Preparation method of PEDOT: PSS-Zn integrated dendrite-free negative electrode

Abstract

The invention designs a manufacturing method of a conductive polymer protective layer poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) modified zinc negative electrode surface, and the PEDOT: PSS with good film-forming property and zinc affinity is selected and simply coated on the zinc negative electrode surface (PEDOT: PSS at Zn) to construct an integrated PEDOT: PSS at Zn dendrite-free zinc negative electrode. The PEDOT: PSS-Zn integrated electrode has excellent flexibility and adhesive force, and can still keep integrity after being bent for 1000 times. Meanwhile, the PEDOT: PSS can block direct contact between electrolyte and a zinc negative electrode interface, and corrosion reaction and by-products are inhibited. Besides, PEDOT: PSS has good conductivity, so that charge distribution on the surface of the zinc negative electrode is more uniform, rich sulfur-containing functional groups on the surface can induce uniform deposition of Zn < 2 + >, selective deposition of zinc ions is effectively avoided, and finally the purpose of inhibiting growth of zinc dendrites is achieved. The preparation method of the integrated zinc negative electrode is simple and efficient, the zinc dendritic crystal inhibition effect is obvious, a choice is provided for realizing a long-circulation water system zinc ion battery, and the preparation method has important research significance.

Description

Technical Field

[0001] The present invention relates to a preparation method of an integrated dendrite-free negative electrode of PEDOT:PSS@Zn. Background Art

[0002] Aqueous zinc-ion secondary batteries show great application potential due to their advantages such as low cost, high safety, and high ionic conductivity, and are the preferred system for large-scale energy storage systems in the future. However, problems such as dendrites and corrosion of zinc negative electrodes seriously hinder the development of aqueous zinc-ion batteries. Therefore, developing negative electrode materials with dendrite-free, long cycle life, and excellent rate performance is the key to the practical application of constructing high-performance aqueous zinc-ion batteries.

[0003] Currently, the research on zinc negative electrode protection mainly focuses on electrolyte engineering, surface modification of zinc metal negative electrodes, and construction of zinc host structures. Among them, surface modification of zinc metal negative electrodes is the most direct means of protecting zinc negative electrodes. Most reports are to coat insulating oxides (such as CaCO 3 , TiO 2 , ZrO 2 etc.), conductive materials (such as carbon black, graphene / reduced graphene oxide, MXene, etc.), polar materials (such as MOF, COF, etc.) combined with binders on the surface of zinc metal to construct a tough protective layer to avoid direct contact between zinc metal and electrolyte, thereby preventing side reactions. More importantly, some conductive coatings can also change the electric field distribution on the electrode surface and induce the uniform deposition of Zn 2+ on the zinc negative electrode surface. Unfortunately, the preparation processes of these coating materials are complex and the film-forming properties are poor. Binders usually need to be added during film formation, which greatly increases the total weight of the battery and seriously reduces the energy density of the battery.

[0004] Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is a commercial conductive polymer composed of positively charged conductive conjugated PEDOT and negatively charged insulating PSS. Among them, PSS is a polymer surfactant that increases the hydrophilicity of PEDOT, thereby enabling PEDOT to be stably dispersed in an aqueous solution to form a PEDOT:PSS aqueous dispersion. Coating a PEDOT:PSS film with high conductivity, hydrophilicity, and high film-forming property on the surface of the zinc negative electrode to inhibit zinc dendrites. This method is simple to operate and does not require any binder, which is beneficial to large-scale production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: aiming at the poor stability of the zinc negative electrode of aqueous zinc-ion batteries, the easy growth of zinc dendrites and corrosion during the cycling process, the present invention provides a preparation method of an integrated zinc negative electrode for aqueous zinc-ion batteries.

[0006] The present invention relates to the preparation of an integrated dendrite-free anode of PEDOT:PSS@Zn. First, a PEDOT:PSS dispersion is prepared, and then through simple coating, drying, and slicing processes, an integrated dendrite-free anode of PEDOT:PSS@Zn is prepared and used as the anode material of an aqueous zinc-ion battery, showing excellent electrochemical performance.

[0007] Preferably, its synthesis steps include the following steps.

[0008] Add 2 mL of PEDOT:PSS dispersion (1.1 wt%) and 2 mL of absolute ethanol into a glass, and ultrasonicate for 30 min to make it evenly dispersed for standby.

