Positive plate as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lead-acid batteries, and particularly discloses a positive plate as well as a preparation method and application thereof. The positive plate provided by the invention comprises the following raw material components: modified PbO2, PbS and carbon fibers, wherein the modified PbO2 is PbO2 wrapped by PbF2 (PbF2). PbO2 is modified, so that the surface of the PbO2 is coated with PbF2, and the problem of excessive sulfation of the PbO2 in a repeated charging process can be obviously avoided; the PbF2 coated on the surface of the PbO2 can also enable the PbO2 to be tightly combined with a metal bond in the PbS through an F chemical bond, so that the PbO2 is uniformly dispersed between PbS layers; chemical bonds in the carbon fibers can also be tightly connected with chemical bonds in PbS, so that the prepared positive plate becomes a tightly connected whole, the three raw material components have a synergistic effect, and the cycle life, the energy density and the rate capability of the battery are greatly improved.

Description

Technical Field

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

[0002] Due to the low price of lead, lead-acid batteries are widely used in transportation, communication, power, and military fields. However, lead-acid batteries have certain problems during use, such as a relatively low energy density, only one-third that of lithium batteries. The content of active material in the positive electrode plate of a lead-acid battery is a crucial parameter determining the battery's energy density. Currently, the common method for preparing the positive electrode plate is as follows: first, prepare lead paste and metal grids; then, evenly apply the lead paste to the grids, followed by curing, formation, cleaning, and drying, and finally cutting to the appropriate size. In this process, the actual solid content of PbO2 in the positive electrode plate is less than 80%, thus limiting the improvement of the energy density of the lead-acid battery's positive electrode plate. However, if the PbO2 content is increased during the positive electrode plate production process, the strength of the positive electrode plate will decrease, resulting in a severe decline in cycle performance. In addition, the cycle life of lead-acid batteries is also relatively short, only around 300-500 cycles. This is because during use or charge-discharge cycles, excessive sulfation of the positive electrode material (increased PbSO4 size and reduced activity) leads to a significant decrease in capacity and reduced cycle performance. To address the problems of low energy density, short cycle life, and poor rate performance of existing positive electrode plates for lead-acid batteries, there is an urgent need to provide a new positive electrode plate and its preparation method. Summary of the Invention

[0003] To address the problems of low energy density, short cycle life, and poor rate performance of existing positive electrode plates, this invention provides a positive electrode plate, its preparation method, and its application.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: The first aspect of the present invention provides a positive electrode plate comprising the following raw material components: modified PbO2, PbS and carbon fiber; The modified PbO2 is PbF2-encapsulated PbO2.

[0005] To address the low rate performance of existing lead-acid battery positive electrode plates, researchers have replaced traditional metal grids with graphene or metal foam as the conductive framework. However, the inventors discovered that when graphene is used, the interfacial bonding between graphene and the lead active material is poor, significantly impacting the conductivity of the positive electrode plate and battery life. Furthermore, graphene is expensive and difficult to mass-produce. When metal foam is used, its high density and cost increase the battery's weight and production cost. Additionally, metal foam may corrode in the electrolyte, affecting battery life. Therefore, providing a new positive electrode plate and its preparation method is of great significance.

[0006] Compared to existing technologies, the positive electrode plate provided by this invention modifies PbO2 to coat its surface with PbF2, which can significantly avoid the problem of excessive sulfation of PbO2 during repeated charging, thereby improving the cycle performance of the positive electrode plate in the battery. The PbF2 coating on the surface of PbO2 also allows PbO2 to be tightly bonded to the metal bonds in PbS through F chemical bonds, so that PbO2 is uniformly dispersed between the PbS layers. This allows the prepared positive electrode plate to form a high-strength whole without the aid of a metal grid, which is beneficial to improving the energy density, rate performance and cycle life of the battery. The interaction forces between PbS can form an interlaced two-dimensional grid structure, further ensuring that PbO2 is uniformly distributed in the positive electrode plate. This reduces the battery's internal resistance and improves its rate performance. The uniformly distributed PbO2 can also further ensure that the battery has high energy density and excellent cycle performance. Furthermore, this invention adds carbon fibers to the positive electrode plate, which can further reduce the resistance of the positive electrode plate and improve the rate performance of the battery. Moreover, the chemical bonds in the carbon fibers can be tightly connected with the chemical bonds in PbS, making the prepared positive electrode plate a tightly connected whole, which greatly improves the cycle life of the battery.

