Secondary battery and method for manufacturing same

Abstract

The present invention provides a secondary battery with which excellent operation characteristics can be achieved. This secondary battery is provided with: a partition wall that allows alkali metal ions to pass therethrough; an outer package member that internally has a positive electrode space and a negative electrode space, which are separated from each other by the intermediary of the partition wall; a positive electrode aqueous electrolyte solution that is contained in the positive electrode space; a negative electrode aqueous electrolyte solution that is contained in the negative electrode space; a positive electrode that is immersed in the positive electrode aqueous electrolyte solution, and occludes and releases alkali metal ions; and a negative electrode that is immersed in the negative electrode aqueous electrolyte solution, and occludes and releases alkali metal ions. The partition wall includes an outer peripheral edge part that is adjacent to the outer package member, and a main body part that is positioned inside the outer peripheral edge part. The main body part includes a cation exchange membrane. At least a part of the outer peripheral edge part contains a first polymer compound, and the first polymer compound contains at least one of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group, and a carboxyl group.

Description

Secondary battery and manufacturing method thereof

[0001] The present technology relates to a secondary battery and a manufacturing method thereof.

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small, lightweight, and have high energy density. Among these, secondary batteries using aqueous electrolytes have been developed, and various studies have been conducted on the structure of these secondary batteries.

[0003] Specifically, the electrochemical device (fuel cell) includes an electrolyte membrane, a resin that adheres to the electrolyte membrane, and a resin that adheres to a metal (see, for example, Patent Document 1). The secondary battery includes a positive electrode and an aqueous electrolyte solution housed in a first space, a partition wall that allows metal ions to pass through, and a negative electrode and an aqueous electrolyte solution housed in a second space (see, for example, Patent Document 2). The metal-air battery includes a battery case, and a positive electrode, a negative electrode, and a separator housed in the battery case (see, for example, Patent Document 3).

[0004] Japanese Patent No. 5130692 International Publication No. 2020 / 218456 Japanese Patent No. 7004461

[0005] Although various studies have been conducted on the construction of secondary batteries using aqueous electrolyte solutions, the operating characteristics of the secondary batteries are still insufficient and there is room for improvement. In this case, it is important not only to improve the operating characteristics but also to establish a manufacturing method for secondary batteries with improved operating characteristics.

[0006] There is a demand for a secondary battery capable of obtaining excellent operating characteristics and a method for manufacturing the same.

[0007] A secondary battery according to an embodiment of the present disclosure includes a partition wall that allows alkali metal ions to pass through, an exterior member having a positive electrode space and a negative electrode space separated from each other by the partition wall, a positive electrode aqueous electrolyte solution accommodated in the positive electrode space, a negative electrode aqueous electrolyte solution accommodated in the negative electrode space, a positive electrode that is immersed in the positive electrode aqueous electrolyte solution and absorbs and releases alkali metal ions, and a negative electrode that is immersed in the negative electrode aqueous electrolyte solution and absorbs and releases alkali metal ions. The partition wall includes an outer peripheral edge portion adjacent to the exterior member and a main body portion located inside the outer peripheral edge portion, and the main body portion includes a cation exchange membrane. At least a portion of the outer peripheral edge portion includes a first polymer compound, and the first polymer compound includes at least one of a hydroxyl group, a carboxyl group, a carboxylic acid anhydride, a carboxylic acid ester, and a nitrogen-containing basic functional group.

[0008] A method for manufacturing a secondary battery according to an embodiment of the present technology forms a partition wall by heat-sealing at least a portion of the outer peripheral edge portion and the main body portion together during the manufacturing process of the secondary battery according to the embodiment of the present technology described above.

[0009] According to a secondary battery in one embodiment of the present technology, the positive electrode space and the negative electrode space are separated from each other by a partition wall, the partition wall includes an outer peripheral edge portion and a main body portion, the main body portion includes a cation exchange membrane, at least a portion of the outer peripheral edge portion includes a first polymer compound, and the first polymer compound includes at least one of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group, and a carboxyl group, thereby achieving excellent operating characteristics.

[0010] According to the manufacturing method of a secondary battery in one embodiment of the present technology, in the manufacturing process of the secondary battery in the above-mentioned embodiment of the present technology, at least a portion of the outer peripheral edge portion and the main body portion are heat-fused to each other to form a partition wall, thereby realizing a secondary battery with excellent operating characteristics.

[0011] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0012] Fig. 1 is a cross-sectional view showing a configuration of a secondary battery according to an embodiment of the present technology. Fig. 2 is a cross-sectional view taken along line A-A of the secondary battery shown in Fig. 1. Fig. 3 is a cross-sectional view showing a configuration of a secondary battery according to Modification 3. Fig. 4 is a cross-sectional view showing a configuration of a secondary battery according to Modification 4. Fig. 5 is a cross-sectional view showing a configuration of a secondary battery according to Modification 5. Fig. 6 is a cross-sectional view showing a configuration of a secondary battery according to Modification 7. Fig. 7 is a cross-sectional view showing a configuration of a secondary battery according to Modification 7. Fig. 8 is a cross-sectional view showing a configuration of a secondary battery according to Modification 7.

[0013] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing method 1-4. Actions and effects 2. Modifications 3. Uses of secondary battery

[0014] 1. Secondary Battery First, a secondary battery according to an embodiment of the present technology will be described.

[0015] Note that the method for manufacturing a secondary battery according to an embodiment of the present technology is a method for manufacturing the secondary battery described herein, and therefore the method for manufacturing a secondary battery according to an embodiment of the present technology will also be described below.

[0016] The secondary battery described here utilizes the absorption and desorption of alkali metal ions and includes a positive electrode, a negative electrode, and an aqueous electrolyte. The aqueous electrolyte is a liquid electrolyte containing an aqueous solvent. In this secondary battery, the absorption and desorption of alkali metal ions is utilized to drive the charge and discharge reactions, thereby achieving battery capacity.

[0017] The type of alkali metal ion is not particularly limited, but specific examples include lithium ions, sodium ions, and potassium ions, because the charge / discharge reaction proceeds stably while a high voltage is ensured.

[0018] <1-1. Structure> Fig. 1 shows a cross-sectional structure of a secondary battery, and Fig. 2 shows a cross-sectional structure of the secondary battery shown in Fig. 1 taken along line AA.

[0019] 1 and 2, this secondary battery includes an exterior member 11, a partition wall 12, a positive electrode 13, a negative electrode 14, a positive electrode aqueous electrolyte solution 15, a negative electrode aqueous electrolyte solution 16, a positive electrode sealing member 17, and a negative electrode sealing member 18. In Fig. 1, the positive electrode aqueous electrolyte solution 15 is lightly hatched, and the negative electrode aqueous electrolyte solution 16 is darkly hatched.

[0020] Each of the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 is the above-described aqueous electrolyte solution and therefore contains an aqueous solvent. This aqueous electrolyte solution contains an ionic substance that can be ionized in the aqueous solvent, and the ionic substance is dissolved or dispersed in the aqueous solvent. Details of the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 will be described later.

[0021] [Exterior Member] Exterior member 11 is a member that houses a series of components, such as partition wall 12, positive electrode 13, negative electrode 14, positive electrode aqueous electrolyte solution 15, and negative electrode aqueous electrolyte solution 16, and has an internal space for housing the series of components. This internal space is divided into two spaces by partition wall 12, and therefore exterior member 11 has therein a positive electrode space S1 and a negative electrode space S2 that are separated from each other by partition wall 12.

[0022] The exterior member 11 preferably has a positive electrode outlet 11PX that is not in communication with the negative electrode space S2 but is in communication with the positive electrode space S1. This is because a positive electrode current collector 13A (connection terminal portion 13AT) described below is led out of the exterior member 11 via the positive electrode outlet 11PX, and the secondary battery can be connected to an external device via the connection terminal portion 13AT. This external device is a device that can operate using the secondary battery as a power source, and the type of external device is not particularly limited.

[0023] Furthermore, the exterior member 11 preferably has a negative electrode outlet 11PY that is not in communication with the positive electrode space S1 but is in communication with the negative electrode space S2. This is because a negative electrode current collector 14A (connection terminal portion 14AT) described below is led out of the exterior member 11 via the negative electrode outlet 11PY, and the secondary battery can be connected to an external device via the connection terminal portion 14AT.

[0024] The exterior member 11 may be a flexible or pliable member, or may be a rigid member. Here, the exterior member 11 is preferably a flexible polymer film, and therefore preferably contains one or more of the second polymer compounds. This gives the exterior member a bag-like structure having the positive electrode space S1 and the negative electrode space S2 therein.

[0025] The second polymer compound contains one or more of polyethylene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene, and polyvinyl chloride, because this allows the exterior member 11 to have a high level of sealing ability.

[0026] Here, it is preferable that exterior member 11 has sufficient hydrophilicity with respect to both positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 .

[0027] Specifically, the exterior member 11 has a positive electrode inner wall surface 11WX inside the positive electrode space S1, and the positive electrode inner wall surface 11WX is in contact with the positive electrode aqueous electrolyte solution 15 contained in the positive electrode space S1.

[0028] The contact angle of positive electrode aqueous electrolyte solution 15 with positive electrode inner wall surface 11WX is not particularly limited, but it is particularly preferable that the contact angle of positive electrode aqueous electrolyte solution 15 with positive electrode inner wall surface 11WX be 150° or less. This is because the wettability of positive electrode inner wall surface 11WX with positive electrode aqueous electrolyte solution 15 is ensured, which facilitates sufficient progress of charge / discharge reactions during charge / discharge. This improves battery characteristics such as charge / discharge efficiency.

[0029] Additionally, the exterior member 11 has a negative electrode inner wall surface 11WY inside the negative electrode space S2, and the negative electrode inner wall surface 11WY is in contact with the negative electrode aqueous electrolyte 16 contained in the negative electrode space S2.

[0030] The contact angle of the negative electrode aqueous electrolyte solution 16 with the negative electrode inner wall surface 11WY is not particularly limited, but it is particularly preferable that the contact angle of the negative electrode aqueous electrolyte solution 16 with the negative electrode inner wall surface 11WY be 150° or less. This is because the wettability of the negative electrode inner wall surface 11WY with the negative electrode aqueous electrolyte solution 16 is ensured, thereby providing the same advantages as when the wettability of the positive electrode inner wall surface 11WX with the positive electrode aqueous electrolyte solution 15 is ensured.

[0031] The contact angle of positive electrode aqueous electrolyte solution 15 with positive electrode inner wall surface 11WX can be adjusted by subjecting positive electrode inner wall surface 11WX to a surface treatment. Similarly, the contact angle of negative electrode aqueous electrolyte solution 16 with negative electrode inner wall surface 11WY can be adjusted by subjecting negative electrode inner wall surface 11WY to a surface treatment. The type of surface treatment is not limited as long as it improves the wettability of positive electrode inner wall surface 11WX and negative electrode inner wall surface 11WY, and specifically includes plasma treatment.

[0032] The contact angle can also be measured by using the sessile drop method.

[0033] [Partition Wall] The partition wall 12 is disposed inside the exterior member 11 between the positive electrode space S1 and the negative electrode space S2, separating the positive electrode space S1 and the negative electrode space S2 from each other. This separates the positive electrode aqueous electrolyte solution 15 contained in the positive electrode space S1 from the negative electrode aqueous electrolyte solution 16 contained in the negative electrode space S2 so that they do not mix with each other. Furthermore, the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 face each other via the partition wall 12.

[0034] This partition wall 12 does not allow anions to pass between the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16, but allows substances (excluding anions) such as alkali metal ions (cations) that are absorbed and released in each of the positive electrode 13 and the negative electrode 14 to pass through. This is because the partition wall 12 allows alkali metal ions to move between the positive electrode 13 and the negative electrode 14 while preventing the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 from mixing with each other. As a result, the partition wall 12 allows alkali metal ions to pass from the positive electrode aqueous electrolyte solution 15 to the negative electrode aqueous electrolyte solution 16, and also allows alkali metal ions to pass from the negative electrode aqueous electrolyte solution 16 to the positive electrode aqueous electrolyte solution 15.

[0035] In particular, the partition wall 12 includes a peripheral edge portion 12A and a body portion 12B.

[0036] (Outer periphery portion) The outer periphery portion 12A is an outer portion of the partition wall 12, more specifically, a portion adjacent to the exterior member 11. This outer periphery portion 12A extends along the entire inner surface of the exterior member 11 to separate the positive electrode space S1 and the negative electrode space S2 from each other, and therefore has a frame-like structure as shown in FIG.

[0037] Here, the entire outer peripheral edge portion 12A is firmly connected to the main body portion 12B, and more specifically, is chemically bonded to the main body portion 12B. As a result, the entire outer peripheral edge portion 12A contains one or more types of first polymer compounds that are chemically bondable to the main body portion 12B. The first polymer compounds contain one or more types of specific functional groups that enable chemical bonding of the outer peripheral edge portion 12A to the main body portion 12B. The first polymer compounds may contain the same functional groups as those contained in the cation exchange membrane contained in the main body portion 12, which will be described later, but they also contain at least one functional group that is different from the functional group contained in the cation exchange membrane.

[0038] The functional group is a hydroxyl group, a carboxyl group, a carboxylic acid anhydride, a carboxylic acid ester, or a basic functional group containing nitrogen, and specific examples thereof include a hydroxyl group (—OH), a primary amino group (—NHR), a secondary amino group (—NR 2　), primary amide group (—C(═O)—NHR), secondary amide group (—C(═O)—NR 2　 ), and a carboxyl group (-C(=O)-OH). However, R is either an alkyl group or an alkylene group, and the type of each of the alkyl group and alkylene group is not particularly limited. Specific examples of the functional group may be a series of divalent groups obtained by eliminating hydrogen from each of the series of monovalent groups described above, and specific examples include an ether group (-OR), a carboxylic acid ester group (-C(=O)-OR), and a carboxylic acid anhydride (-C(=O)-O-C(=O)-R).

