JP7027363B2 - Lithium-zinc rechargeable batteries, battery packs, vehicles and stationary power supplies - Google Patents

Description

Embodiments of the present invention relate to lithium zinc secondary batteries, battery packs, vehicles and stationary power supplies.

In recent years, as a high energy density type secondary battery, a battery using a non-aqueous solvent such as a lithium ion secondary battery has been developed. Lithium-ion secondary batteries are superior in energy density and cycle characteristics to lead-acid batteries and nickel-hydrogen secondary batteries, and are expected as power sources for large-scale storage such as power sources for vehicles such as hybrid vehicles and electric vehicles. .. As the electrolyte of the lithium ion secondary battery, a non-aqueous solvent such as ethylene carbonate, diethyl carbonate, or propylene carbonate is used from the viewpoint of having a wide potential window. Since these solvents are flammable, there is a problem in safety. If this can be replaced with an aqueous electrolyte, this problem can be fundamentally solved. In addition, the water-based electrolyte is cheaper than the non-aqueous solvent-based electrolyte, and the manufacturing process does not need to have an inert atmosphere. Therefore, a significant cost reduction can be expected by replacing the non-aqueous solvent-based electrolyte with an aqueous electrolyte. However, there is a big problem in using an aqueous electrolyte in a lithium ion secondary battery. That is, since the theoretical decomposition voltage calculated by the chemical equilibrium of water is 1.23V, if the battery is configured with a design voltage exceeding that, oxygen is generated at the positive electrode and hydrogen is generated at the negative electrode. In order to solve this, the oxygen overvoltage is increased on the oxidation side (positive electrode side) and the hydrogen overvoltage is increased on the reduction side (negative electrode side) to improve the battery design from the viewpoint of kinetics.

In a lithium ion secondary battery using an aqueous solution, charging and discharging of the positive electrode is relatively easy, and there are many reported examples of positive electrode active materials such as LiCoO ₂ , LiMn ₂ O ₄ , and LiFePO ₄ . On the other hand, as negative electrode oxides, there are reports of active materials such as LiTi ₂ (PO ₄ ) ₃ , Tip ₂ O ₇ , and VO ₂ (B) whose lithium occlusion / release potential is about -0.5 V (vs. SHE). However, there are few reports using active materials that operate at lower potentials. This is because charging and discharging are difficult due to the progress of hydrogen generation at the negative electrode. Even if the above-mentioned active material is used as the negative electrode active material, the average operating potential when the battery is configured is less than 2 V. In this case, it is difficult to increase the energy density of the battery, and there is no aqueous secondary battery having an energy density higher than that of the lead storage battery and the nickel hydrogen secondary battery.

Therefore, in an aqueous solution-based lithium ion secondary battery, a lithium-zinc secondary battery in which an oxide material that occludes and releases lithium is used for the positive electrode and a zinc metal is used for the negative electrode is attracting attention. The theoretical capacity of zinc metal is as large as 820 mAh / g, and a lithium-zinc secondary battery that combines a negative electrode using zinc metal as a positive electrode with a positive electrode that stores and releases lithium is the energy of a secondary battery using an aqueous solution. It is expected to be one of the candidates for high-density secondary batteries. However, since dendrites are deposited on the electrode surface during the zinc dissolution / precipitation reaction, there is a problem that the life characteristics are deteriorated due to an increase in overvoltage during charging / discharging.

Japanese Unexamined Patent Publication No. 2018-32646 International Publication No. 2017/135323

An object to be solved by the present invention is to provide a secondary battery, a battery pack, a vehicle and a stationary power source capable of having excellent cycle life performance.

The lithium-zinc secondary battery of the embodiment has a positive electrode, a metal body in which zinc is dissolved and precipitated, and a negative electrode having an oxide on at least a part of the surface of the metal body, and zinc and a lithium salt. It is a secondary battery equipped with an aqueous electrolyte containing and a separator existing between the positive and negative electrodes, and the oxide is in the potential region of -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) or less. Lithium is absorbed and released, the specific surface area of the oxide is 10 m ² / g or more and 350 m ² / g or less, and the mol concentration ratio Zn / Li of zinc and lithium contained in the aqueous electrolyte is 1.0 × 10 ^-5 or more. It is 0.3 or less.

According to another embodiment, a battery pack including the secondary battery according to the above embodiment is provided.

According to still another embodiment, a vehicle including the battery pack according to the above embodiment is provided.

According to still another embodiment, a stationary power source including the battery pack according to the above embodiment is provided.

A partial cutaway sectional view showing an example of a secondary battery according to the first embodiment. The side view about the battery of FIG. The partial cut-out perspective view which shows the other example of the secondary battery which concerns on 1st Embodiment. FIG. 3 is an enlarged cross-sectional view of part A in FIG. The perspective view which shows an example of the assembled battery which concerns on 2nd Embodiment. The perspective view which shows an example of the battery pack which concerns on 3rd Embodiment. An exploded perspective view of another example of the battery pack according to the third embodiment. The block diagram which shows the electric circuit of the battery pack of FIG. FIG. 3 is a cross-sectional view schematically showing an example vehicle according to a fourth embodiment. The figure schematically showing the vehicle of another example which concerns on 4th Embodiment. The block diagram which shows an example of the system including the stationary power source which concerns on 5th Embodiment.

Hereinafter, embodiments will be described with reference to the drawings. It should be noted that the same reference numerals are given to the common configurations throughout the embodiments, and duplicate description will be omitted. In addition, each figure is a schematic diagram for explaining the embodiment and promoting its understanding, and the shape, dimensions, ratio, etc. are different from those of the actual device, but these are described below and known techniques. The design can be changed as appropriate by taking into consideration.

(First Embodiment)
The lithium-zinc secondary battery according to the first embodiment has a positive electrode, a metal body in which zinc is dissolved and precipitated, and a negative electrode having a plurality of oxides on at least a part of the surface of the metal body. It is a secondary battery equipped with an aqueous electrolyte containing zinc and lithium salt and a separator existing between the positive electrode and the negative electrode, and multiple oxides are -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE). ) Lithium is absorbed and released in the potential region below, the specific surface area of the oxide is 10 m ² / g or more and 350 m ² / g or less, and the mol concentration ratio Zn / Li of zinc and lithium contained in the aqueous electrolyte is 1.0 × 10 ^-5 or more and 0.3 or less. The lithium zinc secondary battery is also referred to as a secondary battery.

The positive electrode includes a positive electrode current collector and a positive electrode mixture layer arranged on the positive electrode current collector. The positive electrode mixture layer is arranged on at least one surface of the positive electrode current collector. The negative electrode includes a metal body containing zinc and a negative electrode oxide layer. The negative electrode oxide layer includes at least an oxide. A metal body containing zinc means a metal body composed of zinc or a metal body having zinc present at least a part of the surface of any metal body. At least a portion of the surface of a metal body containing zinc comprises a single or multiple oxides. Further, zinc may be present together with the oxide on the surface of the metal body containing zinc. This zinc can be present on the surface of a metal body that is particulate and contains zinc. The oxide is present, for example, on the surface of a metal body containing zinc in the form of particles. The oxide is, for example, titanium oxide or tungsten oxide. The negative electrode included in the secondary battery according to the present embodiment preferably contains at least one selected from the group consisting of titanium oxide and tungsten oxide as the oxide.

Zinc refers to at least one selected from the group consisting of elemental zinc metals, oxides, chlorides, nitrates, sulfates, basic carbonate compounds, and hydroxides, and may also indicate two or more. be.

The zinc-containing metal body provided in the negative electrode can serve as a current collector and an active material.

The oxide contained in the negative electrode oxide layer occludes lithium during charging. At this time, the self-discharge reaction accompanied by the release of lithium proceeds. When the electrolyte does not contain zinc, the problem is that the self-discharge reaction of the secondary battery proceeds with the generation of hydrogen due to the decomposition of water. Therefore, by applying an oxide having a potential region of Li storage / release near the dissolution / precipitation potential of zinc in the present embodiment, zinc precipitation proceeds in preference to hydrogen generation. Can be done. By precipitating this zinc, zinc can be present on at least a part of the surface of the oxide of the negative electrode, and hydrogen generation due to desorption of lithium can be suppressed. For example, when lithium chloride is used as the supporting salt as an example of the present embodiment, the reaction shown in the following (Equation 1) occurs with self-discharge, so that the active material of the negative electrode for the occlusion / release of lithium occurs. Precipitation of zinc progresses on the surface of oxides such as titanium oxide and tungsten oxide. Lithium is inserted and removed from titanium oxide and tungsten oxide.

When zinc is present on the surface of the oxide, it is not in the shape of a dendrite, but in the form of zinc covering at least a portion of the surface of the oxide. Therefore, unlike the secondary battery according to the present embodiment, it is possible to suppress the precipitation of dendrites on the oxide surface by causing the dissolution-precipitation reaction of zinc via self-discharge as in (Equation 1). can. Furthermore, the presence of zinc in the form of covering the oxide surface makes it possible to suppress hydrogen generation. Therefore, the secondary battery according to the present embodiment can suppress the generation of hydrogen due to self-discharge and the precipitation of zinc dendrite on the surface of the negative electrode during charging, so that the secondary battery is short-circuited at the negative electrode. Can be prevented. Therefore, stable charging / discharging is possible. Further, since the charge / discharge reaction is a mixed reaction of the dissolution and precipitation of zinc and the occlusion and release reaction into the oxide particles of lithium, the charge / discharge is performed in a potential region lower than the dissolution and precipitation potential of zinc. It is possible to improve the battery operating voltage of the cell.

In addition, this zinc precipitation also occurs in the conductive agent of the negative electrode, which will be described later, the current collecting part such as the binder, the tab, and the lead, and the portion of the metal body containing zinc that is not covered with the oxide. The surface of the metal body containing the conductive agent or zinc may also be at least partially covered with zinc.

The material of each member that can be used in the secondary battery according to the first embodiment will be described in detail.

1) Negative electrode The negative electrode includes a metal body containing zinc and a negative electrode oxide layer arranged on the metal body containing zinc. The negative electrode oxide layer is arranged on at least one surface of the metal body containing zinc. For example, the negative electrode oxide layer may be arranged on one surface on the metal body containing zinc, or the negative electrode oxide layer may be arranged on one surface on the metal body containing zinc and its back surface. May be good.

The negative electrode oxide layer preferably contains at least one of titanium oxide and tungsten oxide as the oxide. These oxides may be used alone or in combination of two or more. In these oxides, the lithium uptake and release reaction occurs in the potential region of -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) or less with respect to the saturated calomel electrode (Saturated Calomel Electrode). Therefore, when these oxides are used, a long life can be realized because the change in volume expansion / contraction due to charge / discharge is small.

The metal body provided with zinc is, for example, a metal foil. Further, the metal body containing zinc is a foil made of an alloy containing at least one metal element A selected from the group consisting of, for example, Ga, In, Bi, Tl, Sn, Pb, Ti, and Al. Such a foil may contain, for example, one or more of the above elements A in addition to zinc. Examples of the shape of the metal body containing zinc include a mesh and a porous body in addition to the foil. In order to improve energy density and output, a foil shape with a small volume and a large surface area is desirable.

