CN113140808A

CN113140808A - Water-based battery

Info

Publication number: CN113140808A
Application number: CN202110433949.0A
Authority: CN
Inventors: 谢健; 孙云坡; 许峥; 赵新兵
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-04-21
Filing date: 2021-04-21
Publication date: 2021-07-20
Anticipated expiration: 2041-04-21
Also published as: CN113140808B

Abstract

The invention discloses an aqueous battery, which comprises a positive electrode, a negative electrode and an aqueous electrolyte, wherein the aqueous electrolyte comprises heavy water and salt. The invention adopts the special water system electrolyte composed of heavy water and salt, which not only widens the electrochemical window of the electrolyte, but also is beneficial to using high-voltage electrode materials, thereby improving the energy density of the battery; in addition, in the aqueous electrolyte, the stability of the electrode material is improved, and the cycle life of the aqueous battery can be improved.

Description

Water-based battery

Technical Field

The invention relates to the technical field of energy storage batteries, in particular to a water system battery.

Background

With the consideration of the increasingly serious energy and environmental problems, the development of clean and renewable energy sources such as solar energy, wind energy, tidal energy and the like is urgent. Such clean and renewable energy sources are greatly influenced by time and climate and have the defects of instability, discontinuity, uncontrollable and the like. To improve the efficiency of use of such clean energy, high-performance energy storage batteries are required, and among them, low cost and safety are important indicators.

The water-based battery is widely interested in low price, safety and environmental protection, but the adopted water-based electrolyte is not beneficial to using high-voltage electrode materials due to the narrow electrochemical window, so that the energy density of the battery is influenced. In addition, the electrode material is unstable in aqueous solution, and particularly when the battery is charged to a high voltage, it is disadvantageous in improving cycle life. Therefore, how to improve the electrochemical window of an aqueous battery and improve the stability of an electric material in an aqueous solution is a problem in this field.

The existing method, such as using high-concentration salt and electrolyte additive, can improve the electrochemical window of the water system battery to a certain extent and improve the stability of the material in aqueous solution, but often faces the problems of high cost and reduction of ion diffusion rate.

In view of the above, there is a need to develop a simple and inexpensive method for increasing the stability of an electrode material while widening the electrochemical window of an aqueous battery.

Disclosure of Invention

Aiming at the problems in the prior art, the invention discloses a water system battery, which adopts a special water system electrolyte consisting of heavy water and salt, thereby widening the electrochemical window of the electrolyte, being beneficial to using high-voltage electrode materials and further improving the energy density of the battery; in addition, in the aqueous electrolyte, the stability of the electrode material is improved, and the cycle life of the aqueous battery can be improved.

The specific technical scheme is as follows:

an aqueous battery includes a positive electrode, a negative electrode, and an aqueous electrolyte solution including heavy water and a salt.

The invention firstly proposes heavy water as a solvent of the aqueous electrolyte, and tests show that the aqueous electrolyte has a higher electrochemical window, is beneficial to using a high-voltage electrode material and improves the energy density of the battery.

The salt, the cation containing Li⁺、Na⁺、K⁺、NH₄ ⁺、Ca²⁺、Zn²⁺、Fe²⁺、Mg²⁺、Al³⁺One or more of; the anion containing NO₃ ^-、SO₄ ^2-、Cl^-、ClO₄ ^-、(CF₃SO₂)₂N^-、CF₃SO₃ ^-、(SO₂F)₂N^-One or more of；

Preferably, the salt, anion is selected from fluorine-containing anions such as (CF)₃SO₂)₂N^-、CF₃SO₃ ^-、(SO₂F)₂N^-The anion has the advantages of good solubility and good stabilizer, but the price is high, and if the effect of widening the electrochemical window of the electrolyte is achieved, the addition amount of the anion needs to reach 21mol/kg, which causes the production cost to be greatly increased.

Preferably, the concentration of the salt in the aqueous electrolyte is 0.5 to 2mol/kg in terms of cation.

According to the invention, the salt concentration is controlled to be lower (0.5-2 mol/kg), the specific auxiliary salt is added, and heavy water is combined, so that the electrochemical window of the electrolyte is widened, and the energy density and the cycle life of the water system battery are improved through the combined action of the salt concentration, the auxiliary salt and the heavy water.

Preferably, the auxiliary salt, cation contains Li⁺、Na⁺、K⁺、NH₄ ⁺、Ca²⁺、Zn²⁺One or more of; the anion containing CH₃COO^-、C₆H₁₁O₇ ^-、C₄H₄O₅ ^2-、C₄H₈O₈ ^2-One or more of;

the concentration of the auxiliary salt in the aqueous electrolyte is 1-30 mol/kg in terms of cations.

