JP2016028374A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome the problem in which an organic electrolyte secondary battery is arranged by using an oxide or the like as a negative electrode active material and achieving high safety, while such an organic electrolyte secondary battery is low in output density because of its low battery voltage so it cannot satisfy the criteria for installation on a hybrid vehicle (HV).SOLUTION: In a power storage device according to the present invention, at least one of active material layers of opposing positive and negative electrodes has an electrically non-conducting property; and the other active material layer is put in close contact therewith at an opposite surface with no separator interposed therebetween, which shortens the distance between the electrodes. In addition, reducing the electrodes in thickness, a power storage device of a high output density can be achieved. This is because the area of the electrodes rises in inverse proportion to the electrode thickness efficiently. Therefore, applying the present invention, even an organic electrolyte secondary battery arranged so as to use an oxide or the like as a negative electrode active material will meet the performance criteria as a battery for installation on HV, and will make a safe and inexpensive next-generation battery of high output density for installation on HV.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device, and more particularly to an electrode structure of a power storage device.

  In recent years, hybrid vehicles combining motor drive and engine drive (hereinafter referred to as HV) are rapidly spreading in Japan due to their excellent environmental performance and fuel efficiency performance. On the other hand, with the advent of lithium-ion batteries, 100% motor-driven electric vehicles (hereinafter referred to as EVs) have been put into practical use and started to be marketed for general users.

Although EV is certainly satisfactory in terms of CO ₂ emissions, fuel efficiency and quietness, EV is unsuitable for long-distance driving because the distance that can be traveled by one charge (charging travel distance) is limited.

On the other hand, HV far surpasses gasoline vehicles in terms of CO ₂ emissions and fuel efficiency, and is the same as gasoline vehicles in terms of cruising distance, so there is no worry about long-distance driving. Therefore, theoretically, all gasoline vehicles in the world can be transferred to HV, and from the viewpoint of preventing global warming, all gasoline vehicles should be transferred to HV as soon as possible.

  In HV, when starting, running at low speed, or suddenly accelerating, the motor drive assists the engine driving to increase the engine operating efficiency. If the power supply capacity to the motor is high, the engine operating efficiency is basically increased. Rise. Therefore, it is desirable to mount a power storage device with as high an output as possible in HV, but since the power storage device mounted at the same time is limited in price and mounting space, the next-generation HV mounting power storage device has a higher output density ( W / L).

  Until now, nickel-metal hydride batteries have been exclusively used for HV-mounted power storage devices. However, as next-generation HV-mounted power storage devices, lithium-ion batteries are considered to be the first candidate, similar to EVs. It seems.

  The lithium ion battery is an organic electrolyte secondary battery that the inventors have succeeded in practical use for the first time in the world, and the present inventor at the 3rd secondary battery seminar held in Florida, USA in March 1990. For the first time, the performance of lithium-ion batteries has been introduced to the world, and the contents have also been posted in battery-specialized magazines (see Non-Patent Document 1). After that, lithium ion batteries were recognized for their superior performance in an instant and were adopted as power sources for many electronic devices.

  However, in a lithium ion battery, the carbon negative electrode doped with lithium ions is sufficiently close to metallic lithium in terms of potential, and therefore has a sufficient ability to reduce the organic electrolyte. Therefore, if the battery temperature rises to 60 ° C or higher due to some cause (battery internal short circuit, external short circuit, overcharge, etc.), the reaction between the carbon of the negative electrode and the electrolyte will become intense, and the battery will run out of heat and become abnormal. May lead to excessive fever and fire. For this reason, the upper limit of the lithium ion battery must be 60 ° C., and the battery temperature must be strictly controlled.

  Compared to lithium-ion batteries that are used as power sources for many electronic devices such as mobile phones and notebook computers, lithium-ion batteries mounted on EVs and HVs require higher output, making it difficult to control battery temperature. . In particular, since the lithium ion battery mounted on the HV has a larger discharge output (W / L) per battery volume, the calorific value (J / L) per battery volume is large and the battery temperature is likely to rise. Therefore, for example, in the HV of a certain company equipped with a lithium ion battery, the battery is mounted 5 ° forward and the cooling effect is enhanced by applying the introduced wind.

  Next-generation HV-equipped power storage devices are required to have a higher “maximum output density (W / L)”, but if the output density (W / L) of a lithium ion battery is further increased, the battery temperature will be reduced. Further ingenuity to keep the temperature at 60 ° C. or lower is also necessary, and it becomes more difficult to ensure safety. Therefore, from the viewpoint of ensuring safety, it is necessary to consider other power storage system options as the next-generation HV-mounted power storage device.

  “Maximum output density (W / L)” means the maximum output per volume of the power storage device, but the maximum output depends on the sustainable time. For example, the maximum output sustainable for 10 seconds is naturally greater than the maximum sustainable output for 120 seconds. Therefore, in this specification, on the premise of HV mounting, a value obtained by dividing the maximum output sustainable for 120 seconds by the volume of the power storage device is defined as “maximum output density (W / L)”.

  The specific HV mounting standard of the maximum power density (W / L) is about 2500 W / L on the basis of the unit cell, judging from the performance of the lithium ion battery currently mounted on the HV. If the maximum power density sustainable for 120 seconds is 2500 W / L, the discharge capacity density at the maximum output is 83 Wh / L or more.

  As a power storage device having a high output density (W / L), there is a capacitor in addition to a secondary battery. Generally, a capacitor has a high output density (W / L) but a low discharge capacity density at the maximum output. Therefore, in order to use the capacitor as an HV-mounted power storage device, it is necessary to increase the capacity density (Wh / L). Conversely, since the secondary battery has a low output density (W / L), it is necessary to increase the output density (W / L) in order to use it as an HV-mounted power storage device.

In recent years, in order to increase the capacitance density (Wh / L) of a capacitor, an active material based on an electrochemical oxidation-reduction reaction such as TiO ₂ or Li ₄ Ti ₅ O ₁₂ is used as a negative electrode active material. Has been actively researched on capacitors with positive electrode active material such as graphite, in which negative ions in the electrolyte are electrochemically intercalated, and reported that the output density was 7000 W / L and the capacity density was 20 Wh / L. (See Non-Patent Documents 2 to 3), but the output density is satisfactory, but the capacity density is not at the level for HV mounting.

  In addition, in order to increase the capacity density (Wh / L), the capacitor also uses an active material based on an electrochemical oxidation-reduction reaction like the secondary battery, making it difficult to distinguish between the capacitor and the secondary battery. However, in this specification, power storage devices that use an active material based on an electrochemical redox reaction for both the positive electrode and the negative electrode are classified as secondary batteries, and an active material based on an electrochemical redox reaction. A power storage device that uses only the positive electrode or the negative electrode is classified as a capacitor.

  On the other hand, as a highly safe organic electrolyte secondary battery, a secondary battery using a negative electrode active material that is not capable of reducing the electrolyte (for example, a metal oxide or sulfide) can be considered. In the present specification, an organic electrolyte secondary battery using a substance having no ability to reduce such an organic electrolyte solution, that is, a noble (high) substance having a redox potential as a negative electrode active material, is hereinafter referred to as “noble negative electrode potential type”. It will be called “secondary battery”.

  Many noble negative electrode potential type secondary batteries have been proposed so far (see Patent Documents 1 to 4). However, in the noble negative electrode type secondary battery, the discharge voltage is considerably lower than the lithium ion battery because the redox potential of the negative electrode active material is noble (high), and the capacity density (Wh / L) is proportional to the discharge voltage. Therefore, it is considerably lower than the lithium ion battery.

  In the use of secondary batteries so far, a battery having a high capacity density (Wh / L) (use for a long time) has been demanded. Therefore, noble negative electrode potential type secondary batteries have a capacity density (Wh / L) of lithium. It is difficult to reach the level of an ion battery (about 250 Wh / L on a unit cell basis), and it has not been put into practical use.

  Incidentally, the nickel-metal hydride secondary battery is about 1/3 of the lithium ion battery in terms of cell voltage, but since the capacity density exceeds 250 Wh / L, it is used in many electronic devices along with the lithium ion battery. ing.

