Electrode plate and method for manufacturing electrode plate

Abstract

An electrode plate as one example of an embodiment of the present invention comprises: a current collector foil (10); a mixture layer (12) formed on the current collector foil (10); and an insulating layer (14) covering the mixture layer (12). The electrode plate is to be divided into a plurality of electrode plates. The thickness of the insulating layer (14) is smaller at an insulating layer slit section (14b), at which the electrode plate is to be cut when divided into the plurality of electrode plates, than at other sections.

Description

Electrode plate and method for manufacturing electrode plate

[0001] The present invention relates to an electrode plate that includes a current collector foil and a mixture layer formed on the current collector foil, and is to be divided into a plurality of pieces.

[0002] Conventionally, in lithium ion batteries, a method of coating a mixture layer with an insulating layer has sometimes been used as a technique for improving the safety of the battery. By coating with an insulating layer, it is possible to secure the strength of the electrode plate and suppress internal short-circuiting while suppressing deterioration of battery performance. In particular, in order to prevent short-circuiting at the end portion of the electrode, a technique is known in which a portion including the end portion of the mixture layer and the end portion of the current collector foil is coated with an insulating layer (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No.2019-75202

[0004] In the aforementioned process, coating the mixture layer and the end portion of the current collector foil with an insulating layer increases the load during electrode cutting (slitting), which gives rise to problems such as wear of the slitter blade and deterioration of cutting quality. In addition, falling off and peeling due to cracking of the insulating layer may occur.

[0005] The electrode plate according to the present disclosure is an electrode plate that includes a current collector foil and a mixture layer formed on the current collector foil, and is to be divided into a plurality of pieces, the electrode plate including an insulating layer covering the mixture layer, wherein the thickness of the insulating layer at an insulating layer slit portion that is to be cut when dividing into a plurality of pieces is smaller than that of other portions.

[0006] The method for manufacturing an electrode plate according to the present disclosure includes: forming a mixture layer on a surface of a long current collector foil while moving the current collector foil; and forming an additional insulating layer on the mixture layer from a plurality of insulating material supply units arranged at predetermined intervals in a width direction while moving the current collector foil on which the mixture layer has been formed, wherein in a portion of the insulating layer corresponding to between the plurality of insulating material supply units, an insulating layer slit portion to be cut, which has a smaller thickness than other portions, is formed.

[0007] According to the present disclosure, by controlling the film thickness of the insulating layer slit portion, it is possible to suppress wear of the slitter blade during slitting and suppress falling off and cracking of the insulating layer.

[0008] This is a plan view showing an example of the configuration of an electrode plate according to the embodiment. This is a cross-sectional view taken along line A-A in Figure 1. This diagram illustrates the formation of an insulating layer using a spray head, where (A) is a front view and (B) is a plan view showing the configuration of the insulating layer. This diagram illustrates the adjustment of the thickness of the insulating layer by setting the height of the spray head. This diagram schematically shows the process of forming the mixture layer and the insulating layer while moving the current collector foil.

[0009] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are not limiting to this disclosure, and configurations formed by selectively combining multiple examples are also included in this disclosure.

[0010] "Electrode Plate Configuration" Figure 1 is a plan view showing an example of the electrode plate configuration according to the embodiment, and Figure 2 is a cross-sectional view taken along line A-A in Figure 1.

[0011] The electrode plate 100 is a long, strip-shaped piece, but in Figure 1, only a portion in the longitudinal direction (vertical direction in the figure) is shown. In this example, the composite layer 12 is formed on the current collector foil 10, leaving both ends in the width direction untouched. The current collector foil 10 is exposed at both ends.

[0012] Then, an insulating layer 14 is formed on the mixture layer 12. This insulating layer 14 includes an insulating layer body portion 14a and an insulating layer slit portion 14b. That is, the insulating layer 14 is formed with three rows of insulating layer body portions 14a arranged in the width direction in the longitudinal direction, and two rows of insulating layer slit portions 14b, which will be cut in a later process, are formed between the three rows of insulating layer body portions 14a (in the width direction).

