CN103985923B - Quasi-solid electrolyte PVA-zinc-air battery - Google Patents

Abstract

The invention discloses a quasi-solid-state electrolyte PVA-zinc-air battery, which includes an air electrode for reduction reaction, a zinc electrode for oxidation reaction, an electrolyte, and a battery casing for containing the air electrode, zinc electrode and electrolyte; The electrolyte is a frozen solid PVA-KOH-H ₂ O basic polymer (PVA quasi-solid electrolyte), and a battery diaphragm is arranged between the air electrode and the zinc electrode. The beneficial effects of the present invention are as follows: 1. The solid electrolyte used is frozen solid and has a certain toughness, which can hinder the growth of zinc dendrites and prevent the formation of zinc dendrite spikes from piercing the diaphragm and causing battery damage. The internal short circuit increases the service life of the battery and improves the overall performance of the battery. 2. The solid electrolyte obviously prevents the occurrence of battery leakage and improves the overall performance of the battery.

Description

Quasi-solid electrolyte PVA-zinc-air battery

technical field

The invention relates to a battery, in particular to a quasi-solid electrolyte-PVA zinc-air battery, which belongs to the technical field of new energy.

Background technique

For a long time, human beings have been using oil and coal as energy in production and life. With the continuous increase in energy demand in recent years, the reserves of non-renewable energy have gradually decreased. The energy crisis has begun to flash, and energy security has become a highly focused focus of every country. problem, but also a huge challenge we face. In this context, energy conservation, emission reduction, and green development are inevitable choices. It is urgent to seek new energy to replace fossil energy. With the continuous development of portable electronic products and the increasing demand for zero-emission electric vehicles, people are looking for a high-energy The battery of the system meets the requirements. As a new technology of efficient, clean and green energy, zinc-air battery has the characteristics of large capacity, high specific energy, low cost, stable discharge performance, safety, zero pollution, high power and renewable materials, etc., and has become the focus of the world's energy field. The focus is a chemical energy source with huge market prospects.

Since 1879, Maiche produced the first neutral electrolyte zinc-air battery with a zinc sheet as the negative electrode and an air electrode made of platinumized porous carbon as the positive electrode of the battery. After continuous development, after the 1960s , Zinc-air disposable batteries have made great progress, and thin air electrodes are introduced into zinc-air batteries, which greatly improves the discharge performance of batteries and makes a major breakthrough in the development of zinc-air batteries. At the end of the 1960s, high-efficiency zinc-air batteries have entered the stage of industrial production and have been widely used. In recent years, with the improvement of battery structure and manufacturing process, the development of gas diffusion electrode manufacturing process, and the improvement of the utilization rate of zinc negative electrode, the comprehensive performance of the battery has been further improved. But the above are all for the zinc-air primary battery, and the rechargeable secondary battery has not developed by leaps and bounds.

The negative active material of the zinc-air battery is encapsulated inside the battery, which has the characteristics of a storage battery; secondly, the positive active material comes from oxygen in the air, theoretically has unlimited capacity, and has the characteristics of a fuel cell. In addition, zinc-air batteries have the following advantages: 1. High specific energy, since the positive electrode active material comes from the outside of the battery, there is no need to occupy the space of the battery. Under the same volume and weight, more zinc-air batteries can be loaded. The negative electrode active material makes the capacity of zinc-air battery much higher than that of ordinary batteries. The theoretical specific energy reaches 1350Wh·kg ^-1 , and the actual specific energy is 220-300Wh·kg ^-1 , which is a large-capacity high-energy chemical power source. 2. The cost is low. The cathode active material is oxygen in the air, which can be said to be inexhaustible, while the anode active material is metal zinc, and its resources are also very rich. 3. Stable performance and stable discharge. Since the air electrode itself does not change when the battery is working, and the voltage of the zinc electrode is stable, the voltage change during discharge will be small. 4. Green and environmentally friendly, safe and reliable, from production to use, from new products to waste recycling, all materials are safe, will not pollute the environment and will not burn and explode, which can be called green energy.

However, the current zinc-air batteries are basically disposable batteries, and there is no rechargeable zinc-air secondary battery. The development of zinc-air batteries is a bottleneck due to the use of porous electrodes in zinc-air batteries and the characteristics of zinc electrodes. The main issues are as follows:

1. The growth of zinc dendrites. Due to the characteristics of the zinc electrode itself, its self-discharge reaction will occur, and in the process of charging it, dendritic zinc will grow out. Its shape is very sharp. When the charge reaches a certain level, the dendrite growth will puncture The diaphragm of the battery, thus causing a short circuit and seriously reducing the performance of the battery.

