formula (2). 21 In detail, the two R 211 and two R 212are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 211 and two R 212 are each independently R in the general formula (2) 21 or may be the same group as each other.

[0070] Specific examples of the compound (2D) represented by such a general formula are shown in the table below.

[0071] [Table 10]

[0072] [ka]

[0073] In formula (2E), R 212 and R 213 is R in Equation (2) 21 In detail, the three R 212 and the three R's 213 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 212 and the three R's 213 are each independently R in the general formula (2) 21 or may be the same group as each other. R 32 are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably divalent hydrocarbon groups having 1 to 10 carbon atoms, and more preferably divalent hydrocarbon groups having 4 to 8 carbon atoms. 32The divalent hydrocarbon group as R may be a divalent saturated aliphatic hydrocarbon group (e.g., an alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g., an alkenylene group). 32 From the viewpoint of further improving cycle characteristics, the divalent hydrocarbon group as R is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group). 32 As a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group), for example, -(CH2) q - (wherein q is an integer of 1 to 20, preferably 1 to 10, more preferably 4 to 8). 32 are each independently 32 or may be the same group as each other. R 33 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably a monovalent hydrocarbon group having 1 to 5 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms. 33 The monovalent hydrocarbon group as R may be a saturated aliphatic hydrocarbon group (e.g., an alkyl group) or an unsaturated aliphatic hydrocarbon group (e.g., an alkenyl group). 33 From the viewpoint of further improving cycle characteristics, the monovalent hydrocarbon group as R is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group). 33 Examples of the monovalent saturated aliphatic hydrocarbon group (particularly an alkyl group) as R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. 33 are each independently 33 or may be the same group as each other. R 34are each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably monovalent hydrocarbon groups having 1 to 10 carbon atoms, and more preferably monovalent hydrocarbon groups having 1 to 5 carbon atoms. 34 The monovalent hydrocarbon group as R may be a saturated aliphatic hydrocarbon group (e.g., an alkyl group) or an unsaturated aliphatic hydrocarbon group (e.g., an alkenyl group). 34 From the viewpoint of further improving cycle characteristics, the monovalent hydrocarbon group as R is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group). 34 Examples of the monovalent saturated aliphatic hydrocarbon group (particularly an alkyl group) as R include a methyl group, an ethyl group, an propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an eicosyl group. 34 are each independently 34 or may be the same group as each other.

[0074] Specific examples of the compound (2E) represented by such a general formula are shown in the table below.

[0075] [Table 11]

[0076] [ka]

[0077] In formula (2F), R 212 , R 213 and R 214 are each independently R in formula (2). 21 In detail, the three R 212 , the three R's213 and the three R's 214 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the cycle characteristics, are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 212 , the three R's 213 and the three R's 214 are each independently R in the general formula (2) 21 or may be the same group as each other. R 32 are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and from the viewpoint of further improving cycle characteristics, are preferably divalent hydrocarbon groups having 1 to 10 carbon atoms, and more preferably divalent hydrocarbon groups having 1 to 5 carbon atoms. 32 The divalent hydrocarbon group as R may be a divalent saturated aliphatic hydrocarbon group (e.g., an alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g., an alkenylene group). 32 From the viewpoint of further improving cycle characteristics, the divalent hydrocarbon group as R is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group). 32 As a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group), for example, -(CH2) q - (wherein q is an integer of 1 to 10, more preferably 1 to 5). 32 are each independently 32 or may be the same group as each other.

[0078] Specific examples of the compound (2F) represented by such a general formula are shown in the table below.

[0079] [Table 12]

[0080] Compound (2A) represented by general formula (2A), compound (2B) represented by general formula (2B), compound (2C) represented by general formula (2C), compound (2D) represented by general formula (2D), compound (2E) represented by general formula (2E), and compound (2F) represented by general formula (2F) can be obtained as a commercially available product or can be produced by a known method. For example, compound (2A) is available as a commercially available product, 1,2-bis(trimethoxysilyl)ethane (manufactured by Tokyo Chemical Industry Co., Ltd.) or 1,6-bis(trimethoxysilyl)hexane (manufactured by Tokyo Chemical Industry Co., Ltd.). Furthermore, for example, compound (2C) is available as a commercially available product X-12-5263HP (manufactured by Shin-Etsu Chemical Co., Ltd.). Furthermore, for example, compound (2D) is available as a commercially available product, dimethyldimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.). Furthermore, for example, compound (2F) can be obtained as a commercially available product, tris[3-(trimethoxysilyl)-propyl]isocyanurate (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0081] The second metal alkoxide may be, for example, a compound represented by general formula (2A), (2B), (2C), (2D), (2E), or (2F), or a mixture thereof. From the viewpoint of further improving cycle characteristics, the second metal alkoxide is preferably a compound represented by general formula (2A), (2B), (2C), or (2D), or a mixture thereof, and more preferably a compound represented by general formula (2A) or (2D), or a mixture thereof.

[0082] When the second metal alkoxide is a metal alkoxide containing only one metal atom-carbon atom bond in one molecule, for example, one of the bonds possessed by the metal is a monovalent hydrocarbon group (-R 12 ) and all remaining hands are alkoxy groups (-OR 11) bonded to the metal atom. Such a second metal alkoxide is sometimes referred to as metal alkoxide 2'. In metal alkoxide 2', the metal atom-carbon atom bond is a direct covalent bond between a metal atom and a carbon atom. In metal alkoxide 2', the carbon atom constituting the metal atom-carbon atom bond is a carbon atom constituting a monovalent hydrocarbon group (e.g., an alkyl group or an alkenyl group). Metal alkoxide 2' contains only one such metal atom-carbon atom bond per molecule. The metal atom of metal alkoxide 2' is silicon. Metal alkoxide 2' reduces the surface free energy of material X and imparts more sufficient slipperiness to the surface of material X. Such sufficient slipperiness is achieved by the monovalent hydrocarbon group (e.g., R 12 ) is thought to be based on

[0083] Specifically, the metal alkoxide 2′ is a compound represented by the following general formula (3).

[0084] [ka]

[0085] In formula (3), R 11 are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the filling property and load characteristics of the positive electrode active material, preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Examples of such alkyl groups include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. All R 11 may each independently be selected from the alkyl groups described above, or all of R 11 may be the same groups selected from the above alkyl groups. R 12is a monovalent hydrocarbon group having 8 to 30 carbon atoms, and from the viewpoint of further improving the filling property and load characteristics of the positive electrode active material, is preferably a monovalent hydrocarbon group having 12 to 24 carbon atoms, and more preferably a monovalent hydrocarbon group having 14 to 20 carbon atoms. 12 The monovalent hydrocarbon group as R may be a saturated aliphatic hydrocarbon group (e.g., an alkyl group) or an unsaturated aliphatic hydrocarbon group (e.g., an alkenyl group). 12 The monovalent hydrocarbon group as R is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group) from the viewpoint of further improving the packing property and load characteristics of the positive electrode active material. 12 Examples of the monovalent saturated aliphatic hydrocarbon group (particularly an alkyl group) as the aryl group include an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an eicosyl group.

