A phosphorus-free low-voltage electrolyte and its preparation method

Abstract

The present invention relates to a phosphorus-free low-voltage electrolyte and a preparation method thereof. The phosphorus-free low-voltage electrolyte comprises the following raw materials in parts by weight: 9-15 parts of ethylene glycol, 13-18 parts of ammonium adipate, 0.5-3 parts of ammonium p-nitrobenzoate, 1-3 parts of citric acid, 1-3 parts of ammonium formate, 0.4-8 parts of p-tert-butylcatechol, and 62-68 parts of water. The present invention prepares a phosphorus-free low-voltage electrolyte by combining p-tert-butylcatechol with raw materials such as ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, and ammonium formate. p-tert-butylcatechol can effectively play an anti-corrosion role in a high-water-content electrolyte and can reduce environmental pollution; the prepared phosphorus-free low-voltage electrolyte is a dephosphorized product, is environmentally friendly, and has the advantages of long service life and good use performance. The preparation method of the phosphorus-free low-voltage electrolyte has a simple process, is convenient to operate, has high production efficiency, and the prepared phosphorus-free low-voltage electrolyte product has stable quality, which is conducive to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, and particularly to a phosphorus-free low-voltage electrolyte and a preparation method thereof. Background Art

[0002] At present, aluminum electrolytic capacitors, as an important basic electronic component, are widely used in industries such as computers, automotive electronics, and household appliances. With the development of the economy and the progress of technology, and the continuous improvement of the performance and quality of electronic products, higher requirements are put forward for the performance of aluminum electrolytic capacitors. In the prior art, a certain amount of phosphide is often added to the electrolyte to meet the performance requirements of the product. However, due to the extensive use of phosphides, it is easy to cause a large amount of phosphorus emissions, resulting in environmental pollution such as eutrophication of water bodies, which has a significant impact on the human body and the environment. With the continuous enhancement of people's environmental protection awareness and the increasing attention to environmental protection issues, it is of great significance to develop a phosphorus-free low-voltage electrolyte to reduce environmental pollution and make the product have good durability and service performance. Summary of the Invention

[0003] In order to solve the above deficiencies of the prior art, one of the objectives of the present invention is to provide a phosphorus-free low-voltage electrolyte, which is a dephosphorized product, can reduce environmental pollution, and has the advantages of long service life and good service performance.

[0004] Another objective of the present invention is to provide a preparation method of a phosphorus-free low-voltage electrolyte. The preparation method of the phosphorus-free low-voltage electrolyte has a simple process, convenient operation, high production efficiency, and the quality of the prepared phosphorus-free low-voltage electrolyte product is stable, which is conducive to industrial production.

[0005] The objective of the present invention is achieved by the following technical solutions: A phosphorus-free low-voltage electrolyte, comprising the following raw materials in parts by weight: 9-15 parts of ethylene glycol, 13-18 parts of ammonium adipate, 0.5-3 parts of ammonium p-nitrobenzoate, 1-3 parts of citric acid, 1-3 parts of ammonium formate, 0.4-8 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0006] Further, the phosphorus-free low-voltage electrolyte comprises the following raw materials in parts by weight: 9.5-14 parts of ethylene glycol, 13-18 parts of ammonium adipate, 1-2 parts of ammonium p-nitrobenzoate, 1-3 parts of citric acid, 1-3 parts of ammonium formate, 0.5-5 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0007] Further, the phosphorus-free low-voltage electrolyte comprises the following raw materials in parts by weight: 9.5-12.5 parts of ethylene glycol, 13-18 parts of ammonium adipate, 1-2 parts of ammonium p-nitrobenzoate, 1.5-2.5 parts of citric acid, 1.5-2.5 parts of ammonium formate, 2-5 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0008] The phosphorus-free low-voltage electrolyte of the present invention is a dephosphorized product, which can effectively reduce environmental pollution and has the advantages of long service life and good performance. Among them, the structural formula of p-tert-butylcatechol (TBC) is as follows:

[0009]

[0010] It can be seen from the above molecular structural formula that p-tert-butylcatechol has two adjacent hydroxyl groups, which can form a complex with aluminum ions on the surface of alumina well. And the p-tert-butyl group can shield the contact between water and the oxide film well, thereby playing a good anti-corrosion effect. The present invention creatively adds p-tert-butylcatechol and prepares a phosphorus-free low-voltage electrolyte by combining it with raw materials such as ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, and ammonium formate. It can effectively play an anti-corrosion role in high-water-content electrolytes, reduce environmental pollution, and at the same time make the phosphorus-free low-voltage electrolyte have good performance and durability, with good anti-corrosion effect, achieving better technical effects.

