Zinc ion secondary battery without electrode structure and preparation method thereof

Abstract

The invention relates to a zinc ion secondary battery without an electrode structure and a preparation method thereof, and belongs to the technical field of zinc ion secondary batteries. The preparation method comprises the following steps: preparing an electrolyte containing zinc ions and manganese ions at the same time; assembling the battery in a manner that the positive current collector and the negative current collector are arranged on two sides and the electrolyte is arranged in the middle, and then packaging; the positive current collector and the negative current collector are conductive substrates; voltage or current is applied to the packaged battery, so that electrons of the zinc ions on the negative electrode side are reduced into elemental zinc and deposited on the negative electrode current collector, and electrons of the manganese ions on the positive electrode side are lost to form oxide and deposited on the positive electrode current collector, and the zinc ion secondary battery with the electrodeless structure is obtained. When the battery is assembled, no active material is loaded on the positive current collector and the negative current collector; the structure and the preparation process of the zinc ion battery can be remarkably simplified, and the material utilization rate is improved, so that the preparation cost of the device is effectively reduced, and popularization and application are promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of zinc ion secondary batteries, and more specifically, relates to a zinc ion secondary battery with an electrode-free structure and a preparation method thereof. Background Art

[0002] As a major branch of electrochemical energy storage technology, aqueous battery technology is widely used in military equipment, aerospace, consumer electronics, transportation and other fields, showing great application value in national defense and people's livelihood.

[0003] In recent years, the frequent occurrence of lithium battery safety accidents and the limitedness of material resources have led people to turn their research attention more to the field of intrinsically safe and low-cost aqueous batteries. Among them, zinc ion batteries using weakly acidic electrolytes have received extensive attention in the academic community due to their high theoretical specific capacity, moderate voltage output and excellent cycle stability. Due to the significant advantages in safety and cost, liquid / quasi-solid zinc ion batteries based on liquid / gel electrolytes have broad application prospects in large-scale static energy storage / flexible electronic devices. Currently, the typical structure of a zinc ion battery includes a zinc negative electrode and a positive electrode active material. Correspondingly, in the preparation process, it is necessary to first use processes such as hydrothermal-coating and electrodeposition to load the active material onto the current collector and then complete the device assembly, resulting in a cumbersome and complex device preparation process, which seriously hinders the application of zinc ion batteries. In recent years, it has been found that when manganese ions are added to the electrolyte of a zinc ion battery, an oxidation deposition reaction of manganese ions occurs during charging and provides capacity, which makes it possible for a zinc ion battery with a "cathode-free" structure (that is, no active material is loaded on the cathode during battery assembly, and then the active material is deposited in-situ). The invention patents with publication numbers CN116742158A, CN114614111A, and CN112599865A all relate to related concepts. The zinc ion battery based on the "cathode-free" structure avoids the complex material synthesis and loading processes before device assembly, greatly simplifying the preparation process. However, currently reported "cathode-free" zinc ion batteries all additionally use a zinc negative electrode during assembly, resulting in waste of the active material zinc. Moreover, due to the thermodynamic instability of zinc, side reactions such as hydrogen evolution and passivation will occur after the assembly of this zinc negative electrode-containing battery, and the shelf life is limited and the performance is unstable. Summary of the Invention

[0004] In view of the above deficiencies or improvement requirements of the prior art, the present invention provides a zinc-ion battery with an electrode-free structure and a preparation method thereof. In the battery of the present invention, the positive and negative active materials are simultaneously in-situ loaded onto the current collector by charging after assembly, which not only greatly simplifies the device preparation process but also avoids the additional use of a zinc negative electrode, thus saving materials. The assembled zinc-ion battery with an electrode-free structure of the present invention can be arbitrarily placed without side reactions such as hydrogen evolution and passivation, thereby solving the technical problems in the prior art that an additional zinc negative electrode is used during the assembly of zinc-ion batteries, resulting in waste of the active material zinc, and due to the thermodynamic instability of zinc, side reactions such as hydrogen evolution and passivation will occur after the assembly of this zinc-negative electrode-containing battery, and the shelf life is limited and the performance is unstable.

