Zinc ion battery with degradable gel electrolyte

Abstract

The invention belongs to the technical field of zinc ion batteries, and particularly discloses a degradable gel electrolyte zinc ion battery, which is prepared by the following steps: preparing a gel electrolyte from a polyethylene-polypropylene copolymer and a hydrolyzable / photolytic polymer, taking aluminum-doped vanadyl phosphate as a positive electrode, and taking zinc as a negative electrode. The polyethylene-polypropylene copolymer as a matrix material provides excellent chemical stability and mechanical toughness, and polylactic acid is modified to introduce hydrophilic groups, so that not only are high mechanical strength and biocompatibility retained, but also a channel and an interface beneficial to zinc ion transmission are constructed. The degradable electrolyte and the degradable flexible quasi-solid-state zinc ion battery are designed, so that the safety and the reliability of the battery are improved, and the flexible quasi-solid-state zinc ion battery is suitable for being applied to various electronic equipment needing flexibility and degradability.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and specifically relates to a degradable zinc-ion battery based on a gel electrolyte. This battery not only has high energy density, long cycle life, and excellent safety, but also realizes the degradability of the electrolyte, providing a new technical solution for environmentally friendly and high-performance energy storage devices. Background Art

[0002] In recent years, with the transformation of the global energy structure and the rapid development of renewable energy, energy storage technology has become a key link connecting energy production and consumption. Aqueous zinc-ion batteries have become a research hotspot in the energy storage field due to their advantages such as rich resources, easy preparation, and high safety. However, traditional aqueous electrolytes have problems such as unstable positive and negative electrode materials and a decrease in battery performance due to the high chemical activity of water, which seriously hinders the commercialization process of aqueous zinc-ion batteries.

[0003] To solve the above problems, hydrogel electrolytes have emerged. Hydrogel polymer electrolytes (HPEs) are quasi-solid electrolytes formed by cross-linking hydrophilic polymers to form a 3D network structure, with a zinc salt solution filled in the porous structure. HPEs are not only widely used in flexible batteries but also show great potential in solving problems related to zinc anodes, including dendrite formation and side reactions. By reducing the water content and the chemical activity of water, HPEs can significantly improve the electrochemical performance and stability of the battery. However, existing hydrogel electrolytes still face many challenges in practical applications, such as poor ionic conductivity, low mechanical strength, insufficient interfacial stability, and a narrow electrochemical stability window. In addition, with the enhancement of environmental awareness and the demand for sustainable development, the degradability of batteries has also become an important research direction. Currently, research on zinc-ion batteries mainly focuses on liquid electrolyte systems, and there is very little research on degradable flexible quasi-solid-state zinc-ion batteries. The present invention combines polyethylene-propylene copolymer with PLA, which is a new attempt in flexible quasi-solid-state zinc-ion batteries.

[0004] In view of the above background, the present invention proposes a zinc-ion battery based on a degradable gel electrolyte. By optimizing the molecular structure and preparation process of the gel electrolyte, the cycle stability and safety of the battery are improved. At the same time, the battery components are prepared using degradable materials, realizing the overall degradability of the battery and providing a new technical path for the development of environmentally friendly energy storage devices. Summary of the Invention

[0005] The present invention relates to a zinc-ion battery with a degradable gel electrolyte, which performs excellently in terms of performance, safety, and environmental friendliness.

[0006] The core of the present invention lies in its unique electrolyte composition, which is composed of a gel with good chemical stability and mechanical properties and a polymer that can be hydrolyzed / photolyzed. This electrolyte combination not only provides good ionic conductivity for the battery but also endows the electrolyte with the property of being degradable.

[0007] Specifically, each 1 g of the electrolyte contains at least 0.6 - 0.9 g of the gel with good chemical stability and mechanical properties. The gel molecular chains are intertwined with each other through physical entanglement. In the electrolyte system, the random movement and interpenetration of the molecular chains cause them to entangle with each other, like a tight large net, to construct a stable three-dimensional network structure. At the same time, the electrolyte also contains 0.1 - 0.4 g of the hydrolyzable / photolyzable polymer, which can undergo hydrolysis or photolysis reactions under appropriate conditions to achieve the degradation of the electrolyte.

