JP4003268B2 - Electrode sheet and battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating technique for an electrode sheet that can be used for a non-aqueous secondary battery with improved productivity, high discharge potential, excellent life stability, and high safety.
[0002]
[Prior art]
In recent years, with the development of devices equipped with secondary batteries, the need for high-capacity secondary batteries is rapidly increasing. Due to this necessity, lithium ion secondary batteries have been developed in place of conventional nickel cadmium batteries and nickel metal hydride batteries. Lithium ion secondary batteries have a higher capacity than conventional secondary batteries. However, the development of electronic devices in recent years is remarkable, and a further increase in capacity is desired. In order to increase the capacity of a battery, it is natural to develop an electrode material, and it is considered to increase the amount of the electrode material filled in the battery container. In order to increase the amount of the electrode material, attempts have been made to increase the electrode material to be applied, and press the electrode sheet after application to reduce the porosity of the electrode material.
[0003]
FIG. 3 is a cross-sectional view of the electrode sheet along the longitudinal direction of the electrode sheet according to the prior art. Usually, the electrode sheet is coated with a coating solution containing an electrode material (hereinafter referred to as a mixture coating solution) on both surfaces of the current collector 51, and mixture layers 52 a and 52 b are formed on both surfaces of the current collector 51. The total film thickness of the mixture layers 52a and 52b on both sides is larger than the thickness of the current collector 51, and the porosity of the mixture layers 52a and 52b is controlled to 10% to 30% after pressure pressing.
[0004]
However, when the above electrode sheet is used, a failure such as the electrode sheet being cut in the pressure pressing process is likely to occur, and there is a problem in manufacturing suitability. That is, when the electrode sheet is conveyed by the press roller in the direction of the arrow 53, the portion of the current collector 51 to which the mixture layer is not applied is first pressed, and then the current collector to which the mixture layers 52a and 52b are applied. The part of the body 51 is pressed. The pressed thickness changes from the thickness of the current collector 51 alone to the combined thickness of the current collector 51 and the mixture layers 52a and 52b. Since the thickness change is steep, the current collector 51 is likely to be cut at the thickness changing portion 54.
[0005]
In addition, since there is a change in the thickness described above, when assembling the battery, when the electrode sheet and the separator are overlapped and wound, the winding start portion (the portion of the current collector 51 where the mixture layer is not applied) There is a drawback that it is difficult to form a uniform arc and it is difficult to obtain a uniform winding group.
[0006]
[Problem to be Solved by the Invention]
The first object of the present invention is to provide an electrode sheet having process suitability with few failures such as cutting in the electrode manufacturing process.
[0007]
The second object of the present invention is to provide an electrode sheet that can increase the roundness of a wound group of electrodes.
[0008]
The third object of the present invention is to provide a high-capacity secondary battery using the above electrode sheet.
[0009]
According to one aspect of the present invention, an electrode sheet for a battery having a wound group of electrodes is an electrode sheet in which an electrode mixture is applied to both sides of a current collector, and the electrode sheet is a current collector. The upper and lower surfaces of both ends of the body have an uncoated portion where no electrode mixture is applied, and a lead is attached to at least one end of the uncoated portion, and the lead is further attached. The electrode mixture coating end on the front and back surfaces of one end has a deviation of 0.3 mm or more and 30 mm or less in the longitudinal direction of the electrode sheet, and is manufactured by pressing .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Although the preferable aspect of this invention is as follows, these are examples and it is not necessary to limit to these.
[0011]
The electrode sheet can be applied to various types of batteries. Hereinafter, a non-aqueous secondary battery using lithium as an active material will be described in detail as an example.
[0012]
1A to 1D show a method for manufacturing an electrode sheet according to an embodiment of the present invention. An electrode sheet is a general term for a positive electrode sheet and a negative electrode sheet. The following manufacturing method can be applied to both the positive electrode sheet and the negative electrode sheet.
[0013]
1A, in the electrode current collector 21, the horizontal direction in the figure is the longitudinal direction, the depth direction in the figure is the width, and the vertical direction in the figure is the thickness. The electrode current collector 21 has a function of collecting electric charges and is also a support for the electrode. The shape of the electrode current collector 21 is, for example, a rectangular thin sheet. The thickness is preferably about 5 μm or more and 30 μm or less.
