Application of pyridine hydrochloride as electrolyte additive in stabilizing zinc negative electrode and realizing four-electron transfer of zinc-iodine secondary battery

Abstract

The invention belongs to the technical field of zinc battery electrolyte, and discloses application of pyridine hydrochloride as an electrolyte additive in stabilizing a zinc negative electrode and realizing four-electron transfer of a zinc-iodine secondary battery. The hydrochloride containing the pyridine structure is used as an electrolyte additive, molecules of the pyridine structure are adsorbed on the surface of the zinc negative electrode to form a shielding layer, the deposition / stripping reversibility of the zinc negative electrode is improved, stabilization of the zinc negative electrode can be achieved, and the problems of zinc dendritic crystal, corrosion and hydrogen evolution are solved. Meanwhile, molecules with pyridine structures can activate and stabilize I- / I0 / I < + > four-electron redox reaction, inhibit I < + > hydrolysis side reaction and improve the energy density and cycling stability of the zinc-iodine battery. The problem of poor electrochemical deposition / stripping reversibility of a zinc negative electrode and the problem of poor stability of positive valence I < + > species of an iodine positive electrode of a four-electron transfer reaction are solved. The electrolyte containing the additive is low in cost, simple in method, easy to produce and high in practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-iodine batteries, and specifically relates to the application of an electrolyte containing pyridine hydrochloride as an additive in a zinc-iodine secondary battery. Background Art

[0002] Aqueous zinc-iodine batteries are secondary batteries that use metallic zinc as the negative electrode, elemental iodine or polyiodides as the positive electrode, and an aqueous zinc salt solution as the electrolyte. Iodine-based cathode materials are attractive due to their potential for multi-electron transfer redox reactions in high-energy-density batteries. They possess advantages such as high theoretical specific capacity, high energy density, excellent rate capability, abundant raw materials, and high safety, and are considered to be one of the most promising electrochemical energy storage systems with low cost, long cycle life, and environmental friendliness. However, the further development of aqueous zinc-iodine batteries is hampered by the severe shuttle effect and sluggish redox conversion kinetics of the iodine cathode, resulting in poor cycling stability, low Coulombic efficiency, and severe self-discharge.

[0003] The traditional zinc-iodine battery adopts a two-electron transfer mechanism (I - / I2, 0.54V vs. SHE), the theoretical specific capacity is only 211mAh g -1 In theory, I2 can be further oxidized to a higher valence state, activating I2 / I + The redox couple is used to obtain a higher redox potential (0.54 / 1.07 V vs. SHE) and twice the specific capacity. However, in conventional aqueous electrolytes, the positive I + The hydrolysis of Zn and the reversibility of Zn anode have seriously restricted the development of four-electron Zn-I batteries. - / I2 / I + The main obstacle to redox is I in aqueous electrolyte + and the instability of the zinc anode. The introduction of chloride ions into the electrolyte can be used to trigger the I + The formation of ICl and stabilization of it by interhalogen compounds. However, ICl is easily hydrolyzed, resulting in poor battery reversibility, low Coulombic efficiency, and severe voltage decay. At the same time, the zinc negative electrode faces serious problems such as dendrite growth, corrosion, and irreversible side reactions, resulting in limited battery cycle life. Especially at high current density, zinc dendrites penetrate the diaphragm and cause short circuits, and Cl - The presence of iodine significantly reduces the electrode stability. These have become key issues restricting the development of aqueous zinc-iodine batteries.

[0004] The electrolyte plays a key role in the performance of zinc-iodine batteries. By designing and regulating the composition, concentration, solvation structure, etc. of the electrolyte, the redox reaction process of iodine can be affected, providing a suitable chemical environment for the realization of the four-electron transfer reaction. For example, the introduction of specific additives or changing the concentration of salts can stabilize the reaction intermediates and promote the progress of the four-electron transfer reaction. However, the cyclic stability of aqueous zinc-iodine batteries with four-electron transfer has encountered major challenges. The main challenges come from the hydrolysis of ICl in the electrolyte and the instability of the zinc negative electrode. Although the formation of ICl halogen is thermodynamically favorable in the presence of nucleophiles (such as halides, cyanides and amines) during the electro-oxidation of iodine, it is very easy to be hydrolyzed. Hydrolysis leads to low coulombic efficiency, capacity decay and poor cycle performance. A continuous ICl cycle stability can be established by optimizing the concentrated aqueous electrolyte formula that inhibits hydrolysis. - / I2 / I + The redox couple is used to obtain a four-electron transfer aqueous zinc-iodine battery. Adding some additives to the electrolyte can improve the performance of the battery. Adding some organic small molecules with specific functions, such as ethylenediamine and citric acid, can adjust the solvation structure of zinc ions, reduce the content of free water molecules, and provide sufficient chloride ions to stabilize I + , slowing down the hydrogen separation side reaction, etc. Certain additives can also interact with iodide ions, inhibiting the dissolution and shuttle effect of polyiodide ions, and improving the coulombic efficiency of the reaction and the cycle life of the battery. Summary of the Invention

