JP6876365B2 - Power storage element - Google Patents

Description

The present invention relates to a power storage element including an electrode body having a positive electrode and a negative electrode.

The conversion from gasoline-powered vehicles to electric vehicles is becoming important as a global approach to environmental issues. For this reason, the development of electric vehicles using a power storage element such as a lithium ion secondary battery as a power source is underway.

Conventionally, a power storage element having a so-called winding type electrode body formed by winding an electrode is widely known (see, for example, Patent Document 1).

Japanese Patent No. 3742144

When there is a part where the electrode is bent like this wound type electrode body, the permeability of the electrolytic solution into the inside of the electrode body may decrease due to the compression of the inner electrode in the part. .. This may cause a decrease in the performance of the power storage element.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power storage element capable of reducing performance deterioration.

In order to achieve the above object, the power storage element according to one aspect of the present invention is a power storage element including an electrode body having a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode has a first surface and a negative electrode. It has a base material layer having a second surface which is a surface opposite to the first surface, and an active material layer formed on the base material layer, and the second surface is the positive electrode and the negative electrode. At the bent portion where at least one of the above is bent, the surface is arranged inside the first surface, and the second surface has a larger surface roughness than the first surface at the bent portion.

Here, inside the bent portion of the positive electrode and the negative electrode, the active material layer is compressed by the bending, so that the voids in the active material layer may become smaller. In this case, the permeability of the electrolytic solution of the power storage element that permeates the inside of the electrode body through such a gap may decrease. Therefore, by arranging the base material layer so that the second surface having a relatively large surface roughness is on the inside in the portion, it is possible to secure a gap between the base material layer and the active material layer. As a result, the electrolytic solution can permeate the inside of the electrode body through the gap between the base material layer and the active material layer inside the portion, so that the performance deterioration of the power storage element can be reduced.

Further, the active material layer is formed on the first surface and the second surface of the base material layer, and the size of the void formed by the base material layer and the active material layer on the second surface side. May be greater than or equal to the size of the voids formed by the base material layer and the active material layer on the first surface side.

As a result, the permeability of the electrolytic solution can be further improved inside the bent portion of the positive electrode and the negative electrode. Here, in the electrode body whose volume changes due to charging and discharging, the electrolytic solution is pushed out when the electrode body expands, and permeates from the outside to the inside when the electrode body contracts and returns. Therefore, particularly in such an electrode body, when the permeability of the electrolytic solution is low inside the bent portion, the performance of the power storage element is significantly deteriorated. Therefore, the size of the voids formed by the base material layer and the active material layer on the second surface side should be equal to or larger than the size of the voids formed by the base material layer and the active material layer on the first surface side. As a result, it is possible to further suppress the deterioration of the performance of the power storage element in the electrode body whose volume changes due to charging and discharging.

Further, the base material layer possessed by either the positive electrode or the negative electrode is a base material layer having the first surface and the second surface, and the porosity of the active material layer possessed by the one is the other. It may be smaller than the porosity of the active material layer to have.

Here, the smaller the porosity of the electrolytic solution in the active material layer, the lower the permeability. Therefore, the above-mentioned decrease in the permeability of the electrolytic solution is likely to occur in the portion where the positive electrode and the negative electrode are bent, particularly in the portion where the active material layer having a small porosity is located. Therefore, in the base material layer in which the active material layer having a small porosity is arranged inside, the place where the permeability of the electrolytic solution is likely to decrease by arranging the second surface having a relatively large surface roughness inside. The decrease in the above can be reduced. That is, it is possible to suppress the deterioration in the place where the deterioration of the power storage element is likely to occur.

Further, the second surface has a larger surface roughness than the first surface as a whole, and the electrode body has the positive electrode so that the second surface is located on the inner peripheral side of the first surface. And the negative electrode may be formed by winding.

As a result, as the base material layer, the first surface, which is one surface, is uniformly configured to have a relatively low surface roughness in the long strip-shaped state before winding (before bending) of the positive electrode and the negative electrode, and the other surface. It is possible to use a surface having a second surface having a uniform surface roughness higher than that of the first surface. By using such a base material layer, it is not necessary to adjust the roughness after specifying the bent portion, so that the cost of the power storage element can be reduced.

Further, the power storage element may further include a current collector connected to the electrode body, and the electrode body may be brought into contact with the current collector on the first surface.

By connecting the electrode body and the current collector on a surface having a relatively small surface roughness in this way, the electrical connection and the mechanical connection between the electrode body and the current collector can be easily secured. be able to.

According to the present invention, it is possible to provide a power storage element including an electrode body having a positive electrode and a negative electrode, which can reduce performance deterioration.

It is a perspective view which shows typically the appearance of the power storage element which concerns on embodiment of this invention. It is a perspective view which shows the component arranged in the container of the power storage element which concerns on embodiment of this invention. It is a perspective view which shows the winding state of the electrode body which concerns on embodiment of this invention by partially developing. FIG. 3 is a cross-sectional view taken along the line AA'of FIG. It is sectional drawing which shows the state before winding of the negative electrode which concerns on embodiment of this invention, and is the partially enlarged view. It is sectional drawing which shows the state of the negative electrode in the bent part of the electrode body which concerns on embodiment of this invention. It is a figure which shows the structure of the electrode body which concerns on the modification 1 of the Embodiment of this invention. It is an enlarged cross-sectional view which shows the structure of the electrode body which concerns on the modification 2 of the Embodiment of this invention.

Hereinafter, the power storage element according to the embodiment of the present invention will be described with reference to the drawings. It should be noted that all of the embodiments described below show a preferred specific example of the present invention. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, manufacturing processes, order of manufacturing processes, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present invention will be described as arbitrary components constituting the more preferable form. Moreover, in each figure, the dimensions and the like do not exactly match.

(Embodiment)
First, the configuration of the power storage element 10 will be described.

FIG. 1 is a perspective view schematically showing the appearance of the power storage element 10 according to the embodiment of the present invention. Further, FIG. 2 is a perspective view showing components arranged inside the container of the power storage element 10 according to the embodiment of the present invention. Specifically, FIG. 2 is a perspective view showing a configuration in which the main body 111 of the container 100 is separated from the power storage element 10. Further, FIG. 3 is a perspective view showing the configuration of the electrode body 400 according to the embodiment of the present invention. Note that FIG. 3 is a partially developed view of the wound state of the electrode body 400 shown in FIG.

The power storage element 10 is a secondary battery capable of charging electricity and discharging electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. For example, the power storage element 10 is applied to an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV). The power storage element 10 is not limited to the non-aqueous electrolyte secondary battery, and may be a secondary battery other than the non-aqueous electrolyte secondary battery, or may be a capacitor.

