JP5672516B2 - Power storage device and vehicle - Google Patents

Description

  The present invention relates to a power storage device and a vehicle, and more particularly to a power storage device having an electrode in which an active material layer is formed on a current collector surface.

Examples of power storage devices include batteries such as lithium ion secondary batteries and capacitors such as electric double layer capacitors. Lithium secondary batteries are small and have high energy density, and are widely used as power sources for portable electronic devices. As a positive electrode active material of a lithium secondary battery, a composite metal oxide such as LiCoO ₂ is mainly used. The battery capacity of a lithium secondary battery using such a composite metal oxide as a positive electrode active material is about 160 mAh / g, and a positive electrode active material having a higher capacity has been desired.

  In order to produce a battery having a high volume energy density, it is necessary to apply a thick electrode material on the current collector.

  In order to produce a positive electrode, a positive electrode active material is used as an active material, mixed with a conductive additive and a binder, and mixed with a viscosity adjusting solvent as necessary to form a slurry. The slurry-like electrode material is applied to a metal current collector to produce a positive electrode. If the electrode material is applied thickly, cracks in the active material layer itself may occur due to volume change due to solvent volatilization during drying after coating, or strain caused by the difference in linear expansion from the current collector. There is a concern that peeling from the current collector occurs.

  In order to prevent cracking and peeling of the active material layer, it is conceivable to increase the amount of binder in the electrode material. However, the ratio of the active material in the active material layer is reduced, and the battery capacity is reduced.

  Therefore, Japanese Patent Laid-Open Nos. 2001-28273, 2002-157997, 2003-68364, 2002-260673, and 5-283107 disclose the front and back of the current collector foil. It has been proposed to form an electrode body by applying and drying an active material layer on both sides to form a belt-like sheet and bending the sheet alternately.

  However, in Japanese Patent Application Laid-Open No. 2001-28273, only one electrode is alternately folded with active material layers formed on both sides of the current collector, and the other electrode is not folded. For this reason, there is a possibility that the active material layer of the unfolded electrode may fall off due to peeling or cracking from the current collector.

  Further, in Japanese Patent Application Laid-Open No. 2002-157997, a positive electrode sheet and a negative electrode sheet are laminated with separators interposed therebetween, and are folded alternately. However, the active material layers are formed on both sides of the current collector only in the negative electrode sheet disposed inside the laminate, and the active material layer is not formed on the positive electrode sheet disposed outside the laminate. . For this reason, the energy density per unit volume of the electrode body is not sufficient.

  In JP 2003-68364 A, an active material layer is formed only on one side of a current collector in both the positive electrode sheet and the negative electrode sheet. For this reason, the energy density per unit volume of the electrode body is not sufficient.

  In Japanese Patent Laid-Open No. 2002-260673, both the positive electrode sheet and the negative electrode sheet are formed with active material layers on both sides of the current collector, but the thickness of the active material layer is insufficient and the energy density is low.

  In JP-A-5-283107, a laminated electrode body formed by laminating a plurality of electrodes is folded. For this reason, the electrolytic solution hardly penetrates into the laminated electrode body, and the battery reaction inside the laminated electrode body cannot be actively performed.

JP 2001-28273 A (paragraph 0014, FIG. 7) JP 2002-157997 (paragraph 0030, FIG. 1) JP 2003-68364 A (paragraph 0046, FIG. 1) JP 2002-260673 A (paragraphs 0067 to 0069, FIG. 2) JP-A-5-283107 (paragraphs 0018 to 21, FIGS. 1 to 5)

  This invention is made | formed in view of this situation, and makes it a subject to provide the electrical storage apparatus and vehicle which can prevent peeling from the electrical power collector of an active material layer.

  (1) The power storage device of the present invention is a power storage device having a positive electrode, a negative electrode, and an electrolyte solution, wherein at least one of the positive electrode and the negative electrode has a current collector sheet having a through hole, and the current collector sheet Active material layers formed on both front and back surfaces of the current collector sheet, and the first active material layer formed on one of the front and back surfaces of the current collector sheet is formed on both front and back surfaces of the current collector. The current collector sheet is thicker than the second active material layer formed on the other second surface, and the current collector sheet is folded while sandwiching the first active material layer with the first surface inside. It is characterized by.

  According to the above configuration, the first active material layer formed on the first surface of the current collector sheet is thicker than the second active material layer formed on the second surface of the current collector sheet. The body sheet is bent so that the first surfaces are disposed inside with the thicker first active material layer interposed therebetween. For this reason, the thicker first active material layer is prevented from peeling off from the current collector sheet.

  On the other hand, the second active material layer is thinner than the first active material layer and hardly peels from the current collector sheet. Therefore, even if the second active material layer is not sandwiched inside the folded current collector sheet, the second active material layer is rarely peeled off from the current collector sheet.

  Further, a through hole is formed in the current collector sheet. For this reason, the front surface side and the back surface side of the current collector sheet are communicated with each other through the through-hole, and the ionic substance and the electrolytic solution can be freely moved to the front and back surfaces of the current collector sheet. Accordingly, the ionic material and the electrolytic solution can be circulated through both the first active material layer and the second active material layer, and power storage characteristics such as battery characteristics are improved.