[0039] Among them, the functional groups include a hydroxyl group (-OH), a primary amino group (-NHR), a secondary amino group (-NR 2　 ), primary amide group (—C(═O)—NHR), secondary amide group (—C(═O)—NR 2　 ) and a carboxyl group (—C(═O)—OH), etc., are preferred because they have high chemical reactivity and can be more firmly bonded to the main body portion 12B, as will be described later.

[0040] To confirm that outer circumferential edge portion 12A contains one or more of the above-described functional groups, outer circumferential edge portion 12A may be analyzed using one or more of analytical methods such as Fourier transform infrared spectroscopy (FT-IR). In this case, the secondary battery is disassembled to recover partition wall 12, and then the peeled surface of outer circumferential edge portion 12A peeled from main body portion 12B is analyzed.

[0041] The first polymer compound contains one or more of the functional groups described above because these functional groups have a high affinity for the main body portion 12B. This ensures the chemical adhesive strength of the outer periphery 12A to the main body portion 12B, thereby firmly connecting the outer periphery 12A to the main body portion 12B as described above. Therefore, the outer periphery 12A is firmly fixed to the main body portion 12B, ensuring liquid sealing within the exterior member 11.

[0042] This makes it difficult for the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 to leak from the exterior member 11, and also makes it difficult for the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16 to mix with each other. In this case, in particular, the partition wall 12 is used to sufficiently suppress mixing of the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16, so that a secondary battery using two types of aqueous electrolytes (the positive electrode aqueous electrolyte solution 15 and the negative electrode aqueous electrolyte solution 16) can be stably realized.

[0043] The first polymer compound includes a skeleton into which one or more of the above-described functional groups are introduced. The type of skeleton is not particularly limited as long as it is a hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but an aliphatic hydrocarbon group is preferable, as this allows the first polymer compound to be easily formed.

[0044] The type of the first polymer compound is not particularly limited as long as it contains one or more of the functional groups described above. Specific examples of the first polymer compound include nylon, polyvinyl alcohol, and ethylene-vinyl alcohol copolymer. This is because the chemical adhesive strength of the outer peripheral edge portion 12A to the main body portion 12B is sufficiently improved.

[0045] The method of bonding the outer peripheral edge portion 12A to the main body portion 12B is not particularly limited. In particular, it is preferable that the outer peripheral edge portion 12A is heat-sealed to the main body portion 12B. This is because the chemical adhesive strength of the outer peripheral edge portion 12A to the main body portion 12B is sufficiently improved. Note that the heat-sealing method is not particularly limited as long as it is a method of connecting two or more types of polymer compounds to each other using heat. As an example, the heat-sealing described here includes a series of heat treatment methods such as heat welding, and what is described here also applies hereinafter.

[0046] The outer circumferential edge portion 12A is also firmly connected to the exterior member 11, and more specifically, is chemically bonded to the exterior member 11. This is because the constituent material of the outer circumferential edge portion 12A (first polymer compound) and the exterior member 11 (second polymer compound) are compatible with each other, resulting in a high mutual affinity. This ensures a strong chemical adhesive force between the exterior member 11 and the outer circumferential edge portion 12A, thereby firmly connecting the exterior member 11 and the outer circumferential edge portion 12A to each other. Therefore, the exterior member 11 and the outer circumferential edge portion 12A are firmly fixed to each other, ensuring liquid sealing within the exterior member 11.

[0047] The details of the method for bonding the outer peripheral edge portion 12A to the exterior member 11 are the same as the details of the method for bonding the outer peripheral edge portion 12A to the main body portion 12B described above.

[0048] As a result, as described above, leakage and mixing of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 are less likely to occur, and a secondary battery using two types of aqueous electrolyte solutions (positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16) can be stably realized.

[0049] (Main body portion) The main body portion 12B is an inner portion of the partition wall 12, more specifically, a portion located more inward than the outer peripheral edge portion 12A. This main body portion 12B includes a functional membrane that allows substances such as alkali metal ions to pass through, more specifically, a cation exchange membrane. This is because an appropriate amount of the aqueous solvent contained in the positive electrode aqueous electrolyte solution 15 can easily permeate into the partition wall 12. Furthermore, this is because an appropriate amount of the aqueous solvent contained in the negative electrode aqueous electrolyte solution 16 can easily permeate into the partition wall 12. This improves ionic conductivity inside the partition wall 12.

[0050] This cation exchange membrane is a porous membrane that is permeable to substances such as alkali metal ions, and as will be explained below, is a polymer membrane having so-called anionic groups.

[0051] The cation exchange membrane contains multiple anion groups (-X -　 ), and its multiple anionic groups are hydrogen ions (H +　) and metal ions (M n+ ), etc., where n is an integer of 1 or more. Specific examples of metal ions include lithium ions, sodium ions, and potassium ions. As a result, the cation exchange membrane has multiple ion exchange groups (for example, -X -　 H +　 and -X -　 M +　 etc.)

[0052] The type of anionic group is not particularly limited. For example, the anionic group may be a sulfonic acid ion group (-S(=O) 2　 -O -　 ) and a carboxylate ion group (—C(═O)—O -　 ) and both thereof. The type of ion exchange group is not particularly limited, but specifically, a sulfonic acid group (-S(=O) 2　 -O -　 H +　 ), a carboxyl group (—C(═O)—O -　 H +　 ), sulfonic acid metal complex (-S(=O) 2　 -O -　 M +　 ) and carboxylic acid metal complexes (—C(═O)—O -　 M +　 The sulfonic acid metal complex is a so-called metal sulfonate base, and the carboxylic acid metal complex is a so-called metal carboxylate base. Of course, the anionic group may be a group other than a sulfonic acid ion group or a carboxylic acid ion group.

[0053] To confirm the type of anionic group, the main body portion 12B may be analyzed using one or more of analytical methods such as FT-IR. In this case, the secondary battery is disassembled to recover the partition wall 12, and then the peeled surface of the main body portion 12B peeled from the outer peripheral edge portion 12A is analyzed.

[0054] The type of skeleton into which multiple ion-exchange groups are introduced is not particularly limited, as long as it is a polymeric compound to which the multiple ion-exchange groups can be bonded. Specific examples of polymeric compounds that form this skeleton include perfluorohydrocarbons, polymeric compounds polymerized from monomers having ethylenically unsaturated double bonds, polysulfones, polyphenylene sulfides, polyether ketones, polyether ether ketones, polyetherimides, polyphenylene oxides, polyether sulfones, polybenzimidazoles, polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymers, polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymers, styrene-divinylbenzene copolymers, and styrene-based elastomers. Polymeric compounds polymerized from monomers having ethylenically unsaturated double bonds include vinyl-based, styrene-based, and acrylic-based polymeric compounds. Styrene-based elastomers include polystyrene-polyisoprene block copolymers and hydrogenated polystyrene-polyisoprene block copolymers.

[0055] In particular, the anionic groups preferably include one or both of sulfonic acid ion groups and carboxylate ion groups. This is because the outer circumferential edge portion 12A has a high affinity for the anionic groups. This ensures chemical adhesion of the main body portion 12B to the outer circumferential edge portion 12A, thereby firmly connecting the main body portion 12B to the outer circumferential edge portion 12A, as described above. Therefore, the main body portion 12B is firmly fixed to the outer circumferential edge portion 12A, ensuring liquid sealing within the exterior member 11.

[0056] As a result, as described above, leakage and mixing of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 are less likely to occur, and a secondary battery using two types of aqueous electrolyte solutions (positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16) can be stably realized.

[0057] Therefore, since the outer peripheral edge portion 12A and the main body portion 12B are firmly fixed to each other, it is preferable that they are integrated with each other, because this sufficiently improves the liquid sealing performance inside the exterior member 11 using the partition wall 12.

[0058] Here, partition wall 12 is disposed inside exterior packaging member 11 so as not to be exposed from exterior packaging member 11. Furthermore, main body portion 12B is housed together with outer circumferential edge portion 12A inside exterior packaging member 11, and is disposed inside exterior packaging member 11 more inward than outer circumferential edge portion 12A. As a result, main body portion 12B is not exposed to the outside of exterior packaging member 11. This is because, unlike when main body portion 12B is exposed to the outside of exterior packaging member 11, positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 are less likely to leak from main body portion 12B to the outside of exterior packaging member 11.

[0059] The positive electrode 13 absorbs and releases alkali metal ions that pass through the partition wall 12. The positive electrode 13 is accommodated in the positive electrode space S1, and more specifically, is immersed in the positive electrode aqueous electrolyte solution 15 accommodated in the positive electrode space S1.

[0060] Specifically, the positive electrode 13 includes a positive electrode current collector 13A and a positive electrode active material layer 13B.

[0061] Positive electrode current collector 13A is a conductive member that supports positive electrode active material layer 13B. Positive electrode current collector 13A contains one or more first metal materials, and specific examples of the first metal materials include titanium, aluminum, and nickel, or may be an alloy of two or more of these metals.

[0062] It is preferable that the positive electrode current collector 13A is insoluble or hardly soluble in the positive electrode aqueous electrolyte solution 15 and is corrosion-resistant, and that it also has low reactivity with the positive electrode active material described below, because this is because deterioration of the positive electrode current collector 13A is suppressed during operation of the secondary battery.

[0063] Here, the positive electrode current collector 13A includes a connection terminal portion 13AT, which is one end portion on which the positive electrode active material layer 13B is not provided, and the connection terminal portion 13AT is led out of the exterior member 11 via the positive electrode lead-out port 11PX. As described above, this is because the secondary battery can be connected to an external device via the connection terminal portion 13AT.

[0064] The positive electrode current collector 13A may be a conductor whose surface is coated with a first metallic material. The material of this conductor is not particularly limited as long as it has conductivity. In this case, the surface of the conductor may be plated with the first metallic material.

[0065] Here, the positive electrode active material layer 13B is provided on the entire positive electrode current collector 13A except for the connection terminal portion 13AT. However, the positive electrode active material layer 13B may be provided on only a part of the positive electrode current collector 13A except for the connection terminal portion 13AT.

[0066] The positive electrode active material layer 13B contains one or more positive electrode active materials that absorb and release alkali metal ions, but may also contain other materials such as a positive electrode binder and a positive electrode conductive agent.

[0067] Positive electrode active materials that absorb and release lithium ions as alkali metal ions include lithium-containing compounds. The type of lithium-containing compound is not particularly limited, but specific examples include lithium composite oxides and lithium phosphate compounds. The lithium composite oxide is an oxide containing lithium and one or more transition metal elements as constituent elements. The lithium phosphate compound is a phosphate compound containing lithium and one or more transition metal elements as constituent elements. The type of transition metal element is not particularly limited, but specific examples include nickel, cobalt, manganese, and iron.

[0068] A specific example of the layered rock salt type lithium composite oxide is LiNiO 2　 , LiCoO 2　 , LiCo 0.98 Al 0.01 Mg 0.01 O 2　 , LiNi 0.5　 Co 0.2　 Mn 0.3　 O 2　 , LiNi 0.8　 Co 0.15 Al 0.05 O 2　 , LiNi 0.33 Co 0.33 Mn 0.33 O 2　, Li 1.2　 Mn 0.52 Co 0.175　 Ni 0.1　 O 2　 and Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 ) O 2　 Specific examples of spinel-type lithium composite oxides include LiMn 2　 O 4　 Specific examples of olivine-type lithium phosphate compounds include LiFePO 4　 , LiMnPO 4　 , LiMn 0.5　 Fe 0.5　 P.O. 4　 , LiMn 0.7　 Fe 0.3　 P.O. 4　 and LiMn 0.75 Fe 0.25 P.O. 4　 And so on.

[0069] The positive electrode active material that absorbs and releases sodium ions as alkali metal ions includes a sodium-containing compound, etc. The type of the sodium-containing compound is not particularly limited, but specifically includes a Prussian blue analogue represented by formula (1).

[0070] Na x　 K y　 M1 z　 Fe(CN) 6　 ・aH 2　 O ... (1) (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. However, y may satisfy 0.05≦y≦0.2.)

[0071] Specific examples of Prussian blue analogs shown in formula (1) include Na 2　 MnFe(CN 6　 ), Na 1.42 K 0.09 Mn 1.13 Fe(CN) 6　 ・3H 2　 O and Na 0.83 K 0.12 Zn1.49 Fe(CN) 6　 ・3.2H 2　 O, etc.

[0072] The positive electrode active material that absorbs and releases potassium ions as alkali metal ions includes potassium-containing compounds. Specific examples of potassium-containing compounds include K 0.7　 Fe 0.6　 Mn 0.6　 O 2　 , K. 0.6　 MnO 2　 , K. 0.3　 MnO 2　 , K. 0.31 CoO 2　 , KCrO 2　 , K. 0.6　 CoO 2　 , K. 2 / 3　 Mn 2 / 3　 Co 1 / 3　 Ni 1 / 3　 O 2　 , K. 2 / 3　 Ni 2 / 3　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 6　 Co 1 / 2　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 2　 Mn 1 / 6　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 2　 Cu 1 / 6　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 3　 Zn 1 / 3　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 6　 Mg 1 / 2　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 2　 Co 1 / 6　 Te 1 / 3　 O 2　 , K. 2 / 3　 Ni 1 / 3　 Mg 1 / 3　 Te 1 / 3　 O 2　and K. 2 / 3　 Ni 1 / 3　 Co 1 / 3　 Te 1 / 3　 O 2　 And so on.

[0073] The positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber and nitrile rubber. Specific examples of polymer compounds include acrylic resin, polyvinylidene fluoride, polytetrafluoroethylene, and polyimide. The acrylic resin is a polymer of acrylic acid ester, methacrylic acid ester, or the like.

