JPH05234620A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To lessen an reacted negative active material inside of a battery so as to improve energy density in a nonaqueous electrolyte secondary battery having a wound electrode formed by winding both strip positive electrode and strip negative electrode via a separator. CONSTITUTION:In a nonaqueous electrolyte secondary battery having a wound electrode formed by winding, thereon, via a separator a positive electrode laminated with positive electrode depolarizing mix 1b, 1c on both sides of a strip collector 1a, and a negative electrode, one side lamination part A on which the positive electrode depolarizing mix layer is laminated on only one side of the strip collector 1a, is provided on at least the outer circumference end X or the inner circumference end Y of the positive electrode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery comprising a wound electrode body in which a belt-shaped positive electrode and a belt-shaped negative electrode are wound with a separator interposed therebetween.

[0002]

2. Description of the Related Art Conventionally, nickel-cadmium batteries and lead batteries have been used as secondary batteries for electronic devices. However, in recent years, along with the progress of electronic technology, electronic devices have become higher in performance, smaller in size, and more portable, and the demand for higher energy density of secondary batteries for electronic devices has increased. A problem with cadmium batteries and lead batteries is that the discharge voltage is low and the energy density cannot be sufficiently increased.

Therefore, recently, as a secondary battery having a high discharge voltage, a small self-discharge and a long cycle life,
In place of nickel / cadmium batteries, lead batteries, etc., a material that can dope / de-dope lithium ions such as carbon material is used for the negative electrode, and a lithium composite oxide such as lithium cobalt composite oxide is used for the positive electrode. Water electrolyte secondary batteries have been actively researched and developed.

In such a non-aqueous electrolyte secondary battery, in order to obtain good characteristics such as heavy load discharge and cycle life, its electrode structure should be a wound electrode body as shown in FIG. Is generally done. That is, the strip-shaped positive electrode 1 formed of the positive electrode mixture layers 1b and 1c formed by applying the positive electrode mixture on both surfaces of the current collector 1a, and the negative electrode formed by applying the negative electrode mixture on both surfaces of the current collector 2a. A strip-shaped negative electrode 2 composed of the mixture layers 2b and 2c is wound with a separator 3 in between,
The wound electrode body 4 is formed. In this case, generally, in order to prevent an internal short circuit due to the deposition of lithium during charging,
Negative electrode 2 facing positive electrode 1 is positive electrode 1 in terms of width and length.
Formed larger than.

[0005]

However, in the conventional spirally wound electrode body 4 shown in FIG. 4, the unreacted negative electrode active material not involved in charging / discharging is formed at the outer peripheral end portion X and the inner peripheral end portion Y of the negative electrode. It has a portion containing a substance (hatched portion in the figure). Therefore, there is a problem that the inside of the battery cannot be effectively used and the energy density cannot be sufficiently increased.

The present invention is intended to solve the problems of the prior art as described above, and by reducing the unreacted negative electrode active material inside the battery and effectively utilizing the inside of the battery, the energy density is increased. An object is to provide a non-aqueous electrolyte secondary battery having a long cycle life.

[0007]

The inventor of the present invention provides a positive electrode mixture layer formed on only one side of a current collector at a peripheral end portion or an inner peripheral end portion of a positive electrode or both of them. The inventors have found that the unreacted negative electrode active material inside the battery can be reduced and the battery inside can be effectively utilized to improve the energy density, and the above object can be achieved, thus completing the present invention. ..

That is, according to the present invention, a non-aqueous electrolytic solution having a wound electrode body in which a positive electrode having a positive electrode material mixture layer laminated on both surfaces of a band-shaped current collector and a band-shaped negative electrode are wound with a separator interposed therebetween. In a secondary battery, a non-aqueous electrolyte secondary battery characterized in that at least an outer peripheral end or an inner peripheral end of a positive electrode is provided with a single-area layer portion in which a positive electrode material mixture layer is laminated only on one surface of a current collector. I will provide a.

The present invention will be described below in detail with reference to the drawings. In the drawings, the same reference numerals represent the same or equivalent constituent elements.

