Negative electrode plate and zinc secondary battery

Abstract

The present invention provides a negative electrode plate that enables a zinc secondary battery to have a prolonged cycle life. The negative electrode plate is for a zinc secondary battery. The negative electrode plate has, on at least one side thereof, at least one functional surface that is to be caused to face to at least one positive electrode plate in the zinc secondary battery. The negative electrode plate includes: a negative electrode active material layer that contains ZnO particles and Zn particles; and a negative electrode current collector that extends through the inside of the negative electrode active material layer and supports the negative electrode active material layer. A groove part, which extends from a central part toward the outer periphery on the functional surface side of the negative electrode plate, is provided so as to divide the functional surface into a plurality of regions. The groove part is constituted by at least a partial lack of the negative electrode active material layer. When the functional surface side of the negative electrode plate is viewed in plan, the ratio A1 / (A1 + A2) of the area A1 occupied by the negative electrode active material layer excluding the groove part to the total area A1 + A2 of the area A1 occupied by the negative electrode active material layer and the area A2 occupied by the groove part is 0.60 to 0.98.

Description

Negative electrode plate and zinc secondary battery

[0001] The present disclosure relates to a negative electrode plate and a zinc secondary battery.

[0002] In zinc secondary batteries, such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc precipitates in the form of dendrites from the negative electrode during charging, penetrates the pores of the separator (e.g., nonwoven fabric) and reaches the positive electrode, resulting in a short circuit. Such short circuits caused by zinc dendrites shorten the battery's life after repeated charging and discharging.

[0003] To address the above-mentioned problems, batteries have been proposed that include a layered double hydroxide (LDH) separator that selectively allows hydroxide ions to pass through while preventing zinc dendrites from penetrating. For example, Patent Document 1 (WO 2013 / 118561) discloses a nickel-zinc secondary battery in which an LDH separator is provided between the positive and negative electrodes. Furthermore, Patent Document 2 (WO 2016 / 076047) discloses a separator structure that includes an LDH separator fitted or bonded to a resin outer frame, and that the LDH separator has such high density that it is gas-impermeable and / or water-impermeable. This document also discloses that the LDH separator can be composited with a porous substrate. Furthermore, Patent Document 3 (WO 2016 / 067884) discloses various methods for forming a dense LDH membrane on the surface of a porous substrate to obtain a composite material. This method includes the steps of uniformly attaching a starting substance capable of providing a starting point for LDH crystal growth to a porous substrate, and then subjecting the porous substrate to hydrothermal treatment in a raw material aqueous solution to form a dense LDH membrane on the surface of the porous substrate.

[0004] Another factor that shortens the lifespan of zinc secondary batteries is morphological changes in the negative electrode active material, zinc. Specifically, as zinc dissolves and precipitates during repeated charge and discharge, the negative electrode undergoes morphological changes, resulting in increased resistance due to pore blockage and a decrease in the charge active material due to the accumulation of isolated zinc, making charging and discharging difficult. To address this issue, Patent Document 4 (WO 2020 / 049902) proposes the use of a negative electrode in combination with at least two selected from (i) metal Zn particles of a predetermined particle size, (ii) a predetermined metal element, and (iii) a binder resin having a hydroxyl group. This negative electrode is said to suppress negative electrode deterioration due to repeated charge and discharge in zinc secondary batteries, improving durability and thereby extending cycle life.

[0005] Furthermore, Patent Document 5 (Japanese Patent No. 6,190,101) discloses a negative electrode composite containing a negative electrode active material such as metallic Zn or ZnO, a polymer such as an aromatic group-containing polymer, an ether group-containing polymer, or a hydroxyl group-containing polymer, and a conductive additive which is a compound of an element such as B, Ba, Bi, Br, Ca, Cd, Ce, Cl, F, Ga, Hg, In, La, or Mn, and describes that the negative electrode composite is suitable for forming a storage battery that exhibits high battery performance such as high cycle characteristics, rate characteristics, and Coulomb efficiency while suppressing shape change of the electrode active material, morphological changes of the electrode active material such as dendrites, dissolution, corrosion, and passivation formation.

[0006] International Publication No. 2013 / 118561 International Publication No. 2016 / 076047 International Publication No. 2016 / 067884 International Publication No. 2020 / 049902 Patent No. 6190101

[0007] As disclosed in Patent Documents 4 and 5, various attempts have been proposed to address the deterioration of cycle characteristics associated with morphological changes in zinc negative electrodes, but further improvement in cycle characteristics is desired.

[0008] The inventors have now discovered that the cycle life of a zinc secondary battery can be extended by providing grooves extending from the center to the outer periphery with a predetermined area ratio on the functional surface of the negative electrode plate that should face the positive electrode plate, so as to divide the functional surface into multiple regions.

[0009] Therefore, an object of the present invention is to provide a negative electrode plate that can extend the cycle life of a zinc secondary battery.

