Electrode for electrochemical device, electrochemical device, and method for manufacturing the same

Abstract

An electrode is provided, which can function as an electrode of an electrochemical device and can prevent electrical short circuit with adjacent electrodes, and can prevent electrical short circuit at the boundary portion between a coated portion and an uncoated portion, and can prevent the active material layer from peeling off from a current collector, and a portion of the uncoated portion can function as an electrode connector. The electrode for an electrochemical device includes: a coated portion in which an active material layer 3 is formed on a current collector 2; an uncoated portion in which the active material layer 3 is not formed; and a resin layer 4, the resin layer 4 being stacked so that a portion of the coated portion and the uncoated portion are covered; wherein: the resin layer 4 contains a high permeability portion 4a having high ion permeability and located on the coated portion; a low permeability portion 4b having low ion permeability and located on a portion of the uncoated portion; and a transition portion 4c whose ion permeability decreases as it moves from the high permeability portion 4a side toward the low permeability portion 4b side and is located between the high permeability portion 4a and the low permeability portion 4b.

Description

[0001] This application is a divisional application of an application with an application date of October 31, 2017, an invention name of “Electrode for electrochemical device, electrochemical device, and method for manufacturing the same”, an international application number of PCT / JP2017 / 039290 and a Chinese national application number of 201780067975.8. Technical Field

[0002] The present invention relates to an electrode for an electrochemical device, an electrochemical device, and a method for manufacturing an electrochemical device and an electrode for an electrochemical device. Background Art

[0003] A stacked electrochemical device is a type of electrochemical device, such as secondary batteries widely used as power sources for mobile phones, digital cameras, laptop computers, electric vehicles, and home energy storage systems. The stacked electrochemical device includes a multilayer electrode body having a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators separating each pair of positive and negative electrodes.

[0004] An electrode sheet for an electrochemical device includes a coated portion coated with an active material on a current collector and an uncoated portion on which the active material is not coated to connect an electrode terminal. A conductive auxiliary agent and / or an adhesive may also be applied. In a stacked electrochemical device, a multilayer electrode body is sealed in an external container. One end of the positive terminal is electrically connected to the non-coated portion of the positive electrode, and the other end extends to the outside of the external container. One end of the negative terminal is electrically connected to the non-coated portion of the negative electrode, and the other end extends to the outside of the external container. The electrolyte is sealed inside the external container together with the multilayer electrode body.

[0005] The capacity of secondary batteries increases year by year, and the heat generated in a short circuit event also increases. Therefore, it is necessary to further take measures for the secondary batteries to meet safety. An example of such a safety measure is a structure in which a belt-type insulating member is provided on the boundary portion between the coating portion and the non-coating portion to prevent a short circuit between the positive electrode and the negative electrode.

[0006] Patent Document 1 discloses an electrode having a structure in which an alumina slurry is applied on a boundary portion between a coated portion and an uncoated portion of a positive electrode to form an alumina-containing layer instead of a tape-type insulating member.

[0007] Patent Document 2 discloses a structure in which the density of the protruding insulating member on the surface of the current collector is different from the density in a region where the thickness of the end portion of the positive electrode active material layer is uneven (ie, uneven region).

[0008] Patent Document 3 discloses a structure in which a heat-resistant porous layer is provided so that the heat-resistant porous layer and a current collector encapsulate an active material layer.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: JP2012-74359A

[0012] Patent Document 2: WO2013 / 176161A

[0013] Patent Document 3: JP2012-99385A SUMMARY OF THE INVENTION

[0014] Problem that the invention aims to solve

[0015] Patent Document 1 describes an example in which an aluminum oxide-containing layer is provided only in a tapered region where the thickness of the active material layer gradually decreases. In the invention of Patent Document 2, one end of a protruding insulating member is provided in an uneven region at the end of the active material layer.

[0016] In Patent Document 1 and Patent Document 2, it is difficult to identify the boundary portion between the flat portion and the portion where the thickness of the active material layer varies. Therefore, the position of the insulating member tends to become unstable. On the other hand, if the length of the portion where the thickness varies is increased, the insulating member can be easily set. However, increasing the length of the portion where the thickness varies is not preferred because the capacitance energy density of that portion is small. There is also a concern that if a protruding insulating member is formed by a coating process using an inkjet method as in Patent Document 2, productivity will be reduced.

[0017] In the invention of Patent Document 3, the entire active material layer is covered with a heat-resistant porous layer. However, no consideration is given to any variation in thickness at the end of the active material layer, nor to the thickness of the heat-resistant porous layer formed on the current collector.

[0018] The present invention provides an electrode for an electrochemical device, an electrochemical device, and a method for manufacturing the electrode and the electrochemical device, which can prevent the occurrence of an electrical short circuit with an adjacent electrode, prevent or reduce the decrease in capacitance energy density, and prevent the peeling of an active material layer applied to the electrode.