  (2) It is preferable that the terminal connection part to which the terminal of the said collector sheet is connected is an active material non-formation part in which the active material layer is not formed. In this case, electricity can be reliably taken out from the terminal connection portion of the current collector sheet.

  (3) It is preferable that at least one of the first surface and the second surface of the bent portion of the current collector sheet is an active material non-formed portion where an active material layer is not formed. A portion of the active material layer formed at the bent portion is a portion that is easily peeled off from the current collector sheet. By making this bent part an active material non-formation part, peeling of the active material layer from the current collector sheet can be reliably suppressed. The active material layer non-formed portion may be provided on either the first surface or the second surface of the bent portion of the current collector sheet, but the bent portion of the second surface disposed on the outer side of the bent current collector sheet Is preferably an active material layer non-formed part. The first active material layer formed on the first surface is held by the first surface near the bent portion when peeled from the current collector sheet, but the second active material layer formed on the second surface is This is because when it is peeled from the current collector sheet, it is not retained and falls off.

  (4) The ratio of the thickness of the first active material layer to the thickness of the second active material layer is preferably 1.05 or more and 5 or less. In this case, the ionic material or the electrolyte solution is sufficiently transferred between the first active material layer formed on the first surface of the current collector sheet and the second active material layer formed on the second surface. The battery capacity and the storage capacity can be increased. On the other hand, when the ratio of the thickness of the first active material layer to the thickness of the second active material layer is less than 1.05, the total amount of the active material layer may be reduced and the battery capacity and the storage capacity may be reduced. There is a possibility that the second active material layer is too thick or the second active material layer is separated from the current collector sheet. On the other hand, when the ratio of the thickness of the first active material layer to the thickness of the second active material layer exceeds 5, the thickness of the first active material layer sandwiched inside the current collector sheet is too large. There is a possibility that the movement of the electrode in the thickness direction of the ionic substance or the electrolytic solution may be restricted.

  (5) The mass of the first active material layer formed per unit area of the first surface is larger than the mass of the second active material layer formed per unit area of the second surface. It is preferable.

  In this case, the first active material layer sandwiched between the current collector sheets is formed thicker than the second active material layer, and the energy density can be improved.

  Moreover, since the 2nd active material layer arrange | positioned on the outer side of a collector sheet is comparatively thin, it does not peel or drop | omit from a collector sheet.

  (6) The ratio of the mass of the first active material layer formed per unit area of the first surface to the mass of the second active material layer formed per unit area of the second surface is 1.05 or more and 5 or less.

  In this case, the energy density of the entire first and second active material layers can be increased while preventing the second active material layer from falling off. On the other hand, the ratio of the mass of the first active material layer formed per unit area of the first surface to the mass of the second active material layer formed per unit area of the second surface is less than 1.05. In such a case, the total amount of the active material layer may be reduced and the battery capacity and the storage capacity may be reduced, or the thickness of the second active material layer may be too large, and the second active material layer may be the current collector sheet. There is a risk of peeling. On the other hand, when the ratio of the mass of the first active material layer formed per unit area of the first surface to the mass of the second active material layer formed per unit area of the second surface exceeds 5 The thickness of the first active material layer sandwiched inside the current collector sheet is too large, and movement of the ionic material or electrolyte solution in the thickness direction may be restricted.

  (7) In both the positive electrode and the negative electrode, a first active material layer formed on the first surface of the current collector sheet is formed on the second surface of the current collector sheet. The current collector sheet is thicker than the active material layer 2 and has a configuration in which the current collector sheet is folded while sandwiching the first active material layer with the first surface inside, and the positive electrode is folded. The current collector sheet is preferably laminated alternately with the current collector sheet folded on the negative electrode with a separator interposed therebetween. In this case, both the positive electrode and the negative electrode can form a large amount of the active material layer while preventing the positive electrode and the negative electrode from falling off, and the energy density of the power storage device can be further improved.

  (8) The power storage device is preferably a battery. When the battery has the above configuration, the active material layer can be prevented from peeling from the current collector sheet, and the battery characteristics can be improved.

  (9) The power storage device is preferably an electric double layer capacitor. When the electric double layer capacitor has the above-described configuration, the active material layer can be prevented from peeling from the current collector sheet, and the power storage characteristics can be improved.

  (10) A vehicle according to the present invention includes the above-described power storage device. A vehicle equipped with the power storage device described above can exhibit high output.

  According to the power storage device of the present invention, the first active material layer formed on the first surface of the current collector sheet is thicker than the second active material layer formed on the second surface of the current collector sheet. The current collector sheet is bent so that the first surfaces are disposed inside with the thicker first active material layer interposed therebetween. For this reason, not only the thinner second active material layer but also the thicker first active material layer can prevent peeling from the current collector sheet.

It is sectional drawing of the battery of Example 1 of this invention. 3 is a plan view of a current collector sheet of Example 1. FIG. It is explanatory drawing which shows the manufacturing method of the positive electrode of Example 1, Comprising: It is a perspective view of the electrical power collector sheet | seat which has arrange | positioned the 2nd surface toward the upper side. It is explanatory drawing which shows the manufacturing method of the positive electrode of Example 1, Comprising: It is a perspective view of the electrical power collector sheet | seat in which the 2nd active material layer was formed on the 2nd surface. It is explanatory drawing which shows the manufacturing method of the positive electrode of Example 1, Comprising: It is a perspective view of the electrical power collector sheet | seat in which the 1st active material layer was formed on the 1st surface. It is explanatory drawing which shows the manufacturing method of the positive electrode of Example 1, Comprising: It is a perspective view of the collector sheet folded in half with the 1st surface inside.

