AgO / Ag composite material and in-situ generation method thereof

Abstract

The invention discloses an AgO / Ag composite material and an in-situ generation method thereof, and belongs to the technical field of electrode materials of new energy solid fuel cells. The preparation method comprises the following steps: mixing silver powder and a pore-forming agent, filling a mold, applying pressure to obtain a silver electrode, sintering the obtained silver electrode in a reducing atmosphere, carrying out heat treatment annealing to obtain a porous silver electrode, pretreating the obtained porous silver electrode, carrying out multi-step charging under different current densities, and finally obtaining the porous silver electrode. And then cyclic charging and discharging are carried out for 1000-5000 times, and a part of Ag can be directly converted into AgO, so that the in-situ generated AgO / Ag composite electrode material is obtained. By controlling electrochemical reaction parameters, generation of Ag2O is reduced, the generation rate of AgO is increased, and the discharge performance of the AgO / Ag composite material electrode is integrally improved. The method is high in generation rate and short in technological process.

Description

Technical Field

[0001] The present invention relates to an AgO / Ag composite material and an in-situ generation method thereof, belonging to the technical field of electrode materials for new energy solid fuel cells. Background Art

[0002] Fuel cells are new power sources that have developed rapidly in the field of new energy in recent years. Among them, the electrochemical reaction of highly active solid electrode materials is used to convert chemical energy into electrical energy, and new electrode materials with excellent discharge service performance need to be vigorously developed. Among them, silver-based materials represented by silver oxide are often used as the positive electrode materials of batteries and are widely used in traditional zinc-silver batteries, aluminum-silver batteries, and new metal lithium-silver batteries. However, the purity of silver-based electrode materials themselves, the conversion rate of the preparation process, the stability of the discharge performance, and the relatively high price cost have become important bottlenecks restricting the use of silver-based materials as battery electrode materials, so the electrode materials prepared by them are often used in specific application scenarios such as aerospace and military fields. How to prepare silver-based electrode materials with high catalytic activity, improve their electrochemical performance during battery discharge, improve the utilization rate of silver-based electrode materials, and thus achieve the improvement of the cost performance of silver-based electrode materials, so that they can be more widely used, is a key battery material preparation technology.

[0003] Typical silver-based electrode materials include two materials, silver oxide (Ag2O) and silver peroxide (AgO). Compared with the two, AgO has the advantage of better electrical conductivity because its resistivity (about 10 -1 Ωm) is much lower than that of Ag2O (about 10 6 Ωm) by many orders of magnitude. At the same time, the specific capacity value (0.43 Ah / g) of AgO as a discharge active material to release electric charge is nearly twice higher than that of Ag2O (0.23 Ah / g), which can effectively improve the performance of battery electrode materials to have higher electric charge per unit weight. Therefore, in the process of preparing silver-based electrode materials, how to control the generation of silver-based oxide AgO through different preparation methods and reduce the adverse effects of Ag2O has important practical application value for improving the discharge service performance of electrode materials.

[0004] Chinese Patent (Publication No. CN102945957A) discloses a preparation method of a spiky silver peroxide positive electrode material. This method specifically controls the morphology of the AgO electrode material. By placing silver powder soaked in an inducer solution in an alkaline solution for electrochemical oxidation and then washing and drying, a spiky AgO positive electrode material is obtained. The spiky AgO positive electrode material prepared by this method has consistent spiky directions and regular morphology, and the ion migration rate in the reaction is increased during discharge, thus realizing the improvement of the performance of AgO. However, the conversion rate of the AgO material obtained by this method is limited, the generation of Ag2O cannot be controlled during the conversion process, and it also needs to be specifically made into an electrode with a current collector before it can be used.