[0014]
The electrode current collector 21 is made of aluminum, stainless steel, nickel, titanium, or an alloy thereof for the positive electrode, and copper, stainless steel, nickel, titanium, or an alloy thereof for the negative electrode. Are foil, expanded metal, punched metal, and wire mesh. The electrode current collector 21 is particularly preferably an aluminum foil for the positive electrode and a copper foil for the negative electrode.
[0015]
The tape 22a is affixed to the upper surface (front surface) of the electrode current collector 21, and the tape 22b is affixed to the lower surface (back surface). The thicknesses of the tapes 22a and 22b are both 10 to 100 μm, preferably 20 to 80 μm, and particularly preferably 30 to 50 μm. One end of the upper surface tape 22a and one end of the lower surface tape 22b are shifted by a length L1 in the longitudinal direction. Either of the tapes 22a and 22b may be long (projected). The length L1 is preferably 0.3 mm or more and 30 mm or less.
[0016]
As shown in FIG. 1B, the electrode mixture 23a is applied so as to cover the upper surfaces of the electrode current collector 21 and the tape 22a, and the electrode mixture 23b is covered so as to cover the lower surfaces of the electrode current collector 21 and the tape 22b. Apply. The electrode mixture 23a, 23b is adjusted and applied so as to have a predetermined thickness after finishing the subsequent drying step and pressing step. The components of the electrode mixture 23a, 23b will be described later. After the application, the electrode sheet is dried and dehydrated. When dried, the electrode mixture 23a, 23b creates voids therein and expands in volume. FIG. 1B shows a state after drying.
[0017]
After drying, the upper surface tape 22 a and the lower surface tape 22 b are peeled from the electrode current collector 21. The upper surface tape 22a is peeled off together with the electrode mixture layer on its upper surface, and the lower surface tape 22b is peeled off together with the electrode mixture layer on its lower surface. As shown in FIG. 1C, the electrode mixture layer 24 a is left on the upper surface of the electrode current collector 21, and the electrode mixture layer 24 b is left on the lower surface of the electrode current collector 21. One end of the upper electrode mixture layer 24a and one end of the lower electrode mixture layer 24b are shifted by a length L1 in the longitudinal direction.
[0018]
After peeling off the tape, the electrode sheet is conveyed in the direction of arrow 26, and the electrode sheet is pressed in the thickness direction by a press roller. First, the portion 31 where neither of the electrode mixture layers 24a and 24b is applied is pressed, then the portion 32 where only the electrode mixture layer 24b is applied is pressed, and then the electrode mixture layers 24a and 24b. The part 33 to which both are applied is pressed. The thickness of the electrode sheet is gradually increased in the above three steps, so that the impact force due to the thickness change can be reduced. By reducing the impact force, it is possible to reduce the accident that the electrode sheet is cut during pressing.
[0019]
As shown in FIG. 1D, the thickness of the subsequent electrode mixture layers 25a and 25b is reduced by the above pressing. Thereafter, the electrode current collector 21 is cut at a predetermined location 28. The final electrode sheet dimensions are as follows. The thickness of the electrode current collector 21 is preferably 5 μm or more and 30 μm or less. Each of the electrode mixture layers 25a and 25b is preferably equal to or greater than the thickness of the electrode current collector 21. More preferably, the thickness of the electrode mixture layers 25a and 25b is 30 μm or more and 400 μm or less, respectively. The longitudinal displacement L1 between the electrode mixture layers 25a and 25b is preferably 0.3 mm or more and 30 mm or less. In particular, the deviation L1 is preferably 0.5 mm or more and 10 mm or less.
[0020]
By having the above-described deviation L1 of 0.3 mm or more and 30 mm or less, the problem of electrode cutting by a press and winding non-uniformity is improved. The optimum values for improving these two problems are different. The optimum value of the deviation amount L1 for avoiding the cutting of the electrode by pressing is 0.3 mm or more and 2 mm or less, and the more preferred value of the deviation amount L1 for improving the non-uniformity of winding is 2 mm or more and 10 mm. The optimum value is 3 mm or more and 7 mm or less.
