CN115483457B

CN115483457B - Aqueous battery and electrolyte thereof

Info

Publication number: CN115483457B
Application number: CN202211256353.9A
Authority: CN
Inventors: 张文旭; 刘胜芳; 王海燕; 谢春霖; 穆旭阳; 徐妍
Original assignee: Northwest Normal University; Central South University
Current assignee: Northwest Normal University; Central South University
Priority date: 2022-10-14
Filing date: 2022-10-14
Publication date: 2025-08-22
Anticipated expiration: 2042-10-14
Also published as: CN115483457A

Abstract

The invention belongs to a water system battery system, in particular to a water system battery electrolyte which is prepared by dissolving electrolyte salt and a compound shown in a formula 1In the formula 1, n is an integer of 1-4, and the concentration of the compound in the formula 1 in the aqueous battery electrolyte is 3-18M. The invention also provides application of the water-based electrolyte, and the electrolyte has excellent low-temperature performance.

Description

Water-based battery and electrolyte thereof

Technical Field

The invention belongs to the technical field of energy storage of water-based batteries, and relates to water-based battery electrolyte.

Technical Field

The explosive development of new energy industry cannot lack the construction of energy storage system because it can meet the convenience of energy use by storing and releasing energy in time. Secondary batteries are therefore favored for use as efficient carriers for energy storage and conversion. Aqueous batteries have the irreplaceable advantage of using water as a solvent over current commercial lithium ion batteries. On the one hand, water is used as a flame retardant, which can prevent the battery from fire and explosion, and in addition, the water and the water-soluble electrolyte have relatively low price, which is helpful for reducing the cost of the battery, and the components of the water-based battery are insensitive to air, can be assembled under the atmosphere, and have simple manufacturing conditions, and the ionic conductivity (about 0.1S cm ^-1) of the water-based electrolyte is far higher than that of the organic electrolyte (1-10 mS cm ^-1), thus having excellent multiplying power performance and power density. The water solvent has the advantages of no toxicity and no environmental hazard, and has great advantages in recycling waste batteries. The advantages enable the water system battery to have great application potential in an energy storage system. At present, many water-based batteries are researched to be water-based lithium ion batteries and water-based zinc ion batteries, but due to an aqueous solution system, the freezing point of electrolyte is generally low (-10 ℃) and the performance of the water-based batteries is greatly reduced when the use temperature is about zero, and when the use temperature reaches about minus ten ℃, the batteries can not be used basically, particularly in the area of north of Yangtze river in China, the water-based batteries can not be used normally throughout the year. Therefore, designing a high-performance aqueous electrolyte resistant to low temperatures is important for practical use of aqueous batteries.

On the other hand, the development of the water-based lithium ion battery is severely restricted due to the erosion of hydrogen protons in water and the instability of the electrode material structure, and is also hindered by the problems of dendrite, corrosion and hydrogen evolution of the zinc cathode. Based on this, designing a high-performance aqueous electrolyte that can be used in a wide temperature range is of great significance for the development of aqueous batteries.

Disclosure of Invention

A first object of the present invention is to provide an electrolyte for an aqueous battery, which aims to improve its low-temperature electrochemical performance.

A second object of the present invention is to provide an application of the electrolytic solution in assembling an aqueous battery.

A third object of the present invention is to provide an aqueous battery containing the aqueous electrolyte.

At low temperatures, aqueous batteries have an tendency for the electrolyte to solidify, which can greatly affect electrochemical performance. Aiming at the problem of non-ideal low-temperature performance of the water system battery, the main idea in the industry is to add a component with a low freezing point for reducing the overall freezing point of the electrolyte, however, in the prior art, the freezing point is reduced, and meanwhile, brand new problems are easily brought, such as easy reduction of solubility, reduction of conductivity, increase of polarization and the like of the electrolyte water system, so that the water system electrolyte is difficult to achieve both good freezing resistance and low-temperature electrochemical performance. The present invention, after extensive research, proposes the following solutions to this problem:

An aqueous battery electrolyte is a homogeneous aqueous solution in which electrolyte salt and a compound of formula 1 are dissolved;

In the formula 1, n is an integer of 1-4;

In the aqueous battery electrolyte, the concentration of the compound of formula 1 is 3-18M.

