JP7215475B2 - lead acid battery - Google Patents

Description

The technology disclosed in this specification relates to lead-acid batteries.

Lead-acid batteries are widely used as secondary batteries. For example, a lead-acid battery is mounted in a vehicle such as an automobile, and is used as a power supply source for a starter when an engine is started, and as a power supply source for various electrical components such as lights.

A lead-acid battery includes a positive plate and a negative plate. The positive plate and the negative plate each have a current collector and an active material supported by the current collector.

Conventionally, there is known a technique of incorporating reinforcing short fibers into an active material in order to increase the strength of the active material and improve the life characteristics of a lead-acid battery (see, for example, Patent Document 1).

JP-A-2000-36305

The inventors of the present application have made extensive studies and newly found that the life characteristics of a lead-acid battery can be improved by adopting a specific configuration as the configuration of a positive electrode material containing fibers.

This specification discloses a technique capable of improving the life characteristics of a lead-acid battery.

The lead-acid battery disclosed herein includes a positive electrode plate having a current collector made of a lead alloy and a positive electrode material supported by the current collector, and a negative electrode plate, wherein all of the positive electrode material is The pore volume is less than 0.172 cm ³ /g, the positive electrode material contains fibers, and the moisture content of the fibers (=(1−mass of the fibers in dry state (g)/wet The mass of said fiber in the state (g)) x 100) is greater than or equal to 28%.

1 is a perspective view showing an external configuration of a lead-acid battery 100 in this embodiment; FIG. FIG. 2 is an explanatory diagram showing the YZ cross-sectional configuration of the lead-acid battery 100 at the position II-II in FIG. 1; FIG. 2 is an explanatory view showing the YZ cross-sectional configuration of the lead-acid battery 100 at the position III-III in FIG. 1; FIG. 5 is an explanatory diagram showing performance evaluation results;

The technology disclosed in this specification can be implemented as the following modes.

(1) A lead-acid battery disclosed in the present specification includes a positive electrode plate having a current collector made of a lead alloy and a positive electrode material supported by the current collector, and a negative electrode plate, wherein the positive electrode The total pore volume of the material is less than 0.172 cm ³ /g, the cathode material contains fibers, and the moisture content of the fibers (=(1−mass of the fibers in dry state (g )/mass of said fiber in wet state (g))×100) is not less than 28%. In addition, the positive electrode plate is composed of a current collector and a positive electrode material. That is, the positive electrode material is obtained by removing the current collector from the positive electrode plate, and is generally called an “active material”. The inventors of the present application have made extensive studies and newly found that the life characteristics of a lead-acid battery can be improved by adopting the configuration of the positive electrode material as described above.

Conventionally, no consideration has been given to the moisture content of fibers contained in positive electrode materials. The inventors of the present application have newly found that the life characteristics of lead-acid batteries can be improved by selectively using fibers with a moisture content of 28% or more as fibers to be contained in the positive electrode material. The reason why the selective use of fibers with a moisture content of 28% or more can improve the life characteristics of lead-acid batteries is not necessarily clear, but such moisture can be contained in a relatively large amount (retention If the fiber is used, the moisture content of the paste can be maintained for a long time in a range in which the oxidation reaction on the surface of the current collector proceeds well during the aging drying process of the positive electrode material. . As a result, it is presumed that the oxidation reaction on the surface of the current collector proceeds satisfactorily and the adhesion between the positive electrode current collector and the positive electrode active material can be enhanced.

However, if the total pore volume of the positive electrode material is excessively large, the density of the positive electrode material is excessively low, resulting in a structure that is prone to crumbling, and it may not be possible to prevent the positive electrode material from falling off from the current collector. . The inventors of the present application have conducted extensive studies and found that if the total pore volume of the positive electrode material is less than 0.172 cm ³ /g, the falling off of the positive electrode material from the current collector of the positive electrode plate can be effectively suppressed. , found that the life characteristics of lead-acid batteries can be improved.

(2) In the above lead-acid battery, the positive electrode material may have a total pore capacity of 0.09 cm ³ /g or more. It is believed that if the total pore volume of the positive electrode material is too low, the reactivity of the positive electrode material will be too low, resulting in poor capacity characteristics of the lead-acid battery. In contrast, in this lead-acid battery, the positive electrode material has a total pore capacity of 0.09 cm ³ /g or more, which is not excessively small. Therefore, in the present lead-acid battery, it is possible to suppress the deterioration of the reactivity of the positive electrode material, and it is possible to improve the capacity characteristics while improving the life characteristics of the lead-acid battery.

(3) In the above lead-acid battery, the positive electrode material may have a total pore capacity of 0.136 cm ³ /g or more. According to the present lead-acid battery, it is possible to effectively suppress the deterioration of the reactivity of the positive electrode material, so that it is possible to effectively improve the capacity characteristics of the lead-acid battery while improving the life characteristics of the lead-acid battery.

(4) In the above lead-acid battery, the fibers may be acrylic fibers. According to the present lead-acid battery, fibers having a water content of 28% or more can be easily obtained.