[0021]
As described above, the shift amount L1 can be controlled with high accuracy by adjusting the positions at which the tapes 22a and 22b are pasted on the electrode current collector 21. In addition, although FIG. 1 (A)-(D) has shown only the end of the electrode sheet, it shows the whole electrode sheet next. Not only the left end of the electrode sheet but also the right end can be formed by the above method. For example, the method shown in FIG. 5 of Japanese Patent Application No. 9-42655 can be applied to the method for manufacturing the electrode sheet.
[0022]
4A to 4C are views showing the entire electrode sheet, and show the relationship between the electrode current collector and the electrode mixture layer applied to both surfaces thereof.
[0023]
As shown in FIG. 4A, the electrode mixture layer 42a is applied to the upper surface of the electrode current collector 41, and the electrode mixture layer 42b is applied to the lower surface. In the upper electrode mixture layer 42a, the left end LT is shifted to the right (in the direction of the center of the electrode sheet) and the right end RT is shifted to the right (in the direction of the right end of the electrode sheet), compared to the electrode mixture layer 42b on the lower surface. Yes. The cross-sectional shape of the both ends in the longitudinal direction of the electrode sheet is translationally symmetric. The electrode mixture layers 42a and 42b have substantially the same length.
[0024]
4B, the electrode mixture layer 43a is applied to the upper surface of the electrode current collector 41, and the electrode mixture layer 43b is applied to the lower surface. In the upper electrode mixture layer 43a, the left end LT is shifted to the right (in the direction of the central portion of the electrode sheet) and the right end RT is shifted to the left (in the direction of the central portion of the electrode sheet) compared to the electrode mixture layer 43b of the lower surface. ing. At both ends in the longitudinal direction of the electrode sheet, the cross-sectional shape is mirror-symmetric.
[0025]
Further, as shown in FIG. 4C, the electrode mixture layer 44a is applied to the upper surface of the electrode current collector 41, and the electrode mixture layer 44b is applied to the lower surface. In the upper electrode mixture layer 44a, the left end LT is shifted to the right (in the direction of the center portion of the electrode sheet) and the right end RT is aligned in the longitudinal direction of the electrode sheet as compared with the lower electrode mixture layer 44b. In the longitudinal direction of the electrode sheet, the electrode mixture layers 44a and 44b are shifted only at the left end LT and are not displaced from the right end RT or are shifted by less than 0.3 mm.
[0026]
As shown in FIGS. 4A to 4C, various shifts can be formed. In particular, the electrode mixture layers 42a and 42b have substantially the same length, and the manufacturing process is simplified. Therefore, the relationship between the electrode mixture layers 42a and 42b shown in FIG. 4A is preferable.
[0027]
The displacement L1 of the electrode mixture layer in the electrode sheet can be adjusted by applying a tape as described above, but is not limited thereto. The shift L1 may be adjusted by controlling the starting position of applying the electrode mixture layer to the upper and lower surfaces of the electrode current collector without applying tape to the electrode current collector. Further, one surface may be affixed with a tape to determine the position of the coating end, and the other surface may control the starting position for coating. Furthermore, the position of the coating end may be controlled to adjust the deviation L1 by mechanically scraping off the uniformly applied electrode mixture layer.
[0028]
A lead plate (not shown) is attached to the uncoated portion 29 of the electrode sheet shown in FIG. A positive electrode sheet and a negative electrode sheet are prepared by the above method. The positive electrode sheet and the negative electrode sheet are wound with a winding machine with a separator interposed therebetween. Since the electrode sheet is gradually thickened in three stages as described above, it is easy to wind and an electrode winding group with high roundness can be created. As a method for creating the winding group, for example, the method shown in FIG. 1 of Japanese Patent Application No. 9-42655 can be applied.
