Secondary battery, secondary battery control system, and battery pack

Abstract

The secondary battery includes: a separation wall disposed between a positive electrode space and a negative electrode space and allowing alkali metal ions to pass therethrough; a positive electrode disposed inside the positive electrode space and capable of intercalating and deintercalating the alkali metal ions; a negative electrode disposed inside the negative electrode space and capable of intercalating and deintercalating the alkali metal ions; a positive electrode electrolyte accommodated inside the positive electrode space and containing an aqueous solvent and the alkali metal ions; a negative electrode electrolyte accommodated inside the negative electrode space and containing an aqueous solvent and the alkali metal ions; and at least one of a negative electrode capacity recovery electrode disposed inside the positive electrode space and a positive electrode capacity recovery electrode disposed inside the negative electrode space. The negative electrode capacity recovery electrode contains at least one of a hydrogen production material and a material that reduces oxygen, and the positive electrode capacity recovery electrode contains at least one of an oxygen production material and a material that oxidizes hydrogen.

Description

Technical Field

[0001] This technology relates to secondary batteries, secondary battery control systems, and battery packs. Background Technology

[0002] With the widespread adoption of mobile phones and other electronic devices, the development of secondary batteries as small, lightweight power sources capable of achieving high energy density is underway. As such secondary batteries, those incorporating an electrolyte containing an aqueous solvent (so-called aqueous electrolyte) have been developed, and various studies have been conducted regarding the structure of secondary batteries incorporating this aqueous electrolyte.

[0003] Specifically, in order to suppress the capacity reduction of secondary batteries with non-aqueous electrolytes, a polymer forming agent or a sacrificial reducing agent is added to the non-aqueous electrolyte, and a voltage is applied between the battery container and the negative electrode (for example, see Patent Document 1). In order to improve the over-discharge characteristics of secondary batteries, a lithium salt solution is added to the electrolyte, lithium is intercalated on the negative electrode side during electrolysis, and decomposition gas is generated on the positive electrode side (for example, see Patent Document 2).

[0004] To improve the charge-discharge efficiency of rocking-chair type secondary batteries with alkaline aqueous electrolytes, an appropriate pH range (=4 to 12) for the aqueous electrolyte is specified (e.g., see Patent Document 3). To shorten the operation time of the secondary battery refresh operation, the secondary battery is discharged to a specified discharge termination capacity value after the current value during the refresh operation is gradually reduced (e.g., see Patent Document 4).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-165343

[0008] Patent Document 2: Japanese Patent Application Publication No. 05-242912

[0009] Patent Document 3: Japanese Patent Application Publication No. 2007-172985

[0010] Patent Document 4: Japanese Patent Application Publication No. 08-138746 Summary of the Invention

[0011] Various studies have been conducted on the structure of secondary batteries with aqueous electrolytes, but the technology to restore the battery capacity of secondary batteries with such aqueous electrolytes is still insufficient.

[0012] Therefore, there is a need for secondary batteries, secondary battery control systems, and battery packs that can restore battery capacity.

[0013] One embodiment of the present technology provides a secondary battery comprising: a separator wall disposed between a positive electrode space and a negative electrode space, allowing alkali metal ions to permeate; a positive electrode disposed inside the positive electrode space, containing intercalated and deintercalated alkali metal ions; a negative electrode disposed inside the negative electrode space, containing intercalated and deintercalated alkali metal ions; a positive electrode electrolyte contained inside the positive electrode space, comprising an aqueous solvent and alkali metal ions; a negative electrode electrolyte contained inside the negative electrode space, comprising an aqueous solvent and alkali metal ions; and at least one of a negative electrode capacity recovery electrode disposed inside the positive electrode space and a positive electrode capacity recovery electrode disposed inside the negative electrode space, wherein the negative electrode capacity recovery electrode comprises at least one of a hydrogen-generating material and an oxygen-reducing material, and the positive electrode capacity recovery electrode comprises at least one of an oxygen-generating material and a hydrogen-oxidizing material.

[0014] One embodiment of the present technology provides a secondary battery control system comprising a control circuit connected to a secondary battery. The control circuit performs at least one of the following processes: switching the connection destination of the positive electrode from the negative electrode to the positive electrode capacity recovery electrode and energizing the positive electrode and the positive electrode capacity recovery electrode; and switching the connection destination of the negative electrode from the positive electrode to the negative electrode capacity recovery electrode and energizing the negative electrode and the negative electrode capacity recovery electrode. The secondary battery has the same structure as the secondary battery of one embodiment of the present technology described above.

[0015] One embodiment of the present technology provides a battery pack comprising a secondary battery and a secondary battery control system. The secondary battery has the same structure as the secondary battery of one embodiment of the present technology described above, and the secondary battery control system has the same structure as the secondary battery control system of one embodiment of the present technology described above.

[0016] According to one embodiment of the present technology, a secondary battery, having a positive electrode, a negative electrode, a positive electrolyte containing an aqueous solvent, and a negative electrolyte containing an aqueous solvent, also has at least one of a negative capacity recovery electrode and a positive capacity recovery electrode, wherein the negative capacity recovery electrode contains at least one of a hydrogen-generating material and an oxygen-reducing material, and the positive capacity recovery electrode contains at least one of an oxygen-generating material and a hydrogen-oxidizing material, is capable of restoring battery capacity.

[0017] According to one embodiment of the present technology, a secondary battery control system is capable of restoring the battery capacity of a secondary battery because it includes a control circuit that performs at least one of the processes of energizing the positive electrode and the positive electrode capacity recovery electrode and the negative electrode capacity recovery electrode.

[0018] According to one embodiment of the present technology, the battery pack, having the aforementioned secondary battery and secondary control system, is able to restore the battery capacity of the secondary battery.

[0019] It should be noted that the effects of this technology are not necessarily limited to those described herein, but can be any of a series of effects associated with this technology as described below. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing the structure of a secondary battery according to one embodiment of the present technology.

[0021] Figure 2 This is a block diagram illustrating the structure of a secondary battery control system according to one embodiment of the present technology.

[0022] Figure 3 This is a cross-sectional view showing the structure of the secondary battery in Modified Example 1.

[0023] Figure 4 This is a cross-sectional view showing the structure of the secondary battery in Modified Example 2.

[0024] Figure 5 This is a cross-sectional view showing the structure of the secondary battery in Modified Example 3.

[0025] Figure 6 This is a cross-sectional view showing the structure of the secondary battery in Modified Example 4.

[0026] Figure 7 This is a cross-sectional view showing the structure of the secondary battery in Modified Example 5.

[0027] Figure 8 This is a block diagram illustrating the structure of a secondary battery application example (battery pack). Detailed Implementation

[0028] The following is a detailed description of one embodiment of the present technology with reference to the accompanying drawings. It should be noted that the description is presented in the following order.

[0029] 1. Secondary battery

[0030] 1-1. Structure

[0031] 1-2. Actions

[0032] 1-3. Manufacturing Method

[0033] 1-4. Functions and Effects

[0034] 2. Secondary battery control system

[0035] 2-1. Structure

[0036] 2-2. Actions

[0037] 2-3. Functions and Effects

[0038] 3. Variations

[0039] 4. Uses of secondary batteries

[0040] <1. Secondary Battery>

[0041] First, a secondary battery according to one embodiment of this technology will be described.

[0042] The secondary battery described here utilizes the insertion and extraction of alkali metal ions, and includes a positive electrode, a negative electrode, and an electrolyte (aqueous electrolyte) as a liquid electrolyte containing an aqueous solvent. In this secondary battery, since the charging and discharging reaction is carried out using the insertion and extraction of alkali metal ions, the battery capacity can be obtained.

[0043] The types of alkali metal ions are not particularly limited, but specifically they include lithium ions, sodium ions, and potassium ions. This is because a stable charge-discharge reaction can be carried out while obtaining a high voltage.

[0044] <1-1. Structure>

[0045] Figure 1 The cross-sectional structure of a secondary battery is shown. (For example...) Figure 1 As shown, the secondary battery includes an outer packaging component 11, a separator 12, a positive electrode 13, a negative electrode 14, a positive electrode electrolyte 15, a negative electrode electrolyte 16, a negative electrode capacity recovery electrode 17, and a positive electrode capacity recovery electrode 18. Figure 1 In the diagram, the positive electrode electrolyte 15 is marked with a light shade, and the negative electrode electrolyte 16 is marked with a dark shade.

[0046] The positive electrode electrolyte 15 and the negative electrode electrolyte 16 are aqueous electrolytes containing the aforementioned aqueous solvent. As described later, the aqueous electrolyte is a solution in which ionizable ionic substances are dissolved or dispersed in an aqueous solvent.

[0047] In the following explanation, for convenience, we will use... Figure 1 The upper side of the middle serves as the upper side of the secondary battery, and... Figure 1 The lower side of the middle serves as the lower side of the secondary battery.

[0048] [Outer Packaging Components]

[0049] The outer packaging component 11 is a generally box-shaped component with internal space for storing the partition wall 12, positive electrode 13, negative electrode 14, positive electrode electrolyte 15, negative electrode electrolyte 16, negative electrode capacity recovery electrode 17, and positive electrode capacity recovery electrode 18.

[0050] The outer packaging component 11 comprises any one or more of the following materials: metal, glass, and polymer compounds. Specifically, the outer packaging component 11 can be a rigid metal can, glass shell, or plastic shell, or it can be a flexible (or pliable) metal foil or polymer film.

[0051] [Separator]

[0052] A partition wall 12 is disposed inside the outer packaging component 11, dividing the internal space of the outer packaging component 11 into two spaces (a positive electrode chamber S1 serving as the positive electrode space and a negative electrode chamber S2 serving as the negative electrode space). That is, since the partition wall 12 is disposed between the positive electrode chamber S1 and the negative electrode chamber S2, the positive electrode chamber S1 and the negative electrode chamber S2 are isolated from each other. As a result, the positive electrode 13 and the negative electrode 14 are positioned opposite each other through the partition wall 12, while being isolated from each other through the partition wall 12.

[0053] The partition wall 12 prevents anions from passing through between the positive electrode chamber S1 and the negative electrode chamber S2, but allows substances such as alkali metal ions (cations) that have been inserted or extracted in each of the positive electrode 13 and the negative electrode 14 (excluding anions) to pass through. That is, the partition wall 12 prevents the positive electrode electrolyte 15 and the negative electrode electrolyte 16 from mixing while allowing substances such as alkali metal ions to pass through. In this case, the partition wall 12 allows alkali metal ions to pass through from the positive electrode chamber S1 to the negative electrode chamber S2, and vice versa.

[0054] Specifically, the separator 12 comprises one or more of the following: a porous membrane and a solid electrolyte. The porous membrane is a cation exchange membrane or the like that that allows cations to pass through, and the solid electrolyte has ionic conductivity of alkali metal ions.

[0055] [positive electrode]

[0056] The positive electrode 13 is disposed inside the positive electrode chamber S1 and is an electrode for inserting and deintercalating alkali metal ions. Here, the positive electrode 13 includes a positive current collector 13A having one and two opposite sides and a positive active material layer 13B disposed on both sides of the positive current collector 13A. Alternatively, the positive active material layer 13B may be disposed on only one side of the positive current collector 13A.

[0057] It should be noted that the positive current collector 13A can also be omitted. Therefore, the positive electrode 13 can be simply the positive active material layer 13B.

[0058] (Positive current collector)

[0059] The positive current collector 13A supports the positive active material layer 13B, which comprises one or more conductive materials, including metallic materials, carbon materials, and conductive ceramic materials. Specific examples of metallic materials include titanium, aluminum, and their alloys. Specific examples of conductive ceramic materials include indium tin oxide (ITO).

[0060] Here, the positive electrode active material layer 13B is not provided on a part of the positive electrode current collector 13A (connection terminal 13AT), and the connection terminal 13AT is led out to the outside of the outer packaging component 11.