[0019] Means of solving the problem

[0020] An electrode for an electrochemical device includes: a coated portion on a current collector, in which an active material layer is formed; an uncoated portion, in which the active material layer is not formed; and a resin layer, which is stacked to cover a portion of the uncoated portion and the coated portion; wherein: the resin layer has: a high permeability portion having high ion permeability and located on the coated portion; a low permeability portion having low ion permeability and located on a portion of the uncoated portion; and a transition portion whose ion permeability decreases as it moves from the high permeability portion side toward the low permeability portion side and which is located between the high permeability portion and the low permeability portion.

[0021] Effects of the Invention

[0022] The present invention can prevent electrical short circuits with adjacent electrodes, while it prevents or reduces a decrease in capacitance energy density.

[0023] Furthermore, the present invention also achieves the effect of preventing the active material layer applied on the electrode from peeling off.

[0024] Furthermore, when the resin layer is formed by applying the coating agent, the thickness may be gradually reduced toward the end of the resin layer. In a conventional structure having an adhesive insulating tape, a difference in thickness occurs at an edge portion of the insulating tape.

[0025] However, the difference in thickness can be prevented or reduced by using the structure of the present invention as described above. Therefore, when multiple electrodes of the present invention are stacked, uniform pressure can be applied to the stacked electrodes when people use them. As a result, the reduction in cycle properties can be prevented or reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A is a side view of an electrode according to an exemplary embodiment of the present invention.

[0027] Figure 1B The electrode is Figure 1A A top view of the electrode is shown in FIG.

[0028] Figure 1C yes Figure 1A An enlarged view of the main part.

[0029] Figure 2A is a top view showing an active material layer forming step of an exemplary embodiment of the method for manufacturing an electrode of the present invention.

[0030] Figure 2B It is shown in Figure 2A 2 is a side view of an active material layer forming step shown in FIG.

[0031] Figure 3A It is shown in Figure 2A and 2B2 is a top view of the resin layer forming step after the active material layer forming step shown in FIG.

[0032] Figure 3B It is shown in Figure 3A 4 is a side view of a resin layer forming step shown in FIG.

[0033] Figure 4 It is a side view schematically showing a resin layer forming step of the method for producing an electrode of the present invention.

[0034] Figure 5 is a side view schematically showing another example of the resin layer forming step of the method for producing an electrode of the present invention.

[0035] Fig. 6A is a side cross-sectional view of a stacked secondary battery as an example of the electrochemical device of the present invention.

[0036] Figure 6B It is along Fig. 6A Cross-sectional view taken along line AA.

[0037] Embodiments of the present invention

[0038] Next, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[0039] The basic structure of the electrode

[0040] Next, the basic structure of an electrode according to an exemplary embodiment of the present invention is described. Figures 1A-1C The electrode 1 shown in FIG. 1 includes a current collector 2 and an active material layer 3 coated on the current collector 2. The active material layer 3 is formed on both sides of the current collector 2 so that coated and uncoated portions of the active material layer 3 exist on both sides of the current collector 2.

[0041] More specifically, one end portion of the active material layer 3 in the longitudinal direction, for example, Figure 1A The left end of the active material layer 3 is far away from the end of the current collector 2, so that the uncoated portion still remains without forming the active material layer 3 on the current collector 2. The other end in the longitudinal direction of the active material layer 3, for example Figure 1A The right end portion of is terminated at the same position as the current collector 2, and there is no uncoated portion in this portion.

[0042] The resin layer 4 is formed to cover the entire active material layer 3. The entire active material layer 3 is the entire coating portion. The resin layer 4 extends beyond the boundary portion between the coating portion and the uncoated portion to cover a portion of the uncoated portion. The resin layer 4 covers a portion of the coating portion and the uncoated portion, but the resin layer 4 does not cover one end portion of the current collector 2.

[0043] For example, a coating agent in which an insulating material such as aluminum oxide powder is dispersed in a solvent together with a polymer is applied on the current collector 2 and the active material layer 3. The solvent is then evaporated. While a micro gap is formed between the insulating material and the polymer, the insulating material and the polymer are hardened to form the resin layer 4.

[0044] The resin layer 4 has a higher heat resistance than the separator 8 described below. Figure 1C As shown in FIG. 1 , the resin layer 4 has a high-permeability portion 4 a , a low-permeability portion 4 b , and a transition portion 4 c .

[0045] The high permeability portion 4a is located on the flat surface 3a which is the upper surface of the active material layer 3 and is thin. The low permeability portion 4b is located on the current collector 2 of the uncoated portion and is thick. The transition portion 4c is located between the high permeability portion 4a and the low permeability portion 4b and has an ion permeability that gradually decreases from the high permeability portion 4a side toward the low permeability portion 4b side. For example, the length of the high permeability portion 4a along the longitudinal direction of the electrode 1 is at least 3mm. One end of the high permeability portion 4a is adjacent to the transition portion 4c. The other end of the high permeability portion 4a is directly on the current collector foil. The length of the transition portion 4c is about 2mm. No specific restrictions are imposed on the length of the low permeability portion 4b, but the length is preferably at least 3mm but not more than 10mm to ensure insulation and prevent the battery from being too large in shape.

