Zinc-based composite metal powder for aqueous zinc ion battery as well as preparation method and application of zinc-based composite metal powder

Abstract

The invention discloses a zinc-based composite metal powder negative electrode for an aqueous zinc ion battery and a preparation method and application of the zinc-based composite metal powder negative electrode. Metal M salt is dissolved in a solvent and stirred to be fully and evenly mixed, and a metal M salt solution is obtained; metal N salt is dissolved in a solvent and stirred to be fully and evenly mixed, and a metal N salt solution is obtained; the metal M is selected from one of Sn, In, Sb and Ti, and the metal N is selected from one of Cu and Ag; and adding the metal M salt solution into the zinc powder dispersion liquid, stirring for full reaction, finally adding the metal N salt solution, and continuously stirring for full reaction to obtain the zinc-based composite metal powder. The zinc-based composite metal powder is prepared through a bimetal replacement strategy of specific metal and a specific reaction sequence, and the prepared aqueous zinc ion battery has excellent cycle stability.

Description

TECHNICAL FIELD

[0001] The application relates to a zinc-based composite metal powder negative electrode for a water-based zinc ion battery and a preparation method and application thereof, and belongs to the technical field of water-based zinc ion batteries. BACKGROUND

[0002] Water-based zinc metal batteries have attracted extensive attention in the field of safe and sustainable energy storage systems, but their development and application depend on highly stable zinc negative electrodes. Due to the dual function of zinc metal foil as a current collector and a negative active material, serious pulverization and fracture easily occur under high area capacity operation (such as > 5 mAh cm −2 ). The zinc powder negative electrode is attractive due to its controllable mass loading and high area capacity, but its high electrochemical activity triggers more serious HER, corrosion, and even collapse of the negative electrode structure. Essentially, this is attributed to two characteristics of zinc powder, including abundant surface reaction sites and mismatch between limited Zn 2+ diffusion kinetics, and mismatch between strong electron transfer tendency caused by reducibility of zinc metal and improper electron acceptor. By compounding zinc powder with other metals, although the adsorption of Zn 2+ can be promoted, as the potential difference between the contact metal or the external circuit provided electrons increases, the negative electrode faces a greater driving force of side reactions and electron redistribution caused by the Gibbs free energy difference. Therefore, the single metal coating realizes the fast electron transfer kinetics and the selective electron transfer method, which seems to be contradictory, and the synergistic effect of the interface microenvironment and functional multi-metal is required, in which the constraints and interactions between electrons and ions are extremely important in theory, and few reports provide insightful discussions.

[0003] In recent years, the importance of zinc powder negative electrodes has been gradually explored and emphasized, but most reports mainly focus on one aspect of electrochemical properties such as reaction activity, corrosion resistance, etc., and the stability of the high reaction activity area in the water-based environment is the main obstacle limiting its further promotion. SUMMARY

[0004] In order to solve the above problems, the purpose of the present application is to provide a zinc-based composite metal powder negative electrode for a water-based zinc ion battery and a preparation method and application thereof, by a bimetallic displacement strategy of specific metals and specific reaction sequences, a zinc-based composite metal powder is prepared, which is used for preparing a water-based zinc ion battery, and has excellent cycle stability.

[0005] In order to achieve the above technical purpose, the technical scheme adopted by the present application is as follows: A preparation method of a zinc-based composite metal powder for a water-based zinc ion battery, comprising the following steps: (1) dispersing zinc powder in a solvent to obtain a zinc dispersion liquid; dissolving a metal M salt in the solvent and stirring until fully mixed to obtain a metal M salt solution; dissolving a metal N salt in the solvent and stirring until fully mixed to obtain a metal N salt solution; the metal M is selected from one of Sn, In, Sb and Ti, and the metal N is selected from one of Cu and Ag; (2) first adding the metal M salt solution into the zinc powder dispersion liquid, stirring and fully reacting, then adding the metal N salt solution and continuing to stir and fully react, to obtain a zinc-based composite metal powder.

