Application of a Hydroxyapatite Separator in a Lead-Carbon Battery

Abstract

The present invention provides a composite separator based on inorganic two-dimensional materials. 1) Prepare an aqueous solution of CaCl2 and an aqueous solution of NaOH with mass concentrations respectively, mix the above two solutions to obtain solution A; prepare an ethanol solution of oleic acid, named solution B, and a NaH2PO4 solution C; 2) Pour solutions A, B, and C into a hydrothermal reactor, keep warm; take out the solid product and wash the solid product with ethanol. This composite separator has the characteristics of avoiding acid stratification and being heat-resistant and fire-resistant at the same time, and is applicable to colloid lead-acid batteries and colloid lead-carbon batteries, especially suitable for colloid lead-carbon batteries.

Description

Technical Field

[0001] The present invention relates to the field of lead-carbon batteries, and particularly to lead-carbon battery separators. Background Art

[0002] In the past decade, due to the resource limitations of traditional fossil fuels and the increase in harmful gas emissions, various alternative energy technologies have gradually attracted the interest of governments, academia, and industry. Currently, mobile energy storage systems are widely used in hybrid electric vehicles (HEVs) as alternative energy and green energy systems. However, advanced alternative energy storage systems, such as supercapacitors and rechargeable batteries, are limited by their low energy density or power density. Among various energy technologies, lead-acid batteries (LABs) are considered a promising energy storage technology because of their advantages of low cost and high safety in HEV applications. In addition to having many advantages, negative electrode sulfation limits the application of lead-acid batteries. During discharge, lead particles are converted into PbSO4. However, in a lead-acid battery system, during the charging process, the conversion process of PbSO4 to spongy metallic Pb in the negative electrode of the lead-acid battery is limited. As the crystal size of PbSO4 continuously increases, the reverse reaction is restricted. To minimize the formation of large lead sulfate crystals and improve the operating efficiency of the battery, researchers incorporated a certain amount of carbon material into the negative electrode active material to construct an internally mixed lead-carbon battery. As an efficient energy storage technology, the internally mixed lead-carbon battery has the advantages of charge-discharge stability, renewability, and high safety, and shows broad application prospects in the fields of HEV, microgrid, and large-scale energy storage.

[0003] Traditional lead-acid batteries use dilute sulfuric acid solution as the electrolyte. Since acid stratification occurs during battery operation, that is, during the use of the battery, as the charge-discharge cycle continues, the concentration of sulfuric acid in the lower part of the battery cell will continuously increase, resulting in a concentration gradient distribution of the electrolyte along the up-down direction inside the battery cell. The too-high acid concentration in the lower part will accelerate the irreversible sulfation of the electrode active material and the corrosion rate of the grid. To solve this problem, the gel lead-acid battery technology emerged.

[0004] In a valve-regulated lead-acid battery (VRLA) using an absorbent glass mat (AGM), sulfuric acid is adsorbed in the absorbent glass mat as the electrolyte. In a gel electrolyte VRLA, a gel electrolyte is formed through the interaction between a gelling agent and the sulfuric acid electrolyte. Fumed silica is commonly used as the gelling agent due to its advantages such as a good three-dimensional network structure, good thixotropy, and high capacity. The performance of a gel VRLA battery is directly affected by the influence of the gel on the battery filling process, which is related to the structure and gel time of the gel electrolyte. Some additives have been used in the literature to improve the conductivity, gel structure (easy to fill without curing), and stability of the fumed silica-based gel electrolyte. In addition, the AGM separator filters the silica sol during the gel injection process, making it difficult for silica particles to enter the AGM separator. Since the AGM separator is impregnated with a liquid electrolyte, the acid stratification phenomenon is difficult to completely eliminate during battery use, thus affecting the cycle life of the battery. The same problem exists in a colloidal lead-carbon battery using an AGM separator. One way to solve this problem is to introduce a colloidal electrolyte into the separator. After acid injection, the liquid acid in the electrolyte sol will penetrate into the separator to form an electrolyte sol in the separator. During the subsequent storage process, the electrolyte sols inside and outside the separator are both transformed into electrolyte gels, which are interconnected to form a conductive network, thus completely eliminating the acid stratification phenomenon inside the battery, slowing down the irreversible sulfation process of the electrode active material at the lower part of the negative plate and the degree of grid corrosion, and improving the service life of the battery. Although the AGM separator is a commonly used separator in VRLA, due to its thick fibers, it is difficult to fix nano-fumed silica in it to make a composite separator. Some companies have launched PVC / fumed silica composite separator products. Although introducing fumed silica into PVC can solve the acid stratification problem, it also brings the problem of reduced safety and reliability. Compared with inorganic AGM, the high-temperature resistance and fire resistance of the PVC / fumed silica composite separator are significantly reduced. Summary of the Invention

