A high-oxidation-degree silver oxide electrode, its preparation method and application

Abstract

The present invention discloses a high-oxidation silver oxide electrode, and its preparation method and application. The oxidation degree of the high-oxidation silver oxide electrode is ≥85%. The preparation method of the high-oxidation silver oxide electrode comprises the following steps: uniformly mixing solid alkali powder with silver powder to obtain mixed silver powder; pressing the mixed silver powder into silver sheets; chemically forming the silver sheets, and then washing and drying them to obtain high-oxidation silver oxide electrodes. The oxidation degree of the silver oxide electrode of the present invention is higher than that of traditional silver oxide electrodes; the method of the present invention has the advantages of low cost, simple and controllable process, and easier mass production; the high-oxidation silver oxide electrode of the present invention is applied to batteries, which prolongs the discharge time of the battery and increases the battery capacity.

Description

Technical Field

[0001] This invention relates to the field of electrode technology, and in particular to a high-oxidation-degree silver oxide electrode, its preparation method, and its application. Background Technology

[0002] Silver oxide electrodes are characterized by high specific energy and high specific power. They are typically used in conjunction with metal anodes such as zinc, cadmium, iron, aluminum, or lithium to form primary or secondary batteries. The electrolyte is generally an alkaline aqueous solution, with zinc-silver batteries being the most widely used. Zinc-silver batteries were initially used in underwater equipment, and their applications have since expanded to include underwater vehicles, buoys, and special test vessels. They also have numerous space applications such as spacecraft launches, missile control, remote sensing, and self-destruct power supplies.

[0003] The positive electrode active material in silver oxide electrodes mainly consists of divalent silver oxide (AgO) and monovalent silver oxide (Ag₂O). The properties of these oxides determine the characteristics of the silver electrode. AgO (0.43 Ah / g) has a specific capacity nearly twice that of Ag₂O (0.23 Ah / g). The specific resistivity of divalent silver AgO is 10~15 Ω·cm, while that of Ag₂O is approximately 10⁸ Ω·cm. Therefore, the higher the content of divalent silver oxide (AgO) in the silver oxide electrode, the higher the discharge capacity and the lower the internal resistance of the battery. The mass percentage of divalent silver oxide (AgO) in the silver oxide electrode is usually expressed as the degree of oxidation, measured using the iodometric method. Currently, silver oxide electrodes are generally prepared using a process of silver powder pressing and formation, with an oxidation degree of approximately 80%.

[0004] Therefore, it is urgent to optimize the preparation process of silver oxide electrodes in order to obtain silver oxide electrodes with high oxidation degree. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and to propose a high-oxidation-degree silver oxide electrode, its preparation method and application, thereby solving the technical problem of low oxidation degree of silver oxide electrodes in the prior art.

[0006] In a first aspect, the present invention provides a high-oxidation-degree silver oxide electrode sheet, wherein the oxidation degree of the high-oxidation-degree silver oxide electrode sheet is ≥85%.

[0007] Secondly, the present invention provides a method for preparing a high-oxidation-degree silver oxide electrode, comprising the following steps:

[0008] Solid alkali powder and silver powder are mixed evenly to obtain mixed silver powder;

[0009] The mixed silver powder is pressed into silver sheets;

[0010] The silver sheet is chemically transformed, then washed and dried to obtain a high-oxidation-degree silver oxide electrode sheet.

[0011] Thirdly, the present invention provides the application of the above-mentioned high-oxidation-degree silver oxide electrode sheet as the positive electrode of a battery.

[0012] Compared with the prior art, the beneficial effects of the present invention include:

[0013] The silver oxide electrode of the present invention has a higher degree of oxidation than that of traditional silver oxide electrodes; the method of the present invention has the advantages of low cost, simple and controllable process, and easy mass production; the high degree of oxidation silver oxide electrode of the present invention, when applied to batteries, extends the discharge time of the battery and improves the battery capacity. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of one embodiment of the preparation method of high-oxidation-degree silver oxide electrode provided by the present invention;

[0015] Figure 2 These are the discharge curves of batteries assembled from silver oxide electrode sheets prepared in Examples 1-5 and Comparative Example 1 of this invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] In a first aspect, the present invention provides a high degree of oxidation silver oxide electrode, wherein the degree of oxidation of the high degree of oxidation silver oxide electrode is ≥85%, preferably ≥88%.

