Gel electrolyte precursor, gel electrolyte and preparation method and application thereof

Abstract

The invention discloses a gel electrolyte precursor, a gel electrolyte and a preparation method and application thereof. The invention provides a gel electrolyte precursor which comprises the following raw materials: 1-40 parts of zinc salt, 5-50 parts of a gel monomer and 0.5-5 parts of a carbon-doped material, and the gel monomer is a monomer capable of cross-linking to form a three-dimensional network under a photo-initiation condition; the carbon-doped material is subjected to modification treatment, and the modification mode comprises oxidation and / or acidification. The gel electrolyte is prepared by adopting an irradiation method, and the gel and the carbon material are covalently crosslinked under high-energy rays to form a special ion channel, so that the conductivity and the mechanical strength of the gel electrolyte are improved, and the cycle life of the zinc ion battery is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to a gel electrolyte precursor, a gel electrolyte and a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand for flexible electronic devices and safe energy storage, aqueous zinc-ion batteries have become a research hotspot in emerging energy storage technologies due to their high safety, low cost and environmental friendliness. However, traditional liquid zinc-ion batteries have problems such as uncontrollable growth of zinc dendrites, hydrogen evolution corrosion and electrolyte leakage, which seriously restrict their cycle life and safety.

[0003] Gel electrolytes can solve the problems of leakage risk and dendrite by solidifying the liquid electrolyte into a three-dimensional network structure. However, existing zinc-based gel electrolytes face key challenges: insufficient ionic conductivity (usually < 150 mS / cm), which makes it difficult to meet high rate requirements; weak mechanical strength, which cannot effectively inhibit zinc dendrite penetration; poor interface compatibility, which leads to the decay of coulombic efficiency due to the side reaction at the zinc anode / electrolyte interface.

[0004] Current gel electrolyte preparation relies on chemical initiation polymerization (such as ammonium persulfate initiation of acrylic acid crosslinking), which requires the introduction of initiator residues, exacerbating zinc corrosion; while thermal curing method causes electrolyte decomposition due to high temperature. Both of them are difficult to achieve zinc ion transmission channels with molecular-level uniform dispersion.

[0005] Therefore, it is necessary to develop a zinc-based gel electrolyte with high ionic conductivity, excellent mechanical properties and good interface stability to improve the cycle life and safety of aqueous zinc-ion batteries. SUMMARY

[0006] The technical problem to be solved by the present application is that the existing gel electrolyte for aqueous zinc-ion batteries has low ionic conductivity, insufficient mechanical strength and poor interface stability, and the preparation process of the existing gel electrolyte requires the introduction of chemical initiators or high-temperature curing, which leads to side reactions and electrolyte decomposition. The present application provides a gel electrolyte precursor, a gel electrolyte and a preparation method and application thereof. The present application provides a new idea for breaking through the above bottleneck through radiation preparation technology and the doping of carbon materials: radiation preparation technology triggers the polymerization and crosslinking reaction of monomers at room temperature through gamma rays or electron beams, without the need for external chemical initiators, thereby avoiding the corrosion and poisoning risk of zinc anode caused by thermal damage and initiator residues; the introduction of carbon materials not only can significantly improve the ionic conductivity of the gel electrolyte (up to more than 200 mS / cm), but also can enhance its mechanical strength and improve the cycle life of zinc-ion batteries.

[0007] In the field, it is generally believed that the direct introduction of carbon materials with high conductivity (such as graphene, carbon nanotubes, etc.) into the electrolyte system will form an electron conduction path, thus causing internal short circuit of the battery, so researchers generally avoid directly adding carbon materials in the electrolyte, and only use them in the electrode or conductive agent system.

[0008] However, the present application overcomes this technical prejudice. The gel electrolyte prepared by irradiation cross-linking will not cause short circuit problem after introducing carbon-doped materials, and the carbon materials will form new ion channels with the gel monomers to improve the ionic conductivity. The present application overcomes the above problems by the following mechanism:

[0009] (1) Covalent bond anchoring and uniform dispersion mechanism:

[0010] In the traditional method, conductive carbon materials (such as graphene, carbon nanotubes) are prone to agglomeration, forming macroscopic conductive aggregates. These aggregates will form a continuous electron path between the positive and negative electrodes, causing internal short circuit of the battery.

