JP2018063881A - Secondary battery, method for manufacturing secondary battery, electrode - Google Patents

Abstract

A secondary battery, a secondary battery manufacturing method, and an electrode having stable performance by suppressing the occurrence of convex portions of the active material-containing layer in the process of coating the active material-containing layer on the metal foil Offer. A positive electrode and a negative electrode in which active material layers 8b and 9b are formed with a predetermined width in a partial region of the current collector, a separator disposed between the positive electrode and the negative electrode, the positive electrode, The secondary battery which has the waveform part 200 in the edge part of the width direction of the said active material layers 8b and 9b of the said collector in at least one of a negative electrode. Further, when the width Wa in the width direction of the active material-containing layers 8b and 9b and the variation width in the width direction of the active material-containing layer are ΔW, (Equation 1) 0.007 ≦ ΔW / Wa Where the height of the intermediate part in the width direction of the active material-containing layers 8b and 9b is ha, and the height of the end part of the active material-containing layer is h, (Expression 2) Secondary battery having. [Selection] Figure 5

Description

  Embodiments described herein relate generally to a secondary battery, a method for manufacturing a secondary battery, and an electrode.

A secondary battery such as a lithium secondary battery includes a step of coating an active material-containing layer on a metal foil. Moreover, the electrode which coated the active material content layer is wound up, and the process of rolling an electrode and making it a roll state is included.

JP 2013-134799 A

In the process of applying the active material-containing layer to the metal foil, a certain height may occur at the end of the active material-containing layer. When such an electrode is used, the productivity and performance of the secondary battery may be affected. Therefore, the problem to be solved by the present invention is to provide a secondary battery, a method of manufacturing a secondary battery, and an electrode that have stable performances by suppressing the occurrence of convex portions.

In order to solve the above problems, the secondary battery of the present embodiment includes a positive electrode and a negative electrode in which an active material layer is formed with a predetermined width in a partial region of the current collector, and the positive electrode and the negative electrode. A separator disposed therebetween, and at least one of the positive electrode and the negative electrode has a corrugated portion at an end in the width direction of the active material layer of the current collector.

The perspective view of the secondary battery which concerns on embodiment. The expansion perspective view of the electrode group used for the secondary battery concerning an embodiment. Schematic of the laminated structure of the electrode group used for the secondary battery which concerns on embodiment. The disassembled perspective view of the secondary battery which concerns on embodiment. The partial enlarged view of the electrode which concerns on embodiment. FIG. 6 is a partial cross-sectional view of the electrode along the line AA ′ in FIG. 5. The graph which shows the height of the convex part which concerns on embodiment, and the relationship of (DELTA) W / Wa.

(First embodiment)
Hereinafter, embodiments will be described with reference to the drawings. As an example of the non-aqueous electrolyte secondary battery, FIGS. 1 and 2 show a non-aqueous electrolyte secondary battery 20. The nonaqueous electrolyte secondary battery 20 includes an outer can 1, a flat wound electrode group 2, a positive electrode lead 3, a negative electrode lead 4, an insulator 40, and a positive electrode terminal 6.
, And negative electrode terminal 7.

The outer can 1 is made of, for example, a metal such as aluminum, an aluminum alloy, iron, or stainless steel. The wound electrode group 2 is inserted from the first surface 61 of the outer can 1, and the outer can 1
It is housed so as to be directed in a direction perpendicular to the winding axis.

The wound electrode group 2 has a positive electrode current collecting tab 8a at one end and a negative electrode current collecting tab 9a at the other end.
FIG. 2 is a development view of the wound electrode group 2, and FIG. 3 shows a laminated structure of the wound electrode group 2. The positive electrode 8 includes a strip-shaped positive electrode current collector 8c made of, for example, a metal foil, and a positive electrode active material layer 8b formed on one or both surfaces thereof. The positive electrode active material layer 8b is formed so that a region (non-coated portion) having a predetermined width remains on one end side along the longitudinal direction of the strip-shaped positive electrode current collector 8c. This non-coated portion is a positive electrode current collector 8
c is the exposed part, and becomes the positive electrode current collecting tab 8a. Similarly, the negative electrode 9 includes a strip-shaped negative electrode current collector 9c made of, for example, a metal foil, and a negative electrode active material layer 9b formed on one surface or both surfaces thereof.
The negative electrode active material layer 9b is formed in the strip-shaped negative electrode current collector 9c such that a region (non-coated portion) having a predetermined width remains on the other end side (the opposite side to one end of the positive electrode 8) along the longitudinal direction. The This uncoated portion is a portion where the negative electrode current collector 9c is exposed, and becomes a negative electrode current collecting tab 9a.