The non-aqueous electrolyte secondary battery of the present invention is provided at either the outer peripheral end portion or the inner peripheral end portion of the positive electrode, or as shown in FIG. A feature is that both end portions Y are provided with a single-area layer portion A in which the positive electrode material mixture layer is laminated only on one surface of the strip-shaped current collector 1a.

In this case, the length in the winding direction of the single-sided layer portion provided on the outer peripheral end of the positive electrode is 5 mm or more and 2πd ₁ or less, preferably 0.5, when the outer diameter of the wound electrode body is d _1.
πd greater than or equal to _one 2πd ₁ below. This makes it possible to improve the energy density without causing an internal short circuit. The length in the winding direction of the single-sided layer portion provided at the inner peripheral end of the positive electrode is 5 mm or more and 3πd ₂ or less when the inner diameter of the hollow portion at the center of the wound electrode body is d ₂ .
It is preferably πd ₂ or more and 3πd ₂ or less.

As a method of forming the single-area layer portion, for example, when the single-area layer portion is formed on both the outer peripheral edge portion X and the inner peripheral edge portion Y of the positive electrode 1 as shown in FIG. As shown in FIG. 2, the positive electrode mixture may be applied to only one surface of the current collector 1a at both ends of the positive electrode 1 without applying the positive electrode mixture to both surfaces of the current collector.

The non-aqueous electrolyte secondary battery of the present invention should be manufactured in the same manner as the conventional non-aqueous electrolyte secondary battery having a wound electrode body except that the positive electrode is provided with the one-sided layer portion as described above. You can

That is, the positive electrode contains Li as its active material.
_x MO ₂ (M represents one or more kinds of transition metals, preferably Co or Ni, and 0.05 ≦ x ≦ 1.10) is used to prepare a positive electrode mixture, and the mixture is formed on the current collector. It can be formed by coating. As a preferable example of the positive electrode active material,
LiCoO ₂ , LiNiO ₂ , LiNi _y Co
A complex oxide such as _(1-y) O ₂ (where 0 <y <1) can be used. In addition, such a composite oxide uses, for example, a carbonate of lithium, cobalt, or nickel as a starting material, and these carbonates are mixed according to the composition of the desired composite oxide, and the mixture is subjected to an atmosphere of oxygen of 600 to 1000.
It is obtained by firing in the temperature range of ° C. Further, even if a hydroxide or an oxide is used without using a carbonate as a starting material, a composite oxide of these can be similarly obtained.

On the other hand, the negative electrode is doped with lithium ions.
As the substance that can be dedoped, for example, a carbon material can be used. Examples of such a carbon material include pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites,
Glassy carbons, organic polymer compound fired bodies (fired products of phenol resin, furan resin, etc.), carbon fibers, activated carbon and the like can be used.

As the electrolytic solution, any conventionally known electrolytic solution can be widely used as long as it contains an electrolyte dissolved in an organic solvent. Examples of such organic solvent include propylene carbonate, ethylene carbonate,
1,2-dimethoxyethane, 1,2-dimexethane, diethyl carbonate, γ-butyl lactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-
1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be mentioned, and these can be used alone or in combination of two or more kinds. Also, as the electrolyte, LiC
_{lO 4, LiAsF 6, LiPF 6} , LiBF 6, Li
B (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃
Li, CF ₃ SO ₃ Li or the like can be used.

[0017]

According to the present invention, in a non-aqueous electrolyte secondary battery in which a positive electrode formed by laminating a positive electrode material mixture layer on both surfaces of a band-shaped current collector and a band-shaped negative electrode are wound with a separator interposed therebetween, Since the positive electrode mixture layer is formed on only one side of the current collector at both the outer peripheral edge or the inner peripheral edge or both the outer peripheral edge and the inner peripheral edge, the unreacted area inside the battery The negative electrode active material can be reduced. Therefore, the effective electrode area can be increased correspondingly, and the inside of the battery can be effectively utilized. Therefore, it is possible to improve the energy density and obtain a non-aqueous electrolyte secondary battery having a long cycle life.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings.