According to the invention, the research shows that the antifreeze additive of the water-based electrolyte is innovatively prepared by taking the formula 1 as the antifreeze additive of the water-based electrolyte, and the concentration is further controlled, so that the synergy can be realized, the antifreeze performance of the water-based electrolyte can be obviously improved, in addition, the problems of reduced solubility and conductivity of electrolyte salt can be avoided, polarization and electrode corrosion can be reduced, and the excellent low-temperature electrochemical performance can be realized on the premise of realizing the antifreeze.

In the invention, the control of the annular-CONH-structure and the concentration thereof in the formula 1 is the key for synergistically improving the freezing resistance of the water-based electrolyte, improving the conductivity, reducing the polarization and further improving the low-temperature electrochemical performance.

Preferably, in the compound of formula 1, n is 2 or 3, preferably 3.

Preferably, in the aqueous battery electrolyte, the concentration of the compound of formula 1 is 4 to 12m, preferably 6 to 8m. It has been found that, at the preferred concentrations, the aqueous electrolyte is capable of achieving both excellent freeze resistance, lower conductivity loss and less polarization enhancement, and thus is capable of improving low temperature electrochemical performance while achieving freeze resistance.

Preferably, the electrolyte salt is at least one of water-soluble zinc salt and water-soluble lithium salt;

Preferably, the water-soluble zinc salt is at least one of zinc sulfate, zinc acetate, zinc chloride, zinc triflate and zinc nitrate.

Preferably, the water-soluble lithium salt is at least one of lithium sulfate, lithium acetate, lithium chloride, lithium triflate and lithium nitrate.

Preferably, the electrolyte salt is zinc sulfate and/or lithium sulfate. The research of the invention finds that the sulfuric acid type electrolyte salt is more susceptible to the influence of the antifreeze additive, and the solubility is reduced to crystallize more easily after the addition, however, in the invention, the influence on the solubility of the sulfuric acid type electrolyte salt under the addition of the formula 1 can be avoided due to the use of the formula 1, so that the high low-temperature electrochemical performance can be obtained under the condition of obtaining good antifreeze property.

Preferably, the concentration of the electrolyte salt is 0.2 to 3M, preferably 1 to 2M.

Preferably, the aqueous battery electrolyte further comprises a water-soluble compound of formula 2:

in formula 2, R is H, C ₁～C₂ alkyl or hydroxyalkyl.

The research of the invention also finds that the water-based electrolyte can realize the synergy unexpectedly by further matching with the formula 2 on the basis of the formula 1, can further improve the low-temperature freezing resistance of the water-based electrolyte, can solve the problems of reduced solubility, influenced conductivity, increased polarization and the like of electrolyte salt caused by the addition of the freezing resistant additive, and can obviously improve the low-temperature electrochemical performance of the water-based electrolyte.

Preferably, in the aqueous battery electrolyte, the molar ratio of the formula 1 to the formula 2 is 6 to 8:0.1 to 2, and more preferably 7 to 7.8:0.2 to 1.

Preferably, in the aqueous battery electrolyte, the concentration of the compound of formula 2 is less than or equal to 2M, preferably 0.5 to 1M.

The invention also provides application of the water-based battery electrolyte, which is used as the electrolyte for assembling and forming the water-based battery;

Preferably, the electrolyte salt is water-soluble zinc salt, the electrolyte is assembled to form a water-based zinc-lithium ion battery, or the electrolyte salt is water-soluble lithium salt, the electrolyte is assembled to form a water-based lithium ion battery, or the electrolyte salt contains water-soluble zinc salt and water-soluble lithium salt, and the electrolyte is assembled to form a water-based zinc-lithium double-ion battery.

The invention also provides an aqueous battery, which comprises the aqueous battery electrolyte.

The aqueous battery of the present invention may be known in the art, and may have other components, structures and materials, except for the electrolyte of the present invention.