[0008] Preferably, the gel with good chemical stability and mechanical properties is a polyethylene - polypropylene copolymer; the hydrolyzable / photolyzable polymer is polylactic acid and carboxymethyl cellulose.

[0009] Furthermore, the mass ratio of polylactic acid to carboxymethyl cellulose is 1:1.

[0010] The synergistic effect of the present invention in selecting the combination of polyethylene - polypropylene copolymer and polylactic acid is as follows:

[0011] First, the polyethylene - polypropylene copolymer, as the matrix material, has excellent ionic conductivity, while PLA provides high mechanical strength and biocompatibility. Phase separation regulation occurs between polylactic acid and the polyethylene - polypropylene copolymer, thereby constructing channels and interfaces conducive to zinc ion transport. The formed microphase separation structure allows zinc ions to diffuse rapidly between different phases and simultaneously inhibits the growth of dendrites.

[0012] Second, the polyethylene - polypropylene copolymer forms a three-dimensional network structure through physical entanglement. The addition of PLA further enhances the integrity and stability of this network. This cross-linked network restricts the movement of polymer chains, reduces the resistance of ions during transmission, and is conducive to ion conduction. The overall mechanical properties and ionic conductivity of the electrolyte are synergistically improved, achieving higher zinc ion storage and release capabilities, while taking into account the flexibility and flexibility of zinc ion batteries.

[0013] Third, PLA has excellent biodegradable properties, and the degradation properties of the polyethylene - polypropylene copolymer in an aqueous environment can complement the degradation mechanism of PLA, enabling the entire flexible zinc ion battery to degrade more efficiently after use.

[0014] IV. The molecular structure of carboxymethyl cellulose contains hydrogen bonds, enabling the battery to be spliced and repaired through the material's own characteristics after being damaged, thus extending its service life.

[0015] The preparation method of the degradable electrolyte is as follows:

[0016] (1) Raw material preparation: Weigh polyethylene-polypropylene copolymer (PP-PE), polylactic acid (PLA), and carboxymethyl cellulose (CMC) as the main components of the electrolyte.

[0017] (2) Mixing and polymerization: Add the above three raw materials to dimethyl sulfoxide and stir at high speed to form a homogeneous mixture. Under water bath conditions, add a cross-linking agent and keep stirring to cause chemical polymerization of the mixture to form a network-type gel electrolyte, and then pour the mixture into a mold;

[0018] (3) Place the obtained mold in a vacuum drying oven (60 - 80 °C) and dry at room temperature for 24 hours to remove excess organic solvents and unreacted raw materials to obtain the degradable electrolyte.

[0019] Among them, the water bath conditions are -10 to 50 °C.

[0020] Among them, in order to further improve the electrochemical performance of the electrolyte, by uniformly dispersing organic phosphonic acid in the raw material mixture before the cross-linking agent, an organic phosphonic acid-modified electrolyte is obtained.

[0021] Among them, the organic phosphonic acid is one or a mixture of hydroxyethylidene diphosphonic acid (HEDP), 1-hydroxyphosphonoacetic acid (HPAA), phenylphosphonic acid (PPA), tetradecylphosphonic acid (TDPA), and preferably tetradecylphosphonic acid. Among them, the mass ratio of the addition amount of the organic phosphonic acid to the polyethylene-polypropylene copolymer is 0.00025 - 0.0004:1.

[0022] In the present invention, different organic phosphonic acids are used to modify the polymer gel electrolyte. The results show that tetradecylphosphonic acid is a chelating agent that forms a stable chelate with zinc ions, can improve the cycle life of the battery and inhibit the growth of zinc dendrites, and preferentially adsorbs on the zinc surface to form an ordered hydrophobic layer, effectively inhibiting the hydrogen evolution reaction and zinc corrosion.

