Electrode mixture sheet, electrode, secondary battery, and method for producing electrode mixture sheet

Abstract

Provided are: an electrode mixture sheet that exhibits a high tensile strength and a low resistance; an electrode and secondary battery that use this electrode mixture sheet; and a method for producing the electrode mixture sheet. The electrode mixture sheet contains polytetrafluoroethylene, a carbon material, and an electrode active material other than the carbon material and / or a fluororesin other than the polytetrafluoroethylene. In an image with a 2,000× visual field of the carbon composition distribution obtained by SEM-EDX analysis, the value X given by interface length / detected amount of carbon is not greater than 2300 for the electrode mixture sheet.

Description

Electrode mixture sheet, electrode, secondary battery, and method for manufacturing electrode mixture sheet

[0001] The present disclosure relates to an electrode mixture sheet, an electrode, a secondary battery, and a method for manufacturing an electrode mixture sheet.

[0002] Secondary batteries such as lithium-ion secondary batteries are used in small, portable electrical and electronic devices such as notebook computers, mobile phones, smartphones, tablet computers, and ultrabooks because of their high voltage, high energy density, low self-discharge, low memory effect, and the ability to be ultra-lightweight, and are also being put into practical use as a wide range of power sources, including on-board power sources for driving automobiles and large-scale stationary power sources. Demand is now being placed on secondary batteries to achieve even higher energy densities, and further improvements in their battery characteristics are being sought.

[0003] Patent Document 1 describes an electrode in which the distribution of polytetrafluoroethylene in the electrode mixture is controlled.

[0004] International Publication No. 2022 / 163186

[0005] An object of the present disclosure is to provide an electrode mixture sheet having high tensile strength and low resistance, an electrode and secondary battery using the same, and a method for manufacturing the electrode mixture sheet.

[0006] The present disclosure (1) is an electrode mixture sheet that includes polytetrafluoroethylene, a carbon material, and an electrode active material other than the carbon material and / or a fluororesin other than the polytetrafluoroethylene, and in an image of a carbon composition distribution obtained by SEM-EDX analysis at a 2000x field of view, a value X indicated by the ratio of interface length to detected amount of carbon is 2300 or less.

[0007] The present disclosure (2) is the electrode mixture sheet according to the present disclosure (1), in which the value X is 300 or more and 2000 or less.

[0008] The present disclosure (3) is the electrode mixture sheet according to the present disclosure (1) or (2), wherein the total content of the polytetrafluoroethylene and the fluororesin other than polytetrafluoroethylene relative to the electrode mixture sheet is 0.1 mass% or more and 10 mass% or less.

[0009] The present disclosure (4) is the electrode mixture sheet according to any one of the present disclosures (1) to (3), in which the carbon material is a conductive additive.

[0010] The present disclosure (5) is an electrode mixture sheet according to any one of the present disclosures (1) to (4), in which the electrode active material other than the carbon material is a positive electrode active material.

[0011] The present disclosure (6) is the electrode mixture sheet according to the present disclosure (5), in which the content of the positive electrode active material is 92% or more and 99% or less by mass with respect to the electrode mixture sheet.

[0012] The present disclosure (7) is an electrode including the electrode mixture sheet according to any one of the present disclosures (1) to (6).

[0013] The present disclosure (8) is a secondary battery including the electrode according to the present disclosure (7).

[0014] The present disclosure (9) is a method for producing an electrode mixture sheet, comprising: a step (1) of mixing polytetrafluoroethylene with an electrode active material other than a carbon material and / or a fluororesin other than the polytetrafluoroethylene; and a step (2) of mixing the mixture obtained in the step (1) with a carbon material.

[0015] The present disclosure (10) is the production method according to the present disclosure (9), in which fibrils of the polytetrafluoroethylene are generated by shear force in the step (1).

[0016] The present disclosure (11) is the production method according to the present disclosure (9) or (10), in which the mixing in step (2) is carried out under a lower shear force than in step (1).

[0017] The present disclosure (12) is the production method according to any one of the present disclosures (9) to (11), in which the components mixed in step (1) are all powders, and step (1) is carried out in the absence of a liquid medium.

[0018] The present disclosure (13) is the manufacturing method according to any one of the present disclosures (9) to (12), in which the treatment temperature in the step (2) is lower than the treatment temperature in the step (1).

[0019] The present disclosure (14) is the manufacturing method according to any one of the present disclosures (9) to (13), in which the steps (1) and (2) are carried out using the same apparatus.

[0020] According to the present disclosure, it is possible to provide an electrode mixture sheet having high tensile strength and low resistance, an electrode and a secondary battery using the same, and a method for manufacturing an electrode mixture sheet.

[0021] Fig. 1 is a diagram showing an example of spectral data obtained by SEM-EDX analysis. Fig. 2 is a diagram showing an example of an image of the carbon composition distribution of an electrode mixture sheet obtained by SEM-EDX analysis at a 2000x field of view. Fig. 3 is a diagram showing an example of an image obtained by binarizing the image obtained by SEM-EDX analysis. Fig. 4 is a diagram showing a schematic diagram of a method for calculating an interface length.

[0022] The present disclosure will be specifically described below.

[0023] The present disclosure provides an electrode mixture sheet that includes polytetrafluoroethylene (PTFE), a carbon material, and an electrode active material other than the carbon material and / or a fluororesin other than the PTFE, and in an image of a carbon composition distribution obtained by SEM-EDX analysis at a 2000x field of view, the value X, which is expressed by the ratio of interface length to the amount of detected carbon, is 2300 or less.

[0024] In the electrode mixture sheet of the present disclosure, by setting the value X to 2300 or less, the tensile strength of the electrode mixture sheet can be improved and the resistance can be reduced. This is thought to be due to the appropriate control of the dispersion state and shape of the PTFE fibrils located around the carbon material. In order to further increase the tensile strength and further reduce the resistance, the value X is preferably 2000 or less, more preferably 1800 or less, even more preferably 1500 or less, even more preferably 1300 or less, and preferably 300 or more, more preferably 450 or more, and even more preferably 750 or more.

[0025] The value X is determined by the following method. <Measurement Sample> The electrode mixture sheet is cut into a size of 1 cm x 1 cm (thickness can be arbitrary) to serve as the measurement sample. When preparing a measurement sample from an electrode, the surface containing the electrode mixture is cut out to the above size to serve as the measurement sample. <Interface Length (pix)> (i) For each measurement sample, three images are obtained using SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy) analysis, with a 2000x field of view of the carbon composition distribution, an acceleration voltage of 3000 V, and an image size of 1280 x 960. For example, the first image is obtained from the center of the measurement sample, and the second and third images are obtained from points shifted 2 mm to the left and right from the center of the measurement sample. For example, an SU8000 manufactured by Hitachi High-Tech Corporation can be used to obtain the images. (ii) The images obtained in (i) are subjected to binarization processing. Images acquired (N = 3) per sample are divided into brightness levels ranging from 0 to 255 for each image, and a threshold is calculated for each image using Otsu's binarization method. The average binarization threshold for each image is then calculated to calculate the average threshold for the sample. Each pre-binarization image is then binarized again using the average threshold. Note that Otsu's binarization method is a method for calculating a binarization threshold that uses the point at which the degree of separation between two peaks obtained when drawing a grayscale histogram as the brightness threshold. (iii) In the images obtained in (ii), the number of elements with non-zero inter-pixel differences is counted to determine the interface length for each image. <Detected Carbon Amount (cps / eV)> ​​The detected carbon amount for each image is calculated using spectral data obtained simultaneously with the image data in (i) above. The spectral data used is the spectral data obtained when measuring with SEM-EDX, with the horizontal axis representing X-ray energy [keV] and the vertical axis representing X-ray intensity [cps / eV]. Figure 1 shows an example of spectral data. From the above spectrum data, the maximum value on the vertical axis of the peak appearing near 0.27 keV, which is the intrinsic energy of carbon, is read, and the read value is taken as the detected carbon amount. <Interface length ÷ detected carbon amount (value X)> From the interface length and detected carbon amount calculated for each image, the interface length ÷ detected carbon amount is calculated for three points for each sample, and the average value of N=3 is taken as the interface length ÷ detected carbon amount (value X) for each sample.

[0026] The method for calculating the interface length will be specifically described with reference to the drawings. Figure 2 shows an example of an image of the carbon composition distribution of an electrode mixture sheet obtained by SEM-EDX analysis at a magnification of 2000 times. The image of Figure 2 is binarized using the above method to obtain the image of Figure 3. In this binarized image, the number of elements for which the difference between elements between pixels is not zero is counted and used as the interface length. Here, a non-zero difference between elements between pixels refers to a state in which the colors (white or black) of adjacent pixels (squares) are different, as shown in Figure 4. An edge (an edge indicated by diagonal lines in the figure) that borders pixels of different colors is counted as an element for which the difference between elements between pixels is not zero. In Figure 4, the number of elements is 21, and the interface length is 21.

