A modified sodium alginate crosslinked hydrogel electrolyte, its preparation method and application

Abstract

This application relates to the field of hydrogel electrolyte technology, specifically disclosing a modified sodium alginate crosslinked hydrogel electrolyte, its preparation method, and its applications. This application reduces environmental toxicity and pollution by introducing modified sodium alginate as a crosslinking agent into the hydrogel electrolyte. The interaction between sodium alginate and zinc ions inhibits zinc dendrite formation, regulates the interfacial growth between the negative electrode and the electrolyte, and thus extends battery life; it also has a certain inhibitory effect on hydrogen evolution reaction. This application can prepare the modified sodium alginate crosslinked hydrogel electrolyte using a simple free radical polymerization method. Furthermore, compared to conventional aqueous batteries, the hydrogel electrolyte can better control the interfacial growth of the positive and negative electrodes.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydrogel electrolytes, in particular to a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method and application thereof. BACKGROUND

[0002] In order to improve the stability of the Zn anode, some strategies have been proposed, such as constructing an interfacial layer, adjusting the electrolyte, controlling the growth / deposition of specific crystal faces, etc. For example, Wang et al. used a highly conductive carbon fiber graphite felt (GF) as a current collector and electrodeposited zinc under constant voltage to manufacture a self-supporting Zn@GF negative electrode. The Zn@GF electrode has a large specific surface area, which can reduce the local current density and achieve dendrite-free behavior. Chen et al. prepared an Ag nanoparticle modified carbon cloth (AgNPs@CC). Due to the zinc affinity of Ag nanoparticles, the AgNPs@CC / Zn electrode exhibits lower overpotential and better cycle performance than the CC / Zn electrode. However, their expensive and complex preparation process often poses a major obstacle to practical application.

[0003] Aqueous zinc-ion batteries (AZIBs) are considered to be a promising candidate for lithium-ion batteries in large-scale energy storage due to their high safety, low cost and environmental friendliness. However, the poor stability of the zinc anode in a slightly acidic system limits the commercial application of AZIBs. The growth of zinc dendrites during zinc plating / de-zincing is a major obstacle to the development of high-stability Zn anodes. In particular, when the cycle capacity increases, zinc dendrites become extremely severe, leading to short circuits in the battery.

[0004] In addition, the hydrogen evolution reaction of zinc is thermodynamically feasible in commonly used electrolytes, such as 2M ZnSO4 weak acid electrolyte, and during the cycle process, the battery will generate a large amount of hydrogen gas, thereby destroying the battery structure and hindering the long cycle life of the battery. After the hydrogen evolution reaction occurs, the aggregation of OH-ions occurs, resulting in the precipitation of insoluble substances, causing corrosion and seriously affecting the coulombic efficiency.

[0005] Therefore, there is an urgent need for a hydrogel electrolyte that can inhibit zinc dendrites and hydrogen evolution reactions and has a simple preparation method. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art and provide a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method and application thereof.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a preparation method of a modified sodium alginate cross-linked hydrogel electrolyte, comprising the following steps:

[0009] S1, dissolving monomer acrylamide in deionized water, then adding ammonium persulfate and modified sodium alginate to obtain a mixed solution;

[0010] S2, adjusting the pH of the mixed solution obtained in step S1 to obtain a prepolymer solution;

[0011] S3, degassing the prepolymer solution, sealing, polymerizing to obtain a hydrogel;

[0012] S4, soaking the hydrogel in an electrolyte to obtain a modified sodium alginate cross-linked hydrogel electrolyte;

[0013] Wherein, the double bond structure of glycidyl methacrylate is grafted onto sodium alginate to form modified sodium alginate.

[0014] The hydrogel electrolyte provided by the application is a quasi-solid electrolyte composed of cross-linked hydrophilic polymers, forming a 3D network filled with zinc salt aqueous solution, so that the hydrogel electrolyte has the advantages of high zinc ion conductivity and low interfacial resistance. The hydrogel electrolyte constructed by the application renews the Zn 2+ Adjusting the transport channel of zinc deposition and inhibiting the growth of zinc dendrites, ultimately prolonging the life of zinc ion battery.

[0015] Sodium alginate itself belongs to a natural polysaccharide, which is environmentally friendly; and sodium alginate itself can be extracted from natural organisms, saving cost. The application introduces modified sodium alginate as a cross-linking agent in the hydrogel electrolyte, reduces environmental toxicity and pollution, utilizes the interaction between sodium alginate and zinc ions to achieve the inhibitory effect on zinc dendrites, adjusts the interface growth between the negative electrode and the electrolyte, and further prolongs the battery life. At the same time, it also has a certain inhibitory effect on hydrogen evolution reaction.

