A composite separator and its application

Abstract

The present invention provides a composite separator, comprising a separator and a carbon material, that is, an activated carbon felt with hydrogen-oxygen reaction catalytic activity is introduced on one side of the AGM separator close to the negative electrode or the positive electrode. The activated carbon felt with catalytic activity is prepared by a technical route of activating the carbon felt, impregnating it, and depositing platinum black by in-situ reduction method. Through the assembly and characterization of the battery, the results show that by introducing an activated carbon felt with hydrogen-oxygen reaction catalytic activity on one side of the AGM separator, the gas generation amount and water consumption of the lead-carbon battery can be significantly reduced, thereby further prolonging its cycle life and further improving its safety.

Description

Technical Field

[0001] The invention relates to the field of lead-carbon batteries, and in particular to a technology for reducing water consumption of lead-carbon batteries. Background Art

[0002] As the oldest rechargeable battery, lead-acid battery (LAB) has a history of more than 150 years. Due to its low cost, high safety and high recycling rate, it is still widely used in telecommunications, hybrid electric vehicles, and electric vehicles (HEV and EV), and has broad application prospects in the field of large-scale energy storage. However, the application in the field of hybrid electric vehicles and electric vehicles requires LAB to often operate under high rate partial state of charge (HRPSoC) conditions, and the large-scale energy storage field requires LAB to often operate under partial state of charge (PSoC) conditions. Cycling under HRPSoC and PSoC conditions will cause irreversible sulfidation of the negative electrode, greatly reducing the service life. In order to improve the HRPSoC and PSoC cycle life of traditional LAB, researchers added a certain amount of activated carbon materials (activated carbon, carbon black, graphite, carbon nanotubes or mixtures of these materials, etc.) to the negative electrode of LAB. LCB is a new electrochemical energy storage technology developed on the basis of traditional lead-acid batteries. LCB combines the advantages of LAB and supercapacitors, has good charge and discharge performance, and is particularly suitable for the storage of electricity produced by renewable energy. The addition of carbon materials increases the specific surface area and conductivity of the negative electrode plate and reduces the pore size of the negative electrode plate, thereby making PbSO 4 The continued growth of the crystal is suppressed. Small-grained PbSO with high reversible solubility 4 The formation of negative electrode sulfation process is effectively inhibited, thereby extending the battery cycle life. However, in LCB, adding more carbon materials to the negative electrode active material will also bring some negative effects, such as increased cost and reduced battery capacity. In addition, the hydrogen evolution overpotential of carbon materials is low, and the negative electrode of the lead-carbon battery will undergo a violent hydrogen evolution reaction during the charging process, which will lead to an increase in the concentration of the electrolyte solution or even dryness. Researchers have done a lot of meaningful work to address these defects in LCB.

[0003] The development of carbon materials with special structures and composite carbon materials, as well as the doping and surface modification of carbon materials, are currently the common means to solve the problem of hydrogen evolution at the negative electrode of lead-carbon batteries. In addition, by optimizing the battery structure design, the gas production and water consumption of lead-carbon batteries can also be reduced to a certain extent. For lean lead-carbon batteries for energy storage that use AGM as a diaphragm, by optimizing the ratio of positive and negative active substances, the potential window of the positive and negative electrodes during the charge and discharge process can be adjusted to reduce the amount of hydrogen evolution at the negative electrode and increase the amount of oxygen evolution at the positive electrode. The oxygen generated at the positive electrode passes through the AGM diaphragm, diffuses to the negative plate, and combines with sponge metal lead to generate PbO. PbO further reacts with sulfuric acid to generate PbSO 4, PbSO 4 During the charging process, it is reduced back to spongy lead again, realizing oxygen circulation inside the battery (Y. Nakayama, K. Kishimoto, S. Sugiyama, S. Sakaguchi, Micro-structural design and function of an improved absorptive glass mat (AGM) separator for valve-regulated lead-acid batteries, Journal of Power Sources, 107(2) 192-200). If the oxygen generated at the positive electrode can be combined with the hydrogen generated at the negative electrode inside the battery to form water, then hydrogen circulation can be realized inside the battery at the same time, thus eliminating the safety hazards brought by hydrogen expulsion and slowing down the water loss of the battery. Summary of the Invention