  However, in applications as HV-mounted batteries, the capacity density (Wh / L) is sacrificed and reduced to about 120 to 150 Wh / L in order to increase the output density (W / L) even in lithium ion batteries. doing. In other words, if the maximum output density (W / L) satisfies the standard, the capacity density (Wh / L) can be mounted on the HV sufficiently even if it is about half that of the original lithium ion battery. Suggests.

  Therefore, if limited to HV-equipped batteries, highly safe noble negative potential type secondary batteries can be used for next-generation HV-equipped batteries as long as the maximum output density (W / L) is met. Can be a strong candidate.

US Pat. No. 4,983,476 Japanese Patent Laid-Open No. 08-022841 Japanese Patent Application Laid-Open No. 08-024117 Japanese Patent Laid-Open No. 08-236115

“Progress in Batteries and Solar Cells”, 1990, Vol.9, p.209 “Journal of Power Sources”, 2007, Vol.169, p375 “Journal of Power Sources”, 2010, Vol.195, p6250

However, in a noble negative potential type secondary battery having a lower voltage than that of a lithium ion battery, the lower voltage is more related to the maximum output density (W / L). That is, the maximum output (Wmax) of a battery having an open circuit voltage of V ₀ and an internal resistance of r has a relationship of Wmax = V ₀ ² / (4 × r), and the maximum output is proportional to the square of the open circuit voltage. . However, here, the internal resistance r of the battery is not a simple AC impedance between the positive electrode and the negative electrode, but a value obtained by dividing all the polarizations such as the resistance polarization, concentration polarization, and activation polarization of the electrolyte by the discharge current.

  Although the maximum output of any battery increases as the battery size increases, in HV the battery mounting space is greatly related to the number of seats in the car, the space in the luggage compartment, etc. It is required to have a large output. That is, a large maximum power density (W / L) is required for the HV-mounted battery.

If the open circuit voltage V _{0 of the} noble negative potential type secondary battery is about 2/3 of that of a lithium ion battery, the capacity density (Wh / L) in the case of manufacturing with a conventional electrode structure similar to the lithium ion battery About 67% of the lithium ion battery can be expected, but the maximum power density (W / L) is proportional to the square of the open circuit voltage V ₀ , and cannot reach about 45% of the lithium ion battery.

  Therefore, in order to raise the maximum output density (W / L) of the noble negative potential type secondary battery to the standard of the HV-mounted battery (about 2500 W / L), it is very difficult with the same conventional electrode structure as the lithium ion battery. It is.

  The present invention has been made in view of the above problems, and the object thereof is to make it possible to remove the separator from the power storage element, thereby increasing the electrode area, reducing the distance between the electrodes, and reducing the voltage. An object of the present invention is to provide a new electrode structure capable of obtaining a high output density even in an organic electrolyte secondary battery.

  In order to solve the above problem, the power storage device is a power storage device in which an active material layer of a positive electrode and a negative electrode is opposed to each other, and each of the positive electrode and the negative electrode is formed in close contact with a current collector, The active material layer of the positive electrode and the active material layer of the negative electrode facing each other are in close contact with each other on the opposing surface.

  In the power storage device with an electrode structure according to the present invention, since the opposing active material layers are in close contact with each other on the opposing surface, the distance between the electrodes is shortened, and the amount corresponding to the separator used in the conventional electrode structure is increased. As a result, the electrode area increases, and the output density increases.

  Problems other than those described above and solutions and effects thereof will be described in more detail with reference to the following embodiments.

It is sectional drawing which shows the positive electrode tab connection part of the electrical storage element which concerns on implementation of this invention, and the arrangement | sequence state of an electrode. It is sectional drawing which shows the negative electrode tab connection part of the electrical storage element which concerns on implementation of this invention, and the arrangement | sequence state of an electrode. It is sectional drawing of the electrical storage apparatus which concerns on implementation of this invention. It is sectional drawing which shows the electrode tab connection part of the electrical storage element in a conventional battery, and the arrangement | sequence state of an electrode. It is a figure which shows the relationship between the thickness of the active material layer of the electrical storage element which concerns on implementation of this invention, and the number of electrode lamination by comparison with the past. It is a schematic diagram which shows the electron conduction path | route and ion conduction path which are ensured by the active material at the time of the first charge of the battery which concerns on implementation of this invention. It is the electrode schematic diagram which showed the first charging mechanism of the battery by this invention. It is the electrode schematic diagram which showed the first charging mechanism of the battery by this invention. It is the electrode schematic diagram which showed the first charging mechanism of the battery by this invention. It is the schematic diagram which showed the generation | occurrence | production mechanism of the electrolyte solution concentration difference of an organic electrolyte battery. It is a figure which shows the discharge curve at the time of 4A constant current discharge of the battery which concerns on implementation of this invention, and a conventional battery. It is a figure which shows the discharge curve at the time of the maximum output of the battery concerning implementation of this invention, and a conventional battery.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an arrangement state of positive electrode tab connection portions and electrodes of a power storage device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an arrangement state of the negative electrode tab connection portion and the electrode of the energy storage device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing a power storage device according to the embodiment of the present invention.

  1 to 3 show a power storage device 100 (FIG. 3) and the power storage element 10 when the present invention is carried out with the electrode thickness reduced to near the limit in order to obtain a secondary battery or capacitor having a high output density. (FIG. 1, 2) was shown with sectional drawing. In the power storage element 10, the positive electrode 31 and the negative electrode 32 are each active material layer 2 (hereinafter also referred to as “positive electrode active material layer 2”) and active material layer 1 (hereinafter also referred to as “negative electrode active material layer 1”). Is an electrode formed in close contact with the current collector 4 (hereinafter also referred to as “positive electrode current collector 4”) and the current collector 3 (hereinafter also referred to as “negative electrode current collector 3”). The active material layer 2 and the negative electrode active material layer 1 are configured to face each other, and the facing active material layers 2 and 1 are in close contact with each other at the facing surface 33.

  FIGS. 1 and 2 show the case where the electrode thickness is reduced to near the limit. Specifically, the positive electrode 31 and the negative electrode 32 are formed on the current collectors 4 and 3 having a thickness of about 10 μm, respectively, and the thickness is about 20 μm or less. An electrode in which the active material layers 2 and 1 are formed on both sides or one side is used, the positive electrode active material layer 2 and the negative electrode active material layer 1 are overlapped to face each other, and the power storage element 10 is configured as a laminated body of electrodes. As shown in FIG. 3, the element 10 is impregnated with an organic electrolyte solution (not shown), placed between an aluminum / polypropylene laminate sheet 11 and a drawn laminate sheet 12, and sealed by heat-sealing the surroundings. The power storage device 100 having an electrode structure according to the present invention is completed.

  FIG. 1 is an enlarged view of the arrangement of the electrode and the portion of the electricity storage element 10, particularly the portion where the positive electrode current collector 4 is connected and connected to the positive electrode tab 7, and FIG. 2 shows the arrangement of the negative electrode current collector 3 in the electricity storage element 10. Thus, the portion connected to the negative electrode tab 6 and the arrangement state of the electrodes are shown enlarged. As shown in FIG. 1, the positive electrode active material layer 2 and the negative electrode active material layer 1 that face each other in the power storage element 10 are in close contact with each other, and the positive electrode current collector 4 is joined together and welded to the positive electrode tab 7. Is wrapped with plastic tape 9, and when the storage element 10 is sealed with the laminate sheets 11 and 12, as shown in FIG. 3, the plastic tape 9 is integrated with the laminate sheets 11 and 12 and heat-sealed. The positive electrode tab 7 is taken out to the external terminal 14 of the positive electrode without disturbing the sealing of the electric storage element 10. Similarly, as shown in FIG. 2, the negative electrode current collector 3 is also collected and welded to the negative electrode tab 6, and the negative electrode tab 6 is taken out to become an external terminal 13 of the negative electrode.

FIG. 4 is a cross-sectional view showing an arrangement state of electrode tab connection portions and electrodes of a storage element in a conventional battery. In addition, each component 1A, 2A, 3A, 4A, 6A, 7A, 10A in FIG. 4 is equivalent to each component 1, 2, 3, 4, 6, 7, 10 in FIGS.

  On the other hand, FIG. 4 shows a cross-sectional view of a power storage device 10A having a conventional electrode structure in the case where the electrode thickness is reduced to the limit in order to obtain a secondary battery or a capacitor having a high output density. In FIG. 4, the current collectors 4A and 3A are combined and connected to the electrode tabs 7A and 6A, and the arrangement state of the electrodes is shown by enlarging the positive electrode tab 7A side and the negative electrode tab 6A side to the left half and the right half, respectively. Yes.

