JP2006156186A - Negative plate for alkaline secondary battery, and alkaline secondary battery with the negative plate applied - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery with a rolled plate group that excels in charge/discharge cycle performance without causing productivity deterioration. <P>SOLUTION: A negative plate for the alkaline secondary battery comprising a rolled plate group of the stack of rectangular a positive plate, separators and a negative plate 1, in which the negative plate is positioned on the outermost circumference of the rolled plate group, has a mix layer 3 whose principal component is active material powder on each side of a base 2 that is a perforated metal plate, has a uniform thickness, and when cut along a line parallel to the longer side, has a base deviated to one side from the middle of the plate section only at the end positioned on the outermost circumference of the rolled plate group or throughout the plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a negative electrode plate for an alkaline secondary battery represented by a cylindrical nickel-metal hydride battery or a nickel cadmium battery having a wound electrode plate group, and a wound electrode plate group to which the negative electrode plate is applied. The present invention relates to an alkaline secondary battery provided.

  Cylindrical nickel metal hydride batteries and nickel cadmium batteries are used as power sources for portable electric devices, hybrid electric vehicles (HEV), electric tools, etc. because of their excellent cycle characteristics, overdischarge resistance, and overcharge resistance. ing. Among these, nickel metal hydride batteries are widely used because of their low pollution and high energy density. In these applications, there is a strong demand for a power source that can withstand long-term use, and the development of secondary batteries having excellent cycle characteristics is underway.

In the electrode plate constituting the wound electrode plate group, the positive electrode plate and the negative electrode plate are usually provided with active material layers on both sides of the conductive substrate (perforated metal plate or metal foil), and the conductive substrate is made of the electrode plate. Although it is arranged at the center of the electrode plate with respect to the thickness direction, the outer surface of the negative electrode plate located at the outermost periphery of the electrode plate group does not face the positive electrode plate. The discharge hardly contributes to the electromotive reaction. In view of such drawbacks of the conventional battery, in a secondary battery including a wound electrode group, an improvement in the structure of the electrode group has been proposed in order to achieve further increase in battery capacity. For example, a wound electrode group having a structure in which the outer surface of a conductive substrate of a negative electrode plate located on the outermost periphery of the electrode group is exposed. According to the proposal, the capacity can be increased by increasing the amount of the active material that contributes to the electromotive reaction except for the active material that hardly contributes to the electromotive reaction on the outer surface of the negative electrode plate located on the outermost periphery of the electrode plate group. Has been tried. (For example, Patent Document 1 and Patent Document 2).
JP-A-1-279578 FIG. 9 is a conceptual diagram (cross-sectional view) for explaining the basic structure of the wound electrode group 4 of the secondary battery proposed in these patent documents. The wound electrode plate group 4 is obtained by winding a laminate of a rectangular positive electrode plate 5, a negative electrode plate 1, and a separator 6. In the negative electrode plate 1, a mixture layer 3 containing active material powder as a main constituent material is disposed on both surfaces of a conductive substrate 2. However, a portion (active material layer non-coating portion) 9 where the mixture layer 3 is not disposed is provided at a location not facing the positive electrode plate 5 of the negative electrode plate 1 with the winding end end portion 8 of the positive electrode plate 5 as a boundary. ing.

  However, in order to produce the electrode plate group having such a configuration, an active material coating portion and a non-coating portion must be provided on one negative electrode plate. For that purpose, intermittent coating or coating is performed. It was necessary to remove part of the active material later to form an active material non-coated part. In intermittent coating, a complicated mechanism must be given to the coating device, and since the thickness of the electrode plate after coating is not uniform, the thick part of one electrode plate It was necessary to perform a two-stage press work separately for parts with a small thickness. On the other hand, the method of removing a part of the active material has a drawback that the process of removing the active material is complicated and the productivity is inferior.

The electrode plate group described in Patent Document 1 and Patent Document 2 has a different configuration, and the negative electrode plate is divided into an inner peripheral portion and an outermost peripheral portion having a thickness smaller than that of the inner peripheral portion. A wound electrode group is shown in which a peripheral portion and an outermost peripheral portion are overlapped and connected. (For example, Patent Document 3)
According to this configuration, since the negative electrode plate is divided into an inner peripheral portion and an outer peripheral portion, an uncoated portion in one negative electrode plate described in Patent Document 1 and Patent Document 2 described above. There is an advantage that the negative electrode plate can be easily manufactured as compared with the configuration in which the portions having different thicknesses of the negative electrode plate are provided. However, in the outer peripheral portion of the negative electrode plate, there is a negative electrode active material that does not contribute to the electromotive reaction, and the active material on the surface (outer surface) of the negative electrode plate outer peripheral portion not facing the positive electrode is excluded. In comparison, there was a drawback that the utilization rate of the negative electrode active material was low. In addition, since the active material layers are in contact with each other in the overlapping portion of the inner peripheral portion and the outermost peripheral portion of the negative electrode plate, the electric resistance of the overlapping portion is large, and high rate discharge characteristics and charge acceptance characteristics when performing quick charge However, there was a disadvantage that was inferior. Because of the drawbacks described above, the method proposed in Patent Document 3 may not provide the effect of improving the cycle characteristics.

  The present invention has been made in view of the disadvantages of the conventional sealed alkaline secondary battery, and is an alkaline secondary battery (hereinafter also simply referred to as a battery) provided with a wound electrode plate group. It is intended to provide a battery having excellent charge / discharge cycle characteristics without lowering.

