JP2013110071A - Electrochemical device - Google Patents

Abstract

An object of the present invention is to provide a battery that can suppress a decrease in lifetime and reliability of an electrochemical device even if the battery has a temperature gradient due to current concentration near each tab.
An electrolyte layer (12) having a function as an ion transfer medium between electrodes, and a negative electrode (4) and a positive electrode (8) provided on both sides of the electrolyte layer (12), In the electrochemical device (1) including the flat power generation element (2) in which ions move between the two electrodes (4, 8) to perform an electrochemical reaction, the in-plane temperature of the power generation element (2) is uniform. Thus, the activity of the electrochemical reaction in the plane of the power generation element (2) is varied.
[Selection] Figure 5

Description

  The present invention relates to an electrochemical device such as a lithium ion secondary battery.

  There is one in which a substantially flat power generation element is covered with a battery outer package, and a battery in which the peripheral portion of the battery outer package is joined by thermal fusion is stacked as a unit (see Patent Document 1). In this case, the first adhesive material having thermal conductivity is applied to the central portion of the battery, and the second adhesive material having adhesive strength is applied to the peripheral portion of the battery, and then the two batteries are bonded together. Yes.

JP 2009-272048 A

  By the way, in said battery, the two tabs for performing at least one of charge or discharge to an electric power generation element are provided in the peripheral part of the electric power generation element. When the group including the present inventor experimented, it has been found for the first time that the temperature in the vicinity of each of the two tabs tends to rise from a portion away from each of the tabs due to the current concentration in the vicinity of the two tabs.

  As described above, a non-uniform temperature gradient is generated in the in-plane direction of the power generation element, resulting in a difference in deterioration progress in the in-plane direction of the power generation element, resulting in a problem that the life and reliability of the entire battery are lowered. Arise.

  However, even if the technique of Patent Document 1 is applied to a battery in which the temperature in the vicinity of each tab tends to rise from a portion away from each tab due to current concentration near each tab, the power generation element in-plane direction It is impossible to eliminate the uneven temperature gradient. The above-mentioned Patent Document 1 is merely a technique that considers that heat radiation from a generally flat battery as a whole is higher in the central part than in the peripheral part, and corresponds to a non-uniform actual temperature gradient in the in-plane direction of the power generation element. Because it is not.

  Therefore, the present invention suppresses deterioration in the lifetime and reliability of electrochemical devices even in a battery having a temperature gradient in which the temperature in the vicinity of each tab rises from a portion away from each tab due to current concentration near each tab. It is an object of the present invention to provide a battery that can be used.

  The electrochemical device of the present invention has an electrolyte layer having a function as an ion transfer medium between electrodes, and a negative electrode and a positive electrode provided on both sides of the electrolyte layer, and electrons and ions pass between the two electrodes. It is premised on an electrochemical device having a flat power generation element that moves and performs an electrochemical reaction. Then, the activity of the electrochemical reaction in the in-plane direction of the power generation element is varied so that the temperature in the in-plane direction of the power generation element becomes uniform.

  When the activity of the electrochemical reaction in the in-plane direction of the power generation element is varied, the charge / discharge reaction heat in the in-plane direction of the power generation element changes. In other words, the activity of the electrochemical reaction in the in-plane direction of the power generation element is made different so that the sum of the electrochemical reaction heat in the in-plane direction of the power generation element and the Joule heat generation in the in-plane direction becomes the same temperature. Thus, the temperature in the in-plane direction of the power generation element can be made uniform. If it is possible to make the temperature in the in-plane direction of the power generation element uniform, it is possible to suppress degradation of the lifetime and reliability of the electrochemical device.

It is a schematic perspective view of the lithium ion secondary battery of 1st Embodiment. It is a disassembled perspective view of an electric power generation element. It is a model figure which shows the surface temperature gradient of the laminate film at the time of discharge of the present battery. It is sectional drawing of the cell layer of a reference example. It is sectional drawing of the cell layer of 1st Embodiment. It is a characteristic view of the temperature gradient in the in-plane direction. It is sectional drawing of the cell layer of 2nd Embodiment. It is a schematic perspective view of the separator of the other example of 2nd Embodiment. It is sectional drawing of the cell layer of 3rd Embodiment. It is a schematic perspective view of the positive electrode active material layer of the other example of 3rd Embodiment. It is sectional drawing of the cell layer of 4th Embodiment. It is sectional drawing of the cell layer of 5th Embodiment. It is a schematic perspective view of the ion block layer of the other example of 5th Embodiment. It is sectional drawing of the cell layer of 6th Embodiment. It is a schematic perspective view of the solid electrolyte layer of the other example of 6th Embodiment. It is sectional drawing of the cell layer of 7th Embodiment. It is sectional drawing of the cell layer of 8th Embodiment. It is sectional drawing of the cell layer of 9th Embodiment. It is a characteristic figure of the temperature gradient of the surface direction of 10th Embodiment. It is a schematic perspective view of the separator of 10th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the dimension ratio of drawing has the location exaggerated on account of description, and the location differs from the actual ratio.

(First embodiment)
The lithium ion secondary battery 1 of this embodiment will be outlined first. FIG. 1 is a schematic perspective view of a lithium ion secondary battery 1, and FIG. 2 is an exploded perspective view of a power generation element 2.

  As shown in FIG. 1, a lithium ion secondary battery 1 has a structure in which a substantially square flat power generation element 2 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 14 that is a battery exterior material. Have. Specifically, the power generation element 2 is housed and sealed by bonding the peripheral portions (peripheral portions) 14a, 14b, 14c, and 14d by thermal fusion using a polymer-metal composite laminate film as a battery exterior material. It has the structure. Here, the polymer-metal composite laminate film generally has a three-layer structure in which a metal film is sandwiched between polymer films (resin films).

  Such a stacked battery 1 is referred to as a “laminated battery” in order to be distinguished from a can battery. A can-type battery is one in which two electrodes are wound and housed in a rigid cylindrical metal outer frame. On the other hand, the laminate type battery is a battery in which the power generation element is sealed by joining the peripheral portion (peripheral portion) of the substantially square flat power generation element 2 by thermal fusion. Hereinafter, the lithium ion secondary battery 1 is referred to as a “laminated battery”. Alternatively, it is simply called “battery”.

  As shown in FIG. 2, the power generation element 2 has a configuration in which a negative electrode 4, a separator 12, and a positive electrode 8 are stacked in this order. Here, the negative electrode 4 is obtained by disposing negative electrode active material layers 6 and 6 on both sides of a rectangular thin plate-like negative electrode current collector 5. Similarly, the positive electrode 8 is obtained by disposing positive electrode active material layers 10 and 10 on both sides of a rectangular thin plate-shaped positive electrode current collector 9. The separator 12 is mainly formed from a porous thermoplastic resin. Since the separator 12 holds the electrolytic solution, an electrolyte layer is formed integrally with the separator 12. In other words, an electrolyte layer having a function as a Li ion transfer medium between two electrodes is composed of a liquid electrolyte and a microporous membrane separator 12 containing a resin.

