Lead-acid battery

Abstract

This lead-acid battery comprises a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate The positive electrode plate includes a positive electrode material, the cumulative pore volume of the positive electrode material in the pore diameter range of 0.006 μm to15 μm being 0.161 cm3 / g to 0.180 cm3 / g. The positive electrode material includes fibers, the average fiber diameter of the fibers being 10 μm or less, and the moisture content of the fibers being 36% or more as calculated from 100 × (1 - mass of fibers in dry state (g) / mass of fibers in wet state (g)).

Description

lead acid battery 【0001】 This invention relates to a lead-acid battery. 【0002】 Patent Document 1 states that "the density of the active material after chemical conversion is 4.5 g / cm³." ３ In the positive electrode plate for a lead-acid battery described above, the amount of pure sulfuric acid added during the mixing of the positive electrode paste is 2.0% by mass or more and 4.5% by mass or less relative to the mass of lead powder, and furthermore, the amount of red lead added is 5.0% by mass or more and 25.0% by mass or less relative to the total amount of lead powder and red lead. In this positive electrode plate for a lead-acid battery described above, it is proposed that short fibers made of polyethylene terephthalate be added to the positive electrode plate at an amount of 0.09% by mass or more and 0.20% by mass or less relative to the mass of lead powder. 【0003】 Patent Document 2 proposes a "positive electrode plate for a lead-acid battery, comprising a positive electrode current collector and a positive electrode active material held by the positive electrode current collector, wherein the positive electrode active material includes fibers with a liquid retention rate of 125% or more." 【0004】 Patent Document 3 proposes a lead-acid battery comprising a paste-type positive electrode plate, a retainer or separator, and a paste-type negative electrode plate laminated together, characterized in that the paste-type positive electrode plate and / or the paste-type negative electrode plate contain hydrophilic short fibers. 【0005】 Japanese Patent Publication No. 2017-183283, Japanese Patent Publication No. 2021-061235, Japanese Patent Publication No. 2006-004688 【0006】With the advent of OTA (Over The Air) technology, the load on lead-acid batteries is increasing, and higher energy density is required. On the other hand, repeated deep-depth charging and discharging makes the positive electrode material of lead-acid batteries more prone to softening and detachment, leading to a premature end of life for the battery. One known technique to suppress softening and detachment due to deep-depth charging and discharging is to increase the density of the positive electrode material, but this causes a decrease in the utilization rate of the positive electrode material. When the utilization rate of the positive electrode material decreases, the discharge capacity decreases, and the mass energy density (Wh / kg) and volumetric energy density (Wh / L) decrease. Conversely, when the utilization rate of the positive electrode material increases, the aforementioned energy density increases. As described above, there is a trade-off relationship between the energy density characteristics of lead-acid batteries and the deep-discharge lifespan. To suppress the softening and detachment of the positive electrode material, it has been proposed to add fibers to the positive electrode material (see Patent Documents 1-3). However, to date, no fiber has been found that achieves both high energy density and excellent deep discharge lifetime, especially when using low-density positive electrode materials. 【0007】 One aspect of the present invention comprises a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate includes a positive electrode material, and the cumulative pore volume of the positive electrode material in the range of pore diameters from 0.006 μm to 15 μm is 0.161 cm³. ３ / g ~ 0.180cm ３ The present invention relates to a lead-acid battery in which the positive electrode material contains fibers, the average fiber diameter of the fibers is 10 μm or less, and the moisture content of the fibers, calculated from 100 × (1 - mass of the fibers in a dry state (g) / mass of the fibers in a wet state (g)), is 36% or more. 【0008】 The lead-acid battery according to the present invention can ensure good lifespan performance when repeatedly performing deep depth charge and discharge cycles. 【0009】 This is a partially cutaway perspective view showing the external appearance and internal structure of a lead-acid battery according to one embodiment of the present invention. This is a SEM image showing the appearance of an example of polyester fiber. 【0010】The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination. 【0011】 Furthermore, this disclosure encompasses any combination of matters described in two or more claims arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims arbitrarily selected from the multiple claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency. 【0012】 The lead-acid battery according to this disclosure can more significantly improve the deep discharge life in liquid-type batteries (vented batteries) where softening and detachment of the positive electrode material are prone to occur. However, the lead-acid battery according to this disclosure may also be a valve-regulated lead-acid battery (VRLA type battery). 【0013】 A lead-acid battery comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte. The electrolyte contains sulfuric acid. Charging and discharging proceed through the movement of sulfate ions between the positive and negative electrode plates and the electrolyte. During discharge, sulfate ions move to the positive and negative electrode plates. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte. 【0014】The positive electrode plate, negative electrode plate, and separator constitute a group of electrode plates. The group of electrode plates and the electrolyte together constitute a cell. One group of electrode plates constitutes one cell. A lead-acid battery includes one or more groups of electrodes and thus includes one or more cells. There is no particular limitation on the number of positive electrode plates and negative electrode plates included in one group of electrode plates. The group of electrode plates included in the lead-acid battery according to the present disclosure includes, for example, a total of 12 or more positive electrode plates and negative electrode plates. The plurality of groups of electrode plates are usually accommodated in respective individual cell chambers and connected in series with each other. 【0015】 The positive electrode plate includes a positive electrode material. The positive electrode material includes, as a positive electrode active material that exhibits capacitance through a redox reaction, at least lead dioxide during charging and at least lead sulfate during discharging. 【0016】 The negative electrode plate includes a negative electrode material. The negative electrode material includes, as a negative electrode active material that exhibits capacitance through a redox reaction, at least lead during charging and at least lead sulfate during discharging. 【0017】 (1) The lead-acid battery according to an embodiment of the present disclosure includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode material. The integrated pore volume of the positive electrode material in the range of 0.006 μm to 15 μm in pore diameter is 0.161 cm ３ / g to 0.180 cm ３ / g. The positive electrode material includes fibers, the average fiber diameter of the fibers is 10 μm or less, and the moisture content of the fibers calculated from 100×(1 - mass (g) of the fibers in the dry state / mass (g) of the fibers in the wet state) is 36% or more. It relates to a lead-acid battery. The fibers function as a reinforcing material for the positive electrode material. 