  The power storage device of the present invention is used for a device having a function of storing a battery, such as a battery or a capacitor. First, a case where the power storage device is a battery will be described.

(battery)
The battery includes a positive electrode, a negative electrode, and an electrolytic solution.

  At least one of the positive electrode and the negative electrode includes a current collector sheet and active material layers formed on both the front and back surfaces of the current collector sheet.

  The current collector sheet has a sheet shape and is formed of a material that is highly conductive and bendable. The current collector sheet is formed of, for example, a metal foil such as an aluminum foil, a copper foil, a nickel foil, or a stainless steel foil, a carbon fiber nonwoven fabric, or the like.

  One or a plurality of through holes are formed in the current collector sheet made of metal foil. This through hole is for allowing an ionic substance or an electrolytic solution generated by the electrode reaction to pass therethrough. The through hole is preferably large enough to allow the ionic substance and the electrolyte component to pass therethrough.

  Roughening treatment is preferably performed on the inner peripheral surface of the through hole. The active material layer bites into the through-hole, and the active material layer can be effectively prevented from falling off.

  The diameter of the through hole is preferably from 0.1 mm to 1.0 mm, and more preferably from 0.3 mm to 0.7 mm. In this case, the active material layer bites into the through-hole, and the first active material layer disposed inside the current collector sheet protrudes outside the current collector sheet through the through-hole and falls off. Can be prevented.

  The opening pitch P of the through holes is preferably from 0.3 mm to 10 mm, and more preferably from 0.3 mm to 5 mm. In this case, an ionic substance or an electrolytic solution can be actively distributed between the front and back of the current collector sheet. The opening pitch P of a through-hole means the distance of the opening periphery of an adjacent through-hole (refer FIG. 2).

  The through holes are preferably arranged in a staggered manner. In this case, a large number of through holes can be arranged per unit area of the current collector sheet, and an ionic substance and an electrolytic solution can be actively distributed between the front and back of the current collector sheet.

  It is preferable that the through hole is not formed in the terminal connection portion. This is because if the through hole is formed in the terminal connection portion, the connection strength of the terminal may be lowered.

  The ratio of the through-hole opening area to the area of the through-hole forming portion of the current collector sheet is preferably 15% or more and 60% or less, and more preferably 20% or more and 50% or less. The area of the through-hole forming portion of the current collector sheet refers to the total area of the region (the general portion 10e in FIG. 2) where the through-hole is formed in the current collector sheet. That is, the area of the part which remove | excluded the part in which the through-hole is not formed from the whole electrical power collector sheet | seat. The through-hole opening area refers to the total area of the opening portions of the through-holes. If the ratio of the through-hole opening area to the area of the through-hole forming portion of the current collector sheet is too small, the flow rate of the ionic substance or electrolyte between the front and back of the current collector sheet may be reduced, and the electrical characteristics may be deteriorated. There is. When the ratio of the through-hole opening area to the area of the through-hole forming portion of the current collector sheet is excessive, the holding area of the current collector sheet with respect to the active material layer is reduced, the active material layer is peeled off, or the current collector The strength of the sheet is weak and may be torn.

  The surface of the current collector sheet may be subjected to a roughening treatment in order to improve the adhesion of the active material layer, or a surface coat layer for adhering the active material layer may be formed.

  An active material layer composed of an active material is formed on the front and back surfaces of the current collector sheet. An active material refers to a material that emits or captures electrons by a chemical reaction with an electrolyte. An active material that emits electrons during current discharge is referred to as a negative electrode active material, and an active material that captures electrons is referred to as a positive electrode active material.

  As for the shape of the active material which comprises an active material layer, there are many powdery and particulate things, for example. The type of active material is not particularly limited. When the active material is a positive electrode active material, the positive electrode active material is, for example, a lithium cobalt complex oxide, a lithium manganese complex, a lithium nickel complex oxide, a lithium complex metal oxide such as lithium iron phosphate, or elemental sulfur. It may be composed of a sulfur carbon compound or the like.

  When the active material is a negative electrode active material, the negative electrode active material may be composed of, for example, carbon, silicon oxide, lithium titanate, or the like. The battery is preferably a battery in which charging and discharging is performed by the active material inserting and extracting lithium ions. In this case, the negative electrode active material is preferably a negative electrode active material capable of inserting and extracting lithium ions.

  Such a negative electrode active material is preferably composed of an element compound capable of being alloyed with lithium and / or an element compound having an element capable of being alloyed with lithium. Elements capable of alloying with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge. , Sn, Pb, Sb, and Bi may be at least one selected from the group. Among these, silicon (Si) or tin (Sn) is preferable. The elemental compound having an element capable of alloying with lithium is preferably a silicon compound or a tin compound. The silicon compound is preferably SiOx (0.5 ≦ x ≦ 1.5). Examples of the tin compound include a tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.), a tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.), and the like.

