JP2020170652A - Manufacturing method of negative electrode for zinc battery and negative electrode for zinc battery - Google Patents

Abstract

To provide a manufacturing method of a negative electrode for a zinc battery enabling the negative electrode to have excellent life performance.SOLUTION: The manufacturing method of a negative electrode for a zinc battery is provided, the negative electrode comprising a negative electrode current collector 21, a first negative electrode material layer provided on one surface 21a of the negative electrode current collector, and a second negative electrode material layer provided on the other surface 21b of the negative electrode current collector 21. The manufacturing method includes a negative electrode material layer forming step of forming a first negative electrode material layer and a second negative electrode material layer by passing the negative electrode current collector 21 between a first wall surface 51 and a second wall surface 52 while contacting the negative electrode material pastes 23a, 23b on both sides with the first wall surface 51 and the second wall surface 52 facing each other in a state where the negative electrode material pastes 23a, 23b adhere to both sides of the negative electrode current collector 21. In the negative electrode material layer forming step, a ratio of a distance D2 between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 to a distance D1 between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 is 0.7 to 1.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for manufacturing a negative electrode for a zinc battery and a negative electrode for a zinc battery.

As the zinc battery, a nickel-zinc battery, a zinc-air battery, a silver-zinc battery and the like are known. For example, a nickel-zinc battery is an aqueous battery that uses an aqueous electrolytic solution such as an aqueous potassium hydroxide solution, so that it has high safety and a high electromotive force as an aqueous battery by combining a zinc electrode and a nickel electrode. It is known to have. Further, since the nickel-zinc battery has excellent input / output performance and low cost, it can be applied to industrial applications (for example, applications such as backup power supply) and automobile applications (for example, applications such as hybrid automobiles). Gender is being considered.

The charge / discharge reaction of the nickel-zinc battery proceeds according to, for example, the following formula (discharge reaction: rightward, charge reaction: leftward).
(Positive _{electrode) 2NiOOH + 2H 2 O + 2e} - → 2Ni (OH) 2 + 2OH -
(Negative electrode) Zn + 2OH ⁻ → Zn (OH) ₂ + 2e ⁻

As shown in the above formula, in a zinc battery, zinc hydroxide (Zn (OH) ₂ ) is produced by a discharge reaction. Zinc hydroxide is soluble in the electrolyte, the zinc hydroxide is dissolved in the electrolytic solution, tetra hydroxide zincate ions _{([Zn (OH) 4]} 2 -) is diffused into the electrolyte. As a result, the morphological change (deformation) of the negative electrode progresses and the distribution of the charging current becomes non-uniform, so that zinc precipitates locally on the negative electrode and dendrites (dendritic crystals) are generated. In a conventional zinc battery, when the dendrite grows due to repeated charging and discharging, the dendrite may penetrate the separator and cause a short circuit. Therefore, various attempts have been made to prevent such a short circuit due to dendrites and improve the life performance. For example, Patent Document 1 below discloses a technique for preventing a short circuit due to dendrite by interposing a nickel-plated non-woven fabric between electrodes.

Japanese Unexamined Patent Publication No. 58-126665

As described above, the zinc battery is required to have further improvement in life performance.

One aspect of the present invention is to provide a method for manufacturing a negative electrode for a zinc battery capable of obtaining excellent life performance, and a negative electrode for a zinc battery.

One aspect of the present invention includes a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and a second negative electrode material layer provided on the other surface of the negative electrode current collector. A method for manufacturing a negative electrode for a zinc battery, wherein the negative electrode material pastes on both sides are brought into contact with the first wall surface and the second wall surface facing each other in a state where the negative electrode material pastes are attached to both sides of the negative electrode current collector. The negative electrode material is provided with a negative electrode material layer forming step of passing a negative electrode current collector between the first wall surface and the second wall surface to form a first negative electrode material layer and a second negative electrode material layer. In the layer forming step, the ratio of the distance between the first wall surface and one surface of the negative electrode current collector to the distance between the second wall surface and the other surface of the negative electrode current collector is 0.7 to 1. Provided is a method for manufacturing a negative electrode for use. A zinc battery using a negative electrode for a zinc battery obtained by this manufacturing method has excellent life performance.

In one aspect, the above ratio may be less than one.

On one side, the difference between the distance between the first wall surface and one surface of the negative electrode current collector and the distance between the second wall surface and the other surface of the negative electrode current collector is preferably 0.03 mm or less.

Another aspect of the present invention is a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and a second negative electrode material provided on the other surface of the negative electrode current collector. Provided is a negative electrode for a zinc battery comprising a layer, wherein the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer is 0.7 to 1. .. The zinc battery using the negative electrode for the zinc battery has excellent life performance.

In another aspect, the above ratio may be less than one.

On the other side, the difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer is preferably 0.03 mm or less.

According to one aspect of the present invention, it is possible to provide a method for manufacturing a negative electrode for a zinc battery capable of obtaining excellent life performance, and a negative electrode for a zinc battery.