The positive electrode 8 and the negative electrode 9 are alternately stacked with the strip-shaped separators 10a and 10b. At this time,
The positive electrode current collecting tab 8a is formed on one end side in the winding axis direction, and the negative electrode current collecting tab 9a is formed on the other end side. The separator 10 a stacked under the positive electrode 8 has one end along the longitudinal direction thereof at the positive electrode 8.
It arrange | positions so that it may be located inside the edge part by the side of the positive electrode current collection tab. Thereby, the positive electrode current collection tab 8a protrudes from the positive electrode active material layer 8b, the negative electrode active material layer 9b, and the separator 10a which comprise the winding electrode group 2. FIG. In addition, the separator 10 a is arranged so that the other end along the longitudinal direction is located outside the other end of the positive electrode 8. The separator 10b sandwiched between the positive electrode 8 and the negative electrode 9 is disposed so that one end along the longitudinal direction is located inside the end portion of the negative electrode 9 on the negative electrode current collecting tab side. Thereby, the negative electrode current collection tab 9a protrudes from the positive electrode active material layer 8b, the negative electrode active material layer 9b, and the separator 10b which comprise the winding electrode group 2. FIG. In addition, separator 1
0b is arranged so that the other end along the longitudinal direction is located outside the other end of the negative electrode 9.

Winding the stacked separator 10a, positive electrode 8, separator 10b, negative electrode 9, and then
The flat wound electrode group 2 is formed by pressing.

The wound wound electrode group 2 is fastened with an insulating tape. The insulating tape covers an area other than the current collecting tab on the outermost periphery of the wound electrode group 2, and makes the area insulative. The number of turns of insulating tape is 1
It may be more than a lap.

  A method of creating the wound electrode group 2 will be described in detail later.

In the outer can 1, the surface 61 on which the terminals are arranged has, for example, a third surface 63 and a fourth surface 6 by welding.
4, the fifth surface 65 and the sixth surface 66 are fixed in an airtight manner. The positive electrode terminal 6 and the negative electrode terminal 7 are caulked and fixed to the first surface 61 via insulating gaskets 14 and 15, respectively. The positive electrode terminal 6 and the negative electrode terminal 7 protrude from the back surface of the first surface 61 toward the inside of the outer can 1. The fixing method of the positive electrode terminal 6 and the negative electrode terminal 7 is the insulating gasket 14,
In addition to caulking and fixing at 15 (not shown), a hermetic seal using glass may be used. The first surface 61 includes an inlet 28 for injecting an electrolytic solution and a gas discharge valve 29 for discharging gas generated in the secondary battery. An insulator 40 is provided on the inner side of the outer can 1 with respect to the first surface 61.

The positive lead 3 includes a connection plate 3a electrically connected to the positive terminal 6, a through hole 3b opened in the connection plate 3a, and a bifurcated branch from the connection plate 3a. First and second clamping strips 3c, which are clamping parts extending in a direction perpendicular to
3d. The connection plate 3a is in contact with the back surface of the first surface 61 at the position of the positive electrode terminal 6 via the insulator 40, and the positive electrode terminal 6 protruding from the back surface of the first surface 61 caulks and fixes the through hole 3b. .

The first and second sandwiching strips 3c and 3d of the positive electrode lead 3 sandwich the positive current collecting tab 8a from the direction perpendicular to the winding axis, and the first and second sandwiching strips 3c and 3d and the positive current collecting tab 8a
Are joined by welding, for example.

Similarly, the negative electrode lead 4 has a connection plate 4a which is a connection part connected to the negative electrode terminal 7,
A through-hole 4b opened in the connection plate 4a, and a first and a second that are bifurcated from the connection plate 4a and that extend to the wound electrode group 2 in a direction perpendicular to the winding axis. Sandwiching strips 4c and 4d. The connection plate 4a is in contact with the back surface of the first surface 61 at the location of the negative electrode terminal 7 via the insulator 40, and through the through hole 4 to the negative electrode terminal 7 protruding from the back surface.
Secure b.

The first and second sandwiching strips 4c and 4d of the negative electrode lead 4 sandwich the negative current collecting tab 9a from the direction perpendicular to the winding axis, and the first and second sandwiching strips 4c and 4d and the negative current collecting tab 9a
Are joined by welding, for example.

