JP2008262827A - Coin-shaped nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coin-shaped nonaqueous electrolytic solution secondary battery high in discharge load characteristics and free of deformation of the battery accompanied with charge and discharge. <P>SOLUTION: As for the coin-shaped nonaqueous electrolytic solution secondary battery, a cylindrical wound body 10 is constituted by means that a belt form positive electrode 1 and a belt form negative electrode 2 are wound via a belt form separator 3, the wound shaft of the wound body 10 is the same as the height direction of a battery can 13, the ratio D/H between the outer diameter D (mm) of the wound body 10 and the height H (mm) of the wound-around shaft of the wound body 10 is 1-25, and when the longest positive electrode active material applying length is L (mm), the cross-sectional area of the positive electrode 1 is B (mm<SP>2</SP>), and the number of the positive electrode lead is n, these ratio L/(B×n) is 2,000-8,000. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coin-type non-aqueous electrolyte secondary battery having high discharge load characteristics.

  Coin-type non-aqueous electrolyte secondary batteries, typified by coin-type lithium ion secondary batteries, are also called button-type or flat-type non-aqueous electrolyte secondary batteries. Headphone sets, clock-type communication devices, body-mounted medical care It is attracting attention as a small battery for heavy loads used in so-called wearable devices worn by people such as devices.

  As a conventional coin-type lithium ion secondary battery, for example, there is a battery using an electrode body in which a positive electrode and a negative electrode punched in a circle are stacked one by one via a separator. However, in this type of battery, since the electrode becomes thick, the diffusion resistance of lithium ions in the thickness direction of the electrode increases, and there is a disadvantage that the discharge load characteristic is deteriorated, which can be used only for low-power applications. There is.

In order to solve the above problem, a method of thinning an electrode by using an electrode body obtained by winding a belt-like positive electrode and a belt-like negative electrode through a belt-like separator has been proposed (for example, Patent Documents). 1, see Patent Literature 2, Patent Literature 3, and Patent Literature 4.)
JP 2003-77543 A JP 2005-310578 A JP-A-11-345626 JP 11-354150 A

  In the batteries proposed in Patent Document 1 and Patent Document 2, a belt-like positive electrode and a belt-like negative electrode are wound through a belt-like separator to form an electrode body, and the electrode body is formed into a flat shape. Thereafter, the electrode body is inserted into the battery can in a state where the winding axis direction of the electrode body and the height direction (thickness direction) of the battery can are orthogonal to each other. In this case, since the electrode body in the battery can is formed in a square shape when viewed from the height direction of the battery, there is a problem that a gap is generated between the electrode body and the battery can, resulting in a volume loss. Moreover, in this electrode structure, since the expansion / contraction direction of the electrode accompanying charging / discharging of the battery coincides with the height direction of the battery can, the battery may be deformed in the height direction when charging / discharging is repeated.

  On the other hand, in the batteries proposed in Patent Document 3 and Patent Document 4, since the winding axis direction of the electrode body and the height direction of the battery can are the same, there is a gap between the electrode body and the battery can. In addition, since the expansion / contraction direction of the electrode accompanying charging / discharging of the battery coincides with the radial direction of the battery can, there is no possibility that the battery will be deformed even if charging / discharging is repeated.

  However, Patent Document 3 and Patent Document 4 merely disclose an electrode structure, and do not disclose any specific configuration for improving heavy load characteristics. Of course, neither Patent Document 1 nor Patent Document 2 discloses any specific configuration for improving heavy load characteristics.

  The present invention solves the above problems and provides a coin-type non-aqueous electrolyte secondary battery having high discharge load characteristics.

