Lead-acid battery

Abstract

DEPCT64 A lead-acid battery consists of a positive electrode plate, a negative electrode plate, and a separator. A solution of 0.03 to 0.3% Na is placed between the positive and negative electrode plates. 0.02 to 0.2 mol / L and / or Al 0.02 to 0.2 mol / L will be present in the electrolyte solution; the separator will have a first ridge. On the negative electrode side, the rib parameter Q, which is expressed by Q=U / (h1 / 2), is 300 or less. That is, where the height of the first ridge protruding from the main surface of the separator is h (mm) and The utilization factor of the electrolyte solution is U(%). -----------------------------------------------------------

Description

lead acid battery

[0001] This invention relates to a lead-acid battery.

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial use. A lead-acid battery consists of a negative electrode plate, a positive electrode plate, a separator interposed between the negative and positive electrodes, and an electrolyte. Generally, an aqueous sulfuric acid solution is used as the electrolyte.

[0003] Patent Document 1 describes a liquid lead-acid battery in which the electrolyte utilization rate is 75% or more, the concentration of alkali metal ions or alkaline earth metal ions in the electrolyte is 0.07 to 0.3 mol / L, and the pore volume of the negative electrode material is 0.08 to 0.16 mL / g.

[0004] Patent Document 2 states that when the total amount of positive electrode active material packed into the positive electrode plate and the negative electrode active material packed into the negative electrode plate is A, and the amount of sulfuric acid contained in the electrolyte is B (initial state when fully charged and not significantly degraded), the ratio of A to B is Y = B / A and the density of positive electrode active material X (g / cm³) is given. ３ It is described that the deposition of needle-shaped crystals of metallic lead at the negative electrode is suppressed by satisfying a certain relationship between the two points.

[0005] International Publication No. 2014 / 128803 Pamphlet, Japanese Patent Publication No. 2000-130516

[0006] Lead-acid batteries are sometimes used in a state of undercharge called a partial charge state (PSOC). For example, lead-acid batteries are used in PSOC during charge control and idle stop-start (ISS) systems. Therefore, lead-acid batteries are required to have excellent lifespan performance (hereinafter referred to as PSOC lifespan performance) in cycle tests under PSOC conditions.

[0007] If used continuously in a PSOC (Polyseptic Tank Oxide) state, stratification of the electrolyte progresses, accelerating the softening of the positive electrode active material and the accumulation of lead sulfate (sulfation) in the positive and negative electrode active materials, resulting in a shorter lifespan. In addition, prolonged use in a stratified state can lead to the reduction of lead ions dissolved in the electrolyte on the negative electrode side, and the precipitated lead crystals may penetrate the separator, potentially causing a penetration short circuit.

[0008] In batteries for idle stop (IS) systems, the amount of active material in both the positive and negative electrodes is increased to ensure higher capacity, resistance to softening of the positive electrode plate, and resistance to sulfation of the negative electrode plate. In this case, the amount of electrolyte is relatively reduced. If the amount of electrolyte is small relative to the amount of active material, the specific gravity of the electrolyte drops drastically during over-discharge, making penetration short circuits more likely.

[0009] Adding metal ions such as Na and Al to the electrolyte is known as a method to suppress penetration short circuits. However, in batteries with relatively small amounts of electrolyte, sufficient effects cannot be obtained. Furthermore, increasing the amount of metal ions reduces charge acceptance and promotes sulfation, making it difficult to increase the metal ion content beyond the current level.

[0010] One aspect of the present invention comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte, wherein the electrolyte contains 0.03 to 0.3 mol / L of Na and / or 0.02 to 0.2 mol / L of Al, the separator has a first rib on the side of the negative electrode plate, the height at which the first rib protrudes from the main surface of the separator is h (mm), and the utilization rate of the electrolyte is U (%), where Q = U / (h １／２ This relates to a lead-acid battery in which the rib parameter Q, expressed as ), is 300 or less.

[0011] In lead-acid batteries, penetration short circuits are suppressed, resulting in excellent PSOC lifespan performance.

[0012] This is a partially cutaway exploded perspective view showing the external appearance and internal structure of a lead-acid battery according to one aspect of the present invention. This is a graph showing the relationship between rib parameters and the probability of penetration short circuit occurrence.

[0013] A lead-acid battery according to one aspect of the present invention comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte, wherein the electrolyte contains 0.03 to 0.3 mol / L of Na and / or 0.02 to 0.2 mol / L of Al. The separator has a first rib on the side facing the negative electrode plate. Let h (mm) be the height at which the first rib protrudes from the main surface of the separator, and let U (%) be the utilization rate of the electrolyte, then Q = U / (h １／２ The rib parameter Q, represented by ), is 300 or less.

[0014] Here, the electrolyte utilization rate U (hereinafter sometimes referred to as "electrolyte utilization rate") means the value obtained by determining the theoretical volume of the electrolyte (amount of sulfate (g) / 3.657) from the amount of sulfate measured from the amount of electrolyte in the cell chamber, and then dividing the 20-hour rate volume by the obtained theoretical volume of the electrolyte.