[0007] Preferably, the mass ratio of the modified PbO2, PbS and carbon fiber is 100:(2~10):1.

[0008] This invention, by limiting the ratio of modified PbO2, PbS and carbon fiber, enables the three substances to synergistically exert their maximum advantages, greatly improving the energy density, rate performance and cycle life of the battery.

[0009] Preferably, the carbon fiber has a diameter of 6μm to 8μm and an electrical conductivity of 700S / m to 900S / m.

[0010] Preferably, the preparation method of the modified PbO2 includes the following steps: mixing PbO2 and hydrofluoric acid evenly, reacting at 60℃~80℃, washing, solid-liquid separation, and drying to obtain the modified PbO2.

[0011] The modified PbO2 preparation method provided by this invention is simple to operate and can prepare PbO2 with PbF2 coated on the surface. The modified PbO2 significantly avoids the problem of excessive sulfation of PbO2 during repeated charging. When applied to the positive electrode plate, it can greatly improve the energy density, rate performance and cycle life of the battery.

[0012] Preferably, the molar ratio of PbO2 to hydrofluoric acid is (5~20):1.

[0013] By limiting the ratio of PbO2 to hydrofluoric acid, the modified PbO2 prepared can be guaranteed to have a specific structure, thereby improving the energy density, rate performance and cycle life of the battery.

[0014] Preferably, the reaction time is 1 hour to 5 hours.

[0015] Preferably, the drying temperature is <100°C.

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned positive electrode plate, comprising the following steps: S1. Weigh each raw material component according to the ratio, disperse the PbS in water to obtain a PbS dispersion; S2. The modified PbO2, carbon fiber and PbS dispersion are mixed evenly and dried at -45℃ to -35℃ to obtain the positive electrode composite material. S3. Hot-press the positive electrode composite material to obtain the positive electrode plate.

[0017] Compared to existing technologies, the positive electrode plate preparation method provided by this invention, in step S2, involves freeze-drying a dispersion of modified PbO2, carbon fiber, and PbS. This process ensures that the mixture does not separate during drying, guaranteeing that the modified PbO2 is uniformly distributed within the PbS, thereby improving the battery's energy density, rate performance, and cycle life. Furthermore, hot-pressing the positive electrode plate composite material not only promotes a tight bond between the modified PbO2 and PbS through chemical bonds but also ensures that PbS and carbon fiber form a cohesive whole through chemical bonds, significantly improving the battery's energy density and cycle performance. Moreover, the positive electrode plate preparation method provided by this invention can further reduce battery resistance, thereby improving the battery's rate performance.

[0018] Preferably, in S1, the concentration of the PbS dispersion is 0.05 mol / L to 0.1 mol / L.

[0019] Preferably, in S2, the drying condition is: until the positive electrode composite material is free of moisture.

[0020] Preferably, in S3, the hot pressing conditions are: pressure of 30MPa~80MPa and temperature of 100℃~200℃.

[0021] The optimized high temperature and high pressure conditions can further improve the bonding force between PbS, carbon fiber, and modified PbO2, thereby improving the energy density, cycle performance, and rate performance of the battery.

[0022] Preferably, in step S3, the hot pressing time is 0.5h to 3h.

[0023] The second aspect of the present invention provides the application of the above-described positive electrode plate or the positive electrode plate prepared by the above-described positive electrode plate preparation method in a lead-acid battery.

[0024] The positive electrode plate provided by this invention can significantly improve the rate performance, cycle performance and energy density of lead-acid batteries. Detailed Implementation

[0025] 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.

[0026] Example 1 This embodiment provides a positive electrode plate, comprising the following raw material components: modified PbO2, PbS, and carbon fiber; The modified PbO2 is PbF2-encapsulated PbO2; the mass ratio of modified PbO2, PbS and carbon fiber is 100:10:1, the diameter of the carbon fiber is 6 μm, and the conductivity is 700 S / m. The preparation method of modified PbO2 includes the following steps: 5 mol PbO2 and 1 mol hydrofluoric acid are mixed evenly, reacted at 80℃ for 1 h, washed, solid-liquid separated, and the drying temperature is controlled to be <100℃ to obtain the modified PbO2.