The coin-type non-aqueous electrolyte secondary battery of the present invention is a coin-type non-aqueous electrolyte secondary battery including a strip-shaped positive electrode, a strip-shaped negative electrode, a strip-shaped separator, and a coin-shaped battery can, The positive electrode and the negative electrode are wound through the separator to form a cylindrical wound body, and the winding axis direction of the wound body is the same as the height direction of the battery can, A ratio D / H between an outer diameter D (mm) of the wound body and a height H (mm) in the winding axis direction of the wound body is 1 to 25, and at least one positive electrode is provided. A positive electrode active material layer is formed on one surface of the positive electrode current collector, and a second positive electrode active material layer is formed on the other surface of the positive electrode current collector. The longest coating length selected from the coating length of the first positive electrode active material layer and the coating length of the second positive electrode active material layer is L (mm), and the cross section of the positive electrode The B (mm ^2), When the number of the positive electrode lead n, the ratios L / (B × n), characterized in that 2,000 to 8,000.

  According to the present invention, it is possible to provide a coin-type non-aqueous electrolyte secondary battery that has high discharge load characteristics and does not deform the battery due to charge / discharge.

  Hereinafter, embodiments of the coin-type non-aqueous electrolyte secondary battery of the present invention will be described.

  A coin-shaped non-aqueous electrolyte secondary battery of the present invention includes a strip-shaped positive electrode, a strip-shaped negative electrode, a strip-shaped separator, and a coin-shaped battery can, and the positive electrode and the negative electrode are wound through the separator. Thus, a cylindrical wound body is formed. With this structure, the electrode can be made thin and the discharge load characteristics can be improved to some extent.

  Further, the winding axis direction of the wound body is the same as the height direction of the battery can. With this structure, the expansion / contraction direction of the electrode coincides with the radial direction of the battery can that is strong in strength, and deformation of the battery can be prevented even when charging and discharging are repeated.

  The ratio D / H (flatness) between the outer diameter D (mm) of the wound body and the height H (mm) of the wound body in the winding axis direction is set to 1 to 25. . If D / H is less than 1, it cannot be said to be a coin-type battery, and is not suitable for a coin-type non-aqueous electrolyte secondary battery for a wearable device that is thin and small and requires a high capacity.

  Moreover, when D / H exceeds 25, it deviates from the tolerance | permissible_range of a normal battery design. That is, since the electrode width that can withstand the manufacturing process of winding the electrode needs to be at least about 2 mm, the minimum value of the height H in the winding axis direction of the wound body is 2 mm. In addition, the maximum value of the outer diameter D of the wound body is considered to be 50 mm from the size of the device on which the battery is mounted. For this reason, the maximum value of D / H is 25. Furthermore, in view of the battery capacity required for the device on which the battery is mounted, the D / H is more preferably 1.5 to 23.

The positive electrode includes at least one positive electrode lead, a first positive electrode active material layer is formed on one surface of the positive electrode current collector, and a second positive electrode current collector is formed on the other surface of the positive electrode current collector. 2 positive electrode active material layers are formed, and the longest coating length selected from the coating length of the first positive electrode active material layer and the coating length of the second positive electrode active material layer (the coating length of the first positive electrode active material layer and the second positive electrode active material layer). When the coating length of the material layer is the same, if any coating length) is L (mm), the cross-sectional area of the positive electrode is B (mm ² ), and the number of positive electrode leads is n, these ratios L / (B × n) is set to 2000 to 8000, more preferably 3000 to 5000. As a result, the discharge load characteristics can be further improved, and the battery is optimal as a battery for various devices that require heavy load characteristics.

  The discharge load characteristics depend on the electrical resistance in the longitudinal direction of the positive electrode active material layer and the electrical resistance in the thickness direction of the positive electrode active material layer. The shorter the distance L / n between the positive electrode leads, The larger the area B, the better.

  However, when the electrode is housed in a battery can having a constant inner diameter and height, if the thickness of the positive electrode active material layer is reduced in order to reduce the electric resistance in the thickness direction of the positive electrode active material layer, the battery capacity is reduced. In order to ensure it, it is necessary to increase the length of the positive electrode, and the resistance value in the longitudinal direction of the positive electrode increases. Further, if the number of positive electrode leads is increased in order to shorten the distance between the positive electrode leads, the volume other than the power generation element increases, which not only causes a decrease in battery capacity, but also complicates the manufacturing process. On the other hand, when the length of the positive electrode is shortened, it is necessary to increase the thickness of the positive electrode active material layer in order to ensure battery capacity, and the resistance value in the thickness direction of the positive electrode active material layer increases. In addition, if the width dimension of the positive electrode is increased to increase the area of the positive electrode, there is a problem that the height dimension of the battery increases.