【0018】 In the lead-acid battery described in (1) above, even when repeated charge and discharge with a deep discharge depth is performed, softening and shedding of the positive electrode material are suppressed, and good life performance can be ensured. The life performance in the case of repeated charge and discharge with a deep discharge depth can be evaluated in the "life test method" described later. 【0019】In the charged state, the positive electrode material forms a network in which lead dioxide particles are bonded to each other. When lead dioxide changes to lead sulfate due to the discharge reaction, its volume expands by about 1.5 times. When repeating charge-discharge cycles with a deep discharge depth, usually, the bonds between the particles of the lead compound contained in the positive electrode material are broken and a part of the lead compound becomes isolated. As a result, softening progresses from the surface of the positive electrode plate, and dropout of the positive electrode material occurs. In order to suppress such softening and dropout, it is necessary to increase the adhesion between the particles of the lead compound (especially PbO ２ ) contained in the positive electrode material. 【0020】 When the average fiber diameter of the fiber functioning as a reinforcing material is reduced to 10 μm or less, the moisture content of the fiber can be increased to 36% or more. And when the moisture content of the fiber becomes 36% or more, a phenomenon is observed in which the aging reaction during the manufacturing process of the positive electrode plate is significantly promoted. 【0021】 Specifically, in the aging process, it is considered that the vaporization rate of the moisture contained in the fiber is slower than the vaporization rate of the other moisture contained in the positive electrode paste. Therefore, by using a fiber with a high moisture content, an appropriate amount of moisture can be retained in the unformed positive electrode plate during aging for a long time. Therefore, the formation of a three-dimensional skeleton by tribasic lead sulfate in the positive electrode plate is promoted, the bonding between the particles of the lead compound after formation becomes strong, and the softening of the lead compound is suppressed. 【0022】 Further, when the positive electrode plate includes a positive electrode current collector containing lead or a lead alloy, in order to increase the adhesion between the lead compound and the positive electrode current collector, it is important to cause an oxidation reaction (corrosion reaction) to proceed on the surface of the positive electrode current collector (contact surface with the positive electrode material) in the aging process. When the oxidation reaction proceeds on the surface of the positive electrode current collector, the adhesion between the positive electrode current collector and the positive electrode material is improved. When the moisture content of the fiber becomes 36% or more, an appropriate amount of moisture can be retained in the positive electrode plate during aging for a long time. Therefore, the oxidation reaction on the surface of the positive electrode current collector is maintained for a long time, and it is considered that the bond between the positive electrode current collector and the positive electrode material also becomes strong. 【0023】 On the other hand, the integrated pore volume in the range of 0.006 μm to 15 μm of the pore diameter of the positive electrode material is 0.161 cm ３ / g to 0.180 cm ３ When it is / g, it can be said that the density of the positive electrode material is sufficiently ensured, the positive electrode material has a structure that is difficult to collapse, and a sufficient number of pores of suitable size are ensured. Therefore, the expansion and contraction accompanying repeated charge and discharge proceed easily while maintaining the contact between the particles of the lead compound. As a result, the bond between the particles of the lead compound is maintained firmly for a long time. Thereby, the effect of suppressing the dropout of the positive electrode material is further enhanced, and better life performance is ensured. Further, when the integrated pore volume is within the above range, the diffusibility of sulfate ions in the positive electrode material is enhanced, so it is easy to ensure higher output. 【0024】 As described above, by using a predetermined fiber and appropriately controlling the integrated pore volume in the range of 0.006 μm to 15 μm of the pore diameter of the positive electrode material, the bonding force between the positive electrode materials is increased, and the deep discharge life of the lead storage battery is significantly enhanced. 【0025】 From the viewpoint of maintaining sufficiently high mechanical strength, the average fiber diameter of the fiber may be 1 μm or more, 2 μm or more, or 5 μm or more. 【0026】 (2) In the lead storage battery described in (1) above, the integrated pore volume in the range of 0.006 μm to 15 μm of the pore diameter of the positive electrode material is 0.172 cm ３ It is preferably / g or less. 【0027】 In the lead storage battery described in (2) above, the density of the positive electrode material is sufficiently high, and the positive electrode material has a structure that is more difficult to collapse. Therefore, the effect of improving the deep discharge life by fibers with a high water content is further significantly enhanced. 【0028】 (3) In the lead storage battery described in (1) or (2) above, the average fiber diameter of the fiber may be 1 μm to 8 μm. 【0029】In the lead-acid battery described in (3) above, the fibers have a large specific surface area and can have a very high moisture content. Therefore, the maturation reaction is significantly accelerated, which increases the bonding force between the positive electrode materials and greatly improves the deep discharge life of the lead-acid battery. In addition, the increased contact area between the lead compound constituting the positive electrode material and the fibers also contributes to the improvement of the deep discharge life. 【0030】 More preferably, the average fiber diameter of the fibers may be 2 μm or more and 8 μm or less, or 5 μm or more and 8 μm or less. 【0031】 (4) In the lead-acid battery described in any one of (1) to (3) above, it is preferable that the surface of the fiber has irregularities. Furthermore, it is preferable that the irregularities on the surface of the fiber are formed along the circumferential direction of the fiber. The circumferential direction of the fiber is any direction that intersects the longitudinal direction of the fiber. Such a direction is, for example, a direction that has an angle of 45° or more on average with the longitudinal direction of the fiber. 【0032】 In the lead-acid battery described in (4) above, the surface area of ​​the fibers increases due to the irregularities on the fiber surface, and the moisture content of the fibers improves. In addition, the irregularities increase the friction between the lead compound particles and the fibers. In particular, when the irregularities on the fiber surface are formed along the circumferential direction of the fiber, the friction is greater when the lead compound particles try to move in the longitudinal direction of the fiber. Therefore, an effect is obtained in which the expansion of the positive electrode material along the longitudinal direction of the fiber is suppressed. 