CN115395109A - Pseudo high-concentration electrolyte of water-based zinc ion battery - Google Patents

Abstract

The invention discloses a pseudo high-concentration electrolyte of a water-system zinc ion battery, which is a zinc-containing ion salt solution added with polyacrylamide. The pseudo high-concentration electrolyte can reduce the problems of high cost and high toxicity of the electrolyte wrapped by high-concentration salt, and still has higher zinc ion conductivity. In addition, the problem of eddy in the electrolyte is reduced, the activity of water is inhibited, the occurrence of side reaction is reduced, the zinc negative electrode is protected, and the dissolution of a positive electrode material is inhibited, so that the cycle performance of the battery is improved.

Description

Pseudo high-concentration electrolyte of water-based zinc ion battery

Technical Field

The invention belongs to the technical field of aqueous zinc ion battery electrolyte, and particularly relates to an aqueous zinc ion battery pseudo high-concentration electrolyte.

Background

The aqueous zinc ion battery uses water as a solvent of metal salt, and is more environment-friendly than an organic polymer solvent, but the water as the solvent has a huge problem. The weakly acidic environment results from the low decomposition potential of water and hydrolysis in the case of metal salts. Thus, for zinc cathodes, there are serious corrosion problems, oxidation problems, dendrite growth problems, etc.; the problem of dissolution of materials (e.g., vanadium dissolution, manganese dissolution, etc.) is particularly acute for positive electrodes. In addition, since water activity is high, serious side reactions may occur with the positive and negative electrodes. The water system has inherent problems that hinder the further development of the water system zinc ion battery. In order to promote the further development of the water system zinc ion battery, how to stabilize and improve the water system environment is a very critical part.

Compared with a lithium zinc ion battery, the water system zinc ion battery has the most obvious advantage of low price, and is particularly suitable for a large-scale energy storage system. However, in aqueous zinc-ion batteries, the high concentration of electrolyte limits the large scale application of zinc-ion batteries due to their expense and toxicity and the dissolution and performance degradation of the positive electrode material. Therefore, how to find alternative electrolyte is an important problem in the development of the water-based zinc ion battery.

Disclosure of Invention

Aiming at the defects of the existing water-system zinc ion battery, the invention aims to provide a water-system zinc ion pseudo high-concentration electrolyte which can obviously inhibit the dissolution problem of a positive electrode, reduce the cost of high-concentration salt and ensure the stability of the battery performance.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a pseudo high-concentration electrolyte of a water-based zinc ion battery is a zinc ion salt solution added with polyacrylamide.

In a preferred scheme, the mass volume ratio of the polyacrylamide to the zinc ion-containing salt solution is 0.1-1g:10ml, and the concentration of zinc ions is 0.5-2mol/L.

In a preferred embodiment, the zinc ion-containing salt solution further contains at least one of aluminum ions, copper ions, magnesium ions, lithium ions, and sodium ions.

In a preferred embodiment, the zinc ion-containing salt solution is at least one of a sulfate, a perchlorate, a triflate, a chloride and a nitrate solution of zinc ions.

The inventor finds that the viscosity of the electrolyte system is increased by taking polyacrylamide as a specific additive, and the increase of the viscosity can cause the conductivity of the electrolyte to be slightly reduced, but at the same time, the invention brings a better advantage that the stability of the cathode material is obviously improved. Polyacrylamide is used as a linear high polymer, and is accumulated near the surface of a negative electrode, so that the growth of zinc dendrites can be inhibited, the solution has a viscous phenomenon, unstable turbulence on the surface of the negative electrode is reduced, an amide group has a certain adsorption effect on zinc ions, the transmission and uniform deposition of the zinc ions can be promoted, and the influence of the addition of trace polyacrylamide on the conductivity is small. And on the positive electrode side, the structure dissolution of the positive electrode material is obviously inhibited. In the cycle curve of the battery, the cycle performance of the battery is obviously improved, the capacity reduction rate is low, and a higher discharge platform is provided.

The pseudo high-concentration electrolyte can reduce the problems of high cost and high toxicity of the electrolyte wrapped by high-concentration salt, and still has higher zinc ion conductivity. In addition, the problem of eddy in the electrolyte is reduced, the activity of water is inhibited, the occurrence of side reaction is reduced, the zinc negative electrode is protected, and the dissolution of the positive electrode material is inhibited, so that the cycle performance of the battery is improved.

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

(1) The pseudo high concentration electrolyte has a high viscosity that reduces electrolyte eddy problems and still has a large number of water molecules that provide sufficient zinc ion conductivity

(2) Due to the interaction of the organic high molecular polymer of the pseudo high-concentration electrolyte and ions, the activity of water molecules can be reduced, and the side reaction of the zinc cathode is inhibited.

(3) The polyacrylamide can also inhibit the dissolution problem of the cathode material and improve the stability of the cathode material.

Drawings

FIG. 1 is a pseudo high electrolyte zinc symmetric cell of example 1;

FIG. 2 is a graph of current density of 0.5Ag at 25 ℃ for a pseudo high concentration electrolyte (5%) in example 1 and a liquid electrolyte (0%) in comparative example 1 using lithium iron phosphate as the positive electrode ^-1 Performance comparison graph of(a) And a current density of 0.1A g at 25 ℃ ^-1 A performance comparison graph (b), an electrochemical impedance comparison graph (c) and a capacity voltage comparison graph (d) of a counter electrode made of stainless steel;

FIG. 3 is a graph comparing CV curves of lithium iron phosphate-zinc full cells for a pseudo high concentration electrolyte (5%) in example 1 and a liquid electrolyte (0%) in comparative example 1;

FIG. 4 is a graph of pseudo high concentration electrolyte high loading performance in example 1;

FIG. 5 is a 0.5Ag solution of pseudo high concentration electrolyte of comparative example 2 using lithium iron phosphate as the positive electrode ^-1 Performance map of (2).