  Therefore, in the coin type non-aqueous electrolyte secondary battery of the present invention, the relationship L / (B × n) between the longitudinal dimension, width dimension, thickness dimension of the positive electrode and the distance between the positive electrode leads is set to 2000 to 8000. It has been found that the discharge load characteristics can be improved.

The volume of the coin-type non-aqueous electrolyte secondary battery of the present invention is preferably 1 cm ³ or more and 7 cm ³ or less. Within this range, it is optimal as a coin-type non-aqueous electrolyte secondary battery for wearable devices that are thin and small and require high capacity.

  Furthermore, in the coin-type non-aqueous electrolyte secondary battery of the present invention, the outer diameter of the battery can is preferably 20 mm or more and 50 mm or less. Within this range, it is optimal as a coin-type non-aqueous electrolyte secondary battery for a wearable device that is thin and small and requires a high capacity as described above.

  Next, an example of the coin type non-aqueous electrolyte secondary battery of the present invention will be described with reference to the drawings. However, in FIGS. 1-10, the same code | symbol is attached | subjected to the same part and the overlapping description may be abbreviate | omitted.

  FIG. 1 is a perspective view of a wound body used in the present invention. In FIG. 1, a wound body 10 is produced by winding a belt-like positive electrode and a belt-like negative electrode through a belt-like separator.

  The positive electrode is obtained by applying a positive electrode mixture paste obtained by sufficiently kneading a mixture containing a positive electrode active material, a positive electrode conductive additive, a positive electrode binder, and the like onto both surfaces of the positive electrode current collector. After drying, the positive electrode mixture layer can be formed by controlling to a predetermined thickness and a predetermined electrode density.

Examples of the positive electrode active material include lithium cobalt oxides such as LiCoO ₂ , lithium manganese oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO _2, etc., and can absorb and release lithium ions. If it is, it will not be limited to these.

  The positive electrode current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the battery. As the positive electrode current collector, for example, an aluminum foil or the like is used.

  One end of the positive electrode current collector is provided with a current collector exposed portion not coated with the positive electrode mixture paste, and the positive electrode lead 11 is formed by folding back the current collector exposed portion. The current collector exposed portions may be provided at both end portions of the current collector, and the positive electrode lead may be provided at both end portions of the current collector. Further, instead of the positive electrode lead formed by folding the current collector exposed portion, a tab as a separate part may be welded to one end portion or both end portions of the positive electrode current collector to form a positive electrode lead.

  The negative electrode is obtained by applying a negative electrode mixture paste obtained by sufficiently adding a solvent to a mixture containing a negative electrode active material, a negative electrode conductive additive, a negative electrode binder, and the like on both surfaces of a negative electrode current collector. After drying, the negative electrode mixture layer can be formed by controlling to a predetermined thickness and a predetermined electrode density.

  Examples of the negative electrode active material include carbon materials such as natural graphite or artificial graphite such as massive graphite, flaky graphite, and earthy graphite, but are not limited thereto as long as lithium ions can be occluded / released. .

  The negative electrode current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the constituted battery. For example, a copper foil or the like is used as the negative electrode current collector.

  A current collector exposed portion not coated with the negative electrode mixture paste is provided at one end portion of the negative electrode current collector, and the negative electrode lead 12 is formed by folding the current collector exposed portion. The current collector exposed portions may be provided at both end portions of the current collector, and the negative electrode lead may be provided at both end portions of the current collector. Furthermore, instead of the negative electrode lead formed by folding back the exposed portion of the current collector, a tab as a separate part may be welded to one or both ends of the negative electrode current collector to form a negative electrode lead.

  In FIG. 1, the positive electrode lead 11 is provided on the outer peripheral side of the wound body 10, and the negative electrode lead 12 is provided on the inner peripheral side of the wound body 10, but the positive electrode lead 11 is provided on the inner peripheral side of the wound body 10, The negative electrode lead 12 may be provided on the outer peripheral side of the wound body 10, and both the positive electrode lead 11 and the negative electrode lead 12 may be provided on the outer peripheral side of the wound body 10.

