Organic carboxylic acid modified super-stable aqueous zinc ion battery electrolyte

Abstract

The invention belongs to the technical field of electrolyte for zinc ion batteries, and relates to organic carboxylic acid modified super-stable aqueous electrolyte for zinc ion batteries. The piperidine carboxylic acid or pyridine carboxylic acid molecules are added into the basic electrolyte, so that the stability of the zinc metal negative electrode in the electrolyte is remarkably improved, and the battery performance is further improved. Firstly, due to the addition of the additive, the solvation structure of the electrolyte is changed, the stability of the zinc negative electrode in the electrolyte is improved, and the inhibition of the side reaction of the zinc negative electrode in the long-time operation process of the battery is facilitated; and secondly, due to the specific structure of piperidine carboxylic acid or picolinic acid, the additive can be adsorbed on the surface of the zinc negative electrode, and the contact angle between the zinc negative electrode and an electrolyte is increased, which is very important for the stability of the battery in a standing state. And finally, due to introduction of the additive, zinc ion transmission of an interface can be adjusted, uniform deposition of zinc ions is promoted, formation of zinc dendrites is reduced, and reversibility and stability of a zinc negative electrode are improved, so that charge-discharge efficiency of the battery is improved, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc ion battery electrolytes and relates to an organic carboxylic acid-modified ultra-stable aqueous zinc ion battery electrolyte and a preparation method thereof. Background Art

[0002] As the world's non-renewable resources are becoming increasingly scarce and global warming is becoming increasingly serious, countries around the world have reached a consensus on related issues, and mankind is in urgent need of developing clean and renewable energy. More and more companies and individuals have responded positively, and a variety of clean energy sources (such as wind energy, tidal energy, and solar energy) have been developed and utilized and have received widespread attention. However, these new energy sources cannot provide stable output for large-scale power grids due to their regional dispersion and time intermittent shortcomings, which has also become a challenge for resource conversion and utilization. Secondary batteries, as key devices for the conversion of chemical energy and electrical energy, have attracted the attention of many researchers because of their ability to store intermittent energy and their ability to supply energy to electronic devices or power grids when humans need it. However, commercial lithium-ion batteries cannot achieve large-scale energy storage due to problems such as high cost and poor safety.

[0003] As a green rechargeable secondary battery, aqueous zinc-ion battery has attracted in-depth research. Its advantages include that the solvent of aqueous battery is water, which is pollution-free, abundant in reserves, and easy to purify; the metal zinc negative electrode has an ultra-high capacity (820mAh g -1 or 5855mAh cm -3 ) and low redox potential (-0.76V vs. SHE); zinc salts are abundant in reserves and low in cost. Using these advantages of zinc-ion batteries to collect and store new energy will greatly alleviate the problem of energy shortage. The mechanism of aqueous zinc-ion batteries is similar to that of lithium-ion batteries, and the conversion of chemical energy to electrical energy is completed by the migration of zinc ions between the positive and negative electrodes. Therefore, one of the keys to the application of aqueous zinc-ion batteries is the reversible stripping and deposition of zinc, that is, to achieve the stability of the zinc negative electrode. In the past few years, many functional materials such as organic small molecules, inorganic ion salts, and organic polymers have been proven to be used for the protection of zinc negative electrodes, but there are still many problems: the uneven distribution of materials leads to poor isolation effect of the protective layer, which cannot play a continuous protective role; the addition of some organic solvents improves the battery cycle stability, but also leads to a serious decrease in conductivity, affecting the rapid transmission of zinc ions. Although these functional additives have played a certain positive effect in some aspects, the electrolyte formula still needs to be explored and studied. In addition, the specific mechanism of action and the optimal ratio also need to be further optimized. At the same time, how to achieve both low cost and high performance is also an urgent problem to be solved in current technology. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an ultra-stable aqueous zinc ion battery electrolyte.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] In a first aspect, the present invention provides an organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte, comprising at least a zinc ion salt, ultrapure water and a functional additive, wherein the functional additive contains piperidinecarboxylic acid or pyridinecarboxylic acid organic molecules.

[0007] Furthermore, in the organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte, the zinc ion concentration is 1 to 3 mol / L, preferably 2 mol / L; and the functional additive concentration is 5 to 10 g / L.

[0008] Furthermore, the zinc ion salt is at least one of zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc perchlorate, and zinc acetate.

[0009] Furthermore, the piperidinecarboxylic acid is 2-piperidinic acid.

[0010] Furthermore, the pyridinecarboxylic acid is 2-pyridinecarboxylic acid.