【0033】 (5) In the lead-acid battery described in (4) above, the surface irregularities of the fibers may be formed in a ripple pattern along the circumferential direction of the fibers. 【0034】 The ripple-like trajectories of the irregularities extending across the fiber surface are long and the irregularities themselves are complex. As a result, the surface area of ​​the fiber increases significantly, and the moisture content of the fiber also improves significantly. Furthermore, such irregularities readily engage with lead compound particles that attempt to move along the length of the fiber. Therefore, the effect of suppressing the expansion of the positive electrode material along the length of the fiber becomes even greater. 【0035】(6) In the lead-acid battery described in (1) to (5) above, the fiber content in the positive electrode material may be, for example, 0.01% by mass or more and 0.23% by mass or less, 0.02% by mass or more and 0.15% by mass or less, 0.03% by mass or more and 0.12% by mass or less, or 0.05% by mass or more and 0.10% by mass or less. 【0036】 The fiber content in the positive electrode material may be 0.01% by mass or more and 0.12% by mass or less, 0.01% by mass or more and 0.07% by mass or less, 0.02% by mass or more and 0.12% by mass or less, 0.02% by mass or more and 0.07% by mass or less, 0.03% by mass or more and 0.12% by mass or less, or 0.03% by mass or more and 0.07% by mass or less. 【0037】 The lead-acid battery described in (6) above has very good fluidity of the positive electrode paste in the manufacturing process of the positive electrode plate, and the effect of improving the deep discharge life of the lead-acid battery by using fibers is significant. 【0038】 (7) In the lead-acid battery described in any one of (1) to (6) above, the resin constituting the fibers may be, for example, polyethylene terephthalate (hereinafter also referred to as "PET"). 【0039】 PET has excellent acid resistance and mechanical strength. Therefore, PET fibers can have a fine average fiber diameter, secure a large surface area even in small quantities, and have a high moisture content, which greatly improves the deep discharge life of lead-acid batteries. Furthermore, PET fibers are inexpensive. 【0040】 The type of resin constituting the fibers contained in the positive electrode material can be identified by analyzing the fibers recovered from the positive electrode material using the method described in JIS L 1030-1:2024. The fibers may be recovered by pulling them out of the positive electrode material with tweezers, or by recovering them from the residue after dissolving the lead compound contained in the positive electrode material. 【0041】(8) In the lead-acid battery described in any one of (1) to (7) above, the negative electrode plate may contain a negative electrode material containing a carbon material, and the carbon material content may be 0.35% by mass or more and 0.80% by mass or less. 【0042】 In the lead-acid battery described in (8) above, the inclusion of a carbon material within the above range in the negative electrode material suppresses sulfation near the negative electrode, thereby improving the IS life. Examples of carbon materials include carbon black, non-graphitizable carbon, easily graphitizable carbon, and graphite. Among these, carbon black is preferred from the viewpoint of having a high surface area and high conductivity. By adding carbon black, conductive paths are formed within the negative electrode material by the carbon black. As a result, the following charging reaction proceeds smoothly even within the negative electrode material, and a significant effect in eliminating sulfation is obtained. PbSO ４ +2H ＋ +2e － →Pb+H ２ SO ４ 【0043】 Preferred carbon blacks include acetylene black and furnace black. Examples of acetylene black include Denka Black (registered trademark). Examples of furnace black include Ketjen Black (registered trademark). 【0044】 (9) In the lead-acid battery described in any one of (1) to (8) above, the density of the positive electrode material is 4.0 g / cm³ ３ The following is also acceptable. 【0045】 In the lead-acid battery described in (9) above, the utilization rate of the electrode material (active material) can be improved by lowering the density of the positive electrode material, thereby reducing the amount of lead used or increasing the initial capacity. On the other hand, lowering the density has the drawback that the positive electrode material is more prone to softening and shedding. However, by using the fibers of the present invention, it is possible to make softening and shedding less likely to occur even when using a low-density positive electrode material, thereby ensuring good lifespan performance. The lower limit of the density of the positive electrode material is not particularly limited. For example, the density of the positive electrode material can be 3.4 g / cm³. ３This is preferable because it sufficiently suppresses the softening and shedding of the positive electrode material by the fibers of the present invention. 【0046】 (10) In the lead-acid battery described in any one of (1) to (9) above, the electrolyte may contain Mg ions, or the electrolyte may contain 2.0 to 10 g / L of Mg ions. 【0047】 In the lead-acid battery described in (10) above, the presence of Mg ions in the electrolyte allows the ions to remain present in the electrolyte even if the lead-acid battery enters an over-discharge state and the sulfuric acid concentration in the electrolyte becomes dilute. This suppresses the dissolution of lead into the electrolyte when an over-discharge state occurs, thereby suppressing the growth of lead dendrites and, as a result, preventing penetration short circuits. Furthermore, Mg ions have the effect of increasing the conductivity of the electrolyte when the lead-acid battery enters an over-discharge state, thus improving the charge acceptance performance in the over-discharge state. These effects can be more pronounced when the Mg ions in the electrolyte are within the above range. Na ions or Li ions may be used instead of Mg ions. However, Na ions have the drawback of reducing regenerative charge acceptance, and Li ions are expensive, so Mg ions are preferred. 【0048】 (11) In the lead-acid battery described in any one of (1) to (10) above, the positive electrode plate further comprises a positive electrode current collector, and the positive electrode current collector may have an Sb content of 1.5% by mass or more and 4.0% by mass or less. The deep discharge life performance is improved by the positive electrode current collector containing antimony within the above range. 【0049】 (12) The lead-acid battery described in any one of (1) to (11) above may be a lead-acid battery used to supply power to an in-vehicle device that transmits and receives data via wireless communication. 【0050】With the advent of OTA technology and the widespread use of dashcams, the current values ​​of lead-acid batteries used in vehicles for auxiliary applications such as air conditioners and electrical components tend to increase while the vehicle is stopped. For such auxiliary lead-acid batteries, there is a stronger need to improve durability when repeatedly performing high-capacity and deep-depth charge-discharge cycles, rather than prioritizing starting performance (high-current discharge) or high-temperature durability, which have been important until now. 【0051】 In other words, the lead-acid battery described in (12) above is suitable as a lead-acid battery used to supply power to in-vehicle equipment that transmits and receives data via wireless communication. 