JP2012089471A - Device and method for recovering battery capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for recovering battery capacities, capable of compensating for a reduction of movable lithium ions due to charge and discharge without complicating a battery structure.SOLUTION: The device for recovering battery capacities includes: a low potential member 21 having an oxidation-reduction potential lower than that of an active material of a positive electrode 221 or a negative electrode 222 of a battery 100 and having an ability to reduce the active material; and an injector 10 that is provided with a cylinder room 11a housing the low potential member 21 and capable of holding an electrolyte 20 filled therein and an injection nozzle 13 that is formed continuously to the cylinder room 11a, is electrically connected to the low potential member 21 and has conductivity.

Description

  The present invention relates to an apparatus and method for recovering battery capacity.

  Lithium ion secondary batteries deteriorate and decrease battery capacity when charging and discharging are repeated. Therefore, in Patent Document 1, a third electrode containing lithium is arranged in the battery. Then, electric power is supplied from an external circuit to the third electrode. Then, lithium ions are released from the third electrode, and the decrease in movable lithium ions due to charge / discharge can be compensated.

JP-A-8-190934

  However, in the above-described prior art, the third electrode must be disposed in the battery. Therefore, the structure of the battery becomes complicated.

  The present invention has been made paying attention to such conventional problems, and a battery capacity recovery device and a battery that can compensate for the decrease in movable lithium ions due to charging and discharging without complicating the structure of the battery. The object is to provide a capacity recovery method.

  The present invention solves the above problems by the following means.

  The battery capacity recovery device of the present invention has a low-potential member that has a lower redox potential than the active material of the positive electrode or negative electrode of the battery and has a reducing ability for the active material. The low-potential member is accommodated, and a cylinder chamber capable of holding the filled electrolyte, and continuously formed in the cylinder chamber, electrically connected to the low-potential member and conductive. And an injector having an injection nozzle.

  According to the present invention, it is not necessary to dispose the third electrode in the battery, and therefore the decrease in movable lithium ions due to charging / discharging can be compensated without complicating the structure of the battery.

It is a figure which shows the structure of a lithium ion secondary battery. 1 is a diagram showing a first embodiment of a battery capacity recovery device according to the present invention. It is a figure explaining the method to recover | restore the battery capacity of the lithium ion secondary battery by this invention. It is a figure which shows 2nd Embodiment of the battery capacity recovery apparatus by this invention.

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

  First, in order to facilitate understanding of the battery capacity recovery device according to the present invention, the structure of a lithium ion secondary battery will be described.

(Structure of lithium ion secondary battery)
FIG. 1 is a diagram showing the structure of a lithium ion secondary battery, FIG. 1 (A) is a perspective view of the lithium ion secondary battery, and FIG. 1 (B) is a cross section taken along line BB in FIG. 1 (A). FIG.

  The lithium ion secondary battery 100 includes a unit cell 200 that is stacked in a predetermined number and is electrically connected in parallel, and an exterior material 300. The exterior material 300 is filled with an electrolyte (electrolytic solution) 20.

  The unit cell 200 includes a separator 210, a positive electrode 221, and a negative electrode 222.

  The separator 210 is an electrolyte layer that holds a fluid electrolyte (electrolyte solution) 20. The electrolyte (electrolytic solution) 20 will be described later. The separator 210 is a nonwoven fabric such as a polyamide nonwoven fabric, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyimide nonwoven fabric, a polyester nonwoven fabric, or an aramid nonwoven fabric. Further, the separator 210 may be a microporous film in which pores are formed by stretching the film. Such a film is used as a separator for an existing lithium ion battery. Further, polyethylene, polypropylene, polyimide film, or a laminate of these may be used. The thickness of the separator 210 is not particularly limited. However, the thinner the battery, the more compact the battery. Therefore, it is desirable that the separator 210 be as thin as possible within a range in which performance can be ensured. Generally, the thickness of the separator 210 is about 10 to 100 μm. However, the thickness may not be constant.