[0004] The technical problem (invention purpose) to be solved by the present invention: The present invention proposes a way to realize hydrogen circulation inside the battery, that is, introducing carbon materials with hydrogen-oxygen reaction catalytic activity on one side or both sides of the AGM separator close to the negative electrode or / and the positive electrode.

[0005] A composite separator, comprising a separator and treated carbon materials.

[0006] The separator is an AGM separator or a PE separator, and the thickness of the carbon material is 0.1-3 mm; the carbon material is one of carbon felt, graphite felt, carbon paper, and carbon cloth; the thickness of the composite separator is 0.1-4 mm.

[0007] The treated carbon material is a carbon material doped with platinum, and the mass percentage of platinum element in the total mass of the treated carbon material is: 0.03%-80%;

[0008] The treatment process is as follows,

[0009] 1) Activation of the carbon material: Take a carbon material and immerse it in an aqueous potassium hydroxide solution for 0.5-5 hours, where the mass ratio of the carbon material to the total mass of the aqueous potassium hydroxide solution is 1:(10-1000) (preferably 1:(50-200)), the concentration of the potassium hydroxide solution is 0.1 mol / L-10 mol / L (preferably 0.5-5 mol / L), take out the impregnated carbon material and dry it, the drying temperature is 40-120 °C (preferably 60-80 °C), the drying time is 1-24 hours (preferably 8-16 hours), transfer the dried carbon material to a nitrogen atmosphere sintering furnace for activation, the activation temperature is 700-1200 °C, and the activation time is 1-10 hours (preferably 800-1000 °C, 4-6 hours);

[0010] 2) Post-treatment of carbon materials: Immerse the activated carbon materials in an aqueous solution of chloroplatinic acid for 1-5 hours, where the mass ratio of the carbon materials to the total mass of the aqueous solution is 1:(10-1000) (preferably 1:(50-200)), the concentration of the chloroplatinic acid solution is 0.1 mol / L-10 mol / L (preferably 0.5-5 mol / L). Take out the impregnated carbon materials and dry them. The drying temperature is 40-120 °C (preferably 60-80 °C), and the drying time is 1-24 hours (preferably 8-16 hours). Immerse the dried carbon materials in a sodium borohydride solution for a reduction reaction for 1-5 hours to obtain the treated carbon materials, where the mass ratio of the activated carbon materials to the total mass of the sodium borohydride solution is 1:(10-1000) (preferably 1:(50-200)), and the concentration of the sodium borohydride solution is 0.1 mol / L-10 mol / L (0.5-5 mol / L).

[0011] The composite separator comprises a separator, with the treated carbon materials compounded on one side of the separator, or consists of a separator, the treated carbon materials, and a separator in three layers, or consists of the treated carbon materials, a separator, and the treated carbon materials in three layers.

[0012] The lead-carbon battery includes electrodes and a separator;

[0013] By weight, the material composition of the lead-carbon battery electrodes is: 500-800 parts of lead powder, 1-20 parts of carbon materials, 6-10 parts of barium sulfate, and 0.1-0.5 parts of polypropylene short fibers with a length of 0.1-5 mm and a diameter of 100 nm-5 μm.