[0086] Specific examples of the compound (3) represented by such a general formula are shown in the table below.

[0087] [Table 13]

[0088] The compound (3) represented by the general formula (3) can be obtained as a commercial product or can be produced by a known method. For example, compound (3) is available as a commercially available product such as octadecyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), hexadecyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), or decyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0089] The content of the second metal alkoxide in material X as a coating material for a conductive material (particularly the content of second metal alkoxides other than metal alkoxide 2' described below) is typically 1% by weight to 99% by weight, based on the total weight (e.g., the total weight of the first metal alkoxide and the second metal alkoxide), and from the viewpoint of further improving cycle characteristics, is preferably 5% by weight to 95% by weight. Material X may contain two or more types of second metal alkoxides, in which case the total amount thereof may be within the above range. The content of the second metal alkoxide in material X may be the ratio of the amount of the second metal alkoxide to the total weight of the first metal alkoxide and the second metal alkoxide.

[0090] Material Y is a lithium-containing composite oxide containing Li (lithium) and one or more elements selected from the group consisting of Group 2 elements, transition metal elements, rare earth elements, Group 13 elements, Group 14 elements, and Group 15 elements (hereinafter, sometimes referred to as "Group I").

[0091] Examples of Group 2 elements include Mg (magnesium). Examples of transition metal elements include W (tungsten). An example of the rare earth element is Ce (cerium). Examples of Group 13 elements include Al (aluminum). Examples of Group 14 elements include B (boron) and Si (silicon). Examples of Group 15 elements include P (phosphorus).

[0092] The lithium-containing composite oxide as material Y may be, for example, a compound represented by general formula (4). [ka]

[0093] In formula (4), M is one or more elements selected from the group consisting of Group I described above. From the viewpoint of further improving cycle characteristics, M is preferably one or more elements selected from the group consisting of transition metal elements, Group 14 elements, and Group 15 elements (hereinafter, sometimes referred to as “Group II”), more preferably one or more elements selected from the group consisting of W (tungsten), B (boron), Si (silicon), and P (phosphorus) (hereinafter, sometimes referred to as “Group III”), even more preferably one or more elements selected from the group consisting of Group 14 elements, particularly preferably containing B (boron), and most preferably containing only B (boron).

[0094] In formula (4), a is an integer of 1 or more and 4 or less, and is preferably an integer of 2 or more and 3 or less from the viewpoint of further improving cycle characteristics. b is an integer of 1 or more and 5 or less, and from the viewpoint of further improving cycle characteristics, is preferably an integer of 2 or more and 4 or less. When M is two or more elements, b is the total number of the values ​​for the respective elements. c is an integer of 2 or more and 8 or less, and is preferably an integer of 3 or more and 7 or less from the viewpoint of further improving the cycle characteristics.

[0095] Concerning the material Y, specific examples of the compound (4) represented by such a general formula include Li2B2O4, Li3BO3, Li2B4O7, and Li4SiO4.

[0096] The compound (4) represented by the general formula (4) can be obtained as a commercial product or can be produced by a known method.

[0097] The fact that at least a portion of the conductive material is covered with a coating material can be confirmed by microscopic observation, and more specifically, by STEM-EDX (Scanning Transmission Electron Microscope-Energy Dispersive X-ray Spectrometer).

[0098] Coating of a conductive material with a coating material can be achieved by stirring the conductive material with a solution containing a predetermined coating material raw material and then removing the solvent. The predetermined coating material raw material varies depending on the type of coating material. For example, if the coating material is material A, the predetermined coating material raw material is a predetermined metal alkoxide (e.g., containing at least a first metal alkoxide and a second metal alkoxide, and optionally further containing metal alkoxide 2'). For example, if the coating material is material B, the predetermined coating material raw material is a predetermined lithium-containing composite oxide (e.g., a compound represented by general formula (4)). For example, if the coating material is a composite material of material A and material B, the predetermined coating material raw material is a mixture of a predetermined metal alkoxide (e.g., containing at least a first metal alkoxide and a second metal alkoxide, and optionally further containing metal alkoxide 2') and a predetermined lithium-containing composite oxide (e.g., a compound represented by general formula (4)).

[0099] The bonding state of the metal atom-carbon atom in material X or material Y contained in the coating material of the conductive material can be confirmed by spectral analysis using XPS (X-ray Photoelectron Spectroscopy). Therefore, for example, the bonding states of the first and second metal alkoxides can be detected by XPS.

[0100] The coating material raw materials are usually dissolved in a solvent before use. The solvent is not particularly limited as long as it can dissolve the coating material raw materials, and may be, for example, ketones, monoalcohols, ethers, glycols, or glycol ethers. In a preferred embodiment, the solvent may be ketones such as N-methyl-2-pyrrolidone or N-ethyl-2-pyrrolidone; monoalcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, 1-pentanol, 2-pentanol, or 2-methyl-2-pentanol; ethers such as 2-methoxyethanol, 2-ethoxyethanol, or 2-butoxyethanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, or propylene glycol; or glycol ethers such as dipropylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, or diethylene glycol monohexyl ether. Ketones are preferred. Furthermore, the solvent may contain water as needed. The solvent may be used alone or in combination of two or more. The solvent may contain various additives such as a catalyst, a pH adjuster, a stabilizer, a thickener, etc. Examples of the additives include acid compounds such as boric acid compounds and base compounds such as ammonia compounds.

[0101] After stirring, specifically, by heating and drying, the solvent is removed, and the conductive material is coated with the coating material. For example, if the coating material is material X, heating and drying causes a dealcoholization reaction of at least the first metal alkoxide and the second metal alkoxide, forming material X having a network structure on the surface of the conductive material. For example, if the coating material is material Y, heating and drying removes the solvent, and material Y adheres to the surface of the conductive material. Note that the coating method is not limited to the above method as long as it achieves coating on the conductive material, and application methods such as spraying and dry mixing may also be used. After stirring and before heating and drying, the conductive material may be filtered and washed. Washing is performed to remove any remaining catalyst. For example, the residue from filtration may be contacted with a washing solvent. The washing solvent is not particularly limited, and may be, for example, acetone.