  The power storage element 10A shown in FIG. 4 is a view shown on the assumption that an electrode having the same thickness as that of the power storage element 10 shown in FIGS. 1 and 2 is used and the thickness of the stacked body is also the same. FIG. 4 also shows a case where the electrode thickness is reduced to near the limit. Specifically, the positive electrode 31A and the negative electrode 32A are respectively provided on the current collectors 4A and 3A having a thickness of about 10 μm and the active thickness of about 20 μm or less. An electrode in which the material layers 2A and 1A are formed on both sides or one side is used, and a separator 5 having a thickness of about 25 μm is used. Considering the mechanical strength and function of the separator 5, 25 μm is almost the limit of thinness.

  In the conventional electrode structure (FIG. 4), as compared with the electrode structure of the present invention (FIGS. 1 and 2), if the volume of the electrode laminate is the same, the amount of the electrode is equivalent to the amount of the separator 5. If the electrodes having the same thickness are used, the electrode area is reduced accordingly.

  FIG. 5 is a diagram showing the relationship between the thickness of the active material layer and the number of stacked electrodes of the electricity storage device according to the embodiment of the present invention in comparison with the conventional art.

  FIG. 5 shows the relationship between the thickness of the active material layer and the number of stacked electrodes when an active material layer is formed on a 10 μm-thick current collector, and the electrode structure and separator using a 25 μm-thick separator. It showed about the case of the electrode structure which does not use.

  As shown in FIG. 5, in the electrode structure using the separator, particularly when the thickness of the active material layer is less than the thickness of the separator (25 μm), the thickness of the active material layer can be reduced. Since the ratio becomes high, the number of stacked electrodes does not increase efficiently. On the other hand, in an electrode structure that does not use a separator, the number of stacked electrodes increases efficiently, particularly when the thickness of the active material layer is 25 μm or less.

  A battery having a high capacity density has been demanded in the past applications of the secondary battery. In the case of a battery having a high capacity density, the thickness of the active material layer is designed to be sufficiently thick (80 to 100 μm) even in the conventional battery structure. Therefore, as shown in FIG. Few separators are a major obstacle to obtaining high capacity density.

  However, in order to obtain a secondary battery with high power density, it is necessary to reduce the electrode thickness and increase the electrode area. In the conventional battery structure, the thickness of the active material layer approaches the thickness of the separator. If so, the ratio of the separator to the power storage element becomes extremely large, and conversely, the ratio of the electrode to the power storage element is greatly reduced, so that the electrode area does not increase efficiently. Therefore, in the conventional battery structure, the separator is an obstacle to obtaining a high output density.

  In the lithium ion battery mounted on the HV, the maximum power density (W / L) is increased by about 3 to 4 times as compared with the EV mounted battery. In the lithium ion battery currently mounted on the EV, the thickness of the positive electrode active material layer is relatively thick and is estimated to be about 100 μm on one side. However, judging from the relationship between the thickness of the active material layer and the number of electrodes shown in FIG. In a lithium ion battery mounted on HV, the active material layer thickness is set to 20 μm or less, so that the electrode area is increased about 3 to 4 times, and the maximum output density (W / L) becomes the standard for mounting on HV. Presumed to have been reached.

  However, as is apparent from FIG. 5, even if the electrode thickness is reduced to the limit, the electrode area is not increased efficiently in the conventional electrode structure (FIG. 4), but the electrode structure of the present invention (FIG. 1, In 2), the electrode area increases efficiently.

For example, if the thickness of the active material layer is 20 μm, the maximum inter-electrode distance (d ₁ ) is 40 μm in the electrode structure of FIG. 1, but the maximum inter-electrode distance in the conventional electrode structure shown in FIG. The distance (d ₂ ) is 65 μm, and in the electrode structure according to the present invention, the maximum inter-electrode distance is about 1 / 1.6 compared with the conventional type, and the thickness of the active material layer is reduced to 10 μm (almost the limit). In this case, it is about 1 / 2.25.

  As described above, when the electrode thickness is reduced to near the limit, according to the electrode structure of the present invention, the electrode facing area is significantly increased as compared with the conventional electrode structure. This is effective for obtaining a battery and a capacitor, and is extremely effective for obtaining a secondary battery having a particularly high output density because the distance between the electrodes is shortened.

  In the power storage device 100 shown in FIG. 3, as shown in FIGS. 1 and 2, the positive electrode 31 and the negative electrode 32 are electrodes formed by bringing the active material layers 2 and 1 into close contact with the current collectors 4 and 3. At least one of the positive electrode active material layer 2 and the negative electrode active material layer 1 is composed of an active material based on an electrochemical redox reaction, and the active material is electrochemically oxidized or reduced in the charging direction. Is selected from materials that are non-electron conductive, and the active material layer does not contain any material that is already electron conductive before being oxidized or reduced electrochemically in the charging direction. Therefore, the active material layer is non-electron conductive in an uncharged state.

  Therefore, in the power storage device 100 according to the present invention, at least one of the positive electrode active material layer 2 and the negative electrode active material layer 1 is non-electron conductive in an uncharged state, and the positive electrode active material layer 2 and the negative electrode active material layer 1 facing each other. Since the electronic continuity is interrupted even if they contact, they can be brought into close contact with the opposing surface 33 without using a separator.

In this specification, “non-electron conductivity” means that there is almost no electron conductivity, and more specifically, electrical conductivity based on electron conduction at room temperature is generally classified as an insulator. It means less than ⁻¹⁰ S / cm. The mechanism of electrical conduction includes electronic conduction when the carrier carrying electricity in the substance is an electron, and ionic conduction when the carrier carrying electricity is an ion (may be referred to as ionic conduction). “Non-electron conductivity” does not matter whether ion conductivity is present.

  1 and 2 has the positive electrode active material layer 2 (or the negative electrode) when the negative electrode active material layer 1 (or the positive electrode active material layer 2) is non-electron conductive in an uncharged state. The active material layer 1) may be electronically conductive. If the positive electrode active material layer 2 (or the negative electrode active material layer 1) is composed of an active material based on an electrochemical redox reaction, the positive electrode 31 and the negative electrode 32 are Since both are made of an active material based on an electrochemical oxidation-reduction reaction, they are power storage elements of a secondary battery. Here, if the positive electrode active material layer 2 (or the negative electrode active material layer 1) is made of an active material that is not based on an electrochemical redox reaction, such as activated carbon, it is a capacitor storage element.

  However, as described above, since the output density (W / L) of the capacitor is already high, the electrode structure according to the present invention is also effective for the capacitor in applications where a capacitor with a higher output density (W / L) is required. Become.

  Since the electrochemical redox reaction (charge / discharge reaction) of the active material involves electrons and ions, the battery active material secures electron conduction between the current collector and ionic conduction between the counter active material. It must be.

  Usually, since there is a hole capable of holding the electrolytic solution in the active material layer of the electrode, if the electrolytic solution is held in the hole, ion conduction between the active materials is ensured by the electrolytic solution. Further, in the conventional battery, since the conductive auxiliary agent is mixed in the active material layer of the electrode, electronic conduction between the active material and the current collector is ensured by the conductive auxiliary agent.

  However, in the battery according to the present invention, at least one of the active material layers is non-electron conductive, and in the non-electron conductive active material layer, the active material that ensures electron conduction with the current collector is the current collector. It is limited to active material particles (secondary particles) that adhere to the surface. However, the present invention is based on the premise that the thickness of the active material layer is reduced, and when the thickness of the active material layer approximates the diameter of the active material particles (secondary particles), most of the active material layer Since the active material particles (secondary particles) are in close contact with the current collector, the majority of the active material ensures electron conduction with the current collector.

  FIG. 6 is a schematic diagram showing an electron conduction path and an ion conduction path ensured in the active material when the battery according to the embodiment of the present invention is charged for the first time.

