TW202044661A - Nickel zinc battery improving overcharge resistance without compromising the excellent energy density of the battery - Google Patents

Abstract

A nickel zinc battery which is provided with a nickel electrode and a zinc electrode, wherein the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode is from 2.1 to 4.5.

Description

Nickel zinc battery

The present invention relates to a nickel-zinc battery.

It is known that nickel-zinc batteries are water-based batteries that use water-based electrolytes such as potassium hydroxide aqueous solutions, and therefore have high safety, and the combination of zinc electrodes and nickel electrodes provides water-based batteries with high electromotive force and excellent energy density. Furthermore, in addition to excellent input/output performance, nickel-zinc batteries are also low-cost, so the possibility of being used in industrial applications (such as backup power supplies) and automotive applications (such as hybrid vehicles) is being studied. .

In addition, in the nickel-zinc battery, due to the difference in the charging efficiency between the nickel electrode and the zinc electrode, in order to be fully charged, overcharge is required. However, when the battery is overcharged, for example, heat is generated inside the battery, resulting in reduction of electrolyte, damage to battery components, etc., thereby reaching the battery life. As such, nickel-zinc batteries sometimes reach their lifespan early due to overcharging.

In contrast, Patent Document 1 discloses a four-stage charging technology for nickel-zinc cells and batteries. With this technology, there is no dendrite formation and harmful overcharge, and the shape change of the zinc electrode is suppressed to Minimize, and suppress oxygen recombination to a minimum, thereby ensuring high cycle life. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2004-523191

[The problem to be solved by the invention]

The purpose of the present invention is to solve the problems caused by overcharging from the viewpoint of battery constitution regardless of the charging technology disclosed in Patent Document 1. More specifically, the main purpose is to avoid compromising the excellent performance of nickel-zinc batteries. In the case of energy density, the overcharge resistance is improved. [Means to solve the problem]

One aspect of the present invention relates to a nickel-zinc battery, which includes a zinc electrode and a nickel electrode, and the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode is 2.1-4.5. The nickel-zinc battery has excellent energy density and excellent overcharge resistance.

In one aspect, the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode may be 3.0 or more. In this case, the nickel-zinc battery shows more excellent overcharge resistance.

In one aspect, the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode may be 3.5 or less. In this case, the nickel-zinc battery has a more excellent energy density. [Effects of the invention]

According to the present invention, it is possible to provide a nickel-zinc battery having excellent energy density and excellent overcharge resistance.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

＜Nickel zinc battery＞ The nickel-zinc battery of this embodiment (for example, a nickel-zinc secondary battery) includes a zinc electrode as a negative electrode and a nickel electrode as a positive electrode. In the nickel-zinc battery of this embodiment, the ratio (N/P) of the electrode capacity of the zinc electrode (negative electrode capacity) N [unit: Ah] to the electrode capacity of the nickel electrode (positive electrode capacity) P [unit: Ah] (N/P) is 2.1 ~4.5. In this embodiment, by setting the electrode capacity ratio of the zinc electrode and the nickel electrode within the above range, it is possible to coexist excellent overcharge resistance and excellent energy density.

The negative electrode capacity N and the positive electrode capacity P can be adjusted to a desired range by changing the amount of the active material used in the electrode and the type and amount of additives. Theoretically, when the Coulomb efficiency (charge and discharge efficiency) is 100%, the product of the amount of zinc contained in a zinc electrode (g) and the theoretical capacity of zinc (Ah/g) becomes the negative electrode capacity N, The product of the amount (g) of nickel hydroxide contained in the nickel electrode and the theoretical capacity (Ah/g) of nickel hydroxide becomes the positive electrode capacity P. Therefore, by experimentally determining the coulombic efficiency in the absence of additives and the influence of the additives on the coulombic efficiency in advance, electrodes (nickel electrodes and zinc electrodes) with electrode capacities closer to the desired value can be obtained. Furthermore, when the active material contained in the zinc electrode is a zinc compound such as zinc oxide, the amount of the zinc component contained in the zinc compound is referred to as the "amount of zinc" instead of the amount of the zinc compound. Is the "quantity of zinc".