[0011] In the irradiation cross-linking process of the present application, the carbon materials are pre-treated on the surface to make the surface rich in active groups (such as carboxyl, hydroxyl) that can react with the gel monomers. Under the action of irradiation (such as gamma rays, electron beam), these active groups will form a firm covalent bond with the gel polymer chain that is being polymerized or cross-linked. This process is equivalent to "anchoring" the carbon materials in the three-dimensional network structure of the gel through chemical bonds, greatly inhibiting their migration and agglomeration tendency, achieving uniform and stable dispersion at the molecular level. The carbon materials are isolated and wrapped by the polymer chain and cannot contact each other to form an electron conduction path throughout the electrolyte.

[0012] (2) "Insulating wrapping" effect:

[0013] Even if the carbon materials are uniformly dispersed, their exposed surfaces may still directly contact with high-activity electrodes such as lithium metal negative electrode, causing local short circuit.

[0014] In the present application, through irradiation cross-linking, a dense and continuous polymer insulating layer is formed around the carbon materials by the gel electrolyte monomers in situ. This polymer is like a "insulating coat" for each carbon nanometer unit. When the electrolyte membrane contacts with the electrode, it is the insulating gel layer that contacts with the electrode, not the conductive carbon material core. Therefore, electrons cannot directly jump from the electrode to the carbon material, effectively blocking the micro-short circuit path.

[0015] (3) Construction of three-dimensional ion / electron isolation channel:

[0016] It is a common view that the introduction of conductive materials will establish electronic channels. The present application ingeniously utilizes the high specific surface area and special morphology of carbon materials (especially two-dimensional graphene or one-dimensional carbon nanotubes). After being covalently anchored and uniformly dispersed, these carbon materials form a large number of stable heterogeneous interfaces with the gel polymer chains. These interfaces have a strong ability to adsorb electrolyte and guide the directional migration of zinc ions (Zn 2 ⁺). The carbon material itself is responsible for providing a fast electron conduction path, while the insulating gel layer wrapped around its surface and the adsorbed liquid electrolyte are responsible for ion transport. In this way, a unique parallel channel of "internal electron conduction, external ion conduction" is formed at the microscale. The electrons are confined within the carbon material and within the limited range of its polymer bonding, and cannot jump to the ion channel, thereby achieving the improvement of ionic conductivity while ensuring electronic insulation.

[0017] In addition, the present application enhances the mechanical strength and interface stability of the gel electrolyte through the following mechanisms:

[0018] When the mechanical strength of the gel electrolyte is insufficient, it is easily pierced by lithium dendrites during battery cycling, leading to physical short circuits. In the present application, carbon materials (especially nanofibers or sheet layers) act as nanoreinforcers and are covalently bonded to the polymer matrix, significantly improving the mechanical strength and toughness (modulus and puncture resistance) of the cross-linked gel electrolyte. This enhanced "rigid" network can effectively inhibit the growth and penetration of lithium dendrites. At the same time, the stable three-dimensional structure also ensures the long-term physical stability of the interface between the electrolyte and the electrode, avoiding the risk of short circuits due to interface damage.

[0019] The principle of the irradiation method used in the present application is to use the energy of high-energy rays to ionize water molecules in the entire solution at almost the same time to obtain various free radicals. The free radicals will attack the double bonds of the gel monomers, thereby initiating a chain reaction. Under the action of high-energy rays, the hydroxyl, carboxyl and other groups on the surface of the carbon material will also participate in the reaction and form covalent bonds with the gel monomers.

[0020] The present application solves the above technical problems through the following technical solutions:

[0021] The present application provides a gel electrolyte precursor, which comprises the following raw materials in parts by weight:

[0022] Zinc salt: 1-40 parts,

[0023] Gel monomer: 5-50 parts,

[0024] Carbon-doped material: 0.5-5 parts,

[0025] The gel monomer is a monomer that can be cross-linked to form a three-dimensional network under light initiation conditions;

[0026] The carbon-doped material is modified, and the modification includes oxidation and / or acidification.

[0027] In the present application, the carbon-doped material includes carbon material and / or carbon-containing composite material; preferably, the carbon material is selected from one or more of natural graphite, graphene, carbon nanotube, conductive carbon black, carbon fiber, and activated carbon; and the carbon-containing composite material is selected from one or more of silicon-carbon composite material, titanium-based carbon composite material, metal oxide-carbon composite material, and sulfide-carbon composite material.