[0011] Another object of the present invention is achieved by the following technical solution: A preparation method of the above phosphorus-free low-voltage electrolyte, comprising the following steps:

[0012] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water in proportion;

[0013] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water evenly to obtain a phosphorus-free low-voltage electrolyte.

[0014] Further, the p-tert-butylcatechol is pretreated before use, and the pretreatment method of the p-tert-butylcatechol comprises the following steps:

[0015] A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1-2:3-4, and heat until the solution is clear;

[0016] A2. Stir the solution obtained in step A1, then cool it, then centrifuge and spin dry, and vacuum dry to obtain pretreated p-tert-butylcatechol.

[0017] Further, in step A1, take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1-2:3-4, stir in a reaction kettle, heat to 75-80 °C until the solution is clear.

[0018] Further, in step A2, stir the solution obtained in step A1 for 20-60 min, then cool to 35-45 °C, then centrifuge and spin dry, and vacuum dry to obtain pretreated p-tert-butylcatechol.

[0019] Further, in step (2), ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, and p-tert-butylcatechol are added to water and stirred evenly at a temperature of 80-92°C to obtain a phosphorus-free low-voltage electrolyte solution.

[0020] The beneficial effects of the present invention are as follows: By combining p-tert-butylcatechol with raw materials such as ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, and ammonium formate, the present invention prepares a phosphorus-free low-voltage electrolyte solution. p-tert-butylcatechol can effectively play an anti-corrosion role in a high-water-content electrolyte solution and can reduce environmental pollution. The prepared phosphorus-free low-voltage electrolyte solution is a dephosphorized product, is environmentally friendly, and has the advantages of a long service life and good use performance. The preparation method of the phosphorus-free low-voltage electrolyte solution has a simple process, is easy to operate, has high production efficiency, and the prepared phosphorus-free low-voltage electrolyte solution product has stable quality, which is conducive to industrial production. Specific Embodiments

[0021] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments. The content mentioned in the embodiments does not limit the present invention.

[0022] In some embodiments of the present invention, a phosphorus-free low-voltage electrolyte solution includes the following raw materials in parts by weight: 9-15 parts of ethylene glycol, 0.5-3 parts of ammonium p-nitrobenzoate, 1-3 parts of citric acid, 1-3 parts of ammonium formate, 0.4-8 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0023] In some embodiments of the present invention, the phosphorus-free low-voltage electrolyte solution includes the following raw materials in parts by weight: 9.5-14 parts of ethylene glycol, 13-18 parts of ammonium adipate, 1-2 parts of ammonium p-nitrobenzoate, 1-3 parts of citric acid, 1-3 parts of ammonium formate, 0.5-5 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0024] In some embodiments of the present invention, the phosphorus-free low-voltage electrolyte solution includes the following raw materials in parts by weight: 9.5-12.5 parts of ethylene glycol, 13-18 parts of ammonium adipate, 1-2 parts of ammonium p-nitrobenzoate, 1.5-2.5 parts of citric acid, 1.5-2.5 parts of ammonium formate, 2-5 parts of p-tert-butylcatechol, and 62-68 parts of water.

[0025] In some embodiments of the present invention, a preparation method of the above phosphorus-free low-voltage electrolyte solution includes the following steps:

[0026] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water in proportion;

[0027] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water evenly to obtain a phosphorus-free low-voltage electrolyte.

[0028] In some embodiments of the present invention, the p-tert-butylcatechol is pretreated before use, and the pretreatment method of the p-tert-butylcatechol includes the following steps:

[0029] A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1-2:3-4, and heat until the solution becomes clear.

[0030] A2. Stir the solution obtained in step A1, then cool it, then centrifuge and spin dry, and vacuum dry to obtain pretreated p-tert-butylcatechol.

[0031] The existing commercially available tert-butylcatechol has a high impurity content. In the present invention, the purchased tert-butylcatechol is purified by the above steps to obtain electronic-grade tert-butylcatechol.