Example 1 As shown in FIG. 3, a positive electrode 1 and a negative electrode 2 are wound around a separator 3 to form a wound electrode body 4, which is then formed into a battery can 5.
The cylindrical non-aqueous electrolyte secondary battery housed in was manufactured as follows.

First, in producing the negative electrode 2, petroleum pitch was used as a starting material, and this was fired to obtain coarse-grained pitch coke. This coarse-grained pitch coke was crushed to obtain a powder having an average particle size of 40 μm, and subsequently, this powder was fired at 1000 ° C. in an inert gas to remove impurities to obtain a coke material powder.

The coke material powder thus obtained was used as a negative electrode active material carrier, 90 parts by weight of the coke material powder, and polyvinylidene fluoride (PVDF) 1 as a binder.
0 parts by weight was mixed to prepare a negative electrode mixture. Then, this negative electrode mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste form).

Next, the obtained negative electrode mixture slurry was made to have a thickness of 1
It is applied to both sides of the negative electrode current collector 2a, which is a 0 μm band-shaped copper foil, dried with a solvent, and compression-molded by a roller press machine, and the width is 41.5 mm, the length is 248 mm, and the thickness of the negative electrode mixture layer is one side. A strip-shaped negative electrode 2 having a thickness of 105 μm was obtained.

Further, the positive electrode 1 was obtained as follows.

That is, LiCoO ₂ was obtained by mixing 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate and baking in air at 900 ° C. for 5 hours.

Using this LiCoO ₂ as the positive electrode active material, Li
91 parts by weight of CoO ₂ , 6 parts by weight of graphite as a conductive agent, polyvinylidene fluoride (PVDF) 3 as a binder
Part by weight was mixed to obtain a positive electrode mixture. Then, this positive electrode mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste form).

Next, the positive electrode mixture slurry thus obtained was made to have a thickness of 2
A length of 210 mm is applied on one surface of the positive electrode current collector 1a, which is a 0 μm band-shaped aluminum foil, and after drying, the positive electrode mixture slurry is applied to the back surface of the positive electrode current collector 1a so that the application start position is the same as the positive electrode mixture slurry. Was applied for a length of 205 mm. This was dried and compression-molded to have a width of 39.5 mm, the length of the part where the positive electrode mixture layer was applied and formed on both sides was 205 mm, and the part where the positive electrode mixture layer was applied and formed on one side (that is, the one-sided layer of the positive electrode). Part), the thickness of the positive electrode material mixture layer is 80 μ on one side.
m strip-shaped positive electrode 1 was obtained.

As the separator 3 interposed between the strip-shaped negative electrode 2 and the strip-shaped positive electrode 1 prepared as described above, a microporous polypropylene film having a thickness of 25 μm and a width of 44 mm is used. Strip positive electrode 1,
The separator 3 is laminated in four layers in this order, and the laminated body is spirally wound many times along the length direction with the one-sided layer portion of the strip positive electrode 1 as the winding start side and the strip negative electrode 2 as the inner side. The final end of the separator 3 was fixed with a tape to prepare a wound electrode body 4. The outer diameter d ₁ of this wound electrode body 4 is 13.0 m.
m, the inner diameter d ₂ of the hollow portion in the center of the spirally wound electrode body is 3.5
It was mm.

The wound electrode body 4 thus prepared was housed in a battery case 5 made of iron plated with nickel. Also,
Insulating plates 6 are provided on both upper and lower surfaces of the spirally wound electrode body 4, and the negative electrode 2
Further, in order to collect the current of the positive electrode 1, the positive electrode lead 7 made of aluminum is drawn out from the positive electrode current collector 1a to the battery lid 8, and the negative electrode lead 9 made of nickel is drawn out from the negative electrode current collector 2a and welded to the battery can 5. did.

