Aqueous zinc ion battery electrolyte and battery

Abstract

The invention belongs to the field of aqueous zinc ion batteries, and discloses an aqueous zinc ion battery electrolyte and a battery. The aqueous zinc ion battery electrolyte comprises solvent water, soluble zinc salt and an electrolyte additive, wherein the electrolyte additive is chitosan oligosaccharide. According to the electrolyte, chitosan oligosaccharide is adopted as an additive, strong and uniform interface adsorption characteristics are provided based on the chain length effect of chitosan oligosaccharide, and interface aggregation and entanglement of a high polymer additive and low adsorption strength of a low-molecular saccharide additive are avoided; and meanwhile, the coulombic efficiency and the cycling stability of the battery assembled based on the electrolyte can be improved at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field related to aqueous zinc-ion batteries, and more specifically, relates to an electrolyte and a battery for an aqueous zinc-ion battery. Background Art

[0002] Due to low cost and high intrinsic safety, aqueous zinc-ion batteries are potential candidates for next-generation energy storage systems. Zinc metal has become an exciting mainstream choice due to its high theoretical capacity and low reduction potential. However, the development of zinc metal anodes is severely restricted by parasitic reactions such as dendrite growth and hydrogen evolution, resulting in low stability and efficiency of zinc metal anodes.

[0003] Electrolyte regulation is considered an important strategy to solve the reversibility of deposition / stripping. As a "low input, high return" method with the greatest economic benefits and feasibility, the utilization of adsorption-type additives has greater prospects for concentrating on solving the interface problems of aqueous zinc-ion batteries without sacrificing the performance of the bulk electrolyte.

[0004] Currently, related research has focused more on the reorganization of metal solvation structures to inhibit dendrite growth on the negative electrode side, but it still suffers from high voltage hysteresis in the deposition / stripping process and shortened long cycle life. Therefore, from the perspective of molecular structure design, developing multifunctional additives that satisfy the synergistic optimization of HER and the deposition / stripping process has broad prospects in the field of designing long-life and high-efficiency zinc-ion batteries with application value. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the present invention provides an electrolyte for an aqueous zinc-ion battery and a preparation method thereof, which optimizes the electrolyte with excellent adsorption characteristics and biocompatibility by introducing a multifunctional chitosan oligosaccharide additive to prepare an aqueous zinc-ion battery with a long life and strong inhibition of hydrogen evolution reaction.

[0006] To achieve the above object, according to the first aspect of the present invention, there is provided an electrolyte for an aqueous zinc-ion battery, comprising: solvent water, a soluble zinc salt, and an electrolyte additive; wherein the electrolyte additive is chitosan oligosaccharide.

[0007] Preferably, the concentration of chitosan oligosaccharide in the electrolyte is 1-20 g / L.

[0008] Preferably, the concentration of chitosan oligosaccharide in the electrolyte is 1-15 g / L.

[0009] Preferably, the concentration of the soluble zinc salt in the electrolyte is 0.1-4 mol / L.

[0010] Preferably, the degree of polymerization of chitosan oligosaccharide is 2-20.

[0011] Preferably, the soluble zinc salt is provided by a soluble inorganic salt and / or an organic zinc salt.

[0012] Preferably, the inorganic zinc salt is selected from at least one of zinc sulfate, zinc chloride, zinc bromide, zinc silicate, zinc carbonate, zinc nitrate, zinc sulfonate, zinc borate, zinc acetate, and zinc perchlorate; the organic zinc salt is selected from at least one of zinc trifluoromethanesulfonate and zinc bis(trifluoromethylsulfonyl)imide.

[0013] Preferably, the solvent water is deionized water or ultrapure water.

[0014] According to the second aspect of the present invention, a water-based zinc ion battery is provided, and the battery includes the water-based zinc ion battery electrolyte as described in the first aspect of the invention.

[0015] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed:

[0016] 1. The present invention provides a water-based zinc ion battery electrolyte, in which the electrolyte additive is chitosan oligosaccharide. Based on the chain length effect of chitosan oligosaccharide, strong and uniform interfacial adsorption characteristics are provided, avoiding the interfacial aggregation and entanglement of polymer additives and the low adsorption strength of low-molecular-weight saccharide additives. The precisely regulated chitosan oligosaccharide interacts with the zinc anode electrolyte interface. Therefore, by using chitosan oligosaccharide as an additive in the present invention, it can be efficiently and densely adsorbed on the surface of the zinc anode, uniformize the zinc ion flow and promote uniform deposition, thereby inhibiting the growth of zinc dendrites; in addition, the glycolipid bond and O-containing group in chitosan oligosaccharide are beneficial to reducing the number of active hydrogens in the hydrogen bond network of water, inhibiting the self-corrosion reaction and hydrogen evolution reaction, and simultaneously achieving a double improvement in Coulomb efficiency and cycle stability.