[0027] The electrode mixture sheet of the present disclosure contains PTFE. The PTFE may be a homopolymer of tetrafluoroethylene (TFE), or may be a modified PTFE containing a polymerized unit based on TFE (TFE unit) and a polymerized unit based on a modified monomer (hereinafter also referred to as "modified monomer unit"). The modified PTFE may contain 99.0% by mass or more of TFE units and 1.0% by mass or less of modified monomer units. The modified PTFE may also consist only of TFE units and modified monomer units. The modified PTFE is preferred as the PTFE because it improves binding strength, sheet strength, and flexibility.

[0028] In order to improve the binding force, sheet strength, and flexibility of the modified PTFE, the content of the modified monomer unit is preferably in the range of 0.00001 to 1.0 mass% relative to the total polymerized units. The lower limit of the content of the modified monomer unit is more preferably 0.0001 mass%, even more preferably 0.001 mass%, even more preferably 0.005 mass%, and particularly preferably 0.010 mass%. The upper limit of the content of the modified monomer unit is preferably 0.90 mass%, more preferably 0.80 mass%, even more preferably 0.50 mass%, even more preferably 0.40 mass%, and even more preferably 0.30 mass%. In this specification, the modified monomer unit refers to a part of the molecular structure of PTFE that is derived from the modified monomer.

[0029] The content of each of the above-mentioned polymerized units can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0030] The above-mentioned modified monomer is not particularly limited as long as it can be copolymerized with TFE, and for example, can be listed perfluoroolefin such as hexafluoropropylene (HFP); hydrogen-containing fluoroolefin such as trifluoroethylene, vinylidene fluoride (VDF); perhaloolefin such as chlorotrifluoroethylene (CTFE); perfluorovinyl ether; perfluoroallyl ether; (perfluoroalkyl) ethylene, ethylene etc. In addition, the modified monomer used can be one kind or multiple kinds.

[0031] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the following general formula (A): CF ２ =CF-ORf １ (A) (wherein, Rf １ represents a perfluoroorganic group. ) and perfluorounsaturated compounds represented by the following formula (I) are included. In this specification, the "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0032] The perfluorovinyl ether may be, for example, a compound represented by the general formula (A) in which Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0033] Examples of the perfluoroalkyl group in the PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0034] The perfluorovinyl ether further includes a compound represented by the general formula (A) below, wherein Rf １is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf １ is of the following formula:

[0035]

[0036] (wherein m represents 0 or an integer of 1 to 4), Rf １ is of the following formula:

[0037]

[0038] (wherein n represents an integer of 1 to 4).

[0039] The (perfluoroalkyl)ethylene [PFAE] is not particularly limited, and examples thereof include (perfluorobutyl)ethylene [PFBE] and (perfluorohexyl)ethylene.

[0040] Examples of perfluoroallyl ethers include those represented by the general formula (B): CF ２ =CF-CF ２ -ORf ２ (B) (wherein, Rf ２ represents a perfluoroorganic group.

[0041] The above Rf ２ is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. ２ =CF-CF ２ -O-CF ３ , C.F. ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ At least one selected from the group consisting of CF ２ =CF-CF ２ -O-C２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ More preferably, at least one selected from the group consisting of CF ２ =CF-CF ２ -O-CF ２ CF ２ CF ３ is more preferred.

[0042] The modified monomer is preferably at least one selected from the group consisting of PAVE, HFP, VDF, and CTFE, and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) [PMVE], HFP, VDF, and CTFE, in terms of improving the stretchability, binding strength, and flexibility of the composite sheet.

[0043] The PTFE may have a core-shell structure. Examples of PTFE having a core-shell structure include modified PTFE particles containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE. Examples of such modified PTFE include the PTFE described in JP-A-2005-527652.

[0044] Examples of commonly available PTFE include F-104, F-106, F-107, F-104C, F-121, F-201, F-205, F-208, and F-302 manufactured by Daikin Industries, Ltd.; 60X, 601X, 602X, 605XTX, 613AX, 62X, 62NX, 62XTX, 640XTX, 641XTX, 650XTX, 669X, 669NX, 6CX, 6CNX, CFP6000X, 6J, 6CJ, 62J, 640J, and 641J manufactured by Chemours; and 3M. Examples of such fluororesin include TF2029, TF2025Z, TF2053Z, TF2073Z, TF2001Z, TF2071USZ, and TF2072Z; CD145, CD123, CD126E, CD097, CD084E, CD086EL, CD086EH, CD090E, CD122E, CD141E, and CD127E manufactured by AGC; and DF681F, DF680F, DF330F, DF291F, DF230F, DF210F, DF132F, DF130F, and DF120F manufactured by Solvay Chemicals.

[0045] The PTFE preferably has an endothermic peak temperature of 320°C or higher, more preferably 325°C or higher, even more preferably 330°C or higher, even more preferably 335°C or higher, even more preferably 340°C or higher, even more preferably 342°C or higher, and particularly preferably 344°C or higher, in order to form a composite sheet with even greater strength. The endothermic peak temperature is also preferably 350°C or lower. The endothermic peak temperature is the temperature corresponding to the minimum point in the heat of fusion curve obtained by performing differential scanning calorimetry (DSC) at a heating rate of 10°C / min on PTFE that has no history of being heated to a temperature of 300°C or higher. When there are two or more minimum points in one melting peak, each of them is taken as the endothermic peak temperature.

[0046] The PTFE preferably exhibits one or more endothermic peaks in the range of 333 to 347°C in the heat of fusion curve when heated at a rate of 10°C / min using a differential scanning calorimeter (DSC), and the heat of fusion at 290 to 350°C calculated from the heat of fusion curve is 62mJ / mg or more.

[0047] The standard specific gravity (SSG) of the PTFE is preferably 2.280 or less, more preferably 2.250 or less, even more preferably 2.220 or less, even more preferably 2.200 or less, even more preferably 2.190 or less, especially preferably 2.180 or less, and particularly preferably 2.170 or less. The SSG is also preferably 2.130 or more. The SSG is measured by the water displacement method according to ASTM D 792 using a sample molded in accordance with ASTM D 4895 89.

[0048] In the electrode mixture sheet of the present disclosure, it is preferable that at least a portion of the PTFE is fibrillated.

[0049] The content of the PTFE is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, relative to the electrode mixture sheet, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0050] The electrode mixture sheet of the present disclosure contains a carbon material. Examples of the carbon material include a conductive additive and a carbon-based negative electrode active material. Among these, a conductive additive is preferred. The content of the carbon material relative to the electrode mixture sheet is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, and is preferably 99% by mass or less, more preferably 96% by mass or less, and even more preferably 92% by mass or less.

[0051] The conductive additive is not particularly limited, but examples thereof include graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon materials such as needle coke, carbon nanotubes, fullerene, and amorphous carbon such as VGCF. These may be used alone or in any combination and ratio of two or more.

[0052] The content of the conductive additive is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, relative to the electrode mixture sheet, and is preferably 30% by mass or less, more preferably 15% by mass or less, and even more preferably 5% by mass or less.

[0053] Examples of the carbon-based negative electrode active material include any one selected from artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon, or a mixture of two or more thereof.

[0054] The content of the carbon-based negative electrode active material is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass or more, relative to the electrode mixture sheet, and is preferably 99% by mass or less, more preferably 96% by mass or less, and even more preferably 92% by mass or less.

[0055] The electrode mixture sheet of the present disclosure contains an electrode active material other than the carbon material and / or a fluororesin other than the PTFE (hereinafter also referred to as other fluororesin). The content of the electrode active material other than the carbon material and / or the fluororesin other than PTFE is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, relative to the electrode mixture sheet, and is also preferably 99% by mass or less, more preferably 96% by mass or less, and even more preferably 92% by mass or less.

[0056] Examples of the electrode active material other than the carbon material include a positive electrode active material and a negative electrode active material other than carbon-based materials, among which a positive electrode active material is preferred.

[0057] The positive electrode active material is not particularly limited as long as it can electrochemically absorb and release alkali metal ions, but for example, a material containing an alkali metal and at least one transition metal is preferred. Specific examples include alkali metal-containing transition metal composite oxides and alkali metal-containing transition metal phosphate compounds. Of these, alkali metal-containing transition metal composite oxides that generate high voltage are particularly preferred as the positive electrode active material. Examples of the alkali metal ions include lithium ions, sodium ions, and potassium ions, with lithium ions being preferred.