2. Direct oxidation of zinc electrodes. Since the oxygen in the air dissolves in the electrolyte, HO2 ^- is formed during the reaction process. If HO2 ^- is not decomposed, it will accumulate in the air electrode, and the zinc electrode will be directly oxidized, causing a negative potential shift, passivating the zinc electrode, and reducing the activity of zinc. .

3. Battery leakage problem. Since the air electrode adopts a porous structure, oxygen circulates through the pores, so that the electrolyte will also flow out of the pores. If the leakage problem cannot be properly solved, it will also bring great problems to the performance of the zinc-air battery and seriously affect its performance. and longevity.

Contents of the invention

The purpose of the present invention is in order to provide a kind of quasi-solid electrolyte PVA-zinc-air battery, to solve the above-mentioned problems of prior art.

The purpose of the present invention can be achieved through the following technical solutions.

A quasi-solid-state electrolyte PVA-zinc-air battery, which includes an air electrode for reduction reaction, a zinc electrode for oxidation reaction, an electrolyte, and a battery case for accommodating the air electrode, zinc electrode, and electrolyte; the electrolyte is frozen It is a solid PVA-KOH-H ₂ O basic polymer (PVA quasi-solid electrolyte), and a battery separator is arranged between the air electrode and the zinc electrode.

The air electrode has a layered structure, and from left to right is a waterproof and breathable layer, a collector layer (foamed nickel) and a catalytic layer; each layer is made with a pore-forming agent to make a number of pores, which are oxygen transport channels.

The preparation method of above-mentioned air electrode, its step is as follows:

1) Preparation of waterproof and breathable layer: Take acetylene black, activated carbon, and pore-forming agent in a ratio of 1:1:1.5 (mass) and mix evenly, then add 40% to 60% (accounting for the total amount) drop by drop with a mass fraction of 60% PTFE Emulsion, stir evenly and set aside;

2) Prepare the catalytic layer: Take acetylene black, activated carbon, pore-forming agent and manganese dioxide in a ratio of 1:9:15:10 (mass) and mix evenly, and then add 40% to 60% (accounting for the total) mass The fraction is 60% PTFE emulsion, stir evenly for use;

3) Then apply the products obtained in step 1) and step 2) evenly on both sides of the foamed nickel respectively, and heat treat for 30-60 minutes at 120-150° C. in a vacuum drying oven or on a hot stage after being evenly applied;

4) Form into tablets with a powder tablet press, with a thickness of 1-2mm, which is the air electrode; after the air electrode is prepared, put it in a constant temperature drying oven for standby.

The pore-forming agent is sodium bicarbonate or anhydrous sodium sulfate. If the pore-forming agent is anhydrous sodium sulfate, it needs to be placed in water at 60°C to form pores.

An appropriate amount of carbon nanotubes can be added to the outside of the catalytic layer to improve the contact between the air electrode and PVA and reduce the internal resistance of the battery.

The preparation method of the above-mentioned PVA-KOH-H ₂ O basic polymer comprises the following steps:

1) Weigh a certain amount of polyvinyl alcohol particles, mix them with water at a ratio of 1:40-1:50, heat and stir in a water bath, the temperature of the water bath is 88-95°C, stir for 50-70 minutes, the transparent polyvinyl alcohol particles gradually disappear, At the same time, the water gradually becomes viscous;

2) After the transparent particles are completely dissolved, continue to heat in a water bath for 8-20 minutes to evaporate excess water, so that the water content of PVA is 60%-70%;

3) adding 40% to 50% of pre-prepared 6-7mol/L KOH dropwise to obtain a PVA solution;

4) Place the PVA solution in step 3) at room temperature and allow it to cool naturally. The PVA solution gradually becomes a frozen solid. When it does not completely become a frozen solid, drop it into the battery case for the final follow-up package.

The preparation method of above-mentioned zinc electrode, its step is:

1) Use zinc powder as the material, add 2% binder and pore-forming agent, and add 3% corrosion inhibitor to reduce the self-corrosion of zinc.

