WO2014087895A1

WO2014087895A1 - Accumulation device, hybrid vehicle, and electric vehicle

Info

Publication number: WO2014087895A1
Application number: PCT/JP2013/081895
Authority: WO
Inventors: 亨永浦
Original assignee: 永浦敦子; 永浦千恵子
Priority date: 2012-12-03
Filing date: 2013-11-27
Publication date: 2014-06-12

Abstract

With an accumulation device according to the present invention, facing surfaces of facing active material layers of a positive electrode and a negative electrode are in close contact with each other. At least one of these active material layers which are in close contact with each other with the facing surfaces is non-electron conductive in a non-charged state, and thus, there is no need for a separator as an additional member to be disposed therebetween. Thus, it is possible, with the accumulation device according to the present invention, to increase electrode area efficiency by reducing the electrode thickness, thereby allowing alleviating energy density deterioration and increasing I/O density.

Description

Power storage device, hybrid vehicle and electric vehicle

The present invention relates to a power storage device and a hybrid vehicle or an electric vehicle equipped with the same. Specifically, the present invention relates to a safe and high-capacity, high-input / output power storage device, a safe and excellent fuel efficiency hybrid vehicle, and a safe and quick-chargeable electric vehicle.

In recent years, hybrid vehicles (hereinafter referred to as “HV”) are rapidly spreading in Japan due to their excellent environmental performance and fuel efficiency performance. In addition, with the advent of lithium ion secondary batteries, electric vehicles such as electric vehicles (hereinafter referred to as “EV”) and electric motorcycles (hereinafter referred to as “EB”) have been put into practical use and are commercially available for general users. Began to be.

大型 Large power storage devices play an important role in securing the excellent fuel economy performance of hybrid vehicles and sufficient cruising range of electric vehicles. As a large power storage device, there are a secondary battery using an electrochemical redox reaction of a substance and a capacitor using a power storage function by an electric double layer. Note that a power storage device that uses an electrochemical redox reaction for one of the positive electrode and the negative electrode and a power storage function by an electric double layer for the other is called a capacitor.

For example, in HV, electric power is supplied to the motor from the installed power storage device when starting, running at a low speed, or suddenly accelerating, and the motor assists in driving the engine to increase the operating efficiency of the engine. Therefore, the higher the power supply capability of the power storage device, the higher the engine operating efficiency.

Therefore, it is desirable to mount a power storage device with as much power supply capability as possible in HV, but the space for mounting the power storage device is strictly limited because it is greatly related to the number of seats in the car, the space in the luggage compartment, and the like. Therefore, a high output density (W / L) is required for the next-generation HV mounting power storage device. Of course, ensuring the safety of the power storage device is an essential condition.

On the other hand, since the EV has a short charge travel distance (distance that can be traveled by one charge), it is desirable that the power storage device mounted on the EV can be recharged as quickly as possible. A high input density (W / L) is required for a power storage device that can be charged in a short time. The output density and the input density of the power storage device are in an integrated relationship, and a power storage device having a high output density (W / L) generally has a high input density (W / L). Note that the input / output density (W / L) of a power storage device is a value obtained by dividing the charge input or discharge output of the power storage device by the volume of the power storage device.

Against this background, research on lithium-ion secondary batteries is being actively conducted with the aim of realizing a power storage device having a high input / output density (W / L). Incidentally, the lithium ion secondary battery was successfully put into practical use in 1990 by the inventors of the present application and named the lithium ion secondary battery (see Non-Patent Document 1 and Non-Patent Document 2).

A lithium ion secondary battery (hereinafter also referred to as a lithium ion battery) is a secondary battery in which a substance that allows lithium ions (Li ⁺ ) to enter and exit electrochemically is disposed on both the positive electrode and the negative electrode. It moves from the positive electrode to the negative electrode, and returns to the positive electrode from the negative electrode during discharge. Here, the amount and speed of lithium ions that move during charging correspond to the charge capacity (Ah) and the charging speed, respectively, and the amount and speed of lithium ions that move during discharging correspond to the discharge capacity (Ah) and the discharge speed, respectively. Equivalent to.

In the lithium ion battery first put into practical use by the inventors of the present application, the positive electrode is lithium cobaltate (Li _1-X CoO ₂ ) and the negative electrode is carbon doped with lithium (hereinafter referred to as Li _X C). . Since Li _X C is very close to metallic lithium in terms of potential (in other words, extremely low in potential), lithium ion batteries using carbon as a negative electrode are characterized by a high operating voltage. However, on the other hand, Li _X C has a strong tendency to react with the organic electrolyte, and it is difficult to ensure safety.

In the present specification, such a lithium ion battery having Li _X C as a negative electrode is hereinafter referred to as a “base negative potential type lithium ion battery” or simply a “base negative potential type battery”. When the battery temperature rises due to high power discharge, etc., especially when the temperature rises to 60 ° C or higher, the reaction between Li _X C and the organic electrolyte becomes intense, and the battery runs out of heat. This can lead to abnormal heat generation and fire accidents. Incidentally, a phenomenon in which the increased temperature inside the battery further accelerates the chemical reaction due to heat generated by the chemical reaction in the battery and the amount of generated heat increases rapidly is called thermal runaway of the battery.

The base negative potential type lithium ion batteries currently used are roughly classified into medium and light load specifications and heavy load specifications. The medium and light load specifications are used as a power source for many electronic devices such as mobile phones and notebook computers, and an extremely large output is not required. Therefore, the battery temperature is generally controlled by natural heat dissipation.

On the other hand, in heavy load type batteries mounted on EVs and HVs, the battery temperature tends to rise with a large output required during acceleration and the like. Therefore, it is necessary to control the battery temperature by forcibly cooling it. In particular, since the battery mounted on the HV has a large required discharge output (W / L) per battery volume, the calorific value (J / L) per battery volume is also large, and the battery temperature tends to rise.

Therefore, for example, in a commercial HV equipped with a base negative potential type lithium ion battery, the battery is mounted 5o forward and the cooling effect is enhanced by efficiently applying the wind introduced from the outside. There is something that has been made.

In recent years, abnormal weather, which seems to be associated with global warming, has frequently occurred in various parts of the world, so HV and EV with excellent environmental performance have spread and expanded in place of existing gasoline vehicles with high CO ₂ emissions. It is strongly desired to go. Therefore, a safe and high input / output density (W / L) power storage device is required for better HV and EV.

However, when the input / output density (W / L) of the base negative electrode potential type lithium ion battery is further increased, further ingenuity is required to keep the battery temperature at 60 ° C. or less, and it becomes more difficult to ensure safety. Therefore, from the viewpoint of ensuring safety, it is necessary to examine options for other highly safe power storage systems for next-generation power storage devices mounted on HVs and EVs.

As a highly safe power storage system, a lithium ion battery using a negative electrode active material as a material having no ability to reduce an organic electrolyte solution, that is, a noble material having a redox potential has been proposed. However, a lithium ion battery that uses a noble material having a redox potential as a negative electrode active material is highly safe, but has a low operating voltage.

Such a lithium ion battery using a noble material having a redox potential as a negative electrode active material is hereinafter referred to as a “noble negative electrode potential type lithium ion battery” or simply a “noble negative electrode potential type battery”. Be

Many noble negative electrode potential type lithium ion batteries have been proposed so far (see, for example, Patent Documents 1 and 2). However, the energy density (Wh / L) of any noble negative electrode type battery is low because the operating voltage is low. Is low. Therefore, noble negative electrode type batteries can be expected to have high safety, but have not yet been put into practical use. Note that the energy density (Wh / L) of the power storage device is an energy amount (J / L) that can be stored per unit volume of the power storage device, and is 1 Wh = 3.6 kJ (kilojoules).

US Pat. No. 5,284,721 Japanese Patent Laid-Open No. 08-236115

As a candidate for a power storage device to be mounted on a next-generation HV or EV, a noble negative potential type lithium ion battery is difficult to throw away from the viewpoint of ensuring safety. However, power storage devices mounted on HVs and EVs are required to have high output performance, rapid charging performance, etc. in addition to safety. There is no technology in the past that adds high output performance and fast charging speed to the power storage device without sacrificing other characteristics.

Considering the acceleration frequency of HV, climbing time, etc., the large output required for the HV power storage device must be a sustainable output, not an instantaneous output. Here, when the sustainable maximum output (W / L) per volume of the power storage device is defined as “maximum power supply capacity (W / L)”, this value depends on the selection of the sustainable time. For example, the maximum output sustainable for a few minutes is naturally less than the maximum output sustainable for a few seconds.

Therefore, in this specification, the “maximum power supply capacity (W / L) of the HV power storage device” is defined as “the maximum output density that can be supplied continuously for 120 seconds”. The “maximum output density (W / L)” of the power storage device generally means an instantaneous maximum output per volume of the power storage device, and in this specification, the maximum power supply capacity (W / L). L) is handled separately.

In a negative and negative electrode type battery mounted on a current commercial HV, the maximum power supply capacity (W / L) is approximately 2500 W / L on a unit cell basis. In order to increase the maximum power supply capacity (W / L), it is generally necessary to reduce the electrode thickness and increase the electrode area (prior art).

However, in this case, the energy density (Wh / L) decreases. The reason is that as the electrode area is increased, the filling ratio of the sheet-like separator or current collector that does not directly contribute to the electricity storage reaction increases, and therefore the energy density (Wh / L) decreases. In addition, a sheet-like separator is a sheet-like porous film interposed between a positive electrode and a negative electrode in a conventional electrode structure. Hereinafter, this is simply referred to as a “separator body”.

Actually, the energy density is reduced to about 120 to 150 Wh / L in the negative electrode potential type battery mounted on the current commercial HV.

However, this suggests that the energy density (Wh / L) does not necessarily have to be large if the maximum power supply capacity (W / L) satisfies the standard of 2500 W / L or more for the HV-mounted power storage device. ing. Therefore, a noble negative electrode potential type lithium ion battery that can be expected to have high safety can be a promising candidate for a next-generation HV-installed power storage device if the maximum power supply capability (W / L) can achieve 2500 W / L or more.

Therefore, once again, let's look at the problem of a noble negative electrode potential type lithium ion battery as a power storage device for next-generation HV.

The voltage of the noble negative electrode type battery is lower than that of the base negative electrode type battery. This low voltage is greatly related to the maximum output and, in turn, the “maximum power supply capacity”. 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.

If the noble negative electrode potential type lithium ion battery and the base negative electrode potential type lithium ion battery have the same electrode structure, the same electrode area, and the same electrolytic solution, the internal resistance r of both is approximately the same level. Become.

However, the open circuit voltage V ₀ of the battery is a difference between the electrode potentials of the positive electrode active material and the negative electrode active material, and the open circuit voltage V ₀ is naturally lower in a noble negative electrode type battery using a negative electrode active material having a noble electrode potential. . Therefore, the maximum output of the noble negative potential type battery is considerably smaller than the base negative potential type battery because it is proportional to the square of the ratio of the open circuit voltage.

For example, in the case of a noble negative electrode potential type lithium ion battery having an open circuit voltage V ₀ of about 2.5 V, the same electrode structure as that of a base negative electrode potential type lithium ion battery (open circuit voltage V ₀ = 3.7 V) mounted on the current HV If produced with the same electrode area, the maximum output density (W / L) of the noble negative potential type battery is only 45.7% of the base negative potential type battery. Therefore, if the maximum output density (W / L) of the noble negative electrode type battery is increased by the conventional technique, it is a reliable method to reduce the electrode thickness and increase the electrode area.

Now, in order to make the maximum output density (W / L) of a noble negative electrode type battery having an open circuit voltage V ₀ of about 2.5 V at the same level as the base negative electrode type battery, at least the electrode area is the base negative electrode type. The battery needs to be (3.7 / 2.5) ² times, that is, 2.19 times.

On the other hand, it is a condition that the maximum power supply capacity (W / L) is 2500 W / L or more for the HV-mounted power storage device. The “maximum power supply capacity (W / L) of the HV power storage device” is defined as “the maximum output density that can be supplied continuously for 120 seconds”. Therefore, realizing the maximum power supply capacity (W / L) of 2500 W / L or more means that the energy density (Wh / L) calculated by 120 seconds of discharge (discharge of 30 C or more) is 2500 W / L × 120 sec = 83 Wh. / L or more.

In general, notations such as 1C discharge, 10C discharge, and 30C discharge mean rate discharge for 60 minutes (1 hour), rate discharge for 6 minutes (1/10 hour), and rate discharge for 2 minutes (1/30 hour), respectively. .

Usually, the energy density of a lithium ion battery calculated by heavy load discharge of 30 C is about 70% of the energy density calculated by 1 C discharge (1 C discharge standard). Therefore, as for the HV-mounted power storage device, the energy density must not reach the standard of 2500 W / L or more of the maximum power supply capacity unless the energy density is about 83 ÷ 0.70≈120 Wh / L or more in the 1C discharge standard. Become.

Therefore, in order to mount the noble negative electrode potential type lithium ion battery on HV, the energy density (1C discharge standard) must be secured about 120 Wh / L or more.

On the other hand, a noble negative electrode type battery with an open circuit voltage V ₀ of about 2.5 V was fabricated with the same electrode structure and the same electrode area as the base negative electrode type battery (open circuit voltage 3.7 V) mounted on the current HV. Even in this case, since the energy density is proportional to the voltage, the energy density (1C discharge standard) of the noble negative electrode type battery is 68% (100 Wh / L) of the base negative electrode type battery (120 to 150 Wh / L) equipped with the current HV. ) I can only expect to

In other words, it is already about 100 Wh / L with the same electrode area. Here, if the electrode area is 2.19 times in the conventional electrode structure, the filling amount of the separator body that does not directly contribute to the storage reaction becomes 2.19 times or more. The amount of the active material that contributes to the electricity storage reaction is greatly reduced. Therefore, even if the electrode area is increased up to 2.19 times and the maximum power density (W / L) is increased to the same level in the conventional electrode structure, the energy density further decreases, and even 100 Wh / L is significantly lower. It will be.

