Near single ion conduction aqueous electrolyte, preparation thereof and application of near single ion conduction aqueous electrolyte in aqueous metal battery

Abstract

The invention belongs to the field of batteries, and particularly relates to a near single ion conduction aqueous electrolyte, preparation thereof and application in an aqueous metal battery, and the electrolyte is an aqueous solution containing main cations, auxiliary cations and multivalent anions; wherein the molar weight of the main cations is more than 1.5 times of the molar weight of the auxiliary cations; wherein the concentration of the main cations is 2-15 M; the main positive ions are positive ions in # imgabs 0 # imgabs 1 #, and the main positive ions are positive ions in # imgabs 0 # imgabs 1 #; the auxiliary positive ions are metal M positive ions, and the metal M contains metal elements which are the same as the negative electrode of the water-based battery applying the near single ion conduction water-based electrolyte. The electrolyte provided by the invention can form a cluster mechanism based on main cations-high valence anions-water, so that metal carriers are decoupled from a solvation environment, and the service life of the battery under wide temperature range and practical conditions is further prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of batteries, and in particular relates to the technical field of aqueous electrolytes. Background Art

[0002] Constructing a new power system with renewable energy as the main body is the basis for achieving carbon neutrality. The development of power storage technology based on high-safety and long-life secondary batteries is the key to the efficient use of renewable energy. Aqueous metal batteries have the advantages of intrinsic safety, abundant raw materials, high energy density and low cost, and are a hot topic in the field of energy storage battery research. Affected by processes such as the desolvation of anions on the surface of the metal negative electrode, metal cations are prone to uneven electrodeposition, which in turn triggers a "tip effect" that causes uncontrolled growth of metal dendrites. These problems are more severe under practical conditions of large surface load and high current. Single-ion conductor electrolytes are the key to solving the problem of dendrite growth at the metal negative electrode and realizing long-life aqueous metal batteries, while traditional aqueous electrolytes cannot have both the high carrier transfer number (t Mn + ), high ionic conductivity (δ), and weak solvation process. Traditional aqueous electrolytes have high ionic conductivity, but their ion transference number is only 0.2-0.4 (ACS Energy Lett. 2, 2563-2575 (2017); J. Am. Chem. Soc. 73, 5650-5652 (1951)). Some studies have achieved near-single-ion conduction by fixing anions on cross-linked polymers, but due to the hindrance of ion conduction by the cross-linked polymer network, such electrolytes exhibit extremely low ionic conductivity (ACS Energy Lett. 7, 4342-4351 (2022); Angew. Chem.-Int. Ed. 63, e202401441 (2024)). In addition, existing aqueous electrolytes have high hydrogen evolution potentials and high freezing points, which cannot meet the performance requirements of electrolytes in practical applications. This is mainly related to the hydrogen bond structure in the electrolyte. Summary of the Invention

[0003] In response to the problems existing in the prior art, the present invention provides a nearly single-ion conductive aqueous electrolyte, aiming to provide an electrolyte with single cation conductivity and excellent performance.

[0004] The second object of the present invention is to provide a method for preparing the nearly single-ion conductive aqueous electrolyte and its application in aqueous metal batteries.

[0005] A third object of the present invention is to provide an aqueous metal battery comprising the nearly single-ion conducting aqueous electrolyte.

[0006] A nearly single-ion conducting aqueous electrolyte, comprising a primary cation, an auxiliary cation (battery active ion, i.e., a metal that is oxidized and reduced at the negative electrode during charging), and a polyvalent anion; wherein the molar amount of the primary cation is at least 1.5 times the molar amount of the auxiliary cation; and wherein the concentration of the primary cation is 2 to 15 M.

[0007] The main cation is a cation having formula 1 to formula 6; the auxiliary cation is a metal M cation, and the metal M element includes an element of the negative electrode of the aqueous battery using the nearly single-ion conductive aqueous electrolyte;

[0008]

[0009] In Formulas 1 to 6, R1 to R5 are one or more of H, C1 to C6 alkyl, amino, nitro, carboxyl or hydroxyl; n is 1 to 8; m is 20 to 1,000,000;

[0010] The multivalent anion is an anion with an absolute value of chemical valence greater than 2.

