JP2011216297A - Wound electrode group, battery including the same, and method of manufacturing battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wound electrode group which includes a winding core, exhibits excellent absorption property and retention property of an electrolyte, and can reduce its size and cost.SOLUTION: The wound electrode group includes the conductive winding core, a first electrode and a second electrode wound around the winding core, and a separator for separating the first electrode and the second electrode. The first electrode includes a band-like first collector, and a first active material layer formed on the first collector. The second electrode includes a band-like second collector, and a second active material layer formed on the second collector. Arithmetic mean roughness Ra of the first active material layer is 0.5-10 μm, and a thickness of the first active material layer is 20-60 μm. The first electrode and second electrode include a part A for exposing the first collector or the second collector. The part A is welded to the winding core.

Description

  The present invention relates to a battery including a wound electrode group having a conductive core, and more particularly to an improvement of the wound electrode group.

In recent years, with the demand for miniaturization of portable electronic devices such as mobile phones, further miniaturization and higher energy density are demanded for batteries as driving power sources.
Conventionally, in a battery equipped with a wound electrode group, after the electrode group is configured, the core of the electrode group is hollow because the winding core is extracted from the center of the electrode group. In order to reduce the size of this battery, a cylindrical battery has been developed in which an electrode group is configured by using either a positive electrode or a negative electrode as a current collector without pulling out the core and electrically connecting either the positive electrode or the negative electrode to the core. .

In such a battery, one end of the winding core is exposed to the outside of the battery, and the exposed portion also serves as an external terminal. For this reason, the process of connecting a current collector to an external terminal is unnecessary, and the process can be simplified. Space for connecting external terminals is not required, and the battery can be easily downsized.
On the other hand, there is a winding core in the center of the electrode group, and a sufficient space cannot be secured in the battery case. Therefore, after inserting the electrode group into the battery case, a sufficient amount of electrolyte solution is put in the battery case. It is difficult to inject. Even if the electrolytic solution can be injected, it is necessary to inject the electrolytic solution little by little so as not to overflow the battery case, and a long time is required for the electrolytic solution injection process.
Therefore, conventionally, in such a battery, the electrode group is inserted into the case after injecting the electrolyte into the battery case. However, if the electrode group is inserted into the battery case after pre-injecting the amount of the electrolyte necessary to obtain stable and good battery characteristics into the battery case, the electrode group will not readily absorb the electrolyte solution. In some cases, the liquid overflows and flows out of the battery case.
In order to prevent the electrolyte from overflowing, it is conceivable to reduce the volume ratio of the electrode group to the internal volume of the battery case, but this causes a problem that the amount of active material decreases and the battery capacity decreases.

Various studies have been conducted on the injection of an electrolyte into a wound electrode group having a winding core.
For example, in Patent Document 1, in a battery including a first electrode, a second electrode, and an electrode group wound with a separator interposed between the first electrode and the second electrode, the first electrode and the second electrode It has been proposed to arrange a member for forming a gap for supplying an electrolytic solution between at least one of the two electrodes and the separator on the surface of at least one of the first electrode and the second electrode. For example, a wire is used as the member. Thereby, electrolyte solution can be rapidly inject | poured and a battery characteristic can be improved.

  In Patent Document 2, in the non-aqueous electrolyte secondary battery including the wound electrode group having the above-described winding core, a portion where the current collector is exposed at the negative electrode is provided in order to weld the negative electrode to the winding core. It has been proposed to form a hole for holding the electrolyte in that portion.

JP 2001-52678 A JP 2008-243704 A

In the battery of Patent Document 1, since a member for forming a void is disposed, it is difficult to secure a volume ratio occupied by an electrode group necessary for obtaining a sufficient capacity. The capacity may decrease due to a decrease in volume ratio (active material amount) occupied by the electrode group. In particular, in a small battery having an electrode group with a diameter of 20 mm or less (particularly 10 mm or less), the volume ratio of the electrode group to the internal volume of the battery case is high, so it is extremely difficult to dispose a member that forms a gap. is there.
If the member is made small (thinning the wire) in order to secure the volume ratio occupied by the electrode group, the gap for supplying the electrolytic solution becomes small, and it becomes difficult to quickly inject the electrolytic solution. In particular, in a small battery, it is difficult to use the member described in Patent Document 1.
In addition, since a member for forming the gap is separately used and a step of disposing the member is required, the number of manufacturing steps increases and the manufacturing cost increases.

  In Patent Document 2, the retention of the electrolytic solution in the winding center portion of the electrode group is improved by the hole formed in the negative electrode where the current collector is exposed. However, the absorbability and retention of the electrolyte solution of the entire electrode group are insufficient. Further, since the hole is formed in the portion where the current collector is exposed, the portion near the hole in the current collector is reduced in strength and easily broken. Furthermore, the portion where the current collector is exposed needs to be relatively large in consideration of the area of the portion welded to the core and the size of the hole. Therefore, the area | region with which a negative electrode active material is filled reduces, and negative electrode capacity | capacitance may fall.

Therefore, the present invention provides a low-cost wound electrode group having a winding core and excellent in the ability to absorb and retain an electrolytic solution and capable of being downsized.
In addition, a low-cost battery including a wound electrode group containing a sufficient amount of electrolyte and having high reliability and capable of being downsized is provided.
Furthermore, the present invention provides a highly reliable and low-cost battery manufacturing method capable of quickly including a sufficient amount of electrolyte in the wound electrode group.

The wound electrode group of the present invention includes a conductive core, a first electrode and a second electrode wound around the core, and a separator that separates the first electrode from the second electrode. ,
The first electrode has a strip-shaped first current collector and a first active material layer formed on a surface of the first current collector,
The second electrode has a band-shaped second current collector and a second active material layer formed on the surface of the second current collector,
The arithmetic average roughness Ra of the first active material layer is 0.5 to 10 μm,
The thickness of the first active material layer is 20 to 60 μm,
One of the first electrode and the second electrode has a portion A where the first current collector or the second current collector is exposed,
The portion A is welded to the winding core.

The arithmetic mean roughness Ra of the first current collector is 0.5 to 10 μm, and the first active material layer is preferably formed by a vapor deposition method.
More preferably, the first active material layer is composed of a layer of SiOx (0 <x <2).
It is preferable that the first electrode has a portion A where the first current collector is exposed.