[0029]
FIG. 2 is a cross-sectional view of a cylindrical battery. The battery shape can be applied to either cylinder or corner. The battery is formed by inserting the electrode sheets 8 and 9 wound together with the separator 10 into the battery can 11, electrically connecting the battery can 11 and the negative electrode sheet 9, and injecting and sealing the electrolytic solution 15. The battery lid 12 has a positive electrode terminal, and is fitted into the upper opening of the battery can 11 via the gasket 13. The positive electrode sheet 8 is electrically connected to the battery lid 12. At this time, the safety valve 14 can be used as a sealing plate. Furthermore, it is preferable to use a positive temperature coefficient (PTC) element 16 in order to guarantee the safety of the battery.
[0030]
The electrode mixture 23a and 23b shown in FIG. 1B is a positive electrode mixture in the positive electrode sheet and a negative electrode mixture in the negative electrode sheet. In addition to the positive electrode active material or the negative electrode material, the positive electrode or the negative electrode mixture can contain a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives, respectively.
[0031]
The positive electrode active material may be any material that can insert and release light metals, but is preferably a lithium-containing transition metal oxide, more preferably Li _x CoO ₂ , Li _x NiO ₂ , Li _x Co _a Ni _1-a O. _{2, Li x Co b V 1} -b O z, Li x Co b Fe 1-b O z, Li x Mn 2 O 4, Li x MnO 2, Li x Mn 2 O 3, Li x Mn b Co 2- _{b O z, Li x Mn b} Ni 2-b O z, Li x Mn b V 2-b O z, Li x Mn b Fe 1-b O z ( where x = 0.05 to 1.2, a = 0.1-0.9, b = 0.8-0.98, z = 1.5-5).
[0032]
Hereinafter, the light metal referred to in the present specification is an element belonging to Group 1A (excluding hydrogen) and Group 2A of the periodic table, preferably lithium, sodium, or potassium, and particularly preferably lithium.
[0033]
The negative electrode material may be any material that can insert and release light metals, but preferably graphite (natural graphite, artificial graphite, vapor-grown graphite), coke (coal or petroleum), organic polymer fired product (polyacrylonitrile resin or Fiber, furan resin, cresol resin, phenol resin), calcined mesophase pitch, metal oxide, metal chalcogenide, lithium-containing transition metal oxide and chalcogenide.
[0034]
In particular, an oxide or chalcogenide made of Ge, Sn, Pb, Bi, Al, Ga, Si, or Sb alone or a combination thereof is preferable. Further, those obtained by adding SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , V ₂ O _5, etc., which are known as network formers, to an amorphous state are particularly preferable. These may be of stoichiometric composition or non-stoichiometric compounds.
[0035]
Preferred examples of these compounds include the following, but are not limited thereto.
[0036]
_{GeO, GeO 2, SnO, SnO} 2, SnSiO 3, PbO, SiO, Sb 2 O 5, Bi 2 O 3, Li 2 SiO 3, Li 4 Si 2 O 7, Li 2 GeO 3, SnAl 0.4 B 0.5 P 0.5 K _0.1 O _3.65 , SnAl _0.4 B _0.5 P _0.5 Cs _0.1 O _3.65 , SnAl _0.4 B _0.5 P _0.5 K _0.1 Ge _0.05 O _3.85 , SnAl _0.4 B _0.5 P _0.5 K _0.1 Mg _0.1 Ge _0.02 O _3.83 , SnAl _0.4 B _0.4 P _0.4 Ba _0.08 O _3.28 , SnAl _0.5 B _0.4 P _0.5 Mg _0.1 F _0.2 O _3.65 , SnAl _0.4 B _0.5 P _0.5 Cs _0.1 Mg _0.1 F _0.2 O _3.65 , SnB _0.5 P _0.5 Cs _0.05 Mg _0.05 F _0.1 O _3.03 , Sn _1.1 Al _0.4 B _0.4 P _0.4 Ba _0.08 O _3.34 , Sn _1.2 Al _0.5 B _0.3 P _0.4 Cs _0.2 O _3.5 , SnSi _0.5 Al _0.2 B _0.1 P _0.1 Mg _0.1 O _2.8 , SnSi _0.5 Al _0.3 B _0.4 P _0.5 O _4.30 , SnSi _0.6 Al _0.1 B _{0. 1} P _0.1 Ba _0.2 O _2.95 , SnSi _0.6 Al _0.4 B _0.2 Mg _0.1 O _3.2 , Sn _0.9 Mn _0.3 B _0.4 P _0.4 Ca _0.1 Rb _0.1 O _2.95 , Sn _0.9 Fe _0.3 B _0.4 P _0.4 Ca _0.1 Rb _0.1 O _2.95 , Sn _{0.3 Ge 0.7 Ba 0.1 P 0.9 O} 3.35, Sn 0.9 Mn 0.1 Mg 0. 1 P 0.9 O 3.35, Sn 0.2 Mn 0.8 Mg 0.1 P 0.9 O 3.35
[0037]
Furthermore, the negative electrode material can be used by inserting a light metal, particularly lithium. The lithium insertion method is preferably an electrochemical, chemical or thermal method.