【0052】 (13) The lead-acid battery described in any one of (1) to (12) above may be a lead-acid battery used as an auxiliary battery for a hybrid vehicle or an electric vehicle. Such a lead-acid battery is not for starting the engine, but rather supplies electricity necessary for the operation of electronic equipment and control systems installed in the vehicle, for example. 【0053】 In this specification, the fully charged state of a liquid lead-acid battery is defined according to the definition in JIS D5301:2019. More specifically, the 20-hour rate current I is used until the terminal voltage (in volts) during charging, measured every 15 minutes in a water bath at 25°C ± 2°C, or the electrolyte density converted to a temperature of 20°C, shows a constant value with three significant figures for three consecutive times. ２０ Twice the current 2I ２０ (Unit: A) The fully charged state is defined as the state in which the lead-acid battery has been charged. Note that the 20-hour rate current I ２０ This refers to a current (A) that is 1 / 20th of the Ah value listed for the rated capacity. The value listed for the rated capacity is a value with the unit Ah (ampere-hour). The unit of the current set based on the value listed for the rated capacity is A (ampere). 【0054】 Furthermore, in the case of a valve-regulated lead-acid battery, a fully charged state is defined as a 20-hour rate current of I in an air chamber at 25°C ± 2°C. ２０ Five times the current 5I ２０ The battery was then charged at a constant current and voltage of 2.67V / cell (16.00V for a lead-acid battery with a nominal voltage of 12V), and the charging process was terminated when the total charging time reached 24 hours. 【0055】A fully charged lead-acid battery is a lead-acid battery that has been charged to its full capacity after chemical formation. The timing for charging a lead-acid battery to its full capacity can be immediately after chemical formation, or after some time has passed since chemical formation (for example, 720 hours or less). For example, a lead-acid battery that has been chemically formed and is in use (preferably in the early stages of use) may be charged. 【0056】 In this specification, a battery in its initial use refers to a battery that has not been used for very long and has not deteriorated much (for example, a battery that has been in use for less than 720 hours, including the time elapsed since chemical preparation). 【0057】 The lead-acid battery according to an embodiment of the present invention will be described in more detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. 【0058】 The following describes examples of components of a lead-acid battery. 【0059】 (Positive electrode plate) The positive electrode plate comprises a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. The positive electrode material is the portion of the positive electrode plate excluding the positive electrode current collector. Note that adhesive members such as conductive layers, mats, and pasting paper may be attached to the positive electrode plate. Since the adhesive members are used integrally with the positive electrode plate, they are included as components of the positive electrode plate. When the positive electrode plate includes adhesive members, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode current collector and the adhesive members. 【0060】 The positive electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. The processing method may be, for example, expansion or punching. Using a grid-like current collector as the positive electrode current collector makes it easier to support the positive electrode material. 【0061】 As the lead alloy used for the positive electrode current collector, Pb-Ca alloys and Pb-Ca-Sn alloys, which have excellent corrosion resistance and mechanical strength, are preferred. The positive electrode current collector may have metal layers with different compositions, and the metal layers may be one layer or multiple layers. 【0062】The positive electrode material includes a positive electrode active material that exhibits capacity through a redox reaction. The positive electrode active material includes lead dioxide, lead sulfate, etc. The positive electrode material also includes fibers as a reinforcing material and may include antimony compounds, etc., as needed. 【0063】 The moisture content of the fibers is 36% or higher, and may be 38% or higher. For example, the moisture content of the fibers may be 36% to 60%, 36% to 50%, 36% to 45%, 36% to 42%, or 38% to 42%. 【0064】 The average fiber diameter of the fibers is, for example, 10 μm or less, but may be between 1 μm and 8 μm. Such fibers can have a high moisture content and a sufficiently large specific surface area. Therefore, the effect of improving the deep discharge life of lead-acid batteries by increasing the bonding strength between positive electrode materials is greatly enhanced. 【0065】 The fiber content in the positive electrode material may be, for example, 0.01% by mass or more and 0.23% by mass or less, 0.02% by mass or more and 0.15% by mass or less, 0.03% by mass or more and 0.12% by mass or less, or 0.05% by mass or more and 0.10% by mass or less. 【0066】 The effect of suppressing softening and shedding by fibers can also depend on the material of the fibers. Preferably, the fibers are made of a resin that is thin yet strong and stable in the presence of sulfuric acid. 【0067】The resin constituting the fiber may be polyester, polyolefin, polystyrene, polyvinyl chloride, etc. Among these, at least one selected from the group consisting of polyester and polyolefin is preferred. Fibers composed of polyester and / or polyolefin have high strength even when thin and are stable in the presence of sulfuric acid. Examples of polyester include polyethylene terephthalate (PET) and polyalkylene arylates such as polybutylene terephthalate (PBT). Examples of polyolefins include polyethylene, polypropylene, and ethylene-propylene copolymer. The fiber may contain one of these resins or two or more. Furthermore, the positive electrode material may contain multiple fibers formed of different resins. In particular, using PET makes it easier to improve the deep discharge life of the lead-acid battery. Note that the type of resin does not significantly affect the moisture content of the fiber. Also, as long as the moisture content of the fiber is 36% or more, regardless of the type of resin, a phenomenon is observed in which the maturation reaction during the manufacturing process of the positive electrode plate is significantly accelerated, and the desired effect can be obtained. 【0068】 For example, 85% or more by mass of the fiber may be at least one selected from the group consisting of polyester and polyolefin. Fibers containing polyester with such a high mass content are usually called polyester fibers. Similarly, fibers containing polyolefin with such a high mass content are usually called polyolefin fibers. 【0069】 The surface of the fiber may have various irregularities. Preferably, the irregularities on the fiber surface are formed along the circumferential direction of the fiber. Irregularities along the circumferential direction of the fiber increase the moisture content of the fiber and increase friction with the particles of the positive electrode active material (lead compound) that tend to move in the longitudinal direction of the fiber, thus having a significant effect in suppressing the expansion of the positive electrode material. The irregularities on the fiber surface may also be observed using a scanning electron microscope (SEM) image of the fiber. 