Further preferably, the auxiliary salt is Ca²⁺、K⁺The cation which is easy to dissolve in water and easy to be hydrated with water destroys the hydrogen bond in water, thereby further widening the electrochemical window of the electrolyte and the stability of the electrode material in the electrolyte by improving the concentration of the cation; selection C₆H₁₁O₇ ^-、C₄H₄O₅ ^2-、C₄H₈O₈ ^2-And the like, which are cheap and easily soluble in water, and the contained groups can form hydrogen bonds with water to destroy the original waterThereby further increasing the water decomposition voltage.

Further preferably:

in the aqueous electrolyte, the concentration of salt is 1-1.5 mol/kg, and the concentration of auxiliary salt is 5-10 mol/kg.

Still more preferably, the aqueous electrolyte solution contains 1mol/kg of NaCF₃SO₃0.1mol/kg of Zn (CF)₃SO₃)₂And 6mol/kg of auxiliary salt;

more preferably, the anion of the auxiliary salt is selected from C₄H₈O₈ ^2-。

With the above-mentioned raw material types and concentrations being preferred, the finally assembled water-based battery has a higher electrochemical window and a better cycle life.

In the water-based battery, the positive electrode is selected from Prussian blue materials and has a structural general formula A_xM_y[Fe(CN)₆]_z·nH₂O, wherein A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺M is selected from one or more of Mn, Fe, Co, Ni, Cu, Zn and Ca; wherein x is more than 1.5 and less than or equal to 2, y is more than 0.6 and less than or equal to 1, z is more than 0.8 and less than or equal to 1, and n is more than 0 and less than or equal to 10.

Preferably, the M is selected from Mn, Fe and Co, and the material has higher capacity; a is Na⁺、K⁺、NH₄ ⁺In this case, the voltage of the aqueous battery is high and the cost is low.

Further preferably, the M is selected from Mn, and tests show that the battery has higher voltage and can improve the energy density.

The Prussian blue material is prepared by adopting the prior art, such as coprecipitation or ion exchange synthesis.

For improving the conductivity and stability in the electrolyte, preference is given to A_xM_y[Fe(CN)₆]_z·nH₂O is subjected to surface coating treatment, the coating material is selected from but not limited to carbon materials, conductive polymers, metals and ceramic electrolytes, preferably, the thickness of the coating layer is 10-100 nanometers, and the coating layer is coated on the positive electrodeThe coating layer accounts for 1-10% of the total weight of the material.

The manufacturing method of the anode piece is to coat or not coat the anode active material (A)_xM_y[Fe(CN)₆]_z·nH₂O), conductive agent and binder are mixed evenly according to a certain proportion, are stirred into slurry, are coated on a conductive substrate, are dried and rolled to prepare a positive electrode, the conductive agent and the binder have no special requirements, and can respectively use commercial conductive carbon and fluorine-containing oily polymer binder, the proportion can adopt the proportion commonly used by commercial batteries, and the conductive substrate can adopt common conductive materials such as carbon cloth, carbon paper, titanium foil, stainless steel foil and the like.

In the water-based battery, the negative electrode is selected from metal, Prussian blue material or titanium phosphate; when the negative electrode uses metal, the water-based battery is a daniel battery, namely, the metal is subjected to dissolution and deposition reaction on the negative electrode side, metal ions are not inserted into the positive electrode, the insertion and extraction reaction of A ions is carried out on the positive electrode, and the A ions are not subjected to deposition and dissolution reaction on the negative electrode; when the prussian blue material and titanium phosphate are used for the negative electrode, the aqueous battery is a rocking chair battery, namely, a ions shuttle between the positive electrode and the negative electrode.

The metal is selected from Zn, Fe, Mg, Al, Ca or alloys and compounds thereof;

the alloy refers to an alloy formed by Zn, Fe, Mg, Al, Ca and other elements, preferably, the other elements are selected from metals with corrosion resistance and no electrochemical activity, such as Mo, Ni, Cr, Ti and the like;

the compound is a material compounded by Zn, Fe, Mg, Al, Ca and other materials, and the other materials are selected from carbon materials such as acetylene black, Ketjen black, carbon nanotubes, carbon fibers, graphene and the like.

Preferably, the metal surface contains a modification layer selected from a solid electrolyte protective layer containing metal ions to protect the metal and inhibit dendrite formation and material corrosion.

The general formula of the Prussian blue material is shown in the specification

Wherein A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺One or more of, M₁One or more selected from Mn, Fe, Co, Ni, Cu and Zn, M₂Is selected from Mn and/or Cr, x is more than 1.5 and less than or equal to 2, y is more than 0.8 and less than or equal to 1, and z is more than 0 and less than or equal to 10; the Prussian blue cathode material has low working voltage and high capacity, and preferably, A is Na⁺、K⁺、NH₄ ⁺In this case, the voltage of the aqueous whole cell is high, and the cost is low.