[0027] This embodiment also provides a method for preparing the above-mentioned positive electrode plate, including the following steps: S1. Weigh each raw material component according to the ratio, disperse PbS in water to obtain a PbS dispersion with a concentration of 0.05 mol / L. S2. The modified PbO2, carbon fiber and PbS dispersion are mixed evenly and dried at -35°C to obtain the positive electrode composite material. S3. The positive electrode composite material is hot-pressed to obtain a positive electrode plate; wherein the hot-pressing pressure is 30MPa, the hot-pressing temperature is 200℃, and the hot-pressing time is 0.5h.

[0028] Example 2 This embodiment provides a positive electrode plate, comprising the following raw material components: modified PbO2, PbS, and carbon fiber; The modified PbO2 is PbF2-encapsulated PbO2; the mass ratio of modified PbO2, PbS and carbon fiber is 100:2:1, the diameter of the carbon fiber is 8 μm, and the conductivity is 900 S / m. The preparation method of modified PbO2 includes the following steps: 20 mol PbO2 and 1 mol hydrofluoric acid are mixed evenly, reacted at 60℃ for 1 h, washed, solid-liquid separated, and the drying temperature is controlled to be <100℃ to obtain the modified PbO2.

[0029] This embodiment also provides a method for preparing the above-mentioned positive electrode plate, including the following steps: S1. Weigh each raw material component according to the ratio, disperse PbS in water to obtain a PbS dispersion with a concentration of 0.1 mol / L. S2. The modified PbO2, carbon fiber and PbS dispersion are mixed evenly and dried at -45°C to obtain the positive electrode composite material. S3. The positive electrode composite material is hot-pressed to obtain a positive electrode plate; wherein the hot-pressing pressure is 80MPa, the hot-pressing temperature is 100℃, and the hot-pressing time is 3h.

[0030] Example 3 This embodiment provides a positive electrode plate, comprising the following raw material components: modified PbO2, PbS, and carbon fiber; The modified PbO2 is PbF2-encapsulated PbO2; the mass ratio of modified PbO2, PbS and carbon fiber is 100:6:1, the diameter of the carbon fiber is 7μm, and the conductivity is 800S / m. The preparation method of modified PbO2 includes the following steps: 10 mol PbO2 and 1 mol hydrofluoric acid are mixed evenly, reacted at 70℃ for 3 h, washed, solid-liquid separated, and the drying temperature is controlled to be <100℃ to obtain the modified PbO2.

[0031] This embodiment also provides a method for preparing the above-mentioned positive electrode plate, including the following steps: S1. Weigh each raw material component according to the ratio, disperse PbS in water to obtain a PbS dispersion with a concentration of 0.07 mol / L. S2. The modified PbO2, carbon fiber and PbS dispersion are mixed evenly and dried at -40°C to obtain the positive electrode composite material. S3. The positive electrode composite material is hot-pressed to obtain a positive electrode plate; wherein the hot-pressing pressure is 50 MPa, the hot-pressing temperature is 130°C, and the hot-pressing time is 1 h.

[0032] Comparative Example 1 This comparative example provides a positive electrode plate, which differs from Example 1 in that the PbS in Example 1 is replaced with an equal amount of MoS2. The specific preparation method of the positive electrode plate includes the following steps: S1. Weigh each raw material component according to the ratio, disperse MoS2 in water to obtain a MoS2 dispersion with a concentration of 0.05 mol / L; S2. The modified PbO2, carbon fiber and MoS2 dispersion are mixed evenly and dried at -35°C to obtain the positive electrode plate composite material. S3. The positive electrode composite material is hot-pressed to obtain a positive electrode plate; wherein the hot-pressing pressure is 30MPa, the hot-pressing temperature is 200℃, and the hot-pressing time is 0.5h.

[0033] The other ingredients and steps are the same as in Example 1.