2) Stir evenly and press into tablets to form, and then the thickness of the tablets is about 1-1.5 mm. Store in an airtight dry place.

The porous zinc electrode made of zinc powder is used to replace the traditional zinc paste. In order to reduce the internal resistance of the battery, a small amount of carbon nanotubes are added during the battery packaging process to improve the contact resistance between the zinc electrode and PVA. During the discharge process, the zinc on the surface and the side edge is first oxidized to ZnO. With this porous structure, the generated ZnO will not block the surface structure, allowing the inner zinc to continue to react, maximizing the use of zinc electrode active materials, and a small amount of carbon. Nanotubes can improve the contact between the zinc electrode and PVA, reduce contact resistance, and also increase its own conductivity. Therefore, such a porous zinc electrode can react more completely during charging and discharging of the battery, and the voltage is more stable, which has a better effect on improving the performance of the zinc-air battery.

The quasi-solid PVA zinc-air secondary battery prepared by the present invention can be applied to hearing aids, electronic watches, portable electronic devices such as mobile phones, and electric vehicles. The liquid leakage and the formation of zinc dendrites during the charging process solve the phenomenon that the zinc dendrites puncture the battery diaphragm during multiple charge and discharge processes and cause a short circuit, prolonging its charge and discharge service life.

The present invention uses PVA-KOH-H2O alkaline polymer to replace the traditional KOH electrolyte. The biggest difference between them is that the PVA used is in the form of solid state inside the battery, which can bring the following obvious advantages :

1. Limit the growth of zinc dendrites. The resulting solid electrolyte exists inside the battery in a frozen state, and it is a polymer with good toughness. During the charging process, ZnO will be re-reduced to Zn. During the re-growth process of the zinc electrode, the deposition is not uniform, so there will be dendritic zinc growth, and the traditional liquid electrolyte or gel electrolyte will not The growth of this zinc dendrite cannot be limited, so the solid electrolyte used is a frozen solid with a certain degree of toughness, which can hinder the growth of zinc dendrites and prevent the diaphragm from being pierced by the formation of zinc dendrite spikes Lead to internal short circuit of the battery, increase the service life of the battery, and improve the overall performance of the battery.

2. Prevent battery leakage. Especially in this zinc-air battery structure, the air anode has pores, and the traditional electrolyte can easily flow out of the pores, and the air electrode itself is a porous structure. In order to ensure its overall function, When the battery is working, it should be ensured that it is soaked and not leaked. The surface of this frozen PVA electrolyte has a good contact with the catalytic layer. We add carbon nanotubes to the catalytic layer to better reduce their contact. Resistance, the infiltration effect on the surface of the catalytic layer is very good, and its solid structure can ensure that the electrolyte will not leak into the pores of the air electrode, which undoubtedly improves the performance of the zinc-air battery. Therefore, the solid electrolyte obviously prevents the occurrence of battery leakage and improves the overall performance of the battery.

Description of drawings

Figure 1 is a SEM image of a zinc electrode at 2000 times;

Figure 2 is the SEM image after charging and discharging with liquid electrolyte;

Figure 3 is the SEM image after charge and discharge using PVA quasi-solid electrolyte;

Fig. 4 is a relationship diagram between the final discharge pressure and the number of cycles using a liquid electrolyte and a PVA quasi-solid electrolyte;

Fig. 5 is the CV curve measured using PVA quasi-solid electrolyte zinc-air battery;

Fig. 6 is a charge-discharge cycle test diagram of the liquid electrolyte;

Fig. 7 is a charge-discharge cycle test diagram of the PVA quasi-solid electrolyte.

detailed description

The technical characteristics of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Preparation of PVA quasi-solid electrolyte:

Example 1: 1) Weigh a certain amount of polyvinyl alcohol particles, mix them with water at 0.5:32, heat and stir in a water bath, the temperature of the water bath is 90°C, stir for 60 minutes, the transparent polyvinyl alcohol particles gradually disappear, and the water gradually becomes Viscous; 2) After the transparent particles are completely dissolved, continue to heat in a water bath for 10 minutes to evaporate excess water, so that the water content of PVA is 60%-70%; 3) Add 40%-50% of pre-prepared 5 ～6mol/L of KOH; obtain PVA solution; 4) place the PVA solution of step 3) at room temperature and allow it to cool naturally, the PVA solution gradually becomes a frozen solid, and when it does not completely become a frozen solid, put It drips into the battery case for final subsequent encapsulation.