As described above, unless the energy density is about 120 Wh / L or more on the 1C discharge standard, the standard of 2500 W / L or more of the maximum power supply capacity is not reached. Therefore, for a noble negative potential type battery having an open circuit voltage V ₀ of about 2.5 V, the standard of HV mounting with a maximum power supply capacity of 2500 W / L or more can be satisfied with the conventional electrode structure because the energy density is greatly reduced. Absent.

On the other hand, the base negative electrode potential type battery mounted on the current EV has a maximum output density of about 800 to 900 W / L, which is thicker than the base negative electrode potential battery mounted on the HV. It can be estimated that the electrode area is small.

However, since the volume (about 100 L) of the EV-equipped battery is large, the maximum output of 80 to 90 kW necessary for the acceleration performance of the current EV is secured even at the maximum output density of about 800 to 900 W / L. In contrast to the HV mounting, a large energy density (about 250 Wh / L) is secured by the small electrode area. This energy density determines the current EV charging mileage (shown in the catalog as 200 km).

However, with the current EV charging mileage (distance that can be driven by one charge), there is always a concern about the remaining mileage. Therefore, to make up for this, the development of a rapid charger infrastructure has become an important issue.

On the other hand, if the infrastructure of the quick charger is established, EVs should be strongly desired to be able to recharge in a shorter time even if the charging mileage is moderate. Therefore, a noble negative electrode potential type lithium ion battery that can be expected to have high safety can be a promising candidate for a next-generation EV-mounted power storage device if the rapid charging performance can be improved.

However, increasing the quick charging performance is the same as increasing the maximum power density, as well as reducing the electrode thickness and increasing the electrode area. However, in the conventional electrode structure, the energy density decreases as the electrode area increases.

The present invention has been made in view of the above problems, and provides a new electrode structure capable of obtaining a high input / output density without greatly reducing the energy density of the power storage device, and further applying this structure. An object of the present invention is to provide a safe and high-capacity, high-input / output power storage device, a safe and excellent fuel efficiency hybrid vehicle, and a safe and quick-chargeable electric vehicle.

In order to achieve the above object, a power storage device according to the present invention includes a positive electrode formed by adhering a positive electrode active material layer to a positive electrode current collector, and a negative electrode active material layer adhering to a negative electrode current collector. In the power storage device in which the negative electrode and the electrolytic solution are hermetically sealed in the battery container, the positive electrode active material layer and the negative electrode active material layer face each other and are in close contact with each other. In addition, at least one of the active material layers in close contact with the opposite surface is non-electron conductive in an uncharged state.

Note that an active material in a power storage device is a substance that can directly contribute to a power storage reaction. The active material layer of an electrode in this specification means an electrode layer composed of this active material, but it does not matter whether 100% of the active material in the active material layer contributes to the electricity storage reaction. . For example, the active material may not contribute to the electricity storage reaction in the active material layer located at the electrode end.

Furthermore, in the present specification, "non-electron-conductive" almost means that there is no electron conductivity, more particularly, ^10-10 electronic conductivity at room temperature is generally to be divided into the insulator It means less than S / cm. The term “electron conductivity” as used in the present specification means that the electron conductivity is 10 ⁻¹⁰ S including the range normally classified as a semiconductor (the electron conductivity is about 10 ³ to 10 ⁻¹⁰ S / cm). / cm or more.

In the power storage device according to the present invention, by making at least one of the active material layers in close contact with the opposing surface non-electron conductive, conduction due to electron conduction is cut off even if the opposing active material layers are in contact. In addition, the active material layers facing each other are porous bodies mainly composed of the active material, and can be impregnated with an appropriate amount of electrolytic solution. Therefore, the active material layers facing each other are impregnated in each active material layer. The conduction path by ionic conduction is ensured by the electrolyte. Therefore, the power storage device according to the present invention has a separator function between the active material layers of the positive and negative electrodes facing each other, and there is no need to interpose a separate separator body.

Note that the function of cutting off conduction due to electron conduction between opposing active material layers and securing a conduction path by ion conduction is a “separator function” in the power storage device. In the conventional electrode structure, a separate separator body is interposed between the active material layers facing each other, and this is impregnated with an electrolytic solution to provide a “separator function”.

In the power storage device according to the present invention, since the separator body is not interposed in the electrode stack as the power storage element, the volume V of the electrode stack is equal to V = S × t. Here, S is the total opposing area of the electrodes, and t is the sum of the thicknesses of the opposing electrodes. However, the thickness of both electrodes is the sum of the thickness of each active material layer and the thickness of the current collector, but in the case of an electrode having electrode active material layers formed on both sides of the current collector, This is the sum of the thickness of the active material layer on one side and the thickness of 1/2 of the current collector.

According to the present invention, when the electrode thickness is reduced in the electrode stack having a constant volume, the electrode area S is efficiently increased in inverse proportion to the electrode thickness t due to the relationship S = V / t, and the input / output density is increased. Can be increased. At this time, if the electrode thickness t is reduced, the occupation ratio of the current collector is increased even if the volume of the electrode is unchanged. Therefore, the filling amount of the active material is reduced by the increment of the current collector, and the energy density of the power storage device is Basically it decreases. However, in the power storage device according to the present invention, even if the electrode thickness is reduced, the separator body is not interposed, and therefore the degree of decrease in energy density is small.

On the other hand, in a power storage device having a conventional electrode structure, since a separator body is interposed in an electrode stack that is a power storage element, the volume V of the electrode stack is equal to V = S × (t + ts). Here, ts is the thickness of the separator body.

That is, in the conventional electrode structure, in the electrode stack V having a constant volume, the electrode area is inversely proportional to the sum of the electrode thickness and the thickness of the separator body (t + ts), so even if only the electrode thickness t is reduced, Since the thickness ts of the separator body is constant, the electrode area does not increase efficiently. Further, the volume ratio a of the separator body occupying the volume V of the electrode laminate has a relationship of a = ts / (t + ts), and if the electrode thickness t is reduced, the occupation ratio of the current collector is increased. Thus, the volume ratio a of the separator body also increases. Therefore, in a power storage device having a conventional electrode structure, if the electrode thickness is reduced, the degree of decrease in the energy density of the power storage device is extremely large.

Further, in one power storage device according to the present invention, at least one of the positive electrode and negative electrode active material layers is an active material layer formed in a two-layer structure. The active material layer having the two-layer structure is formed so that the conductive active material layer is in close contact with the current collector, and the second non-electron conductive active material layer is the first conductive layer. It is formed on the active material layer. Also in this case, the one power storage device according to the present invention is based on the electron conduction by the non-electron conductive active material layer in an uncharged state, in which the active material layer of the positive electrode and the active material layer of the negative electrode which are opposed to each other exist. The continuity is cut off.

In the power storage device according to the present invention, the active material layer that is non-electron conductive in an uncharged state changes to an electron conductive active material layer with charging, but charging is completed when charging is appropriately completed. Even at this time, the non-electron conductive active material layer still remains in an uncharged state between the positive electrode active material layer and the negative electrode active material layer. That is, in the power storage device according to the present invention, after the initial charge, the non-electron conductive active material layer that remains in an uncharged state on the opposite surface is cut off from conduction by electron conduction. It is a feature.

In one power storage device according to the present invention, an electrode having an active material layer that is non-electron conductive in an uncharged state has a chargeable current capacity larger than a chargeable current capacity of an opposite electrode. Features.

Thus, in the one power storage device to which the present invention is applied, since the charging is completed when the electrode having the smaller chargeable current capacity is completed, the positive electrode active material layer and the negative electrode active material layer are formed when the charging is completed. In the meantime, it is possible to leave a non-electron conductive active material layer in an uncharged state with an optimum thickness. The active material layer of the positive electrode and the active material layer of the negative electrode facing each other are provided with a separator function by an uncharged non-electron conductive active material layer having an optimum thickness existing on the opposing surface.

Further, in one power storage device according to the present invention, the negative electrode active material constituting the non-electron conductive active material layer is non-electron conductive unless it is electrochemically reduced. Selected from materials that change conductivity. In this case, when the power storage device is charged, the negative electrode active material layer that is non-electron conductive in an uncharged state is also electrochemically reduced sequentially from the negative electrode active material particles that are in close contact with the negative electrode current collector. Since it changes to active material particles, the negative electrode active material layer sequentially changes from the negative electrode current collector side.

In this case, since the potential of the positive electrode is applied to the negative electrode active material particles that are in contact with the positive electrode active material layer on the opposite surface, they are never reduced electrochemically. Therefore, the negative electrode active material particles in contact with the positive electrode active material layer always remain non-electron conductive, and the negative electrode active material layer composed of the non-electron conductive negative electrode active material particles is made electronically conductive. It is located between the changed negative electrode active material layer and positive electrode active material layer, and always functions as a separator.

Also, one power storage device according to the present invention, the negative electrode active material constituting the non-electron conductivity of the active material layer is a lithium titanate represented by the chemical formula Li ₄ Ti ₅ O _12. Li ₄ Ti ₅ O ₁₂ is non-electron conductive unless it is electrochemically reduced, and changes to electron conductivity when it is electrochemically reduced. That is, the negative electrode active material layer composed of Li ₄ Ti ₅ O ₁₂ is non-electron conductive unless charged (electrochemically reduced), and changes to electronic conductivity when charged (electrochemically reduced). To do. Therefore, it is a negative electrode active material suitable for constituting one power storage device according to the present invention.

In the power storage device according to the present invention, the positive electrode active material constituting the non-electron conductive active material layer is non-electron conductive unless it is electrochemically oxidized. Selected from materials that change conductivity. In this case, when the power storage device is charged, the positive electrode active material layer that is non-electron conductive in an uncharged state is also electrochemically oxidized sequentially from the positive electrode active material particles that are in close contact with the positive electrode current collector. Since it changes to active material particles, the positive electrode active material layer sequentially changes from the positive electrode current collector side.

In this case, since the negative electrode potential is applied to the positive electrode active material particles that are in contact with the negative electrode active material layer on the opposite surface, they are never oxidized electrochemically. Therefore, the positive electrode active material particles that are in contact with the negative electrode active material layer always remain non-electron conductive, and the positive electrode active material layer composed of the positive electrode active material particles that remain non-electron conductive has electronic conductivity. It is located between the changed positive electrode active material layer and negative electrode active material layer, and always functions as a separator.

Also, one power storage device according to the present invention, the positive electrode active material constituting the non-electron conductivity of the active material layer is a lithium iron phosphate represented by the chemical formula LiFePO _4. LiFePO ₄ is non-electron conductive unless it is oxidized electrochemically, and changes to electron conductivity if it is electrochemically oxidized to Li _X FePO ₄ (where 0 <x <1). That is, the positive electrode active material layer made of LiFePO ₄ is non-electron conductive unless charged (electrochemically oxidized), and changes to electronic conductivity when charged (electrochemically oxidized). Therefore, it is a positive electrode active material suitable for constituting one power storage device according to the present invention.

In a power storage device having a conventional electrode structure, if the electrode thickness is reduced, the volume ratio of the separator body increases, and thus the degree of decrease in the energy density of the power storage device is extremely large. However, in the power storage device according to the present invention, since a separator body is not interposed in the electrode stack that is a power storage element, the degree of decrease in the energy density of the power storage device is small even when the electrode thickness is reduced, and the electrode If the thickness is reduced, the electrode area increases efficiently in inverse proportion to the electrode thickness. Therefore, according to the present invention, a power storage device with a high input / output density can be realized without greatly reducing the energy density.

In addition, the active material based on the electrochemical oxidation-reduction reaction means a substance that charges and discharges according to “Faraday's Electrolysis Law”. Such a material is electrochemically reduced in the charging direction in the case of the negative electrode active material, and is electrochemically oxidized in the charging direction in the case of the positive electrode active material.

A secondary battery is a power storage device that uses an active material based on an electrochemical redox reaction for both a positive electrode and a negative electrode, and the electrode structure of the present invention can be applied to a secondary battery. Alternatively, a power storage device that uses an active material based on an electrochemical redox reaction for only one of a positive electrode and a negative electrode is classified as a capacitor. The electrode structure of the present invention can also be applied to such a capacitor.

As described above, the power storage device according to the present invention can increase the input / output density by reducing the degree of decrease in energy density. Therefore, if the power storage device according to the present invention is mounted on a hybrid vehicle, the power supply capacity to the motor is high, so that the operating efficiency of the engine increases and the fuel consumption performance increases.

Moreover, if the power storage device according to the present invention is mounted on a 100% motor-driven electric vehicle, it is possible to improve the quick charging performance. The electric vehicle referred to here includes not only EV but also EB and other small and light electric vehicles.

From the viewpoint of ensuring safety, noble negative electrode potential type lithium ion batteries are difficult to throw away as power storage devices for next-generation HVs and EVs. However, conventional technologies sacrifice the energy density of power storage devices greatly. Therefore, it was impossible to add the high output performance and the high charging speed necessary as a power storage device for mounting HV or EV.

However, by applying the present invention to a noble negative electrode potential type lithium ion battery, the input / output density can be increased without greatly sacrificing the energy density, so that it is safe with high output performance and fast charging speed. A highly efficient power storage device can be provided for HV and EV mounting.

It is sectional drawing which shows the positive electrode tab connection part of the electrical storage element which concerns on one Embodiment 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 one Embodiment of this invention, and the arrangement | sequence state of an electrode. It is sectional drawing of the electrical storage apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows the electronic conduction path | route and ion electric path | route ensured by an active material at the time of the initial charge of the battery which concerns on one Embodiment of this invention. It is the electrode schematic diagram which showed the initial charging mechanism of the battery which concerns on one Embodiment of this invention. It is the electrode schematic diagram which showed the initial charging mechanism of the battery which concerns on one Embodiment of this invention. It is the electrode schematic diagram which showed the initial charging mechanism of the battery which concerns on one Embodiment 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 one Embodiment of this invention, and the number of electrode lamination by comparison with the past. It is a figure which shows the discharge curve at the time of 4A constant current discharge of the battery which concerns on one Embodiment of this invention, and a conventional battery. It is a figure which shows the discharge curve at the time of discharge with the maximum electric power supply capability of the battery which concerns on one Embodiment of this invention, and a conventional battery. It is sectional drawing which expanded and showed the negative electrode which comprises the electrical storage element which concerns on one Embodiment of this invention, and the positive electrode facing this.