[0011] In a second aspect, the present invention provides an aqueous zinc ion battery, which includes positive and negative electrodes, a separator and an electrolyte, wherein the electrolyte is the organic carboxylic acid-modified ultra-stable aqueous zinc ion battery electrolyte described in the first aspect.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) The present invention uses piperidinecarboxylic acid or pyridinecarboxylic acid as an electrolyte additive for aqueous zinc ion batteries, and exhibits excellent stability in aqueous zinc ion batteries.

[0014] (2) Compared with other additives, piperidinecarboxylic acid or pyridinecarboxylic acid can enter the solvation shell of zinc ions, change the solvation structure of zinc ions, reduce the proportion of active water, and inhibit side reactions.

[0015] (3) The electronegative carboxyl groups can be adsorbed on the surface of the zinc negative electrode, and the structure of the piperidine ring / pyridine ring can play a hydrophobic role, effectively reducing contact with water.

[0016] (4) The adsorbed piperidine carboxylic acid or pyridine carboxylic acid can regulate the double electrical layer near the zinc negative electrode, control the distribution and transport of zinc ions, optimize the zinc ion deposition behavior, and promote the formation of a uniform and dense zinc layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Graph showing the cycle performance of a Zn||Zn symmetrical battery prepared based on the basic electrolyte and the modified electrolyte in Example 1;

[0018] Figure 2 The coulombic efficiency diagram of the Zn||Cu asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1;

[0019] Figure 3 The performance test diagram of the basic electrolyte and the modified electrolyte described in Example 1, wherein: a is the LSV curve; b is the Tafel curve;

[0020] Figure 4 CV curve diagram of the Zn||Ti asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1;

[0021] Figure 5 A comparison diagram of the contact angles between the basic electrolyte (a) and the modified electrolyte (b) described in Example 1 and zinc metal;

[0022] Figure 6 is a chronoamperometric curve of a Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1;

[0023] Figure 7 Graph showing the cycle performance of a Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 2;

[0024] Figure 8 The coulombic efficiency diagram of the Zn||Cu asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 2;

[0025] Fig. 9 Graph showing the cycle performance of a Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 3;

[0026] Fig.10 Graph showing the cycle performance of a Zn||Zn symmetric battery prepared based on the modified electrolyte of different concentrations of 2-piperidinic acid in Example 4;

[0027] Fig.11 This is a cycle performance diagram of the Zn||Zn symmetric battery prepared based on the modified electrolyte with different concentrations of 2-pyridinecarboxylic acid in Example 5. DETAILED DESCRIPTION

[0028] The present invention will be further described below through specific embodiments and accompanying drawings.

[0029] The concept of the present invention is: the present invention uses piperidine carboxylic acid or pyridine carboxylic acid organic molecules as additives for aqueous zinc ion batteries, and realizes the stability of the zinc negative electrode through the cooperation of the functional groups of the additives, thereby extending the service life of the battery. After a certain amount of the additive is added to the prepared basic electrolyte, a modified electrolyte is obtained. On the one hand, the carboxyl group of piperidine carboxylic acid or pyridine carboxylic acid is electronegative, which increases the solubility of the additive molecule, and can be adsorbed on the surface of the zinc negative electrode through electrostatic action to form an adsorption layer; on the other hand, the piperidine ring of piperidine carboxylic acid and the pyridine ring of pyridine carboxylic acid are organic hydrophobic structures, which can repel water molecules in the electrolyte near the zinc negative electrode and reduce the interface contact of the electrode / electrolyte; in addition, the additive molecules promote the uniform distribution of zinc ions during zinc deposition, stabilize the interface transmission and nucleation of zinc ions, thereby increasing the stability of the zinc negative electrode, and greatly improving the battery life.

[0030] The batteries assembled in all the embodiments are button-type batteries, the separators are glass fiber separators, and the batteries are tested at 25°C.

[0031] Example 1

[0032] A method for preparing an organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte comprises the following steps:

[0033] 11.5 g of zinc sulfate heptahydrate was added to 15 mL of ultrapure water and ultrasonically stirred for 20 min until completely dissolved to obtain 20 mL of 2 mol / L ZnSO4 solution, which was used as the basic electrolyte (ZSO);

[0034] 0.2 g of 2-piperidinic acid was weighed and mixed with 20 mL of the basic electrolyte by ultrasound until the solution was clear and transparent, thereby obtaining a modified electrolyte (ZSO-PPCA) containing 10 g / L of the additive.