[0005] The technical problem (invention objective) to be solved by the present invention:

[0006] The present invention provides an application of a hydroxyapatite separator based on an inorganic two-dimensional material in a lead-carbon battery,

[0007] 1) Prepare an aqueous solution of CaCl2 with a mass concentration of 0.1 - 100 g / L (preferably 0.5 - 60, more preferably 1 - 50 g / L) and an aqueous solution of NaOH with a mass concentration of 10 - 150 g / L (preferably 12.5 - 125 g / L, more preferably 25 - 100 g / L) respectively, and mix the above two solutions to obtain solution A; the volume ratio of the aqueous solution of CaCl2 to the aqueous solution of NaOH is (0.01 - 10):1, preferably (0.1 - 5):1, more preferably (0.5 - 2):1;

[0008] Prepare an ethanol solution of oleic acid, named Solution B, where the mass ratio of ethanol to oleic acid is 0.1 - 10:10 - 0.1, preferably 0.5 - 2:2 - 0.5;

[0009] Prepare a NaH2PO4 solution C with a mass concentration of 0.1 - 200 g / L (preferably 0.5 - 120 g / L, more preferably 1 - 100 g / L);

[0010] 2) Pour the ABC solutions into a hydrothermal autoclave and keep them at 120 - 300 °C for 1 - 72 hours (preferably 12 - 48 hours); Take out the solid product, wash the solid product with ethanol, dry the product and press it into a hydroxyapatite separator with a thickness of 0.1 - 10 mm. The volume ratio of the ABC solutions is (0.1 - 10):(0.1 - 10):1, preferably (0.5 - 5):(0.5 - 5):1, more preferably (2 - 4):(1 - 3):1.

[0011] The prepared hydroxyapatite separator is used as a separator for a colloidal lead-carbon battery, with a membrane thickness of 0.1 - 2 mm, a pore diameter of 1 - 50 nm, and a porosity of 40% - 80%.

[0012] The preparation process of the colloidal lead-carbon battery is as follows:

[0013] A. (1) By weight, premix 500 - 800 parts of lead powder, 0.01 - 20 parts of carbon material, 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 while stirring, and add 50 - 100 parts of deionized water to the premixed powder while stirring, and continuously stir for 1 - 60 min to obtain lead paste;

[0014] (2) Spread the lead paste onto a metallic lead grid, fill the through-holes on the metallic lead grid with the lead paste, and obtain a negative electrode of the lead-carbon battery after curing and drying; 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] B. Preparation of the positive electrode: Prepare a positive electrode of a lead-acid battery according to the same process steps as in steps (1) and (2) of the negative electrode preparation A above, the difference being that no carbon material is added to the positive electrode;

[0016] C. After assembling into a lead-carbon battery, the added electrolyte of the lead-carbon battery is a colloidal electrolyte, with a mass concentration of: 1.1 g / ml - 1.4 g / ml, preferably: 1.275 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances other than the metallic lead grid of the negative electrode is 60 - 120:50, preferably 83:57.2.

[0017] The size of the metallic lead grid is 50 - 1000 mm in length, 20 - 80 mm in width, and 0.5 - 4 mm in thickness;

[0018] The size of the hydroxyapatite separator prepared in Step 1 used is 50 - 1000 mm in length, 20 - 80 mm in width, and 0.5 - 4 mm in thickness.

[0019] The colloidal electrolyte is a sulfuric acid solution with a mass fraction of 0.01% - 20% of fumed silica, preferably 0.5 - 5%.