[0058] Examples of the alkali metal-containing transition metal composite oxide include those represented by the formula: M ａ Mn ２－ｂ M １ ｂ O ４ (Wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0.9≦a; 0≦b≦1.5; M １ is at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge), alkali metal-manganese spinel composite oxides (such as lithium-manganese spinel composite oxides) represented by the formula: MNi １－ｃ M ２ ｃ O ２ (Wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≦c≦0.5; M ２ is at least one metal selected from the group consisting of Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge), or an alkali metal-nickel composite oxide (such as a lithium-nickel composite oxide) represented by the formula: MCo １－ｄ M ３ ｄ O ２ (Wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≦d≦0.5; M ３is at least one metal selected from the group consisting of Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge. In the above, M is preferably one metal selected from the group consisting of Li, Na, and K, more preferably Li or Na, and even more preferably Li.

[0059] Among these, MCoO is preferred because it can provide a secondary battery with high energy density and high output. ２ , M MnO ２ , MNiO ２ , M.M. ２ O ４ , MNi ０．８ Co ０．１５ Al ０．０５ O ２ , or MNi １／３ Co １／３ Mn １／３ O ２ and the like are preferred, and a compound represented by the following general formula is preferred: MNi ｈ Co ｉ Mn ｊ M ５ ｋ O ２ (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ５ represents at least one selected from the group consisting of Fe, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge, and (h+i+j+k)=1.0, 0≦h≦1.0, 0≦i≦1.0, 0≦j≦1.5, 0≦k≦0.2.

[0060] Examples of the alkali metal-containing transition metal phosphate compound include those represented by the following general formula: ｅ M ４ ｆ (P.O. ４ ) ｇ (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ４represents at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, and 0.5≦e≦3, 1≦f≦2, and 1≦g≦3. In the above, M is preferably one metal selected from the group consisting of Li, Na, and K, more preferably Li or Na, and even more preferably Li. That is, the alkali metal-containing transition metal phosphate compound is preferably a lithium-containing transition metal phosphate compound.

[0061] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, or the like, and specific examples thereof include LiFePO ４ , Li ３ Fe ２ (P.O. ４ ) ３ , LiFeP ２ O ７ Iron phosphates such as LiCoPO ４ and lithium transition metal phosphate compounds in which a part of the transition metal atoms constituting the main component of these compounds is substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc. The lithium-containing transition metal phosphate compounds preferably have an olivine structure.

[0062] Other examples of the positive electrode active material include lithium-nickel-based composite oxides. The lithium-nickel-based composite oxides are represented by the following general formula: Li ｙ Ni １－ｘ M ｘ O ２ (wherein x is 0.01≦x≦0.7, y is 0.9≦y≦2.0, and M is a metal atom (excluding Li and Ni)) is preferred.

[0063] Other positive electrode active materials include MFePO ４ , MNi ０．８ Co ０．２ O ２ , M １．２ Fe ０．４ Mn ０．４ O ２ , MNi０．５ Mn １．５ O ２ , M.V. ３ O ６ , M ２ MnO ３ In particular, M ２ MnO ３ , MNi ０．５ Mn １．５ O ２ These positive electrode active materials are preferred in that their crystalline structure does not collapse even when the secondary battery is operated at a voltage exceeding 4.4 V or a voltage of 4.6 V or higher. Therefore, electrochemical devices such as secondary batteries using positive electrode materials containing the above-mentioned positive electrode active materials are preferred because they are less likely to reduce their remaining capacity and change their resistance increase rate even when stored at high temperatures, and their battery performance does not deteriorate even when operated at high voltages.

[0064] Other positive electrode active materials include M ２ MnO ３ and M.M. ６ O ２ (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ６ Examples of the material include solid solution materials with transition metals such as Co, Ni, Mn, and Fe.

[0065] The solid solution material may be, for example, a material represented by the general formula Mx [Mn （１－ｙ） M ７ ｙ ]O ｚ In the formula, M is at least one metal selected from the group consisting of Li, Na, and K, and M ７ is composed of at least one metal element other than M and Mn, and contains, for example, one or more elements selected from the group consisting of Co, Ni, Fe, Ti, Mo, W, Cr, Zr and Sn. The values ​​of x, y and z in the formula are in the ranges of 1<x<2, 0≦y<1 and 1.5<z<3. Among them, Li １．２ Mn ０．５ Co ０．１４ Ni ０．１４ O ２ Li like ２ MnO ３ Based on LiNiO２ and LiCoO ２ A manganese-containing solid solution material containing manganese is preferred in that it can provide an alkali metal ion secondary battery having a high energy density.

[0066] Furthermore, it is preferable to include lithium phosphate in the positive electrode active material, since this improves continuous charging characteristics. Although there is no limitation on the use of lithium phosphate, it is preferable to use a mixture of the positive electrode active material and lithium phosphate. The amount of lithium phosphate used, based on the total amount of the positive electrode active material and lithium phosphate, is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

[0067] Alternatively, a substance having a different composition may be attached to the surface of the positive electrode active material, such as an oxide, such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, or bismuth oxide; a sulfate, such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, or aluminum sulfate; a carbonate, such as lithium carbonate, calcium carbonate, or magnesium carbonate; or carbon.

[0068] The positive electrode active material may be used alone or in any combination or ratio of two or more different types of materials. ２ and LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ combination with ternary systems such as LiCoO ２ and LiMn ２ O ４ Or a combination of this with a material in which a part of Mn is replaced with another transition metal, or LiFePO ４ and LiCoO ２ Alternatively, a combination of Co with other transition metals or the like may be used.

[0069] The content of the positive electrode active material relative to the electrode mixture sheet is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 75% by mass or more, and most preferably 92% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0070] Examples of the negative electrode active material other than the carbon-based material include lithium metal, silicon and silicon alloys and other silicon-containing compounds, Li ４ Ti ５ O １２ and the like, or a mixture of two or more thereof.

[0071] The above-mentioned non-carbon-based negative electrode active materials preferably contain silicon as a constituent element, which allows the production of a high-capacity battery.

[0072] The silicon-containing material is preferably silicon particles, particles having a structure in which silicon fine particles are dispersed in a silicon-based compound, silicon oxide particles represented by the general formula SiOx (0.5≦x≦1.6), or a mixture thereof. By using these, a negative electrode mixture for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycle characteristics can be obtained.

[0073] In this disclosure, silicon oxide is a general term for amorphous silicon oxide, and silicon oxide before disproportionation is represented by the general formula SiOx (0.5≦x≦1.6). Preferably, x is 0.8≦x<1.6, and more preferably 0.8≦x<1.3. This silicon oxide can be obtained, for example, by heating a mixture of silicon dioxide and metallic silicon to produce silicon monoxide gas, which is then cooled and precipitated.

[0074] The content of the negative electrode active material other than the carbon material is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 5% by mass or more, and particularly preferably 8% by mass or more, relative to the electrode mixture sheet, and is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0075] Examples of the other fluororesin include PTFE different from the PTFE as the essential component described above (hereinafter also referred to as other PTFE), melt-processable fluororesin, etc. The other PTFE is preferred in that it can further increase the tensile strength and further decrease the resistance.

[0076] The other PTFE may be a PTFE having a composition and / or physical properties different from those of the PTFE as the essential component described above.

[0077] Examples of PTFE having different compositions include PTFE having different types of modified monomers copolymerizable with tetrafluoroethylene (TFE) and / or different contents of polymerized units (modified monomer units) based on the modified monomers.

[0078] The combination of the PTFE as the essential component and the PTFE with different composition may be, for example, a combination of a TFE homopolymer and modified PTFE, or a combination of two or more modified PTFEs with different types of modified monomers, or a combination of two or more PTFEs with the same modified monomer unit but with different content ratios of the modified monomer unit. "Different content ratios of modified monomer units" means that the difference in content ratio (mass% value) of the modified monomer unit in all polymerized units is 0.005 or more. The difference in content ratio is preferably 0.10 or more, more preferably 0.15 or more, even more preferably 0.20 or more, and preferably 0.80 or less, more preferably 0.60 or less, and even more preferably 0.40 or less.

[0079] As the above combination, a combination of a homopolymer of tetrafluoroethylene (TFE) and modified PTFE is particularly preferred.

[0080] The homopolymer of TFE refers to one in which the content of modified monomer units relative to all polymerized units is less than 0.0001% by mass.

[0081] Examples of the modified PTFE as the PTFE having a different composition include the same modified PTFE as described above for the PTFE as an essential component.

[0082] The other PTFE may be a PTFE having a different standard specific gravity (SSG) from the PTFE used as the essential component. "Different SSG" means that the difference in SSG is 0.005 or more. The difference in SSG is preferably 0.010 or more, more preferably 0.015 or more, and even more preferably 0.020 or more. It is also preferably 0.050 or less, more preferably 0.040 or less, and even more preferably 0.030 or less.