[0005] According to the first aspect of the present invention, there is provided a preparation method of a zinc-ion secondary battery with an electrode-free structure, comprising the following steps:

[0006] (1) Assemble a battery with the positive current collector and the negative current collector on both sides and the electrolyte in the middle. The electrolyte contains zinc ions and manganese ions, and then perform encapsulation; the positive current collector and the negative current collector are conductive substrates;

[0007] (2) Apply a voltage or current to the battery obtained by encapsulating in step (1), so that zinc ions on the negative electrode side gain electrons and are reduced to zinc metal and deposited on the negative current collector, and manganese ions on the positive electrode side lose electrons to form oxides and are deposited on the positive current collector, thus obtaining a zinc-ion secondary battery with an electrode-free structure.

[0008] Preferably, the electrolyte is a liquid electrolyte, and this liquid electrolyte is obtained by dissolving zinc salt and manganese salt in water;

[0009] Alternatively, the electrolyte is a gel electrolyte, and the gel electrolyte is obtained by a gel skeleton carrying a liquid electrolyte, and the liquid electrolyte is obtained by dissolving zinc salt and manganese salt in water.

[0010] Preferably, when the electrolyte is a liquid electrolyte, a separator is used to isolate the positive current collector and the negative current collector during battery assembly.

[0011] Preferably, the gel skeleton is selected from at least one of polyacrylamide gel, polyvinyl alcohol gel, and gelatin gel.

[0012] Preferably, the zinc salt is zinc sulfate, zinc acetate, or zinc trifluoromethanesulfonate.

[0013] Preferably, the manganese salt is manganese nitrate, manganese formate, or manganese chloride.

[0014] Preferably, the liquid electrolyte further contains sulfuric acid, potassium iodide, or ethanol.

[0015] Preferably, in the method for preparing the zinc ion secondary battery with an electrode-free structure, the magnitude of the current is 0.1 mA / cm 2 - 10 mA / cm 2 .

[0016] Preferably, the magnitude of the voltage is 1.5 V - 2.5 V.

[0017] According to another aspect of the present invention, there is provided a zinc ion secondary battery with an electrode-free structure prepared thereby.

[0018] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

[0019] (1) After the battery in the present invention is assembled, it can be arbitrarily placed. Because there is no electrode structure and no zinc negative electrode, side reactions such as hydrogen evolution and passivation will not occur, and the shelf life is longer and the performance is more stable.

[0020] (2) The present invention avoids the additional use of zinc negative electrodes in the battery and saves materials.

[0021] (3) Compared with the cases of zinc powder or electrodeposited zinc negative electrodes, etc., the electrode-free battery does not require a complex negative electrode preparation process. Compared with the cases of zinc foil negative electrodes, etc., the electrode-free battery can use a current collector with good flexibility, thereby improving the mechanical properties of the flexible battery.

[0022] (4) The electrode-free structure zinc ion battery of the present invention reduces the requirements for the current collector, making the selection of the current collector more diverse.

[0023] (5) The electrode-free structure zinc ion battery prepared by the present invention has great application prospects in the fields of static energy storage, flexible electronics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic cross-sectional view of an assembled zinc ion battery with an electrode-free structure.

[0025] Figure 2 is a schematic cross-sectional view of a zinc ion battery with an electrode-free structure when in-situ loading active materials.

[0026] Figure 3 is a process flow chart of the preparation process of a zinc ion battery with an electrode-free structure.

[0027] Figure 4 is a charge and discharge curve graph of the zinc ion battery prepared in Example 1.

[0028] Figure 5 is a cycle stability curve graph of the zinc ion battery prepared in Example 1.

[0029] In all the drawings, the same reference numerals are used to denote the same elements or structures, where:

[0030] Figure 1 and Figure 2 the meanings of the reference numerals in each drawing are as follows: 1 - positive current collector, 2 - electrolyte, 3 - negative current collector, 4 - positive active material, 5 - negative active material. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] A method for preparing a zinc-ion secondary battery with an electrode-free structure according to the present invention includes the following steps:

[0033] (1) Prepare an electrolyte containing zinc ions and manganese ions, which can be directly used as a liquid electrolyte according to the battery form or combined with a gel material to form a quasi-solid electrolyte; prepare positive and negative current collectors, which can directly select conductive substrates such as carbon cloth, or load conductive materials on the surface of any substrate to make parameters such as its conductivity and specific surface area meet the requirements;

[0034] (2) Assemble the battery. The method is to orderly combine the positive current collector, electrolyte, and negative current collector in a "sandwich" structure (the positive current collector and the negative current collector are on both sides, and the electrolyte is in the middle), so that the electrolyte is in good contact with the current collector, and the battery is encapsulated as needed. For liquid electrolytes, a separator is also required to isolate the positive and negative current collectors;

[0035] (3) Apply certain control signals such as current or voltage to the assembled battery to induce the in-situ deposition of active materials on the surfaces of the positive and negative current collectors, that is: the loading method of the positive and negative electrode active materials of the battery is in-situ loading on the current collector by "charging" after assembly, that is, zinc ions on the negative electrode side gain electrons and are reduced to zinc metal and deposited on the negative current collector, and manganese ions on the positive electrode side lose electrons to form oxides and are deposited on the positive current collector.