[0020] Advantages of the present invention

[0021] The present invention prepares a lead-carbon battery using a composite separator based on inorganic two-dimensional materials. This composite separator simultaneously has the characteristics of avoiding acid stratification and being heat-resistant and fire-resistant, and is applicable to colloidal lead-acid batteries and colloidal lead-carbon batteries, especially suitable for colloidal lead-carbon batteries. Applying this composite separator to a colloidal lead-carbon battery significantly improves the high-temperature capacity and charge-discharge cycle performance of the battery. Specific embodiments

[0022] Example 1

[0023] The following steps are used to prepare the hydroxyapatite separator for the lead-carbon battery. Dissolve 11 g of CaCl2 in 2000 ml of water and 100 g of NaOH in 2000 ml of water respectively, and mix the above two solutions to obtain Solution A. Dissolve 1200 g of absolute ethanol in 1200 g of oleic acid to obtain Solution B. Dissolve 40 g of NaH2PO4 in 1000 ml of water to obtain Solution C. Pour Solutions A, B, and C into a 10000 ml hydrothermal reactor. Operate the hydrothermal reactor at 180 °C for 24 hours. Wash with an absolute ethanol aqueous solution multiple times to obtain the final product, dry it, and press it into a film with a thickness of 1 mm. Cut out a rectangle with a length of 60 mm and a width of 50 mm from this film for use as the separator of the colloidal lead-carbon battery.

[0024] 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 activated carbon, 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 with 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 plate with a grid size of 70 mm in length, 50 mm in width, and 2 mm in thickness, and the negative electrode of the lead-carbon battery is obtained through curing and drying. 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) for preparing the negative electrode, the difference being that no carbon material is added to the positive electrode; 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, and the prepared hydroxyapatite separator with a size of 74 mm in length, 60 mm in width, and 2 mm in thickness is placed between the positive electrode plate and the negative electrode plate. The two negative electrode plates are respectively connected in parallel by welding, and the three positive electrode plates are connected in parallel by welding. Among them, the total mass of the positive electrode active material (the total mass of the lead paste after drying on the three positive electrode plates) of the lead-acid battery is 20.0 g. The total mass of the positive electrode 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 electrode 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 electrode 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 grid plates adopt conventional lead grid plates 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 with a length of 76 mm, a width of 40 mm, and a height of 100 mm, and 83 g of colloidal electrolyte with a density of 1.275 g / ml and a mass fraction of silicon dioxide of 1% is injected into the battery case;

[0025] The high-temperature capacity retention rate of the battery is tested, and the test method is as follows: At room temperature, a constant current discharge is carried out at 0.52 A until the battery voltage reaches 1.8 V, and the normal-temperature capacity of the battery is recorded. A constant current and constant voltage charge is carried out at 0.52 A current and 2.4 V voltage for 24 hours, and then the battery is left standing at 40 °C for 10 hours. After 10 hours, a discharge is carried out at 0.52 A current until the battery voltage is 1.8 V, and the low-temperature capacity of the battery is recorded.

[0026] The lead-carbon battery using the composite separator of inorganic two-dimensional materials can reach a high-temperature discharge capacity of 6140 mAh under this condition, and the ratio of the high-temperature capacity to the normal-temperature capacity is 125%. Compared with the test results of a common lead-carbon battery under the same test conditions (the high-temperature discharge capacity is 5869 mAh, and the ratio of the high-temperature capacity to the normal-temperature capacity is 112%), the high-temperature capacity of the lead-carbon battery using the composite separator of inorganic two-dimensional materials is increased by 13% compared with that of the common lead-carbon battery.

[0027] The battery was subjected to a normal-temperature life test: it was discharged at a constant current of 4.2 A for 59 seconds, 18 A for 1 second, and charged at a constant current and constant voltage of 6.3 A current and 2.3 V voltage for 60 seconds. This charge-discharge condition was cycled 3,600 times, then left standing for 40 hours. After 40 hours, the cycle started again. The termination condition for the life test was that the battery voltage dropped below 1.2 V; the starting voltage of the assembled internal mixing type battery in the normal-temperature fully charged state was 2.1257 V, and the internal mixing type battery could run 18,004 cycles in the normal-temperature life test. Compared with the test results of a lead-carbon battery with the same lead element content using a conventional AGM separator under the same test conditions (7,219 cycles), the normal-temperature cycle life of the internal mixing lead-carbon battery could reach 2.5 times that of it.

