A positive plate for lead-acid batteries and a method of making and using the same

Abstract

The application belongs to the technical field of lead-acid batteries, and discloses a positive plate of a lead-acid battery and a preparation method and application thereof. The application provides a positive plate of a lead-acid battery, which comprises PbO2 and fluorine-boron co-doped carbon fibers dispersed therein. The positive plate does not need a metal plate grid, and has the advantages of small internal resistance, excellent energy density and cycle performance. Compared with conventional positive plates, the internal resistance of a lead-acid battery prepared by using the positive plate of the application is reduced by 15.2% to 32.1%, and the energy density is increased by 34.3% to 42.9%. The application further provides a preparation method of the positive plate of the lead-acid battery, which specifically comprises: uniformly mixing fluorine-boron co-doped carbon fibers with PbO2, and hot-pressing, so that the positive plate of the lead-acid battery is prepared. The preparation method has the advantages of simple process, green environmental protection and the like, and is convenient to popularize and apply.

Description

Technical Field

[0001] This invention belongs to the field of lead-acid battery technology, and relates to a positive electrode plate for lead-acid batteries, its preparation method, and its application. Background Technology

[0002] Lead-acid batteries have advantages such as mature technology, low cost, high safety, and good high-current discharge performance, and are widely used in transportation, communication, power, military, and many other fields. However, lead-acid batteries have a relatively low energy density, only one-third that of lithium batteries. The content of active material in the positive electrode plate is a crucial parameter determining the battery's energy density. Currently, the manufacturing process for lead-acid battery positive electrode plates involves first preparing lead paste and metal grids, then uniformly applying the lead paste to the grids, followed by curing, formation, cleaning, and drying, and finally cutting it to the appropriate size. Under this process, the actual solid content of PbO2 in the positive electrode is less than 80%, limiting the improvement of energy density. If the PbO2 content is increased during the positive electrode plate production process, the strength of the positive electrode plate will decrease, leading to a severe decline in cycle performance.

[0003] Furthermore, during the charging and discharging process of lead-acid batteries, the positive electrode grid can experience significant corrosion due to factors such as excessively high battery temperature, excessively high electrolyte density, and the presence of corrosive acids or organic salts in the electrolyte. Corrosion of the grid not only reduces its mechanical strength, increasing the risk of deformation and breakage, thus affecting the normal use and lifespan of the battery, but also forms low-grade PbO on the grid surface. x The presence of layers increases the contact resistance between the grid and the active material, reducing charge and discharge efficiency. Furthermore, traditional grid alloys (such as lead-antimony-cadmium alloys) contain heavy metals that pollute the environment, leading to stricter restrictions on their use. While some high-performance grid alloys with added rare earth elements can improve grid performance, these alloys are relatively expensive, increasing the manufacturing cost of lead-acid batteries. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a lead-acid battery positive electrode plate with a high proportion of active materials that does not require a metal grid, as well as its preparation process and application.

[0005] To achieve the above-mentioned objectives, the embodiments of the present invention employ the following technical solutions:

[0006] In a first aspect, the present invention provides a positive electrode plate for a lead-acid battery, comprising PbO2 and fluorine-boron co-doped carbon fibers dispersed therein.

[0007] The lead-acid battery positive electrode plate provided by this invention, lacking a metal grid, significantly increases the content of active material and substantially improves energy density. Furthermore, co-doping fluorine and boron into the carbon fibers not only allows the carbon fibers to form a high-strength whole through fluorine and boron chemical bonds, but also ensures a strong bond between PbO2 and the fluorine in the carbon fibers, preventing PbO2 aggregation and over-acidification, thus greatly improving cycle performance. In addition, the interconnected carbon fibers act as a conductive network, reducing the resistance of the positive electrode and improving rate performance.

[0008] Preferably, the mass ratio of the fluorine-boron co-doped carbon fiber to PbO2 is 1:50 to 1:200.

[0009] Preferably, the preparation method of the fluorine-boron co-doped carbon fiber includes the following steps: mixing carbon fiber, fluoroborate and water, evaporating the water to obtain dry powder; keeping the dry powder at 400℃~600℃ for 2h~4h under a protective gas atmosphere, and cooling to obtain the fluorine-boron co-doped carbon fiber.

[0010] The protective gas includes inert gases such as argon and helium; the cooling includes furnace cooling under the protective gas. After cooling, the carbon fibers are washed with water 2-4 times and dried at 60℃-90℃ to obtain the fluorine-boron co-doped carbon fibers.

[0011] Preferably, the mass ratio of the carbon fiber to fluoroborate is 5:1 to 1:2.