The negative electrode capacity N of a nickel-zinc battery can be measured, for example, by taking out the zinc electrode from the nickel-zinc battery and combining it with a nickel electrode having a sufficiently larger capacity than the target zinc electrode to perform full charge and full discharge. The positive electrode capacity P can also be measured by taking out the nickel electrode from the nickel-zinc battery and combining it with a zinc electrode having a sufficiently larger capacity than the target nickel electrode to perform the charging and discharging.

The nickel-zinc battery of this embodiment may be compounded or uncombined. As the basic structure of the nickel-zinc battery of this embodiment, the same structure as the conventional nickel-zinc battery can be used. Hereinafter, as an example, a nickel-zinc battery including an electrolytic cell, an electrode group accommodated in the electrolytic cell, and an electrolyte will be described. In addition, the "negative electrode" in the following description can be replaced by a "zinc electrode", and the "positive electrode" can be replaced by a "nickel electrode". The same applies to the descriptions of "negative electrode material" and "positive electrode material".

(Electrode group) The electrode group includes a negative electrode (for example, a negative electrode plate), a positive electrode (for example, a positive electrode plate), and a spacer disposed between the two electrodes. There may be multiple negative electrodes, positive electrodes, and spacers in the electrode group. The plurality of negative electrodes and the plurality of positive electrodes may be connected by, for example, a strap.

The negative electrode has a negative electrode current collector and a negative electrode material (electrode material) supported by the negative electrode current collector.

The negative electrode current collector constitutes a conductive circuit for the current from the negative electrode material. The negative electrode current collector has, for example, a flat plate shape, a sheet shape, or the like. The negative electrode current collector may be a current collector having a three-dimensional mesh structure composed of foamed metal, expanded metal, punching metal, felt of metal fibers, or the like. The negative electrode current collector includes a material having conductivity and alkali resistance. As such a material, for example, a material that is stable even under the reaction potential of the negative electrode (a material having an oxidation-reduction potential higher than the reaction potential of the negative electrode, or a protective film such as an oxide film formed on the surface of the substrate in an alkaline aqueous solution) can be used. Stabilized materials, etc.). In addition, in the negative electrode, the decomposition reaction of the electrolytic solution as a side reaction proceeds to generate hydrogen gas, but in terms of suppressing the progress of such side reaction, a material with a high hydrogen overvoltage is preferable. Specific examples of the material constituting the negative electrode current collector include zinc; lead; tin; metal materials (copper, brass, steel, nickel, etc.) plated with metals such as tin.

The negative electrode material has a layered shape, for example. That is, the negative electrode may have a negative electrode material layer. The anode material layer may be formed on the anode current collector. In the case where the portion of the negative electrode current collector supporting the negative electrode material has a three-dimensional mesh structure, the negative electrode material may be filled between the meshes of the current collector to form the negative electrode material layer.

The negative electrode material contains a zinc-containing negative electrode active material (electrode active material). Examples of the negative electrode active material include metallic zinc, zinc oxide, and zinc hydroxide. The negative electrode active material may contain one of these components alone, or may contain multiple types. For example, the negative electrode material contains metallic zinc in a fully charged state, and contains zinc oxide and zinc hydroxide in a final state of discharge. The negative electrode active material is in the form of particles, for example. Based on the total mass of the negative electrode material, the content of the negative electrode active material is, for example, 50% to 95% by mass.

The negative electrode material may further contain a negative electrode additive (additive). In this specification, the term "negative electrode additive" refers to components other than the negative electrode active material among the components contained in the negative electrode material. Examples of negative electrode additives include adhesives, conductive agents, and the like. The negative electrode additives can be used alone or in combination of multiple types.

Examples of the binder include polytetrafluoroethylene, hydroxyethyl cellulose, polyethylene oxide, polyethylene, polypropylene, and the like. The content of the binder can be, for example, 0.5 parts by mass to 10 parts by mass relative to 100 parts by mass of the negative electrode active material.