The battery of the present invention comprises a substantially cylindrical battery case with one end closed, the wound electrode group housed in the battery case, and an electrolyte contained in the wound electrode group,
One end of the winding core is exposed to the outside of the battery case as an electrode terminal.
The nominal capacity of the battery is preferably 5 to 100 mAh.
The other of the first electrode and the second electrode has a portion B where the first current collector or the second current collector is exposed, and the portion B is in direct contact with the battery case. Is preferred.
The outer diameter of the battery case is preferably 10 mm or less. Further, the height of the battery case is preferably 40 mm or less, and more preferably 30 mm or less.

The battery manufacturing method of the present invention comprises:
(1) a step of forming the wound electrode group described above;
(2) a step of including an electrolyte in the wound electrode group;
(3) After the step (2), inserting the wound electrode group containing the electrolyte into a battery case;
(4) After the step (3), sealing the battery case;
It is characterized by including.
In the step (1), a first active material having an arithmetic average roughness Ra of 0.5 to 10 μm is formed on the surface of the first current collector having an arithmetic average roughness Ra of 0.5 to 10 μm by vapor deposition. Preferably, the method includes forming a layer to obtain a first electrode.

ADVANTAGE OF THE INVENTION According to this invention, it can provide the low cost wound type electrode group which has a winding core and was excellent in the absorptivity and the retainability of electrolyte solution, and can be reduced in size.
In addition, it is possible to provide a low-cost battery that is provided with a wound electrode group including a sufficient amount of electrolytic solution, has high reliability, and can be reduced in size.
Further, it is possible to provide a highly reliable and low-cost battery manufacturing method capable of quickly including a sufficient amount of electrolyte in the wound electrode group.

It is a schematic longitudinal cross-sectional view of the cylindrical battery which is one Embodiment of this invention.

The present invention relates to a wound core group including a conductive core, first and second electrodes wound around the core, and a separator that separates the first electrode from the second electrode. . In the present invention, the first electrode has a strip-shaped first current collector and a first active material layer formed on the surface of the first current collector, and the second electrode has a strip-shaped A second current collector, and a second active material layer formed on a surface of the second current collector,
The arithmetic average roughness Ra of the first active material layer is 0.5 to 10 μm,
The thickness of the first active material layer is 20 to 60 μm,
One of the first electrode and the second electrode has a portion A where the first current collector or the second current collector is exposed,
The portion A is characterized in that it is welded to the winding core.
The portion A is a portion where the active material layer is not formed on both surfaces of the current collector, and is formed at one end portion in the longitudinal direction of the first electrode disposed on the core side.
Arithmetic average roughness Ra is a numerical value representing the degree of surface roughness based on JIS B 0601-2001, and the larger the numerical value, the rougher the surface.

When the wound electrode group is configured, a large number of minute gaps for holding the electrolytic solution are formed between the rough surface having the arithmetic average roughness Ra of the first active material layer of 0.5 to 10 μm and the separator. Therefore, the absorbability and retention of the electrolyte solution of the wound electrode group are improved. In particular, it is effective for a small-sized wound electrode group (battery) that hardly absorbs and retains the electrolytic solution. The present invention is suitable, for example, for a small battery having a battery case having a maximum outer diameter of 3 to 20 mm and a core having a maximum diameter of 1 to 10 mm.
In addition, the surface form of the first active material layer can be used without using a separate member to improve the electrolyte solution absorbability and retention of the electrode group, which is advantageous in terms of cost.

  When the arithmetic average roughness Ra of the first active material layer is less than 0.5 μm, it becomes difficult to form a large number of minute voids between the first active material layer and the separator, Sufficient retention may not be obtained. When the arithmetic average roughness Ra of the first active material layer is more than 10 μm, the proportion of voids in the electrode group becomes excessively large, the packing density of the active material in the active material layer is reduced, and the battery capacity is reduced. May decrease.

  The arithmetic average roughness Ra of the first active material layer is preferably 2 μm or more. In this case, in particular, even in a region that is difficult to absorb and hold the electrolytic solution and is close to the core (for example, a region A having a curvature radius of 3 mm or less in a plane perpendicular to the axial direction of the electrode group), the electrolytic solution is rapidly absorbed, Excellent absorbability and retention of the electrolyte can be obtained in the entire electrode group.

  In particular, due to winding, in an area close to the core (for example, an area B having a radius of curvature of 2 mm or less in a plane perpendicular to the axial direction of the electrode group), the compressive stress of the active material layer disposed inside the electrode is large. Therefore, the arithmetic average roughness Ra of the first active material layer is more preferably 5 μm or more. Even if the electrode is wound and the active material layer inside the electrode in the region B is compressed, the arithmetic average roughness Ra of the active material layer can be secured to 0.5 μm or more. Excellent electrolyte absorption and retention can be obtained.

  The thickness of the first active material layer is 20 to 60 μm. If the thickness of the first active material layer is more than 60 μm, it may be difficult to reduce the size of the battery. When the thickness of the first active material layer is less than 20 μm, the filling amount of the first active material may decrease, and the battery capacity may decrease.

  The arithmetic mean roughness Ra of the first current collector is 0.5 to 10 μm, and the first active material layer is preferably formed by a vapor deposition method. The surface form of the first active material layer can follow the surface form of the first current collector, and the first active material layer having an arithmetic average roughness Ra of 0.5 to 10 μm can be easily formed. it can.

The first electrode preferably has a portion A where the first current collector is exposed. The portion A is a portion where the first active material layer is not formed on both surfaces of the first current collector, and is formed at one end portion in the longitudinal direction of the first electrode disposed on the core side.
Thereby, the whole surface of the 1st electrode can be made into the rough surface whose arithmetic mean roughness Ra is 0.5-10 micrometers. That is, the arithmetic average roughness Ra of both the portion A where the first current collector is exposed and the active material layer can be set to 0.5 to 10 μm. The absorptivity and retention of the electrolyte solution of the entire electrode group are further improved. In particular, in the portion near the core of the electrode group that is difficult to absorb and retain the electrolyte, the absorbability and retention of the electrolyte are greatly improved.
Further, since the portion A where the first current collector is exposed has a rough surface, the portion A can form a core and a stable welded portion, and firmly connects the first electrode and the core. be able to. In order to further strengthen the connection between the first electrode and the core, the arithmetic average roughness Ra of the first current collector is more preferably 2 to 10 μm.

  Further, the arithmetic average roughness Ra of the second electrode (second active material layer and second current collector) may be 0.5 to 10 μm.