[0032] In some embodiments of the present invention, in step A1, take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1-2:3-4, stir in a reaction kettle, and heat to 75-80 °C until the solution becomes clear.

[0033] In some embodiments of the present invention, in step A2, stir the solution obtained in step A1 for 20-60 min, then cool to 35-45 °C, then centrifuge and spin dry, and vacuum dry to obtain pretreated p-tert-butylcatechol.

[0034] In some embodiments of the present invention, in step (2), add ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, and p-tert-butylcatechol to water, and stir evenly at a temperature of 80-92 °C to obtain a phosphorus-free low-voltage electrolyte.

[0035] Example 1

[0036] In this example, a phosphorus-free low-voltage electrolyte includes the following raw materials in parts by weight: 14 parts of ethylene glycol, 15 parts of ammonium adipate, 1.5 parts of ammonium p-nitrobenzoate, 2 parts of citric acid, 2 parts of ammonium formate, 0.5 part of p-tert-butylcatechol, and 65 parts of water.

[0037] The preparation method of the above phosphorus-free low-voltage electrolyte includes the following steps:

[0038] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water in proportion.

[0039] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water evenly to obtain a phosphorus-free low-voltage electrolyte.

[0040] Further, the p-tert-butylcatechol is pretreated before use, and the pretreatment method of the p-tert-butylcatechol includes the following steps:

[0041] A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 3:7, stir in a reaction kettle, heat to 78 °C until the solution is clear.

[0042] A2. Stir the solution obtained in step A1, then cool it, then centrifuge and spin dry, and dry it under vacuum to obtain pretreated p-tert-butylcatechol.

[0043] Further, in step A2, the solution obtained in step A1 is stirred for 30 min, then quickly cooled to 40 °C, then centrifuged and spin dried, and dried under vacuum to obtain pretreated p-tert-butylcatechol.

[0044] Further, in step (2), add ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol to water, and stir evenly at a temperature of 85 °C to obtain a phosphorus-free low-voltage electrolyte.

[0045] Example 2

[0046] In this example, a phosphorus-free low-voltage electrolyte includes the following raw materials in parts by weight: 13.5 parts of ethylene glycol, 15 parts of ammonium adipate, 1.5 parts of ammonium p-nitrobenzoate, 2 parts of citric acid, 2 parts of ammonium formate, 1 part of p-tert-butylcatechol, and 65 parts of water.

[0047] The preparation method of the above phosphorus-free low-voltage electrolyte includes the following steps:

[0048] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water in proportion;

[0049] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water evenly to obtain a phosphorus-free low-voltage electrolyte.

[0050] Further, the p-tert-butylcatechol is pretreated before use, and the pretreatment method of the p-tert-butylcatechol includes the following steps:

[0051] A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 3:7, stir in a reaction kettle, heat to 78 °C until the solution is clear.

[0052] A2. Stir the solution obtained in step A1, then cool it, followed by centrifugal drying and vacuum drying to obtain pretreated p-tert-butylcatechol.

[0053] Further, in step A2, the solution obtained in step A1 is stirred for 30 min, then rapidly cooled to 40 °C, followed by centrifugal drying and vacuum drying to obtain pretreated p-tert-butylcatechol.

[0054] Further, in step (2), ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, and p-tert-butylcatechol are added to water and stirred evenly at 85 °C to obtain a phosphorus-free low-voltage electrolyte.

[0055] Example 3

[0056] In this example, a phosphorus-free low-voltage electrolyte comprises the following raw materials in parts by weight: 12.5 parts of ethylene glycol, 15 parts of ammonium adipate, 1.5 parts of ammonium p-nitrobenzoate, 2 parts of citric acid, 2 parts of ammonium formate, 2 parts of p-tert-butylcatechol, and 65 parts of water.

[0057] The preparation method of the above phosphorus-free low-voltage electrolyte comprises the following steps:

[0058] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water in proportion.

[0059] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water evenly to obtain a phosphorus-free low-voltage electrolyte.

[0060] Further, the p-tert-butylcatechol is pretreated before use. The pretreatment method of the p-tert-butylcatechol comprises the following steps:

[0061] A1. Take p-tert-butylcatechol and water and mix them evenly at a weight ratio of 3:7, stir in a reaction kettle, and heat to 78 °C until the solution becomes clear.