  In this invention, the said subject is solved by making the structure of a battery into the following structures.

The negative electrode plate for an alkaline secondary battery according to the present invention includes a wound electrode plate group in which a rectangular positive electrode plate, a separator, and a negative electrode plate are laminated, and the negative electrode plate is disposed on the outermost periphery of the wound electrode plate group. A negative electrode plate for an alkaline secondary battery, having a mixture layer comprising active material powder as a main constituent material on both sides of a substrate made of a metal plate having perforations, having a uniform thickness, In the negative electrode plate in which the position of the substrate with respect to the thickness direction of the electrode plate does not change in the width direction (direction parallel to the short side), when the electrode plate is cut along a plane parallel to the long side, the wound electrode plate group A negative electrode plate for an alkaline secondary battery, wherein the substrate is decentered to one side with respect to the center of the cut surface of the electrode plate only over the end located on the outermost peripheral side of the electrode plate or over the entire electrode plate. . (Claim 1)
The negative electrode plate according to claim 1, wherein only the end located on the outermost peripheral side of the wound electrode plate group is decentered to one side with respect to the center of the cut surface of the electrode plate. In this case, the electrode plate other than the end portion does not decenter the substrate. Here, that the substrate is not decentered means that the substrate is disposed at the center of the cut surface of the electrode plate (hereinafter referred to as the electrode plate cut surface).

In the negative electrode plate for an alkaline secondary battery according to the present invention, the ratio of the thicknesses of the mixture layers on the front and back surfaces of the substrate where the substrate is decentered is 1: 9 to 4: 6. It is a negative electrode plate for alkaline secondary batteries of Claim 1 characterized by the above-mentioned. (Claim 2)
3. The alkaline secondary battery according to claim 1, wherein the alkaline secondary battery according to the present invention is configured such that the substrate is eccentric to one side only with respect to the center of the cut surface of the electrode plate at an end portion located on the outermost peripheral side. A winding type electrode plate group to which a negative electrode plate for a secondary battery is applied, wherein a negative electrode plate mixture layer whose thickness is increased by decentering the substrate is opposed to the positive electrode plate. An alkaline secondary battery comprising an electrode plate group. (Claim 3)
The alkaline secondary battery according to the present invention is the negative electrode for an alkaline secondary battery according to claim 1 or 2, wherein the substrate is eccentric to one side with respect to the center of the cut surface of the electrode plate over the entire electrode plate. A wound-type electrode plate group to which a plate is applied, wherein a mixture layer of a negative electrode plate whose thickness is increased from the substrate by decentering the substrate is arranged inside, and the negative electrode plate having a reduced thickness An alkaline secondary battery comprising a wound electrode plate group having a mixture layer disposed outside. (Claim 4)

  According to the first aspect of the present invention, the active material of the negative electrode plate can be obtained without lowering the productivity of the negative electrode plate as compared with the conventional negative electrode plate for an alkaline secondary battery in which the substrate is not eccentric over the entire electrode plate. It is possible to provide a wound electrode plate group for alkaline secondary batteries having a high utilization rate.

  According to the second aspect of the present invention, it is possible to provide a wound electrode plate group for an alkaline secondary battery having a high active material utilization rate of the negative electrode plate and excellent charge / discharge cycle characteristics.

  According to claim 3 and claim 4, in an alkaline secondary battery having a wound electrode group, productivity is not lowered, and charge / discharge cycle characteristics are improved by increasing the active material utilization of the negative electrode plate. An excellent alkaline secondary battery can be provided.

  The battery according to the present invention includes a negative electrode plate in which a mixture layer is disposed on both surfaces of a conductive substrate having perforations. Although the thickness of a negative electrode plate is not specifically limited, It is preferable to set it as 0.25-0.40 mm normally used. If the thickness is less than 0.25 mm, the active material filling amount may be reduced. Conversely, if the thickness exceeds 0.40 mm, the current collecting function of the negative electrode plate is lowered and the utilization rate of the active material is lowered. There is a fear.

  A perforated plate made of nickel or a nickel-plated steel plate is suitable for the substrate of the negative electrode plate. The thickness of the substrate, the shape and size of the perforations, and the aperture ratio are not particularly limited, but the thickness is preferably 0.03 to 0.06 mm. If the thickness is less than 0.03 mm, the tensile strength is insufficient, so that there is a risk of the substrate being cut in the process of manufacturing the electrode plate or the wound electrode plate group. There is a risk that the amount will decrease. The shape of the perforations may be any of a polygon, an oval, and a circle, but a circle with good productivity is preferable. In the case of circular perforations, the diameter is preferably 0.5-2 mm. If the diameter is less than 0.5 mm, it is difficult to produce and the productivity is inferior. Further, the opening ratio of the substrate is preferably 35 to 60%, and more preferably 40 to 55%. When the opening ratio is less than 35%, the substrate inhibits the movement of ions in the electrolyte contained in the negative electrode slope, and the thickness of the mixture layer is shifted because of the eccentricity of the substrate among the mixture layers arranged on the front and back surfaces of the negative electrode plate. The utilization factor of the active material contained in the mixture layer with increased thickness may decrease, or the utilization factor of the active material contained in the entire mixture layer may be reduced. If the opening ratio exceeds 60%, the negative electrode There is a possibility that the current collecting function of the plate is lowered and the active material utilization rate is lowered.