[0061] The material forming the positive current collector 13A is preferably insoluble, poorly soluble, and corrosion-resistant to the positive electrolyte 15, and has low reactivity to the positive active material described later. Specifically, the positive current collector 13A preferably comprises the aforementioned metallic materials, i.e., preferably titanium, aluminum, and their alloys. This is because the positive current collector 13A is not easily degraded even when the secondary battery is charged and discharged.

[0062] It should be noted that the positive current collector 13A can be a conductor whose surface is coated with any one or more of the aforementioned metallic materials, carbon materials, and conductive ceramic materials. The material of the conductor only needs to be conductive; there are no particular limitations.

[0063] (Positive electrode active material layer)

[0064] The positive electrode active material layer 13B comprises any one or more positive electrode active materials that are capable of intercalating or deintercalating alkali metal ions. Furthermore, the positive electrode active material layer 13B may further comprise any one or more other materials such as a positive electrode binder and a positive electrode conductive agent.

[0065] Positive electrode active materials for lithium ions, which are alkali metal ions, include lithium-containing compounds. The types of lithium-containing compounds are not particularly limited; specifically, they include lithium complex oxides and lithium phosphate compounds. Lithium complex oxides are oxides containing lithium and one or more transition metal elements as constituent elements, and lithium phosphate compounds are phosphate compounds containing lithium and one or more transition metal elements as constituent elements. The types of transition metal elements are not particularly limited; specifically, they include nickel, cobalt, manganese, and iron.

[0066] Specific examples of lithium composite oxides with a layered rock salt-type crystal structure are LiNiO2, LiCoO2, and LiCo. 0.98 Al 0.01 Mg 0.01 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi0.8 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2 and Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 Lithium complex oxides with spinel-type crystal structures include LiMn₂O₄, etc. Specific examples of lithium phosphate compounds with olivine-type crystal structures include LiFePO₄, LiMnPO₄, and LiMn₂O₄. 0.5 Fe 0.5 PO4, LiMn 0.7 Fe 0.3 PO4 and LiMn 0.75 Fe 0.25 PO4, etc.

[0067] Positive electrode active materials for the intercalation and deintercalation of sodium ions by alkali metal ions include sodium-containing compounds. The types of sodium-containing compounds are not particularly limited, but specifically, they include Prussian blue analogues represented by formula (1).

[0068] Na x K y M1 z Fe(CN)6·aH2O…(1)

[0069] (M1 is at least one of Mn and Zn. x, y, and z satisfy 0.5 < x ≤ 2, 0 ≤ y ≤ 0.5, and 0 ≤ z ≤ 2. a is an arbitrary value. Among them, y can also satisfy 0.05 ≤ y ≤ 0.2.)

[0070] Specific examples of Prussian blue analogues are Na₂MnFe(CN₆), Na 1.42 K 0.09 Mn 1.13 Fe(CN)6·3H2O and Na 0.83 K 0.12 Zn 1.49 Fe(CN)6·3.2H2O, etc.

[0071] Potassium-containing compounds are among the positive electrode active materials used for the insertion and extraction of potassium ions from alkali metal ions. Specific examples of potassium-containing compounds include K... 0.7 Fe 0.6 Mn 0.6 O2, K 0.6 MnO2, K0.3 MnO2, K 0.31 CoO2, KCrO2, K 0.6 CoO2, K 2 / 3 Mn 2 / 3 Co 1 / 3Ni 1 / 3 O2, K 2 / 3 Ni 2 / 3 Te 1 / 3 O2, K 2 / 3 Ni 1 / 6 Co 1 / 2 Te 1 / 3 O2, K 2 / 3 Ni 1 / 2 Mn 1 / 6 Te 1 / 3 O2, K 2 / 3 Ni 1 / 2 Cu 1 / 6 Te 1 / 3 O2, K 2 / 3Ni 1 / 3 Zn 1 / 3 Te 1 / 3 O2, K 2 / 3 Ni 1 / 6 Mg 1 / 2 Te 1 / 3 O2, K 2 / 3 Ni 1 / 2 Co 1 / 6 Te 1 / 3 O2, K 2 / 3 Ni 1 / 3 Mg 1 / 3 Te 1 / 3 O2 and K 2 / 3Ni 1 / 3 Co 1 / 3 Te 1 / 3 O2, etc.

[0072] The positive electrode 13 preferably comprises a positive electrode active material capable of intercalating or deintercalating alkali metal ions at a potential above 0.4V, based on the potential of a standard hydrogen electrode. Specific examples of such positive electrode active materials are LiNiO2, LiCoO2, LiMn2O4, and LiNi. 0.80 Co 0.15 Al 0.05 O2 and LiNi 0.33 Co 0.33 Mn 0.33O2, etc. This is because, in the capacity recovery process of the secondary battery described later, even if almost no potential is applied from an external power source (not shown) between the positive electrode 13 and the positive electrode capacity recovery electrode 18, the potential region where the capacity recovery reaction occurs spontaneously will increase. Therefore, the capacity recovery reaction of the secondary battery can be easily carried out with almost no power consumption, and the battery capacity is easily recovered during the capacity recovery process.

[0073] The positive electrode binder includes any one or more of synthetic rubbers and polymeric compounds. Specific examples of synthetic rubbers include styrene-butadiene rubber. Specific examples of polymeric compounds include polyvinylidene fluoride and polyimide.

[0074] The positive electrode conductive agent includes one or more conductive materials such as carbon materials. Specific examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black. In addition, conductive materials can also be metallic materials, conductive ceramic materials, and conductive polymers.

[0075] [negative electrode]

[0076] The negative electrode 14 is disposed inside the negative electrode chamber S2 and is an electrode for inserting and deintercalating alkali metal ions. Here, the negative electrode 14 includes a negative electrode current collector 14A having one opposite side and a negative electrode active material layer 14B disposed on both sides of the negative electrode current collector 14A. Alternatively, the negative electrode active material layer 14B may be disposed on only one side of the negative electrode current collector 14A.

[0077] It should be noted that the negative current collector 14A can also be omitted. Therefore, the negative electrode 14 can be simply the negative electrode active material layer 14B.

[0078] (Negative current collector)

[0079] The negative electrode current collector 14A supports the negative electrode active material layer 14B, which comprises one or more conductive materials, including metallic materials, carbon materials, and conductive ceramic materials. Specific examples of metallic materials include stainless steel (SUS), titanium, zinc, tin, lead, and their alloys. The stainless steel may also be a highly corrosion-resistant stainless steel with one or more additive elements such as niobium and molybdenum. Specifically, the stainless steel may also be SUS444, etc., with molybdenum added as an additive element. Details regarding the conductive ceramic materials are as described above.

[0080] Here, the negative electrode active material layer 14B is not provided on a portion of the negative electrode current collector 14A (connection terminal portion 14AT), so the connection terminal portion 14AT is led out to the outside of the outer packaging component 11. The lead-out direction of the connection terminal portion 14AT is not particularly limited, but specifically, it is the same as the lead-out direction of the connection terminal portion 13AT.

[0081] The material forming the negative electrode current collector 14A is preferably insoluble, poorly soluble, and corrosion-resistant to the negative electrode electrolyte 16, and has low reactivity to the negative electrode active material described later. Specifically, the negative electrode current collector 14A preferably comprises the aforementioned metallic materials, i.e., preferably stainless steel, titanium, zinc, tin, lead, and their alloys. This is because the negative electrode current collector 14A is not easily degraded even when the secondary battery is charged and discharged.

[0082] It should be noted that the negative current collector 14A can be a conductor whose surface is coated with any one or more of the aforementioned metallic materials, carbon materials, and conductive ceramic materials. The material of this conductor only needs to be conductive; there are no particular limitations.

[0083] (Negative electrode active material layer)

[0084] The negative electrode active material layer 14B comprises any one or more negative electrode active materials that are capable of intercalating or deintercalating alkali metal ions. Furthermore, the negative electrode active material layer 14B may further comprise any one or more other materials such as a negative electrode binder and a negative electrode conductive agent. Details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

[0085] The negative electrode active material is a titanium-containing compound, a niobium-containing compound, a vanadium-containing compound, an iron-containing compound, and a molybdenum-containing compound, etc. This is because even when using positive electrode electrolyte 15 and negative electrode electrolyte 16, the charge-discharge reaction proceeds smoothly and stably.

[0086] Titanium-containing compounds include titanium oxides, alkali metal titanium complex oxides, titanium phosphates, alkali metal titanium phosphates, and hydrogen titanium compounds.

[0087] Titanium oxides are compounds represented by formula (2), such as bronze-type titanium oxide.

[0088] TiO w …(2)

[0089] (w satisfies 1.85≤w≤2.15.)

[0090] The titanium oxide is any one or more of anatase, rutile, and brookite titanium oxide (TiO2). Alternatively, the titanium oxide can also be a composite oxide containing any one or more of phosphorus, vanadium, tin, copper, nickel, iron, and cobalt as constituent elements. Specific examples of such composite oxides are TiO2-P2O5, TiO2-V2O5, TiO2-P2O5-SnO2, and TiO2-P2O5-MeO, etc. Where Me is any one or more of Cu, Ni, Fe, and Co.

[0091] Lithium-titanium composite oxides in alkali metal titanium composite oxides are compounds represented by formulas (3) to (5), such as orthorhombic manganese oxide type lithium titanate. M3 shown in formula (3) is a metal element that can become a divalent ion. M4 shown in formula (4) is a metal element that can become a trivalent ion. M5 shown in formula (5) is a metal element that can become a tetravalent ion.

[0092] Li[Li x M3 (1-3x) / 2 Ti (3+x) / 2 ]O4…(3)

[0093] (M3 is at least one of Mg, Ca, Cu, Zn, and Sr. x satisfies 0 ≤ x ≤ 1 / 3.)

[0094] Li[Li y M4 1-3y Ti 1+2y ]O4…(4)

[0095] (M4 is at least one of Al, Sc, Cr, Mn, Fe, Ge, and Y. y satisfies 0 ≤ y ≤ 1 / 3.)

[0096] Li[Li 1 / 3 M5 z Ti (5 / 3)-z ]O4…(5)

[0097] (M5 is at least one of V, Zr, and Nb. z satisfies 0 ≤ z ≤ 2 / 3.)

[0098] A specific example of the lithium-titanium composite oxide shown in equation (3) is Li 3.75 Ti 4.875 Mg 0.375 O 12 Etc. Specific examples of lithium-titanium composite oxides shown in equation (4) are LiCrTiO4, etc. Specific examples of lithium-titanium composite oxides shown in equation (5) are Li4Ti5O, etc. 12 and Li4Ti 4.95 Nb 0.05 O 12wait.

[0099] Specific examples of potassium-titanium composite oxides in alkali metal titanium composite oxides are K₂Ti₃O₇ and K₄Ti₅O₇. 12 wait.

[0100] Specific examples of titanium phosphate oxides include titanium phosphate (TiP₂O₇). Specific examples of lithium titanium phosphate compounds in alkali metals include LiTi₂(PO₄)₃. Specific examples of sodium titanium phosphate compounds in alkali metals include NaTi₂(PO₄)₃. Specific examples of hydrogen titanium compounds include H₂Ti₃O₇ (3TiO₂·1H₂O) and H₆Ti. 12 O 27 (3TiO2·0.75H2O), H2Ti6O 13 (3TiO2·0.5H2O), H2Ti7O 15 (3TiO2·0.43H2O) and H2Ti 12 O 25 (3TiO2·0.25H2O), etc.

[0101] Niobium-containing compounds include alkali metal niobium composite oxides, niobium hydrogen compounds, and titanium-niobium composite oxides. Furthermore, materials equivalent to niobium-containing compounds are not included in titanium-containing compounds.