[0102] The temperature of the mixture during stirring is not particularly limited as long as the coating material raw material can be uniformly distributed on the surface of the conductive material, and is, for example, 10°C or higher and 70°C or lower, preferably 15°C or higher and 35°C or lower. The stirring time is also not particularly limited as long as the coating material raw material can be uniformly distributed on the surface of the conductive material, and is, for example, from 10 minutes to 5 hours, preferably from 30 minutes to 3 hours.

[0103] In the heat drying, the heating temperature is usually 15° C. or higher (particularly 15° C. or higher and 250° C. or lower), and from the viewpoint of solvent removal, preferably 15° C. or higher and 200° C. or lower. The heating time is usually 30 minutes or longer (particularly 30 minutes or higher and 24 hours or lower), and from the viewpoint of solvent removal, preferably 60 minutes or higher and 12 hours or lower.

[0104] In electrodes with a conductive material coating structure, the coating amount of the coating material relative to the conductive material is 0.0008 mmol / m 2 More than 0.06mmol / m 2 From the viewpoint of further improving cycle characteristics, it is preferably 0.0008 mmol / m or less. 2 More than 0.05mmol / m 2 or less, more preferably 0.0008 mmol / m2 More than 0.035mmol / m 2 More preferably, it is 0.0008 mmol / m or less. 2 More than 0.015mmol / m 2 If the amount of coating on the conductive material is too large, the resistance will become too high, leading to deterioration of cycle characteristics. On the other hand, if the amount of coating is too small, the electrolyte will decompose on the conductive material, and the resulting by-products will accumulate, resulting in an increase in resistance and deterioration of cycle characteristics. In the present invention, by controlling the amount of coating on the conductive material as described above, it is possible to achieve a high capacity retention rate after cycling and suppress the rate of increase in resistance.

[0105] The amount of coating material applied to the conductive material can be controlled by adjusting the amount of the coating material dissolved in the solvent.

[0106] When the coating material is material X, the coating amount of the conductive material is the total amount of the first metal alkoxide and second metal alkoxide that make up material X per unit surface area of ​​the conductive material. When the coating material is material Y, the coating amount of the conductive material is the total amount of material Y mixed per unit surface area of ​​the conductive material.

[0107] For example, the coating amount of the coating material relative to the conductive material is calculated by the following formula. Amount of coating material on conductive material [mmol / m 2 ]=A / B In the above formula, A is calculated by the following formula. A [mmol] = 1000 × (electrode coating material content [g] - electrode active material coating material content [g]) ÷ molecular weight of coating material B is the surface area [m 2 ]. The above formula for calculating A is a formula for when the electrode active material has an electrode active material coating structure as described below. However, when the electrode active material does not have an electrode active material coating structure as described below, the coating material content [g] of the electrode active material in the formula for calculating A becomes 0.

[0108] The method for measuring the coating material content of the electrode is not particularly limited, and for example, the coating material content of the electrode can be calculated by subjecting the electrode to an inductively coupled plasma optical emission spectrometer.

[0109] The method for measuring the coating material content of the electrode active material is not particularly limited, and for example, the coating material content of the electrode active material can be calculated by the following method. The electrode is immersed in n-methylpyrrolidone or other solution that can swell and dissolve the electrode, and only the electrode active material is extracted from the electrode. This is then subjected to emission spectroscopy using the same method as for measuring the coating material content of the electrode, to calculate the coating material content of the electrode active material.

[0110] In the present invention, the electrode having a conductive material coating structure may or may not have an electrode active material coating structure in which at least a portion of the electrode active material is covered with a coating material. When the electrode having a conductive material coating structure has an electrode active material coating structure and the coating material content of the electrode active material is within a specific range, the cycle characteristics can be further improved. For example, when the electrode having a conductive material coating structure is a positive electrode and the positive electrode has an electrode active material coating structure, the electrode active material refers to a positive electrode active material. Furthermore, when the electrode having a conductive material coating structure is a negative electrode and the negative electrode has an electrode active material coating structure, the electrode active material refers to a negative electrode active material.

[0111] The positive electrode active material is a material that contributes to the absorption and desorption of ions that move between the positive electrode and the negative electrode and transfer electrons. From the viewpoint of increasing battery capacity, it is preferable that the positive electrode active material contributes to the absorption and desorption of lithium ions. From this viewpoint, the positive electrode active material may be, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese, and iron. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, or a material in which part of the transition metal is replaced with another metal. Such positive electrode active materials may be contained alone or in combination of two or more types. In a more preferred embodiment, the positive electrode active material core material is lithium nickel oxide (NCA). The average primary particle size of the positive electrode active material is not particularly limited and may be, for example, 1 μm or more and 50 μm or less, particularly 3 μm or more and 30 μm or less.

[0112] The negative electrode active material is preferably a material that contributes to the absorption and desorption of lithium ions. From this perspective, the negative electrode active material may be, for example, various carbon materials, oxides, or lithium alloys. Examples of various carbon materials for the negative electrode active material include graphite (natural graphite, artificial graphite), hard carbon, soft carbon, and diamond-like carbon. Graphite is particularly preferred due to its high electronic conductivity and excellent adhesion to the negative electrode current collector. Examples of oxides for the negative electrode active material include at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, and lithium oxide. The lithium alloy for the negative electrode active material may be any metal that can form an alloy with lithium, such as a binary, ternary, or higher alloy of lithium with a metal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, or La. Such oxides may have an amorphous structure. This is because deterioration caused by non-uniformities such as grain boundaries or defects is less likely to occur. In a more preferred embodiment, the negative electrode active material of the negative electrode layer is artificial graphite. The average primary particle size of the negative electrode active material is not particularly limited and may be, for example, 1 μm or more and 50 μm or less, particularly 3 μm or more and 30 μm or less.

[0113] Like the conductive material, the electrode active material may be composed of primary particles and / or secondary particles formed by aggregation of multiple primary particles. The phrase "at least a portion of the electrode active material is covered with a coating material" means that in such a particulate electrode active material, the coating material is present in partial or total contact with the surface of at least some of the primary particles. For example, the coating material of the electrode active material may be present on at least some of the surfaces of the primary particles and / or at least some of the voids between the primary particles in the electrode active material.

[0114] The coating material for the electrode active material includes the above-mentioned material X, Y, or a mixture thereof. From the viewpoint of further improving the cycle characteristics, the coating material preferably includes material X, and more preferably may consist of only material X. Materials X and Y as the coating material for the electrode active material may each be selected from the same range as materials X and Y as the coating material for the conductive material described above. When an electrode having a conductive material coating structure has an electrode active material coating structure, from the viewpoint of further improving the cycle characteristics, the coating material for the electrode active material is preferably substantially the same material as the coating material for the conductive material. The coating material for the electrode active material being substantially the same material as the coating material for the conductive material means that the coating material for the electrode active material and the coating material for the conductive material contain at least one same element derived from the same coating raw material (particularly, contain the same coating raw material).