[0015] The method for calculating the electrolyte utilization rate is described below. In a fully charged battery, the electrode group is removed from the single cell containing the electrolyte, washed with water, and dried to remove sulfuric acid. Whether the sulfuric acid has been removed can be confirmed using pH test paper or similar. If washing takes a long time, the electrode group may be cut into positive electrode plate, negative electrode plate, separator, and lead connector, and each may be washed and dried. The amount of electrolyte in a single cell is obtained by subtracting the mass of the electrode group, battery case, and lid after washing and drying from the mass of the single cell containing the electrolyte. Next, the specific gravity of the electrolyte is measured, and the amount of sulfate ions is calculated from the amount of electrolyte and the measured specific gravity. The calculated amount of sulfate ions (g) is divided by 3.657 to obtain the theoretical electrolyte capacity (Ah), and the value obtained by dividing the 20-hour rate capacity by the obtained theoretical electrolyte capacity is the electrolyte utilization rate. The 20-hour rate capacity is determined in accordance with SBA S 0101:2014.

[0016] Furthermore, the height h at which the first rib protrudes from the main surface of the separator (height of the first rib) can be determined by averaging the heights of multiple first ribs provided in the region of the main surface of the separator facing the negative electrode plate.

[0017] The rib parameter Q is expressed as the value obtained by dividing the liquid utilization rate U by the square root of the height h of the first rib. The higher the liquid utilization rate U and the lower the height h of the first rib, the more likely it is that seepage short circuits will occur. In this case, the rib parameter Q increases. Therefore, the smaller the rib parameter Q, the more seepage short circuits are suppressed.

[0018] However, the inventors of this application have found that, instead of simply dividing the liquid utilization rate U by the first rib height h, by limiting the rib parameter Q, obtained by dividing the liquid utilization rate U (%) by the square root of the first rib height h (mm), to a certain value or less (300 or less), dramatically suppresses penetration short circuits regardless of the liquid utilization rate.

[0019] In lead-acid batteries, during discharge, lead sulfate is produced at both the positive and negative electrodes, and water is also produced at the positive electrode. On the other hand, during charging, metallic lead, lead dioxide, and sulfuric acid are produced from lead sulfate and water.

[0020] If a battery continues to be used in an undercharged state, the amount of lead sulfate will inevitably increase towards the end of the PSOC's lifespan, causing the specific gravity of the electrolyte to decrease. This decrease in the specific gravity of the electrolyte is particularly noticeable during over-discharge. Furthermore, if the electrolyte is not sufficiently agitated during charging, a concentration difference of sulfuric acid will occur between the upper and lower parts of the electrolyte (stratification). Continued use under such conditions makes penetration short circuits more likely to occur in the upper part of the electrolyte where the specific gravity is lower.

[0021] The separator is provided with a first rib on the negative electrode plate side. The first rib prevents the separator from adhering tightly to the negative electrode plate and secures a space between the negative electrode plate and the separator to hold the electrolyte. The first rib enhances the diffusivity of the electrolyte and suppresses penetration short circuits. This makes it possible to realize a lead-acid battery with excellent PSOC life performance.

[0022] The higher the height of the first rib, the greater the effect of suppressing seepage short circuits. By determining the height of the first rib according to the liquid utilization rate so that the rib parameter Q is below a certain value (300 or less), seepage short circuits can be effectively suppressed.

[0023] Furthermore, the first rib maintains the diffusivity of the electrolyte near the negative electrode during both charging and discharging, suppressing a decrease in charge / discharge performance. Because the first rib improves the diffusivity of the electrolyte near the negative electrode plate, the decrease in specific gravity of the electrolyte near the negative electrode during discharge is suppressed, thus suppressing a decrease in discharge performance. In addition, the accumulation of lead sulfate is suppressed. Moreover, during charging, the sulfuric acid released from the negative electrode plate can diffuse into the space between the negative electrode plate and the separator, suppressing an increase in the specific gravity of the electrolyte near the negative electrode, thus improving charging efficiency.

[0024] The electrolyte contains 0.03 to 0.3 mol / L of Na and / or 0.02 to 0.2 mol / L of Al.

[0025] Adding Na, K, Mg, or Al to the electrolyte has the effect of suppressing penetration short circuits and improving charge recovery after being left in a state of over-discharge. On the other hand, the addition of Na, K, or Mg can lead to a decrease in charge acceptance and can easily promote the accumulation of lead sulfate (sulfation) at the negative electrode. When the electrolyte contains Na, the Na content is preferably 0.03 to 0.3 mol / L. By setting the Na content to 0.03 mol / L or higher, the effect of suppressing penetration short circuits can be obtained. On the other hand, from the viewpoint of suppressing the accumulation of lead sulfate, it is preferable to set the Na content to 0.3 mol / L or lower. Similarly, when the electrolyte contains Al, the Al content is preferably 0.02 to 0.2 mol / L. By setting the Al content to 0.02 mol / L or higher, the effect of suppressing penetration short circuits and the effect of suppressing lead sulfate accumulation can be obtained. On the other hand, from the viewpoint of suppressing a decrease in discharge performance, it is preferable to set the Al content to 0.2 mol / L or lower.

[0026] Furthermore, the electrolyte may contain alkali metal ions such as Li, or alkaline earth metal ions, in addition to Na and / or Al. The content of Na, Al, or other metal ions in the electrolyte can be determined by disassembling a fully charged lead-acid battery from a previously manufactured company, extracting the electrolyte, and performing inductively coupled plasma (ICP) emission spectrometry. More specifically, atomic absorption spectrometry is performed using an ICP emission spectrometer (ICPS-8000, manufactured by Shimadzu Corporation), and the concentration of metal ions is determined using a calibration curve.