  Thereby, the adjacent negative electrode 4, separator 12 (including the electrolytic solution), and positive electrode 8 constitute one single cell layer 13 (single cell). In the single cell layer 13, electrons and ions move between the two electrodes to perform a charge / discharge reaction (electrochemical reaction) of the battery. Therefore, it can be said that the laminate type battery 1 of the present embodiment has a configuration in which the single battery layers 13 are stacked to be electrically connected in parallel. Further, a seal portion (insulating layer) for insulating between the adjacent negative electrode current collector 5 and positive electrode current collector 9 may be provided on the outer periphery of the unit cell layer 13. The outermost negative electrode current collectors 5 located on both outermost layers of the power generating element 2 are all only on one side (in FIG. 2, the uppermost negative electrode current collector 5 has only the lower surface, the lowermost negative electrode current collector 5 has Is disposed on the upper surface only). Note that the arrangement of the negative electrode and the positive electrode is reversed from that in FIG. 2 so that the outermost positive electrode current collector is positioned in both outermost layers of the power generation element 2, and the positive electrode is provided only on one side of the outermost positive electrode current collector. An active material layer may be disposed.

  The negative current collector 5 and the positive current collector 9 are attached with two high-power tabs, a negative electrode tab 15 and a positive electrode tab 16, which take out electrons entering and exiting from each electrode (negative electrode and positive electrode) to the outside, and a peripheral portion of the laminate film 14. So as to be sandwiched between the laminated films 14. Since the power generation element 2 is formed in a square flat shape having four sides as a whole, the two high-power tabs 15 and 16 are collectively led out from only one side of the four sides (see FIG. 1). The high voltage tabs 15 and 16 are ultrasonically applied to the negative electrode current collector 5 and the positive electrode current collector 9 of each electrode via a positive electrode terminal lead (not shown) and a negative electrode terminal lead (not shown) as necessary. You may attach by welding and resistance welding. In addition, it cannot be overemphasized that each negative electrode tab 15 in FIG. 2 and each positive electrode tab 16 are electrically connected.

  Now, in order to investigate the temperature gradient in the in-plane direction of the battery 1, the group including the present inventor manufactured the battery 1 and measured the surface temperature of the laminate film by charging and discharging, and the result shown in FIG. 3 was obtained. FIG. 3 shows a model of the surface temperature gradient of the laminate film at the time of discharge first discovered by the group including the present inventor. In FIG. 3, the darker the color, the higher the laminate film surface temperature due to heat generation. According to FIG. 3, the heat generation temperature is highest in the vicinity of each of the two high-power tabs 15 and 16, and the heat generation temperature decreases as the distance from the two high-power tabs 15 and 16 increases (downward in FIG. 3). Yes. Further, in FIG. 3, the portion of the right half region on the positive electrode tab 16 side has a higher temperature than the left half region on the negative electrode tab 15 side.

  The analysis of this phenomenon is as follows. That is, the battery 1 generates heat. This heat generation is roughly divided into charge / discharge reaction heat (electrochemical reaction heat), polarization heat generation, and Joule heat generated when electrons diffuse in the member. In the battery 1 including the two high-power tabs 15 and 16 for entering and exiting electrons, current (electrons) concentrates in the vicinity of each of the high-power tabs 15 and 16 due to its structure, and the temperature rise due to Joule heat generation locally. It is thought to occur.

  In this way, the temperature rises as the two high power tabs 15 and 16 are closer to each other in the plane of the power generation element 2, that is, if a non-uniform temperature gradient (temperature distribution) occurs in the in-plane direction of the power generation element 2, the relative In particular, the vicinity of the high-power tabs 15 and 16 that are high-temperature portions deteriorates first. As a result of the difference in deterioration progress in the in-plane direction of the power generation element 2, there arises a problem that the life and reliability of the entire battery 1 are lowered. Here, the “surface of the power generation element” refers to the upper and lower surfaces of this flat paper when the power generation element is regarded as one flat paper. In addition, the “in-plane direction of the power generation element” refers to an arbitrary direction along the plane of the flat paper when the power generation element is regarded as one flat paper. The “in-plane direction of the power generation element” is also simply used as the “in-plane direction”.

  More specifically, the positive electrode active material includes Li / Mn composite oxides, Li / Ni composite oxides, Li / Co composite oxides, etc., and these three types of composite oxides have recently been mixed. The group including the present inventor has intensively studied the positive electrode active material used in the above. If the positive electrode active material having a configuration in which these three complex oxides are mixed is referred to as “ternary NMC”, in particular, in this ternary NMC, a non-uniform temperature gradient (distribution) in the in-plane direction of the power generation element 2. ) Is found to occur greatly.

  Therefore, in the present invention, charge / discharge reaction heat (electrochemical reaction heat), which is a heat generation factor other than Joule heat generation, has a temperature gradient opposite to Joule heat generation in the in-plane direction of the power generation element 2. That is, the charge / discharge reaction heat (electrochemical reaction heat) in the in-plane direction of the power generation element 2 is varied so that the temperature in the in-plane direction of the power generation element 2 is uniform. Here, in order to vary the charge / discharge reaction heat in the in-plane direction of the power generation element 2, the activity of the charge / discharge reaction in the in-plane direction of the power generation element 2 is varied. The power generation element 2 is configured to have a temperature gradient in which the charge / discharge reaction heat becomes small. As a result, the temperature gradient in the in-plane direction due to Joule heat generation can be canceled, and as a result, the temperature in the in-plane direction of the power generation element 2 can be made uniform.

  The charge / discharge reaction heat can be controlled using the ionic conductivity as the activity of the charge / discharge reaction. The “ion” here means Li ion in the embodiment. Li ions move in the electrolyte layer from the positive electrode to the negative electrode or vice versa to perform a charge / discharge reaction. “Ion conductivity” is an index representing the ease of movement of Li ions. On the other hand, the “activity of charge / discharge reaction” refers to the ease with which the charge / discharge reaction occurs. Therefore, when the ionic conductivity of the electrolyte is low, Li ions are relatively difficult to move and the activity of the charge / discharge reaction is lowered. Conversely, when the ionic conductivity of the electrolyte is high, Li ions are relatively moved. It becomes easy to increase the activity of the charge / discharge reaction. In addition, the ionic conductivity is in a proportional relationship with the electrical conductivity representing the ease of electrical conduction.

  When the electrolyte is a liquid electrolyte, the ionic conductivity of the electrolyte can be changed in the in-plane direction of the power generation element 2 by changing the porosity of the separator 12, the thickness of the separator 12, and the thickness of the electrode. When the ion block layer 21 is provided on the electrode surface, the ion conductivity can be changed in the in-plane direction of the power generation element 2 by changing the porosity of the ion block layer 21 and the thickness of the ion block layer 21. When the electrolyte is a semi-solid electrolyte or a solid electrolyte, the ionic conductivity is increased in the in-plane direction of the power generation element 2 by changing the thickness, viscosity, dielectric constant, and electrolyte salt concentration of the semi-solid electrolyte or solid electrolyte. Can change.