(First embodiment)
The first embodiment is an embodiment in which the substrate of the negative electrode plate is eccentric only at the end located on the outermost peripheral side of the wound electrode plate group. FIG. 1 relates to the first embodiment of the present invention, and shows a plane parallel to the long side of the negative electrode plate 1 for an alkaline secondary battery after pressing to adjust the thickness of the electrode plate to a predetermined thickness. It is sectional drawing which shows the cut | disconnected cross section typically. In FIG. 1, 2 is a substrate made of perforated steel sheet, for example, plated with nickel, and 3 is an active material powder comprising a mixture of hydrogen storage alloy powder or cadmium powder and cadmium hydroxide powder carried on both sides of the substrate. It is a mixture layer containing as a main constituent material. In addition to the active material powder, the mixture layer may contain a conductive agent powder such as nickel powder, or a synthetic resin such as styrene butadiene rubber (SBR) or polytetrafluoroethylene (PTFE) as a binder.

  As shown in FIG. 1, the negative electrode plate 1 is a single electrode plate that is seamless in the longitudinal direction and has a uniform thickness. As shown in FIG. 1, the substrate 2 is positioned at the center (thickness) of the electrode plate at the portion on the right side from X in the drawing (corresponding to the outermost peripheral end of the wound electrode plate group of the negative electrode plate). It is eccentric to the upper side of the figure with respect to the direction center). The negative electrode plate has a uniform thickness at least in the longitudinal direction, similar to the negative electrode plate in which the conventional substrate is not eccentric. In the negative electrode plate according to the first embodiment, the negative electrode plate is divided into a plurality of pieces as in the prior art and joined together in the middle, or the thickness of the mixture layer is changed from the middle in the longitudinal direction of the electrode plate. Compared to the negative electrode plate with the electrode plate thickness itself being changed, the coating process is simpler and the thickness is uniform. It is.

  FIG. 2 is a diagram schematically showing a cross-sectional structure of the wound electrode group 4 in which the negative electrode plate 1 shown in FIG. 1 is laminated with the positive electrode plate 5 via the separator 6 and wound in a spiral shape. . In the present invention, as shown in FIG. 2, the negative electrode plate is disposed outside the positive electrode plate at the outermost periphery (winding end periphery) of the wound electrode group, and the negative electrode plate is disposed at the outermost periphery. A portion where the substrate is decentered is disposed, and a surface where the thickness of the mixture layer 3 is large is disposed opposite to the positive electrode plate 5 with the substrate decentered as the boundary.

  The configuration of the electrode plate group is the same as that shown in FIG. 2, so that the substrate shown in FIG. The amount of the active material of the negative electrode plate 1 facing the positive electrode plate 5 can be increased without changing the thickness and size of the negative electrode plate and the filling amount of the hydrogen storage alloy powder.

  When the amount of the hydrogen storage alloy powder facing the positive electrode plate 5 of the negative electrode plate 1 is increased, the capacity of the apparent negative electrode plate (N: simply the negative electrode active material) Even if the ratio (N / P) to the capacity (P) of the negative electrode plate) and the capacity (P) of the positive electrode plate is the same, it operates when charging / discharging at a high rate (for the electromotive reaction) The value of the ratio (N ′ / P) of the capacity (N ′) of the negative electrode plate calculated from the amount of the negative electrode active material to the capacity (P) of the positive electrode plate can be increased.

  In the case of an alkaline secondary battery, the capacity of the negative electrode plate is generally made larger than the capacity of the positive electrode plate to ensure the discharge reserve and the charge reserve. Therefore, at the initial stage of the charge / discharge cycle, the discharge capacity is regulated by the capacity of the positive electrode plate, so that it is difficult for the discharge capacity to vary depending on the charge reserve amount, but the charge reserve amount of the negative electrode plate decreases after the cycle. Accordingly, the discharge capacity is regulated by the capacity of the negative electrode plate, and the discharge capacity decreases with the passage of the cycle. As described above, the battery according to the invention of the present application increases the value of N ′ / P and secures a large charge reserve amount as compared with the conventional battery, so that the discharge capacity of the battery is the capacity of the negative electrode plate. The cycle characteristics in high rate charge / discharge when charging and discharging are performed at a rate of 1 ItA or more can be enhanced.

  The length of the portion where the substrate 2 is eccentric (the portion on the right side of X in FIG. 1) is not particularly limited. However, as shown in FIG. 2, the length of the portion where the substrate is eccentric is extremely long. It is preferable that the length of the negative electrode plate on the outermost periphery of the plate group is substantially the same because the amount of the active material contained in the mixture layer not facing the positive electrode plate can be minimized. The ratio of the thickness of the mixture layer with a small thickness and the mixture layer with a large thickness at the part where the substrate is eccentric is not particularly limited, but is 1: 9 to 4 : 6 is preferable, and 1: 9 to 3: 7 is more preferable. When the ratio is less than 1: 9, the electrode plate is deformed or the active material (hydrogen storage alloy powder) falls off in the step of pressing the electrode plate after supporting the mixture layer on the substrate. There is a fear. If the ratio exceeds 4: 6, the effect of increasing the active material utilization of the negative electrode plate cannot be obtained.

  Note that the portion of the negative electrode plate where the substrate is not eccentric (the portion on the left side of X in FIG. 1) positions the substrate at the center of the cut surface of the electrode plate, as shown in FIG. This part has both sides facing the positive electrode plate, and by positioning the substrate at the center of the cut surface of the electrode plate, both the front and back surfaces of the electrode plate contribute equally to the electromotive reaction, maximizing the utilization rate of the negative electrode plate It is preferable because it can be increased to the limit.