The present invention relates to a battery including the above wound electrode group. That is, the battery of the present invention comprises a substantially cylindrical battery case with one end closed, the wound electrode group housed in the battery case, and the electrolyte contained in the wound electrode group. Prepared,
One end of the winding core is exposed to the outside of the battery case and is used as an external terminal of the first electrode or the second electrode.
As a result, it is possible to provide a low-cost battery that is provided with a wound electrode group including a sufficient amount of electrolytic solution, has high reliability, and can be reduced in size.
The battery of the present invention is preferably a small battery having a nominal capacity of 5 to 100 mAh.
The battery of the present invention is preferably a small cylindrical battery in which the outer diameter of the substantially cylindrical battery case with one end closed is 3 to 20 mm, and the diameter of the substantially cylindrical core is 1 to 10 mm. . From the viewpoint of further miniaturization, the outer diameter of the substantially cylindrical battery case with one end closed is more preferably 3 to 10 mm, and the diameter of the substantially cylindrical core is 1 to 5 mm.

The other of the first electrode and the second electrode has a portion B where the first current collector or the second current collector is exposed, and the portion B is preferably in direct contact with the battery case. Portion B has a second active material layer on one surface of the second current collector (surface facing the battery case) at one end in the longitudinal direction of the electrode (the portion corresponding to the outermost peripheral portion of the electrode). It is a part that is not formed.
Thereby, a battery case is used as a terminal of any one electrode of a 1st electrode and a 2nd electrode.
By press-fitting the electrode group into the battery case, the surface of the part B can be brought into close contact with the inner surface of the battery case, and a good contact state can be obtained between the part B and the battery case. Therefore, either one of the first electrode and the second electrode can be brought into electrical stable contact with the battery case.
This is current collection by directly contacting a part of the electrode and the inner surface of the battery case, and there is no need to weld the electrode and the battery case using a member such as a lead. For this reason, it is effective when inserting the electrode group containing electrolyte solution into a battery case, or when reducing a battery.

The second electrode preferably has a portion B where the second current collector is exposed, and the arithmetic average roughness Ra of the portion B is preferably 0.2 μm or less. Part B is formed on one surface of the second current collector (surface facing the battery case) at one end in the longitudinal direction of the second electrode (the part corresponding to the outermost peripheral part of the electrode). This is the part where the material layer is not formed.
When the surface of the portion B is a smooth surface with an arithmetic average roughness Ra of 0.2 μm or less, it is easy to insert into the battery case, and the yield in the insertion process into the battery case increases. The contact state between the surface of the second current collector exposed portion and the inner surface of the battery case is further improved, and the contact resistance can be greatly reduced.

  When the first electrode has a portion B where the first current collector is exposed, in the first current collector, only the portion B is a smooth surface with an arithmetic average roughness Ra of 0.2 μm or less. The region is preferably a rough surface having an arithmetic average roughness Ra of 0.5 to 10 μm.

The present invention relates to a method for producing a battery having the above wound electrode group. That is, the manufacturing method of the battery of the present invention includes:
(1) a first step constituting the wound electrode group,
(2) a second step of including an electrolytic solution in the wound electrode group;
(3) After the second step, a third step of inserting the wound electrode group containing the electrolytic solution into a battery case;
(4) After the third step, a fourth step of sealing the battery case;
It has the feature in the point containing.

In the first step, the electrode group is configured without separately using a member for improving the absorbability and retention of the electrolytic solution. Therefore, the step can be simplified, which is advantageous in terms of cost. Inconveniences such as displacement of members during winding of the electrode group do not occur.
The wound electrode group is excellent in the absorbability and retention of the electrolytic solution. For this reason, in the second step, a sufficient amount of the electrolytic solution can be quickly contained in the wound electrode group.
Further, in the third step, when the electrode group is inserted into the battery case, the electrolyte solution is suppressed from flowing out from the electrode group. In order to bring the inner surface of the battery case into close contact with the portion B where the first current collector or the second current collector is exposed, the electrode group is press-fitted into the battery case in a state where the electrolyte solution is included in the electrode group. It is possible.
Therefore, a method for manufacturing a battery with excellent reliability can be provided.

In the first step, a first active material layer having an arithmetic average roughness Ra of 0.5 to 10 μm is formed on the surface of the first current collector having an arithmetic average roughness Ra of 0.5 to 10 μm by vapor deposition. Preferably, the step of forming is included. Using the rough surface of the first current collector, the rough surface can be easily formed on the surface of the first active material layer.
Since the surface form of the first electrode can be used to improve the absorbability and retention of the electrode group without using a separate member, this is advantageous in terms of cost.

Hereinafter, an embodiment of a battery according to the present invention will be described with reference to the drawings. In the present embodiment, a case where the negative electrode has a rough surface will be described.
As shown in FIG. 1, a lithium ion secondary battery 10 includes a bottomed cylindrical battery case 11, a wound electrode group 12 housed in the battery case 11, and an insulating gasket 31 that seals the battery case 11. It has. The outer surface of the battery case 11 is covered with an insulating cover 34.
The electrode group 12 includes a conductive core 14, a negative electrode 15 as a first electrode, a positive electrode 16 as a second electrode, and a separator 17 that separates the negative electrode 15 from the positive electrode 16. . The electrode group 12 is in contact with a nonaqueous electrolyte.

A positive electrode 16 is disposed on the outermost periphery of the electrode group 12 and is in electrical contact with the inner surface of the battery case 11. The bottom and side surfaces of the battery case 11 are exposed to the outside and used as an external positive terminal.
One end 32 of the core 14 is exposed to the outside of the battery case and used as a negative electrode terminal. One end of the core 14 is press-fitted into the hole of the insulating gasket 31. An insulating cap 33 is attached to the other end of the core 14 so as not to short-circuit the battery case 11.

When the insulating plate is disposed on the inner bottom surface of the battery case 11, the insulating cap 33 may not be used.
In the following cases, the insulating cap 33 may not be used. After the electrode group is configured such that one end portion of the separator on the battery case side protrudes, the protruding portion of the separator is thermally condensed, and one end surface of the electrode group is covered with the separator. The electrode group is accommodated in the battery case such that one end surface of the electrode group faces the inner bottom surface of the battery case.
In these cases, even if the insulating cap 33 is not provided, a short circuit between the bottom of the battery case 11 and the core 14 can be prevented.

One end of the negative electrode 15 is welded to the core 14. Thereby, the negative electrode 15 is electrically connected to the core 14.
The negative electrode 15 has a strip-shaped negative electrode current collector and a negative electrode active material layer formed on both surfaces of the negative electrode current collector. The total thickness of the negative electrode 15 is preferably 35 to 150 μm.
A portion A where the negative electrode active material layer is not formed on both surfaces of the current collector 21 and the negative electrode current collector is exposed is formed at one end of the negative electrode 15. This portion A is welded to the core 14.
For the negative electrode current collector, a material that does not cause a chemical change in the potential range at the time of charge and discharge of the negative electrode active material used is used.