Example 2: Same as the above steps, the difference is: 1) The mixing ratio of polyvinyl alcohol particles and water is: 1:40, the temperature of the water bath is 88 ° C, and stirred for 70 minutes; 2) After the particles are dissolved, continue heating in the water bath 20 minutes; 3) Add 40% of pre-prepared 7 mol/L KOH dropwise.

Example 3: The steps are the same as in Example 1, the difference is: 1) The mixing ratio of polyvinyl alcohol particles and water is: 1:30, the temperature of the water bath is 95°C, and stirred for 50 minutes; 2) After the particles are dissolved, continue Heat in a water bath for 20 minutes; 3) Add 50% of pre-prepared 7 mol/L KOH dropwise.

Preparation of zinc electrode:

Example 4: 1) Zinc powder is used as material, 2% of binder and pore-forming agent are added, and 3% of corrosion inhibitor is added to reduce the self-corrosion of zinc. 2) Stir evenly and press into tablets to form, and then the thickness of the tablets is about 1-1.5mm. Store in a sealed dry place for later use.

The SEM image of the prepared zinc electrode at 2000 times is shown in Figure 1.

Prepare the air electrode:

Example 5: 1) Preparation of a waterproof and breathable layer: Take acetylene black, activated carbon, and pore-forming agent in a ratio of 1:1:1.5 and mix evenly, then add 50% mass fraction of 60% PTFE emulsion dropwise, and stir evenly for later use; 2) Prepare the catalytic layer: Take acetylene black, activated carbon, pore-forming agent and manganese dioxide and mix them evenly in a ratio of 1:9:15:10, then add 40% mass fraction of 60% PTFE emulsion dropwise, and stir evenly for later use ; 3) then uniformly smear the product obtained in step 1) and step 2) on both sides of the foamed nickel, after being evenly smeared, heat treatment at 150°C for 30 minutes in a vacuum drying oven or on a hot table; 4) use The powder tablet press is pressed into tablets with a thickness of 1-2mm, which is the air electrode; after the air electrode is prepared, it is placed in a constant temperature drying oven for use.

Example 6: 1) Preparation of a waterproof and breathable layer: Take acetylene black, activated carbon, and pore-forming agent in a ratio of 1:1:1.5 and mix evenly, then add 60% PTFE emulsion with a mass fraction of 60% dropwise, and stir evenly for later use; 2) Prepare the catalytic layer: Take acetylene black, activated carbon, pore-forming agent and manganese dioxide and mix them uniformly in a ratio of 1:9:15:10, then add 50% mass fraction of 60% PTFE emulsion dropwise, and stir evenly for later use ; 3) then uniformly smear the product obtained in step 1) and step 2) on both sides of the foamed nickel, after being evenly smeared, heat treatment at 150°C for 30 minutes in a vacuum drying oven or on a hot table; 4) use The powder tablet press is pressed into tablets with a thickness of 1-2mm, which is the air electrode; after the air electrode is prepared, it is placed in a constant temperature drying oven for use.

Package:

Embodiment 6: Put the prepared zinc electrode (Example 4), PVA solid electrolyte (any one of Examples 1-3), battery separator and air electrode (Example 5) into the battery in sequence. It should be noted that the PVA solid electrolyte needs to be dripped when it has not completely become a frozen solid. In addition, a small amount of carbon nanotubes are added to the catalytic layer of the air electrode and the part where the zinc electrode is in contact with PVA, so that the electrode has a better contact with the PVA solid electrolyte to reduce the internal resistance of the battery. Then package it. Pass the packaged battery through the following tests:

Figure 2 and Figure 3 are SEM images after charging and discharging using liquid electrolyte and PVA quasi-solid electrolyte, respectively. It can be seen that the surface of the electrode after charging and discharging with PVA is smoother than that of the liquid electrolyte, which largely limits the growth of edges and zinc dendrites, so it is very beneficial for the battery to work repeatedly.

Figure 4 shows the relationship between the final discharge voltage and the number of cycles when using liquid electrolyte and PVA quasi-solid electrolyte. It can be seen that the discharge medium voltage is similar, but after 100 cycles, the voltage of the sample using liquid electrolyte drops rapidly, while using PVA The voltage attenuation of the sample is much smaller, which obviously maintains the performance of the battery after multiple cycles. Improve battery life to some extent.