[0102] Specific examples of alkali metal niobium composite oxides include LiNbO2. Specific examples of hydrogen niobium compounds include H4Nb6O. 17 Specific examples of titanium-niobium composite oxides are TiNb₂O₇ and Ti₂Nb₂. 10 O 29 Alternatively, alkali metals can be inserted into titanium-niobium composite oxides.

[0103] Vanadium-containing compounds include vanadium oxides and alkali metal vanadium complex oxides, etc. Furthermore, materials equivalent to vanadium-containing compounds are not included in each of the categories of titanium-containing compounds and niobium-containing compounds.

[0104] Specific examples of vanadium oxides include vanadium dioxide (VO2). Specific examples of alkali metal vanadium composite oxides include LiV2O4 and LiV3O8.

[0105] Iron-containing compounds include iron hydroxides, etc. Furthermore, materials equivalent to iron-containing compounds are not included in each of the categories of titanium-containing compounds, niobium-containing compounds, and vanadium-containing compounds.

[0106] Specific examples of iron hydroxides include iron hydroxyl oxide (FeOOH). Furthermore, iron hydroxyl oxide can be α-iron hydroxyl oxide, β-iron hydroxyl oxide, γ-iron hydroxyl oxide, δ-iron hydroxyl oxide, or any two or more of these.

[0107] Molybdenum-containing compounds include molybdenum oxides and cobalt-molybdenum composite oxides. Furthermore, materials equivalent to molybdenum-containing compounds are not included in each of the categories of titanium-containing compounds, niobium-containing compounds, vanadium-containing compounds, and iron-containing compounds.

[0108] Specific examples of molybdenum oxides include molybdenum dioxide (MoO2). Specific examples of cobalt-molybdenum composite oxides include CoMoO4.

[0109] Preferably, the negative electrode 14 comprises a negative electrode active material capable of inserting and deintercalating alkali metal ions at a potential below 0V, based on the potential of a standard hydrogen electrode. Specific examples of such negative electrode active materials are TiO2 and Li4Ti5O. 12 Li4Ti 4.95 Nb 0.05 O 12 And NaTi2(PO4)3, etc. This is because, in the capacity recovery process of the secondary battery described later, even if almost no potential is applied from an external power source between the negative electrode 14 and the negative electrode capacity recovery electrode 17, the potential region where the capacity recovery reaction occurs spontaneously will increase. Therefore, the capacity recovery reaction of the secondary battery can be easily carried out with almost no power consumption, and the battery capacity is easily recovered during the capacity recovery process.

[0110] [Positive Electrolyte and Negative Electrolyte]

[0111] The positive electrolyte 15 is contained inside the positive electrode chamber S1, and the negative electrolyte 16 is contained inside the negative electrode chamber S2. Therefore, the positive electrolyte 15 and the negative electrolyte 16 are separated from each other by the partition wall 12, so that the positive electrolyte 15 and the negative electrolyte 16 will not mix with each other.

[0112] Here, the positive electrode electrolyte 15 is contained inside the positive electrode chamber S1 in such a way that no space is created where the positive electrode electrolyte 15 is absent, and the negative electrode electrolyte 16 is contained inside the negative electrode chamber S2 in such a way that no space is created where the negative electrode electrolyte 16 is absent. That is, the positive electrode electrolyte 15 fills the interior of the positive electrode chamber S1, and the negative electrode electrolyte 16 fills the interior of the negative electrode chamber S2. In this case, since the positive electrode active material layer 13B is immersed in the positive electrode electrolyte 15, the entire positive electrode active material layer 13B is in contact with the positive electrode electrolyte 15, and since the negative electrode active material layer 14B is immersed in the negative electrode electrolyte 16, the entire negative electrode active material layer 14B is in contact with the negative electrode electrolyte 16.

[0113] Specifically, the positive electrode electrolyte 15 and the negative electrode electrolyte 16 each contain one or more of an aqueous solvent and an ionic substance capable of ionization in the aqueous solvent. Furthermore, the positive electrode electrolyte 15 and the negative electrode electrolyte 16 each contain alkali metal ions that are intercalated or deintercalated in each of the positive electrode 13 and the negative electrode 14.

[0114] There are no particular limitations on the types of aqueous solvents; specifically, it includes pure water, etc. There are no particular limitations on the types of ionic substances; specifically, it includes any one or more of acids, bases, and electrolyte salts, etc. Specific examples of acids include carbonic acid, oxalic acid, nitric acid, sulfuric acid, hydrochloric acid, acetic acid, and citric acid, etc.

[0115] Electrolyte salts are salts containing both cations and anions; more specifically, they are any one or more metal salts. The types of metal salts are not particularly limited, but specifically include alkali metal salts, alkaline earth metal salts, and transition metal salts, etc.

[0116] Alkali metal salts include lithium, sodium, and potassium salts. Specific examples of lithium salts include lithium carbonate, lithium oxalate, lithium nitrate, lithium sulfate, lithium chloride, lithium acetate, lithium citrate, lithium hydroxide, and imide salts. These imide salts include lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. Specific examples of sodium salts are compounds in which lithium is substituted with sodium, as described in the examples of lithium salts above. Specific examples of potassium salts are compounds in which lithium is substituted with potassium, as described in the examples of lithium salts above.

[0117] The types of alkaline earth metal salts are not particularly limited; specifically, they are compounds in which the lithium in the aforementioned lithium salts is replaced by an alkaline earth metal element. These alkaline earth metal salts are, for example, calcium salts. The types of transition metal salts are not particularly limited; specifically, they are compounds in which the lithium in the aforementioned lithium salts is replaced by a transition metal element.

[0118] The content of ionic substances, i.e. the concentration (mol / kg) of the positive electrolyte 15 and the negative electrolyte 16, can be set arbitrarily.

[0119] The composition of the positive electrode electrolyte 15 (the type of aqueous solvent and the type of electrolyte salt) and the composition of the negative electrode electrolyte 16 (the type of aqueous solvent and the type of electrolyte salt) can be the same or different from each other.

[0120] Here, the pH of the positive electrode electrolyte 15 and the pH of the negative electrode electrolyte 16 can be the same as or different from each other. That is, the pH of the negative electrode electrolyte 16 can be lower than the pH of the positive electrode electrolyte 15, the same as the pH of the positive electrode electrolyte 15, or higher than the pH of the positive electrode electrolyte 15.

[0121] Preferably, the pH of the negative electrode electrolyte 16 is higher than that of the positive electrode electrolyte 15. This is because, compared to the case where the pH of the negative electrode electrolyte 16 is lower than that of the positive electrode electrolyte 15, the decomposition potential of the aqueous solvent shifts. Therefore, during charging and discharging, while thermodynamically suppressing the decomposition reaction of the aqueous solvent, the potential window of the aqueous solvent expands. Thus, while obtaining a high voltage, the charge-discharge reaction utilizing the insertion and extraction of alkali metal ions proceeds fully and stably. Furthermore, in the capacity recovery process of the secondary battery described later, the potential region where the capacity recovery reaction occurs spontaneously increases even without applying a potential from an external power source. Therefore, the capacity recovery reaction of the secondary battery can be easily carried out with almost no power consumption, and the battery capacity is easily recovered during the capacity recovery process.

[0122] Therefore, the composition (types of electrolyte salts) of the positive electrode electrolyte 15 and the composition (types of electrolyte salts) of the negative electrode electrolyte 16 are preferably different from each other. This is because it is easier to control the pH of both, so that the pH of the negative electrode electrolyte 16 is greater than the pH of the positive electrode electrolyte 15.

[0123] As long as the pH of the negative electrode electrolyte 16 is greater than the pH of the positive electrode electrolyte 15, there are no particular limitations on the pH values ​​of the positive electrode electrolyte 15 and the negative electrode electrolyte 16.

[0124] The pH of the negative electrode electrolyte 16 is preferably 11 or higher, more preferably 12 or higher, and even more preferably 13 or higher. This is because, since the pH of the negative electrode electrolyte 16 becomes sufficiently high, it is easy for the pH of the negative electrode electrolyte 16 to become higher than that of the positive electrode electrolyte 15. Furthermore, this is because, since the pH difference between the positive electrode electrolyte 15 and the negative electrode electrolyte 16 becomes sufficiently large, it is easy to maintain the pH relationship between the two. Moreover, this is because, in the capacity recovery process of the secondary battery described later, the potential region where the capacity recovery reaction spontaneously occurs increases even without applying a potential from an external power source. Therefore, the capacity recovery reaction of the secondary battery can be easily carried out with almost no power consumption, and the battery capacity is easily recovered during the capacity recovery process.

[0125] Furthermore, the pH of the positive electrode electrolyte 15 is preferably 3 to 8, more preferably 4 to 8, and even more preferably 4 to 6. This is because the pH difference between the positive electrode electrolyte 15 and the negative electrode electrolyte 16 is sufficiently large, making it easy to maintain the pH relationship between the two. Additionally, this is because the outer packaging component 11 is less susceptible to corrosion, and battery structural components such as the positive electrode current collector 13A and the negative electrode current collector 14A are less susceptible to corrosion, thus improving the electrochemical durability (stability) of the secondary battery. Moreover, for the same reasons as when the pH of the negative electrode electrolyte 16 is 11 or higher, the capacity recovery reaction of the secondary battery can be easily carried out with almost no power consumption, and the battery capacity is easily recovered during the capacity recovery process.

[0126] The electrolyte salt comprises an alkali metal salt having alkali metal ions inserted or extracted in each of the positive electrode 13 and the negative electrode 14 as cations. In this case, the electrolyte salt may further comprise any electrolyte salt (excluding alkali metal salts having alkali metal ions inserted or extracted in each of the positive electrode 13 and the negative electrode 14 as cations) and any one or more non-electrolytes. The type of the arbitrary electrolyte salt (the type of cation and the type of anion) is not particularly limited and can be arbitrarily selected.

[0127] Here, as described above, the positive electrode electrolyte 15 and the negative electrode electrolyte 16 respectively contain alkali metal ions that are intercalated or deintercalated in each of the positive electrode 13 and the negative electrode 14, that is, they contain alkali metal salts with alkali metal ions as cations. The type of alkali metal salt is not particularly limited; it can be only one type or two or more types.

[0128] In this case, one or both of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 may further contain any one or more other metal salts, wherein the other metal salts are cations of metal ions different from the alkali metal ions that are intercalated or deintercalated in each of the positive electrode 13 and the negative electrode 14. These other metal ions may be intercalated or deintercalated metal ions in each of the positive electrode 13 and the negative electrode 14, or they may be metal ions that are not intercalated or deintercalated in each of the positive electrode 13 and the negative electrode 14, or they may be both types of metal ions.

[0129] The types of other metal ions that may be inserted or extracted into each of the positive electrode 13 and the negative electrode 14 are not particularly limited, and may be only one type or two or more types. These other metal ions are alkali metal ions other than the alkali metal ions that may be inserted or extracted into each of the positive electrode 13 and the negative electrode 14.

[0130] The types of other metal ions that do not intercalate or deintercalate in each of the positive electrode 13 and the negative electrode 14 are not particularly limited; they can be one or more. These other metal ions are any one or more of any metal ions other than alkali metal ions that intercalate or deintercalate in each of the positive electrode 13 and the negative electrode 14, such as alkali metal ions, alkaline earth metal ions, transition metal ions, and other metal ions.

[0131] More specifically, one or both of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 contain lithium salts with lithium ions as cations, which are alkali metal salts with alkali metal ions inserted or extracted in each of the positive electrode 13 and the negative electrode 14 as cations.

[0132] In this case, it is preferable that one or both of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 further contain any one or more of other metal salts with the aforementioned other metal ions as cations. This is because, by using two or more metal salts (alkali metal salts and other metal salts) together, the pH of both the positive electrode electrolyte 15 and the pH of the negative electrode electrolyte 16 can be easily controlled compared to using only one metal salt (alkali metal salt).