A. Embodiment:
A-1. composition:
(Configuration of lead-acid battery 100)
FIG. 1 is a perspective view showing the external configuration of a lead-acid battery 100 according to this embodiment. FIG. FIG. 2 is an explanatory view showing the YZ cross-sectional configuration of the lead-acid battery 100 at the position III-III in FIG. 1; 2 and 3, for the sake of convenience, the configuration of the electrode plate group 20, which will be described later, is represented in a form different from the actual configuration so that the configuration can be easily understood. Each drawing shows mutually orthogonal XYZ axes for specifying directions. In this specification, for the sake of convenience, the Z-axis positive direction is referred to as the "upward direction" and the Z-axis negative direction is referred to as the "downward direction." Orientation may be set.

The lead-acid battery 100 can discharge a large current in a short period of time, and also exhibit stable performance under various environments. Therefore, for example, it is mounted on a vehicle such as an automobile, and is used as a power supply source for a starter when the engine is started, and as a power supply source for various electrical components such as lights. As shown in FIGS. 1 to 3 , the lead-acid battery 100 includes a housing 10 , a positive terminal portion 30 , a negative terminal portion 40 , and a plurality of electrode plate groups 20 . Hereinafter, the positive electrode side terminal portion 30 and the negative electrode side terminal portion 40 are also collectively referred to as “terminal portions 30 and 40”.

(Configuration of housing 10)
The housing 10 has a battery case 12 and a lid 14 . The container 12 is a substantially rectangular parallelepiped container having an opening on the upper surface, and is made of synthetic resin, for example. The lid 14 is a member arranged to close the opening of the container 12, and is made of synthetic resin, for example. A space hermetically sealed with the outside is formed in the housing 10 by joining the peripheral edge portion of the lower surface of the lid 14 and the peripheral edge portion of the opening of the container 12 by, for example, thermal welding. A space in the housing 10 is partitioned into a plurality of (for example, six) cell chambers 16 arranged in a predetermined direction (the X-axis direction in this embodiment) by partition walls 58 . Hereinafter, the direction in which the plurality of cell chambers 16 are arranged (the X-axis direction) is referred to as the "cell arrangement direction".

Each cell chamber 16 in the housing 10 accommodates one electrode plate group 20 . Therefore, for example, when the space within the housing 10 is partitioned into six cell chambers 16 , the lead-acid battery 100 includes six electrode plate groups 20 . Each cell chamber 16 in the housing 10 contains an electrolytic solution 18 containing dilute sulfuric acid, and the entire electrode plate group 20 is immersed in the electrolytic solution 18 . The electrolytic solution 18 is injected into the cell chamber 16 through an injection port (not shown) provided in the lid 14 . The electrolytic solution 18 may contain aluminum ions in addition to dilute sulfuric acid.

(Structure of electrode plate group 20)
The electrode plate group 20 includes a plurality of positive electrode plates 210 , a plurality of negative electrode plates 220 and a separator 230 . The plurality of positive plates 210 and the plurality of negative plates 220 are arranged so that the positive plates 210 and the negative plates 220 are alternately arranged.

The cathode plate 210 has a cathode current collector 212 and a cathode active material 216 supported by the cathode current collector 212 . The positive electrode current collector 212 is a conductive member having ribs arranged in a substantially grid-like or mesh-like shape, and is made of a lead alloy. In addition, the positive electrode current collector 212 has a positive electrode tab 214 protruding upward near its upper end. The positive electrode active material 216 contains lead dioxide and positive electrode fibers 217 to be described later. The positive electrode active material 216 may further contain other known additives. The positive electrode plate 210 having such a configuration is obtained by, for example, coating or filling the positive electrode current collector 212 with a positive electrode active material paste containing lead monoxide, water, and dilute sulfuric acid as main components, and aging the positive electrode active material paste. It can be prepared by performing a known chemical conversion treatment after drying. The positive electrode active material 216 in this embodiment is obtained by removing the positive electrode current collector 212 from the positive electrode plate 210, and corresponds to the positive electrode material in the claims.

The negative plate 220 has a negative current collector 222 and a negative active material 226 supported by the negative current collector 222 . The negative electrode current collector 222 is a conductive member having ribs arranged in a substantially lattice or mesh pattern, and is made of lead or a lead alloy, for example. In addition, the negative electrode current collector 222 has a negative electrode ear portion 224 protruding upward near its upper end. The negative electrode active material 226 contains lead (spongy lead) and negative electrode fibers 227 . The negative electrode active material 226 may further contain other known additives (for example, carbon, lignin, barium sulfate, etc.). For example, the negative electrode plate 220 having such a configuration is obtained by coating or filling the negative electrode current collector 222 with a negative electrode active material paste containing lead, aging and drying the negative electrode active material paste, and then performing a known chemical conversion treatment. It can be made by doing.

The separator 230 is made of an electrically insulating material (for example, glass or synthetic resin). The separator 230 is arranged so as to be interposed between the positive electrode plate 210 and the negative electrode plate 220 that are adjacent to each other.

The positive tabs 214 of the plurality of positive plates 210 forming the plate group 20 are connected to a positive strap 52 made of lead or a lead alloy, for example. That is, the plurality of positive plates 210 are electrically connected in parallel via the positive strap 52 . Similarly, the negative tabs 224 of the plurality of negative plates 220 forming the plate group 20 are connected to a negative strap 54 made of lead or a lead alloy, for example. That is, the plurality of negative plates 220 are electrically connected in parallel via the negative strap 54 .