[0010] According to the present disclosure, the following aspects are provided: [Aspect 1] A negative electrode plate for a zinc secondary battery, the negative electrode plate having at least one functional surface on at least one side thereof to be opposed to at least one positive electrode plate in the zinc secondary battery, the negative electrode plate comprising: a negative electrode active material layer containing ZnO particles and Zn particles; and a negative electrode current collector extending through the negative electrode active material layer and supporting the negative electrode active material layer, wherein a groove extending from a center portion to an outer periphery is provided on the functional surface side of the negative electrode plate so as to divide the functional surface into a plurality of regions, the groove being formed by at least a partial absence of the negative electrode active material layer, and when the functional surface side of the negative electrode plate is viewed in plan, an area A occupied by the negative electrode active material layer excluding the groove is １ and the area A occupied by the groove portion ２ Total area A １ +A ２ The area A occupied by the negative electrode active material layer relative to １ Percentage A １ / (A １ +A ２) is 0.60 to 0.98. [Aspect 2] The negative electrode plate according to Aspect 1, wherein the grooves are provided in a cross-shaped, radial, or diagonal pattern. [Aspect 3] The negative electrode plate according to Aspect 1 or 2, wherein a ratio D / L of a depth D of the groove to a length L from a center position in the thickness direction of the negative electrode current collector to the functional surface is 0.57 to 1.00. [Aspect 4] The negative electrode plate according to any one of Aspects 1 to 3, wherein the grooves have a tapered cross-sectional shape whose width decreases from the functional surface toward the negative electrode current collector. [Aspect 5] The negative electrode plate according to any one of Aspects 1 to 4, wherein, in a cross-sectional view of the negative electrode plate, an angle formed between a wall surface of the groove and an imaginary center line in the thickness direction of the negative electrode current collector is 35 to 70 degrees. [Aspect 6] The negative electrode plate according to any one of Aspects 1 to 5, wherein the negative electrode plate further comprises a polymer that forms the functional surface by coating the surface of the negative electrode active material layer on the functional surface side excluding the groove portion, and that is impregnated with a polymer so that the concentration decreases toward the inside of the negative electrode active material layer, whereby the negative electrode active material layer has a polymer-rich portion that is adjacent to the functional surface and is rich in the polymer, and a polymer-poor portion that is distant from the functional surface and is poor in the polymer. [Aspect 7] The polymer-rich portion is a polymer-rich portion that is adjacent to the functional surface and is rich in the polymer, and the polymer-poor portion that is distant from the functional surface and is poor in the polymer, when an image analysis of a cross section of the negative electrode plate is performed. Ａ The negative electrode plate according to aspect 6, wherein the polymer-poor portion is a polymer-poor portion having a polymer content of 5 to 40% by area when a cross section of the negative electrode plate is image-analyzed. Ｂ is 0 to 20 area %, and Ａ is the P ＢThe negative electrode plate according to any one of Aspects 6 or 7, wherein the polymer is a nonionic water-absorbing polymer. Aspect 9: The negative electrode plate according to any one of Aspects 6 to 8, wherein the polymer is a nonionic water-absorbing polymer. Aspect 10: The negative electrode plate according to any one of Aspects 1 to 9, wherein the negative electrode plate has the functional surface on both sides thereof. Aspect 11: The negative electrode plate according to any one of Aspects 1 to 10, wherein the negative electrode active material layer further contains one or more metal elements selected from In and Bi. Aspect 12: The negative electrode plate according to any one of Aspects 1 to 11, wherein the negative electrode plate is a sheet-like pressed compact. Aspect 13: A zinc secondary battery comprising: the negative electrode plate according to any one of Aspects 1 to 12; a positive electrode plate provided opposite the functional surface of the negative electrode plate; a separator separating the positive electrode plate and the negative electrode plate in a manner capable of conducting hydroxide ions; and an electrolyte. [Aspect 14] The zinc secondary battery according to Aspect 13, wherein the separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound. [Aspect 15] The zinc secondary battery according to Aspect 13 or 14, wherein the LDH separator is composited with a porous substrate.

[0011] 1B is a schematic top view showing one embodiment of the negative electrode plate of the present invention, as viewed from the functional surface side. FIG. 1C is a schematic top view showing another example of the shape of the groove portion. FIG. 1B is a schematic cross-sectional view of the negative electrode plate shown in FIG. 1A, showing an enlarged view of the groove portion provided in the negative electrode plate. FIG. 1C is an enlarged view of the central portion surrounded by the dashed line of the negative electrode plate shown in FIG. 1A, conceptually showing that the groove portion serves as a gas escape channel. FIG. 1D is a diagram for explaining the ratio D / L of the depth D of the groove portion to the length L from the central position in the thickness direction of the negative electrode current collector to the functional surface. FIG. 1E is a schematic cross-sectional view showing another embodiment of the negative electrode plate of the present invention, showing that the negative electrode active material layer has a polymer-rich portion and a polymer-poor portion. ３ 1 is a graph showing an example of the relationship between the amount of absorbed water and the amount of collected KOH per unit time, and the KOH concentration.

[0012] The negative electrode plate of the present invention is a negative electrode plate used in a zinc secondary battery. Figures 1A, 1B, and 2 show one embodiment of the negative electrode plate of the present invention. The negative electrode plate 10 shown in these figures has at least one functional surface 10a on at least one side thereof, which is to face at least one positive electrode plate in a zinc secondary battery. The negative electrode plate 10 includes a negative electrode active material layer 12 and a negative electrode current collector 14. The negative electrode active material layer 12 contains ZnO particles and Zn particles. The negative electrode current collector 14 extends through the negative electrode active material layer and supports the negative electrode active material layer. As shown in Figures 1A and 1B, the negative electrode plate 10 has grooves G extending from the center toward the periphery on the functional surface 10a side, dividing the functional surface 10a into multiple regions. In this specification, the "center" of the negative electrode plate refers to the central region when the functional surface 10a of the negative electrode plate is divided into five equal regions in the vertical direction, and also refers to the central region when the functional surface 10a of the negative electrode plate is divided into five equal regions in the horizontal direction. As shown in FIG. 2, the groove G is formed by at least a partial absence of the negative electrode active material layer 12. When the functional surface 10a of the negative electrode plate is viewed in plan, the area A occupied by the negative electrode active material layer 12 excluding the groove G is １ and the area A occupied by the groove G ２ Total area A １ +A ２ The area A occupied by the negative electrode active material layer 12 relative to １ Percentage A １ / (A １ +A ２ ) is 0.60 to 0.98. １ / (A １ +A ２ ) is sometimes referred to as the "area ratio of the negative electrode active material layer to the functional surface." In this way, by providing grooves G extending from the center toward the periphery at a predetermined area ratio on the functional surface 10a of the negative electrode plate that is to face the positive electrode plate so as to divide the functional surface 10a into a plurality of regions, the cycle life of the zinc secondary battery can be extended.

[0013] The mechanism by which the grooves G extend the cycle life of zinc secondary batteries is not entirely clear, but it is believed to be as follows. Specifically, when a zinc secondary battery is constructed using a negative electrode plate and charge / discharge reactions are allowed to proceed, gas (e.g., hydrogen gas) is generated from the negative electrode plate due to side reactions. The gas generated inside the negative electrode plate 10 tends to accumulate, particularly near the center of the negative electrode plate. This gas accumulation is thought to cause uneven reactions in the center of the negative electrode plate 10, adversely affecting cycle characteristics. The negative electrode plate 10 of the present invention effectively eliminates this uneven reaction due to gas accumulation. Here, FIG. 3 shows an enlarged view of the center of the negative electrode plate 10 shown in FIG. 1A. As shown in FIG. 3, gas generated inside the negative electrode plate 10 is discharged to the outside of the negative electrode through the grooves G extending from the center of the negative electrode plate 10 toward the periphery. In other words, the grooves G function as gas escape channels, effectively suppressing gas accumulation. Furthermore, the grooves G also function as a flow path for supplying the electrolyte, which further suppresses uneven reaction near the center of the negative electrode plate 10. It is believed that the use of the negative electrode plate 10 can thus extend the cycle life of the zinc secondary battery.