[0005] Chinese Patent (Publication No. CN114620690A) discloses a preparation method of silver peroxide cathode material for water-activated batteries. In this method, solutions of sodium persulfate and sodium hydroxide with prepared concentrations are added to an aqueous solution mixed with nano-silver powder at appropriate temperatures, titration rates, etc. High-purity AgO powder is obtained through chemical reactions in the aqueous solution. Then, the AgO powder is mixed with a binder, a conductive agent, etc. and pressed into an AgO cathode material. The purity of the AgO material obtained by this method reaches 90% - 99.5%, which is very high, and the formation efficiency of AgO is high. However, this method only prepares AgO powder, and appropriate technologies need to be developed to make an AgO electrode for application. Summary of the Invention

[0006] Aiming at the problems existing in the above-mentioned prior art, one of the purposes of the present invention is to provide an in-situ generation method of AgO / Ag composite materials. By controlling the electro-chemical reaction parameters, the present invention reduces the formation of Ag2O and increases the formation rate of AgO. After obtaining the AgO / Ag composite material electrode, the conductivity of the electrode is increased by Ag, and the internal resistance of the electrode is reduced; the pre-discharge volume shrinkage of AgO forms pores to guide the infiltration of the electrolyte and fully react with active AgO, thereby overall improving the discharge performance of the AgO / Ag composite material electrode. The method of the present invention has precise control over the reaction product AgO, high formation rate, and short process flow, and is suitable for directly preparing AgO / Ag composite material electrodes with high chemical activity.

[0007] Another purpose of the present invention is to provide an AgO / Ag composite electrode material with high chemical activity.

[0008] To achieve the above purposes, the first aspect of the present invention is to provide an in-situ generation method of AgO / Ag composite materials, which includes:

[0009] (1) Silver powder loading into the mold: The silver powder is mixed with a pore-forming agent to obtain a mixed silver powder, and the mixed silver powder and a powder skeleton made of silver mesh or silver-plated copper mesh are jointly laid in a mold to obtain Intermediate I;

[0010] (2) Sintering and heat treatment annealing: In a reducing atmosphere, the Intermediate I is sequentially subjected to hot pressing sintering and heat treatment annealing to obtain a porous silver electrode; the reducing atmosphere is a mixed gas of CO and CO2;

[0011] (3) Electrolytic pretreatment of the porous silver electrode: The auxiliary electrode and the porous silver electrode are placed in an electrolyte for soaking treatment. The auxiliary electrodes are placed on both sides of the porous silver electrode, and the distance between the auxiliary electrode and the porous silver electrode is 1 mm - 10 mm;

[0012] (4) Electrolysis: using the first current density A1 mA / cm 2 After the charging capacity reaches B1% of the theoretical capacity of the silver positive electrode material, the charging is continued at the second current density A2 mA / cm 2 After the charging capacity reaches B2% of the theoretical capacity of the silver positive electrode material, the third current density A3 mA / cm 2 After the charging capacity reaches B3% of the theoretical capacity of the silver positive electrode material, the fourth current density A4 mA / cm 2 Charging is performed so that the charging amount reaches B4% of the theoretical capacity of the silver positive electrode material;

[0013] And 30≤A1≤50, 15≤A2≤25, 8≤A3<15, 3≤A4≤6, 10≤B1<20, 20≤B2<40, 40≤B3<50, 50≤B4≤60;

[0014] (5) Electrode charge and discharge cycle: using the fifth current density A5 mA / cm 2 The silver electrode material is charged for 5 to 10 seconds and then charged at a sixth current density of A6 mA / cm 2 Discharging the silver electrode material for 1 to 5 seconds, and repeating step (5) 1000 to 5000 times to obtain an AgO / Ag composite electrode; and 3≤A5≤6, 1≤A6<3;

[0015] (6) Cleaning and drying the AgO / Ag composite electrode to obtain an in-situ generated AgO / Ag composite electrode material.

[0016] The present invention uses Ag powder as a raw material for preparing the positive electrode material of the AgO battery, and also uses the high conductivity of the Ag powder and the prepared catalytically active AgO to obtain the AgO / Ag composite electrode material, wherein AgO becomes the positive electrode material of the battery to participate in the discharge reaction, and Ag plays the role of current collection and conduction to lead out the current generated by the discharge reaction of AgO. In order to realize the combined role of the above-mentioned AgO / Ag composite electrode material participating in the discharge reaction and current collection and conduction, it is necessary to fully and completely combine AgO and Ag, and the method provided by the present invention can achieve the full combination of the above-mentioned two materials.