[0038]
The amount of lithium inserted into the negative electrode material may be close to the lithium deposition potential, but is preferably 50 to 700 mol% per negative electrode material. 100 to 600 mol% is particularly preferable.
[0039]
The conductive agent in the positive electrode and the negative electrode is graphite, acetylene black, carbon black, ketjen black, carbon fiber or metal powder, metal fiber or polyphenylene derivative, and graphite and acetylene black are particularly preferable.
[0040]
The binder in the positive and negative electrodes is polyacrylic acid, carboxymethylcellulose, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, starch, regenerated cellulose, diacetylcellulose, hydroxypropylcellulose, polyvinyl chloride, polyvinylpyrrolidone, polyethylene, polypropylene SBR (styrene-butadiene-tubeber), EPDM (ethylene-propylene-diethylene methyllinkage), sulfonated EPDM, fluororubber, polybutadiene, polyethylene oxide, especially polyacrylic acid, carboxymethylcellulose, polytetrafluoroethylene, polyfluorinated Vinylidene is preferred. These are more preferably used as an aqueous dispersion latex having a particle size of 1 micron or less.
[0041]
Separator 10 (FIG. 2) that can be used for a battery has only to have a large ion permeability, a predetermined mechanical strength, and an insulating thin film. As a material, an olefin polymer, a fluorine polymer, a cellulose polymer, Polyimide, nylon, glass fiber, and alumina (Al ₂ O ₃ ) fiber are used, and non-woven fabric, woven fabric, and microporous film are used as forms. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, or a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable.
[0042]
The electrolyte solution 15 (FIG. 2) that can be used in the battery is composed of propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl as an organic solvent. Sufoxide, dioxolane, 1,3-dioxolane, formamide, dimethylformamide, nitromethane, acetonitrile, methyl formate, methyl acetate, methyl propionate, phosphate triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2- A mixture of at least one of oxazolidinone, propylene carbonate derivative, tetrahydro derivative, diethyl ether, 1,3-propane sultone, As _{quality, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, lower aliphatic lithium _{carboxylate, LiAlCl 4, LiCl, LiBr,} LiI, chloro What melt | dissolved the 1 or more types of salt of borane lithium and lithium tetraphenylborate is preferable. In particular, a solution obtained by dissolving LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ , and / or LiPF ₆ in a mixed solvent of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate is preferable. It preferably contains carbonate and LiPF ₆ .
[0043]
The bottomed battery outer can 11 (FIG. 2) that can be used for the battery is made of steel plate, stainless steel plate (SUS304, SUS304L, SUS304N, SUS316, SUS316L, SUS430, SUS444, etc.), nickel-plated. Stainless steel plate (same as above), aluminum or an alloy thereof, nickel, titanium, and copper, and the shape is a true circular cylindrical shape, an elliptical cylindrical shape, a square cylindrical shape, or a rectangular cylindrical shape. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate and a nickel-plated steel plate are preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum, or an alloy thereof is preferable.
[0044]
The gasket 13 (FIG. 2) that can be used for the battery is made of an olefin polymer, a fluorine polymer, a cellulose polymer, a polyimide, a polyamide as a material, and an olefin polymer is preferable from the viewpoint of organic solvent resistance and low moisture permeability. A propylene-based polymer is particularly preferable. Furthermore, a block copolymer of propylene and ethylene is preferable.
