An electrolyte for an aqueous secondary battery, a secondary battery, and applications thereof

Abstract

An electrolyte for an aqueous secondary battery, a secondary battery and its application, belonging to the technical field of aqueous batteries, overcomes the defect that oxygen evolution occurs on the positive electrode of the existing aqueous battery, resulting in insufficient cycle stability of the battery. The present invention provides an electrolyte for an aqueous secondary battery, comprising water, a metal salt and an additive, wherein the additive is a tin salt, and the concentration of the additive is 0.01 to 0.02 mol / L. The present invention increases the oxygen evolution overpotential at the oxygen evolution sites, thereby inhibiting the oxygen evolution reaction activity on the surface of the positive electrode, reducing the oxygen evolution decomposition of water in the aqueous electrolyte, and at the same time avoiding the interference of the oxygen evolution overpotential layer with the normal charge and discharge reactions of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous batteries, and particularly relates to an electrolyte for an aqueous secondary battery, a secondary battery and its applications. Background Art

[0002] The extensive application of fossil energy has led to energy crises and environmental pollution problems, and the development of renewable clean energy has become a trend. Renewable clean energies, such as wind energy, water energy, and solar energy, mostly have the characteristic of intermittency. This makes energy storage one of the key technologies for the development of renewable energy. Among various energy storage methods, electrochemical energy storage has received extensive attention from scholars and the industrial community due to its high conversion efficiency, small limitations, and low maintenance costs. Among them, aqueous secondary batteries are very valuable electrochemical energy storage devices because they are safe, non-toxic, and low-cost. However, limited by the decomposition window of water (1.23 V), aqueous secondary batteries have the disadvantage of oxygen evolution on the positive electrode, which in turn leads to insufficient cycle stability of the battery.

[0003] The occurrence of oxygen evolution reaction on the positive electrode will result in low Coulombic efficiency of the battery. On the other hand, the accumulation of the evolved oxygen will not only cause the rupture of the battery casing, but also pose a great safety hazard due to the flammability of hydrogen. And the pH of the electrolyte will decrease due to the oxygen evolution reaction, which puts forward requirements for the acid resistance of both the positive and negative electrode materials.

[0004] Currently, there is little work on suppressing oxygen evolution on the positive electrode. The reported solutions are to separate the positive and negative electrode electrolytes with bipolar membranes and use organic-inorganic mixed electrolytes. Separating the positive and negative electrode electrolytes with different pH values by bipolar membranes will lead to a complex battery structure, which is not conducive to industrial production, and the technical route is quite different from that of traditional organic lithium batteries, and the compatibility with the current technology is not good. Organic-inorganic mixed electrolytes will greatly increase the cost of the electrolyte, and the flammability and pollution of the electrolyte are likely to cause aqueous batteries to lose their traditional advantages of being green, safe, and environmentally friendly. Therefore, studying a low-cost and reliable oxygen evolution suppression scheme is the key to current aqueous alkali metal secondary batteries. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect that oxygen evolution occurs on the positive electrode of the aqueous battery in the prior art, resulting in insufficient cycle stability of the battery, so as to provide an electrolyte for an aqueous secondary battery, a secondary battery and its applications.

[0006] To this end, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides an electrolyte for an aqueous secondary battery, which includes water, a metal salt, and an additive. The additive is a tin salt, and the concentration of the additive is 0.01 - 0.02 mol / L.

[0008] Further, the metal salt is an alkali metal salt.

[0009] Further, the tin salt is one or more of tin tetrachloride, tin sulfate, tin alkylsulfonate, and tin alkanolsulfonate.

[0010] Further, the tin alkylsulfonate is tin methylsulfonate, tin ethanesulfonate, tin propanesulfonate, or tin 2-propanesulfonate;

[0011] The tin alkanolsulfonate is tin hydroxymethanesulfonate, tin 2-hydroxyethyl-1-sulfonate, or tin 2-hydroxybutyl-1-sulfonate.

[0012] Further, in the alkali metal salt, the cations include Li + , Na + , K + and at least one of them.

[0013] Further, in the alkali metal salt, the anions include ClO 4 - , NO 3- , SO 4 2- , PO 4 3- , CO 3 2- , CH 3 COO - , CF 3 SO 3 - , TFSI - (bis(trifluoromethanesulfonyl)imide), FSI - (bis(fluorosulfonyl)imide) and at least one of them.

[0014] Further, in the electrolyte, the concentration of each component in the alkali metal salt is 0.5 - 2 mol / L.

[0015] In the second aspect, the present invention provides a method for preparing an electrolyte for an aqueous secondary battery, adding a tin salt and a metal salt to water and stirring to form a transparent liquid.

[0016] In the third aspect, the present invention provides an aqueous secondary battery including the electrolyte.

[0017] Optionally, the aqueous secondary battery is an aqueous alkaline secondary battery.

