CN114520302A - Aqueous metal battery and modified negative electrode thereof - Google Patents

Abstract

Modified negative electrode for aqueous metal batteries. The preparation method of the negative electrode includes hydrothermal crystallization of a mixed aqueous solution formed by silicon ions, aluminum ions and sodium hydroxide, and then ion-exchanges the crystallized product with the zinc ion solution for multiple times, and then exchanges the exchanged product with a binder and a solvent. A coating agent is formed together to coat the zinc foil to form a modified negative electrode. The present invention finely controls the ion channel from the atomic size level, suppresses the contact of large-diameter groups with the metal negative electrode, so as to reduce the occurrence of side reactions on the electrode surface and at the same time guide the uniform deposition of metal ions. Through the coordination with multivalent metal ions, the activity of water molecules directly in contact with the surface of the metal foil is reduced, and the corrosion resistance of the electrode is enhanced; the polarization voltage is reduced by the application of a negatively charged modified substance layer; at the same time, the metal is uniformized through the tunneling mechanism. The deposition of dendrites inhibits the growth of dendrites and achieves long-term stable cycling of metal electrodes.

Description

Aqueous metal battery and its modified negative electrode

technical field

The present invention generally relates to an aqueous metal battery, and more particularly, to a modified negative electrode of the battery.

Background technique

In order to solve the major problems of current international concern such as dependence on fossil energy, ecological environment crisis and climate change, the current demand for clean and renewable energy such as wind, solar, tidal and geothermal energy is increasing. Due to the instability of energy sources, electrochemical energy storage systems are an important link in the storage and utilization of these new energy sources. As the most advanced secondary battery system at present, lithium-ion batteries not only play an important role in people's daily life, such as portable electronic devices and new energy power battery vehicles, but also provide short-term storage for large-scale renewable energy. s solution. However, due to the use of flammable organic electrolytes, the safety performance of lithium-ion batteries is poor, and there is a danger of combustion and explosion; the elements required for the production of lithium-ion batteries, such as lithium, nickel, cobalt, etc., are relatively concentrated, and there are potential supply risk. In summary, it is urgent to find a battery system that is safe, more stable in supply, high in energy density, environmentally friendly and low-cost.

Multivalent metal-ion batteries are considered to be the most potential substitutes for lithium batteries, such as zinc-ion batteries and aluminum-ion batteries, which use divalent zinc ions or trivalent aluminum ions as charge carriers, and have the potential to provide lithium ion batteries. Double or triple the charge of ions. At the same time, replacing the flammable organic electrolyte with an aqueous electrolyte can solve the safety problem of the battery and greatly reduce the production cost of the battery. Zinc and aluminum metals also have the characteristics of stable ion valence, low price, small radius, low reduction voltage and high theoretical mass specific capacity (Zn: 825mAh g ^-1 , Al: 2 980mAh g ^-1 ), etc. Unlike metallic lithium, sodium, etc., which react violently with water, they have the potential to be directly used in aqueous batteries. However, there are still problems that cannot be ignored during the use of metal zinc and metal aluminum: when zinc is deposited on the surface of the zinc negative electrode, it will form a flaky disorder and accumulate on the surface of the electrode. Causes battery short-circuit failure; Affected by working conditions, the surface of the electrode is prone to hydrogen evolution reaction, which reduces the coulombic efficiency of the battery and causes electrolyte leakage; due to the increase in local hydroxide concentration caused by the hydrogen evolution reaction, it is easy to interact with metals and electrolytes existing in the electrolyte. Other ions react to form a passivation film on the electrode surface and reduce the cycle performance of the battery. The problems of surface hydrogen evolution and electrode surface passivation also exist in the aluminum metal negative electrode.

In order to solve these problems existing in metal anodes, optimization is currently carried out from four aspects: SEI film, electrode body structure, electrolyte and separator: one is the construction of a multifunctional artificial protective layer to suppress side reactions and dendrite growth; The structural composition of the metal electrode body is optimized; the third is to use a water-in-salt electrolyte to suppress the occurrence of the hydrogen evolution reaction; the fourth is to construct a functional separator that induces uniform ion deposition. The above method inhibits the occurrence of side reactions to a certain extent, but it is limited in the application process. For example, the process of optimizing the structure and composition of the metal electrode body is complicated, the water-in-salt electrolyte is sensitive to temperature changes, and the functional diaphragm cannot inhibit the hydrogen evolution reaction. happened.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a modified negative electrode for an aqueous metal battery, especially a zinc ion battery, which can at least overcome one or some of the above-mentioned defects.

