Aqueous zinc ion battery electrolyte and aqueous zinc ion battery

Abstract

The invention belongs to the technical field of aqueous zinc ion batteries, and relates to an aqueous zinc ion battery electrolyte and an aqueous zinc ion battery. A negative electrode material of the aqueous zinc ion battery is metal zinc, a positive electrode material of the aqueous zinc ion battery is sodium vanadium phosphate, an electrolyte is zinc trifluoromethanesulfonate, and an electrolyte additive is aluminum trifluoromethanesulfonate. Wherein aluminum trifluoromethanesulfonate inhibits hydrogen evolution, corrosion and passivation of the zinc negative electrode and other side reactions by changing a solvation structure of zinc ions, reducing active water molecules generated in an electroplating process, changing a hydrogen bond network of an electrolyte system, regulating and controlling an electrode / electrolyte interface and reducing direct contact between the zinc negative electrode and H2O molecules; and the effect of optimizing the electrode / electrolyte interface is achieved. Meanwhile, the embedded material sodium vanadium phosphate serving as the positive electrode has a stable three-dimensional framework, and zinc ions, aluminum ions and sodium ions can be reversibly embedded / separated, so that the zinc ion battery has excellent cycling stability under the large current density of 2A / g.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous zinc-ion batteries, and particularly relates to an additive for an electrolyte of an aqueous zinc-ion battery and an aqueous zinc-ion battery. Background Art

[0002] With the global energy transition and the rapid development of renewable energy, the energy storage industry has shown explosive growth in recent years. Compared with other energy storage technologies such as mechanical, electromagnetic, and thermal energy storage, electrochemical energy storage has advantages such as flexibility and adaptability. Among them, rechargeable batteries are considered to be one of the most attractive electrochemical energy storage and conversion devices, especially for storing renewable energy.

[0003] As one of the most promising candidates in energy storage systems, aqueous zinc-ion batteries have become a research hotspot due to their high theoretical specific capacity, low zinc metal redox potential, excellent natural abundance, low cost, and environmental friendliness. However, interface problems between the aqueous electrolyte and the metal anode, such as zinc dendrite growth, hydrogen evolution reaction, zinc corrosion, and passivation, may ultimately lead to reduced reversibility, decreased cycle stability of the zinc anode, and low coulombic efficiency, hindering the widespread application of zinc-ion batteries.

[0004] At the same time, common zinc-ion battery cathodes such as manganese dioxide have poor cycle stability due to structural collapse, which cannot meet the requirements of the industrialization of zinc-ion batteries.

[0005] Currently, Patent CN 118017034 A uses a zinc sulfate electrolyte and an aluminum nitrate additive. After adding aluminum nitrate, the side reactions such as dendrites are slowed down due to the electrostatic shielding effect of aluminum ions. In the present invention, after adding aluminum trifluoromethanesulfonate, the solvation structure and hydrogen bond network of the electrolyte change to inhibit side reactions.

[0006] Patent CN 114784384 A uses aluminum trifluoromethanesulfonate and a hydrogen bond acceptor substance to prepare a eutectic solvent electrolyte. A eutectic solvent electrolyte with good low-temperature performance and air stability is prepared by reacting aluminum trifluoromethanesulfonate and a hydrogen bond acceptor substance at high temperature. In the present invention, through the competitive coordination of aluminum trifluoromethanesulfonate with zinc salt and water at room temperature, and by changing the number of hydrogen bond donors and hydrogen bond acceptors, the solvation structure and hydrogen bond network of the electrolyte system are affected.

[0007] Based on the above research background and technical difficulties, it is crucial to explore a suitable additive for the electrolyte of an aqueous zinc-ion battery to inhibit side reactions between the electrolyte and the zinc anode, and at the same time match a suitable cathode material to improve the cycle stability and widespread application of zinc-ion batteries. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention proposes an aqueous zinc ion battery electrolyte additive and an aqueous zinc ion battery system. The use of this additive can change the solvation structure of zinc ions and regulate the growth of zinc dendrites; at the same time, due to the change in the number of hydrogen bond donors and hydrogen bond acceptors in the aqueous electrolyte, the hydrogen bond network of water changes, thereby reducing the activity of water, improving interface problems such as hydrogen evolution reaction and corrosion, and greatly alleviating the problems of low reversibility of aqueous zinc ion batteries caused by a series of side reactions such as dendrites and corrosion, poor cycle stability of zinc anodes, and low coulomb efficiency. The zinc ion battery system using this electrolyte additive and matching suitable positive and negative electrodes can have excellent cycle stability at a large current density of 2A / g.