[0018] Please see Figure 1 Secondly, the present invention provides a method for preparing a high-oxidation-degree silver oxide electrode, comprising the following steps:

[0019] S1. Mix the solid alkali powder and silver powder evenly to obtain mixed silver powder;

[0020] S2. Press the mixed silver powder into silver sheets;

[0021] S3. The silver sheet is chemically converted, and then washed and dried to obtain a high-oxidation-degree silver oxide electrode sheet.

[0022] This invention involves uniformly mixing solid alkali powder and silver powder, pressing the mixture into silver sheets, and then forming the silver sheets to obtain a high-oxidation-degree silver oxide electrode. Because the silver sheets contain solid alkali powder, during formation, the silver sheets are immersed in an alkaline solution. The solid alkali powder gradually dissolves, forming a continuous micron-level three-dimensional channel structure within the silver sheet. This facilitates thorough wetting of the alkaline solution during the formation and charging process. Simultaneously, the dissolution of the solid alkali powder maintains a high local alkali concentration on the electrode. The dissolution process releases heat, raising the electrode temperature. Both the high alkali concentration and the electrode temperature are beneficial for silver oxidation, ultimately resulting in a high-oxidation-degree silver oxide electrode. This method has the advantages of low cost, simple and controllable process, and ease of mass production. The prepared silver oxide electrode has a high oxidation degree, improving the battery's discharge capacity.

[0023] In this embodiment, in step S1, the solid alkali powder is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0024] In this embodiment, in step S1, the D50 particle size of the solid alkali powder is 4-15 μm, including but not limited to 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm. This invention controls the particle size of the solid alkali powder within the aforementioned micron-level range, facilitating the formation of a micron-level three-dimensional pore structure during the deposition process of the pressed electrode, which is beneficial for the wetting of the electrode. If the solid alkali powder particles are too large, the internal structure of the electrode will be too loose after dissolution, resulting in low mechanical strength. If the solid alkali powder particles are too small, the pore structure formed after dissolution will be small, which is not conducive to the wetting of the electrode.

[0025] In some specific embodiments of the present invention, in step S1, the solid alkali powder is obtained by crushing and sieving the solid alkali.

[0026] In this embodiment, in step S1, the D50 particle size of the silver powder is 5-100 μm, including but not limited to 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, and 100 μm. By controlling the particle size of the silver powder within this range, this invention facilitates the pressing and formation of the electrode. If the particle size of the silver powder is too high, the specific surface area will be too low, which is not conducive to the full reaction of the active material during formation and electrochemical reactions. If the particle size of the silver powder is too low, the porosity of the electrode (the ratio of the internal pore volume to the three-dimensional volume of the electrode) will be too low, which is not conducive to the entry of the electrolyte into the electrode during formation and electrochemical reactions.

[0027] In this embodiment, in step S1, the solid alkali powder accounts for 10%-20% of the mass of the mixed silver powder. By controlling the proportion of solid alkali powder within this range, the present invention facilitates the formation of continuous channels inside the electrode during formation, while not affecting the mechanical strength of the electrode. If the proportion of solid alkali powder is too high, the silver powder structure will be loose, and the silver sheet will lack structural support after the alkali particles dissolve, resulting in reduced mechanical strength. If the proportion of solid alkali powder is too low, the solid alkali powder will not be able to form three-dimensional continuous channels inside the electrode after dissolving, resulting in poor formation effect.

[0028] In this embodiment, step S2, the pressing process includes: spreading the mixed silver powder and current collector into the pressing mold, and pressing it into a silver sheet under pressure.

[0029] The current collector is a silver mesh with a mesh count of 5-20, including but not limited to 5, 10, 15, and 20 meshes, and a thickness of 0.05-0.5 mm, including but not limited to 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, and 0.5 mm.