[0017] 2. In the present invention, an electrolyte is obtained by adding a small amount of low-cost additive to a zinc salt solution and applying it to a zinc ion energy storage battery, which has good cycle stability and reversibility.

[0018] 3. In the present invention, the concentration of the soluble zinc salt is relatively low. Compared with high-concentration salt electrolytes, the low-concentration soluble zinc salt improves the overall ionic conductivity of the electrolyte and has a higher cost advantage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The laser confocal test results after 100 h of cycle stability test under the conditions of 1 mA cm -2 and 1 mAh cm -2 for the zinc symmetric battery assembled with the conventional 2M zinc sulfate electrolyte (a), glucosamine (b), chitosan oligosaccharide (c), and chitosan (d) with a concentration of 5 g / L in the 2M zinc sulfate composite electrolyte constructed in the examples of the present invention.

[0020] Figure 2 The SEM images of the zinc symmetric battery assembled with the 2 mol / L zinc sulfate + 5 g / L chitosan oligosaccharide aqueous zinc ion battery electrolyte constructed according to the embodiments of the present invention and the conventional 2 M zinc sulfate electrolyte were tested after 500 cycles under the conditions of a current density of 1 mA cm -2 and 1 mAh cm -2 Condition.

[0021] Figure 3 The long-cycle test performance display of the cycling stability test of the zinc symmetric battery assembled with the composite electrolytes of 2 M zinc sulfate containing chitosan oligosaccharide concentrations of 1 g / L, 5 g / L, 10 g / L, and 20 g / L respectively constructed according to the embodiments of the present invention and the conventional 2 M zinc sulfate electrolyte at 1 mA cm -2 and 1 mAh cm -2 Condition.

[0022] Figure 4 The comparison of the cycling stability test of the zinc symmetric battery assembled with the composite electrolyte of 2 M zinc sulfate with chitosan oligosaccharide, glucosamine, and chitosan concentrations all being 5 g / L constructed according to the embodiments of the present invention at 1 mA cm -2 and 1 mAh cm -2 Condition.

[0023] Figure 5 The long-cycle test performance display of the cycling stability test of the zinc symmetric battery assembled with the electrolyte of 2 mol / L zinc trifluoromethanesulfonate + 5 g / L chitosan oligosaccharide and 2 mol / L zinc trifluoromethanesulfonate + 5 g / L chitosan oligosaccharide constructed according to the embodiments of the present invention at 1 mA cm -2 and 1 mAh cm -2 Condition; wherein, Zn(OTF)2 refers to the 2 mol / L zinc trifluoromethanesulfonate + 5 g / L chitosan oligosaccharide solution, and Zn(ClO4)2 refers to the 2 mol / L zinc trifluoromethanesulfonate + 5 g / L chitosan oligosaccharide solution.

[0024] Figure 6 The voltage-current curve of the Tafel test of the zinc symmetric battery assembled with the 2 mol / L zinc sulfate + 5 g / L chitosan oligosaccharide aqueous zinc ion battery electrolyte constructed according to the embodiments of the present invention.

[0025] Figure 7 The capacity performance and Coulomb efficiency of the full battery of zinc / / V6O 13 assembled with the electrolyte of 2 mol / L zinc sulfate + 5 g / L chitosan oligosaccharide composite constructed according to the embodiments of the present invention under the condition of 5 A g -1 Condition during cycling. Detailed implementation mode

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, that is, they are meant to include but not limited to.