【0070】The irregularities may be formed on the fibers beforehand, or they may be formed on smooth fibers by a predetermined method, or they may be formed during the manufacturing process of the lead-acid battery. One method to improve the moisture content of the fibers is chemical treatment, which modifies the fiber surface using chemicals such as acids and alkalis. Other methods to improve the moisture content of the fibers include plasma treatment, which modifies the fiber surface using plasma, corona treatment, which modifies the fiber surface using high-voltage discharge, and UV irradiation treatment, which modifies the fiber surface using ultraviolet light. Yet another method is sandblasting, for example. Sandblasting is a process in which fine powder harder than the fibers is impacted onto the fibers. 【0071】 When using methods such as plasma treatment, corona treatment, or UV irradiation to create irregularities on fibers, the state of the irregularities may be altered by changing the output value of the processing device, the processing time, or both. In sandblasting, the speed of the fine powder impacting the fibers and the processing time can also be changed. 【0072】 It is more preferable that the surface irregularities of the fiber are formed in a wave-like pattern along the circumferential direction of the fiber. The wave-like irregularities increase the moisture content of the fiber and, because the friction with the particles of the positive electrode active material that try to move in the longitudinal direction of the fiber is very large, the effect of suppressing the expansion of the positive electrode material is further enhanced. The surface of the fiber made of PET is also preferable in that it may have irregularities formed in a wave-like pattern along the circumferential direction. 【0073】 The cumulative pore volume of the positive electrode material with pore diameters ranging from 0.006 μm to 15 μm is, for example, 0.161 cm³. ３ / g ~ 0.180cm ３ It is / g and 0.161cm ３ / g ~ 0.172cm ３ It may also be / g. In this case, as described above, the bonding force between the positive electrode materials is significantly increased. Therefore, good life performance can be ensured when repeatedly performing deep charge and discharge cycles. 【0074】 The cumulative pore volume of the positive electrode material with pore sizes ranging from 0.006 μm to 15 μm is 0.161 cm³. ３ / g or more (or 0.165cm) ３ / g or more) 0.180cm ３ It is also acceptable to have a value of less than / g, such as 0.161 cm. ３ / g or more (or 0.165cm) ３ / g or more) 0.172cm ３ It is also acceptable to have a value of less than / g, such as 0.161 cm. ３ / g or more 0.168cm ３ It is also acceptable to use less than / g. 【0075】 The cumulative pore volume (V(all)) of the positive electrode material in the pore size range of 0.006 μm to 15 μm is determined by the mercury intrusion method. Specifically, V(all) of the positive electrode material is measured using a mercury porosimeter (Shimadzu Corporation, Autopore IV9510) with an unground sample of the positive electrode material. The measurement pressure range is from 1 psia (≈6.9 kPa) to 60,000 psia (≈414 MPa). 【0076】 Samples of uncrushed positive electrode material are taken from positive electrode plates removed from fully charged lead-acid batteries. 【0077】 The positive electrode material is recovered from the positive electrode plate by the following procedure. First, a fully charged lead-acid battery is disassembled, and the obtained positive electrode plate is washed with water for 3 to 4 hours to remove the electrolyte from the positive electrode plate. The washed positive electrode plate is dried in a constant temperature bath at 60°C ± 5°C for 5 hours or more. After drying, if the positive electrode plate contains adhesive material, the adhesive material is removed from the positive electrode plate by peeling. A sample of the positive electrode material for analysis can be obtained by taking a sample of the positive electrode material without crushing it from near the center of the top, bottom, left, and right sides when viewed from the front of the positive electrode plate. For V(all) measurement, a sample of about 1.2 g is sufficient. 【0078】 The fibers are recovered from a sample of positive electrode material weighing approximately 70g (Wg) using the following procedure. First, the Wg sample of positive electrode material is crushed and accurately weighed. At this time, the sample may consist of positive electrode material from one or more positive electrode plates. 【0079】Next, the pulverized sample is added to a mixed solution of acetic acid-sodium acetate solution and sodium thiosulfate solution (acetic acid concentration 1.7 mol / L, sodium acetate concentration 6.1 mol / L, sodium thiosulfate concentration 0.5 mol / L), and the soluble components are dissolved while stirring at room temperature. After that, it is washed with deionized water. Then, the resulting residue is filtered using a membrane filter (average pore size: 0.45 μm or less). This allows the fibers contained in the positive electrode material to be obtained as solid matter on the filter paper. If carbonaceous material is contained in the obtained solid matter, only the fibers contained in the sample are recovered as solid matter by centrifugation or sieving. 【0080】 A fiber sample for analysis is obtained by washing and drying the resulting solid. The mass w of the fiber sample is measured. The percentage of the mass w of the fiber sample relative to the mass W of the positive electrode material sample represents the fiber content in the positive electrode material. Note that the fiber content in the positive electrode material in Table 1 below is the value obtained by the method described here. 【0081】 The moisture content of the fibers is measured using the following procedure. First, filter paper is placed in a funnel, the fibers are placed on the filter paper, and deionized water is added. The deionized water is drained from the funnel until no more water drips for 30 seconds, obtaining the fibers in a wet state. Only the wet fibers are placed in a petri dish and their mass Wwet is measured. Then, the fibers are dried at 70°C for 24 hours, and the mass Wdry of the wet fibers is measured. The moisture content Cwater (%) of the fibers can be calculated using the following formula. 【0082】 Cwater (%) = 100 × (1-Wdry (g) / Wwet (g)) 【0083】 The resin constituting the fibers can be identified by analyzing the infrared absorption spectrum of the fiber sample. Method B (film method) specified in JIS L 1030-1:2024 may be used as the analytical method. 【0084】Specifically, the fiber sample is dissolved in an appropriate dissolving reagent (see Table A), poured into an evaporating dish, and dried under vacuum or by heating to a temperature that does not decompose the sample. Next, the dried film is peeled off without tearing, cut to an appropriate size, and the infrared absorption spectrum is measured in accordance with JIS K 0117:2017. The film should be transparent. Also, the size of the film will vary depending on the infrared spectrophotometer used, so it should be at least 1 cm. ２ That concludes this section. 【0085】 Table A exemplifies the main absorption bands and characteristic wavenumbers of the infrared absorption spectra of various fibers, as well as the dissolving reagents. The absorption bands and characteristic wavenumbers of each fiber vary by ±20 cm depending on the infrared spectrophotometer used. －１ There are differences in degree. 