[0030] In this embodiment, during step S2, the molding pressure is 5-20 MPa, including but not limited to 5 MPa, 7 MPa, 9 MPa, 11 MPa, 13 MPa, 15 MPa, 17 MPa, 19 MPa, 20 MPa, etc.; the holding time is 1-10 s, including but not limited to 1 s, 3 s, 5 s, 7 s, 9 s, 10 s, etc.

[0031] In this embodiment, in step S2, the thickness of the silver sheet is 0.5-2.5mm, including but not limited to 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, etc.

[0032] In this embodiment, steps S1 and S2 must be performed in an environment with humidity ≤10%.

[0033] In this embodiment, during step S3, the electrolyte is at least one of sodium hydroxide solution or potassium hydroxide solution.

[0034] Furthermore, the concentration of the electrolyte is 1-10 mol / L, including but not limited to 1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, etc.

[0035] In this embodiment, during step S3, the auxiliary electrode is a stainless steel sheet.

[0036] In this embodiment, during step S3, the charging current is 0.5-5A, including but not limited to 0.5A, 1A, 2A, 3A, 4A, 5A, etc., and the charging time is 12-72h, including but not limited to 12h, 24h, 36h, 48h, 60h, 72h, etc.

[0037] In some specific embodiments of the present invention, in step S3, during the formation process, the device is first charged with a current of 2-4A for 8-12 hours, then charged with a current of 1-2A for 16-20 hours, and finally charged with a current of 0.5-2A for 22-26 hours.

[0038] In this embodiment, in step S3, during the formation process, a silver sheet is used as the anode and an auxiliary electrode is used as the cathode, separated by a separator, to assemble a formation battery. After injecting electrolyte, the battery is charged and formed.

[0039] Thirdly, the present invention provides the application of the above-mentioned high-oxidation-degree silver oxide electrode sheet as the positive electrode of a battery.

[0040] In this embodiment, the battery includes a zinc-silver battery, a cadmium-silver battery, an iron-silver battery, an aluminum-silver battery, or a lithium-silver battery.

[0041] Example 1

[0042] The method for preparing a high-oxidation-degree silver oxide electrode provided in this embodiment includes the following steps:

[0043] (1) Preparation of micron-sized NaOH powder: In a drying room with humidity ≤10%, weigh 500g of NaOH granular alkali for later use. Pour the weighed NaOH granular alkali into a pulverizer, turn on the pulverizer to pulverize, and finally obtain micron-sized NaOH powder with a D50 particle size of 10.9μm;

[0044] (2) Mixing micron-sized NaOH powder with silver powder: In a drying room with humidity ≤10%, weigh 500g of the prepared micron-sized NaOH powder and 4.5kg of silver powder (D50=12.8μm), pour them into a mixer, and mix for 20min;

[0045] (3) Silver sheet pressing: In a drying room with humidity ≤10%, place a collecting mesh (silver mesh with a mesh size of 10 and a thickness of 0.1mm) in the pressing mold, weigh 100g of mixed silver powder and pour it into the pressing mold, spread the powder evenly, cover the mold, set the pressure to 7Mpa and press for 5s to obtain silver sheet;

[0046] (4) Silver sheet formation: 10 silver sheet electrodes obtained by molding are connected in series with 10 stainless steel sheets, separated by a nylon mesh, and immersed in 6 mol / L KOH solution. Positive and negative charging cables are connected to both ends respectively, and the electrodes are charged according to the charging program of 3A / 10h+1.5A / 18h+1A / 24h. After charging is completed, the electrodes are washed and dried to obtain high-oxidation silver oxide electrodes.

[0047] Example 2

[0048] The method for preparing a high-oxidation-degree silver oxide electrode provided in this embodiment includes the following steps:

[0049] (1) Preparation of micron-sized NaOH powder: 750g of NaOH granular alkali was weighed in a drying room with humidity ≤10%. The weighed NaOH granular alkali was poured into a pulverizer and pulverized. The final micron-sized NaOH powder had a D50 particle size of 7.4μm.