In the lead-acid battery 100, a negative strap 54 housed in one cell chamber 16 is connected to one side of the one cell chamber 16 (for example, the X-axis positive direction side) is connected to the positive electrode side strap 52 housed in another cell chamber 16 adjacent thereto. In addition, the positive strap 52 housed in the one cell chamber 16 is connected to the other cell chamber 16 adjacent to the other cell chamber 16 on the other side (for example, the X-axis negative direction side) via the connection member 56 . is connected to the negative strap 54 housed in the . That is, the plurality of electrode plate groups 20 included in the lead-acid battery 100 are electrically connected in series via the positive electrode strap 52 , the negative electrode strap 54 and the connection member 56 . As shown in FIG. 2, the positive electrode strap 52 accommodated in the cell chamber 16 located at one end (X-axis negative direction side) in the cell arrangement direction is not the connection member 56, but the positive electrode column described later. 34. Further, as shown in FIG. 3, the negative electrode strap 54 accommodated in the cell chamber 16 located at the end of the other side (X-axis positive direction side) in the cell arrangement direction is not the connection member 56 but the negative electrode column (to be described later). 44.

(Configuration of terminal portions 30 and 40)
The positive terminal portion 30 is arranged near the end portion on one side (X-axis negative direction side) in the cell arrangement direction of the housing 10 . , and the negative terminal portion 40 is arranged near the end portion of the housing 10 on the other side (positive direction side of the X-axis) in the cell arrangement direction.

As shown in FIG. 2 , the positive terminal portion 30 includes a positive bushing 32 and a positive column 34 . The positive electrode side bushing 32 is a substantially cylindrical conductive member having a vertically penetrating hole, and is made of, for example, a lead alloy. The lower portion of the positive electrode side bushing 32 is embedded in the lid 14 by insert molding. An upper portion of the positive electrode side bushing 32 protrudes upward from the upper surface of the lid 14 . The positive pole 34 is a substantially cylindrical conductive member made of, for example, a lead alloy. The positive electrode column 34 is inserted into the hole of the positive electrode side bushing 32 . The upper end of the positive electrode column 34 is positioned substantially at the same position as the upper end of the positive electrode side bushing 32 and is joined to the positive electrode side bushing 32 by welding, for example. The lower end of the positive pole 34 protrudes downward from the lower end of the positive electrode side bushing 32 and further protrudes downward from the lower surface of the lid 14. ) is connected to a positive strap 52 housed in the cell chamber 16 located at the end of the .

As shown in FIG. 3 , the negative terminal portion 40 includes a negative bushing 42 and a negative column 44 . The negative electrode side bushing 42 is a substantially cylindrical conductive member having a vertically penetrating hole, and is made of, for example, a lead alloy. A lower portion of the negative electrode side bushing 42 is embedded in the lid 14 by insert molding. An upper portion of the negative electrode side bushing 42 protrudes upward from the upper surface of the lid 14 . The negative pole 44 is a substantially cylindrical conductive member made of, for example, a lead alloy. The negative electrode column 44 is inserted into the hole of the negative electrode side bushing 42 . The upper end portion of the negative pole 44 is positioned substantially at the same position as the upper end portion of the negative electrode side bushing 42 and is joined to the negative electrode side bushing 42 by, for example, welding. The lower end of the negative electrode column 44 protrudes downward from the lower end of the negative electrode side bushing 42 and further protrudes downward from the lower surface of the lid 14. ) is connected to a negative strap 54 housed in the cell chamber 16 located at the end of the .

When the lead-acid battery 100 is discharged, a load (not shown) is connected to the positive bushing 32 of the positive terminal portion 30 and the negative bushing 42 of the negative terminal portion 40 . The electric power generated by the reaction at the positive electrode plate 210 (reaction to produce lead sulfate from lead dioxide) and the reaction at the negative electrode plate 220 (reaction to produce lead sulfate from lead (spongy lead)) of each electrode plate group 20 is applied to the load. supplied to When charging the lead-acid battery 100 , a power supply (not shown) is connected to the positive bushing 32 of the positive terminal portion 30 and the negative bushing 42 of the negative terminal portion 40 . The power supplied from the power supply causes a reaction at the positive electrode plate 210 of each electrode plate group 20 (reaction to produce lead dioxide from lead sulfate) and a reaction at the negative electrode plate 220 (reaction to produce lead (spongy lead) from lead sulfate). ) occurs and the lead-acid battery 100 is charged.