Examples of the conductive agent include indium compounds (indium oxide, etc.). The content of the conductive agent is, for example, 1 part by mass to 20 parts by mass relative to 100 parts by mass of the negative electrode active material.

From the viewpoint of obtaining excellent life performance, the density of the negative electrode material is preferably 4.0 g/cm ³ or more, more preferably 4.5 g/cm ³ or more, and still more preferably 4.8 g/cm ³ or more. From the viewpoint of obtaining excellent high-efficiency discharge performance, the density of the negative electrode material is preferably 5.8 g/cm ³ or less, more preferably 5.5 g/cm ³ or less, and still more preferably 5.0 g/cm ³ or less. From these viewpoints, the density of the negative electrode material may be 4.0 g/cm ³ ～5.8 g/cm ³ , 4.0 g/cm ³ ～5.5 g/cm ³ , 4.0 g/cm ³ ～5.0 g/cm ³ , 4.5 g/cm ³ ～5.0 g/cm ³ or 4.8 g/cm ³ ～5.0 g/cm ³ .

The density of the negative electrode material (unit: g/cm ³ ) can be adjusted by, for example, the following method: when the negative electrode material is filled in the current collector, the negative electrode material is pressurized to fill; the negative electrode material is pressurized to produce的片 etc. The method of applying pressure to the negative electrode material is not particularly limited, and for example, a method of applying pressure by roll pressing or the like can be mentioned.

The density (unit: g/cm ³ ) of the negative electrode material can be measured as follows, for example. First, cut the negative electrode (the negative electrode before compounding) into a 2 cm square from the center, measure the thickness and weight of the negative electrode, and calculate the volume and density of the negative electrode. After that, the negative electrode material of the negative electrode was removed using a rag wetted with water, thereby obtaining a current collector. The obtained current collector was immersed in ethanol to replace water, and then dried. Then, the thickness and weight of the current collector after drying were measured, and the volume and density of the current collector were calculated. The difference in volume between the negative electrode and the current collector is divided by the difference in weight between the negative electrode and the current collector, thereby obtaining the density of the negative electrode material.

From the viewpoint of obtaining more excellent life performance, the density of the negative electrode material converted to the negative electrode capacity N is preferably 2.4 Ah/cm ³ or more, more preferably 2.7 Ah/cm ³ or more, and still more preferably 2.9 Ah/cm ³ the above. From the viewpoint of obtaining more excellent high-efficiency discharge performance, the density of the negative electrode material converted to the negative electrode capacity N is preferably 3.6 Ah/cm ³ or less, more preferably 3.4 Ah/cm ³ or less, and still more preferably 3.1 Ah/cm ³ or less. From these viewpoints, the density of the negative electrode material converted from the negative electrode capacity N can be, for example, 2.4 Ah/cm ³ ～3.6 Ah/cm ³ , 2.4 Ah/cm ³ ～3.4 Ah/cm ³ or 2.4 Ah/cm ³ ～3.1 Ah/cm ³ .

The negative electrode capacity N can be appropriately set according to the application. From the viewpoint of easily obtaining the effects of the present invention, the negative electrode capacity N can be, for example, 0.01 Ah or more, 0.05 Ah or more, 0.1 Ah or more, 1 Ah or more, 10 Ah or more, 15 Ah or more, or 20 Ah or more, and can be 700 Ah. Or less, 650 Ah or less, 600 Ah or less, 100 Ah or less, 50 Ah or less, or 30 Ah or less.

The positive electrode has a positive electrode current collector (current collector) and a positive electrode material (electrode material) supported by the positive electrode current collector. As the positive electrode current collector, the same current collector as the negative electrode current collector can be used.

The positive electrode material has a layered shape, for example. That is, the positive electrode may have a positive electrode material layer. The positive electrode material layer may be formed on the positive electrode current collector. In the case where the positive electrode material support portion of the positive electrode current collector has a three-dimensional mesh structure, the positive electrode material may be filled between the meshes of the current collector to form a positive electrode material layer.