  Moreover, as a negative electrode active material which can occlude / release lithium ions, for example, natural graphite, artificial graphite, an organic compound heating body such as a phenol resin, and a powdery body of a carbon material such as coke can be used. Further, as the negative electrode active material capable of inserting and extracting lithium ions, metallic lithium or a lithium alloy may be used. A battery using metallic lithium or a lithium alloy as the negative electrode active material is called a lithium secondary battery. A battery using an element other than metallic lithium or a lithium alloy as a negative electrode active material is called a lithium ion secondary battery.

  The negative electrode active material may contain Si (silicon). This is because the negative electrode active material containing Si has a large discharge capacity. The negative electrode active material containing Si has a large volume change due to insertion and extraction of Li ions during charge and discharge. Since the film formed on the surface of the negative electrode active material has a relatively small thickness, it flexibly follows the volume change of the negative electrode active material. For this reason, even if it repeats charging / discharging, a film is hard to destroy and it is excellent in charging / discharging cycling characteristics. The negative electrode active material containing Si may be capable of occluding and releasing lithium ions and may be made of silicon or / and a silicon compound. The negative electrode active material may have SiOx (0.5 ≦ x ≦ 1.5). Silicon has a large theoretical discharge capacity. On the other hand, since the volume change during charging / discharging is large, the volume change can be reduced by using SiOx.

  The active material layer contains an active material as an essential component, and may contain a binder and a conductive aid as necessary. The binder is not particularly limited, and a known one may be used. For example, a resin that does not decompose even at a high potential, such as a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, can be used. The blending ratio of the binder is preferably a mass ratio of active material: binder = 1: 0.05 to 1: 0.5. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  As the conductive aid, a material generally used for battery electrodes may be used. For example, it is preferable to use conductive carbon materials such as carbon black (carbonaceous fine particles) such as acetylene black and ketjen black, and carbon fibers. Besides conductive carbon materials, known conductive materials such as conductive organic compounds are also used. An auxiliary agent may be used. One of these may be used alone or in combination of two or more. The blending ratio of the conductive additive is preferably a mass ratio of negative electrode active material: conductive additive = 1: 0.01 to 1: 0.5. This is because if the amount of the conductive aid is too small, an efficient conductive path cannot be formed, and if the amount of the conductive aid is too large, the moldability of the electrode is deteriorated and the energy density of the electrode is lowered.

  The thickness of the first active material layer formed on one of the front and back surfaces of the current collector sheet is the second thickness formed on the second surface of the current collector sheet. It is larger than the thickness of the active material layer. The ratio (T1 / T2) of the thickness (T1) of the first active material layer to the thickness (T2) of the second active material layer is preferably 1.05 or more and 5 or less, and more preferably 1.2 or more. It is desirable that it is 2.0 or less. In this case, while the active material layer is formed on the second surface which is outside when the current collector sheet is folded, the active material layer is not peeled off or hardly peeled off. A larger amount of the active material layer than the first active material layer can be formed on one surface to increase the energy density of the power storage device.

  The thickness of the first active material layer may be large enough to be peeled off from the current collector sheet or easily peeled off when applied to a planar current collector sheet. The thickness of the active material layer that can be peeled off or easily peeled off depends on the type of components of the active material layer, but is, for example, a thickness exceeding 70 μm, and further a thickness exceeding 80 μm. Even if the first active material layer is applied thickly, the first active material layer is sandwiched between the folded current collector sheets, and therefore does not fall off from the current collector sheet.

  The thickness of the first active material layer is preferably 30 μm or more and 200 μm or less, more than 70 μm and 150 μm or less, and further preferably more than 80 μm and 150 μm or less. In this case, the energy density of the battery can be increased by forming a large amount of active material layer on the first surface. On the other hand, when the thickness of the first active material layer is too small, the capacity of the battery may be reduced. When the thickness of the first active material layer is too large, the surface portion of the first active material layer Electrons generated in the above are difficult to reach the current collector sheet, and the high rate characteristics of the battery may be degraded.

The thickness of the second active material layer is preferably such that it is not peeled off or hardly peeled off from the current collector sheet when coated on a planar current collector sheet. At least the thickness of the second active material layer needs to be smaller than the thickness of the first active material layer. Here, the thickness of the second active material layer which is not peeled off or hardly peeled off is, for example, 80 μm or less, and further 70 μm or less. The mass of the second active material layer formed per unit area of the second surface that does not peel is, for example, 3.5 g / m ² or less. By coating the second active material layer so thin that it does not peel, it is difficult to peel from the second surface located outside the folded current collector sheet.

  The thickness of the second active material layer is preferably 30 μm or more and 200 μm or less, and the upper limit of the thickness of the second active material layer is preferably 150 μm, 80 μm, and more preferably 70 μm. In this case, peeling and cracking of the second active material layer from the current collector sheet can be prevented. On the other hand, when the thickness of the second active material layer is too small, the capacity of the battery may be lowered. When the thickness of the second active material layer is excessive, the second active material layer is collected. There is a risk of peeling from the electrical sheet.

  The mass of the first active material layer formed per unit area of the first surface of the current collector sheet is equal to the second active material layer formed per unit area of the second surface of the current collector sheet. It is preferable that it is larger than the mass. The energy density of the first active material layer can be increased while preventing the second active material layer from falling off the current collector sheet.