[0036] In some embodiments, the positive and negative current collectors are substrates with conductive surfaces, and there is no active material loading on the conductive surfaces during battery assembly. The substrate can be a single conductive material, such as carbon cloth, carbon paper, carbon felt, etc., or a "composite" material with a conductive material on its surface, such as paper with conductive carbon black loaded on its surface. The composite conductive materials include, but are not limited to, conductive agents such as carbon black, carbon nanotubes, and graphene. The substrate can be subjected to various treatments before use to adjust its physical and chemical properties such as conductivity, specific surface area, hydrophilicity, and hydrophobicity. The loading methods of the conductive materials include, but are not limited to, wet electrode processes, dry electrode processes, etc.

[0037] In some embodiments, the electrolyte uses water as the main solvent or plasticizer. The electrolyte contains zinc ions and manganese ions, and the concentration of each is not less than 0.01 mol / L. It can be dissociated from various zinc salts and manganese salts, such as zinc sulfate, zinc acetate, zinc trifluoromethanesulfonate, manganese nitrate, manganese formate, manganese chloride, etc. In addition to zinc salts and manganese salts, various additives can also be present in the electrolyte, such as sulfuric acid, potassium iodide, ethanol, etc. The electrolyte is in a liquid or gel state. The gel-state electrolyte is obtained by a gel skeleton carrying the electrolyte. The gel skeleton includes, but is not limited to, polyacrylamide gel, polyvinyl alcohol gel, gelatin gel, etc.

[0038] In some embodiments, the liquid electrolyte in step (1) is obtained by dissolving zinc salts, manganese salts, and additives, etc. in a solvent. The gel electrolyte is obtained by gelating the gel precursor and then soaking it in the liquid electrolyte or gelating the electrolyte solution containing the gel precursor. The gelation methods include, but are not limited to, thermal-initiated free radical polymerization, photo-initiated free radical polymerization, freeze-thaw, etc.

[0039] In some embodiments, the control signal can be a current signal, a voltage signal, or any combination of the two. The current signal and the voltage signal can be constant or variable. The current density calculated based on the effective working area of the battery is between 0.1 mA / cm 2 - 10 mA / cm 2 , and the voltage is between 1.5 V and 2.5 V.

[0040] A zinc-ion secondary battery with a non-electrode structure according to the present invention, the structure during battery assembly includes: (1) a positive current collector without active material loading during assembly; (2) a negative current collector without active material loading during assembly; (3) an electrolyte containing zinc ions and manganese ions.

[0041] The meaning of "non-electrode structure" in the present invention is that there is no active material loading on the positive and negative current collectors during battery assembly. The active material is a manganese-containing oxide for the positive electrode, such as MnO 2 , ZnxMn 3 O 7 etc.; for the negative electrode, it is zinc metal or an insertion / extraction type zinc storage material, such as MoO3 , BiOI, etc.

[0042] Such as Figure 1 As shown, the zinc-ion battery proposed by the present invention adopts an electrode-free structure design. It only requires that the positive electrode current collector 1 and the negative electrode current collector 3 have a conductive surface (the contact surface between the current collector and the electrolyte), and the electrolyte 2 contains zinc ions and manganese ions to assemble the device. Moreover, when assembling the device, there is no active material loaded on the positive and negative electrode current collectors. Compared with the prior art, the preparation process is simplified, the use of negative electrode active materials is saved, side reactions such as hydrogen evolution and passivation are avoided, and the shelf life and stability of the battery are improved.

[0043] Such as Figure 2 As shown, the loading method of the positive and negative electrode active materials of the zinc-ion battery proposed by the present invention is as follows: After assembly, certain current, voltage and other control signals are applied to the battery to in-situ deposit the active materials. During this process, manganese ions lose electrons and are oxidized to form oxides (i.e., the positive electrode active material 4) and deposit on the positive electrode current collector, and zinc ions gain electrons and are reduced to zinc atoms (i.e., the negative electrode active material 5) and deposit on the negative electrode current collector, thus completing the loading of the active materials and the preparation of the battery.