[0045]
The battery is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, and a plastic case. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be known.
[0046]
A plurality of batteries are assembled in series and / or in parallel as required, and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, temperature fuses, fuses and / or current interrupting elements, the battery pack also requires safety circuits (monitoring the voltage, temperature, current, etc. of each battery and / or the entire battery pack) In this case, a circuit having a function of interrupting current may be provided. In addition to the positive and negative terminals of the entire assembled battery, the battery pack should be provided with the positive and negative terminals of each battery, the entire assembled battery, the temperature detection terminal of each battery, the current detection terminal of the entire assembled battery, etc. as external terminals. You can also. The battery pack may incorporate a voltage conversion circuit (such as a DC-DC converter). The connection of each battery may be fixed by welding a lead plate, or may be fixed so that it can be easily attached and detached with a socket or the like. Further, the battery pack may be provided with display functions such as the remaining battery capacity, the presence / absence of charging, and the number of uses.
[0047]
Batteries are used in various devices. In particular, video movie, portable video deck with built-in monitor, movie camera with built-in monitor, compact camera, single-lens reflex camera, disposable camera, film with lens, notebook computer, notebook type word processor, electronic notebook, mobile phone, cordless phone, beard, It is preferably used for electric tools, electric mixers, automobiles and the like.
[0048]
Hereinafter, the present invention will be described in more detail with specific examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.
[0049]
First, a positive electrode sheet was prepared. As shown in FIG. 1A, tapes 22a and 22b were pasted on both surfaces of a positive electrode current collector 21 made of aluminum foil with a thickness of 20 μm by a length L1 = 5 mm. Both the tapes 22a and 22b had a thickness of 40 μm. In order to form a positive electrode mixture, LiCoO ₂ (87 parts by weight) was used as an active material. Scale graphite (6 parts by weight) and acetylene black (3 parts by weight) as a conductive agent, and polytetrafluoroethylene aqueous dispersion (3 parts by weight) and sodium polyacrylate (1 part by weight) as a binder In addition to the active material, a slurry was obtained by kneading with water as a medium. The obtained slurry (positive electrode mixture 23a and 23b) was applied to both surfaces of the positive electrode current collector 21 by an extrusion method. Positive electrode mixture layers 23 a and 23 b each having a thickness of 130 μm were formed on both surfaces of the positive electrode current collector 21. After the coated material was dried, the tapes 22a and 22b were peeled off. Then, it was compression molded and cut with a calendar press machine to obtain a belt-like positive electrode having a width of 56 mm, a length of 400 mm and a thickness of 250 μm. The trouble that the positive electrode was cut by the above press did not occur.
[0050]
Next, a negative electrode sheet was prepared. Tapes 22a and 22b were affixed on both surfaces of a negative electrode current collector 21 made of copper foil and having a thickness of L1 = 0.5 mm. In order to form a negative electrode material, tin monoxide (73.3 parts by weight), silicon dioxide (19.5 parts by weight), magnesium oxide (3.5 parts by weight), and boron oxide (3.7 parts by weight) were dry-processed. After mixing and firing for 10 hours (1200 ° C.) in an argon atmosphere, the mixture was cooled and pulverized to obtain SnSi _0.6 Mg _0.2 B _0.2 O _2.7 having an average particle size of 4.5 μm as a negative electrode material.
[0051]
In order to form a negative electrode mixture, flake graphite (6 parts by weight) as a conductive agent in the above negative electrode material (88 parts by weight), an aqueous dispersion (4 parts by weight) of polyvinylidene fluoride as a binder, and carboxymethylcellulose (1 part by weight) and lithium acetate (1 part by weight) were added and kneaded using water as a medium to obtain a slurry. The obtained slurry (negative electrode mixture 23a and 23b) was applied to both surfaces of the negative electrode current collector 21 by the extrusion method, and, like the positive electrode, dried, tape peeled, compression molded, and cut, and the width was 58 mm. A strip-shaped negative electrode having a thickness of 440 mm and a thickness of 78 μm was obtained. Similar to the positive electrode, there was no trouble that the negative electrode was cut by the press.