  Hereinafter, the ionic conductivity of the electrolyte is changed by changing the porosity of the separator 12 in the first embodiment, the thickness of the separator 12 in the second embodiment, and the thickness of the electrode in the third embodiment. Explain the case. In the fourth embodiment, the case where the ionic conductivity of the electrolyte is changed by changing the porosity of the ion blocking layer 21 and in the fifth embodiment by changing the thickness of the ion blocking layer 21 will be described. In the sixth embodiment, the thickness of the semisolid electrolyte layer (or solid electrolyte layer) 25 is set. In the seventh, eighth, and ninth embodiments, the viscosity, dielectric constant, and electrolyte of the semisolid electrolyte layer (or solid electrolyte layer) 25 are set. The case where the ionic conductivity of the electrolyte is changed by changing the salt concentration will be described.

  First, FIGS. 4 and 5 are cross-sectional views of the unit cell layer 13 that shows only one unit cell layer 13 taken out from the power generation element 2, and FIG. 4 shows the unit cell layer 13 of the reference example, and FIG. It is the cell layer 13 of one embodiment.

  However, the separator 12 is shown slightly apart from the two electrodes 4 and 8 in the vertical direction. 4 and 5, unlike the case of FIG. 2, the high power tabs 15 and 16 are described as being on extensions of the current collectors 5 and 9. The same applies to FIGS. 7, 9, 11, 12, 14, 16, 17, and 18.

  4 and 5, the separator 12 is composed of a microporous film containing a resin such as a porous resin or a nonwoven fabric entangled with resin fibers. A large number of pores in the membrane are filled with the electrolyte. Therefore, Li ions in the electrolytic solution can move between the negative electrode 4 and the positive electrode 8 through a large number of holes in the membrane. For this reason, when the battery 1 is discharged, Li ions in the electrolytic solution move from the negative electrode 4 to the positive electrode 8 as shown in FIGS.

  Here, in the reference example shown in FIG. 4, the porosity of the separator 12 is uniform in the in-plane direction of the separator 12 (left and right direction in FIG. 4). On the other hand, in the first embodiment shown in FIG. 5, in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation, the porosity of the separator 12 is set in the in-plane direction of the separator 12 (power generation element 2) (in the horizontal direction in FIG. 5). ), The closer to the two high-power tabs 15 and 16, the smaller the tab. When the porosity of the separator 12 is made smaller in the in-plane direction of the power generating element 2 as it is closer to each of the high-power tabs 15 and 16, Li ions are less likely to move through the electrolyte, and the ionic conductivity of the electrolyte is determined by the high-power tabs 15 and 16 respectively. The closer it is, the lower it will be.

  As in the first embodiment, when the porosity of the separator 12 is made smaller in the in-plane direction of the separator 12 as it approaches the high-power tabs 15 and 16, each high-power tab 15 as shown in FIG. The amount of Li ion separator movement on the 16 side (see the thick arrow in FIG. 5) is smaller than the amount of Li ion separator movement on the side opposite to the high voltage tabs 15 and 16 (see the thin arrow in FIG. 5). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. . On the other hand, in the reference example, since the porosity of the separator 12 is uniform in the in-plane direction of the separator 12 and the charge / discharge reaction occurs uniformly in the in-plane direction, the temperature gradient in the in-plane direction due to Joule heat generation is offset. I can't.

  Next, three methods for adjusting the porosity of the separator 12 will be described.

<1> Method of Adjusting with Separator Molding Method Since the holes in the separator are usually formed after the solvent in the solution has evaporated, the concentration of the solution changes in one direction in the plane when the separator is molded. In this way, a gradient of concentration is provided (either the concentration of the solution gradually increases or the concentration of the solution gradually decreases). Then, since the solvent is relatively small on the side where the concentration of the solution is relatively high, the number of pores is relatively small, and on the contrary, the side where the concentration of the solution is relatively thin has a relatively large amount of solvent. Therefore, the number of holes is relatively increased. As a result, the amount of movement of Li ions on the side of each of the high voltage tabs 15 and 16 having a relatively small number of holes is smaller than that on the side opposite to the high voltage tabs 15 and 16 having a relatively large number of holes. Charge / discharge reaction heat becomes relatively small.

<2> Method of Adjusting by Separator Stretching Method If the separator is stretched during molding, the diameter of the holes becomes larger than before stretching. Therefore, when the separator is molded, a gradient of the stretching ratio is given so that the stretching ratio changes in one direction in the plane (either gradually increasing the stretching ratio or gradually decreasing the stretching ratio). . Then, even if the number of holes per unit volume is the same, the diameter of the holes is relatively small on the side where the stretching ratio is relatively small, and the diameter of the holes is relatively small on the side where the stretching ratio is relatively large. growing. As a result, the amount of Li ion movement on each of the high-power tabs 15 and 16 having a relatively small hole diameter is smaller than that on the side opposite to the high-power tabs 15 and 16 having a relatively large hole diameter. The discharge reaction heat becomes relatively small.

<3> First, after forming a separator having a uniform porosity, a method of fixing an inert substance in the pores with a spray device or the like. An inert substance adheres to the wall surface and solidifies to reduce the diameter of the hole. Therefore, after forming a separator with a uniform porosity, the spray amount from the spray device changes in one direction within the surface (either gradually increasing the spray amount or gradually decreasing the spray amount). Or) Give the spray amount distribution. Then, the diameter of the hole is relatively small on the side where the spray amount is relatively large, and the diameter of the hole is relatively large on the side where the spray amount is relatively small. As a result, the amount of movement of Li ions on the side of the high voltage tabs 15 and 16 having a relatively small hole diameter is smaller than that on the side opposite to the high voltage tabs 15 and 16 having a relatively large hole diameter. The discharge reaction heat becomes relatively small.

  Further, in FIG. 3, when the power generating element 2 is divided into two substantially vertically and the temperature gradient in the vertical direction (in-plane direction) is overlapped for each of the left and right regions, there is a positive electrode tab 16 as shown in FIG. The temperature gradient in the in-plane direction is different between the right region and the left region where the negative electrode tab 15 is provided. That is, the positive electrode tab 16 side is wider than the negative electrode tab 15 side in a range having a temperature gradient in the in-plane direction of the power generation element 2 (left and right direction in FIG. 6). Therefore, in FIG. 3, the separator 12 is almost equally divided into the right region with the positive electrode tab 16 and the left region with the negative electrode tab 15, and the porosity of the separator 12 in each of the two divided regions is expressed in this plane. It is preferable to set according to two types of temperature gradients in the inward direction. For example, when compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the porosity of the separator 12 in the right region where the positive electrode tab 16 is present is expressed as the porosity of the separator 12 in the left region where the negative electrode tab 15 is present. It is made smaller than the porosity (low in ionic conductivity).

  Here, the function and effect of the first embodiment will be described.

  According to the first embodiment, it has an electrolyte layer (separator 12 and electrolyte) having a function as a Li ion transfer medium between electrodes, and a negative electrode 4 and a positive electrode 8 provided on both sides of the electrolyte layer, In a battery 1 (electrochemical device) including a flat power generation element 2 in which electrons and ions move between the two electrodes 4 and 8 to perform a charge / discharge reaction (electrochemical reaction), an in-plane temperature of the power generation element 2 The activity of the charge / discharge reaction (electrochemical reaction) in the in-plane direction of the power generation element 2 is made different so as to be uniform.