[0074] The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, a conductive ceramic material, a conductive polymer, etc. Specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black.

[0075] The negative electrode 14 occludes and releases alkali metal ions that pass through the partition wall 12. The negative electrode 14 is accommodated in the negative electrode space S2, and more specifically, is immersed in the negative electrode aqueous electrolyte solution 16 accommodated in the negative electrode space S2.

[0076] Specifically, the negative electrode 14 includes a negative electrode current collector 14A and a negative electrode active material layer 14B.

[0077] The negative electrode current collector 14A is a conductive member that supports the negative electrode active material layer 14B. The negative electrode current collector 14A contains one or more types of second metal materials, and specific examples of the second metal materials include stainless steel (SUS), titanium, zinc, tin, and lead, and may also be an alloy of two or more types of these materials.

[0078] The stainless steel may be a highly corrosion-resistant stainless steel to which one or more of the additive elements such as niobium and molybdenum have been added. Specifically, the stainless steel may be SUS444 to which molybdenum has been added. A specific example of the conductive ceramic material is indium tin oxide (ITO).

[0079] It is preferable that the negative electrode current collector 14A is insoluble or hardly soluble in the negative electrode aqueous electrolyte solution 16 and is corrosion-resistant, and also has low reactivity with the negative electrode active material described below, because this suppresses deterioration of the negative electrode current collector 14A during operation of the secondary battery.

[0080] Here, the negative electrode current collector 14A includes a connection terminal portion 14AT, which is one end portion on which the negative electrode active material layer 14B is not provided, and the connection terminal portion 14AT is led out of the exterior member 11 via the negative electrode lead-out port 11PY. This is because, as described above, the secondary battery can be connected to an external device via the connection terminal portion 14AT.

[0081] 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.

[0082] However, the leading direction of the connection terminal portion 14AT and the leading direction of the connection terminal portion 13AT may be different from each other. For example, the angle between the leading direction of the connection terminal portion 14AT and the leading direction of the connection terminal portion 13AT may be 180°, 90°, or any other angle. This is because the positive electrode 13 and the negative electrode 14 are disposed apart from each other, which improves the handling of the secondary battery and reduces the possibility of a short circuit.

[0083] The negative electrode current collector 14A may be a conductor whose surface is coated with a second metal material. The material of this conductor is not particularly limited as long as it has conductivity. In this case, the surface of the conductor may be plated with the second metal material.

[0084] Here, the anode active material layer 14B is provided on the entire anode current collector 14A except for the connection terminal portion 14AT. However, the anode active material layer 14B may be provided on only a part of the anode current collector 14A except for the connection terminal portion 14AT.

[0085] The negative electrode active material layer 14B contains one or more negative electrode active materials that absorb and release alkali metal ions, but may also contain other materials such as a negative electrode binder and a negative electrode conductive agent.

[0086] The negative electrode active material is a titanium-containing compound, a niobium-containing compound, a vanadium-containing compound, an iron-containing compound, a molybdenum-containing compound, etc. This is because the charge / discharge reaction tends to proceed smoothly and stably even when two types of aqueous electrolytes (positive electrode aqueous electrolyte 15 and negative electrode aqueous electrolyte 16) are used.

[0087] The titanium-containing compound includes titanium oxide, alkali metal titanium composite oxide, titanium phosphate, alkali metal titanium phosphate compound, and hydrogen titanium compound.

[0088] The titanium oxide is a compound represented by formula (2), that is, bronze-type titanium oxide, etc.

[0089] TiO w　 ... (2) (W satisfies 1.85≦W≦2.15.)

[0090] Specific examples of titanium oxide include anatase, rutile, or brookite titanium oxide (TiO 2　 However, the titanium oxide may be a composite oxide containing one or more of phosphorus, vanadium, tin, copper, nickel, iron, cobalt, etc. as constituent elements in addition to titanium. Specific examples of composite oxides include TiO 2　 -P 2　 O 5　 , TiO 2　 -V 2　 O 5　 , TiO 2　 -P 2　 O 5　 -SnO 2　 and TiO 2　 -P 2　 O 5　 -MeO, etc., where Me is one or more of copper, nickel, iron, cobalt, etc.

[0091] Among alkali metal titanium composite oxides, lithium titanium composite oxides include compounds represented by formulas (3) to (5), such as ramsdellite-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　 ]O 4　 ... (3) (M3 is at least one of Mg, Ca, Cu, Zn, and Sr. x satisfies 0≦x≦1 / 3.)

[0093] Li [Li y　 M4 1-3y Ti 1+2y ]O 4　 ... (4) (M4 is at least one of Al, Sc, Cr, Mn, Fe, Ge, and Y, and y satisfies 0≦y≦1 / 3.)

[0094] Li [Li 1 / 3　 M5 z　 Ti (5 / 3)-z　 ]O 4　 ... (5) (M5 is at least one of V, Zr, and Nb. z satisfies 0≦z≦2 / 3.)

[0095] Specific examples of the lithium titanium composite oxide shown in formula (3) include Li 3.75 Ti 4.875　 Mg 0.375　 O 12 Specific examples of the lithium titanium composite oxide shown in formula (4) include LiCrTiO 4　 Specific examples of the lithium titanium composite oxide shown in formula (5) include Li 4　 Ti 5　 O 12 and Li 4　 Ti 4.95 Nb 0.05 O 12 And so on.

[0096] Specific examples of potassium titanium composite oxides among alkali metal titanium composite oxides include K 2　 Ti 3　 O 7　 and K. 4　 Ti 5　 O 12 And so on.

[0097] A specific example of titanium phosphate is titanium phosphate (TiP 2　 O 7　 ) and the like. Specific examples of lithium titanium phosphate compounds among alkali metal titanium phosphate compounds include LiTi 2　 (P.O. 4　 ) 3　 Specific examples of sodium titanium phosphate compounds among alkali metal titanium phosphate compounds include NaTi 2　 (P.O. 4　 ) 3　 Specific examples of hydrogen titanium compounds include H 2　 Ti 3　 O 7　 (3TiO 2　 ・1H 2　 O), H 6　 Ti 12 O 27 (3TiO 2　 ・0.75H 2　 O), H 2　 Ti 6　 O 13 (3TiO 2　 ・0.5H 2　 O), H 2　 Ti 7　 O 15 (3TiO 2　 ・0.43H 2　 O) and H 2　 Ti 12 O 25 (3TiO 2　 ・0.25H 2　 O) etc.

[0098] Niobium-containing compounds include alkali metal niobium composite oxides, hydrogen niobium compounds, and titanium niobium composite oxides, although materials that fall under the category of niobium-containing compounds are excluded from titanium-containing compounds.

[0099] A specific example of the alkali metal niobium composite oxide is LiNbO 2　 Specific examples of hydrogen niobium compounds include H 4　 Nb 6　 O 17 Specific examples of titanium-niobium composite oxides include TiNb 2　 O 7　 and Ti 2　 Nb 10 O 29 However, the titanium-niobium composite oxide may be intercalated with an alkali metal.

[0100] The vanadium-containing compounds include vanadium oxides and alkali metal vanadium composite oxides, etc. However, materials that fall under the category of vanadium-containing compounds are excluded from both titanium-containing compounds and niobium-containing compounds.

[0101] A specific example of vanadium oxide is vanadium dioxide (VO 2　 ) and the like. Specific examples of alkali metal vanadium composite oxides include LiV 2　 O 4　 and LiV 3　 O 8　 And so on.

[0102] The iron-containing compound is iron hydroxide, etc. However, materials that fall under the category of iron-containing compounds are excluded from each of titanium-containing compounds, niobium-containing compounds, and vanadium-containing compounds.

[0103] A specific example of iron hydroxide is iron oxyhydroxide (FeOOH), etc. However, the iron oxyhydroxide may be α-iron oxyhydroxide, β-iron oxyhydroxide, γ-iron oxyhydroxide, δ-iron oxyhydroxide, or any two or more of them.

[0104] The molybdenum-containing compounds include molybdenum oxides and cobalt-molybdenum composite oxides, etc. However, materials that fall under the category of molybdenum-containing compounds are excluded from the titanium-containing compounds, niobium-containing compounds, vanadium-containing compounds, and iron-containing compounds.

[0105] Specific examples of molybdenum oxide include molybdenum dioxide (MoO2　 ) and the like. A specific example of the cobalt-molybdenum composite oxide is CoMoO 4　 And so on.

[0106] The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

[0107] [Positive electrode aqueous electrolyte] Positive electrode aqueous electrolyte 15 is accommodated in positive electrode space S1. As a result, positive electrode aqueous electrolyte 15 is separated from negative electrode aqueous electrolyte 16 accommodated in negative electrode space S2 via partition wall 12.

[0108] The amount of cathode aqueous electrolyte solution 15 contained in the cathode space S1 is not particularly limited. Therefore, the cathode aqueous electrolyte solution 15 may be contained in the entire cathode space S1, or may be contained in only a portion of the cathode space S1. Fig. 1 shows a case where the cathode aqueous electrolyte solution 15 is contained in only a portion of the cathode space S1 so that the entire cathode active material layer 13B is immersed in the cathode aqueous electrolyte solution 15.

[0109] Specifically, the positive electrode aqueous electrolyte solution 15 contains an aqueous solvent and an ionic substance. The ionic substance is a substance that ionizes in the aqueous solvent and contains alkali metal ions.

[0110] (Aqueous Solvent) The type of aqueous solvent is not particularly limited, but specifically, it is one or more of pure water and the like.

[0111] (Ionic Substance) The type of ionic substance is not particularly limited, but specifically, it is any one or two or more types of electrolyte salts. However, the ionic substance may further contain any one or two or more types of acids and bases. Specific examples of acids include carbonic acid, oxalic acid, nitric acid, sulfuric acid, hydrochloric acid, acetic acid, and citric acid.

[0112] The electrolyte salt is a salt containing a cation and an anion. More specifically, the electrolyte salt contains, as cations, alkali metal ions that are absorbed and released in the positive electrode 13 and the negative electrode 14, and therefore contains one or more types of alkali metal salts that have these alkali metal ions as cations. This is because a high voltage can be obtained.

[0113] Hereinafter, the alkali metal ions absorbed and released in the positive electrode 13 and the negative electrode 14 will also be simply referred to as "alkali metal ions."

[0114] The types of alkali metal ions absorbed and released in the positive electrode 13 and the negative electrode 14 are not particularly limited, but specific examples include lithium ions, sodium ions, and potassium ions.

[0115] Alkali metal salts having the alkali metal ions absorbed and released in the positive electrode 13 and the negative electrode 14 as cations include lithium salts, sodium salts, 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. Examples of imide salts include lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. Specific examples of sodium salts include compounds in which the lithium ions of the above-mentioned specific lithium salts are substituted with sodium ions. Specific examples of potassium salts include compounds in which the lithium ions of the above-mentioned specific lithium salts are substituted with potassium ions.

[0116] In addition, since the electrolyte salt further contains one or more types of alkali metal ions that are not absorbed or released in the positive electrode 13 and the negative electrode 14, it may also contain one or more types of alkali metal salts that have these alkali metal ions as cations.

[0117] Specific examples of alkali metal ions that are not occluded or released in the positive electrode 13 and the negative electrode 14 are the same as the specific examples of alkali metal ions that are occluded or released in the positive electrode 13 and the negative electrode 14. However, the types of alkali metal ions that are not occluded or released in the positive electrode 13 and the negative electrode 14 are different from the types of alkali metal ions that are occluded or released in the positive electrode 13 and the negative electrode 14.

[0118] Specific examples of alkali metal salts having as their cations alkali metal ions that are not occluded or released in the positive electrode 13 and the negative electrode 14 are the same as the specific examples of alkali metal salts having as their cations alkali metal ions that are occluded or released in the positive electrode 13 and the negative electrode 14. However, the types of alkali metal salts having as their cations alkali metal ions that are not occluded or released in the positive electrode 13 and the negative electrode 14 are different from the types of alkali metal salts having as their cations alkali metal ions that are occluded or released in the positive electrode 13 and the negative electrode 14.

[0119] Furthermore, the electrolyte salt further contains one or more types of other metal ions different from the alkali metal ions that are absorbed and released in the positive electrode 13 and the negative electrode 14, respectively, and the alkali metal ions that are not absorbed and released in the positive electrode 13 and the negative electrode 14, respectively, and therefore may contain one or more types of other metal salts having the other metal ions as cations.

[0120] The other metal ions are alkaline earth metal ions, transition metal ions, and other metal ions. Specific examples of alkaline earth metal ions include magnesium ions and calcium ions. Specific examples of transition metal ions include titanium ions, vanadium ions, iron ions, manganese ions, nickel ions, cobalt ions, and copper ions. Specific examples of other metal ions include aluminum ions and zinc ions.

[0121] Specific examples of other metal salts having other metal ions as cations include compounds in which the lithium ions of the specific examples of lithium salts mentioned above are substituted with alkaline earth metal ions, transition metal ions, or other metal ions.

[0122] In particular, the electrolyte salt preferably contains alkali metal ions that are occluded and released in each of the positive electrode 13 and the negative electrode 14, as well as alkali metal ions that are not occluded and released in each of the positive electrode 13 and the negative electrode 14. As a result, the electrolyte salt preferably contains one or more types of alkali metal salts having cations that are alkali metal ions that are occluded and released in each of the positive electrode 13 and the negative electrode 14, as well as one or more types of alkali metal salts having cations that are not occluded and released in each of the positive electrode 13 and the negative electrode 14. This is because, as will be described later, the pH of the negative electrode aqueous electrolyte solution 16 can be easily controlled to be sufficiently higher than the pH of the positive electrode aqueous electrolyte solution 15. As a result, the relationship between the pH of the positive electrode aqueous electrolyte solution 15 and the pH of the negative electrode aqueous electrolyte solution 16 can be easily maintained.