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 storage element 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 of a power storage device according to an embodiment of the present invention.

1 to 3 are sectional views showing a power storage device 100 (FIG. 3) and a power storage element 10 (FIGS. 1 and 2) according to an embodiment of the present invention. In the power storage element 10, the positive electrode 31 is formed such that the active material layer 2 (hereinafter also referred to as “positive electrode active material layer 2”) is in close contact with the current collector 4 (hereinafter also referred to as “positive electrode current collector 4”). Electrode. In addition, the negative electrode 32 is also formed in such a manner that the active material layer 1 (hereinafter also referred to as “negative electrode active material layer 1”) is in close contact with the current collector 3 (hereinafter also referred to as “negative electrode current collector 3”). Electrode. The power storage element 10 is configured such that the positive electrode active material layer 2 and the negative electrode active material layer 1 are opposed to each other, and the opposed

active material layers

2 and 1 are in contact (adhering) at the opposed surface 33.

The positive electrode active material layer 2 and the negative electrode active material layer 1 are characterized by being in contact (adhering) at the opposing surface 33. This is because at least one of the opposing

active material layers

2 or 1 is non-charged. In order to achieve electron conductivity, even if the

active material layers

2 and 1 facing each other are brought into contact with each other, they do not conduct due to electron conduction.

The power storage element 10 and the power storage device 100 shown in FIGS. 1 to 3 have the electrode structure of a secondary battery or a capacitor when the present invention is implemented by reducing the electrode thickness to the limit to achieve a high output density. is there. Of course, when the present invention is implemented in a power storage device that does not require high power density, the thickness of the positive electrode active material layer 2 and that of the negative electrode active material layer 1 do not need to be as thin as those described below.

The positive electrode 31 shown in FIGS. 1 and 2 is an electrode in which a positive electrode active material layer 2 having a thickness of about 10 μm to 40 μm is formed on both sides or one side on a positive electrode current collector 4 having a thickness of about 10 μm to 20 μm. . Similarly, the negative electrode 32 is an electrode in which the negative electrode active material layer 1 having a thickness of about 10 μm to 40 μm is formed on both sides or one side of the negative electrode current collector 3 having a thickness of about 10 μm to 20 μm. The power storage element 10 is configured as an electrode stack by stacking the positive electrode active material layer 2 and the negative electrode active material layer 1 so as to face each other. As shown in FIG. 3, the power storage element 10 is impregnated with an organic electrolyte (not shown), and is placed between aluminum and

polypropylene laminate sheets

11 and 12, and the periphery is heat-sealed and sealed. Thereby, the power storage device 100 having the electrode structure according to the present embodiment is completed.

In any power storage device, a “separator function” is indispensable between the positive electrode and the negative electrode facing each other in the cell. Here, the separator function means a function in which the positive electrode and the negative electrode facing each other are conducted by ion conduction and the conduction is cut off by electron conduction.

In the power storage device 100 (FIG. 3) in which the power storage element 10 shown in FIGS. 1 and 2 is impregnated with an organic electrolyte and sealed in a laminate sheet, the ion conduction between the

active material layers

2 and 1 facing each other is the power storage element. 10 is ensured by the organic electrolytic solution impregnated in 10. Further, even if the opposing

active material layers

2 or 1 are in direct contact (adhesion) at the opposing surface 33, at least one of them is non-electron conductive in an uncharged state. The electronic conduction between them is cut off. That is, at least in an uncharged state, the power storage device 100 having the electrode structure according to the present embodiment does not use a separator body, but has a separator function in the cell.

FIG. 1 shows an enlarged arrangement state of electrodes and a portion where the positive electrode current collector 4 in the power storage element 10 is collected and connected to the positive electrode tab 7. FIG. 2 is an enlarged view showing the arrangement state of the electrode and the portion where the negative electrode current collector 3 is collectively connected to the negative electrode tab 6 in the electricity storage element 10.

As shown in FIG. 1, the positive electrode active material layer 2 and the negative electrode active material layer 1 that are opposed to each other in the power storage element 10 are in contact (adhered), and the positive electrode current collector 4 is collectively joined to the positive electrode tab 7 and welded. A plastic tape 9 is welded to the positive electrode tab 7 in advance. As shown in FIG. 3, when the electrical storage element 10 is sealed with the

laminate sheets

11 and 12, the plastic tape 9 is integrated with the laminate sheet and thermally fused. As a result, the positive electrode tab 7 is taken out to the external terminal 14 of the positive electrode without hindering the sealing of the electric storage element 10. Similarly, as shown in FIG. 2, the negative electrode current collector 3 is gathered and welded to the negative electrode tab 6, and as shown in FIG. 3, the negative electrode tab 6 is taken out to become the external terminal 13 of the negative electrode. Yes.

Here, the difference between the storage element having the electrode structure according to the present embodiment described above and the storage element having the conventional electrode structure will be compared.

FIG. 6 is a cross-sectional view showing an arrangement state of electrode tab connection portions and electrodes of a storage element in a conventional electrode structure. 6 correspond to the

constituent elements

1, 2, 3, 4, 6, 7, and 10 in FIGS. 1 to 3, respectively.

FIG. 6 shows a cross-sectional view of the electricity storage device 10A when the electrode area is increased (the electrode thickness is reduced) in order to achieve a high output density and the conventional electrode structure is used. In FIG. 6, the portion where the current collector 4 </ b> A is gathered and connected to the electrode tab 7 </ b> A and the arrangement state of the electrodes, that is, the positive electrode tab 7 </ b> A side are shown enlarged in the left half. Further, a portion where the current collector 3A is gathered and connected to the electrode tab 6A and the arrangement state of the electrodes, that is, the negative electrode tab 6A side is shown enlarged to the right half.

6 is based on the premise that an electrode having the same thickness as the power storage element 10 shown in FIGS. 1 and 2 is used and the thickness of the electrode stack is the same. Specifically, the positive electrode 31A shown in FIG. 6 is an electrode in which a positive electrode active material layer 2A having a thickness of about 10 μm to 40 μm is formed on both sides or one side of a positive electrode current collector 4A having a thickness of about 10 μm to 20 μm. Similarly, the negative electrode 32A is an electrode in which a negative electrode active material layer 1A having a thickness of about 10 μm to 40 μm is formed on both sides or one side of a negative electrode current collector 3A having a thickness of about 10 μm to 20 μm. Here, the

active material layers

2A and 1A are each composed of a positive electrode active material and a negative electrode active material. Usually, both of the active material layers are made by mixing a conductive additive into the active material, and the positive electrode active material layer 2A is also composed of the negative electrode active material layer. 1A is also an electron conductive active material layer.

Therefore, in the conventional power storage element 10A, it is necessary to interpose a separate separator body 5 between the positive electrode active material layer 2A and the negative electrode active material layer 1A in order to cut off conduction due to electron conduction. Whether or not it is necessary to interpose the separator body 5 as another member is the most different point between the electricity storage element of the conventional electrode structure and the electricity storage element of the electrode structure according to the present invention.

The separator body 5 is generally made of a plastic porous membrane sheet having a thickness of about 25 μm. The thickness of 25 μm is almost the limit of thinness considering the mechanical strength and separator function of the separator body 5.

In the electricity storage device 10A shown in FIG. 6, the separator body 5 of the plastic porous membrane sheet not only cuts off the electrical conduction between the positive electrode 31A and the negative electrode 32A, but also impregnated with the positive electrode 31A by impregnating the electrolytic solution. Ion conduction between the negative electrode 32A is ensured. Thus, in the conventional electrode structure, the separator function is provided by interposing the sheet-like separator body 5 between the positive electrode and the negative electrode.

The power storage device to which the electrode structure (FIGS. 1 and 2) according to the present embodiment is applied is different from the power storage device to which the conventional electrode structure (FIG. 6) is applied as long as the volume of the electrode stack is the same. The electrode filling amount increases by an amount corresponding to the amount of the separator body 5 of the member. Further, if the electrode thickness is the same, the number of electrodes increases as the electrode filling amount increases, and the electrode area increases, and the input / output performance of the power storage device increases in proportion to the electrode area.

FIG. 7 is a diagram showing the relationship between the thickness of the active material layer and the number of stacked electrodes of the energy storage device according to one embodiment of the present invention in comparison with the conventional electrode structure. In FIG. 7, in the case where an active material layer is formed on a current collector having a thickness of 10 μm, the thickness of the active material layer is shown on the horizontal axis, the number of electrodes that can be stacked on the vertical axis, and the separator body having a thickness of 25 μm. The conventional electrode structure 16 using the electrode and the electrode structure 15 according to the present invention not using the separator body are shown.

As shown in FIG. 7, in the electrode structure that does not use a separator, the number of stacked electrodes increases efficiently, especially when the thickness of the active material layer is reduced compared to the electrode structure that uses a separator.

In the past use of secondary batteries, priority was given to being able to be used for a long time with a single charge, and a high capacity density has been demanded. In order to achieve a high capacity density, the heat of the active material layer is designed to be sufficiently thick (80 μm to 100 μm). In this case, as shown in FIG. 7, there was little difference depending on the presence or absence of the separator, and the separator was not a major obstacle for realizing a high capacity density.

However, in order to realize a high input / output density of the secondary battery, it is necessary to reduce the electrode thickness and increase the electrode area. In the conventional electrode structure, when the heat of the active material layer approximates the thickness of the separator, the ratio of the separator to the power storage element becomes extremely large. Therefore, in the conventional electrode structure, the separator is an obstacle for realizing a high output density.

As described above, when the electrode thickness is reduced as much as possible, the electrode structure according to this embodiment greatly increases the electrode facing area as compared with the conventional electrode structure. Therefore, the electrode structure according to the present embodiment is extremely effective for realizing a secondary battery and a capacitor having a high output density.

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 formed such that the

active material layers

2 and 1 are in close contact with the

current collectors

4 and 3, respectively. 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. The active material is selected from materials that are non-electron conductive until electrochemically oxidized (in the case of the positive electrode active material) or reduced (in the case of the negative electrode active material) in the charging direction. The active material based on the electrochemical oxidation-reduction reaction means a material that charges and discharges according to “Faraday's Electrolysis Law”. When such a material is a negative electrode active material, it is electrochemically reduced in the charging direction, and when it is a positive electrode active material, it is electrochemically oxidized in the charging direction.

In the electrode structure according to the present embodiment, when the negative electrode active material layer is composed of an active material selected from materials that are non-electron conductive, it is not reduced electrochemically but is electron conductive. Therefore, the negative electrode active material layer is non-electron conductive in an uncharged state because it is formed without mixing any material (excluding substances that are electrochemically reduced and become electron conductive). Similarly, when the positive electrode active material layer is formed of an active material selected from non-electron conductive materials, the material is not oxidized electrochemically but is electron conductive (electrochemical). Is formed without mixing at all. Therefore, the positive electrode active material layer is non-electron conductive in an uncharged state.

In addition, in order to improve the electronic conductivity of the active material layer, the electron conductive material mixed in the active material layer is generally called a conduction aid or a conduction aid.

Therefore, in the power storage device 100 according to this embodiment, 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 that face each other. Even if the layer 1 is in contact, the electronic conduction is interrupted. Therefore, the positive electrode active material layer 2 and the negative electrode active material layer 1 can be contacted (adhered) on the facing surface 33 without using a separate separator body.

1 and 2, the negative electrode active material layer 1 may be non-electron conductive, the positive electrode active material layer 2 may be electron conductive, or the positive electrode active material layer 2 may be uncharged. Is made non-electron conductive, the negative electrode active material layer 1 may be electron conductive. Further, when both the positive electrode active material layer 2 and the negative electrode active material layer 1 are composed of an active material based on an electrochemical redox reaction, both the positive electrode 31 and the negative electrode 32 are based on an electrochemical redox reaction. Since it is comprised with an active material, the electrical storage element 10 becomes an electrical storage element of a secondary battery.

On the other hand, either 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, and the other is an active material that is not based on an electrochemical redox reaction, such as activated carbon. In the case where the power storage element 10 is configured, the power storage element 10 is a power storage element of a capacitor. In general, a capacitor is a power storage device having a high output density (W / L). However, when it is desired to further increase the output density or to reduce the raw material cost (by removing the separator), this embodiment relates to the capacitor. The electrode structure is also effective for capacitors.

The embodiment of the present invention has been described above with reference to the drawings, particularly with regard to the electrode structure. Hereinafter, the mechanism of power storage of the power storage device according to the present invention will be described.

Since the electrochemical redox reaction (charge / discharge reaction) of the electrode active material involves electrons and ions, the active material includes the transfer of electrons to and from the current collector and the ion conduction between the active material and the counter electrode. Must be possible.

Usually, the active material layer of the electrode has a hole capable of holding the electrolytic solution, and by holding the electrolytic solution in the hole, ionic conduction between the active material of the positive electrode and the negative electrode is ensured by the electrolytic solution. Is done. Further, in the conventional battery, since a conductive assistant is mixed in the active material layer of the electrode, electrons can be exchanged between the active material and the current collector through the conductive assistant.

Even in the power storage device according to the present embodiment, the active material layer of the electrode has a hole capable of holding the electrolytic solution, and by holding the electrolytic solution in the hole, the ionic conduction between the positive and negative active materials is related to the electrolysis. Secured with liquid. However, in the power storage device according to the present embodiment, at least one of the active material layers is non-electron conductive, and the non-electron conductive active material layer is configured without mixing a conduction assistant in the non-electron conductive active material. Is done. It is doubtful whether electrons can be exchanged between the active material in the non-electron conductive active material layer and the current collector.