[0011] The present invention aims to provide an aqueous electrolyte that combines high carrier mobility, high ionic conductivity, and a weak solvation process. However, previous studies have found that the high-concentration salt electrolyte strategy improves ionic conductivity but sacrifices the carrier mobility and increases the desolvation energy, while the polymer gel electrolyte strategy improves the carrier mobility at the expense of reduced ionic conductivity. To address this problem, the present invention provides a new electrolyte, which innovatively uses cations of Formulas 1 to 6 as main ions and active ions as auxiliary cations, and further coordinates the ratio of the two, the concentration of the main cations and the combination of multivalent anions. This can unexpectedly achieve synergy, and can form clusters based on the main cations-high-valent anions-water, thereby inhibiting the conduction migration of anions, thereby achieving single conduction migration of auxiliary cations. In this way, single cation conduction can be achieved based on a new mechanism without the need to add gel, solid electrolyte, etc., thereby improving the ion conduction effect, increasing the carrier migration number, ionic conductivity (δ) and weak solvation, and thus significantly improving its stability and electrochemical performance. For example, the electrolyte described in the present invention can achieve long-term circulation under high positive electrode surface load. Not only that, it can also significantly optimize its low-temperature long-cycle stability.

[0012] In the present invention, the main cation may be a cation of the structure of Formula 1.

[0013] In the present invention, the auxiliary cation is an active ion of the battery, for example, it can be a metal that is oxidized and reduced on the negative electrode during charging, and further can be the same metal element as the negative electrode of the battery.

[0014] As an optional solution, the metal M in the metal M cation is at least one of sodium, lithium, potassium, magnesium, zinc, copper, iron, tin, and aluminum.

[0015] In the present invention, the main cation, main cation concentration, main cation / auxiliary cation ratio and combination of multivalent anions are the key to achieving single auxiliary cation migration based on the new cluster mechanism and thus improving its performance.

[0016] Preferably, the molar ratio of the primary cation to the auxiliary cation is 1.5-15:1, more preferably 2-10:1. Research in the present invention has shown that, when the ratio required by the present invention is controlled, single conduction of the auxiliary cation can be further achieved based on the clustering mechanism of the primary cation, high-valent anion, and water, thereby improving its performance. In the present invention, the term "near single-ion conduction" refers to essentially auxiliary cation conduction.

[0017] In the present invention, in the nearly single-ion conductive aqueous electrolyte, the concentration of the main cation is 4 to 10M; further, it can be 5 to 8M.

[0018] In the present invention, the polyvalent anions include at least one of sulfate, phosphate and carbonate.

[0019] In the present invention, the amount of the polyvalent anions can be determined according to the types and contents of the main cations and auxiliary cations, as long as the chemical balance between the main cations and the auxiliary cations is met.

[0020] In the present invention, the solvent of the single ion conducting aqueous electrolyte can be water only. In this way, the single conduction of auxiliary cations can be achieved based on the cluster mechanism of main cation-multivalent anion-water described in the present invention.

[0021] In addition, the nearly single-ion conductive aqueous electrolyte of the present invention further comprises a water-soluble organic solvent; preferably comprising one or more of methanol, ethanol, polyethylene glycol, glycerol, dimethyl sulfoxide, N,N-dimethylformamide, formamide, tetrahydrofuran, 1,2-dimethoxyethane, acetonitrile, and trimethyl phosphate;

[0022] Preferably, the volume ratio of the water-soluble organic solvent to water is 0.01 to 0.05:1.

[0023] The present invention also provides a method for preparing the nearly single-ion conducting aqueous electrolyte, which comprises dissolving a polyvalent anion salt of a main cation and a polyvalent anion salt of an auxiliary cation in water to prepare the nearly single-ion conducting aqueous electrolyte.

[0024] The present invention also provides an application of the nearly single-ion conductive aqueous electrolyte, which is used as an electrolyte to prepare an aqueous metal M battery.

[0025] In the present invention, based on existing conventional principles and ideas, the nearly single-ion conductive aqueous electrolyte described in the present invention can be used as an electrolyte to prepare the required aqueous metal M battery.

[0026] The present invention also provides an aqueous metal M battery, which comprises the nearly single-ion conductive aqueous electrolyte of the present invention.

[0027] The aqueous metal M battery of the present invention may contain, in addition to the electrolyte of the present invention, other components and structural relationships of the battery may be known.

[0028] For example, in the aqueous metal M battery of the present invention, the negative electrode of the aqueous metal M battery is a metal M negative electrode, or a negative electrode containing a negative electrode active material of metal M (for example, a smear-type negative electrode composited with the negative electrode active material). The negative electrode active material can be a material known in the industry that can provide metal M active ions, for example, lithium titanate, lithium titanium phosphate, sodium titanium phosphate, lithium-containing ternary oxide, sodium-containing ternary oxide, etc.

[0029] For example, the positive electrode active material in the positive electrode of the aqueous metal M battery includes at least one of manganese oxide, lithium manganate, and quaternary ammonium bromide.