  In the production of the negative electrode plate, the method of decentering the substrate at one end of the electrode plate (the end located on the outermost peripheral side when the wound electrode plate group is configured) is not particularly limited. For example, a paste of a hydrogen storage alloy powder (a paste obtained by adding a thickener such as carboxymethylcellulose (CMC) to water in which a hydrogen storage alloy powder or a binder is dispersed in water) is used as a paste. In the process in which excess paste is supported on both sides of the substrate through the contained paste tank and then passed through the slits with a predetermined interval, the excess paste is scraped off so that the substrate is not eccentric. When manufacturing the part, adjust the position of the substrate and the slit so that the substrate passes through the center of the gap of the slit, and when manufacturing the part where the substrate is eccentric, change the position of the substrate or the position of the slit and The The position of the substrate and the slit so as to pass through a position offset to one Tsu City of spacing can be produced by adjusting the. In this method, when the position of the substrate or the position of the slit is changed, a large tension is applied to the portion passing through the slit at the time of changing the position, so that the substrate may be cut at the portion.

  The substrate 2 shown in FIG. 4 has an effect of preventing the substrate from being cut, and is a portion of the substrate in which the perforations 7 are provided as a whole (the thickness of the negative electrode plate 1). The portion where the position of the substrate 2 changes with respect to the vertical direction) The number of perforations of X is reduced (the aperture ratio is low, the perforations are eliminated in the figure, and the aperture ratio is 0%), and the tensile strength of the substrate is increased. . The numerical aperture of the portion X is not particularly limited, and may be set so as to obtain a strength that does not cause the substrate to be cut when the substrate is decentered in the process of scraping off the paste. Although there is no particular limitation on the width of the portion where the aperture ratio in the portion X is lowered, it is preferably 2 to 5 mm. If the width is less than 2 mm, it is difficult to obtain the effect of providing a portion with a low aperture ratio. On the other hand, if the width exceeds 5 mm, the active material may easily fall off, or the movement of ions may be hindered by the substrate, resulting in a decrease in electrical characteristics.

(Second Embodiment)
The second embodiment is an embodiment in which the substrate is eccentric over the entire negative electrode plate. FIG. 5 is a cross-sectional view schematically showing a cross section of the negative electrode plate 1 according to the second embodiment of the present invention cut along a plane parallel to the long side. In the present invention, as shown in the first embodiment, in addition to decentering the substrate at one end of the negative electrode plate, as shown in FIG. It can also be made. However, also in the second embodiment, as in the first embodiment, the thickness of the negative electrode plate is uniform and the negative electrode plate is excellent in productivity.

  When the negative electrode plate 1 is applied to form a wound electrode plate group, the surface of the negative electrode plate 1 where the mixture layer 3 is thickened with the substrate 2 as a boundary, and the surface where the mixture layer 3 is thinned On the outside. With this configuration, the thick surface of the mixture layer of the negative electrode plate is opposed to the positive electrode plate 5 on the outermost periphery of the electrode plate group, and a large amount of the active material of the negative electrode plate contributing to the electromotive reaction can be secured. .

  By adopting this configuration of the electrode plate group, the amount of the active material of the negative electrode plate that does not face the positive electrode plate is reduced and the charge / discharge is performed at a high rate, as in the first embodiment. The ratio (N '/ P) of the negative electrode plate capacity (N') to the positive electrode capacity (P) calculated from the amount of the negative electrode active material (deposited in the electromotive reaction) can be increased, and charging / discharging Cycle performance can be improved. In the second embodiment, since it is not necessary to change the position of the substrate in the process of applying the active material to both surfaces of the substrate, it is easier to manufacture the negative electrode plate than in the first embodiment.

  In the second embodiment, the aperture ratio of the substrate of the negative electrode plate is preferably 35 to 60%, more preferably 40 to 55%, as in the first embodiment. It was found that good cycle performance could be obtained because the charge reserve amount could be secured by suppressing the decrease in the utilization factor of the negative electrode active material. In the second embodiment, the thickness of the mixture layer is different at the inner periphery of the electrode group with the substrate of the negative electrode plate as the boundary (the inner layer of the electrode plate group with the substrate as the boundary). The thickness of the agent layer is large, and the thickness of the outer mixture layer is small.) In this way, when the thickness of the mixture layer is made different from the substrate (the amount of the active material powder is also different in proportion to the ratio of the thickness of the mixture layer), the thick mixture layer It is expected that the utilization rate of the active material contained in the substrate will be low, but it is good by setting the aperture ratio of the substrate of the negative electrode plate to 35 to 60%, more preferably 40 to 55% as described above. Cycle performance was obtained.

  Also in the second embodiment, the ratio of the thickness of the mixture layer having a small thickness and the mixture layer having a large thickness with respect to the substrate of the negative electrode plate is not particularly limited. : It is preferable to set to 9 to 4: 6, and it is more preferable to set to 1: 9 to 3: 7. When the ratio is less than 1: 9, the electrode plate may be deformed or the active material powder may fall off in the step of pressing the electrode plate after supporting the mixture layer on the substrate. In addition, when the substrate is exposed on one side of the electrode plate, when the electrode plate group is configured, the substrate is brought close to the surface of the positive electrode plate via the separator. An electromotive reaction is unlikely to occur, and the active material utilization rate may be reduced.