However, even in the non-electron conductive active material layer, the active material particles that are in close contact with the current collector can exchange electrons with the current collector.

Therefore, even in a non-electron conductive active material, the particles that are in close contact with the current collector undergo a charging reaction by transferring electrons to and from the current collector. However, the charge reaction of the active material is an electrochemical reduction reaction that receives electrons in the case of the negative electrode active material, and is an electrochemical oxidation reaction that releases electrons in the case of the positive electrode active material.

The active material primary particles that are in close contact with the current collector even when they are non-electron conductive active materials are charged to become electron conductive active materials, and the active materials that are not in direct contact with the current collector through the active materials These primary particles can also exchange electrons. Thus, even in the non-electron conductive active material layer, the non-electron conductive active material is sequentially charged.

FIG. 4 shows an electron conduction path and an ion conduction path secured in the positive electrode active material and the negative electrode active material at the time of initial charge for the power storage device according to the present invention when the negative electrode active material layer is non-electron conductive. It is the shown schematic diagram.

In FIG. 4, the negative electrode active material A is an active material constituting the negative electrode active material layer 1. The positive electrode active material C is an active material constituting the positive electrode active material layer 2. In the example shown in FIG. 4, ionic conduction between the negative electrode active material A and the positive electrode active material C is ensured by an electrolyte solution (not shown) held in the active material layer as in the conventional case. On the other hand, since the negative electrode active material A is in direct contact with the negative electrode current collector 3 and the positive electrode active material C is also in direct contact with the positive electrode current collector 4, it is possible to ensure electronic conduction between the active material particles and the current collector. The conduction aid is not always necessary.

However, since FIG. 4 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 conductive additive. Further, the negative electrode active material A in contact with the negative electrode current collector 3 ensures better electron conduction with the current collector, so that the non-electron conductivity of the negative electrode active material layer 1 is not destroyed so that the surface of the negative electrode current collector A thin carbon layer or the like may be formed.

The storage element 10 shown in FIGS. 1 and 2 will be described again. The storage element 10 shown in FIGS. 1 and 2 is based on the assumption 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. However, the active material particles that are in close contact with the current collector in the non-electron conductive active material layer ensure electron conduction with the current collector. Even if the positive electrode active material layer 2 and the negative electrode active material layer 1 are in close contact with each other on the opposing surface, the positive electrode 31 and the negative electrode 32 are not electrically connected by electronic conduction. On the other hand, in the power storage device 100 shown in FIG. 3, since the power storage element 10 is impregnated with an organic electrolytic solution, the positive electrode active material and the negative electrode active material are in conduction by ion conduction. Therefore, when 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.

Note that in the electricity storage element 10 as well, the non-electron conductive active material particles that are in close contact with the current collector can exchange electrons with the current collector, so that the charging reaction proceeds. That is, in the non-electron conductive active material layer, the active material particles (primary particles) that are in close contact with the current collector are charged to be changed into electron conductive active materials. Then, since the active material particles (primary particles) that are not in direct contact with the current collector can also exchange electrons through the charged active material, the charging reaction proceeds sequentially.

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

All of these non-electron conductive active materials change to 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 due to an oxidation-reduction reaction. The other primary particles can exchange electrons through the changed primary particles. In this way, it can be understood that the redox reaction proceeds sequentially.

The active material particles are generally secondary particles formed by collecting primary particles. Therefore, it is only between the current collector and the secondary particles that the electron conduction can be ensured by the conduction aid, and more specifically, between the current collector and a part of the primary particles forming the secondary particles. It is. Therefore, even when electronic conduction is ensured by the conduction aid, the charge / discharge reaction proceeds sequentially from the active material particles (primary particles) in close contact with the conduction aid to other active material particles (primary particles). There is no change. In a conventional power storage device, not only a non-electron conductive active material but also an electron conductive active material is used, a conductive assistant such as carbon is mixed in the active material layer. Thereby, both the positive electrode and the negative electrode become electrodes on which a good electron conductive active material layer is formed. Therefore, in the conventional power storage device, it is necessary to interpose a separator body between the positive electrode and the negative electrode in order to cut off the electronic continuity between the positive electrode and the negative electrode.

In addition, in conventional power storage devices, it has been common knowledge for many years to ensure good electronic conduction between the active material and the current collector by mixing a conductive additive in the active material layer, and even to a power storage device with a high output density. When trying to obtain it, there has never been an idea that seems to be the opposite of removing the conduction aid from the active material layer.

Ordinary 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. 5A to 5C are schematic electrode diagrams illustrating an initial charging mechanism of the power storage device according to the embodiment of the present invention.

FIGS. 5A to 5C further show the electrodes facing each other in the power storage element 10 of the power storage device 100 shown in FIG. 3, and show the mechanism of the initial charge of the power storage device according to this embodiment. is there. The active material layer 41, the active material layer 42, the current collector 43, and the current collector 44 shown in FIGS. 5A to 5C are the negative electrode active material layer 1 and the positive electrode active material layer 2 shown in FIGS. , And negative electrode current collector 3 and positive electrode current collector 4 (in this case, negative electrode active material layer 1 shown in FIGS. 1 and 2 is non-electron conductive). However, when the positive electrode active material layer 2 shown in FIGS. 1 and 2 is non-electron conductive, the active material layer 41, the active material layer 42, the current collector 43, and the current collector 44 are respectively shown in FIG. 2 corresponds to the positive electrode active material layer 2, the negative electrode active material layer 1, the positive electrode current collector 4, and the negative electrode current collector 3 shown in FIG.

5A to 5C, the chargeable capacity of the non-electron conductive active material layer 41 is configured to be larger than the chargeable capacity of the counter electrode active material layer 42. FIG. 5A shows the state before the first charge, and the active material layer 41 and the active material layer 42 facing each other are in close contact with each other, but since one active material layer 41 is non-electron conductive, The current collector 44 is not electrically connected.

Moreover, since the active material layer 41 and the active material layer 42 hold | maintain electrolyte solution in a void | hole, each active material in the active material layer 41 and the active material layer 42 conduct | electrically_connects by ion conduction with this electrolyte solution. Yes. That is, before charging, the active material layer 41 has a separator function (electrical conduction is cut off but ion conduction is conducted). Therefore, charging is started by applying a charging voltage to the current collector 43 and the current collector 44.

In charging, the active material contained in the non-electron conductive active material layer 41 starts to be charged from the active material (primary particles) in close contact with the current collector 43, and the charged active material (primary particles) is an electron. Become conductive. Thereafter, the active material (primary particles) separated from the current collector 43 can also exchange electrons through the already charged active material, and the active materials (primary particles) sequentially separated from the current collector. Is also charged.

Then, as shown in FIG. 5B, the non-electron conductive active material layer 41 is divided into a charged active material layer 41 a and an uncharged active material layer 41. That is, the separator function is provided by the active material layer 41 in an uncharged state even during charging.

As shown in FIG. 5B, the counter electrode active material layer 42 is divided into a charged active material layer 42 a and an uncharged active material layer 42. However, the active material layer 42 is not necessarily separated into the charged active material layer 42a and the uncharged active material layer 42. If the active material layer 42 is electronically conductive, the active material in the active material layer 42 normally satisfies the condition for charging because any active material is electronically connected to the current collector 44. In the active material layer 42, the charged active material and the uncharged active material are mixed.

Thus, as shown in FIG. 5C, the charging is completed when all of the active material layer 42 is changed to the active material layer 42a. When charging is completed, an uncharged non-electron conductive active material layer 41 remains between the charged active material layer 42a and the active material layer 41a. As a result, even when charging is completed, the uncharged active material layer 41 remaining between the active material layer 42a and the active material layer 41a has a separator function.

As described above, the uncharged non-electron conductive active material layer 41 always functions as a separator, and the charged active material layer 41a and the active material layer 42a are not electrically connected. That is, the power storage device is charged (power storage) without an internal short circuit.

In FIG. 5A, by designing the chargeable capacity of the non-electron conductive active material layer 41 to be larger than the chargeable capacity of the counter electrode active material layer 42, as shown in FIG. It is possible to reliably leave as many active material layers 41 in a charged state as necessary.

As described above, in the power storage device according to the present embodiment, about 70 to 90% of the active material (primary particles) is sequentially charged in the non-electron conductive active material layer from the one close to the current collector. After the first charge, the active material once charged always plays a role of charge / discharge, and the remaining about 10 to 30% of the non-electron conductive active material (1 The secondary particles remain uncharged, that is, remain non-electron conductive, and continue to play a role of preventing electronic conduction between the positive electrode and the negative electrode.

Since the storage capacity (Ah) of the power storage device is restricted to the smaller chargeable capacity of the positive electrode and the negative electrode, it is ideal to make the chargeable capacity of the positive electrode and the negative electrode equal. However, in order to make the charging characteristics of each cell uniform, generally, the chargeable capacity of either the positive electrode or the negative electrode is increased, and the cell is designed by either negative electrode capacity regulation or positive electrode capacity regulation.

By the way, the existing negative electrode potential type lithium ion battery has a negative electrode capacity of about 1.4 times the positive electrode capacity, and the nickel metal hydride battery has a negative electrode capacity of about 1.2 times the positive electrode capacity. ing.

Therefore, even if the chargeable capacity of the non-electron conductive active material layer is designed to be about 1.3 times the chargeable capacity of the counter electrode active material layer as in this embodiment, the positive electrode capacity and the negative electrode capacity are The balance is not much different from the design of conventional secondary batteries. That is, in the secondary battery according to the present invention, an extra active material is used rather than the conventional secondary battery in order to leave an uncharged non-electron conductive active material layer between the positive electrode and the negative electrode. is not.

The power storage mechanism of the power storage device according to the present invention has been described above. Hereinafter, as a specific example of the power storage device to which the present invention is applied, a case where it is applied to a noble negative electrode potential type lithium ion battery will be described.

Since the noble negative electrode potential type lithium ion battery is highly safe, it is difficult to dispose of it as a next-generation power storage device for HV and EV. However, it has been difficult to obtain the high input / output performance required for HV and EV with the conventional electrode structure.

A major feature of the electrode structure according to the present invention is that it is not necessary to interpose a separate separator body which is indispensable for the conventional electrode structure. Therefore, according to the present invention, a noble negative electrode potential type lithium ion battery having a high input / output density can be realized.

Therefore, a case where the present invention is specifically applied to a noble negative electrode potential type lithium ion battery will be described in more detail.

Specifically, spinel lithium titanium oxide (lithium titanate) is selected as the negative electrode active material, and spinel lithium manganese oxide (lithium manganate) is selected as the positive electrode active material for carrying out the present invention. explain.

The spinel type 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. Li ₄ Ti ₅ O ₁₂ (hereinafter also referred to as LTO) corresponding to x = 1 in the above general formula is non-electron conductive (electron conductivity is about 10 ⁻¹³ S / cm) and is reduced electrochemically. Will change to electronic conductivity. Therefore, LTO is a negative electrode active material that can form a suitable non-electron conductive active material layer in the practice of the present invention.

In addition, LTO can reversibly electrochemically reduce and oxidize in an organic electrolyte at a potential of about 1.5 V with respect to the potential of metallic lithium. Therefore, a battery using LTO as a negative electrode active material is a noble negative electrode potential type lithium ion battery.

On the other hand, spinel-type lithium manganate represented by the chemical formula LiMn ₂ O ₄ (hereinafter also referred to as LMO) undergoes an electrochemical redox reaction at a potential of about 4 V with respect to the potential of metallic lithium in an organic electrolyte. In a noble negative electrode type battery using the LMO as a positive electrode active material and the LTO as a negative electrode active material, the open circuit voltage is about 2.5V.

When a noble negative electrode type battery using LTO as a negative electrode active material and LMO as a positive electrode active material is manufactured by applying the present invention, the negative electrode and the positive electrode are manufactured as follows.

The LTO used as the negative electrode active material is solidified with a binder without mixing any carbon or other conductive aid, and a non-electroconductive negative electrode active material layer is formed on the metal foil used as the negative electrode current collector. Is made. Also, the LMO used as the positive electrode active material is mixed with a conductive agent such as carbon and solidified with a binder to form an electron conductive positive electrode active material layer on the metal foil used as the positive electrode current collector. Make it.

As shown in FIGS. 1 and 2, the positive electrode and the negative electrode are configured such that the positive electrode active material layer 2 and the negative electrode active material layer 1 are opposed to each other, and stacked to constitute a storage element 10. Thereafter, the storage element 10 is impregnated with an organic electrolyte and sealed in a battery container as shown in FIG.

In the noble negative electrode potential type lithium ion battery according to this embodiment manufactured as described above, the negative electrode active material layer is non-electron conductive even though the positive electrode active material layer and the negative electrode active material layer are in close contact with each other. The positive electrode and the negative electrode are not conductive by electronic conduction. On the other hand, since the positive electrode active material layer and the negative electrode active material layer are sufficiently impregnated with an organic electrolyte, the positive electrode active material (LMO) and the negative electrode active material (LTO) are electrically connected by ion conduction. Therefore, by applying a charging voltage of about 3 V to the positive electrode and the negative electrode, the active material (LMO) in the positive electrode active material layer is electrochemically oxidized, and the active material (LTO) in the negative electrode active material layer is electrochemical. Will be reduced and charged.

The active material (Li ₄ Ti ₅ O ₁₂ ) particles in the negative electrode active material layer are sequentially charged from the particles that are in close contact with the negative electrode current collector to be changed to electron conductive Li ₇ Ti ₅ O ₁₂ . In the Li ₄ Ti ₅ O ₁₂ particles, all of the titanium in the crystal is tetravalent (Ti ⁴⁺ ). However, when Li ₄ Ti ₅ O ₁₂ is supplied with electrons through a current collector by charging and Li ⁺ is supplied from the electrolyte to change to Li ₇ Ti ₅ O ₁₂ , the Li ₇ Ti ₅ In the O ₁₂ crystal, Ti ⁴⁺ and Ti ³⁺ are mixed at a ratio of 2: 3.