[0083] The other PTFE may be a PTFE having a different extrusion pressure from the PTFE used as the essential component. "Different extrusion pressure" means that the difference in extrusion pressure is 5 MPa or more. The difference in extrusion pressure is preferably 10 MPa or more, more preferably 15 MPa or more, even more preferably 20 MPa or more, and preferably 35 MPa or less, more preferably 30 MPa or less, and even more preferably 25 MPa or less. The extrusion pressure is measured by the following method. In the latter half of the extrusion operation of the paste extrusion described below, the load (N) when the pressure reaches equilibrium is divided by the cross-sectional area of ​​the cylinder, and this value is taken as the extrusion pressure (MPa). (Paste Extrusion) 60 g of PTFE powder and 12.3 g of hydrocarbon oil (trade name: Isopar G (registered trademark), manufactured by ExxonMobil) serving as an extrusion aid are mixed in a polyethylene container for 3 minutes. The mixture is filled into the cylinder of an extruder at room temperature (25±2°C), and a load of 0.47 MPa is applied to the piston inserted in the cylinder and maintained for 1 minute. The mixture is then extruded through an orifice at a ram speed of 20 mm / min. The ratio of the cross-sectional area of ​​the cylinder to the cross-sectional area of ​​the orifice is 200.

[0084] Examples of the melt-processable fluororesin include tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA], TFE / hexafluoropropylene [HFP] copolymer [FEP], ethylene [Et] / TFE copolymer [ETFE], Et / TFE / HFP copolymer [EFEP], polychlorotrifluoroethylene [PCTFE], chlorotrifluoroethylene [CTFE] / TFE copolymer, CTFE / TFE / P Examples of the perfluoroalkyl allyl ether include AVE copolymer, Et / CTFE copolymer, polyvinyl fluoride [PVF], polyvinylidene fluoride [PVdF], vinylidene fluoride [VdF] / TFE copolymer, VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / HFP / (meth)acrylic acid copolymer, VdF / CTFE copolymer, VdF / pentafluoropropylene copolymer, VdF / PAVE / TFE copolymer, and TFE / perfluoroalkyl allyl ether copolymer. ２ =CFCF ２ -O-Rf ３ (Rf ３ is a perfluoroalkyl group having 1 to 5 carbon atoms). Among these, polyvinylidene fluoride [PVdF] is preferred.

[0085] As used herein, "melt-processable" means that the polymer can be melted and processed using conventional processing equipment such as an extruder or an injection molding machine. The melt-processable fluororesin preferably has a melt flow rate (MFR) of 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and preferably 100 g / 10 min or less, more preferably 50 g / 10 min or less. In this specification, MFR is a value obtained in accordance with ASTM D1238 using a melt indexer, as the mass (g / 10 min) of polymer flowing out of a nozzle with an inner diameter of 2 mm and a length of 8 mm per 10 minutes at a measurement temperature determined depending on the type of fluoropolymer (e.g., 372°C for PFA and FEP, 297°C for ETFE) and a load (e.g., 5 kg for PFA, FEP, and ETFE).

[0086] The mass ratio of PTFE as the essential component to the other fluororesin (PTFE / other fluororesin) is preferably 1 / 99 or more, more preferably 5 / 95 or more, even more preferably 10 / 90 or more, even more preferably 15 / 85 or more, and particularly preferably 20 / 80 or more, and is preferably 99 / 1 or less, more preferably 95 / 5 or less, even more preferably 90 / 10 or less, even more preferably 85 / 15 or less, and particularly preferably 80 / 20 or less.

[0087] The total content of PTFE as the essential component and the other fluororesin is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, relative to the electrode mixture sheet, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0088] The electrode mixture sheet of the present disclosure particularly preferably contains PTFE, a carbon material as a conductive additive, and a positive electrode active material. The electrode mixture sheet may be a positive electrode mixture sheet. The PTFE, conductive additive, and positive electrode active material in this embodiment may be those described above. The PTFE content in this embodiment is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, relative to the electrode mixture sheet, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. The carbon material (conductive additive) content in this embodiment is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, relative to the electrode mixture sheet, and is preferably 30% by mass or less, more preferably 15% by mass or less, and even more preferably 5% by mass or less. The content of the positive electrode active material in the above embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass or more, relative to the electrode mixture sheet, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0089] In the electrode mixture sheet of the present disclosure, the PTFE as the essential component and the other fluororesin (if present) act as binders, but other binders may also be included. The other binder is not particularly limited, and examples thereof include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or hydrogenated products thereof; thermoplastic elastomeric polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymers, and styrene-isoprene-styrene block copolymers or hydrogenated products thereof; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; and polymer compositions having ionic conductivity for alkali metal ions (particularly lithium ions). These may be used alone or in any combination of two or more in any ratio.

[0090] The content of the other binder is usually 0.01 to 3% by mass relative to the electrode mixture sheet.

[0091] The electrode mixture sheet of the present disclosure may further include a solid electrolyte. That is, the electrode mixture sheet of the present disclosure may be an electrode mixture sheet for a solid battery including an electrode active material and a solid electrolyte.

[0092] The solid electrolyte may be a sulfide-based solid electrolyte or an oxide-based solid electrolyte. In particular, when a sulfide-based solid electrolyte is used, there is an advantage in that the flexibility of the sheet is improved.

[0093] The sulfide-based solid electrolyte is not particularly limited, and may be Li ２ S-P ２ S ５ , Li ２ S-P ２S ３ 、 ２ S-@ ２ S ３ -P ２ S ５ 、 ２ Ψ-SiΨ ２ 、---- ２ Ψ-SiΨ ２ 、---- ２ S-@ ２ S ５ 、---- ２ S-@ ２ O ５ 、---- ３ 2O ４ -P ２ S ５ 、---- ２ Ψ-SiΨ ２ -P ２ S ５ 、 ２ Ψ-SiΨ ２ -L) ４ SiO ４ 、 ２ Ψ-SiΨ ２ -L) ３ 2O ４ 、 ３ PS ４ -L) ４ GeS ４ 、 ３．４ P ０．６ Si ０．４ S ４ 、 ３．２５ P ０．２５ Ge ０．７６ S ４ 、 ４－ｘ Ge １－ｘ P ｘ S ４ (8=0.6~0.8), L- ４＋ｙ Ge １－ｙ G ｙ S ４ (y=0.2~0.3),L-PS&-、L-&.、- ７－ｘ－２ｙ PS ６－ｘ－ｙ C- ｘ (0.8≦x≦1.7、0<y≦-0.258+0.5), Li １０ SnP ２ S １２Any one selected from the above, or a mixture of two or more thereof, can be used.

[0094] The sulfide-based solid electrolyte preferably contains lithium. Sulfide-based solid electrolytes containing lithium are used in solid-state batteries that use lithium ions as a carrier, and are particularly preferred in that the electrochemical devices have a high energy density.

[0095] The oxide-based solid electrolyte is preferably a compound that contains oxygen atoms (O), has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties.

[0096] Specific examples of the compound include Li ｘａ La ｙａ TiO ３ [xa=0.3~0.7, ya=0.3~0.7] (LLT), Li ｘｂ La ｙｂ Zr ｚｂ M ｂｂ ｍｂ O ｎｂ (M ｂｂ is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, where xb satisfies 5≦xb≦10, yb satisfies 1≦yb≦4, zb satisfies 1≦zb≦4, mb satisfies 0≦mb≦2, and nb satisfies 5≦nb≦20.), Li ｘｃ B ｙｃ M ｃｃ ｚｃ O ｎｃ (M ｃｃ is at least one element selected from C, S, Al, Si, Ga, Ge, In, and Sn, where xc satisfies 0≦xc≦5, yc satisfies 0≦yc≦1, zc satisfies 0≦zc≦1, and nc satisfies 0≦nc≦6.), Li ｘｄ (Al, Ga) ｙｄ (Ti, Ge) ｚｄ Si ａｄ P ｍｄ O ｎｄ (where 1≦xd≦3, 0≦yd≦2, 0≦zd≦2, 0≦ad≦2, 1≦md≦7, 3≦nd≦15), Li （３－２ｘｅ） M ｅｅｘｅ D ｅｅ O(xe represents a number between 0 and 0.1, and M ｅｅ represents a divalent metal atom. ｅｅ represents a halogen atom or a combination of two or more halogen atoms.), Li ｘｆ Si ｙｆ O ｚｆ (1≦xf≦5, 0<yf≦3, 1≦zf≦10), Li ｘｇ S ｙｇ O ｚｇ (1≦xg≦3, 0<yg≦2, 1≦zg≦10), Li ３ BO ３ -Li ２ SO ４ , Li ２ Alumni ２ O ３ -P ２ O ５ , Li ２ O—SiO ２ , Li ６ BaLa ２ Ta ２ O １２ , Li ３ P.O. （４－３／２ｗ） N ｗ (w is w<1), Li having a LISICON (Lithium super ionic conductor) type crystal structure ３．５ Zn ０．２５ GeO ４ , La having a perovskite crystal structure ０．５１ Li ０．３４ TiO ２．９４ , La ０．５５ Li ０．３５ TiO ３ , LiTi having a NASICON (sodium super ionic conductor) type crystal structure ２ P ３ O １２ , Li １＋ｘｈ＋ｙｈ (Al, Ga) ｘｈ (Ti, Ge) ２－ｘｈ Si ｙｈ P ３－ｙｈ O １２ (where 0≦xh≦1, 0≦yh≦1), Li having a garnet-type crystal structure ７ La ３ Zr２ O １２ Also, ceramic materials in which elements are substituted for LLZ are known. For example, Li ６．２４ La ３ Zr ２ Al ０．２４ O １１．９８ , Li ６．２５ Al ０．２５ La ３ Zr ２ O １２ and Li substituted with Ta ６．６ La ３ Zr １．６ Ta ０．４ O １２ , Nb-substituted Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２ Other examples include LLZ-based ceramic materials in which at least one element of Mg (magnesium) and A (A is at least one element selected from the group consisting of Ca (calcium), Sr (strontium), and Ba (barium)) is substituted for LLZ. Phosphorus compounds containing Li, P, and O are also desirable. For example, lithium phosphate (Li ３ P.O. ４ ), LiPON, LiPOD, in which some of the oxygen in lithium phosphate is replaced with nitrogen １ (D １ is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc. １ ON (A １ is at least one selected from Si, B, Ge, Al, C, Ga, etc.) can also be preferably used. ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ -GeO ２ , Li ２ O-Al ２ O３ -SiO ２ -P ２ O ５ -TiO ２ etc.