[0009] Cut a zinc foil (purity > 99.99%) into strips about 2.5 cm * 15 cm, and scrub the surface stains clean with absolute ethanol for standby.

[0010] Evenly coat the above-prepared dispersion on the surface of the strip-shaped zinc foil with a spatula, dry it in a vacuum oven at 80 °C for 10 h, and cut it into circular pieces with a diameter of 12 mm, named PEDOT:PSS@Zn.

[0011] The positive beneficial effects of the present invention:

[0012] 1. Through a simple coating method, the present invention covers a uniform PEDOT:PSS protective layer, namely the protective layer of the present invention, on the surface of the zinc metal anode. This protective layer has good film-forming properties and can be directly coated on the zinc metal surface without using a binder to prepare an integrated anode of PEDOT:PSS@Zn.

[0013] 2. The S group in PEDOT can anchor Zn 2+ , and at the same time, the PEDOT:PSS protective layer balances the interfacial electric field, which can greatly avoid the selective deposition of zinc ions, inhibit the growth of zinc dendrites, achieve the purpose of protecting the zinc anode, and thus greatly improve the cycle stability and electrochemical performance of the battery.

[0014] 3. PEDOT:PSS used in the technical solution of the present invention has a wide commercial foundation, showing characteristics such as low cost and scalability, and can meet the requirements of large-scale production.

[0015] 4. The technical solution of the present invention proposes a concept of constructing an integrated zinc anode for an aqueous zinc-ion battery with PEDOT:PSS. By simply coating PEDOT:PSS on the surface of the zinc anode, a zinc anode with excellent stability can be obtained, realizing a high-performance aqueous zinc battery.

[0016] 5. The PEDOT:PSS@Zn integrated anode prepared by the technical solution of the present invention is safe and reliable. The PEDOT:PSS@Zn / / PEDOT:PSS@Zn symmetric battery prepared therefrom has a cycle life of up to 2670 h at a current density of 0.5 mA cm -2 (0.5 mAh cm -2 ), far exceeding the cycle life of the unprotected zinc anode. Description of the Drawings

[0017] Figure 1 Fig. is the optical image, cross-sectional SEM and AFM images of the PEDOT:PSS@Zn integrated dendrite-free anode prepared by the present invention with PEDOT:PSS as the artificial coating using a simple coating method. It can be seen from the optical image that PEDOT:PSS is uniformly coated on the surface of the Zn foil. It can be proved from the cross-sectional SEM image that the thickness of the prepared PEDOT:PSS coating is about 6 μm; AFM is used to observe the surface of the modified and unmodified zinc anodes. Through the comparison of Figure 1 d and e, it can be seen that the surface of the electrode after coating with PEDOT:PSS is smoother, which can avoid the aggregation and deposition of zinc ions at a certain site to grow into dendrites to a certain extent.

[0018] Figure 2 Fig. is the Raman spectrum and XPS spectrum of the PEDOT:PSS@Zn integrated dendrite-free anode. The peaks at the red stars in the Raman figure represent asymmetric Cα = Cβ, the peaks at the blue stars are symmetric Cα = Cβ, the peaks at the green stars come from the stretching Cβ = Cβ, and finally the peaks at the purple stars originate from the inter-ring stretching vibration of Cα = Cα'; all the peaks marked with * are the representative peaks of PSS. In addition, from the X-ray photoelectron spectrum of PEDOT:PSS@Zn, it can be seen that PEDOT:PSS@Zn contains S, C, O and Zn atoms. By analyzing the S2p fine spectrum, the two peaks at 169.4 eV and 168.1 eV are attributed to the sulfonic acid groups in PSS, and the peaks at 164.7 eV and 163.5 eV come from the thiophene groups in the PEDOT molecule as Figure 2 shown in a, proving the successful preparation of the PEDOT:PSS@Zn integrated dendrite-free anode.

[0019] Figure 3 Fig. is the electrochemical performance diagram of the PEDOT:PSS@Zn integrated dendrite-free anode prepared by the present invention. Figure 3 a and b are respectively the long-cycle performance diagrams of the symmetric batteries of unprotected Zn and PEDOT:PSS@Zn. In Figure 3 a, at a current density of 0.5 mA cm -2 and 0.5 mAh cm -2At the areal specific capacity, the PEDOT:PSS@Zn / / PEDOT:PSS@Zn symmetric cell can be stably cycled for 2670 h, showing good cycling stability, while the symmetric cell with unprotected Zn short-circuited after 83 h of cycling. At a high current density of 10 mA cm -2 the PEDOT:PSS@Zn / / PEDOT:PSS@Zn symmetric cell can still be stably cycled for 420 h, far superior to the electrochemical performance of unprotected Zn.