  The positive electrode 221 includes a thin plate current collector 22 and a positive electrode layer 221a formed on both surfaces thereof. The positive electrode 221 disposed on the outermost layer has the positive electrode layer 221 a formed only on one side of the current collector 22. The positive current collectors 22 are gathered together and electrically connected in parallel. In FIG. 1B, the current collectors 22 gather together on the left side. This assembly portion is a positive electrode current collector.

  The current collector 22 is formed by heating a metal paste obtained by mixing a binder (resin) and a solvent with metal powder as a main component. Examples of the metal powder include aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. One type of these metal powders may be used alone, or two or more types may be mixed and used. Different metal powders may be laminated in multiple layers. The binder is a conventionally known resin binder material such as an epoxy resin. The binder may be a conductive polymer material. Although the thickness of the electrical power collector 22 is not specifically limited, Usually, it is about 1-100 micrometers.

The positive electrode layer 221a includes a positive electrode active material. The positive electrode active material is particularly preferably a lithium-transition metal composite oxide. Specifically, for example, a Li · Mn composite oxide such as spinel LiMn ₂ O _4, a Li · Co composite oxide such as LiCoO ₂ , a Li · Ni composite oxide such as LiNiO ₂ , LiFeO _2, etc. Li / Fe-based composite oxide. Alternatively, a transition metal such as LiFePO ₄ and a lithium phosphate compound or a sulfate compound may be used. Furthermore, transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ may be used. Further, PbO ₂ , AgO, NiOOH or the like may be used. Such a positive electrode active material can constitute a battery having excellent battery capacity and output characteristics.

  The particle size of the positive electrode active material may be such that the positive electrode material can be made into a paste and formed by spray coating or the like, but a smaller one can reduce the electrode resistance. Specifically, the average particle diameter of the positive electrode active material is preferably 0.1 to 10 μm.

  In addition to this, the positive electrode active material may contain an electrolyte, a lithium salt, a conductive auxiliary agent, and the like in order to enhance ion conductivity. Examples of the conductive assistant include acetylene black, carbon black, and graphite.

  The compounding amount of the positive electrode active material, the electrolyte (preferably a solid polymer electrolyte), the lithium salt, and the conductive auxiliary agent is set in consideration of the intended use of the battery (emphasis on output, energy, etc.) and ion conductivity. For example, if the amount of the electrolyte, particularly the solid polymer electrolyte, is too small, the ionic conduction resistance and the ionic diffusion resistance in the active material layer become large, and the battery performance deteriorates. On the other hand, when the amount of the electrolyte, particularly the solid polymer electrolyte is excessive, the energy density of the battery is lowered. Therefore, taking these into consideration, a specific blending amount is set.

  The thickness of the positive electrode layer 221a is not particularly limited. The battery is set in consideration of the purpose of use of the battery (emphasis on output, energy, etc.) and ion conductivity. A typical positive electrode has a thickness of about 1 to 500 μm.

  The negative electrode 222 includes a thin plate current collector 22 and a negative electrode layer 222a formed on both surfaces thereof. Note that the negative electrode 222 disposed on the outermost layer has the negative electrode layer 222 a formed only on one side of the current collector 22. The negative electrode current collectors 22 are assembled together and electrically connected in parallel. In FIG. 1B, the current collectors 22 gather together on the right side. This aggregate portion is a negative electrode current collector. The current collector 22 may be the same as that used for the positive electrode or a different one.

  The negative electrode layer 222a includes a negative electrode active material. Specifically, the negative electrode layer 222a is made of metal oxide, lithium-metal composite oxide metal, carbon, titanium oxide, lithium-titanium composite oxide, or the like. In particular, carbon, transition metal oxide, and lithium-transition metal composite oxide are preferable. Among these, carbon or lithium-transition metal composite oxide can increase the battery capacity and output of the battery. These may be used alone or in combination of two or more.