[0012] Preferably, the fluoroborate includes sodium fluoroborate or potassium fluoroborate.

[0013] Preferably, the carbon fiber comprises conductive carbon fiber with a diameter of 5μm to 10μm. Its conductivity is greater than 600S / m.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned lead-acid battery positive electrode plate, the method comprising the following steps: mixing fluorine-boron co-doped carbon fibers with PbO2 and hot pressing to obtain the lead-acid battery positive electrode plate.

[0015] This invention provides a method for preparing a lead-acid battery positive electrode plate without using a metal grid. This method has advantages such as simple process, ease of industrial production, and environmental friendliness. The lead-acid battery positive electrode plate prepared by this method overcomes the defects caused by metal grids, has lower internal resistance, and significantly improves energy density and cycle performance.

[0016] Under the high temperature and pressure of hot pressing, not only is contact between carbon fibers promoted, but they also become a unified whole through the interaction of FB bonds. Furthermore, it promotes the tight bonding between PbO2 and fluorine in the carbon fibers. Compared to cathode plates made from undoped carbon fibers, the cathode plate provided by this invention exhibits a tighter bond between carbon fibers and lead dioxide through fluorine-lead bonds, better lead dioxide dispersion, lower internal resistance, and superior energy density and cycle performance.

[0017] Preferably, the mixing includes mixing with a ball mill at a speed of 100 r / min to 600 r / min for 0.5 h to 5 h.

[0018] In this invention, a high-energy ball mill is used under the above conditions to significantly reduce the PbO2 grain size and increase the specific surface area of ​​the material. This allows for more thorough contact between PbO2 and fluorine-boron-doped carbon fibers at the microscopic level, providing more active sites for subsequent physicochemical reactions. In addition, the strong mechanical force may cause lattice distortion in PbO2 and fluorine-boron-doped carbon fibers, generating various lattice defects, optimizing their electron transport paths, reducing the material's resistance, increasing the electron migration rate, and thus improving the overall conductivity of the material.

[0019] Preferably, the hot pressing pressure is 10MPa~100MPa, the temperature is 150℃~300℃, and the time is 0.5h~1h.

[0020] Thirdly, given the superior electrochemical performance of the lead-acid battery positive electrode plate provided in the second aspect of the present invention, it can be used to prepare lead-acid batteries.

[0021] In summary, this invention provides a lead-acid battery positive electrode plate that does not require a metal grid, exhibiting excellent energy density and cycle performance. Furthermore, this invention also provides a method for preparing a lead-acid battery positive electrode plate that offers advantages such as simple processing, environmental friendliness, and ease of industrial production. This invention can be applied to the field of lead-acid battery manufacturing. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the art.

[0024] The carbon fiber used in the embodiments of the present invention is a commonly used conductive carbon fiber in the field. The present invention takes carbon fiber purchased from Weihai Guangwei Composite Materials Co., Ltd., with a diameter of 5μm~10μm and a conductivity of 3500S / m as an example for illustration.

[0025] Example 1

[0026] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:100.

[0027] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0028] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 200 rpm for 1 hour to obtain a mixture. The mixture was then hot-pressed at 20 MPa and 250 °C for 0.8 hours to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate I.

[0029] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, sodium fluoroborate and deionized water are mixed in a mass ratio of 2:1:15, and the water is evaporated at 90°C to obtain dry powder; the obtained dry powder is heated to 500°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 3 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0030] Example 2

[0031] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:200.

[0032] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0033] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 100 rpm for 5 hours to obtain a mixture. The mixture was then hot-pressed at 100 MPa and 150 °C for 1 hour to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate II.

[0034] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, sodium fluoroborate and deionized water are mixed in a mass ratio of 5:1:20, and the water is evaporated at 80°C to obtain dry powder; the obtained dry powder is heated to 400°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 4 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0035] Example 3

[0036] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:150.

[0037] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0038] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 600 rpm for 0.5 h. The mixture was then hot-pressed at 10 MPa and 300 °C for 0.5 h to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate III.

[0039] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, potassium fluoroborate and deionized water are mixed in a mass ratio of 1:1:8, and the water is evaporated at 90°C to obtain dry powder; the obtained dry powder is heated to 600°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 2 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0040] Example 4

[0041] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:150.

[0042] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0043] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 400 rpm for 0.6 h to obtain a mixture. The mixture was then hot-pressed at 50 MPa and 200 °C for 0.5 h to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate IV.