[0005] In view of the above problems, a pyridine hydrochloride electrolyte additive for high-performance zinc-iodine secondary batteries was invented. The additive can not only effectively activate and stabilize the four-electron I - / I2 / I + reaction, and at the same time can effectively improve the stability of the zinc negative electrode.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] Pyridine hydrochloride is used as an electrolyte additive to stabilize the zinc negative electrode and realize four-electron transfer in zinc-iodine secondary batteries.

[0008] The pyridine hydrochloride is composed of a pyridine structure derivative and hydrochloric acid, and its general structural formula is C5H4RN˙HCl, where R = alkyl, dimethylamino or halogen group.

[0009] Furthermore, the pyridine hydrochloride includes ethylpyridine hydrochloride, 4-dimethylaminopyridine hydrochloride or 4-chloropyridine hydrochloride.

[0010] The electrolyte comprises solvent water, soluble zinc salt and pyridine hydrochloride; the soluble zinc salt is dissolved in deionized water, and then the pyridine hydrochloride is added and mixed until it is completely dissolved to obtain the electrolyte for the zinc-iodine battery.

[0011] The soluble zinc salt is any one of zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, zinc nitrate, and zinc tetrafluoroborate.

[0012] In the electrolyte, the concentration of the zinc sulfate is 0.1 mol / L to 3.0 mol / L; the concentration of the pyridine hydrochloride is 0.01 mol / L to 0.5 mol / L.

[0013] Preferably, in the electrolyte, the concentration of zinc sulfate is 2.0 mol / L; the concentration of pyridine hydrochloride is 0.2 mol / L.

[0014] The zinc-iodine secondary battery is a zinc / / zinc symmetrical battery or a zinc-iodine secondary battery.

[0015] Furthermore, the zinc-iodine secondary battery includes a positive electrode, a negative electrode and an electrolyte;

[0016] The positive electrode is an iodine-loaded carbon material, and the carbon material includes at least one of activated carbon, carbon fiber, graphene, microporous carbon, carbon nanotubes, or carbon dots / graphite felt;

[0017] The negative electrode is made of one of zinc metal sheet, zinc foil, zinc plate, zinc powder, zinc foam or zinc alloy;

[0018] The diaphragm is one of glass fiber, filter paper, water-based polyolefin diaphragm or composite diaphragm.

[0019] The beneficial effects of the present invention are:

[0020] (1) The invention is innovative in that pyridine hydrochloride is added as an electrolyte additive to the aqueous zinc-iodine battery electrolyte. The aqueous zinc-iodine battery after adding pyridine hydrochloride exhibits higher energy density and longer cycle life in the Zn / / Zn symmetrical battery. The pyridine hydrochloride added based on the Lewis acid-base theory realizes the high-valent iodine intermediate (I + ) stability is improved, and the dual synergistic mechanism of pyridine nitrogen atoms and chloride ions is used to effectively activate I - / I2 / I + Four-electron redox reaction and inhibition of I + Hydrolysis side reaction. Pyridine forms a dynamic shielding layer on the surface of the zinc anode through specific adsorption, enabling reversible deposition / stripping of the zinc anode.