[0027] The smaller the rib parameter value, the greater the effect of suppressing penetration short circuits, but the required height of the first rib also increases. However, to maintain the same performance while increasing the height of the first rib, the total thickness of the separator (the thickness obtained by adding the rib height to the base thickness of the separator) must be increased, or, if the total thickness of the separator is not changed, the height of the rib provided on the positive electrode side (second rib) must be decreased. Increasing the total thickness of the separator leads to a decrease in capacity, making it difficult to adopt in IS batteries, which use a plate group consisting of multiple stacked positive and negative electrodes. On the other hand, lowering the rib on the positive electrode side leads to oxidative degradation of the separator, which tends to shorten its lifespan.

[0028] However, if the above rib parameter is in the range of 150 or higher, the effect of suppressing penetration short circuits can be maximized in IS batteries without causing a decrease in capacity or oxidative degradation of the separator.

[0029] According to one aspect of the present invention, by providing an electrolyte with 0.03 to 0.3 mol / L of Na and / or 0.02 to 0.2 mol / L of Al, and by providing a first rib on the negative electrode plate side, and controlling the height of the first rib according to the electrolyte utilization rate so that the rib parameter is within a certain range, penetration short circuits can be effectively suppressed. Since the minimum height of the first rib necessary for suppressing penetration short circuits can be obtained according to the electrolyte utilization rate, the design of lead-acid batteries for IS becomes easier. The electrolyte utilization rate U is preferably in the range of 70% to 90%.

[0030] The separator may further include a second rib provided on the side of the positive electrode plate. The second rib prevents the separator from adhering closely to the positive electrode plate. The second rib improves the diffusivity of the electrolyte near the positive electrode plate and suppresses oxidative degradation of the separator, thereby further improving the PSOC lifespan performance.

[0031] The separator may be in the form of a bag. When a bag-shaped separator is used, the electrolyte tends to accumulate, but by providing a first rib and a second rib, the diffusivity of the electrolyte within the separator is increased, further improving the PSOC life performance. At the positive electrode, water is generated during discharge, so the change in the specific gravity of the electrolyte near the positive electrode plate is greater than near the negative electrode plate. However, because the bag-shaped separator houses the positive electrode plate, the diffusivity of the electrolyte near the positive electrode plate is increased, making it easier to suppress stratification of the electrolyte. On the other hand, when the bag-shaped separator houses the negative electrode plate, it is easier to suppress short circuits due to the elongation of the positive electrode grid. In addition, the formation of a first rib inside the bag increases the diffusivity of the electrolyte near the negative electrode plate, making it easier to suppress stratification.

[0032] A lead-acid battery may include a fiber mat interposed between the positive and negative electrode plates. When a fiber mat is provided, the electrode plates are compressed by the fiber mat, reducing the amount of electrolyte around the electrode plates and decreasing its diffusivity. However, by providing at least a first rib on the negative electrode plate side of the separator, it is possible to retain electrolyte near the negative electrode plate and improve the diffusivity of the electrolyte, even when a fiber mat is provided.

[0033] In this specification, a fully charged lead-acid battery is defined as a state in which, in the case of an electrolyte-type battery, constant current charging is performed in a 25°C water bath with a current of 0.2 CA until the voltage reaches 2.5 V / cell, followed by a further constant current charging of 0.2 CA for 2 hours. In the case of a valve-regulated battery, a fully charged state is defined as a state in a 25°C air bath with constant current and constant voltage charging at 0.2 CA, resulting in a voltage of 2.23 V / cell, and charging is terminated when the charging current during constant voltage charging falls below 1 mCA. In this specification, 1 CA is the same current value (A) as the nominal capacity (Ah) of the battery. For example, if the nominal capacity of the battery is 30 Ah, then 1 CA is 30 A and 1 mCA is 30 mA.

[0034] The following describes a lead-acid battery according to an embodiment of the present invention, focusing on its main constituent elements. However, the present invention is not limited to the following embodiments.

[0035] (Separator) The separator comprises a base portion made of a microporous membrane and ribs protruding from one main surface of the base portion. More preferably, it may further comprise ribs protruding from the other main surface of the base portion. The ribs protruding from one main surface of the base portion are positioned on the negative electrode plate side. These ribs located on the negative electrode plate side are called the first ribs. The ribs protruding from the other main surface of the base portion are positioned on the positive electrode plate side (i.e., facing the positive electrode plate). These ribs located on the positive electrode plate side are called the second ribs. The first ribs can improve the diffusivity of the electrolyte near the negative electrode plate, thereby further improving the PSOC lifetime performance and suppressing penetration short circuits.

[0036] The separator is formed of a polymer material. At least the base portion is a porous sheet, which can also be called a porous film. The separator may contain a filler (for example, particulate fillers such as silica and / or fibrous fillers) dispersed in a matrix formed of a polymer material. The separator is preferably composed of a polymer material having acid resistance. Such polymer materials preferably include polyolefins such as polyethylene and polypropylene.

[0037] The average pore diameter of the base portion of the separator is, for example, 0.01 μm or more and 0.5 μm or less, preferably 0.03 μm or more and 0.3 μm or less. When the average pore diameter is in such a range, it is advantageous because low electrical resistance and excellent short-circuit resistance performance can be achieved simultaneously.