[0044] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, sodium fluoroborate and deionized water are mixed in a mass ratio of 1:2:10, and the water is evaporated at 90°C to obtain dry powder; the obtained dry powder is heated to 500°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 3 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0045] Example 5

[0046] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:300.

[0047] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0048] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 400 rpm for 1 hour to obtain a mixture. The mixture was then hot-pressed at 10 MPa and 150 °C for 1 hour to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate V.

[0049] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, sodium fluoroborate and deionized water are mixed in a mass ratio of 8:1:30, and the water is evaporated at 90°C to obtain dry powder; the obtained dry powder is heated to 500°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 3 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0050] Example 6

[0051] This invention provides a positive electrode plate for a lead-acid battery, which is made from carbon fibers co-doped with fluorine and boron and PbO2 in a mass ratio of 1:150.

[0052] This invention also provides a method for preparing the above-mentioned positive electrode plate of a lead-acid battery, the method comprising the following steps:

[0053] Fluorine-boron co-doped carbon fibers and PbO2 were mixed in a high-energy ball mill at 200 rpm for 1 hour to obtain a mixture. The mixture was then hot-pressed at 5 MPa and 200 °C for 0.6 hours to obtain a lead-acid battery positive electrode plate, denoted as positive electrode plate VI.

[0054] In this embodiment, the preparation method of fluorine-boron co-doped carbon fiber includes the following steps: carbon fiber, sodium fluoroborate and deionized water are mixed in a mass ratio of 10:1:36, and the water is evaporated at 90°C to obtain dry powder; the obtained dry powder is heated to 500°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 3 hours, and then cooled in the furnace under an argon atmosphere to obtain the fluorine-boron co-doped carbon fiber.

[0055] Comparative Example 1

[0056] The present invention provides a lead-acid battery positive electrode plate, which is made of carbon fiber and PbO2 in a mass ratio of 1:150.

[0057] This comparative example also provides a method for preparing the above-mentioned lead-acid battery positive electrode plate, which is basically the same as the method provided in Example 1, except that the "fluorine-boron co-doped carbon fiber" in Example 1 is replaced with an equal amount of "carbon fiber". The remaining reaction steps and parameters are the same as in Example 1 and will not be repeated. The finally obtained positive electrode plate is denoted as positive electrode plate pair I.

[0058] Comparative Example 2

[0059] The present invention provides a lead-acid battery positive electrode plate, which is made of fluorine-doped carbon fiber and PbO2 in a mass ratio of 1:150.

[0060] This comparative example also provides a method for preparing the above-mentioned lead-acid battery positive electrode plate, which is basically the same as the method provided in Example 1, except that the "fluorine-boron co-doped carbon fiber" in Example 1 is replaced with an equal amount of "fluorine-doped carbon fiber". The remaining reaction steps and parameters are the same as in Example 1 and will not be repeated. The method for preparing the fluorine-doped carbon fiber is as follows: carbon fiber, sodium fluoride, and deionized water are mixed in a mass ratio of 2:1:15, and the water is evaporated at 90°C to obtain a dry powder. The obtained dry powder is heated to 500°C at a heating rate of 5°C / min under an argon atmosphere and held at that temperature for 3 hours. It is then cooled in the furnace under an argon atmosphere to obtain the fluorine-doped carbon fiber. The final positive electrode plate is designated as Positive Electrode Plate II.

[0061] Comparative Example 3

[0062] This invention provides a comparative example of a positive electrode plate for a lead-acid battery. This positive electrode plate is a conventional type in the art, comprising a metal grid. The preparation method specifically includes the following steps: Lead dioxide powder, carbon black, polypropylene short fibers, water, and sulfuric acid are mixed in a mass ratio of 80:1:0.5:9:9.5 to form an electrode paste. The electrode paste is uniformly coated onto a lead-antimony alloy metal grid to form a 2.5 mm thick electrode plate. The coated electrode plate is dried at 150°C to remove moisture and solvent, making the electrode plate hard. The resulting positive electrode plate is designated as positive electrode plate III.

[0063] Example of effect

[0064] The electrochemical performance of the positive electrode plates prepared in Examples 1-6 and Comparative Examples 1-3 was measured in this invention. The specific test methods are as follows:

[0065] Positive plates I-VI and positive plate pairs I-II were cut to the same size as positive plate pair III, all 20cm×20cm. The thickness of the positive plates was within the range of 2.5mm±0.2mm. Using 1.3mol / L sulfuric acid as the electrolyte solution, they were assembled with negative plates to form lead-acid full cells, which were respectively denoted as lead-acid batteries I-VI and lead-acid battery pairs I-III. The energy density, internal resistance, and cycle capacity retention of different lead-acid batteries were measured. The specific measurement results are shown in Table 1.