[0009] To achieve the above object, the present invention adopts the following technical solutions: An aqueous zinc ion battery electrolyte, comprising an additive, a soluble zinc salt and deionized water; the additive is aluminum trifluoromethanesulfonate, the chemical formula of which is Al(CF 3 SO 3 ) 3 The soluble zinc salt is zinc trifluoromethanesulfonate, and the chemical formula is Zn(CF 3 SO 3 ) 2 .

[0010] Furthermore, the concentration of zinc trifluoromethanesulfonate in the electrolyte is 0.5-2 mol / L, preferably 1 mol / L.

[0011] Furthermore, the concentration of aluminum trifluoromethanesulfonate in the electrolyte is 0.5-2 mol / L, preferably 1 mol / L.

[0012] The present invention also provides a method for preparing the aqueous zinc ion battery electrolyte, wherein Zn(CF 3 SO 3 ) 2 and Al(CF 3 SO 3 ) 3 Dissolve in deionized water and stir to mix well.

[0013] The present invention also provides an aqueous zinc ion battery, comprising a positive electrode material sodium vanadium phosphate, the chemical formula of which is Na 3 V 2 (PO 4 ) 3 , negative electrode material zinc foil, diaphragm glass fiber and the above aqueous zinc ion battery electrolyte. The preparation method comprises the following steps: 1) Sodium vanadium phosphate, a conductive agent and a binder are fully mixed and ground for 20 minutes to obtain a positive electrode material mixture; 2) Add the positive electrode material mixture obtained in step 1) into N-methylpyrrolidone, stir well, and continue to grind to obtain a mixed slurry; 3) Knife-coat the mixed slurry prepared in step 2) on a titanium foil and vacuum dry it overnight to obtain the positive electrode material; 4) Use the positive electrode material obtained in step 3) to make a 12-mm diameter disc as the positive electrode with a manual tablet press, use a 16-mm diameter zinc foil made with a manual tablet press as the negative electrode, assemble the positive electrode, separator, and negative electrode in sequence, and add the electrolyte to finally obtain a stable aqueous zinc-ion battery.

[0014] Furthermore, in step 1) of the above preparation method, the conductive agent is one of Super P and Ketjenblack.

[0015] Furthermore, in step 1) of the above preparation method, the binder is polyvinylidene fluoride PVDF.

[0016] Furthermore, in step 1) of the above preparation method, the mass ratio of sodium vanadium phosphate, conductive agent, and binder is 7:2:1.

[0017] Furthermore, in step 3) of the above preparation method, the coating amount of the mixed slurry on the titanium foil is 1.03 - 1.75 mg / cm 2 .

[0018] Furthermore, in step 3) of the above preparation method, the temperature of the vacuum drying is 70 - 80 °C.

[0019] Furthermore, in step 4) of the above preparation method, the electrolyte is a mixed salt solution of zinc salt and aluminum salt.

[0020] Even further, in step 4) of the above preparation method, the concentration of the zinc salt is 1 mol / L.

[0021] Even further, in step 4) of the above preparation method, the concentration of the aluminum salt is 1 mol / L.

[0022] Even further, in step 4) of the above preparation method, the zinc salt is zinc trifluoromethanesulfonate with the chemical formula Zn(CF 3 SO 3 ) 2 .

[0023] Even further, in step 4) of the above preparation method, the aluminum salt is aluminum trifluoromethanesulfonate with the chemical formula Al(CF 3 SO 3 ) 3 .