As shown in FIG. 1, the power storage element 10 includes a container 100, a positive electrode terminal 200, and a negative electrode terminal 300. Further, as shown in FIG. 2, a positive current collector 120, a negative negative current collector 130, and an electrode body 400 are housed inside the container 100.

In addition to the above components, spacers arranged on the sides of the positive electrode current collector 120 and the negative electrode current collector 130, a safety valve for releasing the pressure in the container 100 when the pressure rises, or An insulating film or the like that wraps the electrode body 400 or the like may be arranged. Further, although a liquid such as an electrolytic solution (non-aqueous electrolyte) is sealed inside the container 100 of the power storage element 10, the illustration of the liquid is omitted. The type of electrolytic solution sealed in the container 100 is not particularly limited as long as it does not impair the performance of the power storage element 10, and various types can be selected.

The container 100 is composed of a main body 111 having a rectangular tubular shape and a bottom, and a lid 110 which is a plate-shaped member that closes the opening of the main body 111. Further, the container 100 can be sealed inside by accommodating the electrode body 400 or the like inside and then welding the lid body 110 and the main body 111 or the like. The materials of the lid 110 and the main body 111 are not particularly limited, but are preferably weldable metals such as stainless steel, aluminum, and aluminum alloy.

The electrode body 400 includes a positive electrode, a negative electrode, and a separator, and is a member capable of storing electricity. The positive electrode is formed by forming a positive electrode active material layer on a long strip-shaped positive electrode base material layer made of aluminum, an aluminum alloy, or the like. The negative electrode is a negative electrode active material layer formed on a long strip-shaped negative electrode base material layer made of copper, a copper alloy, or the like. The separator is a microporous sheet made of resin. The detailed configuration of the electrode body 400 will be described later.

Then, as shown in FIG. 3, the electrode body 400 is formed by winding those arranged in layers so that the separator is sandwiched between the positive electrode and the negative electrode. In the figure, the shape of the electrode body 400 is an oval shape, but it may be a circular shape or an elliptical shape.

Returning to FIG. 2, the positive electrode terminal 200 is an electrode terminal electrically connected to the positive electrode of the electrode body 400, and the negative electrode terminal 300 is an electrode terminal electrically connected to the negative electrode of the electrode body 400. That is, the positive electrode terminal 200 and the negative electrode terminal 300 lead the electricity stored in the electrode body 400 to the external space of the power storage element 10, and the electric power is stored in the internal space of the power storage element 10 in order to store the electricity in the electrode body 400. It is a metal electrode terminal for introducing. Further, the positive electrode terminal 200 and the negative electrode terminal 300 are attached to a lid 110 arranged above the electrode body 400.

The positive electrode current collector 120 is arranged between the positive electrode of the electrode body 400 and the wall surface of the main body 111 of the container 100, and has conductivity and rigidity that are electrically connected to the positive electrode terminal 200 and the positive electrode of the electrode body 400. It is a provided member. The positive electrode current collector 120 is made of aluminum, an aluminum alloy, or the like, like the positive electrode base material layer of the electrode body 400.

The negative electrode current collector 130 is arranged between the negative electrode body 400 and the wall surface of the main body 111 of the container 100, and has conductivity and rigidity that are electrically connected to the negative electrode terminal 300 and the negative electrode body 400. It is a provided member. The negative electrode current collector 130 is made of copper, a copper alloy, or the like, like the negative electrode base material layer of the electrode body 400.

Specifically, the positive electrode current collector 120 and the negative electrode current collector 130 are metal plate-shaped members arranged in a bent state along the wall surface and the lid 110 from the wall surface of the main body 111 to the lid 110. Is. Further, the positive electrode current collector 120 and the negative electrode current collector 130 are fixedly connected to the lid body 110, and are fixedly connected to the positive electrode body 400 and the negative electrode body 400 by welding or the like, respectively. As a result, the electrode body 400 is held inside the container 100 in a state of being suspended from the lid body 110 by the positive electrode current collector 120 and the negative electrode current collector 130.

Next, the configuration of the electrode body 400 will be described in detail.

FIG. 4 is a cross-sectional view showing the configuration of the electrode body 400 according to the embodiment of the present invention. Specifically, the figure is a diagram showing a cross section when a portion of the electrode body 400 shown in FIG. 3 in which the wound state is developed is cut along an AA'cross section.

In FIG. 4, only one set of a plurality of sets of the positive electrode 410, the negative electrode 420, and the separator 430, which are repeatedly laminated by being wound, is shown, and the illustration of the other sets is omitted.

As shown in FIGS. 3 and 4, the electrode body 400 is formed by laminating a positive electrode 410, a negative electrode 420, and two separators 430. Specifically, the electrode body 400 is formed by being wound so that the separator 430, the negative electrode 420, the separator 430, and the positive electrode 410 are arranged in this order.

The positive electrode 410 is an electrode plate in which a positive electrode active material layer is formed on the surface of a long strip-shaped conductive positive electrode current collecting foil made of aluminum or an aluminum alloy. Specifically, as shown in FIG. 4, the positive electrode 410 has a positive electrode base material layer 411 and positive electrode active material layers 412 and 413.

The positive electrode base material layer 411 is a metal foil formed by polymerization rolling, and is, for example, a long strip-shaped conductive current collecting foil made of aluminum, an aluminum alloy, or the like.

The positive electrode active material layers 412 and 413 are active material layers formed on the positive electrode base material layer 411.

Specifically, the positive electrode active material layer 412 is an active material layer arranged on the inner peripheral side (plus side in the Y-axis direction in FIG. 4) of the positive electrode base material layer 411, and the positive electrode active material layer 413 is a positive electrode group. It is an active material layer arranged on the outer peripheral side (minus side in the Y-axis direction in FIG. 4) of the material layer 411.

Here, the positive electrode active material layers 412 and 413 contain the positive electrode active material and the binder. As the positive electrode active material used for the positive electrode active material layers 412 and 413, known materials can be appropriately used as long as they are positive electrode active materials capable of occluding and releasing lithium ions. For example, _{a composite oxide represented by Li x} MO _y (M represents at least one transition metal) (Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x MnO ₃ , Li _x Ni). _y Co _(1-y) O ₂ , Li _x N _y Mn _z Co _(1-y-z) O ₂ , Li _x N _y Mn _(2-y) O ₄ etc.), or Li _w Me _x (XO) _y ) _z (Me represents at least one transition metal, X represents, for example, P, Si, B, V) polyanionic compounds (LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO) ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F, etc.) can be selected. Further, the element or polyanion in these compounds may be partially replaced with another element or anion species, and the surface is coated with a metal oxide such as _{ZrO 2} , MgO, Al ₂ O _{3 or carbon.} May be good. Further, examples thereof include, but are not limited to, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyparastyrene, polyacetylene, and polyacene-based materials, and pseudo-graphite structural carbonaceous materials. Further, these compounds may be used alone or in combination of two or more.

