Aqueous zinc ion battery electrolyte and aqueous zinc ion battery

Abstract

The invention discloses an aqueous zinc ion battery electrolyte and an aqueous zinc ion battery, and belongs to the field of batteries. The electrolyte comprises an additive; the additive at least comprises a zinc-philic group and an N-containing cyclic structure; and the zinc-philic group is selected from at least one of-C = O and-OH. The aqueous zinc ion battery comprises a positive electrode, a Zn negative electrode and the electrolyte. The diprophylline, the aminophylline, the theophylline and the theobromine are used as electrolyte additives of the aqueous zinc ion battery, so that uniform deposition of a Zn negative electrode can be effectively induced, formation of dendritic crystals is reduced, and the cycling stability of the zinc ion battery is improved. Compared with a battery without the electrolyte additive, the total battery added with the diprophylline can stably circulate for 9000 circles under the current density of 10A g <-1 >.

Description

Technical Field

[0001] The present application relates to an aqueous zinc-ion battery electrolyte and an aqueous zinc-ion battery, belonging to the field of batteries. Background Art

[0002] Due to the rapid development of today's social economy and technology, the demand for renewable energy by humans is increasing. However, due to its often being affected by factors such as the environment and weather, it is difficult to achieve continuous supply. Therefore, energy storage batteries are the focus of current research. Aqueous zinc-ion batteries have become one of the strong candidates for large-scale energy storage devices and a research hotspot in recent years because of their high theoretical capacity (820 mAh g -1 ), high safety, low cost, and environmental friendliness.

[0003] Among them, great progress has been made in cathode materials in materials such as vanadium-based compounds, manganese-based compounds, and metal / covalent organic frameworks. As an indispensable part of AZIBs, the zinc anode has a great influence on the performance of the battery during the cycling process in terms of the stability of the electrode interface. Among them, problems such as zinc dendrite growth, hydrogen evolution reaction (HER), and corrosion limit the development of AZIBs. Therefore, regulating the stability of the zinc anode interface is beneficial to improving the overall performance of AZIBs. Zn 2+ always tends to deposit and form tips at the position with the lowest surface energy on the zinc anode surface. The protrusion rate of the surface near the tips is higher than other parts, forming the "tip effect", resulting in the enrichment of the electric field and Zn 2+ concentration field at the tips, which destroys the stable deposition / dissolution process of Zn 2+ , and gradually leads to the formation of zinc dendrites with loose structure and rough surface. In addition, this behavior has a cumulative effect. Without interference, zinc dendrites will continue to evolve to a larger size until they break and peel off from the zinc anode to form "dead zinc" or pierce the separator, seriously damaging the stability of the zinc anode interface. Therefore, it is crucial to maintain the uniform deposition of Zn 2+ during the cycling process. Due to the direct contact between the zinc anode and the aqueous electrolyte, side reactions such as hydrogen evolution (HER) and corrosion are also challenges that cannot be ignored for the zinc anode. Due to the thermodynamic instability of the zinc anode in neutral or weakly acidic electrolytes, theoretically, HER is easier to occur than the deposition of Zn 2+ . Therefore, once the zinc anode comes into contact with the electrolyte, hydrogen gas will inevitably be generated. The increase in zinc dendrites will increase the contact area between the zinc anode and the electrolyte, and hydrogen gas will inevitably be generated. HER consumes the electrons that should have been transferred to Zn 2+ , consumes the electrolyte and active Zn 2+ , significantly reducing the coulombic efficiency of the battery. Secondly, the hydrogen gas generated by HER increases the internal pressure of the sealed battery, which may cause the battery to expand or even explode.

[0004] The surface passivation of zinc metal also affects battery performance. In the ZnSO4 electrolyte, the main by-products of the electrochemical corrosion of the zinc negative electrode are Zn4SO4(OH)6·xH2O. In the Zn(OTf)2 electrolyte, the main by-products are Zn x (OTf) y (OH)2 x-y ·nH2O, ZnO and Zn(OH)2. These insoluble and insulating by-products adhere to the surface of the zinc negative electrode, covering the active deposition sites of Zn 2+ and inducing the formation of dendrites. In addition, these by-products also hinder the transport of ions / electrons at the zinc negative electrode interface, which is not conducive to the interface stability of the zinc negative electrode, resulting in a larger battery internal resistance and passivating the zinc negative electrode. These by-products have a porous structure and will continuously consume the negative electrode and the electrolyte, ultimately leading to the inactivation of the zinc negative electrode surface.