[0016] The application uses acrylamide as a monomer, ammonium persulfate as an initiator, and the initiator decomposes to produce free radicals under heat, which can link monomers into molecular chains, and the cross-linking agent can cross-link the molecular chains into hydrogel. The application can prepare a modified sodium alginate cross-linked hydrogel electrolyte by a simple free radical polymerization method, and compared with conventional aqueous batteries, the hydrogel electrolyte can better regulate the interface growth of the positive and negative electrodes.

[0017] In some specific embodiments, the prepolymer solution is degassed to prevent the influence of oxygen on polymerization, added to a sealed mold, and polymerized at 60°C for two hours to obtain a hydrogel; the hydrogel is soaked in an electrolyte for one day to obtain a hydrogel electrolyte.

[0018] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte described in the application, the preparation method of the modified sodium alginate comprises the following steps:

[0019] 1) Dissolve sodium alginate in deionized water to obtain a pre-liquid, adjust the pH of the pre-liquid to be alkaline to obtain a mixed liquid;

[0020] 2) Add glycidyl methacrylate to the mixed liquid and mix, then precipitate, then vacuum filter, wash and freeze dry to obtain modified sodium alginate.

[0021] The application first modifies sodium alginate, and the added glycidyl methacrylate itself has a double bond structure. The double bond structure of glycidyl methacrylate is grafted onto sodium alginate, so that sodium alginate has a double bond structure, which can be used as a crosslinking agent. The modified sodium alginate has an interaction with zinc ions, which can effectively inhibit the growth of zinc dendrites and regulate the interface growth between the negative electrode and the electrolyte; at the same time, it also has a certain inhibitory effect on the hydrogen evolution reaction, prolonging the service life of the zinc ion battery.

[0022] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte described in the application, the ratio of sodium alginate to glycidyl methacrylate is 4g:0.675μL.

[0023] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte described in the application, the reagent for adjusting the pH of the pre-liquid includes NaOH, and the pH of the pre-liquid is 10-11.

[0024] In some specific embodiments, the preparation method of the modified sodium alginate comprises the following steps:

[0025] Using a 250mL three-necked flask, 4g of sodium alginate is dissolved in 100mL of deionized water, continuously stirred until completely dissolved, as a pre-liquid; 6M NaOH is prepared and slowly added to the pre-liquid to adjust the pH of the pre-liquid to 10, continue to stir for 15min to obtain a mixed liquid; then 0.675μL of glycidyl methacrylate (GMA) is added to the mixed liquid, and stirred at 60℃ for 24h; the solution after reaction is precipitated by adding an appropriate amount of ethanol, and the white product is obtained by vacuum filtration, washed with ethanol for 2-3 times, and freeze-dried to obtain modified sodium alginate.

[0026] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte described in the application, the mass ratio of ammonium persulfate to modified sodium alginate is 1:(1-2).

[0027] In the technical solution of the application, ammonium persulfate and modified sodium alginate are used as initiators and crosslinking agents, and the above amount of modified sodium alginate is used to improve the swelling rate and water retention of the hydrogel electrolyte, thereby prolonging the service life of the battery and reducing the capacity decay of the battery after multiple charge-discharge cycles.

[0028] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte, the mass ratio of the ammonium persulfate and the modified sodium alginate is 3:5.

[0029] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte, the reagent for adjusting the pH of the mixed solution obtained in step S1 in step S2 includes acrylic acid.

[0030] The application uses acrylic acid as a pH adjuster for adjusting the mixed solution.

[0031] As a preferred embodiment of the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte, the electrolyte in step S4 includes ZnSO4.

[0032] The application also provides a modified sodium alginate cross-linked hydrogel electrolyte prepared by the above preparation method of the modified sodium alginate cross-linked hydrogel electrolyte.

[0033] The thickness of the modified sodium alginate cross-linked hydrogel electrolyte is 1-2 mm.

[0034] The application also provides an application of the modified sodium alginate cross-linked hydrogel electrolyte in preparing a battery.

[0035] The application of the modified sodium alginate cross-linked hydrogel electrolyte prepared above in the battery improves the capacity retention rate of the battery, and further improves the service life of the battery, and reduces the capacity decay of the battery after multiple charge-discharge cycles.