Detailed Description

The invention is further illustrated by the following examples, which are intended to be illustrative of the invention and are not intended to be limiting, and the starting materials commercially available and the preparation of the invention is conventional in the art unless otherwise specified.

Example 1

(1) Preparing 0.5g of polyacrylamide;

(2) Dissolving zinc sulfate and lithium sulfate in zinc ion removing water to obtain zinc ion and lithium zinc ion with concentration of 1mol L respectively ^-1 、2mol L ^-1 The mixed salt solution of (4);

(3) Mixing polyacrylamide and a mixed salt solution according to a mass-volume ratio of 0.5g: and mixing the 10mL of the electrolyte uniformly to obtain pseudo high-concentration electrolyte.

As shown in fig. 1, the zinc symmetric cell of example 1 is shown to support cycling of the zinc anode.

As shown in FIG. 2, the pseudo high-concentration electrolyte of example 1 and the liquid electrolyte of comparative example 1 each used lithium iron phosphate as a positive electrode and had a current density of 0.5Ag at 25 deg.C ^-1 Comparison of Performance of (a), current Density of 0.1Ag at 25 deg.C ^-1 A performance comparison graph (b), an electrochemical impedance comparison graph (c) using a stainless steel counter electrode, and a capacity voltage comparison graph (d). At 25 ℃ and 0.5Ag ^-1 Initial capacity of liquid electrolyte (0% polyacrylamide) at current density of 120mAh g ^-1 After 200 cyclesCapacity decreased to 40mAh g ^-1 The capacity retention rate was 33.3%. The capacity of pseudo high-concentration electrolyte is increased from initial 110mAh g ^-1 After 100 cycles, the capacity is reduced to 97mAh g ^-1 The capacity retention ratio was 88%. At 0.1Ag ^-1 The average capacity of pseudo high-concentration electrolyte under the current density is 120mAh g ^-1 And the liquid electrolyte is 115mAh g ^-1 . Illustrating that pseudo high concentration electrolytes can provide high capacity while suppressing capacity fade. Compared with the conductivity, the conductivity of the pseudo high-concentration electrolyte obtained by adding polyacrylamide is only slightly reduced, which shows that the pseudo high-concentration electrolyte still has excellent zinc ion conductivity. And in the capacity-voltage curve, the average discharge voltage of the pseudo high-concentration electrolyte is 1.12V, while the discharge voltage of the liquid electrolyte is only 1.08V, so that the pseudo high-concentration electrolyte has higher discharge voltage and discharge capacity.

As shown in fig. 3, when comparing the CV curves of the lithium iron phosphate-zinc full cell in the pseudo high-concentration electrolyte (5%) in example 1 and the liquid electrolyte (0%) in comparative example 1, it can be seen that the pseudo high-concentration electrolyte has a more stable CV curve, which indicates that the pseudo high-concentration electrolyte (5%) has better cycle performance, and the higher height of the peak indicates that the reaction has better reversibility.

FIG. 4 is a graph of the high load cycling performance of the pseudo high concentration electrolyte of example 1 at 0.2Ag ^-1 Under the current density, the initial capacity can reach 0.4mAh, and after 100 cycles, the capacity of 0.3mAh still exists, which indicates that the pseudo high-concentration electrolyte can be used for large battery tests and can keep better cycle performance.

Comparative example 1

Dissolving zinc sulfate and lithium sulfate in deionized water to obtain zinc ion and lithium zinc ion with concentration of 1mol L respectively ^-1 、2mol L ^-1 The mixed salt solution of (2) is directly used as a liquid electrolyte.

Comparative example 2

(1) Preparing 0.5g of polyethylene glycol 400;

(2) Dissolving zinc sulfate and lithium sulfate in deionized water to prepare zinc ions and lithium zinc ions with the concentrations of 1mol L respectively ^-1 、2mol L ^-1 The mixed salt solution of (4);

(3) Mixing polyethylene glycol 400 and a mixed salt solution according to a mass-volume ratio of 0.5g:10mL of pseudo high-concentration electrolyte is obtained after uniform mixing.

As shown in FIG. 5, 0.5Ag was performed using lithium iron phosphate as a positive electrode ^-1 Current density cycling it can be seen that the use of the same amount of polyethylene glycol as additive showed poor cycling performance, with a rapid decay at 20 cycles.

Claims (4)

1. A pseudo high-concentration electrolyte of a water-based zinc ion battery is characterized in that: the water-based zinc ion battery pseudo high-concentration electrolyte is a zinc ion salt solution added with polyacrylamide.

2. The aqueous zinc ion battery pseudohigh concentration electrolyte of claim 1, wherein: the mass volume ratio of the polyacrylamide to the zinc ion-containing salt solution is 0.1-1g:10ml, and the concentration of zinc ions is 0.5-2mol/L.

3. The aqueous zinc ion battery pseudo high-concentration electrolyte of claim 1, wherein: the zinc ion-containing salt solution also contains at least one of aluminum ions, copper ions, magnesium ions, lithium ions and sodium ions.

4. The aqueous zinc ion battery pseudo high-concentration electrolyte of claim 1, wherein: the zinc ion-containing salt solution is at least one of sulfate, perchlorate, trifluoromethylsulfonate, chloride and nitrate solutions of zinc ions.

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