[0028] In the present application, the modification includes that the carbon-doped material is reacted under the action of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of the concentrated nitric acid to the concentrated sulfuric acid can be (1-3):1, for example, 2:1; the reaction temperature can be 80-120℃; and the reaction time can be 4-8 hours.

[0029] In the present application, the concentrated nitric acid generally refers to nitric acid with a mass fraction of 65-68 wt%, and the concentrated sulfuric acid generally refers to sulfuric acid with a mass fraction of 95-98 wt%.

[0030] In the present application, the carbon material raw material needs to be further modified (oxidized or acidified) before use, i.e. the carbon material itself is provided with hydroxyl or carboxyl groups, so as to covalently cross-link the gel and the carbon material in the irradiation environment, and lay a foundation for forming special ion channels.

[0031] In the present application, the zinc salt can be selected from one or more of zinc sulfate, zinc nitrate, zinc chloride, zinc triflate, zinc acetate, zinc perchlorate, zinc bis(trifluoromethylsulfonyl)imide, zinc borate, and zinc phosphate, preferably zinc sulfate, zinc nitrate, zinc acetate, or zinc chloride, and more preferably zinc nitrate.

[0032] In the present application, the weight fraction of the zinc salt can be 5-25 parts, preferably 10-20 parts, for example, 10 parts, 12 parts, or 15 parts, and more preferably 10-17 parts, for example, 12-15 parts.

[0033] In the present application, the gel monomer comprises one or more of a hydrophilic monomer, a carboxyl-containing monomer, a sulfonic acid group-containing monomer, a zinc complexing monomer, and a hydroxyl group-containing monomer; preferably, the hydrophilic monomer is selected from one or more of acrylamide, 2-hydroxyethyl methacrylate, N-vinyl pyrrolidone, and N-isopropyl acrylamide; the carboxyl-containing monomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, and maleic anhydride; the sulfonic acid group-containing monomer is selected from one or both of sodium acrylsulfonate and sodium styrene sulfonate; the zinc complexing monomer is selected from one or more of a polyvinyl alcohol derivative, a precursor of a zinc complex of polyacrylic acid, and polyethylene glycol diacrylate; the hydroxyl group-containing monomer is selected from one or more of polyethylene glycol methacrylate, glycerol monomethacrylate, and 2-hydroxyethyl acrylate; and the gel monomer is preferably a mixture of acrylic acid and acrylamide, sodium acrylate, a mixture of methacrylic acid and glycerol monomethacrylate, or a mixture of sodium styrene sulfonate and methacrylic acid; and more preferably a mixture of acrylamide and acrylic acid, such as a mixture of acrylamide and acrylic acid in a mass ratio of (2-4):(1-3).

[0034] The known material "precursor of a complex of polyacrylic acid (PAA) and zinc ions (Zn²⁺)" generally refers to an initial compound or a mixed system used in a reaction or preparation before a final zinc complex or zinc polyacrylate polymer is formed.

[0035] In the present application, the gel monomer can be in a weight fraction of 15-40 parts, preferably 20-25 parts, such as 20 parts, 25 parts, or 30 parts.

[0036] In the present application, the carbon-doped material can be graphene, carbon nanotubes, a mixture of conductive carbon black and carbon nanotubes, a mixture of activated carbon and graphene, or a mixture of activated carbon and short carbon fibers.

[0037] In the present application, the carbon-doped material can be in a weight fraction of 1-5 parts, preferably 1 part, 2 parts, or 3 parts.

[0038] In the present application, the gel electrolyte precursor is dissolved in water to be used in the form of a gel electrolyte solution, and the total weight fraction of the gel electrolyte precursor and the water is 100 parts.

[0039] In the present application, the gel electrolyte precursor can comprise the following raw materials in the following weight fractions:

[0040] Zinc salt: 10-20 parts;

[0041] Gel monomer: 20-30 parts;

[0042] Carbon-doped material: 1-5 parts;

[0043] Preferably, the zinc salt is selected from one or more of zinc sulfate, zinc nitrate, zinc acetate and zinc chloride, for example zinc nitrate; the gel monomer is selected from one or more of acrylic acid, acrylamide, sodium acrylate, methacrylic acid, glycerol monomethacrylate and sodium styrene sulfonate, for example a mixture of acrylamide and acrylic acid; and the carbon-doped material is selected from one or more of graphene, carbon nanotubes, conductive carbon black, activated carbon and short carbon fibers, for example carbon nanotubes.