  Furthermore, the ratio of the mass of the first active material layer formed per unit area of the first surface to the mass of the second active material layer formed per unit area of the second surface is 1.05. It is preferably 5 or more and more preferably 1.2 or more and 2.0 or less. In this case, the energy density of the entire first and second active material layers can be increased while preventing the second active material layer from falling off.

  It is preferable that the terminal connection part to which the terminal of a collector sheet is connected is an active material non-formation part in which the active material layer is not formed. In this case, electricity can be reliably taken out from the terminal connection portion of the current collector sheet.

  At least one of the positive electrode and the negative electrode, preferably both the positive electrode and the negative electrode, are formed by folding a current collector sheet having an active material layer on both the front and back surfaces, and are arranged inside the folded current collector sheet. One active material layer is thicker than the second active material layer disposed outside. In this case, both the positive electrode and the negative electrode can carry a large amount of active material layer on the current collector sheet, and the energy density per unit volume is improved.

  At least one of the first surface and the second surface of the bent portion of the folded current collector sheet may be an active material non-formed portion where an active material layer is not formed. In addition, it is preferable to provide an active material non-formation part on the second surface of the bent part of the current collector sheet that becomes the outer side when folded, and further, the active material is not formed on both the first and second surfaces of the bent part. A substance-unformed part is preferably provided. In this case, the active material layer is less likely to be peeled off or cracked at the bent portion of the current collector sheet.

  Moreover, it is preferable not to provide a through-hole in the bending part of a collector sheet. The first active material layer sandwiched inside through the through hole protrudes to the outside of the current collector sheet, and the active material layer is peeled off or cracked from the current collector sheet. This is because the strength is low and there is a risk of tearing.

  The current collector sheet may be folded in half by bending a substantially central portion in the longitudinal direction. When the current collector sheet is folded, it may be, for example, a slurry or a paste before the first or / and second active material layer is dried. In this case, the first or second active material layer can flexibly follow the bent shape of the current collector sheet, and the first and second active material layers can be prevented from peeling off during the bending process. .

  The positive electrode and the negative electrode formed by folding the current collector sheet in two are preferably stacked alternately with a sheet-like separator interposed therebetween to constitute an electrode body. The electrode body is housed in the housing member together with the electrolytic solution to produce a battery.

  The electrode body is a laminated electrode body formed by laminating a plurality of positive electrodes and a plurality of negative electrodes in the thickness direction with a separator interposed therebetween, or stacking the positive electrode and the negative electrode with a separator interposed therebetween. It is good also as a wound type electrode body by winding.

The electrolytic solution refers to a solution in which an electrolyte is dissolved in a solvent. The electrolytic solution may be, for example, a nonaqueous electrolytic solution. The nonaqueous electrolytic solution is obtained by dissolving an electrolyte in an organic solvent. The electrolyte is preferably a fluorine compound. The fluorine-based compound that is an electrolyte is preferably an alkali metal fluoride salt that is soluble in an organic solvent. The alkali metal fluoride salt, _{e.g., LiPF 6, LiBF 4, LiAsF} 6, NaPF 6, NaBF 4, and may be used at least one selected from the group of NaAsF _6. The organic solvent of the non-aqueous electrolyte is preferably an aprotic organic solvent, such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate ( One or more selected from EMC) and the like can be used.

  The electrolyte solution may be an aqueous electrolyte solution or an ionic liquid electrolyte solution in addition to the non-aqueous electrolyte solution, and the type thereof is not limited.

  The battery may be a nickel hydride secondary battery or a nickel cadmium battery in addition to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery or a lithium secondary battery. The shape of the battery is not particularly limited, and various shapes such as a cylindrical shape, a laminated shape, a coin shape, and a laminated shape can be employed. Regardless of the shape, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body, and the space between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal is used for current collection. After connecting using a lead or the like, this electrode body is hermetically sealed in a battery container together with a non-aqueous electrolyte to obtain a battery.

(Capacitor)
In the case where the power storage device is a capacitor, the active material forming the electrode is preferably a polarizable active material. For example, activated carbon can be used as the active material. Also in the capacitor, the active material layer may contain the active material as an essential component, and may contain a binder and a conductive aid as necessary. The electrolytic solution used for the capacitor is formed by, for example, dissolving an electrolyte composed of a cation and an anion in a solvent. As the cation, for example, tetraethylammonium salt is used. As the anion, for example, tetrafluoroborate ion or the like is used. As the solvent, the same solvent as the battery can be used. In addition, the configuration of the battery described above can be applied to the capacitor of the present embodiment as long as it can be applied to the capacitor.

  As the capacitor, an electric double layer capacitor is preferably used. Thus, even when the power storage device is a capacitor, by adopting the same configuration as that of the battery, the active material layer can be prevented from peeling from the current collector sheet, and the power storage characteristics of the capacitor are improved. be able to.

  The power storage device of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from the power storage device for all or a part of its power source, for example, an electric vehicle, a hybrid vehicle, or the like. Examples of power storage devices include various home appliances, office devices, and industrial devices driven by batteries, such as personal computers and portable communication devices, in addition to vehicles.