[0046] Next, the technical significance of the resin layer 4 of the present invention is described. At the time of charge / discharge of an electrochemical device such as a secondary battery, transfer of ions such as lithium ions is performed between the active material layer 3 and the electrolyte. If the ion permeability of the resin layer 4 covering the active material layer 3 is too low, sufficient ion transfer cannot be performed and the active material layer 3 of the electrode 2 will not be able to perform satisfactory charge / discharge operations. Therefore, the resin layer 4 located on the upper surface 3a of the active material layer 3 must be a high permeability portion 4a having high ion permeability.

[0047] On the other hand, the uncoated portion is located at the end of the electrode. If the separator 8 shrinks due to the heat generated in the battery, the uncoated portion at the end of the electrode is easy to contact the adjacent electrode. The adjacent electrodes have different polarities. Therefore, the low permeability portion 4b in the uncoated portion should have high insulation and high resistivity.

[0048] Here, a method of forming the active material layer 3 is considered. The active material layer 3 is generally formed by applying a coating agent as a mixture containing an active material on the current collector 2a and hardening it. At this time, the end of the active material layer 3 at the boundary portion between the coated portion and the uncoated portion is not easily formed in a vertically steep shape. Generally, the end of the active material layer 3 is formed in a vertically steep shape as in Figure 1C and 2B The inclined surface shape shown in is formed. Figure 1C The slope-shaped portion in the middle functions as an electrode. A transition portion 4c is provided in which the ion permeability changes along the slope-shaped portion 3b.

[0049] The bevel-shaped portion 3b of the active material layer 3 is formed so that the thickness decreases from the center side of the electrode toward the end side. The high permeability portion 4a is on the center side of the electrode. The low permeability portion 4b is on the end side. The transition portion 4c of the resin layer 4 is formed so that the thickness increases from the high permeability portion 4a side toward the low permeability portion 4b side. The thickness of the bevel-shaped portion 3b decreases from the center side toward the end side. From the high permeability portion 4a side toward the low permeability portion 4b side, the thickness of the transition portion 4c increases and the ion permeability of the transition portion 4b decreases. The portion of the transition portion 4c with higher ion permeability covers the portion of the bevel-shaped portion 3b with a large amount of active material. The portion of the bevel-shaped portion 3b with a large amount of active material is thick and has a large contribution to the capacity. The portion of the transition portion 4c with higher ion permeability is thin. As a result, ions can be transferred between the portion of the bevel-shaped portion 3b and the electrolyte.

[0050] On the other hand, the portion of the transition portion 4c having lower ion permeability covers the portion of the slope-shaped portion 3b having a small amount of active material. The portion of the slope-shaped portion 3b having a small amount of active material is thin and has a small contribution to the capacity. There is a high possibility that when abnormal shrinkage of the separator 8 occurs, the portion of the slope-shaped portion 3b having a small amount of active material contacts the opposing electrode. The portion of the transition portion 4c having lower ion permeability is thick. The insulation is thus increased.

[0051] Such a change in the ion permeability of the transition portion 4 c of the resin layer 4 along the longitudinal direction of the electrode 1 achieves both prevention or reduction of a decrease in battery capacity and securing of insulation.

[0052] The change in the layer thickness of the slope-shaped portion 3 b of the active material layer 3 and the change in the layer thickness of the transition portion 4 c of the resin layer 4 do not need to be inversely proportional.

[0053] One reason for this relationship is that the function of the bevel-shaped portion 3b of the active material layer 3 as an electrode depends on the amount of active material, but the amount of active material is not necessarily proportional to the layer thickness. For example, when the density of the active material layer 3 changes, the amount of active material and the layer thickness may not be proportional. As a result, the layer thicknesses of the bevel-shaped portion 3b and the transition portion 4c do not need to be inversely proportional.

[0054] Furthermore, the present invention is not limited to a configuration in which the layer thickness of the bevel-shaped portion 3b and the transition portion 4c decreases continuously. The present invention may also include a configuration in which these thicknesses decrease stepwise or a configuration in which these thicknesses decrease irregularly.

[0055] The above explanation assumes that the ion permeability of the resin layer 4 depends on the layer thickness. However, the ion permeability of the resin layer 4 may also depend on other factors.

[0056] For example, the ion permeability is low in a portion of the resin layer 4 where the insulation resistance is high, and the ion permeability is high in a portion where the insulation resistance is low.