[0044] In the present application, the gel electrolyte precursor can comprise the following raw materials in any one of the following proportions by weight:

[0045] (1) 15 parts of zinc nitrate, 15 parts of acrylamide, 10 parts of acrylic acid and 3 parts of carbon nanotubes;

[0046] (2) 10 parts of zinc sulfate, 25 parts of acrylic acid and 1 part of graphene;

[0047] (3) 12 parts of zinc sulfate, 25 parts of sodium acrylate, 1 part of conductive carbon black and 1 part of carbon nanotubes;

[0048] (4) 10 parts of zinc acetate, 15 parts of methacrylic acid, 5 parts of glycerol monomethacrylate, 1 part of activated carbon and 1 part of graphene;

[0049] (5) 10 parts of zinc chloride, 5 parts of sodium styrene sulfonate, 15 parts of methacrylic acid, 1 part of activated carbon and 2 parts of short carbon fibers.

[0050] The present application also provides a gel electrolyte prepared from an aqueous solution of the gel electrolyte precursor as described above under conditions in which the oxygen concentration is less than 5% by means of irradiation, the dose of which is 20-200 kGy and the dose absorption rate of which is 1-10 kGy / h.

[0051] In the present application, the dose of the irradiation can be 20-100 kGy, preferably 30-90 kGy, for example 40 kGy, 50 kGy, 60 kGy or 80 kGy; and the dose absorption rate of the irradiation can be 5-10 kGy / h, for example 5 kGy / h or 8 kGy / h.

[0052] The present application also provides a method for preparing a gel electrolyte as described above, characterized in that it comprises the following steps: irradiating an aqueous solution of the gel electrolyte precursor as described above under conditions in which the oxygen concentration is less than 5%, thereby obtaining the gel electrolyte; and the dose and dose absorption rate of the irradiation are as described above.

[0053] In the present application, the stirring speed of the aqueous solution of the gel electrolyte precursor can be 200-1000 rpm, preferably 500 rpm.

[0054] In the present application, the mixing time of the aqueous solution of the gel electrolyte precursor can be 30-120 minutes, preferably 60 minutes.

[0055] In the present application, the oxygen concentration is controlled to be below 5% during the irradiation process, preferably below 1%.

[0056] In the present application, the irradiation reaction can use gamma ray irradiation, and the gamma ray is preferably Co-60 gamma ray.

[0057] The present application also provides a use of the gel electrolyte as described above in the preparation of a zinc ion battery.

[0058] Without departing from the common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining various preferred examples of the present application.

[0059] The reagents and raw materials used in the present application are commercially available.

[0060] The positive progress effect of the present application is that:

[0061] The present application realizes efficient zinc ion transmission and dual stability of the negative electrode interface by constructing a gel network containing zinc coordination groups (such as acrylic acid-Zn2+ coordination bond) in situ under oxygen-free conditions through high-energy ray, combining the double-layer ion enrichment effect and pseudo-capacitance effect of carbon-doped materials (such as activated carbon / porous carbon / amorphous carbon).

[0062] The present application uses irradiation method to prepare gel electrolyte, and the irradiation method can regulate the polymerization process by regulating the irradiation dose and dose rate. The experimental process is green and environmentally friendly, and the whole process is easy to be scaled up.

[0063] The gel electrolyte of the present application is blended with carbon-doped materials and gel monomers and zinc ion solution, and is polymerized under high-energy ray. The gel and carbon materials are covalently crosslinked under high-energy ray, forming special ion channels, which improves the conductivity, mechanical strength of the gel electrolyte and the cycle life of the zinc ion battery. The carbon material and the gel are no longer simply physically adsorbed, because of the action of covalent bond, the mechanical properties of the gel are further improved. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 It is a schematic diagram of the preparation process of the gel electrolyte.

[0065] Figure 2 It is a schematic diagram of preparing the gel electrolyte into dumbbell shape during the tensile elongation test. DETAILED DESCRIPTION

[0066] The application will be further described in the following examples without limiting the application to the examples described. The experimental methods in the following examples, unless otherwise specified, are selected according to the conventional methods and conditions, or according to the commercial instructions.