The metal body containing zinc preferably contains the element A. These elements may be used in one of these elements, or a plurality of types of elements may be used, and may be contained as a metal or a metal alloy. Such metals and metal alloys may be contained alone or may be contained in combination of two or more. When these elements A are contained in the metal body containing zinc, the mechanical strength of the metal body containing zinc is increased, and the processing performance is improved. Further, the effect of suppressing the electrolysis of the aqueous solvent and suppressing the generation of hydrogen is increased. Among the above elements, Pb, Ti and Al are more preferable.

Further, the metal body containing zinc can include a substrate containing zinc or a metal different from the element A. In such a case, the presence of zinc or a compound containing the element A on at least a part of the surface of the substrate can suppress hydrogen generation. It is desirable that the zinc present on the surface and the compound containing the element A are arranged so as to be in contact with the negative electrode oxide layer. For example, the substrate can be plated with zinc or element A so that zinc or element A can be present on the surface of the substrate. Alternatively, the surface of the substrate can be plated with an alloy containing zinc or element A.

The substrate preferably contains at least one metal selected from the group consisting of Al, Fe, Cu, Ni and Ti. These metals can also be included as alloys. Further, the substrate may contain such a metal and a metal alloy alone, or may contain two or more kinds in a mixture. From the viewpoint of weight reduction, it is preferable that the substrate contains Al, Ti, or an alloy thereof.

The metal body containing zinc may contain at least one compound selected from the group consisting of element A. These oxides of element A, and / or hydroxides of element A, and / or basic carbonic acid compounds of element A, and / or sulfuric acid compounds of element A, and the like can be further added on the surface of the metal body containing zinc. It may be coated. When coating, it is preferable that the surface of the metal body is uniformly covered and the film thickness is 1 nm or more and 100 μm or less.

An example of zinc oxide is ZnO, an example of zinc hydroxide is Zn (OH) ₂ , an example of zinc basic carbonate compound is _2ZnCO 3.3 Zn (OH) ₂ , and a zinc sulfate compound. Examples of the above include ZnSO _{4.7H 2} O and the like.

When at least one of an oxide of element A, a hydroxide of element A, a basic carbonic acid compound of element A, and a sulfuric acid compound of element A is present on the surface of a metal body containing zinc, hydrogen generation is suppressed. be able to. Further, when these compounds are present on the surface of the metal body containing zinc, the adhesion between the metal body containing zinc and the oxide can be improved, and the path of electron conduction can be increased, so that the cycle characteristics are improved and the value is low. Resistance is possible.

Whether or not the metal body containing zinc contains a compound containing the element A can be investigated by disassembling the battery as described below and then performing, for example, inductively coupled plasma (ICP) emission analysis. ..

The battery can be disassembled as follows. For example, after discharging the battery that has been charged for the first time, the battery is disassembled and the negative electrode is taken out. The removed negative electrode is washed with pure water for 30 minutes and then vacuum dried in a temperature environment of 80 ° C. for 24 hours. After drying, the temperature is returned to 25 ° C. and the negative electrode is taken out.

The thickness of the metal body containing zinc can be appropriately set.

The oxide is preferably any one selected from titanium oxide and tungsten oxide. Since such an oxide occludes and releases lithium in a potential region of -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) or less, it is close to the dissolution and precipitation potential of zinc. Therefore, a hybrid reaction of lithium occlusion and release and zinc dissolution and precipitation can be performed. Tungsten trioxide is, for example, a compound having a monoclinic structure and represented by the composition formula WO _3-x (0 ≦ x ≦ 0.2). Titanium oxide is, for example, a compound represented by the composition formula TiO _2-x (0 ≦ x ≦ 0.2), and examples of titanium oxide include titanium oxide having a monoclinic structure and titanium oxide having a rutile structure. Includes titanium oxide with anatase structure. The composition of titanium oxide having each crystal structure can be expressed as TiO ₂ before charging and Li _x TiO ₂ (x is 0 ≦ x ≦ 1) after charging. Further, the pre-charging structure of titanium oxide having a monoclinic structure can be expressed as TiO ₂ (B). It is more preferable to use anatase-type titanium oxide because it has a large capacity during lithium storage and release, so that the self-discharge reaction amount can be increased, and the zinc precipitation amount can be improved to increase the negative electrode capacity. ..

The potential region of the oxide is measured as follows.

The occlusion / release potential of lithium constitutes a three-electrode cell with a reference electrode as a saturated calomel electrode, and the position of the peak assigned to the occlusion / release potential of lithium by performing cyclic voltammetry measurement (CV measurement). It can be measured by confirming. The measurement conditions are, for example, that the electrolyte has a molar concentration of lithium that is the same as the concentration of the electrolyte composed of the secondary battery, the LiCl salt is used as the supporting salt, and the sweep rate is 10 mV / sec.

Further, in addition to the above-mentioned titanium oxide and / and tungsten oxide, one kind or two or more kinds of compounds selected from the group consisting of lithium titanium oxide and lithium titanium composite oxide may be contained. In the lithium titanium oxide and the lithium titanium composite oxide, the lithium occlusion / release reaction proceeds in a potential region lower than the potential region of dissolution and precipitation of zinc. Therefore, by mixing with titanium oxide and tungsten oxide, for example, it can be expected to be used for controlling a steep potential change due to overcharging on the negative electrode side during charging.

Examples of lithium-titanium composite oxides include niobium-titanium oxide and sodium niobium-titanium oxide. The lithium occlusion potential of these compounds is preferably in the range of 1 V (vs. Li / Li ⁺ ) or more and 3 V (vs. Li / Li ⁺ ) or less.

Examples of lithium titanium oxides include spinel-structured lithium titanium oxides (for example, the general formula Li _{4 + x} Ti ₅ O ₁₂ (x is -1 ≦ x ≦ 3)) and rams delite structure lithium titanium oxides (for example, Li _{2 + x} Ti). ₃ O ₇ (-1 ≤ x ≤ 3)), Li _{1 + x} Ti ₂ O ₄ (0 ≤ x ≤ 1), Li _{1.1 + x} Ti _1.8 O ₄ (0 ≤ x ≤ 1), Li _{1.07 + x} Ti _1.86 O ₄ (0 ≦ x ≦ 1), Li _x TiO ₂ (0 <x ≦ 1) and the like are included. Further, the lithium titanium oxide includes, for example, a lithium titanium composite oxide in which a different element is introduced into the lithium titanium oxide having a spinel structure or a rams delight structure.

Examples of niobium titanium oxides include Li _a TiM _b Nb _{2 ± β} O _{7 ± σ} (0 ≦ a ≦ 5, 0 ≦ b ≦ 0.3, 0 ≦ β ≦ 0.3, 0 ≦ σ ≦ 0.3, M includes those represented by at least one element selected from the group consisting of Fe, V, Mo and Ta).

An example of sodium niobium titanium oxide is the general formula Li _{2 + v} Na _2-w M1 _x Ti _{6-y-z Nby} M2 _z O _{14 + δ} (0 ≦ v ≦ 4, 0 <w <2, 0 ≦ x <2, 0 <y <6, 0 ≦ z <3, y + z <6, −0.5 ≦ δ ≦ 0.5, M1 contains at least one selected from Cs, K, Sr, Ba, Ca, and M2 is Includes an orthodox Na-containing niobium-titanium composite oxide represented by (including at least one selected from Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, Al).

Examples of the oxide that can be contained in addition to the above-mentioned titanium oxide and tungsten oxide include lithium titanium oxide having a spinel structure as a more preferable compound. Since the lithium titanium oxide having a spinel structure has a lithium occlusion potential in the range of 1.4 V (vs. Li / Li ⁺ ) or more and 2 V (vs. Li / Li ⁺ ) or less, for example, lithium manganese oxidation as a positive electrode active material. It is more preferable to combine it with an object because a high electromotive force can be obtained and the volume change due to the charge / discharge reaction is extremely small.

The composition of the oxide contained in the negative electrode can be measured by ICP emission spectroscopy. To measure the composition of the oxide by ICP emission spectroscopy, the procedure is specifically as follows.

First, the negative electrode is taken out from the secondary battery and cleaned by the procedure described above. The washed negative electrode is placed in a suitable solvent and irradiated with ultrasonic waves. For example, the negative electrode oxide layer can be peeled off from the metal body containing zinc by putting the negative electrode in the ethyl methyl carbonate put in the glass beaker and vibrating it in the ultrasonic cleaner. Next, vacuum drying is performed to dry the peeled negative electrode oxide layer. By pulverizing the obtained negative electrode oxide layer with a mortar or pestle, a powder containing the target oxide, a conductive agent, a binder and the like can be obtained. By dissolving this powder with an acid, a liquid sample containing an oxide can be prepared. At this time, hydrochloric acid, nitric acid, sulfuric acid, hydrogen fluoride and the like can be used as the acid. By subjecting this liquid sample to ICP emission spectroscopic analysis, the composition of the oxide can be specified.

To determine whether the oxide contains at least one of titanium oxide and tungsten oxide, observe the peak position by X-ray diffraction, and check the peak position of titanium oxide and oxidation in the X-ray diffraction database. It can be investigated by confirming the matching with the peak position derived from the crystal structure of tungsten.

The oxide can be contained in the negative electrode oxide layer in the form of particles. The negative electrode oxide can be a single primary particle, a secondary particle which is an aggregate of the primary particles, or a mixture of a single primary particle and a secondary particle. The shape of the particles is not particularly limited, and may be, for example, spherical, elliptical, flat, fibrous, or the like.

The average particle size (diameter) of the secondary particles of the oxide is preferably 3 μm or more. More preferably, it is 5 μm or more and 20 μm or less. Within this range, the surface area of the oxide is small, so that the effect of suppressing hydrogen generation can be enhanced.

Negative electrode oxides having an average particle size of secondary particles of 3 μm or more can be obtained, for example, by the following method. First, an oxide raw material is reacted and synthesized to prepare an oxide precursor having an average particle diameter of 1 μm or less. After that, the oxide precursor is fired and then crushed using a crusher such as a ball mill or a jet mill. Then, in the calcination process, the oxide precursor is aggregated and grown into secondary particles having a large particle size.

The average primary particle size of the oxide contained in the negative electrode is preferably 0.01 μm or more and 0.1 μm or less. When the average primary particle size of the oxide is within this range, it is possible to reduce the precipitation diameter of zinc dendrites, and it is possible to suppress an increase in overvoltage and a short circuit due to dendrite precipitation. Further, by setting the crystallite diameter of the oxide to 1 nm or more and 50 nm or less, the state becomes close to amorphous, and the potential concentration can be suppressed, so that the precipitation of dendrite can be further suppressed. The crystallite diameter can be calculated by the Scherrer equation calculated from the main peak observed in the wide-angle X-ray scattering measurement on the oxide powder or the electrode.