  In FIG. 6, the electron conduction path | route and ion conduction path | route ensured by the negative electrode active material A and the positive electrode active material C at the time of first time charge were shown with the schematic diagram. The negative electrode active material A is an active material constituting the negative electrode active material layer 1. On the other hand, the positive electrode active material C is an active material constituting the positive electrode active material layer 2. In FIG. 6, the ionic conduction between the negative electrode active material A and the positive electrode active material C is ensured by the electrolytic solution held in the active material layer as in the conventional case, and the negative electrode active material A is in direct contact with the negative electrode current collector 3. In addition, since the positive electrode active material C is also in direct contact with the positive electrode current collector 4, a conduction aid is not necessarily required to ensure electronic conduction between the active material particles and the current collector.

  That is, when the thickness of the active material layer is about the same as the diameter of the active material particles (secondary particles), there is no need to mix a conduction aid. However, since FIG. 6 shows the case where the negative electrode active material layer 1 is non-electron conductive, the positive electrode active material layer 2 may be formed by mixing a conduction aid.

  Looking back at the storage element 10 shown in FIGS. 1 and 2, it is assumed that the electrode thickness is reduced, and at least one of the positive electrode active material layer 2 and the negative electrode active material layer 1 is non-electron conductive. Although most active material particles (secondary particles) in the non-electron conductive active material layer are in close contact with the current collector, most of the active material is ensured to conduct electrons with the current collector. Yes. Further, even if the positive electrode active material layer 2 and the negative electrode active material layer 1 are in close contact with each other at the facing surface 33, the positive electrode 31 and the negative electrode 32 are not electrically connected by electronic conduction. In the battery shown in FIG. Since the liquid is impregnated, the positive electrode active material and the negative electrode active material are conductive by ion conduction. Therefore, if a charging voltage is applied to the positive electrode terminal 14 and the negative electrode terminal 13, the positive electrode active material in the positive electrode active material layer 2 and the negative electrode active material in the negative electrode active material layer 1 are charged.

  Particles that adhere to the current collector even with non-electron conductive active materials can exchange electrons with the current collector, so the charging reaction proceeds, and the non-electron conductive active material layer adheres to the current collector. Since the active material primary particles are charged to change into an electron conductive active material, and the active material primary particles that are not directly adhered to the current collector can also exchange electrons through the charged active material, It will be charged sequentially.

Incidentally, a battery using a non-electron conductive active material is not uncommon even in a conventional battery. For example, in a primary battery, Ag ₂ O as a positive electrode active material of a silver battery, HgO as a positive electrode active material of a mercury battery, (CF) n of a positive electrode active material of a graphite fluoride lithium battery are all non-electron conductive. Both of the positive active material PbSO _{4 in} the discharged state of the lead battery and the uncharged positive active material Ni (OH) _{2 of the} nickel metal hydride battery in the secondary battery are non-electron conductive active materials. is there.

  All of these non-electron conductive active materials change to electrical conductivity when electrochemically reduced or oxidized. In other words, a non-electron conductive substance that can undergo an oxidation-reduction reaction electrochemically changes from a primary particle capable of transferring electrons to an electron-conducting substance through an oxidation-reduction reaction that mediates this. It can be understood that the redox reaction proceeds in sequence since electrons can be transferred to and from the primary particles.

  In addition, since the active material particles generally collect primary particles to form secondary particles, it is only between the current collector and the secondary particles that electronic conduction can be ensured by the conduction auxiliary agent. Is between the current collector and a portion of the primary particles forming the secondary particles. Therefore, even when electronic conduction is ensured by the conduction auxiliary agent, the active material primary particles that are in close contact with the conduction auxiliary agent are successively charged in a chain manner to other particles. In the conventional battery, good conduction of electrons between the active material (secondary particles) and the current collector is ensured by mixing a conductive additive such as carbon in the active material layer. Accordingly, even when a non-electron conductive active material is used in a conventional battery, the active material layer of both the positive electrode and the negative electrode is electron conductive, and therefore a separator is indispensable.

  As shown in FIG. 6, when the thickness of the active material layer is about the same as the diameter of the active material particles (secondary particles), it is not necessary to mix a conductive auxiliary agent. It has long been common knowledge to ensure good electron conduction between the active material and the current collector by mixing auxiliary agents. There has never been an idea that seems to be the opposite of removing an adjuvant.

  As described above, in a conventional battery, even when a non-electron conductive active material is used, by mixing a conductive auxiliary agent such as carbon, both a positive electrode and a negative electrode have a good electron conductive active material. Since an electrode is formed by forming a layer, it is necessary to interpose a separator between the positive electrode and the negative electrode in order to cut off the electronic conduction between the positive electrode and the negative electrode.

  Usually, active material particles are secondary particles in which primary particles are gathered. In a charge / discharge reaction based on an electrochemical oxidation-reduction reaction, charge / discharge proceeds by a chain charge / discharge reaction of the primary particles.

  7A to 7C are schematic electrode diagrams illustrating an initial charging mechanism of a battery according to the present invention.

  7A to 7C further illustrate the mechanism of the initial charging of the battery according to the present invention by further enlarging the opposing electrodes in the electricity storage device 10 shown in FIGS. 1 and 2. The active material layers 21 and 22 and the current collectors 23 and 24 shown in FIGS. 7A to 7C correspond to the active material layers 2 and 1 and the current collectors 4 and 3 shown in FIG. The active material layers 1 and 2 and the current collectors 3 and 4 shown in FIG. FIG. 7A shows a state before the first charge, and the active material layers 21 and 22 facing each other are in close contact, but one of the active material layers 21 is non-electron conductive, so that the current collectors 23 and 24 are electronic. Does not conduct. Further, since the active material layers 21 and 22 hold the electrolyte solution in the pores and are conductive by ion conduction, charging starts when a charging voltage is applied to the current collectors 23 and 24.

  In charging, the active material contained in the non-electron conductive active material layer 21 starts to be charged from the active material (primary particles) in close contact with the current collector 23, and the charged active material (primary particles) is an electron. The active material (primary particles) that become conductive and sequentially separated from the current collector is also charged in sequence, and as shown in FIG. 7B, the non-electron conductive active material layer is the active material layer 21a in a charged state. And the active material layer 21 in an uncharged state.

  Even if the charging is completed, as shown in FIG. 7C, if the uncharged active material layer 21 remains between the charged active material layers 21a and 22a, the uncharged non-electron conductive active material layer always remains. Since the active material layers 21a and 22a in the charged state 21 do not function electronically as a separator, they are charged.

  7A, the chargeable capacity of the non-electron conductive active material layer 21 is designed to be larger than the chargeable capacity of the opposite active material layer 22, thereby uncharged as a separator as shown in FIG. 7C. It is possible to reliably leave the active material layer 21 in a state as necessary.

  As described above, in the battery according to the present invention, in the non-electron conductive active material layer, about 70 to 90% of the active material (primary particles) is sequentially charged from the one close to the current collector, and after the first charge, The active material once charged always plays a role of contributing to charge / discharge, and the remaining non-electron conductive active material (primary particles) of about 10 to 30% located away from the current collector is not charged. As it is, it remains non-electron conductive, and continues to play a role of preventing electronic conduction between the positive electrode and the negative electrode (separator role). The battery according to the present invention does not require the use of a separator.

  Assuming that 30% of the uncharged active material layer that plays the role of the separator remains, if the initial thickness of the non-electron conductive active material layer is about 10 μm, the active material layer that plays the role of the separator is thick. It will remain at about 3 μm. The active material layer that plays the role of a separator of about 3 μm is about 1/10 of the thickness of a conventional battery separator (thickness of 25 to 35 μm), and the distance between the positive and negative electrodes is greatly reduced. The diffusion rate of ions between the positive and negative electrodes increases, and the output performance increases.

  The amount of charge (Ah) of the secondary battery is restricted to the smaller chargeable capacity of the positive electrode and the negative electrode, so it is ideal to make the chargeable capacity of the positive electrode and the negative electrode equal, but the charge characteristics of each battery In order to make it uniform, it is common to increase the chargeable capacity of either the positive electrode or the negative electrode to be either negative electrode capacity regulation or positive electrode capacity regulation. By the way, in the case of existing lithium ion batteries, the negative electrode capacity is about 1.4 times the positive electrode capacity, and in the nickel metal hydride battery, it is also about 1.2 times.

  Therefore, in the present invention, even when the chargeable capacity of the non-electron conductive active material layer is designed to be about 1.3 times larger than the chargeable capacity of the counter electrode active material layer, the conventional method has a balance between the positive electrode capacity and the negative electrode capacity. This is not much different from the secondary battery design.