The Prussian blue material is prepared by adopting the prior art, such as coprecipitation or ion exchange synthesis. In order to improve the conductivity and the stability in the electrolyte, the surface of the anode material is preferably coated, the coating material is selected from but not limited to carbon materials, conductive polymers, metals and ceramic electrolytes, the thickness of the coating layer is preferably 10-100 nanometers, and the coating layer accounts for 1% -10% of the total weight of the anode material.

The general formula of the titanium phosphate is ATi₂(PO₄)₃In the formula, A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺One or more of; preferably, A is selected from Na⁺、K⁺、NH₄ ⁺In this case, the voltage of the aqueous battery is high, and the cost is low. The titanium phosphate is prepared by a solid-phase method or a solvothermal method, and is subjected to surface coating treatment for improving the electric rate and the stability in electrolyte, wherein a coating material is selected from but not limited to carbon materials, conductive polymers, metals and solid electrolytes, preferably, the thickness of the coating layer is 10-100 nanometers, and the coating layer accounts for 1-10% of the total weight of the negative electrode material.

The preparation method of the negative electrode comprises the steps of uniformly mixing a negative electrode active material, a conductive agent and a binder according to a certain proportion, stirring into slurry, coating the slurry on a conductive substrate, drying and rolling to prepare the positive electrode, wherein the conductive agent and the binder have no special requirements, commercial conductive carbon and fluorine-containing oily polymer binders can be used respectively, the proportion can be the proportion commonly used in commercial batteries, and the conductive substrate can be made of common conductive materials such as carbon cloth, carbon paper, titanium foil, stainless steel foil, copper foil and the like.

The method for manufacturing the water-based battery is to assemble the positive electrode, the negative electrode and the water-based electrolyte into the water-based full battery, the assembling mode and the shape of the battery are not particularly specified, and the battery is assembled into a cylindrical battery or a square battery according to the mode of a commercial battery. The batteries can also be connected in parallel or in series to form a battery pack.

Compared with the prior art, the invention has the following advantages:

1. the invention can improve the electrochemical window by using the heavy water only by using the water as the solvent, and the heavy water is cooperated with the auxiliary salt to further improve the electrochemical window, is suitable for high-voltage electrode materials, and is beneficial to improving the energy density of the water-based battery.

2. The water-based battery has the advantages of safety, low cost and environmental protection.

3. The preparation method has the advantages of simple process, low cost, short period, low energy consumption and the like.

Drawings

Fig. 1 is a schematic structural view of an assembled water-based battery of example 1;

fig. 2 is a charge-discharge curve of the assembled water-based battery of example 1;

fig. 3 is a cycle life of the assembled water-based battery of example 1;

FIG. 4 is a water splitting voltage test curve of the assembled water system battery of example 1;

fig. 5 is a cycle life of the assembled water system battery of comparative example 1;

fig. 6 is a water splitting voltage test curve of the assembled water system battery of comparative example 1.

Detailed Description

To further clarify the objects, technical solutions and advantages of the present invention, the following detailed description of the present invention is provided with reference to specific examples, which should not be construed as limiting the scope of the present invention.

Example 1

Preparation of Na by coprecipitation method_1.87Mn_0.78[Fe(CN)₆]·2.1H₂Taking O as a positive active material and preparing a positive pole piece, wherein the specific preparation process comprises the following steps: simultaneously injecting 50 ml of 0.2mol/L sodium ferrocyanide solution (water is used as a solvent if no special description exists) and 50 ml of 0.2mol/L manganese sulfate solution into 100 ml of 0.3mol/L disodium ethylene diamine tetraacetate solution, and carrying out coprecipitation reaction at 60 ℃ to obtain a positive active material; mixing a positive electrode active material, conductive carbon and polyvinylidene fluoride according to a weight ratio of 7: 2: 1, stirring, coating, drying and rolling to obtain the positive pole piece.

Assembling the positive pole piece, the zinc sheet and the aqueous electrolyte into an aqueous battery, wherein the solvent in the aqueous electrolyte is heavy water, and the salt in the solute is 1mol/kg NaCF₃SO₃With 0.1mol/kg of Zn (CF)₃SO₃)₂The auxiliary salt is 6mol/kg NaC₆H₁₁O₇。

When the battery is subjected to 100 cycles under the voltage range of 0.2-2.15V and the current of 5C (1C is 80mAh/g), the capacity is 125mAh/g, as shown in figure 2, and the capacity retention rate is 63 percent under the current of 5C, as shown in figure 3, and when the water decomposition voltage test is carried out on the battery, the decomposition voltage can reach 2.2V, as shown in figure 4.

Comparative example 1

The electrode was fabricated and the battery was assembled as in example 1 except that ordinary water was used as a solvent, and sodium salt, zinc salt and auxiliary salt were used in the same type and concentration, and the obtained battery was subjected to 100 cycles under the same test conditions as in example 1 at a current of 5C and had a capacity retention of only 47%, see fig. 5, and when the battery was subjected to a water decomposition voltage test, it was seen that the decomposition voltage was 2.1V, see fig. 6.