Further, in the positive electrode 410, the end portion on the negative side in the X-axis direction (the end portion of the positive electrode base material layer 411 in which the positive electrode active material layers 412 and 413 are not formed), which is a portion connected to the positive electrode current collector 120, is formed. It is arranged so as to project from the separator 430, and is electrically and mechanically connected to the positive electrode current collector 120 at the projecting portion. That is, the electrode body 400 comes into contact with the positive electrode current collector 120 on the outer peripheral side surface of the positive electrode base material layer 411 located on the outermost circumference.

The negative electrode 420 is an electrode plate in which a negative electrode active material layer is formed on the surface of a long strip-shaped conductive negative electrode current collecting foil made of copper or a copper alloy. Specifically, as shown in FIG. 4, the negative electrode 420 has a negative electrode base material layer 421 and negative electrode active material layers 422 and 423.

The negative electrode base material layer 421 is a metal foil formed by electrolytic precipitation, and is, for example, a long strip-shaped conductive current collecting foil made of copper, a copper alloy, or the like.

The negative electrode active material layers 422 and 423 are active material layers formed on the negative electrode base material layer 421. Specifically, the negative electrode active material layer 422 is an active material layer arranged on the inner peripheral side (plus side in the Y-axis direction in FIG. 4) of the negative electrode base material layer 421, and the negative electrode active material layer 423 is a negative electrode group. It is an active material layer arranged on the outer peripheral side (minus side in the Y-axis direction in FIG. 4) of the material layer 421.

Here, the negative electrode active material layers 422 and 423 contain the negative electrode active material and the binder. As the negative electrode active material used for the negative electrode active material layers 422 and 423, a known material can be appropriately used as long as it is a negative electrode active material capable of occluding and releasing lithium ions. For example, in addition to lithium metals and lithium alloys (lithium metal-containing alloys such as lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys), lithium can be stored and released. Alloys, carbon materials (eg graphite, non-graphitizable carbon, easily graphitized carbon, low temperature fired carbon, amorphous carbon, etc.), metal oxides, lithium metal oxides (Li ₄ Ti ₅ O _12, etc.), polyphosphate compounds And so on.

The separator 430 is a microporous sheet made of resin, and is impregnated with an electrolytic solution containing an organic solvent and an electrolyte salt. Here, as the separator 430, a synthetic resin microporous film made of a woven fabric insoluble in an organic solvent, a non-woven fabric, or a polyolefin resin such as polyethylene is used, and a plurality of microporous films having different materials, weight average molecular weights, and porosity are used. Those that are laminated, those that contain appropriate amounts of additives such as various plasticizers, antioxidants, and flame retardants in these microporous films, and those that are coated with inorganic oxides such as silica on one or both sides. It may be a thing. In particular, a synthetic resin microporous membrane can be preferably used. Among them, polyolefin-based microporous membranes such as polyethylene and polypropylene microporous membranes, polyethylene and polypropylene microporous membranes composited with aramid and polypropylene, and microporous membranes composited of these are the thickness, film strength, and film. It is preferably used in terms of resistance and the like.

Further, in the negative electrode 420, the end portion on the positive side in the X-axis direction (the end portion of the negative electrode base material layer 421 in which the negative electrode active material layers 422 and 423 are not formed), which is a portion connected to the negative electrode current collector 130, is formed. It is arranged so as to project from the separator 430, and is electrically and mechanically connected to the negative electrode current collector 130 at the projecting portion. That is, the electrode body 400 comes into contact with the negative electrode current collector 130 on the outer peripheral side surface of the negative electrode base material layer 421 located on the outermost circumference.

The separator 430 is a long strip-shaped separator arranged between the positive electrode 410 and the negative electrode 420, specifically, a microporous sheet made of resin, and an electrolytic solution containing an organic solvent and an electrolyte salt. Is impregnated. Here, as the separator 430, a synthetic resin microporous film made of a woven fabric insoluble in an organic solvent, a non-woven fabric, or a polyolefin resin such as polyethylene is used, and a plurality of microporous films having different materials, weight average molecular weights, and porosity are used. Those that are laminated, those that contain appropriate amounts of additives such as various plasticizers, antioxidants, and flame retardants in these microporous films, and those that are coated with inorganic oxides such as silica on one or both sides. It may be a thing. In particular, a synthetic resin microporous membrane can be preferably used. Among them, polyolefin-based microporous membranes such as polyethylene and polypropylene microporous membranes, polyethylene and polypropylene microporous membranes composited with aramid and polypropylene, and microporous membranes composited of these are the thickness, film strength, and film. It is preferably used in terms of resistance and the like.

As shown in FIG. 3, the separator 430 is arranged so that the end portion in the winding direction protrudes from the end portion in the winding direction of the positive electrode 410 and the negative electrode 420.

In this way, the electrode body 400 is formed by winding the positive electrode 410 and the negative electrode 420.

Here, in recent years, the energy storage element 10 is required to have a higher energy density. Therefore, it is required to reduce the thickness of the positive electrode base material layer 411 of the positive electrode 410 and the negative electrode base material layer 421 of the negative electrode 420 described above.

Therefore, in the present embodiment, the positive electrode base material layer 411 is thinned by using a metal foil formed by polymerization rolling as the positive electrode base material layer 411. Further, by using a metal foil formed by electrolytic precipitation as the negative electrode base material layer 421, the negative electrode base material layer 421 is thinned.

In polymerization rolling, a plurality of (for example, two) metal foils are passed between rolling rolls in a state of being stacked, so that the thickness is smaller (thin wall) than when one metal foil is passed between the rolling rolls. ) This is a method of manufacturing metal foil.

At this time, in the manufactured metal foil, the surface in contact with the rolling rolls is formed relatively flat when passing between the rolling rolls, whereas the surface opposite to the surface is another metal foil. The surface in contact with the surface is formed in a relatively uneven shape. Therefore, the positive electrode base material layer 411 of the positive electrode 410 has a smooth surface and a rough surface having a surface roughness larger than that of the smooth surface. Therefore, metal foils having different surface roughness on one surface and the other surface can be easily obtained.