[0038] The average pore diameter of the separator can be determined by the mercury intrusion method. More specifically, the separator is placed in a measurement container, evacuated, and then pressure is applied to fill it with mercury. The pore distribution is determined from the relationship between the pressure at this time and the volume of mercury pushed into the separator, and the average pore diameter is determined from this pore distribution. For the measurement of the average pore diameter, an automatic porosimeter (AutoPore IV 9505) manufactured by Shimadzu Corporation is used.

[0039] The average thickness of the base portion is, for example, 100 μm or more and 300 μm or less, preferably 150 μm or more and 250 μm or less. When the average thickness of the base portion is in such a range, it becomes easier to ensure the height of the first rib and, if necessary, the second rib while ensuring a high capacity. The average thickness of the base portion is determined by measuring the thickness of the base portion at five arbitrarily selected locations in a cross-sectional photograph of the separator and averaging them.

[0040] The first rib is formed on the surface of the separator facing the negative electrode plate. The average height of the first rib is determined according to the liquid utilization rate U such that the rib parameter Q described above is below a certain value. As long as the rib parameter Q satisfies the above conditions, the average height of the first rib is, for example, 0.05 mm or more, preferably 0.07 mm or more. When the average height of the first rib is within such a range, the electrolytic solution becomes easier to diffuse. From the viewpoint of ensuring high capacity, as long as the rib parameter Q satisfies the above conditions, the average height of the first rib is, for example, 0.40 mm or less, preferably 0.20 mm or less. These lower limit values and upper limit values can be arbitrarily combined.

[0041] Note that the height of the first rib refers to the distance from one main surface of the base portion at a predetermined position of the first rib to the top of the first rib. When the main surface of the base portion is not flat, when the separator is placed flat with the first rib side facing up, the distance from the highest position of one main surface of the base portion to the top of the first rib at a predetermined position of the first rib is defined as the height of the first rib. The average height of the first rib is obtained by averaging the heights of the first rib measured at 10 arbitrarily selected positions of the first rib on one main surface of the base portion.

[0042] The pattern of the first rib on one main surface of the base portion is not particularly limited, and the first rib may be formed randomly, or may be formed in a stripe shape, a curved shape, a lattice shape, etc. From the viewpoint of making the electrolytic solution easier to diffuse, it is preferable to form a plurality of first ribs in a stripe pattern on one main surface of the base portion. The direction of the stripe-shaped first rib is not particularly limited. For example, a plurality of first ribs may be formed along the height direction or the width direction of the negative electrode plate. Since the specific gravity of the electrolytic solution is likely to differ between the upper and lower parts of the electrode plate, from the viewpoint of further enhancing the diffusibility of the electrolytic solution, it is preferable to form a plurality of first ribs in a stripe shape along the height direction of the negative electrode plate.

[0043] Note that, typically, a lug is formed at one end of the negative and positive electrode plates to draw current from the electrode group. The vertical direction of the negative and positive electrode plates when these lugs are facing upwards is referred to as the height direction of the negative and positive electrode plates. The width direction of the negative and positive electrode plates is perpendicular to the height direction and crosses the main surface of the negative and positive electrode plates.

[0044] The pitch of the striped or grid-like first ribs is preferably, for example, 0.3 mm to 10 mm, and more preferably 0.5 mm to 5 mm. When the separator includes a region in which the first ribs are formed with a pitch within this range, it is easier to obtain the effect of improving the diffusivity of the electrolyte near the negative electrode plate. In the separator, it is preferable that the first ribs are formed with such a pitch in the region facing the negative electrode plate. For example, it is preferable that the first ribs with such a pitch are formed in 70% or more of the area of ​​the region facing the negative electrode plate. In regions that do not face the negative electrode plate, such as the ends of the separator, the first ribs may or may not be formed, and multiple first ribs may be formed densely (for example, with an average pitch of 0.5 mm to 5 mm).

[0045] The pitch of the first rib is the distance between the tops of adjacent first ribs (more specifically, the distance between the centers of adjacent first ribs in the direction crossing the first rib). The average pitch of the first rib is obtained by averaging the pitch of the first rib measured at 10 arbitrarily selected locations. If the first ribs are densely formed in a region that does not face the negative electrode plate, the average pitch can be calculated excluding this region. The average pitch of the first rib in the region that does not face the negative electrode plate can be calculated in the same manner as described above.

[0046] The second rib is formed on the side of the separator facing the positive electrode plate. The average height of the second rib is, for example, 0.3 mm or more, preferably 0.4 mm or more. When the average height of the second rib is within this range, oxidative degradation of the separator is more easily suppressed. From the viewpoint of ensuring high capacity, the average height of the second rib may be, for example, 1.0 mm or less, and 0.7 mm or less. These lower and upper limits can be arbitrarily combined. The average height of the second rib is determined in accordance with the case of the first rib. The height of the second rib is defined in accordance with the case of the first rib, and refers to the distance from the other main surface of the base portion of the second rib at a predetermined position to the top of the second rib.