It is a micrograph which observed the state of the cross section of the negative electrode as the number of battery cycles elapses in the conventional double-sided coating type negative electrode. It is a schematic diagram which shows an example of the apparatus used in the manufacturing method of the negative electrode for a zinc battery which concerns on one Embodiment. It is a schematic cross-sectional view which shows the layer forming part in the apparatus shown in FIG. It is a top view which shows an example of the measurement part of the thickness of a negative electrode material layer.

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 variously modified and implemented within the scope of the gist thereof. The sizes of the components in each figure are conceptual, and the relative size relationships between the components are not limited to those shown in each figure.

In the present specification, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. “A or B” may include either A or B, or both. Unless otherwise specified, the materials exemplified in the present specification may be used alone or in combination of two or more. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means. Further, in the present specification, the term "layer" includes not only a structure having a shape formed on the entire surface but also a structure having a shape partially formed when observed as a plan view. Further, in the present specification, the term "process" is used not only as an independent process but also as a term as long as the desired action of the process is achieved even when it cannot be clearly distinguished from other processes. included.

The negative electrode obtained by the manufacturing method according to the following embodiment is a negative electrode used for a zinc battery (negative electrode for a zinc battery). Examples of the zinc battery (for example, a zinc secondary battery) include a nickel-zinc battery, a zinc-air battery, a silver-zinc battery, and the like. As the basic configuration of the zinc battery, the same configuration as that of the conventional zinc battery can be used. The zinc battery in the present specification may be either post-chemical or non-chemical.

The method for manufacturing a negative electrode for a zinc battery according to one embodiment is provided on a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and the other surface of the negative electrode current collector. A method for manufacturing a negative electrode for a zinc battery including a second negative electrode material layer, wherein the negative electrode material paste is attached to both sides of the negative electrode current collector, and the negative electrode material paste is attached to the first wall surface and the second wall surface facing each other. A negative electrode material layer that forms a first negative electrode material layer and a second negative electrode material layer by passing a negative electrode current collector between the first wall surface and the second wall surface while bringing the negative electrode material pastes on both sides into contact with each other. In the negative electrode material layer forming step, the ratio of the distance between the first wall surface and one surface of the negative electrode current collector to the distance between the second wall surface and the other surface of the negative electrode current collector is 0.7. 1 is a method for manufacturing a negative electrode for a zinc battery.

Further, the negative electrode for a zinc battery according to one embodiment includes a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and a first negative electrode material layer provided on the other surface of the negative electrode current collector. A negative electrode for a zinc battery comprising 2 negative electrode material layers, wherein the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer is 0.7 to 1. It is a negative electrode.

By using the negative electrode for a zinc battery according to these embodiments, excellent life performance can be obtained in the zinc battery. The reason why such an effect is obtained is not clear, but the present inventors speculate as follows.

In the negative electrode for zinc batteries (hereinafter, also simply referred to as “negative electrode”), metallic zinc, which is the negative electrode active material, is eluted as tetrahydroxydozincate ion ([Zn (OH) ₄ ] ₂ ⁻ ) by the discharge reaction. [Zn (OH) ₄ ] ₂ ⁻ is supersaturated in the electrolytic solution and is precipitated as zinc oxide (ZnO) on the negative electrode material layer. Here, it is considered that the concentration of [Zn (OH) ₄ ] ₂ ⁻ and the amount of ZnO deposited are affected by the thickness of the negative electrode material layer in the negative electrode. When the negative electrode material layer is thick, the concentration of [Zn (OH) ₄ ] ₂ ⁻ eluted from the negative electrode material layer becomes high, and accordingly, when the negative electrode material layer is thick, the amount of ZnO precipitated on the negative electrode material layer is high. Will also increase. Since ZnO is slightly soluble in the electrolytic solution, [Zn (OH) ₄ ] ₂ ⁻ exists in a supersaturated state in the vicinity of the ZnO particles, and the precipitation of ZnO is further promoted.

The negative electrode includes a so-called double-sided coating type negative electrode in which negative electrode material layers are provided on both sides of the current collector. As described above, the larger the thickness of the negative electrode material layer, the greater the amount of ZnO deposited. Therefore, in the double-sided coating type negative electrode, there is a difference in thickness between the negative electrode material layer on one side and the negative electrode material layer on the other side. If it is large, an environment is created in which ZnO is likely to be deposited unevenly on the surface of the thick negative electrode material layer, and it is considered that the difference in thickness between the front and back surfaces of the same negative electrode increases as the number of battery cycles elapses.

FIG. 1 is a photomicrograph (using a scanning electron microscope, magnification of 200 times) of a conventional double-sided coating type negative electrode in which the state of the cross section of the negative electrode is observed as the number of battery cycles elapses. FIG. 1 (a) shows the state of the negative electrode before use, and shows that the number of cycles is increasing in the order of FIGS. 1 (b), 1 (c), and 1 (d). In the double-sided coating type negative electrode 10 shown in FIG. 1, as shown in FIG. 1A, the first negative electrode material layer 12 provided on one surface of the negative electrode current collector 11 and the negative electrode current collector 1 There is a difference in the thickness of the second negative electrode material layer 13 provided on the other surface. That is, the first negative electrode material layer 12 is thicker than the second negative electrode material layer 13. In such a negative electrode 10, as shown in FIGS. 1 (b) to 1 (d), the thickness between the first negative electrode material layer 12 and the second negative electrode material layer 13 increases as the number of cycles elapses. The difference between the two is widening. It is considered that this is because ZnO is unevenly deposited as the thickness of the negative electrode material layer is increased for the above-mentioned reason.