[0005] The electrolyte has a crucial impact on the optimization of the negative electrode. Optimizing the electrolyte structure can effectively improve the reversibility of the zinc negative electrode, thereby enhancing the electrochemical performance of the battery. However, the use of pure ZnSO4 or Zn(OTf)2 alone cannot fully ensure the cycling stability of the zinc negative electrode. Therefore, the optimized design of the electrolyte is considered to be one of the simplest and most effective methods to improve the interface stability of the Zn negative electrode. Summary of the Invention

[0006] According to the first aspect of the present application, an aqueous zinc-ion battery electrolyte is provided. Diprophylline, aminophylline, theophylline, and theobromine contain -C=O, -OH and an N-containing ring structure. These zincophilic groups can preferentially adsorb on the Zn negative electrode over water, and the methyl group, as a hydrophobic group, can displace the adsorbed water, reducing the contact between water and the Zn negative electrode and reducing side reactions such as HER caused by H2O.

[0007] An aqueous zinc-ion battery electrolyte, the electrolyte comprising an additive;

[0008] The additive at least contains a zincophilic group and an N-containing ring structure;

[0009] The zincophilic group is selected from at least one of -C=O and -OH.

[0010] Optionally, the additive is selected from at least one of diprophylline, aminophylline, theophylline, and theobromine.

[0011] Specifically, the additive is diprophylline (DHTP).

[0012] Optionally, the electrolyte further comprises a zinc salt and water.

[0013] Optionally, the molar ratio of the zinc salt to the additive is 1:0.05 to 0.1.

[0014] Optionally, the molar ratio of the zinc salt to the additive is independently selected from any value of 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1 or a range value between any two values.

[0015] Optionally, the concentration of the zinc salt in the electrolyte is 1 to 3 mol / L -1 .

[0016] Optionally, the molar concentration of the zinc salt is independently selected from any value of 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.7 mol / L, 2.0 mol / L, 2.2 mol / L, 2.5 mol / L, 2.7 mol / L, 3.0 mol / L or a range value between any two values.

[0017] Optionally, the zinc salt is selected from at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc trifluoromethanesulfonate, zinc trifluoromethanesulfonylsulfonate, and zinc acetate.

[0018] Specifically, the zinc salt is selected from Zn(CF3SO3)2.

[0019] Optionally, the aqueous zinc ion battery electrolyte includes an additive, a zinc salt, and water.

[0020] Optionally, the aqueous zinc ion battery electrolyte consists of an additive, a zinc salt, and water.

[0021] According to the second aspect of the present application, a preparation method of an aqueous zinc ion battery electrolyte is provided.

[0022] In the above-mentioned preparation method of the aqueous zinc ion battery electrolyte, an additive is added to the zinc salt aqueous solution;

[0023] Or

[0024] An aqueous solution of an additive is added to the zinc salt aqueous solution.

[0025] According to the third aspect of the present application, an aqueous zinc ion battery is provided. Diprophylline, aminophylline, theophylline, or theobromine as an electrolyte additive of the aqueous zinc ion battery can effectively induce the uniform deposition of the Zn negative electrode, reduce dendrite formation, and improve the cycle stability of the zinc ion battery. Compared with the battery without the electrolyte additive, the full battery with diprophylline added can stably cycle 9000 times at a current density of 10 A / g -1 .

[0026] An aqueous zinc ion battery, the aqueous zinc ion battery includes a positive electrode, a Zn negative electrode, and an electrolyte;

[0027] The electrolyte is the aqueous zinc-ion battery electrolyte described above.

[0028] Optionally, the active material of the positive electrode is selected from at least one of vanadium-based materials, manganese-based materials, and Prussian blue compounds.

[0029] Optionally, the vanadium-based material is selected from at least one of sodium vanadate, potassium vanadate, and vanadium pentoxide.

[0030] Optionally, the Zn negative electrode is selected from at least one of zinc foil, zinc sheet, zinc foam, zinc powder, and zinc rod.

[0031] The beneficial effects that this application can produce include:

[0032] (1) The aqueous zinc-ion battery electrolyte and aqueous zinc-ion battery provided by this application, diprophylline, aminophylline, theophylline, and theobromine contain -C=O, -OH, and an N-containing ring structure. These zincophilic groups can preferentially adsorb on the Zn negative electrode over water, and the methyl group, as a hydrophobic group, can displace the adsorbed water, reducing the contact between water and the Zn negative electrode and reducing side reactions such as HER caused by H2O.

