JP5761310B2 - battery - Google Patents

Description

  The present invention relates to a battery provided with a wound power generation element in which a strip electrode plate is wound.

  As a power generation element of a nonaqueous electrolyte secondary battery, a winding type in which a strip electrode plate is wound and a laminated type in which a plate electrode plate is laminated are used. Among these, the wound power generation element is obtained by winding a strip-like positive electrode plate and a strip-like negative electrode plate having a mixture layer provided on the surface of a current collector with a separator interposed therebetween.

  As the current collector, an aluminum foil or a copper foil is used, and the mixture layer contains an active material, a binder, a conductive assistant, and the like.

  FIGS. 5 and 6 show a strip electrode plate of a small nonaqueous electrolyte secondary battery having a capacity smaller than 1 Ah. FIG. 5 shows the plane of the strip electrode plate before cutting, FIG. 6 shows the strip electrode plate after cut, FIG. 6 (A) is a plane, and FIG. 6 (B) is AA of FIG. 6 (A). 'Show cross section. 5 and 6, 21 is a mixture layer, 22 is a current collector, 23 is an uncoated portion of the mixture layer, X is a width direction, and Y is a length direction.

  As shown in FIG. 5, the strip electrode plate of the conventional small non-aqueous electrolyte secondary battery is coated with a mixture layer on the surface of a metal strip collector, dried, and then pressed with a roll press. By adjusting the thickness of the mixture layer, it is produced in a state where several strip electrode plates are continuous in the width direction, and as shown by the dotted line in FIG. 5, it is cut into several sheets in the length direction. A single strip electrode plate shown in FIG. 6 is obtained. In this strip-shaped electrode plate, as shown in FIG. 6 (A), when a mixture layer uncoated portion is provided at one end in the lengthwise direction and wound into a power generation element, this mixture layer is not applied. A current collecting lead is attached to the application part.

In the sheet-like electrode, when the sheet-like current collector is pressed in order to increase the density of the mixture layer, there is a problem that undulation or distortion occurs on the surface of the sheet-like electrode, and a technique for correcting this distortion is disclosed in Patent Document 1. And Patent Document 2.
JP 2004-335374 A JP 2007-273390 A

  As shown in FIG. 5, the conventional strip electrode plate has a mixture layer applied to the entire width direction of the strip collector. A mixture layer is formed on the entire surface of the electric body. When roll pressing is performed in this state, a uniform pressure is applied to the entire surface of the current collector, so that the current collector is not deformed and a strip-shaped electrode plate without bending can be obtained.

  However, when winding such an uncurved strip electrode plate as a power generation element, there is a problem that the electrode plate is displaced in the width direction during winding, the capacity of the battery is reduced, and sufficient output cannot be obtained. It was.

  Moreover, in the technique for correcting the distortion of the sheet-like electrode described in Patent Document 1 or Patent Document 2, the distortion of the uncoated part of the mixture layer is corrected, but how much is finally obtained in the electrode plate It was unknown whether the distortion remained.

Accordingly, an object of the present invention is to provide a battery including a power generating element in which winding deviation is suppressed using a curved strip electrode plate.

According to the first aspect of the present invention, a strip-shaped positive electrode plate in which a mixture layer and a mixture layer uncoated portion are formed, and a strip-shaped negative electrode plate in which a mixture layer and a mixture layer uncoated portion are formed are interposed via a separator. In the battery including the wound-type power generation element wound by winding, the belt-like positive electrode plate and the belt-like negative electrode plate are each formed in a truncated cone shape having a curvature in the length direction of 0.4 to 2.5 mm / m. In the wound power generation element, the smaller one of the strip-shaped positive plates formed in a truncated cone shape and the larger one of the strip-shaped negative plates formed in a truncated cone shape are opposite to each other. It is located on the side .

According to invention of Claim 1, the electric power generation element by which winding deviation was suppressed can be provided.