[0006] Further, in step (1), the molar ratio of the zinc powder, the metal M in the metal M salt and the metal N in the metal N salt is 1:0.01-0.1:0.005-0.05.

[0007] Further, in step (1), the solvent is one of water, ethanol, methanol, polyethylene glycol, acetonitrile, dimethyl sulfoxide, acetone, formamide, diethyl ether, n-propanol, isopropanol, ethyl acetate, chloroform.

[0008] Further, in step (1), the metal M salt and the metal N salt are both selected from one of the respective sulfate, acetate, nitrate, perchlorate, chloride, tetrafluoroborate, hexafluorosilicate, trifluoromethanesulfonate, bis(trifluoromethylsulfonylimide) salt.

[0009] Further, in step (2), the time of the two reactions is both 2-5 min.

[0010] In the present application, first, the metal M salt (taking Sn as an example) is added, and the reaction equation is Sn 2+ + Zn → Sn + Zn 2 + and Sn + O2 + H2O → Sn(OH)4 → SnO2 + H2O, and under conventional conditions, Sn 2+ is relatively close to Cu 2+ in terms of potential difference and weak alloying tendency, the Sn metal after displacement tends to be adsorbed on the surface of zinc powder in the form of fine particles, and then the more active Sn metal forms a SnO2 film on its surface under the action of a small amount of moisture and air oxygen; then the metal N salt (taking Cu as an example) is added, and the reaction equation is Cu 2+ + Zn → Cu + Zn x Cu y + Zn 2+ and Cu 2+ + Sn → Cu + Sn 2+, copper has higher electrode potential, fast reaction and nucleation growth with Zn, and high tendency to form alloy, but is restrained by the fine Sn02 / Sn layer formed in the previous step, Cu 2+ will not be quickly reduced into surface bulk particles, but can slowly diffuse into the zinc powder phase along the gap between Sn02 / Sn fine particles and form a uniform alloy layer on the surface layer of zinc powder particles in a larger scale range. At the same time, Cu 2+ can also displace the Sn metal formed in the previous step and induce Sn 2+ diffusion through the Sn02 film to form a hollow structure. Overall, the specific structure of the zinc-based composite metal powder finally obtained is: ① the outermost layer is a fine Sn02 film, ② the second outer layer is a composite layer with a large number of cavities and a small amount of Sn metal, ③ the inner layer is a Zn x Cu y alloy composite layer, and ④ the pure Zn metal in the bulk phase of the powder particles. Among them, the fine Sn02 film on the outermost layer to some extent isolates the immersion of a large number of free water molecules in the electrolyte and corrodes the inner layer zinc metal, the cavities in the second outer layer constitute a Zn 2+ / Zn deposition / peeling reaction microenvironment to shorten the ion desolvation process and diffusion distance, and the Zn metal in the inner layer and bulk phase structure as a zinc source and the built-in electric field at the contact interface between the Zn x Cu y alloy can promote the kinetics of Zn 2+ / Zn deposition / peeling reaction.

[0011] The inventors have also found that if the metal N salt (take Cu as an example) is added first, and then the metal M salt (take Sn as an example), Cu 2+ will quickly displace and nucleate and grow into bulk particles on the surface and occupy most of the surface area, inhibiting the tendency of more Cu 2+ to diffuse inward to form Zn x Cu y alloy, and also inhibiting the process of Sn 2+ displacement reaction with Zn metal. Overall, the specific structure of the zinc-based composite metal powder finally obtained is: ① the outermost layer is a rough Cu particle and a small amount of Sn02 / Sn solid particle, and ② the pure Zn metal in the bulk phase of the powder particles. It not only does not have the hollow microenvironment structure wrapped by the Sn02 film as described above, but also the direct contact between the Cu metal and the Zn metal will exacerbate the galvanic corrosion in the electrolyte solution, and even exhibit worse corrosion resistance than pure Zn powder.