[0014] The preparation process of the lead-carbon battery electrodes is as follows: (1) By weight, mix 500-800 parts of lead powder, 1-20 parts of carbon materials, 6-10 parts of barium sulfate, and 0.1-0.5 parts of polypropylene short fibers with a length of 0.1-5 mm and a diameter of 100 nm-5 μm by stirring. While stirring, add 50-100 parts by weight of water to the premixed powder and continuously stir for 1-60 min to obtain the lead paste; (2) Apply the lead paste onto a metallic lead grid, and dry and cure it to obtain the negative electrode of the lead-carbon battery; the curing temperature is 30-50 °C, the humidity is 70-95%, and the curing time is 10-30 hours; the drying temperature is 60-120 °C, and the time is 10-30 hours.

[0015] The size of the metallic lead grid is 0.5-1000 mm in length, 0.2-80 mm in width, and 0.5-4 mm in thickness.

[0016] The lead-carbon battery electrode is the negative electrode of the lead-carbon battery.

[0017] Advantages of the present invention

[0018] The catalytically active carbon material is prepared by a technical route of activating the carbon material, impregnating it, and depositing platinum black by in-situ reduction. It is characterized by assembling a battery. The results show that by introducing a carbon material with hydrogen-oxygen reaction catalytic activity on one side of the AGM separator, the gas generation amount and water consumption of the lead-carbon battery can be significantly reduced, thereby further prolonging its cycle life and further improving its safety. Detailed implementation mode

[0019] The present invention will be described in detail below with reference to the embodiments.

[0020] Unless otherwise specified, the raw materials in the embodiments are purchased commercially and used directly without treatment; for the instruments and equipment used, the parameters recommended by the manufacturer are adopted.

[0021] In the embodiments, the cycle life of the lead-carbon battery is tested using a Blue Power charge-discharge instrument and a Neware charge-discharge tester.

[0022] Example 1:

[0023] 1. Activation of carbon felt: Take 4 pieces of carbon felt with a length of 70 mm, a width of 50 mm, and a thickness of 1 mm (total mass of carbon felt is 1 g) and immerse them in 100 ml of 3 mol / L potassium hydroxide aqueous solution for 1 hour. Take out the impregnated carbon felt and dry it. The drying temperature is 80 °C and the drying time is 12 hours. Transfer the dried carbon felt to a nitrogen atmosphere sintering furnace for activation. The activation temperature is 800 °C and the activation time is 5 hours.

[0024] 2. Preparation of carbon felt with hydrogen-oxygen composite function: Take the activated carbon felt and immerse it in 100 ml of 3 mol / l chloroplatinic acid aqueous solution for 1 hour. Take out the impregnated carbon felt and dry it. The drying temperature is 80 °C and the drying time is 12 hours. Immerse the dried carbon felt in 100 ml of 3 mol / l sodium borohydride solution for a reduction reaction for 1 hour.

[0025] The composite separator consists of a separator, the treated carbon felt, and a separator. The separator is an AGM separator (glass fiber separator for AGM type battery) with the same size as the carbon felt, and the thickness of the AGM separator is 1 mm.

[0026] 3. The lead-carbon battery is prepared by the following steps: 1. Preparation of the negative electrode: (1) 600 g of lead powder, 9 g of carbon material, 8.4 g of barium sulfate, and 0.3 g of polypropylene short fibers with a length of 5 mm and a diameter of 0.5 - 1.5 μm are premixed using a high-speed mixer. While stirring, 84 g of deionized water is added to the premixed powder, and continuous stirring is carried out for 10 min to obtain lead paste; (2) The lead paste is scraped onto a metallic lead grid. The grid size is 70 mm in length, 50 mm in width, and 2 mm in thickness. The curing temperature is 40 °C, the humidity is 80%, and the curing time is 20 hours; the drying temperature is 80 °C, and the time is 24 hours; 2. Preparation of the positive electrode: The positive electrode of the lead-acid battery is prepared according to the same technological steps as those in steps (1) and (2) of the negative electrode preparation. The difference is that no carbon material is added during the positive electrode preparation process; 3. Preparation of the lead-carbon battery: Three positive electrode plates and two negative electrode plates are alternately and parallelly arranged at intervals in sequence. The separator used between the positive electrode plate and the negative electrode plate is the prepared composite separator.