By producing the metal leaf by polymerization rolling, it is possible to obtain a metal leaf having a large crystal size and excellent flexibility as compared with the case of forming by electrolytic precipitation described later. Further, a thin metal foil can be obtained with a smaller number of rolling times than when one metal foil is rolled. Since the number of rolling times can be reduced, it is possible to obtain a metal foil that is hard to tear as compared with a metal foil having the same thickness produced by a normal rolling method. It is considered that this is because the work hardening of the metal is suppressed by reducing the number of times the metal foil is passed through the press roll.

Further, electrolytic precipitation is a method of producing a metal foil having a smaller thickness (thin wall) than when one metal foil is passed between the rolling rolls by electrodepositing a metal on a rotating electrolytic roll. Is.

At this time, in the manufactured metal foil, the surface in contact with the electrolytic roll is formed relatively flat, whereas the surface on the opposite side of the surface that does not come into contact with the electrolytic roll is relatively uneven. Formed into a shape. Therefore, the negative electrode base material layer 421 of the negative electrode 420 has a smooth surface and a rough surface having a surface roughness larger than that of the smooth surface, similarly to the positive electrode base material layer 411. Therefore, metal foils having different surface roughness on one surface and the other surface can be easily obtained.

By producing the metal leaf by electrolytic precipitation, it is possible to obtain a metal leaf with less man-hours and higher accuracy and thickness accuracy than in the case of forming by polymerization rolling. This is because the amount of metal electrodeposited on the electrolytic roll can be changed by adjusting the amount of electricity applied during electrolytic precipitation.

In the present embodiment, the smooth surface of each of the positive electrode base material layer 411 and the negative electrode base material layer 421 corresponds to the "first surface" described in the claims, and the positive electrode base material layer 411 and the negative electrode base material layer 411 and the negative electrode. The rough surface of each of the substrate layers 421 corresponds to the "second surface" described in the claims. Further, in the present embodiment, the rough surface is described as having a surface roughness larger than that of the smooth surface as a whole, but at least in the bent portion described later, the surface roughness may be larger than that of the smooth surface. For example, in the portion other than the bent portion, the surface roughness of the rough surface may be equal to the surface roughness of the smooth surface, or may be smaller than the surface roughness of the smooth surface.

The surface roughness is defined by the center line average roughness (Ra) and can be measured with a laser microscope in accordance with JIS B 0601-1994. Specifically, the active material is removed by ultrasonically cleaning each of the positive electrode 410 and the negative electrode 420. After that, for each of the positive electrode base material layer 411 and the negative electrode base material layer 421, the average roughness of the center lines of the first and second surfaces of the positive electrode 410 and the negative electrode 420 was measured by a laser microscope conforming to JIS B 0601-1994. (Ra) can be measured.

In the present embodiment, the central average roughness (Ra) of the smooth surface of the positive electrode base material layer 411 is preferably 0.01 to 0.1 μm, and the central average of the rough surfaces of the positive electrode base material layer 411. The roughness (Ra) is preferably 0.1 to 2 μm. Further, in the present embodiment, the central average roughness (Ra) of the smooth surface of the negative electrode base material layer 421 is preferably 0.01 to 0.2 μm, and the rough surface of the negative electrode base material layer 421 has. The central average roughness (Ra) is preferably 0.2 to 2 μm.

In the present embodiment, the electrode body 400 is formed by winding the positive electrode 410 and the negative electrode 420 so that the rough surfaces of the positive electrode base material layer 411 and the negative electrode base material layer 421 are on the inner peripheral side. There is. In other words, the rough surfaces of the positive electrode base material layer 411 and the negative electrode base material layer 421 are arranged inside in the portion bent by winding the positive electrode 410 and the negative electrode 420. With this configuration, the power storage element 10 according to the present embodiment can reduce the deterioration of the battery performance.

The reason for this can be described below while explaining the detailed configuration of the negative electrode 420.

In the present embodiment, the negative electrode 420 and the positive electrode 410 are different in material and size, but are the same in that the rough surface of the base material layer (current collector foil) is wound so as to be on the inner peripheral side. Is. Therefore, in the following, the matters relating to the negative electrode 420 will be mainly described, and the matters relating to the positive electrode 410 will be omitted as appropriate. Further, the negative electrode active material layer 422 contains the negative electrode active material and the binder as described above, but in the following figures, the illustration of the binder and the like other than the negative electrode active material will be omitted.

FIG. 5 is a cross-sectional view showing a state before winding of the negative electrode 420 according to the embodiment of the present invention, and a partially enlarged view thereof. Specifically, (a) in the figure is a diagram showing a cross section when the negative electrode 420 in the state before winding is cut in the thickness direction (Y-axis direction), and (b) in the figure is a diagram showing a cross section. The vicinity of the boundary between the negative electrode base material layer 421 and the negative electrode active material layer 423 of (a) of the figure is enlarged and shown, and (c) of the figure is the negative electrode base material layer of (a) of the figure. It is a figure which enlarges and shows the vicinity of the boundary between 421 and a negative electrode active material layer 422.

Further, FIG. 6 is a cross-sectional view showing a state of the negative electrode 420 at the bent portion 400a of the electrode body 400 according to the embodiment of the present invention. Specifically, (a) in the figure is a schematic view when the electrode body 400 is cut on a plane (YZ plane) perpendicular to the winding axis of the electrode body 400, and (b) in the figure is a schematic view. , It is a partially enlarged view of (a) of the figure. The bent portion 400a of the electrode body 400 refers to a portion of the electrode body 400 in which the positive electrode 410 and the negative electrode 420 are bent.

As shown in FIG. 5, the negative electrode base material layer 421 has a rough surface 421a and a smooth surface 421b, and the negative electrode active material layers 422 and 423 are applied, for example, on the rough surface 421a and the smooth surface 421b. Is placed by.

Here, voids 422a and 423a are formed between each of the negative electrode active material layers 422 and 423 and the negative electrode base material layer 421. The voids 422a are specifically formed between the rough surface 421a of the negative electrode base material layer 421 and the negative electrode active material layer 422, and more specifically, are contained in the rough surface 421a and the negative electrode active material layer 422. It is formed by a negative electrode active material 501, a binder, and the like. Further, the void 423a is specifically formed between the smooth surface 421b of the negative electrode base material layer 421 and the negative electrode active material layer 423, and more specifically, on the smooth surface 421b and the negative electrode active material layer 423. It is formed by the negative electrode active material 501 contained and a binder or the like.