A-2. Detailed configuration of the positive electrode active material 216:
As shown in FIG. 2 , in the lead-acid battery 100 of the present embodiment, the positive electrode active material 216 contains fibers (hereinafter referred to as “positive electrode fibers”) 217 in addition to lead dioxide. The moisture content Cw of the positive electrode fiber 217 used in the lead-acid battery 100 of this embodiment is 28% or more. Here, the moisture content Cw of the positive electrode fibers 217 is an index indicating how much moisture the positive electrode fibers 217 can contain (can retain), and is calculated by the following formula (1). The water content Cw of the positive electrode fiber 217 becomes a high value, for example, when there are many voids capable of retaining water inside the fiber, or when there are many wrinkles capable of retaining water on the surface of the fiber. . It should be noted that the moisture content Cw of the positive electrode fibers 217 is more preferably 32% or more.
Moisture content Cw (%) = (1-mass of fiber in dry state (g)/mass of fiber in wet state (g)) x 100 (1)
Here, the weight of fibers in a wet state and the weight of fibers in a dry state refer to the weights in the following conditions, respectively.
Weight of fiber in wet state: The weight of the fiber in the state (wet state, details will be described below) at the time when the filtrate does not come off after washing the fiber on the filter paper with water until the filtrate becomes neutral Fiber in dry state Mass of: The mass of the fiber in a state (dry state) in which the fiber in a wet state is dried at 75 ° C. for 24 hours

The positive electrode fiber 217 is, for example, acrylic fiber, polypropylene fiber, polyester fiber, polyethylene fiber, PET fiber, or rayon fiber. Acrylic fibers are produced by wet spinning, in which a polymer is dissolved in a solvent and fibers are spun in a liquid called a coagulant. At this time, it separates (segregates) into the fiber portion and the solvent portion, and the portion from which the solvent portion has been removed appears as wrinkles. Therefore, in general, many fine wrinkles capable of retaining moisture are formed on the surface of the acrylic fiber. Therefore, it is preferable to use acrylic fiber as the positive electrode fiber 217 because the positive electrode fiber 217 having the moisture content Cw within the numerical range described above can be easily obtained.

Moreover, in the lead-acid battery 100 of the present embodiment, the total pore capacity of the positive electrode active material 216 is less than 0.172 cm ³ /g. Note that the total pore capacity (per unit mass) of the positive electrode active material 216 is more preferably 0.09 cm ³ /g or more, and further preferably 0.136 cm ³ /g or more. The total pore capacity of the positive electrode active material 216 can be adjusted by changing the recipe (mixing ratio of lead powder, water, and dilute sulfuric acid) when producing the positive electrode active material 216 . For example, if the mixing ratio of dilute sulfuric acid and water is increased, the total pore capacity of the positive electrode active material 216 is increased.

In the following description, the positive electrode active material 216 has a total pore volume of less than 0.172 cm ³ /g, the positive electrode active material 216 contains the positive electrode fibers 217, and the positive electrode fibers 217 have a moisture content of The condition that Cw is 28% or more is referred to as "specific condition for positive electrode active material".

The moisture content Cw of the positive electrode fiber 217 contained in the positive electrode active material 216 forming the positive electrode plate 210 of the lead-acid battery 100 is specified as follows.
(1) The lead-acid battery 100 is disassembled, and the positive electrode plate 210 is extracted.
(2) The collected positive electrode plate 210 is washed with water to remove sulfuric acid.
(3) Collecting the positive electrode active material 216 from the positive electrode plate 210 .
(4) The collected positive electrode active material 216 is dissolved in a mixture of nitric acid and hydrogen peroxide.
(5) Filter the solution of (4).
(6) The residue (fiber) on the filter paper is washed with deionized water. This water washing is continued until the washed filtrate becomes neutral (the neutrality is confirmed using pH test paper or the like). After washing with water, wait for excess filtrate to fall off the filter paper. The wet state is defined as the time when the next filtrate does not drop even after 30 seconds have passed since the filtrate has dropped. Immediately after becoming wet, the mass measurement of (7) is performed. This is to prevent moisture from evaporating into the air from the sample (fiber) in a wet state, thereby preventing a change in mass.
(7) Measure the weight of the wet sample (fiber).
(8) The wet sample is dried at 75° C. for 24 hours to obtain a dry state, and the mass of the dry sample (fiber) is measured.
(9) Using the measured weight of the sample (fiber) in the wet state and the weight of the sample (fiber) in the dry state, the moisture content Cw is calculated according to the above formula (1).

Also, the total pore capacity of the positive electrode active material 216 forming the positive electrode plate 210 of the lead-acid battery 100 is specified as follows.
(1) The lead-acid battery 100 is disassembled, and the positive electrode plate 210 is extracted.
(2) The collected positive electrode plate 210 is washed with water to remove sulfuric acid.
(3) About 1 g of sample (positive electrode active material 216 ) is sampled from the positive electrode plate 210 .
(4) Using a mercury porosimeter (Autopore IV9500 series manufactured by Shimadzu Corporation) for the sampled positive electrode active material 216, the total pore capacity is measured by a mercury intrusion method. In this measurement, the contact angle is 130°, the surface tension is 485 dynes/cm, and the specific gravity of mercury is 13.5335 g/cm.
(5) Let the average value of the measured values of the total pore capacity of each positive electrode active material 216 be the total pore capacity of the positive electrode active material 216 .

A-3. Performance evaluation:
A plurality of lead-acid battery samples (S1 to S18) were produced, and performance evaluation was performed on the samples. FIG. 4 is an explanatory diagram showing performance evaluation results.

A-3-1. For each sample:
As shown in FIG. 4, each sample has a different total pore volume of the positive electrode active material. For reference, FIG. 4 also shows the value of the filling density of the positive electrode active material paste, which is an index that correlates with the total pore volume of the positive electrode active material.