Example 1
The battery of this example is a laminated battery produced by laminating a positive electrode and a negative electrode with a separator interposed therebetween.

  As shown in FIG. 1, the positive electrode 1 includes a current collector sheet 10 and first and second active material layers 11 a and 11 b formed on both front and back surfaces of the current collector sheet 10.

  As shown in FIG. 2, the current collector sheet 10 has a rectangular shape extending in the longitudinal direction L, is made of an aluminum foil having a thickness of 20 μm, and a large number of through holes 13 are opened. The through-hole 13 is formed in the general part 10e excluding the terminal connection part 10d. The terminal connection portion 10 d is provided at one end portion in the longitudinal direction L of the current collector sheet 10. An electrode tab 61 is connected to the terminal connecting portion 10d by ultrasonic welding.

  The general portion 10e of the current collector sheet 10 is formed with a plurality of through hole rows 13a in which a large number of through holes 13 are arranged in the longitudinal direction L. Each through hole row 13a is in the width direction of the current collector sheet 10. There are multiple arrays. The diameter of each through-hole 13 is 0.3 mm, and the opening pitch P in the extending direction of the through-hole row 13a of each through-hole 13 is 0.52 mm. The opening pitch P of the adjacent through holes 13 existing in different through hole rows 13a is 0.52 mm, and the arrangement direction thereof is inclined at an angle α of 60 ° with respect to the extending direction of the through hole rows 13a. Yes. The through holes 13 are arranged in a staggered manner in the entire general portion 10 e of the current collector sheet 10. The ratio of the total opening area of all the through holes 13 to the area of the general portion 10e of the current collector sheet 10 is 30%.

  As shown in FIGS. 1 and 2, the current collector sheet 10 is bent in half at a substantially central portion in the longitudinal direction L, leaving the terminal connection portion 10d. The front surface located on the inner side of the folded current collector sheet 10 is a first surface 10a, and the rear surface located on the outer side is a second surface 10b.

A first active material layer 11 a is formed on the first surface 10 a of the current collector sheet 10, and a second active material layer 11 b is formed on the second surface 10 b of the current collector sheet 10. The first and second active material layers 11a and 11b are formed on the flat surface portion 10g excluding the terminal connection portion 10d and the bent portion 10f. The thickness of the first active material layer 11a is 80 μm, and the mass of the first active material layer 11a with respect to the unit area of the first surface 10a is 4.0 g / m ² . The thickness of the second active material layer 11b is 65 μm, and the mass of the second active material layer 11b with respect to the unit area of the second surface 10b is 3.3 g / m ² . The ratio of the thickness of the first active material layer 11a to the thickness of the second active material layer 11b is 1.23 (80 μm / 65 μm). Further, the first active material layer 11a formed per unit area of the first surface 10a with respect to the mass of the second active material layer 11b formed per unit area of the second surface 10b of the current collector sheet 10. The mass ratio is 1.21 (4.0 g / m ² /3.3 g / m ² ).

  Both the first and second active material layers 11a and 11b are composed of a positive electrode active material, a conductive assistant, and a binder, and each blending mass ratio is 90% for the positive electrode active material, 7% for the conductive assistant, and 3% for the binder. is there. The positive electrode active material is made of lithium cobalt oxide, the conductive additive is made of acetylene black, and the binder is made of polyvinylidene fluoride (PVdF).

  In manufacturing the positive electrode 1, the positive electrode active material, the conductive additive, and the binder are mixed at the above mixing ratio, and the same volume of NMP (N-methyl-) as the total volume of the positive electrode active material, the conductive additive, and the binder 2-pyrrolidone) is added and mixed to form a slurry.

  As shown in FIG. 3A, the second surface 10b of the current collector sheet 10 for positive electrode is arranged facing upward. As shown in FIG. 3B, the slurry is applied to the second surface 10b of the current collector sheet 10 to a thickness of 65 μm and dried to form the second active material layer 11b. The second active material layer 11b is formed only on the flat surface portion 10g excluding the terminal connection portion 10d and the bent portion 10f of the second surface 10b of the current collector sheet 10.

  Next, as shown in FIG. 3C, the current collector sheet 10 is turned over, the first surface 10a of the current collector sheet 10 is directed upward, and the slurry is added so that the thickness of the first surface 10a is 80 μm. The first active material layer 11a is formed by coating. The first active material layer 11a is formed only on the flat surface portion 10g excluding the terminal connection portion 10d and the bent portion 10f of the first surface 10a of the current collector sheet 10. As shown in FIG. 3D, before the first active material layer 11a is dried, the current collector sheet 10 is folded in half at a substantially central portion in the longitudinal direction L with the first surface 10a inside. At this time, the terminal connection part 10d provided at one end part in the longitudinal direction L of the current collector sheet 10 is made not to overlap. Next, after drying the 1st active material layer 11a on a hotplate, the collector sheet 10 folded in half is pressed in the thickness direction. Thereafter, the current collector sheet 10 is cut into a predetermined size to be a positive electrode 1.

  The negative electrode 2 includes a current collector sheet 20 and first and second active material layers 21 a and 21 b formed on the front and back surfaces of the current collector sheet 20.