[0017] The present invention obtains a silver electrode by mixing silver powder and a pore-forming agent, molding the mixture, and applying pressure thereto, and sintering and heat-treating the obtained silver electrode in a reducing atmosphere to obtain a porous silver electrode. The obtained porous silver electrode is pretreated, multi-step charged at current densities of different magnitudes, and then cyclically charged and discharged for 1000 to 5000 times, so that a part of Ag can be directly converted into AgO, thereby obtaining an AgO / Ag composite electrode material.

[0018] The inventors found that introducing a reducing gas can, firstly, prevent the conversion of Ag into Ag2O and, secondly, carry away the gas generated by the volatilization of the pore-forming agent. Performing multi-step charging at different current densities is beneficial to improving the conversion efficiency of Ag to AgO and controlling the conversion amount of AgO, thereby effectively regulating the ratio of AgO to Ag. Through the cycle of charge and discharge, the high potential plateau during electrode discharge can be eliminated, enabling the conversion of Ag2O with low catalytic activity generated during the electrolysis reaction into AgO, and improving the overall yield of AgO.

[0019] The preparation method provided by the present invention generates AgO in situ from Ag, without the need to add additional additives, and the process parameters are controllable, suitable for continuous production. By precisely controlling the electrochemical parameters, the problem of high plateau potential for Ag to generate AgO instead of Ag2O can be effectively solved, thereby obtaining AgO with higher purity and conversion rate, and also making the utilization rate of the AgO positive electrode material with catalytic activity in the entire battery electrode material higher.

[0020] As a preferred embodiment, the purity of the silver powder is not less than 99.0 wt%, and the particle size is 50 nm to 50 μm.

[0021] As a preferred embodiment, the reducing atmosphere is a mixed gas of CO and CO2 with a volume ratio of 1:0.7 to 1.

[0022] As a preferred embodiment, the flow rate of the introduced reducing atmosphere is 1000 to 1200 mL / min.

[0023] As a preferred embodiment, the porosity of the porous silver electrode is 40 to 90%.

[0024] As a preferred embodiment, the thickness of the porous silver electrode is 0.1 to 2 mm.

[0025] As a preferred embodiment, based on the total volume of the silver powder and the pore-forming agent, the volume dosage of the pore-forming agent is 10% to 60%.

[0026] As a preferred embodiment, the pore-forming agent is carbamide. The inventors found that under this preferred condition, the prepared porous silver electrode has a higher porosity and low cost, suitable for industrial application.

[0027] As a preferred embodiment, the conditions for hot press sintering include: temperature of 600 to 900 °C, pressure of 25 to 50 MPa, and time of 3 to 15 min. Under this preferred condition, not only can the preparation time be shortened and the process be optimized, but also the growth of silver powder particles and silver grains at high temperature can be reduced, thereby maintaining a fine microstructure of the silver electrode and enabling better electrolysis effect.

[0028] As a preferred solution, the conditions for the heat treatment annealing include: a temperature of 100 to 300 °C, a pressure of 25 to 50 MPa, and a time of 5 to 60 min.

[0029] As a preferred solution, the auxiliary electrode is a graphite and / or platinum metal electrode.

[0030] As a preferred solution, the porous silver electrode is connected to the positive pole of the external power supply, and the auxiliary electrode is connected to the negative pole of the external power supply.

[0031] As a preferred solution, the electrolyte is a 10% to 50 wt% sodium hydroxide solution.

[0032] As a preferred solution, the temperature of the electrolyte in step (3) is 40 to 80 °C

[0033] As a preferred solution, the temperature of the electrolyte in step (4) is 40 to 80 °C.

[0034] As a preferred solution, in step (5), the charge and discharge cycle of the electrode is carried out on an electrochemical instrument with a set charge and discharge program.

[0035] As a preferred solution, the temperature of the electrolyte in step (5) is 10 to 30 °C.

[0036] As a preferred solution, the steps of the cleaning include: rinsing or soaking the AgO / Ag composite electrode with water 5 to 8 times, and the cleaning time is 10 to 20 min.

[0037] As a preferred solution, the cleaned AgO / Ag composite electrode is dried at 500 to 100 °C for 2 to 6 h.