[0067] In the following examples, the multi-walled carbon nanotubes used were provided by Yifeng Technology Carbon Nanotube Factory, the carbon nanotubes used were multi-walled carbon nanotubes (MWCNTs) with a particle size of 30-80 nm; the graphite was provided by Sigma-Aldrich Company, the graphite used was flake graphite with an average particle size of 500 μm. The remaining raw materials were provided by Sinopharm Chemical Reagent Co., Ltd.

[0068] The carbon-doped materials (including but not limited to graphene, carbon nanotubes, acetylene black, etc.) are subjected to the following nitric acid acidification pretreatment before being used to prepare gel electrolytes, so as to introduce oxygen-containing functional groups on the surface thereof.

[0069] Acidification treatment: a certain amount of original carbon material is placed in a round-bottom flask, and an excess amount (40-60 times the mass of the carbon material) of concentrated nitric acid (concentration: 65%-68%) is poured. In order to promote the reaction, a certain volume of concentrated sulfuric acid is added at the same time (the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 2:1), forming a mixed acid system to enhance the oxidation effect.

[0070] Reflux reaction: the above-mentioned mixed system is placed on a heating magnetic stirrer, and a condenser tube is installed for reflux. Under continuous stirring, the reaction is carried out at a temperature of 80-120°C for 4-8 hours. This process can enable nitric acid molecules to embed and etch the structural defects and ends of the carbon material, so as to connect polar functional groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH) on the surface and edges thereof.

[0071] Washing and filtering: after the reaction is completed, the system is naturally cooled to room temperature, and a large amount of deionized water is used to repeatedly dilute and suction filter the mixture until the pH value of the filtrate approaches neutrality (about 6.5-7.5) to ensure that the residual acid liquid is completely removed.

[0072] Drying: the filter cake after washing is transferred to a vacuum drying oven, and dried at 60-80°C for 12-24 hours to obtain a functionalized carbon material powder.

[0073] Grinding and storage: the blocky material after drying is gently ground into a uniform powder in an agate mortar, and sealed and stored in a desiccator for use.

[0074] The mass percentage of each component in the gel electrolyte precursor mixture of the examples and comparative examples in the application and the irradiation conditions are shown in Table 1. The short-cut carbon fibers in Table 1 are 0.1 mm glue-free carbon fibers.

[0075] Table 1

[0076]

[0077] Example 1

[0078] A gel electrolyte, whose formulation is shown in Table 1, is prepared by the following method:

[0079] (1) Preparation of gel electrolyte precursor mixture:

[0080] Dissolve the zinc salt in deionized water, and stir until completely dissolved to form a zinc salt solution.

[0081] Add the gel monomer to the zinc salt solution, and stir for 30 minutes at a stirring speed of 500 rpm until uniform.

[0082] Add the carbon-doped material, and ultrasonically shake for 15 minutes to ensure uniform dispersion, to obtain the gel electrolyte precursor mixture.

[0083] (2) Preparation of gel electrolyte:

[0084] Transfer the above gel electrolyte precursor mixture into a sealed reactor, and introduce nitrogen gas at a flow rate of 200 mL / min for 5 minutes to remove oxygen, so as to ensure that the oxygen concentration is less than 5%, which is determined by a DK-190 headspace gas analyzer (Jinan Sai Cheng).

[0085] Use Co-60 γ rays for irradiation, with an absorbed dose of 40 kGy and an absorbed dose rate of 8 kGy / h.

[0086] The gel electrolyte is obtained.

[0087] Example 2

[0088] A gel electrolyte, whose formulation is shown in Table 1, is prepared by the same process as in Example 1, except that the irradiation condition is that Co-60 γ rays are used for irradiation, with an absorbed dose of 60 kGy and an absorbed dose rate of 5 kGy / h.

[0089] Example 3

[0090] A gel electrolyte, whose formulation is shown in Table 1, is prepared by the same process as in Example 1, except that the irradiation condition is that Co-60 γ rays are used for irradiation, with an absorbed dose of 50 kGy and an absorbed dose rate of 5 kGy / h.

[0091] Example 4

[0092] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that the irradiation condition was using Co-60 γ-ray irradiation with an absorbed dose of 80 kGy and a dose rate of 5 kGy / h.

[0093] Example 5

[0094] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that the irradiation condition was using Co-60 γ-ray irradiation with an absorbed dose of 80 kGy and a dose rate of 5 kGy / h.

[0095] Comparative Example 1

[0096] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that the amount of carbon nanotubes was 0.1%, and the rest of the preparation steps and reaction environment control conditions were the same as Example 1.