[0097] The oxide-based solid electrolyte preferably contains lithium. The oxide-based solid electrolyte containing lithium is used in a solid-state battery that uses lithium ions as a carrier, and is particularly preferred in terms of electrochemical devices having a high energy density.

[0098] The oxide-based solid electrolyte is preferably an oxide having a crystalline structure. Oxides having a crystalline structure are particularly preferred in terms of good Li ion conductivity. Examples of oxides having a crystalline structure include perovskite-type (La ０．５１ Li ０．３４ TiO ２．９４ ), NASICON type (Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３ etc.), garnet type (Li ７ La ３ Zr ２ O １２ (LLZ), etc. Among these, NASICON type is preferred.

[0099] The volume-average particle size of the oxide-based solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.03 μm or more. The upper limit is preferably 100 μm or less, and more preferably 50 μm or less. The average particle size of oxide-based solid electrolyte particles is measured using the following procedure. Oxide-based solid electrolyte particles are diluted with water (or heptane in the case of substances unstable in water) in a 20 ml sample bottle to prepare a 1 mass % dispersion. The diluted dispersion sample is irradiated with 1 kHz ultrasound for 10 minutes and used for testing immediately thereafter. Using this dispersion sample, data is acquired 50 times at 25°C using a quartz measurement cell using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by HORIBA), to obtain the volume-average particle size. For other detailed conditions, please refer to the description in JIS Z8828:2013, "Particle Size Analysis - Dynamic Light Scattering Method," as necessary. Five samples are prepared for each level, and the average value is used.

[0100] The content of the solid electrolyte relative to the electrode mixture sheet is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0101] The electrode mixture sheet of the present disclosure preferably has a thickness of 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, even more preferably 180 μm or less, particularly preferably 150 μm or less, and preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more.

[0102] The electrode mixture sheet of the present disclosure has a tensile strength of 0.10 N / mm ２ It is preferable that the resistance is 0.15 N / mm or more. ２ More preferably, it is 0.20 N / mm or more. ２ More preferably, it is 0.25 N / mm ２ It is even more preferable that the value is 0.30 N / mm or more. ２ It is particularly preferable that the strength is 1.5 N / mm or more.２ may be less than or equal to 1.0 N / mm ２ The tensile strength may be less than or equal to the above. The tensile strength is measured by the following method. An electrode mixture sheet is cut out to prepare a 4 mm wide strip-shaped test piece. Measurement is performed using a tensile tester (AGS-100NX manufactured by Shimadzu Corporation) under the condition of 100 mm / min. The distance between chucks is 40 mm. Displacement is applied until breakage occurs, and the maximum stress of the measurement result is taken as the tensile strength.

[0103] The electrode mixture sheet of the present disclosure preferably has a resistance value of less than 200 Ω·cm, more preferably less than 150 Ω·cm, even more preferably 100 Ω·cm or less, even more preferably 80 Ω·cm or less, particularly preferably 50 Ω·cm or less, and may be 0.1 Ω·cm or more. The resistance value is measured by the following method. The electrode mixture sheet is measured for the surface resistivity (Ω / □) of the mixture layer using a four-terminal four-probe method (Loresta GP (MCP-T610) manufactured by Mitsubishi Chemical Analytech). After measurement, the surface resistivity is multiplied by the thickness of the mixture layer to obtain the volume resistivity (Ω·cm) of the electrode mixture sheet. The thickness of the mixture layer is measured at three points in the electrode mixture sheet using a microgauge, and the average value is used.

[0104] The electrode mixture sheet of the present disclosure can be obtained, for example, by a manufacturing method for an electrode mixture sheet including: a step (1) of mixing PTFE with an electrode active material other than a carbon material and / or a fluororesin other than the PTFE (another fluororesin); and a step (2) of mixing the mixture obtained in the step (1) with a carbon material. The present disclosure also relates to the manufacturing method. By adding the carbon material later, damage to the carbon material due to shear forces that generate fibrils can be reduced, and it is thought that the conductive paths are less likely to be damaged and resistance is reduced.

[0105] The electrode active materials other than PTFE and carbon materials and other fluororesins in the above step (1) are the same as those described in the electrode mixture sheet of the present disclosure. When a solid electrolyte is used, it is preferably mixed in step (1). The components mixed in step (1) are preferably in the form of powder. It is preferable that no carbon material is mixed in step (1).

[0106] The above step (1) is preferably carried out in the absence of a liquid medium.

[0107] Examples of mixing methods in step (1) include methods using a single-screw kneader, a twin-screw kneader, a mix muller, a high-speed stirring mixer, a planetary mixer, a jet mill, or the like. In step (1), the mixing conditions can be appropriately set by adjusting the rotation speed and mixing time. For example, the rotation speed is preferably 10,000 rpm or less. It is preferably 500 rpm or more, more preferably 1,000 rpm or more, and even more preferably 1,500 rpm or more, and is preferably 8,000 rpm or less, more preferably 6,000 rpm or less, and even more preferably 5,000 rpm or less. If the rotation speed is below the above range, mixing will take a long time, adversely affecting productivity. Furthermore, if the rotation speed exceeds the above range, excessive fibrillation may occur, resulting in an electrode mixture sheet with poor strength and flexibility. For example, the mixing time is preferably 60 minutes or less. The time is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 3 minutes or more, and is preferably 30 minutes or less, more preferably 20 minutes or less, and even more preferably 10 minutes or less.

[0108] In the step (1), it is preferable to generate fibrils of the PTFE by shearing force.

[0109] In the above step (1), the treatment temperature may be appropriately set. For example, the treatment temperature is preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower, and is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher.

[0110] In the above step (1), the materials may be mixed and then shaped into a bulk form. Specific methods for shaping into a bulk form include extrusion molding, press molding, etc. The term "bulk form" does not particularly specify a shape, and may refer to a state in which the material is in the form of a single mass, including rods, sheets, spheres, cubes, etc.

[0111] In the above-described production method, after the end of step (1), it is preferable not to newly add any electrode active material other than the carbon material or any other fluororesin.

[0112] In the step (2), the mixture obtained in the step (1) is mixed with a carbon material. By mixing the carbon material after the electrode active material other than the carbon material and the other fluororesin, the value X can be easily adjusted to fall within the above-mentioned range, and an electrode mixture sheet having high tensile strength and low resistance can be produced.

[0113] The carbon material in the above step (2) is the same as that described in the electrode mixture sheet of the present disclosure.

[0114] The above step (2) is preferably carried out in the absence of a liquid medium.

[0115] The mixing method in the above step (2) includes the mixing method in the above step (1) as well as a method of mixing using a W-type mixer, V-type mixer, drum-type mixer, ribbon mixer, conical screw-type mixer, etc.

[0116] The mixing in step (2) is preferably performed using a shear force lower than that in step (1). By mixing in this manner, the value X can be more easily adjusted within the above-mentioned range, and an electrode mixture sheet with higher tensile strength and lower resistance can be produced. The shear force in step (2) can be adjusted to a range lower than that in step (1) by using an apparatus capable of applying a shear force lower than that in step (1) or by setting one or more of the processing time, rotation speed of the apparatus, input amount, and processing temperature lower than those in step (1).