[0030] Beneficial effects

[0031] The present invention innovatively uses cations of Formulas 1 to 6 as main ions and active ions as auxiliary cations, and further coordinates the ratio of the two, the concentration of the main cations, and the combination of multivalent anions. In this way, based on the cluster formation mechanism of the main cation-high-valent anion-water, the metal carriers are decoupled from the solvation environment, achieving rapid single-ion conduction and weakening the solvation energy, thereby inhibiting the growth of metal negative electrode dendrites and lowering the freezing point of the electrolyte. The new electrolyte can then improve the battery life under wide temperature range and practical conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The ion migration number and ion conductivity test results of each case in Example 1, wherein the solid points are the test results of the effective technical solution, and the hollow points are the control group;

[0033] Figure 2 1 is a cycle capacity curve diagram of Examples 4 and 5 and Comparative Examples 5 and 6, wherein curve 1 is Example 4, curve 2 is Example 5, curve 3 is Comparative Example 5, and curve 4 is Comparative Example 6;

[0034] Figure 3 1 are the battery charge and discharge curves of Examples 6-8 and Comparative Example 7, wherein Curve 1 is Example 6, Curve 2 is Example 7, Curve 3 is Example 8, and Curve 4 is Comparative Example 7;

[0035] Figure 4 The photoluminescence and EXAFS graphs of Group A and its control group in Example 1 are shown. DETAILED DESCRIPTION

[0036] The present invention is described below by way of examples.

[0037] In the present invention, the main cation can be exemplified by the cation of formula 1.

[0038] The polyvalent anion can be exemplified by sulfate ion.

[0039] In the present invention, the electrolyte can be prepared based on conventional electrolyte preparation methods and ideas, and the sulfate of the main cation and the sulfate of the metal M cation are dissolved in water to obtain the required concentration.

[0040] Example 1

[0041] Electrolyte: a solution comprising water, a sulfate of metal M, and a sulfate of formula 1;

[0042] In the present invention, according to the different metal M ions, they are divided into the following groups:

[0043] Group A (also labeled as 1Zn8GS group): the metal M ion is zinc ion;

[0044] Group B (also labeled as 1Cu8GS group): the metal M ion is copper ion;

[0045] Group C (also labeled as 1Fe8GS group): the metal M ion is ferrous ion;

[0046] Group D (also labeled as 1Sn8GS group): The metal M ion is stannous ion; its concentration is 0.2 M. In addition, 3 M sulfuric acid is added to prevent tin hydrolysis;

[0047] Group E (also labeled as 1Li8GS group): the metal M ion is lithium ion;

[0048] Control group: Compared with groups A to E, the only difference is that no sulfate of formula 1 was added, and other operations and parameters were the same;

[0049] The molar ratio of Formula 1 to metal M is 8:1; except for group D, the concentration of Formula 1 in the electrolyte is 8M;

[0050] The electrolyte prepared by the technical solution of the present invention was tested for ion mobility and ion conductivity at room temperature (25°C). Figure 1 The ion transfer number and ionic conductivity of the electrolyte are provided (solid dots).

[0051] Example 2

[0052] Compared with Group A in Example 1, the only difference is that the sulfate of Formula 1 in the electrolyte is changed to the sulfate of Formula 2, wherein R1 in Formula 2 is a methyl group, R2 to R5 are hydrogen atoms, and the concentration ratio is the same as in Example 1;

[0053] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and ion conductivity of 0.91 and 43.2 mS cm respectively. -1 , achieving near single-ion conduction.

[0054] Example 3

[0055] Compared with Group A in Example 1, the only difference is that the concentration of Formula 1 in the electrolyte is 5M, and the molar ratio of Formula 1 to metal M is 5:2;

[0056] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and ion conductivity of 0.94 and 48.4 mS cm respectively. -1 , achieving near single-ion conduction.

[0057] Comparative Example 1

[0058] Compared with Group A in Example 1, the only difference is that the concentration of Formula 1 in the electrolyte is changed to 1M.

[0059] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and an ion conductivity of 0.23 and 13.6 mS cm respectively. -1 , and near single-ion conduction cannot be achieved.

[0060] Comparative Example 2

[0061] Compared with Group A in Example 1, the only difference is that the sulfate of Formula 1 in the electrolyte is changed to equimolar sulfuric acid (cations are hydrogen protons), and the concentration ratio is the same as in Example 1;

[0062] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and an ion conductivity of 0.12 and 64.2 mS cm respectively. -1 , and near single-ion conduction cannot be achieved.