[0014] On the other hand, as described above, since the groove portion G is formed by at least a partial absence of the negative electrode active material layer 12, if the amount of negative electrode active material on the surface facing the positive electrode (i.e., the functional surface 10 a) is too small, the current density load applied to the negative electrode plate increases, and the negative electrode is more likely to deteriorate. In this regard, by providing the groove portion G so that the area ratio of the negative electrode active material layer 12 to the functional surface 10 a is within the above-mentioned predetermined range, it is possible to suppress the increase in the current density load applied to the negative electrode plate 10 while improving the cycle characteristics of the zinc secondary battery by improving gas leakage as described above.

[0015] Therefore, when the functional surface 10a of the negative electrode plate is viewed in plan, the area A occupied by the negative electrode active material layer 12 excluding the groove portion G is １ and the area A occupied by the groove G ２ Total area A １ +A ２ The area A occupied by the negative electrode active material layer 12 relative to １ A is the ratio of１ / (A １ +A ２ ) is 0.60 to 0.98, preferably 0.70 to 0.98, more preferably 0.80 to 0.98, and even more preferably 0.90 to 0.98. The area ratio of the negative electrode active material layer 12 to the functional surface 10a can be controlled by appropriately changing the width and / or number of the grooves G to be formed.

[0016] The grooves G are preferably provided in a cross shape (see FIG. 1B), a radial shape, or a diagonal shape (see FIG. 1A) on the functional surface 10a of the negative electrode plate, which makes it easier to discharge gas generated on the negative electrode plate 10 to the outside of the negative electrode. The number of regions of the functional surface 10a divided by the grooves G is typically 4 or more, and more typically 4 to 32.

[0017] As described above, the groove G is formed by at least a partial absence of the negative electrode active material layer 12. That is, as shown in FIG. 4 , the negative electrode active material layer 12 may remain inside the negative electrode plate 10 (including inside the negative electrode current collector 14) directly below the groove G. Alternatively, the groove G may be formed by a complete absence of the negative electrode active material layer 12. In other words, the groove G may have a depth that extends from the functional surface 10 a to the center position in the thickness direction of the negative electrode current collector 14.

[0018] Therefore, the negative electrode plate 10 preferably has a ratio D / L of the groove depth D to the length L from the center position in the thickness direction of the negative electrode current collector 14 to the functional surface 10a of 0.57 to 1.00, more preferably 0.70 to 1.00, even more preferably 0.80 to 1.00, and particularly preferably 0.90 to 1.00. By forming grooves G of such depth, the effect of improving gas leakage by dividing the functional surface 10a can be further exerted, and the cycle characteristics of the zinc secondary battery can be further improved. Hereinafter, the ratio D / L may be referred to as the "groove depth ratio."

[0019] As shown in Fig. 2, the grooves G preferably have a tapered cross-sectional shape in which the width decreases from the functional surface 10a toward the negative electrode current collector 14. Groove G having such a shape allows gas generated inside the negative electrode plate 10 to be more efficiently discharged to the outside of the negative electrode. The taper angle of the grooves G, that is, the angle formed by the wall surface (and its extension) of the grooves G and the imaginary center line C in the thickness direction of the negative electrode current collector 14 when the negative electrode plate 10 is viewed in cross section, is not particularly limited, but is typically 35 to 70°, more typically 40 to 70°, and even more typically 50 to 70°.

[0020] The negative electrode plate 10 may have a functional surface on only one side, or may have functional surfaces on both sides. For example, when a stacked battery is constructed by combining multiple negative electrode plates and multiple positive electrode plates, both sides of the negative electrode plate may face the positive electrode plate. In this regard, it is preferable to provide the above-mentioned grooves G on both sides of the negative electrode plate 10, thereby more efficiently discharging gas generated in the negative electrode plate 10 to the outside of the negative electrode. When the negative electrode plate 10 has functional surfaces on both sides, the grooves G provided on one side of the negative electrode plate 10 and the grooves G provided on the other side may be connected via the negative electrode current collector 14. In this case, the negative electrode active material layer 12 may be present inside the negative electrode current collector 14 separating the grooves G on both sides of the negative electrode plate 10, or the negative electrode active material layer 12 may be removed. Furthermore, the overlapping portions of the wall surfaces of the grooves G provided on both sides of the negative electrode plate 10 (corners of the grooves G) may be rounded. The grooves G provided on both sides of the negative electrode plate 10 may have different opening widths, or the centers of the opening widths may be offset from each other. The grooves G provided on both sides of the negative electrode plate 10 may have different cross-sectional shapes (e.g., tapered shapes) from each other.

[0021] The negative electrode plate 10 preferably comprises a functional surface 10a formed by coating the surface of the negative electrode active material layer 12 on the functional surface 10a side, excluding the groove portion G, and further comprises a polymer impregnated so that the concentration decreases toward the inside of the negative electrode active material layer 12. That is, as shown in Fig. 5, the negative electrode active material layer 12 preferably has a polymer-rich portion 12a adjacent to the functional surface 10a and a polymer-poor portion 12b away from the functional surface 10a. In this way, by including a polymer in the negative electrode plate 10, the cycle characteristics of the zinc secondary battery can be further improved.

[0022] As mentioned above, in conventional negative electrodes, as zinc dissolves and precipitates repeatedly during charge and discharge, the morphology of the negative electrode changes, resulting in high resistance due to pore blockage and a decrease in the charge active material due to the accumulation of isolated zinc, which results in problems such as difficulty in charge and discharge. In this regard, the negative electrode reaction is particularly likely to proceed on the negative electrode surface (i.e., the functional surface) close to the positive electrode and separator, so zinc segregation or accumulation is likely to occur near this negative electrode surface. Specifically, during the charge reaction, ZnO + H ２ O + 2e － →Zn + 2OH － As the charging reaction progresses, the OH － The OH concentration on the negative electrode surface is close to the positive electrode and separator. － As a result, the reaction on the surface of the negative electrode proceeds, while the reaction inside the negative electrode slows down. － →ZnO+H ２ O + 2e － As the discharge reaction progresses, the OH － The concentration of zinc in the negative electrode is lower than that on the surface of the negative electrode near the positive electrode and separator, slowing down the reaction inside the negative electrode. This is thought to be why the charge-discharge reaction in conventional negative electrodes is uneven, causing zinc to segregate near the surface of the negative electrode.