  As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Moreover, what has the function to block | close a micropore and to raise resistance above a fixed temperature (100-140 degreeC) is preferable from the point of the safety | security improvement of a battery. Specifically, as the separator, a sheet, a nonwoven fabric, a woven fabric, or an olefin-based particle made of an olefin-based polymer or glass fiber such as polypropylene and polyethylene having organic solvent resistance and hydrophobicity is fixed with an adhesive. A porous body layer or the like is used.

  FIG. 2 is a perspective view showing a process of inserting the wound body 10 into the cylindrical battery can 13. The wound body 10 is inserted into the battery can 13 such that the winding axis direction N is the same as the height direction M of the battery can 13. The battery can 13 is made of aluminum or the like. A lower insulating plate (not shown) is disposed at the bottom of the battery can 13. The material of the lower insulating plate is not particularly limited, and a polymer material such as polyphenylene sulfide (PPS) can be used.

  FIG. 3 is a perspective view illustrating a process in which the upper insulating plate 14 is disposed on the wound body 10 after the wound body 10 is inserted into the battery can 13. The material of the upper insulating plate 14 can be the same material as the lower insulating plate.

  FIG. 4 is a perspective view of a state in which the upper insulating plate 14 is placed on the wound body 10 and the back of the negative terminal 16 disposed at the center of the lid 15 and the negative lead 12 are welded. The lid 15 and the negative electrode terminal 16 are insulated by an insulating packing 17. As the material of the lid 15, aluminum or the like is used similarly to the battery can 13. The material of the negative electrode terminal 16 is nickel or the like. The insulating packing 17 can be made of a polymer material such as polypropylene (PP).

  FIG. 5A is a perspective view of a state in which the battery can 13 and the lid 15 are joined by laser welding or the like. 5B is a cross-sectional view taken along line BB in FIG. 5A. In FIG. 5B, the wound body 10 is housed in a sealed container formed by a lid 15 and a battery can 13, and a lower insulating plate 19 is disposed at the bottom of the battery can 13. However, in FIG. 5B, the inner peripheral side portion of the wound body 10 is not cross-sectional. As described above, the wound body 10 has a structure in which the strip-shaped positive electrode 1 and the strip-shaped negative electrode 2 are wound in a spiral shape with the strip-shaped separator 3 interposed therebetween. The positive electrode lead 11 is joined in a state of being sandwiched between the battery can 13 and the lid 15. Thereby, the battery can 13 and the lid | cover 15 function as a positive electrode terminal. However, depending on the material of the battery can 13, the battery can 13 and the lid 15 may be a negative electrode. Finally, an electrolytic solution is injected from the injection port 18, and the injection port 18 is sealed by a sealing body (not shown), thereby completing a coin-type non-aqueous electrolyte secondary battery.

Examples of the electrolyte include vinylene carbonate (VC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), the organic solvent of γ- butyrolactone to one or more kinds mixed solvent, for example, at least one lithium salt selected from _{LiClO 4, LiPF 6, LiBF 4} , LiAsF 6, LiSbF 6, LiCF 3 SO 3 , etc. An electrolytic solution in which is dissolved may be used. The concentration of Li ions in the electrolytic solution may be 0.5 to 1.5 mol / L.

FIG. 6 is a schematic diagram of the wound body 10. In FIG. 6, illustration of the positive electrode lead and the negative electrode lead is omitted. The ratio D / H between the outer diameter D (mm) of the wound body 10 and the height H (mm) in the winding axis direction of the wound body 10 is set to 1 to 25. The ratio R / A between the area A (mm ² ) of the upper surface portion of the wound body 10 and the effective reaction area R (mm ² ) where the positive electrode and the negative electrode face each other is set to 9 to 25. Is preferred.