[0123] In this case, the alkali metal ions absorbed and released in each of the positive electrode 13 and the negative electrode 14 preferably contain lithium ions, because this allows a sufficiently high voltage to be obtained and also allows a high energy density to be obtained.

[0124] Furthermore, when the alkali metal ions absorbed and released in each of positive electrode 13 and negative electrode 14 contain lithium ions, the alkali metal ions not absorbed and released in each of positive electrode 13 and negative electrode 14 preferably contain potassium ions. That is, the electrolyte salt preferably contains potassium ions as cations in addition to lithium ions, because this makes it easier to sufficiently maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16.

[0125] The electrolyte salt may further contain one or more non-electrolytes.

[0126] The type of anion is not particularly limited. Among these, the anion preferably includes one or more of nitrate ions, sulfate ions, hydrogen sulfate ions, carbonate ions, hydrogen carbonate ions, phosphate ions, monohydrogen phosphate ions, dihydrogen phosphate ions, and carboxylate ions. This is because fluctuations in the pH of positive electrode aqueous electrolyte solution 15 are sufficiently suppressed, making it easier to maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16. Specific examples of carboxylate ions include formate ions, acetate ions, propionate ions, tartrate ions, and citrate ions.

[0127] In particular, it is more preferable that the anions include one or more of nitrate ions, sulfate ions, hydrogensulfate ions, carbonate ions, hydrogencarbonate ions, phosphate ions, monohydrogenphosphate ions, and dihydrogenphosphate ions, because this further suppresses fluctuations in the pH of positive electrode aqueous electrolyte solution 15, making it easier to maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16.

[0128] The composition of the positive electrode aqueous electrolyte solution 15 (type of aqueous solvent and type of electrolyte salt) and the composition of the negative electrode aqueous electrolyte solution 16 (type of aqueous solvent and type of electrolyte salt) may be the same as or different from each other.

[0129] The content of the ionic substance in the positive electrode aqueous electrolyte solution 15, that is, the concentration (mol / kg) of the positive electrode aqueous electrolyte solution 15, is not particularly limited and can be set arbitrarily.

[0130] (pH) Since the positive electrode aqueous electrolyte solution 15 has a lower pH than the negative electrode aqueous electrolyte solution 16 , the negative electrode aqueous electrolyte solution 16 has a higher pH than the positive electrode aqueous electrolyte solution 15 .

[0131] The reason why the negative electrode aqueous electrolyte solution 16 has a higher pH than the positive electrode aqueous electrolyte solution 15 is that the difference in pH between the two solutions shifts the decomposition potential of the aqueous solvent, compared to when the negative electrode aqueous electrolyte solution 16 has a pH equal to or lower than the pH of the positive electrode aqueous electrolyte solution 15. As a result, the decomposition reaction of the aqueous solvent is thermodynamically suppressed during charge and discharge, and the potential window of the aqueous solvent is expanded. This allows a high voltage to be obtained, and the charge and discharge reaction utilizing the absorption and release of alkali metal ions proceeds sufficiently and stably.

[0132] In particular, it is preferable that the composition (type of electrolyte salt) of cathode aqueous electrolyte solution 15 and the composition (type of electrolyte salt) of anode aqueous electrolyte solution 16 are different from each other. This is because the pH of anode aqueous electrolyte solution 16 can be more easily controlled to be higher than the pH of cathode aqueous electrolyte solution 15.

[0133] As long as the negative electrode aqueous electrolyte solution 16 has a higher pH than the positive electrode aqueous electrolyte solution 15, the pH of the positive electrode aqueous electrolyte solution 15 is not particularly limited. In particular, the pH of the positive electrode aqueous electrolyte solution 15 is preferably 3 to 8, more preferably 4 to 8, and even more preferably 4 to 6. This is because the pH of the positive electrode aqueous electrolyte solution 15 becomes sufficiently low, so that the pH of the positive electrode aqueous electrolyte solution 15 is likely to become lower than the pH of the negative electrode aqueous electrolyte solution 16. Furthermore, this is because the difference between the pH of the positive electrode aqueous electrolyte solution 15 and the pH of the negative electrode aqueous electrolyte solution 16 becomes sufficiently large, so that the relationship between the pH of the positive electrode aqueous electrolyte solution 15 and the pH of the negative electrode aqueous electrolyte solution 16 is easily maintained. Furthermore, this is because corrosion of the exterior member 11, the positive electrode current collector 13A, the negative electrode current collector 14A, and the like is suppressed.

[0134] The pH of positive electrode aqueous electrolyte 15 is preferably set so as to make it difficult for positive electrode current collector 13A and positive electrode active material layer 13B to corrode, because this makes it easier for the charge / discharge reaction using positive electrode 13 to proceed stably and continuously.

[0135] (Preferred Configuration) Positive electrode aqueous electrolyte solution 15 preferably contains a saturated solution of an electrolyte salt, that is, a saturated solution of an alkali metal salt whose cations are the alkali metal ions absorbed and released in positive electrode 13 and negative electrode 14. This is because the alkali metal ion absorption and release reaction tends to proceed stably during charge and discharge, and therefore the charge and discharge reaction tends to proceed easily.

[0136] To confirm whether the positive electrode aqueous electrolyte solution 15 is a saturated solution of electrolyte salt, the secondary battery is disassembled and then visually inspected to determine whether electrolyte salt is precipitated within the positive electrode space S1. Specifically, the inside of the positive electrode space S1 refers to the positive electrode aqueous electrolyte solution 15, the surface of the partition wall 12, the surface of the positive electrode 13, and the positive electrode inner wall surface 11WX of the exterior member 11. When the positive electrode aqueous electrolyte solution 15 (liquid) and a precipitate of electrolyte salt (solid) coexist within the positive electrode space S1 due to the precipitation of electrolyte salt, the positive electrode aqueous electrolyte solution 15 is considered to be a saturated solution of electrolyte salt. The composition of the precipitate may be determined using a surface analysis method such as X-ray photoelectron spectroscopy (XPS) or a composition analysis method such as inductively coupled plasma (ICP) optical emission spectroscopy.

[0137] Positive electrode aqueous electrolyte solution 15 may also be a pH buffer solution. This pH buffer solution may be an aqueous solution in which a weak acid and its conjugate base are mixed, or an aqueous solution in which a weak base and its conjugate acid are mixed, or both. This is because pH fluctuations are sufficiently suppressed, making it easier to maintain the pH of positive electrode aqueous electrolyte solution 15.

[0138] Positive electrode aqueous electrolyte 15 may further contain one or more buffers, such as trishydroxymethylaminomethane and ethylenediaminetetraacetic acid.

[0139] Furthermore, positive electrode aqueous electrolyte solution 15 may be an isotonic solution that is isotonic with negative electrode aqueous electrolyte solution 16. This is because the osmotic pressure of positive electrode aqueous electrolyte solution 15 is optimized, making it easier to maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16.

[0140] [Negative Electrolyte] Negative electrode aqueous electrolyte 16 is accommodated in negative electrode space S2. As a result, negative electrode aqueous electrolyte 16 is separated from positive electrode aqueous electrolyte 15 accommodated in positive electrode space S1 via partition wall 12.

[0141] The amount of the anode aqueous electrolyte solution 16 contained in the anode space S2 is not particularly limited. Therefore, the anode aqueous electrolyte solution 16 may be contained in the entire anode space S2, or may be contained in only a portion of the anode space S2. Fig. 1 shows a case where the anode aqueous electrolyte solution 16 is contained in only a portion of the anode space S2 so that the entire anode active material layer 14B is immersed in the anode aqueous electrolyte solution 16.

[0142] The configuration of the negative electrode aqueous electrolyte solution 16 is the same as the configuration of the above-described positive electrode aqueous electrolyte solution 15, except as described below. That is, the details regarding the aqueous solvent and the ionic substance are as described above.

[0143] The type of anion is not particularly limited. In particular, the anion preferably includes a hydroxide ion. This is because fluctuations in the pH of negative electrode aqueous electrolyte solution 16 are sufficiently suppressed, making it easier to sufficiently maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16.

[0144] The content of the ionic substance in the negative electrode aqueous electrolyte 16, that is, the concentration (mol / kg) of the negative electrode aqueous electrolyte 16, is not particularly limited and can be set arbitrarily.

[0145] As described above, the negative electrode aqueous electrolyte 16 has a pH higher than the pH of the positive electrode aqueous electrolyte 15 .

[0146] The composition (type of electrolyte salt) of the negative electrode aqueous electrolyte solution 16 and the composition (type of electrolyte salt) of the positive electrode aqueous electrolyte solution 15 are preferably different from each other. This is because the pH of the negative electrode aqueous electrolyte solution 16 can be more easily controlled to be higher than the pH of the positive electrode aqueous electrolyte solution 15.

[0147] There are no particular limitations on the pH of negative electrode aqueous electrolyte solution 16, as long as it has a higher pH than the pH of positive electrode aqueous electrolyte solution 15. In particular, the pH of negative electrode aqueous electrolyte solution 16 is preferably 11 or higher, more preferably 12 or higher, and even more preferably 13 or higher. This is because the pH of negative electrode aqueous electrolyte solution 16 becomes sufficiently high, and therefore the pH of positive electrode aqueous electrolyte solution 15 is likely to become higher than the pH of negative electrode aqueous electrolyte solution 16. Furthermore, the difference between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16 becomes sufficiently large, and therefore the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16 is more likely to be maintained.

[0148] The pH of the negative electrode aqueous electrolyte solution 16 is preferably set so as to make the negative electrode current collector 14A and the negative electrode active material layer 14B less susceptible to corrosion, because this makes it easier for the charge / discharge reaction using the negative electrode 14 to proceed stably and continuously.

[0149] Negative electrode aqueous electrolyte solution 16 is preferably a saturated solution of an electrolyte salt, that is, a saturated solution of an alkali metal salt having, as cations, alkali metal ions absorbed and released in positive electrode 13 and negative electrode 14. This is because the alkali metal ion absorption and release reaction tends to proceed stably during charge and discharge, and thus the charge and discharge reaction tends to proceed easily.

[0150] The method for determining whether or not the negative electrode aqueous electrolyte solution 16 is a saturated solution of the electrolyte salt is the same as the method for determining whether or not the positive electrode aqueous electrolyte solution 15 is a saturated solution of the electrolyte salt, except that the negative electrode space S2 is examined instead of the positive electrode space S1.

[0151] Furthermore, the negative electrode aqueous electrolyte 16 may be a pH buffer solution, because this sufficiently suppresses pH fluctuations, making it easier to maintain the pH of the negative electrode aqueous electrolyte 16.

[0152] The negative electrode aqueous electrolyte solution 16 may further contain one or more buffers, as described above in detail.

[0153] Furthermore, negative electrode aqueous electrolyte solution 16 may be an isotonic solution that is isotonic with positive electrode aqueous electrolyte solution 15. This is because the osmotic pressure of negative electrode aqueous electrolyte solution 16 is optimized, making it easier to maintain the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16.

[0154] [Positive Electrode Sealing Member] The positive electrode sealing member 17 is a member that is disposed inside the positive electrode lead-out 11PX to seal the gap between the exterior member 11 and the positive electrode current collector 13A (connection terminal portion 13AT). As a result, the positive electrode sealing member 17 is disposed between the exterior member 11 and the connection terminal portion 13AT inside the positive electrode lead-out 11PX, and is adjacent to both the exterior member 11 and the connection terminal portion 13AT.

[0155] This positive electrode sealing member 17 contains one or more types of third polymer compounds that can be adhered to both the exterior member 11 and the connection terminal portion 13AT in order to seal the gap between the exterior member 11 and the connection terminal portion 13AT inside the positive electrode outlet 11PX.

[0156] The type of the third polymer compound is not particularly limited as long as it can adhere to both the exterior member 11 and the connection terminal portion 13AT. A specific example of the third polymer compound is an acid-modified polyolefin. This is because the adhesive strength of the positive electrode sealing member 17 to both the exterior member 11 and the connection terminal portion 13AT is sufficiently improved, thereby sufficiently sealing the gap between the exterior member 11 and the connection terminal portion 13AT inside the positive electrode lead-out port 11PX.

[0157] This ensures liquid sealing and gas sealing properties inside the exterior member 11 (the positive electrode space S1) where the positive electrode outlet 11PX is provided, thereby making it difficult for the positive electrode aqueous electrolyte solution 15 to leak from the exterior member 11 and for the liquid and gas to enter and exit via the positive electrode outlet 11PX.

[0158] There are no particular limitations on the method for adhering positive electrode sealing member 17 to each of exterior member 11 and connection terminal portion 13AT. In particular, positive electrode sealing member 17 is preferably heat-sealed to each of exterior member 11 and connection terminal portion 13AT. This is because the chemical adhesive strength of positive electrode sealing member 17 to exterior member 11 and connection terminal portion 13AT is sufficiently improved.

[0159] [Negative Electrode Sealing Member] The negative electrode sealing member 18 is a member that is disposed inside the negative electrode lead-out 11PY to seal the gap between the exterior member 11 and the negative electrode current collector 14A (connection terminal portion 14AT). As a result, the negative electrode sealing member 18 is disposed inside the negative electrode lead-out 11PY between the exterior member 11 and the connection terminal portion 14AT, and is adjacent to both the exterior member 11 and the connection terminal portion 14AT.

[0160] This negative electrode sealing member 18 contains one or more types of fourth polymer compounds that can be adhered to each of the exterior member 11 and the connection terminal portion 14AT in order to seal the gap between the exterior member 11 and the connection terminal portion 14AT inside the negative electrode outlet 11PY.

[0161] The details of the fourth polymer compound are the same as those of the third polymer compound described above, that is, a specific example of the fourth polymer compound is an acid-modified polyolefin.