[0023] In contrast, when the negative electrode active material layer 12 has a polymer-rich portion 12a adjacent to the functional surface 10a and a polymer-poor portion 12b distant from the functional surface 10a, the charge and discharge reactions are uniform throughout the negative electrode plate 10. In other words, because polymers contribute to the resistance that inhibits the negative electrode reaction, increasing the polymer concentration can limit the reactive areas of the negative electrode plate 10 with Zn particles and / or ZnO particles. Therefore, the negative electrode reaction is less likely to proceed in the polymer-rich portion 12a than in the polymer-poor portion 12b. This effectively suppresses the negative electrode reaction, which tends to proceed excessively in the region of the negative electrode plate 10 near the functional surface 10a, thereby uniforming the charge and discharge reactions throughout the negative electrode plate 10. As a result, zinc segregation is suppressed, which is believed to extend the cycle life of the zinc secondary battery. On the other hand, if the surface of the negative electrode active material layer 12 facing the functional surface 10a is coated with a polymer, gas generated in the negative electrode plate 10 is less likely to be discharged to the outside through the functional surface 10a. In this regard, by providing the grooves G described above on the functional surface 10a of the negative electrode plate, the problem of gas leakage being deteriorated due to the polymer coating can be effectively solved.

[0024] When the cross section of the negative electrode plate 10 is image-analyzed, the polymer-rich portion 12 a is determined to be a polymer ratio P Ａ The polymer concentration is preferably 5 to 40 area %, more preferably 6 to 40 area %, and even more preferably 10 to 30 area %. This effectively suppresses the negative electrode reaction, which tends to proceed excessively on the functional surface 10a of the negative electrode plate 10, while suppressing increases in resistance due to excessively high polymer concentration. As a result, the reaction throughout the negative electrode plate 10 can be more effectively uniformed, further extending the cycle life of the zinc secondary battery. As described above, the polymer-rich portion 12a is the portion of the negative electrode active material layer 12 adjacent to the functional surface 10a. For example, if the length (depth) from the functional surface 10a to the center position in the thickness direction of the negative electrode current collector 14 is taken as 100%, the polymer-rich portion 12a is typically a region from the functional surface 10a that is greater than 0% and less than 30%, more typically greater than 0% and less than 15%, of the functional surface 10a.

[0025] When the cross section of the negative electrode plate 10 is image-analyzed, the polymer-poor portion 12b is determined to be a polymer proportion P Ｂ is preferably 0 to 20 area %, more preferably 0 to 10 area %, and further preferably 0 to 5 area %. However, the polymer ratio P in the polymer-rich portion 12a is Ａ is the proportion P of the polymer in the polymer-poor portion 12b Ｂ Preferably, the P Ａ and the above P Ｂ The difference between Ａ -P Ｂ ) is 5 to 25 area %, more preferably 10 to 25 area %. In this way, by providing regions with different polymer concentrations, such as the polymer-rich portion 12a and the polymer-poor portion 12b, in the thickness direction of the negative electrode plate 10, it is possible to effectively eliminate non-uniform charge / discharge reactions in the negative electrode plate 10, and further improve the cycle characteristics of the zinc secondary battery.

[0026] The proportion P of the polymer Ａ and P Ｂ can be identified by image analysis of the cross section of the negative electrode plate 10. For example, the cross section of the negative electrode plate 10 is observed with a field emission scanning electron microscope (FE-SEM) at a predetermined magnification (for example, 30,000 times magnification, field of view: 2.6 μm × 3.6 μm). An elemental mapping image of the cross section is obtained with an energy dispersive X-ray analyzer (EDX) attached to the FE-SEM. The obtained elemental mapping image is then imported into image processing software, and the ratio of the area occupied by elements (for example, C element and F element) that constitute the polymer to the total area of ​​the measurement field is calculated, thereby determining the polymer ratio P Ａ and P Ｂ can be identified.

[0027] The polymer is not particularly limited as long as it can restrict the reactive portions of Zn particles and / or ZnO particles in the negative electrode active material layer 12. A preferred example of such a polymer is a nonionic water-absorbing polymer. Because polymers such as nonionic water-absorbing polymers lack ion permeability, the reactive portions of Zn particles and / or ZnO particles in the negative electrode active material layer 12 are restricted to areas not in contact with the polymer. As a result, the negative electrode reaction, which tends to proceed excessively on the functional surface 10a of the negative electrode plate 10, can be more effectively suppressed. The nonionic water-absorbing polymer can be any commercially available nonionic water-absorbing polymer, but it is preferable that it has the property of changing its absorbency in response to pH fluctuations. In other words, the nonionic water-absorbing polymer advantageously absorbs water from the discharge reaction that generates water, allowing the discharge reaction to continue within the negative electrode plate 10 and making the discharge reaction more uniform. As a result, zinc accumulation is suppressed, which is believed to further extend the cycle life of the zinc secondary battery. Figure 6 shows a graph of 1 cm of such a nonionic water-absorbing polymer. ３ The figure shows an example of the relationship between the amount of water absorbed and the amount of KOH collected per unit area and the KOH concentration. As shown in FIG. 6, the amount of water absorbed changes with changes in the KOH concentration in the electrolyte (i.e., changes in pH), but those that do not significantly change the amount of KOH collected are preferred because they can absorb or release only water with pH fluctuations. In particular, those that exhibit a behavior in which the amount of water absorbed decreases with increasing pH are preferred. Preferred examples of such nonionic water-absorbing polymers include polyalkylene oxide-based water-absorbing resins, polyvinyl acetamide-based water-absorbing resins, polyvinyl alcohol (PVA resin), and polyvinyl butyral (PVB resin), with polyalkylene oxide-based water-absorbing resins being more preferred. Commercially available polyalkylene oxide-based water-absorbing resins can be used. The nonionic water-absorbing polymer may contain at least one selected from hydrophilic ether groups, hydroxyl groups, amide groups, and acetamide groups. The presence of these functional groups can provide water absorption and release functions that are more favorable for battery reactions.