In a zinc battery, a charge / discharge reaction proceeds by diffusing hydroxide ions (OH ⁻ ), which are charge carriers, between the positive electrode and the negative electrode facing each other via a separator such as a microporous membrane or a non-woven fabric. As shown in FIG. 1, when one of the negative electrode material layers of the negative electrode is unevenly reduced in weight, it is considered that the charge / discharge reaction is hindered because smooth transfer of OH ^{− to} and from the opposite positive electrode cannot be performed.

More specifically, in the discharge reaction, since the OH ⁻ diffused from the positive electrode is consumed by the negative electrode, the active material in the negative electrode material layer facing the positive electrode can react most smoothly. However, when the amount of the negative electrode material layer facing the positive electrode is reduced, it is necessary for OH ⁻ to diffuse to the active material in the negative electrode material layer opposite to the positive electrode facing surface via the negative electrode current collector such as punching metal. Will increase. Therefore, it is estimated that the diffusion resistance increases and the discharge capacity is gradually impaired. Further, the charging reaction is a reaction in the opposite direction to the discharging reaction, and it is necessary to diffuse OH ⁻ from the negative electrode side to the positive electrode side. Therefore, when the amount of the negative electrode material layer facing the positive electrode is reduced, the charge capacity is impaired by increasing the diffusion resistance as in the discharge reaction. When the charge capacity is impaired, it is considered that the decrease in the discharge capacity is further accelerated.

On the other hand, the negative electrode obtained by the manufacturing method according to the present embodiment has the thickness of the first negative electrode material layer provided on one surface of the negative electrode current collector and the second negative electrode material layer provided on the other surface of the negative electrode current collector. Since the difference in thickness from the negative electrode material layer is small, it is possible to suppress the precipitation of ZnO biased to one negative electrode material layer. Therefore, smooth transfer of OH ^{− to} and from the opposite positive electrode is possible, and inhibition of the charge / discharge reaction can be suppressed. As a result, it is considered that the life performance of the zinc battery can be improved.

<Manufacturing method of negative electrode for zinc battery>
In the method for manufacturing a negative electrode for a zinc battery according to one embodiment, the negative electrode material pastes on both sides are brought into contact with the first wall surface and the second wall surface facing each other in a state where the negative electrode material pastes are attached to both sides of the negative electrode current collector. A negative electrode material layer forming step is provided in which a negative electrode current collector is passed between the first wall surface and the second wall surface to form a first negative electrode material layer and a second negative electrode material layer.

The negative electrode current collector has a shape such as a flat plate shape or a sheet shape. The negative electrode current collector may be a current collector having a three-dimensional network structure composed of foamed metal, expanded metal, punching metal, felt-like material of metal fibers, or the like. The negative electrode current collector is made of a material having conductivity and alkali resistance. Examples of such a material include a material that is stable even at the reaction potential of the negative electrode (a material having an oxidation-reduction potential noble than the reaction potential of the negative electrode, and a protective film such as an oxide film is formed on the surface of the base material in an alkaline aqueous solution. A material that stabilizes the material) can be used. Further, in the negative electrode, the decomposition reaction of the electrolytic solution proceeds as a side reaction to generate hydrogen, and a material having a high hydrogen overvoltage is preferable in that the progress of such a side reaction can be suppressed. Specific examples of the material constituting the negative electrode current collector include metal materials (copper, brass, steel, nickel, etc.) plated with metals such as zinc, lead, tin, and tin.

The negative electrode material paste is a paste containing components constituting the negative electrode material layer. The negative electrode material paste may be, for example, a paste obtained by adding the components constituting the negative electrode material layer to a dispersion medium such as water and kneading the paste.

The negative electrode material paste contains a negative electrode active material containing zinc. Examples of the negative electrode active material include metallic zinc, zinc oxide, zinc hydroxide and the like. The negative electrode material paste contains, for example, metallic zinc in a fully charged state, and zinc oxide and zinc hydroxide in a discharge end state.

The amount of the negative electrode active material is preferably in the following range based on the total mass of the non-volatile content (component of the negative electrode material paste excluding the dispersion medium) of the negative electrode material paste. The amount of the negative electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 75% by mass or more, from the viewpoint of easily achieving both excellent life performance and discharge performance. The amount of the negative electrode active material is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, from the viewpoint of easily achieving both excellent life performance and discharge performance. From these viewpoints, the amount of the negative electrode active material is preferably 50 to 95% by mass.

The negative electrode material paste can contain additives other than the negative electrode active material. Examples of the additive include a binder, a conductive agent and the like. Examples of the binder include polytetrafluoroethylene, hydroxyethyl cellulose, polyethylene oxide, polyethylene, polypropylene and the like. The amount of the binder may be, for example, 0.5 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. Examples of the conductive agent include indium compounds (indium oxide and the like). The amount of the conductive agent may be, for example, 1 to 20 parts by mass with respect to 100 parts by mass of the negative electrode active material.