[0020] Figure 4 is the electrochemical performance diagram of the full cell assembled with the PEDOT:PSS@Zn integrated dendrite-free anode prepared by the invention. The PEDOT:PSS@Zn / / DBT full cell can be cycled more than 650 times, and its cycle life is significantly better than that of the unprotected Zn anode. Detailed implementation mode

[0021] Example 1 (1) Add 2 mL of PEDOT:PSS dispersion (1.1 wt%) and 2 mL of absolute ethanol to a glass, and ultrasonicate for 30 min to make it evenly dispersed for later use. (2) Cut the zinc foil (purity > 99.99%) into strips about 2.5 cm * 15 cm, and wipe the surface stains clean with absolute ethanol for later use. (3) Evenly coat the above-prepared dispersion on the surface of the strip-shaped zinc foil with a spatula, dry it in a vacuum oven at 80 °C for 10 h, and cut it into discs with a diameter of 12 mm, named PEDOT:PSS@Zn.

[0022] Example 2 (1) Add 2 mL of PEDOT:PSS dispersion (1.1 wt%) and 2 mL of absolute ethanol to a glass, and ultrasonicate for 30 min to make it evenly dispersed for later use. (2) Cut the titanium foil (purity > 99%) into strips about 2.5 cm * 15 cm, and wipe the surface stains clean with absolute ethanol for later use. (3) Evenly coat the above-prepared dispersion on the surface of the strip-shaped titanium foil with a spatula, dry it in a vacuum oven at 80 °C for 10 h, and cut it into discs with a diameter of 12 mm, named PEDOT:PSS@Ti.

[0023] Example 3

[0024] Using the method for preparing the metal zinc anode of the aqueous zinc-ion battery with the protective layer described in Example 1, the integrated zinc anode obtained by preparation, 2 mol / L ZnSO 4An electrolyte and a glass fiber separator are assembled into a PEDOT:PSS@Zn / / PEDOT:PSS@Zn symmetric button cell, which can stably cycle for 2670 h at a current density of 0.5 mA cm -2 and an areal capacity of 0.5 mAh cm -2 , showing good cycling stability (as shown in the appendix Figure 3 ). Using an organic quinone 4,4'-dimethyl-[1,1'-bis(cyclohexane)]-3,3',6,6'-tetraene-2,2',5,5'-tetraone (DBT) as the cathode and a 2M ZnSO 4 electrolyte, a full cell assembled with the PEDOT:PSS@Zn anode can cycle more than 650 times, and its cycling life is significantly better than that of the unprotected Zn anode (as shown in the appendix Figure 4 ).

[0025] Example 4

[0026] A method for preparing an integrated titanium electrode using the protective layer described in Example 2 is used to assemble a Zn / / PEDOT:PSS@Ti half cell with the prepared integrated titanium electrode, a 2mol / L ZnSO 4 electrolyte and a glass fiber separator. Electrochemical tests are carried out at a constant current density of 2 mA cm -2 and an areal capacity of 2 mAh cm -2 (as shown in the appendix Figure 3 ). The battery without the coated protective layer begins to show large fluctuations after 30 cycles, while the battery assembled with PEDOT:PSS@Ti can stably cycle 150 times, which strongly confirms that the PEDOT:PSS coating can effectively improve the reversibility of zinc electroplating / stripping.

Claims

1. A preparation method of a PEDOT:PSS@Zn integrated dendrite-free anode, characterized in that, it is carried out according to the following steps: (1) Solution preparation: Ultrasonically disperse the PEDOT:PSS dispersion (1.1 wt%) and absolute ethanol evenly at a volume ratio of 1:1; (2) Cut the zinc foil into strips about 2.5 cm * 15 cm, scrub the surface stains clean with absolute ethanol, coat the above dispersion on the surface of the strip-shaped zinc foil with a scraper, dry it in a vacuum oven at 80 °C, and name it PEDOT:PSS@Zn.

2. According to the preparation method described in the claims, the obtained PEDOT:PSS@Zn can be used as the anode material of a zinc-ion battery.

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