[0050] (2) Mixing micron-sized NaOH powder with silver powder: In a drying room with humidity ≤10%, weigh 750g of the prepared micron-sized NaOH powder and 4.25kg of silver powder (D50=12.8μm), pour them into a mixer, and mix for 20min;

[0051] (3) Silver sheet pressing: In a drying room with humidity ≤10%, place a collecting mesh (silver mesh with a mesh size of 10 and a thickness of 0.1mm) in the pressing mold, weigh 105.9g of mixed silver powder and pour it into the pressing mold, spread the powder evenly, cover it with a cover plate, set the pressure to 10Mpa for pressing, hold the pressure for 5s, and obtain silver sheet;

[0052] (4) Silver sheet formation: 10 silver sheet electrodes obtained by molding are connected in series with 10 stainless steel sheets, separated by a nylon mesh, and immersed in 6 mol / L KOH solution. Positive and negative charging cables are connected to both ends respectively, and the electrodes are charged according to the charging program of 3A / 10h+1.5A / 18h+1A / 24h. After charging is completed, the electrodes are washed and dried to obtain high-oxidation silver oxide electrodes.

[0053] Example 3

[0054] The method for preparing a high-oxidation-degree silver oxide electrode provided in this embodiment includes the following steps:

[0055] (1) Preparation of micron-sized NaOH powder: In a drying room with humidity ≤10%, weigh 1000g of NaOH granular alkali for later use. Pour the weighed NaOH granular alkali into a pulverizer, turn on the pulverizer to pulverize, and finally obtain micron-sized NaOH powder with a D50 particle size of 4.9μm;

[0056] (2) Mixing micron-sized NaOH powder with silver powder: In a drying room with humidity ≤10%, weigh 1000g of the prepared micron-sized NaOH powder and 4kg of silver powder (D50=12.8μm), pour them into a mixer, and mix for 20min;

[0057] (3) Silver sheet pressing: In a drying room with humidity ≤10%, place a collecting mesh (silver mesh with a mesh size of 10 and a thickness of 0.1mm) in the pressing mold, weigh 112.5g of mixed silver powder and pour it into the pressing mold, spread the powder evenly, cover the mold, set the pressure to 13Mpa and press for 5s to obtain silver sheet;

[0058] (4) Silver sheet formation: 10 silver sheet electrodes obtained by molding are connected in series with 10 stainless steel sheets, separated by a nylon mesh, and immersed in 6 mol / L KOH solution. Positive and negative charging cables are connected to both ends respectively, and the electrodes are charged according to the charging program of 3A / 10h+1.5A / 18h+1A / 24h. After charging is completed, the electrodes are washed and dried to obtain high-oxidation silver oxide electrodes.

[0059] Example 4

[0060] Compared with Example 1, the only difference is that the proportion of micron-sized NaOH powder to the mixed silver powder is 25%. All other specific parameters and conditions are the same as in Example 1.

[0061] Example 5

[0062] Compared to Example 1, the only difference is that the final obtained micron-sized NaOH powder has a D50 particle size of 1.1 μm. All other specific parameters and conditions are the same as in Example 1.

[0063] Comparative Example 1

[0064] Compared with Example 1, the only difference is that silver powder is directly pressed into an electrode sheet and then subjected to chemical formation to obtain a silver oxide electrode sheet. All other specific parameters and conditions are the same as in Example 1.

[0065] Comparative Example 2

[0066] Compared to Example 1, the only difference is that the NaOH granules were not pulverized but directly mixed with silver powder, and the mixed silver powder was pressed into an electrode sheet. All other specific parameters and conditions are the same as in Example 1.

[0067] The results showed that the undiluted NaOH particles had a particle size of 1-10 mm and could not be molded when mixed with silver powder and pressed.

[0068] Performance testing:

[0069] Oxidation degree test: The oxidation degree of the electrode was measured by iodometric titration. The test results are shown in Table 1.

[0070] Electrochemical performance testing: A single-cell battery was assembled using a silver oxide electrode as the positive electrode and a zinc sheet of the same shape as the negative electrode, with cotton paper placed in between as a separator. The battery was housed in a nylon battery case. The electrolyte was a 6 mol / L KOH solution. Constant current discharge was performed at 50 A. The discharge curves are shown below. Figure 1 The discharge time is shown in Table 1.

[0071] Table 1. Oxidation degree and discharge results of silver oxide electrodes in different embodiments and comparative examples.