[0162] In this case, the adhesive strength of the negative electrode sealing member 18 to each of the exterior member 11 and the connection terminal 14AT is sufficiently improved, so that the gap between the exterior member 11 and the connection terminal 14AT inside the negative electrode outlet 11PY is sufficiently sealed. This ensures liquid sealing and gas sealing properties inside the exterior member 11 where the negative electrode outlet 11PY is provided (negative electrode space S2). This makes it difficult for the negative electrode aqueous electrolyte 16 to leak from the exterior member 11, and also makes it difficult for the liquid and gas to enter and exit via the negative electrode outlet 11PY.

[0163] There are no particular limitations on the method for bonding negative electrode sealing member 18 to each of exterior member 11 and connection terminal portion 14AT. In particular, negative electrode sealing member 18 is preferably heat-sealed to each of exterior member 11 and connection terminal portion 14AT. This is because the chemical adhesive strength of negative electrode sealing member 18 to exterior member 11 and connection terminal portion 14AT is sufficiently improved.

[0164] <1-2. Operation> This secondary battery operates as described below during charging and discharging.

[0165] During charging, alkali metal ions are released from positive electrode 13 and move to negative electrode 14 via positive electrode aqueous electrolyte 15, partition wall 12, and negative electrode aqueous electrolyte 16 in this order, and are thereby absorbed in negative electrode 14.

[0166] During discharge, alkali metal ions are released from negative electrode 14 and move to positive electrode 13 via negative electrode aqueous electrolyte 16, partition wall 12, and positive electrode aqueous electrolyte 15 in this order, and are thereby occluded in positive electrode 13.

[0167] <1-3. Manufacturing Method> This secondary battery is manufactured using the procedure described below.

[0168] [Fabrication of Positive Electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. Next, the positive electrode mixture is added to a solvent to prepare a paste-like positive electrode mixture slurry. The solvent may be an aqueous solvent or an organic solvent. Finally, the positive electrode mixture slurry is applied to the surface of the positive electrode current collector 13A excluding the connection terminal portion 13AT to form the positive electrode active material layer 13B. The positive electrode active material layer 13B may then be compression-molded using a compression device such as a roll press. In this case, the positive electrode active material layer 13B may be heated, or the compression molding may be repeated multiple times. This results in the positive electrode active material layers 13B being formed on both sides of the positive electrode current collector 13A, thereby fabricating the positive electrode 13.

[0169] [Fabrication of Negative Electrode] Using a procedure similar to that for fabricating the positive electrode 13 described above, the negative electrode active material layers 14B are formed on both sides of the negative electrode current collector 14A. Specifically, the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are mixed together to form a negative electrode mixture, and the negative electrode mixture is then poured into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to the surface of the negative electrode current collector 14A excluding the connection terminal portion 14AT to form the negative electrode active material layer 14B. The negative electrode active material layer 14B may then be compression-molded. As a result, the negative electrode active material layers 14B are formed on both sides of the negative electrode current collector 14A, thereby fabricating the negative electrode 14.

[0170] [Preparation of Positive Electrolyte Aqueous Solution] An ionic substance is added to an aqueous solvent, whereby the ionic substance is dispersed or dissolved in the aqueous solvent, thereby preparing positive electrode aqueous electrolyte solution 15.

[0171] [Preparation of Negative Electrolyte Aqueous Solution] Negative electrode aqueous electrolyte solution 16 is prepared using the same procedure as the procedure for preparing positive electrode aqueous electrolyte solution 15 described above, so as to have a higher pH than that of positive electrode aqueous electrolyte solution 15.

[0172] [Assembly of Secondary Battery] First, the outer peripheral edge portion 12A and the main body portion 12B are brought into contact with each other, and then the outer peripheral edge portion 12A and the main body portion 12B are heated. This causes the outer peripheral edge portion 12A and the main body portion 12B to be thermally fused together, thereby firmly connecting the outer peripheral edge portion 12A and the main body portion 12B to each other. Thus, the partition wall 12 including the outer peripheral edge portion 12A and the main body portion 12B is obtained.

[0173] The heating temperature during heat fusion is not particularly limited and can be set as desired. Specifically, the heating temperature is preferably 100°C or higher, and more preferably 200°C or higher, because this ensures that the outer peripheral edge portion 12A and the main body portion 12B are sufficiently heat fused to each other.

[0174] Next, the partition wall 12 is installed inside the exterior member 11 .

[0175] In this case, the exterior member 11 and the outer peripheral edge portion 12A are brought into contact with each other, and then the exterior member 11 and the outer peripheral edge portion 12A are heated. As a result, the exterior member 11 and the outer peripheral edge portion 12A are thermally fused together, and therefore the exterior member 11 and the outer peripheral edge portion 12A are firmly connected to each other.

[0176] The details of the heating temperature when heat-sealing the exterior member 11 and the outer peripheral edge portion 12A to each other are the same as the details of the heating temperature when heat-sealing the outer peripheral edge portion 12A and the main body portion 12B to each other.

[0177] Therefore, since the partition wall 12 is provided inside the exterior member 11, a positive electrode space S1 and a negative electrode space S2 are formed, which are separated from each other via the partition wall 12.

[0178] Next, the positive electrode 13 and the negative electrode 14 are placed inside the exterior member 11 .

[0179] In this case, the positive electrode 13 is inserted into the positive electrode space S1 through the positive electrode outlet 11PX, and the positive electrode 13 is stored in the positive electrode space S1 so that the connection terminal portion 13AT is led out to the outside of the exterior member 11 via the positive electrode outlet 11PX.

[0180] Furthermore, by inserting the negative electrode 14 into the negative electrode space S2 from the negative electrode outlet 11PY, the negative electrode 14 is stored in the negative electrode space S2 so that the connection terminal portion 14AT is led out to the outside of the exterior member 11 via the negative electrode outlet 11PY.

[0181] Next, cathode aqueous electrolyte 15 is supplied to cathode space S1 through a gap between exterior member 11 provided inside cathode outlet 11PX and connection terminal portion 13AT. As a result, cathode aqueous electrolyte 15 is accommodated in cathode space S1, and cathode 13 is immersed in cathode aqueous electrolyte 15.

[0182] Furthermore, the negative electrode aqueous electrolyte solution 16 is supplied to the negative electrode space S2 through a gap between the exterior member 11 provided inside the negative electrode outlet 11PY and the connection terminal portion 14AT. As a result, the negative electrode aqueous electrolyte solution 16 is accommodated in the negative electrode space S2, and the negative electrode 14 is immersed in the negative electrode aqueous electrolyte solution 16.

[0183] Finally, the positive electrode outlet 11PX is sealed with the positive electrode sealing member 17, and the negative electrode outlet 11PY is sealed with the negative electrode sealing member 18.

[0184] In this case, a positive electrode sealing member 17 is placed inside the positive electrode outlet 11PX between the exterior member 11 and the connection terminal 13AT, and then the positive electrode sealing member 17 is heated. As a result, the positive electrode sealing member 17 is heat-sealed to each of the exterior member 11 and the connection terminal 13AT, and the positive electrode sealing member 17 is used to seal the positive electrode outlet 11PX.

[0185] Furthermore, inside the negative electrode outlet 11PY, a negative electrode sealing member 18 is placed between the exterior member 11 and the connection terminal portion 14AT, and then the negative electrode sealing member 18 is heated. As a result, the negative electrode sealing member 18 is heat-sealed to each of the exterior member 11 and the connection terminal portion 14AT, and the negative electrode sealing member 18 is used to seal the negative electrode outlet 11PY.

[0186] As a result, the partition wall 12, the positive electrode 13, the negative electrode 14, the positive electrode aqueous electrolyte 15, and the negative electrode aqueous electrolyte 16 are housed in the exterior member 11, thereby completing the secondary battery.

[0187] <1-4. Actions and Effects> In this secondary battery, the positive electrode space S1 and the negative electrode space S2 are separated from each other by the partition wall 12, and the partition wall 12 includes an outer peripheral edge portion 12A and a main body portion 12B. The main body portion includes a cation exchange membrane. The outer peripheral edge portion 12A includes a first polymer compound, and the first polymer compound includes one or more of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group, and a carboxyl group.

[0188] In this case, as described above, a series of actions described below are obtained.

[0189] First, because main body 12B includes a cation exchange membrane, an appropriate amount of the aqueous solvent contained in positive electrode aqueous electrolyte 15 can easily penetrate into main body 12B, and an appropriate amount of the aqueous solvent contained in negative electrode aqueous electrolyte 16 can easily penetrate into main body 12B, thereby improving ionic conductivity inside main body 12B.

[0190] Second, because outer peripheral edge portion 12A containing the first polymer compound has the appropriate functional group described above, chemical adhesion is ensured between outer peripheral edge portion 12A and main body portion 12B. This firmly connects outer peripheral edge portion 12A and main body portion 12B, thereby firmly fixing outer peripheral edge portion 12A and main body portion 12B to each other. In this case, outer peripheral edge portion 12A and main body portion 12B are particularly well fixed to each other by being thermally fused to each other. This ensures liquid sealing within exterior member 11, thereby suppressing leakage of cathode aqueous electrolyte solution 15 and anode aqueous electrolyte solution 16 and also suppressing mixing of cathode aqueous electrolyte solution 15 and anode aqueous electrolyte solution 16.

[0191] For these reasons, in a secondary battery including two types of aqueous electrolyte solutions (positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16), the ionic conductivity of alkali metal ions in partition wall 12 is ensured, while the sealed state of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 inside exterior member 11 is ensured, and the separation state of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 via partition wall 12 is also ensured.

[0192] Therefore, even when two types of aqueous electrolytes are used, the charge / discharge reaction proceeds stably, and excellent operating characteristics can be obtained.

[0193] In particular, if the entire outer peripheral edge portion 12A contains the first polymer compound, the entire outer peripheral edge portion 12A and the main body portion 12B are firmly fixed to each other, thereby further improving the liquid sealing property inside the exterior member 11 and achieving a greater effect.

[0194] Furthermore, if the outer peripheral edge portion 12A and the main body portion 12B are integrated with each other, the liquid sealing property using the partition wall 12 inside the exterior member 11 is sufficiently improved, and therefore a greater effect can be obtained.

[0195] Furthermore, because main body portion 12B is positioned inside outer periphery portion 12A within exterior member 11, if main body portion 12B is not exposed to the outside of exterior member 11, positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 are less likely to leak from main body portion 12B to the outside of exterior member 11, thereby achieving a greater effect.

[0196] Furthermore, if the cation exchange membrane contains one or both of sulfonic acid ion groups and carboxylic acid ion groups as anionic groups, the outer peripheral portion 12A has a high affinity for the anionic groups, and therefore the outer peripheral portion 12A and the main body portion 12B are more firmly fixed to each other, thereby achieving a greater effect.

[0197] Furthermore, if the first polymer compound contains one or more of nylon, polyvinyl alcohol, and ethylene-vinyl alcohol copolymer, the adhesive strength between the outer peripheral edge portion 12A and the main body portion 12B is sufficiently improved, thereby achieving a greater effect.

[0198] Furthermore, if the outer casing member 11 contains a second polymer compound, and the second polymer compound contains one or more of polyethylene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene, and polyvinyl chloride, high sealing properties can be obtained in the outer casing member 11, thereby achieving a greater effect.

[0199] In this case, the compatibility between the constituent material of the outer periphery 12A (first polymer compound) and the exterior member 11 (second polymer compound) is good, so the exterior member 11 and the outer periphery 12A are firmly connected to each other, thereby further improving the liquid sealing property inside the exterior member 11 and achieving even greater effects.

[0200] Furthermore, the positive electrode current collector 13A (connection terminal 13AT) is led out of the exterior member 11 via the positive electrode outlet 11PX, the positive electrode sealing member 17 is adjacent to each of the exterior member 11 and the connection terminal 13AT inside the positive electrode outlet 11PX, the connection terminal 13AT contains a first metal material, and the positive electrode sealing member 17 contains a third polymer compound, the details of which are as described above. In this case, the adhesive strength of the positive electrode sealing member 17 to each of the exterior member 11 and the connection terminal 13AT is sufficiently improved, and the gap between the exterior member 11 and the connection terminal 13AT inside the positive electrode outlet 11PX is sufficiently sealed. This ensures liquid sealing and gas sealing properties inside the exterior member 11 (positive electrode space S1) where the positive electrode outlet 11PX is provided, thereby achieving a greater effect.

[0201] Furthermore, the negative electrode current collector 14A (connection terminal portion 14AT) is led out of the exterior member 11 via the negative electrode outlet 11PY, the negative electrode sealing member 18 is adjacent to each of the exterior member 11 and the connection terminal portion 14AT inside the negative electrode outlet 11PY, the connection terminal portion 14AT contains a second metal material, and the negative electrode sealing member 18 contains a fourth polymer compound, the details of which are as described above. In this case, the adhesive strength of the negative electrode sealing member 18 to each of the exterior member 11 and the connection terminal portion 14AT is sufficiently improved, and the gap between the exterior member 11 and the connection terminal portion 14AT inside the negative electrode outlet 11PY is sufficiently sealed. This ensures liquid sealing and gas sealing properties inside the exterior member 11 where the negative electrode outlet 11PY is provided (negative electrode space S2), thereby achieving even greater effects.

[0202] Furthermore, if the contact angle of positive electrode aqueous electrolyte solution 15 with positive electrode inner wall surface 11WX of exterior member 11 is 150° or less, the wettability of positive electrode inner wall surface 11WX with positive electrode aqueous electrolyte solution 15 is ensured. This allows the charge / discharge reaction to proceed sufficiently during charge / discharge, thereby achieving a greater effect.