The positive electrode material contains a positive electrode active material (electrode active material) containing nickel. Examples of the positive electrode active material include nickel oxyhydroxide (NiOOH), nickel hydroxide, and the like. The positive electrode material contains nickel oxyhydroxide in a fully charged state, and nickel hydroxide in an end-of-discharge state, for example. Based on the total mass of the positive electrode material, the content of the positive electrode active material may be, for example, 50% to 95% by mass.

The positive electrode material may further contain components other than the positive electrode active material as additives. Examples of additives include adhesives (adhesives), conductive agents, swelling inhibitors, and the like.

Examples of the binder include hydrophilic or hydrophobic polymers. Specifically, for example, carboxymethyl cellulose (Carboxymethyl Cellulose, CMC), hydroxyethyl cellulose (Hydroxyethyl Cellulose, HEC), hydroxypropyl methyl cellulose (Hydroxypropyl Methylcellulose, HPMC), sodium polyacrylate (Sodium Polyacrylate, SPA), fluorine-based polymers (polytetrafluoroethylene (PTFE), etc.) are used as adhesives. The content of the binder is, for example, 0.01 parts by mass to 5 parts by mass relative to 100 parts by mass of the positive electrode active material.

Examples of the conductive agent include cobalt compounds (metal cobalt, cobalt oxide, cobalt hydroxide, etc.). The content of the conductive agent is, for example, 1 part by mass to 20 parts by mass relative to 100 parts by mass of the positive electrode active material.

As the swelling inhibitor, zinc oxide and the like can be cited. The content of the expansion inhibitor is, for example, 0.01 to 5 parts by mass relative to 100 parts by mass of the positive electrode active material.

From the viewpoint of obtaining excellent lifetime performance, the density of the positive electrode material is preferably 4.0 g/cm ³ or more, more preferably 4.5 g/cm ³ or more, and still more preferably 4.8 g/cm ³ or more. From the viewpoint of obtaining excellent high-efficiency discharge performance, the density of the positive electrode material is preferably 5.8 g/cm ³ or less, more preferably 5.5 g/cm ³ or less, and still more preferably 5.0 g/cm ³ or less. From these viewpoints, the density of the cathode material may be 4.0 g/cm ³ ～5.8 g/cm ³ , 4.0 g/cm ³ ～5.5 g/cm ³ , 4.0 g/cm ³ ～5.0 g/cm ³ , 4.5 g/cm ³ ～5.0 g/cm ³ or 4.8 g/cm ³ ～5.0 g/cm ³ . The density of the positive electrode material (unit: g/cm ³ ) can be adjusted in the same way as the density of the negative electrode material. In addition, the density (unit: g/cm ³ ) of the positive electrode material can be measured by the same method as the method for measuring the density of the negative electrode material.

From the viewpoint of obtaining more excellent life performance, the density of the cathode material converted to the cathode capacity P is preferably 2.4 Ah/cm ³ or more, more preferably 2.7 Ah/cm ³ or more, and still more preferably 2.9 Ah/cm ³ the above. From the viewpoint of obtaining more excellent high-efficiency discharge performance, the density of the cathode material converted to the cathode capacity P is preferably 3.6 Ah/cm ³ or less, more preferably 3.4 Ah/cm ³ or less, and still more preferably 3.1 Ah/cm ³ or less. From these viewpoints, the density of the positive electrode material converted from the positive electrode capacity P can be, for example, 2.4 Ah/cm ³ ～3.6 Ah/cm ³ , 2.4 Ah/cm ³ ～3.4 Ah/cm ³ or 2.4 Ah/cm ³ ～3.1 Ah/cm ³ .

The positive electrode capacity P can be appropriately set according to the application. From the viewpoint of easily obtaining the effects of the present invention, the positive electrode capacity P may be, for example, 0.0025 Ah or more, 0.005 Ah or more, 0.025 Ah or more, 0.1 Ah or more, 1.0 Ah or more, 6.0 Ah or more, or 9.0 Ah or more, and can be 350 Ah. Or less, 310 Ah or less, 285 Ah or less, 100 Ah or less, or 10 Ah or less.