[0057] In addition, in the portion where the density of the resin layer 4 is high, the ion permeability is low, and in the portion where the density is low, the ion permeability is high. When these factors are taken into consideration, the transition portion 4c of the present invention may have the above-mentioned configuration in which the layer thickness increases from the center portion side toward the end portion side of the electrode. The transition portion 4c of the present invention may also have a configuration in which the insulation resistance increases from the center portion side toward the end portion side of the electrode.

[0058] Furthermore, the transition portion 4 c of the present invention may have a configuration in which the density increases from the center portion side toward the end portion side of the electrode.

[0059] By combining these configurations, the transition portion 4 c can have a configuration in which two or all of the layer thickness, insulation resistance, and density increase from the central portion side toward the end portion side of the electrode.

[0060] For example, the material of the resin layer 4 preferably has a 12 Ω·cm and more preferably at least 1×10 14 The volume resistivity is Ω·cm. The thickness of the high permeability portion 4a on the upper surface of the active material layer 3 is preferably not more than 5 μm.

[0061] The resin layer 4 is preferably a mixture of one or more types of polymer resin and insulating particles. The high permeability portion 4a, the low permeability portion 4b, and the transition portion 4c preferably contain the same resin. In addition, in the low permeability portion 4b, pressing the resin layer reduces the gap between the insulating particles and the polymer and thus can increase the insulation resistance. Alternatively, a heating member is pressed against the resin to melt the resin, and the insulation resistance can be increased by reducing the gap.

[0062] Method for manufacturing an electrode

[0063] Next, a method for manufacturing the Figures 1A-1C In order to efficiently manufacture the electrode 1, as in Figure 2A and 2B As shown in FIG. 1 , an active material layer 3 is formed on a plurality of portions of a long sheet-shaped current collector 2, and then as shown in FIG. Figure 3A and 3B As shown in FIG. 1 , a resin layer 4 is formed. The formation of the active material layer 3 and the formation of the resin layer 4 are performed on both sides of the current collector 2. Figure 3AThe plurality of electrodes 1 are obtained by cutting along the imaginary cutting line 19 shown in FIG. Figures 1A-1C ).

[0064] In this method for manufacturing the electrode 1, the resin layer 4 is formed by applying a coating agent mainly composed of a polymer resin to cover the entire active material layer 3 as a coating portion. In addition, the resin layer 4 extends beyond the boundary portion between the coating portion and the uncoated portion, and thus covers a portion of the uncoated portion.

[0065] As in Figure 1C As shown in FIG. 1 , the resin layer 4 includes a high permeability portion 4a located on the upper surface 3a of the active material layer 3, a low permeability portion 4b located on the uncoated portion, and a transition portion 4c located between the high permeability portion 4a and the low permeability portion 4b. The transition portion 4c is formed so that the layer thickness increases continuously from the center portion side toward the end portion side of the electrode and the ion permeability and insulation resistance decrease.

[0066] More specifically, a mixture containing an active material is applied to the surface of the current collector 2 while the long sheet-shaped current collector 2 is moved in the longitudinal direction to form the active material layer 3. At this time, the coating agent is intermittently applied at certain intervals, rather than continuously applying the coating agent without a gap on the surface of the current collector 2. As a result, a plurality of active material layers 3 spaced apart from each other in the longitudinal direction are formed on the surface of the current collector 2.

[0067] These active material layers 3 are pressed and flattened, and then a resin layer 4 is formed. Figure 4 The resin layer 4 is formed by injecting a coating agent containing a resin as its main component from the die head 16 while moving in the longitudinal direction of the arrow 20. The die head 16 can be moved close to or away from the conveying path of the current collector 2. For convenience, Figure 4 The die head 16 is shown to move and the current collector 2 is not moved, or a plurality of die heads 16 are provided. However, a single die head 16 is disposed at a position facing the conveying path of the moving current collector 2. Figure 4 As shown on the left side of FIG. 1 , when a specific portion of the current collector 2 reaches a position facing the die head 16, the die head 16 starts injecting the coating agent. The specific portion of the current collector 2 is located before and separated from the end portion on which the active material layer 3 is formed by a predetermined distance.

[0068] The starting position is set so that the uncoated portion of the current collector remains, and the uncoated portion becomes a positive electrode tab or a negative electrode tab. First, the amount of the coating agent injected is increased to form the low permeability portion 4b.

[0069] Next, at a position facing the slope-shaped portion 3 b of the active material layer 3 , the die head 16 gradually decreases the amount of the coating agent injected to form the transition portion 4 c .

[0070] After that, the die head 16 injects a fixed small amount of coating agent to form the high permeability portion 4a at a position facing the upper surface 3a of the active material layer 3. At this time, the die head 16 moves away from the conveying path of the current collector 2 so that the die head 16 does not collide with the upper surface of the active material layer 3.

[0071] The current collector 2 moves thereafter, and coating stops when the active material layer 3 passes a position facing the die 16 and the die 16 approaches the conveyance path of the current collector 2 again.