[0115] The contents of the first metal alkoxide and the second metal alkoxide in material X as a coating material for an electrode active material (particularly the content of the second metal alkoxide other than metal alkoxide 2′ described below) and their preferred contents may be within the same ranges as the contents of the first metal alkoxide and the second metal alkoxide in material X as a coating material for a conductive material (particularly the content of the second metal alkoxide other than metal alkoxide 2′ described below) and their preferred contents.

[0116] The fact that at least a portion of the electrode active material is covered with a coating material can be confirmed by microscopic observation, and more specifically, by STEM-EDX (Scanning Transmission Electron Microscope-Energy Dispersive X-ray Spectrometer).

[0117] Coating of the electrode active material with the coating material can be achieved by the same method as that for coating the conductive material with the coating material, except that the electrode active material is used instead of the conductive material.

[0118] In an electrode having an electrode active material coating structure, the coating amount of the coating material relative to the electrode active material is usually 0.001 mmol / m 2 More than 0.40mmol / m 2 From the viewpoint of further improving cycle characteristics, it is preferably 0.0025 mmol / m or less. 2 More than 0.22mmol / m 2 or less, more preferably 0.01 mmol / m 2 More than 0.22mmol / m 2 More preferably, it is 0.03 mmol / m or less. 2 More than 0.22mmol / m 2 In the present invention, by controlling not only the amount of coating on the conductive material but also the amount of coating on the electrode active material as described above, it is possible to achieve a sufficiently high capacity retention rate and a sufficient suppression of the rate of increase in resistance after cycling.

[0119] The amount of the coating material applied to the electrode active material can be controlled by adjusting the amount of the coating raw material dissolved in the solvent.

[0120] When the coating material is material X, the coating amount of the coating material on the electrode active material is the total amount of the first metal alkoxide and second metal alkoxide constituting material X per unit surface area of ​​the electrode active material. When the coating material is material Y, the coating amount of the coating material on the electrode active material is the total blend amount of material Y per unit surface area of ​​the electrode active material.

[0121] For example, the coating amount of the coating material relative to the electrode active material is calculated by the following formula. Amount of coating material on electrode active material [mmol / m 2 ]=C / D In the above formula, C is calculated by the following formula. C [mmol] = 1000 × (content of coating material of electrode active material [g]) ÷ molecular weight of coating material D is the surface area [m 2 ].

[0122] The method for measuring the coating material content of the electrode is not particularly limited, and for example, the coating material content of the electrode can be measured by subjecting the electrode to an inductively coupled plasma optical emission spectrometer.

[0123] The method for measuring the coating material content of the electrode active material is not particularly limited, and the coating material content of the electrode active material can be calculated by the method described above.

[0124] When an electrode having a conductive material coating structure has an electrode active material coating structure, from the viewpoint of further improving cycle characteristics, the coating amount M of the coating material on the conductive material and the coating amount N of the coating material on the electrode active material preferably satisfy the following relational formula P1, more preferably the following relational formula P2, even more preferably the following relational formula P3, particularly preferably the following relational formula P4, and most preferably the following relational formula P5. Relational formula P1: M / N = 0.1 / 99.9 or more and 95 / 5 or less: Relational formula P2: M / N = 0.1 / 99.9 or more and 80 / 20 or less: Relational formula P3: M / N = 0.1 / 99.9 or more and 60 / 40 or less: Relational expression P4: M / N=0.1 / 99.9 or more and 40 / 60 or less: Relationship P5: M / N = 0.3 / 99.7 or more and 30 / 70 or less.

[0125] From the viewpoint of further improving cycle characteristics, the electrodes (positive electrode and negative electrode) of the present invention preferably have the following embodiment 1, and more preferably have the following embodiment 2. In the following embodiments, not having an electrode active material coating structure means that the electrode active material is not covered with a coating material, and in particular is not used after being coated with a coating material.

[0126] Embodiment 1: The positive electrode has a conductive material coating structure and does not have an electrode active material coating structure; The negative electrode may or may not contain a conductive material, and typically does not. When the negative electrode contains a conductive material, it may or may not have a conductive material coating structure. In this case, the negative electrode may or may not have an electrode active material coating structure, and typically does not have one.

[0127] Embodiment 2: The positive electrode has a conductive material coating structure and an electrode active material coating structure; The negative electrode may or may not contain a conductive material, and typically does not. When the negative electrode contains a conductive material, it may or may not have a conductive material coating structure. In this case, the negative electrode may or may not have an electrode active material coating structure, and typically does not have one.

[0128] [Basic structure of secondary batteries] The basic structure of the secondary battery of the present invention will be described in detail below. The secondary battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte sealed in an outer casing. In the secondary battery of the present invention, the positive electrode, the negative electrode, and the separator disposed between the positive and negative electrodes constitute an electrode assembly. The electrode assembly of the secondary battery of the present invention may have any structure. Examples of structures that the electrode assembly may have include a laminated structure (planar laminated structure), a wound structure (jelly roll structure), or a stack-and-folded structure. Specifically, the electrode assembly may have a planar laminated structure in which one or more positive electrodes and one or more negative electrodes are stacked in a planar manner with a separator interposed therebetween. Alternatively, the electrode assembly may have a wound structure (jelly roll type) in which the positive electrode, the negative electrode, and the separator disposed between the positive and negative electrodes are wound into a roll. Alternatively, the electrode assembly may have a so-called stack-and-folded structure in which the positive electrode, the separator, and the negative electrode are stacked on a long film and then folded.

[0129] (positive electrode) The positive electrode is composed of at least a positive electrode layer and a positive electrode current collector (foil). The positive electrode layer typically contains a positive electrode active material and a conductive material. The positive electrode active material and conductive material of the positive electrode layer are, for example, granular, and a binder may be included in the positive electrode layer to ensure sufficient contact between the particles and to maintain the shape. Because the positive electrode layer is thus composed of multiple components, it can also be referred to as a "positive electrode composite layer."

[0130] The positive electrode (particularly the positive electrode layer) preferably has a conductive material coating structure, and may or may not have an electrode active material coating structure. When the positive electrode (particularly the positive electrode layer) has a conductive material coating structure, a conductive material that has been coated with a coating material by the above-described method is used to manufacture the positive electrode (particularly the positive electrode layer). When the positive electrode (particularly the positive electrode layer) has an electrode active material coated structure, the positive electrode (particularly the positive electrode layer) is produced using a positive electrode active material that has been coated with a coating material by the above-mentioned method. When the positive electrode (particularly the positive electrode layer) does not have an electrode active material coating structure, the positive electrode (particularly the positive electrode layer) is produced using the above-mentioned positive electrode active material that has not been coated with a coating material.