It is desirable that the specific surface area of the oxide by the BET method by N ₂ precipitation is in the range of 10 m ² / g or more and 350 m ² / g or less. As a result, since the reaction surface increases, the precipitation area on the zinc oxide surface increases, so that dendrite-like precipitation can be further suppressed, and the zinc precipitation amount increases, so that the secondary battery You can increase the capacity of. If it is less than 10 m ² / g, since there are few reaction surfaces on which zinc can be dissolved and deposited, a discharge capacity cannot be obtained and dendrites are likely to be formed, which is not preferable. Further, if it exceeds 350 m ² / g, it becomes amorphous and the skeleton structure of the oxide is collapsed, so that the occlusion and release of lithium cannot proceed reversibly, which is not preferable. Further, a more preferable range of the specific surface area is 10 m ² / g or more and 300 m ² / g or less. This is because it has a sufficient area for advancing the zinc precipitation and dissolution reaction, and the reversible zinc precipitation and dissolution reaction can be promoted while suppressing the precipitation of dendrite.

Further, the negative electrode oxide layer may be a porous layer containing a negative electrode oxide, a conductive agent and a binder supported on a metal body containing zinc.

The specific surface area of the oxide is measured by adsorbing a molecule having a known adsorption area on the surface of the powder particles at the temperature of liquid nitrogen and obtaining the specific surface area of the sample from the amount thereof. The most commonly used is the BET method by low-temperature, low-humidity physical adsorption of an inert gas. This BET method is a method based on the BET theory, which is the most famous method for calculating the specific surface area, which is an extension of the Langmuir theory, which is a single-layer adsorption theory, to multi-layer adsorption. The specific surface area obtained by this is referred to as a BET specific surface area.

When the oxide is taken out from the negative electrode of the secondary battery and the specific surface area is confirmed, it is carried out by the following method. First, the negative electrode is taken out from the secondary battery and thoroughly washed. Next, the negative electrode oxide layer is peeled off from the removed negative electrode. The peeled negative electrode oxide layer is crushed in a mortar to make a powder. The obtained powder is measured by the BET method. At this time, if the amount of the conductive agent or the binder is large, it may not be possible to obtain an accurate specific surface area value of the oxide contained in the negative electrode. In such a case, it is preferable to dissolve the binder using, for example, a solvent in which the binder is soluble, and separate the accessory agent by centrifugation to perform the evaluation. At this time, care should be taken not to change the surface morphology of the oxide. The change in surface shape due to the separation process and whether or not the separation is sufficient should be determined using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Can be done.

The porosity of the negative electrode (excluding the metal body containing zinc) is preferably in the range of 20% to 50%. As a result, it is possible to obtain a negative electrode having excellent affinity between the negative electrode and the electrolyte and having a high density. A more preferred range of porosity is 25% -40%.

Examples of the conductive agent include carbon materials such as acetylene black, carbon black, coke, carbon fiber and graphite, and metal powders such as nickel and zinc. The type of the conductive agent can be one type or two or more types. Since hydrogen is generated from the carbon material itself, it is desirable to use a metal powder as the conductive agent.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, ethylene-butadiene rubber, polypropylene (PP), polyethylene (PE), carboxymethyl cellulose (CMC), and polyimide ( PI), polyacrylicimide (PAI) and the like can be mentioned. The type of binder may be one type or two or more types.

Regarding the compounding ratio of the oxide, the conductive agent and the binder in the negative electrode oxide layer, the oxide is 70% by weight or more and 95% by weight or less, the conductive agent is 3% by weight or more and 20% by weight or less, and the binder is 2% by weight. It is preferably in the range of% or more and 10% by weight or less. When the compounding ratio of the conductive agent is 3% by weight or more, the conductivity of the negative electrode can be improved, and when it is 20% by weight or less, the decomposition of the electrolyte on the surface of the conductive agent can be reduced. When the compounding ratio of the binder is 2% by weight or more, sufficient electrode strength can be obtained, and when it is 10% by weight or less, the insulating portion of the electrode can be reduced.

The negative electrode can be manufactured, for example, as follows. First, an oxide, a conductive agent and a binder are dispersed in an appropriate solvent to prepare a slurry. This slurry is applied to a metal body containing zinc and the coating film is dried to form a negative electrode oxide layer on the metal body containing zinc. Here, for example, the slurry may be applied to one surface on the metal body containing zinc, or the slurry may be applied to one surface on the metal body containing zinc and its back surface. Next, the negative electrode can be produced by applying a press such as a heating press to the metal body containing zinc and the negative electrode oxide layer.

2) Positive electrode This positive electrode has a positive electrode current collector and a positive electrode mixture layer (positive electrode active material-containing layer) supported on one or both sides of the positive electrode current collector and containing an active material, a conductive agent and a binder. be able to.

As the positive electrode current collector, it is preferable to use a foil, a porous body, or a mesh made of a metal such as stainless steel, Al, or Ti. In order to prevent corrosion of the current collector due to the reaction between the current collector and the electrolyte, the surface of the current collector may be coated with a different element. It may also contain zinc.

As the positive electrode active material, a substance capable of occluding and releasing lithium or sodium can be used. The positive electrode may contain one kind of positive electrode active material, or may contain two or more kinds of positive electrode active materials. Examples of positive electrode active materials include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt aluminum composite oxide, lithium nickel cobalt manganese composite oxide, spinel type lithium manganese nickel composite oxide, and lithium manganese cobalt composite oxide. , Lithium iron oxide, lithium fluorinated iron sulfate, phosphoric acid compounds having an olivine crystal structure (for example, Li _x FePO ₄ (0 ≦ x ≦ 1), Li _x MnPO ₄ (0 ≦ x ≦ 1)) and the like. .. The phosphoric acid compound having an olivine crystal structure has excellent thermal stability.

Examples of positive electrode active materials that can obtain a high positive electrode potential are described below. For example, lithium manganese composite oxides such as Li _x Mn ₂ O ₄ (0 <x ≦ 1) and Li _x MnO ₂ (0 <x ≦ 1) having a spinel structure, for example, Li _x Ni _{1-y Ally} O ₂ (0). Lithium nickel-aluminum composite oxides such as <x ≦ 1, 0 <y ≦ 1), such as lithium cobalt composite oxides such as Li _x CoO ₂ (0 <x ≦ 1), such as Li _x Ni _1-yz Co. Lithium nickel-cobalt composite oxides such as _y Mn _z O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 0 ≦ z ≦ 1), such as Li _x Mn _y Co _1-y O ₂ (0 <x ≦ 1). , 0 <y ≦ 1) and other lithium manganese cobalt composite oxides, for example spinel type lithium manganese nickel composite oxides such as Li _x Mn _{2-y Ny} O ₄ (0 <x ≦ 1, 0 <y <2). For example, Li _x FePO ₄ (0 <x ≦ 1), Li _x Fe _1-y Mn _y PO ₄ (0 <x ≦ 1, 0 ≦ y ≦ 1), Li _x CoPO ₄ (0 <x ≦ 1), etc. Examples thereof include a lithium phosphorus oxide having an olivine structure and iron fluorinated iron sulfate (for example, Li _x FeSO ₄ F (0 <x ≦ 1)).

In addition, sodium manganese composite oxide, sodium nickel composite oxide, Natrim cobalt composite oxide, Natrim nickel cobalt manganese composite oxide, sodium iron composite oxide, sodium phosphate oxide (for example, iron sodium phosphate, vanadium sodium phosphate). ), Sodium iron manganese composite oxide, sodium nickel titanium composite oxide, sodium nickel iron composite oxide, sodium nickel manganese composite oxide and the like.

Examples of preferred positive electrode active materials include iron composite oxides (eg, Ny FeO ₂ , 0 ≦ _y ≦ 1), iron manganese composite oxides (eg, _Ny Fe _1-x Mn _x O ₂ , 0 <x <1, 0 ≦ y ≦ 1), nickel-titanium composite oxide (for example, Na _y Ni _1-x Ti _x O ₂ , 0 <x <1, 0 ≦ y ≦ 1), nickel iron composite oxide (for example, Na _y Ni _1- ). _x Fe _x O ₂ , 0 <x <1, 0 ≦ _y ≦ 1), nickel-manganese composite oxide (eg, Ny Ni _1-x Mn _x O ₂ , 0 <x <1, 0 ≦ y ≦ 1), Nickel manganese iron composite oxide (for example, Ny Ni _{1-x-z Mn x} Fe _z O ₂ , 0 <x <1, 0 ≦ y ≦ 1, 0 <z <1, 0 <1-x-z <1 ), Iron phosphate (eg, Nay FePO ₄ , 0 ≦ _y ≦ 1).

The particles of the positive electrode active material can be single primary particles, secondary particles that are aggregates of primary particles, or both single primary particles and secondary particles. The average particle diameter (diameter) of the primary particles of the positive electrode active material is preferably 10 μm or less, more preferably 0.1 μm to 5 μm. The average particle diameter (diameter) of the secondary particles of the positive electrode active material is preferably 100 μm or less, and more preferably 10 μm to 50 μm.

It is preferable that at least a part of the particle surface of the positive electrode active material is covered with a carbon material. The carbon material can be in the form of a layered structure, a particle structure, or an aggregate of particles.

Examples of the conductive agent for increasing the electron conductivity of the positive electrode mixture layer and suppressing the contact resistance with the current collector include acetylene black, carbon black, graphite, and carbon fibers having an average fiber diameter of 1 μm or less. can. The type of the conductive agent can be one type or two or more types.

The binder for binding the active material and the conductive agent is, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, ethylene-butadiene rubber (SBR), polypropylene (PP). , Polyethylene (PE), Carboxymethylcellulose (CMC), Polyimide (PI), Polyacrylicimide (PAI). The type of binder may be one type or two or more types.

Regarding the compounding ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode mixture layer, the positive electrode active material is 70% by weight or more and 95% by weight or less, the conductive agent is 3% by weight or more and 20% by weight or less, and the binder is. It is preferably in the range of 2% by weight or more and 10% by weight or less. When the compounding ratio of the conductive agent is 3% by weight or more, the conductivity of the positive electrode can be improved, and when it is 20% by weight or less, the decomposition of the electrolyte on the surface of the conductive agent can be reduced. When the compounding ratio of the binder is 2% by weight or more, sufficient electrode strength can be obtained, and when it is 10% by weight or less, the insulating portion of the electrode can be reduced.

The positive electrode can be produced, for example, as follows. First, a positive electrode active material, a conductive agent and a binder are dispersed in an appropriate solvent to prepare a slurry. This slurry is applied to the current collector and the coating film is dried to form a positive electrode mixture layer on the current collector. Here, for example, the slurry may be applied to one surface on the current collector, or the slurry may be applied to one surface on the current collector and its back surface. Next, the positive electrode can be produced by applying a press such as a heating press to the current collector and the positive electrode mixture layer.