[0203] Furthermore, if the contact angle of anode aqueous electrolyte solution 16 with anode inner wall surface 11WY of exterior member 11 is 150° or less, the wettability of anode inner wall surface 11WY with anode aqueous electrolyte solution 16 is ensured. This allows charge / discharge reactions to proceed sufficiently during charge / discharge, thereby achieving a greater effect.

[0204] Furthermore, if negative electrode aqueous electrolyte solution 16 has a higher pH than positive electrode aqueous electrolyte solution 15, the decomposition potential of the aqueous solvent is shifted, and the decomposition reaction of the aqueous solvent is thermodynamically suppressed during charge and discharge, and the potential window of the aqueous solvent is expanded. As a result, a high voltage is obtained, and the charge and discharge reaction utilizing the absorption and release of alkali metal ions proceeds sufficiently and stably, resulting in greater effects.

[0205] In this case, if the pH of negative electrode aqueous electrolyte solution 16 is 11 or higher and the pH of positive electrode aqueous electrolyte solution 15 is 3 to 8, the relationship between the pH of positive electrode aqueous electrolyte solution 15 and the pH of negative electrode aqueous electrolyte solution 16 is more easily maintained, and an even greater effect can be obtained.

[0206] In addition, in the manufacturing process of the secondary battery described above, partition wall 12 is formed by heat-sealing outer periphery 12A and main body 12B together, so that outer periphery 12A and main body 12B are firmly fixed together, as described above. Therefore, for the reasons described above, even when two types of aqueous electrolytes (cathode aqueous electrolyte 15 and negative electrode aqueous electrolyte 16) are used, the charge / discharge reaction proceeds stably, and a secondary battery with excellent operating characteristics can be realized.

[0207] 2. Modifications Next, modifications of the secondary battery will be described.

[0208] The configuration of the secondary battery described above can be modified as appropriate, as described below, although any two or more of the series of modifications described below may be combined with each other.

[0209] 1 and 2, the entire outer peripheral edge portion 12A contains the first polymer compound. However, although not specifically shown here, only a part of the outer peripheral edge portion 12A may contain the first polymer compound.

[0210] The number of portions of the outer peripheral portion 12A that contain the first polymer compound may be one or may be two or more portions that are spaced apart from each other. Note that the portions of the outer peripheral portion 12A that do not contain the first polymer compound contain a cation exchange membrane, similar to the main body portion 12B.

[0211] In this case, the liquid sealing property inside the exterior member 11 is improved compared to when all of the outer peripheral edge portion 12A does not contain the first polymer compound, so the same effect can be obtained.

[0212] 1 , the secondary battery includes both the positive electrode sealing member 17 and the negative electrode sealing member 18. However, the secondary battery may include only one of the positive electrode sealing member 17 and the negative electrode sealing member 18, or may not include both the positive electrode sealing member 17 and the negative electrode sealing member 18.

[0213] Specifically, the secondary battery may include only the positive electrode sealing member 17 without including the negative electrode sealing member 18. In this case, the positive electrode lead-out port 11PX is sealed by the positive electrode sealing member 17, whereas the method for sealing the negative electrode lead-out port 11PY is not particularly limited. Specifically, the negative electrode lead-out port 11PY may be sealed with an insulating polymer compound such as an epoxy resin, a silicone resin, a phenol resin, or a polyimide resin.

[0214] In this case, the liquid sealing property and gas sealing property in the positive electrode space S1 are improved compared to when the secondary battery does not have either the positive electrode sealing member 17 or the negative electrode sealing member 18, and therefore the same effect can be obtained.

[0215] Alternatively, the secondary battery may include only the negative electrode sealing member 18 without including the positive electrode sealing member 17. In this case, the negative electrode outlet 11PY is sealed by the negative electrode sealing member 18, whereas the method for sealing the positive electrode outlet 11PX is not particularly limited. Specifically, the positive electrode outlet 11PX may be sealed with an insulating polymer compound such as an epoxy resin, a silicone resin, a phenol resin, or a polyimide resin.

[0216] In this case, the liquid sealing property and gas sealing property in the negative electrode space S2 are improved compared to when the secondary battery does not have either the positive electrode sealing member 17 or the negative electrode sealing member 18, and therefore the same effect can be obtained.

[0217] [Modification 3] In FIG. 1, the outer peripheral edge portion 12A is disposed inside the exterior member 11 and is therefore not exposed to the outside of the exterior member 11.

[0218] However, as shown in Fig. 3 corresponding to Fig. 1, the outer peripheral edge 12A may be exposed from the exterior member 11. In this case, the exterior member 11 may be divided into two exterior containers 11X and 11Y, and the exterior containers 11X and 11Y may be connected to each other via the outer peripheral edge 12A.

[0219] In this case, the outer peripheral edge portion 12A and the main body portion 12B are also firmly connected to each other, so the same effect can be obtained.

[0220] [Variation 4] In Fig. 1, the outer peripheral edge portion 12A has an integral structure. However, as shown in Fig. 4, which corresponds to Fig. 1, the outer peripheral edge portion 12A may have a structure including end portions 12AX and 12AY, and the end portions 12AX and 12AY may be connected to each other.

[0221] The configuration of the secondary battery shown in FIG. 4 is similar to the configuration of the secondary battery shown in FIG. 1, except as described below.

[0222] The exterior member 11 includes a pair of exterior containers 11X and 11Y that are separated from each other based on the location of the partition wall 12 .

[0223] The ends 12AX and 12AY are chemically bonded to each other to form the outer circumferential edge portion 12A. The outer circumferential edge portion 12A is chemically bonded to the main body portion 12B and to the exterior member 11.

[0224] The method for manufacturing the secondary battery shown in FIG. 4 is the same as the method for manufacturing the secondary battery shown in FIG. 1, except for the points described below.

[0225] When assembling the secondary battery, first, the exterior containers 11X and 11Y separated from each other are prepared.

[0226] The outer casing 11X has a vessel-like structure with an opening and includes a positive electrode outlet 11PX. The outer casing 11Y has a vessel-like structure with an opening and includes a negative electrode outlet 11PY.

[0227] Here, the end 12AX is heat-sealed to the outer casing 11X in advance, and the end 12AY is heat-sealed to the outer casing 11Y in advance. However, the end portions 12AX and 12AY are arranged in positions that allow them to face each other so that they can be heat-sealed to each other in the process of forming the outer casing member 11, which will be described later.

[0228] Next, the outer containers 11X and 11Y are arranged so that the openings thereof face each other and the ends 12AX and 12AY thereof face each other, and then the outer containers 11X and 11Y are moved closer to each other until the ends 12AX and 12AY come into contact with each other. In this case, the main body 12B is placed between the outer containers 11X and 11Y, and the main body 12B is housed inside the outer containers 11X and 11Y.

[0229] Finally, the ends 12AX, 12AY are heated to heat-seal the ends 12AX, 12AY to each other and to heat-seal the ends 12AX, 12AY to the main body portion 12B.

[0230] As a result, the outer casings 11X and 11Y are connected to each other via the outer periphery 12A (ends 12AX and 12AY), thereby forming the outer casing member 11. In addition, the outer periphery 12A (ends 12AX and 12AY) are firmly connected to the main body 12B, thereby completing the secondary battery.

[0231] In this case, the outer peripheral edge portion 12A and the main body portion 12B are also firmly connected to each other, so the same effect can be obtained.

[0232] In this case, even if the outer peripheral edge portion 12A and the main body portion 12B are separated in advance, the ends 12AX, 12AY can be easily heat-sealed to the main body portion 12B, and therefore the outer peripheral edge portion 12A can be easily fixed to the main body portion 12B. This can further improve the operational stability and also facilitate the production of the secondary battery.

[0233] [Modification 5] In Modification 4, the ends 12AX and 12AY that are the outer circumferential edge portion 12A are used, but the configuration of each of the ends 12AX and 12AY may be changed.

[0234] Specifically, as shown in Figure 5 corresponding to Figure 4, each of the end portions 12AX, 12AY may be partially recessed so that a recess portion 12U is formed when the end portions 12AX, 12AY are connected to each other. Since the main body portion 12B is inserted into this recess portion 12U, the main body portion 12B is held by the end portions 12AX, 12AY when inserted into the recess portion 12U.

[0235] In this case, the end of the outer container 11X to which the end 12AX is previously heat-sealed may extend along the main body 12B, and the end of the outer container 11Y to which the end 12AY is previously heat-sealed may extend along the main body 12B. As a result, the end of the outer container 11X may be bent toward the inside of the outer container 11X, and the end of the outer container 11Y may be bent toward the inside of the outer container 11Y.

[0236] This secondary battery is assembled using an outer case 11X to which an end 12AX has been heat-sealed in advance and an outer case 11Y to which an end 12AY has been heat-sealed in advance. The method for manufacturing the secondary battery in Modification 5 is the same as the method for manufacturing the secondary battery in Modification 4, except that the configurations of the ends 12AX and 12AY are different.

[0237] In this case, the outer peripheral edge portion 12A and the main body portion 12B are also firmly connected to each other, so the same effect can be obtained.

[0238] In this case, as described above, the main body portion 12B is inserted into the recessed portion 12U. This allows the main body portion 12B to be stably held by utilizing the ends 12AX and 12AY, thereby suppressing displacement of the partition wall 12. Furthermore, the contact area between the outer peripheral edge portion 12A and the main body portion 12B increases, allowing the outer peripheral edge portion 12A to be more stably thermally bonded to the main body portion 12B.

[0239] [Variation 6] Examples of the negative electrode active material include a titanium-containing compound, a niobium-containing compound, a vanadium-containing compound, an iron-containing compound, and a molybdenum-containing compound. However, the negative electrode active material may be other compounds as long as the charge / discharge reaction proceeds smoothly and stably even when two types of aqueous electrolytes (positive electrode aqueous electrolyte 15 and negative electrode aqueous electrolyte 16) are used. In this case, the same effect can be obtained.

[0240] 1, electrolyte solutions (positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16) that are liquid electrolytes are used. However, as shown in FIG. 6, which corresponds to FIG. 1, electrolyte layers 21 and 22 that are gel electrolytes may be used instead of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16.

[0241] 6 , when the electrolyte layers 21 and 22 are used, the electrolyte layer 21 is interposed between the partition wall 12 and the positive electrode 13, and the electrolyte layer 22 is interposed between the partition wall 12 and the negative electrode 14. As a result, the electrolyte layer 21 is adjacent to the partition wall 12 and the positive electrode 13, and the electrolyte layer 22 is adjacent to the partition wall 12 and the negative electrode 14, respectively.

[0242] Specifically, electrolyte layer 21 contains a polymer compound together with cathode aqueous electrolyte solution 15, and cathode aqueous electrolyte solution 15 is held in place by the polymer compound. This is because leakage of cathode aqueous electrolyte solution 15 is prevented. In Figure 6, electrolyte layer 21 containing cathode aqueous electrolyte solution 15 is lightly shaded.

[0243] The electrolyte layer 22 contains a polymer compound together with the anode aqueous electrolyte solution 16, and the anode aqueous electrolyte solution 16 is held in place by the polymer compound. This is because leakage of the anode aqueous electrolyte solution 16 is prevented. In Fig. 6, the electrolyte layer 22 containing the anode aqueous electrolyte solution 16 is shaded darkly.

[0244] The type of polymer compound is not particularly limited, but specifically, it is one or more of polyvinylidene fluoride, polyethylene oxide, and the like.

[0245] When forming electrolyte layer 21, a precursor solution containing positive electrode aqueous electrolyte solution 15, a polymer compound, and an organic solvent is prepared, and then the precursor solution is applied to positive electrode 13. When forming electrolyte layer 22, a precursor solution containing negative electrode aqueous electrolyte solution 16, a polymer compound, and an organic solvent is prepared, and then the precursor solution is applied to negative electrode 14.

[0246] In this case, alkali metal ions can also move between the positive electrode 13 and the negative electrode 14 via the electrolyte layers 21 and 22, so that the same effect can be obtained.

[0247] In this case, as described above, leakage of both the positive electrode aqueous electrolyte 15 and the negative electrode aqueous electrolyte 16 is prevented, and therefore a greater effect can be obtained.

[0248] 1 , when the positive electrode aqueous electrolyte 15 is contained in only a portion of the positive electrode space S1, a positive electrode outlet 11PX is provided on the upper surface of the exterior member 11 and a connection terminal 13AT extends from above the exterior member 11, thereby preventing the positive electrode sealing member 17 from coming into contact with the positive electrode aqueous electrolyte 15. When the negative electrode aqueous electrolyte 16 is contained in only a portion of the negative electrode space S2, a negative electrode outlet 11PY is provided on the upper surface of the exterior member 11 and a connection terminal 14AT extends from above the exterior member 11, thereby preventing the negative electrode sealing member 18 from coming into contact with the negative electrode aqueous electrolyte 16.

[0249] However, by changing the position at which the positive electrode outlet 11PX is provided in the exterior member 11, the positive electrode sealing member 17 may come into contact with the positive electrode aqueous electrolyte solution 15, and by changing the position at which the negative electrode outlet 11PY is provided in the exterior member 11, the negative electrode sealing member 18 may come into contact with the negative electrode aqueous electrolyte solution 16.

[0250] 7 corresponding to FIG. 1 , a positive electrode outlet 11PX may be provided on a side surface of exterior member 11, and connection terminal portion 13AT may be led out from the side of exterior member 11, so that positive electrode sealing member 17 comes into contact with positive electrode aqueous electrolyte solution 15. Alternatively, a negative electrode outlet 11PY may be provided on a side surface of exterior member 11, and connection terminal portion 14AT may be led out from the side of exterior member 11, so that negative electrode sealing member 18 comes into contact with negative electrode aqueous electrolyte solution 16 (variation 8).

