JP2013114858A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which can ensure a high capacity efficiently, by reducing the voltage difference between the charge time and discharge time when using a high capacity electrode material.SOLUTION: In a secondary battery having a first electrode, a nonaqueous electrolyte, and a second electrode, at least the first electrode contains at least a first active material, and a second active material having an electromotive force larger than that of the first active material. When the secondary battery is charged, it is charged by connecting the first active material and the second electrode electrically, and subsequently charged by connecting the second active material and the second electrode electrically. When the secondary battery is discharged, it is discharged by connecting the second active material and the second electrode electrically, and subsequently discharged by connecting the first active material and the second electrode electrically.

Description

  The present invention relates to a high-capacity secondary battery using a non-aqueous electrolyte.

  In recent years, with the development of digital mobile devices, there is a need for high-capacity secondary batteries that can be discharged for a long time after being charged. Attempts have been made to improve the filling rate.

In recent years, new materials such as LiNiO ₂ , Li (Ni, Co, Al) O ₂ , and Li (Co, Ni, Mn) O ₂ have been used as active materials for positive electrodes as high-capacity material systems (for example, patents) In addition, as an active material for the negative electrode, an alloy material of Si and Sn (see, for example, Patent Document 2) has been developed and put into practical use.

Japanese Patent No. 3550783 Japanese Patent No. 4207958

  However, these material systems have a large change in electromotive force due to charge / discharge, and in order to increase the capacity of the secondary battery, it is necessary to expand the range of the charge / discharge voltage than before. Generally, in the positive electrode, the electromotive force increases as the charging progresses, and the electromotive force decreases as the discharging progresses, whereas in the negative electrode, the electromotive force decreases as the charging progresses, and the electromotive force decreases as the discharging progresses. Since the voltage rises, the electromotive force of the battery, which is the difference between the electromotive forces of the positive electrode and the negative electrode, greatly increases during charging and greatly decreases during discharging. Therefore, even if an attempt is made to improve the battery capacity by using a high-capacity material having a large electromotive force as the positive electrode of the secondary battery, the charge end voltage is usually 4.2 V and the discharge end voltage is 3. At 0V, the voltage difference is 1.2V. For example, the charge end voltage needs to be increased to 4.3V, the discharge end voltage 2.0V, and the voltage difference increased to 2.3V. There is a problem that the voltage difference of becomes large and the characteristics of the device using the secondary battery become unstable.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a secondary battery that can reduce a voltage difference during charge and discharge and can efficiently obtain a high capacity.

  The secondary battery of the present invention is a secondary battery having a first electrode, a nonaqueous electrolyte, and a second electrode, wherein at least the first electrode is at least a first active material, A second active material having an electromotive force greater than that of the active material, and when charging the secondary battery, the first active material and the second electrode are electrically connected and charged, Subsequently, the second active material and the second electrode are electrically connected and charged, and at the time of discharging, the second active material and the second electrode are electrically connected and discharged. The first active material and the second electrode are electrically connected to discharge.

  ADVANTAGE OF THE INVENTION According to this invention, the secondary battery which can reduce the voltage difference at the time of charging / discharging and can obtain a high capacity | capacitance efficiently can be provided.

It is a schematic diagram of the cross section of the secondary battery which is one Embodiment of this invention. It is a schematic diagram of the cross section of the cell for evaluation of charging / discharging behavior. It is the figure which showed the charging / discharging behavior of Example 1.

  An embodiment of the present invention will be described with reference to FIG. In the secondary battery of the present embodiment, a power generation element 4 having a separator 3 between a first electrode 1 as a negative electrode and a second electrode 2 as a positive electrode is filled with a nonaqueous electrolyte (not shown). The battery case 5 is housed. The first electrode 1 and the second electrode 2 have, as constituent elements, an active material that generates an electromotive force upon charging and discharging, and a current collector that draws electricity from the active material, and a conductive agent as necessary Or a binder.

  The first electrode 1 includes a second active material containing a second active material in which the potential difference between the first active material layer 1a containing the first active material and the second electrode 2 is smaller than that of the first active material. The layer 1b is laminated via the intervening layer 1c, and the second active material layer 1b is disposed so as to be in contact with the separator 3. The wirings 6a, 6b and 6c are provided so as to be connected to the first active material layer 1a, the second active material layer 1b and the second electrode 2, respectively.