[0033] (2) Diprophylline, aminophylline, theophylline, or theobromine as an electrolyte additive for aqueous zinc-ion batteries can effectively induce uniform deposition of the Zn negative electrode, reduce dendrite formation, and improve the cycle stability of zinc-ion batteries. Compared with the battery without the electrolyte additive, the full battery with diprophylline can stably cycle 9000 times at a current density of 10 A g -1 -1. Description of the Drawings

[0034] Figure 1 It is a comparison chart of the cycle life of the NVO||Zn full battery assembled with the ZOT-0.15DHTP electrolyte of Example 1 and the ZOT electrolyte of Comparative Example 1.

[0035] Figure 2 It is a cycle life chart of the Zn||Zn symmetric battery assembled with the ZOT-0.15DHTP electrolyte of Example 2 and the ZOT electrolyte of Comparative Example 2.

[0036] Figure 3 It is a cycle life chart of the Zn||Cu asymmetric battery assembled with the ZOT-0.15DHTP electrolyte of Example 5 and the ZOT electrolyte of Comparative Example 5.

[0037] Figure 4SEM images of the Zn anodes of the Zn||Zn symmetric cells of Example 2 and Comparative Example 2 after cycling are shown. Figures (a) and (b) are images of the Zn anode after cycling in the ZOT electrolyte. The scale of Figure (a) is 100 μm, and the scale of Figure (b) is 20 μm. Figures (c) and (d) are images of the Zn anode after cycling the cell in the ZOT-0.15DHTP electrolyte. The scale of Figure (c) is 100 μm, and the scale of Figure (d) is 20 μm. Detailed implementation manners

[0038] The present application will be described in detail below in conjunction with the embodiments, but the present application is not limited to these embodiments.

[0039] Unless otherwise specified, the raw materials in the embodiments of the present application are all purchased through commercial channels.

[0040] Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all the settings recommended by the manufacturers.

[0041] Material characterization methods:

[0042] The crystal structures of the samples were obtained by an X-ray diffractometer (XRD, Miniflex600, Cu Kα), and the morphologies of the samples were characterized by a scanning electron microscope (SEM, SU8010). The contact angles of different electrolytes on the Zn foil surface were measured using a contact angle tester (DSA25). The influence of functional groups in the electrolyte was analyzed using an in-situ laser confocal Raman spectrometer (LabRAM, Thermo Fisher Scientific). The Fourier transform infrared spectra of different electrolytes were recorded using an infrared spectrometer (VERTEX70).

[0043] Battery test methods:

[0044] Cyclic voltammetry (CV) tests were performed on the Zn||cathode dual cells on a Princeton electrochemical workstation at a scan rate of 0.1 mV s -1 , and the voltage range was 0.2 - 1.6 V. The CV test voltage ranges for Zn||Cu and Zn||Ti were -0.3 V to -0.2 V, and the scan rate was 0.1 mV s -1 . The acquisition range of the electrochemical impedance spectroscopy (EIS) was between 100000 Hz and 0.1 Hz. Galvanostatic charge-discharge tests and galvanostatic intermittent titration technique (GITT) tests were performed on a Neware test system. In a three-electrode system, a zinc foil was used as the working electrode (W), a platinum wire was used as the counter electrode (C), and Ag / AgCl was used as the reference electrode (R). Linear sweep voltammetry (LSV) and linear polarization curve tests were performed in different electrolytes. The scan rate was 2 mV s -1, the scanning potential range is -1.25 to -0.75 V. All batteries were assembled under open-air conditions and aged for 4 hours before electrochemical testing.

[0045] Example 1

[0046] Preparation of the positive electrode material

[0047] 1 g of commercial V2O5 powder was added to 15 mL of an aqueous NaCl solution (2 M). After stirring at 30 °C for 96 h, it was washed several times with deionized water. Finally, a black-red powder, NaV3O8·1.5H2O (NVO), was obtained by freeze-drying.

[0048] Preparation of the positive electrode

[0049] The active material NaV3O8·1.5H2O (NVO), conductive carbon black, and PVDF were mixed in a weight ratio of 7:2:1 in NMP solvent, and the slurry was ball-milled for 3 hours (300 r min -1 ) to prepare the slurry. The graphite paper was cut into a circle with a diameter of Φ = 14 mm, and the prepared slurry was evenly coated on the graphite paper and dried in a forced-air drying oven at 80 °C for 24 h. The NVO positive electrode was prepared. The loading mass of the active material per electrode was about 2 mg / electrode.

[0050] Preparation of the negative electrode material: The pure zinc foil was cut into a pole piece with a diameter of 14 mm using a slicing machine, and the pole piece was immersed in an anhydrous ethanol solution and ultrasonically cleaned for 1 - 2 s. The cleaned pole piece was laid flat and dried in the natural environment for use as the negative electrode.