FIG. 7 is a schematic diagram of a positive electrode for explaining parameters of the present invention. In FIG. 7, the first positive electrode active material layer 22 and the second positive electrode active material layer 23 formed shorter than the first positive electrode active material layer 22 are formed on both surfaces of the positive electrode current collector 21 of the belt-like positive electrode 20. Has been. The end portion of the positive electrode current collector 21 where the positive electrode active material layer is not formed is bent to form a positive electrode lead 24. Here, when the length of the first positive electrode active material layer 22 is L (mm), the length of the second positive electrode active material layer 23 is J (mm), and the width of the positive electrode current collector 21 is W (mm), The effective reaction area R (mm ² ) is R = (L + J) × W.

Further, assuming that the cross-sectional area of the positive electrode 20 including the positive electrode current collector 21, the first positive electrode active material layer 22, and the second positive electrode active material layer 23 is B (mm ² ) and the number of positive electrode leads is n, the ratio L / (B × n) is set to 2000 to 8000.

8 is a cross-sectional view taken along the line II of FIG. FIG. 9 is a sectional view taken along line II-II in FIG. Here, assuming that the cross-sectional area of the positive electrode lead 24 is C (mm ² ), the number of positive electrode leads is n, and the cross-sectional area of the positive electrode current collector 21 is S (mm ² ), these ratios (C × n) / S Is preferably 1 or more.

  FIG. 10 is a perspective view showing another form of the positive electrode lead of FIG. In FIG. 10, the positive electrode lead 25 is formed by welding a tab to the end of the positive electrode current collector 21. Even in the embodiment of FIG. 10, the preferred ranges of the ratio L / (B × n) and ratio (C × n) / S are the same.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to a following example.

Example 1
<Preparation of positive electrode>
LiCoO _{2 as a} positive electrode active material: 80 parts by weight, acetylene black as a conductive auxiliary agent: 10 parts by weight, polyvinylidene fluoride (PVDF) as a binder: 5 parts by weight, N-methyl-2-pyrrolidone ( NMP) was added as a solvent and mixed uniformly to prepare a positive electrode mixture-containing paste. This positive electrode mixture-containing paste was applied to both surfaces of an aluminum foil having a thickness of 20 μm serving as a positive electrode current collector so that the active material application length on the front surface side was 1221 mm and the active material application length on the back surface side was 1155 mm. Dried. Thereafter, calendering was performed, the thickness of the electrode was adjusted so that the total thickness was 134 μm, and the electrode was cut so as to have a width of 3.0 mm to produce a strip-like positive electrode. Active material uncoated portions are formed at both ends of the produced belt-like positive electrode.

  Here, the surface side of the positive electrode current collector refers to the outer peripheral side when the wound body is formed, and the back surface side refers to the inner peripheral side when the wound body is formed. The same applies to the current collector.

<Production of negative electrode>
A negative electrode mixture-containing paste was prepared by adding NMP as a solvent to graphite: 90 parts by weight of negative electrode active material and PVDF: 5 parts by weight of binder and mixing uniformly. This negative electrode mixture-containing paste was applied to both sides of a 12 μm thick copper foil serving as a negative electrode current collector so that the active material application length on the front surface side was 1207 mm and the active material application length on the back surface side was 1207 mm. Dried. Thereafter, calendering was performed, the thickness of the electrode was adjusted so that the total thickness was 142 μm, and the electrode was cut so as to have a width of 3.5 mm to produce a strip-shaped negative electrode. Active material uncoated portions are formed at both ends of the produced strip-shaped negative electrode.

<Production of wound body>
A separator made of a polyethylene microporous film having a thickness of 20 μm and a width of 4.3 mm was placed between the belt-like positive electrode and the negative electrode prepared as described above, and wound to prepare a wound body. The wound body was formed so that all the positive electrode active material application portions on both sides of the positive electrode were opposed to the negative electrode active material application portions. Next, the aluminum foil in the positive electrode active material uncoated portion was folded back from the end on the outer peripheral side of the wound body, and one positive electrode lead was formed. Further, the copper foil in the negative electrode active material uncoated portion was folded back from the end on the inner peripheral side (center side) of the wound body to form one negative electrode lead.