[0028] Example 2

[0029] The process was the same as that of Example 1, the difference being that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, the addition amount of CaCl2 was changed to 90 g. The high-temperature discharge capacity of the assembled lead-carbon battery was 6,234 mAh, and the ratio of the high-temperature discharge capacity to the normal-temperature capacity was 121%. Compared with the test results of a common lead-carbon battery under the same test conditions (high-temperature discharge capacity 5,869 mAh, ratio of high-temperature capacity to normal-temperature capacity 112%), the high-temperature capacity of the lead-carbon battery using the composite separator of inorganic two-dimensional materials was 9% higher than that of the common lead-carbon battery. The starting voltage of the assembled internal mixing type battery in the normal-temperature fully charged state was 2.1337 V, and the internal mixing type battery could run 17,979 cycles in the normal-temperature life test. Compared with the test results of a lead-carbon battery with the same lead element content using a conventional AGM separator under the same test conditions (7,219 cycles), the normal-temperature cycle life of the internal mixing lead-carbon battery could reach 2.5 times that of it.

[0030] Example 3

[0031] The process was the same as that of Example 1, the difference being that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, the addition amount of oleic acid was changed to 2,400 g. The high-temperature discharge capacity of the assembled lead-carbon battery was 6,053 mAh, and the ratio of the high-temperature discharge capacity to the normal-temperature capacity was 119%. Compared with the test results of a common lead-carbon battery under the same test conditions (high-temperature discharge capacity 5,869 mAh, ratio of high-temperature capacity to normal-temperature capacity 112%), the high-temperature capacity of the lead-carbon battery using the composite separator of inorganic two-dimensional materials was 7% higher than that of the common lead-carbon battery. The starting voltage of the assembled internal mixing type battery in the normal-temperature fully charged state was 2.1631 V, and the internal mixing type battery could run 18,172 cycles in the normal-temperature life test. Compared with the test results of a lead-carbon battery with the same lead element content using a conventional AGM separator under the same test conditions (7,219 cycles), the normal-temperature cycle life of the internal mixing lead-carbon battery could reach 2.5 times that of it.

[0032] Example 4

[0033] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, the addition amount of NaH2PO4 is changed to 90 g. The high-temperature discharge capacity of the assembled lead-carbon battery is 6164 mAh, and the ratio of the high-temperature discharge capacity to the normal-temperature capacity is 118%. Compared with the test results of a common lead-carbon battery under the same test conditions (the high-temperature discharge capacity is 5869 mAh, and the ratio of the high-temperature capacity to the normal-temperature capacity is 112%), the high-temperature capacity of the lead-carbon battery with the composite separator of the inorganic two-dimensional material is 6% higher than that of the common lead-carbon battery. The initial voltage of the assembled internal mixing type battery in the fully charged state at normal temperature is 2.1953 V, and the internal mixing type battery can run for 17991 cycles in the normal-temperature life test. Compared with the test results of a lead-carbon battery with a conventional AGM separator having the same lead element content under the same test conditions (7219 cycles), the normal-temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of it.

[0034] Example 5

[0035] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, the addition amount of activated carbon is changed to 0.02 g. The high-temperature discharge capacity of the assembled lead-carbon battery is 6094 mAh, and the ratio of the high-temperature discharge capacity to the normal-temperature capacity is 122%. Compared with the test results of a common lead-carbon battery under the same test conditions (the high-temperature discharge capacity is 5869 mAh, and the ratio of the high-temperature capacity to the normal-temperature capacity is 112%), the high-temperature capacity of the lead-carbon battery with the composite separator of the inorganic two-dimensional material is 10% higher than that of the common lead-carbon battery. The initial voltage of the assembled internal mixing type battery in the fully charged state at normal temperature is 2.1258 V, and the internal mixing type battery can run for 18763 cycles in the normal-temperature life test. Compared with the test results of a lead-carbon battery with a conventional AGM separator having the same lead element content under the same test conditions (7219 cycles), the normal-temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of it.

[0036] Comparative Example 1

[0037] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, no hydroxyapatite separator is prepared, and a commercial AGM separator with the same size and thickness is used in the process of assembling the lead-carbon battery to prepare a colloidal lead-carbon battery. The high-temperature discharge capacity of this battery is 5869 mAh, which is lower than that of the lead-carbon battery with a hydroxyapatite separator. At the same time, this battery can only run for 7219 cycles in the life test under normal temperature conditions.

[0038] Comparative Example 2

[0039] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, a hydroxyapatite separator with a thickness of 6 mm is used to replace the battery separator used in Example 1 to prepare a colloidal lead-carbon battery. Due to the excessively high thickness of the separator used, the internal resistance of the electrolyte is increased, resulting in a service life test of 3351 cycles for this battery under normal temperature conditions.