[0131] The content of the positive electrode active material in the positive electrode layer is usually 50% by weight or more and 98% by weight or less, relative to the total weight of the positive electrode layer, and from the viewpoint of further improving the cycle characteristics, it is preferably 70% by weight or more and 98% by weight or less, and more preferably 80% by weight or more and 98% by weight or less.

[0132] The content of the conductive material in the positive electrode layer is usually 1% by weight or more and 20% by weight or less, relative to the total weight of the positive electrode layer, and from the viewpoint of further improving the cycle characteristics, it is preferably 1% by weight or more and 10% by weight or less, more preferably 1% by weight or more and 8% by weight or less, and even more preferably 2% by weight or more and 8% by weight or less.

[0133] The binder that can be contained in the positive electrode layer is not particularly limited, but may include at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, etc. In a more preferred embodiment, the binder of the positive electrode layer is polyvinylidene fluoride.

[0134] The content of the binder in the positive electrode layer is usually 1% by weight to 20% by weight, both inclusive, relative to the total weight of the positive electrode layer. From the viewpoint of further improving cycle characteristics, the content is preferably 1% by weight to 10% by weight, more preferably 1% by weight to 8% by weight, and even more preferably 2% by weight to 8% by weight.

[0135] The thickness of the positive electrode layer is not particularly limited and may be, for example, 1 μm to 300 μm, particularly 5 μm to 200 μm. The thickness of the positive electrode layer is the thickness inside the battery (particularly the secondary battery), and is the average value of measurements taken at 50 random locations.

[0136] The positive electrode current collector is a member that contributes to collecting and supplying electrons generated in the active material due to the battery reaction. Such a current collector may be a sheet-like metal member and may be porous or perforated. For example, the current collector may be a metal foil, punched metal, mesh, expanded metal, or the like. The positive electrode current collector used in the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel, and the like, and may be, for example, aluminum foil.

[0137] In the positive electrode, a positive electrode layer may be provided on at least one side of a positive electrode current collector. For example, the positive electrode may have a positive electrode layer provided on both sides of the positive electrode current collector, or may have a positive electrode layer provided on one side of the positive electrode current collector. From the viewpoint of further increasing the capacity of a battery (particularly a secondary battery), a preferred positive electrode has a positive electrode layer provided on both sides of the positive electrode current collector.

[0138] The positive electrode can be obtained, for example, by applying a positive electrode layer slurry prepared by mixing a positive electrode active material, a conductive material, and a binder in a dispersion medium to a positive electrode current collector, drying the slurry, and then rolling the dried coating film with a roll press or the like.

[0139] The linear pressure during rolling may be, for example, 0.1 t / cm or more and 1.0 t / cm or less, and from the viewpoint of further improving cycle characteristics, preferably 0.5 t / cm or more and 1.0 t / cm or less. The roll temperature is usually 100°C or more and 200°C or less, and from the viewpoint of further improving cycle characteristics, preferably 110°C or more and 150°C or less. The press speed is usually 1 m / min or more and 20 m / min or less, and from the viewpoint of further improving cycle characteristics, preferably 5 m / min or more and 15 m / min or less.

[0140] (Negative electrode) The negative electrode is composed of at least a negative electrode layer and a negative electrode current collector (foil), and the negative electrode layer may be provided on at least one side of the negative electrode current collector. For example, the negative electrode may have a negative electrode layer provided on both sides of the negative electrode current collector, or may have a negative electrode layer provided on one side of the negative electrode current collector. From the viewpoint of further increasing the capacity of the secondary battery, a preferred negative electrode has a negative electrode layer provided on both sides of the negative electrode current collector.

[0141] The negative electrode (particularly the negative electrode layer) contains at least a negative electrode active material, and may or may not contain a conductive material. When the negative electrode contains a conductive material, the negative electrode may or may not have a conductive material coating structure. The negative electrode may or may not have an electrode active material coating structure. When the negative electrode (particularly the negative electrode layer) has a conductive material coating structure, a conductive material that has been coated with a coating material by the above-mentioned method is used to manufacture the negative electrode (particularly the negative electrode layer). When the negative electrode (particularly the negative electrode layer) does not have a conductive material coating structure, the above-mentioned conductive material that has not been coated with a coating material is used as is to manufacture the negative electrode (particularly the negative electrode layer). When the negative electrode (particularly the negative electrode layer) has an electrode active material coated structure, the negative electrode (particularly the negative electrode layer) is produced using a negative electrode active material that has been coated with a coating material by the above-mentioned method. When the negative electrode (particularly the negative electrode layer) does not have an electrode active material coating structure, the above-mentioned negative electrode active material that has not been coated with a coating material is used as is to manufacture the negative electrode (particularly the negative electrode layer).

[0142] The positive electrode active material contained in the positive electrode layer and the negative electrode active material contained in the negative electrode layer are materials directly involved in the transfer of electrons in the secondary battery and are the main materials of the positive and negative electrodes responsible for charge and discharge, i.e., the battery reaction. More specifically, the "positive electrode active material contained in the positive electrode layer" and the "negative electrode active material contained in the negative electrode layer" provide ions to the electrolyte, and these ions move between the positive and negative electrodes to transfer electrons and perform charge and discharge. In the present invention, the mediator ions are not particularly limited as long as they are capable of charge and discharge, and examples include lithium ions or sodium ions (particularly lithium ions). The positive and negative electrodes are preferably electrodes capable of absorbing and desorbing lithium ions, i.e., the positive and negative electrode layers are preferably layers capable of absorbing and desorbing lithium ions. In other words, a secondary battery in which lithium ions move between the positive and negative electrodes via the electrolyte to charge and discharge the battery is preferred. When lithium ions are involved in charge and discharge, the secondary battery according to this embodiment corresponds to a so-called "lithium ion battery."

[0143] The content of the negative electrode active material in the negative electrode layer is usually 50% by weight or more and 98% by weight or less, relative to the total weight of the negative electrode layer, and from the viewpoint of further improving the cycle characteristics, it is preferably 70% by weight or more and 98% by weight or less, and more preferably 85% by weight or more and 98% by weight or less.

[0144] The content of the conductive material in the negative electrode layer is usually 0 to 20% by weight, based on the total weight of the negative electrode layer, and from the viewpoint of further improving cycle characteristics, is preferably 0 to 10% by weight, more preferably 0 to 8% by weight, and even more preferably 0 to 8% by weight. The content of the conductive material in the negative electrode layer being 0% by weight means that the negative electrode layer does not contain any conductive material.