The wound body produced had an outer diameter D of 23.5 mm, a wound body height H of 3.7 mm, and a ratio D / H thereof of 6.4. Further, the longest active material application length L of the positive electrode was 1221 mm, the cross-sectional area B of the positive electrode was 0.402 mm ² , the number n of positive electrode leads was 1, and the ratio L / (B × n) was 3037.

<Preparation of electrolyte>
An electrolyte solution was prepared by dissolving LiPF _{6 in an amount} of 1.2 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC: DEC mixed volume ratio is 1: 2).

<Production of battery>
An aluminum battery can having an outer diameter of 24 mm, a height of 5.0 mm, a side surface thickness of 0.25 mm, and a bottom surface thickness of 0.3 mm, and an aluminum lid having a diameter of 24 mm and a thickness of 0.4 mm were prepared. In the center of the lid, a nickel negative electrode terminal having a diameter of 6 mm is fitted through a polypropylene packing. Next, a PPS lower insulating plate having a thickness of 0.05 mm is disposed at the bottom of the battery can, and then the winding axis direction of the winding body is the same as the height direction of the battery can. The wound body was inserted into the battery can. Next, after placing an upper insulating plate made of PPS having a thickness of 0.05 mm on the upper part of the wound body, the negative electrode lead was welded to the back side of the negative electrode terminal. Thereafter, the battery can and the lid were joined by laser welding while the positive electrode lead was sandwiched between the battery can and the lid.

Finally, the electrolyte solution is injected from a 1.5 mm diameter injection port provided on the lid, and after the electrolyte solution is sufficiently infiltrated into the electrode body, a sealing pin is inserted into the injection port and the laser is inserted. Sealing was performed by welding to produce a coin-type lithium ion secondary battery having a battery volume of 2.3 cm ³ .

(Example 2)
<Preparation of positive electrode>
The positive electrode current collector was the same as in Example 1 except that the thickness of the positive electrode current collector was 25 μm, the active material coating length was 678 mm on the front surface side, 624 mm on the back surface side, the total thickness after calendar treatment was 162 μm, and the width was 2.0 mm. Was made.

<Production of negative electrode>
A negative electrode current collector as in Example 1, except that the thickness of the negative electrode current collector was 20 μm, the active material coating length was 667 mm on the front surface side, 667 mm on the back surface side, the total thickness after calendering was 177 μm, and the width was 2.5 mm. Was made.

The battery volume was 1.3 cm ^{3 in the same} manner as in Example 1 except that the positive electrode and the negative electrode were used, the separator width was 3.3 mm, and a battery can with an outer diameter of 20 mm and a height of 4.0 mm was used. A coin type non-aqueous electrolyte secondary battery was prepared.

The outer diameter D of the wound body of this example was 19.5 mm, the height H of the wound body was 2.7 mm, and the ratio D / H thereof was 7.2. Further, the longest active material coating length L of the positive electrode was 678 mm, the cross-sectional area B of the positive electrode was 0.324 mm ² , the number n of positive electrode leads was 1, and the ratio L / (B × n) was 2093.

(Example 3)
<Preparation of positive electrode>
A positive electrode was produced in the same manner as in Example 1 except that the active material coating length was 3146 mm on the front surface side, 3047 mm on the back surface side, the total thickness after the calendar treatment was 115 μm, and the width was 3.5 mm.

<Production of negative electrode>
A negative electrode was produced in the same manner as in Example 1 except that the active material coating length was 2734 mm on the front surface side, 3734 mm on the back surface side, the total thickness after calendar treatment was 142 μm, and the width was 4.0 mm.

The battery volume was 5.3 cm ^{3 in the same} manner as in Example 1 except that the positive electrode and the negative electrode were used, the battery width was 4.8 mm, the outer diameter was 35 mm, and the height was 5.5 mm. A coin type non-aqueous electrolyte secondary battery was prepared.

The outer diameter D of the wound body of this example was 34.5 mm, the height H of the wound body was 4.2 mm, and the ratio D / H thereof was 8.2. Further, the longest active material coating length L of the positive electrode was 3146 mm, the cross-sectional area B of the positive electrode was 0.403 mm ² , the number n of positive electrode leads was 1, and the ratio L / (B × n) thereof was 7816.