[0133] Preferably, one or both of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 contain lithium salt (lithium ions) as an alkali metal salt and sodium salt (sodium ions) and potassium salt (potassium ions) as other metal salts. This is because it is easy to control the pH of the negative electrode electrolyte 16 to be sufficiently higher than the pH of the positive electrode electrolyte 15, thus making it easier to maintain the pH relationship between the two.

[0134] It should be noted that preferably one or both of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 are saturated solutions of alkali metal salts with alkali metal ions inserted or extracted into each of the positive electrode 13 and the negative electrode 14 as cations. More preferably, both the positive electrode electrolyte 15 and the negative electrode electrolyte 16 are saturated solutions of the aforementioned alkali metal salts. This is because during charging and discharging, the charging and discharging reaction, i.e., the insertion and extraction reaction of alkali metal ions, proceeds stably.

[0135] To confirm whether the positive electrode electrolyte 15 is a saturated solution of electrolyte salt (alkali metal salt), the electrolyte salt can be checked for precipitation inside the positive electrode chamber S1 after disassembling the secondary battery. Specifically, the interior of the positive electrode chamber S1 refers to the liquid portion of the positive electrode electrolyte 15, the surface of the separator wall 12, the surface of the positive electrode 13, and the inner wall of the outer packaging component 11. If the positive electrode electrolyte 15 (liquid) and the precipitated electrolyte salt (solid) coexist inside the positive electrode chamber S1 due to the precipitation of electrolyte salt, the positive electrode electrolyte 15 can be considered a saturated solution of electrolyte salt. It should be noted that, to investigate the composition of the precipitated material, surface analysis methods such as X-ray photoelectron spectrometry (XPS) and compositional analysis methods such as inductively coupled plasma (ICP) emission spectroscopy are used.

[0136] The method for confirming whether the negative electrode electrolyte 16 is a saturated solution of electrolyte salt (alkali metal salt) is the same as the method described above for confirming whether the positive electrode electrolyte 15 is a saturated solution of electrolyte salt (alkali metal salt), except that the inside of the negative electrode chamber S2 is investigated instead of the inside of the positive electrode chamber S1.

[0137] Furthermore, each of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 can be a pH buffer solution. This pH buffer solution can be an aqueous solution mixed with a weak acid and its conjugate base, or an aqueous solution mixed with a weak base and its conjugate acid. This is because pH fluctuations can be sufficiently suppressed, thus easily maintaining the pH of each of the aforementioned positive electrode electrolyte 15 and negative electrode electrolyte 16.

[0138] The positive electrode electrolyte 15 preferably contains one or more of the following as anions: sulfate ions, bisulfate ions, nitrate ions, carbonate ions, bicarbonate ions, phosphate ions, monohydrogen phosphate ions, dihydrogen phosphate ions, and carboxylic acid ions. This is because it effectively suppresses pH fluctuations in the positive electrode electrolyte 15, thus easily maintaining the pH of both the positive electrode electrolyte 15 and the negative electrode electrolyte 16. The carboxylic acid ions are one or more of the following: formic acid ions, acetate ions, propionic acid ions, tartaric acid ions, and citrate ions.

[0139] It should be noted that the positive electrode electrolyte 15 and the negative electrode electrolyte 16 may each contain one or more of the following as buffers: tris(hydroxymethyl)aminomethane and ethylenediaminetetraacetic acid.

[0140] More specifically, the positive electrode electrolyte 15 preferably contains one or more of the following as anions: sulfate ions, bisulfate ions, nitrate ions, carbonate ions, bicarbonate ions, phosphate ions, monohydrogen phosphate ions, and dihydrogen phosphate ions, and the negative electrode electrolyte 16 preferably contains hydroxide ions as anions. This is because it is easy to control the pH of the positive electrode electrolyte 15 to a sufficiently low level and the pH of the negative electrode electrolyte 16 to a sufficiently high level.

[0141] Here, the positive electrode electrolyte 15 and the negative electrode electrolyte 16 are preferably isotonic solutions with an isotonic relationship. This is because, since the osmotic pressure of the positive electrode electrolyte 15 and the negative electrode electrolyte 16 is appropriately adjusted, it is easy to maintain the pH relationship between the two.

[0142] It should be noted that the pH value of the positive electrode electrolyte 15 is preferably set so that each of the positive electrode current collector 13A and the positive electrode active material layer 13B is not easily corroded. Similarly, the pH value of the negative electrode electrolyte 16 is preferably set so that each of the negative electrode current collector 14A and the negative electrode active material layer 14B is not easily corroded. This is because the charge-discharge reaction using the positive electrode 13 and the negative electrode 14 is easier to carry out stably and continuously.

[0143] [Negative electrode capacity recovery electrode]

[0144] The negative capacity recovery electrode 17 is disposed inside the positive electrode chamber S1 in a manner isolated from the positive electrode 13. The negative capacity recovery electrode 17 may be an electrode that does not intercalate or deintercalate alkali metal ions, unlike the positive electrode 13, or it may be an electrode that intercalates or deintercalates alkali metal ions, just like the positive electrode 13.

[0145] Here, a portion of the negative capacity recovery electrode 17 is immersed in the positive electrolyte 15. Thus, the negative capacity recovery electrode 17 is in contact with the positive electrolyte 15.

[0146] In particular, during the capacity recovery process of the secondary battery described later, the negative capacity recovery electrode 17 is switched from the positive electrode 13 so that it can be energized together with the negative electrode 14. Thus, the negative capacity recovery electrode 17 is connected to the negative electrode 14 and is energized together with the negative electrode 14.

[0147] The negative electrode capacity recovery electrode 17 comprises one or both of a hydrogen-producing material and an oxygen-reducing material. Therefore, the negative electrode capacity recovery electrode 17 is used to recover the battery capacity that has decreased with the charging and discharging of the secondary battery by restoring the rechargeable margin of the negative electrode 14.

[0148] The hydrogen-generating material is a material that generates hydrogen when the negative electrode capacity recovery electrode 17 is energized. The negative electrode capacity recovery electrode 17 containing this hydrogen-generating material generates hydrogen in the positive electrode electrolyte 15, resulting in a reaction (discharge reaction) that causes alkali metal ions to be removed from the negative electrode 14.

[0149] Specifically, the hydrogen-generating material contains one or more of the following as constituent elements: platinum, iridium, nickel, iron, and palladium. This is because the hydrogen-generating material readily produces hydrogen under low voltage, thus easily generating a sufficient amount of hydrogen in the negative electrode capacity recovery electrode 17.

[0150] Furthermore, hydrogen-generating materials can be monomers (metallic materials), alloys, compounds such as oxides, or composites of two or more of these. Additionally, hydrogen-generating materials can also be materials in which multiple particles containing the hydrogen-generating material are carried on a conductive matrix (current collector foil).

[0151] The oxygen-reducing material is a material that reduces oxygen as the negative electrode capacity recovery electrode 17 is energized. The negative electrode capacity recovery electrode 17 containing this oxygen-reducing material reduces oxygen in the positive electrode electrolyte 15, generating a reaction (discharge reaction) that causes alkali metal ions to be removed from the negative electrode 14.

[0152] The material used for reducing oxygen can be materials that are used as catalysts in fuel cells, such as those used as the air electrode (oxygen electrode). Specifically, the material for reducing oxygen contains one or more of the following: platinum, platinum-ruthenium alloy, porous carbon, niobium oxide, tin oxide, and titanium oxide. This is because the material for reducing oxygen readily reduces oxygen at low voltages, thus facilitating the reduction of a sufficient amount of oxygen in the negative electrode capacity recovery electrode 17.

[0153] Alternatively, the oxygen-reducing material can also be a material in which multiple particles containing the oxygen-reducing material are supported on a conductive substrate (current collector foil). In this case, the oxygen-reducing material contains any one or more of the aforementioned niobium oxide, tin oxide, and titanium oxide.

[0154] It should be noted that platinum and the like are materials that serve as both hydrogen-generating and oxygen-reducing materials (hereinafter referred to as "hydrogen-generating and oxygen-reducing materials"). When this hydrogen-generating and oxygen-reducing material is used, as the negative electrode capacity recovery electrode 17 is energized, hydrogen is generated while oxygen is reduced.

[0155] A portion of the negative capacity recovery electrode 17 is led out to the outside of the outer packaging component 11 in the same manner as the connecting terminal portion 13AT. The lead-out direction of the negative capacity recovery electrode 17 is not particularly limited, but specifically, it is the same as the lead-out direction of the connecting terminal portion 13AT.

[0156] It should be noted that, in order to isolate the negative capacity recovery electrode 17 from the positive electrode 13, a separator (not shown) can also be disposed between the positive electrode 13 and the negative capacity recovery electrode 17. This separator can be a porous membrane comprising any one or more insulating materials such as synthetic resin and ceramics, or it can be a laminated membrane composed of two or more porous membranes stacked together. Specific examples of synthetic resins include polypropylene and polypropylene nonwoven fabric.

[0157] [Positive Capacity Recovery Electrode]

[0158] The positive capacity recovery electrode 18 is disposed inside the negative electrode chamber S2 in a manner isolated from the negative electrode 14. The positive capacity recovery electrode 18 may be an electrode that does not intercalate or deintercalate alkali metal ions, unlike the negative electrode 14, or it may be an electrode that intercalates or deintercalates alkali metal ions, just like the negative electrode 14.

[0159] Here, a portion of the positive capacity recovery electrode 18 is immersed in the negative electrolyte 16. Thus, the positive capacity recovery electrode 18 is in contact with the negative electrolyte 16.

[0160] In particular, during the capacity recovery process of the secondary battery described later, the positive capacity recovery electrode 18 is switched from the negative electrode 14 so that it can be energized together with the positive electrode 13. Thus, the positive capacity recovery electrode 18 is connected to the positive electrode 13 and is energized together with the positive electrode 13.

[0161] The positive capacity recovery electrode 18 comprises one or both of an oxygen-generating material and a hydrogen-oxidizing material. Therefore, the positive capacity recovery electrode 18 is used to recover the battery capacity that has decreased with the charging and discharging of the secondary battery by restoring the rechargeable margin of the positive electrode 13.

[0162] The oxygen-generating material is a material that generates oxygen when the positive capacity recovery electrode 18 is energized. The positive capacity recovery electrode 18 containing this oxygen-generating material generates oxygen in the negative electrolyte 16, thereby producing a reaction (discharge reaction) that allows alkali metal ions to insert into the positive electrode 13.

[0163] Specifically, the oxygen-generating material contains one or more of nickel, manganese, iridium, palladium, tantalum, and platinum as constituent elements. This is because the oxygen-generating material readily generates oxygen at low voltages, thus easily producing a sufficient amount of oxygen in the positive capacity recovery electrode 18. Furthermore, the oxygen-generating material can be a monomer (metallic material), an alloy, an oxide or other compound, or a composite material of two or more of these.

[0164] The hydrogen oxide material is a material that undergoes hydrogen oxidation when energized at the positive capacity recovery electrode 18. The positive capacity recovery electrode 18, containing this hydrogen oxide material, undergoes a reaction (discharge reaction) in which alkali metal ions are inserted into the positive electrode 13 by oxidizing the hydrogen oxide in the negative electrolyte 16.

[0165] The hydrogen oxide material can be any material used as a catalyst in a fuel cell (hydrogen electrode). Specifically, the hydrogen oxide material contains one or more of the following: platinum, silver, silver oxide, zirconium oxide, and nickel-chromium alloy. This is because hydrogen is easily oxidized at low voltages in the hydrogen oxide material, thus ensuring that a sufficient amount of hydrogen in the positive capacity recovery electrode 18 is easily oxidized.