[0023] Among them, the cross-linking agent is dicumyl peroxide DCP, and the mass ratio of the cross-linking agent to the total amount of the polymer is 1:30 - 50.

[0024] The preparation method of a zinc-ion battery with a degradable gel electrolyte. The battery is assembled as follows: a cathode material containing aluminum-doped vanadium phosphate, zinc as the anode material, and the gel electrolyte are assembled in sequence into a sandwich structure and encapsulated in a flexible battery.

[0025] Among them, the raw material composition of the positive electrode material is: vanadium oxyphosphate powder doped with aluminum is used as the active component, and a positive electrode is prepared with a conductive agent and a binder.

[0026] The method for preparing the positive electrode is as follows: mix the vanadium oxyphosphate powder doped with aluminum with the conductive agent and the binder according to a mass ratio, add a solvent, and grind them thoroughly in a ceramic mortar until a uniform slurry is formed. Then, coat it evenly on the current collector, and then place it in a vacuum drying oven for drying and pressing to obtain the positive electrode.

[0027] Furthermore, the doping molar amount of aluminum in the vanadium oxyphosphate powder doped with aluminum is 0.5 - 10%, and more preferably, the doping molar amount is 5%.

[0028] Furthermore, the conductive agent is acetylene black; the binder is polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), and the current collector is aluminum foil.

[0029] Furthermore, the mass ratio of the vanadium oxyphosphate powder doped with aluminum, the conductive agent, and the binder is 7:2:1.

[0030] The beneficial effects of the present invention are as follows:

[0031] The electrolyte of the present invention has a splicing and repair function. When the battery is subjected to an external force and the electrolyte breaks, the polymer gel and polymer molecules on the fracture surface can be reconnected through physical actions, thereby realizing the repair of the electrolyte. This repair function enables the battery to continue to supply power stably after being spliced after being damaged, improving the durability and reliability of the battery.

[0032] Based on the above analysis, the degradable zinc-ion battery of the present invention has excellent electrochemical performance, a physical repair function, and degradability, and is a new type of battery with broad application prospects. This battery is not only applicable to various fields such as portable electronic devices and electric vehicles, but can also be an important part of the energy storage system, providing strong support for the utilization of renewable energy. At the same time, its degradable characteristics also conform to the current environmental protection and sustainable development concepts, and have significant social and economic benefits. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0034] Figure 1 It is the electrochemical impedance diagram under different electrolyte types;

[0035] Figure 2Ionic conductivity comparison chart of different electrolytes;

[0036] Figure 3 Photographs of the gel electrolyte (a) and the degradable material (b);

[0037] Figure 4 Actual power supply diagram of the repaired zinc-ion battery after shearing and splicing;

[0038] Figure 5 CA diagrams of different organic phosphonic acids;

[0039] Figure 6 For vanadium oxyphosphate doped with aluminum at 0.1Ag -1 Cycle performance diagram;

[0040] Figure 7 Ionic conductivities of 25 μL of different organic phosphonic acids. Detailed implementation method

[0041] Example 1: Preparation of a degradable zinc-ion battery

[0042] 1. Preparation of electrolyte:

[0043] Raw material preparation: Weigh 1 g of polyethylene-polypropylene copolymer (PP-PE), 0.1 g of polylactic acid (PLA), and 0.1 g of carboxymethyl cellulose (CMC) as the main components of the electrolyte.

[0044] Mixing and polymerization: Add the above three raw materials into a beaker, and add 10 mL of dimethyl sulfoxide for high-speed stirring to form a homogeneous mixture. Then, under water bath conditions (set temperature at 30 °C), add 30 mg of cross-linking agent (DCP) and keep stirring to cause chemical polymerization of the mixture to form a network-type gel electrolyte, and then pour the mixture into a mold.

[0045] Post-treatment: Place the obtained mold in a vacuum drying oven (60 - 80 °C) and dry it at room temperature for 24 hours to remove excess organic solvents and unreacted raw materials, and initially obtain a composite gel. The ionic conductivity of the composite gel electrolyte (PP-PE copolymer + PLA) prepared in Example 1 is 9.6 mS / cm.