[0038] The present invention also provides an AgO / Ag composite electrode material prepared by the in-situ generation method of the aforementioned AgO / Ag composite material. This AgO / Ag composite electrode material has high chemical activity, and because AgO is in-situ generated on the Ag matrix, the two have good adaptability, and the conductive current collection effect of Ag can be fully utilized to conduct and output the electric energy generated by the excellent electrochemical reaction of AgO, becoming an excellent composite electrode.

[0039] Compared with the prior art, the present invention has at least the following advantages:

[0040] The preparation method provided by the present invention has a higher conversion rate of AgO, the required process is simpler, and it is easier to control the preparation process of the AgO / Ag composite electrode, thereby greatly improving the electrochemical utilization rate, average working voltage, specific capacity and other discharge performances of the electrode material. Description of the Drawings

[0041] Figure 1 The electron micrograph of the surface morphology of the AgO / Ag composite electrode material prepared in Example 3;

[0042] Figure 2 The electron micrograph of the cross-sectional morphology of the AgO / Ag composite electrode material prepared in Example 3;

[0043] Figure 3 The element distribution and content diagram of the AgO / Ag composite electrode material prepared in Example 3;

[0044] Figure 4 The X-ray diagram of the AgO / Ag composite electrode materials prepared in each example;

[0045] Figure 5 The discharge curve diagram of the AgO / Ag composite electrodes prepared in Example 3 and Comparative Example 1. Detailed implementation manners

[0046] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0047] In the present invention, room temperature refers to 25 ± 2 °C.

[0048] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those of ordinary skill in the art without creative efforts still fall within the protection scope of the present invention.

[0049] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0050] Example 1

[0051] Step S1: Loading silver powder into a mold. After mixing silver powder with a pore-forming agent to obtain mixed silver powder, paving the powder skeleton made of the mixed silver powder and silver mesh in a flat mold, using a scraper to flatten the silver powder, and covering and fixing the mold. The purity of the silver powder is 99.0 wt%, and the average particle size is 50 nm; 10% by volume of the pore-forming agent urea is added to the silver powder.

[0052] Step S2: Sintering and heat treatment annealing. For the loaded silver powder, under the combined action of temperature and pressure, hot pressing sintering and heat treatment annealing are carried out in a reducing atmosphere mixed with CO and CO2. Specifically, in the reducing atmosphere, first heat up to the sintering temperature of 600 °C, the sintering pressure is 25 MPa, the sintering time is 3 min. After sintering, while maintaining the pressure (25 MPa), continue to keep warm at 100 °C for 5 min. After the heat treatment, the silver electrode is cooled to room temperature and then demolded to obtain a porous silver electrode with a porosity of 40% and a thickness of 0.1 mm.

[0053] Among them, the reducing atmosphere is a mixed gas of CO and CO2 with a volume ratio of 1:1, and the inlet flow rate is 1000 mL / min;

[0054] Step S3: Electrolytic pretreatment of the porous silver electrode. Make a graphite auxiliary electrode and place it on both sides of the silver electrode, with a 1 mm interval from the pure silver electrode, and soak it in a NaOH solution with a temperature of 40 °C and a concentration of 10 wt% for standby; Connect the assembled silver electrode to the positive pole of the external power supply, and the auxiliary electrode to the negative pole of the external power supply.

[0055] Step S4: Electrolysis. First, charge the silver electrode and the auxiliary electrode at a current density of 30 mA / cm 2 until the charging capacity reaches 10% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 15 mA / cm 2 until the charging capacity reaches 20% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 8 mA / cm 2 until the charging capacity reaches 40% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 3 mA / cm 2 until the charging capacity reaches 50% of the theoretical capacity of the silver positive electrode material.

[0056] Among them, the temperature of the electrolyte is 40 °C.

[0057] Step S5: Charge and discharge cycle of the electrode. Charge the silver electrode material at a current density of 3 mA / cm 2 for 5 s, and then discharge the silver electrode material at a current density of 1 mA / cm 2 for 1 s. Repeat this charge and discharge process 1000 times on an electrochemical instrument with a set charge and discharge program.

[0058] Among them, the temperature of the electrolyte is room temperature.