[0027] The two negative electrode plates are respectively connected in parallel by welding, and the three positive electrode plates are respectively connected in parallel by welding. Among them, the total mass of the positive active material of the lead-acid battery (the total mass of the lead paste after drying on the three positive electrode plates) is 20.0 g. The total mass of the positive active material refers to the total mass of the lead paste contained in the three positive electrode plates connected in parallel by welding. The total mass of the negative active material (the total mass of the lead paste after drying on the two negative electrode plates) is 14.3 g. The total mass of the negative active material refers to the total mass of the lead paste contained in the two negative electrode plates connected in parallel by welding. The positive and negative electrode grids adopt conventional lead grids with a size of 70 mm in length, 50 mm in width, and 2 mm in thickness; the positive and negative electrodes are placed in a tightly assembled battery case. The length of the battery case is 76 mm, the width is 44 mm, and the height is 100 mm. 88 g of sulfuric acid electrolyte with a density of 1.275 g / ml is injected into the battery case;

[0028] The battery is subjected to a cycle life test. The test conditions are as follows: at 25 °C: constant current discharge at 4.2 A for 59 s, discharge at 18 A for 1 s, constant current and constant voltage charging at 6.3 A current and 2.3 V voltage for 60 s. The above charge-discharge conditions are cycled 3600 times, and then it is left standing for 40 hours. After 40 hours, the cycle starts again. The termination condition of the life test is that the battery voltage drops below 1.2 V;

[0029] The starting voltage of the assembled internal mixing type battery in the fully charged state at room temperature is 2.1435 V. The internal mixing type battery can operate for 18025 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7198 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0030] Example 2:

[0031] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the length and width dimensions of the composite carbon felt are respectively reduced to 1 / 5 of the original size in proportion to prepare the lead-carbon battery.

[0032] The starting voltage of the assembled internal mixing type battery in a fully charged state at room temperature is 2.1763V. The internal mixing type battery can operate for 17,934 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,198 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0033] Example 3:

[0034] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, a composite carbon felt with a thickness of 2mm is used as the raw material to prepare the composite carbon felt and the lead-carbon battery.

[0035] The starting voltage of the assembled internal mixing type battery in a fully charged state at room temperature is 2.1962V. The internal mixing type battery can operate for 17,254 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,198 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0036] Example 4:

[0037] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the composite separator used is composed of a composite carbon felt and an AGM separator with the same size as that in Example 1, and the composite separator is composed of a separator and a processed composite carbon felt compounded on one side of the separator to prepare the lead-carbon battery.

[0038] The starting voltage of the assembled internal mixing type battery in a fully charged state at room temperature is 2.1734V. The internal mixing type battery can operate for 18,267 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,198 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0039] Example 5:

[0040] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the composite separator used is composed of a composite carbon felt and an AGM separator with the same size as that in Example 1, and the composite separator is composed of a separator and processed composite carbon felts compounded on both sides of the separator to prepare the lead-carbon battery.

[0041] The initial voltage of the assembled internal mixing type battery at room temperature in a fully charged state is 2.1634V. The internal mixing type battery can operate for 18,027 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,198 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery life.

[0042] Comparative Example 1

[0043] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the preparation of the carbon felt is not carried out, no carbon felt material is added during the preparation of the lead-acid battery, and only one layer of AGM separator with a thickness of 1mm is used for battery assembly. The initial voltage of the assembled internal mixing type battery at room temperature in a fully charged state is 2.1885V, and the battery can operate for 5,198 cycles in the room temperature life test.

[0044] Comparative Example 2

[0045] Lead-carbon battery: The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the preparation of the carbon felt composite material is not carried out, and only the same mass and the same size of untreated carbon felt material are added as the battery separator during the preparation of the lead-acid battery, and two AGM separators of the same size are covered on both sides of the carbon felt.