[0018] The aqueous secondary battery is specifically: an aqueous lithium-ion battery, an aqueous sodium-ion battery, an aqueous potassium-ion battery, an aqueous lithium-sodium hybrid battery, an aqueous lithium-potassium hybrid battery, or an aqueous sodium-potassium hybrid battery.

[0019] Application of the aqueous secondary battery in energy storage power stations, portable devices, electric vehicles or hybrid vehicles.

[0020] The technical solution of the present invention has the following advantages:

[0021] 1. The electrolyte for the aqueous alkali metal secondary battery provided by the present invention includes water, an alkali metal salt and an additive. The additive is a tin salt, and the concentration of the additive is 0.01 - 0.02 mol / L.

[0022] By adding a tin salt to the electrolyte, during the charging process, tin ions generate tin oxide (SnO 2 ) deposition at the positive electrode. SnO 2 has a large overpotential, which can greatly improve the oxygen evolution overpotential at the oxygen evolution sites, thereby inhibiting the oxygen evolution reaction activity on the surface of the positive electrode, reducing the oxygen evolution decomposition of water in the aqueous electrolyte, effectively inhibiting gas swelling, and thus improving the safety performance, cycle performance and service life of the aqueous secondary battery.

[0023] The present invention does not need to change the battery structure, has good compatibility with the current technology, and can control costs. Moreover, it does not need to add organic compounds, and is green, safe and environmentally friendly.

[0024] The concentration of the additive will affect the deposition amount of the oxygen evolution overpotential layer, and further affect the oxygen evolution overpotential of the electrode. The concentration of the additive in the present invention can ensure the inhibition effect of oxygen evolution at the positive electrode, while avoiding the oxygen evolution overpotential layer from interfering with the normal charge and discharge reactions of the battery. Description of the Drawings

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 is the physical diagram of the electrolyte in Example 1;

[0027] Figure 2 is the charge and discharge curve diagram of the batteries prepared in Example 1 and Comparative Example 1 at room temperature;

[0028] Figure 3 is the linear voltammetry curve diagram of the electrolytes prepared in Example 1 and Comparative Example 1 at room temperature;

[0029] Figure 4 is the long cycle - capacity retention rate diagram of the batteries prepared in Example 1 and Comparative Example 1 at room temperature;

[0030] Figure 5 It is the long - cycle Coulomb efficiency graph of the batteries prepared in Example 1 and Comparative Example 1 at room temperature. Detailed implementation manners

[0031] The following embodiments are provided to better further understand the present invention. It is not limited to the described optimal implementation manner, and does not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior - art features falls within the protection scope of the present invention.

[0032] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0033] Example 1

[0034] This example provides a method for preparing an electrolyte: Dissolve 127.96 g (1 mol) of lithium sulfate monohydrate, 142.04 g (1 mol) of sodium sulfate, and 5.20 g (0.02 mol) of tin tetrachloride in an appropriate amount of water to form a 1 - L solution, stir and disperse evenly to obtain a homogeneous and stable electrolyte. As Figure 1 shown, this electrolyte is clear and transparent.

[0035] Add the above - mentioned neutral electrolyte into a battery with LiMn 2 O 4 as the positive electrode and NaTi 2 (PO 4 ) 3 as the negative electrode. The active material loading is 94 mg / cm 2 for lithium manganate and 61 mg / cm 2 for sodium titanium phosphate.

[0036] Example 2

[0037] This example provides a method for preparing an electrolyte: Dissolve 255.92 g (2 mol) of lithium sulfate monohydrate, 213.06 g (1.5 mol) of sodium sulfate, and 2.60 g (0.01 mol) of tin tetrachloride in an appropriate amount of water to form a 1 - L solution, stir and disperse evenly to obtain a homogeneous and stable electrolyte.

[0038] Add the above - mentioned neutral electrolyte into a battery with LiMn 2 O 4 as the positive electrode and NaTi 2 (PO 4 ) 3In the battery with the negative electrode, the active material loading is 94 mg / cm of lithium manganate 2 and 61 mg / cm of sodium titanium phosphate 2 .

[0039] Example 3

[0040] This example provides a method for preparing an electrolyte: Dissolve 217.53 g (1.7 mol) of lithium sulfate monohydrate, 142.04 g (1 mol) of sodium sulfate, and 2.60 g (0.01 mol) of tin tetrachloride in an appropriate amount of water to form a 1 L solution, stir and disperse evenly to obtain a homogeneous and stable electrolyte.

[0041] Add the above neutral electrolyte to a battery with LiMn 2 O 4 as the positive electrode and NaTi 2 (PO 4 ) 3 as the negative electrode, where the active material loading is 94 mg / cm of lithium manganate 2 and 61 mg / cm of sodium titanium phosphate 2 .

[0042] Example 4

[0043] This example provides a method for preparing an electrolyte: Dissolve 142.04 g (1 mol) of sodium sulfate and 26.02 g (0.1 mol) of tin tetrachloride in an appropriate amount of water to form a 1 L solution, stir and disperse evenly to obtain a homogeneous and stable solution.