FIG. 2 is a schematic view showing an example of an apparatus used in the method for manufacturing a negative electrode for a zinc battery according to the present embodiment. The negative electrode for a zinc battery according to the present embodiment can be manufactured by using, for example, the apparatus shown in FIG.

In this manufacturing method, first, the roll-shaped negative electrode current collector 21 is unwound by the unwinding portion 30, and then the negative electrode current collector 21 is passed through the tank 40 in which the negative electrode material paste is charged to collect the negative electrode. The negative electrode material paste is attached to the electric body 21. In this manufacturing method, the roll-shaped negative electrode current collector 21 is unwound by the unwinding portion 30, but a flat plate-shaped or sheet-shaped negative electrode current collector is prepared and the negative electrode current collector is put into the tank 40. You may. Subsequently, the negative electrode current collector is pulled up from the tank 40. The negative electrode material paste adheres to both surfaces of the pulled-up negative electrode current collector 21 (one surface and the other surface of the negative electrode current collector 21). Thereby, the negative electrode current collector 22 in which the negative electrode material paste is adhered to both surfaces can be obtained. In the negative electrode current collector 22 in which the negative electrode material paste is adhered to both sides, the negative electrode material paste may be adhered to one surface and a part of the other surface of the negative electrode current collector 21, or may be adhered to the entire surface. Good.

Next, the negative electrode current collector 22 to which the negative electrode material paste is adhered on both sides is passed through the layer forming portion 50.

FIG. 3 is a schematic cross-sectional view showing a layer forming portion 50 in the apparatus shown in FIG. The layer forming portion 50 has a gap 53 formed from a first wall surface 51 and a second wall surface 52 facing each other. The negative electrode current collector 22 with the negative electrode material paste adhered to both sides is passed through the gap 53 in the direction of the arrow. At this time, the negative electrode material paste 23a attached to the one surface 21a of the negative electrode current collector 21 is brought into contact with the first wall surface 51, and the negative electrode material paste 23b attached to the other surface 21b of the negative electrode current collector 21 is applied. The negative electrode current collector 22 with the negative electrode material paste adhered to both sides is passed through the gap 53 while being in contact with the second wall surface 52.

In the negative electrode current collector 22 in which the negative electrode material paste immediately after being pulled up from the tank 40 (before passing through the layer forming portion 50) adheres to both sides, unevenness is generated on the surface of the negative electrode material paste as shown in FIG. In some cases, the amount of the negative electrode material paste adhered may be uneven. By passing this through the layer forming portion 50 while contacting the first wall surface 51 and the second wall surface 52 of the layer forming portion 50, the surface irregularities of the negative electrode material pastes 23a and 23b can be made uniform.

Further, in the manufacturing method of this embodiment, with respect to the distance D ₁ of the the one surface 21a of the first wall 51 and the anode current collector 21, the other surface 21b of the second wall 52 and the anode current collector 21 The ratio of the distances D ₂ (D ₂ / D ₁ ) is 0.7 to ₁ . As a result, the thickness of the first negative electrode material layer finally formed on one surface 21a of the negative electrode current collector 21 and the second negative electrode material layer formed on the other surface 21b of the negative electrode current collector 21. It is possible to obtain a negative electrode having a small difference from the thickness of. Is the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 longer than the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21? The distance between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 is the same as the distance D ₂ .

The distance ratio (D ₂ / D ₁ ) is preferably 0.8 or more, more preferably 0.9 or more, still more preferably 0.95 or more, from the viewpoint of facilitating the acquisition of a negative electrode for zinc batteries having excellent life performance. Is. The distance ratio (D ₂ / D ₁ ) is particularly preferably 1 but may be less than 1.

The ratio of the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 to the distance D ₁ between the first wall surface 51 and the one surface 21a of the negative electrode current collector 21 is in the gap 53. It can be adjusted by adjusting the position through which the negative electrode current collector 21 passes.

The difference between the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the other surface 21b of the negative electrode current collector 21 is a negative electrode for a zinc battery having excellent life performance. From the viewpoint of making it easy to obtain, it is preferably 0.03 mm or less, more preferably 0.02 mm or less, and further preferably 0.01 mm or less. The difference between the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the other surface 21b of the negative electrode current collector 21 is particularly preferably 0, but more than 0. It may be large.

The distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 are charge reserves (on the negative electrode side). From the viewpoint of securing (capacity that can be overcharged), each is preferably 0.2 mm or more, more preferably 0.3 mm or more, and further preferably 0.35 mm or more. The distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 are from the viewpoint of ensuring energy density. , Each is preferably 0.5 mm or less, more preferably 0.45 mm or less, still more preferably 0.4 mm or less.

The distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 are, for example, the layer forming portion 50. It can be adjusted by the gap adjusting portion 54 provided in. The gap adjusting portion 54 can change the positions of the first wall surface 51 and the second wall surface 52, and can adjust the size of the gap 53. As a result, the magnitude of the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 are also adjusted. To. The method of adjusting the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 and the distance D ₂ between the second wall surface 52 and the other surface 21b of the negative electrode current collector 21 is limited to this. Not done.