【0086】 【0087】 The average fiber diameter D of a fiber can be determined by selecting any 20 fibers from a fiber sample, measuring the fiber diameter (the dimension perpendicular to the length of the fiber) at any point on each fiber, and taking the arithmetic mean of the measured values. The average fiber diameter D of a fiber may also be measured using a scanning electron microscope (SEM) image of the fiber. 【0088】 Unformed positive electrode plates are obtained by maturing and drying a positive electrode current collector and a positive electrode paste filled in the positive electrode current collector. The positive electrode paste is prepared by kneading a mixture containing lead powder, fibers, water, and sulfuric acid. The positive electrode paste may contain additives as needed. These additives may include antimony compounds, for example. Such positive electrode plates are also called paste-type positive electrode plates. 【0089】 A positive electrode plate can be obtained by chemically treating an untreated positive electrode plate. Chemical treatment may be carried out by immersing the electrode plate group, including the untreated positive electrode plate, in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery, and charging the electrode plate group. Chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group. 【0090】(Negative electrode plate) The negative electrode plate comprises a negative electrode current collector and a negative electrode material. The negative electrode material is held by the negative electrode current collector. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. Note that adhesive members such as conductive layers, mats, and pasting paper may be attached to the negative electrode plate. The adhesive members are included as components of the negative electrode plate. When the negative electrode plate includes adhesive members, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive members. 【0091】 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. The processing method may be expansion or punching. Using a grid-like current collector as the negative electrode current collector makes it easier to support the negative electrode material. 【0092】 The lead alloy used for the negative electrode current collector may be any of the following: a Pb-Sb alloy, a Pb-Ca alloy, or a Pb-Ca-Sn alloy. The lead alloy used for the negative electrode current collector may also contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. The negative electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers. 【0093】 The negative electrode material contains a negative electrode active material that exhibits capacity through an oxidation-reduction reaction. The negative electrode active material includes lead, lead sulfate, etc. The negative electrode material may also contain 100 ppm to 300 ppm of element Bi by mass. The negative electrode material may contain other additives as needed. The additives may include organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc. 【0094】 Examples of organic shrinkage inhibitors include lignin, lignin sulfonic acid, and synthetic organic shrinkage inhibitors. Synthetic organic shrinkage inhibitors may include, for example, formaldehyde condensates of phenolic compounds. Organic shrinkage inhibitors may be used individually or in combination of two or more. The content of organic shrinkage inhibitors in the negative electrode material is, for example, 0.01% by mass or more and 1% by mass or less. 【0095】As carbonaceous materials, carbon black, artificial graphite, natural graphite, hard carbon, soft carbon, etc., can be used. One type of carbonaceous material may be used alone, or two or more types may be used in combination. The carbonaceous material content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less. 【0096】 The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less. 【0097】 Unformed negative electrode plates are obtained by aging and drying a negative electrode current collector and a negative electrode paste filled in the negative electrode current collector. Aging is preferably carried out in an atmosphere with a temperature higher than room temperature and high humidity. The negative electrode paste is prepared by kneading a mixture containing lead powder, water, and sulfuric acid. The negative electrode paste may contain additives as needed. Additives may include bismuth compounds (e.g., bismuth sulfate), organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc. 【0098】 A negative electrode plate can be obtained by chemically treating an untreated negative electrode plate. Chemical treatment may be carried out by immersing a group of electrode plates, including the untreated negative electrode plate, in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery, and charging the electrode plate group. Chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group. The charged negative electrode active material contains spongy lead. 【0099】 (Separator) Lead-acid batteries typically have a separator interposed between the negative and positive electrodes. The separator may be a microporous membrane or a glass fiber mat (AGM (Absorbed Glass Mat)). 【0100】 A microporous membrane is a porous sheet mainly composed of materials other than fiber components. Preferably, the amount of materials other than fiber components is, for example, 60% by mass or more. A microporous membrane can be obtained, for example, by extruding a resin composition containing a pore-forming agent into a sheet, and then removing the pore-forming agent to form pores. A microporous membrane is preferably composed of an acid-resistant polymer component. Polyolefin is preferred as the polymer component. On the other hand, a glass fiber mat preferably contains, for example, 60% by mass or more glass fibers. 【0101】The thickness of the separator placed between the negative electrode plate and the positive electrode plate should be selected according to the distance between the two plates. 【0102】 (Electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte may be gelled as needed. The electrolyte may optionally contain cations (e.g., metal cations) and / or anions (e.g., phosphate ions) that do not originate from sulfuric acid. Examples of metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions. 【0103】 The density of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 g / cm³. ３ The above is 1.25 g / cm³. ３ The above is also acceptable. The density of the electrolyte at 20°C is 1.35 g / cm³. ３ The following is the value: 1.32 g / cm³ ３ The following is preferable: 【0104】 (Example of a lead-acid battery) Figure 1 shows the external appearance and part of the internal structure of a lead-acid battery according to one embodiment. 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 replenished. The liquid inlet plug 18 may also have the function of discharging gas generated in the cell chamber 14 to the outside of the battery. 【0105】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 that houses 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 strap 6 that connects multiple negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode strap 5 that 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 strap 6, and a through connector 8 is connected to the positive electrode strap 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. 【0106】 Note that Figure 1 is merely one example of a liquid-type lead-acid battery, and the structure of the lead-acid battery according to this disclosure is not limited to the example shown. 【0107】 [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. 【0108】 The following describes the evaluation method for lead-acid batteries. 