[0051] Preparation of the electrolyte

[0052] A 2 M aqueous solution of 2 mol L -1 Zn(CF3SO3)2 was used as the reference solution. 0.1 mol L -1 , 0.15 mol L -1 , and 0.2 mol L -1 of the aqueous solution of diprophylline (DHTP, molecular formula C -1 H 10 H 14N4O4, with a molecular weight of 254.243, also known as 7-(2,3-dihydroxypropyl)theophylline, 1,3-dimethyl-7-(2,3-dihydroxypropyl)-3,7-dihydro-1H-purine-2,6-dione. The electrolytes are denoted as ZOT-0.1DHTP, ZOT-0.15DHTP, and ZOT-0.2DHTP respectively. Among them, the molar ratios of Zn(CF3SO3)2 to DHTP are 1:0.05, 1:0.08, and 1:0.1 respectively, and the concentrations of Zn(CF3SO3)2 in the electrolytes are 1 mol L -1 、2 mol L -1 、3 mol L -1 。

[0053] Battery assembly

[0054] Use a CR2025 battery case to assemble the battery. The assembly sequence is the positive electrode case, the positive electrode, the glass fiber separator, the Zn negative electrode, the gasket, the shrapnel, and the negative electrode case in turn. Different electrolytes are added and encapsulated into a full battery.

[0055] Comparative Example 1

[0056] The operation is the same as that in Example 1, except that an NVO positive electrode, a glass fiber separator, and a Zn negative electrode are stacked and assembled in turn, and 2 mol L -1 of 2M Zn(CF3SO3)2 is added, denoted as ZOT aqueous solution and encapsulated into an NVO||Zn battery.

[0057] Example 2

[0058] The operation is the same as that in Example 1, except that a zinc (Zn) positive electrode replaces the NVO positive electrode. A zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode are stacked and assembled in turn, and ZOT-0.15DHTP electrolyte is added and encapsulated into a Zn||Zn battery.

[0059] Comparative Example 2

[0060] The operation is the same as that in Example 2, except that a zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode are stacked and assembled in turn, and ZOT electrolyte is added and encapsulated into a Zn||Zn battery.

[0061] Example 3

[0062] The operation is the same as that in Example 1, except that a zinc (Zn) positive electrode replaces the NVO positive electrode. A zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode are stacked and assembled in turn, and ZOT-0.1DHTP electrolyte is added and encapsulated into a Zn||Zn battery.

[0063] Comparative Example 3

[0064] The operation was the same as that in Example 3, except that a zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode were stacked and assembled in sequence, and the ZOT electrolyte was added and encapsulated into a Zn||Zn battery.

[0065] Example 4

[0066] The operation was the same as that in Example 1, except that a zinc (Zn) positive electrode was used instead of the NVO positive electrode, a zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode were stacked and assembled in sequence, and the ZOT-0.2DHTP electrolyte was added and encapsulated into a Zn||Zn battery.

[0067] Comparative Example 4

[0068] The operation was the same as that in Example 4, except that a zinc (Zn) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode were stacked and assembled in sequence, and the ZOT electrolyte was added and encapsulated into a Zn||Zn battery.

[0069] Example 5

[0070] The operation was the same as that in Example 1, except that a copper (Cu) positive electrode was used instead of the NVO positive electrode, a copper (Cu) positive electrode, a glass fiber separator, and a zinc (Zn) negative electrode were stacked and assembled in sequence, and the ZOT-0.15DHTP electrolyte was added and encapsulated into a Zn||Cu battery.

[0071] Comparative Example 5

[0072] The operation was the same as that in Example 5, except that a copper (Cu) positive electrode was stacked and assembled in sequence, and the ZOT electrolyte was added and encapsulated into a Zn||Cu battery.

[0073] Results and Analysis

[0074] Effect of DHTP on the performance of the full cell and the stability of the vanadium-based positive electrode

[0075] Figure 1 Figure showing the comparison of charge-discharge cycle life of the NVO||Zn aqueous zinc-ion full cell assembled with the ZOT-0.15DHTP electrolyte of Example 1 and the ZOT electrolyte of Comparative Example 1 at a current of 10 A / g. -1 The full cell with the ZOT electrolyte rapidly decayed, and after 1500 charge-discharge cycles, the capacity retention rate of the aqueous zinc-ion battery was less than 80%. However, the electrolyte ZOT-0.15DHTP with the electrolyte additive DHTP of the present invention significantly improved the cycle life of the aqueous zinc-ion battery, and the capacity retention rate of the aqueous zinc-ion battery was 89% after 8000 charge-discharge cycles.