The electrical connection method between the wound electrode group 2 and the positive electrode terminal 6 and the negative electrode terminal 7 described above is merely an example, and may be electrically connected by other methods.

For example, the secondary battery is manufactured in this way, but the positive electrode active material layer 8 in the wound electrode group 2 is used.
b and the negative electrode active material layer 9b can be applied onto the metal foil by, for example, a die coater. The die coater can apply the material of the active material layer on the metal foil by discharging the material of the active material layer toward the current collector.

FIG. 5 is an enlarged view of the boundary between the coated portion and the non-coated portion of the active material layer in the positive electrode 8 or the negative electrode 9. As shown in FIG. 5, in at least one active material layer of the positive electrode active material layer 8b and the negative electrode active material layer 9b, the boundary portion with the non-coated portion is a straight line parallel to the end portion of the metal foil. Instead, the positive electrode active material layer 8b or the negative electrode active material layer 9b having a variation (wave shape portion) in the shape of the coating end portion 200 is formed by changing to a wave shape.

Here, when the coating width excluding the corrugated portion at the coating end portion 200 of the positive electrode active material layer 8b or the negative electrode active material layer 9b is Wa, and the width at the corrugated portion at the coating end portion 200 is ΔW. It is preferable that the ratio of both (the fluctuation ratio) satisfies the condition of the following formula (1).
0.007 ≦ ΔW / Wa (1)

More preferably, it is preferable that the condition of the following formula (2) is satisfied.
0.010 ≦ ΔW / Wa (2)

6 is a cross-sectional view taken along the line AA ′ in FIG. In the height of the coating part, when the height of the coating end part 200 is h, and the height of the intermediate part in the width direction of the coating part is ha,
It is preferable that the condition of the following formula (3) is satisfied.
ha ≦ h (3)

The coating width Wa, the height of the coating portion, and the height of the coating end portion 200 can be changed by changing the distance (large gap) between the die coater and the metal foil. Therefore, the above formula (1)
, (2), (3) can be adjusted so as to satisfy the conditions. For example, Wa can be increased by increasing the die gap, and Wa can be decreased by decreasing the die gap.

For example, if the die gap is increased under the condition that a constant Wa can be obtained, ΔW
And ΔW can be reduced by reducing the die gap. By using such a method, ΔW / Wa can be adjusted.

The relationship between h and ha can also be adjusted by changing the die gap, discharge speed, and the like.

A die coater was mentioned as a method for forming an active material layer on a metal foil, but the fluctuation ratio (ΔW / Wa
) May be used. For example, a gravure coater, a slide coater, or a caten coater may be used.

In this way, the metal foil (electrode) coated with the active material-containing layer is subjected to a drying process for removing volatile components in the active material-containing layer, and the electrode is wound up and rolled into a rolled state. Have

As described above, in at least one of the positive electrode and the negative electrode, the end portion in the width direction of the active material layer of the current collector forms a wave shape, so that the position of the coating end changes. It is possible to suppress the occurrence of convex portions near the coating end when the rolled roll state is obtained. In addition, even when the electrode is wound together with another member (for example, a separator), it is possible to suppress the occurrence of convex portions near the coating end. The height of the convex portion is mainly defined by the difference between h and ha.

FIG. 7 shows the relationship with the height of the convex portion near the coating end in the electrode-rolled roll state when the variation ratio (ΔW / Wa) is changed. For example, when ΔW / Wa ≦ 0.007, the height of the convex portion increases, while when 0.007 ≦ ΔW / Wa, the height of the convex portion can be significantly reduced. Further, when 0.010 ≦ ΔW / Wa, the height of the convex portion can be further reduced. This data is for when the number of wrinkles is 1000.

Moreover, the fracture | rupture of metal foil can be suppressed by suppressing the convex part generation | occurrence | production of coating end vicinity.

In particular, when the condition of the above expression (3) is satisfied, that is, when the height of the coating end is higher than the height of the other coating part, the above expression (1) or the above expression (2) is satisfied. Thus, it is possible to suppress the occurrence of convex portions near the coating end. Moreover, breakage of the metal foil can be suppressed.

Thus, in the process of forming the active material layer on the metal foil, the quality of the electrode is maintained by satisfying the above conditions. In addition, performance variations such as capacity and input / output characteristics of a secondary battery using the electrode can be suppressed.

The secondary battery according to the embodiment can be, for example, a nonaqueous electrolyte secondary battery. Alternatively, the secondary battery according to the embodiment may be a secondary battery using an aqueous solution as an electrolyte.