In addition, in each sample, the positive electrode active material contains positive electrode fibers, similarly to the lead-acid battery 100 of the above-described embodiment. Specifically, in sample S6, PET-based fibers are used as positive electrode fibers. , and other samples (S1 to S5, S7 to S18), acrylic fibers are used as positive electrode fibers. As shown in FIG. 4, the samples differ from each other in the moisture content Cw of the positive electrode fiber (as described above, an index indicating how much moisture can be contained (can be retained)). The content ratio of the positive electrode fiber in the positive electrode active material of each sample is 0.05 mass % (wt %) to 0.40 mass %. Further, in each sample, the negative electrode active material constituting the negative electrode plate contained PET-based fibers as negative electrode fibers.

In FIG. 4, each sample is arranged in ascending order of the total pore volume of the positive electrode active material, and each sample having the same total pore volume of the positive electrode active material (seven samples of S6 to S12, S14 to S15). Two samples) are arranged in ascending order of the moisture content Cw of the positive electrode fiber.

As shown in FIG. 4, samples S1 to S3, S5, S8 to S13, S15, and S16 are specific conditions regarding the positive electrode active material (total pore capacity of the positive electrode active material is less than 0.172 cm ³ /g, the positive electrode active material contains positive electrode fibers, and the moisture content Cw of the positive electrode fibers is 28% or more).

On the other hand, samples S4, S6, S7, S14, S17, and S18 do not satisfy the specific conditions regarding the positive electrode active material described above. Specifically, in samples S4, S6, S7, and S14, the moisture content Cw of the positive electrode fiber is less than 28%. In samples S17 and S18, the total pore capacity of the positive electrode active material is 0.172 cm ³ /g or more.

The method for producing each sample is as follows.
(1) Preparation of positive electrode plate Raw material lead powder (a mixture of lead oxide containing lead and lead monoxide as main components), water, and dilute sulfuric acid (density: 1.40 g/cm ³ ) A positive electrode active material paste was obtained by mixing with cut synthetic resin fibers (hereinafter referred to as “positive electrode fibers”).
It is known that the density of the positive electrode active material can be changed by changing the blending ratio of dilute sulfuric acid and water. The positive electrode active material used in this performance evaluation was also realized by changing the compounding ratio of the dilute sulfuric acid and water.
Moreover, the following was used as the fiber for positive electrodes.
- Sample S6: Trade name "Tetoron" (Toray PET: polyester fiber), fiber diameter 13.3 µm, fiber length 3 mm.
Samples S4, S7, S14: Trade name "Bonnel" (acrylic fiber manufactured by Mitsubishi Rayon), fiber diameter 20.4 µm, fiber length 3 mm.
- Samples other than the above: The acrylic fiber of the present embodiment, with a fiber diameter of 16.7 μm and a fiber length of 3 mm.
Also, a lead sheet made of a ternary alloy of lead, calcium, and tin (hereinafter referred to as “Pb—Ca—Sn alloy”) was expanded, and then a positive electrode grid (positive electrode current collector) was produced.
An unformed positive electrode plate (height: 115 mm, width: 137.5 mm, thickness: 1.5 mm) was obtained by filling the expanded mesh of the positive electrode current collector with the positive electrode active material paste and aging and drying it by a conventional method. got
(2) Preparation of Negative Electrode Plate Raw material lead powder (mixture of lead oxide containing lead and lead monoxide as main components), water, and dilute sulfuric acid (density: 1.40 g/cm ³ ) A negative electrode active material paste was obtained by mixing the cut synthetic resin fibers (hereinafter referred to as “negative electrode fibers”) with a predetermined ratio of negative electrode additives (lignin, carbon, barium sulfate).
Moreover, the following was used as the fiber for negative electrodes.
・ All samples: Product name “Tetoron” (Toray PET: polyester fiber)
A lead plate sheet made of a Pb—Ca—Sn alloy was expanded in the same manner as for the positive electrode grid (positive electrode current collector), and then a negative electrode grid (negative electrode current collector) was produced.
An unformed negative electrode plate (height: 115 mm, width: 137.5 mm, thickness: 1) was obtained by filling the expanded mesh of the negative electrode current collector with the paste for the negative electrode active material and aging and drying it by a conventional method in the same manner as the positive electrode plate. .3 mm).
(3) Preparation of sample battery Using the positive electrode plate and the negative electrode plate prepared in (1) and (2) above, the negative electrode plate was packed with a polyethylene separator, and then the positive electrode plate and the bagged negative electrode plate were alternately placed. After stacking, the plurality of positive electrode plates and the plurality of negative electrode plates were welded together with lead parts to manufacture an electrode plate group.
The above electrode plate group is inserted into a resin (polypropylene) container so that 6 cells are connected in series, and after welding the electrode plate groups (5 points) between the cells, a resin (polypropylene) lid is attached. The battery case was joined, and then both terminal portions (positive electrode and negative electrode terminal portions) were welded to produce a sample battery.
After initial charging by a conventional method, a sample battery having an electrolyte density of 1.285 was obtained.