  The packaging material 300 accommodates the stacked unit cells 200. The exterior material 300 is formed of a sheet material of a polymer-metal composite laminate film in which a metal such as aluminum is covered with an insulator such as a polypropylene film. The exterior material 300 is heat-sealed around the unit cell 200 in a state where it is accommodated. The packaging material 300 includes a positive electrode tab 310 and a negative electrode tab 320 for taking out the electric power of the unit cell 200 to the outside.

  One end of the positive electrode tab 310 is connected to the positive electrode current collector inside the exterior material 300, and the other end goes out of the exterior material 300.

  One end of the negative electrode tab 320 is connected to the negative electrode current collector inside the exterior material 300, and the other end goes out of the exterior material 300.

  The electrolyte (electrolytic solution) 20 is, for example, a gel electrolyte in which an electrolytic solution is held in the polymer skeleton by about several to 99% by weight. A polymer gel electrolyte is particularly preferable. The polymer gel electrolyte includes, for example, a solid polymer electrolyte having ion conductivity and an electrolytic solution usually used in a lithium ion battery. Moreover, what hold | maintained the electrolyte solution normally used with a lithium ion battery in the polymeric frame | skeleton which does not have lithium ion conductivity may be used.

  The polymer gel electrolyte may be anything other than that made of 100% polymer electrolyte and may contain an electrolyte solution in the polymer skeleton. In particular, the ratio (mass ratio) between the electrolytic solution and the polymer is preferably about 20:80 to 98: 2. If it is such a ratio, the fluidity | liquidity by an electrolyte and the performance as an electrolyte will be compatible.

  The polymer skeleton may be either a thermosetting polymer or a thermoplastic polymer. Specifically, for example, a polymer having polyethylene oxide in the main chain or side chain (PEO), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVDF), a copolymer of polyvinylidene fluoride and hexafluoropropylene. Polymer (PVDF-HFP), polymethyl methacrylate (PMMA) and the like. However, it is not limited to these.

The electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte is usually used in a lithium ion battery. For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li Cyclic carbonates such as propylene carbonate and ethylene carbonate containing at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as (C ₂ F ₅ SO ₂ ) ₂ N. Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate may be used. Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane may be used. Lactones such as γ-butyrolactone may be used. Nitriles such as acetonitrile may be used. Esters such as methyl propionate may be used. Amides such as dimethylformamide may be used. An organic solvent (plasticizer) such as an aprotic solvent in which at least one selected from methyl acetate and methyl formate is mixed may be used. However, it is not limited to these.

  FIG. 2 is a diagram showing a first embodiment of a battery capacity recovery device according to the present invention.

  The battery capacity recovery device 1 includes an injector 10. The injector 10 includes a cylinder 11, a plunger 12, and a nozzle 13.

  The plunger 12 is inserted into the cylinder 11. A space formed by the cylinder 11 and the plunger 12 is a cylinder chamber 11a. A low potential member 21 is stored in the cylinder chamber 11a. The low potential member 21 will be described later. The cylinder chamber 11a is filled with an electrolyte 20.

  The nozzle 13 is connected to the port 11 b of the cylinder 11. The nozzle 13 has a needle shape. The nozzle 13 is conductive.

  The low potential member 21 is in contact with the nozzle 13 and is electrically connected. The low potential member 21 has a lower oxidation-reduction potential than the active material of the positive electrode 221 or the negative electrode 222 of the lithium ion secondary battery 100 and has a reducing ability with respect to the active material. The low potential member 21 has a lower oxidation-reduction potential than the current collector 22 and has a reducing ability with respect to the current collector 22. In other words, the current collector 22 has a higher redox potential than the low potential member 21. The low potential member 21 is, for example, lithium metal or a lithium-containing compound.

(Lithium ion secondary battery capacity recovery method)
FIG. 3 is a diagram for explaining a method for recovering the battery capacity of the lithium ion secondary battery according to the present invention. FIG. 3 (A) shows a specific method for recovery, and FIG. The mechanism of is shown.