Comparing the sizes of the voids 422a and 423a, the voids 422a are larger than the voids 423a. This is because the void 422a is formed by a plurality of local protrusions forming the rough surface 421a and the negative electrode active material layer 422, whereas the void 422b is formed by a substantially flat surface and the negative electrode active material layer 423. By being formed.

Here, the sizes of the voids 422a and 422b can be measured as follows. Specifically, the negative electrode 420 or the positive electrode 410 is cross-section polisher (CP) processed, and a cross section cut in the thickness direction is observed by SEM. The area of at least 100 randomly selected voids among the voids between the base material layer and the rough surface observed in the SEM observation image is measured. The size of the void 422a can be measured by calculating the average value of the measured void areas. In addition, the areas of at least 100 randomly selected voids among the voids between the base material layer and the smooth surface observed in the SEM observation image are measured. The size of the void 422b can be measured by calculating the average value of the measured void areas.

The negative electrode 420 configured in this way is wound so that the rough surface 421a of the negative electrode base material layer 421 is on the inner peripheral side, so that the electrode body 400 is bent as shown in FIG. 6B. In the portion 400a, the rough surface 421a of the negative electrode base material layer 421 is arranged inside.

At this time, inside the bent portion 400a, the gap between the negative electrode base material layer 421 and the negative electrode active material layer 422 becomes smaller than that before bending due to the bending of the negative electrode 420. Therefore, when both sides of the negative electrode base material layer 421 are both formed of the smooth surface 421b, the following problems may occur.

The electrolytic solution of the power storage element 10 permeates into the electrode body 400 by diffusing through the voids in the positive electrode 410 and the negative electrode 420. Therefore, there is a problem that the electrolytic solution is difficult to permeate inside the bent portion 400a where the void becomes small.

Further, in particular, when the negative electrode active material layer 422 contains a negative electrode active material 501 or the like whose volume changes due to charging / discharging of the power storage element 10, the voids may become smaller depending on the charging / discharging cycle. Further, in this case, the electrolytic solution repeats the following movement according to the charge / discharge cycle of the power storage element 10. Specifically, the electrolytic solution is extruded from the inside of the electrode body 400 to the outside when the negative electrode active material 501 expands, and permeates and returns from the outside to the inside when the negative electrode active material 501 contracts.

Therefore, when both sides of the negative electrode base material layer 421 are composed of smooth surfaces 421b, the positive electrode 410 and the negative electrode are opposed to the progress of charging / discharging of the power storage element 10 inside the bent portion 400a where the voids are small. The reaction at 420 may not catch up. That is, the reaction of the electrode body 400 may become non-uniform, and in this case, there is a high possibility that local deterioration such as a decrease in capacitance or an increase in resistance will occur.

This tendency becomes remarkable as the size of the power storage element 10 increases. That is, the voids in the positive electrode 410 and the negative electrode 420 are configured to be small due to the demand for high energy density, and the permeation path of the surplus electrolytic solution, which is the electrolytic solution arranged outside the electrode body 400, is long. For example, it becomes remarkable in medium and large-sized in-vehicle lithium ion secondary batteries and the like.

The reason for this is that the permeation distance until the electrolytic solution extruded to the outside of the electrode body 400 returns to the center of the electrode body 400 becomes long, so that a non-uniform reaction is likely to occur. When a heterogeneous reaction occurs, there is an active material that does not or does not contribute to the electrochemical reaction. The presence of such an active material may cause deterioration in the performance of the power storage element 10, such as a decrease in capacity or an increase in resistance of the power storage element 10.

In this way, when both sides of the negative electrode base material layer 421 are both formed of smooth surfaces 421b, voids formed by the negative electrode base material layer 421 and the inner negative electrode active material layer 422 are formed in the bent portion 400a. , It is smaller than the voids formed by the negative electrode base material layer 421 and the outer negative electrode active material layer 423. Therefore, there is a problem that the reaction of the electrode body 400 becomes non-uniform and the battery performance is locally deteriorated.

On the other hand, in the present embodiment, the negative electrode base material layer 421 has a smooth surface 421b and a rough surface 421a, and the rough surface 421a is arranged inside in the bent portion 400a. That is, the electrode body 400 is formed so that the rough surface 421a is on the inner peripheral side.

Thereby, in the present embodiment, in the state before bending shown in FIG. 5, the gap 422a on the inner peripheral side can be made larger than the gap 423a on the outer peripheral side. Therefore, even in the state after bending shown in FIG. 6, the gap 422b on the inner peripheral side can be maintained at, for example, equal to or higher than the gap 423b on the outer peripheral side. That is, in the bent portion 400a, the void 422b formed by the negative electrode base material layer 421 and the negative electrode active material layer 422 on the rough surface 421a side is formed by the negative electrode base material layer 421 and the negative electrode active material layer 423 on the smooth surface 421b side. The size is equal to or larger than the formed void 423b.

In the above description, in the bent portion 400a, the gap 422b has a size equal to or larger than the gap 423b, but the space 422b may be smaller than the gap 423b.

That is, the magnitude relationship between the void 422b and the void 423b is defined by various factors such as the difference in size between the void 422a and the void 423a in the state before bending and the curvature of the bending portion 400a. Therefore, even if the gap 422a is larger than the gap 423a before bending, the gap 422b may be smaller than the gap 423b after bending.

In this case, although slightly inferior to the present embodiment, the electrolytic solution passes through the void between the negative electrode base material layer 421 and the negative electrode active material layer 422 inside the bent portion 400a as in the present embodiment. Since it can penetrate into the body, it is possible to reduce the deterioration of the performance of the power storage element 10.

As described above, according to the power storage element 10 according to the embodiment of the present invention, at least one of the positive electrode base material layer 411 and the negative electrode base material layer 421 (both in the present embodiment) has a smooth surface and a rough surface. The rough surface is arranged inside in a portion (bent portion 400a) in which at least one of the positive electrode 410 and the negative electrode 420 is bent.

Here, inside the bent portion 400a, the active material layer is compressed by the bending, so that the voids in the active material layer may become smaller. In this case, the permeability of the electrolytic solution of the power storage element 10 that permeates the inside of the electrode body 400 through such a gap may decrease. Therefore, by arranging the positive electrode base material layer 411 and the negative electrode base material layer 421 so that the rough surface having a relatively large surface roughness is on the inside in the bent portion 400a, the positive electrode base material layer 411 and the positive electrode active material layer are arranged. It is possible to secure a gap between the 412 and the negative electrode base material layer 421 and the negative electrode active material layer 422. As a result, inside the bent portion 400a, the gap between the positive electrode base material layer 411 and the positive electrode active material layer 412 and the gap between the negative electrode base material layer 421 and the negative electrode active material layer 422 pass through. Since the electrolytic solution can permeate the inside of the electrode body 400, it is possible to reduce the deterioration of the performance of the power storage element 10.