[0166] It should be noted that platinum and the like are materials that can function as both oxygen-generating and hydrogen-oxidizing materials (hereinafter referred to as "oxygen-generating and hydrogen-oxidizing materials"). When this material that can function as both oxygen-generating and hydrogen-oxidizing is used, hydrogen is oxidized while oxygen is generated when the positive capacity recovery electrode 18 is energized.

[0167] A portion of the positive capacity recovery electrode 18 is led out to the outside of the outer packaging component 11 in the same manner as the connection terminal portion 14AT. The lead-out direction of the positive capacity recovery electrode 18 is not particularly limited, but specifically, it is the same as the lead-out direction of the connection terminal portion 14AT.

[0168] It should be noted that, in order to isolate the positive capacity recovery electrode 18 from the negative electrode 14, a separator (not shown) may also be disposed between the negative electrode 14 and the positive capacity recovery electrode 18. Details of the separator for this isolation are as described above.

[0169] <1-2. Actions>

[0170] As explained below, the secondary battery undergoes charge-discharge processing and capacity recovery processing. The charge-discharge processing involves electrode reactions that generate battery capacity within the secondary battery. Conversely, the capacity recovery processing involves electrode reactions that restore battery capacity when it decreases due to charge-discharge cycles.

[0171] [Charging and discharging process]

[0172] When the secondary battery is being charged and discharged, the positive electrode 13 and the negative electrode 14 are connected to each other.

[0173] During charging, when alkali metal ions are deintercalated from the positive electrode 13, they move sequentially through the positive electrode electrolyte 15, the separator 12, and the negative electrode electrolyte 16 to the negative electrode 14, thus embedding the alkali metal ions into the negative electrode 14.

[0174] On the other hand, during discharge, when alkali metal ions are deintercalated from the negative electrode 14, the alkali metal moves sequentially through the negative electrode electrolyte 16, the separator wall 12 and the positive electrode electrolyte 15 to the positive electrode 13, thus the alkali metal ions are intercalated into the positive electrode 13.

[0175] [Capacity Restoration Process]

[0176] In this secondary battery, capacity recovery is performed using either the negative capacity recovery electrode 17 or the positive capacity recovery electrode 18. The capacity recovery process of the secondary battery described below is performed using the secondary battery control system described later.

[0177] (Capacity recovery process at the positive electrode)

[0178] In the case of capacity recovery processing of the positive electrode 13, a positive capacity recovery electrode 18 is used. In this case, since the positive capacity recovery electrode 18 is selected instead of the negative electrode 14, the positive electrode 13 and the positive capacity recovery electrode 18 are connected to each other and energized. As a result, the battery capacity is recovered because the positive electrode 13 is discharged using the positive capacity recovery electrode 18.

[0179] In detail, during the charging and discharging of the secondary battery, the aqueous solvent in the negative electrode electrolyte 16 is decomposed in the negative electrode 14 during charging, thus producing hydrogen. In this case, due to the discharge of the negative electrode 14, the potential shifts to a higher potential side. Consequently, the state of charge of the negative electrode 14 deviates from that of the positive electrode 13, thus reducing the amount of lithium ions inserted and extracted in the secondary battery. Therefore, the battery capacity decreases.

[0180] In contrast, during the capacity recovery process of the positive electrode 13, the positive electrode 13 is discharged using the positive electrode capacity recovery electrode 18. Specifically, when the positive electrode capacity recovery electrode 18 contains an oxygen-generating material, the water in the negative electrode electrolyte 16 is oxidized, thus the positive electrode 13 is discharged while oxygen is being generated. When the positive electrode capacity recovery electrode 18 contains a hydrogen oxide material, the hydrogen dissolved in the negative electrode electrolyte 16 is oxidized, thus the positive electrode 13 is discharged while the hydrogen is being consumed. As a result, the state of charge of the positive electrode 13 can be made close to that of the negative electrode 14, thus restoring (increasing) the amount of lithium ions inserted and extracted in the secondary battery. Therefore, due to the capacity recovery reaction, the battery capacity is restored.

[0181] It should be noted that when the positive capacity recovery electrode 18 contains a material that is both an oxygen-generating material and a hydrogen-oxidizing material, such as platinum, by using only one material as the constituent material of the positive capacity recovery electrode 18, hydrogen is consumed while oxygen is generated.

[0182] (Capacity recovery process for the negative electrode)

[0183] In the case of capacity recovery processing of the negative electrode 14, a negative electrode capacity recovery electrode 17 is used. In this case, since the negative electrode capacity recovery electrode 17 is selected instead of the positive electrode 13, the negative electrode 14 and the negative electrode capacity recovery electrode 17 are connected to each other and energized. As a result, the battery capacity is recovered because the negative electrode 14 is discharged using the negative electrode capacity recovery electrode 17.

[0184] In detail, during the charging and discharging of the secondary battery, the aqueous solvent in the positive electrode electrolyte 15 is decomposed in the positive electrode 13 during charging, thus generating oxygen. In this case, as the positive electrode 13 is discharged, its potential shifts to a lower potential side. Consequently, the state of charge of the positive electrode 13 deviates from that of the negative electrode 14, thus reducing the amount of lithium ions inserted and extracted in the secondary battery. Therefore, the battery capacity decreases.

[0185] In contrast, during the capacity recovery process of the negative electrode 14, the negative electrode 14 is discharged using the negative electrode capacity recovery electrode 17. Specifically, when the negative electrode capacity recovery electrode 17 contains a hydrogen-generating material, the water in the positive electrode electrolyte 15 is reduced, thus the negative electrode 14 is discharged while hydrogen is being generated. When the negative electrode capacity recovery electrode 17 contains an oxygen-reducing material, the oxygen dissolved in the positive electrode electrolyte 15 is reduced, thus the negative electrode 14 is discharged while the oxygen is being consumed. As a result, the state of charge of the negative electrode 14 can be made close to that of the positive electrode 13, thus restoring (increasing) the amount of lithium ions inserted and extracted in the secondary battery. Therefore, due to the capacity recovery reaction, the battery capacity is restored.

[0186] It should be noted that when the negative electrode capacity recovery electrode 17 contains a material that generates hydrogen and reduces oxygen, such as platinum, by using only one material as the constituent material of the negative electrode capacity recovery electrode 17, oxygen is consumed while hydrogen is generated.

[0187] <1-3. Manufacturing Method>

[0188] In the case of manufacturing a secondary battery, as described below, a positive electrode 13 and a negative electrode 14 are fabricated, and a positive electrolyte 15 and a negative electrolyte 16 are prepared, and then the secondary battery is manufactured.

[0189] [The production of the positive electrode]

[0190] First, the positive electrode active material is mixed with a positive electrode binder and a positive electrode conductive agent to prepare a positive electrode mixture. Next, the positive electrode mixture is added to an aqueous solvent to prepare a paste-like positive electrode mixture slurry. Finally, the positive electrode mixture slurry is coated onto both sides of the positive electrode current collector 13A (excluding the connecting terminal portion 13AT) to form a positive electrode active material layer 13B. Thereafter, the positive electrode active material layer 13B can be compressed and molded using a roller press or the like. In this case, the positive electrode active material layer 13B can be heated, or the compression molding process can be repeated multiple times. Thus, the positive electrode 13 is manufactured.

[0191] [Making the negative electrode]

[0192] By following the same steps as those used in the fabrication of the positive electrode 13, a negative electrode active material layer 14B is formed on both sides of the negative electrode current collector 14A. Specifically, the negative electrode active material is mixed with a negative electrode binder and a negative electrode conductive agent to prepare a negative electrode mixture. This mixture is then added to an aqueous solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is coated onto both sides of the negative electrode current collector 14A (excluding the connecting terminal portion 14AT) to form the negative electrode active material layer 14B. The negative electrode active material layer 14B can then be compressed and molded. Thus, the negative electrode 14 is fabricated.

[0193] [Preparation of the positive and negative electrolytes]

[0194] Positive electrolyte 15 and negative electrolyte 16 were prepared by adding ionic substances to an aqueous solvent.

[0195] [Assembly of a secondary battery]

[0196] First, prepare an outer packaging component 11 (positive electrode chamber S1 and negative electrode chamber S2) with a partition wall 12 pre-installed inside. Next, house the positive electrode 13 and the negative electrode capacity recovery electrode 17 inside the positive electrode chamber S1, and house the negative electrode 14 and the positive electrode capacity recovery electrode 18 inside the negative electrode chamber S2. In this case, extend the connection terminal 13AT to the outside of the positive electrode chamber S1, and extend the connection terminal 14AT to the outside of the negative electrode chamber S2. Additionally, extend a portion of the negative electrode capacity recovery electrode 17 to the outside of the positive electrode chamber S1, and extend a portion of the positive electrode capacity recovery electrode 18 to the outside of the negative electrode chamber S2. Finally, supply the positive electrode electrolyte 15 into the positive electrode chamber S1 through a positive electrode injection port (not shown) communicating with the positive electrode chamber S1, and supply the negative electrode electrolyte 16 into the negative electrode chamber S2 through a negative electrode injection port (not shown) communicating with the negative electrode chamber S2. After that, the positive electrode injection port and the negative electrode injection port were sealed respectively.

[0197] Thus, the positive electrode electrolyte 15 is contained inside the positive electrode chamber S1, which is respectively equipped with a positive electrode 13 and a negative electrode capacity recovery electrode 17, and the negative electrode electrolyte 16 is contained inside the negative electrode chamber S2, which is respectively equipped with a negative electrode 14 and a positive electrode capacity recovery electrode 18. Therefore, a secondary battery using two aqueous electrolytes (positive electrode electrolyte 15 and negative electrode electrolyte 16) is completed.

[0198] <1-4. Functions and Effects>

[0199] According to the secondary battery, it includes a positive electrode 13, a negative electrode 14, and two aqueous electrolytes (positive electrolyte 15 and negative electrolyte 16), and also includes a negative capacity recovery electrode 17 and a positive capacity recovery electrode 18. The negative capacity recovery electrode 17 includes one or both of a hydrogen-generating material and an oxygen-reducing material, and the positive capacity recovery electrode 18 includes one or both of an oxygen-generating material and a hydrogen-oxidizing material.

[0200] In this case, as described above, when the secondary battery is being charged and discharged, even if the battery capacity decreases due to the increase in the potential of the positive electrode 13, the potential of the positive electrode 13 will decrease as the positive electrode 13 and the positive electrode capacity recovery electrode 18 are energized together, thus restoring the battery capacity.

[0201] In addition, as described above, when the secondary battery is being charged and discharged, even if the battery capacity decreases due to the increase in the potential of the negative electrode 14, the potential of the negative electrode 14 will increase as the negative electrode 14 and the negative electrode capacity recovery electrode 17 are energized together, thus restoring the battery capacity.

[0202] As described above, even if the battery capacity decreases with the use of the secondary battery, the states of the positive electrode 13 and the negative electrode 14 can be restored by using the negative electrode capacity recovery electrode 17 and the positive electrode capacity recovery electrode 18 respectively, thus enabling the battery capacity to be restored.

[0203] In this case, no special additives need to be added to either the positive electrolyte 15 or the negative electrolyte 16 to restore battery capacity. Furthermore, as long as the aqueous solvents in each of the positive and negative electrolytes 15 do not dry up, the battery capacity can be restored through repeated cycles. Therefore, battery capacity can be easily and continuously restored.

[0204] In particular, if the hydrogen-producing material contains one or more of platinum, iridium, nickel, iron, and palladium as constituent elements, it is easy to generate a sufficient amount of hydrogen under low voltage, thus achieving higher efficiency. If the oxygen-reducing material contains one or more of platinum, platinum-ruthenium alloy, porous carbon, niobium oxide, silicon oxide, and titanium oxide, a sufficient amount of oxygen is easily reduced under low voltage, thus achieving higher efficiency.