  In the second electrode 2, the current collector may be provided on a surface different from the surface in contact with the separator 3. In the first electrode 1, the first active material layer 1a and the second active material layer 1b may be provided so as not to contact each other on the surface not in contact with the intervening layer 1c. In order to secure the contact between each active material constituting the first electrode 1 and the second electrode 2 and the non-aqueous electrolyte, the current collector may have a mesh shape or a porous film shape. preferable. In addition, the electrode itself may have a current collecting function by mixing the conductive agent and the active material to form the electrode.

  The first active material layer 1a, the second active material layer 1b, and the second electrode 2 may each be a mixture of two or more active materials.

  In the secondary battery of this embodiment, when the first electrode 1 is a negative electrode and the second electrode 2 is a positive electrode, at the time of charging, first, the wirings 6a and 6c are connected to connect the first active material layer 1a. After charging, the wirings 6b and 6c are continuously connected to charge the second active material layer 1b having a smaller potential difference from the positive electrode, that is, having a higher electromotive force. In discharging, the wirings 6b and 6c are connected. Then, after discharging the second active material layer 1b having a higher electromotive force, the wirings 6a and 6c are connected to discharge the first active material layer 1a.

  By adopting such a configuration, the negative electrode is switched to the second active material having a higher electromotive force when the positive electrode electromotive force increases during charging, and the positive electromotive force decreases during discharging. Accordingly, the negative electrode can be switched to the first active material having a smaller electromotive force, and it becomes possible to charge and discharge electricity more efficiently.

When the first electrode 1 is a positive electrode and the second electrode 2 is a negative electrode, the positive electrode is switched to a second active material having a smaller electromotive force as the electromotive force of the negative electrode decreases. In discharging, the positive electrode can be switched to the first active material having a larger electromotive force as the electromotive force of the negative electrode increases, and similarly, electricity can be charged and discharged more efficiently. Specifically, at the time of charging, first, the wirings 6a and 6c are connected to charge the first active material layer 1a, and then the wirings 6b and 6c are connected, so that the potential difference from the negative electrode is smaller, that is, lower. The second active material layer 1b having an electromotive force is charged, and at the time of discharging, the wires 6b and 6c are connected to discharge the second active material layer 1b having a lower electromotive force, and then the wires 6a and 6c are continuously connected. The first active material layer 1a is discharged by connection.

  The connection switching operation between the wirings 6a and 6b and the wiring 6c can be performed using, for example, an external power supply and a circuit control system. For example, a change in electrode current or voltage due to charge / discharge is measured, or a volume change in at least one of the first active material layer 1a and the second active material layer 1b due to charge / discharge is detected by a displacement sensor or a pressure sensor. Then, according to these measured values, the connection between the wirings 6a and 6b and the wiring 6c may be controlled so that the voltage difference between charging and discharging is reduced. In this case, a solid electrolyte may be used as the electrolyte.

  Further, by using a material that changes in volume by charge and discharge as the first and second active materials, and using an anisotropic conductive material as the intervening layer 1c, the first active material layer 1a, the second active material layer 1b, The connection switching operation with the two electrodes 2 can be performed more easily. For example, it is assumed that the first active material layer 1a and the second active material layer 1b include a material that expands in volume upon charging, and an anisotropic conductive paste or adhesive is used as the intervening layer 1c to configure the power generation element. When the first active material layer 1a, the intervening layer 1c, the second active material layer 1b, the separator, and the second electrode 2 are stacked in this order, the wirings 6a and 6b are simultaneously connected to the 6c, First, the first active material layer 1a having a larger potential difference from the second electrode 2 is charged. The first active material layer 1a expands as the charging progresses and compresses the intervening layer 1c, and the electrical resistance between the first active material layer 1a and the second active material layer 1b decreases, and the first active material layer 1a When the second active material layer 1b is electrically connected to the second electrode 2 through the intervening layer 1c, charging of the second active material layer 1b starts. And if the 2nd active material layer 1b expands with progress of charge of the 2nd active material layer 1b, the space which exists between the 2nd active material layer 1b and the battery case 5 will be shielded, and the 1st active material layer 1a and The flow of the electrolytic solution between the second electrodes 2 and the exchange of conduction ions are shielded, and charging to the first active material layer 1a is stopped. During the discharge, the second active material layer 1b contracts as the discharge progresses, and a space is generated between the second active material layer 1b and the battery case 5, and the first active material layer 1a and the second electrode are formed. The electrolyte solution and the conduction ions can be exchanged between the first active material layer 1 and the first active material layer 1a. Further, when the first active material layer 1a is discharged and contracts, the electrical resistance between the first active material layer 1a and the second active material layer 1b increases, and the electrical current between the second active material layer 1b and the second electrode 2 increases. The connection is interrupted and the initial state is restored.