For example, preferably, the aqueous battery is an aqueous zinc ion battery, and the electrolyte salt is a water-soluble zinc salt in the electrolyte;

Or the water-based battery is a water-based lithium ion battery, and in the electrolyte, the electrolyte salt is water-soluble lithium salt;

Or the water-based battery is a water-based zinc-lithium double-ion battery, and in the electrolyte, the electrolyte salt is water-soluble zinc salt and water-soluble lithium salt;

Preferably, in the water-based zinc ion battery, the active material of the positive electrode is at least one of active carbon, polyaniline, manganese dioxide, vanadium pentoxide, polypyrrole and vanadium disulfide;

Preferably, in the aqueous lithium ion battery, the active material of the positive electrode is at least one of lithium iron phosphate, lithium manganate and lithium cobaltate, and the active material of the negative electrode is at least one of vanadium dioxide and LiV ₃O₈.

Advantageous effects

In the electrolyte, the use of the solid component with the high freezing point of the formula 1 is beneficial, and the combination control of the addition concentration of the formula 1 is further matched, so that the freezing point of the water-based electrolyte can be unexpectedly and remarkably reduced, the reduction of the solubility and the conductivity of the water-soluble electrolyte salt can be unexpectedly avoided, the electrode corrosion and the polarization can be reduced, and the low-temperature electrochemical performance of the water-based electrolyte can be remarkably improved.

Under the innovative use of the formula 1, the formula 2 is further matched, so that the synergy can be realized unexpectedly, the low-temperature performance of the water-based electrolyte can be further synergistically improved, and the low-temperature electrochemical performance can be further improved.

The aqueous electrolyte provided by the invention has strong universality and can obtain good low-temperature electrochemical performance under an aqueous lithium ion battery system.

Drawings

Fig. 1 shows freezing point test data of an aqueous electrolyte and freezing conditions of an electrolyte containing 0, 1, 6, 12, 18M formula 1 (n=3) at-22 ℃.

Fig. 2 is a molecular dynamics simulation of an aqueous zinc electrolyte system and corresponding radial distribution function.

Fig. 3 is a cycle life comparison of a water system Zn symmetric battery at normal temperature.

Fig. 4 is a cycle life comparison of aqueous Zn battery at-20 ℃.

Fig. 5 shows a linear polarization curve comparison of water system Zn.

Fig. 6 is a hydrogen evolution potential test of a lithium sulfate electrolyte.

Fig. 7 is cycle data of an aqueous lithium ion battery containing a lithium sulfate electrolyte of formula 1 (n=3).

Fig. 8 is cycle data of an aqueous zinc ion battery containing a zinc sulfate electrolyte of formula 1 (n=3).

Fig. 9 is full cell cycle data for aqueous zinc/lithium dual ion batteries containing formulas 1 (n=3) and 2 at-50 ℃ low temperature.

Detailed Description

Example 1

1M of an aqueous zinc sulfate solution and 1M of a mixed aqueous solution of zinc sulfate and formula 1 (n=3) were prepared, wherein the concentration of formula 1 (n=3) was 1,3,6,8,12,18M. The freezing point curve of the 12M solution of formula 1 (n=3) obtained by thermogravimetry is shown in fig. 1, wherein the freezing point of the solution containing formula 1 (n=3) can reach-58 ℃, whereas the common zinc sulfate solution only freezes at-22 ℃ (the zinc sulfate freezing point reported in the literature is-9 ℃), and the solution containing the concentration of formula 1 (n=3) is always kept clear and transparent, indicating that the addition of formula 1 (n=3) can significantly lower the freezing point of the aqueous electrolyte. The experiments also determined the relationship between the concentration of the different formula 1 and the conductivity, polarization, freezing point, solubility of zinc sulfate, as shown in table 1. This indicates that the concentration of formula 1 (n=3) is most preferably 6 to 12M.