Example 4
<Preparation of positive electrode>
A positive electrode was produced in the same manner as in Example 1 except that the active material coating length was 1966 mm on the front surface side, 1902 mm on the back surface side, and the total thickness after the calendar treatment was 77 μm.

<Production of negative electrode>
A negative electrode was produced in the same manner as in Example 1 except that the active material coating length was 1950 mm on the front surface side, 1950 mm on the back surface side, and the total thickness after the calendar treatment was 78 μm.

Using the positive electrode and the negative electrode, the aluminum foil in the positive electrode active material uncoated part is folded back from the outer peripheral side end and the inner peripheral side end of the wound body to form two positive leads. A coin-type nonaqueous electrolyte secondary battery with a battery volume of 2.3 cm ³ was produced in the same manner as in Example 1 except that.

The outer diameter D of the wound body of this example was 23.5 mm, the height H of the wound body was 3.7 mm, and the ratio D / H thereof was 6.4. Further, the longest active material coating length L of the positive electrode was 1966 mm, the cross-sectional area B of the positive electrode was 0.231 mm ² , the number n of positive electrode leads was 2, and the ratio L / (B × n) was 4255.

(Comparative Example 1)
The aluminum foil in the positive electrode active material-uncoated part was folded back and taken out from the end on the outer peripheral side of the wound body, and a single positive electrode lead was formed. A 3 cm ³ coin-type non-aqueous electrolyte secondary battery was produced.

The outer diameter D of the wound body of this comparative example was 23.5 mm, the height H of the wound body was 3.7 mm, and the ratio D / H thereof was 6.4. Further, the longest active material coating length L of the positive electrode was 1966 mm, the cross-sectional area B of the positive electrode was 0.231 mm ² , the number n of positive electrode leads was 1, and the ratio L / (B × n) was 8511.

(Comparative Example 2)
<Preparation of positive electrode>
The positive electrode current collector was the same as in Example 1 except that the thickness of the positive electrode current collector was 25 μm, the active material coating length was 603 mm on the front surface side, 548 mm on the back surface side, the total thickness after calendering was 185 μm, and the width was 2.0 mm. Was made.

<Production of negative electrode>
The negative electrode current collector was 20 μm, the active material coating length was 592 mm on the front surface side, 592 mm on the back surface side, the total thickness after calendar treatment was 203 μm, and the width was 2.5 mm. Was made.

The battery volume was 1.3 cm ^{3 in the same} manner as in Example 1 except that the positive electrode and the negative electrode were used, the separator width was 3.3 mm, and a battery can with an outer diameter of 20 mm and a height of 4.0 mm was used. A coin type non-aqueous electrolyte secondary battery was prepared.

The outer diameter D of the wound body of this comparative example was 19.5 mm, the height H of the wound body was 2.7 mm, and the ratio D / H thereof was 7.2. Further, the longest active material application length L of the positive electrode was 603 mm, the cross-sectional area B of the positive electrode was 0.370 mm ² , the number n of positive electrode leads was 1, and the ratio L / (B × n) was 1630.

  Tables 1 and 2 collectively show the dimensions of the positive and negative electrodes of Examples 1 to 4 and Comparative Examples 1 and 2.

  Table 3 and Table 4 show battery parameters and electrode parameters of Examples 1 to 4 and Comparative Examples 1 and 2.

<Evaluation of battery characteristics>
About each battery of Examples 1-4 and Comparative Examples 1 and 2, the constant current charge was performed to 4.3V at 0.2C, and the constant voltage charge was performed until the electric current value was set to 0.02C after that. Next, constant current discharge was performed to 0.2V at 0.2 C, and the initial capacity (a) was obtained. Note that “C” means a current value when the design capacity of the battery is discharged in one hour.

  Subsequently, each battery was subjected to constant current charging at 0.2 C to 4.3 V, and thereafter, constant voltage charging was performed until the current value reached 0.02 C. Next, a constant current discharge was performed at 2C up to 3.0 V to obtain a heavy load capacity (b).