(Outline of the present invention)
First, the outline of the battery according to the present invention will be described.

The battery according to the present invention includes a strip-like positive electrode plate in which a mixture layer and a mixture layer uncoated portion are formed, and a strip-shaped negative electrode plate in which a mixture layer and a mixture layer uncoated portion are formed via a separator. In the battery including the wound-type power generation element wound by winding, the belt-like positive electrode plate and the belt-like negative electrode plate are each formed in a truncated cone shape having a curvature in the length direction of 0.4 to 2.5 mm / m. In the wound power generation element, the smaller one of the strip-shaped positive plates formed in a truncated cone shape and the larger one of the strip-shaped negative plates formed in a truncated cone shape are opposite to each other. It is a battery located on the side.

The battery according to the present invention relates to a non-aqueous electrolyte secondary battery including a wound positive power generation element in which a strip-like positive electrode plate and a strip-like negative electrode plate having a mixture layer provided on the surface of a current collector are wound through a separator. Therefore, a mixture layer uncoated portion is provided at one end in the width direction of the belt-like current collector on both the belt-like positive electrode plate and the belt-like negative electrode plate, and the curvature rate in the length direction of these belt-like current collectors is 0. 4 to 2.5 mm / m, and in this winding type power generation element, winding was performed so that the mixture layer uncoated portion of the strip-shaped positive plate and the mixture layer uncoated portion of the strip-shaped negative plate protruded from the opposite sides You may do it.

In this case, by using a strip electrode plate having a longitudinal curvature of the strip current collector in the range of 0.4 to 2.5 mm / m, the winding displacement of the strip electrode of the wound power generation element is suppressed. Thus, a non-aqueous electrolyte secondary battery with stable capacity and output can be obtained.

  A strip electrode plate of the nonaqueous electrolyte secondary battery of the present invention will be described with reference to FIGS. 1 and 2. 1 is a plan view of a strip electrode plate before cutting, FIG. 2 is a plan view of a strip electrode plate after cut, and in FIGS. 1 and 2, 1 is a mixture layer, 2 is a mixture layer of a current collector An application part, X is a width direction, Y shows a length direction.

  As shown in FIG. 1, the strip electrode plate of a large non-aqueous electrolyte secondary battery having a capacity larger than 5 Ah is not coated with a mixture layer at both ends in the width direction on the surface of a metal strip collector. The mixture layer 1 is applied so that the part 2 is formed, dried, and then pressed by a roll press to adjust the thickness of the mixture layer. And as shown with the dotted line of FIG. 1, the strip | belt-shaped electrode plate shown in FIG. 2 is obtained by cutting into two pieces in a length direction. As shown in FIG. 2, the obtained strip-shaped electrode plate is provided with a mixture layer uncoated portion at one end in the width direction. Current collecting leads are attached to a plurality of locations.

  In the strip-shaped electrode plate shown in FIG. 1, when the mixture layer is pressed with a roll press after drying, the mixture layer 1 is at the center in the width direction of the current collector, and the mixture layer is not formed at both ends in the width direction. Since the application part 2 is formed, pressure is applied only to the central part of the current collector, and no pressure is applied to the mixture layer uncoated part at both ends in the width direction. Therefore, since the deformation of the current collector is different between the mixture layer application portion and the mixture layer non-application portion of the current collector, a curved strip electrode plate as shown in FIG. 2 is obtained.

  That is, as shown in FIG. 2, one end of the mixture layer uncoated portion in the width direction of the strip electrode plate is A, the other end is B, and the middle point of the mixture layer uncoated portion is C, A Assuming that the middle point connecting B and B with a straight line is D, there is a slight gap between C and D, and the mixture layer uncoated portion is a curve with A-C-B connected.