[0046] 2. Preparation of the positive electrode:

[0047] Raw material preparation: Weigh 4.8 g of V2O5, 26.6 mL of H3PO4 and 115.4 mL of deionized water, and add them to a three-necked flask respectively. Then add 10 mL of HNO3, and carry out magnetic stirring for 30 min. Then heat the mixture at 110 °C for 16 h. After cooling to room temperature, collect the yellow precipitate from the bottom, and collect the yellow precipitate by centrifugation. Wash it three times with deionized water and acetone respectively. Dry the obtained bright yellow VOPO4 sample in a vacuum oven at 60 °C. Then disperse the synthesized VOPO4·2H2O and Al2(SO4)3 in 50 mL of NMP. After sufficient stirring, transfer the mixture to a 100 mL Teflon-lined stainless steel autoclave and keep it at 120 °C for 2 h. After cooling, the product is also washed with ultrapure water, centrifuged and collected to obtain aluminum-doped vanadium phosphate oxide, where the doping amount of aluminum is 5% in mole fraction (based on vanadium phosphate oxide).

[0048] Positive electrode preparation: Mix the aluminum-doped vanadium phosphate oxide powder (140 mg), conductive agent (acetylene black) (40 mg) and binder (polytetrafluoroethylene PTFE) in a mass ratio of 7:2:1, add an appropriate amount of solvent (N-methylpyrrolidone NMP), and grind it thoroughly in a ceramic mortar until a uniform slurry is formed. Then coat it evenly on the current collector (aluminum foil), and then put it into a vacuum drying oven to dry and press into a positive electrode.

[0049] 3. Negative electrode preparation:

[0050] Material selection: Select high-purity zinc sheet as the negative electrode.

[0051] Post-treatment: Clean and dry the zinc sheet to ensure that its surface is clean and free of impurities.

[0052] 4. Battery assembly:

[0053] Structure: Assemble the prepared positive electrode, negative electrode and gel electrolyte into a sandwich structure in sequence and encapsulate them in a flexible battery.

[0054] Sealing: Use heat-sealing technology to seal the flexible battery to ensure no leakage inside the battery.

[0055] 5. Performance test:

[0056] Artificially cut the assembled battery. After cutting and splicing, observe whether the battery can continue to supply power stably. Figure 4 The actual power supply diagram of the repaired zinc-ion battery after cutting and splicing. From Figure 4It can be seen from [reference] that after artificial shearing and splicing along the cross-section, stable power supply can still be achieved. Degradability test: Disassemble the waste battery, dissolve the disassembled electrolyte in water, heat it to 40 °C, and heat for 12 h. Measure the solubility of the electrolyte. Solubility % = ((Wbefore - Wafter) / Wbefore) × 100%. Here, (Wbefore - Wafter) represents the weight of the dissolved substance, and Wbefore is the total weight of the initial substance. Through the above formula, the dissolution percentage of the substance is calculated. After 4 h, its solubility is about 20%, as Figure 3 Physical diagram of the gel electrolyte (a) and physical diagram of the degradable material (b), Figure 3 (a) shows the state of the gel before degradation, Figure 3 (b) On the left is the size of the gel before degradation, and on the right is the comparison state of the size of the gel after degradation.

[0057] Example 2: Preparation of electrolytes modified with different organic phosphonic acids and optimization of battery performance

[0058] 1. Electrolyte modification:

[0059] Raw material preparation: On the basis of Example 1, add 25 μL of different organic phosphonic acid dimethyl sulfoxide (DMSO) solutions with a concentration of 10 g / L (such as hydroxyethylidene diphosphonic acid, 1-hydroxyphosphonoacetic acid, phenylphosphonic acid, tetradecylphosphonic acid) to the electrolyte.