[0028] The polymer is preferably particulate. In this case, the particle size of the polymer is preferably 10 to 200 μm, more preferably 15 to 180 μm, even more preferably 20 to 160 μm, and particularly preferably 30 to 150 μm. It is not necessary for all of the polymer particles to be within the above-mentioned numerical range, as long as the average particle size D50 falls within the above-mentioned numerical range. In this specification, the average particle size D50 means the particle size at which the cumulative volume from the small particle size side in the particle size distribution obtained by laser diffraction scattering method is 50%.

[0029] The negative electrode active material layer 12 contains Zn particles and ZnO particles. The Zn particles are typically metallic Zn particles, but particles of a Zn alloy or Zn compound may also be used. While metallic Zn particles commonly used in zinc secondary batteries can be used, the use of smaller metallic Zn particles is more preferable from the perspective of extending the cycle life of the battery. Specifically, the average particle size D50 of the metallic Zn particles is preferably 5 to 200 μm, more preferably 50 to 200 μm, and even more preferably 70 to 160 μm. The preferred content of Zn particles in the negative electrode plate 10 is preferably 1.0 to 87.5 parts by weight, more preferably 3.0 to 70.0 parts by weight, and even more preferably 5.0 to 55.0 parts by weight, based on 100 parts by weight of the ZnO particles. The metallic Zn particles may be doped with a dopant such as In or Bi. The ZnO particles are not particularly limited, and may be a commercially available zinc oxide powder used in zinc secondary batteries, or a zinc oxide powder obtained by growing particles from such a starting material through a solid-state reaction, etc. The average particle size D50 of the ZnO particles is preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, and even more preferably 0.1 to 5 μm.

[0030] The negative electrode active material layer 12 preferably further contains one or more metal elements selected from In and Bi. These metal elements can suppress the generation of undesirable hydrogen gas due to self-discharge of the negative electrode plate 10. These metal elements may be contained in the negative electrode plate 10 in any form, such as metal, oxide, hydroxide, or other compound, but are preferably contained in the form of oxide or hydroxide, and more preferably in the form of oxide particles. Examples of oxides of the above metal elements include In, ２ O ３ , Bi ２ O ３ Examples of hydroxides of the above metal elements include In(OH) ３ , Bi(OH) ３ Examples include. In any case, when the content of ZnO particles is 100 parts by weight, the In content is preferably 0 to 2 parts by weight in terms of oxide, and the Bi content is preferably 0 to 6 parts by weight in terms of oxide, more preferably 0 to 1.5 parts by weight in terms of oxide, and the Bi content is preferably 0 to 4.5 parts by weight in terms of oxide. When In and / or Bi are contained in the negative electrode plate 10 in the form of oxide or hydroxide, it is not necessary for all of the In and / or Bi to be in the form of oxide or hydroxide; some of them may be contained in the negative electrode in other forms, such as metal or other compounds. For example, the above metal elements may be doped into the metal Zn particles as trace elements. In this case, the In concentration in the metal Zn particles is preferably 50 to 2000 ppm by weight, more preferably 200 to 1500 ppm by weight, and the Bi concentration in the metal Zn particles is preferably 50 to 2000 ppm by weight, more preferably 100 to 1300 ppm by weight.

[0031] The negative electrode active material layer 12 may further contain a conductive additive, such as carbon, metal powder (tin, lead, copper, cobalt, etc.), and noble metal paste.

[0032] The negative electrode active material layer 12 may further contain a binder resin. When the negative electrode active material layer 12 contains a binder, the negative electrode shape is more easily maintained. Various known binders can be used as the binder resin, but preferred examples include polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE). It is particularly preferred to use a combination of both PVA and PTFE as the binder.

[0033] The negative electrode plate 10 is preferably a sheet-shaped pressed body. This can prevent the negative electrode active material from falling off, improve the electrode density, and more effectively suppress deformation of the negative electrode plate 10. Such a sheet-shaped pressed body can be produced by adding a binder to the negative electrode material and kneading the mixture, and then subjecting the resulting kneaded mixture to press molding such as roll pressing to form it into a sheet.

[0034] As described above, the negative electrode plate 10 includes a negative electrode current collector 14 that extends through the negative electrode active material layer 12 and supports the negative electrode active material layer 12. Preferred examples of the negative electrode current collector 14 include copper punched metal and copper expanded metal. In this case, a negative electrode plate consisting of the negative electrode active material layer 12 / negative electrode current collector 14 can be preferably produced by, for example, applying a mixture containing Zn particles, ZnO particles, and, optionally, a binder resin (e.g., polytetrafluoroethylene) to the copper punched metal or copper expanded metal. In this case, it is also preferable to press the dried negative electrode plate (i.e., the negative electrode active material layer 12 / negative electrode current collector 14) to prevent the negative electrode active material from falling off and improve electrode density. Alternatively, the above-described sheet-shaped pressed compact may be pressure-bonded to a negative electrode current collector 14 such as copper expanded metal. Thereafter, the negative electrode active material layer 12 present on at least one surface of the dried negative electrode plate is partially ground to form the desired grooves G, thereby obtaining a negative electrode plate 10 having a functional surface 10a. The grinding method for the negative electrode active material layer 12 is not particularly limited and any method may be used. For example, the grooves G can be preferably formed by a hand grinder, an ultrasonic cutter, brushing, laser processing, or the like. Alternatively, the negative electrode active material layer 12 present in the negative electrode current collector 14 may be removed by blowing air or the like against the formed grooves G.

[0035] If desired, the surface of the dried negative electrode plate may be coated with a solvent containing a polymer before forming the grooves G. In this way, a negative electrode active material layer 12 having a polymer-rich portion 12 a and a polymer-poor portion 12 b can be formed. The polymer coating method is not particularly limited, and can be preferably carried out by, for example, dropping a solvent in which a polymer is dissolved, dip coating, screen printing, gravure printing, or dispenser application.