From the viewpoint of obtaining excellent overcharge resistance, the ratio (N/P) of the negative electrode capacity N to the positive electrode capacity P is 2.1 or more, preferably 2.3 or more, more preferably 2.5 or more, and still more preferably 2.8 or more, Especially preferably, it is 3.0 or more. From the viewpoint of obtaining an excellent energy density, the ratio (N/P) of the negative electrode capacity N to the positive electrode capacity P is 4.5 or less, preferably 4.0 or less, more preferably 3.9 or less, and still more preferably 3.5 or less.

The spacer may be, for example, a spacer having a flat plate shape, a sheet shape, or the like. As the separator, a polyolefin-based microporous film, a nylon-based microporous film, an oxidation-resistant ion exchange resin film, a cellophane-based recycled resin film, an inorganic-organic separator, a polyolefin-based nonwoven fabric, etc. may be mentioned.

(Electrolyte) The electrolyte contains, for example, a solvent and an electrolyte. As a solvent, water (for example, ion exchange water) etc. are mentioned. Examples of the electrolyte include alkaline compounds. Examples of basic compounds include alkali metal hydroxides such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide (LiOH). That is, the nickel-zinc battery of this embodiment can be used in the form of an alkaline zinc battery using an alkaline electrolyte. The electrolyte may contain components other than the solvent and the electrolyte, and may contain potassium phosphate, potassium fluoride, potassium carbonate, sodium phosphate, sodium fluoride, zinc oxide, antimony oxide, titanium dioxide, and the like, for example. The electrolyte may be retained (for example, impregnated) in the spacer, for example.

The method of manufacturing a nickel-zinc battery described above includes, for example, a step of manufacturing a constituent member of the nickel-zinc battery; and a step of assembling the constituent member to obtain a zinc battery. In the manufacturing step of the constituent member, at least electrodes (a negative electrode and a positive electrode) are obtained.

The electrode can be obtained, for example, by adding a solvent (such as water) to the raw material of the electrode material (negative electrode material and positive electrode material) and kneading to obtain an electrode material paste (paste electrode material), and then using the electrode Material paste to form the electrode material layer.

Examples of the raw material of the negative electrode material include raw materials of the negative electrode active material (for example, metallic zinc, zinc oxide, and zinc hydroxide), additives (for example, the binder), and the like. Examples of the raw material of the positive electrode material include raw materials of the positive electrode active material (for example, nickel hydroxide), additives (for example, the binder), and the like.

As a method of forming an electrode material layer, for example, a method of obtaining an electrode material layer by applying or filling an electrode material paste on a current collector and then drying. The electrode material layer can be pressed to increase the density as needed.

In the assembling step, for example, the negative and positive electrodes obtained in the manufacturing step of the constituent member are alternately laminated with spacers interposed therebetween, and then the negative electrodes and the positive electrodes are connected to each other with a strap to produce an electrode group. Then, after disposing the electrode group in the electrolytic cell, the cover is attached to the upper surface of the electrolytic cell to obtain an uncombined nickel-zinc battery.

Then, after injecting the electrolyte into the electrolytic cell of the uncombined nickel-zinc battery, it is left for a certain period of time. Then, it is compounded by charging under specified conditions, thereby obtaining a nickel-zinc battery. The compounding conditions can be adjusted according to the properties of the electrode active materials (negative electrode active material and positive electrode active material).

As mentioned above, although the nickel zinc battery as an example of the zinc battery of this embodiment was demonstrated, this invention is not limited to the said embodiment. [Example]

Then, the present invention is further described in detail with the following examples, but these examples do not limit the present invention in any way.