A-3-2. Evaluation items and evaluation methods:
Using each sample of the lead-acid battery, two items of life characteristics (idling stop life characteristics) and capacity characteristics (20-hour rate capacity characteristics) were evaluated.

Evaluation of longevity was performed as follows. That is, each sample of the lead-acid battery was subjected to a life test by the following methods a) to e), and the number of cycles (life cycle number) at the end of the test was obtained. Taking the number of life cycles in sample S6 as 100 (indicated by a thick line in FIG. 4), the number of life cycles in each sample was expressed as a relative value. In this evaluation, the charge/discharge cycle is repeated in a PSOC (Partial State of Charge, incompletely charged state) like a lead-acid battery for vehicles having an idling stop function, so the positive electrode plate was subjected to softening conditions. It is possible to evaluate the life characteristics of lead-acid batteries.
a) Place the sample in the gas phase at 25±2° C. for the entire duration of the test. The wind speed in the vicinity of the sample shall be 2.0 m/s or less.
b) Connect the sample to the life test apparatus and continuously repeat the following cycles of discharge (“discharge 1” and “discharge 2”) and charge. The cycle of this discharge and charge is defined as one lifetime.
・Discharge 1: Discharge current 28±1A for 59.0±0.2 seconds ・Discharge 2: Discharge current 300±1A for 1.0±0.2 seconds ・Charge: Charge voltage 14.00±0.03V (limited Current 100.0±0.5 A) for 60.0±0.3 seconds During the test, measure the final discharge voltage of "Discharge 2".
c) Every 3,600 cycles during the test, after resting for 40-48 hours, start the cycle again.
d) The end of the test shall be when it is confirmed that the discharge voltage during the test has become less than 7.2V.
e) Do not refill water up to 30,000 times.

In addition, evaluation of capacity characteristics was performed as follows. That is, for each sample of the lead-acid battery, the 20-hour rate capacity was measured by the method shown in a) to d) below, and the 20-hour rate capacity of sample S6 was set to 100 (indicated by a thick line in FIG. 4). The 20-hour rate capacity in the sample was expressed as a relative value.
a) Charge the sample at a current 3.42 times the ₂₀ -hour rate current I20 until the terminal voltage or temperature-converted electrolyte density during charging measured every 15 minutes shows a constant value three times in succession. I do. Also, the electrolyte level is filled up to the maximum liquid level.
The temperature conversion of the electrolyte solution density is based on the following formula.
D ₂₀ = D _T + 0.0007 (T-20)
Here, D20 _{, DT,} and T represent the following numerical values, respectively.
D ₂₀ : Density of electrolyte at 20°C (g/cm ³ )
D _T : Density of electrolyte at T°C (g/cm ³ )
T: temperature of electrolyte when measuring density (°C)
b) Place the samples in a water bath at 25±2° C. for the entire duration of the test. The water surface should be between 15 and 25 mm below the upper surface of the sample. If multiple samples are placed in the same water tank, the distance between each other and to the water tank wall should be at least 25 mm.
c) After 1 to 5 hours from the completion of charging in a) above, confirm that the electrolyte temperature is 25±2°C. The sample is then discharged at a ₂₀ hour rate current I20 until the terminal voltage drops to 10.50±0.05 V and the discharge duration t hours is recorded.
d) Calculate the effective 20 hour rate capacity C _20,e (Ah) of the battery according to the following formula:
C _20,e =I ₂₀ ×t
Here, I _20, t represents the following numerical values, respectively.
I20: ₂₀ hour rate current (A)
t: discharge duration (hours)

A-3-3. Evaluation results:
As shown in FIG. 4, the above-described specific conditions for the positive electrode active material (the total pore volume of the positive electrode active material is less than 0.172 cm ³ /g, the positive electrode active material contains positive electrode fibers, and Samples S1 to S3, S5, S8 to S13, S15, and S16, which satisfy the condition that the moisture content Cw of the positive electrode fiber is 28% or more, all resulted in the evaluation of life characteristics of "123" or more. , the life characteristic was improved compared to the evaluation result "100" of the life characteristic of sample S6.

On the other hand, in the samples S4, S6, S7, and S14, which do not satisfy the specific condition regarding the positive electrode active material because the moisture content Cw of the positive electrode fiber is less than 28%, the evaluation of the life characteristics is "120" or less. Not a good result. In addition, in the samples S17 and S18, which do not satisfy the specific conditions regarding the positive electrode active material because the total pore capacity of the positive electrode active material is 0.172 cm ³ /g or more, the evaluation of the life characteristics is "82" or less, which is not good. No result.

Samples (Samples S1 to S3, S5, S8 The reason why the life characteristics are improved in S13, S15, and S16) is considered as follows.

In samples S17 and S18, which do not satisfy the specific conditions for the positive electrode active material because the total pore capacity of the positive electrode active material is 0.172 cm ³ /g or more, the density of the positive electrode active material is excessively low, and the structure is likely to collapse. It's becoming Therefore, in these samples, it is considered that the positive electrode active material collapsed and fell off the positive electrode current collector as the lead-acid battery was repeatedly charged and discharged, and the life characteristics were reduced. On the other hand, in the samples other than the samples S17 and S18, the total pore capacity of the positive electrode active material is less than 0.172 cm ³ /g, so the density of the positive electrode active material is ensured at a certain level or more, and the charging and discharging of the lead storage battery is possible. It is considered that the positive electrode active material was prevented from falling off from the positive electrode current collector due to the collapse of the positive electrode active material due to the repetition of the above.