[0072]

[0073] Through Table 1 and Figure 1 It can be seen that the degree of oxidation of the silver oxide electrodes prepared in Examples 1-3 is higher than that of the traditional silver oxide electrodes. Furthermore, due to the increase in the degree of oxidation, the capacity of the positive electrode is also increased accordingly. Under the same discharge conditions, the discharge time of the silver oxide electrodes in Examples 1-3 is longer than that of the traditional silver oxide electrodes.

[0074] Compared with Example 1, Comparative Example 1 did not add micron-sized NaOH powder, and the oxidation degree and discharge time of the prepared silver oxide electrode were significantly lower than those of the silver oxide electrode in Example 1. The reason is that no micron-sized NaOH powder was added in Comparative Example 1, so the heat released by the dissolution of the micron-sized NaOH powder in the mixed silver powder and the high local alkali concentration generated could not be used to promote the oxidation of the silver sheet during the formation process.

[0075] Compared with Example 1, Example 4 added too much micron-sized NaOH powder alkali, and the oxidation degree of the prepared silver oxide electrode was slightly higher than that of the silver oxide electrode in Example 1. However, the discharge time was shorter than that of the silver oxide electrode in Example 1. The reason is that due to the high proportion of alkali particles, the silver sheet lacks structural support after dissolution, and the mechanical strength is reduced. During the discharge process, the electrode with low mechanical strength is soaked in alkali solution and chemically reacted, and the surface of the electrode will peel off and break, which will cause the electrode voltage to fluctuate and drop prematurely at the end of the discharge.

[0076] Compared with Example 1, the D50 particle size of the micron-sized NaOH powder alkali in Example 5 is too small. The oxidation degree and discharge time of the prepared silver oxide electrode are lower than those of the silver oxide electrode in Example 1. The reason is that the NaOH powder particle size is too small. Some of the smaller NaOH powder particles fill the gaps between the silver powder particles. After the alkali particles dissolve in the alkali, the three-dimensional channels formed inside are discontinuous, resulting in poor formation effect. The oxidation degree is lower than that of the electrode in Example 1, and the discharge time of the single cell is also shorter than that of the silver oxide electrode in Example 1.

[0077] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-oxidation-degree silver oxide electrode, characterized in that, Includes the following steps: Solid alkali powder and silver powder are mixed evenly to obtain mixed silver powder; The mixed silver powder is pressed into silver sheets; The silver sheet is subjected to oxidation, followed by washing and drying to obtain a high-oxidation-degree silver oxide electrode sheet; wherein, The oxidation degree of the high-oxidation-degree silver oxide electrode is ≥85%.

2. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, The solid alkali powder is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

3. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, The solid alkali powder has a D50 particle size of 4-15 μm.

4. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, The D50 particle size of the silver powder is 5-100 μm.

5. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, The solid alkali powder accounts for 10%-20% of the mass of the mixed silver powder.

6. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, The pressing process includes: spreading the mixed silver powder and current collector into a pressing mold, and pressing it under pressure to form a silver sheet; wherein... The current collector is a silver mesh, and the mesh size of the silver mesh is 5-20 mesh, and the thickness of the silver mesh is 0.05-0.5 mm; and / or, During the pressing process, the molding pressure is 5-20 MPa, and the holding time is 1-10 s; and / or, The thickness of the silver sheet is 0.5-2.5 mm.

7. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, During the formation process, the electrolyte is at least one of sodium hydroxide solution or potassium hydroxide solution; and / or, The electrolyte concentration is 1-10 mol / L; and / or, The auxiliary electrode is a stainless steel sheet.

8. The method for preparing a high-oxidation-degree silver oxide electrode according to claim 1, characterized in that, During the formation process, the charging current is 0.5-5A and the charging time is 12-72h.

9. A high-oxidation-degree silver oxide electrode, characterized in that, The high-oxidation-degree silver oxide electrode sheet is obtained by the preparation method of the high-oxidation-degree silver oxide electrode sheet according to any one of claims 1 to 8; wherein, The oxidation degree of the high-oxidation-degree silver oxide electrode is ≥85%.

10. An application of the high-oxidation-degree silver oxide electrode sheet as described in claim 9 as a positive electrode of a battery.

Images