(Third embodiment)
The third embodiment is an embodiment in which the substrate is decentered over the entire negative electrode plate, and is an embodiment different from the second embodiment. In the second embodiment, as shown in FIG. 5, when the electrode plate is cut along a line parallel to the long side, the position of the substrate 2 in the thickness direction of the electrode plate 1 does not change. On the other hand, in the third embodiment, the substrate is decentered to one side with respect to the center of the thickness of the electrode plate over the entire negative electrode plate, but as shown in FIG. In the longitudinal direction of the electrode plate, the position with respect to the thickness direction of the substrate is changed halfway. For example, in FIG. 1, the thickness of the mixture layer of the negative electrode plate on the right side of X (the outermost peripheral end of the wound electrode plate group among the negative electrode plates) is 1: 9, and the negative electrode plate on the left side of X is combined. The thickness ratio of the agent layer is set to 3: 7. However, also in the third embodiment, in order to increase the active material utilization rate of the negative electrode plate, the degree of eccentricity of the substrate at the outermost end of the wound electrode plate group (the thickness of the substrate and the electrode plate) The distance between the center of the negative electrode plate and the other part is set larger than the other part, and the ratio of the thickness of the mixture layer at the boundary of the negative electrode substrate is 4: 6 to 1: 9. It is preferable to set the range.

  In the third embodiment, as in the first embodiment, the aperture ratio of the substrate is lowered in the portion X where the position of the substrate changes in the thickness direction of the electrode plate (for example, only the portion X is perforated). If it is set, it is preferable because cutting of the substrate is suppressed. Further, for example, when the position of the substrate is changed across the center of the thickness of the negative electrode plate in the portion X, the change in the position of the substrate becomes large, and the process of manufacturing the negative electrode plate or the electrode plate group is manufactured (捲There is a high risk that the substrate will be cut in the process of turning.

  Hereinafter, a nickel metal hydride battery using a hydrogen storage electrode using a hydrogen storage alloy powder as an active material for the negative electrode plate will be described as an example. However, the present invention is not limited to a nickel metal hydride battery. For example, a cadmium electrode is used as a negative electrode. The present invention can also be applied to nickel cadmium batteries.

Example 1
(Battery configuration)
Surface coating comprising 5% by weight of cobalt oxyhydroxide having a core layer of nickel hydroxide containing 3% by weight of zinc in terms of metal and 1% by weight of cobalt in a solid solution state with respect to 95% by weight of the core layer A positive electrode plate having a thickness of 0.7 mm, a length of 96 mm, and a width of 44 mm in which a positive electrode active material powder provided with a layer was filled in a nickel foam substrate was used. The capacity of the positive electrode plate {positive electrode active material filling amount (g) × capacity per unit weight of positive electrode active material (mAh / g)} was 2300 mAh.

A perforated steel sheet (nickel-plated product) having a circular perforation having a thickness of 0.04 mm and a diameter of 1 mm and having an aperture ratio of 45% is used as a substrate, and Mm _1.0 Ni _3.9 Co _0.7 Mn _0.3 Al _0.2 ( Mm represents a misch metal) and an active material layer composed of 98.8% by weight of a hydrogen storage alloy having an average particle diameter of 40 μm, 1% by weight of SBR (styrene butadiene rubber), and 0.2% by weight of MC (methyl cellulose). An electrode plate having a thickness of 0.34 mm, a length of 137 mm, and a width of 44 mm was prepared. The substrate is decentered at a position where the distance from the short side on the winding start side of the negative electrode plate is 94 mm (in FIG. 1, X is set to a position 94 mm from the left end side in FIG. 1). The thickness of the mixture layer on one side of the substrate is 0.03 mm, the thickness of the mixture layer on the other side is 0.27 mm (thickness of the mixture layer with a small thickness: The thickness of the agent layer was 1: 9).

A non-woven fabric made of polypropylene fibers having a thickness of 0.1 mm, a basis weight of 40 g / m ² , a width of 46 mm, and subjected to hydrophilic treatment was applied to the separator.

  Laminating the positive electrode plate, the separator and the negative electrode plate, applying a winding core having a diameter of 2 mm, arranging the negative electrode plate so that the eccentric part of the substrate is the end of winding of the pole group, In the outer periphery of the electrode plate group, the thickness of the mixture layer formed by decentering the substrate in the periphery was increased to 0.27 mm so that the negative electrode plate was on the outer side and the positive electrode plate was on the inner side. It arrange | positioned so that the side might oppose a positive electrode plate. The electrode plate group is housed in a bottomed cylindrical metal battery case with a diameter (inner diameter) of 13.6 mm, and an electrolytic solution comprising an aqueous solution containing 6.8 mol / l KOH and 0.8 mol / l LiOH is prepared. A predetermined amount was injected, and the open end of the battery case was hermetically sealed with a cover with an exhaust valve and a cap-like positive electrode terminal to produce an AA size cylindrical nickel-metal hydride storage battery. Note that the capacity of the negative electrode plate {capacity per gram of hydrogen storage alloy powder (mAh / g) × filling amount of hydrogen storage alloy powder (g) located at a position facing the positive electrode plate with the substrate of the negative electrode plate as a boundary} and The ratio (N / P ratio) of the capacity of the positive electrode plate {capacity per gram of positive electrode active material (mAh / g) x positive electrode active material filling amount (g)} was 1.30. This example is referred to as Example 1.