In addition, among the samples other than the samples S17 and S18, the reason why the life characteristics were improved in the samples (samples S1 to S3, S5, S8 to S13, S15, and S16) satisfying the specific conditions regarding the positive electrode active material is not necessarily clear. However, it is presumed to be due to the following reasons.

That is, in order to improve the life characteristics of a lead-acid battery, it is important to improve the binding property between the positive electrode current collector and the positive electrode active material. This is because, in general, the positive electrode active material (for example, lead dioxide) has a higher resistivity (about two orders of magnitude higher) than the positive electrode current collector (for example, lead). This is because when the adhesion is lowered, the contact resistance between the positive electrode current collector and the positive electrode active material increases as the lead-acid battery is repeatedly charged and discharged. This is different from the negative electrode side, which uses a negative electrode active material with a relatively low resistivity.

As described above, when the positive electrode plate is produced, the expanded mesh of the positive electrode current collector is filled with the positive electrode active material paste, and then the aging drying process is performed. In this aging drying treatment, the positive electrode current collector and the positive electrode active material are bound. Here, in order to enhance the binding property between the positive electrode current collector and the positive electrode active material, oxidation reaction (corrosion reaction) occurs on the surface of the positive electrode current collector (contact surface with the positive electrode active material) during the aging drying process. It is important to proceed with In addition, the oxidation reaction on the surface of the positive electrode current collector during the aging drying process is rapid when the water content in the positive electrode active material paste is within a predetermined narrow range (7.0 to 8.5% range). (e.g., M.E.D. Humphreys, 2 others, "The Curing of Lead-Acid Battery Plates", Power Power Sources 2, 1968, p.55-67)). Therefore, in order to improve the binding property between the positive electrode current collector and the positive electrode active material, the water content of the positive electrode active material paste must be within the narrow range (7.0 to 8.5% range) during the aging drying process. ) is maintained for as long as possible so that the oxidation reaction on the surface of the positive electrode current collector proceeds favorably.

In the samples (Samples S1 to S3, S5, S8 to S13, S15 and S16) satisfying the specific conditions regarding the positive electrode active material, the moisture content Cw of the positive electrode fibers is relatively high at 28% or more. That is, these samples use positive electrode fibers that can contain (hold) a relatively large amount of moisture. During the aging drying process, the vaporization rate of the moisture contained (held) in the positive electrode fiber is considered to be slower than the vaporization rate of other moisture contained in the positive electrode active material paste. Therefore, in these samples, the water content of the positive electrode active material paste can be maintained in the narrow range (7.0 to 8.5% range) for a long time during the aging and drying process. Therefore, it is presumed that the oxidation reaction on the surface of the positive electrode current collector could proceed satisfactorily, and as a result, the adhesion between the positive electrode current collector and the positive electrode active material could be enhanced.

Typically, sample S13 (a sample that satisfies the specific conditions regarding the positive electrode active material) and sample S6 (the moisture content Cw of the positive electrode fiber is less than 28%, so that the specific conditions regarding the positive electrode active material are satisfied). After the aging drying treatment, the positive electrode active material was peeled off from the positive electrode current collector and the surface state of the positive electrode current collector was observed. It was confirmed that the oxidation (corrosion) on the surface of the body progressed further, and the positive electrode active material adhered to the positive electrode current collector. It can be said that this supports the correctness of the mechanism described above.

In this way, according to this performance evaluation, the lead-acid battery satisfies the above-described specific conditions regarding the positive electrode active material (the total pore capacity of the positive electrode active material is less than 0.172 cm ³ /g, and the positive electrode active material contains positive electrode fibers and the moisture content Cw of the positive electrode fiber is 28% or more), the binding between the positive electrode current collector and the positive electrode active material can be improved, and the lead-acid battery It was confirmed that the life characteristics of the battery can be improved.

Among the samples (Samples S1 to S3, S5, S8 to S13, S15 and S16) that obtained good results in the life characteristic evaluation, in Samples S5, S8 to S13, S15 and S16, all of the positive electrode active material was A pore volume of 0.09 cm ³ /g or more (and less than 0.172 cm ³ /g). All of these samples obtained good results of "123" or more in the evaluation of the life characteristics, and also obtained good results of "84" or more in the evaluation of the capacity characteristics. According to this result, if the lead-acid battery satisfies the specific conditions regarding the positive electrode active material described above and the total pore capacity of the positive electrode active material is 0.09 cm ³ /g or more, the life characteristics of the lead-acid battery are improved. However, it can be said that it is possible to suppress deterioration of the capacity characteristics of the lead-acid battery due to excessively low reactivity of the positive electrode active material due to excessive decrease in the total pore capacity of the positive electrode active material. Therefore, in the lead-acid battery, it is more preferable that the specific conditions for the positive electrode active material are satisfied and the total pore volume of the positive electrode active material is 0.09 cm ³ /g or more.