  In this case, the second electrode 2, the first active material layer 1a, and the second active material layer 1b are simultaneously electrically connected to each other by the ionic conductivity inside the second active material layer 1b even at the end of charging and the start of discharging. The first active material layer 1a is slightly charged / discharged, but by suppressing the ionic conductivity during expansion of the second active material layer 1b, the first active material layer 1a appears. Charging / discharging to 1a is suppressed and charging / discharging to the second active material layer 1b becomes dominant, that is, the potential of the first electrode 1 is mainly due to the contribution of the second active material layer 1b.

  As described above, in order to suppress the ionic conductivity when the second active material layer 1b expands, the amount of binder compressed in the second active material layer 1b when the second active material layer 1b expands is adjusted. That's fine.

  One of the first and second active materials is used as an active material that expands in volume by charging, and the first active material layer 1a and the second active material layer 2a are combined with the volume expansion of the active material and an external circuit control system. Switching operation of the electrical connection between the active material layer 1b and the second electrode 2 can also be performed.

As the positive electrode active material, lithium-containing transition metal oxides are preferably used. Specifically, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt manganese composite oxide, phosphoric acid And lithium lithium composite oxide, lithium titanium composite oxide, and the like. When the positive electrode is the first electrode 1, for example, as a combination of the first and second active materials, LiCoO ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiCoO ₂ and LiFePO ₄ , LiCo A combination such as _1/2 Ni _1/2 O ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ may be selected. Further, those of volume expansion by Li-ion desorption during charging, for _{example, LiCoO 2, LiCo 1/2 Ni 1/2} O 2, and LiNiO ₂ and the like are known, using the change in volume of the active material Therefore, it is preferable for switching operation of electrical connection between the first active material layer 1a and the second active material layer 1b and the second electrode 2.

  As the negative electrode active material, materials capable of occluding and releasing lithium ions are preferably used. Specifically, carbon-based materials such as graphite, hard carbon, and soft carbon, tin (Sn), silicon (Si), aluminum Examples thereof include metals such as (Al), antimony (Sb), zinc (Zn), and bismuth (Bi), alloys thereof, and oxides such as SnO and SiO. When the negative electrode is the first electrode 1, for example, a combination of carbon and Si, Si, Sn, etc. may be selected as the combination of the first and second active materials. Si and Sn are both known to have a high capacity and large volume expansion due to occlusion of conductive ions during charging. The first active material layer 1a and the second active material are utilized by utilizing the volume change of the active material. When performing the switching operation of the electrical connection between the layer 1b and the second electrode 2, it is preferable to use a combination of these materials.

  The first electrode 1 and the second electrode 2 are formed by applying and drying a slurry containing an active material on the surface of a current collector, such as a metal foil, or by a sol-gel method or a chemical vapor deposition method. A method of forming an active material layer on the surface of the current collector by forming a film, or a sheet containing the active material on a base film such as polyethylene terephthalate (PET), and heat treatment or baking as necessary Then, it can be produced by bonding to a non-porous or perforated metal foil or mesh metal, or forming a conductive film by sputtering or vapor deposition.

  When applying a slurry containing an active material on the surface of a current collector, a conductive agent or a binder is added to the raw material powder of the active material as necessary, and the active material is mixed and dispersed in a solvent. A method of preparing a slurry, coating the slurry on the surface of a metal foil or the like as a current collector by a known method such as a doctor blade, drying, volatilizing the solvent, and compressing with a press if necessary May be used. Examples of the conductive agent include carbon materials such as carbon black, metal powder, and the like, and examples of the binder include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

  As a method for forming an active material layer by forming a film on the surface of a current collector, in addition to a sol-gel method and a chemical vapor deposition method, an active material powder aerosol is used as a current collector metal foil, etc. For example, an impact solidification method of spraying on the surface of the material. Further, when a metal is used as the active material, it may be formed by a plating method.