[0072] In this way, preparation is made to inject the coating agent onto a portion located before and separated from the end of the next active material layer 3 by a predetermined distance.

[0073] In this way, the coating agent is injected while the die head 16 moves relative to the conveyance path of the current collector 2 , so that an excellent resin layer 4 can be formed easily and accurately.

[0074] Furthermore, the high permeability portion 4a may be formed on the entire surface of the flat portion of the active material layer, or may be formed on only a portion of the flat portion. However, the coating end position is preferably set so that the resin layer is formed to protrude beyond the active material layer and onto the current collector.

[0075] The end portion in the longitudinal direction of the side on which the joint is not formed is later cut into a predetermined electrode shape. As a result, the portion where the resin is formed on the current collector is discarded, but the effect of preventing the thin portion of the active material layer from peeling off from the end of the electrode can be obtained. A high-quality electrode can be obtained.

[0076] Figure 5 Another example of the formation step of the resin layer 4 is shown. In this example, the die head 16 does not approach or move away from the conveying path of the current collector 2. Instead, the amount of the coating agent injected from the die head 16 is changed, and the coating position and coating thickness are thus controlled to enable the formation of an excellent and highly accurate insulating resin layer 4.

[0077] Figure 5 A schematic diagram of the reduced pressure region 21 due to a change in the amount of the coating agent injected from the die 16 is provided.

[0078] If the tape-type insulating material is adhered to the boundary portion between the coated portion and the uncoated portion, it is important to place the tape-type insulating material at an inclined position at the boundary portion in order not to cause a large thickness difference in the electrode including the tape-type insulating material. However, it is difficult to distinguish the boundary portion between the upper surface 3a of the active material layer and the inclined portion 3b. This problem raises concerns about reduced productivity.

[0079] In the present invention, a coating agent mainly composed of resin is applied. As a result, the layer thickness of the insulating resin layer 4 can be changed by adjusting the amount of coating agent applied and by changing the distance between the die head as part of the coating device and the current collector foil.

[0080] Furthermore, a high-permeability section 4 a of a resin layer 4 having a substantially uniform thickness of not more than 10 μm, and more preferably not more than 5 μm, is provided on the upper surface 3 a of the active material layer 3 .

[0081] As a result, there is no portion having a thickness greater than that of other portions. Changes in electrical characteristics or reductions in cycle characteristics can be prevented or reduced.

[0082] Therefore, the high permeability portion 4a may be provided only near the boundary portion with the transition portion, rather than being provided on the entire upper surface 3a of the active material layer 3 (not shown in the figure). Since the thickness of the high permeability portion 4a is very small, even when the electrodes are stacked to manufacture a laminate, the protrusion of this portion of the resin layer 4 can be extremely small.

[0083] In addition, in the present invention, the amount of the coating agent, the distance between the die and the current collector, or these two factors can be adjusted by the die. The thickness of the resin layer 4 can be adjusted to form the resin layer 4 so that the resin layer 4 can have any thickness based on the position of the electrode.

[0084] The thickness of the low permeability portion 4b is preferably smaller than the sum of the thicknesses of the active material layer 3 and the high permeability portion 4a. When the thickness of the low permeability portion 4b is greater than the sum of the thicknesses of the active material layer 3 and the high permeability portion 4a, the thickness of the negative electrode can be reduced to prevent local protrusion of the laminate due to the insulating resin. However, when the thickness on the negative electrode side is reduced, it is necessary to prevent the A / C balance on the negative electrode side from being partially inverted.

[0085] In the manufacturing method of the electrode in the aforementioned exemplary embodiment of the present invention, after the active material layer 3 is formed, a pressing process is performed, and then the resin layer 4 is formed. However, the resin layer 4 can also be formed after the active material layer 3 is formed without performing a pressing process. Then the pressing process can be performed after the active material layer and the insulating resin layer are stacked. At this time, an additional process of increasing the resistance by using another compression process or a melting process can be performed on the high resistance component 4b. Alternatively, another resin can be provided to fill the gap in the resin layer. For example, the resin can be filled in the gap by an inkjet method.

[0086] In addition, the electrode 1 of the present invention is not limited to the configuration in which the active material layer 3 and the resin layer 4 are formed on both surfaces of the current collector 2 as described previously. The electrode 1 may have a configuration in which the active material layer 3 and the resin layer 4 are formed only on one surface of the current collector 2.

[0087] The long current collector 2 on which the active material layer 3 and the resin layer 4 are formed in this manner can be wound in a roll without being cut to form an electrode roll (not shown in the figure). The electrode roll can be stored to enable the manufacture of a plurality of electrochemical devices with extremely high efficiency.

[0088] Next, an electrochemical device manufactured using the electrode 1 described above is described. In the example described below, the aforementioned electrode 1 is used as a positive electrode of a laminated secondary battery (a type of electrochemical device). The electrode 1 is referred to as "positive electrode 1", the current collector 2 is referred to as "positive electrode current collector 2", and the active material layer 3 is referred to as "positive electrode active material 3". The electrode 1 may be a component cut from an electrode roll.