(Example 1) [Preparation of negative electrode] As a negative electrode current collector, a tin-plated steel sheet punched metal with an aperture ratio of 60% was prepared. Then, a predetermined amount of zinc oxide, metallic zinc, PTFE, and ion-exchanged water are weighed and mixed, and the obtained mixed solution is stirred to prepare a negative electrode material paste. At this time, the mass ratio of the solid content was adjusted to "zinc oxide: metallic zinc: PTFE=80:15:5". The moisture content of the negative electrode material paste was adjusted to 32.5 mass% based on the total mass of the negative electrode material paste. Then, after applying the negative electrode material paste on the negative electrode current collector, it was dried at 80°C for 30 minutes. Thereafter, press molding was performed by roll pressing, thereby obtaining an uncombined negative electrode having 43.5 g of a negative electrode material (anode material layer) with a density of 4.9 g/cm ³ . Furthermore, the influence of PTFE on the coulombic efficiency of the negative electrode is determined through experiments in advance, and the blending amounts of zinc oxide, metallic zinc, and PTFE are adjusted so that the negative electrode capacity N becomes the target value.

[Production of positive electrode] Foamed nickel with a porosity of 90% was prepared as a positive electrode current collector. Then, a predetermined amount of nickel hydroxide powder, metal cobalt, cobalt hydroxide, CMC, PTFE, and ion exchange water are weighed and mixed, and the mixed solution is stirred to prepare a positive electrode material paste. At this time, the mass ratio of the solid content was adjusted to "nickel hydroxide: metallic cobalt: cobalt hydroxide: CMC: PTFE=85:8:5:1:1". The moisture content of the positive electrode material paste was adjusted to 27.5% by mass based on the total mass of the positive electrode material paste. Then, after coating the positive electrode material paste on the positive electrode current collector, it was dried at 80° C. for 30 minutes. Thereafter, press molding was performed by roll pressing, thereby obtaining an uncombined positive electrode having 40.6 g of a positive electrode material (positive electrode material layer) with a density of 3.17 g/cm ³ . Furthermore, the effects of metallic cobalt, cobalt hydroxide, CMC, and PTFE on the coulombic efficiency of the positive electrode were determined through experiments in advance, and the nickel hydroxide powder, metallic cobalt, and hydroxide were adjusted so that the positive electrode capacity P became the target value. The blending amount of cobalt, CMC and PTFE.

[Preparation of spacer] In the spacers, Celgard 2500 was used as the microporous membrane, and VL100 (manufactured by Nippon High Paper Industry) was used as the non-woven fabric. Before the battery is assembled, the microporous membrane is hydrophilized using the surfactant Triton-X100 (manufactured by Dow Chemical Co., Ltd.). The hydrophilization treatment is performed by a method of immersing the microporous membrane in an aqueous solution containing Triton-X100 in an amount of 1% by mass for 24 hours, and then drying it at room temperature for 1 hour. Furthermore, the microporous film is cut into a predetermined size, folded in half, and heat-welded the side surfaces to form a bag shape. The non-woven fabric is cut to the specified size.

[Preparation of electrolyte] Potassium hydroxide (KOH) and lithium hydroxide (LiOH) were added to ion exchange water and mixed, thereby preparing an electrolyte (potassium hydroxide concentration: 30% by mass, lithium hydroxide concentration: 1% by mass).

＜Production of nickel-zinc battery＞ The positive electrode (uncombined positive electrode) and one negative electrode (uncombined negative electrode) are housed in a microporous membrane processed into a bag shape. After laminating the positive electrode contained in the bag-shaped microporous film, the negative electrode contained in the bag-shaped microporous film, and the non-woven fabric, the electrode plates of the same polarity are connected to each other by the lap sheet to produce an electrode group (electrode group) group). The electrode group is composed of one positive electrode and two negative electrodes, and a non-woven fabric is arranged between the positive electrode and the negative electrode. After disposing the electrode group in the electrolytic cell, the cover is attached to the upper surface of the electrolytic cell to obtain an uncombined nickel-zinc battery. Then, after injecting the electrolyte into the electrolytic cell of the uncombined nickel-zinc battery, it was left for 24 hours. Thereafter, a constant current and constant voltage charge of 5.6 A and 1.9 V was performed for 15 hours to produce a nickel-zinc battery with a nominal capacity of 8 Ah. The negative electrode capacity N of the obtained nickel-zinc battery was 25.0 Ah, the positive electrode capacity P was 8.05 Ah, and the ratio (N/P) of the negative electrode capacity N to the positive electrode capacity P was 3.10.