[0047] The pattern and orientation of the second ribs are not particularly limited and can be selected from, for example, those described for the first ribs. The pitch of the striped or grid-like second ribs is, for example, 1 mm to 15 mm, and preferably 5 mm to 10 mm. If the separator includes a region in which the second ribs are formed with a pitch within this range, the effect of suppressing oxidative degradation of the separator is further enhanced. In the separator, it is preferable that the second ribs are formed with such a pitch in the region facing the positive electrode plate. For example, it is preferable that the second ribs with such a pitch are formed in 70% or more of the area of ​​the region facing the positive electrode plate. In regions that do not face the positive electrode plate, such as the ends of the separator, the second ribs may or may not be formed, and multiple second ribs may be formed densely (for example, with an average pitch of 0.5 mm to 5 mm). The pitch of the second ribs is the distance between the tops of adjacent second ribs (more specifically, the distance between the centers of adjacent second ribs in the direction crossing the second rib). The average pitch of the second rib can be calculated based on the average pitch of the first rib.

[0048] A sheet-shaped separator may be placed between the negative electrode plate and the positive electrode plate, or the negative electrode plate or positive electrode plate may be housed in a bag-shaped separator, thereby interposing the separator between the negative electrode plate and the positive electrode plate. When a bag-shaped separator is used, the electrolyte will not diffuse easily, but the diffusion will be improved by providing first and second ribs. When the negative electrode plate is housed in a bag-shaped separator, the first rib makes it easier to increase the diffusion of the electrolyte near the negative electrode plate, and also suppresses short circuits due to separator rupture even if the positive electrode current collector stretches. When the positive electrode plate is housed in a bag-shaped separator, stratification of the electrolyte will be easier to suppress.

[0049] A separator can be obtained, for example, by extruding a resin composition containing a pore-forming agent (such as a solid pore-forming agent like polymer powder, and / or a liquid pore-forming agent like oil) and a polymer material into a sheet, then removing the pore-forming agent to form pores in the matrix of the polymer material. Ribs may be formed, for example, during extrusion molding, or after forming into a sheet or after removing the pore-forming agent, by pressing with a roller having grooves corresponding to the ribs. If a filler is used, it is preferable to add it to the resin composition.

[0050] (Electrolyte) The electrolyte contains sulfuric acid in an aqueous solution. The electrolyte may be gelled as needed. The electrolyte may optionally contain additives used in lead-acid batteries. In this embodiment, the electrolyte contains Na at a concentration of 0.03 to 0.3 mol / L and / or Al at a concentration of 0.02 to 0.2 mol / L. The specific gravity of the electrolyte in a fully charged lead-acid battery after chemical conversion at 20°C is, for example, 1.10 g / cm³. 3 1.35g / cm or more 3 The following applies:

[0051] (Positive electrode plate) Lead-acid batteries have two types of positive electrode plates: paste type and clad type. A paste-type positive electrode plate comprises a positive electrode current collector and a positive electrode material. The positive electrode material is held in place by the positive electrode current collector. In a paste-type positive electrode plate, the positive electrode material is the positive electrode plate with the positive electrode current collector removed. The positive electrode current collector can be formed in the same way as the negative electrode current collector, and can be formed by casting lead or a lead alloy, or by processing a lead or lead alloy sheet.

[0052] A clad cathode plate comprises multiple porous tubes, a core inserted into each tube, a cathode electrode material filled into the tubes with the cores inserted, and a connecting seat that links the multiple tubes. In a clad cathode plate, the cathode electrode material is the cathode plate without the tubes, cores, and connecting seat.

[0053] For the positive electrode current collector, Pb-Ca alloys and Pb-Ca-Sn alloys are preferred as lead alloys in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers of different compositions, and may have multiple alloy layers. For the core metal, it is preferable to use Pb-Ca alloys or Pb-Sb alloys.

[0054] The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacity through a redox reaction. The positive electrode material may also contain other additives as needed.

[0055] Unformed paste-type positive electrode plates are obtained by filling a positive electrode current collector with positive electrode paste, followed by maturation and drying, similar to the process for negative electrode plates. Subsequently, the unformed positive electrode plates are formed. The positive electrode paste is prepared by mixing lead powder, additives, water, and sulfuric acid. Unformed clad-type positive electrode plates are formed by filling tubes into which core metals are inserted with an additive and lead powder or slurry-like lead powder, and then joining multiple tubes together in a linkage.

[0056] (Negative electrode plate) The negative electrode plate of a lead-acid battery includes negative electrode material. Typically, the negative electrode plate of a lead-acid battery consists of a negative electrode current collector and negative electrode material. The negative electrode material is the negative electrode plate with the negative electrode current collector removed. The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. Examples of processing methods include expansion and punching. Using a negative electrode grid as the negative electrode current collector is preferable because it makes it easier to support the negative electrode material.

[0057] The lead alloy used for the negative electrode current collector may be any of the following: Pb-Sb alloy, Pb-Ca alloy, or Pb-Ca-Sn alloy. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc.

[0058] The negative electrode material contains a negative electrode active material (lead or lead sulfate) that exhibits capacity through an oxidation-reduction reaction, and may also contain shrinkage inhibitors, carbonaceous materials such as carbon black, barium sulfate, and other additives as needed. As an organic shrinkage inhibitor, sodium ligninsulfonate or bisphenol compounds can be used.

[0059] The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually made using lead powder.

[0060] The negative electrode material may contain carbon particles as an additive. Carbon particles are typically conductive. Examples of carbon particles include carbon black, graphite, hard carbon, and soft carbon. Examples of carbon black include acetylene black, furnace black, channel black, and lamp black. Graphite can be any carbon material containing a graphite-type crystal structure, and may be either artificial graphite or natural graphite. The negative electrode material may contain one type of these carbon particles, or two or more types.