[0059] Step S6: Cleaning. The AgO / Ag composite electrode generated by electrolysis in Step S5 (at this time, part of the pure silver Ag has been converted into AgO) is rinsed 5 times with running water under the state of being soaked in normal temperature distilled water, and the soaking and rinsing time for each time is 10 min.

[0060] Step S7: Drying. The AgO / Ag electrode cleaned in Step S6 is placed in a vacuum drying oven and dried at 50 °C for 2 h. After taking it out, the in-situ generated AgO / Ag composite electrode material is obtained.

[0061] Example 2

[0062] Step S1: Loading silver powder into the mold. The silver powder and the pore-forming agent are mixed to obtain the mixed silver powder. The powder skeleton made of the mixed silver powder and the silver mesh is paved in a flat mold, and the silver powder is leveled with a scraper, and then the mold is covered and fixed. The purity of the silver powder is 99.0 wt%, and the average particle size is 50 μm; the pore-forming agent urea with a volume percentage content of 60% is added to the silver powder.

[0063] Step S2: Sintering and heat treatment annealing. For the loaded silver powder, hot pressing sintering and heat treatment annealing are carried out under the combined action of temperature and pressure in a reducing atmosphere mixed with CO and CO2. Specifically, in the reducing atmosphere, first heat up to the sintering temperature of 900 °C, the sintering pressure is 50 MPa, and the sintering time is 15 min. After sintering is completed, while maintaining the pressure (50 MPa), continue to keep the temperature at 300 °C for 60 min. After the heat-treated silver electrode is cooled to room temperature, it is demolded to obtain a porous silver electrode with a porosity of 90% and a thickness of 2 mm.

[0064] Among them, the reducing atmosphere is a mixed gas of CO and CO2 with a volume ratio of 1:1, and the inlet flow rate is 1000 mL / min;

[0065] Step S3: Electrolytic pretreatment of the porous silver electrode. The metal platinum is made into an auxiliary electrode and placed on both sides of the silver electrode, both spaced 10 mm from the pure silver electrode, and soaked in a NaOH solution with a temperature of 80 °C and a concentration of 50 wt% for standby; the assembled silver electrode is connected to the positive pole of the external power supply, and the auxiliary electrode is connected to the negative pole of the external power supply.

[0066] Step S4: Electrolysis. First, charge the silver electrode and the auxiliary electrode at a current density of 50 mA / cm 2 until the charging amount reaches 19% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 25 mA / cm 2 until the charging amount reaches 39% of the theoretical capacity of the silver positive electrode material; then charge at a current density of 14 mA / cm 2Charge the silver electrode and the auxiliary electrode at a current density of [charge density value 1], and the charge amount reaches 49% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 2 6 mA / cm², and the charge amount reaches 60% of the theoretical capacity of the silver positive electrode material.

[0067] Among them, the temperature of the electrolyte is 80 °C.

[0068] Step S5: Electrode charge and discharge cycle. Charge the silver electrode material at a current density of 6 mA / cm² for 10 s, and then discharge the silver electrode material at a current density of 2 3 mA / cm² for 5 s. Repeat this charge and discharge process 5000 times on an electrochemical instrument with a set charge and discharge program. 2 Among them, the temperature of the electrolyte is room temperature.

[0069] Among them, the temperature of the electrolyte is room temperature.

[0070] Step S6: Cleaning. The AgO / Ag composite electrode (at this time, part of the pure silver Ag has been converted into AgO) generated by electrolysis in Step S5 is rinsed with running water 8 times in a state of being soaked in deionized water at room temperature, and the soaking and rinsing time for each time is 20 min.

[0071] Step S7: Drying. Place the AgO / Ag electrode cleaned in Step S6 in a vacuum drying oven, dry it at 100 °C for 6 h, and then take it out to obtain the in-situ generated AgO / Ag composite electrode material.

[0072] Example 3

[0073] Step S1: Loading silver powder into a mold. Mix silver powder with a pore-forming agent to obtain mixed silver powder, lay the powder skeleton made of the mixed silver powder and silver mesh in a flat mold, use a spatula to spread the silver powder evenly, and cover and fix the mold. Among them, the purity of the silver powder is 99.0 wt%, the average particle size is 1 μm; the pore-forming agent urea with a volume percentage of 30% is added to the silver powder.