Claims

1. Application of hydroxyapatite separator based on inorganic two-dimensional materials in lead-carbon batteries, characterized in that: 1) Prepare an aqueous CaCl2 solution with a mass concentration of 0.1-100 g / L and an aqueous NaOH solution with a mass concentration of 10-150 g / L respectively, mix the above two solutions to obtain solution A; the volume ratio of the aqueous CaCl2 solution to the aqueous NaOH solution is (0.01-10):1; Prepare an ethanol solution of oleic acid, named solution B, where the mass ratio of ethanol to oleic acid is 0.1-10:10-0.1; Prepare a NaH2PO4 solution C with a mass concentration of 0.1-200 g / L; 2) Pour solutions A, B, and C into a hydrothermal reactor, and keep it at 120-300 °C for 1-72 hours; Take out the solid product, wash the solid product with ethanol, dry the product and press it into a hydroxyapatite separator with a thickness of 0.1-10 mm; the volume ratio of solutions A, B, and C is (0.1-10):(0.1-10):

1.

2. The application according to claim 1, characterized in that: 1) Prepare an aqueous CaCl2 solution with a mass concentration of 0.5-60 g / L and an aqueous NaOH solution with a mass concentration of 12.5-125 g / L respectively, mix the above two solutions to obtain solution A; the volume ratio of the aqueous CaCl2 solution to the aqueous NaOH solution is (0.1-5):1; Prepare an ethanol solution of oleic acid, named solution B, where the mass ratio of ethanol to oleic acid is 0.5-2:2-0.5; Prepare a NaH2PO4 solution C with a mass concentration of 0.5-120 g / L; 2) Pour solutions A, B, and C into a hydrothermal reactor, and keep it at 120-300 °C for 12-48 hours; take out the solid product, wash the solid product with ethanol, dry the product and press it into a hydroxyapatite separator with a thickness of 0.1-10 mm; the volume ratio of solutions A, B, and C is (0.5-5):(0.5-5):

1.

3. The application according to claim 1, characterized in that: The prepared hydroxyapatite separator is used as a separator for colloidal lead-carbon batteries, with a membrane thickness of 0.1-2 mm, a pore diameter of 1-50 nm, and a porosity of 40%-80%.

4. The application according to claim 3, characterized in that: The preparation process of the colloidal lead-carbon battery is as follows: A. (1) By weight, premix 500-800 parts of lead powder, 0.01-20 parts of carbon material, 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 while stirring, and add 50-100 parts of deionized water to the premixed powder while stirring, and continue to stir for 1-60 min to obtain lead paste; (2) Scrape the lead paste onto the metallic lead grid, fill the through-holes on the metallic lead grid with the lead paste, and obtain the negative electrode of the lead-carbon battery through curing and drying; the curing temperature is 30 - 50 o °C, the humidity is 70 - 95%, and the curing time is 10 - 30 hours; the drying temperature is 60 - 120 o °C, and the time is 10 - 30 hours; B. Preparation of the positive electrode: Prepare the positive electrode of the lead-acid battery according to the same process steps as in steps (1) and (2) of the negative electrode preparation A above, the difference being that no carbon material is added to the positive electrode; C. After assembling into a lead-carbon battery, the electrolyte added to the lead-carbon battery is a colloidal electrolyte, and its mass concentration is: 1.1 g / ml - 1.4 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances other than the metal lead grid of the negative electrode is 60-120:

50.

5. The application according to claim 4, characterized in that: After being assembled into a lead-carbon battery in Step C, the electrolyte added to the lead-carbon battery is a colloidal electrolyte with a mass concentration of 1.275 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances other than the metallic lead grid in the negative electrode is 83:57.

2.

6. The application according to claim 4, characterized in that: The metallic lead grid has dimensions of 50 - 1000 mm in length, 20 - 80 mm in width, and 0.5 - 4 mm in thickness; The hydroxyapatite separator used has dimensions of 50 - 1000 mm in length, 20 - 80 mm in width, and 0.5 - 4 mm in thickness.

7. The application according to claim 4, wherein: The colloidal electrolyte is a sulfuric acid solution with a mass fraction of fumed silica of 0.01% - 20%.

8. The application according to claim 7, characterized in that: The mass fraction of fumed silica in the colloidal electrolyte is 0.5 - 5%.