Then, since Ti ⁴⁺ and Ti ³⁺ in the crystal can exchange electrons freely, the Li ₇ Ti ₅ O ₁₂ particles after charging are electron conductive. In addition, the Li ₄ Ti ₅ O ₁₂ particles that are not in direct contact with the current collector in the negative electrode active material layer are electrically connected to the current collector through the Li ₇ Ti ₅ O ₁₂ changed to electron conductivity. As a result, the batteries are sequentially charged.

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 It is sex. In addition, by mixing a conductive additive such as carbon in the positive electrode active material layer, all of the LiMn ₂ O ₄ particles in the positive electrode active material are sufficiently conducted to the current collector through electronic conduction, and thus can participate in the charging reaction. Therefore, LiMn ₂ O ₄ particles in the positive electrode active material are sequentially charged from LiMn ₂ O ₄ particles suitable as a counter electrode for the negative electrode active material in which the charging reaction is in progress.

When the LTO in the negative electrode active material layer is designed so that the real chargeable capacity of the LTO exceeds the real chargeable capacity of the LMO in the positive electrode active material layer, the charging ends when the LMO that can participate in the charge reaction is completely charged. . At the end of charging, uncharged LTO in the negative electrode active material layer remains uncharged at the boundary with the counter electrode active material layer farthest from the negative electrode current collector.

For example, when the actual chargeable capacity of the LTO in the negative electrode active material layer is designed to be about 1.3 times that of the LMO in the positive electrode active material layer, 0.3 times the excess LTO is uncharged at the end of charging. It remains in the vicinity of the boundary with the counter electrode active material layer. Therefore, of course, the non-electron conductive active material layer in an uncharged state is always interposed between the positive electrode active material layer and the negative electrode active material layer even before or after the charge is completed, before the start of charging. Fulfill. Thereby, it is not necessary to interpose a separator body between a positive electrode active material layer and a negative electrode active material layer.

A noble negative electrode potential type lithium ion battery using LTO as a negative electrode active material and LMO as a positive electrode active material is a promising candidate for a next-generation HV-equipped battery, in particular, because it is excellent in safety. However, such a noble negative electrode type lithium ion battery has a low discharge voltage, so that the energy density is originally low. If the electrode area is increased in order to secure a large output density, the energy density is further lowered in the conventional battery structure in which the separator is interposed.

Therefore, noble negative electrode potential type lithium ion batteries using LTO as a negative electrode active material and LMO as a positive electrode active material have a standard battery structure with an HV mounting standard (energy density of 120 Wh / L or more, maximum power supply) The capacity (W / L) is not more than 2500 W / L).

However, in the electrode structure according to the present invention, since no separator is interposed, a decrease in energy density can be suppressed even if the electrode area is increased. Therefore, the electricity storage element having an electrode structure according to the present invention is extremely effective for increasing the electrode area and ensuring a high output density.

Therefore, according to the electrode structure of the present invention, the noble negative electrode potential type lithium ion battery using LTO as the negative electrode active material and LMO as the positive electrode active material can sufficiently satisfy the mounting standard for HV.

As mentioned above, although the specific example which applies this invention to the noble negative electrode potential type lithium ion battery which uses LMO and LTO as an active material of a positive electrode and a negative electrode, respectively, application of this invention is not limited to this.

When the electrode structure according to the present invention is applied to other noble negative electrode potential type lithium ion batteries, titanium oxide (TiO ₂ ) or spinel lithium iron is used instead of the above-mentioned LTO as a non-electron conductive negative electrode active material. An oxide (LiFe ₅ O ₈ ) or the like can be selected. Although these are all non-electron conductive materials, they change to electronic conductivity when charged (electrochemically reduced) as a negative electrode active material. Therefore, preferred negative electrode active material candidates in the practice of the present invention It is.

In addition, when the electrode structure according to the present invention is applied to a noble negative electrode potential type lithium ion battery, any material used as a positive electrode active material of a base negative electrode potential type lithium ion battery can be basically used as the positive electrode active material. . For example, in addition to spinel lithium manganese oxide (LiMn ₂ O ₄ ), LiFePO _4, LiCoO ₂ , LiNiO _{2 and the} like can be selected.

The electrode structure according to the present invention can also be applied to a capacitor. For example, the negative electrode is an electrode based on an electrochemical redox reaction, and the positive electrode is an electrode based on an electric double layer. In this case, a material (for example, Li ₄ Ti ₅ O ₁₂ or TiO ₂ ) that is non-electron conductive until it is electrochemically reduced is selected as the negative electrode active material. The non-electron conductive negative electrode active material layer composed of such a negative electrode active material can be disposed to face a positive electrode active material layer composed of graphite, activated carbon or the like as a positive electrode active material without interposing a separator. In the conventional capacitor electrode structure, the positive electrode active material layer and the negative electrode active material layer are both electronically conductive, as in the conventional secondary battery. It is necessary to face through.

Furthermore, the electrode structure according to the present invention can dope / dedope lithium ions with a positive electrode having a non-electron conductive positive electrode active material layer made of a non-electron conductive positive electrode active material (for example, LiFePO ₄ ). The present invention can also be applied to a base negative electrode potential type lithium ion battery in combination with a negative electrode made of carbon.

Also, a high output density can be expected from the secondary battery (power storage device excluding the capacitor) to which the present invention is applied due to the following effects.

A power storage device with a large output density (V · A = W / L) is a power storage device capable of discharging with a large current while maintaining a high voltage. However, in the case of a secondary battery, when discharging with a large current as in the case of a primary battery, a difference in the concentration of ions involved in the electrode reaction occurs between the positive electrode and the negative electrode according to the discharge current density. The discharge voltage of the battery drops due to concentration polarization based on the difference in ion concentration. Therefore, regardless of the primary battery or the secondary battery, a battery having a small voltage drop due to such concentration polarization is a battery having a high output density.

On the other hand, in the charging of the secondary battery, a concentration difference of ions involved in the electrode reaction occurs between the positive electrode and the negative electrode according to the charging current density. The charge voltage rises due to concentration polarization based on the difference in ion concentration. Therefore, a battery with a smaller increase in charging voltage due to such concentration polarization is a battery having a higher charging input density, that is, a secondary battery having a higher charging speed.

For example, in the discharge of a lithium ion battery using an electrolytic 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. On the other hand, in the battery, electricity is carried between the negative electrode and the positive electrode by Li ⁺ ions and PF ₆ ^- ions. At this time, the ratio of Li ⁺ ions and PF ₆ ⁻ ions carrying electricity, that is, the transport number of ions is t ⁺ and t ⁻ , respectively, and t ⁺ + t ⁻ = 1.

If transport number t ⁺ = 1 for Li ⁺ ions, all Li ⁺ ions released from the anode active material to move to the positive electrode by electrophoresis, the Li ⁺ ions of the same number as the positive electrode was released from the anode active material It is taken in the positive electrode active material. Therefore, when the Li ⁺ ion transport number t ⁺ = 1, there is no difference in concentration between the electrolyte near the positive electrode and the negative electrode.

However, 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. The anion transport number is 0.5 or more. Therefore, for example, in the discharge of a lithium ion battery using an electrolytic solution in which LiPF ₆ is dissolved, half of the Li ⁺ ions released from the negative electrode active material cannot move to the positive electrode by electrophoresis. On the other hand, in the positive electrode, the same number of Li ⁺ ions as Li ⁺ ions released from the negative electrode active material are taken into the positive electrode active material. Therefore, the Li ⁺ ion concentration is low near the positive electrode, and conversely, the Li ⁺ ion concentration is high near the negative electrode.

Conversely, in charge, while Li ⁺ ions released from the positive electrode active material can not be moved to the anode half of electrophoresis, the negative electrode the same number of Li ⁺ ions released from the positive electrode active material Li ⁺ Ions are incorporated into the negative electrode active material. Therefore, the Li ⁺ ion concentration is low near the negative electrode, and conversely, the Li ⁺ ion concentration is high near the positive electrode.

However, the concentration difference between the electrolyte solution in the vicinity of the positive electrode and the negative electrode thus generated is corrected by the diffusion of electrolyte ions. A battery with a small voltage drop due to concentration polarization is a battery with a large output density. Eventually, concentration polarization is corrected by diffusion of electrolyte ions. Therefore, a battery having good diffusion of electrolyte ions in the vicinity of the positive electrode and in the vicinity of the negative electrode is a battery having a high output density.

From this, the inventor of the present invention generally has a sustainable maximum charge / discharge current I (A) in a large current charge / discharge of a secondary battery using an organic electrolyte, which is I = 2FSDC ^* / d · (1−t ⁺ ), Or the theoretical formula that it is in a relation of i = 2FSDC ^* / d · t ⁻ was derived. Where F is the Faraday constant, S is the electrode area, D is the diffusion coefficient (cm ² · s ⁻¹ ), C ^* is the electrolyte concentration, d is the distance between the electrodes, t ⁺ is the transport number of Li ⁺ ions, and t ^−. Is the negative ion transport number.

This theoretical formula indicates that the sustainable maximum charge / discharge current I (A) is proportional to the electrode area S and inversely proportional to the interelectrode distance (d). If the distance (d) between the positive electrode and the negative electrode is shortened, the concentration gradient of the electrolyte is increased and the ion diffusion rate is increased. Since the concentration difference of the electrolytic solution caused by the Li ⁺ ion transport number is alleviated by the diffusion of the electrolyte ions, reducing the distance between the positive electrode and the negative electrode is an effective means for making a battery with a large output density.

Since the secondary battery (power storage device excluding the capacitor) to which the present invention is applied does not use a separator, the distance (d) between the electrodes is small, and the electrode area S can be increased by reducing the thickness of the electrodes. Therefore, by applying the present invention, the sustainable maximum charge / discharge current I (A) of the secondary battery can be increased, and therefore, a secondary battery with high power supply capability and high charging speed can be provided.

If the power storage device mounted on the EV can be charged in an extremely short time, the short EV charging distance will not be a major drawback. Therefore, the electrode structure according to the present embodiment can also realize a highly safe noble negative electrode type lithium ion battery as a power storage device for next-generation EV mounting.

The electrode of the power storage device to which the present invention is applied is the same method as that of the conventional power storage device, for example, by solidifying the active material with a binder or the like and forming an active material layer on the current collector of the metal foil. Can be produced. In addition, the electrode element according to the present invention can be produced as a laminate of electrodes as in the case of a conventional power storage device by stacking a plurality of electrodes with the active material layers of the positive electrode and the negative electrode facing each other. Can do.

In addition, the storage element having the electrode structure according to the present invention is manufactured as a wound body in the same manner as a conventional storage device by winding a positive electrode and a negative electrode in a spiral shape with the active material layers facing each other. You can also.

Such a power storage element of a laminated body or a wound body is impregnated with an electrolytic solution and sealed in a container by the same method as that of a conventional power storage device, whereby a power storage device to which the present invention is applied is completed. As described above, the power storage device to which the present invention is applied can be manufactured almost in the same process as the conventional power storage device, and thus can be manufactured at a lower cost than the conventional power storage device because a separator is not used for the power storage element.

As described above, according to the present invention, a high-capacity, high-output power storage device that has a fast charging time can be supplied at low cost. Therefore, a highly safe noble negative potential type lithium ion battery can store power for HV and EV. It can be provided as a device, and the industrial value of the present invention is great.

Note that the power storage device to which the present invention is applied can be applied not only to HV mounting and EV mounting, but also to power storage devices used for other purposes. For example, it can be used as a driving power source for an electric motorcycle, a power source for storing nighttime power or surplus power, and the like. Even in this case, the cost of raw materials can be reduced by the configuration without using the separator.

Hereinafter, examples of the present invention will be described.

First, Example 1 and Comparative Example 1 will be described. In the following description, a noble negative electrode potential type lithium ion battery (Example 1) to which an electrode structure according to the present invention is applied and a noble negative electrode potential type lithium ion battery (Comparative Example 1) having an electrode structure with a conventional separator body interposed therebetween. ) Performance comparison.

(1) Battery preparation of Example 1 In Example 1, spinel type lithium manganese oxide (LiMn ₂ O ₄ ) is used as the positive electrode active material, and spinel type lithium titanium oxide (Li ₄ Ti ₅ ) as the negative electrode active material. Using O ₁₂ ), a noble negative electrode potential type lithium ion battery having an output performance matching that of an HV-mounted battery was produced with the electrode structure according to the embodiment of the present invention.

LiMn ₂ O ₄ was produced by firing a mixture of manganese dioxide and lithium carbonate in air at 850 ° C. and synthesizing 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.

The synthesized LiMn ₂ O ₄ is dry-mixed with carbon black and graphite as conduction aids and polyvinylidene fluoride (PVDF) as a binder, followed by wet mixing with N-methyl-2-pyrrolidone (NMP) as a solvent. Thus, a pasty slurry was obtained. This slurry was applied and dried on one side of a 250 mm wide aluminum foil serving as a current collector, leaving uncoated portions of 20 mm at both ends.

Thereafter, the slurry was applied to the other surface with the same specifications and dried. A sheet-like electrode in which an active material layer is formed on both sides of an aluminum foil is cut to a predetermined size and then pressed with a roller press to give a density of the coated product of 2.65 to 2.9 g / cm ^3. Thus, a sheet-like positive electrode was produced in which the active material layer was formed in close contact with both surfaces of the aluminum foil current collector.

The final positive electrode of the double-sided active material layer has a thickness of 30 to 32 μm, a vertical width of 130 mm, and a horizontal width of 220 mm including an uncoated aluminum foil portion of 20 mm at one end. The aluminum foil part exposed by 20 mm width of the said sheet-like positive electrode becomes an attachment part of a positive electrode tab. Further, an insulating tape having a width of 10 mm was pasted on the attachment portion of the positive electrode tab following the active material application portion.