[0046] The initial voltage of the assembled internal mixing type battery at room temperature in a fully charged state is 2.1053V, and the internal mixing type battery can operate for 10,354 cycles in the room temperature life test.

[0047] Comparative Example 3

[0048] The process is the same as that of Example 1. The difference is that, according to the requirements of Example 1, without changing other conditions, the concentration of the chloroplatinic acid solution is changed to 0.001mol / L. After thermogravimetric test, the mass of platinum element in the sample accounts for 0.0001% of the total mass of the carbon felt. Due to the almost non-existence of the hydrogen-oxygen composite catalyst in the carbon felt, the hydrogen evolution situation of the battery is aggravated. The initial voltage of the assembled internal mixing type battery at room temperature in a fully charged state is 2.1146V, and the battery can operate for 10,076 cycles in the room temperature life test.

[0049] Comparative Example 4

[0050] The process is the same as that of Example 1, except that, in accordance with the requirements of Example 1, without changing other conditions, the concentration of the sodium borohydride solution is changed to 0.001 mol / L. Through thermogravimetric testing, the mass of platinum element in the sample accounts for 0.0001% of the total mass of the carbon felt. Due to the decrease in the content of sodium borohydride, the amount of platinum reduction decreases, and there is no hydrogen-oxygen composite catalyst in the carbon felt, resulting in an aggravated hydrogen evolution situation in the battery. The starting voltage of the assembled internal mixing type battery under normal temperature and full charge state is 2.1435 V, and the battery can be tested for 10,178 cycles under normal temperature conditions.

[0051] Comparative Example 5

[0052] Lead-carbon battery: The process is the same as that of Example 1, except that, in accordance with the requirements of Example 1, without changing other conditions, the composite separator used is composed of an AGM separator with the same size as that in Example 1 and a composite carbon felt with different sizes, wherein the thickness of the composite carbon felt is 5 mm, and the remaining battery preparation process and separator stacking method are exactly the same as those in Example 1.

[0053] The starting voltage of the assembled internal mixing type battery under normal temperature and full charge state is 2.1585 V, and the internal mixing type battery can operate for 4,457 cycles in the normal temperature life test. Due to the too high thickness of the composite carbon felt separator, the internal resistance of the battery is high, and the battery cycle life is severely reduced.

Claims

1. A composite diaphragm, comprising a diaphragm and a treated carbon material; The treated carbon material is a platinum-doped carbon material, and the mass percentage of platinum element in the total mass of the treated carbon material is: 0.03% - 80%; The process of treating the carbon material is as follows: 1) Activation of the carbon material: Take a carbon material and immerse it in an aqueous potassium hydroxide solution for 0.5 - 5 hours, where the mass ratio of the carbon material to the total mass of the aqueous potassium hydroxide solution is 1:(10 - 1000), the concentration of the potassium hydroxide solution is 0.1 mol / L - 10 mol / L. Take out the immersed carbon material and dry it. The drying temperature is 40 - 120°C, and the drying time is 1 - 24 hours. Transfer the dried carbon material to a nitrogen atmosphere sintering furnace for activation. The activation temperature is 700 - 1200°C, and the activation time is 1 - 10 hours; 2) Post-treatment of the carbon material: Take the activated carbon material and immerse it in an aqueous chloroplatinic acid solution for 1 - 5 hours, where the mass ratio of the carbon material to the total mass of the aqueous solution is 1:(10 - 1000), the concentration of the chloroplatinic acid solution is 0.1 mol / L - 10 mol / L. Take out the immersed carbon material and dry it. The drying temperature is 40 - 120°C, and the drying time is 1 - 24 hours. Immerse the dried carbon material in a sodium borohydride solution for a reduction reaction for 1 - 5 hours to obtain the treated carbon material, where the mass ratio of the activated carbon material to the total mass of the sodium borohydride solution is 1:(10 - 1000), and the concentration of the sodium borohydride solution is 0.1 mol / L - 10 mol / L.