  Therefore, in the present invention, the “curvature ratio in the length direction of the belt-like current collector” (hereinafter simply referred to as “curvature ratio”) is “C when the distance between A and B in FIG. -Distance between -D (mm / m) ". And in the strip | belt-shaped electrode plate used for the nonaqueous electrolyte secondary battery of this invention, a curvature is made into the range of 0.4-2.5 mm / m.

  Next, a procedure for producing a power generation element using the strip-shaped current collector shown in FIG. 2 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing a strip-shaped positive electrode plate, a strip-shaped negative electrode plate, and a separator before being made into a power generation element, and FIG. 4 is a diagram showing an appearance of the wound power generation element of the present invention. 3 and 4, 11 is a strip-like positive electrode plate, 12 is a positive electrode mixture layer, 13 is a positive electrode mixture layer uncoated portion, 14 is a belt-like negative electrode plate, 15 is a negative electrode mixture layer, and 16 is a negative electrode mixture. A layer non-application part, 17 is a separator, 18 is a winding type electric power generation element.

  First, as shown in FIG. 3, the strip-shaped positive electrode plate 11, the separator 17, and the strip-shaped negative electrode plate 14, and the positive electrode mixture layer uncoated portion 13 and the negative electrode mixture layer uncoated portion 16 are mutually connected to the strip electrode. Laminate and wind so that the separator (17) / strip negative electrode plate (14) / separator (17) / strip positive electrode plate (11) are arranged in order from the bottom so that they are on the opposite side of the plate width direction. Thus, the cylindrical wound power generation element shown in FIG. 4 is obtained.

  As shown in FIG. 4, in the wound power generation element 18, the belt-like positive electrode plate 11 and the belt-like negative electrode plate 14 are each formed by winding a curved belt-like electrode plate. The diameter E of the end portion of the agent layer non-applied portion 13 has a truncated cone shape smaller than the diameter F of the end portion to which the mixture layer is applied. Similarly, the strip-shaped negative electrode plate 14 also has a truncated cone shape.

  As a result, in the wound power generation element 18, the smaller diameter of the frustoconical strip-shaped positive electrode plate 11 and the smaller diameter of the frustoconical strip-shaped negative electrode plate 14 are positioned on opposite sides. The smaller diameter of the frustoconical strip-shaped positive plate 11 and the larger diameter of the frustoconical strip-shaped negative plate 14 are in the same direction, and the larger diameter of the truncated conical strip-shaped positive plate 11 and the cone Since the smaller diameter of the trapezoidal strip-shaped negative electrode plate 14 is in the same direction, the larger diameter of the truncated cone shape is compressed by the smaller diameter. Due to this compression force, frictional force is generated at both ends of the central axis of the power generating element and tightened, and the belt-like positive electrode plate and the belt-like negative electrode plate are prevented from shifting in the direction of the central axis of the power generating element.

  In the present invention, the curvature rate of the strip electrode plate is in the range of 0.4 to 2.5 mm / m, but when the curvature rate is smaller than 0.4 mm / m, the frictional force is small, so In the case where the curving rate is larger than 2.5 mm, the winding deviation is increased in the shape of a bamboo shoot in the winding process, so that the positive electrode and the negative electrode are opposed to each other.

  The non-aqueous electrolyte secondary battery can be obtained by storing the power generation element thus produced in a battery case, welding a battery lid, and injecting an electrolytic solution.

  Examples and Comparative Examples of the present invention will be described using a non-aqueous electrolyte secondary battery as an example. However, it goes without saying that the power generation element of the present invention is applicable not only to non-aqueous electrolyte secondary batteries but also to other batteries.

[Example 1]
The positive electrode plate was produced by the following procedure. First, a mixture comprising 87% by weight of LiCoO ₂ powder as a positive electrode active material, 5% by weight of acetylene black as a conductive additive and 8% by weight of polyvinylidene fluoride (hereinafter referred to as “PVdF”) as a binder. N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”) was added to the mixture to prepare a positive electrode mixture paste.