[0036] Zinc Secondary Battery The negative electrode plate 10 of the present invention is preferably applied to a zinc secondary battery. Therefore, according to a preferred embodiment of the present invention, a zinc secondary battery is provided, comprising the negative electrode plate 10, a positive electrode plate disposed opposite the functional surface 10a of the negative electrode plate 10, a separator separating the positive electrode plate and the negative electrode plate 10 in a manner that allows hydroxide ion conductivity, and an electrolyte. As described above, the negative electrode reaction is particularly likely to proceed on the surface of the negative electrode close to the positive electrode. Therefore, by positioning the functional surface 10a closer to the positive electrode plate, gas generated on the negative electrode plate 10 is effectively discharged to the outside of the negative electrode through the grooves G formed on the functional surface 10a, thereby improving the cycle characteristics of the zinc secondary battery. The zinc secondary battery of the present invention is not particularly limited as long as it uses the negative electrode plate 10 described above and an electrolyte (typically an aqueous alkali metal hydroxide solution). Therefore, it can be a nickel-zinc secondary battery, a silver oxide-zinc secondary battery, a manganese oxide-zinc secondary battery, a zinc-air secondary battery, or any other alkaline zinc secondary battery. For example, the positive electrode preferably contains nickel hydroxide and / or nickel oxyhydroxide, thereby making the zinc secondary battery a nickel-zinc secondary battery. Alternatively, the positive electrode may be an air electrode, thereby making the zinc secondary battery a zinc-air secondary battery.

[0037] The separator is preferably a layered double hydroxide (LDH) separator. That is, as mentioned above, LDH separators are known in the fields of nickel-zinc secondary batteries and air-zinc secondary batteries (see Patent Documents 1 to 3), and this LDH separator can also be preferably used in the zinc secondary battery of the present invention. The LDH separator can selectively allow hydroxide ions to pass through while preventing the penetration of zinc dendrites. Combined with the effects of the negative electrode plate of the present invention, this can further improve the durability of zinc secondary batteries. In this specification, an LDH separator is defined as a separator containing a layered double hydroxide (LDH) and / or an LDH-like compound (hereinafter collectively referred to as a hydroxide ion-conducting layered compound) that selectively passes hydroxide ions solely by utilizing the hydroxide ion conductivity of the hydroxide ion-conducting layered compound. In this specification, an "LDH-like compound" refers to a hydroxide and / or oxide with a layered crystal structure similar to LDH, even if it may not be called an LDH, and can be considered an equivalent of LDH. However, in a broader sense, "LDH" can be interpreted as including not only LDH but also LDH-like compounds.

[0038] The LDH separator may be composited with a porous substrate, as disclosed in Patent Documents 1 to 3. The porous substrate may be composed of a ceramic material, a metal material, or a polymeric material, but a polymeric material is particularly preferred. Polymeric porous substrates have the following advantages: 1) flexibility (hence, they are less likely to crack even when thinned); 2) ease of achieving high porosity; 3) ease of achieving high conductivity (because thickness can be reduced while increasing porosity); and 4) ease of manufacturing and handling. Particularly preferred polymeric materials are polyolefins such as polypropylene and polyethylene, with polypropylene being the most preferred, due to their excellent hot water resistance, acid resistance, and alkali resistance, as well as low cost. When the porous substrate is composed of a polymeric material, it is particularly preferred that the hydroxide ion-conducting layered compound be incorporated throughout the entire thickness of the porous substrate (e.g., most or almost all of the pores within the porous substrate are filled with the hydroxide ion-conducting layered compound). In this case, the preferred thickness of the polymeric porous substrate is 5 to 200 μm, more preferably 5 to 100 μm, and even more preferably 5 to 30 μm. As such a polymeric porous substrate, a microporous membrane such as those commercially available as separators for lithium batteries can be preferably used.

[0039] The electrolyte preferably contains an aqueous solution of an alkali metal hydroxide. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being more preferred. Zinc oxide, zinc hydroxide, or the like may be added to the electrolyte to suppress self-dissolution of the zinc-containing material.

[0040] LDH-Like Compound According to a preferred embodiment of the present invention, the LDH separator may contain an LDH-like compound. The definition of the LDH-like compound is as described above. Preferred LDH-like compounds are: (a) hydroxides and / or oxides having a layered crystal structure containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al; or (b) hydroxides and / or oxides having a layered crystal structure containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) at least one additional element M selected from the group consisting of In, Bi, Ca, Sr, and Ba; or (c) hydroxides and / or oxides having a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In, wherein the LDH-like compound in (c) is In(OH). ３ It exists in the form of a mixture with

[0041] According to a preferred aspect (a) of the present invention, the LDH-like compound may be a hydroxide and / or oxide having a layered crystal structure containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al. Therefore, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Mg, Ti, optionally Y, and optionally Al. While the above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, it is preferable that the LDH-like compound does not contain Ni. For example, the LDH-like compound may further contain Zn and / or K. This can further improve the ionic conductivity of the LDH separator.

[0042] LDH-like compounds can be identified by X-ray diffraction. Specifically, when X-ray diffraction is performed on the surface of an LDH separator, peaks attributable to LDH-like compounds are typically detected in the range of 5°≦2θ≦10°, more typically in the range of 7°≦2θ≦10°. As described above, LDHs are formed by stacking hydroxide base layers, with exchangeable anions and H as intermediate layers. ２O is present. In this regard, when LDH is measured by X-ray diffraction, a peak due to the crystalline structure of LDH (i.e., the (003) peak of LDH) is inherently detected at 2θ = 11 to 12°. In contrast, when an LDH-like compound is measured by X-ray diffraction, a peak is typically detected in the above-mentioned range, which is shifted to a lower angle than the peak position of LDH. Furthermore, the interlayer distance of the layered crystalline structure can be determined by the Bragg equation using 2θ corresponding to the peak due to the LDH-like compound in X-ray diffraction. The interlayer distance of the layered crystalline structure constituting the LDH-like compound determined in this manner is typically 0.883 to 1.8 nm, more typically 0.883 to 1.3 nm.

[0043] In the LDH separator according to the above aspect (a), the atomic ratio of Mg / (Mg + Ti + Y + Al) in the LDH-like compound, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.03 to 0.25, more preferably 0.05 to 0.2. The atomic ratio of Ti / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0.40 to 0.97, more preferably 0.47 to 0.94. The atomic ratio of Y / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0 to 0.45, more preferably 0 to 0.37. The atomic ratio of Al / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.03. Within the above range, the alkali resistance is more excellent, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the atomic ratio in the LDH-like compound generally deviates from the general formula of LDH. Therefore, it can be said that the LDH-like compound in this embodiment generally has a composition ratio (atomic ratio) different from that of conventional LDH. Note that EDS analysis is preferably performed using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000x, 2) performing three-point analysis in point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of a total of six points.

[0044] According to another preferred aspect (b) of the present invention, the LDH-like compound may be a hydroxide and / or oxide having a layered crystal structure containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) an additional element M. Thus, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Ti, Y, the additional element M, optionally Al, and optionally Mg. The additional element M is In, Bi, Ca, Sr, Ba, or a combination thereof. While the above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, it is preferred that the LDH-like compound does not contain Ni.