Further, in the bent portion 400a, since the inner active material layer (positive electrode active material layer 412 and the negative electrode active material layer 422) is compressed by bending, the inner active material layer and the outer active material layer (positive electrode active material layer) are compressed. The size of the void may differ between 413 and the negative electrode active material layer 423). In this case, since the permeability of the electrolytic solution differs between the inner active material layer and the outer active material layer, the reaction of the electrode body 400 may become non-uniform and local deterioration may occur. Therefore, by arranging the positive electrode base material layer 411 and the negative electrode base material layer 421 so that the rough surface having a relatively large surface roughness is on the inside in the bent portion 400a, the inner active material layer and the outer active material layer are arranged. Since the permeability of the electrolytic solution can be made uniform, local deterioration of the power storage element 10 can be suppressed.

Further, in the bent portion 400a, the void 422b formed by the negative electrode base material layer 421 and the negative electrode active material layer 422 on the rough surface 421a side is formed by the negative electrode base material layer 421 and the negative electrode active material layer 423 on the smooth surface 421b side. The size is equal to or larger than the formed void 423b.

As a result, the permeability of the electrolytic solution can be further improved inside the bent portion 400a. Here, in the electrode body 400 whose volume changes due to charging and discharging, the electrolytic solution is pushed out of the electrode body 400 at the time of expansion, and the electrolytic solution permeates from the outside to the inside of the electrode body 400 at the time of contraction and returns. .. Therefore, particularly in such an electrode body 400, when the permeability of the electrolytic solution is low inside the bent portion 400a, the performance deterioration of the power storage element 10 becomes remarkable. Therefore, the size of the voids formed by the positive electrode base material layer 411 and the negative electrode base material layer 421 and the active material layer on the rough surface side (positive electrode active material layer 412 and the negative electrode active material layer 422) is set to the size of the positive electrode base material layer 411. The volume is changed by charging and discharging by making the size of the voids formed by the negative electrode base material layer 421 and the active material layer on the smooth surface side (positive electrode active material layer 413 and the negative electrode active material layer 423) larger than the size of the voids. In the electrode body 400, the deterioration of the performance of the power storage element 10 can be further suppressed.

Further, the electrode body 400 is formed by winding the positive electrode 410 and the negative electrode 420 so that the rough surfaces of the positive electrode base material layer 411 and the negative electrode base material layer 421 are on the inner peripheral side.

As a result, as each of the positive electrode base material layer 411 and the negative electrode base material layer 421, one surface is uniformly formed as a smooth surface in a long strip-like state before winding (before bending) of the positive electrode 410 and the negative electrode 420. It is possible to use a foil in which the other surface is uniformly rough. By using such a positive electrode base material layer 411 or a negative electrode base material layer 421, it is not necessary to adjust the roughness after specifying the bent portion, so that the cost of the power storage element can be reduced.

Further, the surface of the positive electrode 410 and the negative electrode 420 exposed to the outside of the electrode body 400 can always be a smooth surface 421b having a relatively small surface roughness. Therefore, by connecting the positive electrode current collector 120 and the negative electrode current collector 130 to the electrode body 400 from the outside of the electrode body 400, the positive electrode current collector 120, the negative electrode current collector 130, and the electrode body 400 are smoothed. Connected on the surface. Therefore, it is possible to easily secure the electrical connection and the mechanical connection between the positive electrode current collector 120 and the negative electrode current collector 130 and the electrode body 400.

Further, at least one of the positive electrode base material layer 411 and the negative electrode base material layer 421 (in the present embodiment, the negative electrode base material layer 421) is a metal foil formed by electrolytic precipitation.

As a result, it is possible to manufacture a metal foil having a smooth surface 421b and a rough surface 421a with less man-hours and higher accuracy than in the case of forming by polymerization rolling.

Further, in the present embodiment, at least one of the positive electrode base material layer 411 and the negative electrode base material layer 421 (in the present embodiment, the positive electrode base material layer 411) is a metal foil formed by polymerization rolling.

As a result, it is possible to produce a metal foil having a smooth surface 421b and a rough surface 421a while having a large crystal size and excellent flexibility as compared with the case of forming by electrolytic precipitation. Here, the requirement is that, in the case of the positive electrode base material layer 411, for example, it exists stably without being dissolved in the power storage element 10 and has high electrical conductivity. Further, in the case of the negative electrode base material layer 421, for example, it does not form an alloy with lithium metal and has high electrical conductivity.

(Modification example 1)
Next, a modification 1 of the present embodiment will be described. FIG. 7 is a diagram showing the configuration of the electrode body 400A according to the first modification of the embodiment of the present invention. Specifically, (a) in the figure is a perspective view showing the electrode body 400A according to the present modification, and (b) in the figure is the negative electrode in the bent portion 400b of the electrode body 400A according to the present modification. It is sectional drawing which shows the state of. Note that (b) in the figure shows a cross section when the bent portion 400b is cut on a plane (YZ plane) perpendicular to the winding axis of the electrode body 400A.

The electrode body 400A according to the present modification shown in the figure is different from the electrode body 400 according to the above embodiment in the following points. That is, in the above embodiment, the electrode body 400 is formed by winding the positive electrode 410 and the negative electrode 420. On the other hand, in this modification, the electrode body 400A is formed by laminating the positive electrode 410 and the negative electrode 420 in a bellows shape by repeating mountain folds and valley folds.

Also in such an electrode body 400A, the rough surface of the base material layer is formed so as to be inside in the bent portion 400b which is a bent portion of the positive electrode 410 and the negative electrode 420. Specifically, as shown in FIG. 7B, in the negative electrode 420, the rough surface 421a of the negative electrode base material layer 421 is arranged inside in the bent portion 400b.

As a result, as shown in FIG. 7B, the gap 422c inside the bent portion 400b can be maintained, for example, equal to or higher than the gap 423c outside the bent portion 400b. The same applies to the positive electrode 410.

As described above, according to the power storage element including the electrode body 400A according to the present modification, the same effect as that of the above-described embodiment can be obtained. That is, inside the bent portion 400b, the electrolytic solution passes through the gap between the positive electrode base material layer 411 and the positive electrode active material layer 412 and the gap between the negative electrode base material layer 421 and the negative electrode active material layer 422. Can penetrate into the electrode body 400A, so that deterioration in the performance of the power storage element can be reduced.