[0028] Aiming at the problems of zinc dendrites and hydrogen evolution in the zinc anode of aqueous zinc-ion batteries, the present invention provides an electrolyte for aqueous zinc-ion batteries, and the electrolyte additive is chitosan oligosaccharide. Based on the chain length effect of chitosan oligosaccharide, it provides strong and uniform interfacial adsorption characteristics, avoiding the interfacial aggregation and entanglement of polymer additives and the low adsorption strength of low-molecular-weight saccharide additives. The precisely regulated chitosan oligosaccharide interacts with the zinc anode electrolyte interface. Therefore, the present invention uses chitosan oligosaccharide as an additive, which can be efficiently and densely adsorbed on the surface of the zinc anode, uniform the zinc ion flow and promote uniform deposition, thereby inhibiting the growth of zinc dendrites; in addition, the glycolipid bond and O-containing group in chitosan oligosaccharide are beneficial to reducing the number of active hydrogens in the hydrogen bond network of water, inhibiting the self-corrosion reaction and hydrogen evolution reaction, and can simultaneously improve the Coulomb efficiency and cycle stability.

[0029] The concentration of chitosan oligosaccharide in the present invention is 1 g / L to 20 g / L, and it has an improving effect on the life of symmetric batteries within the specified concentration range.

[0030] The concentration of chitosan oligosaccharide in the present invention is preferably 5 g / L. Below 5 g / L, increasing the concentration can greatly extend the life of symmetric batteries, and the improvement effect decreases after further increase.

[0031] The concentration of soluble zinc salt in the present invention is relatively low. Compared with high-concentration salt electrolytes, the low-concentration soluble zinc salt improves the overall ionic conductivity of the electrolyte and has a higher cost advantage.

[0032] This embodiment provides a preparation method for an electrolyte of an aqueous zinc-ion battery, including: weighing an appropriate amount of soluble zinc salt and chitosan oligosaccharide, dissolving them in solvent water, making up the volume, and mixing and stirring the solution until it is clear to prepare an electrolyte for an aqueous zinc-ion battery. Unless otherwise specified, the room temperature in the embodiments of the present invention refers to 25 ± 2 °C.

[0033] The soluble zinc salts involved in the present invention and the embodiments are all commercially available and used according to commercial standards. The chitosan oligosaccharide referred to in the present invention is also called oligosaccharide, which is a low-polymerization product obtained by degrading chitosan by special bioenzyme technology (there are also reports of using chemical degradation and microwave degradation technology). Specifically, the chitosan oligosaccharide in the embodiment of the present invention was purchased from Aladdin Co., Ltd., with a molecular weight of ≤2000Da and a degree of polymerization of 2 to 20.

[0034] The aqueous zinc ion battery electrolyte provided by the present invention is further described in detail below in conjunction with the embodiments and drawings.

[0035] Embodiment 1:

[0036] Weigh appropriate amounts of ZnSO4 and chitosan oligosaccharide, mix and dissolve them in deionized water, make the volume up to 20 mL, stir the solution until it becomes clear, and prepare a 2M ZnSO4+1g / L chitosan oligosaccharide electrolyte, recorded as COS1.

[0037] Embodiment 2:

[0038] Weigh appropriate amounts of ZnSO4 and chitosan oligosaccharide, mix and dissolve them in deionized water, make the volume up to 20 mL, stir the solution until it becomes clear, and prepare a 2M ZnSO4+5g / L chitosan oligosaccharide electrolyte, recorded as COS5.

[0039] Embodiment 3:

[0040] Weigh appropriate amounts of ZnSO4 and chitosan oligosaccharide, mix and dissolve them in deionized water, make the volume up to 20 mL, stir the solution until it becomes clear, and prepare a 2M ZnSO4+10g / L chitosan oligosaccharide electrolyte, recorded as COS10.

[0041] Embodiment 4:

[0042] Weigh appropriate amounts of ZnSO4 and chitosan oligosaccharide, mix and dissolve them in deionized water, make the volume up to 20 mL, stir the solution until it becomes clear, and prepare a 2M ZnSO4+15g / L chitosan oligosaccharide electrolyte, recorded as COS15.

[0043] Embodiment 5:

[0044] Weigh appropriate amounts of ZnSO4 and chitosan oligosaccharide, mix and dissolve them in deionized water, make the volume up to 20 mL, stir the solution until it becomes clear, and prepare a 2M ZnSO4+20g / L chitosan oligosaccharide electrolyte, recorded as COS20.

[0045] Embodiment 6:

[0046] Weigh an appropriate amount of zinc trifluoromethanesulfonate (Zn(OTF)2) and chitosan oligosaccharide, mix and dissolve them in deionized water, make up the volume to 20 mL, stir the solution until it is clear, and prepare a 2 M (Zn(OTF)2 + 5 g / L chitosan oligosaccharide electrolyte, denoted as COS5-Zn(OTF)2).