  When the activity of the charge / discharge reaction in the in-plane direction of the power generation element 2 is varied, the charge / discharge reaction heat in the in-plane direction of the power generation element 2 changes. That is, in the in-plane direction of the power generation element 2, the sum of the charge / discharge reaction heat (electrochemical reaction heat) in the in-plane direction of the power generation element 2 and the Joule heat generation in the in-plane direction becomes the same temperature. By varying the activity of the charge / discharge reaction (electrochemical reaction), the temperature in the in-plane direction of the power generation element 2 can be made uniform. If the temperature in the in-plane direction of the power generation element 2 can be made uniform, it is possible to suppress a decrease in the life and reliability of the battery 1 (electrochemical device).

  According to the first embodiment, the electrolyte layer (separator 12 and the electrolyte solution) having a function as a Li ion (ion) transfer medium between the electrodes, and the negative electrode 4 and the positive electrode 8 provided on both sides of the electrolyte layer are provided. A flat power generation element 2 in which electrons and Li ions move between the two electrodes 4 and 8 to perform a charge / discharge reaction (electrochemical reaction), and electrons that enter and exit from the negative electrode 4 and the positive electrode 8 are taken out to the outside. In the battery 1 (electrochemical device) including the negative electrode tab 15 and the positive electrode tab 16, charge / discharge reaction heat (electrochemical) in the in-plane direction of the power generation element 2 so that the in-plane direction temperature of the power generation element 2 becomes uniform. Therefore, it is possible to make the temperature in the in-plane direction of the power generation element 2 uniform, and it is possible to suppress a decrease in life and reliability of the battery 1 (electrochemical device).

  According to the first embodiment, Li ions that move through the electrolyte layer are less likely to move closer to the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2, and thus the two high-power tabs 15 and 16. Li ions are less likely to move toward the periphery of the substrate, and the charge / discharge reaction (electrochemical reaction) is suppressed, and the charge / discharge reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16.

  In accordance with the first embodiment, the separator 12 (electrolyte layer) moves further on the positive electrode tab 16 side than on the negative electrode tab 15 side in accordance with the fact that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. Li ions (ions) to be moved are less likely to move. Therefore, Li ions are more difficult to move on the positive electrode tab 16 side than on the negative electrode tab 15 side, and charge / discharge reaction (electrochemical reaction) on the positive electrode tab 16 side is reduced. As a result, even if the degree of heat generation is different between the positive electrode tab 16 side and the negative electrode tab 15 side, the temperature can be made uniform in the in-plane direction of the power generation element 2.

  According to the first embodiment, the ease of movement of ions is ionic conductivity, and this ionic conductivity is lowered as it approaches the two high-power tabs 15, 16 in the in-plane direction of the power generation element 3. The charge / discharge reaction heat (electrochemical reaction heat) on the high-power tabs 15 and 16 side can be made relatively smaller than the side away from the high-power tabs 15 and 16.

  According to the first embodiment, since the heat generation is higher on the positive electrode tab 16 side than on the negative electrode tab 15 side, the ionic conductivity is further lowered on the positive electrode tab 16 side than on the negative electrode tab 15 side. The heat generation on the side of the positive electrode tab 16 having a relatively wide temperature gradient in the in-plane direction 2 is suppressed to be equivalent to the heat generation on the side of the negative electrode tab 15 having a relatively narrow temperature gradient in the in-plane direction. be able to.

  According to the first embodiment, the porosity of the separator 17 is made smaller as it is closer to the two high-power tabs 15 and 16 (tabs) in the in-plane direction of the power generation element 2. The charging / discharging reaction is suppressed toward the periphery, and the charging / discharging reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the first embodiment, according to the first embodiment, the porosity of the separator 12 is further made smaller on the positive electrode tab 16 side than on the negative electrode tab 15 side, so that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. The temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Second Embodiment)
FIG. 7 is a cross-sectional view of the cell layer 13 of the second embodiment, which replaces FIG. 5 of the first embodiment. The same parts as those in FIG.

  As shown in FIG. 7, in the second embodiment, the thickness of the separator 12 (the thickness in the vertical direction in FIG. 7) is close to the high voltage tabs 15 and 16 in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation. It will be thicker. When the thickness of the separator 12 is increased in the in-plane direction of the power generation element 2 so as to be closer to the high-power tabs 15 and 16, Li ions hardly move in the electrolyte, and the ionic conductivity of the electrolyte is close to the high-power tabs 15 and 16. It gets lower.

  On the side of the high-power tabs 15 and 16 where the separator 12 is relatively thick, the distance that Li ions move through the separator 12 is longer than the side opposite to the side where the separator 12 is relatively thin. As a result, the amount of movement of Li ions on the side of the high-power tabs 15 and 16 where the thickness of the separator 12 is relatively large becomes smaller than the side opposite to the side of the high-power tabs 15 and 16 where the thickness of the separator 12 is relatively small. The charge / discharge reaction heat (electrochemical reaction heat) in the direction becomes relatively small.

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the separator 12 is almost divided into a right region 12 a with the positive electrode tab 16 and a left region 12 b with the negative electrode tab 15, and the thickness of the separator 12 in each of the divided regions 12 a and 12 b is divided into two. Set as follows. That is, according to two types of temperature gradients in the in-plane direction, when compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the thickness of the separator 12 in the region 12a with the positive electrode tab 16 as shown in FIG. Is made thicker than the thickness of the separator 12 in the region 12b where the negative electrode tab 15 is present. Here, FIG. 8 is a schematic perspective view of only the separator 12.

  According to the second embodiment, the thickness of the separator 12 increases in the in-plane direction of the power generation element 2 as it is closer to the two high-power tabs 15 and 16, so that charging and discharging is performed in the vicinity of the two high-power tabs 15 and 16. The reaction is suppressed, and the charge / discharge reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the second embodiment, the thickness of the separator 12 is further increased on the positive electrode tab 16 side than on the negative electrode tab 15 side in accordance with the fact that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. Regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different inward temperature gradients, the temperature can be made uniform in the in-plane direction of the power generation element 2.

(Third embodiment)
FIG. 9 is a cross-sectional view of the unit cell layer 13 of the third embodiment, which replaces FIG. 5 of the first embodiment. The same parts as those in FIG.

  As shown in FIG. 9, in the third embodiment, the thickness of the electrode active material layers 6 and 10 (electrodes) (the thickness in the vertical direction in FIG. 9) is used to cancel out the in-plane temperature gradient caused by Joule heat generation. Is made thicker as it approaches the high voltage tabs 15 and 16. When the thickness of the electrode active material layers 6 and 10 is increased in the in-plane direction of the power generating element 2 so as to be closer to the high-power tabs 15 and 16, Li ions are less likely to move through the electrolyte, and the ionic conductivity of the electrolyte is determined by the high-power tabs. The closer to 15, 16, the lower the value.