[0061] It is preferable that the carbon particles include carbon particles (first carbon particles) having a particle size smaller than the average pore size of the separator.

[0062] The first carbon particles preferably contain carbon black. First carbon particles, such as carbon black, are prone to leaching into the electrolyte. However, even if they leach into the electrolyte, the action of the first ribs prevents the pores of the separator from being blocked by carbon particles such as carbon black. Furthermore, using first carbon particles such as carbon black facilitates the formation of a more uniform conductive network within the negative electrode material.

[0063] The carbon particle content in the negative electrode material is preferably, for example, 0.2% by mass or more and 3.0% by mass or less, and more preferably 0.3% by mass or more and 2.5% by mass or less. When the carbon particle content is within this range, the conductive network tends to spread easily while ensuring high capacity.

[0064] The negative electrode plate can be formed by filling a negative electrode current collector with negative electrode paste, aging and drying it to produce an unformed negative electrode plate, and then forming the unformed negative electrode plate. The negative electrode paste is prepared by kneading lead powder, an organic shrinkage inhibitor, and various additives as needed, with water and sulfuric acid. In the aging process, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and at high humidity.

[0065] The chemical conversion can be carried out by immersing the electrode plate group, including the unconverted negative electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and then charging the electrode plate group. However, the chemical conversion may also be performed before the assembly of the lead-acid battery or the electrode plate group. Spongy lead is produced by the chemical conversion.

[0066] (Fiber Mat) The lead-acid battery may further include a fiber mat interposed between the positive electrode plate and the negative electrode plate. When a fiber mat is provided, the electrode plates are compressed by the fiber mat, making it difficult to retain electrolyte around the electrode plates. In the above aspect of the present invention, since the separator is provided with a first rib, it becomes easier to secure electrolyte near the negative electrode plate and high diffusivity of the electrolyte can be ensured.

[0067] Unlike separators, fiber mats are composed of sheet-like fiber aggregates. Such fiber aggregates typically consist of sheets of interwoven fibers that are insoluble in electrolyte solutions. Examples of such sheets include nonwoven fabrics, woven fabrics, and knitted fabrics.

[0068] As for the fibers, glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers such as polyethylene terephthalate fibers, etc.), and pulp fibers can be used. Among polymer fibers, polyolefin fibers are preferred.

[0069] The fiber mat may contain components other than fibers, such as acid-resistant inorganic powders and polymers as binders. Examples of inorganic powders include silica powder, glass powder, and diatomaceous earth. However, the fiber mat is primarily composed of fibers. For example, 60% or more by mass of the fiber mat is made up of fibers.

[0070] The fiber mat can be placed between the negative electrode plate and the positive electrode plate. Since a separator is also placed between the negative electrode plate and the positive electrode plate, the fiber mat may be placed between the negative electrode plate and the positive electrode plate, for example, between the negative electrode plate and the separator, and / or between the separator and the positive electrode plate. From the viewpoint of suppressing stratification of the electrolyte, it is preferable to place the fiber mat so that it is in contact with the negative electrode plate. Also, from the viewpoint of suppressing softening and detachment of the positive electrode material, it is preferable to place the fiber mat so that it is in contact with the positive electrode plate. From the viewpoint of increasing the effect of suppressing softening and detachment, it is preferable to place the fiber mat in a compressed state against the positive electrode plate, but in this case, the electrolyte near the negative electrode plate tends to become insufficient. In this embodiment, since the first rib is provided on the side of the separator facing the negative electrode plate, even when the fiber mat is placed on the positive electrode plate side, electrolyte can be secured near the negative electrode plate.

[0071] Figure 1 shows the external appearance of an example of a lead-acid battery according to an embodiment of the present invention. The lead-acid battery 1 comprises a battery case 12 that houses an electrode plate group 11 and an electrolyte (not shown). The inside of the battery case 12 is divided into a plurality of cell chambers 14 by a partition wall 13. Each cell chamber 14 houses one electrode plate group 11. The opening of the battery case 12 is closed with a lid 15 equipped with a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a liquid inlet plug 18 for each cell chamber. When replenishing water, the liquid inlet plug 18 is removed and the water is supplied. The liquid inlet plug 18 may also have a function of discharging gas generated in the cell chamber 14 to the outside of the battery.

[0072] Each electrode plate group 11 is constructed by stacking multiple negative electrode plates 2 and positive electrode plates 3 via separators 4. Here, a bag-shaped separator 4 for housing the negative electrode plates 2 is shown, but the shape of the separator is not particularly limited. In the cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6, which connects multiple negative electrode plates 2 in parallel, is connected to a through connector 8, and a positive electrode shelf 5, which connects multiple positive electrode plates 3 in parallel, is connected to a positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 on the outside of the lid 15. In the cell chamber 14 located at the other end of the battery case 12, a negative electrode column 9 is connected to the negative electrode shelf 6, and a through connector 8 is connected to the positive electrode shelf 5. The negative electrode column 9 is connected to a negative electrode terminal 16 on the outside of the lid 15. Each through connector 8 passes through a through hole provided in the partition wall 13 and connects the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0073] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0074] <Lead-acid battery A1> (1) Preparation of negative electrode plate: Lead powder, water, sulfuric acid, carbon, barium sulfate (BaSO4) ４ ), tin sulfate (SnSO ４), an organic shrinkage inhibitor, and a reinforcing material (Susa) were mixed to prepare a negative electrode paste. The negative electrode paste was filled into the mesh portion of an expanded grid made of a Pb-Ca-Sn alloy as a negative electrode current collector (grid step: 14.5 steps), aged, and dried to obtain an unformed negative electrode plate. Sodium lignosulfonate was used as the organic shrinkage inhibitor. The size of the negative electrode plate was 100 mm in width × 112 mm in height.