[0066] The negative electrode plate is prepared as follows: Lead powder, carbon black, short fibers, water, and sulfuric acid are mixed in a ratio of 80:1:0.5:9:9.5 to form an electrode paste. The electrode paste is evenly coated onto a metal grid to form a 2.5 mm thick electrode plate. The coated electrode plate is dried at 150°C to remove moisture and solvent, making the electrode plate hard, thus obtaining a 20 cm × 20 cm negative electrode plate.

[0067] The battery energy density test method is as follows: using the Blue Electric test system, the battery is discharged at a constant current of 10mA to 1.5V in an environment of 25℃, and the discharge energy density is obtained.

[0068] Battery internal resistance measurement method: Use a battery internal resistance tester to read the value directly.

[0069] Cycle capacity retention: Using the Blue Electric test system, under 25℃ environment, in the range of 1.5V~2.5V, constant current charge and discharge of 10mA for 200 cycles, the capacity retention after 200 cycles is obtained by dividing the capacity of the 200th cycle by the capacity of the first cycle.

[0070] Table 1

[0071]

[0072] As shown in Table 1, compared with lead-acid batteries fabricated using conventional positive plates that rely on metal mesh grids, lead-acid batteries fabricated using the positive plates provided in Examples 1-6 exhibit superior energy density and lower internal resistance, and their capacity retention after 200 cycles is also significantly improved. Specifically, the internal resistance is reduced by 15.2% to 32.1%, and the energy density is increased by 34.3% to 42.9%.

[0073] By comparing the performance of lead-acid batteries prepared using the positive electrode plates provided in Example 1 with those in Comparative Examples 1 and 2, it can be seen that lead-acid battery I has the highest internal resistance and the worst cycle capacity retention performance, followed by lead-acid battery II. Lead-acid battery I has the lowest internal resistance and the best energy density and cycle capacity retention performance. This may be because, although the amount of active material in the positive electrode plates prepared in Comparative Examples 1 and 2 is comparable to that in Example 1, it is not a stable, high-strength whole, resulting in higher internal resistance and greater polarization, thus reducing capacity. Regarding internal resistance, the positive electrode plate prepared in Comparative Example 1 only involves the physical combination of lead dioxide and carbon fibers, significantly increasing contact resistance, thus resulting in a significantly higher internal resistance than in Example 1. In Comparative Example 2, only fluorine doping is used, and the connection between carbon fibers is not as tight as in Example 1, also resulting in higher internal resistance. Capacity retention is closely related to internal resistance; the lower the internal resistance within a certain range, the less material loss from repeated cycles, and the higher the battery's capacity retention, and vice versa.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive plate for a lead-acid battery, characterized by: It comprises PbO2 and fluorine-boron co-doped carbon fibers dispersed in the PbO2; the mass ratio of the fluorine-boron co-doped carbon fibers to the PbO2 is 1:50-1:

200.

2. The lead-acid battery positive plate of claim 1, wherein: The preparation method of the fluorine-boron co-doped carbon fibers comprises the following steps: mixing carbon fibers, a fluoroborate and water, and removing the water to obtain a dry powder; under a protective gas atmosphere, the dry powder is kept at 400-600 DEG C for 2-4 hours, and then cooled to obtain the fluorine-boron co-doped carbon fibers.

3. The lead-acid battery positive plate of claim 2, wherein: The mass ratio of the carbon fibers to the fluoroborate is 5:1-1:

2.

4. The lead-acid battery positive plate of claim 2, wherein: The fluoroborate comprises sodium fluoroborate or potassium fluoroborate.

5. The lead-acid battery positive plate of claim 2, wherein: The carbon fibers comprise conductive carbon fibers with a diameter of 5-10 microns.

6. The method of making a lead-acid battery positive plate of any one of claims 1-5, wherein: The preparation method comprises the following steps: uniformly mixing the fluorine-boron co-doped carbon fibers with PbO2, and hot-pressing to obtain a positive plate of a lead-acid battery.

7. The method of making a lead acid battery positive plate of claim 6, wherein: The mixing comprises using a ball mill to mix at a speed of 100-600 r / min for 0.5-5 hours.

8. The method of making a lead acid battery positive plate of claim 6, wherein: The hot-pressing is performed at a pressure of 10-100 MPa, a temperature of 150-300 DEG C, and for 0.5-1 hour.

9. A lead-acid battery characterised in that, The positive plate of the lead-acid battery comprises the positive plate of the lead-acid battery according to any one of claims 1-5.

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