[0045] In the LDH separator according to the above aspect (b), the atomic ratio of Ti / (Mg+Al+Ti+Y+M) in the LDH-like compound, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.50 to 0.85, more preferably 0.56 to 0.81. The atomic ratio of Y / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.20, more preferably 0.07 to 0.15. The atomic ratio of M / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.35, more preferably 0.03 to 0.32. The atomic ratio of Mg / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.10, more preferably 0 to 0.02. The atomic ratio of Al / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.04. Within the above range, the alkali resistance is more excellent, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. Incidentally, LDHs conventionally known for LDH separators have the general formula: M ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the atomic ratio in the LDH-like compound generally deviates from the general formula of LDH. Therefore, it can be said that the LDH-like compound in this embodiment generally has a composition ratio (atomic ratio) different from that of conventional LDH. Note that EDS analysis is preferably performed using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000x, 2) performing three-point analysis in point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of a total of six points.

[0046] According to yet another preferred embodiment (c) of the present invention, the LDH-like compound is a hydroxide and / or oxide of a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In, and the LDH-like compound is In(OH) ３ The LDH-like compound of this embodiment is a hydroxide and / or oxide having a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In. Therefore, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Mg, Ti, Y, optionally Al, and optionally In. Note that the In that can be contained in the LDH-like compound is not only that which is intentionally added to the LDH-like compound, but also In(OH) ３ The above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, but it is preferable that the LDH-like compound does not contain Ni. Incidentally, LDHs conventionally known for LDH separators are represented by the general formula: M ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. In contrast, the atomic ratios in LDH-like compounds generally deviate from the above general formula of LDH. Therefore, it can be said that the LDH-like compounds in this embodiment generally have composition ratios (atomic ratios) different from those of conventional LDHs.

[0047] The mixture according to the above embodiment (c) contains not only LDH-like compounds but also In(OH) ３ (typically LDH-like compounds and In(OH) ３ It is composed of In(OH) ３ The inclusion of In(OH) in the mixture can effectively improve the alkali resistance and dendrite resistance of the LDH separator. ３ The content of In(OH) is preferably an amount that can improve the alkali resistance and dendrite resistance of the LDH separator without substantially impairing the hydroxide ion conductivity, and is not particularly limited. ３ may have a cubic crystal structure, and In(OH) ３ The crystal may be surrounded by an LDH-like compound. ３ can be identified by X-ray diffraction.

[0048] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0049] Examples 1 to 26 (1) Preparation of positive electrode Paste-type nickel hydroxide positive electrode (capacity density: approximately 700 mAh / cm ３ ) was prepared.

[0050] (2) Preparation of Negative Electrode Plate The following raw material powders were prepared: ZnO powder (manufactured by Seido Chemical Industry Co., Ltd., JIS Class 1 grade, average particle size D50: 0.2 μm) Metallic Zn powder (manufactured by Dowa Electronics Co., Ltd., doped with Bi and In, Bi: 70 ppm by weight, In: 200 ppm by weight, average particle size D50: 120 μm)

[0051] To 100 parts by weight of ZnO powder, 5.7 parts by weight of metal Zn powder and 1 part by weight of polytetrafluoroethylene (PTFE) were added, and the mixture was kneaded with propylene glycol. The resulting kneaded mixture was rolled using a roll press to obtain a negative electrode active material sheet. The negative electrode active material sheet was pressed onto a tin-plated copper expand metal and dried. For Examples 2 to 26, the negative electrode active material was ground on both sides of the dried negative electrode active material sheet using a hand grinder with a resin brush, thereby forming diagonal grooves as shown in FIG. 1A. At this time, by appropriately changing the grinding width and grinding depth of the negative electrode active material, the area ratio A of the negative electrode active material layer occupying the functional surface as shown in Table 1 was obtained. １ / (A １ +A ２ The thickness of the negative electrode plate was 700 μm, and the groove depth ratio D / L was adjusted accordingly. On the other hand, no grooves were formed in Example 1. In this way, a negative electrode plate having a thickness of 700 μm was obtained.

[0052] (3) Preparation of Electrolyte Solution Ion-exchanged water was added to a 48% aqueous potassium hydroxide solution (special grade, manufactured by Kanto Chemical Co., Inc.) to adjust the KOH concentration to 5.4 mol%, and zinc oxide was then dissolved in the solution by heating and stirring to a concentration of 0.42 mol / L, thereby obtaining an electrolyte solution.

[0053] (4) Preparation of Evaluation Cell The positive and negative electrode plates were each wrapped in nonwoven fabric, and a current extraction terminal was welded. The positive and negative electrode plates thus prepared were placed opposite each other with an LDH separator interposed therebetween, sandwiched between laminate films with current extraction ports, and three sides of the laminate film were heat-sealed. An electrolyte solution was added to the resulting open-top cell container, and the electrolyte solution was thoroughly permeated into the positive and negative electrode plates by evacuation or the like. The remaining side of the laminate film was then heat-sealed to form a simple sealed cell.

[0054] (5) Evaluation <Taper Angle> A cross section of the obtained negative electrode plate was cut out so as to include the formed grooves, and observed using a scanning electron microscope (SEM, model: SU3500, manufactured by Hitachi High-Tech Corporation) at an acceleration voltage of 15 kV and a magnification of 50x. For reference, an SEM image obtained from the cross section of the negative electrode of Example 6 is shown in FIG. 7. From the SEM image of the obtained negative electrode cross section, the angle formed by the wall surface of each groove and the imaginary center line in the thickness direction of the negative electrode current collector was measured. The above operation was performed at three different locations, and the average value was used as the taper angle. The results are shown in Table 1.

[0055] <Cycle Characteristics> Using a charge / discharge device (TOSCAT3100, manufactured by Toyo Systems Co., Ltd.), the simple sealed cell was subjected to chemical formation with 0.1 C charge and 0.2 C discharge. A 0.5 C charge / discharge cycle was then performed. Repeated charge / discharge cycles were performed under the same conditions, and the number of charge / discharge cycles until the discharge capacity of the prototype battery decreased to 70% of the discharge capacity of the first cycle was recorded. The number of charge / discharge cycles for each example was calculated as a relative value when the number of charge / discharge cycles in Example 1 was set to 1.00, and this was used as an index of cycle characteristics (cycle characteristic ratio). The results are shown in Table 1. The area ratio A of the negative electrode active material layer occupying the functional surface was 0.5 C. １ / (A １ +A ２ It has been confirmed that the cycle characteristics are improved by providing grooves in the negative electrode plate 10 so that the difference between the positive and negative electrodes is 0.60 to 0.98.