(Example 2)
In Example 1, the thickness of the mixture layer on one side is 0.06 mm and the thickness of the mixture layer on the other side is 0.24 mm (thickness) with the substrate of the portion where the substrate of the negative electrode plate is eccentric as a boundary. The thickness of the small mixture layer: the thickness of the large mixture layer = 2: 8). Otherwise, the configuration was the same as in Example 1. This example is referred to as Example 2. The N / P ratio in this example was 1.30.

(Example 3)
In Example 1, the thickness of the mixture layer on one side is 0.09 mm and the thickness of the mixture layer on the other side is 0.21 mm (thickness) with the substrate of the part of the negative electrode plate eccentric. The thickness of the small mixture layer: the thickness of the large mixture layer = 3: 7). Otherwise, the configuration was the same as in Example 1. This example is referred to as Example 3. The N / P ratio in this example was 1.30.

Example 4
In Example 1, the thickness of the mixture layer on one side is 0.12 mm and the thickness of the mixture layer on the other side is 0.18 mm (thickness) with the substrate of the portion of the negative electrode plate eccentric. The thickness of the small mixture layer: the thickness of the large mixture layer = 4: 6). Otherwise, the configuration was the same as in Example 1. This example is referred to as Example 4. The N / P ratio in this example was 1.30.

(Comparative Example 1)
In Example 1, without providing the portion of the negative electrode substrate that was eccentric, the thickness of the mixture layer was 0.15 mm across the entire substrate in the longitudinal direction of the electrode plate (with the substrate as the boundary, The thickness of the mixture layer on one side: the thickness of the mixture layer on the other side = 5: 5). Otherwise, the configuration was the same as in Example 1. This example is referred to as Comparative Example 1. The N / P ratio in this example was 1.30.

(Comparative Example 2)
In Example 1, the thickness of the mixture layer on one side is set to 0.0 mm and the thickness of the mixture layer on the other side is set to 0.30 mm (thickness) with the substrate of the portion where the substrate of the negative electrode plate is eccentric. The thickness of the small mixture layer: the thickness of the large mixture layer = 0: 10). Otherwise, the configuration was the same as in Example 1. This example is referred to as Comparative Example 4. The N / P ratio in this example was 1.30.

(Initialization)
The batteries according to Examples 1 to 4 and Comparative Examples 1 and 2 were initialized at an ambient temperature of 20 ° C. The first charge (first cycle) was charged with 0.02 ItA for 13 hours, and then charged with 0.1 ItA for 10 hours. After being left for 1 hour, the battery was discharged with a discharge current of 0.2 ItA and a discharge cut voltage of 1.0 V. From the 2nd to the 10th cycle, the battery was charged with 0.1 ItA for 16 hours and then left for 1 hour, the discharge current was 0.2 ItA, the discharge cut voltage was 1.0 V, and the charge / discharge was repeated as one cycle.

(Discharge capacity evaluation test)
The batteries according to Examples 1 to 4 and Comparative Examples 1 and 2, each of which was prepared with 10 formed storage batteries, charged at an ambient temperature of 20 ° C. with a charging current of 0.1 ItA for 16 hours, and then 1 hour After being left standing, the battery was discharged at a discharge cut voltage of 1.0 V at a discharge current of 0.2 ItA, and the discharge capacity was determined.

(Charge / discharge cycle test)
Each of the batteries according to Examples 1 to 4 and Comparative Examples 1 and 2 was prepared, and 10 formed storage batteries were prepared. The storage batteries were charged at an ambient temperature of 20 ° C. with a charging current of 1 ItA for 1.05 hours ( 105%) and left for 1 hour, and then discharged at a discharge cut voltage of 1.0 V at a discharge current of 1 ItA. The charge / discharge cycle was repeated for one cycle. The cycle number of the storage battery was defined as the number of cycles in which the discharge capacity was reduced to 60% of the discharge capacity in the first cycle of the cycle.

  Table 1 shows the results of the discharge capacity evaluation test and the charge / discharge cycle test (10 average values). FIG. 6 shows the relationship between the number of charge / discharge cycles and the discharge capacity.

表１の放電容量に示したように、実施例１〜実施例４、比較例１、比較例２に係る電池を０．２ＩｔＡで充電および放電を行ったときには、これらの電池の間に放電容量に大きな差が認められない。しかし、表１および図６に示したように、実施例１〜実施例４のサイクル特性に比べて比較例１、比較例２のサイクル特性は劣っている。比較例１、比較例２ともにＮ／Ｐが１．３０であり実施例１〜実施例４と等しいが、負極板の基板を偏心させてない比較例１においては負極板の最外周の外側の合剤層に含まれる活物質が殆ど起電反応に寄与しないために充電リザーブ量が少なく、サイクル性能が劣るものと考えられる。また、薄い合剤層の厚さ／厚い合剤層の厚さの比を０：１０とした比較例２は、充電および放電を１ＩｔＡで行ったときに、充電受け入れ性能が劣るためか、あるいは、合剤層と基板との密着性でサイクルとともに合剤層と基板との接触界面の電気抵抗が増大するためか、実施例１〜実施例４に比べてサイクル性能が劣るものと考えられる。