Further, the positive electrode mixture layer may contain zinc in the form of particles.
3) Electrolyte Examples of the electrolyte include an electrolyte containing zinc, a lithium salt, and an aqueous solvent, and a gel-like electrolyte in which a polymer material is compounded with the electrolyte. This electrolyte is also called an aqueous electrolyte. Examples of the above-mentioned polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO) and the like. Here, the electrolyte will be described. Zinc may be a simple substance of metal, or one or more selected from the group consisting of elemental metals, oxides, chlorides, sulfides, nitrates, sulfates, and hydroxide salts. It may be a combination of. Zinc can also be present in the electrolyte as an ion or as a solid.

As the lithium salt, one that dissociates when dissolved in an aqueous solvent to generate an anion can be used. In particular, a lithium salt that dissociates between Li ions and anions is preferable. Examples of such lithium salts include LiNO ₃ , LiCl, Li ₂ SO ₄ , LiOH and the like.

In addition, the lithium salt that dissociates into Li ions and anions has a relatively high solubility in an aqueous solvent. Therefore, an electrolyte having a high anion concentration of 1M-10M and good Li ion diffusivity can be obtained.

The electrolyte containing NO _3- ^and / or Cl- can be used in a wide range of anion concentrations of about 0.1M-10M. From the viewpoint of achieving both ionic conductivity and lithium equilibrium potential, the concentration of these anions is preferably as high as 3M-12M. It is more preferable that the anion concentration of the electrolyte containing NO _3- or Cl ^- is 8M ^- 12M.

The electrolyte containing LiSO _4- ^and / or SO _4-2- can be used in the range of anion concentration of about 0.05M ^- 2.5M. From the viewpoint of ionic conductivity, the concentration of these anions is preferably as high as 1.5M-2.5M.

The OH ^- concentration in the electrolyte is preferably ^10-10 M-0.1 M. The electrolyte can include at least one anion selected from the group consisting of NO _3- , ^{Cl- ,} LiSO _{4-, SO 4 2-} ^{, and OH-} . These anions contained in the electrolyte may be one kind or may contain two or more kinds of anions. The electrolyte as a solute is referred to as a first electrolyte for convenience in order to distinguish between the electrolyte used to collectively refer to the electrolyte as a solution and the gel-like electrolyte and the electrolyte as a solute (for example, a lithium salt). In some cases.

As the aqueous solvent, a solution containing water can be used. Here, the solution containing water may be pure water, or may be a mixed solution of water and a substance other than water, or a mixed solvent.

The amount of the aqueous solvent (for example, the amount of water in the aqueous solvent) is preferably 1 mol or more with respect to 1 mol of the salt as the solute. A more preferable form is that the amount of the aqueous solvent with respect to 1 mol of the salt as a solute is 3.5 mol or more.

Also, the electrolyte can contain both lithium and sodium ions.

The pH of the electrolyte is preferably 4 or more and 13 or less. When the pH is less than 4, the electrolyte is acidic, so that the decomposition of the active substance is likely to proceed. When the pH exceeds 13, the oxygen evolution overvoltage at the positive electrode decreases, so that the electrolysis of the aqueous solvent easily proceeds.

The solute in the electrolyte, i.e., the first electrolyte, can be qualitatively and quantified, for example, by ion chromatography. The ion chromatograph method is particularly preferable as an analytical method because of its high sensitivity.

An example of specific measurement conditions for qualitative quantitative analysis of the solute contained in the electrolyte by the ion chromatograph method is shown below:
System: Prominence HIC-SP
Analytical column: Shim-pack IC-SA3
Guard column: Shim-pack IC-SA3 (G)
Eluent: 3.6 mmol / L sodium carbonate aqueous solution Flow rate: 0.8 mL / min
Column temperature: 45 ° C
Injection volume: 50 μL
Detection: Electrical conductivity.

Whether or not water is contained in the electrolyte can be confirmed by gas chromatography-mass spectrometry (GC-MS) measurement. Further, the calculation of the water content in the electrolyte can be measured by, for example, ICP emission analysis. In addition, the number of moles of the solvent can be calculated by measuring the specific gravity of the electrolyte. The same electrolyte may be used on the positive electrode side and the negative electrode side, or different electrolytes may be used. When different electrolytes are used on the positive electrode side and the negative electrode side, the pH of the electrolyte on the positive electrode is preferably 1 or more and 7 or less. When the pH of the electrolyte of the positive electrode is 8 or more, the oxygen evolution reaction caused by the electrolysis of water proceeds advantageously, and when the pH is less than 1, the decomposition of the active substance proceeds, which is not preferable. The pH of the electrolyte of the negative electrode is preferably 7 or more, and if it is less than 7, the hydrogen generation reaction caused by the electrolysis of water proceeds advantageously, which is not preferable.

Additives can also be added to the electrolyte. For example, a metal containing zinc can be added. When a metal containing zinc is used as an additive (additional metal) to the electrolyte, if the concentration of the metal contained in the electrolyte becomes excessive, the zinc precipitation reaction by electrodeposition increases more than the zinc precipitation reaction accompanied by self-discharge. Therefore, be careful not to make the metal concentration in the electrolyte excessive. To add the additive, it may be added as a simple substance metal or oxide powder when the slurry of the negative electrode is prepared, added to the electrolyte, or both may be used at the same time. Further, when zinc is contained in the current collector or the container described later, it may be used together with the additive in the same manner. The form of the metal to be added may be a single metal or any one selected from the group consisting of oxides, chlorides, sulfides, nitrates, sulfates and hydroxide salts. .. Alternatively, the form of the added metal may be a combination of two or more of these. In addition, the added metal can be present in the electrolyte as an ion or a solid. The added metal can be examined by ICP.

In the electrolyte, the mol concentration ratio Zn / Li of zinc and lithium contained in the aqueous electrolyte is 1.0 × ^10-5 or more and 0.3 or less. When Zn / Li = 0.3 or less, lithium occlusion occurs preferentially over zinc precipitation in the charging process. For this reason, the precipitation of zinc accompanying the self-discharge process proceeds preferentially in the shape of a coating rather than the shape of the dendrite, so that the precipitation of zinc dendrite can be suppressed. The more preferable molar concentration ratio Zn / Li of zinc to lithium is 1.0 × 10 ^-4 or more and 0.1 or less. When the mol concentration ratio Zn / Li is less than 1.0 × ^10-5 , the zinc concentration is too low with respect to the lithium concentration, and it becomes difficult to smoothly dissolve and precipitate zinc. Further, when the mol concentration ratio Zn / Li is larger than 0.3, the zinc concentration is too high with respect to the lithium concentration, and the zinc electrodeposition tends to cause dendrite to be deposited, which is not preferable.

The upper limit of the current value at the time of charging the secondary battery is preferably 1 C or less, more preferably 0.5 C or less. At a current value exceeding 1C, the balance between Li insertion and zinc precipitation associated with self-discharge cannot be maintained, and Li insertion proceeds unilaterally. However, by setting the current value low, it is possible to increase the amount of self-discharge reaction during charging to increase the amount of zinc deposited due to the negative electrode self-discharge during charging. As a result, it is possible to increase the charge capacity due to zinc precipitation on the negative electrode.

4) Separator A separator can be placed between the positive electrode and the negative electrode. By forming the separator with an insulating material, it is possible to prevent the positive electrode and the negative electrode from electrically contacting each other. Further, it is desirable to use a shape in which the electrolyte can move between the positive electrode and the negative electrode. Examples of separators include non-woven fabrics, films, paper and the like. Examples of the constituent materials of the separator include polyolefins such as polyethylene and polypropylene, and cellulose. Examples of preferred separators include non-woven fabrics containing cellulose fibers and porous films containing polyolefin fibers. The porosity of the separator is preferably 60% or more. The fiber diameter is preferably 10 μm or less. By setting the fiber diameter to 10 μm or less, the affinity of the separator with respect to the electrolyte is improved, so that the battery resistance can be reduced. A more preferable range of the fiber diameter is 3 μm or less. A cellulose fiber-containing non-woven fabric having a porosity of 60% or more has good impregnation property of an electrolyte and can exhibit high output performance from low temperature to high temperature. In addition, it does not react with the negative electrode even during long-term charge storage, float charging, and overcharging, and a short circuit between the negative electrode and the positive electrode does not occur due to dendrite precipitation of the lithium metal. A more preferable range is 62% to 80%.

Further, a solid electrolyte can also be used as the separator. As the solid electrolyte, LATP (Li _{1 + x} Al _x Ti _2-x (PO ₄ ) 3; 0.1 ≦ x ≦ 0.4) having a NASICON type skeleton having lithium ion conductivity and amorphous LIPON (Li _2. Oxides such as ₉ PO _3.3 N _0.46 ) and garnet-type LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) are preferred. By including such a solid electrolyte, it is possible to maintain the strength of the separator and suppress an internal short circuit due to dendrite precipitation, so that the life can be further extended.

Further, β-alumina, Na _{1 + x} Zr ₂ Si _x P _3-x O ₁₂ (0 ≦ x ≦ 3), NaAlSi ₃ O ₈ and the like can also be mentioned.

The separator preferably has a thickness of 20 μm or more and 200 μm or less and a density of 0.2 g / cm ³ or more and 0.9 g / cm ³ or less. Within this range, a balance between mechanical strength and reduction of battery resistance can be achieved, and a secondary battery having high output and suppressed internal short circuit can be provided. In addition, the separator has little heat shrinkage in a high temperature environment, and good high temperature storage performance can be obtained.

5) Container As the container in which the positive electrode, the negative electrode and the electrolyte are housed, a metal container, a laminated film container, or a resin container such as polyethylene or polypropylene can be used.

As the metal container, a metal can made of nickel, iron, stainless steel, zinc or the like and having a square or cylindrical shape can be used.

The plate thickness of each of the resin container and the metal container is preferably 1 mm or less, and a more preferable range is 0.5 mm or less. A more preferable range is 0.3 mm or less. Further, it is desirable that the lower limit of the plate thickness is 0.05 mm.

Examples of the laminated film include a multilayer film in which a metal layer is coated with a resin layer. Examples of metal layers include stainless steel foils, aluminum foils, aluminum alloy foils. As the resin layer, a polymer such as polypropylene (PP), polyethylene (PE), nylon, or polyethylene terephthalate (PET) can be used. The preferred range of thickness of the laminated film is 0.5 mm or less. A more preferable range is 0.2 mm or less. Further, it is desirable that the lower limit of the thickness of the laminated film is 0.01 mm.

In addition, zinc may be contained in the container. Including here means, for example, making the container zinc itself, making the container an alloy containing zinc, applying zinc to the inside of the container, or coating the inside of the container with zinc. By doing so, it is possible to come into contact with the electrolyte.

The secondary battery according to the embodiment can be applied to various types of secondary batteries such as a square type, a cylindrical type, a flat type, a thin type, and a coin type. Further, it is preferable that the secondary battery has a bipolar structure. This has the advantage that a plurality of series of cells can be produced by one cell.

An example of the secondary battery according to the embodiment will be described with reference to FIGS. 1 to 4.

1 and 2 show an example of a secondary battery using a metal container.