According to a first aspect of the present invention, a method for preparing a negative electrode of a zinc ion battery is provided, comprising:

provide zinc foil;

providing a silicon ion source selected from at least one of the group consisting of silica gel, water glass, sodium silicate and ethyl orthosilicate;

providing a source of aluminum ions selected from at least one of the group consisting of hydrated aluminum sulfate and sodium metaaluminate;

The silicon ion source, the aluminum ion source and the sodium hydroxide are formed into a mixed aqueous solution, wherein the molar ratios of silicon ions, sodium ions and water molecules to aluminum ions are respectively 1.5-1, 5-3 and 90-80;

Control the temperature of the mixed aqueous solution to carry out hydrothermal crystallization between 25°C and 90°C for at least 5 hours;

The crystallized product was separated by centrifugation;

The crystallized product is dried and added to zinc ion aqueous solutions of different concentrations to carry out ion exchange in turn, wherein the molar amount of zinc ions and the mass ratio of the dried product are between 0.01 mol/g and 1 mol/g, and the ion exchange is carried out according to the zinc ion aqueous solution. The concentration is carried out in sequence from low to high, and centrifugal drying is carried out after each ion exchange;

The drying product obtained after the last ion exchange is mixed with a binder and a solvent to obtain a coating agent;

The obtained coating agent is uniformly coated on the zinc foil to form a coating, wherein the coating thickness is 5 μm-75 μm after the solvent is evaporated.

According to the method of the present invention, at least three aqueous solutions of zinc ions with different concentrations are used in the ion exchange, for example, 0.01 mol/g, 0.05 mol/g, 0.1 mol/g, 0.2 mol/g, 0.5 mol/g and 1 mol respectively. /g of zinc ion aqueous solution.

According to the method of the present invention, the mass ratio of the obtained dried product to the binder is preferably between 20:1 and 7:1.

According to the method of the present invention, wherein the binder may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO) and carboxymethyl cellulose (CMC). When PVDF or PEO is used as the binder, NMP can be used as the solvent for forming the coating agent, and when the binder is CMC, water can be used as the solvent.

According to the method of the present invention, sodium silicate is preferably used as the source of silicon ions. In addition, as the source of aluminum ions, sodium metaaluminate can be preferably used.

According to the method of the present invention, vacuum or non-vacuum drying can be used for each drying process, and the temperature can be set to 50°C to 200°C, preferably 60°C to 80°C; the drying time can be 2h to 48h, preferably 12h to 24h.

According to the method of the present invention, the binder can be coated on the surface of the negative electrode or the zinc foil with a controllable thickness by suitable methods such as blade coating, spin coating, spray coating, etc.

As an alternative embodiment of the present invention, an aluminum foil can also be used instead of a zinc foil to prepare a negative electrode for an aluminum battery.

According to another aspect of the present invention, there is provided a negative electrode of a zinc ion battery, which is prepared by the above method.

According to yet another aspect of the present invention, an aqueous zinc-ion battery is provided, which includes the above-mentioned negative electrode.

According to the battery of the present invention, wherein the electrolyte salt is preferably zinc sulfate and manganese sulfate or zinc triflate. In addition, the membrane material can be glass fiber, filter paper or non-woven fabric.

In addition, as an alternative embodiment of the present invention, the present invention can also be applied to an aluminum ion battery or a multi-ion battery containing zinc ions, such as a mixed ion battery of zinc and aluminum ions. When applied to aluminum ion batteries, the electrolyte salts can be aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum perchlorate, aluminum trifluoromethanesulfonate, etc.; when applied to multi-ion batteries, zinc salts and aluminum salts can be used. mixture.

The invention can finely control the ion channel from the atomic size level, inhibit the contact between the group with a diameter larger than 0.52 nm and the metal negative electrode, thereby reducing the occurrence of side reactions on the electrode surface, and at the same time, the water molecule in the multivalent ion hydration group can be reduced through the steric effect. active. Through the coordination with multivalent metal ions, the number of water molecules in direct contact with the surface of the metal foil is reduced, the corrosion resistance of the electrode is enhanced, and the polarization voltage is reduced; at the same time, the uniform metal deposition is guided by the tunneling mechanism, and the growth of dendrites is inhibited. Long-term stable cycling of metal electrodes.

The modified electrode prepared according to the invention can reduce the polarization voltage of the metal symmetric battery in the aqueous battery, improve the stability of the whole battery, and improve the battery efficiency.

In conclusion, the method of the present invention is simple in operation and low in cost, and the modified and modified metal negative electrode is anti-corrosion and effectively inhibits the occurrence of side reactions.

Description of drawings

FIG. 1 is a BET nitrogen adsorption diagram of the modified layer obtained in Example 8 of the present invention.