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds aluminum trifluoromethanesulfonate additive to the electrolyte of an aqueous zinc-ion battery. Aluminum trifluoromethanesulfonate achieves a wide electrochemical stability window, stabilizes the electrode / electrolyte interface, and realizes high-efficiency zinc electroplating / stripping efficiency.

[0025] The present invention uses sodium vanadium phosphate as the positive electrode, a mixed solution of aluminum salt and zinc salt as the electrolyte, and zinc foil as the negative electrode. The presence of aluminum salt will participate in the zinc-ion solvation structure, reduce the generation of active water during the desolvation process of zinc ions, inhibit the activity of water, and suppress the side reactions at the negative electrode of the aqueous zinc-ion battery. Due to its stable three-dimensional framework, the electrochemical reaction of sodium vanadium phosphate as the positive electrode of the battery enables the reversible co-insertion / extraction of zinc ions, aluminum ions, and sodium ions, thereby enabling the aqueous zinc-ion battery to have a high working voltage and excellent cycle stability.

[0026] The aqueous zinc-ion battery provided by the present invention has a working voltage of 1.35 V at a high current density of 2 A / g, can be stably cycled more than 2000 times, with an average Coulombic efficiency of 99.8% and a capacity retention rate of 94%.

[0027] The preparation process of the electrolyte of the aqueous zinc-ion battery provided by the present invention is simple and feasible. It only requires preparing two salt solutions according to the concentration, stirring and mixing them evenly, and then assembling the battery. Description of the Drawings

[0028] Figure 1 It is a liquid infrared test result diagram of the electrolyte system of the aqueous zinc-ion battery in Example 1 and Comparative Example 1 of the present invention.

[0029] Figure 2 It is a Tafel comparison diagram of the electrolyte of the aqueous zinc-ion battery in Example 2 and Comparative Example 2 of the present invention.

[0030] Figure 3 It is an XRD comparison diagram of the surface of the zinc-ion battery in Example 3 and Comparative Example 3 of the present invention.

[0031] Figure 4 It is a CV comparison diagram of the zinc-ion battery in Example 3 and Comparative Example 3 of the present invention.

[0032] Figure 5 It is a SEM photo of the sodium vanadium phosphate positive electrode of the zinc-ion battery in Example 3 of the present invention after constant current charge and discharge.

[0033] Figure 6 It is an EDS spectrum of the sodium vanadium phosphate positive electrode of the zinc-ion battery in Example 3 of the present invention after constant current charge and discharge.

[0034] Figure 7 It is a cycle life diagram of the zinc-ion battery in Example 3 and Comparative Example 4 of the present invention. Detailed Embodiments

[0035] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. Those skilled in the art should understand that the specific embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0036] The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0037] Example 1 An aqueous zinc-ion battery electrolyte is prepared by the following steps: Dissolve 3.64 g of Zn(CF 3 SO 3 ) 2 and 4.74 g of Al(CF 3 SO 3 ) 3 in 10 ml of deionized water, stir and mix evenly to obtain an aqueous zinc-ion battery electrolyte, wherein the concentration of Zn(CF 3 SO 3 ) 2 is 1 mol / L, and the concentration of Al(CF 3 SO 3 ) 3 is 1 mol / L.

[0038] Comparative Example 1 An aqueous zinc-ion battery electrolyte, which is different from Example 1 in that Al(CF 3 SO 3 ) 3 is not added, and only 3.64 g of Zn(CF 3 SO 3 ) 2 is dissolved in 10 ml of deionized water, and the concentration of Zn(CF 3 SO 3 ) 2 is 1 mol / L.

[0039] Test Scheme and Analysis Results The liquid infrared results are as Figure 1 shown. It can be seen from Figure 1 (b) that the -SO 3 vibration peak shifts to the left, indicating that Al(CF 3 SO 3 ) 3 coordinates with Zn 2+ , and the interaction between Zn 2+ and H 2 O weakens; Figure 1(c) The O-H bending vibration moves towards lower wavenumbers after adding Al(CF 3 SO 3 ) 3 , which is attributed to the coordination of the CF 3 SO 3 ) 3 group in Al(CF 3 SO 3 − and the H 2 O molecule through hydrogen bonding; while Figure 1 (d) The O-H stretching vibration moves towards higher wavenumbers, which is attributed to the destruction of the strong hydrogen bonding of water by Al(CF 3 SO 3 ) 3 , resulting in an increase in the number of free H 2 O molecules.