[0117] In step (2), the mixing conditions may be any conditions capable of applying a lower shear force than in step (1), and processing equipment having a mechanism that does not apply a strong shear force, such as a W-type mixer, V-type mixer, drum mixer, ribbon mixer, or conical screw mixer, can be used. Furthermore, even in processing equipment that can be used in step (1), by setting any one or more of the processing time, rotation speed, input amount, and processing temperature lower than those in step (1), the materials can be mixed and dispersed while weakening the shear force. The processing time is preferably shorter than that in step (1), and is preferably 0.9 times or less, more preferably 0.8 times or less, and even more preferably 0.6 times or less, based on the time in step (1), and is preferably 0.1 times or more, more preferably 0.2 times or more, and even more preferably 0.3 times or more. The rotation speed is preferably lower than that of the above step (1), and is preferably 0.9 times or less, more preferably 0.8 times or less, even more preferably 0.7 times or less, and preferably 0.01 times or more, more preferably 0.05 times or more, even more preferably 0.1 times or more, and even more preferably 0.2 times or more, based on the reference value of the above step (1). The input amount is preferably lower than that of the above step (1), and is preferably 0.9 times or less, more preferably 0.8 times or less, even more preferably 0.6 times or less, and preferably 0.2 times or more, more preferably 0.3 times or more, and even more preferably 0.4 times or more, based on the reference value of the above step (1). The treatment temperature is preferably lower than that of the above step (1), and is preferably 10°C or less lower, more preferably 20°C or less lower, even more preferably 30°C or less lower, and preferably 200°C or more lower, more preferably 150°C or more lower, and even more preferably 100°C or more lower, based on the reference value of the above step (1). It is preferable that the step (2) is carried out using the same apparatus as the step (1), and it is particularly preferable that the same apparatus as the step (1) is used, but the rotation speed and processing time are changed.

[0118] The above-mentioned manufacturing method preferably further comprises a step (3) of rolling the electrode mixture obtained in the above-mentioned step (2) into a sheet.

[0119] Specific rolling methods in the above step (3) include rolling methods using a roll press, a plate press, a calendar roll, etc. Among these, a roll press in which metal rolls are arranged opposite each other and a calendar roll in which multiple metal rolls are arranged are preferred. In this case, it is preferable that there is a speed difference between the pair of metal rolls. The conveying speed of the downstream roll is preferably 1.1 times or more, more preferably 1.3 times or more, and even more preferably 1.5 times or more, based on the conveying speed of the upstream roll. Although there is no particular upper limit, it is preferable that the upstream roll is moved at a low speed without being stopped.

[0120] Furthermore, after the above step (3), a step (4) may be performed in which a larger load is applied to the obtained rolled sheet to roll it into an even thinner sheet, or step (4) may be repeatedly performed. In this way, by rolling the rolled sheet little by little in stages rather than thinning it all at once, flexibility is improved. The number of times step (4) is performed is preferably 2 to 10 times, more preferably 3 to 9 times. A specific rolling method includes, for example, a method in which two or more rolls are rotated and the rolled sheet is passed between them to process it into a thinner sheet. Furthermore, in the above steps (3) and (4), the processing temperature may be appropriately set. For example, the processing temperature is preferably 250°C or less, more preferably 200°C or less, even more preferably 180°C or less, and preferably 30°C or more, more preferably 40°C or more, and even more preferably 50°C or more. Heating the material makes it more flexible and improves its processability.

[0121] The electrode mixture sheet of the present disclosure can be used as an electrode mixture sheet for a secondary battery. It can be used for either a negative electrode or a positive electrode. In particular, the electrode mixture sheet is suitable for a lithium ion secondary battery.

[0122] The present disclosure also provides an electrode including the electrode mixture sheet of the present disclosure. The electrode of the present disclosure has high tensile strength and low resistance.

[0123] The electrode of the present disclosure may include the electrode mixture sheet of the present disclosure described above and a current collector.

[0124] The electrodes of the present disclosure may be positive or negative electrodes.

[0125] The positive electrode is preferably composed of a current collector and an electrode mixture sheet containing the positive electrode active material. Examples of materials for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, and nickel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Among these, metal materials, particularly aluminum or its alloys, are preferred.

[0126] Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punched metal, and foam metal in the case of a metal material, and carbon plate, carbon thin film, and carbon cylinder in the case of a carbon material. Of these, metal foil is preferred. The metal foil may be appropriately formed into a mesh shape. The thickness of the metal foil is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more, and is usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the metal foil is thicker than this range, handling may be impaired.

[0127] In addition, it is also preferable that the surface of the current collector is coated with a conductive additive, from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive additive include carbon and precious metals such as gold, platinum, and silver.

[0128] The positive electrode may be manufactured by a conventional method, for example, by laminating an electrode mixture sheet and a current collector with an adhesive therebetween, followed by vacuum drying.

[0129] The density of the positive electrode mixture sheet is preferably 2.80 g / cm ３ More preferably, 3.00 g / cm ３ More preferably, 3.20 g / cm ３ or more, and preferably 3.80 g / cm ３ or less, more preferably 3.75 g / cm３ More preferably, 3.70 g / cm or less ３ The range is as follows. If the temperature exceeds this range, the permeability of the electrolyte to the vicinity of the current collector / active material interface will decrease, and the charge / discharge characteristics, especially at high current densities, will decrease, and high output may not be obtained. If the temperature falls below this range, the conductivity between the active materials will decrease, and the battery resistance will increase, and high output may not be obtained.

[0130] The negative electrode is preferably composed of a current collector and an electrode mixture sheet containing the negative electrode active material. Examples of materials for the negative electrode current collector include metals such as copper, nickel, titanium, tantalum, and stainless steel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Among these, metal materials, particularly copper, nickel, and alloys thereof, are preferred.

[0131] Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punched metal, and foam metal in the case of a metal material, and carbon plate, carbon thin film, and carbon cylinder in the case of a carbon material. Of these, metal foil is preferred. The metal foil may be appropriately formed into a mesh shape. The thickness of the metal foil is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more, and is usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the metal foil is thicker than this range, handling may be impaired.

[0132] The negative electrode may be produced by a conventional method, for example, by laminating the electrode mixture sheet and a current collector with an adhesive therebetween, followed by vacuum drying.

[0133] The density of the negative electrode mixture is preferably 1.3 g / cm ３ More preferably, 1.4 g / cm ３ More preferably, 1.5 g / cm ３ or more, and preferably 2.0 g / cm ３ or less, more preferably 1.9 g / cm ３ More preferably, 1.8 g / cm or less ３The range is as follows. If the temperature exceeds this range, the permeability of the electrolyte to the vicinity of the current collector / active material interface will decrease, and the charge / discharge characteristics, especially at high current densities, will decrease, and high output may not be obtained. If the temperature falls below this range, the conductivity between the active materials will decrease, and the battery resistance will increase, and high output may not be obtained.

[0134] The present disclosure also provides a secondary battery comprising the electrode of the present disclosure described above.

[0135] The secondary battery may be a secondary battery using an electrolytic solution or a solid-state secondary battery. In this specification, the solid-state secondary battery may be a secondary battery containing a solid electrolyte, and may be a semi-solid-state secondary battery containing a solid electrolyte and a liquid component as the electrolyte, or an all-solid-state secondary battery containing only a solid electrolyte as the electrolyte.

[0136] The secondary battery using the above-mentioned electrolyte solution can use the electrolyte solution, separator, etc. used in known secondary batteries, which will be described in detail below.

[0137] The electrolyte is preferably a non-aqueous electrolyte, which may be prepared by dissolving a known electrolyte salt in a known organic solvent for dissolving electrolyte salts.

[0138] The organic solvent for dissolving the electrolyte salt is not particularly limited, and one or more of known hydrocarbon solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and fluorine-based solvents such as fluoroethylene carbonate, fluoroethers, and fluorinated carbonates can be used.

[0139] The electrolyte salt may be a lithium salt, such as LiClO ４ , LiAsF ６ , LiBF ４ , LiPF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２F ５ ) ２ In particular, LiPF is preferred because of its excellent cycle characteristics. ６ , LiBF ４ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ Or a combination of these is preferred.

[0140] The concentration of the electrolyte salt is preferably 0.8 mol / L or more, more preferably 1.0 mol / L or more, and the upper limit is usually 2.0 mol / L or less, although this depends on the organic solvent used to dissolve the electrolyte salt.

[0141] A secondary battery using the above-mentioned electrolyte solution preferably further includes a separator. The material and shape of the separator are not particularly limited as long as it is stable to the electrolyte solution and has excellent liquid retention properties, and any known separator can be used. Among them, it is preferable to use a material that is stable to the electrolyte solution, such as resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric with excellent liquid retention properties.