Comparative example 2

Electrode manufacture and cell assembly as in example 1, except that no auxiliary salt NaC was used₆H₁₁O₇The obtained battery has the capacity retention rate of only 54% after 100 cycles under the same test conditions and 5C current as example 1 by using the sodium salt and the zinc salt with the same type and concentration.

Example 2

The preparation of the positive pole piece is the same as that of the positive pole pieceExample 1 an aqueous battery was assembled from a positive electrode sheet, a zinc sheet and an aqueous electrolyte solution in which the solvent was heavy water and the solute was NaCF of 1mol/kg₃SO₃0.1mol/kg of Zn (CF)₃SO₃)₂And 6mol/kg of Na₂C₄H₈O₈. The capacity retention rate of the battery is 71% after 100 cycles under the current of 5C within the voltage range of 0.2-2.15V.

Example 3

Preparation of K by ion exchange_1.77Fe[Fe(CN)₆]_0.94·1.2H₂Taking O as a positive active material and preparing a positive pole piece, wherein the specific preparation process comprises the following steps: simultaneously injecting 50 ml of 0.2mol/L potassium ferrocyanide solution (water is used as a solvent if no special description exists) and 50 ml of 0.2mol/L ferrous sulfate solution into 100 ml of 0.3mol/L disodium ethylene diamine tetraacetate solution, and carrying out coprecipitation reaction at room temperature to obtain a positive active material; mixing a positive electrode active material, conductive carbon and polyvinylidene fluoride according to a weight ratio of 7: 2: 1, stirring, coating, drying and rolling to obtain the positive pole piece.

Assembling the positive pole piece, the zinc sheet and the aqueous electrolyte into an aqueous battery, wherein the solvent in the aqueous electrolyte is heavy water, and the solute is NaCF with the concentration of 1mol/kg₃SO₃0.1mol/kg of Zn (CF)₃SO₃)₂And 6mol/kg of CH₃And COOK (cooling). The capacity retention rate of the battery is 63% after 100 cycles under the current of 5C within the voltage range of 0.2-2.15V.

Claims

1. An aqueous battery comprising a positive electrode, a negative electrode and an aqueous electrolyte, characterized in that the aqueous electrolyte comprises heavy water and a salt.

2. The aqueous battery according to claim 1, wherein the salt and the cation contain Li⁺、Na⁺、K⁺、NH₄ ⁺、Ca²⁺、Zn²⁺、Fe²⁺、Mg²⁺、Al³⁺One or more of; the anion containing NO₃ ^-、SO₄ ^2-、Cl^-、ClO₄ ^-、(CF₃SO₂)₂N^-、CF₃SO₃ ^-、(SO₂F)₂N^-One or more of;

the concentration of the salt in the aqueous electrolyte is 0.5-2 mol/kg in terms of cation.

3. The aqueous battery according to claim 1, further comprising an auxiliary salt in which a cation contains Li⁺、Na⁺、K⁺、NH₄ ⁺、Ca²⁺、Zn²⁺One or more of; the anion containing CH₃COO^-、C₆H₁₁O₇ ^-、C₄H₄O₅ ^2-、C₄H₈O₈ ^2-One or more of;

4. The aqueous battery according to claim 3, wherein the concentration of the salt in the aqueous electrolyte is 1 to 1.5mol/kg, and the concentration of the auxiliary salt is 5 to 10 mol/kg.

5. The aqueous battery according to claim 1, wherein the positive electrode is selected from Prussian blue materials and has a general structural formula A_xM_y[Fe(CN)₆]_z·nH₂O；

Wherein A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺M is selected from one or more of Mn, Fe, Co, Ni, Cu, Zn and Ca; wherein x is more than 1.5 and less than or equal to 2, y is more than 0.6 and less than or equal to 1, z is more than 0.8 and less than or equal to 1, and n is more than 0 and less than or equal to 10.

6. The aqueous battery according to claim 1, wherein the negative electrode is selected from a metal, a prussian blue material, or a titanium phosphate;

the metal is selected from Zn, Fe, Mg, Al, Ca or alloys and compounds thereof;

the general formula of the Prussian blue material is shown in the specification

Wherein A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺One or more of, M₁One or more selected from Mn, Fe, Co, Ni, Cu and Zn, M₂Is selected from Mn and/or Cr, x is more than 1.5 and less than or equal to 2, y is more than 0.8 and less than or equal to 1, and z is more than 0 and less than or equal to 10;

the general formula of the titanium phosphate is ATi₂(PO₄)₃In the formula, A is selected from Li⁺、Na⁺、K⁺、NH₄ ⁺One or more of (a).