[0089] Structure of stacked secondary battery

[0090] Next, refer to Fig. 6A and 6B A laminated secondary battery 23 is described as an example of an electrochemical device including the aforementioned electrode 1 as a positive electrode. Fig. 6A and 6B A laminated secondary battery 23 including the positive electrode 1 manufactured according to the present invention is schematically shown. Fig. 6A It is a top view viewed vertically from above the main surface (flat surface) of the secondary battery 23 . Figure 6B It is along Fig. 6A Cross-sectional view taken along line AA.

[0091] For convenience, Fig. 6A and 6B The resin layer 4 is omitted, and the shape of the active material layer 3 is further simplified. Figures 1A-1C The positive electrodes 1 shown in FIG. 1 each include a resin layer 4. The negative electrodes 5 each include a negative current collector 6 and a negative active material layer 7 applied to the negative current collector 6. The negative electrode 5 has a coated portion and an uncoated portion on both sides of the negative current collector 6.

[0092] The secondary battery 23 of the present exemplary embodiment is provided with a storage element which is a multilayer electrode body 9. In the multilayer electrode body 5, positive electrode sheets 1 and negative electrode sheets 5 are alternately layered with separators 8 interposed therebetween.

[0093] The multilayer electrode body 9 is housed together with the electrolyte 10 in an outer container 12 composed of a laminated flexible film 11. One end of a positive electrode terminal 13 is connected to the positive electrode 1 of the multilayer electrode body 9. One end of a negative electrode terminal 14 is connected to the negative electrode 5. The other end of the positive electrode terminal 13 and the other end of the negative electrode terminal 14 extend to the outside of the outer container 12 composed of the flexible film 11.

[0094] exist Figure 6B In FIG. 1 , the layers in the center portion in the thickness direction constituting the multilayer electrode body 9 are omitted from the figure to show the electrolyte 10. Figure 6B , for clarity, the positive electrode 1, the negative electrode 5, the separator 8, and the flexible film 11 are each shown as not in contact with each other. However, these components are actually stacked in close contact with each other.

[0095] The outer dimension of the negative electrode active material layer 7 is longer than the outer dimension of the positive electrode active material layer 3. The negative electrode active material layer 7 is a coating portion of the negative electrode 5. The positive electrode active material layer 3 is a coating portion of the positive electrode 1. The outer dimension of the negative electrode active material layer 7 is equal to or smaller than the outer dimension of the separator 8. The positive electrode active material layer 3 has a smaller area than the negative electrode active material layer 7. Therefore, it is preferable to provide a resin layer 4 for preventing electrical short circuit at the end of the positive electrode active material layer 3.

[0096] The negative electrode active material layer 7 has a large area and there is little concern about electrical short circuit. However, it is preferred to form the low permeability portion 4b of the resin layer 4 on the negative electrode active material layer 7. When the separator 8 is damaged by heat, for example, the low permeability portion 4b prevents electrical short circuit with the adjacent positive electrode 1. In this case, the negative electrode 5 can be formed by the aforementioned method for manufacturing an electrode of the present invention.

[0097] When manufacturing such a secondary battery 23, the positive electrode 1 and the negative electrode 5 are alternately stacked with the separator 8 inserted therebetween. The positive terminal 13 and the negative terminal 14 are connected afterwards. More specifically, the positive electrode tabs of the positive electrode 1 are stacked in close contact with each other on one end of the positive terminal 13. The positive electrode tab is a non-coated portion of the positive electrode collector 2. The positive electrode tab and the positive terminal 13 are bonded together by, for example, ultrasonic welding.

[0098] At the negative electrode 5, a plurality of negative electrode tabs are stacked together on one end of the negative electrode terminal 14. The negative electrode tab is a non-coated portion of the negative electrode collector 6. The negative electrode tab and the negative electrode terminal 14 are bonded by, for example, ultrasonic welding. The positive electrode tab and the negative electrode tab are not covered by the resin layer 4.

[0099] In this way, the multilayer electrode body 9 has been completed by connecting the positive electrode terminal 13 to the positive electrode collector 2 and by connecting the negative electrode terminal 14 to the negative electrode collector 6. The multilayer electrode body 9 is covered with the flexible film 11 from both sides of the main surface.

[0100] Thereafter, pressure and heat are applied to the portions where the flexible films 11 overlap each other except for the portions on the outside of the periphery of the multilayer electrode body 9 viewed in a plane. The inner resin layers composed of the heat-fusible resin of the flexible films 11 are bonded together by heat fusion. At this time, the positive terminal 13 and the negative terminal 14 are fixed to the periphery of the flexible film 11 by means of the sealant 18 that has been provided.