[0040] Figure 2 is a comparative plot of the Tafel curves of Example 1 and Comparative Example 1. It can be seen from Figure 2 that after adding Al(CF 3 SO 3 ) 3 to the electrolyte, the corrosion current decreases and the corrosion potential increases, indicating that the corrosion is effectively inhibited.

[0041] Example 2 An aqueous zinc-ion symmetric battery is prepared by the following steps: Cut the zinc foil into a pole piece with a diameter of 12 mm. Subsequently, place it in an ethanol solution and ultrasonicate for 5 min, and dry it in a blast drying oven to obtain the zinc electrode pole piece as the positive and negative electrode pole pieces. Assemble the zinc symmetric battery using the electrolyte of Example 1 and a glass fiber separator according to the negative electrode shell, negative electrode, separator, electrolyte, positive electrode, gasket, spring piece, and positive electrode shell.

[0042] Comparative Example 2 An aqueous zinc-ion symmetric battery, which is different from Example 2 in that the electrolyte of Comparative Example 1 is used.

[0043] Test Scheme and Analysis Results For the symmetric batteries assembled in Example 2 and Comparative Example 2, after cycling 30 weeks at 0.5 mA / cm 2 and 0.5 mAh / cm 2 , the XRD comparison results of the zinc anode surface are as shown in Figure 3 . There are diffraction peaks of by-products on the zinc anode surface of the battery in Comparative Example 2; there are no diffraction peaks of by-products on the zinc anode surface of the battery in Example 2. Introducing aluminum trifluoromethanesulfonate on the surface can inhibit the occurrence of side reactions. At the same time, no peaks of aluminum salt-related products are detected on the surface of the battery in Example 2, indicating that it is more likely that the CF 3 SO of aluminum trifluoromethanesulfonate3 − The groups and water molecules compete for coordination, and the changes in hydrogen bond donors and hydrogen bond acceptors are used to affect the hydrogen bond network of the electrolyte system, reduce the activity of water, and inhibit side reactions.

[0044] Example 3 An aqueous zinc ion battery, comprising a positive electrode material sodium vanadium phosphate, a negative electrode material, a separator and an electrolyte. The aqueous zinc ion battery is prepared by the following steps: 1) Sodium vanadium phosphate, conductive agent (Super P), and binder (PVDF) were fully mixed and ground at a mass ratio of 7:2:1 for 20 minutes to obtain a positive electrode material mixture; 2) Add the cathode material mixture into N-methylpyrrolidone (NMP), stir thoroughly, and continue grinding to obtain a mixed slurry; 3) The mixed slurry is scraped onto titanium foil and vacuum dried overnight to obtain the positive electrode material; the coating amount of the mixed slurry on the titanium foil is 1.03-1.75 mg / cm 2 ; 4) Battery assembly: The positive electrode material was pressed into a 12 mm diameter disc using a manual tablet press as the positive electrode, and a 16 mm diameter zinc foil was pressed into a manual tablet press as the negative electrode. The positive electrode, glass fiber separator and negative electrode were assembled in sequence, and an electrolyte was added. The electrolyte was a mixed salt solution of zinc trifluoromethanesulfonate (1 mol / L) and aluminum trifluoromethanesulfonate (1 mol / L) (i.e., the electrolyte in Example 1), and a stable aqueous zinc ion battery was obtained.