  When producing a sheet containing an active material, for example, a slurry containing an active material is mixed with more binder and, if necessary, a conductive agent than when applied on the surface of a current collector, The slurry is coated on a base material such as a polyethylene terephthalate (PET) film by a known method such as a doctor blade, and then dried to volatilize the solvent, and press-compress as required. Moreover, you may heat-process and baking processing to the sheet | seat containing the obtained active material. Note that by forming the electrode into a sheet containing a conductive agent, even if the active material itself does not have conductivity, the sheet itself can be provided with conductivity and have a current collecting function. Even if a current collector is not separately provided on the electrode surface, sufficient battery characteristics can be obtained by connecting a part of the electrode to a wiring or a circuit. Similarly, when a conductive material is used as the active material, a part of the electrode may be connected to a wiring or a circuit.

The first electrode is formed by laminating the first active material layer 1a and the second active material layer 1b produced as described above via the intervening layer 1c. In addition, it arrange | positions so that the side which is not in contact with the electrical power collector of the 1st active material layer 1a and the 2nd active material layer 1b may oppose through the intervening layer 1c, and contact between each electrical power collector is carried out. It is preferable in preventing. As the material of the intervening layer 1c, a material whose electron conductivity is changed by an external pressure and whose lithium ion conductivity is low is used. As such a material, it is preferable to use a paste or film having anisotropic conductivity in which conductive particles are uniformly dispersed in an insulating resin or the like. An anisotropic conductive paste or film is an insulating resin that is compressed by the application of pressure, and the conductive particles dispersed in the resin come into contact with each other and become conductive in the pressure application direction. It is. Further, the intervening layer 1c may be formed by mixing conductive particles or fillers with polymer particles having elasticity, or by dispersing them in a gel material containing a porous material or an electrolytic solution.

  When a material having high lithium ion conductivity is used, lithium ion conduction occurs between the first active material layer 1a and the second active material layer 1b, and the first active material layer 1a and the second active material layer 1b. There is a possibility that control of the connection switching operation between the first electrode 2 and the second electrode 2 becomes difficult.

  By interposing such a material between the first active material layer 1a and the second active material layer 1b, electrical connection between the first active material layer 1a and the second active material layer 1b and the second electrode 2 is achieved. The connection switching operation can be controlled by the volume change of the first active material layer 1a and the second active material layer 1b, and the lithium between the first active material layer 1a and the second active material layer 1b can be controlled. It is also possible to suppress ionic conduction.

  As the current collector, a conductive metal foil is preferably used. As the material, aluminum (Al), platinum (Pt), gold (Au) or the like is preferably used on the positive electrode side, and on the negative electrode side. Preferably, copper (Cu), platinum (Pt), gold (Au), or the like is used.

  In the first electrode 1, a current collector may be provided only in the first active material layer 1a, but a current collector is provided in each of the first active material layer 1a and the second active material layer 1b. It is preferable that the electrical connection between each active material layer and the second electrode 2 can be controlled independently.

  As the nonaqueous electrolyte, a solid electrolyte, an organic electrolyte, an ionic liquid, or the like having lithium ion conductivity may be used. When using a solid electrolyte, it replaces with the separator 3 and arrange | positions a solid electrolyte. Note that the first active material layer 1a, the second active material layer 1b, and the second electrode 2 are utilized by utilizing the volume change of the first active material layer 1a and the second active material layer 1b regardless of an external circuit control system. When the switching operation of the electrical connection is performed, it is preferable to arrange the separator 3 between the first electrode 1 and the second electrode 2 and use an organic electrolytic solution or an ionic liquid. The organic electrolyte or ionic liquid has high ion conductivity, and can penetrate into the pores existing in the first electrode 1 and the second electrode 2 to realize high battery performance.

  The organic electrolyte is composed of an organic solvent and an electrolyte salt, and if necessary, additives for the purpose of suppressing formation of a solid electrolyte layer on the electrode surface, preventing overcharge, imparting flame retardancy, etc. may be added. Good.

  As the organic solvent, those having a high dielectric constant, low viscosity and low vapor pressure are preferably used. Examples of such materials include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, Mix one or more selected from 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, etc. Solvent.

Examples of the electrolyte salt include LiClO ₄ , LiBF ₄ , LiPF ₆ , and LiCF ₃ SO _3.
, LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _{2 and the} like.