A representative sample was taken out from the produced sheet-like positive electrode. For this representative sample, Li metal was used for the counter electrode, and 1 mol / L of LiPF ₆ was dissolved in the electrolyte and ethylene carbonate (EC) and diethyl carbonate (DEC). A test cell was assembled using a mixed solution (hereinafter referred to as LiPF ₆ electrolyte). This test cell was subjected to a charge / discharge test at a voltage range of 4.3 to 3.0V. As a result, it was confirmed that the chargeable capacity of the produced sheet-like positive electrode was 78 mAh / electrode single side.

Next, spinel-type lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ), which becomes the negative electrode active material, is a mixture of lithium hydroxide (LiOH) and titanium dioxide (TiO ₂ ) in a molar ratio of 4: 5. It was prepared by press-molding and putting it in an alumina container covered with nickel foil and baking it at 800 ° C. in a helium atmosphere.

There was no unreacted TiO _{2 in} the XRD pattern of the composite, and it was a Li ₄ Ti ₅ O ₁₂ monolayer. Further, it was confirmed from the SEM photograph of the composite (6600 times magnification) 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 NMP as a solvent together with PVDF as a binder to obtain a paste slurry. This slurry was applied and dried on one side of a 250 mm wide aluminum foil serving as a current collector, leaving 20 mm uncoated portions at both ends. The aluminum foil used here was previously coated with a conductive carbon paint on both sides according to the application width of the slurry.

Similarly, the slurry was applied to the other surface with the same specifications and dried. A sheet-like electrode having an active material layer formed on both sides of the current collector is cut to a predetermined size, and then pressed with a roller press to make the density of the coated product 2.0 to 2.2 g / cm ^3. Thus, a sheet-like negative electrode was produced in which an active material layer was formed in close contact with both surfaces of an aluminum foil current collector. However, a sheet-like electrode that is partially coated on one side is cut into a predetermined size and then pressed with a roller press to make the density of the coated product 2.0-2.2 g / cm ³ . The sheet-like negative electrode in which the active material layer was formed only on one side of the aluminum foil current collector was also produced.

The final negative electrode of the double-sided active material layer has a thickness of 36 to 38 μm, a vertical width of 140 mm, and a horizontal width of 230 mm including an uncoated aluminum foil part with 20 mm at one end. The aluminum foil portion exposed at a width of 20 mm of the sheet-like negative electrode serves as a mounting portion for the negative electrode tab.

Note that the fabricated sheet-shaped negative electrode taken out a representative sample for the representative sample, a counter electrode and Li metal were assembled test cell using a LiPF ₆ electrolyte. This test cell was subjected to a charge / discharge test in a voltage range of 1.2 to 2.5V. As a result, the chargeable capacity of the produced sheet-like negative electrode was 115 mAh / electrode single side. The chargeable capacity of the sheet-like negative electrode is about 1.47 times the chargeable capacity of the sheet-like positive electrode.

Of the positive electrode and the negative electrode prepared as described above, first, an uncoated portion of the negative electrode current collector and the positive electrode current collector are formed on the negative electrode active material layer in which the active material layer is formed only on one side of the current collector. The positive electrode active material layers having active material layers formed on both sides of the current collector were stacked in close contact so that the uncoated portions of the electric current were opposite to each other.

At this time, the lateral width of the negative electrode at the intermediate position of the insulating tape affixed to the uncoated portion of the positive electrode current collector, that is, at a position on the uncoated portion side by 5 mm from the boundary between the active material coated portion and the uncoated portion of the positive electrode current collector The positive electrode was overlapped so that the end of the direction was arranged. If it does so, the positive electrode end located in the other end part side of the horizontal direction of a negative electrode will overlap in the position which leaves about 5 mm of negative electrode application parts. In the longitudinal width direction of the electrode, both ends of the negative electrode protruded from the positive electrode end by 5 mm and overlapped.

Next, the intermediate position of the insulating tape affixed to the uncoated portion of the positive electrode current collector so that the uncoated portion of the current collector is opposite to the uncoated portion of the positive electrode on the positive electrode active material layer The active material layers of the negative electrode in which the active material layers were formed on both sides of the current collector were stacked so that the ends in the width direction of the negative electrode were placed on the surfaces.

In the same manner, the positive electrode and the negative electrode were alternately stacked, and the negative electrode on which the active material layer was formed only on one side was again stacked on the 44th positive electrode with the active material layers in close contact with each other. Thereafter, uncoated portions of the current collectors of the respective electrodes were collectively welded to the electrode tabs, and electrode elements similar to the laminate shown in FIGS. 1 and 2 were assembled, although the number of electrodes was different.

After the assembled electrode element is sufficiently dried, it is placed in a laminate sheet of aluminum and polypropylene that has been drawn into a shape that can accommodate the electrode element, and the same type of laminate sheet is stacked, leaving one place around the laminate sheet. Heat-sealed.

The electrode tab welded with the current collector of each electrode was taken out from between the two laminate sheets. A plastic special tape was previously pressure-bonded to the electrode tab at a portion located in the heat-sealed portion of the laminate sheet, and the special tape and the two laminate sheets were integrated and heat-sealed.

LiPF ₆ (1M) electrolyte is injected from the unfused portion of the laminate sheet into the electrode element housed in the laminate sheet thus produced, impregnated with vacuum, and finally the unfused laminate sheet is filled. The landing part was heat-sealed. Thus, a noble negative potential type secondary battery having a battery volume of 115 cc was completed with the battery structure shown in FIGS. However, the battery volume 115 cc is equal to the volume in which the water volume increases when this battery is submerged in water, and is the so-called true volume of the battery.

Since the noble negative electrode potential type lithium ion battery produced in Example 1 has a negative electrode chargeable capacity of 1.46 times that of the positive electrode chargeable capacity, 0.46 times the excess in the negative electrode active material at the end of charging. Li ₄ Ti ₅ O ₁₂ remains in the vicinity of the boundary with the counter electrode active material layer in an uncharged state. Therefore, an uncharged non-electron conductive negative electrode active material layer is always interposed between the positive electrode active material layer and the negative electrode active material layer, both before and after charging, as well as before charging. Performs the separator function. Therefore, in the noble negative electrode potential type lithium ion battery produced in Example 1, it is not necessary to interpose a separator between the positive electrode active material layer and the negative electrode active material layer.

(2) Production of Battery of Comparative Example 1 The noble negative electrode potential type lithium ion battery produced in Comparative Example 1 is the same as the battery produced in Example 1 in terms of electrode thickness and power storage element volume according to the following procedure. It produced as follows.

In Comparative Example 1, a separator is used because it is manufactured with a conventional electrode structure. Therefore, in the case where a storage element having the same volume is constituted by a positive electrode having the same dimensions and a negative electrode appropriately balanced with this, the number of electrodes constituting the storage element is smaller than that in the first embodiment. In Comparative Example 1, a polypropylene porous film having a thickness of 25 μm is used as the separator body.

In this case, the number of the positive electrode and the negative electrode when the power storage device having the same volume as that of the power storage device manufactured in Example 1 is manufactured with the conventional electrode structure is 22.5 each. However, 0.5 electrode means an electrode in which an active material layer is formed only on one side of the current collector.

First, a positive electrode was produced with the same specifications as in Example 1. However, in addition to the positive electrode in which the active material layer was formed on both sides of the current collector, a positive electrode in which the active material layer was formed only on one side of the current collector was also prepared. Since the separator is used in the conventional electrode structure, it is not necessary to apply an insulating tape to the uncoated portion of the positive electrode current collector.

Each of the sheet-like positive electrodes having the active material layer formed on one side or both sides has a vertical width of 130 mm and a horizontal width of 220 mm including an uncoated portion of 20 mm aluminum foil at one end. The aluminum foil part exposed at a width of 20 mm of the sheet-like positive electrode serves as a mounting part for the positive electrode tab.

A representative sample was taken out from the produced sheet-like positive electrode, and for this representative sample, a test cell was assembled using Li metal as the counter electrode and LiPF ₆ electrolyte as the electrolyte. This test cell was subjected to a charge / discharge test at a voltage range of 4.3 to 3.0V. As a result, it was confirmed that the chargeable capacity of the produced sheet-like positive electrode was 78 mAh / electrode single side.

On the other hand, Li ₄ Ti ₅ O ₁₂ synthesized in Example 1 is used as the negative electrode active material. However, since the separator is used in Comparative Example 1, the negative electrode active material layer does not need to be non-electron conductive. On the contrary, in order to obtain a battery with high output performance, it is advantageous to form an electron-conductive negative electrode active material layer constituted by mixing a conductive assistant with a negative electrode active material as in the past.

Therefore, in the production of the negative electrode according to Comparative Example 1, carbon black and graphite are added to Li ₄ Ti ₅ O ₁₂ as a conductive additive and mixed well, and then wet mixed with PVDF and NMP as a solvent as a binder. To make a paste slurry.

The slurry was uniformly applied on one side of a 250 mm wide aluminum foil serving as a current collector, leaving uncoated portions of 20 mm at both ends, and dried. Thereafter, a part of the single-sided coated body was left for preparation of a single-sided electrode, and the other single-sided coated body was coated with the above slurry on the other side with the same specifications and dried.

The double-sided coated body and single-sided coated body of aluminum foil are each cut to a predetermined negative electrode size and then pressed with a roller press so that the density of the coated product becomes 2.0 to 2.1 g / cm ^3. The sheet-shaped negative electrode was formed by forming and forming an active material layer in close contact with both surfaces or one surface of the aluminum foil current collector.

The sheet-like negative electrode having the active material layer formed on one side or both sides is 220 mm including the uncoated portion of the aluminum foil having a vertical width of 130 mm and a horizontal width of 20 mm at one end. The aluminum foil part exposed by 20 mm width of the said sheet-like negative electrode becomes an attachment part of a negative electrode tab.

Note that the fabricated sheet-shaped negative electrode taken out a representative sample for the representative sample, a counter electrode and Li metal were assembled test cell using a LiPF ₆ electrolyte. This test cell was subjected to a charge / discharge test in a voltage range of 1.2 to 2.5V. As a result, the chargeable capacity of the produced sheet-like negative electrode was 115 mAh / electrode single side. Therefore, the chargeable capacity of the sheet-like negative electrode is about 1.47 times the chargeable capacity of the sheet-like positive electrode.

Generally, in order to align the charging characteristics of each battery, the chargeable capacity of either the positive electrode or the negative electrode is increased, and the battery is designed by either the negative electrode capacity regulation or the positive electrode capacity regulation. Incidentally, the existing negative electrode potential type lithium ion battery has a negative electrode capacity of about 1.4 times the positive electrode capacity, and is designed with positive electrode capacity regulation.

Among the positive electrode and negative electrode prepared as described above, a porous polypropylene separator having a thickness of 25 μm was first stacked on the active material layer of the positive electrode on which the active material layer was formed only on one side of the current collector. Further, on the separator, a negative electrode in which an active material layer was formed on both sides of the current collector was overlapped so that the uncoated part of the current collector was opposite to the uncoated part of the positive electrode.

Further, a separator body having a thickness of 25 μm is stacked on the active material layer of the negative electrode, and a positive electrode in which the active material layer is formed on both sides of the current collector is applied to the separator body. The parts were aligned on the same side as the other positive electrodes.

In the same manner, 25.5 positive electrodes and 25.5 negative electrodes were alternately stacked with the separator interposed therebetween, and the active material layers of the positive electrode and the negative electrode were stacked to face each other with the separator interposed therebetween. Thereafter, an uncoated portion of the current collector of each electrode was welded to an 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 laminar 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 type of laminate sheet is stacked on the periphery And heat-sealed.

The electrode tab welded with the current collector of each electrode is taken out from between the two laminated sheets in the same manner as in Example 1 and becomes an external terminal.

The electrode element produced as described above and accommodated in the laminate sheet is injected with LiPF ₆ (1M) electrolyte from the unfused portion of the laminate sheet, impregnated with vacuum, and finally the unmelted laminate sheet. The landing part was heat-sealed. Thus, the noble negative electrode potential type lithium ion battery having the conventional electrode structure shown in FIG. 6 was completed with the same battery volume (115 cc) as the noble negative electrode potential type battery according to Example 1.

(3) Performance evaluation test 1
For each of the batteries produced in Example 1 and Comparative Example 1, a 24 hour aging period was allowed to elapse for the purpose of stabilizing the inside of the battery, and the first charge / discharge was performed. In the first charging / discharging, all the batteries were set to a charging upper limit voltage of 3.0 V, charged for 8 hours, and then discharged to a final voltage of 2.0 V by 4 A constant current discharging.

FIG. 8 is a diagram showing a discharge curve in 4 A constant current discharge of each battery produced in Example 1 and Comparative Example 1. The discharge curve of the battery according to Example 1 is denoted by reference numeral 17, and the discharge curve of the battery according to Comparative Example 1 is denoted by reference numeral 18.

As shown in FIG. 8, the discharge capacity of the battery according to Example 1 is 6.3 Ah (4 A × 94 minutes), and the discharge capacity of the battery according to Comparative Example 1 is 3.6 Ah (4 A × 54 minutes). This difference in discharge capacity is apparently due to the difference between the electrode structure according to the present invention which does not require a separator body and the conventional electrode structure which requires a separator body.

Both the battery according to Example 1 and the battery according to Comparative Example 1 have a negative electrode chargeable capacity that is about 1.5 times larger than the positive electrode chargeable capacity. In such a battery, the excessive chargeable capacity of the negative electrode also contributes to the generation of the separator function.

That is, in the battery according to Example 1, the substantially chargeable capacity of Li ₄ Ti ₅ O _{12 in} the negative electrode active material layer is about 1.46 times larger than the substantial chargeable capacity of LiMn ₂ O ₄ in the positive electrode active material layer. Therefore, about 30% of Li ₄ Ti ₅ O ₁₂ remains in the vicinity of the boundary with the positive electrode active material layer in an uncharged state at the end of charging. Therefore, of course, before the start of charging, the non-electron conductive active material layer in an uncharged state is always present at the boundary between the positive electrode active material layer and the negative electrode active material layer even during charging or after charging is finished. Plays.