  On the side of the high voltage tabs 15 and 16 where the electrode active materials 6 and 10 are relatively thick, the Li ion movement distance is smaller than that on the side opposite to the high voltage tabs 15 and 16 where the electrode active materials 6 and 10 are relatively thin. become longer. As a result, the amount of movement of Li ions on the side of the high voltage tab where the thicknesses of the electrode active materials 6 and 10 are relatively thick (see the thick arrows in FIG. 9) is high. This is less than the amount of Li ion movement on the opposite side of the tab (see the thin arrow in FIG. 9). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, each electrode active material 6, 10 is almost bisected into a right region with the positive electrode tab 16 and a left region with the negative electrode tab 15, and the electrode active material 6 in each bisected region, The thickness of 10 is set as follows. That is, according to two types of temperature gradients in the in-plane direction, when compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the positive electrode active material 10 in the region 10a with the positive electrode tab 16 as shown in FIG. Is made thicker than the thickness of the positive electrode active material 10 in the region 10b where the negative electrode tab 15 is present. Here, FIG. 10 is a schematic perspective view of the positive electrode active material layer 10 disposed on the upper portion of the positive electrode current collector 9. Although not shown, the positive electrode active material layer 10 and the negative electrode active material layer 6 disposed below the positive electrode current collector 9 are similarly configured.

  In the third embodiment, the two electrode active material layers 6 and 10 are made thicker as they are closer to the high voltage tabs 15 and 16, but the thickness of at least one of the two electrode active material layers 6 and 10 is set to the power generation element 2. In the in-plane direction, the thicker the closer to the two high electric power tabs 15 and 16, the thicker it is.

  According to the third embodiment, the thickness of at least one of the two electrode active material layers 6 and 10 (electrodes) is increased toward the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The charge / discharge reaction is suppressed toward the periphery of each of the two high-power tabs 15, 16, and the charge / discharge reaction heat becomes smaller as it approaches the two high-power tabs 15, 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the third embodiment, according to the third embodiment, the thickness of at least one of the two electrode active material layers 6 and 10 (electrodes) is further increased by the negative electrode tab 15 in accordance with the fact that the heat generation is larger on the positive electrode tab 15 side than on the negative electrode tab 15 side. Since the positive electrode tab 16 side is made thicker than the side, the temperature can be made uniform in the in-plane direction of the power generating element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Fourth embodiment)
FIG. 11 is a cross-sectional view of the cell layer 13 of the fourth embodiment, which replaces FIG. 5 of the first embodiment. The same parts as those in FIG.

  As shown in FIG. 11, in the fourth embodiment, an ion blocking layer 21 that shields the diffusion of Li ions is provided on the surface of the electrode active material layers 6 and 10, and the temperature gradient in the in-plane direction due to Joule heat generation is offset. In order to do so, the porosity of the ion blocking layer 21 is made smaller as it is closer to the high voltage tabs 15 and 16. When the porosity of the ion blocking layer 21 is made smaller in the in-plane direction of the power generation element 2 as it approaches the high-power tabs 15, 16, Li ions hardly move in the electrolyte, and the ionic conductivity of the electrolyte is determined by the high-power tab 15. , The lower the value is, the lower the value is.

  The ion block layer 21 can be formed by spraying ceramic powder onto the electrode surface. If the ceramic powder is sprayed thickly, the porosity of the ion block layer is reduced. Conversely, if the ceramic powder is sprayed thinly, the porosity of the ion block layer is increased. Therefore, in order to reduce the porosity of the ion block layer 21 as it is closer to the high-power tabs 15, 16, it is only necessary to increase the amount of ceramic powder sprayed away from the high-power tabs 15, 16.

  On the high-power tabs 15 and 16 side where the porosity of the ion block layer is relatively small, Li ions are less likely to move from the side opposite to the high-power tabs 15 and 16 where the porosity of the ion block layer is relatively large. As a result, the movement amount of Li ions on the high voltage tabs 15 and 16 side where the porosity of the ion block layer is relatively small (see the thick arrows in FIG. 11) is relatively large. This is smaller than the amount of Li ion movement on the opposite side of the high voltage tabs 15 and 16 (see thin arrows in FIG. 11). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the right region with the positive electrode tab 16 and the left region with the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the ion blocking layer 21 is almost equally divided into a right region with the positive electrode tab 16 and a left region with the negative electrode tab 15, and the porosity of the ion blocking layer 21 in each of the divided regions. Is set as follows. That is, when compared with two types of temperature gradients in the in-plane direction and compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the vacancy of the ion block layer in a region where the positive electrode tab 16 is present as shown in FIG. The porosity is made smaller than the porosity of the ion block layer in the region where the negative electrode tab 15 is present.

  According to the fourth embodiment, the porosity of the ion blocking layer 21 is reduced in the in-plane direction of the power generation element 2 as it is closer to the two high-power tabs 15, 16. The charging / discharging reaction is further suppressed, and the charging / discharging reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the fourth embodiment, the heat generation is smaller on the positive electrode tab 15 side than on the negative electrode tab 15 side. According to the fourth embodiment, the porosity of the ion blocking layer 21 is further reduced on the positive electrode tab 16 side than on the negative electrode tab 15 side. Therefore, the temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Fifth embodiment)
FIG. 12 is a cross-sectional view of the cell layer 13 of the fifth embodiment, which replaces FIG. 11 of the fourth embodiment. The same parts as those in FIG. 11 are denoted by the same reference numerals.

  As shown in FIG. 12, in the fifth embodiment, an ion blocking layer 21 that shields the diffusion of Li ions is provided on the surface of the electrode active material layers 6 and 10, and the temperature gradient in the in-plane direction due to Joule heat generation is offset. For this purpose, the thickness of the ion blocking layer 21 is increased as it is closer to the high voltage tabs 15 and 16. When the thickness of the ion blocking layer 21 is increased in the in-plane direction of the power generating element 2 so as to be closer to the high-power tabs 15 and 16, the Li ions are less likely to move in the electrolyte, and the ionic conductivity of the electrolyte is determined by the high-power tabs 15 and 16. The closer it is, the lower it will be.

  On the high-power tabs 15 and 16 side where the thickness of the ion block layer 21 is relatively thick, the distance that Li ions move through the ion block layer 21 is opposite to that of the high-power tabs 15 and 16 where the ion block layer 21 is relatively thin. Longer than the side. As a result, the amount of movement of Li ions on the high-power tab side where the ion block layer 21 is relatively thick (see the thick arrow in FIG. 12) is opposite to the high-power tab where the ion block layer 21 is relatively thin. Less than the amount of Li ion movement (see the thin arrow in FIG. 12). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the right region with the positive electrode tab 16 and the left region with the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the ion blocking layer 21 is almost divided into a right region with the positive electrode tab 16 and a left region with the negative electrode tab 15, and the thickness of the ion blocking layer 21 in each of the divided regions is as follows. Set as follows. That is, when compared with two types of temperature gradients in the in-plane direction and compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the thickness of the ion block layer in the region where the positive electrode tab 16 is present as shown in FIG. Is made thicker than the thickness of the ion blocking layer in the region where the negative electrode tab 15 is present. Here, FIG. 13 is a schematic perspective view of the ion block layer 21 disposed on the positive electrode active material layer 10. Although not shown, the other three ion blocking layers 21 are similarly configured.