  When the battery capacity of the lithium ion secondary battery 100 becomes small, as shown in FIG. 3A, the nozzle 13 of the injector 10 is pierced through the exterior material 300 of the lithium ion secondary battery 100, and the nozzle of the injector 10 is inserted. 13 is brought into contact with the current collector 22. As a result, the low potential member 21 is electrically connected (short circuited) to the current collector 22 (short circuit process).

  Then, the plunger 12 is pressed. Then, as shown in FIG. 3B, the electrolyte 20 is injected from the tip of the nozzle 13 (electrolyte injection process). Here, if the electrolyte 20 is in a gel form, a single line of electrolyte 20 reaches the positive electrode current collector 22.

At this time, if the low potential member 21 is lithium metal, the low potential member (lithium metal) 21 has a lower redox potential than the active material of the electrode layer (positive electrode layer 221a) and the electrode layer (positive electrode layer 221a). Therefore, the cation derived from the low potential member (lithium ion Li ^{+ in} FIG. 3B) is released into the electrolyte and the electron e ⁻ flows to the current collector 22. . Then, a positive ion (lithium ion Li ^{+ in} FIG. 3B) originally present in the electrolyte is taken into the positive electrode layer 221a formed on the current collector 22. Thus, the movement of positive ions can compensate for the decrease in mobile ions due to charge and discharge. The low potential member 21 b has a lower oxidation-reduction potential than the current collector 22 and has a reducing ability with respect to the current collector 22. That is, since the current collector 22 has a higher oxidation-reduction potential than the low potential member 21, the phenomenon that the current collector 22 is not melted, not the low potential member 21, does not occur.

Theoretically, if the redox potential of the low potential member 21 is lower than the redox potential of the active material of the electrode layer and the low potential member 21 has a reducing ability for the active material, the low potential member 21 is When the electrolyte 20 in the cylinder chamber 11a of the injector 10 and the electrolyte (electrolyte solution) 20 filled in the exterior material 300 are in liquid junction with the current collector 22, cations are released into the electrolyte. Mobile ions can be supplemented. However, some cations may have some adverse effects on the electrodes. Therefore, in this embodiment, lithium metal is particularly used as the low potential member 21. In this manner, when the low potential member 21 is short-circuited to the current collector 22, the electrolyte 20 in the cylinder chamber 11 a of the injector 10 and the electrolyte (electrolyte) 20 filled in the exterior material 300 are in liquid junction. Lithium ions Li ⁺ are released into the electrolyte as cations. Lithium ion Li ⁺ can compensate for the decrease in mobile lithium ions due to charge and discharge. Since lithium ion Li ⁺ is originally present in the electrolyte, it does not have an adverse effect. Lithium metal is desirable because it is excellent in energy density.

(Second Embodiment)
FIG. 4 is a diagram showing a second embodiment of the battery capacity recovery device according to the present invention.

  In the following description, parts having the same functions as those described above are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  The battery capacity recovery device 1 of the present embodiment uses a lithium-suppliable material 21 that can supply lithium to the positive electrode or negative electrode active material of the battery. Further, it further includes a potential difference adjuster that electrically connects the lithium supplyable material 21 and the negative electrode current collector 22. Since the negative electrode current collector 22 is connected to the negative electrode tab 320 as described above, the potential difference adjuster may be connected to the lithium supplyable material 21 and the negative electrode tab 320. Then, the potential difference between the lithium-suppliable material 21 and the negative electrode tab 320 is adjusted according to the reduction degree of the battery capacity, that is, the reduction degree of the movable lithium ions (adjustment process). If it does in this way, movable lithium ion can be adjusted precisely and appropriately. The degree of decrease in battery capacity may be estimated based on battery usage time, usage history, current value, voltage value, and the like.