[0021] (2) The present invention is low-cost and environmentally friendly. The additive (pyridine hydrochloride) is relatively low in price, and the additional cost for aqueous zinc-iodine batteries is relatively low. Furthermore, the additive is non-toxic and harmless, making it a green product with high practical value and market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a charge-discharge curve test of the zinc-iodine battery in Example 1 of the present application in an electrolyte containing 2.0 mol / L zinc sulfate and 0.2 mol / L ethylpyridine hydrochloride;

[0023] Figure 2 This is a cycling stability test of the zinc-iodine battery in Example 1 of the present application in an electrolyte containing 2.0 mol / L zinc sulfate and 0.2 mol / L ethylpyridine hydrochloride;

[0024] Figure 3 This is a time-voltage test graph of a zinc / / zinc symmetrical battery in Example 2 of the present application in an electrolyte containing 2.0 mol / L zinc sulfate and 0.2 mol / L ethylpyridine hydrochloride;

[0025] Figure 4 is the Tafel plot of the zinc / / zinc symmetrical battery in Example 2 of the present application in an electrolyte containing 2.0 mol / L zinc sulfate and 0.2 mol / L ethylpyridine hydrochloride;

[0026] Figure 5 This is the charge and discharge curve of the zinc-iodine battery in Example 3 of the present application in an electrolyte containing 2.0 mol / L zinc sulfate and 0.2 mol / L 4-dimethylaminopyridine hydrochloride. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following further describes the drawings required for the specific embodiments or the description of the prior art. The embodiments described in the present invention are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0028] Unless otherwise specified, the raw materials and reagents used in this application were purchased from commercial channels and used directly without further treatment, and all were of analytical grade.

[0029] Example 1

[0030] The invention discloses a method for preparing a zinc-iodine battery electrolyte containing ethylpyridine hydrochloride (EPyCl) as an additive.

[0031] The electrolyte is prepared as follows: zinc sulfate is added to water to prepare a 2.0 mol / L electrolyte, 0.2 mol / L ethylpyridine hydrochloride (EPyCl) is added, and the mixture is magnetically stirred at room temperature to form a uniform solution, thereby obtaining the zinc-iodine battery electrolyte (ZnSO4-0.2EPyCl).

[0032] The ZnSO4-0.2EPyCl electrolyte of this example was used in an aqueous zinc-iodine secondary battery. A button-type cell (CR2032) was assembled using an iodine-loaded activated carbon positive electrode, a Zn negative electrode, filter paper, a gasket, and a spring. The battery was charged and discharged in the voltage range of 0.6-1.8V at a current density of 0.2A / g, and its cycle stability was tested. To compare the effect of the electrolyte additive in activating the four-electron electrochemical activity, a 2.0 mol / L zinc sulfate electrolyte was prepared in this example.

[0033] like Figure 1 As shown, in the ZnSO4 electrolyte without additives, the zinc-iodine battery only shows a single discharge plateau with a specific capacity of 210 mAh g -1 The zinc-iodine secondary battery using zinc sulfate electrolyte (ZnSO4-0.2EPyCl) containing ethylpyridinium hydrochloride (EPyCl) additive showed two discharge platforms, and its specific capacity reached 550mAh g -1 .

[0034] like Figure 2 As shown, at 1.0Ag -1 After 400 cycles at a current density of 1.5 mmol / l, the zinc-iodine battery using the ZnSO4-0.2EPyCl electrolyte system can still maintain 420 mAh g -1 The specific capacity of the battery with a 2.0 mol / L zinc sulfate electrolyte system without additives is only 210 mAh g -1 , the capacity retention rate is 71.4%.

[0035] Example 2

[0036] Preparation of zinc / / zinc symmetrical battery: drop 100 μL of electrolyte on the separator and assemble the symmetrical battery in the order of negative electrode shell-negative zinc sheet-separator-electrolyte-positive zinc sheet-gasket-positive electrode shell.

[0037] In order to compare the zinc dendrite inhibition effect of the electrolyte additive, a 2.0 mol / L zinc sulfate electrolyte was prepared in this example. The two electrolytes were applied to the zinc / / zinc symmetrical battery. The test battery was tested at 8.0 mA cm -2 Current density, 1.0 mAh cm -2Time-voltage test diagram under deposition capacity.

[0038] like Figure 3 As shown, the symmetrical battery containing zinc sulfate electrolyte (ZnSO4-0.2EPyCl) with ethylpyridine hydrochloride (EPyCl) additive can be stably cycled for 2000 hours without abnormal voltage fluctuations, which is better than the zinc sulfate (2.0ZnSO4) electrolyte without additive, which only lasts for 30 hours, indicating that the ethylpyridine hydrochloride (EPyCl) additive promotes the deposition / stripping stability of zinc ions.