[0063] Comparative Example 3

[0064] Compared with Group A in Example 1, the only difference is that the concentration of Formula 1 in the electrolyte is changed to 2M, and the molar ratio of Formula 1 to metal M is changed to 1:1;

[0065] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and an ion conductivity of 0.44 and 27.9 mS cm respectively. -1 , and near single-ion conduction cannot be achieved.

[0066] Comparative Example 4

[0067] Compared with Group A in Example 1, the only difference is that the sulfate of Formula 1 in the electrolyte is changed to an equimolar chloride of Formula 1, and the concentration ratio is the same as in Example 1;

[0068] The electrolyte prepared by the technical solution of the present invention has an ion transfer number and an ion conductivity of 0.22 and 45.8 mS cm respectively. -1 , and near single-ion conduction cannot be achieved.

[0069] Example 4

[0070] Compared with Group A of Example 1, the only difference is that the sulfate of metal M is changed to zinc sulfate and lithium sulfate, the molar amounts of the two are equal, and the total concentration of metal M is the same as that of Example 1.

[0071] Assemble the electrolyte prepared in Example 4 with the positive electrode and the negative electrode to form a battery;

[0072] The positive electrode used is a conventional lithium ion deintercalation type positive electrode containing lithium manganese oxide, Super P conductive carbon and PVDF binder in a mass ratio of 8:1:1, with a surface capacity of 0.75 mAh cm -2 (The proportion needs to be recorded, and if possible, it is recommended to record the area);

[0073] The negative electrode uses 0.01mm zinc foil from Qingyuan Metal Materials Co., Ltd.

[0074] The charge and discharge test was carried out at room temperature with a current density of 1C. Figure 2 The battery has a cycle capacity curve (curve 1), and the capacity retention rate is >80% after the battery is cycled 100 times.

[0075] Example 5

[0076] Compared with Group A of Example 1, the only difference is that the sulfate of metal M is changed to copper sulfate and lithium sulfate, the molar amounts of the two are equal, and the total concentration of metal M is the same as that of Example 1.

[0077] Assemble the electrolyte prepared in Example 5 with the positive electrode and the negative electrode to form a battery;

[0078] The positive electrode used is a conventional lithium ion deintercalation type positive electrode containing lithium manganese oxide, Super P conductive carbon and PVDF binder in a mass ratio of 8:1:1, with a surface capacity of 0.75 mAh cm -2 ;

[0079] The negative electrode was changed to 0.01mm copper foil from Qingyuan Metal Materials Co., Ltd.

[0080] The charge and discharge test was carried out at room temperature with a current density of 1C. Figure 2The battery has a cycle capacity curve (curve 2), and the capacity retention rate is >80% after the battery is cycled 100 times.

[0081] Comparative Example 5

[0082] Compared with Example 4, the only difference is that the electrolyte does not contain the sulfate of formula 1. Other operations and parameters are the same as those of Example 4. The cycle capacity curve of the battery is shown in FIG. Figure 2 Curve 3, the capacity retention rate of the battery after 100 cycles is <60%.

[0083] Comparative Example 6

[0084] Compared with Example 5, the only difference is that the electrolyte does not contain the sulfate of formula 1. Other operations and parameters are the same as those of Example 5. The cycle capacity curve of the battery is shown in FIG. Figure 2 Curve 4, the capacity retention rate of the battery after 100 cycles is <30%.

[0085] Example 6

[0086] Compared with Example 1, the only difference is that the sulfate of metal M is zinc sulfate, and the concentration is the same as that of Example 1;

[0087] Assemble the electrolyte prepared in Example 6 with the positive electrode and the negative electrode to form a battery;

[0088] The positive electrode used was a conventional static bromine conversion positive electrode containing hexylpyridinium bromide, zinc bromide, Super P conductive carbon, and sodium carboxymethyl cellulose binder in a mass ratio of 3.7:3.7:2:0.6;

[0089] The negative electrode uses 0.01mm zinc foil from Qingyuan Metal Materials Co., Ltd.

[0090] The charge and discharge test was carried out at room temperature with a current density of 0.25C. Figure 3 The charge and discharge curve of the battery is provided (curve 1), and the specific capacity reaches 128mAh g -1 , the surface capacity reaches 5mAh cm -2 , the capacity retention rate reached 88.1% after 600 cycles at 25℃.

[0091] Example 7

[0092] Compared with Example 6, the only difference is that the charge and discharge test temperature after assembling the battery is changed to 0°C;

[0093] Figure 3 The charge and discharge curve of the battery is provided (curve 2), and the surface capacity reaches 4 mAh cm -2 , the battery capacity retention rate reached 96.8% after 800 cycles.