[0035] Example 2

[0036] A method for preparing an organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte comprises the following steps:

[0037] 5.75 g of zinc sulfate heptahydrate was added to 17.5 mL of ultrapure water and ultrasonically stirred for 20 min until completely dissolved to obtain 20 mL of 1 mol / L ZnSO4 solution, which was used as the basic electrolyte (ZSO');

[0038] 0.2 g of 2-piperidinylcarboxylic acid was weighed and mixed with 20 mL of the basic electrolyte solution by ultrasound until the solution became clear and transparent, thereby obtaining a modified electrolyte solution (ZSO'-PPCA) containing 10 g / L of the additive.

[0039] Example 3

[0040] A method for preparing an organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte comprises the following steps:

[0041] 14.54 g of zinc trifluoromethanesulfonate was added to 20 mL of ultrapure water and ultrasonically stirred for 20 min until completely dissolved to obtain 20 mL of 2 mol / L Zn(CF3SO3)2 solution, which was used as the basic electrolyte (ZnOTF);

[0042] 0.2 g of 2-piperidinic acid was weighed and mixed with 20 mL of the basic electrolyte by ultrasound until the solution was clear and transparent, thereby obtaining a modified electrolyte (ZnOTF-PPCA) containing 10 g / L of the additive.

[0043] Example 4

[0044] The other processes are the same as in Example 1. 0.1 g and 0.3 g of 2-piperidinic acid are weighed in sequence to obtain a modified electrolyte containing 5 g / L of additive (ZSO-PPCA-5g / L) and a modified electrolyte containing 15 g / L of additive (ZSO-PPCA-15g / L), respectively.

[0045] Example 5

[0046] The other processes are the same as in Example 1. 0.02 g, 0.1 g and 0.2 g of 2-pyridinecarboxylic acid are weighed in sequence to obtain a modified electrolyte containing 1 g / L of additive (ZSO-PDCA-1 g / L), a modified electrolyte containing 5 g / L of additive (ZSO-PDCA-5 g / L) and a modified electrolyte containing 10 g / L of additive (ZSO-PDCA-10 g / L), respectively.

[0047] Figure 1 is a cycle performance diagram of the Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1, as shown in Figure 1 As shown in the figure, the Zn||Zn symmetric battery assembled with the basic electrolyte has a current density of 1 mA cm -2 The surface capacity density is 1 mAh cm -2 Under the same conditions, the cycle time is less than 70h. After modification with 2-piperidinic acid molecules, the cycle time increases to more than 4300h under the same conditions, and the cycle life is greatly enhanced.

[0048] Figure 2 The coulombic efficiency diagram of the Zn||Cu asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1 is shown in the figure. As shown in the figure, the Zn||Cu symmetric battery assembled by the electrolyte before and after modification has a current density of 1 mA cm -2 The surface capacity density is 1 mAh cm -2The coulombic efficiency under different conditions is obviously different. When the electrolyte of the present invention is used, the coulombic efficiency is maintained at above 99.4% on average, and the number of cycles is increased to 1500 (>3000h).

[0049] Figure 3 The performance test diagrams of the basic electrolyte and the modified electrolyte described in Example 1, a is the LSV curve, b is the Tafel curve, Figure 3 It can be seen from the figure that the electrolyte of the present invention is used at a reaction current density of 10 mA cm -2 Under the standard, the hydrogen evolution potential is -1.854V (vs.Ag / AgCl), which is a negative shift of 0.216V compared to the hydrogen evolution potential of the electrolyte without additives -1.638V (vs.Ag / AgCl). This indicates that the addition of 2-piperidinic acid has a significant inhibitory effect on the hydrogen evolution reaction. Figure 3 b is a Tafel curve tested by constant potential polarization method. It can be clearly observed that the corrosion potential of the electrolyte of the present invention is -0.976V (vs.Ag / AgCl), which is higher than -0.963V (vs.Ag / AgCl) of the basic electrolyte. At the same time, the corrosion current of the present invention is 2.943mAcm -2 , which is much lower than the 6.946 mA cm of the basic electrolyte. -2 This indicates that the electrolyte of the present invention has stronger corrosion resistance and plays an important role in the stability of the metal zinc negative electrode.

[0050] Figure 4 is a CV curve diagram of the Zn||Ti asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1, from Figure 4 It can be clearly seen that at a scanning speed of 1 mV / s, using the electrolyte battery of the present invention, the nucleation potential of zinc ions increases by 21 mV compared with the basic electrolyte, and a larger nucleation potential is beneficial to the density and uniformity of zinc deposition.