[0052]
Prior to cutting, the positive electrode and the negative electrode obtained above were dehydrated and dried in a low-humidity atmosphere (dew point: −50 ° C.). Dehydration drying was performed at a temperature of 200 to 250 ° C. for 2 hours using a far infrared heater. Thereafter, a nickel lead plate was ultrasonically welded to the uncoated portion of the negative electrode sheet (copper current collector). Furthermore, the lead plate was ultrasonically welded to the exposed portion of the positive electrode sheet (aluminum current collector) having a thickness of 20 μm. The base material was polyimide and an adhesive tape using a silicone-based adhesive was applied to the welded portion of the lead for protection. As shown in FIG. 2, the obtained positive electrode sheet 8 with leads, microporous polyethylene film separator 10, and negative electrode sheet 9 were used and wound with a winding machine. This winding was performed smoothly and easily, and an electrode winding group with high roundness was obtained.
[0053]
The wound body was housed in a nickel-plated iron-bottomed cylindrical battery can 11 serving also as a negative electrode terminal. The electrolyte 15 contains 0.9 and 0.1 mol of LiPF ₆ and LiBF ₄ per liter, respectively, and the solvent has a volume ratio of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl propionate in a 2: 4: 3: 1 ratio. Consisting of a mixture of This electrolyte 15 was injected into the battery can 11. A battery lid 12 having a positive electrode terminal was caulked through a gasket 13 to produce a cylindrical battery. The positive electrode terminal 12 was connected to the positive electrode sheet 8 and the battery can 11 was connected to the negative electrode sheet 9 in advance by a lead terminal. The safety valve 14 was attached to the battery can 11 via the gasket 13. A battery was produced by the above method.
[0054]
This electrode sheet did not cause manufacturing troubles such as a roller press or abnormal shape during winding. A plurality of batteries were produced by changing the displacement L1 of the electrode mixture on the current collector. When the deviation L1 of the positive electrode was 0.1 mm, some of the plurality of positive electrodes were cut during pressing, and the trouble was that some of the positive electrodes were not uniform in shape and could not be inserted into the battery can. When the displacement L1 was shifted beyond 30 mm, the above trouble did not occur, but the battery capacity was greatly reduced. The deviation L1 is preferably 0.3 mm or more and 30 mm or less.
[0055]
As described above, by providing the electrode mixture layer on both surfaces of the electrode current collector by shifting the length L1 from each other, it is possible to reduce the inconvenience of the electrode sheet being cut during electrode sheet manufacture (particularly during press working). it can. Moreover, since an electrode sheet can be wound by high roundness and can be accommodated in a battery can, manufacture and performance efficiency of a battery can be made high.
[0056]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0057]
【The invention's effect】
As in the present invention, an electrode sheet having high productivity can be obtained by shifting the electrode mixture coating ends on both sides by 0.3 mm or more and 30 mm or less.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method for manufacturing an electrode sheet according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a cylindrical battery used in Examples.
FIG. 3 is a cross-sectional view showing a conventional electrode sheet.
FIG. 4 is a cross-sectional view of an electrode sheet.