[0075] (2) Preparation of positive electrode plate Lead powder, water, sulfuric acid, antimony trioxide (Sb ２ O ３ ), tin sulfate (SnSO ４ ), and a reinforcing material were kneaded to prepare a positive electrode paste. The positive electrode paste was filled into the mesh portion of an expanded grid made of a Pb-Ca-Sn alloy as a positive electrode current collector (grid step: 14 steps), aged, and dried to obtain an unformed positive electrode plate. The size of the positive electrode plate was 100 mm in width × 112 mm in height.

[0076] (3) Preparation of lead-acid battery Each unformed negative electrode plate was housed in a bag-shaped separator made of a microporous polyethylene film (width 115 mm × height 115 mm), and a plate group was formed with 7 unformed negative electrode plates and 6 unformed positive electrode plates per cell. The separator had a plurality of first ribs on the stripe on the inner side of the bag and a plurality of second ribs in a stripe shape on the outer side of the bag. The plurality of first ribs were each formed along the width direction of the negative electrode plate, and the average height of the first ribs in the region facing the negative electrode plate was 0.1 mm. The plurality of second ribs were each formed along the height direction of the positive electrode plate, the average height of the second ribs was 0.7 mm, and the pitch of the second ribs in the region facing the positive electrode plate was 10 mm. Also, the average thickness of the base portion of the separator was 0.2 mm. The total thickness of the separator was 1.0 mm. The average pore diameter of the separator was 0.1 μm.

[0077] A liquid-type lead-acid battery A1 with a nominal voltage of 12V and a nominal capacity of 40Ah (20-hour rate) was assembled by inserting the electrode plates into the cell chamber of a polypropylene battery case, pouring in the electrolyte, and performing a chemical conversion within the battery case. The electrolyte used was an aqueous solution containing sulfuric acid with a specific gravity of 1.28 at 20°C, to which 0.1 mol / L of Na was added. The amount of electrolyte was 520 g / cell, of which sulfuric acid accounted for 196 g / cell. Based on the amount of sulfuric acid in the electrolyte, the theoretical capacity of the lead-acid battery was calculated to be 53.5Ah / cell. The 20-hour rate capacity was 43.0Ah / cell. Therefore, the electrolyte utilization rate U was calculated to be 80%. The electrolyte utilization rate was rounded to the third decimal place (rounded to the first decimal place of the electrolyte utilization rate in %).

[0078] Based on the height h (mm) of the first rib and the liquid utilization rate U (%), the rib parameter Q was estimated to be approximately 250.

[0079] The thickness of the positive electrode plate after chemical formation was 1.60 mm. The sheet thickness (the thickness of the unexpanded portion of the expanded grid, such as the tabs and frame) was 1.10 mm. The mass of the positive electrode plate after chemical formation was 93.0 g / sheet excluding the tabs, of which the mass occupied by the positive electrode grid excluding the tabs was 37.0 g / sheet, and the mass occupied by the positive electrode active material was 56.0 g (336 g / cell). Based on the amount of positive electrode active material, the theoretical capacity of the lead-acid battery is calculated to be 75.3 Ah / cell. The density of the positive electrode material was 4.00 g / mL, and the specific surface area and pore volume of the positive electrode material were 6.80 m², respectively. ２ The values ​​were / g and 0.14 mL / g.

[0080] In the positive electrode material, antimony oxide, tin sulfate, and reinforcing materials were present in amounts of 0.035% by mass, 0.13% by mass, and 0.09% by mass, respectively, based on 100% by mass of the positive electrode active material after chemical formation. The content of antimony oxide and tin sulfate were calculated from the Sn and Sb content, respectively, in the positive electrode material.

[0081] The thickness of the negative electrode plate after chemical formation was 1.40 mm. The sheet thickness (the thickness of the unexpanded portion of the expanded grid, such as the tabs and frame) was 0.90 mm. The mass of the negative electrode plate after chemical formation was 75.0 g / sheet, excluding the tabs, of which the negative electrode grid accounted for 32.0 g / sheet, excluding the tabs, and the negative electrode active material accounted for 42.0 g (294 g / cell). Based on the amount of negative electrode active material, the theoretical capacity of the lead-acid battery is calculated to be 76.1 Ah / cell. The density of the negative electrode material was 4.10 g / mL, and the specific surface area and pore volume of the negative electrode material were 0.54 m², respectively. ２ The values ​​were / g and 0.12 mL / g.

[0082] In the negative electrode material, carbon, barium sulfate, tin sulfate, and reinforcing materials were present in amounts of 1.5% by mass, 0.9% by mass, 0.020% by mass, and 0.02% by mass, respectively, based on 100% by mass of the negative electrode active material after chemical conversion. The tin sulfate content was calculated from the Sn content in the negative electrode material.