[0062] A2. Stir the solution obtained in step A1, then cool it, followed by centrifugal drying and vacuum drying to obtain pretreated p-tert-butylcatechol.

[0063] Further, in step A2, the solution obtained in step A1 is stirred for 30 min, then rapidly cooled to 40 °C, followed by centrifugal drying and vacuum drying to obtain pretreated p-tert-butylcatechol.

[0064] Further, in step (2), ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, and p-tert-butylcatechol are added to water and stirred evenly at a temperature of 85 °C to obtain a phosphorus-free low-voltage electrolyte solution.

[0065] Example 4

[0066] In this example, a phosphorus-free low-voltage electrolyte solution comprises the following raw materials in parts by weight: 9.5 parts of ethylene glycol, 15 parts of ammonium adipate, 1.5 parts of ammonium p-nitrobenzoate, 2 parts of citric acid, 2 parts of ammonium formate, 5 parts of p-tert-butylcatechol, and 65 parts of water.

[0067] The preparation method of the above phosphorus-free low-voltage electrolyte solution comprises the following steps:

[0068] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water in proportion;

[0069] (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol, and water evenly to obtain a phosphorus-free low-voltage electrolyte solution.

[0070] Further, the p-tert-butylcatechol is pretreated before use. The pretreatment method of the p-tert-butylcatechol comprises the following steps:

[0071] A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 3:7, stir in a reaction kettle, and heat to 78 °C until the solution becomes clear.

[0072] A2. Stir the solution obtained in step A1, then cool it, then centrifuge and spin-dry it, and dry it under vacuum to obtain pretreated p-tert-butylcatechol.

[0073] Further, in step A2, the solution obtained in step A1 is stirred for 30 min, then rapidly cooled to 40 °C, then centrifuged and spin-dried, and dried under vacuum to obtain pretreated p-tert-butylcatechol.

[0074] Further, in step (2), ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol are added to water and stirred evenly at a temperature of 85 °C to obtain a phosphorus-free low-voltage electrolyte solution.

[0075] Comparative Example 1

[0076] In this example, a low-voltage electrolyte solution comprises the following raw materials in parts by weight: 12.5 parts of ethylene glycol, 15 parts of ammonium adipate, 1.5 parts of ammonium p-nitrobenzoate, 2 parts of citric acid, 2 parts of ammonium formate, 2 parts of phosphoric acid, and 65 parts of water.

[0077] The preparation method of the above low-voltage electrolyte comprises the following steps:

[0078] (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, phosphoric acid and water in proportion;

[0079] (2) Add ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate and phosphoric acid to water, and stir evenly at 85°C to obtain a phosphorus-free low-voltage electrolyte.

[0080] The raw material ratios and conductivities of the phosphorus-free low-voltage electrolytes of Examples 1-4 and the phosphorus-containing low-voltage electrolyte of Comparative Example 1 are shown in Table 1 below:

[0081]

[0082] Among them, the test method for conductivity comprises the following steps: Turn on the switch of the DDSJ-308A instrument, and calibrate the instrument with the HANAHI7030 standard solution; Take a beaker that has been washed and dried with pure water, take 100 mL of the sample to be tested, and keep it at a constant temperature of 30±1°C; Clean the test electrode and thermometer with pure water and dry them with filter paper; Put the measuring electrode and thermometer into the sample to be tested. When the temperature is 30°C, the value displayed by the instrument is the conductivity of the solution to be tested; After the test is completed, turn off the power supply, wash the thermometer and electrode rod with pure water, and store the electrode in the protection bottle.

[0083] The phosphorus-free low-voltage electrolytes of Examples 1-4 and the phosphorus-containing low-voltage electrolyte of Comparative Example 1 are respectively made into aluminum electrolytic capacitors with the model of 220 μF / 25V, 08*12, and the performance of the capacitors is measured with reference to GB / T 5993-2003. After multiple measurements and taking the average value, the test data of 110°C 2000h load are shown in Table 2 below:

[0084]

[0085] Among them: The service life of the electrolytic capacitor is represented by the capacity difference (ΔC / C0) and the tangent value of the loss angle (DF) before and after the test. ΔC / C0 = (capacitance capacity after the test - capacitance capacity before the test) / capacitance capacity before the test. The smaller ΔC / C0 is, the smaller the capacity attenuation is; DF = ESR×W×C, where ESR is the equivalent series resistance, W = 2πf, f is the frequency of the AC power supply, and C is the capacitance capacity. The smaller the tangent value of the loss angle is, the less heat the capacitor generates. The judgment standard for passing is: ΔC / C < ±20%, DF < 12%, LC (leakage current) < 250 μA, Appearance: No abnormality.