Among these samples S5, S8 to S13, S15, and S16, in samples S13, S15, and S16, the total pore capacity of the positive electrode active material is 0.136 cm ³ /g or more (and 0.172 cm ³ /g less than). All of these samples obtained good results of "123" or more in the evaluation of the life characteristics, and also obtained good results of "130" or more in the evaluation of the capacity characteristics. According to this result, if the lead-acid battery satisfies the specific conditions regarding the positive electrode active material described above and the total pore capacity of the positive electrode active material is 0.136 cm ³ /g or more, the life characteristics of the lead-acid battery are improved. It can be said that it is possible to effectively suppress the deterioration of the reactivity of the positive electrode active material and effectively suppress the deterioration of the capacity characteristics of the lead-acid battery. Therefore, in the lead-acid battery, it is more preferable that the specific conditions for the positive electrode active material are satisfied and the total pore volume of the positive electrode active material is 0.136 cm ³ /g or more.

In this performance evaluation, among the samples (samples S1 to S3, S5, S8 to S13, S15, and S16) that obtained good results, samples S8 to S12 had a total pore capacity value of the positive electrode active material of While they are the same as each other, the moisture contents Cw of the positive electrode fibers are different from each other. Comparing the evaluation results of the life characteristics and the capacity characteristics of these samples, the samples S10 to S12, in which the moisture content Cw of the positive electrode fiber is 32% or more, have a higher capacity characteristics than the other samples S8 and S9. are almost the same, while the life characteristics are good (“159” or more). Therefore, it can be said that it is more preferable that the moisture content Cw of the positive electrode fiber is 32% or more in order to improve the binding property between the positive electrode current collector and the positive electrode active material and improve the life characteristics of the lead-acid battery. .

Acrylic fibers were used as the positive electrode fibers in samples S1 to S3, S5, S8 to S13, S15, and S16, which gave good results in all evaluation items. If an acrylic fiber is used as the positive electrode fiber, a fiber having a water content Cw of 28% or more can be easily obtained.

Moreover, the length of the positive electrode fiber is preferably 2 to 7 mm, and the aspect ratio of the positive electrode fiber is preferably 150 to 400.

In samples S1 to S3, S5, S8 to S13, S15, and S16, which gave good results in all evaluation items, acrylic fibers were used as positive electrode fibers. However, even if other fibers (polypropylene-based fiber, polyester-based fiber, polyethylene-based fiber, PET-based fiber, rayon-based fiber) are used as the positive electrode fiber, the positive electrode active material containing the positive electrode fiber is the above-described positive electrode active material. If the specific conditions for are satisfied, it is strongly speculated that the binding between the positive electrode current collector and the positive electrode active material can be similarly enhanced, and the life characteristics of the lead-acid battery can be improved.

B. Variant:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.

The configuration of the lead-acid battery 100 in the above embodiment is merely an example, and various modifications are possible. For example, in the above-described embodiment, acrylic fiber, polypropylene fiber, polyester fiber, polyethylene fiber, PET fiber, and rayon fiber are exemplified as the positive electrode fiber 217, but the positive electrode fiber 217 does not contain moisture. Other types of fibers may be used as long as the content Cw is 28% or more.

In addition, in the lead-acid battery 100 of the above embodiment, the negative electrode active material 226 forming the negative electrode plate 220 may satisfy the same specific conditions as the positive electrode active material described above.

Moreover, the manufacturing method of the lead-acid battery 100 in the above-described embodiment is merely an example, and various modifications are possible.

10: Housing 12: Battery case 14: Lid 16: Cell chamber 18: Electrolyte solution 20: Electrode plate group 30: Positive electrode side terminal portion 32: Positive electrode side bushing 34: Positive electrode column 40: Negative electrode side terminal portion 42: Negative electrode side bushing 44: Negative pole 52: Positive electrode side strap 54: Negative electrode side strap 56: Connection member 58: Partition wall 100: Lead-acid battery 210: Positive electrode plate 212: Positive electrode current collector 214: Positive electrode ear 216: Positive electrode active material 217: Positive electrode fiber 220: Negative electrode plate 222: Negative electrode current collector 224: Negative electrode ear portion 226: Negative electrode active material 227: Negative electrode fiber 230: Separator

Claims (4)

A lead-acid battery,
a positive electrode plate having a current collector made of a lead alloy and a positive electrode material supported by the current collector;
a negative electrode plate;
with
The positive electrode material has a total pore volume of 0.159 cm ³ /g or less ,
The positive electrode material contains fibers,
The moisture content of the fiber (=(1−mass of the fiber in dry state (g)/mass of fiber in wet state (g))×100) is 28% or more ,
The lead-acid battery , wherein the content of fibers in the positive electrode material is 0.05% by mass to 0.40% by mass . The lead-acid battery according to claim 1,
The lead-acid battery, wherein the positive electrode material has a total pore capacity of 0.09 cm ³ /g or more. The lead-acid battery according to claim 2,
The lead-acid battery, wherein the positive electrode material has a total pore capacity of 0.136 cm ³ /g or more. The lead-acid battery according to any one of claims 1 to 3,
The lead-acid battery, wherein the fibers are acrylic fibers.

Images