[0045] Comparative Example 3 An aqueous zinc ion battery, comprising a positive electrode material sodium vanadium phosphate, a negative electrode material, a separator and an electrolyte. The aqueous zinc ion battery is prepared by the following steps: (1) Sodium vanadium phosphate, a conductive agent (Super P), and a binder (PVDF) were fully mixed and ground at a mass ratio of 7:2:1 for 20 minutes to obtain a positive electrode material mixture; (2) Add the cathode material mixture into N-methylpyrrolidone (NMP), stir thoroughly, and continue grinding to obtain a mixed slurry; (3) The mixed slurry is coated on a titanium foil and vacuum dried overnight to obtain a positive electrode material; the coating amount of the mixed slurry on the titanium foil is the same as that in Example 3; (4) Battery assembly: The positive electrode material was pressed into a 12 mm diameter disc using a manual tablet press as the positive electrode, and the zinc foil was pressed into a 16 mm diameter disc using a manual tablet press as the negative electrode. The positive electrode, glass fiber separator, and negative electrode were assembled in sequence, and an electrolyte was added. The electrolyte was a zinc trifluoromethanesulfonate (1 mol / L) solution, and a stable aqueous zinc ion battery was obtained.

[0046] The zinc-ion battery electrolyte is prepared by the following steps: Dissolve 3.64 g of Zn(CF 3 SO 3 ) 2 in 10 ml of deionized water and stir to mix evenly.

[0047] Comparative Example 4 An aqueous zinc-ion battery, which includes a positive electrode material manganese dioxide, a negative electrode material, a separator and an electrolyte. The aqueous zinc-ion battery is prepared by the following steps: (1) Thoroughly mix and grind manganese dioxide, a conductive agent (Super P), and a binder (PVDF) in a mass ratio of 7:2:1 for 20 min to obtain a positive electrode material mixture; (2) Add the positive electrode material mixture to N-methylpyrrolidone (NMP), stir thoroughly, and continue grinding to obtain a mixed slurry; (3) Knife-coat the mixed slurry on a titanium foil and dry it overnight in a vacuum to obtain a positive electrode material; the coating amount of the mixed slurry on the titanium foil is the same as that in Example 3; (4) Battery assembly: Use a manual tablet press to make the positive electrode material into a 12-mm diameter disc as the positive electrode, use a manual tablet press to make a 16-mm diameter zinc foil as the negative electrode, assemble the positive electrode, glass fiber separator and negative electrode in sequence, and add an electrolyte, which is a mixed salt solution of zinc trifluoromethanesulfonate (1 mol / L) and aluminum trifluoromethanesulfonate (1 mol / L), to obtain a stable aqueous zinc-ion battery.

[0048] Test Scheme and Analysis Results For the aqueous zinc-ion batteries assembled in Example 3 and Comparative Example 3, the cyclic voltammetry (CV) test results at a scanning rate of 0.01 V / s for 4 weeks are shown as Figure 4 follows. The oxidation peak at ~1.75 V in the first week of cycling corresponds to the deintercalation of two sodium ions in sodium vanadium phosphate. The oxidation-reduction peaks of Example 3 are 1.62 / 1.10 V( Figure 4 (a)), corresponding to the reversible cointercalation / deintercalation of sodium ions, zinc ions, and aluminum ions; different from the oxidation-reduction peaks of Comparative Example 3, which are 1.50 / 1.19 V( Figure 4 (b)), corresponding to the reversible cointercalation / deintercalation of sodium ions and zinc ions.

[0049] For the aqueous zinc-ion battery assembled in Example 3, cyclic tests are carried out at a large current density of 2 A / g. After 400 cycles, the battery is disassembled and the sodium vanadium phosphate positive electrode is tested by SEM and EDS.

[0050] Figure 5SEM photograph after 400 cycles of the sodium vanadium phosphate cathode in Example 3. It can be clearly seen from the cross-sectional SEM of Figure 5 (a, b) that due to the presence of aluminum salt, more zinc ions are inserted into sodium vanadium phosphate along the (002) crystal plane, accompanied by the insertion of sodium ions and aluminum ions. Figure 5 (c, d) The planar SEM further shows that zinc ions, sodium ions, and aluminum ions are uniformly inserted and deposited, and basically no large dendrites are generated. At the same time, combined with the Figure 6 EDS spectrum of zinc ions, aluminum ions, and sodium ions in the uniform deposition and distribution in sodium vanadium phosphate, it proves the reversible co-insertion / extraction of zinc ions, aluminum ions, and sodium ions during the battery cycle.