  For the separator, a nonwoven fabric of organic resin fibers, a nonwoven fabric of inorganic fibers, a porous ceramic material, etc. can be used. Ceramic particles are mixed in an organic porous film mainly composed of polyolefin such as polypropylene or polyethylene. It is preferable to use a ceramic, a porous membrane containing a ceramic filler, a non-woven fabric of inorganic fibers, a composite porous membrane of an organic material and an inorganic material, or a porous ceramic material. These have high heat resistance, and in particular, when a secondary battery is formed using a material having a high capacity as the active material of the first and second electrodes, the safety of the secondary battery against thermal runaway is further increased. be able to.

  As the material of the battery case, metal, resin, ceramic, or a composite material thereof is used. In particular, the first active material is obtained by utilizing the volume change of the first active material layer 1a and the second active material layer 1b. When controlling the switching operation of the electrical connection between the layer 1a and the second active material layer 1b and the second electrode 2, by using an insulating material such as ceramic or glass that has little deformation, the first Even if the volume of the active material layer 1a and the second active material layer 1b expands and comes into contact with the battery case, the power generating element 4 does not short-circuit, and the first active material layer 1a, the second active material layer 1b, and the second The switching operation of the electrical connection with the electrode 2 can be performed with good reproducibility, and a secondary battery with stable charge / discharge behavior is obtained.

  The shape of the battery of the present invention may be any of a square shape, a cylindrical shape, a button shape, a coin shape, a flat shape, and the like, and is not particularly limited.

  Hereinafter, the present invention will be described specifically by way of examples.

First, LiCoO ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O are used as positive electrode active materials.
_2. An active material-containing sheet with a current collector was prepared using graphite, Si, and Sn as the negative electrode active material.

LiCoO ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ are LiCO ₃ powder, Co
Using O powder, NiO powder, and MnO powder, they are prepared so as to have respective composition ratios, mixed with a ball mill using alcohol as a solvent, LiCoO ₂ is 600 ° C. in the air, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ was heat treated at 900 ° C. to obtain an average particle size of 5 μm.
m raw material powder was obtained. From the obtained raw material powder, it was confirmed by X-ray diffraction (XRD) measurement that crystal phases of LiCoO ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ were formed, respectively.

Using the obtained LiCoO ₂ raw material powder, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ raw material powder, Si raw material powder having an average particle diameter of 1 μm, and Sn raw material powder having an average particle diameter of 1 μm, raw material powder 90 Add 5% by mass of polyvinylidene fluoride (PVDF) as a binder, 5% by mass of carbon black as a conductive agent, and add N-methylpyrrolidone (NMP) solvent to the mass%. After the work and drying, pressing was performed to produce active material-containing sheets (thicknesses 20 μm and 40 μm) with current collectors, and cut into electrode sizes having a diameter of 15 mm.

  In the case of graphite, 95% by mass of graphite powder having an average particle size of 10 μm as raw material powder, 5% by mass of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) solvent are added and kneaded. After coating and drying on the copper foil, pressing was performed to produce a graphite-containing sheet with a current collector (thickness 40 μm and 80 μm), and similarly cut into an electrode size of 15 mm in diameter.

  Using these produced electrode materials, the first active material layer 1a, the second active material layer 1b, and the second electrode 2 constitute a power generation element 4 having a combination as shown in Table 1, and the battery capacity and charge / discharge characteristics. Was evaluated. In addition, as the intervening layer 1c located between the 1st active material layer 1a and the 2nd active material layer 1b, what was shown in Table 1 was used.

  As shown in FIG. 2, the evaluation cell used was one in which one opening of a glass tube 7 having an inner diameter of 15 mm and a length of 10 mm was bonded to a platinum foil 8. Inside the glass tube 7 of the evaluation cell, the platinum foil 8, the first active material layer 1a, the intervening layer 1c, the second active material layer 1b, the separator 3 and the second electrode 2 are arranged in this order, After injecting the electrolytic solution to configure the power generation element, a SUS-made heavy stone 9 was further placed on the second electrode 2 to press the entire power generation element 4 against the platinum foil 8. At this time, the first active material layer 1a is arranged so that the copper foil as a current collector faces the platinum foil 8, and the second active material layer 1b is arranged so that the copper foil faces the intervening layer 1c, and the second The electrode 2 was arranged so that the copper foil was in contact with the weight 9. In addition, the whole cell for evaluation was installed in the container substituted with argon, and charge / discharge behavior was evaluated.