Then, 2.90 g of a non-aqueous electrolytic solution prepared by dissolving LiPF _{6 in a} mixed solvent of equal volumes of propylene carbonate and diethyl carbonate at a ratio of 1 mol / liter was injected into the battery can 5 to form a wound electrode. The body 4 was impregnated.

Then, the battery lid 5 was fixed by caulking the battery can 5 through the insulating sealing gasket 10 whose surface was coated with asphalt, and the airtightness inside the battery was maintained.

As described above, the diameter is 14 mm and the height is 5
A 0 mm cylindrical non-aqueous electrolyte secondary battery was prepared.

Examples 2 to 5 and Comparative Example 1 An electrode having the one-sided coating length of the outer peripheral end of the positive electrode, that is, the length of the one-sided layer portion as shown in Table 1 was used, and otherwise the same as in Example 1. A water electrolyte secondary battery was created. In this case, the outer diameter of the wound electrode body after winding the strip positive electrode and the strip negative electrode is 1
The both-side coating length of the mixture slurry was adjusted for both electrodes so as to be 3.0 mm.

Examples 6 to 8 and Comparative Example 2 An electrode having the one-side coating length of the inner peripheral end of the positive electrode, that is, the length of the one-area layer portion as shown in Table 1 was used, and otherwise the same as in Example 1. A non-aqueous electrolyte secondary battery was created. In this case, the outer diameter of the wound electrode body after winding the strip positive electrode and the strip negative electrode is 1
The both-side coating length of the mixture slurry was adjusted for both electrodes so as to be 3.0 mm.

Example 9 A non-aqueous electrode was used in the same manner as in Example 1 except that an electrode was used in which the coating length on one side of the outer peripheral edge and the inner peripheral edge of the positive electrode, that is, the length of the single-area layer was as shown in Table 1. An electrolyte secondary battery was created.
In this case, the both-side coating length of the mixture slurry was adjusted for both electrodes so that the outer diameter of the wound electrode body after winding the belt-shaped positive electrode and the belt-shaped negative electrode was 13.0 mm.

Comparative Example 3 A belt-shaped positive electrode having a double-sided coating length of 205 mm, which has no single-sided coating portion on both the outer and inner peripheral edges, and a single-sided coating portion on both the outer and inner circumferential edges. A non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except that a strip-shaped negative electrode having a double-sided coating length of 248 mm was used.

The battery prepared as described above was charged at a charging voltage of 4.10 V and a charging current of 100 mA for 8 hours, and then discharged to 2.75 V under a load of 18Ω to measure the capacity. The energy density ratio of each battery was calculated from the obtained measured values when Comparative Example 3 was set to 100, and the results are also shown in Table 1.

From Table 1, as compared with Comparative Example 3 in which the single-sided coating portion was not provided, the single-sided coating length of the outer peripheral edge portion was 5 mm (0.
The energy density is increased in Examples 1 to 5 in which the energy density is 12 πd ₁ ) or more and 80 mm (2.0 πd ₁ ) or less.
It can be seen that in Comparative Example 1 where 0 mm (2.4πd ₁ ) is set, the energy density is rather lowered. In addition, the one-sided coating length of the inner peripheral edge is 5 mm (0.4
The energy density is increased in Examples 6 to 8 in which the energy density is 5 πd ₂ ) or more and 30 mm (2.7 πd ₂ ) or less, but 50 m
In Comparative Example 2 in which m (4.6πd ₂ ), the energy density is rather lowered. And
It can be seen that the energy density was further improved in Example 9 in which the single-sided coated portions were formed on both the outer peripheral edge and the inner peripheral edge.