  According to the fifth embodiment, the thickness of the ion blocking layer 21 is increased in the in-plane direction of the power generation element 2 as it is closer to the two high-power tabs 15 and 16, so that the periphery of the two high-power tabs 15 and 16 is filled. The discharge reaction is suppressed, and the charge / discharge reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the fifth embodiment, since the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side, the thickness of the ion blocking layer 21 is further increased on the positive electrode tab 16 side than on the negative electrode tab 15 side. The temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Sixth embodiment)
FIG. 14 is a cross-sectional view of the unit cell layer 13 of the sixth embodiment, which replaces FIG. 5 of the first embodiment. The same parts as those in FIG.

  In the sixth embodiment, the configuration of the electrolyte layer is different from that of the first embodiment. That is, in the sixth embodiment, the electrolyte layer is composed of the semi-solid electrolyte layer (or solid electrolyte layer) 25. Here, the “semi-solid electrolyte” refers to a gel electrolyte. The “solid electrolyte” refers to a sol electrolyte. Since a semi-solid electrolyte layer or a solid electrolyte layer can prevent direct contact between the electrodes 4 and 8, a separator is unnecessary.

  As shown in FIG. 14, in the sixth embodiment, the thickness of the semisolid electrolyte layer (or solid electrolyte layer) 25 is close to that of the high voltage tabs 15 and 16 in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation. It will be thicker. When the thickness of the semi-solid electrolyte layer 25 is increased in the in-plane direction of the power generation element 2 so as to be closer to the strong electric tabs 15, 16, Li ions hardly move in the electrolyte, and the ionic conductivity of the electrolyte is determined by the strong electric tabs 15, 16. The closer to 16, the lower.

  On the high-power tabs 15 and 16 side where the thickness of the semi-solid electrolyte layer 25 is relatively thick, the distance that Li ions move through the semi-solid electrolyte 25 is the high-power tabs 15 and 16 where the thickness of the semi-solid electrolyte layer 25 is relatively thin. And longer than the opposite side. Thereby, the movement amount of Li ions on the high-power tab side where the thickness of the semi-solid electrolyte layer 25 is relatively thick (see the thick arrow in FIG. 14), and the high-power tab where the thickness of the semi-solid electrolyte layer 25 is relatively thin This is less than the amount of Li ion movement on the opposite side (see thin arrows in FIG. 14). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the semi-solid electrolyte layer 25 is divided into approximately two equal parts, the separator 12 being divided into a right region 25a with the positive electrode tab 16 and a left region 25b with the negative electrode tab 15, and the two regions 25a and 25b are divided into two equal parts. The thickness of the semi-solid electrolyte layer 25 is set as follows. That is, when compared with two types of temperature gradients in the in-plane direction and compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the semi-solid electrolyte layer 25 in the region where the positive electrode tab 16 is present as shown in FIG. Is made thicker than the thickness of the semi-solid electrolyte layer 25 in the region where the negative electrode tab 15 is present. Here, FIG. 15 is a schematic perspective view of only the semi-solid electrolyte layer 25.

  According to the sixth embodiment, the thickness of the semi-solid electrolyte 25 is increased in the in-plane direction of the power generation element 2 as it is closer to the two high-power tabs 15 and 16, so that the periphery of the two high-power tabs 15 and 16 is filled. The discharge reaction is suppressed, and the charge / discharge reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generation element.

  According to the sixth embodiment, the thickness of the semi-solid electrolyte 25 is further increased on the positive electrode tab 16 side than on the negative electrode tab 15 side in accordance with the fact that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. The temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Seventh embodiment)
FIG. 16 is a cross-sectional view of the cell layer 13 of the seventh embodiment, which replaces FIG. 14 of the sixth embodiment. The same parts as those in FIG. 14 are denoted by the same reference numerals.

  As shown in FIG. 16, in the seventh embodiment, the viscosity of the semi-solid electrolyte layer (or solid electrolyte layer) 25 is close to that of the high voltage tabs 15 and 16 in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation. It will be so high. When the viscosity of the semi-solid electrolyte layer 25 is increased in the in-plane direction of the power generation element 2 as it is closer to each of the high-power tabs 15 and 16, Li ions are less likely to move in the electrolyte, and the ionic conductivity of the electrolyte is The closer to 16, the lower.

  If the thickener added to the semisolid electrolyte is increased, the viscosity of the semisolid electrolyte is increased. Conversely, if the thickener added to the semisolid electrolyte is decreased, the viscosity of the semisolid electrolyte is decreased. Therefore, in order to increase the viscosity of the semi-solid electrolyte layer 25 as it approaches the high-power tabs 15 and 16, the thickener added to the semi-solid electrolyte may be increased as it approaches the high-power tabs 15 and 16.

  On the high-power tabs 15 and 16 side where the viscosity of the semi-solid electrolyte layer 25 is relatively high, the speed at which Li ions move through the semi-solid electrolyte 25 is opposite to the high-power tab where the viscosity of the semi-solid electrolyte layer 25 is relatively low. It will be slower. Thereby, the movement amount of Li ions on the high-power tab side where the viscosity of the semi-solid electrolyte layer 25 is relatively high (see the thick arrow in FIG. 16), the high-power tab 15 where the viscosity of the semi-solid electrolyte layer 25 is relatively low. , 16 on the opposite side to the amount of movement of Li ions (see thin arrows in FIG. 16). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the semi-solid electrolyte layer 25 is divided into approximately two equal parts, the right region 25a with the positive electrode tab 16 and the left region 25 with the negative electrode tab 15, and the semi-solid in each region 25a, 25b divided into two equal parts. The viscosity of the electrolyte layer 25 is set as follows. That is, in accordance with two types of temperature gradients in the in-plane direction, when compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the viscosity of the semi-solid electrolyte layer 25 in the region 25a with the positive electrode tab 16 is The viscosity is higher than the viscosity of the semi-solid electrolyte layer 25 in the region 25b where the negative electrode tab 15 is present.

  According to the seventh embodiment, the viscosity of the semi-solid electrolyte 25 is increased as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The discharge reaction is suppressed, and the charge / discharge reaction heat becomes smaller as it approaches the two tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the seventh embodiment, according to the seventh embodiment, the viscosity of the semi-solid electrolyte 25 is further increased on the positive electrode tab 16 side than on the negative electrode tab 15 side in accordance with the fact that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. The temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Eighth embodiment)
FIG. 17 is a cross-sectional view of the cell layer 13 of the eighth embodiment, which replaces FIG. 14 of the sixth embodiment. The same parts as those in FIG. 14 are denoted by the same reference numerals.

  As shown in FIG. 17, in the eighth embodiment, the dielectric constant of the semi-solid electrolyte layer (or solid electrolyte layer) 25 is changed to the high voltage tabs 15 and 16 in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation. The closer it is, the lower it is. When the dielectric constant of the semi-solid electrolyte layer 25 is lowered in the in-plane direction of the power generating element 2 so as to be closer to each of the high voltage tabs 15 and 16, Li ions do not easily move through the electrolyte, and the ionic conductivity of the electrolyte is determined by each high voltage tab 15. , The lower the value is, the lower the value is.