[0101] On the other hand, in the portion where the flexible films 11 overlap each other, the portion to which pressure and heat are not applied remains unbonded. The unbonded portion is an opening serving as an injection port.

[0102] Typically, an injection port is formed in a portion of one side of the outer container 12 other than the side on which the positive electrode terminal 13 and the negative electrode terminal 14 are provided.

[0103] Then, the electrolyte 10 is injected into the outer container 12 from the injection port. The side other than the injection port has been sealed. Therefore, the injected electrolyte 10 will not leak. In addition, the electrolyte 10 will not invade the overlapping portion of the flexible film 11 in the sealed side. Then, pressure and heat are applied to the injection port. The inner resin layer composed of the heat-fusible resin of the flexible film 11 is combined together by heat fusion. In this way, the secondary battery 23 as an example of an electrochemical device is completed.

[0104] In the secondary battery 23 of the present exemplary embodiment, the active material that can constitute the positive electrode active material layer 3 includes a layered oxide-based material such as LiC o O2, LiNiO2, LiMn2O2, Li2MO3-LiMO2, or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2; spinel materials such as LiMn2O4; olivine materials such as LiMPO4; olivine-fluoride materials such as Li2MPO4F and Li2MSiO4F; and vanadium oxide materials such as V2O5. M is a transition metal. In each positive electrode active material, a part of the elements constituting these active materials may be substituted by other elements. In addition, Li may be an excessive composition. One type of these active materials or a mixture of two or more types may be used.

[0105] The active materials that can constitute the negative electrode active material layer 7 include: carbon materials such as graphite, amorphous carbon, diamond carbon, fullerene, carbon nanotubes, and carbon nanohorns; lithium metal materials; alloy materials such as silicon or tin; oxide materials such as Nb2O5 or TiO2; or composite materials of these materials.

[0106] The active material mixture constituting the positive electrode active material layer 3 and the negative electrode active material layer 7 is realized by appropriately adding a binder or a conductive auxiliary agent to each of the aforementioned active materials. For example, one type or a combination of two or more types of carbon black, carbon fiber, and graphite can be used as a conductive auxiliary agent. As a binder, polyvinylidene fluoride, styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, and modified acrylonitrile rubber particles can be used. In the positive electrode active material layer 3 and the negative electrode active material layer 7, the inevitable tilt, unevenness, and bending in each layer are allowed. The tilt, unevenness, and bending in each layer occur due to, for example, changes in the manufacturing process or layer forming ability.

[0107] As the positive electrode current collector 2, aluminum, stainless steel, nickel, titanium, or an alloy of these metals can be used. In particular, aluminum is preferred. As the negative electrode current collector 6, copper, stainless steel, nickel, titanium, or an alloy of these metals can be used.

[0108] As the electrolyte 10, one type or a mixture of two or more types of the following organic solvents can be used: for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, and butylene carbonate; chain carbonates such as ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC); aliphatic carboxylic acid esters; γ-lactones such as γ-butyrolactone; chain ethers and cyclic ethers. Further, lithium salts can be dissolved in these organic solvents.

[0109] Separator 8 is mainly composed of porous membranes, textiles and nonwovens made of resin. Resin components that can be used include, for example, polyolefin resins such as polypropylene and polyethylene, polyester resins, acrylic resins, styrene resins, nylon resins, aromatic polyamide resins and polyimide resins. In particular, polyolefin-based microporous membranes are preferred due to their ion permeability and excellent ability to physically separate the positive and negative electrodes. In addition, as required, a layer containing inorganic particles can be formed in separator 8. Materials that can be used as inorganic particles include insulating oxides, nitrides, sulfides, and carbides. Materials including TiO2 and Al2O3 are particularly preferred. Including insulating inorganic particles not only in the electrode but also in the separator can provide a safe battery.

[0110] The outer container 12 is a lightweight outer shell composed of a flexible film 11. The flexible film 11 is a laminated film. The resin layer is arranged on both surfaces of the metal foil as the base material in the flexible film 11. The metal foil can be selected from a material having a barrier property for preventing leakage of the electrolyte 10 or for preventing moisture from intruding from the outside. Aluminum, stainless steel, etc. can be used as the metal foil. A heat-fusible resin layer such as a modified polyolefin is arranged on at least one surface of the metal foil. The heat-fusible resin layers of the flexible film 11 are arranged relative to each other. The heat-fusible resin layers are heat-fused together around the portion accommodating the multilayer electrode body 9 to form the outer container 12. As the surface of the outer container 12, a resin layer such as a nylon film, a polyethylene terephthalate film, or a polyester film can be arranged on the surface of the metal foil. The surface is on the opposite side of the surface on which the heat-fusible resin layer is formed.

[0111] Aluminum or an aluminum alloy can be used as the positive terminal 13. Copper, a copper alloy, nickel-plated copper or a copper alloy, or nickel can be used as the negative terminal 14. The other end side of each of the terminals 13 and 14 extends to the outside of the outer container 12. A sealant 18 of a heat-fusible resin has been provided on a portion of each of the terminals 13 and 14. This portion corresponds to a portion where the outer periphery of the outer container 12 is heat-welded.