Further, as shown in FIG. 8, the average discharge voltage is about 2.45V for all the batteries. Since the energy density (Wh / L) of the battery is given by discharge capacity (Ah) × average discharge voltage (V) ÷ battery volume (L), the energy density of the battery of Example 1 is 134 Wh / L. On the other hand, the battery of the comparative example 1 is 77 Wh / L. That is, it can be seen that the energy density (Wh / L) is greatly increased according to the electrode structure of the present invention that does not require a separator body.

Subsequently, the charging upper limit voltage of each of the battery manufactured in Example 1 and the battery manufactured in Comparative Example 1 was set to 3.0 V again, charging was performed for 8 hours, and then terminated at a constant current discharge of 70 A. The voltage was increased to 1.8V. As a result, the discharge time of the battery according to Example 1 was 307 seconds, and the discharge time of the battery according to Comparative Example 1 was 110 seconds.

Furthermore, for the battery according to Example 1, a discharge test from a fully charged state to a final voltage of 1.8 V was performed by further increasing the discharge current value. As a result, the discharge time was 120 seconds with 160 A constant current discharge.

In the graph shown in FIG. 9, the discharge output curve of 70 A constant current discharge of Comparative Example 1 is indicated by reference numeral 20, and the discharge output curve of 160 A constant current discharge of Example 1 is indicated by reference numeral 19. The horizontal axis of the graph is the discharge time (seconds), the vertical axis is the discharge output, the scale on the left of the vertical axis is scaled with the battery output (W), and the scale on the right is the battery output density (W / L). It is graduated.

As shown at 20 in FIG. 9, in the constant current discharge of 70 A of the battery according to Comparative Example 1, the battery can be discharged for about 110 seconds at an average discharge output (average discharge voltage is about 2.2 V) at about 154 W. However, as described above, if the maximum power supply capacity (W / L) is defined as a value obtained by dividing the maximum output sustainable for 120 seconds by the volume of the battery, the maximum power supply capacity of the battery according to Comparative Example 1 is 154W / 0.115L or less, that is, 1340W / L or less. In other words. The maximum power supply capacity (W / L) of Comparative Example 1 is far below the 2500 W / L of the HV mounting standard.

On the other hand, as shown at 19 in FIG. 9, in the 160 A constant current discharge of the battery according to Example 1, the battery can be continuously discharged for about 120 seconds at an average discharge output (average discharge voltage is about 2.2 V) at about 352 W. Therefore, the maximum power supply capacity (W / L) of the battery according to Example 1 is 352 / 0.115, that is, 3060 W / L. This maximum power supply capacity (W / L) sufficiently satisfies the HV mounting standards.

As described above, when the electrode structure according to the present invention is applied to a noble negative electrode type battery, the battery has an energy density of 134 Wh / L as in the battery according to Example 1, and the maximum power supply capacity (W / L). However, it is possible to have 3060 W / L, and the performance required for a battery for HV mounting is sufficiently satisfied both in energy density (120 Wh / L or more) and maximum power supply capacity (2500 W / L or more). .

Subsequently, Example 2 and Comparative Example 2 will be described. In Example 2 shown below, a noble negative electrode potential type lithium ion battery premised on EV mounting is divided into a battery having an electrode structure to which the present invention is applied (Example 2) and a battery having a conventional electrode structure (Comparative Example). 1) was prepared, and the performance was compared.

(4) Production of Battery of Example 2 In Example 2, LMO is used as the positive electrode active material and LTO is used as the negative electrode active material, and the electrode structure to which the present invention is applied is premised on EV mounting. A noble negative electrode potential type lithium ion battery was produced.

Since the base negative electrode potential type battery mounted on the current EV has a maximum output density of 800 to 900 W / L, the noble negative electrode potential type battery according to Example 2 also has a maximum output density of 800 to 900 W / L or more. It was designed as a prerequisite.

The battery voltage of the noble negative electrode type battery to be produced in Example 2 is about 2.5V. On the other hand, the battery voltage of the base negative electrode type battery mounted on the current EV is about 3.7 V, which is about 1.48 times that of the battery to be manufactured in Example 2. Therefore, in Example 2, in order to have the maximum output density (W / L) equivalent to the current EV-equipped battery, the electrode area density is 1.48 ² (= 2.2) times that of the current EV-equipped battery. Designed. Incidentally, the electrode area density of the current EV-equipped battery is about 3.4 m ² / L.

The storage element of the battery according to Example 2 is configured as an electrode laminate in which the positive electrode and the negative electrode are alternately stacked without interposing a sheet-like separator like the battery according to Example 1, but the cross-sectional structure of the negative electrode Is slightly different from the battery according to Example 1.

A cross-sectional structure of the battery element of the battery according to Example 2 will be described with reference to FIG. FIG. 10 shows an enlarged part of a cross section of the battery element of the battery according to Example 2. As shown in FIG. 10, the battery element 21 of the battery according to Example 2 includes a positive electrode 22 and a negative electrode 23.

The negative electrode 23 has an electron conductive active material layer 24a formed by mixing a negative electrode active material with a conductive additive in close contact with the negative electrode current collector 25. The negative electrode active material layer 24a further includes a negative electrode This is an electrode formed by adhering the active material layer 24b. However, here, the negative electrode active material layer 24b is a non-electron conductive active material layer configured without mixing a conductive additive in a non-electron conductive negative electrode active material.

On the other hand, in the positive electrode 22, the positive electrode active material layer 27 formed in close contact with the positive electrode current collector 26 may be electronically conductive, like the batteries according to Example 1 and Comparative Example 1.

Therefore, in the electrode blocking 21, the negative electrode active material layer 24b facing the positive electrode active material layer 27 is non-electron conductive in an uncharged state, and therefore, the opposed positive electrode active material layer and negative electrode active material layer face each other. Even if the surface 28 is in contact, the positive electrode 22 and the negative electrode 23 do not conduct electronically.

Note that the active material constituting the negative electrode active material layer 24a and the active material constituting the negative electrode active material layer 24b may be the same active material or different active materials. However, in the case of different active materials, the active material that constitutes the negative electrode active material layer 24b needs to be selected from materials that are non-electron conductive in an uncharged state, but the active material that constitutes the negative electrode active material layer 24a. The material need not be non-electron conductive in an uncharged state.

In Example 2, LTO was used as the active material constituting the negative electrode active material layer 24a and the negative electrode active material layer 24b of the negative electrode 23, as in Example 1. As described above, LTO (Li ₄ Ti ₅ O ₁₂ ) is completely electronically insulating with a small electronic conductivity (about 10 ⁻¹³ S / cm) and is electrochemically reduced in an organic electrolyte. For example, it changes to Li ₇ Ti ₅ O ₁₂ having both good electronic conductivity and ionic conductivity.

In the production of the negative electrode 23, the LTO synthesized in Example 1 was mixed with acetylene black and graphite as a conduction aid, and wet-mixed with a solvent in which PVDF (polyvinylidene fluoride) as a binder was dissolved. Prepared. In addition, a negative electrode slurry B was prepared by mixing the same LTO with a solvent in which a binder was dissolved, without mixing a conductive auxiliary agent such as acetylene black.

First, slurry A was applied uniformly to a coating width of 210 mm and dried to form a coated film of slurry A, leaving an uncoated portion of 20 mm on both sides on one side of an aluminum foil having a width of 250 mm and a thickness of 0.015 mm. . Then, the slurry B was apply | coated on the coating film of the slurry A with the same application width, it was apply | coated, and it was made to dry. Furthermore, the slurry A was applied and dried on the other surface so that the application positions on both surfaces overlapped with the same application width, and then the slurry B was applied in an overlapping manner and dried.

Next, after the aluminum foil coated with the slurry A and the slurry B on both sides is cut into a predetermined size of the negative electrode 23, the density of the coated product becomes 2.0 to 2.2 g / cm ^3. It was pressure molded with a roller press.

As shown in FIG. 10, the negative electrode 23 of Example 2 produced in this way was formed by adhering a negative electrode active material layer 24a to both surfaces of an aluminum foil current collector 25, and the negative electrode active material layer 24b was formed of a negative electrode active material. This is a sheet-like electrode formed in close contact with the layer 24a.

The negative electrode 23 of Example 2 finally has a thickness of 90 to 92 μm, a vertical width of 140 mm, and a horizontal width of 230 mm including an uncoated aluminum foil portion of 20 mm at one end. The aluminum foil part exposed at a width of 20 mm of the sheet-like negative electrode 23 becomes an attachment part of the negative electrode tab.

A representative sample was taken out from the produced sheet-like negative electrode 23, and for this representative sample, the counter electrode was made of Li metal and a test cell was assembled using LiPF ₆ electrolyte. This test cell was subjected to a charge / discharge test in a voltage range of 1.2 to 2.5V. As a result, the chargeable capacity per electrode single side of the negative electrode 23 of Example 2 was 328 mAh.

Further, in the production of the positive electrode 22, acetylene black and graphite were mixed as a conductive additive in LMO, and wet mixed with a solvent in which the binder PVDF was dissolved to prepare a positive electrode slurry. This slurry was uniformly applied with a coating width of 170 mm and dried on one side of an aluminum foil having a width of 250 mm and a thickness of 0.015 mm, leaving uncoated portions of 40 mm at both ends. Furthermore, the same slurry was applied to the other surface with the same specification and dried so that the application position on both surfaces overlapped with the same application width.

Thereafter, the aluminum foil having the coated product formed on both sides is cut into a predetermined size of the positive electrode 22, and then the roller press is applied so that the coated product has a density of 2.65 to 2.9 g / cm ^3. Press molding with a machine.

The positive electrode 22 of Example 2 has a final thickness of 82 to 84 μm, a vertical width of 130 mm, and a horizontal width of 220 mm including an uncoated aluminum foil portion with 20 mm at one end. The exposed aluminum foil portion of the positive electrode with a width of 20 mm becomes an attachment portion of the positive electrode tab. Further, an insulating tape having a width of 10 mm was attached to the attachment portion of the positive electrode tab following the active material application portion.

A representative sample was also taken out from the sheet-like positive electrode 22 produced in this way, and for this representative sample, the counter electrode was made of Li metal and a test cell was assembled using a LiPF ₆ electrolyte. This test cell was subjected to a charge / discharge test in a voltage range of 4.3 to 3.0V. As a result, the chargeable capacity per one electrode surface of the produced positive electrode 22 was 258 mAh. After all, in Example 2, the chargeable capacity of the negative electrode 23 prepared earlier is 1.27 times the chargeable capacity of the positive electrode 22.

In the positive electrode 22 and the negative electrode 23 manufactured as described above, the uncoated portions of the current collectors of the respective electrodes are opposite to each other, and first, on one negative electrode active material layer, The positive electrode active material layers were stacked in close contact.

At this time, the negative electrode is positioned at an intermediate position of the insulating tape affixed to the uncoated portion of the positive electrode current collector, that is, a position on the uncoated portion side by 5 mm from the boundary between the active material coated portion and the uncoated portion of the positive electrode current collector 26. The positive electrode 22 was overlapped so that the end portions in the width direction of 23 were arranged. If it does so, the positive electrode end located in the other edge part side of the horizontal direction of the negative electrode 23 will overlap in the position which leaves about 5 mm of negative electrode application parts.

Also, in the longitudinal width direction of the electrode, both ends of the negative electrode 23 protruded from the positive electrode end by 5 mm and overlapped. In the same manner, the uncoated portion of the current collector is pasted on the uncoated portion of the positive electrode current collector 26 on the positive electrode active material layer 27 so that the uncoated portion of the current collector is opposite to the uncoated portion of the positive electrode 22. The negative electrode 23 was stacked with the negative electrode active material layer 24b in close contact with the positive electrode active material layer 27 so that the end in the width direction of the negative electrode 23 was disposed at the intermediate position of the insulating tape.

In this way, the positive electrodes 22 and the negative electrodes 23 are alternately stacked, and the eighteenth negative electrode 23 is stacked on the seventeenth positive electrode 22, and then the uncoated portions of the current collectors of the electrodes are collectively welded to the electrode tabs. Although the electrode structure itself is different, an electrode element similar to the laminate shown in FIGS. 1 and 2 was assembled.

After the assembled electrode element is sufficiently dried, it is placed in a laminate sheet in the same procedure as in Example 1, and the periphery of the laminate sheet is heat-sealed, and the electrolyte is injected, and then the unfused portion of the laminate sheet is removed. Heat-sealed. Thus, a noble negative electrode type battery having a battery volume of 115 cc was completed. However, the battery volume 115 cc is equal to the volume in which the water volume increases when the battery is submerged in water, and is the so-called true volume of the battery.

In the noble negative electrode potential type lithium ion battery prepared in Example 2, in the first charge, the negative electrode active material is charged from the LTO in the electron conductive negative electrode active material layer 24a, and the negative electrode active material layer is charged. Proceed to LTO in 24b.

Since the chargeable capacity of the negative electrode 23 is 1.27 times the chargeable capacity of the positive electrode 22, 0.27 times the LTO remains uncharged at the end of charging, but most of them are the counter electrode active material layer and It remains in the negative electrode active material layer 24b near the boundary. Therefore, the layer in which the uncharged LTO remains in the negative electrode active material layer 24b is an active material layer that remains non-electron conductive. Therefore, the positive electrode active material is not only before the start of charging, but also during charging and after the end of charging. An uncharged non-electron conductive negative electrode active material layer is always interposed between the material layer and the negative electrode active material layer to perform a separator function. Therefore, it is not necessary to interpose a separator body between the positive electrode active material layer and the negative electrode active material layer.

(5) Production of Battery of Comparative Example 2 The noble negative electrode potential type lithium ion battery according to Comparative Example 2 uses LMO as the positive electrode active material and LTO as the negative electrode active material, and has a conventional electrode structure. Produced.

Since the noble negative electrode type battery according to Comparative Example 2 also has the maximum output density (800 to 900 W / L) equivalent to the base negative electrode type battery mounted on the current EV, the electrode area density ( It was designed as 2.2 times of about 3.7 m ² / L).