As shown in the discharge capacity of Table 1, when the batteries according to Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were charged and discharged at 0.2 ItA, the discharge capacity was between these batteries. There is no significant difference. However, as shown in Table 1 and FIG. 6, the cycle characteristics of Comparative Example 1 and Comparative Example 2 are inferior to the cycle characteristics of Examples 1 to 4. In both Comparative Example 1 and Comparative Example 2, N / P is 1.30, which is equal to Example 1 to Example 4, but in Comparative Example 1 in which the substrate of the negative electrode plate is not decentered, the outer periphery of the outermost periphery of the negative electrode plate is outside. Since the active material contained in the mixture layer hardly contributes to the electromotive reaction, it is considered that the charge reserve amount is small and the cycle performance is inferior. Further, in Comparative Example 2 in which the ratio of the thickness of the thin mixture layer / the thickness of the thick mixture layer is 0:10, the charge acceptance performance is inferior when charging and discharging are performed at 1 ItA, or It is considered that the cycle performance is inferior to those of Examples 1 to 4 because the electrical resistance at the contact interface between the mixture layer and the substrate increases with the cycle due to the adhesion between the mixture layer and the substrate.

  Further, among Examples 1 to 4, since Examples 1 to 3 have particularly excellent cycle characteristics, the mixture of the negative electrode plate with the substrate at the portion where the substrate is decentered as a boundary. The layer thickness ratio is preferably set to 1: 9 to 4: 6, and more preferably set to 1: 9 to 3: 7.

(Example 5)
In Example 1, the substrate was decentered in the entire area of the negative electrode plate as shown in FIG. The thickness of the mixture layer on one side is 0.03 mm from the substrate, and the thickness of the mixture layer on the other side is 0.27 mm (thickness of the mixture layer having a small thickness: the mixture having a large thickness) Layer thickness = 1: 9). By decentering the substrate so that the negative electrode plate is on the outer side and the positive electrode plate is on the inner side at the end of winding of the pole group (the outermost circumference of the pole group), the thickness is increased to 0.27 mm with the substrate as a boundary. The mixture layer was arranged on the inside, and the mixture layer was arranged on the outside with a small thickness of 0.03 mm. Otherwise, the configuration was the same as in Example 1. This example is referred to as Example 5.

(Example 6)
In Example 5, the thickness of the mixture layer on one side was 0.09 mm, and the thickness of the mixture layer on the other side was 0.21 mm (thickness of the mixture layer having a small thickness: The thickness of the mixture layer having a large thickness was set to 3: 7). Otherwise, the configuration was the same as in Example 5. This example is referred to as Example 6.

  Table 2 shows the results of the discharge capacity evaluation test and charge / discharge cycle test of Example 5 and Example 6 together with Comparative Example 1 (10 average values). FIG. 7 shows the relationship between the number of charge / discharge cycles and the discharge capacity.

実施例５および実施６に係る電池は、前記実施例１、実施例３に比べるとサイクル特性が劣るが、負極板の基板を極板の全領域において偏心させたにも拘わらず、表２のサイクル寿命および図７に示したように、比較例１に比べて優れたサイクル特性を有している。負極板の基板に高い開口率（開口率４５％）を有する穿孔金属基板を用いたことと、最外周部分の正極板に対向しない部分の負極活物質量を減らしたことによって比較例１に比べて大きい充電リザーブ量を確保することができ、比較例１を上回るサイクル特性が得られたものと考えられる。

The batteries according to Example 5 and Example 6 are inferior in cycle characteristics as compared to Examples 1 and 3, but the negative electrode substrate is eccentric in the entire region of the electrode plate, but the battery of Table 2 As shown in the cycle life and FIG. 7, the cycle characteristics are superior to those of Comparative Example 1. Compared to Comparative Example 1 by using a perforated metal substrate having a high aperture ratio (aperture ratio 45%) for the substrate of the negative electrode plate and reducing the amount of the negative electrode active material in the portion not facing the positive electrode plate in the outermost peripheral portion. Thus, it is considered that a large charge reserve amount can be ensured, and the cycle characteristics exceeding Comparative Example 1 are obtained.

(Example 7)
In Example 1, the portion where the position of the substrate changes with respect to the thickness direction of the negative electrode plate (X in FIG. 1) was not provided with a perforation over a width of 3 mm. Otherwise, it was the same as Example 1. This example is referred to as Example 7.

(Example 8)
In Example 3, the portion where the position of the substrate changes with respect to the thickness direction of the negative electrode plate (X in FIG. 1) was not provided with a perforation over a width of 3 mm. Otherwise, it was the same as Example 3. This example is referred to as Example 8.

(Pole group mass production trial production)
The electrode plate group according to Example 1, Example 3, Example 7, Example 8, Comparative Example 1, and Comparative Example 2 was manufactured by applying 5,000 each to the production line for mass production, and the electrode plate group Was disassembled and examined for the presence of defects (cutting of the negative electrode plate, dropping of the active material of the negative electrode plate). Further, ten electrode plate groups of Example 7 and Example 8 were extracted, and a cylindrical nickel-metal hydride battery was produced in the same manner as described above and subjected to a discharge capacity test and a charge / discharge cycle test.

  Table 3 shows the results of the mass production trial production (defective rate and discharge capacity test, charge / discharge cycle test). FIG. 8 shows the relationship between the number of charge / discharge cycles and the discharge capacity.