[0205] Furthermore, if the oxygen-generating material contains one or more of nickel, manganese, iridium, palladium, tantalum, and platinum as constituent elements, it can easily generate a sufficient amount of oxygen under low voltage, thus achieving a higher efficiency. If the hydrogen-oxidizing material contains at least one of platinum, silver, silver oxide, zirconium oxide, and nickel-chromium alloy, it can easily reduce a sufficient amount of hydrogen under low voltage, thus achieving a higher efficiency.

[0206] Furthermore, if the positive electrode 13 contains a positive electrode active material that can insert or deintercalate alkali metal ions at a potential of 0.4V or higher based on the potential of the standard hydrogen electrode, then the capacity recovery reaction can be easily carried out in the positive electrode 13 and the positive electrode capacity recovery electrode 18 with almost no power consumption, and the battery capacity can be easily recovered during the capacity recovery process, thus achieving a higher effect.

[0207] Similarly, if the negative electrode 14 contains a negative electrode active material that inserts or deinserts alkali metal ions at a potential below 0V based on the potential of the standard hydrogen electrode, then the capacity recovery reaction can be easily carried out in the negative electrode 14 and the negative electrode capacity recovery electrode 17 with almost no power consumption, and the battery capacity can be easily recovered during the capacity recovery process, thus achieving a higher effect.

[0208] Furthermore, if the pH of the negative electrode electrolyte 16 is higher than that of the positive electrode electrolyte 15, capacity recovery can be easily performed with almost no power consumption, and the battery capacity is easily recovered during this process, thus achieving higher efficiency. In this case, if the pH of the positive electrode electrolyte 15 is 3 to 8 and the pH of the negative electrode electrolyte 16 is 11 or higher, the capacity recovery reaction can easily and fully proceed, and the battery capacity can be fully recovered during this process, thus achieving even higher efficiency.

[0209] <2. Secondary Battery Control System>

[0210] Next, the secondary battery control system that uses the aforementioned secondary battery will be explained.

[0211] This secondary battery control system restores the battery capacity of a secondary battery by performing a capacity recovery process. Please refer to the following description. Figure 1 Furthermore, it references the constituent elements of a secondary battery that have already been explained.

[0212] <2-1. Structure>

[0213] Figure 2 The framework structure of the secondary battery control system is shown. Figure 2The image shows the secondary battery 1, which is the aforementioned secondary battery, installed (connected) to the secondary battery control system, and the secondary battery 1 is marked with a light shading.

[0214] like Figure 2 As shown, the secondary battery control system includes a control unit 21, a mounting unit 22, and connecting wiring 23 to 26.

[0215] It should be noted that, in Figure 2 In this design, the control unit 21 and the mounting unit 22 are separate units. However, the control unit 21 and the mounting unit 22 can also be integrated.

[0216] [Control Department]

[0217] The control unit 21 is a control circuit that centrally manages and executes the capacity recovery process of the secondary battery, including a central processing unit (CPU) and a memory. When the secondary battery 1 is installed on the mounting unit 22, the control unit 21 is connected to the secondary battery 1 via connecting wires 23 to 26. Thus, the control unit 21 is connected to the positive electrode 13, negative electrode 14, negative electrode capacity recovery electrode 17, and positive electrode capacity recovery electrode 18 via connecting wires 23 to 26, thereby enabling power to be supplied to each of these electrodes.

[0218] It should be noted that the control unit 21 may include one or both of a potentiostat and a galvanostat. The potentiostat and galvanostat are respectively connected to two or more of the positive electrode 13, negative electrode 14, negative electrode capacity recovery electrode 17, positive electrode capacity recovery electrode 18, and the reference electrode described later. Therefore, when energized for capacity recovery processing, any one or more of the voltage, current, and electrical force can be maintained constant.

[0219] In addition, the control unit 21 may also be equipped with a measuring instrument that detects the potential of each electrode and the current between interconnected electrodes. Specifically, the measuring instrument is a current detection unit and a current measuring unit connected to one or more of the positive electrode 13, negative electrode 14, negative electrode capacity recovery electrode 17, positive electrode capacity recovery electrode 18, and reference electrode.

[0220] Therefore, the control unit 21 can control the power supply during the capacity recovery process by referring to the potential difference between two or more electrodes among the positive electrode 13, negative electrode 14, negative electrode capacity recovery electrode 17, positive electrode capacity recovery electrode 18 and reference electrode, as well as the current and power flowing between the electrodes.

[0221] Specifically, after connecting the positive electrode 13 and the positive capacity recovery electrode 18, the control unit 21 can perform capacity recovery processing by energizing the positive electrode 13 and the positive capacity recovery electrode 18. Similarly, after connecting the negative electrode 14 and the negative capacity recovery electrode 17, the control unit 21 can perform capacity recovery processing by energizing the negative electrode 14 and the negative capacity recovery electrode 17. Furthermore, when the current value during energization or the voltage value between the connected electrodes reaches a predetermined value, the control unit 21 can terminate the capacity recovery processing by switching the connection destination to connect the positive electrode 13 and the negative electrode 14.

[0222] More specifically, after the secondary battery discharges until the predetermined discharge termination condition is met, the control unit 21 switches the connection destination of the positive electrode 13 from the negative electrode 14 to the positive capacity recovery electrode 18, and energizes the positive electrode 13 and the positive capacity recovery electrode 18 to perform a capacity recovery process. Subsequently, if the current value during energization becomes lower than the predetermined current value after performing capacity recovery under constant voltage conditions, the control unit 21 switches the connection destination of the positive electrode 13 from the positive capacity recovery electrode 18 to the negative electrode 14, ending the capacity recovery process.

[0223] [Installation Department]

[0224] Mounting section 22 holds secondary battery 1 and connects secondary battery 1 to control section 21 via connecting wires 23 to 26.

[0225] [Connection cabling]

[0226] Connecting wires 23 to 26 are connected to the control unit 21 and to four connecting terminals (not shown) provided on the mounting unit 22. Thus, when the secondary battery 1 is installed on the mounting unit 22, the secondary battery 1 is connected to the control unit 21 via connecting wires 23 to 26.

[0227] Specifically, since the negative capacity recovery electrode 17 is connected to the connection terminal of the connection wiring 23, the negative capacity recovery electrode 17 is connected to the control unit 21 via the connection wiring 23. Since the connection terminal 13AT is connected to the connection terminal of the connection wiring 24, the positive electrode 13 is connected to the control unit 21 via the connection wiring 24. Since the connection terminal 14AT is connected to the connection terminal of the connection wiring 25, the negative electrode 14 is connected to the control unit 21 via the connection wiring 25. Since the positive capacity recovery electrode 18 is connected to the connection terminal of the connection wiring 26, the positive capacity recovery electrode 18 is connected to the control unit 21 via the connection wiring 26.

[0228] [Other Constituent Elements]

[0229] It should be noted that the secondary battery may further include any one or more of the other constituent elements not shown in the figure.

[0230] Specifically, the secondary battery may also have an external power source connected to the control unit 21. It should be noted that, as described later, when the battery pack has multiple secondary batteries, secondary batteries other than those undergoing capacity recovery processing can also be used as external power sources. In this case, there is no particular limitation as long as there is one or more secondary batteries undergoing capacity recovery processing, and similarly, there is no particular limitation as long as there is one or more secondary batteries used as external power sources.

[0231] Additionally, the secondary battery may also include a reference electrode connected to the control unit 21. This reference electrode preferably comprises a material with resistance to acid, alkali, oxidation, and reduction. Furthermore, a porous material is preferred. This is because a large capacity can be obtained, and degradation of the reference electrode caused by self-discharge can be suppressed. It should be noted that the reference electrode can be disposed in either the positive electrolyte 15 or the negative electrolyte 16.

[0232] <2-2. Actions>

[0233] In this secondary battery control system, when the secondary battery 1 is installed on the mounting part 22, the secondary battery 1 is connected to the control part 21, and therefore, as described below, the control part 21 performs capacity recovery processing on the secondary battery 1.

[0234] Specifically, the control unit 21 switches the connection destination of the positive electrode 13 from the negative electrode 14 to the positive electrode capacity recovery electrode 18, and connects the positive electrode 13 and the positive electrode capacity recovery electrode 18 to each other, thereby energizing the positive electrode 13 and the positive electrode capacity recovery electrode 18. As described above, the potential of the positive electrode 13 decreases, thus initiating a capacity recovery reaction. Therefore, due to the capacity recovery process of the positive electrode 13, the battery capacity is restored.

[0235] Furthermore, the control unit 21 switches the connection destination of the negative electrode 14 from the positive electrode 13 to the negative electrode capacity recovery electrode 17, and connects the negative electrode 14 and the negative electrode capacity recovery electrode 17 to each other, thereby energizing the negative electrode 14 and the negative electrode capacity recovery electrode 17. As described above, the potential of the negative electrode 14 rises, thus initiating a capacity recovery reaction. Therefore, the capacity recovery process of the negative electrode 14 is performed, and the battery capacity is restored.

[0236] It should be noted that the control unit 21 can perform capacity recovery processing of the positive electrode 13 and the negative electrode 14 separately, or it can perform capacity recovery processing of the positive electrode 13 and the negative electrode 14 simultaneously.

[0237] Alternatively, the control unit 21 can also use an external power source to perform capacity recovery processing. Specifically, the control unit 21 can also use an external power source to energize the positive electrode 13 and the positive capacity recovery electrode 18 to perform capacity recovery processing. Additionally, the control unit 21 can also use an external power source to energize the negative electrode 14 and the negative capacity recovery electrode 17 to perform capacity recovery processing.

[0238] <2-3. Functions and Effects>

[0239] According to the secondary battery control system, a control unit 21 is included. This control unit 21 performs both capacity recovery processing, which involves energizing the positive electrode 13 and the positive electrode capacity recovery electrode 18, and capacity recovery processing, which involves energizing the negative electrode 14 and the negative electrode capacity recovery electrode 17. Therefore, as described above, since the control unit 21 performs capacity recovery processing on the positive electrode 13 and the negative electrode 14, the battery capacity of a secondary battery equipped with two aqueous electrolytes (positive electrode electrolyte 15 and negative electrode electrolyte 16) can be restored.

[0240] It should be noted that the other functions and effects of the secondary battery control system are the same as those of the secondary battery described above.

[0241] <3. Variations>

[0242] As explained below, the structures of the aforementioned secondary battery and secondary battery control system can be modified appropriately. Furthermore, any two or more of the variations described below can be combined with each other.

[0243] [Variations 1 and 2]

[0244] exist Figure 1 In this secondary battery, both a negative capacity recovery electrode 17 and a positive capacity recovery electrode 18 are present. However, it can also be used as follows: Figure 1 corresponding Figure 3 As shown, the secondary battery does not have a negative capacity recovery electrode 17 but only a positive capacity recovery electrode 18 (Modification 1), and can also be used as described above. Figure 1 corresponding Figure 4 As shown, the secondary battery does not have a positive capacity recovery electrode 18 but only a negative capacity recovery electrode 17 (Modification 2).

[0245] In these cases, as described above, capacity recovery processing is also performed on the positive electrode 13 using the positive capacity recovery electrode 18, and capacity recovery processing is also performed on the negative electrode 14 using the negative capacity recovery electrode 17, thus enabling the achievement of the same capacity recovery process as described above. Figure 1 The same effect is shown.

[0246] [Variation Example 3]

[0247] exist Figure 1 In this secondary battery, two aqueous electrolytes (positive electrode electrolyte 15 and negative electrode electrolyte 16) are used as liquid electrolytes. However, as with... Figure 1 corresponding Figure 5 As shown, a secondary battery can also replace two aqueous electrolytes and have two aqueous electrolyte layers (positive electrode electrolyte layer 19 and negative electrode electrolyte layer 20) as a gel-like electrolyte. Except as described below, Figure 5 The structure of the secondary battery shown is similar to Figure 1 The secondary battery shown has the same structure.