The negative electrode current collector has a rough surface with an arithmetic average roughness Ra of 0.5 to 10 μm. The rough surface of the negative electrode current collector is formed on the entire surface of the negative electrode current collector (the surface facing the separator).
A good weld can be formed between the rough surface portion A and the core.
When the arithmetic mean roughness Ra of the negative electrode current collector is less than 0.5 μm, the negative electrode active material layer and the negative electrode current collector are in close contact with each other in a region where the radius of curvature of the electrode group in the negative electrode is small (portion close to the core). May decrease. Moreover, it is difficult to form a negative electrode active material layer having a rough surface with an arithmetic average roughness Ra of 0.5 to 10 μm by vapor deposition.
When the arithmetic average roughness Ra of the negative electrode current collector exceeds 10 μm, the proportion of voids in the electrode group becomes excessively large, the packing density of the active material in the active material layer is decreased, and the battery capacity is decreased. There is a case. Moreover, it is difficult to form a negative electrode active material layer having a rough surface with an arithmetic average roughness Ra of 10 μm or less by vapor deposition.
Preferably, the negative electrode current collector has a rough surface with an arithmetic average roughness Ra of 2 to 10 μm.

  From the viewpoint of battery size reduction and the strength of the negative electrode current collector, the negative electrode current collector preferably has a thickness of 8 to 50 μm.

A metal foil is preferably used for the negative electrode current collector. Examples of the metal foil include stainless steel, nickel, copper, an alloy containing copper, and a titanium foil.
A layer of carbon, nickel, titanium, or the like may be formed on the surface of the metal foil.
Examples of a method for producing a negative electrode current collector having a rough surface include a plating method, a vapor deposition method, a sputtering method, a chemical vapor deposition method, and a sintering method that sinters the material constituting the convex portion and the substrate. It is done.
In particular, the negative electrode current collector is preferably copper. Examples of a method for forming a rough surface on the copper foil include a method of chemically etching the copper foil by immersing the copper foil in a solution, A method of wearing is used.

The negative electrode active material layer has a rough surface with an arithmetic average roughness Ra of 0.5 to 10 μm. The rough surface of the negative electrode active material is formed on the entire surface of the negative electrode active material layer facing the separator.
In addition, when the negative electrode active material has an irreversible capacity, the arithmetic average roughness Ra is the arithmetic average roughness of the negative electrode active material layer when the negative electrode active material layer has previously stored an amount of lithium corresponding to the irreversible capacity. Although Ra is shown, it is substantially the same value as the arithmetic mean roughness Ra of the negative electrode active material layer before the lithium is occluded.

Since fine irregularities are formed on the surface of the negative electrode active material layer, the absorbability and retention of the electrolytic solution in the electrode group are improved. Since the negative electrode active material layer has a rough surface, the surface area of the negative electrode active material layer increases, and the generation of dentlite at the negative electrode is suppressed.
Since the whole negative electrode (part A where the negative electrode active material layer and the negative electrode current collector are exposed) has a rough surface, excellent absorbability and retention of the electrolytic solution can be obtained in the entire electrode group.

The rough surface of the negative electrode active material layer is formed so as to follow the rough surface of the negative electrode current collector.
From the viewpoint of following the unevenness of the negative electrode current collector surface on the negative electrode active material surface, (arithmetic average roughness Ra of negative electrode active material layer) / (arithmetic average roughness Ra of negative electrode current collector) is 0.90. ˜1.10 is preferable, and 1.00 is more preferable.
From the viewpoint of the diffusion of the electrolyte in the negative electrode active material layer and the energy density, the porosity of the negative electrode active material layer (after occluding an amount of lithium corresponding to the irreversible capacity) is preferably 20 to 35%.
A negative electrode active material layer having substantially the same thickness is formed on the surface of the concave portion and the convex portion of the negative electrode current collector, respectively. In the case where the negative electrode active material layer having s is formed, the porosity is preferably 20 to 29%.
Note that the thicknesses in the above are substantially the same: the ratio of the thickness A of the negative electrode active material layer formed on the surface of the concave portion to the thickness B of the negative electrode active material layer formed on the surface of the convex portion: thickness A / thickness It means that B is in the range of 0.85 to 1.15.

  A negative electrode active material layer (corresponding to an irreversible capacity) formed by vapor deposition is used in order to make the unevenness of the negative electrode current collector having an arithmetic average roughness Ra of 0.5 to 10 μm easily follow the surface of the negative electrode active material layer. The thickness (before occlusion of an amount of lithium) is preferably 0.5 to 40 μm.

  The negative electrode active material layer having such a rough surface can be obtained by forming a negative electrode active material film on the surface (rough surface) of the negative electrode current collector using a general film forming method. Examples of the film forming method include a vapor deposition method (vacuum vapor deposition method, CVD method), a sputtering method, a gas deposition method, and a plating method. Among these, the vapor deposition method is preferable from the viewpoint of workability.

  When the arithmetic average roughness Ra of the negative electrode active material layer is less than 0.5 μm, the absorbability and retention of the electrolyte solution of the electrode group may be insufficient. When the arithmetic average roughness Ra of the negative electrode active material layer is more than 10 μm, the proportion of voids in the electrode group becomes excessively large, the packing density of the negative electrode active material in the negative electrode active material layer decreases, and the battery capacity May decrease.

  The arithmetic average roughness Ra of the negative electrode active material layer is preferably 2 μm or more. In this case, in particular, even in a region that is difficult to absorb and hold the electrolytic solution and is close to the core (for example, a region A having a curvature radius of 3 mm or less in a plane perpendicular to the axial direction of the electrode group), the electrolytic solution is rapidly absorbed, Excellent absorbability and retention of the electrolyte can be obtained in the entire electrode group.

  In particular, in a region close to the core due to winding (for example, a region B having a radius of curvature of 2 mm or less in a plane perpendicular to the axial direction of the electrode group), the compressive stress of the negative electrode active material layer disposed inside the negative electrode is reduced. In order to increase, the arithmetic average roughness Ra of the negative electrode active material layer is more preferably 5 μm or more. In this case, even if the negative electrode is wound and the negative electrode active material layer disposed inside the negative electrode in the region B is compressed, the arithmetic average roughness Ra of the negative electrode active material layer is set to 0.5 μm or more in the region B. It can be ensured, and excellent absorbability and retention of the electrolyte can be obtained in the entire electrode group.