2. The composite diaphragm according to claim 1, characterized in that: The diaphragm is an AGM diaphragm or a PE diaphragm, and the thickness of the carbon material is 0.1 - 3 mm; the carbon material is one of carbon felt, graphite felt, carbon paper, and carbon cloth; the thickness of the composite diaphragm is 0.1 - 4 mm.

3. The composite diaphragm according to claim 1, characterized in that: The process of treating the carbon material is as follows: 1) Activation of the carbon material: Take a carbon material and immerse it in an aqueous potassium hydroxide solution for 0.5 - 5 hours, where the mass ratio of the carbon material to the total mass of the aqueous potassium hydroxide solution is 1:(50 - 200), the concentration of the potassium hydroxide solution is 0.5 - 5 mol / L. Take out the immersed carbon material and dry it. The drying temperature is 60 - 80°C, and the drying time is 8 - 16 hours. Transfer the dried carbon material to a nitrogen atmosphere sintering furnace for activation. The activation temperature is 800 - 1200°C, and the activation time is 4 - 6 hours; 2) Post-treatment of carbon materials: The activated carbon materials are immersed in an aqueous solution of chloroplatinic acid for 1 - 5 hours, where the mass ratio of the carbon materials to the total mass of the aqueous solution is 1:(50 - 200), and the concentration of the chloroplatinic acid solution is 0.5 - 5 mol / L. The impregnated carbon materials are taken out and dried. The drying temperature is 60 - 80 °C, and the drying time is 8 - 16 hours. The dried carbon materials are immersed in a sodium borohydride solution for a reduction reaction for 1 - 5 hours to obtain the treated carbon materials, where the mass ratio of the activated carbon materials to the total mass of the sodium borohydride solution is 1:(50 - 200), and the concentration of the sodium borohydride solution is 0.5 - 5 mol / L.

4. Application of the composite separator according to claim 1 or 2 or 3 in a lead-carbon battery. The composite separator comprises a separator, with treated carbon materials compounded on one side of the separator, or consists of a separator, treated carbon materials, and a separator in three layers, or consists of treated carbon materials, a separator, and treated carbon materials in three layers.

5. According to the application described in claim 4, it is characterized in that: the lead-carbon battery includes electrodes and a separator; By weight, the material composition of the lead-carbon battery electrode is: 500 - 800 parts of lead powder, 1 - 20 parts of carbon materials, 6 - 10 parts of barium sulfate, and 0.1 - 0.5 part of polypropylene short fibers with a length of 0.1 - 5 mm and a diameter of 100 nm - 5 μm.

6. According to the application described in claim 4, it is characterized in that: The preparation process of the lead-carbon battery electrode is as follows: (1) By weight, 500 - 800 parts of lead powder, 1 - 20 parts of carbon materials, 6 - 10 parts of barium sulfate, and 0.1 - 0.5 part of polypropylene short fibers with a length of 0.1 - 5 mm and a diameter of 100 nm - 5 μm are stirred and premixed. While stirring, 50 - 100 parts by weight of water are added to the premixed powder, and stirring is continued for 1 - 60 min to obtain a lead paste; (2) The lead paste is scraped onto a metallic lead grid and dried and cured to obtain the negative electrode of the lead-carbon battery; the curing temperature is 30 - 50 °C, the humidity is 70 - 95%, and the curing time is 10 - 30 hours; the drying temperature is 60 - 120 °C, and the time is 10 - 30 hours.

7. According to the application described in claim 4, it is characterized in that: The size of the metallic lead grid is 0.5 - 1000 mm in length, 0.2 - 80 mm in width, and 0.5 - 4 mm in thickness.

8. According to any one of the applications described in claims 4 - 7, it is characterized in that: the lead-carbon battery electrode is the negative electrode of the lead-carbon battery.