  Since the electricity storage device according to the present invention does not include a separator, the volume of the electricity storage device is the volume of the electrode as it is, and is equal to the product of the electrode area and the electrode thickness. Accordingly, if the electrode thickness of the electricity storage device according to the present invention is reduced, the electrode area increases efficiently in inverse proportion to the electrode thickness in the electricity storage device having a constant volume. Therefore, in order to obtain a secondary battery having a high output density. It is extremely effective.

  Since the output density is low in the conventional electrode structure, the noble negative potential type secondary battery, which is considered difficult to mount on HV, becomes a high output organic electrolyte secondary battery by applying the present invention. There is a possibility of satisfying the mounting standards. Therefore, the case where the present invention is specifically applied to a noble negative electrode potential type secondary battery will be described in more detail.

Specifically, a case where spinel lithium titanium oxide is selected as the negative electrode active material and spinel lithium manganese oxide (LiMn ₂ O ₄ ) is selected as the positive electrode active material will be described.

Spinel lithium titanium oxide (lithium titanate) is represented by the general formula Li _{3 + x} Ti _6-x O ₁₂ and exists in the range of 0 ≦ x ≦ 1, but at x≈1, lithium titanate is non-electron conductive. sex is (electronic conductivity of about ¹⁰ -13 S / cm), carrying out the present invention, spinel type lithium-titanium oxide _{Li 4 Ti 5 O 12 (x} = 1) is a suitable non-electron conductivity It is a negative electrode active material.

LiMn ₂ O ₄ can reversibly undergo an electrochemical redox reaction at a potential of about 4 V (vs Li / Li ⁺ ) in the organic electrolyte, and Li ₄ Ti ₅ O ₁₂ can be about about 4 V in the organic electrolyte. Electrochemical reduction and oxidation reactions are reversibly possible at a potential of 1.5 V (vs Li / Li ⁺ ). Accordingly, the average discharge voltage of the noble negative electrode type secondary battery using LiMn ₂ O ₄ as the positive electrode active material and Li ₄ Ti ₅ O ₁₂ as the negative electrode active material is about 2.5V.

When the present invention is applied to a battery using spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) as a negative electrode active material and spinel lithium manganese oxide (LiMn ₂ O ₄ ) as a positive electrode active material, Li ₄ Ti ₅ O ₁₂ used as a material is not mixed with a conductive auxiliary agent such as carbon, but is solidified with a binder to form a non-electroconductive negative electrode active material layer on a thin metal foil used as a negative electrode current collector LiMn ₂ O _{4 used} as a negative electrode and a positive electrode active material is mixed with a conductive auxiliary agent such as carbon and solidified with a binder to form an electron conductive positive electrode active material layer on a thin metal foil used as a positive electrode current collector. To form a positive electrode. 1 and 2, the positive electrode active material layer 2 and the negative electrode active material layer 1 are opposed to each other so as to form a power storage element 10 and impregnated with an organic electrolyte, as shown in FIGS. As shown in FIG.

  In the noble negative electrode potential type secondary battery according to the present invention implemented as described above, the negative electrode active material layer is non-electron conductive even if the positive electrode active material layer and the negative electrode active material layer are in close contact with each other. The negative electrode is not conductive in electronic conduction, and the positive electrode active material layer and the negative electrode active material layer are sufficiently impregnated with an organic electrolyte solution, so that the positive electrode active material and the negative electrode active material are conductive in ion conduction. Therefore, if a charging voltage of about 3 V is applied to the positive electrode and the negative electrode, the respective active materials in the positive electrode active material layer and the negative electrode active material layer are charged.

The particles of Li ₄ Ti ₅ O _{12 in} the negative electrode active material are sequentially charged from the particles adhering to the negative electrode current collector, and changed to dark blue electron-conductive Li ₇ Ti ₅ O ₁₂ . In the crystal of Li ₄ Ti ₅ O ₁₂ , titanium is all tetravalent (Ti ⁴⁺ ), but electrons are supplied through the negative electrode current collector by charging, and Li ⁺ is supplied from the electrolytic solution to form Li ₇ Ti. If it is changed to ₅ O ₁₂ , Ti ⁴⁺ and Ti ³⁺ are mixed in a ratio of 2: 3 in the crystal, and Ti ⁴⁺ and Ti ³⁺ in the crystal can freely exchange electrons. ₇ Ti ₅ O ₁₂ is electronically conductive. Therefore, the Li ₄ Ti ₅ O ₁₂ particles that are not directly adhered to the negative electrode current collector in the negative electrode active material layer are also electrically conductive with the negative electrode current collector through the Li ₇ Ti ₅ O ₁₂ changed to electron conductivity. Since it conducts, it will be charged sequentially.

In the positive electrode active material layer, LiMn ₂ O ₄ is charged and changed to λ-MnO ₂ . Crystal of the LiMn ₂ O ₄ ^{Mn 4+} and ^{Mn 3+} is 1: 1 mixed at a ratio, since ^{Mn 4+} and ^{Mn 3+} in the crystal can be performed freely electronic exchange, LiMn ₂ O ₄ itself is electron conduction In addition, if a conductive auxiliary agent such as carbon is mixed in the positive electrode active material layer, all LiMn ₂ O ₄ particles in the positive electrode active material are electrically connected to the positive electrode current collector through electronic conduction. , since it involved in any of the charge reaction LiMn ₂ O ₄ particles, so that the charge reaction is sequentially charged from the negative electrode active material and suitable LiMn ₂ O ₄ particles as electrochemical counter ongoing.

_Li 4 _Ti 5 _{O 12} of the negative electrode active material layer is if designed to exceed the LiMn ₂ O ₄ positive electrode active material layer in substantially the chargeable capacity, the LiMn ₂ O ₄ that can be involved in the charge reaction is charged If it runs out, the charging will end. At the end of charging, uncharged Li ₄ Ti ₅ O ₁₂ in the negative electrode active material layer remains uncharged at the boundary with the counter electrode active material layer farthest from the current collector.

For example, in substantially the chargeable capacity, if _Li 4 _Ti 5 _{O 12} of the negative electrode active material layer is only to be designed in 1.3 times the LiMn ₂ O ₄ in the positive electrode active material layer, _Li 4 Ti ₅ is at the end of charge About 30% of O ₁₂ will remain in the vicinity of the boundary with the counter electrode active material layer in an uncharged state, and of course between the active material layer of the positive electrode and the negative electrode both before and after charging. Since the non-electron conductive active material layer in an uncharged state always acts as a separator, there is no need to interpose a separator between the positive electrode and negative electrode active material layers.

A noble negative potential type secondary battery using Li ₄ Ti ₅ O ₁₂ as a negative electrode active material and LiMn ₂ O ₄ as a positive electrode active material is excellent in safety, and is a promising candidate for a next-generation HV-equipped battery. However, since the voltage is low, the maximum power density (W / L) cannot reach the mounting standard for HV in the conventional battery structure in which the separator is interposed. However, since the electrode structure according to the present invention does not include a separator, not only the distance between the electrodes is shortened, but particularly when the thickness of the electrodes is reduced, the electrode area that can be secured is greatly increased, so that the output density ( It is extremely effective in making a battery with a high (W / L), and if the present invention is applied, a noble negative potential type secondary battery having a low voltage can sufficiently satisfy the HV mounting standard.

Since the present invention is extremely effective in producing a battery having a high output density (W / L), it can be most expected to be applied to a noble negative electrode type secondary battery for HV mounting. When the present invention is applied to a noble negative electrode potential type secondary battery, the non-electron conductive negative electrode active material includes titanium oxide in addition to the above spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ). (TiO ₂ ), spinel-based lithium iron oxide (LiFe ₅ O ₈ ), and the like can be selected. Although these are all non-electron conductive materials, they change to electronic conductivity when charged as a negative electrode active material, and thus are preferable negative electrode active material candidates in the practice of the present invention.

In addition to spinel lithium manganese oxide (LiMn ₂ O ₄ ), LiFePO _4, LiCoO ₂ , LiNiO _{2 and the} like can be selected as the positive electrode active material of the noble negative potential type secondary battery. Any of the materials used as the positive electrode active material of the lithium ion battery can be used.