[0145] The negative electrode layer may be made of, for example, granular material, and preferably contains a binder to ensure sufficient contact between the particles and to maintain their shape. The negative electrode layer may also contain a conductive material to facilitate the transfer of electrons that promote the battery reaction. Because the negative electrode layer contains multiple components, it may also be called a "negative electrode composite layer."

[0146] The binder that can be contained in the negative electrode layer is not particularly limited, but can include at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin, and polyamide-imide resin. In a more preferred embodiment, the binder contained in the negative electrode layer is styrene-butadiene rubber. The conductive additive that can be contained in the negative electrode layer is not particularly limited, but can include at least one selected from carbon blacks 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. The negative electrode layer may also contain components derived from thickeners (e.g., carboxymethyl cellulose) used during battery production.

[0147] In a more preferred embodiment, the negative electrode active material and binder in the negative electrode layer are a combination of graphite and polyimide.

[0148] The thickness of the negative electrode layer is not particularly limited and may be, for example, 1 μm to 300 μm, particularly 5 μm to 200 μm. The thickness of the negative electrode layer is the thickness inside the secondary battery, and is the average value of measurements taken at 50 random locations.

[0149] The negative electrode current collector used in the negative electrode is a member that contributes to collecting and supplying electrons generated in the active material due to the battery reaction. Like the positive electrode current collector, the negative electrode current collector may be a sheet-like metal member and may have a porous or perforated form. For example, the negative electrode current collector may be a metal foil, punched metal, mesh, expanded metal, or the like. The negative electrode current collector used in the negative electrode is preferably made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, and the like, and may be, for example, a copper foil.

[0150] The negative electrode can be obtained, for example, by applying a negative electrode layer slurry prepared by mixing at least a negative electrode active material and a binder in a dispersion medium to a negative electrode current collector, drying the slurry, and then rolling the dried coating film with a roll press or the like.

[0151] When producing a negative electrode, the line pressure, roll temperature, and press speed during rolling are not particularly limited and may be, for example, within the same ranges as those for the line pressure, roll temperature, and press speed during rolling when producing a positive electrode.

[0152] (separator) The separator is a component provided to prevent short circuits due to contact between the positive and negative electrodes and to maintain electrolyte integrity. In other words, the separator is a component that allows ions to pass through while preventing electronic contact between the positive and negative electrodes. Preferably, the separator is a porous or microporous insulating component, and has a membrane shape due to its small thickness. By way of example only, a microporous membrane made of polyolefin may be used as the separator. In this regard, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or only polypropylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of a "microporous membrane made of PE" and a "microporous membrane made of PP." The surface of the separator may be covered with an inorganic particle coating layer and / or an adhesive layer, etc. The surface of the separator may have adhesive properties.

[0153] The thickness of the separator is not particularly limited and may be, for example, 1 μm to 100 μm, particularly 5 μm to 20 μm. The separator thickness is the thickness inside the secondary battery (particularly the thickness between the positive electrode and the negative electrode), and is the average value of measurements taken at 50 random locations.

[0154] (electrolyte) The electrolyte aids in the migration of metal ions released from the electrodes (positive and negative electrodes). The electrolyte may be a "non-aqueous" electrolyte such as an organic electrolyte or an organic solvent, or an "aqueous" electrolyte containing water. The secondary battery of the present invention is preferably a non-aqueous electrolyte secondary battery that uses an electrolyte containing a "non-aqueous" solvent and a solute. The electrolyte may be in a liquid or gel form (note that in this specification, a "liquid" non-aqueous electrolyte is also referred to as a "nonaqueous electrolyte solution").

[0155] Specific examples of non-aqueous electrolyte solvents include those containing at least a carbonate. Such carbonates may be cyclic carbonates and / or chain carbonates. While not particularly limited, examples of cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC). Examples of chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC). In one preferred embodiment of the present invention, a combination of a cyclic carbonate and a chain carbonate is used as the non-aqueous electrolyte, such as a mixture of ethylene carbonate and ethyl methyl carbonate. As a specific solute of the non-aqueous electrolyte, for example, Li salts such as LiPF6 and LiBF4 are preferably used.

[0156] (exterior body) The exterior body is not particularly limited, and may be, for example, a flexible pouch (soft bag) or a hard case (hard housing).

[0157] When the outer packaging body is a flexible pouch, the flexible pouch is typically formed from a laminate film, and sealing is achieved by heat-sealing the periphery. Laminate films are typically films in which a metal foil and a polymer film are laminated together. Specific examples include a three-layer structure consisting of an outer polymer film, a metal foil, and an inner polymer film. The outer polymer film is intended to prevent damage to the metal foil due to moisture permeation and contact, and polymers such as polyamide and polyester are preferably used. The metal foil is intended to prevent moisture and gas permeation, and foils such as copper, aluminum, and stainless steel are preferably used. The inner polymer film is intended to protect the metal foil from the electrolyte contained therein and to melt-seal the opening during heat sealing, and polyolefins (e.g., polypropylene) or acid-modified polyolefins are preferably used. The thickness of the laminate film is not particularly limited and may be, for example, 1 μm or more and 1 mm or less.

[0158] When the exterior is a hard case, the hard case is usually formed from a metal plate, and the sealing is achieved by irradiating the peripheral portion with a laser. The metal plate is generally made of a metal material such as aluminum, nickel, iron, copper, or stainless steel. The thickness of the metal plate is not particularly limited and may be, for example, from 1 μm to 1 mm. [Example]

[0159] <Cathode active material> LiNi as the positive electrode active material 0.8 Co 0.15 Al 0.05 O2 (NCA) was prepared.

[0160] <Conductive materials> Carbon black was prepared as the conductive material.

[0161] (Coating treatment for conductive materials) The conductive material was mixed with the coating solution containing the coating raw materials and stirred. Specifically, the first metal alkoxide and the second metal alkoxide were mixed with a solvent (NMP: N-methyl-2-pyrrolidone) in the mass ratio shown in Table 14, and stirred for 10 minutes until dissolved. The conductive material was then added and stirred at room temperature for 30 minutes. The solvent was then removed by heating and drying at 100°C for 10 hours, yielding a coated conductive material. In addition, a desired coating amount can be obtained for the conductive material by adjusting the amount of the coating raw material dissolved in the solvent.

[0162] (Coating treatment for positive electrode active material) The coating treatment for the positive electrode active material was carried out in the same manner as the coating treatment for the conductive material, except that the positive electrode active material was used instead of the conductive material, to obtain a coated positive electrode active material. A desired coating amount can be obtained on the positive electrode active material by adjusting the amount of the coating raw material dissolved in the solvent.