[0044] Such as Figure 3 As shown, the preparation method of the zinc-ion secondary battery with an electrode-free structure proposed by the present invention includes the following steps:

[0045] (a) Prepare an electrolyte containing zinc ions and manganese ions as described above, and directly use it as a liquid electrolyte according to the battery form or combine it with a gel material to form a quasi-solid electrolyte;

[0046] (b) Prepare the positive and negative electrode current collectors as described above. Conductive substrates such as carbon cloth can be directly selected, or conductive materials can be loaded on the surface of any substrate to make its conductivity, specific surface area and other parameters meet the requirements;

[0047] (c) Assemble the battery by orderly combining the positive electrode current collector, the electrolyte, and the negative electrode current collector in a "sandwich" structure, so that the electrolyte is in good contact with the current collector, and encapsulate the battery as needed. For liquid electrolytes, a separator is also required to isolate the positive and negative electrode current collectors;

[0048] (d) Apply certain current or voltage and other control signals to the assembled battery to induce the in-situ deposition of active materials on the surfaces of the positive and negative electrode current collectors, and complete the material loading and battery preparation.

[0049] The following are specific examples

[0050] Example 1

[0051] The preparation method of the zinc-ion secondary battery with an electrode-free structure of the present invention, and the preparation flow chart is as Figure 3 shown.

[0052] (1) Preparation of electrolyte: Weigh 10.9755 g of zinc acetate dihydrate and 12.2545 g of manganese acetate tetrahydrate and transfer them to a beaker. Then add deionized water to the beaker and make up the volume to 50 mL. Stir well until completely dissolved to obtain a liquid electrolyte containing 1 mol / L zinc ions and 1 mol / L manganese ions. Subsequently, weigh 2 g of acrylamide, 15 mg of potassium persulfate, and 2 mg of N,N'-methylenebisacrylamide and transfer them to a clean beaker. Add deionized water and make up the volume to 10 mL. Stir well until completely dissolved. Transfer the above solution to a mold and place it in an oven at 60 °C for 3 hours to obtain a polyacrylamide hydrogel. Immerse the prepared polyacrylamide hydrogel in the prepared liquid electrolyte for more than 12 hours to obtain a gel-state electrolyte containing zinc ions and manganese ions;

[0053] (2) Preparation of positive and negative current collectors: Directly use commercial graphite paper as the positive and negative current collectors, and clean and dry the graphite paper with ethanol and deionized water;

[0054] (3) Battery assembly: Stack the graphite paper, polyacrylamide gel electrolyte, and graphite paper vertically in a sandwich structure to obtain a battery with a non-electrode structure, as Figure 1 shown. Then use a thermoplastic sealing film to encapsulate the battery;

[0055] (4) Loading of active material: Use a Blue Power battery test system to charge the battery at a constant voltage of 1.9 V, and use a charging capacity of 0.125 mAh / cm 2 as the cut-off condition;

[0056] (5) Performance test: Perform constant current discharge on the above-prepared battery at a current density of 0.25 mA / cm 2 , and the voltage curve is as Figure 4 shown; According to the above charge-discharge regime (constant voltage charging at 1.9 V until the areal specific capacity reaches 0.125 mAh / cm 2 , constant current discharge at 0.25 mA / cm 2 until 0.1 V), perform 50 charge-discharge cycles on the battery, and the performance of the device is as Figure 5 shown.

[0057] Example 2

[0058] The preparation method of the zinc-ion secondary battery with a non-electrode structure of the present invention, and the preparation flow chart is as Figure 3 shown.

[0059] (1) Preparation of electrolyte: Weigh 4.3902 g of zinc acetate dihydrate, 4.9018 g of manganese acetate tetrahydrate and 2 g of gelatin and transfer them to a beaker. Then add deionized water to the beaker and make up the volume to 20 mL. Place the beaker in a water bath at 80 °C and stir well until the gelatin is completely dissolved to obtain a sol-state electrolyte containing 1 mol / L zinc ions and 1 mol / L manganese ions. Subsequently, transfer the above liquid to a mold and naturally cool it to solidify at room temperature to obtain a gelatin-based gel electrolyte containing zinc ions and manganese ions;