  Next, at the center of the surface of the strip-shaped aluminum current collector having a width of 200 mm and a thickness of 20 μm, 14 mm of uncoated portions are left at both ends in the width direction, and the current collector is continuously joined in the length direction. After the agent layer was applied and dried, the mixture layer was pressurized with a roll press.

Next, after the electrode plate is cut in half, the mixture layer is applied to the central portion of the current collector by heating and drying to 120 ° C. in a state where the pressure is reduced to a vacuum, and 14 mm each is applied to both ends in the width direction. A coiled positive electrode plate having a portion was obtained. This positive electrode plate had a width of 100 mm, an uncoated portion of 14 mm was formed at one end in the width direction, and the curvature was 0.4 mm / m.

The negative electrode plate was produced by the following procedure. First, NMP was added to a mixture of 94% by weight of graphite (Gr) as a negative electrode active material and 6% by weight of PVdF as a binder to prepare a negative electrode mixture paste in a paste form.

  Next, in the center of the surface of the strip-shaped copper current collector having a width of 196 mm and a thickness of 15 μm, 10 mm of uncoated portions are left at both ends in the width direction, and the mixture is continuously mixed in the length direction of the current collector. After the layer was applied and dried, the mixture layer was pressed with a roll press.

  Next, after this electrode plate is cut in half, the mixture layer is applied to the central part of the current collector by heating and drying at 120 ° C. in a state where the pressure is reduced to a vacuum, and 10 mm each is applied to both ends in the width direction. A coiled negative electrode plate having a portion was obtained. This negative electrode plate had a width of 98 mm, an uncoated portion of 10 mm was formed at one end in the width direction, and the curvature was 0.4 mm / m.

  And the winding type which wound the positive electrode plate (length 4000mm) and the negative electrode plate (length 4200mm) through the separator using the polyethylene / polypropylene two-layer separator of length 8900mm, width 96mm, and thickness 15μm. Power generation element.

  Next, the positive electrode terminal provided on the battery lid and the positive electrode plate of the power generation element are connected by lead wires, the negative electrode terminal and the negative electrode plate of the power generation element are connected by lead wires, and the power generation element is stored in the battery case, The battery case and the battery lid are laser welded. And the non-aqueous electrolyte secondary battery A of Example 1 was obtained by inject | pouring electrolyte solution from the electrolyte solution injection port provided in the battery cover, and sealing an electrolyte solution injection port.

As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / L of LiPF ₆ in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC) in a volume ratio of 30:40:30 is used. It was. The design capacity of the obtained battery was 6 Ah. In addition, all processes from production of the positive electrode plate and the negative electrode plate to battery assembly were performed in a dry room having a dew point of −50 ° C. or less.

[Example 2]
The non-aqueous solution of Example 2 was obtained in the same manner as in Example 1 except that the curvature of the belt-like positive electrode plate and the belt-like negative electrode plate was 1.0 mm / m by controlling the roll bend and tension of the roll press apparatus. An electrolyte secondary battery B was obtained. In Example 2, the roll vent was increased and the tension was reduced compared to Example 1.

[Example 3]
The non-aqueous solution of Example 3 is the same as Example 1 except that the curvature of the belt-like positive electrode plate and the belt-like negative electrode plate is set to 2.5 mm / m by controlling the roll bend and tension of the roll press apparatus. An electrolyte secondary battery C was obtained. In Example 3, the roll vent was increased and the tension was reduced compared to Example 2.

[Comparative Example 1]
The non-aqueous solution of Comparative Example 1 was prepared in the same manner as in Example 1 except that the curvature of the belt-like positive electrode plate and the belt-like negative electrode plate was set to 0.2 mm / m by controlling the roll bend and tension of the roll press apparatus. An electrolyte secondary battery D was obtained. In Comparative Example 1, the roll vent was reduced and the tension was increased compared to Example 1.