[0248] The positive electrode electrolyte layer 19 is disposed between the positive electrode 13 and the separator wall 12, and the negative electrode electrolyte layer 20 is disposed between the negative electrode 14 and the separator wall 12. That is, the positive electrode electrolyte layer 19 is adjacent to the positive electrode 13 and the separator wall 12, respectively, and the negative electrode electrolyte layer 20 is adjacent to the negative electrode 14 and the separator wall 12, respectively.

[0249] Specifically, the positive electrode electrolyte layer 19 comprises a positive electrode electrolyte 15 and a polymer compound, wherein the positive electrode electrolyte 15 is held in place by the polymer compound. The negative electrode electrolyte layer 20 comprises a negative electrode electrolyte 16 and a polymer compound, wherein the negative electrode electrolyte 16 is held in place by the polymer compound. The type of polymer compound is not particularly limited; specifically, it is any one or more of polyvinylidene fluoride and polyethylene oxide. Figure 5 In the diagram, the positive electrolyte layer 19 containing the positive electrolyte 15 is marked with a light shade, and the negative electrolyte layer 20 containing the negative electrolyte 16 is marked with a dark shade.

[0250] When forming the positive electrode electrolyte layer 19, a sol-like precursor solution is prepared by mixing a solvent with the positive electrode electrolyte 15 and a polymer compound, and then the precursor solution is coated onto the surface of the positive electrode 13. When forming the negative electrode electrolyte layer 20, a sol-like precursor solution is prepared by mixing a solvent with the negative electrode electrolyte 16 and a polymer compound, and then the precursor solution is coated onto the surface of the negative electrode 14. Alternatively, the precursor solution can be coated onto the surface of the separator wall 12 to form the positive electrode electrolyte layer 19, and the precursor solution can also be coated onto the surface of the separator wall 12 to form the negative electrode electrolyte layer 20.

[0251] In this case, lithium ions can move between the positive electrode 13 and the negative electrode 14 via the positive electrode electrolyte layer 19 and the negative electrode electrolyte layer 20, thus achieving the same efficiency as... Figure 1The same effect is achieved as shown. It should be noted that positive electrolyte 15 and negative electrolyte layer 20 can be used together, as can positive electrolyte layer 19 and negative electrolyte 16.

[0252] [Variation Example 4]

[0253] exist Figure 1 In this configuration, since the positive electrode chamber S1 is filled with positive electrolyte 15, there is no remaining space S1Z inside the positive electrode chamber S1. Similarly, since the negative electrode chamber S2 is filled with negative electrolyte 16, there is no remaining space S2Z inside the negative electrode chamber S2. The remaining space S1Z is the space inside the positive electrode chamber S2 where the positive electrolyte 15 is not present, and the remaining space S2Z is ​​the space inside the negative electrode chamber S2 where the negative electrolyte 16 is not present.

[0254] However, it can also be like... Figure 1 corresponding Figure 6 As shown, due to certain reasons, the capacity of the positive electrode electrolyte 15 decreases, resulting in a remaining space S1Z inside the positive electrode chamber S1. Similarly, due to certain reasons, the capacity of the negative electrode electrolyte 16 decreases, resulting in a remaining space S2Z inside the negative electrode chamber S2. The decrease in the capacity of the positive electrode electrolyte 15 is caused by its evaporation and leakage, and the decrease in the capacity of the negative electrode electrolyte 16 is caused by its evaporation and leakage.

[0255] In this case, as the amount of positive electrolyte 15 decreases, a portion of the positive active material layer 13B in the positive electrode 13 may be exposed, or a portion of the positive active material layer 13B may not be exposed. Similarly, as the amount of negative electrolyte 16 decreases, a portion of the negative active material layer 14B in the negative electrode 14 may be exposed, or a portion of the negative active material layer 14B may not be exposed.

[0256] It should be noted that the position of the liquid surface (upper surface) of the positive electrode electrolyte 15 is not particularly limited, and therefore can be arbitrarily set within the range where the positive electrode electrolyte 15 can contact the positive electrode active material layer 13B. Similarly, the position of the liquid surface (upper surface) of the negative electrode electrolyte 16 is not particularly limited, and therefore can be arbitrarily set within the range where the negative electrode electrolyte 16 can contact the negative electrode active material layer 14B.

[0257] In this case, as described above, capacity recovery processing is also performed on the positive electrode 13 using the positive capacity recovery electrode 18, and capacity recovery processing is also performed on the negative electrode 14 using the negative capacity recovery electrode 17, thus enabling the achievement of the same capacity recovery process as described above. Figure 1 The same effect is shown.

[0258] In this case, in particular, the negative capacity recovery electrode 17 using a material containing reduced oxygen not only reduces the oxygen dissolved in the positive electrolyte 15, but also reduces the oxygen present in the remaining space S1Z. Therefore, due to the increased oxygen consumption, a higher efficiency can be obtained.

[0259] Furthermore, by using a positive capacity recovery electrode 18 made of a material containing hydrogen oxide, not only is the hydrogen dissolved in the negative electrode electrolyte 16 oxidized, but the hydrogen present in the remaining space S2Z is ​​also oxidized. Therefore, due to the increased consumption of hydrogen, a higher efficiency can be obtained.

[0260] It should be noted that although no specific illustration is provided, the variation 4 described here is not limited to... Figure 1 It can also be applied to Figure 3 It can also be applied to Figure 4 In these situations, it is also possible to obtain... Figure 6 The same effect is shown. Of course, it is also possible that there is a remaining space S1Z inside the positive electrode chamber S1 but no remaining space S2Z inside the negative electrode chamber S2, or that there is a remaining space S2Z inside the negative electrode chamber S2 but no remaining space S1Z inside the positive electrode chamber S1.

[0261] [Variation Example 5]

[0262] In the above variation 4 ( Figure 6 In the process, since a portion of the negative capacity recovery electrode 17 is immersed in the positive electrolyte 15, the negative capacity recovery electrode 17 is in contact with the positive electrolyte 15, and since a portion of the positive capacity recovery electrode 18 is immersed in the negative electrolyte 16, the positive capacity recovery electrode 18 is in contact with the negative electrolyte 16.

[0263] However, it can also be like... Figure 6 corresponding Figure 7 As shown, a portion of the negative capacity recovery electrode 17 is not immersed in the positive electrolyte 15 and terminates in the remaining space S1Z, so the negative capacity recovery electrode 17 is not in contact with the positive electrolyte 15. Similarly, a portion of the positive capacity recovery electrode 18 is not immersed in the negative electrolyte 16 and terminates in the remaining space S2Z, so the positive capacity recovery electrode 18 is not in contact with the negative electrolyte 16.

[0264] In this case, as described above, capacity recovery processing is also performed on the positive electrode 13 using the positive capacity recovery electrode 18, and capacity recovery processing is also performed on the negative electrode 14 using the negative capacity recovery electrode 17, thus enabling the achievement of the same capacity recovery process as described above. Figure 6 The same effect is shown.

[0265] It should be noted that, although no specific illustration is provided, it is also possible that, since a portion of the negative capacity recovery electrode 17 is not immersed in the positive electrolyte 15, it is not in contact with the positive electrolyte 15. Conversely, since a portion of the positive capacity recovery electrode 18 is immersed in the negative electrolyte 16, it is in contact with the negative electrolyte 16. Alternatively, it is also possible that, since a portion of the negative capacity recovery electrode 17 is immersed in the positive electrolyte 15, it is in contact with the positive electrolyte 15. Conversely, since a portion of the positive capacity recovery electrode 18 is not immersed in the negative electrolyte 16, it is not in contact with the negative electrolyte 16.

[0266] [Variation Example 6]

[0267] exist Figure 2 In the secondary battery control system shown, the control unit 21 performs both capacity recovery processing, which involves energizing the positive electrode 13 and the positive capacity recovery electrode 18, and capacity recovery processing, which involves energizing the negative electrode 14 and the negative capacity recovery electrode 17. However, the control unit 21 may also perform only one of the capacity recovery processing methods: energizing the positive electrode 13 and the positive capacity recovery electrode 18, or energizing the negative electrode 14 and the negative capacity recovery electrode 17.

[0268] In this case, the same effect can be obtained by using either the negative capacity recovery electrode 17 or the positive capacity recovery electrode 18 to restore the battery capacity.

[0269] <4. Uses of Secondary Batteries>

[0270] There are no particular limitations on the uses (application examples) of secondary batteries. Secondary batteries used as power sources can be the main power source for electronic devices and electric vehicles, or they can be an auxiliary power source. The main power source is the power source used preferentially, regardless of the availability of other power sources. An auxiliary power source is a power source used in place of the main power source, or a power source switched from the main power source.

[0271] Specific examples of applications for rechargeable batteries are as follows: Electronic devices such as camcorders, digital still cameras, mobile phones, laptops, stereo headphones, portable radios, and portable information terminals. Backup power supplies and storage devices such as memory cards. Power tools such as electric drills and chainsaws. Battery packs integrated into electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid vehicles). Power storage systems such as household or industrial battery systems that pre-store power in preparation for emergencies. In these applications, one or multiple rechargeable batteries can be used.

[0272] Battery packs can use a single battery (one secondary battery) or a battery array (multiple secondary batteries). Electric vehicles are vehicles that operate (drive) using secondary batteries as a power source, and can also be hybrid vehicles that have a power source other than the secondary battery. In home power storage systems, electricity stored in secondary batteries, which act as power storage sources, can be used to operate household electrical products, etc.

[0273] Here, we will specifically illustrate one application example of secondary batteries. Figure 8 The frame structure of the battery pack is shown. The battery pack described here is a simplified type (so-called pouch) that uses a single rechargeable battery and is used in electronic devices such as smartphones.

[0274] like Figure 8 As shown, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0275] The power supply 51 includes a secondary battery, the structure of which is described above. In this secondary battery, the positive lead is connected to the positive terminal 53, and the negative lead is connected to the negative terminal 54. The power supply 51 can be connected to an external source via the positive terminal 53 and the negative terminal 54, and thus can be charged and discharged. The circuit board 52 includes a control unit 56, a switch 57, a thermistor (PTC) element 58, and a temperature detection unit 59. Alternatively, the PTC element 58 may be omitted.

[0276] The control unit 56 has the same structure as the secondary battery control system described above, and controls the operation of the entire battery pack. This control unit 56 detects and controls the operating status of the power supply 51 as needed.

[0277] It should be noted that when the voltage of the power supply 51 (secondary battery) reaches the overcharge detection voltage, the control unit 56 cuts off the switch 57 to prevent the charging current from flowing through the current path of the power supply 51.

[0278] Switch 57 includes a charging control switch, a discharging control switch, a charging diode, and a discharging diode, etc., and switches the connection between power supply 51 and external devices according to the instructions of control unit 56. Switch 57 includes a field-effect transistor (MOSFET) using metal-oxide-semiconductor, and the charging / discharging current is detected based on the on-resistance of switch 57.

[0279] The temperature detection unit 59 includes a temperature detection element such as a thermistor, measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the temperature measurement result to the control unit 56. The temperature measurement result measured by the temperature detection unit 59 is used for situations such as charging and discharging control by the control unit 56 when abnormal heating occurs, and for correction processing by the control unit 56 when calculating the remaining capacity.

[0280] Of course, secondary batteries can also be used for purposes other than those listed here.

[0281] Example

[0282] The embodiments of this technology are described below.

[0283] <Examples 1, 2 and Comparative Example 1>

[0284] As explained below, the battery characteristics of a secondary battery were evaluated after it was fabricated using lithium ions, which are alkali metal ions.