【0109】 (Life Test Method) In this specification, the deep discharge life of a lead-acid battery is evaluated by the number of charge-discharge cycles in a life test that involves repeated deep charge-discharge cycles. Here, a lead-acid battery (nominal voltage 12V) is used for the life test, which consists of six cells (connected in series) each comprising four JIS B size positive electrodes and five JIS B size negative electrodes. This lead-acid battery is designed so that the positive electrodes are prone to degradation, and its lifespan is determined by the degradation of the positive electrodes. 【0110】 A fully charged lead-acid battery with a nominal voltage of 12V will be subjected to repeated discharge and charging under the following conditions. Except for water replenishment in (b) and (g), (a) to (h) will be carried out in a water tank environment at 25°C ± 2°C. (a) 20-hour rate current I ２０Charge at twice the current until the terminal voltage measured every 15 minutes shows a constant value for three consecutive times. (b) Refill with distilled water up to the upper level. (c) 20-hour rate current I ２０ Discharge at a constant current of 12 times the current for 12 minutes. (d) 20-hour rate current I ２０ Charge at a constant current of 12 times the current for 11.4 minutes. (e) 20-hour rate current I ２０ Constant current charging is performed for 4.8 minutes at a current value that is 1 / 4 of 12 times the current. (f) Repeat steps (c) to (e) 350 times. (g) Replenish with distilled water up to the upper level. (h) Repeat steps (c) to (g) until the lead-acid battery reaches the end of its lifespan. The end of its lifespan is defined as the point when the battery voltage falls below 7.2V during the discharge in step (c). 【0111】 Furthermore, for lead-acid batteries, the 20-hour rate capacity is measured using the methods shown in (i) to (l) below and used as an indicator of capacity characteristics. 【0112】 (i) 20 hour rate current I ２０ Charging is performed at 3.42 times the normal current until the terminal voltage during charging, or the electrolyte density converted to temperature, measured every 15 minutes, shows a constant value for three consecutive times. The electrolyte level is also kept filled to the upper level. 【0113】 The temperature conversion of the electrolyte density is given by the following formula: D ２０ = D Ｔ +0.0007 (T-20) Here, D ２０、 D Ｔ、 T represents the following values: D ２０ : Density of electrolyte at 20°C (g / cm³) ３ ) D Ｔ : Density of electrolyte at T℃ (g / cm³) ３ ) T: Temperature of the electrolyte when measuring density (°C) 【0114】 (j) Throughout the entire test period, the lead-acid batteries shall be placed in a water tank at 25±2°C, with the electrolyte level between 15 and 25 mm below the top surface of the lead-acid batteries. If multiple lead-acid batteries are placed in the same water tank, the distance between them and the distance to the water tank wall shall be at least 25 mm. 【0115】(k) After the charging described in (i) above is complete, confirm that the electrolyte temperature is 25±2℃ after another 1 to 5 hours. Then, the lead-acid battery is charged with a 20-hour rate current I until the terminal voltage drops to 10.50±0.05V. ２０ Discharge the battery and record the discharge duration t hours. 【0116】 (l) The 20-hour rate capacity C of a lead-acid battery is calculated using the following formula. ２０ Calculate (Ah). C ２０ = I ２０ ×t 【0117】 《Lead-acid batteries E1-E19 and R1-R9》 (1) Preparation of negative electrode plates A negative electrode paste is prepared by mixing lead oxide, carbon black, barium sulfate, lignin, water and sulfuric acid. The negative electrode paste is filled into the mesh of an expanded grid made of antimony-free Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed negative electrode plate of JIS B size. The amounts of carbon black, barium sulfate and lignin are adjusted so that when measured in a fully charged state after formation, they are 0.3 mass%, 2.1 mass%, and 0.1 mass%, respectively. 【0118】 (2) Preparation of the positive electrode plate A positive electrode paste is prepared by mixing lead oxide, fibers, water, and sulfuric acid. At this time, the amounts of water and sulfuric acid are adjusted so that the cumulative pore volume (V(all)) of the positive electrode material in the range of pore diameters from 0.006 μm to 15 μm, as measured by the procedure described above, is the value shown in Table 1. In addition, fibers with different moisture content and an uneven surface are added to the positive electrode paste in advance so that their content in the positive electrode material is as shown in Table 1. The positive electrode paste is filled into the mesh of an expanded grid made of antimony-free Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed positive electrode plate of JIS B size. 【0119】 Figure 2 shows an SEM image of an example of the fiber used. The surface of the fiber shows complex, wavy-shaped irregularities that extend along the circumferential direction of the fiber. 【0120】 (3) Preparation of separators Prepare a bag-shaped separator by folding a polyethylene microporous membrane in half. 【0121】(4) Manufacturing of the lead-acid battery Each untreated negative electrode plate is placed in a bag-shaped separator, and five untreated negative electrode plates and four untreated positive electrode plates are stacked alternately to form an electrode plate group. The tabs of the positive electrode plates and the tabs of the negative electrode plates are welded to the positive and negative electrode straps, respectively, using the cast-on-strap (COS) method. The electrode plate group is inserted into a polypropylene battery case, electrolyte is poured in, and the electrode plate group is treated inside the battery case to assemble a liquid-type lead-acid battery with a nominal voltage of 12V and a rated capacity of 30Ah (20-hour rate capacity). Six electrode plate groups are connected in series inside the battery case. 【0122】 The density of the electrolyte after chemical conversion is between 1.255 and 1.315 g / cm³. ３ Adjust within the range. 【0123】 (5) The evaluated lead-acid battery is fully charged using the procedure described above, and its lifespan performance (number of cycles until the terminal voltage of the lead-acid battery falls below 7.2V) is determined. The results are shown in Table 1. Each evaluation is shown as a relative value (%) with the result of lead-acid battery R1 set to 100%. 【0124】 【0125】 Lead-acid battery E20: Except for using fibers with no surface irregularities, battery E20 was manufactured and evaluated in the same manner as battery E11. The results are shown in Table 2. 【0126】 【0127】 Table 1 shows that when the moisture content of the fibers in the positive electrode material is 36% or more, the average fiber diameter is 10 μm or less, and V(all) is in the range of 0.161 to 0.180, the lifespan performance is significantly improved and the capacity characteristics are also good. Table 2 shows that using fibers with surface irregularities significantly improves the lifespan performance. 【0128】The lead-acid battery according to the above aspects of the present invention is suitable for applications such as IS (idle stop) (e.g., lead-acid batteries for ISS (idle stop start) vehicles), starting power sources for various vehicles (automobiles, motorcycles, etc.), and auxiliary power sources for hybrid or electric vehicles. However, these applications are merely examples, and the lead-acid battery according to the above aspects of the present invention is not limited to these applications. 【0129】 1: Lead-acid battery, 2: Negative electrode plate, 3: Positive electrode plate, 4: Separator, 5: Positive electrode strap, 6: Negative electrode strap, 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