Figure 5 is a CV curve measured using a PVA quasi-solid electrolyte-zinc-air battery.

Figure 6 and Figure 7 are the charge-discharge cycle tests of liquid electrolyte and PVA quasi-solid electrolyte respectively. It can be clearly seen that the battery in Figure 6 basically fails after three cycles, while the PVA-zinc-air battery is used in the previous The discharge time of the two cycles is not long enough, but it can maintain a stable charge and discharge, and the 20 cycles are good.

Claims (6)

1. a quasi-solid-state electrolyte PVA-zinc-air battery is characterized in that: it comprises the air electrode that reduction reaction occurs, the zinc electrode of oxidation reaction, electrolyte and the battery housing that accommodates air electrode, zinc electrode and electrolyte; The electrolyte described above is a frozen solid PVA-KOH-H ₂ O basic polymer, and a battery diaphragm is arranged between the air electrode and the zinc electrode; The preparation method of the PVA-KOH-H ₂ O basic polymer comprises the following steps: 1) Weigh a certain amount of polyvinyl alcohol particles, mix them with water at a ratio of 1:40-1:50, heat and stir in a water bath, the temperature of the water bath is 88-95°C, stir for 50-70 minutes, the transparent polyvinyl alcohol particles gradually disappear, and at the same time The water gradually becomes transparent and viscous; 2) After the transparent particles are completely dissolved, continue to heat in a water bath for 8-20 minutes to evaporate excess water, so that the water content of PVA is 60%-70%; 3) adding 40% to 60% of pre-prepared 6-7mol/L KOH dropwise to obtain a PVA solution; 4) Place the PVA solution in step 3) at room temperature and allow it to cool naturally. The PVA solution gradually becomes a frozen solid. When it does not completely become a frozen solid, drop it into the battery case for the final follow-up package. 2. A kind of quasi-solid electrolyte PVA-zinc-air battery according to claim 1, is characterized in that: described air electrode is laminar structure, is successively from left to right waterproof air-permeable layer, current-collecting layer and catalytic layer; on each layer, a number of pores are made with a pore-forming agent, which is an oxygen delivery channel; the preparation steps are as follows: 1) Prepare a waterproof and breathable layer: Take acetylene black, activated carbon, and pore-forming agent in a ratio of 1:1:1.5 and mix evenly, then add 40% to 60% of the mass fraction of 60% PTFE emulsion drop by drop, and stir evenly for later use; 2) Prepare the catalytic layer: Take acetylene black, activated carbon, pore-forming agent and manganese dioxide in a ratio of 1:9:15:10 and mix evenly, then add 40% to 60% mass fraction of 60% PTFE emulsion drop by drop, evenly Stir and set aside; 3) Then apply the products obtained in step 1) and step 2) evenly on both sides of the foamed nickel respectively, and heat treat for 30-60 minutes at 120-150° C. in a vacuum drying oven or on a hot stage after being evenly applied; 4) Form into tablets with a powder tablet press, with a thickness of 1-2mm, which is the air electrode; after the air electrode is prepared, put it in a constant temperature drying oven for standby. 3. a kind of quasi-solid electrolyte PVA-zinc-air battery according to claim 2, is characterized in that: described pore forming agent is sodium bicarbonate or anhydrous sodium sulfate. 4. A kind of quasi-solid electrolyte PVA-zinc-air battery according to claim 3, characterized in that: when the described pore forming agent is anhydrous sodium sulfate, it needs to be put into 40～60°C water to form pores, When the pore-forming agent is ammonium bicarbonate, it is heat-treated on a hot stage at 120-150° C. for 30-60 minutes to form pores. 5. A quasi-solid electrolyte PVA-zinc-air battery according to claim 2, characterized in that: an appropriate amount of carbon nanotubes can be added to the outside of the catalytic layer. 6. A kind of quasi-solid electrolyte PVA-zinc-air battery according to claim 1, is characterized in that: the preparation method of described zinc electrode, its steps are: 1) Use zinc powder as the material, add 2% to 5% of binder and pore-forming agent, and add 3% to 5% of corrosion inhibitor to reduce the self-corrosion of zinc; 2) Stir evenly and press into tablets to form, and then the thickness of the tablets is about 1-1.5mm; store them in a sealed and dry place for later use.