[0097] Comparative Example 2

[0098] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that the amount of carbon nanotubes was 9%, and the rest of the preparation steps and reaction environment control conditions were the same as Example 1.

[0099] Comparative Example 3

[0100] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that no carbon-doped material was added, and the rest of the preparation steps and reaction environment control conditions were the same as Example 1.

[0101] Comparative Example 4

[0102] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that no zinc salt was added, and the rest of the preparation steps and reaction environment control conditions were the same as Example 1.

[0103] Comparative Example 5

[0104] A gel electrolyte, whose formulation is shown in Table 1, was prepared according to the same procedure as Example 1, except that the gel electrolyte was prepared under aerobic conditions, and the rest of the preparation steps and reaction environment control conditions were the same as Example 1. Due to the "oxygen inhibition" effect, the gel electrolyte was not formed, and the synthesis failed.

[0105] Effect Example

[0106] The electrolytes prepared in the working examples and comparative examples were tested for ion conductivity, compression mechanical strength, and maximum degree of stretching, and the electrolytes were prepared into zinc ion batteries, and the cycle life of the batteries was tested.

[0107] (1) Test method of ionic conductivity

[0108] Test instrument: Autolab electrochemical workstation.

[0109] Test procedure: Two-electrode EIS was used to test the ionic conductivity of the gel electrolyte:

[0110] ① First, cut the gel electrolyte into a 2 x 2 cm square, with an area A = 4 cm 2 ; use a thickness gauge to test the thickness of the gel electrolyte, and record the thickness as T. Use two 0.1 mm x 2 cm x 6 cm thin steel sheets (316 steel) to sandwich the gel electrolyte, and then use an aluminum plastic film to package and fix it, forming a gel electrolyte blocking battery system.

[0111] ② Electrode connection: the working electrode (WE) is connected to a stainless steel sheet; the counter electrode / reference electrode: after connecting CE and RE with a short circuit head, they are connected together to another stainless steel sheet. Ensure that the electrode clamp only contacts the stainless steel sheet to avoid short circuiting between the clamps.

[0112] ③ Software operation steps: open the Nova software, create a new experiment; select the impedance spectrum (Impedance) measurement technique; mode selection two-electrode (2-electrode). In the settings interface, input the following parameters: start frequency 1 MHz, end frequency 0.1 Hz. AC amplitude 10 mV. Bias voltage 0 V, points / decade: 10. Condition settings: stability condition: select automatic stability. Delay time: 10 seconds.

[0113] ④ Import the data into the Zview software, find the intersection point of the high frequency part of the curve and the real axis (Z'), and the real axis value corresponding to this intersection point is the resistance value R of the gel electrolyte.

[0114] The conductivity (σ) was calculated from the obtained impedance spectrum using the following formula:

[0115]

[0116] In the formula, σ is the conductivity of the gel electrolyte, T, R and A represent the thickness, bulk resistance and test area of the polymer electrolyte, respectively.

[0117] (2) Test method of compression mechanical strength

[0118] Test instrument: universal testing machine.

[0119] Test procedure: The gel electrolyte was made into a cylinder (diameter 15 mm, height 10 mm); the upper and lower end faces were flat and parallel, with no obvious bubbles or defects. The upper and lower platens were hardened and parallel to within 0.01 mm. Test mode: compression (single cycle). Speed: 5 mm / min (common for soft gels). Target displacement / strain: compression to 50% strain (5 mm). max =F max / A0, where σ max : compressive strength (MPa); F max : the maximum compression force (N) measured during the test; A0: the original cross-sectional area in the direction of compression (mm2), 47.1 mm2.

[0120] (3) Test method for tensile elongation at break

[0121] Test instrument: universal testing machine (NETZSCH TG 209 F3 Tarsus).

[0122] Test procedure: The gel electrolyte was made into a dumbbell shape (as shown in Figure 2 ), and clamped on both sides of the fixture. A special flat clamp face for soft materials was installed, and the clamping surface could be padded with thin paper / PE film to prevent slipping and damage. The test speed was set to 5-10 mm / min; the initial gauge length was 20 mm. The elongation at break ε = (L b -L0) / L0 x 100%. L0 was the initial length, 25 mm; L b was the length at the moment of breakage.