[0060] Mixing and polymerization: Follow the steps of Example 1 for mixing and polymerization, but different organic phosphonic acids need to be evenly dispersed in the raw materials before adding the cross-linking agent. Specifically: Add 1 g of PP-PE, 0.1 g of PLA, and 0.1 g of CMC to a beaker, and add 10 mL of DMSO for high-speed stirring to form a homogeneous mixture. Then, add 25 μL of organic phosphonic acid. Under the water bath condition (set temperature at 30 °C), add 30 mg of cross-linking agent (dicumyl peroxide DCP) and keep stirring to cause chemical polymerization of the mixture to form a network-type gel electrolyte, and then pour the mixture into a mold.

[0061] Post-treatment: The same as Example 1, different organic phosphonic acid-modified electrolytes are prepared.

[0062] 2. Battery assembly:

[0063] Assembly: Assemble the battery according to the steps of Example 1.

[0064] 3. Performance test:

[0065] Electrochemical workstation test: Test the zinc ion migration efficiency of the battery to verify the influence of different organic phosphonic acid modifications on battery performance. From Figure 5It can be seen that in the absence of additives, the migration efficiency of zinc ions is not high, and after modification with organic phosphonic acid, the migration efficiency of zinc ions can be significantly improved.

[0066] Table 8 shows the electrolyte ionic conductivities after modification with 25 μL of different organic phosphonic acid solutions. The ionic conductivity of the electrolyte with 1-hydroxyphosphonocarboxylic acid (HPAA) added is 15.5 mS / cm, the ionic conductivity of the electrolyte with tetradecylphosphonic acid (TDPA) added is 17.3 mS / cm, the ionic conductivity of the electrolyte with phenylphosphonic acid (PPA) added is 11.4 mS / cm, and the ionic conductivity of the electrolyte with 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) added is 14.3 mS / cm. It can be seen that the modification effect of adding tetradecylphosphonic acid is the best.

[0067] Example 3: Effect of different contents of tetradecylphosphonic acid on the repair performance after battery splicing

[0068] 1. Electrolyte modification:

[0069] Raw material preparation: On the basis of Example 2, 25 μL, 30 μL, 35 μL, and 40 μL of tetradecylphosphonic acid (concentration 10 g / L) were added to the electrolyte respectively.

[0070] Mixing and polymerization: Mixing and polymerization were carried out according to the steps of Example 2.

[0071] Post-treatment: The same as Example 1, electrolytes modified with different contents of tetradecylphosphonic acid were prepared.

[0072] 2. Battery assembly and testing:

[0073] Assembly: Batteries were assembled according to the steps of Example 1 using different contents of additives.

[0074] Repair test: The assembled batteries were artificially cut. After cutting and splicing, the influence of different contents of tetradecylphosphonic acid on the battery repair ability at room temperature was compared. The repair rates are shown in the following table. Repair rate = (battery voltage after repair - battery voltage before repair) / (initial battery voltage - battery voltage before repair) × 100%).

[0075] Sample Addition amount of tetradecylphosphonic acid (μL) Repair rate % PP-PE / PLA / CMC 25 80 PP-PE / PLA / CMC 30 85 PP-PE / PLA / CMC 35 100 PP-PE / PLA / CMC 40 85

[0076] Among them, the ionic conductivity of the gel electrolyte (PP-PE / PLA / CMC) modified with 35 μL of tetradecylphosphonic acid is 21.1 mS / cm.

[0077] Example 4: Comparison of the performance of vanadium phosphate oxide cathodes doped with different amounts of aluminum

[0078] The electrolyte in Example 4 is the tetradecylphosphonic acid modified electrolyte (PP / PE / PLA / CMC + 35 μL TDPA) of Example 3.

[0079] 1. Cathode preparation:

[0080] Raw material preparation: Prepare vanadium oxyphosphate cathodes doped with 0.5%, 5%, and 10% molar amounts of aluminum, respectively.

[0081] Electrode preparation: Prepare the cathode according to the steps of Example 1.

[0082] 2. Anode preparation: The same as Example 1.

[0083] 3. Battery assembly and testing:

[0084] Assembly: Assemble the battery using cathodes with different doping amounts.