Table 1 properties of different concentrations of formula 1 (n=3)

Example 2

And constructing a molecular dynamics simulation system of a 1M zinc sulfate electrolyte system, wherein 20 zinc ions, 20 sulfate ions and 1100 water molecules are subjected to molecular dynamics simulation, calculating a solvation structure of the zinc ions, and determining water molecules and anions around the zinc ions. A molecular dynamics simulation system was again constructed for the 1M zinc acid electrolyte of formula 1 (n=3) containing 6M and 12M. The effect between zinc ions and molecules of formula 1 (n=3) was simulated using Material Studio software. As can be seen from fig. 2, formula 1 (n=3) occupies the original coordination position of water molecules, participates in solvation of zinc ions, and the coordination number of zinc ions and sulfate ions of the electrolyte added in formula 1 (n=3) is also found to be significantly increased, which can explain the reason that the freezing point of the electrolyte is lowered, namely, the molecule in formula 1 (n=3) has strong coordination with cations, reduces the charge density of the cations, promotes coordination and coupling between the cations and anions, weakens hydrogen bonds in the electrolyte, and lowers the freezing point of the electrolyte.

Example 3

A 1M zinc sulfate aqueous solution (electrolyte a), a 1M zinc sulfate aqueous-formula 1 (n=3) mixed solution in which the concentration of formula 1 (n=3) is 6M (electrolyte B), and a 2025 symmetric battery was assembled with an electrolyte A, B as an electrolyte and zinc foil and glass fiber, respectively, and constant-current charge and discharge were performed under the condition of 1mA cm ^-2-1mAh cm^-2 to evaluate polarization and cycle life of the electrolyte. As can be seen from fig. 3, the aqueous zinc-ion battery with the additive of formula 1 (n=3) can be cycled for more than 900 hours at normal temperature, but the pure zinc sulfate electrolyte is not significantly unstable at 100 hours, and the electrolyte with the additive of formula 1 (n=3) has lower polarization voltage, which is beneficial to improving the overall performance of the zinc-ion battery.

Example 4

Using the two electrolytes (electrolyte a or electrolyte B) of example 3, a zinc-zinc symmetrical battery was assembled and subjected to a constant current charge-discharge test at-20 ℃ with a test current density of 0.5mA cm ^-2-0.5mAh cm^-2, it can be seen from fig. 4 that the electrolyte containing formula 1 (n=3) can stably operate at low temperature for more than 1000 hours, whereas the electrolyte not containing formula 1 (n=3) cannot operate at low temperature, which can be attributed to the increase in ion transport resistance caused by solidification of the normal zinc sulfate electrolyte at low temperature, whereas the electrolyte containing formula 1 (n=3) still has low viscosity and high ion conductivity at low temperature.

Example 5

The linear polarization curves of the zinc-zinc symmetric cells were tested using the two electrolytes in example 3 (electrolyte a or electrolyte B) to characterize the corrosion current and corrosion potential of zinc in the electrolyte, as can be seen from fig. 5, zinc cells using electrolytes containing formula 1 (n=3) have lower corrosion current and negative corrosion potential, demonstrating that electrolytes containing formula 1 (n=3) significantly inhibit corrosion of the zinc anode. Also, the electrochemical hydrogen evolution potential of the 1M aqueous lithium sulfate solution and the 1M aqueous lithium sulfate-aqueous solution of formula 1 (n=3) was tested, and as can be seen from fig. 6, the hydrogen evolution potential of the electrolyte containing formula 1 (n=3) was significantly negative to that of the normal electrolyte, which suggests that the addition of formula 1 (n=3) can significantly suppress the decomposition of water, increasing the energy density of the aqueous lithium/zinc ion battery.

Example 6

1M lithium sulfate aqueous solution (electrolyte a) and 1M lithium sulfate-water-8M solution electrolyte (electrolyte b) of formula 1 (n=3) were tested, aqueous lithium ion batteries were assembled respectively, lithium manganate was used as a positive electrode, vanadium pentoxide was used as a negative electrode, and the preparation of the positive electrode and the negative electrode followed the following process that lithium manganate (vanadium dioxide), conductive carbon black and (PVDF) were mixed in NMP solvent at a weight ratio of 7:2:1, the obtained slurry was coated on a stainless steel mesh, dried at 80 ℃ for 12 hours, and cut into wafers with a diameter of 11mm, thereby obtaining the relevant positive electrode, wherein the active material loading amount was about 1.8mg cm ^-2. As can be seen from the cycle data of the aqueous lithium ion battery in fig. 7, the addition of the electrolyte of formula 1 (n=3) can provide the battery with higher specific discharge capacity and cycle life, and at the same time, the modified electrolyte can still normally and stably circulate at-20 ℃, while the electrolyte not containing the electrolyte of formula 1 (n=3) is frozen and cannot be operated at low temperature.