[0123] (4) Test method for cycle life of zinc ion battery

[0124] Test instrument: Wuhan Lan electric test system.

[0125] Steps for preparing the electrolyte into a zinc ion battery: The positive electrode sheet (zinc sheet) of vanadium pentoxide steel foil substrate was cut into a 2x2 cm square sheet, then the nickel tab was adhered to the positive electrode sheet steel surface (zinc sheet) with a polyimide tape, to obtain the positive electrode (negative electrode) of the battery. The gel electrolyte was cut into a 2x2 cm square sheet and combined with the positive and negative electrodes to form a sandwich structure. Finally, the gel battery was packaged with an aluminum plastic film.

[0126] Test procedure: The positive and negative electrodes of the gel battery were clamped onto the corresponding clamps of the Wuhan Lan electric test system, and the settings were 20 min per cycle, a safety voltage of 2.5V-0.4V, and a current of 0.1 mA / cm 2Constant current charge and discharge, cycle number is set to 65000 times. Single discharge time is greater than or equal to 10 min or voltage is less than or equal to 1.1V, enter the charging condition, when the charging time is greater than or equal to 10 min or the voltage is higher than or equal to 1.8V, enter the next condition. If Ea changes with temperature is not obvious (linear Arrhenius behavior), and the value is higher (Ea>0.3), it shows that ion migration depends on polymer chain segment movement, which is consistent with the characteristics of solid state.

[0127] (5) The test results are shown in Table 2:

[0128] Table 2

[0129]

[0130] From Table 2, it can be seen that the gel electrolyte of Examples 1-5 has high ion conductivity, compression mechanical strength and tensile elongation at break, and the zinc ion battery prepared has long cycle life. Comparative Examples 1-3 show that the amount of carbon-doped material plays an important role in the good performance of the gel electrolyte. Comparative Example 4 does not add zinc salt, and the ion conductivity of the gel electrolyte is low, which needs to be adsorbed with electrolyte before use.

[0131] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A gel electrolyte precursor, characterized in that, The gel electrolyte precursor comprises the following raw materials in parts by weight: Zinc salt: 1-40 parts Gel monomer: 5-50 parts Carbon-doped material: 0.5-5 parts, The gel monomer is a monomer that can crosslink to form a three-dimensional network under photoinitiation conditions; The carbon-doped material is modified, and the modification methods include oxidation and / or acidification.

2. The gel electrolyte precursor as described in claim 1, characterized in that, The carbon-doped material includes carbon materials and / or carbon-containing composite materials; preferably, the carbon material is selected from one or more of the following: natural graphite, graphene, carbon nanotubes, conductive carbon black, carbon fiber, and activated carbon; the carbon-containing composite material is selected from one or more of the following: silicon-carbon composite materials, titanium-based and carbon composite materials, metal oxide and carbon composite materials, and sulfide and carbon composite materials. And / or, the modification method includes: the carbon doped material reacting under the action of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is (1~3):1, for example 2:1; the reaction temperature is 80~120℃; and the reaction time is 4~8 hours.

3. The gel electrolyte precursor as described in claim 1, characterized in that, It satisfies at least one of the following conditions: (1) The zinc salt is selected from one or more of zinc sulfate, zinc nitrate, zinc chloride, zinc trifluoromethanesulfonate, zinc acetate, zinc perchlorate, zinc bis(trifluoromethanesulfonyl)imide, zinc borate and zinc phosphate, preferably zinc sulfate, zinc nitrate, zinc acetate or zinc chloride, more preferably zinc nitrate; (2) The zinc salt is 5-25 parts by weight, preferably 10-20 parts, for example 10 parts, 12 parts or 15 parts, more preferably 10-17 parts, for example 12-15 parts; (3) The gel monomer includes one or more of hydrophilic monomers, carboxyl-containing monomers, sulfonic acid-containing monomers, zinc coordination monomers, and hydroxyl monomers; preferably, the hydrophilic monomer is selected from one or more of acrylamide, 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, and N-isopropylacrylamide; the carboxyl-containing monomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, and maleic anhydride; the sulfonic acid-containing monomer is selected from one or two of sodium propylene sulfonate and sodium styrene sulfonate; the zinc coordination monomer is selected from one or more of polyvinyl alcohol derivatives, precursors of polyacrylic acid and zinc complexes, and polyethylene glycol diacrylate; the hydroxyl monomer is selected from one or more of polyethylene glycol methacrylate, glycerol monomethacrylate, and 2-hydroxyethyl acrylate; the gel monomer is preferably a mixture of acrylic acid, acrylamide, and acrylic acid, sodium acrylate, methacrylic acid, and glycerol monomethacrylate, or a mixture of sodium styrene sulfonate and methacrylic acid; the gel monomer is more preferably a mixture of acrylamide and acrylic acid, for example, a mixture of acrylamide and acrylic acid in a mass ratio of (2-4):(1-3); (4) The weight of the gel monomer is 15-40 parts, preferably 20-25 parts, for example 20 parts, 25 parts or 30 parts; (5) The carbon doped material is graphene, carbon nanotubes, a mixture of conductive carbon black and carbon nanotubes, a mixture of activated carbon and graphene, or a mixture of activated carbon and chopped carbon fibers. (6) The carbon-doped material is 1-5 parts by weight, preferably 1 part, 2 parts or 3 parts; (7) The gel electrolyte precursor is dissolved in water and used in the form of a gel electrolyte solution, wherein the total weight of the gel electrolyte precursor and the water is 100 parts.

