Aqueous zinc ion battery pseudo-high concentration electrolyte

Abstract

The application discloses a water-based zinc ion battery pseudo-high-concentration electrolyte, which is a zinc ion salt solution containing polyacrylamide. The pseudo-high-concentration electrolyte can reduce the problems of high cost and high toxicity of the high-concentration salt water-containing electrolyte, and still has high zinc ion conductivity. In addition, the problem of eddy current in the electrolyte is reduced, the activity of water is inhibited, the occurrence of side reactions is reduced, the zinc negative electrode is protected, the dissolution of the positive electrode material is inhibited, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery electrolyte technology, specifically relating to a pseudo-high concentration electrolyte for aqueous zinc-ion batteries. Background Technology

[0002] Aqueous zinc-ion batteries utilize water as a solvent for metal salts, which is more environmentally friendly than organic polymer solvents. However, water as a solvent also presents significant challenges. Due to its low decomposition potential and the hydrolysis of metal salts, water creates a weakly acidic environment. This leads to severe corrosion, oxidation, and dendrite growth problems for the zinc anode; and particularly serious material dissolution issues (such as vanadium and manganese dissolution) for the cathode. Furthermore, water's high reactivity can cause severe side reactions with both the anode and cathode. These inherent problems hinder the further development of aqueous zinc-ion batteries. Stabilizing and improving the aqueous system environment is crucial for advancing these batteries.

[0003] Aqueous zinc-ion batteries, compared to lithium-zinc-ion batteries, have the significant advantage of lower cost, making them particularly suitable for large-scale energy storage systems. However, the high concentration of electrolyte in aqueous zinc-ion batteries, due to its high cost and toxicity, as well as the dissolution and performance degradation of the cathode material, limits their large-scale application. Therefore, finding alternative electrolytes is a crucial issue in the development of aqueous zinc-ion batteries. Summary of the Invention

[0004] To address the shortcomings of existing aqueous zinc-ion batteries, the present invention aims to provide an aqueous zinc-ion pseudo-high-concentration electrolyte that can significantly suppress cathode dissolution, reduce the cost of high-concentration salts, and ensure battery performance stability.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0006] A pseudo-high-concentration electrolyte for aqueous zinc-ion batteries is a zinc ion salt solution with added polyacrylamide.

[0007] In a preferred embodiment, the mass-to-volume ratio of the polyacrylamide to the zinc ion salt solution is 0.1-1g:10ml, and the concentration of zinc ions is 0.5-2mol / L.

[0008] In a preferred embodiment, the zinc ion salt solution further contains at least one of aluminum ions, copper ions, magnesium ions, lithium ions, and sodium ions.

[0009] In a preferred embodiment, the zinc ion salt solution is at least one of zinc ion sulfate, perchlorate, trifluoromethanesulfonate, chloride, and nitrate solutions.

[0010] The inventors discovered that by using polyacrylamide as a specific additive, the viscosity of the electrolyte system increases. While this increased viscosity leads to a slight decrease in electrolyte conductivity, it also brings significant benefits, namely a marked improvement in the stability of the positive electrode material. As a linear polymer, polyacrylamide accumulates near the negative electrode surface, inhibiting zinc dendrite growth. Simultaneously, the viscous solution reduces unstable turbulence at the negative electrode surface, and the amide groups also have a certain adsorption effect on zinc ions, promoting their transport and uniform deposition. Therefore, the addition of trace amounts of polyacrylamide has a minimal impact on conductivity. On the positive electrode side, it significantly inhibits the dissolution of the positive electrode material structure. The battery's cycle curves show a significant improvement in cycle performance, a lower capacity decay rate, and a higher discharge plateau.

[0011] The pseudo-high-concentration electrolyte of this invention reduces the high cost and high toxicity issues associated with high-concentration salt-encapsulated water electrolytes, while still maintaining high zinc ion conductivity. Furthermore, by reducing eddy currents in the electrolyte and suppressing water activity, it also reduces side reactions, protecting the zinc anode while inhibiting the dissolution of the cathode material, thereby improving the battery's cycle performance.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) The pseudo-high concentration electrolyte has high viscosity, which can reduce the problem of electrolyte eddy current, and there are still a large number of water molecules to provide sufficient zinc ion conductivity.

[0014] (2) Due to the interaction between the organic polymer and ions in the pseudo-high concentration electrolyte, the activity of water molecules can be reduced, thereby inhibiting the side reactions of the zinc anode.

[0015] (3) Polyacrylamide can also suppress the dissolution of positive electrode materials and improve the stability of positive electrode materials. Attached Figure Description

[0016] Figure 1 The zinc symmetric cell with the pseudo-high concentration electrolyte in Example 1;

[0017] Figure 2 The pseudo-high concentration electrolyte (5%) in Example 1 and the liquid electrolyte (0%) in Comparative Example 1 were tested at a current density of 0.5 Ag at 25°C using lithium iron phosphate as the positive electrode. -1 Performance comparison chart (a), current density of 0.1 A g at 25℃ -1 The performance comparison chart (b), the electrochemical impedance comparison chart (c) with stainless steel as the counter electrode, and the capacity-voltage comparison chart (d) are shown.

[0018] Figure 3A comparison of the CV curves of lithium iron phosphate-zinc full cells using the pseudo-high concentration electrolyte (5%) in Example 1 and the liquid electrolyte (0%) in Comparative Example 1;

[0019] Figure 4 This is a performance diagram of the pseudo-high concentration electrolyte with high loading capacity in Example 1;

[0020] Figure 5 To demonstrate the use of the pseudo-high concentration electrolyte in Comparative Example 2, 0.5 Ag of lithium iron phosphate was used as the positive electrode. -1 Performance graph. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. The raw materials described in the present invention are all obtained through commercial means. Unless otherwise specified, the preparation methods described in the present invention are conventional preparation methods in the art. The following embodiments are intended to illustrate the present invention and not to further limit the present invention.