The electrode structure according to the present invention can also be applied to a capacitor. In this case, only the negative electrode active material is an active material based on an electrochemical redox reaction, and is a material that is non-electron conductive until it is electrochemically reduced in the charging direction (for example, Li ₄ Ti ₅ O ₁₂ or TiO ₂ or the like), and the negative electrode active material constitutes a non-electron conductive negative electrode active material layer, and the negative electrode active material layer is interposed between a positive electrode active material layer comprising graphite or activated carbon as a positive electrode active material and a separator Make them face each other. The electrode structure of the conventional capacitor is the same as that of the conventional secondary battery, and the positive electrode active material layer and the negative electrode active material layer are both electronically conductive, so that they are opposed to each other via a separator.

  Furthermore, the present invention can be applied to a lithium ion battery having a negative electrode made of carbon that can be doped / undoped with lithium ions if a non-electron conductive positive electrode active material is selected to form a non-electron conductive positive electrode active material layer. You can also

  A battery with a large output density (V · A = W / L) is a battery that can be discharged with a large current while maintaining a high voltage. Generally, a battery is discharged between a positive electrode and a negative electrode when discharged with a large current. Depending on the current density, there is a concentration difference in the ions involved in the electrode reaction, and the battery voltage drops due to concentration polarization based on the difference in ion concentration. Therefore, a battery with a small voltage drop due to such concentration polarization is a battery with a high output density.

For example, in the discharge of an organic electrolyte battery using an electrolyte solution in which LiPF ₆ is dissolved, Li ⁺ ions are released from the negative electrode active material at the negative electrode, and Li ⁺ ions are taken into the positive electrode active material at the positive electrode. the inner between anode and cathode Li ⁺ and PF ₆ ^- electricity carried by. At this time, when Li ⁺ and PF ₆ ⁻ carry electricity, that is, when the ion transport number is t ⁺ and t ⁻ , respectively, the relationship is t ⁺ + t ⁻ = 1, and on the negative electrode side, the transport number of PF ₆ ⁻ t ^- high amount corresponding Li ⁺ ion concentration (anion transference number of ions) (electrolyte concentration), an amount corresponding Li ⁺ ion concentration transport number of the anion (electrolyte concentration) is thin in the positive electrode side,斯Concentration polarization based on the difference in electrolyte concentration depresses the discharge voltage. Conversely, in charging, the Li ⁺ ion concentration is light on the negative electrode side, the Li ⁺ ion concentration is high on the positive electrode side, and the concentration polarization increases the charging voltage, so that it is difficult to charge.

  FIG. 8 is a schematic diagram illustrating a mechanism of occurrence of a difference in electrolyte concentration in an organic electrolyte battery.

FIG. 8 is a schematic diagram showing the mechanism of the occurrence of a difference in electrolyte concentration in the discharge of the organic electrolyte battery when the transport number of Li ⁺ ions is assumed to be 0.5. As shown in FIG. 8, when eight Li ⁺ ions are released into the electrolyte at the negative electrode, eight electrons (e ⁻ ) reach the positive electrode via an external circuit, but at the same time, four electrons in the battery Li ⁺ ions and four PF ₆ ⁻ ions carry electricity, and eight Li ⁺ ions are taken from the electrolyte in the positive electrode.

Therefore, in this case, the negative electrode near the four Li ⁺ ions and four PF ₆ ^- increased ion, four Li ⁺ ions and four PF ₆ in vicinity of the positive electrode ^- it can be seen that ions is reduced. That is, when an organic electrolyte battery using the LiPF ₆ solution as an electrolyte is discharged, the LiPF ₆ concentration increases near the negative electrode, and the LiPF ₆ concentration decreases near the positive electrode. From this, the present inventor has found that the discharge current density i (A / cm ² ) is i = 2 × F × D × C ^* / (d × t ⁻ ) in the large current discharge of the organic electrolyte secondary battery. The theoretical formula that it is related was derived. Where F is the Faraday constant (c / mol), D is the diffusion coefficient (cm ² / s), C ^* is the concentration of the electrolyte used in the battery (mol / cm ³ ), d is the distance between electrodes (cm), t ^- is the transport number of negative ions. For convenience of explanation, “cm” is used as a unit indicating the length, but other units such as “m” may be used.

In an organic electrolyte solution in which a lithium salt is dissolved, Li ⁺ ions are solvated and have a large ion radius, so that they are difficult to move. Generally, the transport number of Li ⁺ ions is 0.5 or less, and an anion The transport number is 0.5 or more. Therefore, in the charge / discharge of the organic electrolyte secondary battery, the electrolyte concentration differs according to the charge / discharge current (current density) by the above-described mechanism between the negative electrode side and the positive electrode side, and the concentration polarization due to the difference in the electrolyte concentration Boosts the battery charge voltage and lowers the discharge voltage. Therefore, in order to obtain a battery with a large output density, it is an effective means to reduce the current density in charge / discharge by increasing the electrode area.

In addition, since the difference in electrolyte concentration caused by the Li ⁺ ion transport number is alleviated by the diffusion of electrolyte ions, it is also effective to make the battery with a high output density close to the distance between the positive electrode and the negative electrode. . When the distance between the positive electrode and the negative electrode is shortened, the concentration gradient is increased and the ion diffusion rate is increased.

  In the electricity storage device according to the present invention, since no separator is interposed between the positive electrode and the negative electrode, the distance between the positive electrode and the negative electrode is extremely close, and the concentration gradient of the electrolyte solution between the positive electrode and the negative electrode is increased, so that the ion diffusion rate is increased. That is, a secondary battery with high output density is obtained.

  Also, in conventional batteries, if the electrode area is increased by significantly reducing the electrode thickness, the amount of separator and current collector increases in proportion to the electrode area, so the amount of active material directly involved in the battery reaction However, since the separator according to the present invention does not intervene, only the current collector increases in proportion to the electrode area, and the capacity density (Wh / L) decreases. ).

  In the power storage device according to the present invention, the electrode can be made in the form of a sheet by solidifying the active material with a binder or the like and forming an active material layer on the current collector, as in the conventional battery. In the storage element, the positive electrode and the negative electrode can be formed by stacking a plurality of opposing electrodes so that the active material layers face each other without interposing a separator, and a sheet-like strip electrode is interposed via a separator. Alternatively, the active material layers may be opposed to each other and closely contacted to form a spiral wound body. If such a storage element is impregnated with an electrolytic solution and sealed in a container, the storage device according to the present invention is completed.

  An object of the present invention is to provide a new electrode structure for obtaining a large maximum power density (W / L), and the thickness of the active material layer in the present invention is 0.030 mm or less on one side as seen from the relationship of FIG. It is preferable to make it 0.020 mm or less.

When the present invention is applied to a noble negative electrode potential type secondary battery, it is a substance having an oxidation-reduction potential in the range of 0.5 to 2.5 V (vs Li / Li ⁺ ) and is electrochemically reduced. Until then, it is desirable to select a negative electrode active material from materials that are non-electron conductive.

  The non-electron conductive active material selected in the present invention is desirably good electron conductivity in a charged state, but as a candidate for such an active material, titanium oxide, lithium titanium oxide, lithium iron oxide, etc. There is.

  In order to increase the output density (W / L) of a battery, it is an effective means to shorten the distance between electrodes and increase the electrode area. As described above, in the electrode structure according to the present invention, Compared to the electrode structure, since no separator is interposed, not only the distance between the electrodes is shortened, but particularly when the thickness of the electrode is reduced, the electrode area that can be secured is remarkably increased. It is effective in making a battery having a high L). In addition, since an expensive separator is not used, particularly when the electrode area is remarkably increased, there is no significant increase in material cost due to an increase in the number of separators.

  As described above, according to the present invention, an organic electrolyte secondary battery having a high output density can be supplied at low cost. Therefore, for HV mounting in which a battery having a particularly high output density (W / L) is required, Since a safe and inexpensive secondary battery can be provided, its industrial value is great.

  Hereinafter, the present invention will be described in more detail with reference to examples.

In this example, spinel lithium manganese oxide (LiMn ₂ O ₄ ) is used as the positive electrode active material, and spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) is used as the negative electrode active material. A noble negative electrode potential type secondary battery having an output performance matching that of the battery for manufacturing was prepared.