In the electrode structure of Comparative Example 2, since the separator body is used, in order to increase the electrode area density by 2.2 times with the storage element having the same volume, the electrode thickness must be made thinner than in Example 2. Don't be. Therefore, the total thickness of the positive electrode and the negative electrode of the electrode manufactured in Example 2 is 170 μm, whereas in Comparative Example 2, the total thickness of the positive electrode and the negative electrode is 120 μm.

In the electrode structure of Comparative Example 2, since a separator body is used, the positive electrode and the negative electrode are both electrodes having an electron-conductive active material layer by mixing a conductive additive in the active material.

The chargeable capacity of the produced sheet-like positive electrode was 168 mAh / electrode single side. Moreover, the chargeable capacity | capacitance of the produced sheet-like negative electrode was 213mAh / electrode single side | surface. After all, also in Comparative Example 2, the chargeable capacity of the negative electrode is 1.27 times the chargeable capacity of the positive electrode as in Example 2.

In Comparative Example 2, the thickness of the electrode and the number of laminated layers are different, but in the same manner as Comparative Example 1, other than that, 17 positive electrodes and 18 negative electrodes were alternately stacked, and the conventional electrode structure shown in FIG. A battery having the same battery volume (115 cc) as the battery according to Example 2 was completed. Of course, in the battery according to Comparative Example 2 and the battery according to Example 2, the total area of the electrodes is almost the same. Moreover, the rechargeable capacity of the negative electrode of each battery is about 1.27 times the rechargeable capacity of the positive electrode, and all batteries are regulated as positive electrode capacity.

(6) Performance evaluation test 2
The performance comparison of the batteries of Example 2 and Comparative Example 2 was performed by the following test procedure.

For each of the batteries produced in Example 2 and Comparative Example 2, a 24-hour aging period was passed for the purpose of stabilizing the inside of the battery, and then the first charge / discharge was performed. All the batteries were charged for 5 hours with the charging upper limit voltage set to 3.0 V and the charging current set to 2 A, respectively. Thereafter, the battery was discharged at a constant current of 5 A to a final voltage of 2.0 V.

The discharge capacity of the battery according to Example 2 was 8 Ah, and the discharge capacity of the battery according to Comparative Example 2 was 5.2 Ah. The average discharge voltage of both the battery according to Example 2 and the battery according to Comparative Example 2 was about 2.45V. Therefore, the energy density of the battery according to Example 2 is 170 Wh / L, and the energy density of the battery according to Comparative Example 2 is 111 Wh / L.

Subsequently, the battery according to Example 2 and the battery according to Comparative Example 2 were each charged with a constant voltage of 3.0 V for 15 minutes, and then discharged with a constant current discharge of 5 A to a final voltage of 2.0 V.

As a result, the discharge capacity of the battery according to Example 2 was 6.5 Ah, and the discharge capacity of the battery according to Comparative Example 2 was 4.2 Ah. From this result, it was confirmed that about 80% of the battery according to Example 2 and the battery according to Comparative Example 2 can be charged by charging for 15 minutes. By the way, it is said that about 80% can be charged by charging for 30 minutes in the negative electrode potential type battery mounted on the current EV.

As for the battery according to Example 2, the battery according to Comparative Example 2 is a noble negative potential type battery (open circuit voltage 2.5 V), and the battery mounted on the current EV is a base negative potential type battery (open circuit voltage 3.7 V). Therefore, in order to secure the maximum output density (800 to 900 W / L) equivalent to the current EV-equipped battery, it was fabricated at 2.2 times the electrode area density (about 3.4 m ² / L) of the current EV battery. This greatly contributes to shortening the charging time. Shortening the charging time can compensate for the shortage of EV charging distance.

However, producing an electrode area density (m ² / L) of 2.2 times leads to a further decrease in energy density. Originally, even if the electrode area density (m ² / L) is made the same, the energy density of the batteries according to Example 2 and Comparative Example 2 is theoretically different from that of the current EV-equipped battery due to the difference in open circuit voltage. Only about 68% can be expected.

The energy density (111 Wh / L) of the battery according to Comparative Example 2 is 45% or less of the energy density (250 Wh / L) of the current EV-equipped battery. In the battery according to Comparative Example 2, producing the electrode area density (m ² / L) by 2.2 times leads to a large decrease in energy density.

Since the charging mileage of the current EV is 200 km, if the battery according to the comparative example 2 is mounted on the EV, the charging mileage of the EV is 90 km or less. Even when the EV application is limited to a moving range within a radius of 50 km, even if considering that about 80% can be charged by charging for 15 minutes, the running distance is not sufficient if the charging running distance at full charge is 90 km or less. .

In other words, even if a noble negative electrode potential type lithium ion battery using LMO as a positive electrode active material and LTO as a negative electrode active material is manufactured with a conventional electrode structure, the energy density is too low to be mounted on an EV. I find it difficult.

On the other hand, the energy density (170 Wh / L) of the battery according to Example 2 is about 68% of the energy density (250 Wh / L) of the current EV-equipped battery. In the battery according to Example 2, the electrode area density (m ² / L) produced by 2.2 times does not lead to a large decrease in energy density. The biggest reason is that the battery according to Example 2 does not use a separate separator body.

The EV equipped with the battery according to the second embodiment is 136 km when fully charged, and a charging distance of 109 km can be secured even with a quick charge of 15 minutes. Therefore, the EV can be used only in a moving range within a radius of 50 km. Is a sufficient mileage.

By the way, the EV on which the current negative-electrode potential type lithium ion battery is mounted can secure a charging mileage of about 160 km by rapid charging for 30 minutes, but the mileage that can be secured by charging for 15 minutes is only about 80 km. Therefore, the noble negative electrode potential type lithium ion battery using LMO as the positive electrode active material and LTO as the negative electrode active material can be charged for a short time according to the electrode structure to which the present invention is applied, Mounting is possible enough.

In the production of the batteries according to Example 1 and Example 2, the non-electron conductive negative electrode active material layer was formed by solidifying the non-electron conductive active material with a binder, but the present invention is not limited to this. The non-electron conductive active material layer constituting the electricity storage device according to the present invention may be formed by an aerosol deposition method or other film forming techniques expected as a future film forming technique.

As described above, the power storage device according to the present invention is characterized in that at least one of the opposing active material layers is non-electron conductive in an uncharged state and is in contact with the counter active material layer on the opposing surface. . Therefore, many performance improvement effects are brought about by the necessity of using the separator body of another member.

There has never been a lithium ion secondary battery or capacitor that does not use a separate separator body.

A lithium iodine battery (Li / I ₂ battery) for cardiac pacemakers has been put to practical use as the only battery that does not require a separate separator body. The Li / I ₂ battery is a solid electrolyte battery that uses metallic lithium (Li) as a negative electrode active material and iodine (I ₂ ) as a positive electrode active material.

In this Li / I ₂ battery, since no separator is interposed, Li of the negative electrode and I _{2 of the} positive electrode are in contact with each other, and the interface is ion-conductive but electronically insulating lithium iodide (LiI). Generated. Therefore, the positive electrode and the negative electrode are made conductive by ionic conduction by the generated LiI, and electronic conduction is blocked, so that the Li / I ₂ battery functions as a battery.

Thus, the Li / I ₂ battery is the same in that the power storage device according to the present invention and the separator are unnecessary. However, it is fundamentally different 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 the active materials are in an uncharged state when the power storage device is assembled.

Further, instead of the separator body, what prevents the electronic conduction between the positive electrode and the negative electrode is a reactive organism of the positive electrode active material and the negative electrode active material in the Li / I ₂ battery, but is not charged in the power storage device according to the present invention. It is a non-electron conductive active material layer in a state.

Further, in the Li / I ₂ battery, the reactive organism itself becomes the ion conduction path between the positive electrode and the negative electrode. Therefore, the internal resistance gradually increases with discharge due to accumulation of reactive organisms accompanying discharge. On the other hand, in the power storage device according to the present invention, the ion conduction path between the positive electrode and the negative electrode is secured by the electrolytic solution impregnated in the active material layer, so that the change in internal resistance due to discharge is small.

Here, the internal resistance of the power storage device according to the present invention will be described. The power storage device according to the present invention can basically reduce the internal resistance by increasing the electrode area.

The power storage device according to the present invention is different from the conventional power storage device in that a non-electron conductive active material is used without mixing a conduction aid. Therefore, it is not surprising that the internal resistance of the power storage device according to the present invention is higher than that of a conventional power storage device in which a conductive assistant is mixed with an active material. But that is not the case.

Non-electron conductive (insulating) materials often have different valence atoms (eg, T ⁺⁴ and Ti ⁺³ , Fe ⁺⁾ that can exchange electrons once oxidized or reduced in the charge direction. ³ and Fe ⁺² ) coexist in the crystal, and many of them change to electronic conductivity. Moreover, if it is reduced or oxidized again in the discharge direction, it is difficult to electrochemically reduce or oxidize until all atoms have the same valence unless they are extremely polarized. Therefore, once a non-electron conductive (insulating) substance is oxidized or reduced to change to electronic conductivity, atoms with different valences always coexist in the crystal, and electron conductivity is maintained. It will not return to the original non-electron conductive material.

In the power storage device according to the present invention, it is 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. . That is, in the power storage device according to the present invention, the active material that changes to electronic conductivity by the first charge always plays a role of contributing to charge / discharge. That is, the active material that has changed to electron conductivity by the first charge functions as an electron conductive active material unless an excessive overdischarge is caused thereafter. Therefore, in the power storage device according to the present invention, the effect of not mixing the conductive aid into the active material hardly appears after the completion of the first charge.

In addition, regardless of whether the battery is a primary battery or a secondary battery, the separator body used in the organic electrolyte battery is a special thin porous membrane and is very expensive. In particular, in a battery having a large electrode facing area, the amount of the separator body used increases, and the price of the separator body greatly increases the material cost.

According to the electrode structure of the present invention, the separator which is indispensable in the conventional electrode structure is not required, the distance between the positive electrode and the negative electrode is shortened, and the volume occupied by the separator is increased in the electrode filling amount. The area also increases. Moreover, since an expensive separator is not used, raw material costs are also reduced. As a result, a power storage device with a high output density can be realized at a low material cost without greatly reducing the energy density section.

The embodiment of the present invention has been described above, but the above embodiment shows an application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment. Various modifications can be made without departing from the scope of the present invention.

Especially when the present invention is applied to a noble negative electrode potential type lithium ion battery, a highly safe power storage device having high output performance and fast charging speed can be provided for HV and EV mounting.

As described above, the present invention provides a safe, high-capacity, high-input / output power storage device, and further applies this to a hybrid vehicle that is safe and has excellent fuel efficiency, and can be safely and rapidly charged. A vehicle can be provided.

DESCRIPTION OF SYMBOLS 1 Negative electrode active material layer 2 Positive electrode active material layer 3 Negative electrode collector 4 Positive electrode collector 5 Separator body 6 Negative electrode tab 7 Positive electrode tab 8 Insulating tape 9 Plastic tape 10 Power storage element 11 Laminate sheet 12 Laminate sheet 13 Negative electrode external terminal 14 Positive electrode external terminal 15 Electrode laminate not using separator 16 Electrode laminate using separator 17 Discharge curve of Example 1 18 Discharge curve of Comparative Example 1 19 Discharge curve of Example 1 20 Discharge curve of Comparative Example 1 21 Storage element 22 Positive electrode 23 Negative electrode 24a Electron conductive negative electrode active material layer 24b Non-electron conductive negative electrode active material layer 25 Negative electrode current collector 26 Positive electrode current collector 27 Positive electrode active material layer 28 Opposing surface 31 Positive electrode 32 Negative electrode 33 Opposing surface 41 Non-electron conductive active material layer 42 Counter electrode active material layer 43 Current collector 44 Current collector 100 Power storage device

Claims

A positive electrode formed by adhering a positive electrode active material layer to a positive electrode current collector, a negative electrode formed by adhering a negative electrode active material layer to a negative electrode current collector, and an electrolyte solution are sealed in a battery container. In the power storage device, the positive electrode active material layer and the negative electrode active material layer face each other and are in close contact with each other on the facing surface.
2. The power storage device according to claim 1, wherein at least one of the active material layers in close contact with the opposite surface is non-electron conductive in an uncharged state.
The active material layer of at least one of the positive electrode and the negative electrode is an active material layer formed in a two-layer structure, and the active material layer having the two-layer structure has a conductive active material layer as a current collector as a first layer. 2. The second layer is characterized in that an active material layer that is non-electron conductive in an uncharged state is formed on the first conductive active material layer as the second layer. The power storage device described.
The active material layer in close contact with the opposing surface is electrically conductive by the non-electron conductive active material layer that is uncharged on the opposing surface after the power storage device is initially charged. The power storage device according to claim 2, wherein the power storage device is cut off.
5. The power storage device according to claim 4, wherein the chargeable current capacity of the electrode having the non-electron conductive active material layer is larger than the chargeable current capacity of the opposing electrode.
The negative electrode active material constituting the non-electron conductive active material layer is selected from materials that are non-electron conductive unless electrochemically reduced, and change to electronic conductivity when electrochemically reduced. The power storage device according to claim 2 or claim 3, wherein
The power storage device according to claim 6, wherein the negative electrode active material constituting the non-electron conductive active material layer is lithium titanate represented by a chemical formula Li 4 Ti 5 O 12 .
The positive electrode active material constituting the non-electron conductive active material layer is selected from materials that are non-electron conductive unless electrochemically oxidized, and change to electronic conductivity when electrochemically oxidized. The power storage device according to claim 2 or claim 3, wherein
9. The power storage device according to claim 8, wherein the positive electrode active material constituting the non-electron conductive active material layer is lithium iron phosphate represented by a chemical formula LiFePO 4 .
A hybrid vehicle equipped with the power storage device according to claim 2 or claim 3.
A 100% motor-driven electric vehicle equipped with the power storage device according to claim 2 or claim 3.