[0163] (Cathode manufacturing) A positive electrode mixture was prepared by mixing 95% by weight of the positive electrode active material, 3% by weight of the conductive material, and 2% by weight of polyvinylidene fluoride (PVdF). This positive electrode mixture was dispersed or dissolved in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode layer slurry. This slurry was uniformly applied to a 15 μm thick strip of aluminum foil (positive electrode current collector) to form a coating film. Next, this coating film was dried with hot air and then compression molded using a hydraulic cylinder or roll press to form a positive electrode sheet with a positive electrode layer. The prepared positive electrode sheet was punched into a diameter of 16.5 mm and vacuum dried using a vacuum dryer at 120°C for 10 hours to prepare a positive electrode sheet for coin cell production.

[0164] (Coin cell manufacturing) A metallic Li (0.24 mm thick, 17 mm diameter) was used as the negative electrode. The metallic Li was punched and attached to a 200 μm thick SUS plate, which was then stacked inside the anode cup. A separator (16 μm thick, 17.5 mm diameter) was then punched and stacked on top of the negative electrode. 150 μL of electrolyte was impregnated onto the separator, allowing the electrolyte to permeate the voids between the negative electrode and the separator. The positive electrode sheet was stacked on a separator, followed by an aluminum plate and a cathode cup. A gasket was placed around the periphery, and the exterior was sealed using a crimping machine to produce a coin cell (2016 type). The electrolyte used was a solution containing 17.8 wt% ethylene carbonate (EC), 48.7 wt% dimethyl carbonate (DMC), 3.0 wt% ethyl methyl carbonate (EMC), 11.5 wt% fluoroethylene carbonate (FEC), 18.6 wt% lithium hexafluorophosphate (LiPF), and 0.4 wt% lithium tetrafluoroborate (LiBF). The coin cell was subjected to initial charging and discharging using a charge-discharge characteristic evaluation device. During the initial charging and discharging, the coin cell was charged at a constant current and constant voltage of 0.1C in a thermostatic chamber at 25°C up to an upper voltage of 4.25V and a lower current of 0.005C, then rested for 10 minutes, and discharged at a current of 0.1C down to a lower voltage of 2.0V.

[0165] (Cycle test) The charge-discharge cycle test was performed in a 60°C thermostatic chamber under the following conditions. After resting the coin cell for three hours, it was charged at a constant current and voltage of 1.0 C up to an upper voltage of 4.25 V and a lower current of 0.01 C. After charging, it was rested for one minute, discharged at a current of 5.0 C down to a lower voltage of 2.5 V, and then rested for five minutes. This charge-discharge test was performed for 100 cycles.

[0166] The capacity ratios expressed by the following formula are shown in Table 14 as cycle retention rates. (Cycle retention rate) = (Discharge capacity after 100 cycles) ÷ (Discharge capacity at the first cycle) × 100 The cycle maintenance rate was evaluated based on the following indexes. ◎: 90% or more (best); ○: 80% or more but less than 90% (excellent); △: 75% or more and less than 80% (no practical problems); ×: Less than 75% (problems in practical use).

[0167] In addition, EIS measurements were performed after 100 cycles. The EIS measurements were performed under the following conditions. In a thermostatic chamber at 25°C, the coin cell was charged at a constant current and constant voltage with a charging current of 0.2C up to an upper voltage of 4.25V and a lower current of 0.005C, and the state of charge (SOC) was set to 100%. The frequency was varied from 1MHz to 0.1Hz, and the voltage amplitude was 10mV. From the measurement results, the semicircle extrapolated from the 100Hz to 10Hz component was used as the positive electrode resistance, and the positive electrode resistance was calculated.

[0168] The resistance ratio expressed by the following formula is shown in Table 14 as the cycle resistance deterioration rate. (Cycle resistance degradation rate) = (positive electrode resistance after 100 cycles) ÷ (positive electrode resistance at the first cycle) × 100 The cycle resistance deterioration rate was evaluated based on the following index. ◎: Less than 500% (best); ○: 500% or more but less than 550% (excellent); △: 550% or more and less than 600% (no practical problems); ×: 600% or more (problems in practical use).

[0169] <Examples 2 to 10 and Comparative Examples 1 and 2> Coin cells were produced in the same manner as in Example 1, except that the type of coating raw material and the amount of coating material applied to the conductive material and the positive electrode active material were adjusted as shown in Table 14, and a cycle test was performed. In Examples 3 and 4 and Comparative Examples 1 and 2, specifically, the positive electrode active material was used as it was without being subjected to a coating treatment. In Example 10, specifically, material Y was used instead of material X when coating the conductive material and the positive electrode active material.

[0170] The positive electrodes produced in each of Examples 1 to 10 were disassembled and observed under a microscope, and it was confirmed that at least a portion of the conductive material was covered with a coating material. The positive electrodes produced in Examples 1 to 2 and 5 to 10 were disassembled and observed under a microscope, and it was confirmed that at least a portion of the positive electrode active material was covered with a coating material.

[0171] <Calculation method for the amount of coating material applied to conductive materials> The coating amount of the coating material relative to the conductive material is calculated by the following formula. Amount of coating material on conductive material [mmol / m 2 ]=A / B In the above formula, A is calculated by the following formula. A [mmol] = 1000 × (electrode coating material content [g] - electrode active material coating material content [g]) ÷ molecular weight of coating material B is the surface area [m 2 ].

[0172] <Method for calculating the amount of coating material applied to the electrode active material> The coating amount of the coating material relative to the electrode active material is calculated by the following formula. Amount of coating material on electrode active material [mmol / m 2 ]=C / D In the above formula, C is calculated by the following formula. C [mmol] = 1000 × (content of coating material of electrode active material [g]) ÷ molecular weight of coating material D is the surface area [m 2 ].

[0173] <Method for measuring the amount of electrode coating material> The electrode was subjected to an inductively coupled plasma optical emission spectrometer to calculate the content of the coating material contained in the electrode.

[0174] <Method for measuring the amount of coating material in electrode active material> The electrodes were immersed in n-methylpyrrolidone or other liquids that can swell and dissolve the electrodes, and only the electrode active material was extracted from the electrodes. This was then subjected to emission spectroscopy analysis using the same method as for measuring the coating material content of the electrodes, to calculate the coating material content of the electrode active material.

[0175] [Table 14] [Industrial Applicability]

[0176] The secondary battery according to the present invention can be used in various fields where battery use or power storage is expected. By way of example only, the secondary battery according to the present invention, particularly the non-aqueous electrolyte secondary battery, can be used in the field of electronics packaging. The secondary battery according to one embodiment of the present invention can also be used in the electrical, information, and communications fields where mobile devices and the like are used (e.g., the electrical and electronic equipment fields including small electronic devices such as mobile phones, smartphones, smart watches, laptops, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, RFID tags, card-type electronic money, and smart watches, or the mobile device field), household and small industrial applications (e.g., power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (e.g., forklifts, elevators, and harbor cranes), transportation systems (e.g., hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (e.g., various power generation systems, road conditioners, smart grids, and general household energy storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (medical management systems), as well as the IoT field, and space and deep-sea applications (e.g., space probes, submersible research vessels, and the like).