Subsequently, as shown in FIG. 2, the negative electrode current collector 22 to which the negative electrode material paste adheres to both sides after passing through the layer forming portion 50 is passed through the drying furnace 60. Examples of the drying oven 60 include a vacuum drying oven, a drying oven equipped with an infrared heater, and the like.

The temperature in the drying oven 60 may be, for example, 90 ° C. or higher, 100 ° C. or higher, or 110 ° C. or higher, and may be 150 ° C. or lower, 140 ° C. or lower, or 130 ° C. or lower. The time (drying time) for passing through the drying oven 60 may be, for example, 1 minute or more, 3 minutes or more, or 5 minutes or more, and may be 60 minutes or less, 30 minutes or less, or 20 minutes or less.

By passing through the drying furnace 60, the dispersion medium contained in the negative electrode material paste is volatilized, a first negative electrode material layer is formed on one surface of the negative electrode current collector 21, and a second negative electrode material is formed on the other surface. It is possible to obtain an unchemical negative electrode 24 on which a layer is formed. As shown in FIG. 2, the continuously manufactured negative electrode 24 can be cut into a predetermined size and used for manufacturing a zinc battery.

The method for manufacturing a negative electrode for a zinc battery according to the above-described embodiment can take various modifications.

For example, in the method for manufacturing a negative electrode for a zinc battery, the method for adhering the negative electrode material paste to the negative electrode current collector may be coating with an applicator or the like. Alternatively, a negative electrode current collector to which the negative electrode material paste has already adhered may be prepared.

The layer forming portion may include two separated members, and the negative electrode material paste adheres between the two members while the negative electrode material paste is brought into contact with the wall surface of each of the two separated members. It may be passed through a current collector.

After passing the negative electrode current collector with the negative electrode material paste adhering to both sides through the layer forming portion, pressing or the like may be performed if necessary. As a result, it is possible to obtain a negative electrode having an increased density of the negative electrode material layer.

In the method of drying the negative electrode material paste, for example, the negative electrode current collector on which the negative electrode material paste layer is formed may be allowed to stand in a room temperature environment without using a drying furnace.

In the above-described embodiment, an apparatus capable of manufacturing a negative electrode for a zinc battery is used as shown in FIG. 2, but a step of adhering a negative electrode material paste to a negative electrode current collector and a layer forming portion of the negative electrode material paste. The step of passing the paste through the negative electrode material and the step of drying the negative electrode material paste may be performed by separate devices.

<Negative electrode for zinc battery>
The negative electrode for a zinc battery according to one embodiment includes a first negative electrode material layer provided on one surface of the negative electrode current collector and a second negative electrode material layer provided on the other surface of the negative electrode current collector. The negative electrode for a zinc battery is provided, and the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer is 0.7 to 1. The negative electrode for a zinc battery may be either post-chemical or non-chemical. The negative electrode for unchemical zinc batteries can be obtained, for example, by the above-mentioned method for manufacturing a negative electrode for zinc batteries.

The mode of the negative electrode current collector may be the same as that of the negative electrode current collector in the above-described method for manufacturing a negative electrode for a zinc battery.

The negative electrode material layer contains a negative electrode active material containing zinc. The mode of the negative electrode active material may be the same as that of the negative electrode active material contained in the negative electrode material paste described above. In addition to the negative electrode active material, the above-mentioned additives may be added to the negative electrode material layer.

The "thickness of the negative electrode material layer" in the present specification is the distance between one surface of the negative electrode current collector and the surface of the negative electrode material layer provided on the one surface opposite to the negative electrode current collector. It means the average value measured at 9 points on the negative electrode material layer. The nine measurement points are the upper left corner, upper center, upper right corner, left center, center, right center, lower left corner, lower center, and right when the negative electrode is viewed from the stacking direction. There may be nine locations in the lower center. FIG. 4 is a plan view showing an example of a measurement location of the thickness of the negative electrode material layer. As shown in FIG. 4, the thickness of the negative electrode material layer 25 provided on the negative electrode current collector 21 is as follows: upper left corner a, upper center b, upper right corner c, left center d, center e, right center. It is measured at nine points, a portion f, a lower left corner portion g, a lower central portion h, and a lower right central portion i, and can be an average value of these measured values. The thickness at each location of the negative electrode can be measured using, for example, a micrometer.

The ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer (thickness of the second negative electrode material layer / thickness of the first negative electrode material layer) is the negative electrode for zinc batteries having excellent life performance. From the viewpoint of making it easy to obtain, it is preferably 0.8 or more, more preferably 0.9 or more, still more preferably 0.95 or more. The thickness ratio (thickness of the second negative electrode material layer / thickness of the first negative electrode material layer) is particularly preferably 1 but may be less than 1. The thickness of the first negative electrode material layer is thicker (larger) than the thickness of the second negative electrode material layer, or is the same thickness as the second negative electrode material layer.

The difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer is preferably 0.03 mm or less, more preferably 0., from the viewpoint of facilitating the acquisition of a negative electrode for a zinc battery having excellent life performance. It is 02 mm or less, more preferably 0.01 mm or less. The difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer is particularly preferably 0, but may be larger than 0.

The thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer are preferably 0.2 mm or more, more preferably 0.3 mm or more, and further preferably 0.35 mm, respectively, from the viewpoint of ensuring the charge reserve. That is all. The thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer are preferably 0.6 mm or less, more preferably 0.5 mm or less, still more preferably 0.4 mm, respectively, from the viewpoint of ensuring energy density. It is as follows. The thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer are the distance D ₁ between the first wall surface 51 and one surface 21a of the negative electrode current collector 21 in the above-described manufacturing method, and the second. It may correspond to the distance D ₂ between the wall surface 52 and the other surface 21b of the negative electrode current collector 21.

<Zinc battery>
Hereinafter, a nickel-zinc battery will be described as an example of the zinc battery according to the present embodiment. The nickel-zinc battery according to one embodiment includes, for example, an electric tank, an electrolytic solution, and an electrode group (for example, a plate group). The electrode group and the electrolytic solution are housed in the electric tank.

The electrode group is composed of, for example, a separator and a positive electrode (positive electrode plate or the like) and a negative electrode (negative electrode plate or the like) facing each other via the separator. In the electrode group, the positive electrodes and the negative electrodes are connected by, for example, a strap. The negative electrode may be the negative electrode for a zinc battery according to the above-described embodiment.

The positive electrode includes, for example, a positive electrode current collector, a first positive electrode material layer provided on one surface of the positive electrode current collector, and a second positive electrode material layer provided on the other surface of the positive electrode current collector. Be prepared. The positive electrode may be either pre-chemical or post-chemical.

The positive electrode current collector has a shape such as a flat plate shape or a sheet shape. The positive electrode current collector may be a current collector having a three-dimensional network structure composed of foamed metal, expanded metal, punching metal, felt-like material of metal fibers, or the like. The positive electrode current collector is made of a material having conductivity and alkali resistance. Examples of such a material include a material that is stable even at the reaction potential of the positive electrode (a material having an oxidation-reduction potential noble than the reaction potential of the positive electrode, and a protective film such as an oxide film is formed on the surface of the substrate in an alkaline aqueous solution. A material that stabilizes the material) can be used. Further, in the positive electrode, the decomposition reaction of the electrolytic solution proceeds as a side reaction to generate oxygen gas, and a material having a high oxygen overvoltage is preferable in that the progress of such a side reaction can be suppressed. Specific examples of the material constituting the positive electrode current collector include platinum; nickel (foamed nickel, etc.); and a metal material plated with metal such as nickel (copper, brass, steel, etc.). Among these, a positive electrode current collector composed of foamed nickel is preferably used. From the viewpoint of further improving the high rate discharge performance, it is preferable that at least the portion of the positive electrode current collector that supports the positive electrode material (positive electrode material supporting portion) is made of foamed nickel.

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

The positive electrode material layer may further contain components other than the positive electrode active material as additives. Examples of the additive include a binder, a conductive agent, an expansion inhibitor and the like.

Examples of the binder include hydrophilic or hydrophobic polymers. Specifically, for example, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), sodium polyacrylate (SPA), fluoropolymer (polytetrafluoroethylene (PTFE), etc.) and the like are bound. It can be used as a coating agent. The content of the binder is, for example, 0.01 to 5 parts by mass with respect 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.) and the like. The content of the conductive agent is, for example, 1 to 20 parts by mass with respect to 100 parts by mass of the positive electrode active material.

Examples of the expansion inhibitor include zinc oxide and the like. The content of the expansion inhibitor is, for example, 0.01 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

The separator may be, for example, a separator having a shape such as a flat plate or a sheet. Examples of the separator include a polyolefin-based microporous membrane, a nylon-based microporous membrane, an oxidation-resistant ion exchange resin membrane, a cellophane-based recycled resin membrane, an inorganic-organic separator, and a polyolefin-based non-woven fabric. The separator may be processed into a bag shape so as to accommodate a positive electrode and / or a negative electrode. In this case, the positive electrode and / or the negative electrode may be housed in the separator. The separator may be used alone or in combination of two or more.

The method for manufacturing a nickel-zinc battery described above includes a component manufacturing step for obtaining a component of the zinc battery and an assembly step for assembling the component to obtain a zinc battery. In the component manufacturing process, at least electrodes (positive electrode and negative electrode) are obtained. The method for manufacturing the negative electrode is the above-mentioned method for manufacturing the negative electrode for zinc batteries.

As the positive electrode, a positive electrode material paste obtained by adding a dispersion medium (for example, water) to the raw material of the positive electrode material layer and kneading is used. Examples of the method for obtaining a positive electrode include the same method as the above-described method for manufacturing a negative electrode for a zinc battery, a method in which a positive electrode material paste is applied or immersed in a positive electrode current collector, and then dried.