LiMn ₂ O ₄ was prepared by calcining a mixture of manganese dioxide and lithium carbonate in air at 850 ° C., and adjusting by a conventional synthesis method. However, the LiMn ₂ O ₄ synthesized here agrees well with the diffraction pattern of spinel type LiMn ₂ O _{4 in} X-ray diffraction. It is thought that Li _1.05 Mn _1.95 O ₄ substituted with lithium.

90 parts by weight of the synthesized LiMn ₂ O ₄ was wet mixed with 3 parts by weight of carbon black, 4 parts by weight of graphite, and 3 parts by weight of polyvinylidene fluoride as a binder together with N-methyl-2-pyrrolidone as a solvent to obtain a paste-like slurry. To do. The slurry is applied uniformly to a coating width of 210 mm and dried on one side of an aluminum foil having a thickness of 0.011 mm and a width of 250 mm using the slurry as a current collector, leaving uncoated portions of 20 mm at both ends. The other surface is coated and dried with the same specifications to form an active material layer on both sides of the aluminum foil, and further pressed with a roller press to have a thickness including the active material layer and the current collector of 0.00. A 031 mm sheet-like electrode was obtained.

  The sheet-like electrode has a vertical width of 130 mm and a horizontal width of 220 mm including the 20 mm uncoated part at one end, and the active material coated part has a dimension of 200 mm wide and 130 mm long as a rectangular positive electrode Prepared. An insulating tape with a width of 10 mm is stretched on the 20 mm uncoated portion at one end of the prepared positive electrode following the active material coated portion.

Next, spinel-type lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) used as the negative electrode active material is well mixed with lithium hydroxide (LiOH) and titanium dioxide (TiO ₂ ) in a molar ratio of 4: 5 to form a pellet. It was pressure-molded, put into an alumina container covered with nickel foil, and baked at 800 ° C. in a helium atmosphere for synthesis. The XRD pattern of the composite had no unreacted TiO _{2 and} was a Li ₄ Ti ₅ O ₁₂ monolayer. Moreover, in the SEM photograph (magnification 6600) of the synthesized product, it was confirmed that primary particles of about 0.2 to 1 μm gathered to form secondary particles of about 3 to 10 μm.

The synthesized Li ₄ Ti ₅ O ₁₂ was wet mixed with N-methyl-2-pyrrolidone as a solvent together with 3 parts by weight of polyvinylidene fluoride having 97 parts by weight of the binder as a paste slurry. The slurry is applied uniformly to a coated width of 210 mm on one side of an aluminum foil having a thickness of 0.011 mm using the slurry as a current collector, leaving uncoated portions of 20 mm at both ends, and dried.

  Then apply to the other side with the same specifications and dry, but with one part applied, pass through a roller press to adjust the thickness to 0.024 mm, and the active material layer only on one side of the current collector In the case of a sheet-like electrode formed on the both sides, the sheet-like electrode in which the thickness was adjusted to 0.037 mm with a roller press and the active material layer was formed on both sides of the current collector. It was.

  The sheet-like electrode with the active material layer formed on one side and both sides is trimmed to 140 mm in length and 230 mm in width including the 20 mm uncoated part at one end. Was prepared as a rectangular sheet-like negative electrode having a width of 210 mm and a length of 140 mm.

  First, prepare the positive and negative electrodes so that the uncoated part of the current collector is opposite to the negative electrode on the active material layer of the negative electrode on which the active material layer is formed only on one side of the current collector. A positive electrode active material layer having an active material layer formed on both sides of the body is adhered and overlapped. At this time, the positive electrode is overlapped so that the end of the negative electrode comes to the middle position of the insulating tape affixed to the unapplied part of the positive electrode current collector. It overlaps at a position where about 5 mm is left. In the electrode longitudinal width direction, both ends of the negative electrode protrude from the positive electrode end by 5 mm and overlap. Next, on the active material layer of the positive electrode, the non-coated portion of the current collector is opposite to the positive electrode, and the end of the negative electrode is positioned in the middle of the insulating tape affixed to the non-coated portion of the positive electrode current collector. The negative electrode active material layer having the active material layer formed thereon is closely adhered and stacked on both sides of the current collector.

  In the same manner, the positive electrode and the negative electrode are alternately stacked, and the negative electrode in which the active material layer is formed on only one side is again stacked on the 44th positive electrode with the active material layers in close contact with each other. An uncoated portion is welded to an electrode tab, and an electrode element similar in structure to the laminate shown in FIGS.

  After the assembled electrode element is sufficiently dried, it is placed in a laminating sheet of aluminum and polypropylene that has been drawn into a dish shape with a vertical width of 145 mm, a horizontal width of 240 mm, and a depth of 3.0 mm, and the same kind of laminated sheet is stacked on the periphery. Heat-sealing leaving

  The electrode tab welded to the current collector of each electrode is taken out from between the two laminate sheets, but the electrode tab has a special tape affixed to the part located in the heat-sealed part. Is integrally heat-sealed with two laminate sheets.

In the electrode element, a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) in which 1 mol / L LiPF ₆ is dissolved is injected as an electrolytic solution from an unfused portion of the laminate sheet, and impregnated with vacuum. Finally, if the unfused portion of the laminate sheet is thermally fused, a noble negative potential type secondary battery having a battery volume of 115 cc is completed with the battery structure shown in FIG.

Comparative example

  In this comparative example, the noble negative electrode potential type secondary battery produced in the example was produced with a conventional electrode structure, and the performance of the battery according to the present invention was compared. The noble negative electrode type secondary battery produced in this comparative example was produced with the same electrode thickness and the same volume of the electricity storage element as in the example.

  Since the separator is used in the conventional electrode structure, the number of electrodes is smaller than that in the above embodiment when the same volume of the storage element is composed of the same size electrodes. Since a separator of 25 μm is used in this comparative example, if the positive electrode and the negative electrode are each composed of 22.5 electrodes, the volume is almost the same as in the example. However, the 0.5 electrode means an electrode in which an active material layer is formed only on one side of the current collector.

  First, the positive electrode is manufactured with the same specifications as in the examples, but in addition to the positive electrode in which the active material layer is formed on both sides of the current collector, a positive electrode in which the active material layer is formed only on one side of the current collector is also prepared. Since a separator is used in this comparative example, it is not necessary to put an insulating tape on the uncoated portion of the positive electrode current collector. As in the embodiment, a sheet-like positive electrode having a width of 200 mm and a length of 130 mm is prepared for the active material application portion.

As the negative electrode active material, Li ₄ Ti ₅ O ₁₂ synthesized in the examples is used. However, since the separator is used in this comparative example, the negative electrode active material layer does not need to be non-electron conductive. On the contrary, in order to obtain a battery having high output performance, it is advantageous to form a negative electrode active material layer having an electron conductivity by mixing a conductive auxiliary agent with the negative electrode active material.

Therefore, in the production of the negative electrode, 3 parts by weight of carbon black and 4 parts by weight of graphite are added to 90 parts by weight of Li ₄ Ti ₅ O ₁₂ and mixed well, and further, N as a solvent together with 3 parts by weight of polyvinylidene fluoride as a binder. -Wet mixed with methyl-2-pyrrolidone to form a paste slurry.

  On one side of an aluminum foil having a thickness of 0.011 mm using this slurry as a current collector, it is uniformly applied with a coating width of 210 mm, leaving an uncoated part of 20 mm on both ends, and then dried, and then a part of the single-sided electrode For this reason, the other side is coated with the same specifications and dried.

  The sheet-like electrode in which the active material layer is formed only on one side of the current collector is adjusted to a thickness of 0.024 mm with a roller press, and the sheet-like electrode in which the active material layer is formed on both sides of the current collector is a roller. The thickness is adjusted to 0.037 mm with a press.

  The sheet-like electrode on which the active material layer is formed on one side and both sides has a vertical width of 130 mm and a horizontal width of 220 mm including the 20 mm uncoated part at one end, and the dimensions of the active material coated part. A rectangular sheet-like negative electrode having a width of 200 mm and a length of 130 mm is prepared.

  The positive electrode and the negative electrode prepared as described above are obtained by first stacking a 25 μm-thick porous polypropylene separator on the surface of the active material layer of the positive electrode in which the active material layer is formed on one surface of the current collector, and further on the current collector. The negative electrode on which the active material layer is formed is overlapped on both sides of the current collector so that the uncoated portion is opposite to the left and right sides of the positive electrode. Furthermore, a positive electrode in which a separator having a thickness of 25 μm is stacked on the active material layer surface of the negative electrode, and an active material layer is formed on both sides of the current collector, and an uncoated portion of the current collector is placed on the same side as the other positive electrodes. Align and layer.