[Explanation of symbols]
8 Positive electrode sheet 9 Negative electrode sheet 10 Separator 11 Battery can 12 Battery lid 13 Gasket 14 Safety valve 15 Electrolytic solution 16 PTC element 21, 51 Electrode current collector 22 Tape 23, 52 Electrode mixture

Claims (15)

An electrode sheet for a battery having a wound group of electrodes , wherein the electrode sheet is formed by applying an electrode mixture on both sides of the current collector, and the electrode sheet is disposed at both ends in the longitudinal direction of the current collector. The lower surface has an unapplied portion to which no electrode mixture is applied, and a lead is attached to at least one end of the unapplied portion, and the electrode mixture is applied to the front and back surfaces of one end where the lead is attached. An electrode sheet having an edge with a deviation of 0.3 mm or more and 30 mm or less in the longitudinal direction of the electrode sheet and produced by pressing .   The electrode sheet according to claim 1, wherein both application ends of the electrode mixture in the longitudinal direction of the electrode sheet have a deviation of 0.3 mm or more and 30 mm or less in the longitudinal direction of the electrode sheet.   The electrode sheet according to claim 1, wherein the current collector has a thickness of 5 μm or more and 30 μm or less.   The electrode sheet according to any one of claims 1 to 3, wherein the dry film thickness of the electrode mixture applied to the front and back surfaces of the electrode sheet is thicker than the thickness of the current collector.   The electrode sheet according to claim 1, wherein the electrode mixture application ends on the front and back surfaces have a deviation of 0.5 mm or more and 10 mm or less in the longitudinal direction.   5. Each end of the electrode mixture on the front and back surfaces in the longitudinal direction has a deviation of 0.3 mm or more and 30 mm or less, and each of the other ends also has a deviation of 0.3 mm or more and 30 mm or less. Electrode sheet.   Each end of the electrode mixture on the front and back surfaces in the longitudinal direction has a deviation of 0.3 mm or more and 30 mm or less, and the deviation of each other end is 0 mm or more and less than 0.3 mm. Electrode sheet.   The electrode sheet according to claim 1, wherein the current collector is made of aluminum or copper.   The electrode sheet according to claim 3, wherein the dry film thickness of the electrode mixture applied to the front and back surfaces of the electrode sheet is 30 µm or more and 400 µm or less, respectively.   The electrode sheet according to claim 5, wherein the electrode mixture application ends on the front and back surfaces have a deviation of 0.3 mm or more and 2 mm or less in the longitudinal direction.   The electrode sheet according to claim 5, wherein the electrode mixture application ends on the front and back surfaces have a deviation of 2 mm or more and 10 mm or less in the longitudinal direction. A battery having a wound group of electrodes, each of which has a positive electrode sheet and a negative electrode sheet that are pressed after applying an electrode mixture on both sides of a current collector, and at least one of the positive electrode and the negative electrode sheet However, at both ends in the longitudinal direction of the current collector, the upper and lower surfaces have an uncoated portion to which no electrode mixture is applied, and a lead is attached at least at one end of the uncoated portion. The battery which the electrode mixture application | coating end of the front and back of the attached one end has a shift | offset | difference of 0.3 mm or more and 30 mm or less, respectively in the longitudinal direction of this sheet | seat. (A) The electrode mixture is applied and dried on both sides of the current collector, and at one end in the longitudinal direction of the electrode sheet, the upper and lower surfaces of the current collector have portions where the electrode mixture is uncoated, and the Forming an electrode mixture layer in which the electrode mixture application ends on both sides are shifted from each other by 0.3 mm or more and 30 mm or less at one end;
(B) In the initial stage of press-pressing the electrode mixture layer formed on the current collector, only the current collector, the portion where the mixture layer is applied only on one side, and the mixture layer on both sides Forming an electrode sheet by press-pressing in three stages with the applied part; and
(C) winding an electrode sheet to form an electrode group;
(D) A method of manufacturing an electrode sheet, comprising: attaching a lead to the uncoated portion . The step (a)
(A-1) forming a tape on the current collector;
(A-2) forming an electrode mixture layer on the current collector so as to cover the tape,
The method for producing an electrode sheet according to claim 13, wherein the step (b) includes a step (b-1) of removing the tape together with the electrode mixture layer thereon from the current collector. (A) The electrode mixture is applied and dried on both sides of the current collector, and at one end in the longitudinal direction of the electrode sheet, the upper and lower surfaces of the current collector have portions where the electrode mixture is uncoated, and the Forming an electrode mixture layer in which the electrode mixture application ends on both sides are shifted from each other by 0.3 mm or more and 30 mm or less at one end;
(B) In the initial stage of press-pressing the electrode mixture layer formed on the current collector, only the current collector, the portion where the mixture layer is applied only on one side, and the mixture layer on both sides Forming an electrode sheet by press-pressing in three stages with the applied part; and
(C) winding an electrode sheet to form an electrode group;
(D) attaching the lead to the uncoated part;
( E ) The manufacturing method of a battery including the process of accommodating an electrode group in a battery can.

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