(Modification 2)
Next, a modification 2 of the present embodiment will be described. In the above embodiment and the first modification thereof, it is assumed that each of the positive electrode 410 and the negative electrode 420 has a smooth surface and a rough surface. On the other hand, in this modification, the base material layer (positive electrode group) in the positive electrode 410 or the negative electrode 420 having the active material layers (positive electrode active material layers 412 and 413 or negative electrode active material layers 422 and 423) having a small porosity. The material layer 411 or the negative electrode base material layer 421) has a smooth surface and a rough surface.

FIG. 8 is an enlarged cross-sectional view showing the configuration of the electrode body according to the second modification of the embodiment of the present invention. Specifically, (a) in the figure shows the boundary between the positive electrode base material layer 411 of the positive electrode 410 and the positive electrode active material layer 412 on the inner peripheral side (plus side in the Y-axis direction) in the electrode body according to the present modification. It is a figure which enlarges and shows the vicinity and the boundary area between the negative electrode base material layer 421 of the negative electrode 420, and the negative electrode active material layer 422 on the inner peripheral side (plus side in the Y axis direction). Further, (b) and (c) in the figure are partially enlarged views of (a) in the figure.

In this modification, the porosity of the negative electrode active material layer 422 of the negative electrode 420 is smaller than the porosity of the positive electrode active material layer 412 of the positive electrode 410. Here, the "porosity of the active material layer" is the volume of the voids located in the active material layer divided by the volume of the active material layer including the voids. Specifically, the porosity of the active material layer is measured by the mercury intrusion method. When measuring the porosity in the negative electrode active material layer 422 and the positive electrode active material layer 412, the battery is discharged so that the negative electrode potential becomes 1.0 V or more, and then the battery is disassembled in a dry atmosphere. Then, the negative electrode 420 and the positive electrode 410 are washed with dimethyl carbonate and then vacuum dried for 2 hours or more. After that, the porosity of the negative electrode active material layer 422 and the positive electrode active material layer 412 can be obtained by carrying out the measurement by the mercury intrusion method.

Such a difference in porosity is, for example, between the particle size of the positive electrode active material 502 or the like contained in the positive electrode active material layer 412 and the particle size of the negative electrode active material 501 or the like contained in the negative electrode active material layer 422. It is caused by the difference or the difference between the press pressure applied when manufacturing the positive electrode active material layer 412 and the press pressure applied when manufacturing the negative electrode active material layer 422. Specifically, assuming that the particle size of the positive electrode active material 502 is d2 and the particle size of the negative electrode active material 501 is d1, the porosity of the negative electrode active material layer 422 can be easily reduced by setting d2> d1. Further, assuming that the press pressure applied when manufacturing the positive electrode active material layer 412 is P1 and the press pressure applied when manufacturing the negative electrode active material layer 422 is P2, then P1> P2, so that the negative electrode active material layer 422 can be pressed. It is easy to reduce the porosity.

Here, the surface roughness of the surface of the positive electrode base material layer 411 on the positive electrode active material layer 412 side (inner peripheral side surface: the surface on the positive side in the Y-axis direction) and the surface roughness of the negative electrode base material layer 421 on the negative electrode active material layer 422 side. When the surface roughness of the surface (the surface on the inner peripheral side: the surface on the positive side in the Y-axis direction) is the same, the following problems occur.

That is, since the voids 422s of the negative electrode active material layer 422 are smaller than the voids 412s of the positive electrode active material layer 412, in this case, the voids formed between the negative electrode base material layer 421 and the negative electrode active material layer 422. Is smaller than the voids formed between the positive electrode base material layer 411 and the positive electrode active material layer 412.

Therefore, in this case, local deterioration of battery performance as described in the embodiment is likely to occur between the negative electrode base material layer 421 and the negative electrode active material layer 422.

Therefore, in this modification, of the positive electrode 410 and the negative electrode 420, the negative electrode base material layer 421 of the negative electrode 420 having the negative electrode active material layer 422, which is an active material layer having a small pore ratio, is a smooth surface 421b (FIGS. 5 and FIG. 6) and a rough surface 421a. Further, similarly to the above-described embodiment and the first modification, the rough surface 421a is arranged inside at the portion where the positive electrode 410 and the negative electrode 420 are bent.

As described above, according to the power storage element according to the present modification, the base material layer (negative electrode base material layer 421 in this modification) of either one of the positive electrode 410 and the negative electrode 420 (negative electrode 420 in this modification) is Has a smooth surface 421b (see FIGS. 5 and 6) and a rough surface 421a. Here, the porosity of the active material layer (negative electrode active material layer 422 in this modified example) possessed by one of them is larger than the porosity of the active material layer (positive electrode active material layer 412 in this modified example) possessed by the other. small.

Here, the smaller the porosity of the electrolytic solution in the active material layer, the lower the permeability. Therefore, in the portion where the positive electrode 410 and the negative electrode 420 are bent (see the bent portion 400a in FIG. 6), particularly in the portion where the active material layer having a small porosity is located, the permeability of the electrolytic solution described above is lowered. Is likely to occur. Therefore, in the base material layer (negative electrode base material layer 421 in this modified example) in which the active material layer having a small porosity (negative electrode active material layer 422 in this modified example) is arranged inside, the surface roughness is relatively large. By arranging the rough surface 421a inside, it is possible to reduce the decrease in the place where the decrease in the permeability of the electrolytic solution is likely to occur. That is, it is possible to suppress the deterioration in the place where the deterioration of the power storage element is likely to occur.

In this modification, the porosity of the negative electrode active material layer 422 is smaller than the porosity of the positive electrode active material layer 412, and the negative electrode base material layer 421 has a smooth surface 421b (see FIGS. 5 and 6) and a rough surface. It was assumed to have 421a. However, the porosity of the positive electrode active material layer 412 may be smaller than the porosity of the negative electrode active material layer 422, and the positive electrode base material layer 411 may have a smooth surface and a rough surface. This also makes it possible to suppress the deterioration in the portion where the deterioration of the power storage element is likely to occur, as in the present modification.

(Other variants)
Although the power storage element according to the embodiment of the present invention and the modified example thereof has been described above, the present invention is not limited to the embodiment and the modified example thereof.

That is, it should be considered that the embodiments disclosed this time and examples thereof are examples in all respects and are not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

For example, in the above-described embodiment and its modification, the smooth surface is assumed to be a substantially flat surface. However, the smooth surface may have a surface roughness smaller than that of the rough surface, and may have irregularities smaller than the irregularities formed on the rough surface, for example.