[0074] Step S2: Sintering and heat treatment annealing. For the loaded silver powder, under the combined action of temperature and pressure, perform hot pressing sintering and heat treatment annealing in a reducing atmosphere mixed with CO and CO₂. Specifically, in the reducing atmosphere, first heat up to the sintering temperature of 750 °C, the sintering pressure is 30 MPa, the sintering time is 9 min. After sintering is completed, while maintaining the pressure (30 MPa), continue to keep it at a temperature of 200 °C for 30 min. After the heat-treated silver electrode is cooled to room temperature, demold it to obtain a porous silver electrode with a porosity of 60% and a thickness of 1 mm.

[0075] Among them, the reducing atmosphere is a mixed gas of CO and CO₂ with a volume ratio of 1:1, and the inlet flow rate is 1000 mL / min.

[0076] Step S3: Electrolytic pretreatment of silver electrode. Make auxiliary electrodes from metals such as platinum and place them on both sides of the silver electrode, with a distance of 5 mm from the pure silver electrode. Immerse them in a NaOH solution at a temperature of 60°C and a concentration of 35 wt% for standby; connect the assembled silver electrode to the positive terminal of an external power supply, and the auxiliary electrode to the negative terminal of the external power supply.

[0077] Step S4: Electrolysis. First, charge the silver electrode and the auxiliary electrode at a current density of 40 mA / cm 2 , and the charging capacity reaches 15% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 20 mA / cm 2 , and the charging capacity reaches 30% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 12 mA / cm 2 , and the charging capacity reaches 45% of the theoretical capacity of the silver positive electrode material; then charge the silver electrode and the auxiliary electrode at a current density of 5 mA / cm 2 , and the charging capacity reaches 55% of the theoretical capacity of the silver positive electrode material.

[0078] Among them, the temperature of the electrolyte is 60°C.

[0079] Step S5: Charge and discharge cycle of the electrode. Charge the silver electrode material at a current density of 4.5 mA / cm 2 for 8 s, and then discharge the silver electrode material at a current density of 2 mA / cm 2 for 3 s. Repeat this charge and discharge process 2500 times on an electrochemical instrument with a set charge and discharge program.

[0080] Among them, the temperature of the electrolyte is room temperature.

[0081] Step S6: Cleaning. The AgO / Ag composite electrode generated by electrolysis in Step S5 (at this time, part of the pure silver Ag has been converted into AgO) is rinsed with running water 6 times in a state of being soaked in deionized water at room temperature, and the soaking and rinsing time for each time is 15 min.

[0082] Step S7: Drying. Place the AgO / Ag electrode cleaned in Step S6 in a vacuum drying oven and dry it at 80°C for 4 h. After taking it out, the in-situ generated AgO / Ag composite electrode material is obtained.

[0083] Comparative Example 1

[0084] Step S1: Loading silver powder into the mold. The silver powder is mixed with a pore-forming agent to obtain a mixed silver powder. The mixed silver powder and the powder skeleton made of silver mesh are paved in a flat mold. A scraper is used to spread the silver powder flat, and then the mold is covered and fixed. The purity of the silver powder is 99.0 wt%, and the average particle size is 20 μm. The pore-forming agent urea is added to the silver powder at a volume percentage of 30%.

[0085] Step S2: Sintering and heat treatment annealing. For the loaded silver powder, under the combined action of temperature and pressure, hot pressing sintering and heat treatment annealing are carried out in a reducing atmosphere mixed with CO and CO2. Specifically, in the reducing atmosphere, first the temperature is raised to the sintering temperature of 500 °C, the sintering pressure is 5 MPa, and the sintering time is 20 min. After sintering, while maintaining the pressure (5 MPa), it is kept at 50 °C for 60 min. After the heat treatment, the silver electrode is cooled to room temperature and then demolded to obtain a porous silver electrode with a porosity of 20% and a thickness of 0.8 mm.

[0086] Among them, the reducing atmosphere is a mixed gas of CO and CO2 with a volume ratio of 1:1, and the flow rate is 1000 mL / min.