The negative electrode active material layer has a thickness (thickness per side) of 20 to 60 μm. In addition, this thickness refers to the thickness of the negative electrode active material layer when the negative electrode active material layer has previously stored an amount of lithium corresponding to the irreversible capacity when the negative electrode active material has an irreversible capacity.
If the thickness of the negative electrode active material layer exceeds 60 μm, it may be difficult to reduce the size of the battery. Moreover, when forming a negative electrode active material layer by a vapor deposition method, it may become difficult to fully reflect the surface form of a negative electrode collector in the surface form of a negative electrode active material layer. If the thickness of the negative electrode active material layer is less than 20 μm, the filling amount of the negative electrode active material may decrease, and the battery capacity may decrease.

In order to increase the capacity in a small battery, the capacity density of the negative electrode active material layer is preferably 1000 mAh / cm ³ or more. This capacity density refers to the capacity per 1 cm ^{3 of} the negative electrode active material layer (reversible capacity) (mAh).
When a thin film containing silicon having a high capacity density is formed on the surface of the negative electrode current collector by vapor deposition, a high negative electrode active material having a capacity density of about 1200 to 1300 mAh / cm ³ is obtained. Even in a small battery, a battery having a high capacity can be obtained by increasing the energy density.

Since the capacity density is high, the negative electrode active material is preferably silicon, an alloy containing silicon, or silicon oxide, and particularly preferably silicon oxide. Alloys and silicon oxides containing silicon have a relatively large expansion / contraction during charging / discharging, but the smaller the battery size, the smaller the absolute value of expansion / contraction, so the effect is reduced. Are preferably used.
The silicon oxide is preferably SiOx (0 <x <2). The capacity of the active material increases as x decreases, but the volume change due to expansion and contraction of the active material during charge / discharge increases. Further, as x increases, the volume change due to expansion and contraction of the active material during charge / discharge decreases, but the irreversible capacity increases. In the small battery of this invention, the influence by the volume change of an active material is comparatively small. Therefore, 0 <x ≦ 1.1 is preferable from the viewpoint of volume change and reversible capacity of the active material in a small battery.
The alloy containing silicon is preferably an alloy of silicon and at least one element selected from the group consisting of iron, cobalt, nickel, copper, and titanium.

As the negative electrode active material, tin, an alloy containing tin, a tin oxide, or an alloy containing lithium can be used. The alloy containing tin is preferably an alloy of tin and at least one element selected from the group consisting of iron, cobalt, nickel, and copper. The alloy containing lithium is preferably an alloy of lithium and at least one element selected from the group consisting of aluminum.
The tin oxide is preferably SnOx (0 <x <2). The capacity of the active material increases as x decreases, but the volume change due to expansion and contraction of the active material during charge / discharge increases. Further, as x increases, the volume change due to expansion and contraction of the active material during charge / discharge decreases, but the irreversible capacity increases. In the small battery of this invention, the influence by the volume change of an active material is comparatively small. Therefore, 0 <x ≦ 1.1 is preferable from the viewpoint of volume change and reversible capacity of the active material in a small battery.

Since the core 14 is electrically connected to the negative electrode 15, a material that does not cause a chemical change in the potential range during charging / discharging of the negative electrode active material to be used may be used. Specifically, stainless steel (SUS), copper, copper alloy, aluminum, stainless steel, iron, nickel, palladium, gold, silver, and platinum are used as the core 14. These may be used alone or in combination of two or more.
The core 14 is preferably made of the same material as the negative electrode current collector 21. The winding core 14 may have any shape suitable for welding with the negative electrode 15. The core 14 is preferably rod-shaped. The rod-shaped winding core 14 preferably has a flat portion along the longitudinal direction. The flat end can be brought into surface contact with the electrode.

The positive electrode 16 includes a positive electrode current collector and a positive electrode active material layer formed on both surfaces of the positive electrode current collector. The total thickness of the positive electrode 16 is preferably 80 to 300 μm.
The positive electrode 16 has a positive electrode active material layer formed on the inner peripheral surface of the positive electrode current collector at the outermost periphery of the electrode group, and a positive electrode active material layer formed on the outer peripheral surface of the positive electrode current collector. A single-side coated portion (portion B where the positive electrode current collector is exposed) that is not formed is provided. The surface of the portion B where the positive electrode current collector is exposed is in close contact with the inner surface of the battery case. In this way, the positive electrode 16 is in electrical contact with the battery case 11.

The positive electrode current collector preferably has an arithmetic average roughness Ra of 0.1 to 5 μm from the viewpoint of reliability with respect to insertion into the battery case and adhesion with the positive electrode active material layer.
The positive electrode current collector has a smooth surface having an arithmetic average roughness Ra of 0.2 μm or less in the region of the portion B, and has an arithmetic average roughness Ra of 0.5 to 5 μm in the region other than the portion B. It is more preferable to have a rough surface. When the arithmetic average roughness Ra of the part B is 0.2 μm or less, the battery case is easy to insert, and the yield in the battery case insertion process is significantly increased. The contact state between the surface of the positive electrode current collector exposed portion and the inner surface of the battery case is further improved, and the contact resistance can be greatly reduced. The positive electrode current collector is excellent between the positive electrode active material layer and the positive electrode current collector when the arithmetic roughness Ra is 0.5 μm or more in a region other than the portion B (portion forming the positive electrode active material layer). High adhesion can be obtained. In particular, in the portion where the radius of curvature of the electrode group in the positive electrode is small (the portion close to the core), the adhesion between the positive electrode active material layer and the positive electrode current collector is greatly improved.

From the viewpoint of battery size reduction and the strength of the positive electrode current collector, the positive electrode current collector preferably has a thickness of 10 to 50 μm.
A strip-shaped metal foil is used for the positive electrode current collector, and preferably an aluminum foil or an aluminum alloy foil.

From the viewpoints of battery miniaturization and positive electrode capacity, the positive electrode active material layer (thickness per side) preferably has a thickness of 30 to 100 μm.
The positive electrode active material layer includes a positive electrode active material, and may further include a positive electrode conductive agent and a positive electrode binder as necessary.