In the assembly process, for example, the positive electrodes and the negative electrodes obtained in the component manufacturing process are alternately laminated via a separator, and then the positive electrodes and the negative electrodes are connected by a strap to prepare an electrode group. Next, after arranging this electrode group in the battery case, a lid is adhered to the upper surface of the battery case to obtain a non-chemical zinc battery (nickel-zinc battery).

Subsequently, the electrolytic solution is injected into the battery case of the unchemical zinc battery, and then left for a certain period of time. Next, a zinc battery (nickel-zinc battery) is obtained by chemical conversion by charging under predetermined conditions. The chemical conversion conditions can be adjusted according to the properties of the positive electrode active material and the negative electrode active material.

The example of a nickel-zinc battery (for example, a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode has been described above, but the zinc battery is an air zinc battery (for example, an air zinc secondary battery) in which the positive electrode is an air electrode. It may be a silver-zinc battery in which the positive electrode is a silver oxide electrode (for example, a silver-zinc secondary battery).

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the following examples.

(Example 1)
<Manufacturing negative electrode for zinc batteries>
A predetermined amount of zinc oxide, metallic zinc, bismuth oxide, hydroxyethyl cellulose and ion-exchanged water were weighed and mixed, and the obtained mixed solution was stirred to prepare a negative electrode material paste. At this time, the mass ratio of the non-volatile content in the negative electrode material paste was adjusted to "zinc oxide: metallic zinc: bismuth oxide: hydroxyethyl cellulose = 72: 20.5: 5: 2.5". As the hydroxyethyl cellulose, AV-15F (trade name) manufactured by Sumitomo Seika Chemical Co., Ltd. was used. The water content of the negative electrode material paste was adjusted to 20.5% by mass based on the total mass of the negative electrode material paste.

A negative electrode for a zinc battery was manufactured using the apparatus shown in FIG. A roll-shaped negative electrode current collector (copper punching metal) was set in the unwinding portion 30. The negative electrode current collector was passed through a tank 40 containing the negative electrode material paste, and the negative electrode material paste was adhered to both sides of the negative electrode current collector. Next, the negative electrode current collector to which the negative electrode material paste was attached was passed through the layer forming portion 50. At this time, the distance of the distance D ₂ between the other surface of the first wall 51 and the distance D ₁ of the the one surface of the negative electrode current _collector, and the second wall 52 and the anode current collector in a layer forming unit 50 0 The width of the gap 53 in the layer forming portion 50 and the position through which the negative electrode current collector passes were adjusted so as to be 0.4 mm. Subsequently, the negative electrode current collector that had passed through the layer forming portion 50 was passed through a drying furnace having a temperature of 110 ° C. in the furnace over 10 minutes to volatilize the water contained in the negative electrode material paste. The dried negative electrode was cut into a rectangular shape having a size of 50 mm × 60 mm to obtain a negative electrode for an unchemical zinc battery according to Example 1.

With respect to the negative electrode according to Example 1, the thicknesses of the first negative electrode material layer and the second negative electrode material layer were measured. The thickness is measured at nine points in FIG. 4, that is, when the negative electrode is viewed from the stacking direction, the upper left corner portion a, the upper center portion b, the upper right corner portion c, the left center portion d, the center portion e, and the right center portion f. The thickness of 9 points of the lower left corner g, the lower center h, and the lower right center i was measured using a micrometer (PMU150-25MX, manufactured by Mitutoyo Co., Ltd.). The thickness at each location, the difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer, and the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer (second). (Thickness of the negative electrode material layer / thickness of the first negative electrode material layer) is shown in Table 1.

<Making zinc batteries>
A lattice body made of foamed nickel having a porosity of 95% was prepared, and the lattice body was pressure-molded to obtain a positive electrode current collector. Next, a predetermined amount of cobalt-coated nickel hydroxide powder, metallic cobalt, cobalt hydroxide, yttrium oxide, carboxymethyl cellulose, polytetrafluoroethylene, and ion-exchanged water are weighed and mixed, and the mixed solution is stirred to prepare a positive electrode material paste. Was produced. At this time, the mass ratio of the solid content was changed to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: carboxymethyl cellulose: polytetrafluoroethylene = 88: 10.3: 1: 0.3: 0.3: 0. .1 ”was adjusted. The water 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. Next, the positive electrode material paste was applied to both sides of the positive electrode current collector, and then dried at 80 ° C. for 30 minutes. Then, it was pressure-molded by a roll press to obtain an unchemical positive electrode having a positive electrode material layer.

The separator is UP3355 (manufactured by Ube Industries, Ltd., trade name, air permeability: 440 seconds / 100 mL) as a microporous membrane, and non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., trade name: VL-100, transparent) as a non-woven fabric. Air temper: 0.3 seconds / 100 mL) was used respectively. The microporous membrane was hydrophilized with a surfactant Triton-X100 (manufactured by Sigma-Aldrich Japan LLC) before assembling the battery. The hydrophilization treatment was carried out by immersing the microporous membrane in an aqueous solution containing Triton-X100 in an amount of 1% by mass for 24 hours and then drying at room temperature for 1 hour. The air permeability of the microporous membrane shows the value after the hydrophilic treatment. Further, the microporous membrane was cut into a predetermined size, folded in half, and heat-welded on the side surface to process it into a bag shape. The non-woven fabric used was cut to a predetermined size.