[0012] The present application also provides a zinc-based composite metal powder prepared by the above preparation method.

[0013] The application also provides a zinc negative electrode, which is prepared by mixing the zinc-based composite metal powder as an active material with a conductive agent, a binder and a solvent, and then performing self-volatilization of the solvent to form a self-supporting film, i.e., a negative electrode sheet.

[0014] In the application, the conductive agent preferably uses graphene or carbon nanotubes having a self-supporting effect, the binder can use commonly used polyvinylidene fluoride, polytetrafluoroethylene or ethylene-vinyl acetate copolymer, and the solvent can use commonly used m-xylene, N-methylpyrrolidone or acetone, and there is no special requirement, which will not be described here.

[0015] The application also provides an aqueous zinc ion battery comprising the zinc negative electrode.

[0016] The application has the following beneficial effects: The zinc-based composite metal powder is prepared by the bimetallic displacement strategy of specific metals and specific reaction sequences, and in addition to inheriting the inherent advantages of metal M and metal N, the EDL charge distribution of metal M and Zn is opposite, compensates for anion adsorption, and inhibits the side reactions related to ZSH; and a large number of in-situ constructed surface metal N oxide gaps can accommodate the exfoliated Zn 2+ , to avoid disordered diffusion, and provide a shorter diffusion distance for the electron acceptance of Zn 2+ , rather than H + , and the prepared aqueous zinc ion battery has excellent cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a cross-section FIB-SEM image of Zn@CS prepared in Comparative Example 1 and Zn@SC prepared in Example 1.

[0018] Figure 2 is a graph of the activation energy test results of the symmetric battery assembled by Zn@CS prepared in Comparative Example 1 and Zn@SC prepared in Example 1.

[0019] Figure 3 is an SEM image of Zn@CS prepared in Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC prepared in Example 1 in the initial state and after being cycled for 50 cycles to assemble a symmetric battery.

[0020] Figure 4 is an LSCM image of Zn@CS prepared in Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC prepared in Example 1 after being cycled for 50 cycles to assemble a symmetric battery.

[0021] Figure 5Cycling coulombic efficiency plot of Zn@CS made from Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC made from Example 1 assembled as zinc copper asymmetric battery.

[0022] Figure 6 Cycling charge-discharge plot of Zn@CS made from Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC made from Example 1 assembled as symmetric battery.

[0023] Figure 7 Cycling performance plot of Zn@CS made from Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC made from Example 1 assembled as symmetric battery.

[0024] Figure 8 Rate capability plot of Zn@CS made from Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC made from Example 1 assembled as zinc vanadium full cell.

[0025] Figure 9 Long cycling performance plot of Zn@CS made from Comparative Example 1, pure Zn of Comparative Example 2 and Zn@SC made from Example 1 assembled as high loading zinc vanadium full cell.

[0026] Figure 10 Cycling performance plot of Zn@SC made from Example 1 assembled as zinc vanadium pouch full cell. DETAILED DESCRIPTION

[0027] The following examples are provided to further illustrate the content of the present application; the scope of the claims of the present application is not limited by the examples.

[0028] Example 1

[0029] Under magnetic stirring, 13.08 g of zinc powder was added to 30 ml of absolute ethanol solution to disperse the zinc powder. Then, 2.26 g of SnCl2·2H2O and 0.68 g of CuCl2·2H2O were separately dissolved in 50 ml of ethanol and stirred until the solution was transparent. Subsequently, the SnCl2solution was added to the stirred Zn powder dispersion solution and reacted for 3 minutes, then the CuCl2solution was added to the above solution and reacted for another 3 minutes, finally centrifuged and washed twice with absolute ethanol, and dried in a vacuum oven at 80 °C for 8 hours to obtain Zn@SC powder.