(Example 2 to Example 3, Comparative Example 1 to Comparative Example 3) Change the usage amount of zinc oxide, metallic zinc, and PTFE so that the negative electrode capacity N becomes the value shown in Table 1, and change the nickel hydroxide, metallic cobalt, and cobalt hydroxide so that the positive electrode capacity P becomes the value shown in Table 1. Except for the usage amounts of CMC and PTFE, a negative electrode and a positive electrode were produced in the same manner as in Example 1, and a nickel-zinc battery was produced in the same manner as in Example 1. The negative electrode capacity N, positive electrode capacity P, and the ratio (N/P) of the negative electrode capacity N to the positive electrode capacity P of the obtained nickel-zinc battery are shown in Table 1.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Negative capacity N[Ah] 25.0 27.0 29.1 31.2 33.3 16.6 Positive electrode capacity P[Ah] 8.05 7.32 6.59 5.85 5.12 11.0 Capacity ratio N/P[-] 3.10 3.69 4.42 5.33 6.50 1.51

＜Battery performance evaluation＞ The nickel-zinc batteries of the examples and comparative examples were used to evaluate the overcharge resistance and energy density.

(Evaluation of overcharge tolerance) The nickel-zinc batteries of the Examples and Comparative Examples were overcharged, and the relationship between the voltage and the charging rate (State of Charge (SOC)) was determined. Specifically, first, the termination current is set to a 20-hour rate, and the charging current is set to a 3-hour rate, and the battery is charged with a constant current and a voltage until 1.9 V, and is set to a fully charged state. Thereafter, the battery was discharged at a current rate of 3 hours until 1.1 V, thereby obtaining the battery capacity of the battery. After the battery is set to a fully charged state again, the battery is discharged for 36 minutes at a current rate of 3 hours, and set to a state of charge rate = 80%. After that, it was overcharged by charging at a current of 2.5 hours for 3 hours. Measure the battery voltage during overcharge and record the peak voltage as Vmax. The results are shown in Figure 1. The vertical axis of FIG. 1 represents the battery voltage (V), and the horizontal axis represents the charging rate (%) of the battery. Furthermore, the charge rate (%) is the value obtained by dividing the difference between the fully charged capacity (battery capacity) and the discharged capacity by the battery capacity, or the fully charged capacity (battery capacity) and the charged capacity The sum of, divided by the battery capacity.

As shown in Fig. 1, it was confirmed that the nickel-zinc battery showed a peak voltage (Vmax), and with the peak voltage as the boundary, the generation of gas and the heat generation of the battery became significant. Therefore, for those having tolerance to overcharge up to the peak voltage, the overcharge tolerance is evaluated by comparing the charging rate at the peak voltage. The results are shown in Table 2.

(Evaluation of energy density) Divide the product of the battery capacity obtained in the overcharge resistance evaluation and the average discharge voltage obtained during the battery capacity measurement (battery capacity x average discharge voltage) by the volume of the battery (volume of the electrolytic cell), thereby The energy density of the nickel-zinc batteries of the examples and comparative examples was determined. The results are shown in Table 2.

[Table 2] Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 SOC at Vmax (%) 134.9 173.8 259.2 352.2 448.5 104.7 Energy density (Wh/L) 97.8 88.9 80.0 71.1 62.2 133.3

no

Fig. 1 is a graph showing voltage shifts during overcharge of nickel-zinc batteries of Examples and Comparative Examples.

Claims (3)

A nickel-zinc battery, which includes a zinc electrode and a nickel electrode, and The ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode is 2.1 to 4.5. The nickel-zinc battery according to the first item of the patent application, wherein the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode is 3.0 or more. The nickel-zinc battery as described in item 1 or item 2 of the scope of patent application, wherein the ratio of the electrode capacity of the zinc electrode to the electrode capacity of the nickel electrode is 3.5 or less.

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