  From the above results, the capacity retention ratio Z (%) was obtained from the following formula and evaluated as discharge load characteristics.

  Z = (b / a) × 100

  The battery characteristics are shown in Table 5 together with parameter D / H and parameter L / (B × n).

<Evaluation of cycle characteristics>
The charge / discharge cycle test was conducted as follows. For each battery, constant current charging was performed at 0.5 C to 4.3 V, and then constant voltage charging was performed until the current value reached 0.02 C. Discharge performed constant current discharge to 3.0V at 1C. This charging / discharging was repeated up to 200 cycles as one cycle. Next, the appearance of the battery was visually observed to confirm whether the battery was deformed. The results are shown in Table 5.

  From Table 5, Examples 1 to 4 in which the parameter L / (B × n) is within the range of 2000 to 8000 are compared with Comparative Examples 1 and 2 that are outside the range, capacity retention rate Z (heavy load characteristics). Is high. Further, in each of the batteries of Examples 1 to 4 and Comparative Examples 1 and 2, no deformation of the battery was observed even when charging / discharging was repeated 200 times.

  As described above, the present invention can provide a coin-type non-aqueous electrolyte secondary battery having high discharge load characteristics and no battery deformation due to charge / discharge. This coin-type non-aqueous electrolyte secondary battery can be widely used not only as a power source for wearable devices but also as a power source for various devices.

It is a perspective view of the winding body used for this invention. It is a perspective view which shows the process of inserting the winding body in the cylindrical battery can. It is a perspective view which shows the process of arrange | positioning an upper insulating board on a winding body, after inserting a winding body in a battery can. It is a perspective view in the state where the upper insulating plate was placed on the winding body and the back of the negative electrode terminal arranged at the center of the lid and the negative electrode lead were welded. FIG. 5A is a perspective view of a state in which a battery can and a lid are joined by laser welding or the like, and FIG. 5B is a cross-sectional view taken along line BB of FIG. 5A. It is a schematic diagram of a wound body. It is a schematic diagram of the positive electrode for demonstrating the parameter of this invention. It is sectional drawing of the II line | wire of FIG. It is sectional drawing of the II-II line | wire of FIG. It is a perspective view which shows the other form of the positive electrode lead of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 10 Winding body 11 Positive electrode lead 12 Negative electrode lead 13 Battery can 14 Upper insulating plate 15 Lid 16 Negative electrode terminal 17 Insulating packing 18 Injection port 19 Lower insulating plate 20 Positive electrode 21 Positive electrode collector 22 First positive electrode Active material layer 23 Second positive electrode active material layer 24 Positive electrode lead 25 Positive electrode lead

Claims (5)

A coin-shaped non-aqueous electrolyte secondary battery including a strip-shaped positive electrode, a strip-shaped negative electrode, a strip-shaped separator, and a coin-shaped battery can,
The positive electrode and the negative electrode are wound through the separator to form a cylindrical wound body,
The winding axis direction of the wound body is the same as the height direction of the battery can,
The ratio D / H between the outer diameter D (mm) of the wound body and the height H (mm) in the winding axis direction of the wound body is 1 to 25,
The positive electrode comprises at least one positive electrode lead,
A first positive electrode active material layer is formed on one surface of the positive electrode current collector,
A second positive electrode active material layer is formed on the other surface of the current collector of the positive electrode,
The longest coating length selected from the coating length of the first positive electrode active material layer and the coating length of the second positive electrode active material layer is L (mm), the cross-sectional area of the positive electrode is B (mm ² ), A coin-type non-aqueous electrolyte secondary battery in which the ratio L / (B × n) is 2000 to 8000, where n is the number.   The coin-type nonaqueous electrolyte secondary battery according to claim 1, wherein the ratio D / H is 1.5 to 23. The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein a volume of the coin-type non-aqueous electrolyte secondary battery is 1 cm ³ or more and 7 cm ³ or less.   The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein an outer diameter of the battery can is 20 mm or more and 50 mm or less.   The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode and the negative electrode are capable of inserting and extracting lithium ions.

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