  An active material-containing sheet having a thickness of 40 μm was used for the first active material layer 1 a and the second active material layer 1 b, and an active material-containing sheet having a thickness of 80 μm was used for the second electrode 2. Sample No. About 5-7, only 1 type of 80-micrometer-thick active material containing sheet | seat was used as a 1st electrode. Moreover, the capacity | capacitance of electrode material independent was arrange | positioned and evaluated so that it might become in order of the platinum foil 8, metal lithium foil, a separator, and an active material containing sheet | seat inside the glass tube 7 of the cell for evaluation.

For any combination described in Table 1, a glass fiber non-woven fabric is used for the separator 3, and the electrolyte is 1 mol / L in an organic solvent in which ethylene carbonate and dimethyl carbonate are mixed at a volume ratio of 3: 7. The one in which LiPF ₆ was dissolved was used.

  A wiring 6 a is connected to the first active material layer 1 a via a platinum foil 8, a wiring 6 b is connected to a current collector in contact with the intervening layer 1 c, and the second electrode 2 is connected to the second electrode 2. The wiring 6c was connected through the SUS-made weight stone 9. The wirings 6a, 6b and 6c were connected to an external power source having a manual switch capable of switching the connection between the wirings 6a and 6b.

  The battery characteristics were evaluated by conducting a charge / discharge test at a rate of 0.1 C with reference to the capacity of the second electrode 2. About the power generation element 4 combining the first electrode 1 and the second electrode 2, the capacity of the electrode material alone used for the first active material layer 1a, the second active material layer 1b, and the second electrode 2, Table 1 shows the charge end voltage, the discharge end voltage, and the battery capacity, which are measurement conditions of the power generation element 4. Sample No. 2, the battery voltage during the charge / discharge test is measured, and the electrical connection between the second electrode 2 and the first active material layer 1a and the second active material layer 1b using a manual switch based on the measured value. A connection switching operation was performed.

  FIG. 1 shows a charge / discharge curve in FIG. At the time of charging, charging of the first active material layer 1a having a lower potential proceeds, and when the potential of the first active material layer 1a further decreases, charging of the second active material layer 1b having a higher potential starts. When the potential of the second active material layer 1b having a higher potential is further increased, the discharge of the first active material layer 1a having a lower potential starts, so that the voltage difference between charging and discharging is small as a whole battery. Yes.

  In this way, sample no. In 1-4, a high capacity could be obtained even with a small voltage difference between charge and discharge. On the other hand, sample No. 1 using only one type of active material as the first electrode 1 was used. In 5-7, when the voltage difference of charging / discharging was small, capacity | capacitance was small, and high capacity | capacitance was obtained by expanding the voltage difference of charging / discharging.

DESCRIPTION OF SYMBOLS 1 ...... 1st electrode 1a ... 1st active material layer 1b ... 2nd active material layer 1c ... Intervening layer 2 ...... 2nd electrode 3 .... Separator 4. ... Power generation element 5 .... Battery case 6a ... Wiring connected to first active material layer 6b ... Wiring connected to second active material layer 6c ... Wiring connected to second electrode 7 .... Glass tube 8 .... Platinum foil 9 .... SUS stainless steel

Claims (6)

In a secondary battery including a first electrode, a non-aqueous electrolyte, and a second electrode, a potential difference between at least the first electrode, at least the first active material, and the second electrode is the first electrode. A second active material smaller than the active material of
When charging the secondary battery, the first active material and the second electrode are electrically connected and charged, and then the second active material and the second electrode are electrically connected. Charge
In discharging, the second active material and the second electrode are electrically connected and discharged, and then the first active material and the second electrode are electrically connected and discharged. Secondary battery characterized.   The secondary battery according to claim 1, wherein at least one of the first active material and the second active material expands in volume by charging.   3. The first electrode according to claim 1, wherein the first electrode includes a first active material layer containing the first active material and a second active material layer containing the second active material. Secondary battery.   The secondary battery according to claim 3, wherein the first active material layer and the second active material layer are laminated via an anisotropic conductive material.   5. The secondary battery according to claim 3, wherein the first active material layer, the second active material layer, the separator, and the second electrode are laminated in this order.   The secondary battery according to claim 1, wherein the first electrode is a negative electrode, and a metal or alloy containing any of Si and Sn is used as the second active material. .

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