[0039] By electrochemical method, the Tafel curve test was carried out on the metal zinc electrode to investigate the inhibitory effect of the electrolyte additive of the present invention on the corrosion and dendrite of the metal zinc electrode. By fitting the Tafel curve, the corresponding electrochemical corrosion potential and current can be obtained. Figure 4 As shown in the results, ethylpyridine hydrochloride (EPyCl) can effectively inhibit the occurrence of corrosion and effectively improve the stability of the zinc electrode.

[0040] Example 3

[0041] A method for preparing a zinc-iodine battery electrolyte containing 4-dimethylaminopyridine hydrochloride as an additive.

[0042] The electrolyte is prepared as follows: zinc sulfate is added to water to prepare a 2.0 mol / L electrolyte, and then 0.2 mol / L of 4-dimethylaminopyridine hydrochloride (NMPyCl) is added and stirred to dissolve until a uniform solution is formed, thereby obtaining the zinc-iodine battery electrolyte (ZnSO4-0.2NMPyCl). The soluble zinc salt in the above embodiment can also be selected from zinc trifluoromethanesulfonate, zinc perchlorate, and zinc nitrate.

[0043] The ZnSO4-0.2NMPyCl electrolyte in this example was used in an aqueous zinc-iodine secondary battery. A button-type cell (CR2032) was assembled using an iodine-loaded activated carbon cathode, a Zn anode, filter paper, a gasket, and a spring. The battery was charged and discharged in the voltage range of 0.6-1.8V at a current density of 0.2A / g, and its cycling stability was tested.

[0044] like Figure 5 As shown in FIG, the charge-discharge curves of the zinc-iodine secondary battery using zinc sulfate electrolyte (ZnSO4-0.2NMPyCl) with 4-dimethylaminopyridine hydrochloride as an additive exhibit two obvious discharge platforms, corresponding to the four-electron transfer reaction process, which enables the battery specific capacity to reach 360 mAh / g.

[0045] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. The use of pyridine hydrochloride as an electrolyte additive in stabilizing the zinc negative electrode and realizing four-electron transfer in zinc-iodine secondary batteries.

2. The use according to claim 1, characterized in that The pyridine hydrochloride is composed of a pyridine structure derivative and hydrochloric acid, and its general structural formula is C5H4RN˙HCl, where R = alkyl, dimethylamino or halogen group.

3. The use according to claim 2, characterized in that The pyridine hydrochloride includes ethylpyridine hydrochloride, 4-dimethylaminopyridine hydrochloride or 4-chloropyridine hydrochloride.

4. The use according to claim 1, wherein The electrolyte comprises solvent water, soluble zinc salt and pyridine hydrochloride; the soluble zinc salt is dissolved in deionized water, and then the pyridine hydrochloride is added and mixed until it is completely dissolved to obtain the electrolyte for the zinc-iodine battery.

5. The use according to claim 4, characterized in that The soluble zinc salt is any one of zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, zinc nitrate, and zinc tetrafluoroborate.

6. The use according to claim 4, characterized in that In the electrolyte, the concentration of the zinc sulfate is 0.1 mol / L to 3.0 mol / L; the concentration of the pyridine hydrochloride is 0.01 mol / L to 0.5 mol / L.

7. The use according to claim 6, characterized in that In the electrolyte, the concentration of zinc sulfate is 2.0 mol / L; the concentration of pyridine hydrochloride is 0.2 mol / L.

8. The use according to claim 1, wherein The zinc-iodine secondary battery is a zinc / / zinc symmetrical battery or a zinc-iodine secondary battery.

9. The use according to claim 8, characterized in that The zinc-iodine secondary battery comprises a positive electrode, a negative electrode and an electrolyte; The positive electrode is an iodine-loaded carbon material, and the carbon material includes at least one of activated carbon, carbon fiber, graphene, microporous carbon, carbon nanotubes, or carbon dots / graphite felt; The negative electrode is made of one of zinc metal sheet, zinc foil, zinc plate, zinc powder, zinc foam or zinc alloy; The diaphragm is one of glass fiber, filter paper, water-based polyolefin diaphragm or composite diaphragm.

Images