Example 7

A 1M zinc sulfate aqueous solution and a 1M zinc sulfate-water-8M solution electrolyte of formula 1 (n=3) were tested, and an aqueous zinc ion battery was assembled, with manganese dioxide as a positive electrode and zinc as a negative electrode, respectively, to assemble a full battery, wherein the positive electrode sheet was prepared by rolling manganese dioxide, conductive carbon black, PTFE in a 7:2:1 mixture on a steel mesh, wherein the loading amount of an active material was about 2mg cm ^-2. It can be seen from fig. 8 that the electrolyte containing formula 1 (n=3) can provide a long cycle life and a high specific capacity, when the cycle performance of the aqueous zinc cell is tested at a current density of 1Ag ^-1 at normal temperature.

Example 8

To demonstrate the synergy of formulas 1 and 2, the relationship between conductivity and freezing point and polarization at different mixture concentrations was experimentally determined as shown in table 2. This demonstrates that formula 1 (n=3) and formula 2 (m=1, r is methyl) have a significant synergistic effect.

Table 2 properties of solutions of different concentrations of formula 1 (n=3) and formula 2 (m=1, r is methyl)

As shown in table 2, by adopting the combination of the formula 1 and the formula 2, particularly controlling the molar ratio of the two to be 6-8:0.1-2, and more preferably 7-7.8:0.2-1, an excellent synergistic effect can be unexpectedly obtained, the anti-freezing new energy can be synergistically improved, in addition, the conductivity loss can be reduced, the polarization can be reduced, and the electrochemical new energy at ultralow temperature can be further improved.

Example 9

As shown in fig. 9, further testing the effect of the mixed electrolyte of group e in table 2 on the lifetime of zinc symmetric cells at-50 ℃ found that zn||zn symmetric cells could be cycled for more than 700 hours in symmetric cells containing electrolytes of formula 1 and formula 2 in concert, whereas electrolyte containing only formula 1 (n=3) (experimental group 5 in table 2) could not be cycled already at-50 ℃. Therefore, the combination of the formula 1 and the formula 2 can realize ultralow-temperature use, not only can realize excellent conductivity and low polarization effect at ultralow temperature, but also has better ultralow-temperature electrochemical cycle stability.

Claims

1. The aqueous zinc ion battery electrolyte is characterized by being a homogeneous aqueous solution composed of electrolyte salt, a compound shown in a formula 1 and water, wherein the electrolyte salt is zinc sulfate;

the water-based zinc ion battery electrolyte also comprises a water-soluble compound of formula 2;

1 (1)

In the formula 1, n is 3;

2, 2

In the formula 2, R is methyl, and m is 1;

The molar ratio of the formula 1 to the formula 2 is 6-8:0.1-2;

in the aqueous zinc ion battery electrolyte, the concentration of the compound of the formula 1 is 3-18M, and the concentration of electrolyte salt is 1-2M.

2. The aqueous zinc-ion battery electrolyte according to claim 1, wherein the concentration of the compound of formula 1 is 4 to 12M.

3. The aqueous zinc-ion battery electrolyte according to claim 1, wherein the concentration of the compound of formula 1 is 6 to 8M.

4. The aqueous zinc-ion battery electrolyte according to claim 1, wherein the molar ratio of formula 1 to formula 2 is 7 to 7.8:0.2 to 1.

5. The aqueous zinc-ion battery electrolyte according to claim 1, wherein the concentration of the compound of formula 2 is 0.2 to 1M.

6. The use of the aqueous zinc-ion battery electrolyte according to any one of claims 1 to 5 as an electrolyte for assembling an aqueous zinc-ion battery.

7. An aqueous zinc-ion battery comprising the aqueous zinc-ion battery electrolyte according to any one of claims 1 to 5;

in the water-based zinc ion battery, the active material of the positive electrode is at least one of active carbon, polyaniline, manganese dioxide, vanadium pentoxide, polypyrrole and vanadium disulfide.