  Similarly, 25.5 positive electrodes and 25.5 negative electrodes are alternately stacked with a separator interposed therebetween, and active material layers of the positive electrode and the negative electrode are stacked to face each other with a separator interposed therebetween. The uncoated portion of the current collector of each electrode is welded to the electrode tab, and an electrode element similar to the laminate shown in FIG.

  After the assembled electrode element is sufficiently dried, it is placed in a laminating sheet of aluminum and polypropylene that has been drawn into a dish shape with a vertical width of 145 mm, a horizontal width of 240 mm, and a depth of 3.0 mm, and the same kind of laminated sheet is stacked on the periphery. Heat-sealing leaving

  The electrode tab welded to the current collector of each electrode is taken out from between the two laminated sheets in the same manner as in the embodiment and becomes an external terminal.

A mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) in which 1 mol / L LiPF ₆ is dissolved as an electrolytic solution is injected into the electrode element from an unfused portion of the laminate sheet, and impregnated in a vacuum. Finally, if the unheated portion of the laminate sheet is heat-sealed, a noble negative potential type secondary battery is completed with the same structure as the battery shown in FIG. The battery volume is 115 cc as in the battery of the example.

[Performance evaluation test]
The batteries produced in the examples and comparative examples were each charged and discharged for the first time after passing an aging period of 24 hours for the purpose of stabilizing the inside of the battery. In any of the batteries, the charge upper limit voltage was set to 3.0V, the battery was charged for 8 hours, and the discharge was performed to a final voltage of 2.0V by 4A constant current discharge. The results are shown in FIG. 9, and the discharge time is 94 minutes for the battery of the example, 53 minutes for the battery of the comparative example, and the discharge capacities are 6.3 Ah and 3.6 Ah, respectively.

  FIG. 9 is a diagram showing a discharge curve at the time of 4 A constant current discharge of the battery according to the embodiment of the present invention and the conventional battery. FIG. 10 is a diagram showing discharge curves at the maximum output of the battery according to the embodiment of the present invention and the conventional battery.

  As shown in FIG. 9, the average discharge voltage is about 2.45 V, and the energy density of the battery of the example is 134 Wh / L, whereas the battery of the comparative example is 77 Wh / L.

  Subsequently, the charging upper limit voltage was set to 3.0 V again for all the batteries, charging was performed for 8 hours, and the battery was discharged at a constant current of 70 A up to a final voltage of 1.8 V. The battery was 307 seconds, and the battery of the comparative example was 110 seconds.

  In the constant current discharge of 70 A, the average discharge voltage of the battery of the comparative example is about 2.2 V, and the average discharge output is 154 W. As described above, if the maximum output density (W / L) is defined as a value obtained by dividing the maximum output sustainable for 120 seconds by the unit cell volume by the unit cell volume, the maximum output density (W / L) of the battery of the comparative example is defined. ) Is 154 ÷ 0.115 or less, that is, 1340 W / L or less, which is far from the level of the HV mounting standard as shown in FIG.

  On the other hand, the battery of the example was subjected to a discharge test from a fully charged state to a final voltage of 1.8 V, further increasing the discharge current value. As a result, the discharge time was 120 seconds with a constant current discharge of 160 A. The average discharge voltage in the constant current discharge of 160 A of the battery of the example is about 2.2 V, and the average discharge output is 352 W. Therefore, the maximum output density (W / L) of the battery of the example is 352 / 0.115, that is, 3060 W / L, and sufficiently satisfies the HV mounting standard as shown in FIG.

  As described above, when the present invention is applied to a noble negative electrode type secondary battery, the energy density is 134 Wh / L, which is 50% or more of the energy density (250 Wh / L) of the original lithium ion battery. The power density (W / L) also sufficiently satisfies the HV mounting standard (2500 W / L).

Among existing batteries, a lithium iodine battery (Li / i ₂ battery) that has been put to practical use as a battery for cardiac pacemakers is the only battery that does not require a separator. The Li / i ₂ battery is a solid electrolyte battery that uses metallic lithium (Li) as the negative electrode active material and iodine (i ₂ ) as the positive electrode active material, but the negative electrode Li and the positive electrode i ₂ are in contact with each other. For example, lithium iodide (Lii) is generated at the interface, and the positive electrode and the negative electrode are made conductive by ionic conduction by Lii, and electronic conduction is blocked, so that the battery functions as a battery.

Thus, the Li / i ₂ battery is the same as the battery according to the present invention in that a separator is unnecessary, but the battery according to the present invention is fundamentally different from the Li / i ₂ battery in the following points.

First, the Li / i ₂ battery is a solid electrolyte battery, which is a primary battery, and there is no uncharged active material when the battery is assembled. On the other hand, the power storage device according to the present invention is a secondary battery or a capacitor, and all active materials are in an uncharged state when the device is assembled. Therefore, what prevents electronic conduction between the positive electrode and the negative electrode in place of the separator is a reaction product of the positive electrode active material and the negative electrode active material in the Li / i ₂ battery, and is not charged in the power storage device according to the present invention. It is an electron conductive active material layer.

Non-electron conductive (insulating) materials often have different valence atoms (eg, T ⁺⁴ and Ti ⁺³ , Fe ⁺³ and Fe ⁺²⁾ that can exchange electrons once oxidized or reduced in the charge direction. ) Coexist in the crystal, and many of them change to electronic conductivity. However, even if reduced or oxidized in the discharge direction, it is difficult to electrochemically reduce or oxidize until all atoms have the same valence, and atoms with different valences still coexist in the crystal. Therefore, in many cases, the electron conductivity is maintained and the original non-electron conductive material does not return.

  In the present invention, it is rather advantageous that the active material once charged and changed to electronic conductivity remains electronically conductive even when discharged, that is, does not return to the original non-electron conductive material. In other words, in the present invention, the active material that changes to electronic conductivity by the first charge always plays a role of contributing to charge and discharge, so that it is positive that it is electron conductive, and is uncharged, non-electron conductive. The active material as it is always plays a role of preventing electronic conduction between the positive electrode and the negative electrode (separator role), so that non-electron conductivity works positively.

  In general, a separator used in an organic electrolyte battery is a special thin porous membrane and is very expensive. However, especially when the electrode facing area is increased, the price of the separator greatly increases the material cost. Since the battery according to the present invention does not require the use of such a special porous membrane for the separator, an inexpensive high-power organic electrolyte secondary battery can be provided.

  As mentioned above, although embodiment of this invention was described, the said embodiment showed one of the application examples of this invention, and in the meaning which limits the technical scope of this invention to the specific structure of the said embodiment. Absent. Various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Negative electrode active material layer 2 Positive electrode active material layer 3 Negative electrode current collector 4 Positive electrode current collector 5 Separator 6 Negative electrode tab 7 Positive electrode tab 8 Insulating tape 9 Plastic tape 10 Power storage element 11, 12 Laminate sheet 13 Negative electrode external terminal 14 Positive electrode external terminal 31 Negative electrode 32 Positive electrode 33 Opposite surface

Claims (5)

  In the power storage device in which the active material layers of the positive electrode and the negative electrode face each other, each of the positive electrode and the negative electrode is formed in close contact with a current collector, and the active material layer of the positive electrode facing the positive electrode and the negative electrode A power storage device, wherein the power storage device is in close contact with an active material layer of a negative electrode on an opposing surface.   The power storage device according to claim 1, wherein at least one of the active material layers in close contact with each other on the opposite surface is non-electron conductive in an uncharged state. The active material layer that is non-electron conductive in an uncharged state is composed of an active material based on an electrochemical redox reaction,
The power storage device according to claim 2, wherein the active material is selected from materials that are non-electron conductive until electrochemically oxidized or reduced in a charging direction.   The active material layer of the positive electrode and the active material layer of the negative electrode are cut off from electronic conduction by an uncharged non-electron conductive active material layer located on the opposing surface. The power storage device according to 1.   5. The power storage device according to claim 4, wherein a chargeable capacity of the non-electron conductive active material layer is larger than a chargeable capacity of an active material layer facing the non-electron conductive active material layer. apparatus.

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