Here, “dielectric constant” refers to the ease of polarization of a dielectric placed in an electric field. The semi-solid electrolyte (gel electrolyte) has a structure in which an electrolyte salt (for example, LiPF which is a lithium salt) is injected into a matrix polymer having Li ion conductivity. LiPF ₆ which is a lithium salt dissociates into Li ⁺ and PF ₆ ⁻ . It can be changed dielectric constant by changing the degree of dissociation ^- li ⁺ and PF _6. Therefore, in order to lower the dielectric constant of the semi-solid electrolyte layer 25 as it is closer to the high-power tabs 15, 16, the degree of dissociation between Li ⁺ and PF ₆ ⁻ may be reduced as it is closer to the high-power tabs 15, 16. Here, LiPF ₆ which is a lithium salt is mentioned, but it is not limited to this.

On the side of the high-power tabs 15 and 16 where the dielectric constant of the semi-solid electrolyte layer 25 is relatively low, the high-voltage tabs 15 and 16 where the dissociation degree of Li ⁺ and PF ₆ ⁻ is relatively high. And smaller than the opposite side. As a result, the amount of movement of Li ions (see thick arrows in FIG. 17) on the side of the high voltage tabs 15 and 16 where the dielectric constant of the semisolid electrolyte layer 25 is relatively low is relatively high. This is less than the amount of Li ion movement on the opposite side of the high-power tabs 15 and 16 (see the thin arrows in FIG. 17). That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the semi-solid electrolyte layer 25 is divided into approximately two equal parts, the right region 25a with the positive electrode tab 16 and the left region 25 with the negative electrode tab 15, and the semi-solid in each region 25a, 25b divided into two equal parts. The dielectric constant of the electrolyte layer 25 is set as follows. That is, according to two kinds of temperature gradients in the in-plane direction, when compared at the same position in the vertical direction (in-plane direction) in FIG. The dielectric constant of the semi-solid electrolyte layer 25 in the region 25b where the negative electrode tab 15 is present is made lower.

  According to the eighth embodiment, the dielectric constant of the semi-solid electrolyte 25 is lowered as it approaches the two high-power tabs 15, 16 in the in-plane direction of the power generation element 2. The charging / discharging reaction is suppressed, and the charging / discharging reaction heat becomes smaller as it approaches the two tabs 15, 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generating element 2.

  According to the eighth embodiment, according to the eighth embodiment, the dielectric constant of the semi-solid electrolyte 25 is further lowered on the positive electrode tab 16 side than on the negative electrode tab 15 side in accordance with the fact that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. Therefore, the temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

(Ninth embodiment)
FIG. 18 is a cross-sectional view of the cell layer 13 of the ninth embodiment, which replaces FIG. 14 of the sixth embodiment. The same parts as those in FIG. 10 are denoted by the same reference numerals.

  As shown in FIG. 18, in the ninth embodiment, in order to cancel out the temperature gradient in the in-plane direction due to Joule heat generation, the electrolyte salt concentration of the semi-solid electrolyte layer (or solid electrolyte layer) 25 is changed to the high voltage tabs 15, 16. The closer it is, the lower it is. When the electrolyte salt concentration of the semi-solid electrolyte layer 25 is lowered in the in-plane direction of the power generation element 2 so as to be closer to each of the strong electric tabs 15 and 16, Li ions are less likely to move through the electrolyte, and the ionic conductivity of the electrolyte is different from the high electric tab. The closer to 15, 16, the lower the value.

Here, the “electrolyte salt” is a salt used for the electrolyte. As described above, the gel electrolyte has a configuration in which an electrolyte salt (for example, LiPF, which is a lithium salt) is injected into a matrix polymer having Li ion conductivity. Accordingly, the “electrolyte salt concentration” is the ratio of the amount of electrolyte salt to the amount of matrix polymer. Or it is the ratio of the amount of electrolyte salt to the sum of the amount of matrix polymer and the amount of electrolyte salt. When LiPF ₆ that is a lithium salt is cited again, the electrolyte salt concentration can be lowered by reducing the amount of LiPF ₆ relative to the amount of the matrix polymer. The lower the electrolyte salt concentration, the less Li ions are produced.

  On the high-power tabs 15 and 16 side where the electrolyte salt concentration of the semi-solid electrolyte layer 25 is relatively low, the amount of Li ions generated is opposite to that of the high-power tabs 15 and 16 where the electrolyte salt concentration of the semi-solid electrolyte layer 25 is relatively high. Less than the side. As a result, the amount of movement of Li ions on the high voltage tab side where the electrolyte salt concentration of the semi-solid electrolyte layer 25 is relatively low (see the thick arrow in FIG. 18) is relatively low. The amount of movement of Li ions on the side opposite to the high high voltage tabs 15 and 16 (see the thin arrows in FIG. 18) is smaller. That is, the charge / discharge reaction heat on the side of each high-power tab 15, 16 becomes smaller than the charge / discharge reaction heat on the side opposite to each high-power tab 15, 16, and the temperature gradient in the in-plane direction due to Joule heat generation can be offset. .

  Further, the temperature gradient in the in-plane direction is different between the region having the positive electrode tab 16 and the region having the negative electrode tab 15 (see FIG. 3). Therefore, in FIG. 3, the semi-solid electrolyte layer 25 is divided into approximately two equal parts, the right region 25a with the positive electrode tab 16 and the left region 25 with the negative electrode tab 15, and the semi-solid in each region 25a, 25b divided into two equal parts. The electrolyte salt concentration of the electrolyte layer 25 is set as follows. That is, according to two types of temperature gradients in the in-plane direction, when compared at the same position in the vertical direction (in-plane direction) in FIG. 3, the electrolyte salt concentration of the semi-solid electrolyte layer 25 in the region 25a where the positive electrode tab 16 is present Is made lower than the electrolyte salt concentration of the semi-solid electrolyte layer 25 in the region 25b where the negative electrode tab 15 is present.

  According to the ninth embodiment, the electrolyte salt concentration of the semi-solid electrolyte 25 is lowered in the in-plane direction of the power generation element 2 so as to be closer to the two high-power tabs 15, 16. The charging / discharging reaction is further suppressed, and the charging / discharging reaction heat becomes smaller as it approaches the two high-power tabs 15 and 16 in the in-plane direction of the power generation element 2. The gradient of the cell reaction heat in the in-plane direction cancels out the in-plane temperature gradient due to Joule heat generation, and the temperature can be made uniform in the in-plane direction of the power generation element.

  According to the ninth embodiment, according to the ninth embodiment, the electrolyte salt concentration of the semi-solid electrolyte 25 is further lowered on the positive electrode tab 16 side than on the negative electrode tab 15 side, so that the heat generation is larger on the positive electrode tab 16 side than on the negative electrode tab 15 side. Therefore, the temperature can be made uniform in the in-plane direction of the power generation element 2 regardless of the positive electrode tab 16 side and the negative electrode tab 15 side having different temperature gradients in the in-plane direction.