A positive electrode active material should just be a material which can be used with a lithium ion secondary battery, and is not specifically limited. As the positive electrode active material, for example, lithium-containing transition metal oxides such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ) can be used.
From the viewpoint of battery miniaturization and high energy density, the positive electrode active material includes a general formula: Li _x Ni _y M _1-y O ₂ (where M is Na, Mg, Sc, Y, Mn, Fe). , Co, Cu, Zn, Al, Cr, Pb, Sb and B, at least one selected from the group consisting of 0 <x ≦ 1.2 and 0.5 <y ≦ 1.0) It is preferable to use the containing composite oxide.
In addition, from the viewpoint of battery miniaturization and high energy density, the positive electrode active material includes a general formula: Li _x Ni _y Co _z M _1-yz O ₂ (where M is Mg, Ba, Al, Ti). , Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, and W, and at least 0.9 ≦ x ≦ 1.2,. 3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3) is preferably used.

As the positive electrode binder, for example, fluorine resin, styrene-butadiene rubber, fluorine rubber, polyacrylic acid, or polyvinylidene fluoride is used.
When using a positive electrode binder, the content of the positive electrode binder in the positive electrode active material is preferably 1 to 5 parts by weight per 100 parts by weight of the positive electrode active material.

As the positive electrode conductive agent, for example, graphites, carbon blacks, carbon fibers, metal fibers, or conductive organic materials are used.
When using a positive electrode conductive agent, the content of the positive electrode conductive agent in the positive electrode active material is preferably 0.5 to 5 parts by weight per 100 parts by weight of the positive electrode active material.

The non-aqueous electrolyte includes a solute and a non-aqueous solvent.
A solute is a supporting salt that dissolves in a non-aqueous solvent. Examples of the supporting salt include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis ( Trifluoromethylsulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ ), lithium bis (pentafluoroethylsulfonyl) imide (LiN (C ₂ F ₅ SO ₂ ) ₂ ), lithium bis (trifluoromethylsulfonyl) (pentafluoro Ethylsulfonyl) imide (LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )) or lithium tris (trifluoromethylsulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ) is used. These may be used alone or in combination of two or more.

Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,2-dimethoxyethane (DME), 1 , 2-diethoxyethane (DEE), γ-butyrolactone (γ-BL), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), N, N-dimethylformamide, tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide, formamide, acetamide, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, trimethoxymethane, dioxolane, dioxolane derivatives, sulfolane, methyl Rusulfolane, a propylene carbonate derivative, or a tetrahydrofuran derivative is used. These may be used alone or in combination of two or more.
Examples of the non-aqueous electrolyte include a liquid electrolyte, a gel electrolyte, and a solid electrolyte (polymer solid electrolyte).

As the separator 17, for example, a microporous thin film, a woven fabric, or a non-woven fabric is used. These have a high ion permeability and preferably have an appropriate mechanical strength and insulating property. Examples of the material of the separator 17 include polyolefin such as polypropylene and polyethylene.
In particular, a microporous thin film made of polyolefin is excellent in durability and has a so-called shutdown function that closes the pores when the temperature rises to a certain temperature. Therefore, it is suitable as a separator for lithium ion secondary batteries such as lithium ion batteries. Used for.

  The thickness of the separator is generally 10 to 300 μm, preferably 40 μm or less, and more preferably 5 to 30 μm. The separator may be a single layer film made of one material, or a composite film or multilayer film made of two or more materials.

  As the material of the insulating gasket 13, for example, a copolymer of polypropylene, polyethylene, polyphenylene sulfide, polyether ether ketone, polyamide, polyimide, liquid crystal polymer, and perfluoroalkoxyethylene is used. These may be used alone or in combination of two or more. You may use these in combination with fillers, such as an inorganic fiber. The insulating gasket may be coated with a sealing material to increase the airtightness of the battery.

The method for manufacturing the battery 10 of the present invention includes, for example,
(1) a first step for forming the wound electrode group 12;
(2) a second step of including an electrolytic solution in the wound electrode group 12;
(3) After the second step, a third step of inserting the wound electrode group 12 containing the electrolyte into the battery case 11;
(4) After the third step, a fourth step of sealing the battery case 11;
including.

  A negative electrode active material layer having an arithmetic average roughness Ra of 0.5 to 10 μm is formed on both surfaces of a strip-shaped negative electrode current collector having an arithmetic average roughness Ra of 0.5 to 10 μm by a vapor deposition method. Get. At this time, at one end in the longitudinal direction of the negative electrode 15, a portion A where the negative electrode active material layer is not formed on both surfaces of the negative electrode current collector is provided as a portion to be welded to the core 14 described later.

  A positive electrode slurry in which a dispersion medium such as N-methyl-2-pyrrolidone is added to the positive electrode active material, the conductive agent, and the binder is applied to both surfaces of the belt-shaped positive electrode current collector to form a coating film. This coating film is dried to form a positive electrode active material layer and compressed to obtain a positive electrode. At this time, a portion B where the positive electrode active material layer is not formed on one surface of the positive electrode current collector is provided at one end in the longitudinal direction of the positive electrode.

The portion A of the negative electrode 15 and the core 14 are overlapped. Next, the needle-like first resistance welding electrode and the flat plate-like second resistance welding electrode are opposed to each other through the negative electrode 15 and the core 14. At this time, the first resistance welding electrode is brought into contact with the surface of the negative electrode 15, and the second resistance welding electrode is brought into contact with the core 14. Thus, current is applied between the first and second resistance welding electrodes, and the negative electrode 15 and the core 14 are joined by resistance welding at a plurality of locations along the axial direction X of the core 14. Thereafter, the negative electrode 15 is wound around the core 14 together with the separator 17 and the positive electrode 16. In this way, the wound electrode group 12 shown in FIG. 1 is obtained (first step). At this time, the portion B is arranged on the side surface of the outermost peripheral portion of the electrode group 12.
After winding the negative electrode 15, the positive electrode 16, and the separator 17, the outermost periphery is fixed with an insulating tape made of polypropylene, for example. Furthermore, the insulating gasket 13 is passed through one end 32 of the core 14, and an insulating cap 33 is attached to the other end.

Thereafter, the wound electrode group 12 is immersed in a predetermined container in which the electrolytic solution is stored, and impregnated with the electrolytic solution (second step). At this time, the electrolytic solution is preferably impregnated under reduced pressure (for example, the internal pressure of the container: 600 Torr or less). The second step can be performed in a short time.
The electrode group sufficiently impregnated with the electrolytic solution is taken out and inserted into the battery case 11 (third step). At this time, it is preferable to quickly insert the electrode group including the electrolytic solution into the battery case. Without the electrolyte flowing out of the electrode group, the electrode group 12 containing the electrolyte can be pressed into the battery case 11 and the portion B can be brought into close contact with the inner surface of the battery case.
Thereafter, the open end 31 of the battery case 11 is caulked to the top of the insulating gasket 13 to seal the battery case 11 (fourth step). In this way, the lithium ion battery 10 shown in FIG. 1 is obtained.