[Comparative Example 2]
The non-aqueous solution of Comparative Example 2 is the same as Example 1 except that the curvature of the belt-like positive electrode plate and the belt-like negative electrode plate is set to 3.0 mm / m by controlling the roll bend and tension of the roll press apparatus. An electrolyte secondary battery E was obtained. In Comparative Example 2, the roll vent was increased and the tension was reduced as compared with Example 3.

[Characteristic measurement]
About the battery of Examples 1-3 and Comparative Examples 1 and 2, the characteristic was evaluated with the following method.

  After charging the battery, it was discharged, and after further charging, it was left in an environment of 40 ° C. for 20 days in an SOC 50% state. Next, after passing through the history of discharge and charge, it was left in an environment at 25 ° C. for 21 days with the SOC adjusted to 20%.

  Thereafter, the battery was vibrated. The conditions are as follows. After the battery was firmly fixed to the vibration test apparatus, 7 Hz → 200 Hz → 7 Hz was changed for 15 min. A total of 9 hours was swept 12 times in 3 directions. The sweep speed was maintained at 1 gn peak acceleration from 7 Hz to 18 Hz, and the vibration was increased until the peak acceleration was 8 gn with the amplitude maintained at 0.8 mm. Thereafter, the peak acceleration of 8 gn was maintained up to 200 Hz. The battery voltage was measured at SOC 20%, 25 ° C., before and after standing for 21 days, and after the vibration test thereafter.

  About the battery of Examples 1-3 and Comparative Examples 1 and 2, the above-mentioned measurement was implemented 200 pieces each. The determination of the slight short circuit was made from the following two. One was to calculate the voltage difference before and after each battery was left, and from the average value of the voltage before being left, the battery voltage drop of 0.3% or more was regarded as a short circuit. The other is that the voltage difference before and after the vibration test of each battery was calculated, and the case where the battery voltage decreased by 2% or more from the average value of the voltage before standing was regarded as the occurrence of a fine short circuit.

  The characteristic measurement results are shown in Table 1.

  From the results of Table 1, in the nonaqueous electrolyte secondary batteries of Examples 1 to 3 having a curvature of 0.4 to 2.5 mm, there was no occurrence of a fine short circuit, whereas the curvature was outside this range. It was found that the non-aqueous electrolyte secondary batteries of Comparative Examples 1 and 2 in FIG.

The figure which shows the plane of the strip | belt-shaped electrode plate before cutting of this invention. The figure which shows the plane of the strip | belt-shaped electrode plate after cutting of this invention. The figure which shows the strip | belt-shaped positive electrode plate, strip | belt-shaped negative electrode plate, and separator before making it an electric power generation element. The figure which shows the external appearance of the wound type electric power generation element of this invention. The figure which shows the plane of the strip | belt-shaped electrode plate before the conventional cut. The figure which shows the plane and cross section of the strip | belt-shaped electrode plate after the conventional cut.

1: Mixture layer 2: Collector layer uncoated portion of current collector 11: Band-shaped positive electrode plate 12: Positive electrode mixture layer 13: Positive electrode mixture layer uncoated portion 14: Band-shaped negative electrode plate 15: Negative electrode mixture layer 16 : Negative electrode mixture layer uncoated portion 17: Separator 18: Winding type power generation element

Claims (1)

A winding type in which a strip-like positive electrode plate in which a mixture layer and a mixture layer uncoated portion are formed, and a strip-shaped negative electrode plate in which a mixture layer and a mixture layer uncoated portion are formed are wound through a separator. In batteries with power generation elements,
The belt-like positive electrode plate and the belt-like negative electrode plate are each formed in a truncated cone shape with a curvature in the length direction of 0.4 to 2.5 mm / m,
In the wound power generation element, the smaller one of the strip-shaped positive plates formed in a truncated cone shape and the smaller one of the strip-shaped negative plates formed in a truncated cone shape are opposite to each other. position be that the non-aqueous electrolyte secondary batteries.