  In the first embodiment, the low potential member 21 needs to have a reducing ability with respect to the active material of the electrode layer, and the redox potential of the low potential member 21 needs to be lower than the redox potential of the active material of the electrode layer. However, in this embodiment, since the difference in oxidation-reduction potential between the lithium-suppliable material 21 and the active material of the electrode layer can be adjusted by the potential difference adjuster, various materials can be used as the lithium-suppliable material 21. For example, a positive electrode active material may be used.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the first embodiment, a potential difference adjuster may be added as in the second embodiment.

  In each of the above embodiments, the injector 10 is filled with a gel electrolyte and injected from the nozzle. If the electrolyte is in a gel form, a single line of electrolyte 20 reaches the current collector 22 as described above, but the effect can be obtained even if a liquid electrolyte (that is, an electrolytic solution) is used.

DESCRIPTION OF SYMBOLS 1 Battery capacity recovery apparatus 10 Injector 11 Cylinder 12 Plunger 13 Nozzle 20 Electrolyte 21 Low-potential member / lithium supplyable material 100 Lithium ion secondary battery 200 Single battery 22 Current collector 221 Positive electrode 221a Positive electrode layer 222 Negative electrode 222a Negative electrode layer 300 Exterior Material

Claims (9)

A low-potential member having a lower redox potential than the active material of the positive electrode or negative electrode of the battery and having a reducing ability for the active material;
A cylinder chamber capable of holding the low potential member and holding the filled electrolyte, and an injection nozzle formed continuously in the cylinder chamber and electrically connected to the low potential member and conductive. An injector comprising:
A battery capacity recovery device. The battery capacity recovery device according to claim 1,
A potential difference adjuster that is connected to the low potential member and the positive or negative electrode of the battery and adjusts the potential difference between the two,
A battery capacity recovery device. A lithium-suppliable material capable of supplying lithium to the positive electrode or negative electrode active material of the battery;
A cylinder chamber capable of storing the lithium-suppliable material and holding the filled electrolyte, and continuously formed in the cylinder chamber, electrically connected to the lithium-suppliable material, and conductive. An injector comprising an injection nozzle;
A potential difference adjuster that is connected to the lithium-suppliable material and the positive electrode or negative electrode of the battery and adjusts the potential difference between the two,
A battery capacity recovery device. In the battery capacity recovery device according to any one of claims 1 to 3,
The injection nozzle of the injector penetrates the battery exterior material, can be short-circuited to the battery current collector, and can inject the electrolyte in the cylinder chamber into the exterior material.
A battery capacity recovery device. In the battery capacity recovery device according to any one of claims 1 to 4,
The low-potential member or the lithium-suppliable material is a lithium metal or a lithium-containing compound.
A battery capacity recovery device. In the battery capacity recovery device according to any one of claims 1 to 5,
The electrolyte is in a gel form,
A battery capacity recovery device. An injection nozzle of a conductive injector that is electrically connected to a low-potential member that has a lower redox potential than the active material of the positive electrode or negative electrode of the battery and that has a reducing ability with respect to the active material. A short-circuit process that penetrates the battery current collector and short-circuits the battery current collector,
An electrolyte injection step of injecting the electrolyte held in the cylinder chamber of the injector together with the low potential member into the interior of the battery exterior material;
A battery capacity recovery method including: The battery capacity recovery method according to claim 7,
An adjustment step of adjusting a potential difference adjuster connected to the low potential member and the positive electrode or the negative electrode of the battery according to the degree of capacity decrease of the battery;
The battery capacity recovery method characterized by the above-mentioned. The current collector of the battery is made by penetrating the battery injection material through an injection nozzle of a conductive injector that is electrically connected to a lithium-suppliable material capable of supplying lithium to the positive or negative electrode active material of the battery. A short-circuit process for short-circuiting,
An electrolyte injection step of injecting the electrolyte held in the cylinder chamber of the injector together with the lithium-suppliable material into the exterior of the battery,
An adjustment step of adjusting the potential difference adjuster connected to the lithium-suppliable material and the positive electrode or negative electrode of the battery according to the capacity reduction degree of the battery,
A battery capacity recovery method including:

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