[0047] Example 7:

[0048] Weigh an appropriate amount of zinc perchlorate (ZnClO4) and chitosan oligosaccharide, mix and dissolve them in deionized water, make up the volume to 20 mL, stir the solution until it is clear, and prepare a 2 M ZnClO4 + 5 g / L chitosan oligosaccharide electrolyte, denoted as COS5-ZnClO4.

[0049] Comparative Example 1:

[0050] Weigh an appropriate amount of ZnSO4, dissolve it in deionized water, make up the volume to 20 mL, stir the solution until it is clear, and prepare a conventional 2 M ZnSO4 electrolyte, denoted as ZSO.

[0051] Comparative Example 2:

[0052] Glucosamine was purchased from Aladdin, and its molecular weight is 179.

[0053] Weigh an appropriate amount of ZnSO4 and small molecule sugar (glucosamine), mix and dissolve them in deionized water, make up the volume to 20 mL, stir the solution until it is clear, and prepare a 2 M ZnSO4 + 5 g / L glucosamine electrolyte, denoted as GIcN5.

[0054] Comparative Example 3:

[0055] Chitosan was purchased from Aladdin, and its molecular weight is 100,000 - 200,000.

[0056] Weigh an appropriate amount of ZnSO4 and polymer sugar (chitosan), mix and dissolve them in deionized water, make up the volume to 20 mL, stir the solution until it is clear, and prepare a 2 M ZnSO4 + 5 g / L chitosan electrolyte, denoted as OS5.

[0057] Assemble the electrolytes prepared in the above examples and comparative examples into batteries, and conduct battery performance characterization on the assembled zinc-ion batteries, as follows:[[]]END]]

[0058] Zinc-ion battery assembly process:

[0059] Use the electrolytes prepared in the examples and comparative examples to assemble Zn / / Zn symmetric batteries respectively. The general preparation process is as follows:

[0060] Electrode treatment: Select high-purity Zn sheets with a diameter of 11 mm (purity > 99.95%), ultrasonically clean them with ethanol and then perform vacuum drying treatment;

[0061] Component assembly: Stack in the order of positive electrode shell → positive electrode sheet → glass fiber GF / C separator → electrolyte (0.1 mL) → negative electrode sheet → gasket → spring sheet → negative electrode shell; both electrodes of the Zn / / Zn symmetric battery use Zn sheets.

[0062] Zn full cell test: Assemble Zn full cells with the optimized chitosan oligosaccharide electrolyte #2 and the reference system (2M zinc sulfate solution). Its general preparation process includes:

[0063] V6O 13 Pole piece preparation: Coat a slurry containing V6O 13 , carbon black and PVDF onto titanium foil in a mass ratio of 7:2:1, then vacuum dry overnight at 80 °C and cut into wafers with a diameter of 8 mm for standby.

[0064] Zn full cell assembly: The positive electrode is a V6O 13 sheet, the negative electrode is a Zn sheet, and stack in the order of positive electrode shell → positive electrode sheet → glass fiber GF / C separator → electrolyte (0.1 mL) → negative electrode sheet → gasket → spring sheet → negative electrode shell.

[0065] Structural performance characterization: Use a laser confocal microscope (LSCM) to characterize the zinc deposition morphology and structure at the zinc negative electrode / electrolyte interface of the batteries assembled with the electrolytes of Example 2 and Comparative Examples 1-3 after cyclic testing.

[0066] As Figure 1 shown, showing the electrode surface after 100 h of continuous deposition and stripping. For ZSO, an uneven surface formed due to uneven deposition was clearly recorded on the GlcN5 anode. Compared with the Zn electrode with a series electrolyte added, the deposited Zn formed a relatively flat surface, where COS 5 had the thickest uniform deposition and uniform distribution. The surface height difference of CS5 was small, but similar to ZSO, the surface was accompanied by irregular "holes", making the surface profile show greater roughness. Overall, the presence of the short-chain structure has a better modification effect than the long-chain structure and small molecule structure. It induces a uniform interface at the interface.

[0067] As Figure 2 shown, a scanning electron microscope (SEM) confirmed the special morphology of the zinc surface. The zinc surface with ZSO as the electrolyte showed disordered deposition stacks with different orientations and did not show a dominant crystal plane, while COS5 showed an overall and flat structure with average deposition.