[0087] Step S3: Electrolytic pretreatment of the silver electrode. An auxiliary electrode made of platinum and other metals is placed on both sides of the silver electrode, and the distance between them and the pure silver electrode is 12 mm. It is immersed in a NaOH solution with a temperature of 30 °C and a concentration of 30 wt% for standby. The assembled silver electrode is connected to the positive pole of the external power supply, and the auxiliary electrode is connected to the negative pole of the external power supply.

[0088] Step S4: Electrolysis. The silver electrode and the auxiliary electrode are charged at a current density of 60 mA / cm 2 , and the charging amount reaches 55% of the theoretical capacity of the silver positive electrode material. Among them, the temperature of the electrolyte is 30 °C.

[0089] Step S5: Charge and discharge cycling of the electrode. The silver electrode material is charged at a current density of 10 mA / cm 2 for 15 s, and then discharged at a current density of 5 mA / cm 2 for 6 s. Such a charge and discharge cycle process is carried out 3000 times on an electrochemical instrument with a set charge and discharge program. Among them, the temperature of the electrolyte is room temperature.

[0090] Step S6: Cleaning. The AgO / Ag composite electrode generated by electrolysis in Step S5 (at this time, part of the pure silver Ag has been converted into AgO) is rinsed with running water 6 times in a state of being soaked in normal temperature distilled water, and the soaking and rinsing time for each time is 15 min.

[0091] Step S7: Drying. Place the cleaned AgO / Ag electrode in Step S6 in a vacuum drying oven and dry it at 75 °C for 5 h. After taking it out, the in-situ generated AgO / Ag composite electrode material is obtained.

[0092] Test Example

[0093] The surface morphology, cross-sectional morphology, element distribution and content of the AgO / Ag composite electrode material prepared in Example 3 were tested. The test results are shown in Figure 1 、 Figure 2 and Figure 3 .

[0094] The phase analysis of the AgO / Ag composite electrode material prepared in the example was carried out, and the results are shown in Figure 4 .

[0095] The AgO / Ag composite electrode materials prepared in Example 3 and Comparative Example 1 were assembled into a battery. Figure 5 Fig. is the discharge curve of the AgO / Ag composite electrodes prepared in Example 3 and Comparative Example 1.

[0096] Figure 1 Fig. is the electron micrograph of the surface morphology of the AgO / Ag composite electrode material prepared in Example 3. It can be seen from the figure that AgO with a columnar morphology grew on the electrode surface.

[0097] Figure 2 Fig. is the electron micrograph of the cross-sectional morphology of the AgO / Ag composite electrode material prepared in Example 3. It can be seen from the figure that the columnar AgO and spherical Ag are distributed alternately, and the AgO / Ag composite positive electrode material was successfully prepared.

[0098] Figure 3 Fig. is the element distribution and content map of the AgO / Ag composite electrode material prepared in Example 3; it can be seen from the figure that the atomic ratio of Ag to O is close to 1:1, indicating that Example 3 is AgO rather than Ag2O with an atomic ratio of 2:1.

[0099] From Figure 4 it can be seen that in Examples 1, 2 and 3, it mainly exists as Ag and AgO, while there is an obvious Ag2O peak in Comparative Example 1.

[0100] From Figure 5 it can be seen that the discharge performance of the battery prepared in Example 3 is significantly better than that of Comparative Example 1. For the battery assembled with the AgO / Ag composite electrode material prepared in Example 3, a solution of 4.5 mol / L NaOH + 20 g / L Na2SnO3 was used as the electrolyte, the electrolyte temperature was about 85 °C, and the current density was 620 mA / cm 2Constant current discharge was carried out under the condition that, during high current discharge, the voltage was relatively stable and no high plateau potential appeared at the initial stage of discharge, indicating that the AgO / Ag composite electrode prepared by the method provided by the present invention successfully eliminated the high plateau potential. However, the high plateau potential that appeared at the initial stage of discharge in the battery assembled with the positive electrode material prepared in Comparative Example 1 was relatively obvious. Moreover, compared with Comparative Example 1, Example 3 also had a larger specific capacity of the battery when the working voltage was above 1.5V, reaching 368.23 mAh / g, which was 85.2% of the theoretical specific capacity; when the cut-off voltage was 1V, the specific capacity was 395.01 mAh / g, reaching 91.4% of the theoretical specific capacity, effectively improving the electrode conversion rate and utilization rate. Therefore, the AgO / Ag composite positive electrode material provided by the present invention can more effectively improve the utilization rate of the active material and the specific capacity of the battery.