[0022] Example 1

[0023] (1) Prepare 0.5g of polyacrylamide;

[0024] (2) Dissolve zinc sulfate and lithium sulfate in dezincified water to prepare zinc ion and lithium zinc ion concentrations of 1 mol / L. -1 2 mol L -1 A mixed salt solution;

[0025] (3) Mix polyacrylamide and mixed salt solution at a mass-volume ratio of 0.5g:10mL to obtain a pseudo-high concentration electrolyte.

[0026] like Figure 1 As shown, this is a zinc symmetric battery in Example 1, demonstrating that it can support cycling of the zinc anode.

[0027] like Figure 2 The image shows the pseudo-high concentration electrolyte in Example 1 and the liquid electrolyte in Comparative Example 1, both using lithium iron phosphate as the positive electrode at a current density of 0.5 Ag at 25°C. -1 Performance comparison chart (a), current density of 0.1Ag at 25℃ -1 The performance comparison charts are shown in (b), (c), and (d) for electrochemical impedance spectroscopy using stainless steel as the counter electrode. (At 25℃ and 0.5Ag) -1 At the given current density, the initial capacity of the liquid electrolyte (0% polyacrylamide) is 120 mAh g. -1 After 200 cycles, the capacity decreased to 40 mAh g. -1 The capacity retention rate was 33.3%. Meanwhile, the capacity of the pseudo-high-concentration electrolyte decreased from the initial 110 mAh g⁻¹. -1After 100 cycles, the capacity decreased to 97 mAh g. -1 The capacity retention rate was 88%. (At 0.1 Ag) -1 At the given current density, the average capacity of the pseudo-high concentration electrolyte is 120 mAh g. -1 The liquid electrolyte has a capacity of 115 mAh g. -1 This demonstrates that the pseudo-high-concentration electrolyte can provide high capacity while suppressing capacity decay. Comparing conductivity, the conductivity of the pseudo-high-concentration electrolyte obtained after adding polyacrylamide showed only a slight decrease, indicating that it still possesses excellent zinc ion conductivity. Furthermore, in the capacity-voltage curve, the average discharge voltage of the pseudo-high-concentration electrolyte was 1.12V, while the discharge voltage of the liquid electrolyte was only 1.08V. Therefore, the pseudo-high-concentration electrolyte exhibits higher discharge voltage and discharge capacity.

[0028] like Figure 3 As shown in the figure, the CV curves of the lithium iron phosphate-zinc full cell of the pseudo-high concentration electrolyte (5%) in Example 1 and the liquid electrolyte (0%) in Comparative Example 1 are compared. It can be seen that the pseudo-high concentration electrolyte has a more stable CV curve, indicating that the pseudo-high concentration electrolyte (5%) has better cycle performance. At the same time, the higher peak height indicates that its reaction has better reversibility.

[0029] like Figure 4 The figure shows the high-load cycling performance of the pseudo-high-concentration electrolyte in Example 1, at 0.2 Ag. -1 At the current density, the initial capacity can reach 0.4mAh, and after 100 cycles, it still has a capacity of 0.3mAh, indicating that the pseudo-high concentration electrolyte can be used for large battery testing and can maintain good cycle performance.

[0030] Comparative Example 1

[0031] Zinc sulfate and lithium sulfate were dissolved in deionized water to prepare zinc ion and lithium zinc ion concentrations of 1 mol / L. -1 2 mol L -1 The mixed salt solution is used directly as the liquid electrolyte.

[0032] Comparative Example 2

[0033] (1) Prepare 0.5g of polyethylene glycol 400;

[0034] (2) Dissolve zinc sulfate and lithium sulfate in deionized water to prepare zinc ion and lithium zinc ion concentrations of 1 mol / L. -1 2 mol L -1 A mixed salt solution;

[0035] (3) Polyethylene glycol 400 and mixed salt solution are mixed evenly at a mass-volume ratio of 0.5g:10mL to obtain a pseudo-high concentration electrolyte.

[0036] like Figure 5 As shown, lithium iron phosphate was used as the positive electrode for 0.5Ag... -1 Current density cycling shows that using the same amount of polyethylene glycol as an additive results in poor cycling performance, with rapid degradation after 20 cycles.

Claims

1. A pseudo-high-concentration electrolyte for aqueous zinc-ion batteries, characterized in that: The pseudo-high concentration electrolyte of the aqueous zinc-ion battery is a zinc ion salt solution with added polyacrylamide; The mass-to-volume ratio of the polyacrylamide to the zinc ion salt solution is 0.5 g: 10 ml.

2. The pseudo-high-concentration electrolyte for aqueous zinc-ion batteries according to claim 1, characterized in that: The concentration of zinc ions in the zinc ion salt solution is 0.5-2 mol / L.

3. The pseudo-high-concentration electrolyte for aqueous zinc-ion batteries according to claim 1, characterized in that: The zinc ion salt solution also contains at least one of aluminum ions, copper ions, magnesium ions, lithium ions, and sodium ions.

4. The pseudo-high-concentration electrolyte for aqueous zinc-ion batteries according to claim 1, characterized in that: The zinc ion salt solution is at least one of zinc ion sulfate, perchlorate, trifluoromethylsulfonate, chloride and nitrate solutions.

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