[0142] Examples of materials that can be used for the resin or glass fiber separator include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. These materials may be used alone or in any combination and ratio, such as polypropylene / polyethylene two-layer films and polypropylene / polyethylene / polypropylene three-layer films. Among these, porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene are preferred for the separator, due to their excellent electrolyte permeability and shutdown effect.

[0143] The thickness of the separator is not particularly limited, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is thinner than the above range, the insulating properties and mechanical strength may be reduced. If the separator is thicker than the above range, not only may the battery performance such as rate characteristics be reduced, but also the energy density of the entire electrolyte battery may be reduced.

[0144] On the other hand, inorganic materials include, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and these are used in particulate or fibrous form.

[0145] As for the form, a thin film such as a nonwoven fabric, a woven fabric, or a microporous film is used. A thin film with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film, a separator can be used in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface layer of the positive electrode and / or negative electrode using a resin binder. For example, a porous layer can be formed on both sides of the positive electrode using alumina particles with a 90% particle size of less than 1 μm and a fibrillar resin as a binder.

[0146] The material of the outer case is not particularly limited as long as it is a substance that is stable against the electrolyte used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminate film of resin and aluminum foil (laminate film) can be used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy and laminate film are preferably used.

[0147] Examples of exterior cases using metals include those in which metals are welded together to form a sealed, airtight structure by laser welding, resistance welding, or ultrasonic welding, or those in which the metals are used via a resin gasket to form a crimped structure. Examples of exterior cases using the above-mentioned laminate film include those in which resin layers are heat-sealed to form a sealed, airtight structure. In order to improve sealing properties, a resin different from the resin used in the laminate film may be interposed between the resin layers. In particular, when a sealed structure is formed by heat-sealing the resin layers via a current collecting terminal, a resin having a polar group or a modified resin into which a polar group has been introduced is preferably used as the interposed resin, since the metal and the resin are bonded together.

[0148] The shape of the secondary battery using the above-mentioned electrolyte solution is arbitrary, and examples thereof include cylindrical, prismatic, laminated, coin, large, etc. The shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0149] The solid-state secondary battery is preferably an all-solid-state secondary battery, and is preferably a lithium-ion battery, and is also preferably a sulfide-based all-solid-state secondary battery.

[0150] The solid secondary battery preferably includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

[0151] Examples of the solid electrolyte used in the solid electrolyte layer include the same solid electrolytes as those that can be used in the electrode mixture sheet of the present disclosure described above.

[0152] The solid secondary battery may include a separator between the positive electrode and the negative electrode. Examples of the separator include a porous membrane such as polyethylene or polypropylene; a nonwoven fabric made of a resin such as polypropylene; and a nonwoven fabric such as a glass fiber nonwoven fabric.

[0153] The solid secondary battery may further include a battery case. The shape of the battery case is not particularly limited as long as it can accommodate the above-mentioned positive electrode, negative electrode, solid electrolyte layer, etc., but specific examples include a cylindrical shape, a square shape, a coin shape, and a laminate shape.

[0154] The solid secondary battery can be produced, for example, by stacking a positive electrode, a solid electrolyte layer sheet, and a negative electrode in this order and pressing them together.

[0155] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0156] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0157] PTFE-1 and PTFE-2 were prepared and analyzed by the following method.

[0158] <Average primary particle diameter> The PTFE aqueous dispersion was diluted with water until the solid content became 0.15% by mass, and the transmittance of the 550 nm projected light per unit length of the diluted latex obtained and the number-based average primary particle diameter determined by measuring the unidirectional diameter by a transmission electron microscope photograph were measured, and a calibration curve was prepared. Using this calibration curve, the average primary particle diameter was determined from the measured transmittance of the 550 nm projected light of each sample.

[0159] <Polymer solid content concentration> 1 g of the aqueous PTFE dispersion was dried in a blower dryer at 150°C for 60 minutes, and the ratio of the mass of the heating residue to the mass (1 g) of the aqueous dispersion was expressed as a percentage and used as the solid content concentration.

[0160] <Content of modified monomer> The CTFE content was determined by press-molding a thin film disk from a PTFE powder or composition, and measuring the infrared absorbance of the thin film disk by FT-IR to obtain a CTFE content of 957 cm －１ Absorbance at / 2360 cm －１ The absorbance ratio was calculated by multiplying the absorbance ratio at 0.58.

[0161] <Standard Specific Gravity (SSG)> Using a sample molded in accordance with ASTM D4895 89, the standard specific gravity was measured by the water displacement method in accordance with ASTM D 792.

[0162] A white solid A was obtained by the method described in Synthesis Example 1 of WO 2021 / 045228.

[0163] Preparation Example 1 A 6-liter stainless steel autoclave equipped with a stirring blade and a temperature-controlling jacket was charged with 3,480 g of deionized water, 100 g of paraffin wax, and 5.3 g of white solid A. The autoclave was heated to 70 ° C. while purging with nitrogen gas to remove oxygen. TFE was injected to adjust the system pressure to 0.78 MPaG, and the system temperature was maintained at 70 ° C. while stirring. Next, an aqueous solution prepared by dissolving 15.0 mg of ammonium persulfate in 20 g of water was injected with TFE to initiate the polymerization reaction. As the polymerization reaction progressed, the system pressure decreased, but TFE was added to maintain the system temperature at 70 ° C. and the system pressure at 0.78 MPaG. When 400 g of TFE had been consumed from the start of polymerization, an aqueous solution prepared by dissolving 18.0 mg of hydroquinone as a radical scavenger in 20 g of water was injected with TFE. Polymerization continues thereafter, and when the polymerization amount of TFE reaches about 1200 g from the start of polymerization, stirring and supply of TFE are stopped, and the gas in the system is immediately released to normal pressure, and polymerization reaction is terminated.The aqueous dispersion is taken out, cooled, and then the paraffin wax is separated, and a PTFE aqueous dispersion is obtained.The average primary particle diameter of the obtained PTFE aqueous dispersion is 310 nm, and the solid content concentration is 25.3 mass%.

[0164] The resulting PTFE aqueous dispersion was diluted to a solids concentration of 13% by mass, and the PTFE was coagulated while stirring in a container. The PTFE was then filtered off from the water to obtain a wet PTFE powder. The resulting wet PTFE powder was dried at 180°C for 18 hours to obtain PTFE-1. The SSG of the resulting PTFE-1 was 2.156.

[0165] Preparation Example 2 A 6-liter stainless steel autoclave equipped with a stirring blade and a temperature-controlling jacket was charged with 3,580 g of deionized water, 100 g of paraffin wax, and 5.4 g of white solid A. The autoclave was heated to 80 ° C. while replacing the atmosphere with nitrogen gas to remove oxygen. After adding 1.20 g of CTFE, TFE was further injected to bring the system pressure to 0.78 MPaG, and the system temperature was maintained at 80 ° C. while stirring. Next, an aqueous solution of 360 mg of disuccinic acid peroxide dissolved in 20 g of water and an aqueous solution of 10 mg of ammonium persulfate dissolved in 20 g of water were injected with TFE to initiate the polymerization reaction. As the polymerization reaction progressed, the system pressure decreased, but TFE was added to maintain the system temperature at 80 ° C. and the system pressure at 0.78 MPaG. When 1530g of TFE was consumed from the start of polymerization (conversion rate 90%), 4.2g of CTFE was added by pressure with TFE. Polymerization continued thereafter, and when the amount of TFE polymerization reached about 1700g from the start of polymerization, stirring and the supply of TFE were stopped, and the gas in the system was immediately released to normal pressure, and the polymerization reaction was terminated. The aqueous dispersion was taken out and cooled, and the paraffin wax was separated to obtain a PTFE aqueous dispersion. The average primary particle size of the obtained PTFE aqueous dispersion was 241nm, and the solid content concentration was 32.0% by mass.

[0166] The resulting PTFE aqueous dispersion was diluted to a solids concentration of 13% by mass, vigorously stirred in a container equipped with a stirrer to coagulate, and then filtered to separate the water, yielding a PTFE wet powder. The resulting PTFE wet powder was dried at 145°C for 18 hours to yield PTFE-2. The resulting PTFE-2 had a CTFE content of 0.23% by mass and an SSG of 2.170.