One positive electrode and one negative electrode were housed in a microporous membrane processed into a bag shape. After laminating a positive electrode housed in a bag-shaped microporous membrane, a negative electrode stored in a bag-shaped microporous membrane, and a non-woven fabric, electrode groups (pole plates) of the same polarity are connected with a strap. Group) was prepared. The electrode group consisted of 11 positive electrodes and 12 negative electrodes, and one non-woven fabric was arranged between the positive electrode and the negative electrode (between the microporous film on the positive electrode side and the microporous film on the negative electrode side). After arranging this electrode group in the electric tank, a lid was adhered to the upper surface of the electric tank, and the electrolytic solution was injected into the electric tank to obtain an unchemical nickel-zinc battery. Then, the battery was charged at 800 mA for 15 hours to prepare a nickel-zinc battery having a nominal capacity of 8000 mAh.

(Comparative Example 1)
<Preparation of negative electrode for zinc battery>
A negative electrode for an unchemical zinc battery manufactured by a conventional method was prepared. In this negative electrode, the negative electrode material paste is attached to both sides of the negative electrode current collector, and then the negative electrode material paste is applied while bringing the adhered negative electrode material pastes 23a and 23b into contact with the first wall surface 51 or the second wall surface 52. Although the process itself passing the anode current collector 22 attached to both sides of the gap 53 is the same as the first embodiment, with respect to the distance D ₁ of the the one surface 21a of the first wall 51 and the anode current collector 21, the The ratio of the distance D ₂ between the wall surface 52 of 2 and the other surface 21b of the negative electrode current collector 21 was manufactured by visually arranging the negative electrode current collector near the center of the gap 53 without adjusting.

The thicknesses of the first negative electrode material layer and the second negative electrode material layer were measured by the same method as in Example 1. The thickness at each location, the difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer, and the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer (second). Table 1 shows the thickness of the negative electrode material layer / the thickness of the first negative electrode material layer).

<Making zinc batteries>
A nickel-zinc battery was produced by the same method as in Example 1 except that the negative electrode in Example 1 was changed to the negative electrode according to Comparative Example 1 described above.

<Evaluation of life performance>
After charging the nickel-zinc battery at a constant voltage of 8000 mA (1C) and 1.9 V at 25 ° C. until the current value attenuates to 400 mA (0.05 C), 8000 mA until the battery voltage reaches 1.1 V. A test was conducted in which one cycle was to discharge the nickel-zinc battery at the constant current of (1C). The test was completed when the discharge capacity was less than 60% of the discharge capacity of the first cycle, and the cycle life performance was evaluated by the number of cycles performed until the end of the test. Table 1 shows the number of cycles performed until the end of the test. As shown in Table 1, the nickel-zinc battery according to Example 1 had an increased number of cycles and was excellent in life performance as compared with the nickel-zinc battery according to Comparative Example 1.

21 ... Negative electrode current collector, 21a ... One surface of the negative electrode current collector, 21b ... The other surface of the negative electrode current collector, 50 ... Layer forming portion, 51 ... First wall surface, 52 ... Second wall surface, 23a, 23b ... Negative electrode material paste, 24 ... Negative electrode (negative electrode for zinc batteries).

Claims (6)

A zinc battery including a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and a second negative electrode material layer provided on the other surface of the negative electrode current collector. It is a manufacturing method of the negative electrode for
With the negative electrode material paste adhered to both sides of the negative electrode current collector, the first wall surface and the second wall surface are brought into contact with the negative electrode material pastes on both sides while being in contact with the first wall surface and the second wall surface facing each other. A negative electrode material layer forming step for forming the first negative electrode material layer and the second negative electrode material layer by passing the negative electrode current collector through the wall surface of the negative electrode material is provided.
In the negative electrode material layer forming step, the ratio of the distance between the second wall surface and the other surface of the negative electrode current collector to the distance between the first wall surface and the one surface of the negative electrode current collector is 0. A method for manufacturing a negative electrode for a zinc battery, which is 7-1. The method for manufacturing a negative electrode for a zinc battery according to claim 1, wherein the ratio is less than 1. Claim that the difference between the distance between the first wall surface and the one surface of the negative electrode current collector and the distance between the second wall surface and the other surface of the negative electrode current collector is 0.03 mm or less. The manufacturing method according to 1 or 2. A zinc battery including a negative electrode current collector, a first negative electrode material layer provided on one surface of the negative electrode current collector, and a second negative electrode material layer provided on the other surface of the negative electrode current collector. Negative electrode for
A negative electrode for a zinc battery, wherein the ratio of the thickness of the second negative electrode material layer to the thickness of the first negative electrode material layer is 0.7 to 1. The negative electrode for a zinc battery according to claim 4, wherein the ratio is less than 1. The negative electrode for a zinc battery according to claim 4 or 5, wherein the difference between the thickness of the first negative electrode material layer and the thickness of the second negative electrode material layer is 0.03 mm or less.