4. The gel electrolyte precursor as described in claim 1, characterized in that, The gel electrolyte precursor comprises the following raw materials in parts by weight: Zinc salt: 10-20 parts; Gel monomer: 20-30 parts; Carbon-doped material: 1-5 parts; Preferably, the zinc salt is selected from one or more of zinc sulfate, zinc nitrate, zinc acetate, and zinc chloride, such as zinc nitrate; the gel monomer is selected from one or more of acrylic acid, acrylamide, sodium acrylate, methacrylic acid, glycerol monomethacrylate, and sodium styrene sulfonate, such as a mixture of acrylamide and acrylic acid; the carbon doping material is selected from one or more of graphene, carbon nanotubes, conductive carbon black, activated carbon, and chopped carbon fibers, such as carbon nanotubes.

5. The gel electrolyte precursor as described in claim 1, characterized in that, The gel electrolyte precursor comprises any of the following raw materials in parts by weight: (1) 15 parts zinc nitrate, 15 parts acrylamide, 10 parts acrylic acid and 3 parts carbon nanotubes; (2) 10 parts zinc sulfate, 25 parts acrylic acid and 1 part graphene; (3) 12 parts zinc sulfate, 25 parts sodium acrylate, 1 part conductive carbon black and 1 part carbon nanotubes; (4) 10 parts zinc acetate, 15 parts methacrylic acid, 5 parts glycerol monomethacrylate, 1 part activated carbon and 1 part graphene; (5) 10 parts zinc chloride, 5 parts sodium styrene sulfonate, 15 parts methacrylic acid, 1 part activated carbon and 2 parts short-cut carbon fiber.

6. A gel electrolyte, characterized in that, It is prepared by irradiation of an aqueous solution of the gel electrolyte precursor as described in any one of claims 1 to 5 under conditions of oxygen concentration below 5%, wherein the irradiation dose is 20-200 kGy and the irradiation dose absorption rate is 1-10 kGy / h.

7. The gel electrolyte as described in claim 6, characterized in that, The irradiation dose is 20-100 kGy, preferably 30-90 kGy, such as 40 kGy, 50 kGy, 60 kGy or 80 kGy; the irradiation dose absorption rate is 5-10 kGy / h, such as 5 kGy / h or 8 kGy / h.

8. A method for preparing a gel electrolyte as described in claim 6 or 7, characterized in that, It includes the following steps: The aqueous solution of the gel electrolyte precursor as described in any one of claims 1-5 is irradiated under conditions where the oxygen concentration is less than 5% to obtain the product; the irradiation dose and dose absorption rate are as described in claim 6 or 7.

9. The method for preparing the gel electrolyte as described in claim 8, characterized in that, It satisfies at least one of the following conditions: (1) The stirring speed of the aqueous solution of the gel electrolyte precursor is 200-1000 rpm, preferably 500 rpm; (2) The mixing time of the aqueous solution of the gel electrolyte precursor is 30-120 minutes, preferably 60 minutes; (3) During the irradiation process, the oxygen concentration is controlled to be below 1%; (4) The irradiation reaction is carried out by γ-ray irradiation, preferably Co-60 γ-ray.

10. The use of a gel electrolyte as described in claim 6 or 7 in the preparation of a zinc-ion battery.

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