[0013] In Figure 1, the cutting line is indicated by a vertical dashed line.

[0014] As shown in Figure 2, the insulating layer slit portion 14b gradually tapers in thickness from the ends of the two insulating layer main portions 14a located on either side toward the center, with the thickness becoming thinner in the central portion. Taking the thickness of the insulating layer main portion 14a, which is the maximum thickness of the insulating layer 14, as 100%, the insulating layer slit portion 14b can have a thickness of 20 to 90%. In other words, the depth of the insulating layer slit portion 14b is 20 to 90% at the bottom of the insulating layer slit portion 14b, with the maximum thickness of the insulating layer 14 being 100%. In Figure 2, the case of a thickness (depth) of 90% is shown by a solid line, and the case of 20% is shown by a dashed line.

[0015] The width of the insulating layer slit portion 14b, specifically the points where the thickness of the insulating layer 14 begins to thin (the ends of the insulating layer body portion 14a), can be made larger than 0.2 mm. This allows the insulating layer slit portion 14b to be properly constructed.

[0016] The electrode plate 100 is, for example, an electrode plate of an energy storage device such as a lithium-ion battery, and is either a positive electrode plate or a negative electrode plate. If the electrode plate 100 is a positive electrode plate, the current collector foil 10 is, for example, a foil made of aluminum or an aluminum alloy, and the composite layer 12 is a layer containing a positive electrode active material mainly composed of a lithium-containing metal composite oxide, a conductive agent, and a binder. If the electrode plate 100 is a negative electrode plate, the current collector foil 10 is a foil made of copper or a copper alloy, and the composite layer 12 is a layer containing a negative electrode active material mainly composed of, for example, a carbon material, and a binder. In an energy storage device such as a lithium-ion battery, the positive electrode plate and the negative electrode plate are arranged via a separator made of a porous sheet that has ion permeability and insulating properties.

[0017] "Manufacturing Method" Figure 3 illustrates the formation of an insulating layer 14 using a spray head 30 as an insulating material supply unit, where (A) is a front view and (B) is a plan view showing the configuration of the insulating layer 14. As shown, one spray head 30 is provided corresponding to one row of the insulating layer body portion 14a. Multiple spray heads 30 are installed at predetermined intervals in the width direction of the electrode plate 100. By spraying insulating material from the spray heads 30, the insulating material is deposited on the mixture layer 12 to form the insulating layer 14. At this time, the thickness of the insulating layer 14 in the overlapping portion where the insulating material is deposited overlaps changes depending on the spacing of the spray heads 30 and the spreading angle when spraying the insulating material. Also, if the spreading angle is constant, the thickness of the insulating layer 14 changes depending on the height of the spray head 30 from the surface of the mixture layer 12.

[0018] In the example shown in Figure 3, by setting a wider spacing between the spray heads 30, the amount of insulating material sprayed is reduced in the area between the spray heads 30, and insulating layer slits 14b are formed there. In this example, the cross-section of the insulating layer slits 14b is an arc-shaped recess.

[0019] Furthermore, a composite layer 12 is formed on the current collector foil 10, and then an insulating layer 14 is formed on the composite layer 12. The composite layer 12 can also be formed by spraying from a spray head.

[0020] Furthermore, the formation of the composite layer 12 and the insulating layer 14 can be carried out while moving the long current collector foil 10, but the spray head may also be moved.

[0021] Furthermore, the mixture layer 12 and the insulating layer 14 can also be formed by coating a liquid material instead of spraying it from a spray head. When forming the insulating layer 14 by coating, a thin insulating layer slit portion 14b can be formed by setting the nozzle shape such that the amount of insulating material supplied gradually decreases from the ends in the width direction (the ends of the insulating layer body portion 14a) toward the center of the insulating layer slit portion 14b.

[0022] Figure 4 illustrates the adjustment of the thickness of the insulating layer 14 by setting the height of the spray head 30.