2 is a polarization voltage diagram of the metal electrode protected by the 20 μm modified layer in Example 8 of the present invention, the non-modified electrode of Comparative Example 1, and the modified metal electrode used in Comparative Example 2.

FIG. 3 is a long cycle capacity-turn comparison diagram of the aqueous zinc-ion batteries in Example 8 and Comparative Example 3. FIG.

Detailed ways

The present invention will be described in detail below with reference to embodiments, comparative examples and accompanying drawings. It should be understood that these contents are only used to illustrate and explain but not to limit the present invention.

In the following examples and comparative examples, the LAND CT2001A tester was purchased from Wuhan Landian Electronics Co., Ltd.

Example 1

(1) Configuration solution A: 2.24 g of sodium silicate dissolved in 15 ml of deionized water; configuration solution B: 2.04 g of sodium metaaluminate dissolved in 15 ml of deionized water. Pour solution A into solution B slowly, stir vigorously, and use sodium hydroxide to adjust the molar ratio Na ₂ O : Al ₂ O ₃ : SiO ₂ : H ₂ O = 3.58: 1:1.24: 171.18. Crystallization at 40°C for 5 days .

(2) After centrifuging and drying the crystallized product, disperse it in deionized water, add zinc sulfate solutions of different concentrations, wherein the ratio of zinc ion to the dried crystallized product is 0.01 mol/g, and after stirring at room temperature for 6 hours Centrifugal drying. Then repeat the ion exchange steps in sequence: the ratios of zinc ions in the zinc sulfate solution to the last drying product are 0.05 mol/g, 0.1 mol/g, 0.2 mol/g, 0.5 mol/g, and 1 mol/g, respectively.

(3) Mix the finally obtained dry product with PVDF, wherein the mass fraction of PVDF is 5%, then add an appropriate amount of NMP and mix evenly to obtain a coating agent, which is coated on the zinc foil by scraping to make the surface evenly covered The coating forms a modified electrode;

(4) vacuum-drying the modified electrode in an oven at 60°C to obtain a protective layer with a coating thickness of 5 μm, cutting the modified negative electrode into 11 mm wafers, and assembling the battery;

(5) Assemble a symmetric battery with modified electrodes, glass fiber as separator, and electrolyte using a mixture of 2 moles per liter of zinc sulfate and 0.2 moles per liter of manganese sulfate. The CR2025 coin cell battery was assembled in the air and tested on the LANDCT2001A tester after standing for 10 h.

Example 2

In step (1), hydrothermal crystallization is carried out in the reaction kettle, the temperature is 95° C., and the time is 6 hours. Others are the same as in Example 1.

Example 3

In step (1), crystallization was carried out in a reaction kettle, the temperature was 70° C., and the time was 6 hours. Others are the same as in Example 1.

Example 4

In step (1), crystallization was carried out in a reaction kettle, the temperature was 45° C., and the time was 6 hours. Others are the same as in Example 1.

Example 5

In step (3), the binder is CMC, and the solvent is water. Others are the same as in Example 1.

Example 6

In step (3), the binder is PEO, and the solvent is NMP. Others are the same as in Example 1.

Example 7

The coating amount of the coating agent in step (3) was adjusted so that the thickness of the coating obtained in step (4) was 10 μm.

Example 8

The coating amount of the coating agent in step (3) was adjusted so that the thickness of the coating obtained in step (4) was 20 μm. Others are the same as in Example 1.

In addition to the symmetrical battery test, this example also conducts a full-cell test: using manganese dioxide as the positive electrode and matching the protected zinc metal negative electrode to assemble a CR2025 coin cell battery, and test it on a LAND CT2001A tester after standing for 10 hours.

The manganese dioxide positive electrode is prepared by mixing alpha manganese dioxide with a conductive agent and a binder, adding an organic solvent to make a slurry, coating it on a carbon cloth, and vacuum drying.

Example 9

The coating amount of the coating agent in step (3) was adjusted so that the thickness of the coating obtained in step (4) was 30 μm.

Example 10

The coating amount of the coating agent in step (3) was adjusted so that the thickness of the coating obtained in step (4) was 60 μm.

Example 11

The coating amount of the coating agent in step (3) was adjusted so that the thickness of the coating obtained in step (4) was 75 μm.

Comparative Example 1

Zinc foil was used as the positive electrode and negative electrode, glass fiber was used as the separator, and the electrolyte was a mixed solution of 2 mol per liter of zinc sulfate and 0.2 mol per liter of manganese sulfate. The CR2025 coin cell battery was assembled in the air and tested on the LAND CT2001A tester after standing for 10 h.

Comparative Example 2

In step (2), only one low-concentration ion exchange is performed, that is, the ratio of zinc ion to dry crystallization product is 0.01 mol/g. Other methods are the same as those described in Example 8.