[0030] Example 1

[0031] Comparative Example 1 Under magnetic stirring, 13.08 g of zinc powder was added to 30 ml of absolute ethanol solution to disperse the zinc powder. Then, 2.26 g of SnCl2·2H2O and 0.68 g of CuCl2·2H2O were dissolved in 50 ml of ethanol, respectively, and stirred until the solution was transparent. Subsequently, the CuCl2solution was added to the stirred Zn powder dispersion solution and reacted for 3 minutes, after which the SnCl2solution was added to the above solution and reacted for another 3 minutes. Finally, centrifugation and washing with absolute ethanol twice, and drying in a vacuum oven at 80 °C for 8 hours, Zn@CS powder was obtained.

[0032] Example 2

[0033] Comparative Example 2 Under magnetic stirring, 13.08 g of zinc powder was added to 30 ml of absolute ethanol solution to disperse the zinc powder. Then, 2.26 g of SnCl2·2H2O and 0.68 g of CuCl2·2H2O were dissolved in 50 ml of ethanol, respectively, and stirred until the solution was transparent. Subsequently, the CuCl2solution was added to the stirred Zn powder dispersion solution and reacted for 3 minutes, after which the SnCl2solution was added to the above solution and reacted for another 3 minutes. Finally, centrifugation and washing with absolute ethanol twice, and drying in a vacuum oven at 80 °C for 8 hours, Zn@CS powder was obtained.

[0034] Performance Test: 1. Zinc-zinc symmetric battery assembly: Stack the cut electrodes in the following order: positive electrode shell - electrode - glass fiber separator - electrode - negative electrode shell. Add 100 μL of 2 M ZnSO4 electrolyte to the glass fiber separator. Finally, seal the assembly with a sealing machine at a pressure of 50 MPa and a pressure of 1 mA cm⁻¹. -2 -5 mAh cm -2 The test conditions are used for cyclic testing.

[0035] 2. Zinc-copper asymmetric battery assembly: Cut copper foil into electrode sheets with a diameter of 15 mm. Stack the cut electrode sheets and copper foil in the following order: positive electrode shell - copper foil - glass fiber separator - electrode sheet - negative electrode shell. Drop 100 μL of 2 M ZnSO4 electrolyte into the glass fiber separator. Finally, seal the assembly with a sealing machine at a pressure of 50 MPa and a pressure of 2 mA cm⁻¹. -2 -1 mAh cm -2 The test conditions were used to perform a cyclic test with initial discharge.

[0036] 3. Zinc-vanadium full cell assembly: The conventional NH4V4O... 10 The positive electrode sheet was cut into sheets with a diameter of 12 mm. The cut electrodes and copper foil were stacked in the following order: positive electrode shell - positive electrode - glass fiber separator - negative electrode - negative electrode shell. 100 μL of 2 M ZnSO4 electrolyte was dropped into the glass fiber separator. Finally, the mixture was sealed tightly with a sealing machine at a pressure of 50 MPa, using a flow rate of 0.5-1-2-3-5-3-2-1-0.5 A g. -1 (5 cycles for each current density) and 3 A g -1 The test conditions were used to conduct rate and long-cycle tests respectively.

[0037] 4. Zinc-vanadium pouch cell assembly: This involves assembling conventional NH4V4O... 10 The positive electrode and the prepared negative electrode were cut into square electrodes with a diameter of 4 cm * 5 cm. The glass fiber separator was cut into a square of 4.5 cm * 5.5 cm. The cut electrodes were stacked in the order of positive electrode - glass fiber separator - negative electrode. 1 mL of 2 M ZnSO4 electrolyte was dropped into the glass fiber separator. The entire battery cell was then placed in an aluminum-plastic film and finally sealed with heat at 0.2 A g. -1 The test conditions are used for cyclic testing.

[0038] like Figure 1 As shown, the uneven distribution of Sn signal on the Zn@SC surface, the obvious voids, and the Cu signal with a certain diffusion direction in the inner layer indicate that Cu 2+ Sn diffuses inward along the gaps between SnO2 / Sn particles and is induced by the Kirkendall effect. 2+ It spreads outwards.