[0068] Electrochemical performance test: Perform cyclic stability tests under the conditions of 1 mA cm -2 and 1 mAh cm -2 as follows:

[0069] AsFigure 3 and Figure 4 As shown in -2 and -2 , the zinc-ion batteries assembled with the corresponding electrolytes in Examples 1-4 and Comparative Examples 1-3 were subjected to cyclic stability tests under the conditions of 1 mA cm -2 and 1 mAh cm -2 . The results showed that the electrolytes in Examples 1-4 exhibited significantly improved stability after assembling into zinc-ion batteries compared with the existing conventional zinc-ion electrolytes. Among them, the electrolytes in Examples 1-3 still had obvious advantages after assembling into zinc-ion batteries compared with the existing electrolytes based on small molecule sugars and polymer sugars. Further, the Zn / / Zn symmetric battery assembled with the electrolyte in Example 2 was stably cycled for more than 3000 h under the conditions of 1 mA cm -2 and 1 mAh cm -2 , showing the most significant improvement in stability.

[0070] As Figure 5 shown, it was demonstrated that the electrolytes prepared from chitosan oligosaccharide and different kinds of soluble zinc salts of the present invention all exhibited excellent improvement in stability.

[0071] As Figure 6 shown, the inhibition effect on the hydrogen evolution corrosion reaction was further understood by using the Tafel curve. The test results showed that the hydrogen evolution corrosion current density of COS5 was one order of magnitude smaller than that of ZSO, indicating excellent inhibition effect on the hydrogen evolution reaction.

[0072] Electrochemical performance test: The cyclic stability test was carried out at a current density of 5 Ag -1 as follows:

[0073] To further investigate the performance of the full cell, as Figure 7 shown, COS5 exhibited a higher full cell capacity retention rate, indicating the synergistic improvement of the stability during the negative electrode deposition process on the overall electrode performance.

[0074] In summary, due to the structure of the oligomer, which induced a stable deposition structure and inhibited the HER reaction, the oligosaccharide exhibited far better cyclic stability than the conventional electrolytes. Compared with the structurally similar small molecules and macromolecules, the oligomeric molecules also benefited from the more uniform structure and thus obtained longer and more advantageous deposition and stripping performance. At the same time, the oligomer additive exhibited a concentration threshold effect. Therefore, the preferred low-concentration molecular additive demonstrated the compatible advantages in performance optimization and cost performance.

[0075] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the present invention and the scope of equivalent technologies thereof, the present invention also intends to include these modifications and variations. The above-described embodiments are merely preferred embodiments given to fully illustrate the present invention, and the scope of protection is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention.

Claims

1. An aqueous zinc-ion battery electrolyte, characterized in that, Comprising: Solvent water, soluble zinc salt and electrolyte additive; Wherein the electrolyte additive is chitosan oligosaccharide.

2. The aqueous zinc-ion battery electrolyte according to claim 1, wherein The concentration of chitosan oligosaccharide in the electrolyte is 1 - 20 g / L.

3. The aqueous zinc-ion battery electrolyte according to claim 1, wherein The concentration of chitosan oligosaccharide in the electrolyte is preferably 1 - 15 g / L.

4. The aqueous zinc-ion battery electrolyte according to claim 1, wherein The concentration of soluble zinc salt in the electrolyte is 0.1 - 4 mol / L.

5. The aqueous zinc ion battery electrolyte according to claim 1, characterized in that, The degree of polymerization of the chitosan oligosaccharide is 2 - 20.

6. The aqueous zinc ion battery electrolyte according to claim 1, wherein, The soluble zinc salt is provided by soluble inorganic zinc salt and / or organic zinc salt.

7. The aqueous zinc ion battery electrolyte according to claim 6, characterized in that, The inorganic zinc salt is selected from at least one of zinc sulfate, zinc chloride, zinc bromide, zinc silicate, zinc carbonate, zinc nitrate, zinc sulfonate, zinc borate, zinc acetate and zinc perchlorate; the organic zinc salt is selected from at least one of zinc trifluoromethanesulfonate and zinc bis(trifluoromethylsulfonyl)imide.

8. The aqueous zinc ion battery electrolyte according to claim 1, wherein The solvent water is deionized water or ultrapure water.

9. A water-based zinc-ion battery, characterized in that, The battery comprises the aqueous zinc ion battery electrolyte according to any one of claims 1 - 8.

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