  As shown in FIG. 2, the current collector sheet 20 of the negative electrode 2 is made of a copper foil having a thickness of 20 μm, has a shape similar to that of the current collector sheet 10 of the positive electrode, and has a large number of through holes 23. Similarly to the through holes 13 formed in the current collector sheet 10 of the positive electrode 1, the through holes 23 of the current collector sheet 20 of the negative electrode 2 have a plurality of through hole arrays 23 a, and the opening pitch P of each through hole is It is 0.52 mm, the diameter of each through hole 23 is 0.3 mm, and is arranged in a staggered manner in the general part 20e excluding the terminal connection part 20d. An electrode tab 62 is connected to the terminal connection portion 20d by ultrasonic welding. The ratio of the total opening area of all the through holes 23 to the area of the general portion 20e of the current collector sheet 20 is 30%.

  The current collector sheet 20 of the negative electrode 2 is bent in half at a substantially central portion in the longitudinal direction L, leaving the terminal connection portion 20d. The front surface located inside the folded current collector sheet 20 is a second surface 20a, and the back surface located outside is a second surface 20b.

As shown in FIGS. 1 and 2, first and second active material layers 21 a and 21 b are formed on the first surface 20 a and the second surface 20 b of the current collector sheet 20, respectively. The first and second active material layers 21a and 21b are formed on the flat surface portion 20g excluding the terminal connection portion 20d and the bent portion 20f. The thickness of the first active material layer 21a is 100 μm, and the mass of the first active material layer 21a formed in the unit area of the first surface 20a is 1.5 g / m ² . The thickness of the second active material layer 21b is 80 μm, and the mass of the second active material layer 21b formed per unit area of the second surface 20b is 1.2 g / m ² . The ratio of the thickness of the first active material layer 21a to the thickness of the second active material layer 21b is 1.25 (100 μm / 80 μm). In addition, the first active material layer 21a formed per unit area of the first surface 20a with respect to the mass of the second active material layer 21b formed per unit area of the second surface 20b of the current collector sheet 20 The mass ratio is 1.25 (1.5 g / m ² /1.2 g / m ² ).

  The first and second active material layers 21a and 21b are both composed of a negative electrode active material, a conductive auxiliary agent, and a binder, and each blending mass ratio is 96% for the negative electrode active material, 2% for the conductive auxiliary agent, and 2% for the binder. is there. The negative electrode active material is made of graphite, the conductive additive is made of acetylene black, and the binder is made of styrene butadiene rubber.

  The manufacturing method of the negative electrode 2 is the same as the manufacturing method of the positive electrode 1.

  The separator 3 is formed of a polypropylene porous thin film having a thickness of 20 μm that allows the electrolytic solution to flow therethrough.

  A plurality of positive electrodes 1 and negative electrodes 2 are alternately stacked with separators 3 interposed therebetween to form an electrode body 4. The total thickness of the electrode body 4 is 2 to 10 mm depending on the number of stacked layers.

The electrode body 4 is impregnated with a nonaqueous electrolytic solution. The nonaqueous electrolytic solution is composed of polyethylene carbonate as an organic solvent and LiPF ₆ as an electrolyte.

  The electrode body 4 and the electrolytic solution are housed in the housing member 5. The housing member 5 is made of a flexible aluminum sheet, and is sealed in a state where the electrode body 4 and the electrolytic solution are housed by thermocompression bonding at the periphery. The electrode tab 61 connected to the current collector sheet 10 of the positive electrode 1 and the electrode tab 62 connected to the current collector sheet 20 of the negative electrode 2 are each drawn out from the thermocompression bonding portion of the housing member 5. Yes.

According to the battery of the present embodiment, the thickness of the first active material layer 11a of the positive electrode 1 is increased to a thickness that normally peels off, and is larger than the thickness of the second active material layer 11b. . In this example, lithium cobaltate is used as the positive electrode active material. In this case, when the active material layer containing lithium cobaltate is formed on the planar current collector sheet, the thickness exceeds 70 μm, or the unit. When the mass per area exceeds 3.5 g / m ² , the active material layer is easily peeled from the current collector sheet 10.

  Even if the first active material layer 11a having such a peelable thickness or mass per unit area is formed on the current collector sheet 10, the first active material layer 11a is folded. 10 is sandwiched between the first surfaces 10a on the inner side of 10 and does not peel off. Further, since a large amount of active material layers can be formed on each current collector sheet, the total amount of active material layers 11a and 11b covering the current collector sheet 10 can be increased, and the battery capacity can be increased. Can be improved.

  On the other hand, the second active material layer 11 b is thinner than the first active material layer 11 a and is less likely to peel from the current collector sheet 10. Therefore, even if the second active material layer 11 b is not sandwiched between the folded current collector sheet 10, it hardly peels from the current collector sheet 10.

  The ratio of the thickness of the first active material layer 11a to the thickness of the second active material layer 11b is 1.23. Further, the first active material layer 11a formed per unit area of the first surface 10a with respect to the mass of the second active material layer 11b formed per unit area of the second surface 10b of the current collector sheet 10. The mass ratio is 1.21. For this reason, an ionic substance or electrolyte solution is formed between the first active material layer 11a formed on the first surface 10a of the current collector sheet 10 and the second active material layer 11b formed on the second surface 10b. The movement is sufficiently performed, and the battery capacity can be increased.