[0101] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An in-situ generation method of AgO / Ag composite material, characterized in that: The method includes: (1) Silver powder loading into the mold: Mix silver powder with a pore-forming agent to obtain a mixed silver powder, and jointly lay the mixed silver powder and a powder skeleton made of a silver mesh or a silver-plated copper mesh in a mold to obtain Intermediate I; (2) Sintering and heat treatment annealing: In a reducing atmosphere, sequentially perform hot pressing sintering and heat treatment annealing on the Intermediate I to obtain a porous silver electrode; the reducing atmosphere is a mixed gas of CO and CO2; (3) Electrolytic pretreatment of the porous silver electrode: Place an auxiliary electrode and the porous silver electrode in an electrolyte for immersion treatment. The auxiliary electrode is placed on both sides of the porous silver electrode, and the spacing distance between the auxiliary electrode and the porous silver electrode is 1 mm to 10 mm; (4) Electrolysis: Charge at the first current density of A1 mA / cm 2 until the charged amount reaches B1% of the theoretical capacity of the silver positive electrode material, and then continue to charge at the second current density of A2 mA / cm 2 until the charged amount reaches B2% of the theoretical capacity of the silver positive electrode material, and then charge at the third current density of A3 mA / cm 2 until the charged amount reaches B3% of the theoretical capacity of the silver positive electrode material, and finally charge at the fourth current density of A4 mA / cm 2 so that the charged amount reaches B4% of the theoretical capacity of the silver positive electrode material; And 30 ≤ A1 ≤ 50, 15 ≤ A2 ≤ 25, 8 ≤ A3 < 15, 3 ≤ A4 ≤ 6, 10 ≤ B1 < 20, 20 ≤ B2 < 40, 40 ≤ B3 < 50, 50 ≤ B4 ≤ 60; (5) Electrode charge and discharge cycle: Using the fifth current density of A5 mA / cm 2 Charge the silver electrode material for 5 - 10 s, and then discharge the silver electrode material for 1 - 5 s at the sixth current density of A6 mA / cm 2 Repeat step (5) 1000 - 5000 times to obtain the AgO / Ag composite electrode; and 3 ≤ A5 ≤ 6, 1 ≤ A6 < 3; (6) Clean and dry the AgO / Ag composite electrode to obtain an in-situ generated AgO / Ag composite electrode material.

2. The in-situ generation method of an AgO / Ag composite material according to claim 1, characterized in that: The purity of the silver powder is not less than 99.0 wt%, and the particle size is 50 nm to 50 μm.

3. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: Based on the total volume of the silver powder and the pore-forming agent, the volume dosage of the pore-forming agent is 10% to 60%.

4. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: The pore-forming agent is carbamide.

5. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: The conditions for the hot pressing sintering include: temperature is 600 to 900 °C, pressure is 25 to 50 MPa, and time is 3 to 15 min; And / or, the conditions for the heat treatment annealing include: temperature is 100 to 300 °C, pressure is 25 to 50 MPa, and time is 5 to 60 min.

6. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: The electrolyte is a 10 to 50 wt% sodium hydroxide solution.

7. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: In step (4), the temperature of the electrolyte is 40 to 80 °C.

8. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: The steps of the cleaning include: Rinse or soak the AgO / Ag composite electrode with water 5 to 8 times, and the cleaning time is 10 to 20 min.

9. The in-situ generation method of an AgO / Ag composite material according to claim 1 or 2, characterized in that: Dry the cleaned AgO / Ag composite electrode at 500 to 100 °C for 2 to 6 h.

10. An AgO / Ag composite electrode material prepared by the in-situ generation method of an AgO / Ag composite material according to any one of claims 1 to 9.

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