Comparative Example 3

With zinc foil as the negative electrode, manganese dioxide as the positive electrode, glass fiber as the separator, the electrolyte uses a mixture of 2 moles per liter of zinc sulfate and 0.2 moles per liter of manganese sulfate. The CR2025 coin cell battery was assembled in the air and tested on the LANDCT2001A tester after standing for 10 h.

Table 1: Polarization voltage and cycle time of metal symmetric battery after stabilization in each example and each comparative example

FIG. 1 is a BET nitrogen adsorption diagram of the modified layer obtained in Example 8 of the present invention. 2 is a polarization voltage diagram of the metal electrode protected by the 20 μm modified layer in Example 8 of the present invention, the non-modified electrode of Comparative Example 1, and the modified metal electrode used in Comparative Example 2. FIG. 3 is a long cycle capacity-turn comparison diagram of the aqueous zinc-ion batteries in Example 8 and Comparative Example 3. FIG.

It can be seen from Table 1 and Figure 1-3 that:

The increase of the crystallization temperature has a negative impact on the polarization voltage and cycle performance of the battery, and the crystallization method at low temperature and long time is preferred.

The used binder basically has no significant effect on the polarization voltage and cycle time of the battery.

The optimal choice for the coating thickness is 20 μm.

In the coating obtained in Example 8, the pores of the molecular sieve were enlarged by ion exchange, with an average pore size of 0.523 nm, and at the same time, most of the sodium ions that could not participate in the deposition process were removed. This can significantly improve the molecular dynamics of the reaction.

The polarization voltage of the zinc metal symmetric battery of each embodiment of the present invention in the aqueous electrolyte is in the range of 15mV-40mV, which is significantly lower than that of the unmodified zinc metal symmetric battery of Comparative Example 1. XRD and Tafel curve tests were performed on the electrode sheet after the cycle, and it was found that the surface of the modified electrode of each embodiment of the present invention did not generate obvious side reaction products, and the corrosion resistance was enhanced, while the surface of the electrode sheet in Comparative Example 1 generated by-product basic formula. Zinc sulfate. This shows that the modified electrode of the present invention inhibits the hydrogen evolution and the passivation reaction of the electrode surface. The metal symmetric battery of the embodiment of the present invention can be stably cycled for more than 2000h, and the stable cycle time is more than 20 times that of the unmodified zinc negative electrode, indicating that the modified electrode of the present invention inhibits the growth of zinc dendrites. The water-based zinc-ion battery of the embodiment of the present invention still shows a higher specific capacity after 8000 cycles, and shows a stronger capacity retention rate than the comparative example 3, indicating that the full battery in the present invention is applied by modifying the negative electrode It has successfully improved the practical application prospects.

Claims (6)

1. A negative electrode preparation method of a zinc ion battery, comprising: provide zinc foil; providing a silicon ion source selected from at least one of the group consisting of silica gel, water glass, sodium silicate and ethyl orthosilicate; providing a source of aluminum ions selected from at least one of the group consisting of hydrated aluminum sulfate and sodium metaaluminate; The silicon ion source, the aluminum ion source and the sodium hydroxide are formed into a mixed aqueous solution, wherein the molar ratios of silicon ions, sodium ions and water molecules to aluminum ions are respectively 1.5-1, 5-3 and 90-80; Control the temperature of the mixed aqueous solution to carry out hydrothermal crystallization between 25°C and 90°C for at least 5 hours; The crystallized product was separated by centrifugation; The crystallized product is dried and added to zinc ion aqueous solutions of different concentrations to carry out ion exchange in turn, wherein the molar amount of zinc ions and the mass ratio of the dried product are between 0.01 mol/g and 1 mol/g, and the ion exchange is carried out according to the zinc ion aqueous solution. The concentration is carried out in sequence from low to high, and centrifugal drying is carried out after each ion exchange; The drying product obtained after the last ion exchange is mixed with a binder and a solvent to obtain a coating agent; The obtained coating agent is uniformly coated on the zinc foil to form a coating, wherein the coating thickness is 5 μm-75 μm after the solvent is evaporated. 2. The method according to claim 1, wherein the mass ratio of the obtained dried product to the binder is between 20:1 and 7:1. 3. The method of claim 1, wherein the binder is at least one selected from the group consisting of polyvinylidene fluoride, polyethylene oxide, and carboxymethyl cellulose. 4. The method of claim 1, wherein the solvent used to form the coating agent is N-methylpyrrolidone or water. 5. A negative electrode for a zinc-ion battery, prepared by the method according to one of claims 1-4. 6. A zinc-ion battery comprising the negative electrode of claim 5.

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