[0251] 8 corresponding to FIG. 1 , a positive electrode outlet 11PX may be provided on the lower surface of exterior member 11, and connection terminal portion 13AT may be led out from below exterior member 11, so that positive electrode sealing member 17 comes into contact with positive electrode aqueous electrolyte solution 15. Alternatively, a negative electrode outlet 11PY may be provided on the lower surface of exterior member 11, and connection terminal portion 14AT may be led out from below exterior member 11, so that negative electrode sealing member 18 comes into contact with negative electrode aqueous electrolyte solution 16 (variation example 9).

[0252] In these cases, the positive electrode sealing member 17 and the negative electrode sealing member 18 are used to ensure liquid sealing and gas sealing, and therefore the same effects can be obtained.

[0253] In this case, in particular, waterproofness is also exhibited in each of positive electrode sealing member 17 and negative electrode sealing member 18. Therefore, liquid sealing properties and gas sealing properties are sufficiently exhibited even when positive electrode sealing member 17 is in contact with positive electrode aqueous electrolyte 15, and liquid sealing properties and gas sealing properties are sufficiently exhibited even when negative electrode sealing member 18 is in contact with negative electrode aqueous electrolyte 16, so that a greater effect can be obtained.

[0254] 3. Uses of Secondary Batteries The uses of secondary batteries are not particularly limited as long as they can be used for machines, devices, instruments, equipment, and systems (assemblies of multiple devices, etc.) that can use the secondary battery as a driving power source and a power storage source for storing power. A secondary battery used as a power source may be a main power source or an auxiliary power source. A main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. An auxiliary power source may be a power source used in place of the main power source, or may be a power source that can be switched from the main power source as needed. When a secondary battery is used as an auxiliary power source, the type of main power source is not limited to a secondary battery.

[0255] Specifically, specific examples of uses of secondary batteries are as follows: Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, notebook computers, cordless phones, headphone stereos, portable radios, portable televisions, and portable information terminals; Portable household appliances such as electric shavers; Storage devices such as backup power supplies and memory cards; Power tools such as power drills and power saws; Battery packs installed in notebook computers and the like as removable power sources; Medical electronic devices such as pacemakers and hearing aids; Electric vehicles such as electric cars (including hybrid cars); Power storage systems such as home battery systems that store power in preparation for emergencies. Of course, secondary batteries may be used for uses other than the series of uses exemplified here.

[0256] An embodiment of the present technology will be described.

[0257] Examples 1 to 9 and Comparative Examples 1 and 2 As will be described below, secondary batteries were fabricated, and then the operating characteristics of the secondary batteries were evaluated.

[0258] [Fabrication of Secondary Battery] A secondary battery shown in FIG. 5 was fabricated according to the procedure described below.

[0259] (Preparation of Positive Electrode) First, a positive electrode active material (a lithium composite oxide, LiMn 2　 O 4　A positive electrode mixture was prepared by mixing 91 parts by mass of ethylenediamine fluoride (Eu), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductive agent (graphite). The positive electrode mixture was then added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. The positive electrode mixture slurry was then applied to the surface of the positive electrode current collector 13A, excluding the connection terminal portion 13AT, using a coating device, and the positive electrode mixture slurry was then dried to form the positive electrode active material layer 13B. Titanium (titanium foil with a thickness of 20 μm) was used as the first metal material for the positive electrode current collector 13A. Thus, the positive electrode 13 was fabricated.

[0260] (Fabrication of Negative Electrode) First, 89 parts by mass of a negative electrode active material (anatase-type titanium oxide, which is a titanium-containing compound (titanium oxide)), 10 parts by mass of a negative electrode binder (polyvinylidene fluoride), and 1 part by mass of a negative electrode conductive agent (graphite) were mixed together to prepare a negative electrode mixture. Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to the surface of the negative electrode current collector 14A excluding the connection terminal portion 14AT using a coating device, and the negative electrode mixture slurry was then dried to form the negative electrode active material layer 14B. Titanium (titanium foil with a thickness of 20 μm), which is the second metal material, was used for this negative electrode current collector 14A. In this way, the negative electrode 14 was fabricated.

[0261] (Preparation of Positive Electrolyte Aqueous Electrolyte) An ionic substance (lithium sulfate (Li), which is an electrolyte salt) is added to an aqueous solvent (pure water). 2　 SO 4　 )) was added, and the aqueous solvent was stirred. This resulted in the preparation of positive electrode aqueous electrolyte solution 15. In this case, the concentration was 2 mol / kg and the pH was 4.

[0262] (Preparation of Aqueous Negative Electrolyte Solution) An ionic substance (lithium hydroxide (LiOH) as an electrolyte salt) was added to an aqueous solvent (pure water), and the aqueous solvent was then stirred. Thus, aqueous negative electrode electrolyte solution 16 was prepared. In this case, the concentration was 4 mol / kg and the pH was 12.

[0263] (Assembly of Secondary Battery) First, an outer case 11X having an opening and an outer case 11Y having an opening were prepared.

[0264] The outer packaging 11X is provided with a positive electrode outlet 11PX and has an end 12AX heat-sealed thereto in advance, and the outer packaging 11Y is provided with a negative electrode outlet 11PY and has an end 12AY heat-sealed thereto in advance.

[0265] The materials (second polymer compounds) used to form the outer containers 11X and 11Y were polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC).

[0266] The contact angle (°) of positive electrode aqueous electrolyte solution 15 with the surface of outer casing 11X (positive electrode inner wall surface 11WX) and the contact angle (°) of negative electrode aqueous electrolyte solution 16 with the surface of outer casing 11Y (negative electrode inner wall surface 11WY) are as shown in Tables 1 to 3. Here, the material (second polymer compound) forming outer casing 11X and the material (second polymer compound) forming outer casing 11Y were the same type, so the contact angle of positive electrode aqueous electrolyte solution 15 with positive electrode inner wall surface 11WX and the contact angle of negative electrode aqueous electrolyte solution 16 with negative electrode inner wall surface 11WY were the same value.

[0267] The materials (first polymer compounds) used to form the ends 12AX and 12AY were nylon (NY), polyvinyl alcohol (PVA), and ethylene-vinyl alcohol copolymer (EVOH). Suitable functional groups contained in the first polymer compounds were a hydroxyl group (-OH) and a primary amide group (-CONHCH 3　 ) was used.

[0268] For comparison, polyethylene (PE) not having the above-mentioned appropriate functional groups was used as the material for forming each of the ends 12AX and 12AY. In Table 2, for convenience, polyethylene is listed in the column for the first polymer compound, but polyethylene not having the appropriate functional groups does not fall under the category of the first polymer compound.

[0269] Subsequently, the positive electrode inner wall surface 11WX and the negative electrode inner wall surface 11WY were subjected to plasma treatment as required. The contact angles after the plasma treatment were as shown in Table 1.

[0270] Next, the outer containers 11X and 11Y were arranged so that the openings faced each other, and then the outer containers 11X and 11Y were brought close to each other until the ends 12AX and 12AY came into contact with each other. In this case, the main body 12B was placed between the outer containers 11X and 11Y, and the main body 12B was housed inside the outer containers 11X and 11Y.

[0271] The main body 12B was made of a cation exchange membrane (Nafion (registered trademark) NRE212, purchased from Sigma-Aldrich Japan LLC). The functional groups contained in this cation exchange membrane were sulfonic acid ion groups (-SO - ) was used.

[0272] Next, the ends 12AX, 12AY were heated (heating temperature = 200°C) to thermally fuse the ends 12AX, 12AY to each other and to the main body portion 12B. As a result, the outer casings 11X, 11Y were connected to each other via the outer circumferential edge portion 12A (ends 12AX, 12AY), thereby forming the outer casing member 11. Furthermore, the outer circumferential edge portion 12A (ends 12AX, 12AY) was firmly connected to the main body portion 12B, thereby forming the partition wall 12 including the outer circumferential edge portion 12A and the main body portion 12B.

[0273] Subsequently, the positive electrode 13 was inserted into the positive electrode space S1 through the positive electrode outlet 11PX, and the negative electrode 14 was inserted into the negative electrode space S2 through the negative electrode outlet 11PY. In this case, the connection terminal 13AT was led out of the outer package 11X via the positive electrode outlet 11PX, and the connection terminal 14AT was led out of the outer package 11Y via the negative electrode outlet 11PY.

[0274] Subsequently, the positive electrode aqueous electrolyte 15 was supplied from the positive electrode outlet 11PX to the positive electrode space S1, whereby the positive electrode aqueous electrolyte 15 was accommodated in the positive electrode space S1 and the positive electrode 13 was immersed in the positive electrode aqueous electrolyte 15.

[0275] Furthermore, the negative electrode aqueous electrolyte 16 was supplied from the negative electrode outlet 11PY to the negative electrode space S2, whereby the negative electrode aqueous electrolyte 16 was accommodated in the negative electrode space S2 and the negative electrode 14 was immersed in the negative electrode aqueous electrolyte 16.

[0276] Finally, as necessary, the positive electrode outlet 11PX was sealed with a positive electrode sealing member 17 (an acid-modified polyolefin as a third polymer compound), and the negative electrode outlet 11PY was sealed with a negative electrode sealing member 18 (an acid-modified polyolefin as a fourth polymer compound).

[0277] In this case, a positive electrode sealing member 17 was placed inside the positive electrode outlet 11PX between the exterior case 11X and the connection terminal portion 13AT, and then the positive electrode sealing member 17 was heated (heating temperature = 200°C). As a result, the positive electrode sealing member 17 was heat-sealed to each of the exterior case 11X and the connection terminal portion 13AT, and the positive electrode sealing member 17 was used to seal the positive electrode outlet 11PX.

[0278] Furthermore, if necessary, a negative electrode sealing member 18 was placed inside the negative electrode outlet 11PY between the exterior case 11Y and the connection terminal portion 14AT, and then the negative electrode sealing member 18 was heated (heating temperature = 200°C). As a result, the negative electrode sealing member 18 was heat-sealed to each of the exterior case 11Y and the connection terminal portion 14AT, and the negative electrode sealing member 18 was used to seal the negative electrode outlet 11PY.

[0279] When the positive electrode sealing member 17 was not used, the positive electrode outlet 11PX was sealed with an insulating polymer compound (silicone resin), and when the negative electrode sealing member 18 was not used, the negative electrode outlet 11PY was sealed with an insulating polymer compound (silicone resin).

[0280] Thus, the partition wall 12, the positive electrode 13, the negative electrode 14, the positive electrode aqueous electrolyte 15, and the negative electrode aqueous electrolyte 16 are housed inside the exterior member 11, and the secondary battery is completed.

[0281] For comparison, a secondary battery was manufactured using the same procedure except that the outer peripheral edge portion 12 A was not used. In this case, the exterior member 11 and the partition wall 12 (main body portion 12 B) were each heated, so that the partition wall 12 (main body portion 12 B) was bonded to the exterior member 11 without the outer peripheral edge portion 12 A interposed therebetween.

[0282] [Evaluation of Battery Characteristics] When the electrolyte retention characteristics and capacity characteristics were evaluated as the operating characteristics, the results shown in Tables 1 to 3 were obtained.

[0283] (Electrolyte Retention Characteristics) When evaluating the electrolyte retention characteristics, first, the total weight (total weight before storage) of the positive electrode aqueous electrolyte 15 and the negative electrode aqueous electrolyte 16 was measured in a room temperature environment (temperature = 23°C). In this case, weight G1 of the partially assembled secondary battery before positive electrode aqueous electrolyte 15 and negative electrode aqueous electrolyte 16 were placed therein was measured, and weight G2 of the partially assembled secondary battery after positive electrode aqueous electrolyte 15 and negative electrode aqueous electrolyte 16 were placed therein was measured. The total weight before storage was calculated by subtracting weight G1 from weight G2.

[0284] Next, the partially assembled secondary battery after positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 were placed therein was stored (storage period = 24 hours) in a high-temperature environment using a thermostatic bath (temperature = 50°C), and the total weight of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 (total weight after storage) was measured. In this case, weight G3 after storage of the partially assembled secondary battery after positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 were measured. The total weight after storage was calculated by subtracting weight G1 from weight G3.

[0285] Next, the weight loss rate (%), which is an index for evaluating the electrolyte retention properties, was calculated based on the formula: weight loss rate (%) = [(total weight before storage - total weight after storage) / total weight before storage] × 100.

[0286] Finally, the weight loss rate was judged based on the value of the weight loss rate. In this case, a weight loss rate of less than 2% was judged as "A." A weight loss rate of 2% or more and less than 5% was judged as "B." A weight loss rate of 5% or more and less than 10% was judged as "C." A weight loss rate of 10% or more was judged as "D."

[0287] (Capacity Characteristics) When evaluating the capacity characteristics, first, the secondary battery was charged and discharged using an electrochemical measurement device to measure the discharge capacity (mAh). Next, the secondary battery was disassembled to recover the positive electrode active material, and the weight (g) of the positive electrode active material was measured. Next, the battery capacity (mAh / g), which is an index for evaluating the capacity characteristics, was calculated based on the formula: battery capacity (mAh / g) = discharge capacity / weight.

[0288] Finally, the battery capacity was judged based on the battery capacity value. In this case, a battery capacity of 80 mAh / g or more was judged as "A." A battery capacity of 60 mAh / g or more but less than 80 mAh / g was judged as "B." A battery capacity of 40 mAh / g or more but less than 60 mAh / g was judged as "C." A battery capacity of less than 40 mAh / g was judged as "D."

[0289]

[0290]

[0291]

[0292] [Discussion] As shown in Tables 1 to 3, the weight loss rate and the battery capacity each varied depending on the configuration of the secondary battery.