In the above embodiment, the negative electrode is electrically connected to the winding core, and the battery case also serves as the external terminal of the positive electrode, but the present invention is not limited to this, the positive electrode is electrically connected to the winding core, and the battery case is the negative electrode It may also serve as an external terminal.
In the said embodiment, although the lithium ion secondary battery was mentioned as an example, this invention is not limited to nonaqueous electrolyte secondary batteries, such as a lithium ion secondary battery. The present invention can also be applied to non-aqueous electrolyte primary batteries such as lithium batteries, and primary and secondary batteries using alkaline or neutral aqueous electrolytes. Moreover, the composition of the electrode material and the electrolytic solution is not particularly limited, and known materials and compositions may be appropriately selected.

Examples of the present invention will be described in detail below, but the present invention is not limited to the examples.
Example 1
The lithium ion battery 10 shown in FIG. 1 was produced according to the following procedure.

(1) Fabrication of negative electrode Vapor deposition device (manufactured by ULVAC, Inc.) using Si (99.9999% pure silicon (manufactured by High Purity Chemical Research Laboratories)) as a negative electrode active material and equipped with electron beam (EB) heating means. ), Oxygen gas having a purity of 99.7% was introduced, and negative electrode active material layers were formed on both sides of a negative electrode current collector made of a strip-shaped copper foil (thickness 30 μm, width 12 mm, and length 28 mm). A negative electrode 15 was obtained.
The obtained negative electrode active material layer was SiOx, and the amount of oxygen contained was quantified by a combustion method. As a result, the composition of the compound containing silicon and oxygen was SiO _0.5 . Moreover, the thickness of the negative electrode active material layer was 40 μm.
Next, lithium metal was deposited on the negative electrode active material layer using a resistance heating vapor deposition apparatus manufactured by ULVAC. At this time, lithium metal was occluded into the negative electrode active material layer. In this way, a negative electrode active material made of SiO _0.5 was supplemented in advance with an amount of lithium corresponding to the irreversible capacity.
The thickness of the negative electrode active material layer after occlusion of an amount of lithium corresponding to the irreversible capacity was 60 μm. The porosity of this negative electrode active material layer was 30%. The volume obtained by subtracting the true volume from the apparent volume of the active material layer formed on the current collector was defined as the total volume of the voids, and the ratio of the total volume of the voids to the apparent volume was determined as the porosity.
In addition, the area | region which does not have a negative electrode active material layer on both surfaces of a negative electrode electrical power collector in the one edge part (area | region of 4 mm in length along a longitudinal direction) of the strip | belt-shaped negative electrode (part A which a negative electrode electrical power collector exposes) Was provided.

  At the time of producing the negative electrode, the arithmetic average roughness Ra of the negative electrode current collector (copper foil) was changed to 0.5 μm, 1 μm, 2 μm, 5 μm, and 10 μm by an electrolytic method. Using these negative electrode current collectors, negative electrodes having negative electrode active material layers having arithmetic average roughness Ra of 0.5 μm, 1 μm, 2 μm, 5 μm, and 10 μm were respectively produced. In addition, even after occlusion of an amount of lithium corresponding to the irreversible capacity, the arithmetic average roughness Ra of the negative electrode active material layer did not change, and was 0.5 μm, 1 μm, 2 μm, 5 μm, and 10 μm, respectively. The arithmetic average roughness Ra was measured based on JIS B 0601-2001.

(2) Preparation of positive electrode 90 parts by weight of lithium cobaltate as a positive electrode active material, 5 parts by weight of acetylene black as a conductive agent, 5 parts by weight of polyvinylidene fluoride as a binder, and N-methyl-2-pyrrolidone (as a dispersion medium) NMP) was added to prepare a positive electrode slurry. This positive electrode slurry was applied to a positive electrode current collector to form a coating film to obtain a positive electrode precursor. As the positive electrode current collector, a strip-shaped aluminum foil (arithmetic average roughness Ra 0.1 μm) having a thickness of 20 μm, a width of 10 mm, and a length of 33 mm was used. The coating amount of the positive electrode active material was 450 g / m ² .
The positive electrode precursor was placed in a dryer, NMP was removed from the coating film, and a positive electrode active material layer was obtained. Next, the positive electrode active material layer was compressed to obtain a positive electrode 16 (thickness 0.16 mm). At the time of producing the positive electrode, on one surface of the positive electrode current collector (surface facing the battery case at the outermost periphery of the electrode group) at one end of the positive electrode (region having a length of 12 mm along the longitudinal direction) A region having no positive electrode active material layer (portion B where the positive electrode current collector is exposed) was provided.

(3) Production of electrode group The insulating gasket 13, the core 14, the negative electrode 15, the positive electrode 16, the separator 17, and the battery case 11, which are battery constituent members, were allowed to stand under a vacuum of 100 ° C., and each part was dried. Then, the battery was produced as follows in an atmosphere with a dew point of −50 ° C. or lower.
A stainless steel round bar (diameter 1 mm) was used for the core 14. The portion A of the negative electrode 15 where the negative electrode current collector is exposed and the core 14 are overlapped to form a needle-like first resistance welding electrode and a flat plate-like second resistance welding electrode. They were opposed to each other through the core 14. The first resistance welding electrode is brought into contact with the surface of the negative electrode 15, the second resistance welding electrode is brought into contact with the current collector 14, a current is applied between the first and second resistance welding electrodes, The negative electrode 15 and the current collector 14 were joined by resistance welding at a plurality of locations along the axial direction X.
Then, the negative electrode 15 was wound around the current collector 14 together with the separator 17 and the positive electrode 16 to obtain the wound electrode group 12 shown in FIG. As the separator 17, a polyethylene microporous film having a thickness of 20 μm was used. After winding the negative electrode 15, the positive electrode 16 and the separator 17, an adhesive tape made of polypropylene was applied to the outermost periphery, and the electrode group was fixed so as not to loosen. Further, the insulating gasket 13 was passed through one end 32 of the core 14, and an insulating cap 33 was attached to the other end.

(4) Preparation of electrolytic solution LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) to obtain a nonaqueous electrolytic solution. The weight ratio of EC and EMC was 1: 1. The concentration of LiPF ₆ in the non-aqueous electrolyte was 1.0 mol / L.