1. The device comprises a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate includes a positive electrode material, and the cumulative pore volume of the positive electrode material in the range of pore diameter 0.006 μm to 15 μm is 0.161 cm³. ３ / g ~ 0.180cm ３ A lead-acid battery wherein the positive electrode material contains fibers, the average fiber diameter of the fibers is 10 μm or less, and the moisture content of the fibers, calculated from 100 × (1 - mass of the fibers in a dry state (g) / mass of the fibers in a wet state (g)), is 36% or more.

2. The cumulative pore volume of the positive electrode material in the range of pore diameters from 0.006 μm to 15 μm is 0.172 cm³. ３ The lead-acid battery according to claim 1, wherein the value is less than or equal to / g.

3. The lead-acid battery according to claim 1, wherein the average fiber diameter of the fibers is 1 μm to 8 μm.

4. The lead-acid battery according to any one of claims 1 to 3, wherein the surface of the fiber has irregularities, and the irregularities are formed along the circumferential direction of the fiber.

5. The lead-acid battery according to claim 1, wherein the fiber content in the positive electrode material is 0.01% by mass or more and 0.23% by mass or less.

6. The lead-acid battery according to claim 1, wherein the resin constituting the fibers is polyethylene terephthalate.

7. The lead-acid battery according to claim 1, wherein the negative electrode plate comprises a negative electrode material containing a carbon material, and the carbon material content is 0.35% by mass or more and 0.80% by mass or less.

8. The density of the positive electrode material is 4.0 g / cm³. ３ The lead-acid battery according to claim 1, which is as follows:

9. The lead-acid battery according to claim 1, wherein the electrolyte contains 2.0 to 10 g / L of Mg ions.

10. The lead-acid battery according to claim 1, wherein the positive electrode plate further comprises a positive electrode current collector, and the positive electrode current collector has an Sb content of 1.5% by mass or more and 4.0% by mass or less.

11. The lead-acid battery according to claim 1, used for supplying power to in-vehicle equipment that transmits and receives data via wireless communication.

12. The lead-acid battery according to claim 1, which is used as an auxiliary battery for a hybrid vehicle or an electric vehicle.

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