[0034] Comparative Example 2 This comparative example provides a positive electrode plate, which differs from Example 1 in that the modified PbO2 is PbO2 coated with PbCl2; The preparation method of modified PbO2 includes the following steps: 5 mol PbO2 and 0.1 mol hydrochloric acid are mixed evenly, reacted at 80℃ for 1 h, washed, solid-liquid separated, and the drying temperature is controlled <100℃ to obtain the modified PbO2; The other ingredients and steps are the same as in Example 1.

[0035] Comparative Example 3 This comparative example provides a positive electrode plate, which differs from Example 1 in that the carbon fiber in Example 1 is replaced with polyaniline fiber; The other ingredients and steps are the same as in Example 1.

[0036] Comparative Example 4 This comparative example provides a positive electrode plate, which differs from Example 1 in that the PbS in Example 1 is replaced with an equal amount of SnS. The other ingredients and steps are the same as in Example 1.

[0037] Comparative Example 5 This comparative example demonstrates the preparation of a positive electrode plate, which is a conventional positive electrode plate 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, thereby hardening the electrode plate.

[0038] The electrochemical performance of the positive electrode plates prepared in Examples 1-3 and Comparative Examples 1-5 was measured in this invention. The specific test methods are as follows: The positive electrode plates prepared in Examples 1-3 and Comparative Examples 1-5 were cut into 20cm×20cm pieces with a thickness in the range of 2.5mm±0.2mm. Using 1.3mol / L sulfuric acid as the electrolyte solution, they were assembled with the negative electrode plates to form lead-acid full cells, which were respectively labeled as lead-acid cells I~III and lead-acid cell pairs I~V. The energy density, internal resistance, and cycle capacity retention of different lead-acid cells were measured. The specific measurement results are shown in Table 1.

[0039] The negative electrode plate is prepared as follows: Lead powder, carbon black, 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 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.

[0040] 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.

[0041] Battery internal resistance measurement method: Use a battery internal resistance tester to read the value directly.

[0042] 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.

[0043] Table 1

[0044] As shown in Table 1, compared with lead-acid batteries made using conventional positive plates that rely on metal mesh grids, lead-acid batteries made using the positive plates provided in Examples 1-3 have superior energy density and lower internal resistance, and the capacity retention rate after 200 cycles is also significantly improved.

[0045] 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 electrode plate, characterized in that, The raw material components include: modified PbO2, PbS, and carbon fiber; The modified PbO2 is PbF2-encapsulated PbO2.

2. The positive electrode plate as described in claim 1, characterized in that, The mass ratio of the modified PbO2, PbS and carbon fiber is 100:(2~10):

1.

3. The positive electrode plate as described in claim 1 or 2, characterized in that, The carbon fiber has a diameter of 6μm to 8μm and an electrical conductivity of 700S / m to 900S / m.

4. The positive electrode plate as described in claim 1, characterized in that, The preparation method of the modified PbO2 includes the following steps: mixing PbO2 and hydrofluoric acid evenly, reacting at 60℃~80℃, washing, solid-liquid separation, and drying to obtain the modified PbO2.

5. The positive electrode plate as described in claim 4, characterized in that, The molar ratio of PbO2 to hydrofluoric acid is (5~20):

1.

6. The positive electrode plate as described in claim 4, characterized in that, The reaction time is 1 hour to 5 hours.

7. A method for preparing a positive electrode plate according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Weigh each raw material component according to the ratio, disperse the PbS in water to obtain a PbS dispersion; S2. The modified PbO2, carbon fiber and PbS dispersion are mixed evenly and dried at -45℃ to -35℃ to obtain the positive electrode composite material. S3. Hot-press the positive electrode composite material to obtain the positive electrode plate.

8. The method for preparing the positive electrode plate as described in claim 7, characterized in that, In S1, the concentration of the PbS dispersion is 0.05 mol / L to 0.1 mol / L; and / or In S3, the hot pressing conditions are: pressure of 30MPa~80MPa, temperature of 100℃~200℃; and / or In S3, the hot pressing time is 0.5h to 3h.

9. The application of a positive electrode plate according to any one of claims 1-6 or a positive electrode plate prepared by the preparation method of the positive electrode plate according to any one of claims 7-8 in a lead-acid battery.

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