[0285] [Preparation of secondary batteries in Examples 1 and 2]

[0286] The following steps were used to create a device with... Figure 3 The secondary battery shown is a positive capacity recovery electrode 18.

[0287] (The production of the positive electrode)

[0288] First, 91 parts by mass of the positive electrode active material (LiMn2O4, a lithium composite oxide with a spinel-type crystal structure), 3 parts by mass of the positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of the positive electrode conductive agent (graphite) are mixed together to prepare a positive electrode mixture. Next, the positive electrode mixture is added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the organic solvent is stirred to prepare a paste-like positive electrode mixture slurry. Finally, using a coating apparatus, the positive electrode mixture slurry is coated on both sides of the positive electrode current collector 13A (a titanium foil with a thickness of 10 μm), excluding the connecting terminal portion 13AT, and then the positive electrode mixture slurry is dried to form the positive electrode active material layer 13B. Thus, the positive electrode 13 is manufactured.

[0289] (Making the negative electrode)

[0290] First, 89 parts by mass of the negative electrode active material (TiO2 (anatase type) as a titanium oxide), 10 parts by mass of the negative electrode binder (polyvinylidene fluoride), and 1 part by mass of the negative electrode conductive agent (graphite) are mixed together to prepare a negative electrode mixture. Next, the negative electrode mixture is added to a solvent (N-methyl-2-pyrrolidone as an organic solvent), and the organic solvent is stirred to prepare a paste-like negative electrode mixture slurry. Finally, using a coating apparatus, the negative electrode mixture slurry is coated on both sides of the negative electrode current collector 14A (a titanium foil with a thickness of 10 μm), excluding the connecting terminal portion 14AT, and then the negative electrode mixture slurry is dried to form a negative electrode active material layer 14B. Thus, the negative electrode 14 is manufactured.

[0291] (Preparation of positive electrode electrolyte)

[0292] An ionic substance (lithium sulfate (Li₂SO₄)) was added to an aqueous solvent (pure water), and the solvent was stirred. Thus, a positive electrode electrolyte 15, serving as an aqueous electrolyte, was prepared because the ionic substance was dispersed or dissolved in the aqueous solvent. Under these conditions, the concentration was 3 mol / kg and the pH was 5.

[0293] (Preparation of negative electrode electrolyte)

[0294] After adding an ionic substance (lithium hydroxide (LiOH)) to an aqueous solvent (pure water), the aqueous solvent was stirred. Thus, since the ionic substance is dispersed or dissolved in the aqueous solvent, a negative electrode electrolyte 16 as an aqueous electrolyte was prepared. In this case, the concentration was 4 mol / kg and the pH was 12. That is, the pH of the negative electrode electrolyte 16 was made higher than the pH of the positive electrode electrolyte 15.

[0295] (Assembly of a secondary battery)

[0296] First, a glass container, namely the outer packaging component 11 (positive electrode chamber S1 and negative electrode chamber S2), with a partition wall 12 (a cation exchange membrane Nafion115 manufactured by Sigma Aldrich Japan Co., Ltd. (registered trademark)) installed inside is prepared.

[0297] Next, the positive electrode 13 is housed inside the positive electrode chamber S1, and the negative electrode 14 and the positive capacity recovery electrode 18 are housed inside the negative electrode chamber S2. The material of the positive capacity recovery electrode 18 is shown in Table 1. Here, nickel (Ni) as an oxygen-generating material and platinum (Pt) as both an oxygen-generating and hydrogen-oxidizing material are used as the material (constituent material) of the positive capacity recovery electrode 18. In this case, the connecting terminals 13AT and 14AT are led out to the outside of the outer packaging component 11, and a portion of the positive capacity recovery electrode 18 is led out to the outside of the outer packaging component 11.

[0298] Finally, positive electrolyte 15 is supplied to the positive electrode chamber S1, and negative electrolyte 16 is supplied to the negative electrode chamber S2. Thus, positive electrolyte 15 is contained inside the positive electrode chamber S1, which contains the positive electrode 13, and negative electrolyte 16 is contained inside the negative electrode chamber S2, which contains the negative electrode 14 and the positive capacity recovery electrode 18. Thus, a secondary battery using two aqueous electrolytes (positive electrolyte 15 and negative electrolyte 16) is completed.

[0299] [The construction of a secondary battery in Comparative Example 1]

[0300] A secondary battery without the positive capacity recovery electrode 18 was fabricated using the same steps, except that the positive capacity recovery electrode 18 was not used. The presence or absence of the positive capacity recovery electrode 18 is shown in Table 1.

[0301] [Evaluation of Battery Characteristics]

[0302] As a secondary battery, the battery characteristics were evaluated, and the capacity recovery characteristics were obtained, as shown in Table 1.

[0303] (Evaluation of the capacity recovery characteristics of the secondary batteries used in Examples 1 and 2)

[0304] First, a secondary battery with positive electrode 13 and negative electrode 14 connected together was charged and discharged at room temperature (temperature = 25°C) to determine the discharge capacity (discharge capacity of the first cycle).

[0305] Next, using a secondary battery with positive electrode 13 and negative electrode 14 connected together, the secondary battery was repeatedly charged and discharged in the same environment until the number of cycles (charge and discharge times) reached 50 cycles, and the discharge capacity (discharge capacity of the 50th cycle) was measured.

[0306] During charging, the secondary battery is charged at a constant current of 2C until the battery voltage reaches 2.0V. During discharging, the secondary battery is discharged at a constant current of 2C until the battery voltage reaches 1.5V. It should be noted that 2C refers to the current value required to fully discharge the battery (theoretical capacity) within 0.5 hours.

[0307] Next, a secondary battery (positive electrode 13) was used where the connection destination of the positive electrode 13 was switched from the negative electrode 14 to the positive electrode capacity recovery electrode 18, and the positive electrode 13 and the positive electrode capacity recovery electrode 18 were interconnected. In this case, the positive electrode 13 was discharged by energizing the positive electrode 13 and the positive electrode capacity recovery electrode 18 in the same environment. During discharge, the secondary battery was discharged with a current of 0.05C until the potential difference (the difference between the potential of the positive electrode 13 and the potential of the positive electrode capacity recovery electrode 18) reached 0V. It should be noted that 0.05C refers to the current value required to completely discharge the battery within 20 hours.

[0308] Next, using a secondary battery in which the connection destination of the positive electrode 13 was switched from the positive capacity recovery electrode 18 to the negative electrode 14 and the positive electrode 13 and the negative electrode 14 were reconnected, the secondary battery was charged and discharged under the same conditions, and the discharge capacity (discharge capacity of the 51st cycle) was measured.

[0309] Finally, based on the formula for calculating capacity recovery rate (%) = [(discharge capacity of the 51st cycle - discharge capacity of the 50th cycle) / discharge capacity of the 1st cycle] × 100, the capacity recovery rate, which is used as an indicator to evaluate capacity recovery characteristics, is calculated.

[0310] (Evaluation of the capacity recovery characteristics of the secondary battery used in Comparative Example 1)

[0311] Since the secondary battery does not have a positive capacity recovery electrode 18, the capacity recovery rate is calculated using the same steps, except that the capacity recovery process of the secondary battery (positive electrode 13) is not performed.

[0312] [Table 1]

[0313] Table 1

[0314]

[0315] [Inspection]

[0316] As shown in Table 1, the capacity recovery rate varies depending on the structure of the secondary battery (whether or not there is a positive capacity recovery electrode 18), i.e. whether or not there is capacity recovery treatment.

[0317] Specifically, since the secondary battery does not have a positive electrode capacity recovery electrode 18, the capacity recovery rate is 0% when no capacity recovery treatment of the positive electrode 13 is performed (Comparative Example 1), and therefore the battery capacity is not recovered. In contrast, since the secondary battery has a positive electrode capacity recovery electrode 18, the capacity recovery rate is 13% and 20% respectively when the capacity recovery treatment of the positive electrode 13 is performed (Examples 1 and 2), and therefore the battery capacity is recovered.

[0318] [Summarize]

[0319] As shown in Table 1, if a secondary battery using a positive electrode 13, a negative electrode 14, and two aqueous electrolytes (positive electrolyte 15 and negative electrolyte 16) has a positive capacity recovery electrode 18, and the positive electrode 13 and the positive capacity recovery electrode 18 are energized together, the capacity recovery rate increases. Therefore, the battery capacity of the secondary battery can be recovered.

[0320] It should be noted that, although there is no specific verification here, it can be speculated that if a secondary battery using a positive electrode 13, a negative electrode 14, and two aqueous electrolytes (positive electrolyte 15 and negative electrolyte 16) has a negative capacity recovery electrode 17, and the negative electrode 14 and the negative capacity recovery electrode 17 are energized together, the capacity recovery rate will increase, thus enabling the secondary battery capacity to be restored.

[0321] The above description illustrates the structure of the secondary battery of this technology through one embodiment and example. However, the structure of the secondary battery of this technology is not limited to the structure described in one embodiment and example, and various modifications are possible.

[0322] The effects described in this specification are merely illustrative, and therefore the effects of this technology are not limited to those described herein. Thus, other effects can also be obtained with this technology.

Claims

1. A secondary battery, comprising: A separator is positioned between the positive and negative electrode spaces, allowing alkali metal ions to permeate. A positive electrode is disposed inside the positive electrode space and has the alkali metal ions inserted or extracted. The negative electrode is disposed inside the negative electrode space and the alkali metal ions are inserted and de-intercalated. The positive electrode electrolyte is contained inside the positive electrode space and contains an aqueous solvent and the alkali metal ions; A negative electrode electrolyte, contained within the negative electrode space, and comprising an aqueous solvent and the alkali metal ions; and At least one of the negative capacity recovery electrode disposed inside the positive electrode space and the positive capacity recovery electrode disposed inside the negative electrode space. The negative electrode capacity recovery electrode comprises at least one of a hydrogen-producing material and an oxygen-reducing material. The positive capacity recovery electrode comprises at least one of an oxygen-generating material and a hydrogen-oxidizing material.

2. The secondary battery according to claim 1, wherein, The hydrogen-producing material contains at least one of platinum, iridium, nickel, iron, and palladium as a constituent element. The oxygen-reducing material contains at least one of platinum, platinum-ruthenium alloy, porous carbon, niobium oxide, tin oxide, and titanium oxide. The oxygen-generating material contains at least one of nickel, manganese, iridium, palladium, tantalum, and platinum as a constituent element. The hydrogen peroxide material contains at least one of platinum, silver, silver oxide, zirconium oxide, and nickel-chromium alloy.

3. The secondary battery according to claim 1 or 2, wherein, The positive electrode comprises a positive electrode active material capable of inserting and deintercalating the alkali metal ions at a potential above 0.4V, based on the potential of a standard hydrogen electrode. The negative electrode contains a negative electrode active material that can insert or deintercalate the alkali metal ions at a potential below 0V, based on the potential of the standard hydrogen electrode.

4. The secondary battery according to any one of claims 1 to 3, wherein, The pH of the negative electrode electrolyte is greater than the pH of the positive electrode electrolyte.

5. The secondary battery according to claim 4, wherein, The pH of the positive electrode electrolyte is above 3 and below 8. The pH of the negative electrode electrolyte is above 11.

6. A secondary battery control system, Equipped with a control circuit connected to the secondary battery as described in any one of claims 1 to 5, The control circuit performs at least one of the following processes: switching the connection destination of the positive electrode from the negative electrode to the positive capacity recovery electrode and energizing the positive electrode and the positive capacity recovery electrode; and switching the connection destination of the negative electrode from the positive electrode to the negative capacity recovery electrode and energizing the negative electrode and the negative capacity recovery electrode.

7. A battery pack, comprising: The secondary battery according to any one of claims 1 to 5; and The secondary battery control system according to claim 6.

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