[0112] The present invention is particularly applicable to lithium ion secondary batteries. However, the present invention is also effectively applied to secondary batteries other than lithium ion batteries, or to electrochemical devices other than batteries such as capacitors (capacitors or condensers).

[0113] Although the present invention has been shown and described with reference to its exemplary embodiment, the present invention is not limited to the exemplary embodiment. It should be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.

[0114] This application is based upon and claims the benefit of priority from Japanese patent application No. 2016-212820, filed on October 31, 2016, the disclosure of which is incorporated herein in its entirety by reference.

[0115] Explanation of Figure Numbers

[0116] 1 Positive electrode

[0117] 2. Positive current collector

[0118] 3. Positive electrode active material layer

[0119] 3a Upper surface

[0120] 3b Beveled section

[0121] 4 Resin layer

[0122] 4a High permeability part

[0123] 4b Low permeability part

[0124] 4c Transition

[0125] 5 Negative electrode

[0126] 6 Negative current collector

[0127] 7 Negative electrode active material layer

[0128] 8 Isolate

[0129] 9 Multilayer electrode body

[0130] 10. Electrolytes

[0131] 11. Flexible film (laminated film)

[0132] 12 outer container

[0133] 13 Positive terminal

[0134] 14 Negative terminal

[0135] 16 Die Head

[0136] 18 Sealant

[0137] 19 Cutting Line

[0138] 23 Laminated secondary battery (electrochemical device)

Claims

1. An electrode for an electrochemical device, the electrode comprising: a coating portion on the current collector, wherein an active material layer is formed; an uncoated portion in which the active material layer is not formed; and a resin layer, which is laminated to cover a portion of the uncoated portion and the coated portion; wherein: The resin layer has: a high permeability portion having high ion permeability and located on the coating portion; a low-permeability portion having low ion permeability and located on a portion of the uncoated portion; and a transition portion in which ion permeability decreases from the high permeability portion side toward the low permeability portion side and the transition portion is located between the high permeability portion and the low permeability portion, wherein the high permeability portion has a low density, The low permeability portion has a high density, The density of the transition portion increases from the high permeability portion side toward the low permeability portion side. and wherein the layer thickness of the high permeability portion is thin, The low permeability portion has a thick layer thickness, And the layer thickness of the transition portion increases from the high-permeability portion side toward the low-permeability portion side.

2. The electrode according to claim 1, The volume resistivity of the resin layer is at least 1×10 12 Ω·cm.

3. The electrode according to claim 1 or 2, wherein the high permeability portion is a thin portion, The low permeability portion is a thick portion, The thickness of the transition portion gradually increases from the high-permeability portion side toward the low-permeability portion side, And the length of the low-permeability portion along the longitudinal direction of the electrode is at least 3 mm but not more than 10 mm.

4. The electrode according to claim 1 or 2, wherein the high permeability portion has a low insulation resistance, The low permeability portion has a high insulation resistance. Furthermore, the insulation resistance of the transition portion increases from the high-permeability portion side toward the low-permeability portion side.

5. The electrode according to claim 1 or 2, The end of the coating portion is formed into a slope shape, And the transition portion is formed on the portion having the inclined surface shape.

6. The electrode according to claim 1 or 2, The resin layer contains an insulating material.

7. The electrode according to claim 6, The insulating material is aluminum oxide powder.

8. An electrochemical device, comprising: A multilayer electrode body, wherein the electrode according to any one of claims 1 to 7 is used as a positive electrode, a negative electrode, or a positive electrode and a negative electrode, and the positive electrode and the negative electrode are alternately layered with a separator interposed therebetween; and An outer container that houses the multilayer electrode body and the electrolyte.

9. A method for manufacturing an electrode for an electrochemical device, the method comprising the steps of: forming an active material layer on a portion of a current collector to provide a coated portion in which the active material layer is formed and an uncoated portion in which the active material layer is not formed on the current collector; and A resin layer is stacked to cover a portion of the uncoated portion and the coated portion; wherein, In the step of laminating the resin layer, as the resin layer, the following is formed: a high permeability portion having high ion permeability and located on the coating portion, a low permeability portion having low ion permeability and located on a portion of the uncoated portion, and a transition portion in which ion permeability decreases from the high permeability portion side toward the low permeability portion side and the transition portion is located between the high permeability portion and the low permeability portion, wherein the high permeability portion has a low density, The low permeability portion has a high density, The density of the transition portion increases from the high permeability portion side toward the low permeability portion side. and wherein the layer thickness of the high permeability portion is thin, The low permeability portion has a thick layer thickness, And the layer thickness of the transition portion increases from the high-permeability portion side toward the low-permeability portion side.

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