[0023] In the left diagram, because the height from the surface of the mixture layer 12 is relatively low, the insulating material does not spread, and an insulating layer slit portion 14b is formed at a position corresponding to the gap between the spray heads 30. In the right diagram, because the height is relatively high, the insulating material from the two spray heads 30 overlaps, and a bulge 14c is formed at a position corresponding to the gap between the spray heads 30. Therefore, the thickness of the insulating layer slit portion 14b can be controlled by adjusting the height of the spray heads 30. For this reason, the distance between the spray heads 30 and the surface of the mixture layer 12 is set to a predetermined distance such that the thickness of the insulating layer slit portion 14b is appropriate.

[0024] Figure 5 schematically shows the process of forming the composite layer 12 and the insulating layer 14 while moving a long current collector foil 10.

[0025] First, the current collector foil 10 is wound onto a roll 40. The current collector foil 10, pulled out from the roll 40, moves along a predetermined track by rollers 42, 42. On the track, a spray head 32 for forming the mixture layer 12 and a spray head 30 for forming the insulating layer 14 are provided in this order, and the insulating layer 14 is formed on the mixture layer 12. This insulating layer 14 includes an insulating layer body portion 14a and an insulating layer slit portion 14b. Once the insulating layer 14 is formed in this way, the mixture layer 12 and the insulating layer 14 are dried in a drying oven 44. Then, the insulating layer is cut longitudinally at the insulating layer slit portion 14b by a rotary cutter 50 having a slit blade provided at a position corresponding to the insulating layer slit portion 14b. After that, it is cut into predetermined lengths to obtain electrode plates for a power storage device.

[0026] "Effects of the Embodiment" According to the electrode plate of this embodiment, the thickness of the insulating layer slit portion 14b of the insulating layer 14 can be made thinner than that of the insulating layer main body portion 14a. Therefore, the load (slit blade wear) when cutting the insulating layer slit portion 14b can be reduced, and detachment and cracking due to cracking of the insulating layer can be suppressed. In particular, by varying only the thickness of the insulating layer slit portion 14b, effective suppression of slit blade wear and improvement of cracking at the edges of the insulating layer 14 can be achieved.

[0027] As a method for controlling the thickness of the insulating layer 14, the thickness of the overlapping area sprayed from multiple spray heads 30 can be controlled by adjusting the height of the spray heads 30.

[0028] Furthermore, by making the thinnest part of the insulating layer slit portion 14b at least 10% of the thickness of the insulating layer main body portion 14a, the insulation requirements can be met.

[0029] 10 Current collector foil, 12 Mixture layer, 14 Insulating layer, 14a Insulating layer main body, 14b Insulating layer slit, 14c Bump, 30 Spray head, 32 Spray head, 40 Roll, 42 Roller, 44 Drying oven, 50 Rotary cutter, 100 Electrode plate

Claims

1. An electrode plate having a current collector foil and a composite layer formed on the current collector foil, and intended to be divided into multiple parts, wherein the electrode plate includes an insulating layer covering the composite layer, and the thickness of the insulating layer is thinner in the insulating layer slit portions that are intended to be cut when the electrode plate is divided into multiple parts.

2. The electrode plate according to claim 1, wherein the depth of the insulating layer slit is 20 to 90% at the bottom of the insulating layer slit, with the maximum thickness of the insulating layer being 100%.

3. The electrode plate according to claim 1 or 2, wherein the width between the points where the thickness of the insulating layer begins to decrease is greater than 0.2 mm.

4. A method for manufacturing an electrode plate, comprising: moving a long current collector foil while forming a composite layer on its surface; moving the current collector foil on which the composite layer has been formed while further forming an insulating layer on the composite layer from a plurality of insulating material supply units arranged at a predetermined distance in the width direction; and forming an insulating layer slit portion, which is thinner than the other portion and is to be cut, in the portion of the insulating layer corresponding to the plurality of insulating material supply units.

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