The secondary battery which concerns on embodiment can also comprise the additional electrodes other than the electrode demonstrated previously.

The secondary battery according to the embodiment typically includes one or more negative electrodes and one or more positive electrodes. The electrode described above is preferably a negative electrode.

The negative electrode can include a negative electrode current collector, a negative electrode active material-containing layer carried on at least one surface of the negative electrode current collector, and a negative electrode current collector tab extending from the negative electrode current collector. The negative electrode current collector and the negative electrode current collector tab may be integrated or separate.

As the negative electrode current collector, for example, a metal foil such as aluminum or copper can be used. As the material of the negative electrode current collector tab, the same material as that of the negative electrode current collector can be used.

The negative electrode active material-containing layer can include a negative electrode active material, an optional negative electrode conductive agent, and an optional negative electrode binder.

When the electrode demonstrated previously is a negative electrode, the negative electrode active material content layer may contain lithium titanate, for example, and may use amorphous graphite etc., for example.

Lithium titanate can act as a negative electrode active material. Examples of lithium titanate include Li4 + xTi5O12 (0≤x≤3) having a spinel structure and Li2 + yTi3O7 (0≤y≤3) having a ramsteride structure.

Such lithium titanate can occlude and release lithium ions at a potential of, for example, 1.55 V (vs. Li / Li +) or higher, so the surface of the negative electrode active material-containing layer containing lithium titanate In principle, lithium dendrite is not deposited even after repeated charge and discharge. Moreover, lithium titanate has almost no volume change accompanying charging / discharging reaction.

Examples of other active materials that can be included in the negative electrode active material-containing layer include carbonaceous materials such as graphite, tin-silicon alloy materials, and the like.

The particle shape of the negative electrode active material may be either granular or fibrous. In the case of a fiber, the fiber diameter is preferably 0.1 μm or less.

Examples of the negative electrode conductive agent include acetylene black, carbon black, and graphite. Examples of the binder for binding the negative electrode active material and the negative electrode conductive agent include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber, and the like.

The positive electrode can include a positive electrode current collector, a positive electrode active material-containing layer supported on at least one surface of the positive electrode current collector, and a positive electrode current collector tab extending from the positive electrode current collector. The positive electrode current collector and the positive electrode current collector tab may be integrated or separate.

As the positive electrode current collector, for example, a metal foil such as aluminum or copper can be used. As a material for the positive electrode current collector tab, the same material as that for the positive electrode current collector can be used.

The positive electrode active material-containing layer can contain a positive electrode active material, an optional positive electrode conductive agent, and an optional positive electrode binder.

As the positive electrode active material, for example, a general lithium transition metal composite oxide can be used. For example, LiCoO2, LiNi1-xCoxO2 (0 <x <0.3), LiMnxNiy
CozO2 (0 <x <0.5, 0 <y <0.5, 0 ≦ z <0.5), LiMn2-xMxO4 (
M is Li, Mg, Co, Al, Ni, 0 <x <0.2), LiMPO4 (M is Fe, Co
, Ni).

Examples of the positive electrode conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite. As the binder, for example, polytetrafluoroethylene (PT
FE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

The secondary battery according to the embodiment may further include an electrolyte. The electrolyte may be impregnated in the electrode group.

In the case of a nonaqueous electrolyte battery, a nonaqueous electrolyte is used as the electrolyte. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, and a gel non-aqueous electrolyte obtained by combining a liquid electrolyte and a polymer material. The liquid non-aqueous electrolyte can be prepared, for example, by dissolving the electrolyte in an organic solvent at a concentration of 0.5 mol / l or more and 2.5 mol / l or less.
Examples of the electrolyte include lithium perchlorate (LiClO 4), lithium hexafluorophosphate (LiPF 6), lithium tetrafluoroborate (LiBF 4), lithium hexafluoroarsenide (LiAsF 6), lithium trifluorometasulfonate ( LiCF3SO3), lithium salts such as bistrifluoromethylsulfonylimitolithium [LiN (CF3SO2) 2], or mixtures thereof can be mentioned. It is preferable that it is difficult to oxidize even at a high potential, and LiPF6 is most preferable.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate, and diethyl carbonate (DE).
C), chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me
THF), dioxolane (DOX) and other cyclic ethers, dimethoxyethane (DME),
Examples include chain ethers such as dietoethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents may be used alone or as a mixture of two or more.

Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

As the nonaqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, or the like may be used.

The secondary battery according to the embodiment may further include a battery container that houses the electrode group and the electrolyte.

As a battery container, the metal can formed from aluminum, aluminum alloy, iron, stainless steel etc. can be used, for example. The plate thickness of the battery container is preferably 0.5 mm or less, and more preferably 0.2 mm or less.

Alternatively, as the battery container, a container formed from a laminate film can be used instead of the metal can. As the laminate film, it is preferable to use a multilayer film composed of a metal foil and a resin film covering the metal foil. Polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) as resin
) And the like can be used. The thickness of the laminate film is desirably 0.2 mm or less.

Various shapes such as a square shape, a cylindrical shape, a thin shape, and a coin shape can be adopted as the shape of the battery container depending on the application.

In addition, the secondary battery according to the embodiment may further include a lead electrically connected to the electrode group. For example, the secondary battery according to the embodiment may include two leads. One lead can be electrically connected to the negative electrode current collecting tab. The other lead can be electrically connected to the positive current collecting tab.

The lead material is not particularly limited, and for example, the same material as the positive electrode current collector and the negative electrode current collector can be used.

The secondary battery according to the embodiment may further include a terminal electrically connected to the lead and drawn out from the battery container. For example, the secondary battery according to the embodiment can include two terminals. One terminal can be connected to a lead electrically connected to the negative current collector tab. The other terminal can be connected to a lead electrically connected to the positive current collecting tab.

Although the material of a terminal is not specifically limited, For example, the same material as a positive electrode collector and a negative electrode collector can be used.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions can be made without departing from the spirit of the invention.
Can be replaced or changed. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Exterior can, 2 ... Winding electrode group, 3 ... Positive electrode lead, 3a ... Connection plate, 3b ... Through-hole, 3
c ... 1st clamping strip, 3d ... 2nd clamping strip, 4 ... Negative electrode lead, 4a ... Connection plate, 4b ... Through-hole, 4c ... 1st clamping strip, 4d ... 2nd clamping strip,
6 ... Positive electrode terminal, 7 ... Negative electrode terminal, 8a ... Positive electrode current collector tab, 8b ... Positive electrode active material layer, 8c ... Positive electrode current collector, 9a ... Negative electrode current collector tab, 9b ... Negative electrode active material layer, 9c ... Negative electrode current collector Body, 10 ... Separator, 11, 12 ... Fixing member, 12a, 12b ... First and second holding parts, 14,15 ... Insulating gasket, 20 ... Battery, 61 ... First surface, 62 ... Second surface 63 ... Third surface, 64 ... Fourth surface, 65 ... Fifth surface, 66 ... Sixth surface, 200 ... Coating end

Claims (8)

A positive electrode and a negative electrode in which an active material layer is formed in a predetermined width in a partial region of the current collector;
A separator disposed between the positive electrode and the negative electrode;
In at least one of the positive electrode and the negative electrode, a corrugated portion at an end in the width direction of the active material layer of the current collector,
A secondary battery comprising: A width Wa in the width direction of the active material-containing layer and a variation width of the width in the width direction of the active material-containing layer are Δ
The secondary battery according to claim 1, wherein, when W, the following relationship is satisfied:
0.007 ≦ ΔW / Wa (Formula 1) When the height of the intermediate portion in the width direction of the active material-containing layer is ha and the height of the end portion of the active material-containing layer is h, the following relationship (Formula 2) is satisfied. The secondary battery according to claim 2.
ha ≦ h (Formula 2) In an electrode having an active material-containing layer,
An electrode having a corrugated portion at an end in the width direction of the active material-containing layer. The width of the active material containing layer in the width direction and a variation width in the width direction of the active material containing layer as ΔW are expressed by the following relationship (Formula 3). electrode.
0.007 ≦ ΔW / Wa (Formula 3) When the height of the intermediate portion in the width direction of the active material-containing layer is ha and the height of the end portion of the active material-containing layer is h, the following relationship (Formula 4) is satisfied. The electrode according to claim 5.
ha ≦ h (Formula 4) An electrode processing step for forming a corrugated portion at an end in the width direction of the active material-containing layer;
Winding the electrode;
A method for producing a secondary battery, comprising: The width of the active material-containing layer in the width direction Wa and a variation width in the width direction of the active material-containing layer are set as ΔW, and the following relationship (Formula 5) is satisfied. Of manufacturing a secondary battery.
0.007 ≦ ΔW / Wa (Formula 5)

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