FIG. 1 is a partially cutaway sectional view of a secondary battery according to an embodiment. FIG. 2 is a side view of the battery of FIG. More specifically, FIG. 2 is a cross-sectional view taken along the line II-II of the square secondary battery shown in FIG.

The electrode group 1 is housed in a rectangular tubular metal container 2. The electrode group 1 has a structure in which a positive electrode 3 and a negative electrode 4 are spirally wound so as to have a flat shape with a separator 5 interposed therebetween. The electrolyte (not shown) is held in the electrode group 1. As shown in FIG. 2, band-shaped positive electrode leads 6 are electrically connected to each of a plurality of ends of the positive electrode 3 located on the end face of the electrode group 1. Further, strip-shaped negative electrode leads 7 are electrically connected to each of a plurality of ends of the negative electrode 4 located on the end face. The plurality of positive electrode leads 6 are electrically connected to the positive electrode conductive tab 8 in a bundled state. The positive electrode terminal is composed of the positive electrode lead 6 and the positive electrode conductive tab 8. Further, the negative electrode leads 7 are connected to the negative electrode conductive tab 9 in a bundled state. The negative electrode terminal is composed of the negative electrode lead 7 and the negative electrode conductive tab 9. The metal sealing plate 10 is fixed to the opening of the metal container 2 by welding or the like. The positive electrode conductive tab 8 and the negative electrode conductive tab 9 are each drawn out from the take-out hole provided in the sealing plate 10. A positive electrode gasket 18 and a negative electrode gasket 19 are arranged on the inner peripheral surface of each take-out hole of the sealing plate 10 in order to avoid a short circuit due to contact with the positive electrode conductive tab 8 and the negative electrode conductive tab 9, respectively. By arranging the positive electrode gasket 18 and the negative electrode gasket 19, the airtightness of the square secondary battery can be maintained.

A control valve 22 (safety valve) is arranged on the sealing plate 10. When the internal pressure in the battery cell increases due to the gas generated by the electrolysis of the aqueous solvent, the generated gas can be dissipated from the control valve 22 to the outside. As the control valve 22, for example, a return type valve that operates when the internal pressure becomes higher than the set value and functions as a sealing plug when the internal pressure drops can be used. Alternatively, a non-return type control valve may be used in which the function as a sealing plug is not restored once it is operated. In FIG. 1, the control valve 22 is arranged in the center of the sealing plate 10, but the position of the control valve 22 may be the end of the sealing plate 10. The control valve 22 may be omitted.

Further, the sealing plate 10 is provided with a liquid injection port 23. The electrolyte can be injected through the injection port 23. The liquid injection port 23 is closed by the sealing plug 24 after the electrolyte is injected. The liquid injection port 23 and the sealing plug 24 may be omitted.

3 and 4 show an example of a secondary battery using a laminated film exterior member.

The laminated electrode group 1 is housed in a bag-shaped container 2 made of a laminated film having a metal layer interposed between two resin films. As shown in FIG. 4, the laminated electrode group 1 has a structure in which a positive electrode 3 and a negative electrode 4 are alternately laminated with a separator 5 interposed therebetween. There are a plurality of positive electrodes 3, each of which comprises a current collector 3a and a positive electrode active material-containing layer 3b formed on both sides of the current collector 3a. There are a plurality of negative electrodes 4, each of which includes a metal body 4a containing zinc and a negative electrode oxide-containing layer 4b formed on both sides of the metal body 4a containing zinc. One side of the metal body 4a including zinc of each negative electrode 4 protrudes from the positive electrode 3. The metal body 4a provided with the protruding zinc is electrically connected to the strip-shaped negative electrode terminal 12. The tip of the strip-shaped negative electrode terminal 12 is pulled out from the container 2. Further, although not shown, in the current collector 3a of the positive electrode 3, a side located on the opposite side of the protruding side of the metal body 4a containing zinc protrudes from the negative electrode 4. The current collector 3a protruding from the negative electrode 4 is electrically connected to the band-shaped positive electrode terminal 13. The tip of the strip-shaped positive electrode terminal 13 is located on the side opposite to the negative electrode terminal 12, and is drawn out from the side of the container 2.

The secondary battery shown in FIGS. 3 and 4 may be provided with a safety valve for releasing the hydrogen gas generated in the container to the outside. The safety valve can be used with either a return type that operates when the internal pressure rises above the set value and functions as a sealing plug when the internal pressure drops, or a non-returning type that does not recover the function as a sealing plug once it operates. Is. Further, although the secondary batteries shown in FIGS. 1 to 4 are closed type, they can be an open system when provided with a circulation system for returning hydrogen gas to water.

According to the embodiment described above, the lithium zinc secondary battery has a positive electrode, a metal body in which zinc is dissolved and precipitated, and a negative electrode having an oxide on at least a part of the surface of the metal body. It is a secondary battery equipped with an aqueous electrolyte containing zinc and lithium salt and a separator existing between the positive and negative electrodes, and the oxide is -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) or less. Lithium is absorbed and released in the potential region of, and the specific surface area of the oxide is 10 m ² / g or more and 350 m ² / g or less, and the mol concentration ratio Zn / Li of zinc and lithium contained in the electrolyte is 1.0 × 10 ^-5 . It is more than 0.3 and less than. With such a secondary battery, it is possible to suppress the generation of hydrogen due to self-discharge and the precipitation of zinc dendrite on the surface of the negative electrode during charging, so that the secondary battery is short-circuited at the negative electrode. Can be prevented. Therefore, stable charging / discharging is possible, and a secondary battery having high cycle life performance can be provided.

(Second embodiment)
According to the second embodiment, it is possible to provide an assembled battery having a secondary battery as a unit cell. As the secondary battery, the lithium zinc secondary battery according to the first embodiment can be used.

Examples of assembled batteries include a plurality of unit cells electrically connected in series or in parallel as a constituent unit, a unit consisting of a plurality of electrically connected unit cells connected in series, or electrically connected in parallel. Examples include those including a unit composed of a plurality of unit cells.

The assembled battery may be housed in a housing. As the housing, a metal can made of aluminum alloy, iron, stainless steel, etc., a plastic container, or the like can be used. Further, it is desirable that the plate thickness of the container is 0.5 mm or more.

Examples of the form in which a plurality of secondary batteries are electrically connected in series or in parallel include those in which a plurality of secondary batteries each having a container are electrically connected in series or in parallel, and are housed in a common housing. This includes those in which a plurality of electrodes are electrically connected in series or in parallel. A specific example of the former is to connect the positive electrode terminal and the negative electrode terminal of a plurality of secondary batteries with a metal bus bar (for example, aluminum, nickel, copper). A specific example of the latter is to accommodate a plurality of electrode groups in a single housing in a state where they are electrochemically insulated by a partition wall, and these electrode groups are electrically connected in series. By setting the number of batteries electrically connected in series in the range of 5 to 7, the voltage compatibility with the lead storage battery is improved. In order to improve the voltage compatibility with the lead storage battery, a configuration in which 5 or 6 unit cells are connected in series is preferable.

An example of the assembled battery will be described with reference to FIG. The assembled battery 31 shown in FIG. ₅ includes a plurality of square secondary batteries (for example, FIGS. 1 and 2) 32 ₁ to 325 according to the first embodiment as unit cells. The positive electrode conductive tab ₈ of the battery 32 ₁ and the negative electrode conductive tab 9 of the battery 322 located next to the positive electrode conductive tab 8 are electrically connected by a lead 33. Further, the positive electrode conductive tab ₈ of the battery 322 and the negative electrode conductive tab ₉ of the battery 323 located next to the positive electrode conductive tab 8 are electrically connected by the lead 33. _In this way, the batteries 32 ₁ to 325 are connected in series.

According to the assembled battery according to the second embodiment, since the secondary battery according to the first embodiment is included, it is possible to provide an assembled battery having a high cycle life performance.

(Third embodiment)
According to the third embodiment, a battery pack is provided. This battery pack comprises the lithium-zinc secondary battery according to the first embodiment.

The battery pack according to the third embodiment may include one or a plurality of secondary batteries (unit cells) according to the first embodiment described above. The plurality of secondary batteries that can be included in the battery pack according to the third embodiment can be electrically connected in series, in parallel, or in combination of series and parallel. Further, the plurality of secondary batteries can also form an electrically connected assembled battery. When the assembled battery is composed of a plurality of secondary batteries, the assembled battery according to the second embodiment can be used.

The battery pack according to the third embodiment may further include a protection circuit. The protection circuit controls the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (for example, an electronic device, a vehicle such as an automobile, etc.) can be used as a protection circuit for the battery pack.

Further, the battery pack according to the third embodiment may further include an external terminal for energization. The external terminal for energization is for outputting the current from the secondary battery to the outside and / or for inputting the current to the unit cell. In other words, when the battery pack is used as a power source, current is supplied to the outside through an external terminal for energization. Further, when charging the battery pack, the charging current (including the regenerative energy of the power of a vehicle such as an automobile) is supplied to the battery pack through an external terminal for energization.

An example of the battery pack according to the third embodiment will be described with reference to FIG. FIG. 6 is a schematic perspective view showing an example of a battery pack.

The battery pack 40 includes, for example, an assembled battery composed of the secondary batteries shown in FIGS. 3 and 4. The battery pack 40 includes a housing 41 and an assembled battery 42 housed in the housing 41. The assembled battery 42 is formed by electrically connecting a plurality of (for example, _five ) secondary batteries 431 to ₄₃₅ in series. The secondary batteries 43 ₁ to ₄₃₅ are laminated in the thickness direction. The housing 41 has openings 44 on each of the upper portion and the four side surfaces. The side surface of the secondary batteries 43 ₁ to 435 from which the positive and negative terminals ₁₂ and 13 project is exposed to the opening 44 of the housing 41. The output positive electrode terminal 45 of the assembled battery 42 has a band shape, one end of which is electrically connected to the positive electrode terminal 13 of any of the secondary batteries 431 to ₄₃₅ , and the _other end of which is the opening 44 of the housing 41. It protrudes from the upper part of the housing 41. On the other hand, the output negative electrode terminal 46 of the assembled battery 42 has a band shape, one end of which is electrically connected to the negative electrode terminal ₁₂ of any of the secondary batteries 431 to 435, and the _other end of which is an opening of the housing 41. It protrudes from the portion 44 and protrudes from the upper part of the housing 41.

Another example of the battery pack according to the third embodiment will be described in detail with reference to FIGS. 7 and 8. FIG. 7 is an exploded perspective view of a battery pack of another example according to the third embodiment. FIG. 8 is a block diagram showing an electric circuit of the battery pack of FIG. 7.

A plurality of unit cells 51 composed of a flat secondary battery are laminated so that the negative electrode terminals 52 and the positive electrode terminals 53 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 54 to form an assembled battery. It constitutes 55. These unit cells 51 are electrically connected in series with each other as shown in FIG.

The printed wiring board 56 is arranged so as to face the side surface of the unit cell 51 in which the negative electrode terminal 52 and the positive electrode terminal 53 extend. As shown in FIG. 8, the printed wiring board 56 is equipped with a thermistor 57, a protection circuit 58, and an external terminal 59 for energization. An insulating plate (not shown) is attached to the surface of the printed wiring board 56 facing the assembled battery 55 in order to avoid unnecessary connection with the wiring of the assembled battery 55.