[0083] Furthermore, ribs were provided on the inner wall of the cell chamber facing the outermost electrode plate (negative electrode plate) of the electrode plate group to fix the position of the electrode plate group within the cell chamber, with a distance of 29.0 mm between the ribs.

[0084] <Lead-acid batteries B1 to B24> In the manufacturing of the above lead-acid batteries, the amount of electrolyte was adjusted to produce batteries with an electrolyte utilization rate of 70% and batteries with an electrolyte utilization rate of 90%. In addition, by keeping the total thickness of the separator and the base thickness constant and adjusting the height of the first and second ribs, the rib parameter Q was varied in the range of 125 to 400, and lead-acid batteries with different rib parameter Q were produced. In this way, multiple lead-acid batteries B1 to B24 with different combinations of electrolyte utilization rate U and rib parameter Q were created and their penetration short-circuit resistance was evaluated. Table 1 shows the electrolyte utilization rate and rib parameter Q values ​​of the lead-acid batteries used in the evaluation.

[0085] [Evaluation 1: Penetration Short Circuit] The lead-acid batteries were repeatedly charged and discharged under the following conditions. Specifically, five cycles were performed at 25°C, with (a) to (d) below considered as one cycle. The specific gravity of the electrolyte was measured after five cycles, and the percentage of batteries in which a penetration short circuit occurred was investigated. (a) Constant current discharge: 0.05 CA (end voltage 1.0 V / cell) (b) Constant resistance discharge: Connected to a 10 Ω resistor and left for 28 days. (c) Constant voltage charge: Charged for 10 minutes with a limiting current of 50 A and a voltage of 2.4 V / cell. (d) Constant current discharge: Discharged at 0.05 CA for 27 hours.

[0086] The specific gravity of the electrolyte at the top of the lead-acid battery after 5 cycles was measured, and the specific gravity was 1.1 g / cm³. ３ In the following cases, it was determined that a short circuit had occurred.

[0087] Twenty lead-acid batteries B1 to B24 were each manufactured, and whether or not a penetration short circuit occurred was investigated using the method described above. The probability of a penetration short circuit occurring was then calculated for each lead-acid battery B1 to B24. Table 1 shows the evaluation results. From Table 1, it can be seen that, regardless of the electrolyte utilization rate, the probability of a penetration short circuit occurring increases sharply when the rib parameter Q is above 300.

[0088] Figure 2 is a graph of the results from Table 1. From Figure 2, it can be seen that in the range where the rib parameter Q is 300 or less, the increase in the probability of penetration short circuit occurrence is gradual with increasing rib parameter Q, regardless of liquid utilization rate, and the probability of penetration short circuit occurrence is kept below 10%. However, when the rib parameter Q exceeds 300, the probability of penetration short circuit occurrence increases rapidly with increasing rib parameter Q.

[0089] On the other hand, when the rib parameter Q was 150 or less, permeation short circuits did not occur regardless of the liquid utilization rate. When the rib parameter Q is less than 150, the height of the first rib has to be made correspondingly higher, leading to a decrease in capacity. In order to maintain capacity, it is conceivable to lower the height of the second rib instead of raising the height of the first rib, but in that case, oxidative degradation of the separator is more likely to occur.

[0090] By setting the rib parameter Q to a range of 150 to 300, it is possible to maximize the effect of suppressing penetration short circuits without causing a decrease in capacity or a shortened lifespan due to oxidative degradation of the separator.

[0091] The above results were obtained when the electrolyte contained 0.1 mol / L of Na, but similar effects were obtained when the Na concentration was in the range of 0.03 to 0.3 mol / L. Furthermore, similar effects were obtained when the electrolyte contained Al and the Al concentration was in the range of 0.02 to 0.2 mol / L.

[0092]

[0093] A lead-acid battery according to one aspect of the present invention is applicable to valve-regulated and liquid-type lead-acid batteries and can be suitably used as a power source for starting automobiles or motorcycles.

[0094] 1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 5: Positive electrode shelf 6: Negative electrode shelf 7: Positive electrode column 8: Through connector 9: Negative electrode column 11: Electrode plate group 12: Battery case 13: Partition wall 14: Cell chamber 15: Cover 16: Negative electrode terminal 17: Positive electrode terminal 18: Electrode cap

Claims

DEPCT641. A lead-acid battery consisting of: a positive electrode plate; a negative electrode plate; a separator placed between the positive and negative electrode plates; and an electrolyte solution where Na 0.03 to 0.3 mol / L and / or Al 0.02 to 0.2 mol / L are present in the electrolyte solution. The separator includes the first ridge on the shore of the negative electrode plate and the ridge parameter Q, which is denoted by Q=U / (h1 / 2), is 300 or less, where the height of the first ridge protruding from the principal surface of the separator is h (mm) and the factor 1. Lead-acid battery under defense 1 where the electrolyte utilization factor is U(%).

2. Lead-acid battery under defense 1 where the rib parameter Q is 150 or more.

3. Lead-acid battery under defense 1 or 2 where the electrolyte utilization factor is 70% to 90%.

4. Lead-acid battery under any one of defenses 1 to 3 where the separator includes the second rib on the positive electrode side.

5. Lead-acid battery under any one of defenses 1 to 4 where the separator is bag-shaped. 6.A lead-acid battery under claim 5 where the separator stores the negative electrode plate.

7. A lead-acid battery under claim 5 where the separator stores the positive electrode plate.