[0044] Add the above neutral electrolyte to a battery with sodium vanadium phosphate as the positive electrode and NaTi 2 (PO 4 ) 3 as the negative electrode.

[0045] Example 5

[0046] This example provides a method for preparing an electrolyte: Dissolve 127.96 g (1 mol) of lithium sulfate monohydrate, 142.04 g (1 mol) of sodium sulfate, and 3.09 g (0.01 mol) of tin methylsulfonate in an appropriate amount of water to form a 1 L solution, stir and disperse evenly to obtain a homogeneous and stable solution.

[0047] Add the above neutral electrolyte to a battery with LiMn 2 O 4 as the positive electrode and NaTi 2 (PO 4 ) 3 as the negative electrode, where the active material loading is 94 mg / cm of lithium manganate 2 and 61 mg / cm of sodium titanium phosphate2 。

[0048] Comparative Example 1

[0049] This comparative example is basically the same as Example 1, except that tin tetrachloride is not added in this comparative example.

[0050] Comparative Example 2

[0051] This comparative example is basically the same as Example 1, except that the additive in this comparative example is manganese sulfate.

[0052] Comparative Example 3

[0053] This comparative example is basically the same as Example 1, except that the concentration of tin tetrachloride is 0.04 mol / L.

[0054] Comparative Example 4

[0055] This comparative example is basically the same as Example 1, except that the concentration of tin tetrachloride is 0.06 mol / L.

[0056] Test Example

[0057] (1) Charge-discharge tests were carried out on the batteries of Example 1 and Comparative Example 1 under the test conditions of a current of 20 mA / g, and the test results are as Figure 2 shown.

[0058] The linear voltammetry curves of the electrolytes of Example 1 and Comparative Example 1 were tested under the test condition of 0.3 mV / s. The test results are as Figure 3 shown.

[0059] It can be seen from Figure 2 that the specific capacity of Example 1 is greater than that of Comparative Example 1, and the charge-discharge polarization of Example 1 is less than that of Comparative Example 1. It can be seen from Figure 3 that the oxygen evolution potential becomes larger after deposition in Example 1. In summary, it can be known that the tin salt of the present invention will increase the oxygen evolution overpotential after deposition on the positive electrode material, and this protective layer will not interfere with the normal charge-discharge reaction of the battery.

[0060] (2) Long cycle tests were carried out on the batteries of the examples and comparative examples at room temperature under the test process of 50 mA / g, and the test results are shown in Table 1 and Figure 4 、 Figure 5 。

[0061] Table 1 Battery Performance

[0062]

[0063] The experimental data of Coulombic efficiency and cycle life can prove that the addition of the oxygen evolution inhibition additive in the present invention inhibits the water decomposition reaction. Therefore, the safety hazard caused by the water decomposition reaction is alleviated, and it is relatively safer. At the same time, the oxygen evolution overpotential layer is avoided from interfering with the normal charge and discharge reactions of the battery.

[0064] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. The obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. An electrolyte for an aqueous secondary battery, characterized in that, it is composed of water, an alkali metal salt and an additive, the additive is a tin salt, and the concentration of the additive is 0.01 - 0.02 mol / L.

2. The electrolyte for an aqueous secondary battery according to claim 1, characterized in that, the tin salt is one or more of tin tetrachloride, tin sulfate, alkylsulfonic acid tin salt, and alkanol sulfonic acid tin salt.

3. The electrolyte for an aqueous secondary battery according to claim 2, characterized in that, the alkylsulfonic acid tin salt is tin methyl sulfonate, tin ethane sulfonate, tin propane sulfonate or tin 2 - propane sulfonate; the alkanol sulfonic acid tin salt is tin hydroxy methane sulfonate, tin 2 - hydroxyethyl - 1 - sulfonate or tin 2 - hydroxybutyl - 1 - sulfonate.

4. The electrolyte for an aqueous secondary battery according to claim 1, characterized in that, Among the alkali metal salts, the cations include Li + , Na + , K + and at least one of them.

5. The electrolyte for an aqueous secondary battery according to claim 4, characterized in that, Among the alkali metal salts, the anions include ClO 4 - , NO 3- , SO 4 2- , PO 4 3- , CO 3 2- , CH 3 COO - , CF 3 SO 3 - , TFSI - , FSI - and at least one of the following.

6. The electrolyte for an aqueous secondary battery according to claim 5, characterized in that, in the electrolyte, the concentration of each component in the alkali metal salt is 0.5 - 2 mol / L.

7. A method for preparing the electrolyte for an aqueous secondary battery according to any one of claims 1 - 6, characterized in that, adding the tin salt and the metal salt into water and stirring to form a transparent liquid.

8. An aqueous secondary battery, characterized in that, it includes the electrolyte according to any one of claims 1 - 6.

9. Application of the aqueous secondary battery according to claim 8 in an energy storage power station, a portable device, an electric vehicle or a hybrid vehicle.

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