[0051] Figure 5 This is a comparison diagram of the contact angles of the basic electrolyte and the modified electrolyte described in Example 1 with metallic zinc. The contact angle of the electrolyte of the present invention with zinc metal is 77.2°, which is 9.2° larger than 68° of the basic electrolyte, indicating that the addition of additives reduces the wetting properties of the electrolyte with zinc metal, which can significantly inhibit side reactions involving water at the interface.

[0052] Figure 6 is the chronoamperometric curve of the Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 1, from Figure 6It can be seen that at a voltage of -150 mV, the diffusion current of the electrolyte of the present invention first increases within 5 minutes and then quickly stabilizes, and the zinc ions show a three-dimensional diffusion form, while the diffusion current of the basic electrolyte continues to increase, showing a two-dimensional diffusion, because the three-dimensional diffusion is more conducive to the uniform deposition of zinc and inhibits the growth of dendrites, indicating that the electrolyte of the present invention can promote the uniform deposition of zinc ions.

[0053] Figure 7 is a cycle performance diagram of the Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 2, from Figure 7 It can be seen that at a current density of 5 mA cm -2 The surface capacity density is 1 mAh cm -2 Under the above conditions, the battery cycle time of the electrolyte of the present invention can reach 1000h, which is 20 times longer than the 50h of the basic electrolyte, indicating that the electrolyte of the present invention can greatly prolong the cycle life of the zinc ion battery.

[0054] Figure 8 The coulombic efficiency diagram of the Zn||Cu asymmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 2 is shown in FIG. Figure 8 It can be seen that at a current density of 1 mA cm -2 The surface capacity density is 1 mAh cm -2 Under the given conditions, the number of cycles of the electrolyte battery of the present invention can reach 500, and the coulomb efficiency is above 99.2% on average.

[0055] Fig. 9 The cycle performance diagram of the Zn||Zn symmetric battery prepared based on the basic electrolyte and the modified electrolyte in Example 3 is shown in FIG. Fig. 9 It can be seen that at a current density of 1 mA cm -2 The surface capacity density is 1 mAh cm -2 Under the above conditions, the battery cycle time using the electrolyte of the present invention can reach 2000h, which is several dozen times longer than the basic electrolyte cycle life, indicating that the electrolyte of the present invention greatly increases the stability of the battery.

[0056] Fig.10 The cycle performance diagram of the Zn||Zn symmetric battery prepared based on the modified electrolyte of 2-piperidinic acid with different concentrations in Example 4 is shown in FIG. Fig.10 It can be seen that at a current density of 1 mA cm -2 , with a capacity density of 1 mAh cm -2 Under the conditions of , the battery ran for 520 h and 1220 h respectively when the 2-piperidinic acid concentration was 5 g / L and 15 g / L, and the cycle time was less than the battery with an additive concentration of 10 g / L, so the optimal concentration of 2-piperidinic acid is 10 g / L as described in Example 1.

[0057] Fig.11 The cycle performance diagram of the Zn||Zn symmetric battery prepared based on the modified electrolyte of 2-pyridinecarboxylic acid with different concentrations in Example 5. By comparison, it can be clearly found that the 10 g / L 2-pyridinecarboxylic acid modified electrolyte has a higher current density of 1 mA cm -2 , with a capacity density of 1 mAh cm -2 The operating time is the longest under the conditions of , which can reach 3500h, indicating that the electrolyte containing pyridinecarboxylic acid in the present invention greatly increases the battery operation stability.

Claims

1. An organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte, comprising at least a zinc ion salt, ultrapure water and a functional additive, characterized in that: The functional additive contains piperidinecarboxylic acid or pyridinecarboxylic acid organic molecules.

2. The organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte according to claim 1, characterized in that: In the ultrastable aqueous zinc ion battery electrolyte, the zinc ion concentration is 1-3 mol / L, preferably 2 mol / L; the functional additive concentration is 5-10 g / L.

3. The organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte according to claim 1, characterized in that: The zinc ion salt is at least one of zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc perchlorate and zinc acetate.

4. The organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte according to claim 1, characterized in that: The piperidinecarboxylic acid is 2-piperidinic acid.

5. The organic carboxylic acid-modified ultrastable aqueous zinc ion battery electrolyte according to claim 1, characterized in that: The pyridinecarboxylic acid is 2-pyridinecarboxylic acid.

6. An aqueous zinc ion battery comprising positive and negative electrodes, a separator and an electrolyte, characterized in that: The electrolyte is an ultra-stable aqueous zinc ion battery electrolyte modified with an organic carboxylic acid as described in any one of claims 1 to 5.

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