Further, the outer diameter of the wound electrode body is set to 18 mm or 20 mm, and the positive electrode is provided with a single-sided coating portion on the outer peripheral edge portion or the inner peripheral edge portion or both of them, as in the above-mentioned embodiment. An electrolyte secondary battery was prepared, and the energy density ratio was calculated with respect to the case where the one-sided coating portion was not provided. It was

[0039]

[Table 1] Positive electrode outer peripheral single side Positive electrode inner peripheral single side Positive electrode double side Negative electrode Energy coating length (mm) Coating length (mm) Coating length (mm) Coating length (mm) Density ratio Example 15-205 248 101.2 Example 2 20-201 244 103.0 Example 3 40-197 240 105.9 Example 4 60-182 245 103.4 Example 5 80-167 250 101.0 Comparative Example 1 100-250 255 98.5 Example 6-5 205 248 101.2 Example 7-15 202 245 102.2 Example 8-30 191 249 100.5 Comparative Example 2-50 176 254 98.0 Example 9 40 10 194 237 106.8 Example 3 --205 248 100

[0040]

According to the present invention, in a non-aqueous electrolyte secondary battery having a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, an unreacted negative electrode active material inside the battery is obtained. Since the amount of substances can be reduced and the inside of the battery can be effectively utilized, a non-aqueous electrolyte secondary battery having a high energy density and a long cycle life can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a wound electrode body of a non-aqueous electrolyte secondary battery of the present invention in a direction perpendicular to a winding axis.

FIG. 2 is a perspective view of a strip positive electrode used in the non-aqueous electrolyte secondary battery of the present invention.

FIG. 3 is a cross-sectional view in the winding axis direction of the non-aqueous electrolyte secondary battery according to the example of the present invention.

FIG. 4 is a cross-sectional view of a wound electrode body of a conventional non-aqueous electrolyte secondary battery in a direction perpendicular to a winding axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 1b, 1c Positive electrode mixture layer 2 Negative electrode 2a Negative electrode collector 2b, 2c Negative electrode mixture layer 3 Separator 4 Winding electrode body 5 Battery can A Single area layer portion X Outer peripheral edge portion Y Inner peripheral edge Department

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[Procedure amendment]

[Submission date] July 3, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In this case, the length in the winding direction of the single-sided layer portion provided on the outer peripheral end of the positive electrode is 5 mm or more and 2πd ₁ or less, preferably 0.5, when the outer diameter of the wound electrode body is d _1.
πd greater than or equal to _one 2πd ₁ below. This makes it possible to improve the energy density without causing an internal short circuit. The length in the winding direction of the single-sided layer portion provided at the inner peripheral end of the positive electrode is 5 mm or more and 3πd ₂ or less when the inner diameter of the hollow portion at the center of the wound electrode body is d ₂ .
It is preferably 0.5 πd ₂ or more and 3 πd ₂ or less.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

As the electrolytic solution, any conventionally known electrolytic solution can be widely used as long as it contains an electrolyte dissolved in an organic solvent. Examples of such organic solvent include propylene carbonate, ethylene carbonate,
1,2-dimethoxyethane, 1,2-dimexieethane, diethyl carbonate, γ-butyl lactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-
1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be mentioned, and these can be used alone or in combination of two or more kinds. Also, as the electrolyte, LiC
_{lO 4, LiAsF 6, LiPF 6} , LiBF 4, Li
B (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃
Li, CF ₃ SO ₃ Li or the like can be used.

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery having a spirally wound electrode body in which a positive electrode formed by laminating a positive electrode mixture layer on both surfaces of a strip-shaped current collector and a strip-shaped negative electrode are wound with a separator interposed therebetween. ,
A non-aqueous electrolyte secondary battery comprising: a positive electrode mixture layer formed by laminating a positive electrode material mixture layer on only one surface of a band-shaped current collector at least at an outer peripheral end or an inner peripheral end of a positive electrode. 2. When the outer diameter of the wound electrode body is d ₁ , the length in the winding direction of the single-area layer portion at the outer peripheral end of the positive electrode is 5 mm.
The non-aqueous electrolyte secondary battery according to claim _{1, wherein the} content is 2πd ₁ or less. 3. The length in the winding direction of the single-area layer portion at the inner peripheral end of the positive electrode is 5 mm or more and 3πd ₂ or less, where d ₂ is the inner diameter of the hollow portion at the center of the wound electrode body. Item 2. A non-aqueous electrolyte secondary battery according to item 1.