実施例７、実施例８においては、前記負極板の位置Ｘに基板に帯状に穿孔を設けない部分を設けたために該部分の基板の機械的強度が大きく、極板厚さを調整するためのプレス加工時あるいは極板群の捲回時において極板切れの発生を抑制することができ、表３の製造不良率に示したように、基板を同じように偏芯させた実施例１、実施例３に比べて製造不良率を低減することができた。一方、負極板の基板を境にして、厚さの小さい合剤層／厚差の大きい合剤層の比を０：１０とした比較例２の場合は、極板厚さを調整するためのプレス加工時あるいは極板群の捲回時において活物質の脱落が発生し、製造不良率が高い結果となった。また、表３のサイクル寿命、図８に示したように、負極板の基板に穿孔を設けない部分を設けた実施例７および実施例８は、基板の全領域に穿孔を設けた実施例１、実施例３に比べて同等以上のサイクル性能を示した。

In Example 7 and Example 8, since the portion where the perforations were not provided in the strip shape in the position X of the negative electrode plate was provided, the mechanical strength of the substrate in the portion was large, and the thickness of the electrode plate was adjusted. Example 1 in which the occurrence of electrode plate breakage can be suppressed during pressing or winding of the electrode plate group, and the substrate is similarly eccentric as shown in the manufacturing failure rate in Table 3. Compared to Example 3, the production failure rate could be reduced. On the other hand, in the case of Comparative Example 2 in which the ratio of the mixture layer having a small thickness / the mixture layer having a large thickness difference was set to 0:10 with the substrate of the negative electrode plate as a boundary, the electrode plate thickness was adjusted. The active material fell off during press working or winding of the electrode plate group, resulting in a high production defect rate. In addition, as shown in FIG. 8, the cycle life in Table 3 and Example 7 and Example 8 in which the substrate of the negative electrode plate was not provided with perforations, Example 1 and Example 8 were provided with perforations in the entire region of the substrate. Compared with Example 3, the cycle performance was equivalent or better.

  The present invention provides an alkaline storage battery excellent in charge / discharge cycle characteristics without reducing productivity in a cylindrical storage battery such as a nickel metal hydride storage battery having a wound electrode group, and has high industrial utility value. Is.

It is the figure which showed typically the cross-sectional structure which cut | disconnected the negative electrode plate for alkaline secondary batteries which concerns on the 1st Embodiment of this invention by the surface parallel to a long side. It is the figure which showed typically the structure of the winding type pole group by cut | disconnecting the winding type pole group which concerns on the 1st Embodiment of this invention by the surface parallel to a winding end surface. It is the figure which showed typically the cross-sectional structure which cut | disconnected the conventional negative electrode plate for alkaline secondary batteries by the surface parallel to a long side. It is a figure which shows typically the planar structure of the board | substrate of the negative electrode plate for alkaline secondary batteries which concerns on embodiment of this invention. It is the figure which showed typically the cross-sectional structure which cut | disconnected the negative electrode plate for alkaline secondary batteries which concerns on the 2nd Embodiment of this invention by the surface parallel to a long side. It is a graph which shows the relationship between the number of charging / discharging cycles of an example battery and a comparative example battery, and discharge capacity. It is a graph which shows the relationship between the number of charging / discharging cycles of an example battery and a comparative example battery, and discharge capacity. It is a graph which shows the relationship between the number of charging / discharging cycles of an example battery and a comparative example battery, and discharge capacity. It is a figure which shows typically the cross-sectional structure of the winding type | formula electrode group of a proposal conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode plate 2 Substrate 3 Mixture layer X The part in which the position of a board | substrate changes with respect to the thickness direction of a negative electrode plate 4 Winding type pole group 7 Perforation

Claims (4)

  A negative electrode plate for an alkaline secondary battery, comprising a wound electrode plate group in which a rectangular positive electrode plate, a separator and a negative electrode plate are laminated, and a negative electrode plate arranged on the outermost periphery of the wound electrode plate group. Having a mixture layer mainly composed of active material powder on both sides of a substrate made of a metal plate having a uniform thickness, and in the width direction of the electrode plate (direction parallel to the short side) In the negative electrode plate where the position of the substrate with respect to the thickness direction of the plate does not change, when the electrode plate is cut by a plane parallel to the long side, only the end located on the outermost peripheral side of the wound electrode plate group, or A negative electrode plate for an alkaline secondary battery, wherein the substrate is eccentric to one side with respect to the center of the cut surface of the electrode plate over the entire electrode plate.   The ratio of the thicknesses of the mixture layers on the front and back surfaces of the substrate that is decentered to one side with respect to the center of the cut surface of the electrode plate is 1: 9 to 4: 6. The negative electrode plate for an alkaline secondary battery according to claim 1, wherein the negative electrode plate is an alkaline secondary battery.   The winding which applied the negative electrode plate for alkaline secondary batteries of Claim 1 or Claim 2 which made the board | substrate eccentric on one side only with respect to the center of the said cut surface of an electrode plate only at the edge part located in the said outermost peripheral side. A negative electrode plate group comprising a negative electrode plate having a thickness increased from the substrate as a boundary by decentering the substrate, and a wound electrode plate group facing the positive electrode plate. Alkaline secondary battery. The wound electrode plate group to which the negative electrode plate for an alkaline secondary battery according to claim 1 or 2 is applied, wherein the substrate is decentered to one side with respect to the center of the cut surface of the electrode plate over the entire electrode plate. The negative electrode plate mixture layer having a thickness increased from the substrate by decentering the substrate is arranged on the inner side, and the negative electrode plate mixture layer having a smaller thickness is arranged on the outer side. An alkaline secondary battery comprising an electrode plate group.

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