[0051] The results of the cycle test of the aqueous zinc-ion batteries assembled in Example 3 and Comparative Example 4 at a high current density of 2 A / g are as shown in Figure 7 . It can be seen from Figure 7 that the capacity of the manganese dioxide cathode decays rapidly due to the structural collapse during the cycle, and the capacity retention rate is only 30% after 2000 cycles; while the sodium vanadium phosphate cathode has a stable three-dimensional skeleton, and the capacity retention rate is as high as 94% after 2000 cycles, showing good cycle stability.

[0052] Aluminum trifluoromethanesulfonate of the present invention changes the solvation structure of zinc ions, reduces the active water molecules generated during the electroplating process, changes the hydrogen bond network of the electrolyte system, and regulates the electrode / electrolyte interface, reducing the direct contact between the zinc negative electrode and H 2 O molecules, thereby inhibiting side reactions such as hydrogen evolution and corrosion and passivation of the zinc negative electrode, achieving the effect of optimizing the electrode / electrolyte interface. At the same time, sodium vanadium phosphate, as an intercalation material for the positive electrode, has a stable three-dimensional skeleton, enabling the reversible co-insertion / extraction of zinc ions, aluminum ions, and sodium ions. Therefore, this zinc-ion battery has excellent cycle stability at a high current density of 2 A / g.

[0053] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the common technical knowledge and general methods in the art, makes equivalent substitutions or changes according to the technical solution and inventive concept of the present invention, and should be covered within the protection scope of the present invention.

Claims

1. An aqueous zinc ion battery electrolyte, consisting of an additive, a soluble zinc salt and deionized water; the additive is aluminum trifluoromethanesulfonate, the chemical formula of which is Al(CF3SO3)3, and the soluble zinc salt is zinc trifluoromethanesulfonate, the chemical formula of which is Zn(CF3SO3)2.

2. The aqueous zinc ion battery electrolyte according to claim 1, wherein The concentration of zinc trifluoromethanesulfonate in the electrolyte is 0.5-2 mol / L, preferably 1 mol / L.

3. The aqueous zinc ion battery electrolyte according to claim 1, wherein The concentration of aluminum trifluoromethanesulfonate in the electrolyte is 0.5-2 mol / L, preferably 1 mol / L.

4. The method for preparing an aqueous zinc ion battery electrolyte as claimed in claim 1, wherein: Dissolve Zn(CF3SO3)2 and Al(CF3SO3)3 in deionized water and stir to mix well.

5. An aqueous zinc ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and the aqueous zinc ion battery electrolyte according to claim 1.

6. The aqueous zinc ion battery according to claim 5, characterized in that: The negative electrode is zinc foil, and the separator is a glass fiber separator.

7. The aqueous zinc ion battery according to claim 5, characterized in that: The positive electrode includes a current collector, a positive electrode active material, a binder, and a conductive agent.

8. The aqueous zinc ion battery according to claim 6 or 7, characterized in that: The positive electrode active material is sodium vanadium phosphate, and the chemical formula is Na3V2(PO4)3.

9. The method for preparing an aqueous zinc ion battery according to claim 8, wherein: The steps include: (1) Sodium vanadium phosphate, a conductive agent and a binder are fully mixed and ground at a mass ratio of 7:2:1 for 20 minutes to obtain a positive electrode material mixture; (2) adding the positive electrode material mixture obtained in step (1) into N-methylpyrrolidone, stirring thoroughly, and continuing grinding to obtain a mixed slurry; (3) coating the mixed slurry obtained in step (1) on a titanium foil, and vacuum drying overnight to obtain a positive electrode material; (4) The positive electrode material obtained in step (1) is pressed into a 12 mm diameter disc using a manual tablet press as the positive electrode, and a zinc foil with a diameter of 16 mm is pressed into a manual tablet press as the negative electrode. The positive electrode, the separator and the negative electrode are assembled in sequence, and an electrolyte is added to finally obtain a stable aqueous zinc ion battery.

10. The method for preparing an aqueous zinc ion battery according to claim 8, wherein: The coating amount of the mixed slurry on the titanium foil in step (3) is 1.03-1.75 mg / cm 2 .

Images