The positive electrode lead 60 is connected to a positive electrode terminal 53 located at the bottom layer of the assembled battery 55, and its tip is inserted into a positive electrode connector 61 of a printed wiring board 56 and electrically connected. The negative electrode lead 62 is connected to the negative electrode terminal 52 located on the uppermost layer of the assembled battery 55, and the tip thereof is inserted into the negative electrode side connector 63 of the printed wiring board 56 and electrically connected. These connectors 61 and 63 are connected to the protection circuit 58 through the wirings 64 and 65 formed on the printed wiring board 56.

The thermistor 57 detects the temperature of the unit cell 51, and the detection signal is transmitted to the protection circuit 58. The protection circuit 58 can cut off the positive wiring (positive electrode side wiring) 66a and the negative wiring (negative electrode side wiring) 66b between the protection circuit 58 and the external terminal 59 for energization under predetermined conditions. The predetermined condition is, for example, when the detection temperature of the thermistor 57 becomes equal to or higher than the predetermined temperature. Further, the predetermined condition is when overcharge, overdischarge, overcurrent, etc. of the unit cell 51 are detected. The detection of this overcharge or the like is performed on each unit cell 51 or the assembled battery 55. When detecting the individual unit cells 51, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 51. In the case of FIGS. 7 and 8, a wiring 67 for voltage detection is connected to each of the unit cells 51, and a detection signal is transmitted to the protection circuit 58 through these wiring 67.

A protective sheet 68 made of rubber or resin is arranged on each of the three side surfaces of the assembled battery 55 except for the side surface on which the positive electrode terminal 53 and the negative electrode terminal 52 protrude.

The assembled battery 55 is housed in the storage container 69 together with the protective sheet 68 and the printed wiring board 56. That is, the protective sheet 68 is arranged on both inner side surfaces in the long side direction and the inner side surface in the short side direction of the storage container 69, and the printed wiring board 56 is arranged on the inner side surface on the opposite side in the short side direction. The assembled battery 55 is located in a space surrounded by the protective sheet 68 and the printed wiring board 56. The lid 70 is attached to the upper surface of the storage container 69.

A heat-shrinkable tape may be used instead of the adhesive tape 54 to fix the assembled battery 55. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat-shrinkable tape is circulated, and then the heat-shrinkable tape is heat-shrinked to bind the assembled battery.

Although FIGS. 7 and 8 show a form in which the unit cells 51 are connected in series, they may be connected in parallel in order to increase the battery capacity. Alternatively, a series connection and a parallel connection may be combined. In addition, the assembled battery packs can be connected in series and / or in parallel.

In addition, the mode of the battery pack is appropriately changed depending on the application. The battery pack is preferably used for charging and discharging with a large current. Specifically, it is used as a power source for digital cameras, in-vehicle vehicles such as two-wheeled to four-wheeled hybrid electric vehicles, two-wheeled to four-wheeled electric vehicles, assisted bicycles, and railway vehicles, and as stationary batteries. Can be mentioned. In particular, it is suitable for in-vehicle use.

In a vehicle such as an automobile equipped with the battery pack according to the third embodiment, the battery pack recovers, for example, the regenerative energy of the power of the vehicle. The vehicle may include a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

According to the battery pack according to the third embodiment described above, it is possible to provide a battery pack having a high cycle life performance because the secondary battery of the first embodiment is included.

(Fourth Embodiment)
According to the fourth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the third embodiment.

In the vehicle according to the fourth embodiment, the battery pack recovers, for example, the regenerative energy of the power of the vehicle. The vehicle according to the fourth embodiment may include a mechanism (regenerator) that converts the kinetic energy of the vehicle into regenerative energy.

Examples of the vehicle according to the fourth embodiment include, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assisted bicycle, and a railroad vehicle.

The mounting position of the battery pack in the vehicle according to the fourth embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile as an example of a vehicle, the battery pack can be mounted in the engine room of the vehicle, behind the vehicle body, or under the seat.

Next, an example of the vehicle according to the fourth embodiment will be described with reference to the drawings.

FIG. 9 is a cross-sectional view schematically showing an example of the vehicle according to the fourth embodiment.

The vehicle 200 shown in FIG. 9 includes a vehicle body 201 and a battery pack 202. The battery pack 202 may be the battery pack according to the third embodiment.

The vehicle 200 shown in FIG. 9 is a four-wheeled vehicle. As the vehicle 200, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assisted bicycle, and a railroad vehicle can be used.

The vehicle 200 may be equipped with a plurality of battery packs 202. In this case, the battery pack 202 may be connected in series, may be connected in parallel, or may be connected in combination of series connection and parallel connection.

The battery pack 202 is mounted in an engine room located in front of the vehicle body 201. The mounting position of the battery pack 202 is not particularly limited. The battery pack 202 may be mounted behind the vehicle body 201 or under the seat. The battery pack 202 can be used as a power source for the vehicle 200. Further, the battery pack 202 can recover the regenerative energy of the power of the vehicle 200.

Next, an embodiment of the vehicle according to the fourth embodiment will be described with reference to FIG. 10.

FIG. 10 is a diagram schematically showing another example of the vehicle according to the fourth embodiment. The vehicle 300 shown in FIG. 10 is an electric vehicle.

The vehicle 300 shown in FIG. 10 includes a vehicle main body 301, a vehicle power supply 302, a vehicle ECU (Electric Control Unit) 380 which is an upper control means of the vehicle power supply 302, and an external terminal (external power supply). (Terminal for connecting to) 370, an inverter 340, and a drive motor 345 are provided.

The vehicle 300 mounts a vehicle power supply 302, for example, in the engine room, behind the vehicle body, or under the seat. In the vehicle 300 shown in FIG. 10, the mounting location of the vehicle power supply 302 is schematically shown.

The vehicle power supply 302 includes a plurality of (for example, three) battery packs 312a, 312b and 312c, a battery management unit (BMU) 311 and a communication bus 310.

The three battery packs 312a, 312b and 312c are electrically connected in series. The battery pack 312a includes an assembled battery 314a and an assembled battery monitoring device (VTM: Voltage Temperature Monitoring) 313a. The battery pack 312b includes an assembled battery 314b and an assembled battery monitoring device 313b. The battery pack 312c includes an assembled battery 314c and an assembled battery monitoring device 313c. The battery packs 312a, 312b, and 312c can be removed independently and replaced with another battery pack.

Each of the assembled batteries 314a to 314c includes a plurality of cells connected in series. At least one of the plurality of cell cells is the secondary battery according to the first embodiment. The assembled batteries 314a to 314c are charged and discharged through the positive electrode terminal 316 and the negative electrode terminal 317, respectively.

The battery management device 311 communicates with the assembled battery monitoring devices 313a to 313c in order to collect information on the maintenance of the vehicle power supply 302, and is included in the assembled batteries 314a to 314c included in the vehicle power supply 302. Collect information about battery voltage, temperature, etc.

A communication bus 310 is connected between the battery management device 311 and the assembled battery monitoring devices 313a to 313c. The communication bus 310 is configured to share a set of communication lines with a plurality of nodes (a battery management device and one or more set battery monitoring devices). The communication bus 310 is, for example, a communication bus configured based on the CAN (Control Area Network) standard.

The assembled battery monitoring devices 313a to 313c measure the voltage and temperature of the individual cells constituting the assembled batteries 314a to 314c based on a command by communication from the battery management device 311. However, the temperature can be measured only at a few points per set battery, and it is not necessary to measure the temperature of all the cells.

The vehicle power supply 302 may also have an electromagnetic contactor (eg, switch device 333 shown in FIG. 10) for turning on and off the electrical connection between the positive electrode terminal 316 and the negative electrode terminal 317. The switch device 333 is a precharge switch (not shown) that is turned on when the assembled batteries 314a to 314c are charged, and a main switch that is turned on when the output from the assembled batteries 314a to 314c is supplied to the load. (Not shown) is included. The precharge switch and the main switch include a relay circuit (not shown) that is turned on or off by a signal supplied to a coil located near the switch element.

The inverter 340 converts the input direct current voltage into a high voltage of three-phase alternating current (AC) for driving the motor. The three-phase output terminals of the inverter 340 are connected to the input terminals of each of the three phases of the drive motor 345. The inverter 340 controls the output voltage based on the control signal from the battery management device 311 or the vehicle ECU 380 for controlling the overall operation of the vehicle 300.

The drive motor 345 is rotated by the electric power supplied from the inverter 340. This rotation is transmitted to the axle and drive wheels W, for example, via a differential gear unit.

Although not shown, the vehicle 300 is provided with a regenerative braking mechanism (that is, a regenerator). The regenerative braking mechanism rotates the drive motor 345 when the vehicle 300 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 340 and converted into a direct current. The direct current is input to the vehicle power supply 302.

One terminal of the connection line L1 is connected to the negative electrode terminal 317 of the vehicle power supply 302 via a current detection unit (not shown) in the battery management device 311. The other terminal of the connection line L1 is connected to the negative electrode input terminal of the inverter 340.

One terminal of the connection line L2 is connected to the positive electrode terminal 316 of the vehicle power supply 302 via the switch device 333. The other terminal of the connection line L2 is connected to the positive electrode input terminal of the inverter 340.

The external terminal 370 is connected to the battery management device 311. The external terminal 370 can be connected to, for example, an external power source.

The vehicle ECU 380 manages the entire vehicle by coordinating and controlling the battery management device 311 together with other devices in response to an operation input from the driver or the like. Data transfer related to maintenance of the vehicle power supply 302, such as the remaining capacity of the vehicle power supply 302, is performed between the battery management device 311 and the vehicle ECU 380 via a communication line.

The vehicle according to the fourth embodiment includes the battery pack according to the third embodiment. That is, since the vehicle has a battery pack having a high life performance, the vehicle according to the fourth embodiment has an excellent cycle life performance, and the battery pack has an excellent life performance, so that a highly reliable vehicle is provided. be able to.

(Fifth Embodiment)
According to the fifth embodiment, a stationary power supply is provided. This stationary power supply is equipped with the battery pack according to the third embodiment. The stationary power supply may be equipped with the assembled battery according to the second embodiment or the lithium zinc secondary battery according to the first embodiment instead of the battery pack according to the third embodiment. ..

The stationary power supply according to the fifth embodiment is equipped with the battery pack according to the third embodiment. Therefore, the stationary power supply according to the fifth embodiment can realize a long life.

FIG. 11 is a block diagram showing an example of a system including a stationary power supply according to a fifth embodiment. FIG. 11 is a diagram showing an application example to the stationary power supplies 112 and 123 as an example of using the battery packs 40A and 40B according to the third embodiment. In the example shown in FIG. 11, the system 110 in which the stationary power supplies 112 and 123 are used is shown. The system 110 includes a power plant 111, a stationary power supply 112, a consumer-side power system 113, and an energy management system (EMS) 115. Further, a power network 116 and a communication network 117 are formed in the system 110, and the power plant 111, the stationary power supply 112, the consumer side power system 113 and the EMS 115 are connected via the power network 116 and the communication network 117. The EMS 115 utilizes the power grid 116 and the communication network 117 to control the entire system 110 to be stabilized.