[0039] As Figure 2 shown, Zn@SC with special surface structure exhibits lower Zn 2+ / Zn deposition / stripping reaction activation energy.

[0040] As Figure 3 shown, Zn 2+ / Zn deposition / stripping reaction in Zn@SC anode mainly occurs inside SnO2 film, which does not obviously induce side reactions such as accumulation of basic zinc sulfate, and the morphology of zinc powder particles can remain relatively complete after cycling.

[0041] As Figure 4 shown, the surface dendrites of Zn@SC anode decrease after cycling, and the roughness is relatively uniform.

[0042] As Figure 5 shown, Zn@SC anode not only can inhibit side reactions induced by high-activity water molecules in electrolyte through its special surface structure to improve coulombic efficiency, but also can prevent short circuit caused by dendrite growth.

[0043] As Figure 6 shown, the Zn metal inside Zn@SC anode and Zn x Cu y alloy and the built-in electric field at the interface can effectively improve the kinetics of Zn 2+ / Zn deposition / stripping reaction, thereby reducing polarization.

[0044] As Figure 7 shown, Zn@SC anode can achieve higher long cycle stability and the degree of polarization remains basically unchanged.

[0045] As Figure 8 shown, the special surface structure of Zn@SC anode can largely limit the stripped Zn 2+ inside SnO2 film, preventing it from diffusing into the electrolyte phase, so that it needs to undergo a longer diffusion distance in the subsequent deposition process. Shorter diffusion distance promotes the performance retention of zinc powder anode at higher current density.

[0046] As Figure 9 shown, the special surface structure of Zn@SC anode can support the pairing of high-activity material-loaded anode, as well as the cycle stability at higher reaction depth.

[0047] As Figure 10 shown, Zn@SC anode has the potential of high reaction depth, scalable preparation, and practical application.

Claims

1. A method for producing a zinc-based composite metal powder for aqueous zinc-ion batteries, characterized by, The method comprises the following steps: (1) dispersing zinc powder in a solvent to obtain a zinc dispersion; dissolving a metal M salt in the solvent and stirring until fully mixed to obtain a metal M salt solution; dissolving a metal N salt in the solvent and stirring until fully mixed to obtain a metal N salt solution; the metal M is selected from one of Sn, In, Sb and Ti, and the metal N is selected from one of Cu and Ag; (2) first adding the metal M salt solution into the zinc powder dispersion, stirring and fully reacting, then adding the metal N salt solution and continuing to stir and fully react, to obtain a zinc-based composite metal powder.

2. The production method according to claim 1, characterized by, In step (1), the molar ratio of the zinc powder, the metal M in the metal M salt and the metal N in the metal N salt is 1:0.01-0.1:0.005-0.

05.

3. The preparation method according to claim 1, characterized in that, In step (1), the solvent is one of water, ethanol, methanol, polyethylene glycol, acetonitrile, dimethyl sulfoxide, acetone, formamide, diethyl ether, n-propanol, isopropanol, ethyl acetate and chloroform.

4. The production method according to claim 1, characterized by, In step (1), the metal M salt and the metal N salt are both selected from one of the respective sulfate, acetate, nitrate, perchlorate, chloride, tetrafluoroborate, hexafluorosilicate, trifluoromethanesulfonate and bis(trifluoromethylsulfonylimide) salts.

5. The preparation method according to claim 1, characterized in that, In step (2), the time for each of the two reactions is 2-5 min.

6. The zinc-based composite metal powder prepared by the method of any one of claims 1-5.

7. A zinc negative electrode characterized in that, The zinc-based composite metal powder of claim 6 is used as an active material, which is mixed with a conductive agent, a binder and a solvent, then the solvent is self-volatilized to form a self-supporting film, which is a negative electrode sheet.

8. An aqueous zinc-ion battery, characterized in that, The zinc negative electrode of claim 7.

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