  A through-hole 13 is formed in the current collector sheet 10. For this reason, the front surface side and the back surface side of the current collector sheet 10 are communicated with each other through the through-holes 13, and the first and second active materials formed on the front and back surfaces of the current collector sheet 10 with the ionic substance and the electrolyte solution. It can be freely moved between the layers 11a and 11b, and the battery characteristics can be improved.

  Moreover, the terminal connection part 10d to which the electrode tab 61 of the current collector sheet 1 is connected is an active material non-formation part in which no active material layer is formed. For this reason, electricity can be reliably taken out from the terminal connection portion 10 d of the current collector sheet 10.

  The first surface 10a and the second surface 10b of the bent portion 10f of the current collector sheet 10 are active material non-formed portions where no active material layer is formed. The bent portion 10 f of the current collector sheet 10 is a portion that is easily peeled off from the current collector sheet 10 due to stress applied to the active material layer. Since the bent portion 10f is an active material non-formed portion, peeling of the active material layer from the current collector sheet 10 can be reliably suppressed.

  As described above, the first active material layer 11a in the positive electrode 1 is made thicker than the second active material layer 11, and is folded in two with the first surface 10a on which the first active material layer 11a is formed inside. Thus, it is described that the first active material layer 11a having a large thickness is prevented from being peeled off. Since the negative electrode 2 has the same configuration as the positive electrode 1, the total amount of the active material layers 21 a and 21 b can be increased similarly to the positive electrode 1, and the current collector sheets of the active material layers 21 a and 21 b can be increased. Peeling from 20 can be prevented.

(Example 2)
The present embodiment is different from the first embodiment in that the through holes 13 and 23 are not formed in the bent portions 10f and 20f of the current collector sheets 10 and 20 of the positive electrode 1 and the negative electrode 2 (FIG. 1). , See FIG.

  In the present embodiment, since the through holes 13 and 23 are not formed in the bent portions 10f and 20f of the current collector sheets 10 and 20, the first active material layers 11a and 21a sandwiched inside are collected. It can protrude to the outer side of the body sheets 10 and 20, and can prevent the first and second active material layers 11a, 11b, 21a and 21b from peeling and cracking from the bent portions 10f and 20f of the current collector sheets 10 and 20. . In addition, the strength of the bent portions 10f and 20f can be maintained stronger than when the through holes are formed in the bent portions 10f and 20f.

1: positive electrode, 2: negative electrode, 3: separator, 4: electrode body, 5: housing member, 10, 20: current collector sheet, 10a, 20a: first surface, 10b, 20b: second surface, 13, 23 : Through-hole, 13a, 23a: through-hole row, 10d, 20d: terminal connection portion, 10e, 20e: general portion, 10f, 20f: bent portion, 10g, 20g: plane portion, 11a: first active material layer ( Positive electrode), 21a: first active material layer (negative electrode), 11b: second active material layer (positive electrode), 21b: second active material layer (negative electrode), 61, 62: electrode tab.

Claims (11)

In a power storage device having a positive electrode, a negative electrode, and an electrolyte,
At least one of the positive electrode and the negative electrode comprises a current collector sheet having a through hole, and an active material layer formed on both front and back surfaces of the current collector sheet,
The first active material layer formed on one of the front and back surfaces of the current collector sheet is a second active material layer formed on the other second surface of the current collector sheet. A power storage device, wherein the current collector sheet is thicker than a material layer, and is folded while sandwiching the first active material layer with the first surface inside.   The first active material layer of the one electrode is folded together with the current collector sheet with the surfaces of the first active material layer facing each other directly, and the second active material layer of the one electrode is folded. The power storage device according to claim 1, wherein the active material layer is opposed to the other electrode via a separator.   3. The power storage device according to claim 1, wherein a terminal connection portion to which a terminal of the current collector sheet is connected is an active material unformed portion where an active material layer is not formed.   The active material unformed part in which at least one of the first surface and the second surface of the bent portion of the current collector sheet is not formed with an active material layer is provided. The power storage device described.   The power storage device according to claim 1, wherein a ratio of a thickness of the first active material layer to a thickness of the second active material layer is 1.05 or more and 5 or less.   2. The mass of the first active material layer formed per unit area of the first surface is larger than the mass of the second active material layer formed per unit area of the second surface. The electrical storage apparatus as described in any one of -5.   The ratio of the mass of the first active material layer formed per unit area of the first surface to the mass of the second active material layer formed per unit area of the second surface is 1. The power storage device according to claim 6, which is 05 or more and 5 or less. In both the positive electrode and the negative electrode, the first active material layer formed on the first surface of the current collector sheet is formed on the second surface of the current collector sheet. It is thicker than the active material layer, and the current collector sheet has a configuration that is folded while sandwiching the first active material layer with the first surface inside.
The current collector sheet folded of the positive electrode is stacked alternately with the current collector sheet folded of the negative electrode with a separator interposed therebetween. Power storage device.   The power storage device according to any one of claims 1 to 8, wherein the power storage device is a battery.   The power storage device according to any one of claims 1 to 8, wherein the power storage device is an electric double layer capacitor.   A vehicle comprising the power storage device according to any one of claims 1 to 10.

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