(5) Production of Cylindrical Lithium Ion Battery After the electrode group 12 was allowed to stand in a plastic container, the electrolyte solution was placed in the container, and the electrode group 12 was immersed in the electrolyte solution. Thereafter, the container was left in the desiccator, the internal pressure in the desiccator was maintained at 525 Torr for 60 seconds, and the electrode group 12 was impregnated with the electrolyte under reduced pressure.
The electrode group 12 containing the electrolytic solution was taken out of the container and inserted into a bottomed cylindrical aluminum battery case (outer diameter 4 mm, height 20 mm). The insulating gasket 13 was disposed in the opening of the battery case 11, and the opening end 31 of the battery case 11 was caulked to the upper part of the insulating gasket 13 to seal the battery case 11. In this way, a small lithium ion secondary battery (diameter 4 mm, height 20 mm) having a nominal capacity of 18 mAh was obtained.
In the above, batteries of Samples 11 to 15 were produced using negative electrodes in which the arithmetic average roughness Ra of the negative electrode current collector and the negative electrode active material layer was changed in the range of 0.5 to 10 μm.

<< Comparative Example 1 >>
A battery was fabricated in the same manner as in Example 1, except that a copper foil that was not roughened, that is, a copper foil having an arithmetic average roughness Ra of 0.1 μm, was used for the negative electrode current collector. This was designated as Sample 21.

[Evaluation]
(A) Measurement of impregnation time of electrolyte solution Ten electrode groups 12 of Examples and Comparative Examples were formed, and the electrode group 12 was allowed to stand in a container in which the electrode group 12 could be sufficiently immersed. Furthermore, the electrolyte solution was injected and the electrode group 12 was immersed. These were left in the desiccator, and the time until the internal pressure in the desiccator reached 525 Torr and no remaining gas (air) from the electrode group was measured. This was defined as the impregnation time. Table 1 shows the average of 10 pieces.

(B) Evaluation of battery characteristics Ten batteries of Examples and Comparative Examples were produced, and these batteries were charged and discharged in the order of the following (1) to (4).
(1) After charging for 4 hours at a constant current of 0.05C, the battery was discharged at a constant current of 0.05C until the closed circuit voltage of the battery reached 2.5V.
(2) The battery was charged with a constant current of 0.1 C until the closed circuit voltage of the battery reached 4.1 V, and then discharged with a constant current of 0.1 C until the closed circuit voltage of the battery reached 2.5 V.
(3) The battery was charged with a constant current of 0.1 C until the closed circuit voltage of the battery reached 4.1 V, and then discharged with a constant current of 0.1 C until the closed circuit voltage of the battery reached 2.5 V.
(4) After charging with a constant current of 0.1 C until the closed circuit voltage of the battery reached 4.2 V, the battery was discharged with a constant current of 0.1 C until the closed circuit voltage of the battery reached 2.5 V.
Note that C represents a time rate. When an amount of electricity corresponding to the design capacity c flows at time t, the current value is expressed as c / t.
In the discharge of (4) above, the discharge voltage was monitored to confirm the discharge capacity. At this time, a battery having a stable discharge voltage and a discharge capacity of 95% or more of the theoretical capacity was judged as good.
The results of the above evaluation are shown in Table 1.

As shown in Table 1, in Samples 11 to 15 which are examples of the present invention, the impregnation time of the electrolytic solution was short, and all the batteries were good.
On the other hand, in Sample 21 as a comparative example, the time required for impregnating the electrode group with the electrolyte increased. In sample 21, which is a comparative example, it was difficult to impregnate the required amount of electrolyte in 60 seconds, resulting in variations in battery characteristics and defects. In addition, one of the defective samples 21 of the comparative example included one defective connection between the winding core and the current collector, which was considered to have been peeled off when the electrode group was configured.

  The battery of the present invention can be suitably used as a power source in various electronic devices, in particular, various portable electronic devices.

DESCRIPTION OF SYMBOLS 10 Lithium ion secondary battery 11 Battery case 12 Electrode group 13 Insulation gasket 14 Winding core 15 Negative electrode 16 Positive electrode 17 Separator 31 Open end of battery case 32 One end of winding core 33 Insulating cap 34 Insulating cover

Claims (10)

A conductive core, a first electrode and a second electrode wound around the core, and a separator that separates the first electrode and the second electrode;
The first electrode has a strip-shaped first current collector and a first active material layer formed on a surface of the first current collector,
The second electrode has a band-shaped second current collector and a second active material layer formed on the surface of the second current collector,
The arithmetic average roughness Ra of the first active material layer is 0.5 to 10 μm,
The thickness of the first active material layer is 20 to 60 μm,
One of the first electrode and the second electrode has a portion A where the first current collector or the second current collector is exposed,
The wound electrode group, wherein the portion A is welded to the core. The arithmetic mean roughness Ra of the first current collector is 0.5 to 10 μm,
The wound electrode group according to claim 1, wherein the first active material layer is formed by a vapor deposition method.   The wound electrode group according to claim 2, wherein the first active material layer is made of a layer of SiOx (0 <x <2).   The wound electrode group according to any one of claims 1 to 3, wherein the first electrode has a portion A where the first current collector is exposed. A substantially cylindrical battery case with one end closed, the wound electrode group according to any one of claims 1 to 4 accommodated in the battery case, and an electrolyte contained in the wound electrode group; With
One end of the winding core is exposed to the outside of the battery case as an electrode terminal.   The battery according to claim 5, wherein a nominal capacity of the battery is 5 to 100 mAh. The other of the first electrode and the second electrode has a portion B where the first current collector or the second current collector is exposed,
The battery according to claim 5, wherein the portion B is in direct contact with the battery case at the outermost periphery of the electrode group.   The battery according to any one of claims 5 to 7, wherein an outer diameter of the battery case is 10 mm or less. (1) a first step constituting the wound electrode group according to any one of claims 1 to 4;
(2) a second step of including an electrolytic solution in the wound electrode group;
(3) After the second step, a third step of inserting the wound electrode group containing the electrolytic solution into a battery case;
(4) After the third step, a fourth step of sealing the battery case;
The manufacturing method of the battery containing this.   In the step (1), a first active material having an arithmetic average roughness Ra of 0.5 to 10 μm is formed on the surface of the first current collector having an arithmetic average roughness Ra of 0.5 to 10 μm by vapor deposition. The method for producing a battery according to claim 9, comprising a step of forming a layer to obtain a first electrode.

Images