Further, in the above modification 2, of the positive electrode 410 and the negative electrode 420, the negative electrode base material layer 421 of the negative electrode 420 having the negative electrode active material layer 422, which is an active material layer having a small porosity, has a smooth surface 421b (FIGS. 5 and 5). (See FIG. 7) and a rough surface 421a. However, of the positive electrode 410 and the negative electrode 420, the positive electrode base material layer 411 of the positive electrode 410 having the positive electrode active material layer 412 which is the active material layer having a large porosity may have a smooth surface and a rough surface. ..

Also by this, since the rough surface is arranged inside in the portion where the positive electrode 410 and the negative electrode 420 are bent, it is possible to reduce the deterioration of the performance of the power storage element.

Further, in the above embodiment, the electrode body 400 is formed by winding the positive electrode 410 and the negative electrode 420 so that the rough surface 421a is on the inner peripheral side. However, it is sufficient that the rough surface 421a is arranged inside at least in the bent portion 400a, and the rough surface 421a is arranged outside in the portion where the positive electrode 410 and the negative electrode 420 other than the bent portion 400a are formed in a flat shape. It doesn't matter if it is done. Further, in the portion formed in the flat shape, the smooth surface 421b may be arranged on either the inside or the outside.

Also by this, since the rough surface is arranged inside in the bent portion of the positive electrode 410 and the negative electrode 420, it is possible to reduce the deterioration of the performance of the power storage element as in the above embodiment and its modified example. it can. In such a configuration, for example, after preparing a base material layer in which the smooth surface 421b is uniformly arranged on both the inside and the outside, the inside of the planned portion of the base material layer to be the bent portion 400a is roughened. This can be achieved by surface treatment. Specific examples of the roughening treatment include polishing, sandblasting, surface unevenness processing by forming grooves or notches, and the like.

Further, in the above-described embodiment and its modification, it is assumed that the positive electrode current collector 120, the negative electrode current collector 130, and the electrode body 400 are connected by a smooth surface. However, the positive electrode current collector 120, the negative electrode current collector 130, and the electrode body 400 may be connected on a rough surface.

In this case, although it may be somewhat difficult to secure the electrical connection and the mechanical connection between the positive electrode current collector 120 and the negative electrode current collector 130 and the electrode body 400, the above-described embodiment and its modification Similarly, it is possible to reduce the deterioration of the performance of the power storage element.

Further, in the above-described embodiment and its modification, the negative electrode base material layer 421 is a metal leaf formed by electrolytic precipitation, and the positive electrode base material layer 411 is a metal foil formed by polymerization rolling. did. However, the positive electrode base material layer 411 may be formed by electrolytic precipitation, and the negative electrode base material layer 421 may be formed by polymerization rolling.

Also by this, since the rough surface is arranged inside in the bent portion of the positive electrode 410 and the negative electrode 420, it is possible to reduce the deterioration of the performance of the power storage element as in the above embodiment and its modified example. it can.

Further, in the above-described embodiment and its modification, the positive electrode base material layer 411 is a metal foil made of aluminum or an aluminum alloy, and the negative electrode base material layer 421 is a metal foil made of copper or a copper alloy or the like. However, the positive electrode base material layer 411 and the negative electrode base material layer 421 may be metal foils using appropriately known metal materials such as nickel, iron, stainless steel, titanium, and Al—Cd alloy. Further, the positive electrode base material layer 411 and the negative electrode base material layer 421 may be foils using appropriately known materials other than metal materials such as calcined carbon, conductive polymer, and conductive glass.

Also by this, since the rough surface is arranged inside in the bent portion of the positive electrode 410 and the negative electrode 420, it is possible to reduce the performance deterioration of the power storage element as in the above embodiment and its modified example. ..

Further, in the above-described embodiment and its modification, it is assumed that the active material layers are arranged on both sides of the base material layer in each of the positive electrode 410 and the negative electrode 420. However, the active material layer may be arranged only on one side of the base material layer such that the positive electrode 410 and the negative electrode 420 are arranged inside in the bent portion.

Further, a form constructed by arbitrarily combining the above-described embodiment and its modifications is also included in the scope of the present invention. Further, the configuration may be a combination of the above-described embodiments and partial configurations of the modifications thereof as appropriate. For example, the configuration may be a combination of the configuration of the modification 1 and the configuration of the modification 2.

Since the present invention can provide a power storage element capable of reducing performance deterioration, it can be applied to a medium- to large-sized power storage element or the like mounted on an automobile or the like where high quality and high output are required.

10 Power storage element 100 Container 110 Lid 111 Main body 120 Positive electrode current collector 130 Negative electrode current collector 200 Positive electrode terminal 300 Negative electrode terminal 400, 400A Electrode body 400a, 400b Bending part 410 Positive electrode 411 Positive electrode base material layer 412, 413 Positive electrode active material layer 420 Negative electrode 421 Negative electrode base material layer 421a Rough surface 421b Smooth surface 422, 423 Negative electrode active material layer 421s, 422s, 422a, 422b, 422c, 423a, 423b, 423c Void 430 Separator 501 Negative electrode active material 502 Positive electrode active material

Claims (4)

An electrode body having a positive electrode and a negative electrode, and a power storage element including an electrolytic solution.
The electrode body has a bent portion in which at least one of the positive electrode and the negative electrode is bent, and a flat portion in which the positive electrode and the negative electrode are formed in a flat shape.
At least one of the positive electrode and the negative electrode
A base material layer having a first surface and a second surface which is the opposite surface of the first surface, and
It has an active material layer formed on the base material layer and has.
The second surface is arranged inside the first surface at the bent portion.
The second surface has a larger surface roughness defined by the center line average roughness (Ra) than the first surface at the bent portion.
The active material layer is formed on the first surface and the second surface of the base material layer.
The size of the voids formed by the base material layer and the active material layer on the second surface side is the size of the voids formed by the base material layer and the active material layer on the first surface side. This is the power storage element. The power storage element further includes a current collector connected to the electrode body.
The power storage element according to claim 1, wherein the electrode body is in contact with the current collector on the first surface. The base material layer possessed by either the positive electrode or the negative electrode is a base material layer having the first surface and the second surface.
The power storage element according to claim 1 or 2 , wherein the porosity of the active material layer possessed by one of them is smaller than the porosity of the active material layer possessed by the other. The second surface has a larger surface roughness defined by the center line average roughness (Ra) than the first surface as a whole.
Any of claims 1 to 3 , wherein the electrode body is formed by winding the positive electrode and the negative electrode so that the second surface is located on the inner peripheral side of the first surface. The power storage element according to item 1.

Images