[0293] Specifically, when partition wall 12 included only main body portion 12B, and when partition wall 12 included outer peripheral edge portion 12A but outer peripheral edge portion 12A did not have an appropriate functional group (Comparative Examples 1 and 2), the amount of volatilization of positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 increased, resulting in an increased rate of weight loss. In addition, the charge / discharge reaction did not proceed sufficiently using partition wall 12, resulting in a decrease in battery capacity. In these cases, in particular, positive electrode aqueous electrolyte solution 15 and negative electrode aqueous electrolyte solution 16 mixed with each other, preventing the secondary battery from substantially charging or discharging.

[0294] In contrast, when the secondary battery included not only main body portion 12B but also outer peripheral edge portion 12A, and outer peripheral edge portion 12A had appropriate functional groups (Examples 1 to 9), the amount of volatilization of each of cathode aqueous electrolyte 15 and anode aqueous electrolyte 16 decreased, thereby reducing the rate of weight loss, and the battery capacity increased because the charge / discharge reaction proceeded sufficiently using partition wall 12. In this case, the cathode aqueous electrolyte 15 and anode aqueous electrolyte 16 did not mix with each other, allowing the secondary battery to be stably charged and discharged.

[0295] In other words, when the main body portion 12B contains a cation exchange membrane and the outer edge portion 12A (first polymer compound) contains a hydroxyl group or a primary amide group having an appropriate functional group, good results were obtained in terms of both the weight loss rate and the battery capacity.

[0296] In this case, in particular, a series of trends were obtained, which are explained below.

[0297] First, when the first polymer compound contained either a primary amide group or a hydroxyl group, the weight loss rate was sufficiently reduced and the battery capacity was sufficiently increased. Although specific experimental results are not shown here, similar trends were observed whether the first polymer compound contained either a primary amino group, a secondary amino group, a secondary amide group, or a carboxyl group.

[0298] Second, when the first polymer compound contained any one of nylon, polyvinyl alcohol, and ethylene-vinyl alcohol copolymer, the weight loss rate was sufficiently reduced and the battery capacity was sufficiently increased.

[0299] Third, when the cation exchange membrane contained sulfonic acid ion groups, the weight loss rate was sufficiently reduced and the battery capacity was sufficiently increased. Although specific experimental results are not presented here, a similar tendency was observed even when the cation exchange membrane contained carboxylate ion groups.

[0300] Fourth, when the second polymer compound contained any one of polyethylene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene, and polyvinyl chloride, the weight loss rate was sufficiently reduced and the battery capacity was sufficiently increased.

[0301] Fifth, when the outer peripheral edge portion 12A and the main body portion 12B are heat-sealed to each other, the weight loss rate is sufficiently reduced and the battery capacity is sufficiently increased.

[0302] Sixth, when the positive electrode outlet 11PX was sealed with the positive electrode sealing member 17 (third polymer compound) and the negative electrode outlet 11PY was sealed with the negative electrode sealing member 18 (fourth polymer compound), the weight loss rate was further reduced and the battery capacity was further increased.

[0303] Seventh, when the contact angle of positive electrode aqueous electrolyte 15 with positive electrode inner wall surface 11WX is 150° or less and the contact angle of negative electrode aqueous electrolyte 16 with negative electrode inner wall surface 11WY is 150° or less, the battery capacity is further increased.

[0304] Eighth, the battery capacity was sufficiently increased when the negative electrode aqueous electrolyte solution 16 had a higher pH than the positive electrode aqueous electrolyte solution 15. In this case, a high battery capacity was obtained when the negative electrode aqueous electrolyte solution 16 had a pH of 11 or higher and the positive electrode aqueous electrolyte solution 15 had a pH of 3 to 8.

[0305] [Summary] The results shown in Tables 1 to 3 indicate that when partition wall 12 includes outer peripheral edge portion 12A and main body portion 12B, main body portion 12B includes a cation exchange membrane, and outer peripheral edge portion 12A includes a first polymer compound, the first polymer compound including one or more of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group, and a carboxyl group, the weight loss rate decreased and the battery capacity increased. Therefore, both the electrolyte retention characteristics and the capacity characteristics were improved, resulting in excellent operating characteristics.

[0306] The configuration of the secondary battery according to the present technology has been described above with reference to an embodiment and examples. However, the configuration of the secondary battery according to the present technology is not limited to the configuration described in the embodiment and examples, and various modifications are possible.

[0307] The effects described in this specification are merely examples, and therefore the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0308] The present technology may also be configured as follows: <1> A secondary battery including: a partition wall that allows alkali metal ions to pass through; an exterior member having therein a positive electrode space and a negative electrode space that are separated from each other by the partition wall; a positive electrode aqueous electrolyte solution accommodated in the positive electrode space; a negative electrode aqueous electrolyte solution accommodated in the negative electrode space; a positive electrode that is immersed in the positive electrode aqueous electrolyte solution and occludes and releases the alkali metal ions; and a negative electrode that is immersed in the negative electrode aqueous electrolyte solution and occludes and releases the alkali metal ions, wherein the partition wall includes: an outer circumferential edge portion adjacent to the exterior member; and a main body portion located inside the outer circumferential edge portion, the main body portion including a cation exchange membrane, the cation exchange membrane including at least one of a sulfonic acid ion group and a carboxylate ion group, at least a portion of the outer circumferential edge portion including a first polymer compound, and the first polymer compound including at least one of a hydroxyl group, a carboxyl group, a carboxylic acid anhydride, a carboxylic acid ester, and a nitrogen-containing basic functional group. <2> The secondary battery according to <1>, wherein the first polymer compound contains at least one of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group, and a carboxyl group. <3> The secondary battery according to <1> or <2>, wherein the entire outer periphery contains the first polymer compound. <4> The secondary battery according to any one of <1> to <3>, wherein the outer periphery and the main body are integrated with each other. <5> The secondary battery according to any one of <1> to <4>, wherein the main body is disposed inside the outer periphery within the exterior member and is not exposed to the outside of the exterior member. <6> The secondary battery according to any one of <1> to <5>, wherein the cation exchange membrane contains at least one of a sulfonic acid ion group and a carboxylate ion group. <7> The secondary battery according to any one of <1> to <6>, wherein the first polymer compound contains at least one of nylon, polyvinyl alcohol, and an ethylene-vinyl alcohol copolymer.<8> The secondary battery according to any one of <1> to <7>, wherein the exterior member includes a second polymer compound, and the second polymer compound includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene, and polyvinyl chloride. <9> The secondary battery according to any one of <1> to <8>, wherein the exterior member has a positive electrode lead-out port communicating with the positive electrode space, the positive electrode includes a positive electrode current collector, and the positive electrode current collector is led to the outside of the exterior member via the positive electrode lead-out port, and further includes positive electrode sealing members disposed inside the positive electrode lead-out port between the exterior member and the positive electrode current collector and adjacent to each of the exterior member and the positive electrode current collector, and the positive electrode current collector includes a first metal material, and the first metal material includes at least one of titanium, aluminum, nickel, and an alloy of two or more types thereof, and the positive electrode sealing member includes a third polymer compound, and the third polymer compound includes an acid-modified polyolefin. <10> The secondary battery according to any one of <1> to <9>, wherein the exterior member has a negative electrode lead-out port communicating with the negative electrode space, the negative electrode includes a negative electrode current collector, and the negative electrode current collector is led to the outside of the exterior member via the negative electrode lead-out port, and further includes a negative electrode sealing member disposed inside the negative electrode lead-out port between the exterior member and the negative electrode current collector and adjacent to each of the exterior member and the negative electrode current collector, the negative electrode current collector including a second metal material, and the second metal material including at least one of stainless steel, titanium, zinc, tin, lead, and an alloy of two or more types thereof, and the negative electrode sealing member including a fourth polymer compound, and the fourth polymer compound including an acid-modified polyolefin. <11> The secondary battery according to any one of <1> to <10>, wherein the exterior member has a positive electrode inner wall surface that contacts the positive electrode aqueous electrolyte inside the positive electrode space, and a contact angle of the positive electrode aqueous electrolyte with the positive electrode inner wall surface is 150° or less.<12> The secondary battery according to any one of <1> to <11>, wherein the exterior member has a negative electrode inner wall surface that contacts the negative electrode aqueous electrolyte inside the negative electrode space, and wherein a contact angle of the negative electrode aqueous electrolyte with the negative electrode inner wall surface is 150° or less. <13> The secondary battery according to any one of <1> to <12>, wherein the negative electrode aqueous electrolyte has a pH higher than a pH of the positive electrode aqueous electrolyte. <14> The secondary battery according to <13>, wherein the negative electrode aqueous electrolyte has a pH of 11 or more, and the positive electrode aqueous electrolyte has a pH of 3 or more and 8 or less. <15> A method for manufacturing a secondary battery according to any one of <1> to <14>, wherein, in a manufacturing process of the secondary battery according to any one of <1> to <14>, the partition wall is formed by heat-sealing at least a part of an outer periphery and a main body portion together.

[0309] 11... exterior member, 11PX... positive electrode outlet, 11PY... negative electrode outlet, 11WX... positive electrode inner wall surface, 11WY... negative electrode inner wall surface, 12... partition wall, 12A... outer peripheral edge portion, 12B... main body portion, 13... positive electrode, 13A... positive electrode current collector, 14... negative electrode, 14A... negative electrode current collector, 15... positive electrode aqueous electrolyte, 16... negative electrode aqueous electrolyte, 17... positive electrode sealing member, 18... negative electrode sealing member, S1... positive electrode space, S2... negative electrode space

Claims

1. A secondary battery comprising: a partition wall that allows alkali metal ions to pass through; an exterior member having a positive electrode space and a negative electrode space therein that are separated from each other by the partition wall; a positive electrode aqueous electrolyte solution contained in the positive electrode space; a negative electrode aqueous electrolyte solution contained in the negative electrode space; a positive electrode that is immersed in the positive electrode aqueous electrolyte solution and absorbs and releases the alkali metal ions; and a negative electrode that is immersed in the negative electrode aqueous electrolyte solution and absorbs and releases the alkali metal ions, wherein the partition wall includes an outer circumferential edge portion adjacent to the exterior member and a main body portion located inside the outer circumferential edge portion, the main body portion includes a cation exchange membrane, at least a portion of the outer circumferential edge portion includes a first polymer compound, and the first polymer compound includes at least one of a hydroxyl group, a carboxyl group, a carboxylic anhydride, a carboxylic acid ester, and a nitrogen-containing basic functional group.

2. The secondary battery according to claim 1, wherein the first polymer compound contains at least one of a hydroxyl group, a primary amino group, a secondary amino group, a primary amide group, a secondary amide group and a carboxyl group.

3. The secondary battery according to claim 1 or 2, wherein the entire outer peripheral edge portion contains the first polymer compound.

4. The secondary battery according to any one of claims 1 to 3, wherein the outer peripheral edge portion and the main body portion are integrated with each other.

5. A secondary battery according to any one of claims 1 to 4, wherein the main body portion is disposed inside the outer periphery portion within the exterior member and is not exposed to the outside of the exterior member.

6. The secondary battery according to any one of claims 1 to 5, wherein the cation exchange membrane contains at least one of a sulfonic acid ion group and a carboxylate ion group.

7. The secondary battery according to any one of claims 1 to 6, wherein the first polymer compound includes at least one of nylon, polyvinyl alcohol, and an ethylene-vinyl alcohol copolymer.

8. The secondary battery according to any one of claims 1 to 7, wherein the exterior member contains a second polymer compound, and the second polymer compound contains at least one of polyethylene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene and polyvinyl chloride.

9. The secondary battery according to any one of claims 1 to 8, wherein the exterior member has a positive electrode outlet connected to the positive electrode space, the positive electrode includes a positive electrode current collector, and the positive electrode current collector is led to the outside of the exterior member via the positive electrode outlet, and further comprises a positive electrode sealing member disposed inside the positive electrode outlet between the exterior member and the positive electrode current collector and adjacent to each of the exterior member and the positive electrode current collector, the positive electrode current collector includes a first metallic material, and the first metallic material includes at least one of titanium, aluminum, nickel, and an alloy of two or more types thereof, the positive electrode sealing member includes a third polymer compound, and the third polymer compound includes an acid-modified polyolefin.

10. The secondary battery according to any one of claims 1 to 9, wherein the exterior member has a negative electrode outlet connected to the negative electrode space, the negative electrode includes a negative electrode current collector, and the negative electrode current collector is led to the outside of the exterior member via the negative electrode outlet, and further includes a negative electrode sealing member disposed inside the negative electrode outlet between the exterior member and the negative electrode current collector and adjacent to each of the exterior member and the negative electrode current collector, the negative electrode current collector includes a second metallic material, and the second metallic material includes at least one of stainless steel, titanium, zinc, tin, lead, and an alloy of two or more types thereof, the negative electrode sealing member includes a fourth polymer compound, and the fourth polymer compound includes an acid-modified polyolefin.

11. The secondary battery according to any one of claims 1 to 10, wherein the exterior member has a positive electrode inner wall surface that contacts the positive electrode aqueous electrolyte inside the positive electrode space, and a contact angle of the positive electrode aqueous electrolyte with the positive electrode inner wall surface is 150° or less.

12. The secondary battery according to any one of claims 1 to 11, wherein the exterior member has a negative electrode inner wall surface that contacts the negative electrode aqueous electrolyte inside the negative electrode space, and a contact angle of the negative electrode aqueous electrolyte with the negative electrode inner wall surface is 150° or less.

13. The secondary battery according to any one of claims 1 to 12, wherein the negative electrode aqueous electrolyte has a pH greater than a pH of the positive electrode aqueous electrolyte.

14. The secondary battery according to claim 13, wherein the negative electrode aqueous electrolyte has a pH of 11 or more, and the positive electrode aqueous electrolyte has a pH of 3 or more and 8 or less.

15. A method for manufacturing a secondary battery according to any one of claims 1 to 14, wherein a partition wall is formed by heat-sealing at least a portion of the outer periphery and the main body.

Images