[0086] As can be seen from the above table, the phosphorus-free low-voltage electrolyte in Embodiments 1-4 of the present invention is a dephosphorized product, which has good conductivity. While effectively reducing environmental pollution, the aluminum electrolytic capacitors prepared have a small capacity attenuation, a long service life and good performance. Among them, in Embodiments 3-4, by optimizing the dosage ratio of each raw material, compared with Comparative Example 1, not only can the phosphorus emission be reduced, but also the capacity attenuation of the capacitor is smaller, and it has more excellent durability.

[0087] For the aluminum electrolytic capacitors made of the phosphorus-free low-voltage electrolyte in Embodiments 1-4 and the phosphorus-containing low-voltage electrolyte in Comparative Example 1, the high-temperature storage performance parameters at 110 °C were measured, and the test data are shown in Table 3 below:

[0088]

[0089] The above specific embodiments further illustrate the technical solutions and beneficial effects of the present invention, and do not limit the implementation manners. For those skilled in the art, any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A non-phosphorus low-voltage electrolyte, characterized in that: It comprises the following raw materials in parts by weight: 9 - 15 parts of ethylene glycol, 13 - 18 parts of ammonium adipate, 0.5 - 3 parts of ammonium p-nitrobenzoate, 1 - 3 parts of citric acid, 1 - 3 parts of ammonium formate, 0.4 - 8 parts of p-tert-butylcatechol, and 62 - 68 parts of water; the p-tert-butylcatechol is pretreated before use, and the pretreatment method of the p-tert-butylcatechol comprises the following steps: A1. Take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1 - 2:3 - 4, and heat until the solution is clear; A2. Stir the solution obtained in step A1, then cool it, and then centrifuge and spin-dry it, and dry it under vacuum to obtain pretreated p-tert-butylcatechol; In step A1, take p-tert-butylcatechol and water and mix them evenly according to a weight ratio of 1 - 2:3 - 4, stir in a reaction kettle, and heat to 75 - 80 °C until the solution is clear.

2. The phosphorus-free low-voltage electrolyte according to claim 1, characterized in that: It comprises the following raw materials in parts by weight: 9.5 - 14 parts of ethylene glycol, 13 - 18 parts of ammonium adipate, 1 - 2 parts of ammonium p-nitrobenzoate, 1 - 3 parts of citric acid, 1 - 3 parts of ammonium formate, 0.5 - 5 parts of p-tert-butylcatechol, and 62 - 68 parts of water.

3. The phosphorus-free low-voltage electrolyte according to claim 1, characterized in that: It comprises the following raw materials in parts by weight: 9.5 - 12.5 parts of ethylene glycol, 13 - 18 parts of ammonium adipate, 1 - 2 parts of ammonium p-nitrobenzoate, 1.5 - 2.5 parts of citric acid, 1.5 - 2.5 parts of ammonium formate, 2 - 5 parts of p-tert-butylcatechol, and 62 - 68 parts of water.

4. The phosphorus-free low-voltage electrolyte according to claim 1, wherein: In step A2, stir the solution obtained in step A1 for 20 - 60 min, then cool it to 35 - 45 °C, and then centrifuge and spin-dry it, and dry it under vacuum to obtain pretreated p-tert-butylcatechol.

5. A method for preparing a phosphorus-free low-voltage electrolyte according to any one of claims 1-4, characterized in that: It comprises the following steps: (1) Take ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water in proportion; (2) Mix ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol and water evenly to obtain a phosphorus-free low-voltage electrolyte.

6. The preparation method of the phosphorus-free low-voltage electrolyte according to claim 5, wherein: In step (2), add ethylene glycol, ammonium adipate, ammonium p-nitrobenzoate, citric acid, ammonium formate, p-tert-butylcatechol into water, and stir evenly at a temperature of 80 - 92 °C to obtain a phosphorus-free low-voltage electrolyte.

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