Claims

1. an electrode including an electrode active material and a conductive material; At least a portion of the conductive material is covered with a coating material, The coating amount of the coating material on the conductive material is 0.0008 mmol / m ２ 0.06 mmol / m or more ２ is as follows: The electrode active material is at least partially covered with the coating material or is not covered with the coating material, When at least a part of the electrode active material is covered with the coating material, the coating amount of the coating material on the electrode active material is 0.0025 mmol / m ２ 0.22 mmol / m or more ２ A secondary battery comprising: the electrode is a positive electrode, the electrode active material is a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese, and iron, the conductive material is at least one selected from the group consisting of carbon black and carbon fiber, The carbon black is at least one selected from the group consisting of thermal black, furnace black, channel black, ketjen black, and acetylene black, the carbon fiber is at least one selected from the group consisting of graphite, carbon nanotubes, and vapor-grown carbon fibers; The coating material is Material X: a reactant material containing at least a first metal alkoxide that does not contain a single metal atom-carbon atom bond in one molecule and a second metal alkoxide that contains one or more metal atom-carbon atom bonds in one molecule; Material Y: a lithium-containing composite oxide containing Li (lithium) and one or more elements selected from the group consisting of Group 2 elements, transition metal elements, rare earth elements, Group 13 elements, Group 14 elements, and Group 15 elements; or mixtures thereof, The first metal alkoxide is represented by the general formula (1): 【Chemistry 1】 (In formula (1), M １ is Si, Ti, Al or Zr; x is M １ and the valence is an integer of 3 or 4; R １ are each independently an alkyl group having 1 to 10 carbon atoms or —C(R ２ )=CH-CO-R ３ (In the formula, R ２ is an alkyl group having 1 to 10 carbon atoms, and R ３ is an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or an alkenyloxy group having 1 to 30 carbon atoms; R １ Among them, the two adjacent R １ When the alkyl group is the alkyl group, the two R １ and the oxygen atom to which said oxygen atom is bonded, １ may form a ring together with the atom. is a compound represented by The second metal alkoxide is General formula (2A): 【Chemistry 2】 (In formula (2A), R ２１１ and R ２１２ are each independently an alkyl group having 1 to 10 carbon atoms; R ３１ is a divalent hydrocarbon group having 1 to 20 carbon atoms. General formula (2B): 【Transformation 3】 (In formula (2B), R ２１１ , R ２１２ , R ２１３ and R ２１４ are each independently an alkyl group having 1 to 10 carbon atoms; R ３２ are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms; R ３３ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms. General formula (2C): 【Chemistry 4】 (In formula (2C), R ２１１ and R ２１２ are each independently an alkyl group having 1 to 10 carbon atoms; R ３４ , R ３５ , and R ３６ are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms. General formula (2D): 【Transformation 5】 (In formula (2D), R ２１１ and R ２１２ are each independently an alkyl group having 1 to 10 carbon atoms. General formula (2E): 【Transformation 6】 (In formula (2E), R ２１２ and R ２１３ are each independently an alkyl group having 1 to 10 carbon atoms; R ３２ are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms; R ３３ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms; R ３４ are each independently a monovalent hydrocarbon group having 8 to 30 carbon atoms. General formula (2F): 【Transformation 7】 (In formula (2F), R ２１２ , R ２１３ and R ２１４ are each independently an alkyl group having 1 to 10 carbon atoms; R ３２ are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms. or a mixture thereof, The material Y is represented by the general formula (4): 【Transformation 8】 (In formula (4), M is one or more elements selected from the group consisting of Group 2 elements, transition metal elements, rare earth elements, Group 13 elements, Group 14 elements, and Group 15 elements, including B (boron); a is an integer of 1 or more and 4 or less; b is an integer of 1 or greater and 5 or less; c is an integer of 2 or more and 8 or less. A secondary battery, which is a compound represented by the formula:

2. 2. The secondary battery according to claim 1, wherein the material X contains, relative to the total weight of the material, 1% by weight or more and 99% by weight or less of the first metal alkoxide and 1% by weight or more and 99% by weight or less of the second metal alkoxide.

3. 2. The secondary battery according to claim 1, wherein in the formula (4), M includes one or more elements selected from the group consisting of W (tungsten), B (boron), Si (silicon), and P (phosphorus).

4. the conductive material is composed of primary particles and / or secondary particles formed by aggregation of a plurality of primary particles, The secondary battery according to claim 1 , wherein the coating material of the conductive material is present on at least a portion of the surfaces of the primary particles of the conductive material and / or in at least a portion of the voids between the primary particles.

5. The secondary battery according to claim 1 , wherein at least a portion of the electrode active material is covered with the coating material.

6. The secondary battery according to claim 5 , wherein the coating material of the electrode active material is substantially the same material as the coating material of the conductive material.

7. 6. The secondary battery according to claim 5, wherein a coating amount M of the coating material on the conductive material and a coating amount N of the coating material on the electrode active material satisfy the following relational expression: M / N=0.1 / 99.9 or more and 40 / 60 or less.

8. the electrode active material is composed of primary particles and / or secondary particles formed by aggregation of a plurality of primary particles, 2. The secondary battery according to claim 1, wherein, when at least a portion of the electrode active material is covered with the coating material, the coating material of the electrode active material is present on at least a portion of the surfaces of the primary particles in the electrode active material and / or in at least a portion of the voids between the primary particles.

9. The secondary battery according to claim 1 , wherein the secondary battery is a lithium ion secondary battery.

10. 2. The secondary battery according to claim 1, wherein the electrodes, the separator, and the electrolyte are sealed in an exterior body.

11. The secondary battery according to claim 10 , wherein the electrolyte is a non-aqueous electrolyte.

12. 2. The secondary battery according to claim 1, wherein the electrode is an electrode capable of absorbing and releasing lithium ions.

13. A method for manufacturing a secondary battery, comprising the steps of: manufacturing the secondary battery according to any one of claims 1 to 12; Stirring the conductive material together with a solution containing a coating material raw material of material X, material Y, or a mixture thereof, and then removing the solvent; When at least a portion of the electrode active material is covered with the coating material, the method for producing a secondary battery further comprises stirring the electrode active material together with a solution containing a coating material raw material of material X, material Y, or a mixture thereof, and then removing the solvent.

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