The power plant 111 produces a large amount of electric power from fuel sources such as thermal power and nuclear power. Power is supplied from the power plant 111 through the power grid 116 and the like. Further, a battery pack 40A is mounted on the stationary power supply 112. The battery pack 40A can store electric power and the like supplied from the power plant 111. Further, the stationary power supply 112 can supply the electric power stored in the battery pack 40A through the power grid 116 or the like. The system 110 is provided with a power converter 118. The power converter 118 includes a converter, an inverter, a transformer and the like. Therefore, the power conversion device 118 can perform conversion between direct current and alternating current, conversion between alternating current having different frequencies with respect to each other, transformation (step-up and step-down), and the like. Therefore, the power conversion device 118 can convert the power from the power plant 111 into the power that can be stored in the battery pack 40A.

The consumer-side power system 113 includes a factory power system, a building power system, a household power system, and the like. The consumer-side power system 113 includes a consumer-side EMS 121, a power conversion device 122, and a stationary power supply 123. The battery pack 40B is mounted on the stationary power supply 123. The consumer-side EMS 121 controls to stabilize the consumer-side power system 113.

The electric power from the power plant 111 and the electric power from the battery pack 40A are supplied to the electric power system 113 on the consumer side through the electric power grid 116. The battery pack 40B can store the electric power supplied to the consumer side electric power system 113. Further, the power conversion device 122 includes a converter, an inverter, a transformer, and the like, similarly to the power conversion device 118. Therefore, the power conversion device 122 can perform conversion between direct current and alternating current, conversion between alternating current having different frequencies with respect to each other, transformation (step-up and step-down), and the like. Therefore, the power conversion device 122 can convert the power supplied to the consumer side power system 113 into power that can be stored in the battery pack 40B.

The electric power stored in the battery pack 40B can be used, for example, for charging a vehicle such as an electric vehicle. Further, the system 110 may be provided with a natural energy source. In this case, the renewable energy source generates electric power by natural energy such as wind power and solar power. Then, power is supplied from the natural energy source in addition to the power plant 111 through the power grid 116.

Examples will be described below, but the embodiments are not limited to the examples described below.

[Example]
Hereinafter, the above-described embodiment will be described in more detail based on the examples, but the present invention is not limited to the examples described below as long as the gist of the present invention is not exceeded.

(Example 1)
As the positive electrode, lithium manganese oxide (LiMn ₂ O ₄ ) particles having a spinel structure were used as the positive electrode active material. The LiMn ₂ O ₄ particles were a mixture of primary particles and secondary particles, and the average secondary particle diameter of the LiMn ₂ O ₄ particles was 5 μm. The positive electrode active material contains 3% by weight of carbon fiber having a gas phase growth with a fiber diameter of 0.1 μm as a conductive agent, 5% by weight of graphite powder, and 5% by weight as a binder with respect to the entire positive electrode. Polytetrafluoroethylene (PTFE) was blended and dispersed in N-methyl-2-pyrrolidone to prepare a slurry. The obtained slurry was applied to both sides of a titanium foil having a thickness of 10 μm, dried, and subjected to a pressing process to prepare a positive electrode having a thickness of a positive electrode active material-containing layer per side of 43 μm and an electrode density of 2.2 g / cm ³ . did.

As a negative electrode, a slurry containing anatase-type titanium oxide as an oxide is uniformly applied to both sides of the zinc metal body so that there are no exposed parts on the metal body of zinc alone having a thickness of 200 μm, and then rolled onto the zinc metal body. A zinc negative electrode containing an oxide that was brought into close contact with the metal was used.

As the electrolyte, an aqueous solution having LiCl (12M) as the lithium-supported salt and ZnCl ₂ (0.1M) as the zinc-supporting salt was used.

Table 1 shows the lithium-supported salt and the zinc-supported salt contained in the negative electrode oxide, the separator and the electrolyte used in Example 1. Table 1 also describes Examples 2 to 19, Comparative Examples 1 to 5, and 7 to 9, which will be described later.

For the negative electrode prepared in this way, the average primary particle size of the oxide, the specific surface area of the oxide, and the crystallite diameter of the oxide were measured, respectively, and the positive electrode, the negative electrode, the electrolyte and the separator prepared as described above were measured. A three-electrode cell using a saturated calomel electrode as a reference electrode was constructed using the above, and a charge / discharge evaluation test was carried out. The exterior of the cell is made of aluminum. The discharge capacity of the three-electrode cell and the average operating potential at the time of discharge were measured. The results of each measurement are shown in Table 2.

(Measurement of average primary particle size of oxide)
For the average primary particle size of the oxide, the negative electrode is taken out from the secondary battery and the surface of the negative electrode is observed using TEM. Ten arbitrary oxides were extracted from the surface of the negative electrode, and the average primary particle size was calculated.

(Specific surface area of oxide)
The layer containing the oxide was peeled off from the surface of the negative electrode, pulverized in a mortar to form a powder, and then the specific surface area was calculated by using the BET method by the gas adsorption method using _N2 gas.

(Oxide crystallite diameter)
The negative electrode was placed on the non-reflective glass sample plate without any positional deviation, and wide-angle X-ray scattering measurement was performed on the electrode surface. The crystallite diameter was calculated by the Scherrer equation from the main peak of 2θ = 25.34 ° attributed to the anatase-type titanium oxide particles.

(Charging / discharging test)
For the above-mentioned three-electrode cell, the charge / discharge conditions are a potential of -1.4 V (vs. SCE) during charging, a constant current test with a capacity termination of 1.5 (mAh / cm ² ), and during discharge. A constant current test was performed with a potential of −0.8 V (vs. SCE) and a capacitance termination of 1.5 (mAh / cm ² ). The capacity (mAh / cm ² ) after 10 cycles was set to 100%, and when the capacity became 80% when zinc was repeatedly dissolved and deposited, or due to dendrite precipitation, charging and discharging became impossible due to a short circuit. The number of charge / discharge cycles up to the hour was defined as the life (times).

(Measurement of zinc concentration and lithium concentration)
After the charge / discharge test, the electrolyte was taken out from the prepared beaker cell. The zinc concentration and lithium concentration in the electrolyte were quantified by ICP analysis, and the mol concentration ratio Zn / Li was calculated.

The measurement results of Examples 2 to 18 and Comparative Examples 1 to 5 and 7 to 9 described later are also shown in Table 2.

(Example 2)
A secondary battery was constructed by the same method as in Example 1 except that a plate of a lithium ion conductive solid electrolyte having a thickness of 0.2 μm was used as a separator, and measurement was performed. As the solid electrolyte, LATP (composition: Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ ) having a NASICON type skeleton was used.

(Example 3)
A secondary battery was prepared and measured by the same method as in Example 1 except that tungsten oxide (composition formula: WO ₃ ) was used as the oxide.

(Example 4)
A secondary battery was prepared and measured by the same method as in Example 1 except that rutile-type titanium oxide was used as the oxide.

(Example 5)
A secondary battery was prepared and measured by the same method as in Example 1 except that monoclinic titanium oxide was used as the oxide.

(Example 6)
A secondary battery was prepared and measured by the same method as in Example 1 except that anatase-type titanium oxide and tungsten oxide were mixed and used as an oxide in a molar ratio of 1: 1.

(Examples 7 and 8)
A secondary battery was prepared by the same method as in Example 1 except that the amount of zinc chloride (composition formula: ZnCl ₂ ) dissolved in the electrolyte as a zinc supporting salt was changed and the Zn / Li ratio of the electrolyte was adjusted. And the measurement was performed.

(Example 9)
The dissolution amount was adjusted using LiNO ₃ as the lithium supporting salt, and a secondary battery was prepared and measured by the same method as in Example 1 except that the zinc supporting salt was not used.

(Example 10)
A secondary battery was prepared by the same method as in Example 1 except that the dissolution amount was adjusted using Li ₂ SO ₄ as the lithium supporting salt and the dissolution amount was adjusted by changing the zinc salt to ZnSO ₄ . Measurements were made.

(Example 11)
A secondary battery was prepared and measured by the same method as in Example 1 except that LiCl (12M) and LiOH (1M) were further added to the electrolyte as a lithium supporting salt.

(Example 12)
A secondary battery was prepared and measured by the same method as in Example 1 except that the zinc salt was not used as the supporting salt of the electrolyte. As shown by the Zn / Li ratio in Table 1, in Example 12, zinc was detected because zinc was eluted from the negative electrode into the electrolyte.

(Example 13)
A secondary battery was prepared and measured by the same method as in Example 12 except that the metal of zinc alone was changed to titanium and zinc metal was used for the exterior portion of the cell. As shown by the Zn / Li ratio in Table 1, in Example 13, zinc was detected because zinc was eluted from the negative electrode into the electrolyte.

(Example 14)
A secondary battery was prepared and measured by the same method as in Example 1 except that the zinc salt was changed to ZnSO ₄ as the zinc supporting salt of the electrolyte and the dissolution amount was adjusted.

(Examples 15 to 17)
A secondary battery was prepared and measured in the same manner as in Example 1 except that the primary particle diameter, specific surface area, and crystallite diameter of anatase-type titanium oxide as an oxide were changed as shown in Table 1. rice field.

(Example 18)
Add 10 wt. Polyacrylonitrile to the liquid aqueous solution electrolyte. A secondary battery was prepared and measured in the same manner as in Example 17 except that the electrolyte was mixed and gelled.

(Example 19)
A secondary battery was prepared and measured by the same method as in Example 2 except that a garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) having a thickness of 200 μm was used as the solid electrolyte used as the separator. ..

(Comparative Example 1)
A secondary battery was produced by the same method as in Example 1 except that the oxide material was not applied as the negative electrode, only the zinc negative electrode was used, and the combination of the supporting salts of the electrolyte was LiCl (12M) + ZnCl ₂ (4M). And the measurement was performed.

(Comparative Example 2)
A secondary battery was produced by the same method as in Example 2 except that the oxide material was not applied as the negative electrode, only the zinc negative electrode was used, and the combination of the supporting salts of the electrolyte was LiCl (12M) + ZnCl ₂ (4M). And the measurement was performed.

(Comparative Examples 3 and 4)
A secondary battery was prepared and measured by the same method as in Example 1 except that the amount of zinc chloride (composition formula: ZnCl ₂ ) dissolved in the electrolyte was changed and the Zn / Li ratio of the electrolyte was adjusted. rice field.

(Comparative Examples 5 and 7)
A secondary battery was prepared in the same manner as in Example 1 except that the primary particle diameter, specific surface area, and crystallite diameter of anatase-type titanium oxide as oxide particles were changed as shown in Table 1, and measurement was performed. went.