[0056]

[0057] In Examples 27 to 53, Examples 28 to 35, Examples 37 to 44, and Examples 46 to 53, a polymer coating was applied to both sides of the negative electrode active material sheet before forming the grooves in the above (2) negative electrode plate preparation. Specifically, the resulting dried negative electrode active material sheet was coated with a nonionic water-absorbing polymer (polyalkylene oxide-based water-absorbing resin, manufactured by Sumitomo Seika Chemicals Co., Ltd., AQUACORK, Grade: TWB-P, product form: powder, average particle size D50: 50 μm) dissolved in propylene glycol, which was then dripped or dip-coated and dried. The nonionic water-absorbing polymer was coated on both sides of the sheet. At this time, the amount of polymer contained in the negative electrode active material sheet was controlled by appropriately changing the polymer concentration, dripping amount, and / or dipping time of the nonionic water-absorbing polymer-containing solution. On the other hand, in Examples 27, 36, and 45, the polymer coating was not applied. Thereafter, the negative electrode active material was ground to prepare negative electrode plates (Examples 27 to 35) having grooves similar to those in Example 6, negative electrode plates (Examples 36 to 44) having grooves similar to those in Example 3, and negative electrode plates (Examples 45 to 53) having grooves similar to those in Example 16. Except for these, evaluation cells were prepared and cycle characteristics were evaluated in the same manner as in Examples 1 to 26. The results are shown in Table 2.

[0058] <Measurement of polymer proportion> A cross section was cut out from the obtained 700 μm thick negative electrode plate 10 so as to include a region where a nonionic water-absorbing polymer-containing solution was dropped or dip-coated. Then, cross sections at a position 50 μm (polymer-rich portion) and a position 350 μm (polymer-poor portion) in the thickness direction from the surface of the negative electrode plate 10 were observed at a magnification of 30,000 times and a field of view of 2.6 μm × 3.6 μm using a field emission scanning electron microscope (FE-SEM, manufactured by JEOL Ltd., JSM-7900F). In addition, an elemental mapping image of the cross section was obtained using an energy dispersive X-ray analyzer (EDX, manufactured by JEOL Ltd., JED-2300) attached to the FE-SEM. The obtained elemental mapping image was imported into image processing software (Adobe Illustrator, manufactured by Adobe), and the ratio of the area occupied by the C element and the F element constituting the polymer to the total area of ​​the measurement field was calculated, and the polymer ratio P Ａand the polymer proportion P in the polymer-poor part Ｂ The results are shown in Table 2.

[0059]

Claims

1. A negative electrode plate for a zinc secondary battery, the negative electrode plate having at least one functional surface on at least one side thereof to be opposed to at least one positive electrode plate in the zinc secondary battery, the negative electrode plate comprising: a negative electrode active material layer including ZnO particles and Zn particles; and a negative electrode current collector extending through the negative electrode active material layer and supporting the negative electrode active material layer, wherein a groove extending from a center portion to an outer periphery is provided on the functional surface side of the negative electrode plate so as to divide the functional surface into a plurality of regions, the groove being formed by at least a partial absence of the negative electrode active material layer, and when the functional surface side of the negative electrode plate is viewed in plan, an area A occupied by the negative electrode active material layer excluding the groove is １ and the area A occupied by the groove portion ２ Total area A １ +A ２ The area A occupied by the negative electrode active material layer relative to １ Proportion A １ / (A １ +A ２ ) is 0.60 to 0.

98.

2. The negative electrode plate according to claim 1, wherein the grooves are provided in a cross shape, a radial shape, or a diagonal shape.

3. The negative electrode plate according to claim 1 or 2, wherein the ratio D / L of the depth D of the groove to the length L from the center position in the thickness direction of the negative electrode current collector to the functional surface is 0.57 to 1.

00.

4. The negative electrode plate according to claim 1 or 2, wherein the groove has a tapered cross-sectional shape whose width decreases from the functional surface toward the negative electrode current collector.

5. A negative electrode plate according to claim 4, wherein, when the negative electrode plate is viewed in cross section, an angle formed between a wall surface of the groove and an imaginary center line in the thickness direction of the negative electrode current collector is 35 to 70 degrees.

6. A negative electrode plate according to claim 1 or 2, wherein the negative electrode plate covers the surface of the functional side of the negative electrode active material layer excluding the groove portion to form the functional surface, and further comprises a polymer impregnated into the negative electrode active material layer so that the polymer concentration decreases toward the inside, whereby the negative electrode active material layer has a polymer-rich portion that is rich in the polymer adjacent to the functional surface, and a polymer-poor portion that is poor in the polymer away from the functional surface.

7. The polymer-rich portion is a polymer-rich portion that is a polymer-rich portion of the negative electrode active material layer when a cross section of the negative electrode plate is image-analyzed. Ａ The negative electrode plate according to claim 6, wherein the amount of the cations is 5 to 40 area %.

8. The polymer poor portion is a proportion P of the polymer in the negative electrode active material layer when a cross section of the negative electrode plate is image-analyzed. Ｂ is 0 to 20 area %, and Ａ is the P Ｂ The negative plate of claim 7 .

9. The negative plate of claim 6, wherein said polymer is a nonionic water-absorbing polymer.

10. The negative plate according to claim 1 or 2, wherein the negative plate has the functional surface on both sides thereof.

11. The negative electrode plate according to claim 1 or 2, wherein the negative electrode active material layer further contains one or more metal elements selected from the group consisting of In and Bi.

12. The negative electrode plate according to claim 1 or 2, which is a sheet-like pressed product.

13. A zinc secondary battery comprising: a negative electrode plate according to claim 1 or 2; a positive electrode plate provided opposite the functional surface of the negative electrode plate; a separator isolating the positive electrode plate and the negative electrode plate in a manner capable of conducting hydroxide ions; and an electrolyte.

14. The zinc secondary battery according to claim 13, wherein the separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound.

15. The zinc secondary battery according to claim 14, wherein the LDH separator is composited with a porous substrate.

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