[0167] The preparation and evaluation of mixture sheets in the examples and comparative examples were carried out according to the following procedures. The composition ratios were adjusted to the values ​​listed in Table 1. (Preparation of Electrode Mixture Sheet) (Example 1) [Step 1] Positive electrode active material A and PTFE-1 were weighed and heated sufficiently in a thermostatic bath at 60 ° C. Then, the mixture was placed in a high-speed stirring mixer and stirred for 1 minute at a blade rotation speed of 6850 rpm to apply shear force, resulting in a mixture with many fibrils. [Step 2] After cooling to 25 ° C, conductive additive AB was added to the resulting mixture as a carbon material, and the mixture was treated at 1500 rpm for 1 minute to disperse the carbon material into the mixture, thereby obtaining an electrode mixture. [Step 3] The electrode mixture was placed in a roll mill capable of rotating at different peripheral speeds to obtain an electrode mixture sheet (temperature: 60 ° C., left roll rotation speed: 1 m / min, right roll rotation speed: 0.8 m / min). [Step 4] The obtained mixture sheet was again placed in the rolling mill and rolled to obtain an electrode mixture sheet with stronger sheet strength. The electrode mixture sheet was then placed in a roll press and the gap was adjusted. The final thickness of the mixture sheet was adjusted to 80 μm.

[0168] Example 2 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 1900 rpm, and the treatment time was changed to 3 minutes.

[0169] Example 3 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 4,300 rpm, and the treatment time was changed to 3 minutes.

[0170] Example 4 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1.

[0171] Example 5 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 3000 rpm, and the treatment time was changed to 10 minutes.

[0172] Example 6 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 3000 rpm, and the treatment time was changed to 20 minutes.

[0173] Example 7 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1 and the treatment time in [Step 1] was changed to 3 minutes.

[0174] Example 8 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1 and the treatment time in [Step 1] was changed to 3 minutes.

[0175] Example 9 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 4,300 rpm, and the treatment time was changed to 3 minutes.

[0176] Example 10 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1 and the treatment time in [Step 1] was changed to 3 minutes.

[0177] Example 11 A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the rotation speed in [Step 1] was changed to 1500 rpm, and the treatment time was changed to 10 minutes.

[0178] Example 12 A composite sheet was prepared in the same manner as in Example 1, except that in [Step 1], silicon oxide was used as the active material other than carbon, the amount of PTFE-1 was 1 mass %, the amount of PTFE-2 was 1 mass %, and the treatment time was 3 minutes, and in [Step 2], graphite was used as the carbon material.

[0179] (Example 13) A mixture sheet was produced in the same manner as in Example 1, except that the material composition was changed to that shown in Table 1, the treatment time in [Step 1] was changed to 3 minutes, and the treatment temperature in [Step 3] was changed to 140°C.

[0180] (Comparative Example 1) [Step 1] The positive electrode active material A, PTFE-1, and conductive additive AB as a carbon material were weighed and heated sufficiently in a constant temperature bath at 60 ° C. Then, the mixture was placed in a high-speed stirring mixer and stirred for 1 minute at a blade rotation speed of 6850 rpm to apply shear force, resulting in a mixture with many fibrils. [Step 2] After cooling to 25 ° C, the resulting mixture was treated at 1500 rpm for 1 minute to obtain an electrode mixture. [Step 3] [Step 4] were performed in the same manner as in Example 1 to prepare a mixture sheet.

[0181] (Method for Confirming the Presence or Absence of Fibrils) The mixture after [Step 1] was observed under SEM (magnification 7000x) to confirm the occurrence of fibrils. In Examples 1 to 12, it was possible to observe the appearance of multiple fibrils occurring from the PTFE.

[0182] (Measurement of Value X) <Measurement Sample> The electrode mixture sheet was cut into a size of 1 cm x 1 cm (thickness can be determined) to serve as a measurement sample. <Interface Length (pix)> (i) For each measurement sample, SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy) analysis was performed to obtain three images of the carbon composition distribution at a 2000x field of view, an acceleration voltage of 3000 V, and an image size of 1280 x 960. The first image was obtained from the center of the measurement sample, and the second and third images were obtained from points shifted 2 mm to the left and right from the center of the measurement sample. An SU8000 manufactured by Hitachi High-Tech Corporation was used to obtain the images. (ii) The images obtained in (i) were subjected to binarization processing. Images obtained with N = 3 per sample were divided into brightness levels of 0 to 255 for each image, and a threshold was determined for each image using Otsu's binarization method. The average value of the binarization threshold for each image was then calculated, and the average threshold for the sample was calculated. Using the average threshold, each pre-binarization image was binarized again. (iii) In the image obtained in (ii), the number of elements where the difference between elements between pixels was not zero was counted and the numerical value was taken as the interface length of each image. <Detected Carbon Amount (cps / eV)> ​​The detected carbon amount of each image was calculated from the spectral data obtained simultaneously with the image data of (i) above. The spectral data used was spectral data obtained when measured using SEM-EDX, with the horizontal axis representing X-ray energy [keV] and the vertical axis representing X-ray intensity [cps / eV]. From the spectral data, the maximum value on the vertical axis of the peak appearing near 0.27 keV, which is the intrinsic energy of carbon, was read, and the read value was taken as the detected carbon amount. <Interface Length ÷ Detected Carbon Amount (Value X)> From the interface length and detected carbon amount calculated for each image, the interface length ÷ detected carbon amount was calculated for three points for each sample, and the average value of N = 3 was taken as the interface length ÷ detected carbon amount (value X) for each sample. The results are shown in Table 2.

[0183] (Measurement of strength of electrode mixture sheet) The electrode mixture sheet was cut out to prepare a 4 mm wide strip-shaped test piece. Measurement was performed using a tensile tester (AGS-100NX manufactured by Shimadzu Corporation) at a rate of 100 mm / min. The distance between chucks was 40 mm. Displacement was applied until breakage, and the maximum stress of the measurement results was taken as the strength of each sample. The results are shown in Table 2.

[0184] (Measurement of Resistance of Electrode Mixture Sheet) The electrode mixture sheet was cut into a 5 cm square sample, and the surface resistivity (Ω / □) of the mixture layer was measured using a four-terminal four-probe method (Loresta GP (MCP-T610) manufactured by Mitsubishi Chemical Analytech). After measurement, the surface resistivity was multiplied by the thickness of the mixture layer to obtain the volume resistivity (Ω cm) of the electrode mixture sheet. The thickness of the mixture layer was measured at three points in the electrode mixture sheet using a microgauge, and the average value was used. The measured volume resistivity was evaluated as follows: A: Less than 100 Ω cm B: 100 Ω cm or more to less than 150 Ω cm C: 150 Ω cm or more to less than 200 Ω cm D: 200 Ω cm or more The results are shown in Table 2.

[0185]

[0186]

[0187] The abbreviations in the table are as follows: Positive electrode active material A: Li(Ni ０．６ Mn ０．２ Co ０．２ ) O ２ Positive electrode active material B: Li (Ni ０．８ Mn ０．１ Co ０．１ ) O ２ AB: Acetylene black Li-100 manufactured by Denka Corporation Super P Li: Carbon black manufactured by Imerys Corporation PVdF-1: Modified PVdF having an acrylic acid functional group (D50 = 2.0 μm)

Claims

1. An electrode mixture sheet comprising polytetrafluoroethylene, a carbon material, and an electrode active material other than the carbon material and / or a fluororesin other than the polytetrafluoroethylene, wherein in an image of a carbon composition distribution obtained by SEM-EDX analysis with a magnification of 2000 times, a value X indicated by the interface length / carbon detection amount is 2300 or less.

2. The electrode mixture sheet according to claim 1, wherein the value X is 300 or more and 2,000 or less.

3. An electrode mixture sheet according to claim 1 or 2, wherein the total content of said polytetrafluoroethylene and said fluororesin other than polytetrafluoroethylene in said electrode mixture sheet is 0.1% by mass or more and 10% by mass or less.

4. The electrode mixture sheet according to any one of claims 1 to 3, wherein the carbon material is a conductive assistant.

5. The electrode mixture sheet according to any one of claims 1 to 4, wherein the electrode active material other than the carbon material is a positive electrode active material.

6. The electrode mixture sheet according to claim 5, wherein the content of the positive electrode active material is 92% or more and 99% or less by mass based on the electrode mixture sheet.

7. An electrode comprising the electrode mixture sheet according to any one of claims 1 to 6.

8. A secondary battery comprising the electrode according to claim 7.

9. A method for producing an electrode mixture sheet, comprising: a step (1) of mixing polytetrafluoroethylene with an electrode active material other than a carbon material and / or a fluororesin other than the polytetrafluoroethylene; and a step (2) of mixing the mixture obtained in the step (1) with a carbon material.

10. The method according to claim 9, wherein in step (1), fibrils of the polytetrafluoroethylene are generated by applying a shear force.

11. The method according to claim 9 or 10, wherein the mixing in step (2) is carried out under a lower shear force than that in step (1).

12. The method according to any one of claims 9 to 11, wherein the components mixed in step (1) are all powders, and step (1) is carried out in the absence of a liquid medium.

13. The method according to any one of claims 9 to 12, wherein the treatment temperature in step (2) is lower than the treatment temperature in step (1).

14. The method according to any one of claims 9 to 13, wherein steps (1) and (2) are carried out using the same apparatus.

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