  In the embodiment, on the assumption that the battery 1 has the temperature gradient in the in-plane direction shown in FIG. 6, the separator 12, the positive electrode active material layer 10, and the ion block as shown in FIGS. 8, 10, 13, and 15. Although the layer 21 and the semi-solid electrolyte layer 25 are configured, the present invention is not limited to this. For example, the battery 1 may have a temperature gradient in the in-plane direction shown in FIG. 19 (tenth embodiment). That is, in FIG. 19, the temperature around the high voltage tabs 15, 16 is different between the tabs 15, 16, and the temperature around the positive electrode tab 16 is higher than the temperature around the negative electrode tab 15. In the case where the temperature gradient in the in-plane direction shown in FIG. 19 is provided, it is necessary to change the shapes of FIGS. 8, 10, 13, and 15 correspondingly. As an example, FIG. 20 shows a case where the shape of the separator 12 in FIG. 8 is changed. That is, in FIG. 20, the area around the tab 12 of the separator 12 having the positive electrode tab 16 is thicker than the area 12 b of the negative electrode tab 15. This is because the ionic conductivity of the separator around the positive electrode tab 16 is made lower than the ionic conductivity of the separator around the negative electrode tab 16 so that the charge / discharge reaction heat on the positive electrode tab 26 side is reduced on the negative electrode tab 15 side. This is to make it smaller than the charge / discharge reaction heat.

  In the embodiment, the case where the two high power tabs 15 and 16 are arranged on the same side of the power generation element 2 has been described, but the case where the two high power tabs are arranged on different sides of the power generation element 2 is also described. There is application.

  In the embodiment, the lithium ion secondary battery has been described as an example. However, the present invention is not limited to the battery, and the present invention can be applied to an electrochemical device such as an electric double layer capacitor.

1 Batteries (electrochemical devices)
2 Power generation element 4 Negative electrode (electrode)
5 Negative electrode current collector 6 Negative electrode active material layer 8 Positive electrode (electrode)
9 Positive current collector 10 Positive active material layer 12 Separator (electrolyte layer)
15 Negative electrode tab (tab)
16 Positive Tab (Tab)
25 Semi-solid electrolyte layer (electrolyte layer)

Claims (25)

A flat surface having an electrolyte layer functioning as an ion transfer medium between electrodes, and a negative electrode and a positive electrode provided on both sides of the electrolyte layer, in which electrons and ions move between the two electrodes to perform an electrochemical reaction. Power generation element
In an electrochemical device comprising a negative electrode tab and a positive electrode tab that take out electrons entering and exiting from the negative electrode and the positive electrode to the outside,
An electrochemical device characterized in that the heat of electrochemical reaction in the in-plane direction of the power generation element is made different so that the temperature in the in-plane direction of the power generation element is uniform.   2. The electrochemical device according to claim 1, wherein ions moving through the electrolyte layer are more difficult to move as they are closer to the two tabs in an in-plane direction of the power generation element.   The electrochemical device according to claim 2, wherein ions moving through the electrolyte layer are more difficult to move on the positive electrode tab side than on the negative electrode tab side. The ease of movement of the ions is ionic conductivity,
3. The electrochemical device according to claim 2, wherein the ionic conductivity is lowered as it approaches the two tabs in an in-plane direction of the power generation element.   The electrochemical device according to claim 4, wherein the ionic conductivity is further lowered on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a liquid electrolyte and a microporous membrane separator containing a resin,
2. The electrochemical device according to claim 1, wherein the porosity of the separator is reduced as it approaches the two tabs in the in-plane direction of the power generation element.   The electrochemical device according to claim 6, wherein the porosity of the separator is further reduced on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a liquid electrolyte and a microporous membrane separator containing a resin,
2. The electrochemical device according to claim 1, wherein a thickness of the separator is increased as it is closer to the two tabs in an in-plane direction of the power generation element.   The electrical device according to claim 8, wherein the thickness of the separator is further increased on the positive electrode tab side than on the negative electrode tab side.   2. The electrochemical device according to claim 1, wherein the thickness of at least one of the two electrodes is increased toward the two tabs in the in-plane direction of the power generation element.   The electrochemical device according to claim 10, wherein the thickness of at least one of the two electrodes is further increased on the positive electrode tab side than on the negative electrode tab side.   The electrochemical device according to claim 1, wherein an ion blocking layer that shields diffusion of ions is formed on a surface of the electrode.   The electrochemical device according to claim 12, wherein the porosity of the ion blocking layer is reduced as it approaches the two tabs in the in-plane direction of the power generation element.   14. The electrochemical device according to claim 13, wherein the porosity of the ion blocking layer is further reduced on the positive electrode tab side than on the negative electrode tab side.   13. The electrochemical device according to claim 12, wherein the ion blocking layer is made thicker as it is closer to the two tabs in the in-plane direction of the power generation element.   16. The electrochemical device according to claim 15, wherein the thickness of the ion blocking layer is further increased on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a solid electrolyte or a semi-solid electrolyte,
2. The electrochemical device according to claim 1, wherein the thickness of the solid electrolyte or semi-solid electrolyte is increased toward the two tabs in the in-plane direction of the power generation element.   The electrochemical device according to claim 17, wherein the thickness of the solid electrolyte or semi-solid electrolyte is further increased on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a solid electrolyte or a semi-solid electrolyte,
2. The electrochemical device according to claim 1, wherein the viscosity of the solid electrolyte or semi-solid electrolyte is increased as the viscosity is closer to the two tabs in the in-plane direction of the power generation element.   20. The electrochemical device according to claim 19, wherein the viscosity of the solid electrolyte or semi-solid electrolyte is further increased on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a solid electrolyte or a semi-solid electrolyte,
2. The electrochemical device according to claim 1, wherein the dielectric constant of the solid electrolyte or semi-solid electrolyte is lowered as the distance between the two tabs increases in the in-plane direction of the power generation element.   The electrochemical device according to claim 21, wherein a dielectric constant of the solid electrolyte or semi-solid electrolyte is further lowered on the positive electrode tab side than on the negative electrode tab side. The electrolyte layer is composed of a solid electrolyte or a semi-solid electrolyte,
2. The electrochemical device according to claim 1, wherein the electrolyte salt concentration of the solid electrolyte or semi-solid electrolyte is lowered as it approaches the two tabs in the in-plane direction of the power generation element.   24. The electrochemical device according to claim 23, wherein the electrolyte salt concentration of the solid electrolyte or semi-solid electrolyte is further lowered on the positive electrode tab side than on the negative electrode tab side. An electrolyte layer having a function as an ion transfer medium between electrodes, and a negative electrode and a positive electrode provided on both sides of the electrolyte layer, and electrons and ions move between the two electrodes to perform an electrochemical reaction. In an electrochemical device including a flat power generation element,
An electrochemical device characterized in that the activity of the electrochemical reaction in the in-plane direction of the power generation element is varied so that the temperature in the in-plane direction of the power generation element is uniform.

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