[0094] Example 8

[0095] Compared with Example 6, the only difference is that the charge and discharge test temperature after assembling the battery is changed to -10°C;

[0096] Figure 3 The charge and discharge curve of the battery is provided (curve 3), and the surface capacity reaches 4 mAh cm -2 , the capacity retention rate reached 80.1% after 500 cycles.

[0097] Comparative Example 7

[0098] Compared with Example 7, the only difference is that the electrolyte does not contain the sulfate of formula 1. Other operations and parameters are the same as those of Example 7. The cycle capacity curve of the battery is shown in FIG. Figure 3 Curve 4, the specific capacity is only 40 mAh g -1 .

[0099] Mechanistic evidence:

[0100] For example, in the electrolyte of group A in Example 1, due to the structural heterogeneity of the ion-water aggregate, the photoluminescence peak will red-shift with the increase of the excitation wavelength ( Figure 4 Curve 1); in the comparative group of Example 1, the photoluminescence peak does not change with the excitation wavelength ( Figure 4 Curve 2);

[0101] As in the control group in Example 1, see Figure 4 Curve 4, X-ray absorption fine structure (EXAFS) test shows that Zn 2+ -H2O coordination In R space, Zn 2+ -SO4 2- coordination See Figure 4 Curve 3, in Example 1, the sulfate concentration in the electrolyte of group A is higher than that of the control group, but the Zn 2+ -SO4 2- The coordination peak weakened instead, proving the aggregation effect.

Claims

1. A nearly single-ion conducting aqueous electrolyte, characterized in that: An aqueous solution comprising a primary cation, an auxiliary cation, and a multivalent anion; wherein the molar amount of the primary cation is 1.5 times or more of the molar amount of the auxiliary cation; wherein the concentration of the primary cation is 2 to 15 M; The main cation is a cation having formula 1 to formula 6; the auxiliary cation is a metal M cation, and the metal M element includes an element of the negative electrode of the aqueous battery using the nearly single-ion conductive aqueous electrolyte; In Formulas 1 to 6, R1 to R5 are one or more of H, C1 to C6 alkyl, amino, nitro, carboxyl or hydroxyl; n is 1 to 8; m is 20 to 1,000,000; The multivalent anion is an anion with an absolute value of chemical valence greater than 2.

2. The nearly single-ion conducting aqueous electrolyte according to claim 1, wherein: The metal M in the metal M cation is at least one of sodium, lithium, potassium, magnesium, zinc, copper, iron, tin, and aluminum.

3. The nearly single-ion conducting aqueous electrolyte according to claim 1, wherein: The molar ratio of the main cation to the auxiliary cation is 1.5 to 15:1, preferably 2 to 10:

1.

4. The nearly single-ion conducting aqueous electrolyte according to claim 1, wherein: In the nearly single-ion conductive aqueous electrolyte, the main cation concentration is 4 to 10M; further, it can be 5 to 8M.

5. The nearly single-ion conducting aqueous electrolyte according to claim 1, wherein: The multivalent anions include at least one of sulfate, phosphate and carbonate.

6. The nearly single-ion conducting aqueous electrolyte according to claim 1, wherein: The nearly single-ion conductive aqueous electrolyte further comprises a water-soluble organic solvent, preferably comprising one or more of methanol, ethanol, polyethylene glycol, glycerol, dimethyl sulfoxide, N,N-dimethylformamide, formamide, tetrahydrofuran, 1,2-dimethoxyethane, acetonitrile, and trimethyl phosphate; Preferably, the volume ratio of the water-soluble organic solvent to water is 0.00-0.05:

1.

7. A method for preparing a nearly single-ion conducting aqueous electrolyte according to any one of claims 1 to 6, characterized in that: The multivalent anion salt of the main cation and the multivalent anion salt of the auxiliary cation are dissolved in water to prepare the nearly single-ion conductive aqueous electrolyte.

8. Use of the nearly single-ion conducting aqueous electrolyte according to any one of claims 1 to 6, characterized in that: It is used as an electrolyte to prepare aqueous metal M batteries.

9. An aqueous metal M battery, characterized in that: The invention comprises the nearly single-ion conducting aqueous electrolyte according to any one of claims 1 to 6.

10. The aqueous metal M battery according to claim 9, wherein The negative electrode of the aqueous metal M battery is a metal M negative electrode, or a negative electrode containing a negative electrode active material of metal M; Preferably, the positive electrode active material in the positive electrode of the aqueous metal M battery includes at least one of manganese oxide, lithium manganate, and quaternary ammonium bromide.

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