[0060] (2) Preparation of positive and negative current collectors: Use commercially available graphite paper modified with carbon nanotubes as the positive and negative current collectors. First, clean the graphite paper with ethanol and deionized water and dry it. Then weigh carbon nanotubes and polyvinylidene fluoride binder in a mass ratio of 9:1 and transfer them to a mortar. Add N-methylpyrrolidone and grind well. Subsequently, coat the carbon nanotube slurry on the surface of the graphite paper and dry it in an oven. The carbon nanotube loading is about 0.4 mg / cm 2 ;

[0061] (3) Battery assembly: Stack the carbon nanotube-coated graphite paper, gelatin-based gel electrolyte, and carbon nanotube-coated graphite paper vertically in a sandwich structure to obtain a battery with a non-electrode structure, as Figure 1 shown, and encapsulate the battery with a thermoplastic sealing film;

[0062] (4) Loading of active materials: Use a Blue Power battery test system to perform constant current charging on the battery at a current density of 0.25 mA / cm 2 , and set the cut-off voltage to 1.9 V.

[0063] Example 3

[0064] The preparation method of the zinc ion secondary battery with a non-electrode structure of the present invention, and the preparation flow chart is as Figure 3 shown.

[0065] (1) Preparation of electrolyte: Weigh 14.378 g of zinc sulfate heptahydrate and 8.451 g of manganese sulfate monohydrate and transfer them to a beaker. Then add deionized water to the beaker and make up the volume to 50 mL. Stir well until completely dissolved. Subsequently, add concentrated sulfuric acid dropwise to the solution and stir until pH = 1 to obtain an acidic liquid electrolyte containing approximately 1 mol / L zinc ions and 1 mol / L manganese ions;

[0066] (2) Preparation of positive and negative current collectors: Directly use commercially available carbon cloth as the positive and negative current collectors. Cut the carbon cloth into circular shapes with appropriate sizes, clean the carbon cloth with ethanol and deionized water and dry it. Then use an oxygen plasma cleaner to treat the carbon cloth for 5 minutes;

[0067] (3) Battery assembly: The button battery is assembled using the standard button battery assembly process. The button battery is assembled in the order of positive electrode case - carbon cloth - electrolyte - glass fiber separator - electrolyte - carbon cloth - gasket - negative electrode case, and then the battery is sealed using a hydraulic battery encapsulation machine;

[0068] (4) Active material loading: The battery is charged at a constant voltage of 2.2V using a Blue Power battery test system, and the charging capacity is set to 0.5 mAh / cm 2 .

[0069] (8) It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a zinc ion secondary battery without an electrode structure, characterized in that: The following steps are involved: (1) Assembling a battery in a manner where a positive electrode current collector and a negative electrode current collector are on both sides and an electrolyte is in the middle, wherein the electrolyte contains zinc ions and manganese ions, and then encapsulating; the positive electrode current collector and the negative electrode current collector are conductive substrates; (2) applying voltage or current to the battery packaged in step (1) so that the zinc ions on the negative electrode side gain electrons to be reduced to zinc element and deposited on the negative electrode current collector, and the manganese ions on the positive electrode side lose electrons to form oxides and deposited on the positive electrode current collector, thereby obtaining a zinc ion secondary battery without an electrode structure.

2. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 1, wherein: The electrolyte is a liquid electrolyte, which is obtained by dissolving zinc salt and manganese salt in water; Alternatively, the electrolyte is a gel electrolyte, the gel electrolyte is obtained by a gel skeleton carrying a liquid electrolyte, and the liquid electrolyte is obtained by dissolving zinc salt and manganese salt in water.

3. The preparation method of the zinc ion secondary battery without electrode structure as claimed in claim 2, characterized in that, When the electrolyte is a liquid electrolyte, a separator is used to isolate the positive electrode current collector from the negative electrode current collector when assembling the battery.

4. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 2, wherein: The gel skeleton is selected from at least one of polyacrylamide gel, polyvinyl alcohol gel and gelatin gel.

5. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 2, wherein: The zinc salt is zinc sulfate, zinc acetate or zinc trifluoromethanesulfonate.

6. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 2, wherein: The manganese salt is manganese nitrate, manganese formate or manganese chloride.

7. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 2, wherein: The liquid electrolyte also contains sulfuric acid, potassium iodide or ethanol.

8. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 1, wherein: The magnitude of the current is 0.1 mA / cm 2 -10mA / cm 2 .

9. The method for preparing a zinc ion secondary battery without an electrode structure as claimed in claim 1, wherein: The voltage is between 1.5V and 2.5V.

10. A zinc ion secondary battery without an electrode structure prepared by the method according to any one of claims 1 to 9.

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