(Comparative Example 8)
A secondary battery was prepared and measured by the same method as in Example 1 except that lithium titanate (composition formula: Li ₄ Ti ₅ O ₁₂ ) was used as the oxide.

(Comparative Example 9)
A secondary battery was prepared and measured by the same method as in Example 1 except that lithium vanadium acid (composition formula: LiV ₃ O ₈ ) was used as the oxide.

From Table 2, in Comparative Example 1 using only a simple zinc dissolution and precipitation reaction, although a high discharge capacity was obtained, the life performance was 100 times due to a short circuit due to dendrite precipitation. Further, in Comparative Example 2 using the solid electrolyte, although the short circuit was prevented, the capacity deteriorated due to the overvoltage accompanying the dendrite precipitation, and the service life performance was 200 times. However, in Example 1, it can be seen that the operating potential becomes low due to the mixed reaction of lithium occlusion and release and the dissolution and precipitation of zinc, and the precipitation of dendrite is suppressed, so that the life performance is improved. Further, it can be seen that the life performance of Example 2 using the solid electrolyte is improved by further suppressing the precipitation of dendrites as compared with Example 1.

Examples 3 to 6 are examples in which the oxide is changed from Example 1, and although the specific surface area, the average primary particle diameter, and the crystallite diameter are changed due to the change in the shape of the oxide, Comparative Examples 1 and 2 It can be seen that a good discharge capacity and a long life are obtained as compared with the above.

Comparative Examples 8 to 9 are examples in which the oxide is changed from Example 1. In Comparative Example 8 in which lithium titanate is used as the oxide particles, the lithium occlusion / release potential is lower than -1.4 V (vs. SCE), but since it does not overlap with the potential region of the dissolution and precipitation of zinc, lithium is used. Generation of hydrogen was observed with the release of occlusion. As a result, the discharge capacity was low because it did not contain zinc precipitation, and the life was shorter than in the examples due to the increase in overvoltage due to the generation of bubbles due to the generation of hydrogen.

In Comparative Example 9 using lithium vanadium, the lithium occlusion / release potential exceeds -1.0 V (vs. SCE). Since the amount of hydrogen generated is small, the reversibility of lithium occlusion and release is good and the life performance is good, but since it does not overlap with the potential region of zinc dissolution precipitation, zinc precipitation is not included. Therefore, the discharge capacity was lower than that of the examples.

Examples 7 and 8 and Comparative Examples 3 and 4 are examples in which the amount of zinc chloride ZnCl ₂ dissolved in the electrolyte as a supporting salt was changed from Example 1 to adjust the Zn / Li ratio. The discharge capacities and the number of lifespans of Examples 7 and 8 are good. On the other hand, in Comparative Example 3 having a high Zn / Li, dendrites tended to precipitate and the life performance could not be obtained. Further, in Comparative Example 4 in which Zn / Li is low, zinc charging / discharging does not proceed and a sufficient discharge capacity cannot be obtained, and self-discharge occurs due to hydrogen generation. Life characteristics deteriorated due to overvoltage due to withering.

Examples 9 to 11 are examples in which the lithium supporting salt is changed from Example 1, and even in that case, good discharge capacity and life characteristics are obtained as compared with Comparative Examples. In particular, the addition of lithium hydroxide changed the dissolution and precipitation morphology of zinc, resulting in better life characteristics. The average operating potential during discharge changed due to the change in salt concentration.

Examples 12 and 13 are examples in which a zinc salt was not used as the electrolyte, and as shown in Table 1, as a result of measuring the Zn / Li ratio in the electrolyte, a value of 1.0 × 10 ^-5 was detected. rice field. In Example 12, since zinc was contained in the electrolyte due to elution from the zinc metal body, good discharge capacity and life characteristics were obtained as compared with the comparative example. Example 13 is a case where the negative electrode does not contain zinc and zinc is used for the exterior portion. Similarly, since zinc metal is eluted and zinc is contained in the electrolyte, the discharge is better than that of the comparative example. Obtained capacity and life characteristics.

Example 14 is an example in which only the supporting salt of zinc is changed from Example 1, but even when anions are mixed, good discharge capacity and life characteristics are obtained as compared with Comparative Example.

Examples 15 to 17 and Comparative Examples 5 and 7 are examples in which the average primary particle diameter, specific surface area, and crystallite diameter of the oxide are changed from Example 1, but Examples 15 to 17 are better than Comparative Examples. Excellent discharge capacity and life characteristics are obtained. In particular, the characteristics are further improved when the crystallite diameter is 1 nm or more and 50 nm or less. On the other hand, in Comparative Example 5 and Comparative Example 7 in which the specific surface area is smaller than 10 m ² / g and the average primary particle diameter is larger than 0.1 μm, the zinc coating surface is reduced, the discharge capacity is lowered, and the life characteristics are due to dendrite precipitation. Is declining.

Example 18 is an example in which the electrolyte used in Example 1 is in the form of a gel. By making the electrolyte in the form of a gel, the formation of dendrites in zinc is suppressed and the life performance is improved. Example 19 is an example in which the type of the solid electrolyte of Example 2 is changed from LATP to LLZ, but the same results as those of other examples are obtained, it is chemically stable, and the Li conductivity is compared. It can be said that any good solid electrolyte can be applied.

According to one or more embodiments and examples described above, the lithium zinc secondary battery dissolves and precipitates the positive electrode and zinc, and the metal body containing zinc and at least a part of the surface of the metal body are provided with an oxide. It is a secondary battery equipped with a negative electrode, an aqueous electrolyte containing zinc and a lithium salt, and a separator existing between the positive electrode and the negative electrode, and the oxide is -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) Lithium is absorbed and released in the potential region below, the specific surface area of the oxide is 10 m ² / g or more and 350 m ² / g or less, and the mol concentration ratio of zinc and lithium contained in the aqueous electrolyte is Zn / Li. It can be seen that excellent cycle characteristics can be obtained when the value is 1.0 × 10 ^-5 or more and 0.3 or less.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Electrode group, 2 ... Container (exterior member), 3 ... Positive electrode, 3a ... Positive electrode current collector, 3b ... Positive electrode active material-containing layer, 4 ... Negative electrode, 4a ... Metal body with zinc, 4b ... Negative electrode oxide containing Layers 5 ... Separator, 6 ... Positive electrode lead, 7 ... Negative electrode lead, 8 ... Positive electrode conductive tab, 9 ... Negative electrode conductive tab, 10 ... Seal plate, 12 ... Negative electrode terminal, 13 ... Positive electrode terminal, 18 ... Positive electrode gasket, 19 ... Negative electrode gasket, 22 ... control valve, 23 ... liquid injection port, 24 ... sealing plug, 31 ... assembled battery, 32 ₁ to 32 ₅ , 43 ₁ to ₄₃₅ ... secondary battery, 33 ... lead, 40, 40A, 40B ... Battery pack, 41 ... Housing, 42 ... Assembly battery, 44 ... Opening, 45 ... Positive electrode terminal for output, 46 ... Negative electrode terminal for output, 51 ... Unit cell, 55 ... Assembly battery, 56 ... Printed wiring board, 57 Thermista, 58 ... protection circuit, 59 ... external terminal for energization, 60 ... positive electrode lead, 61, 63 ... connector, 62 ... negative electrode lead, 64, 65 ... wiring, 66a ... plus wiring, 66b ... minus wiring, 67 ... Wiring, 68 ... protective sheet, 69 ... storage container, 70 ... lid, 110 ... system, 111 ... power plant, 112 ... stationary power supply, 113 ... consumer side power system, 115 ... energy management system, 116 ... power network, 117 ... communication network, 118 ... power converter, 121 ... consumer side EMS, 122 ... power converter, 123 ... stationary power supply, 200 ... vehicle, 201 ... vehicle body, 202 ... battery pack, 300 ... vehicle, 301 ... vehicle Main body, 302 ... Vehicle power supply, 310 ... Communication bus, 311 ... Battery management device, 312a to 312c ... Battery pack, 313a to 313c ... Group battery monitoring device, 314a to 314c ... Group battery, 316 ... Positive terminal, 317 ... Negative electrode Terminals, 333 ... Switch devices, 340 ... Inverters, 345 ... Drive motors, 370 ... External terminals, 380 ... Vehicle ECUs, L1, L2 ... Connection lines, W ... Drive wheels.

Claims (17)

With the positive electrode
A metal body containing zinc and a negative electrode having an oxide on at least a part of the surface of the metal body in which zinc is dissolved and precipitated.
Water-based electrolytes containing zinc and lithium salts,
A separator existing between the positive electrode and the negative electrode,
It is a secondary battery equipped with
The oxide occludes and releases lithium in a potential region of -1.4 V (vs. SCE) or more and -1.0 V (vs. SCE) or less, and the specific surface area of the oxide is 10 m ² / g or more and 350 m ² /. A lithium-zinc secondary battery having a g or less and a mol concentration ratio Zn / Li of the zinc and the lithium contained in the aqueous electrolyte of 1.0 × 10 ^-5 or more and 0.3 or less. The lithium zinc secondary battery according to claim 1, wherein the charge / discharge reaction is a mixed reaction of the dissolution and precipitation of zinc and the storage and release reaction of the lithium in the oxide particles. The lithium-zinc secondary battery according to claim 1 or 2, wherein the metal body acts as a current collector and an active material. The lithium zinc secondary battery according to any one of claims 1 to 3 , wherein the zinc is present on at least a part of the surface of the oxide. The lithium zinc secondary battery according to any one of claims 1 to 4, wherein the oxide contains at least one selected from the group consisting of titanium oxide and tungsten oxide. The lithium zinc secondary battery according to any one of claims 1 to 4, wherein the oxide contains tungsten oxide. The lithium zinc secondary battery according to any one of claims 1 to 6 , wherein the average primary particle size of the oxide is 0.01 μm or more and 0.1 μm or less. The lithium-zinc secondary battery according to any one of claims 1 to 7 , wherein the crystallite diameter of the oxide is 1 nm or more and 50 nm or less. The lithium zinc secondary battery according to any one of claims 1 to 8 , wherein the mol concentration ratio Zn / Li of the zinc contained in the aqueous electrolyte is 1.0 × 10 ^-4 or more and 0.1 or less. .. The lithium-zinc secondary battery according to any one of claims 1 to 9 , wherein the separator contains a solid electrolyte having lithium ion conductivity. A battery pack comprising the lithium-zinc secondary battery according to any one of claims 1 to 10 . External terminal for energization and
The battery pack according to claim 11 , further comprising a protection circuit. The battery pack according to claim 11 or 12 , further comprising the plurality of the lithium-zinc secondary batteries, wherein the lithium-zinc secondary batteries are electrically connected in series, in parallel, or in series and in parallel. A vehicle equipped with the battery pack according to any one of claims 11 to 13 . The vehicle according to claim 14 , wherein the battery pack recovers the regenerative energy of the power of the vehicle. The vehicle according to claim 14 , further comprising a mechanism for converting the kinetic energy of the vehicle into regenerative energy. A stationary power supply comprising the battery pack according to any one of claims 11 to 13 .

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