[0076] Number Cycle life (times) Example 1 8000 Comparative Example 1 1500

[0077] Effect of DHTP on the cycle stability of the Zn||Zn symmetric battery

[0078] Figure 2 Cycling life graphs of Zn||Zn symmetric cells assembled with the ZOT-0.15DHTP electrolyte of Example 2 and the ZOT electrolyte of Comparative Example 2. Under the conditions of 1 mA cm -2 / 1 mAh cm -2 , the cycling stability of the Zn||Zn symmetric cell assembled with the ZOT-0.15DHTP electrolyte is significantly improved compared to ZOT, and ZOT-0.15DHTP can cycle for more than 800 h.

[0079] The cycling life tests were also carried out on the Zn||Zn symmetric cells assembled in Examples 3 and 4, and the data are shown in the following table.

[0080] Number Cycle life (h) Example 2 810h Example 3 421h Example 4 603h Comparative Example 2 25h

[0081] Effect of DHTP on the cycling stability of Zn||Cu asymmetric cells

[0082] Figure 3 Cycling life graphs of Zn||Cu asymmetric cells assembled with the ZOT-0.15DHTP electrolyte of Example 5 and the ZOT electrolyte of Comparative Example 5. Under the conditions of 1 mA cm -2 / 1 mAh cm -2 , the cycling stability of Zn||Cu assembled with the ZOT-0.15DHTP electrolyte is significantly improved compared to ZOT, and ZOT-0.15DHTP can cycle more than 200 times.

[0083] Test on improving the surface flatness of zinc anode by DHTP additive

[0084] The morphologies of the Zn anodes of the Zn||Zn symmetric cells in Example 2 and Comparative Example 2 after cycling were studied. Figure 4 (a) and (b) are SEM images of the Zn anode of Comparative Example 2. It can be seen that in the ZOT electrolyte, the surface is uneven and the degree of crystal phase orientation is not high. Figure 4 (c) and (d) are SEM images of the Zn anode of Example 2. It can be seen that in the ZOT-0.15DHTP electrolyte, the surface of the Zn anode is relatively flat and the degree of crystal phase orientation is relatively high, which can stabilize the Zn anode.

[0085] In summary, by using diprophylline, etc. as electrolyte additives for aqueous zinc-ion batteries in this application, the uniform deposition of the Zn anode can be effectively induced, the formation of dendrites can be reduced, the degree of crystal phase orientation is relatively high, the Zn anode can be stabilized, and the cycling stability of the zinc-ion battery can be improved. Compared with the battery without electrolyte additives, the cycling stability of the battery is significantly improved.

[0086] As described above, these are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the relevant art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the technical content disclosed above is equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An aqueous zinc-ion battery electrolyte, characterized in that, The electrolyte includes additives; The additives at least contain a zincophilic group and an N-containing cyclic structure; The zincophilic group is selected from at least one of -C=O and -OH.

2. The aqueous zinc ion battery electrolyte according to claim 1, characterized in that, The additives are selected from at least one of diprophylline, aminophylline, theophylline, and theobromine.

3. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The electrolyte further includes a zinc salt and water.

4. The aqueous zinc-ion battery electrolyte according to claim 3, characterized in that, In the electrolyte, the molar ratio of the zinc salt to the additive is 1:0.05 to 0.

1.

5. The aqueous zinc ion battery electrolyte according to claim 3, wherein In the electrolyte, the concentration of zinc salt is 1-3 mol / L -1 .

6. The aqueous zinc-ion battery electrolyte according to claim 3, wherein The zinc salt is selected from at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc trifluoromethanesulfonate, zinc trifluoromethanesulfonylimide, and zinc acetate.

7. The preparation method of the aqueous zinc ion battery electrolyte according to any one of claims 3 to 6, characterized in that, Additives are added to an aqueous zinc salt solution; or An aqueous solution of additives is added to an aqueous zinc salt solution.

8. A water-based zinc-ion battery, characterized in that, The aqueous zinc ion battery includes a positive electrode, a Zn negative electrode, and an electrolyte; The electrolyte is the aqueous zinc ion battery electrolyte according to any one of claims 1 to 6.

9. The aqueous zinc ion battery according to claim 8, wherein The active material of the positive electrode is selected from at least one of vanadium-based materials, manganese-based materials, and Prussian blue compounds; Preferably, the vanadium-based material is selected from at least one of sodium vanadate, potassium vanadate, and vanadium pentoxide.

10. The aqueous zinc-ion battery according to claim 8, characterized in that, The Zn negative electrode is selected from at least one of zinc foil, zinc sheet, zinc foam, zinc powder, and zinc rod.

Images