[0085] Performance testing: Compare the charge-discharge performance of different batteries, including capacity, cycle stability, etc. Among them, the performance of the vanadium oxyphosphate cathode with 5% aluminum doping is the best. For example, Figure 6 . The detection conditions are: 26 °C, 0.1 A / g -1 . The conclusion is: Initially, the battery with 5% doping has the highest specific capacity, about 140 mAh / g. As the number of cycles increases, all curves show a certain degree of downward trend. The specific capacity of the battery with 5% doping is relatively stable. When the number of cycles reaches 500, the specific capacity still remains at about 130 mA h / g. The initial specific capacities of the batteries with 10%, 0.5%, and undoped are close. During the cycling process, the specific capacity of the battery with 10% doping is slightly higher than that of the batteries with 0.5% doping and undoped. The decrease in the specific capacity of the undoped battery is relatively obvious. The specific capacity is about 105 mAh / g after 500 cycles.

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 1 is that: polylactic acid was not added to the raw materials for electrolyte preparation, and it was only PP-PE 1 g and CMC. Other operations are the same as in Example 1, and a PP-PE electrolyte was prepared.

[0088] The ionic conductivity of the polyethylene-polypropylene copolymer electrolyte prepared in Comparative Example 1 is 7.5 mS / cm.

[0089] To further study the effect of the introduction of PLA on the ionic conductivity of PP-PE, different gel electrolytes were tested by electrochemical impedance spectroscopy, such as Figure 1 and 2As shown. The results show that adding PLA can make the pore structure inside the electrolyte more regular and continuous, provide a low-resistance path for ion migration, reduce the hindrance during ion transport, and thus improve the ionic conductivity.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A zinc-ion battery with a degradable gel electrolyte, characterized in that: The electrolyte in the zinc-ion battery is a degradable gel electrolyte, and the cathode material is vanadium oxyphosphate doped with aluminum; Among them, the raw material components of the degradable gel electrolyte include a gel with good chemical stability and mechanical properties, and also include a degradable polymer; the gel with chemical stability and mechanical properties is a polyethylene-polypropylene copolymer; the degradable polymer is polylactic acid and carboxymethyl cellulose.

2. The zinc ion battery with a degradable gel electrolyte according to claim 1, characterized in that: The mass ratio of the gel with good chemical stability and mechanical properties to the degradable polymer is 6-9:1-4.

3. The zinc-ion battery with a degradable gel electrolyte according to claim 1, characterized in that: The mass ratio of polylactic acid to carboxymethyl cellulose is 1:

1.

4. The zinc ion battery with the degradable gel electrolyte according to claim 1, characterized in that: The degradable gel electrolyte also includes an organic phosphonic acid; the organic phosphonic acid is one of hydroxyethylidene diphosphonic acid, 1-hydroxyphosphonoacetic acid, phenylphosphonic acid, and tetradecylphosphonic acid.

5. The zinc-ion battery with the degradable gel electrolyte according to claim 4, characterized in that: The preparation method of the degradable gel electrolyte is: adding a polyethylene-polypropylene copolymer, polylactic acid, and carboxymethyl cellulose into dimethyl sulfoxide and stirring at high speed to form a homogeneous mixture, then adding an organic phosphonic acid, and under the condition of a water bath, adding a cross-linking agent and continuously stirring to cause the mixture to undergo chemical polymerization to form a network-type gel electrolyte, and then pouring the mixture into a mold and drying to obtain a gel electrolyte material.

6. The zinc ion battery with the degradable gel electrolyte according to claim 5, characterized in that: The mass ratio of the addition amount of the organic phosphonic acid to the polyethylene-polypropylene copolymer is 0.00025-0.0004:

1.

7. The zinc ion battery with the degradable gel electrolyte according to claim 5, characterized in that: The cross-linking agent is dicumyl peroxide (DCP).

8. The zinc ion battery with a degradable gel electrolyte according to claim 1, characterized in that: The molar doping amount of aluminum in vanadium oxyphosphate doped with aluminum is 0.5-10%.

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