[0036] Compared with the prior art, the application has the following beneficial effects:

[0037] The application provides a modified sodium alginate cross-linked hydrogel electrolyte, a preparation method and an application thereof. The application introduces modified sodium alginate as a cross-linking agent in the hydrogel electrolyte, reduces environmental toxicity and pollution, utilizes the interaction between sodium alginate and zinc ions to achieve inhibition of zinc dendrites, adjusts the interface growth between the negative electrode and the electrolyte, and further prolongs the service life of the battery; at the same time, the application also has a certain inhibition effect on the hydrogen evolution reaction, and can greatly prolong the cycle life of the battery, which can be verified by subsequent battery cycle tests. The application uses acrylamide as a monomer and ammonium persulfate as an initiator. The initiator is decomposed to produce free radicals under heat, can link the monomers into molecular chains, and the cross-linking agent can cross-link the molecular chains into a hydrogel. The application can prepare the modified sodium alginate cross-linked hydrogel electrolyte by a simple free radical polymerization method, and compared with conventional aqueous batteries, the hydrogel electrolyte can better regulate the interface growth of the positive and negative electrodes. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Micro-FTIR spectra of modified sodium alginate and unmodified sodium alginate and GMA (glycidyl methacrylate);

[0039] Figure 2 Physical picture of modified sodium alginate cross-linked hydrogel electrolyte prepared in Example 2;

[0040] Figure 3 Electrochemical impedance test result picture of symmetric battery assembled with hydrogel prepared in Example 2;

[0041] Figure 4 Ionic conductivity result picture of hydrogel prepared in Example 2;

[0042] Figure 5 Cycle performance picture of symmetric battery assembled with hydrogel prepared in Example 2 at 0.5 mA cm-2current density and 1 mAh cm-2surface capacity; -2 -2

[0043] Figure 6 Cycle performance picture of symmetric battery assembled with MBAA cross-linked hydrogel prepared in Comparative Example 1 at 0.5 mA cm-2current density and 1 mAh cm-2surface capacity; -2 -2

[0044] Figure 7 Cycle performance picture of symmetric battery assembled with hydrogel prepared in Example 2 at 1.5 mA cm-2current density and 1 mAh cm-2surface capacity; -2 -2

[0045] Figure 8 Rate performance picture of full battery assembled with modified sodium alginate cross-linked hydrogel electrolyte prepared in Example 2, manganese dioxide as positive electrode at 0.1 c, 0.2 c, 0.5 c, 1 c and 2 c different current densities;

[0046] Figure 9 Cycle performance picture of full battery assembled with modified sodium alginate cross-linked hydrogel electrolyte prepared in Example 2, manganese dioxide as positive electrode at 0.5 A g-1current density;

[0047] Figure 10 Application effect of modified sodium alginate cross-linked hydrogel flexible battery prepared in Example 6 under different conditions

[0048] Figure 11 Principle schematic diagram of modified sodium alginate prepared in Example 1;

[0049] Figure 12 ​​​​​​The assembled symmetric cell of the MBAA cross-linked hydrogel prepared for Comparative Example 1 at a current density of 0.5 mA cm -2 at 1 mAh cm -2 The cycle performance graph at the surface capacity of the assembled symmetric cell of the MBAA cross-linked hydrogel prepared for Comparative Example 1 at a current density of 0.5 mA cm

[0050] Figure 13 The cycle performance graph at a current density of 0.5 A g -1 of the full cell assembled with the MBAA cross-linked hydrogel electrolyte prepared for Comparative Example 1 and manganese dioxide as the positive electrode.

[0051] Figure 14 The swelling rate graph of the modified sodium alginate cross-linked hydrogels prepared for Examples 2-5 and the control hydrogel.

[0052] Figure 15 The cycle performance graph at a current density of 0.5 mA cm -2 at 1 mAh cm -2 of the assembled symmetric cell of the modified sodium alginate cross-linked hydrogels prepared for Examples 2-5.

[0053] Figure 16 The cycle performance bar comparison graph at a current density of 0.5 mA cm -2 at 1 mAh cm -2 of the assembled symmetric cell of the modified sodium alginate cross-linked hydrogels prepared for Examples 1-5. DETAILED DESCRIPTION

[0054] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with the drawings and specific examples.

[0055] In the following examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified, and the components used in each parallel experiment are the same.

[0056] The zinc foil used in the present application was polished with 800 mesh sandpaper, and the polished zinc foil was soaked in ethanol for 10 minutes under ultrasonic, the purpose being to remove the oxidation layer on the surface of the zinc foil, and the zinc foil was cut into a circular piece with a diameter of 14 mm for assembling the negative electrode of the battery.

[0057] The preparation of the manganese dioxide positive electrode material used in the present application is as follows:

[0058] Manganese dioxide, conductive carbon black and binder PVDF were dissolved in NMP solvent in a ratio of 7:2:1, and the concentration of PVDF and NMP solution was 20 mg mL -1Ball milling at 400 rpm for 24 hours. The slurry was coated on titanium foil as the current collector and dried in a vacuum drying oven at 60℃ for 20 hours. After drying, the manganese dioxide positive electrode sheet with a diameter of 14 mm was cut using a sheet cutting machine.

[0059] Example 1, preparation of modified sodium alginate

[0060] The present example provides a method for preparing modified sodium alginate, comprising the following steps:

[0061] 1) Using a 250 mL three-necked flask, 4 g of sodium alginate was dissolved in 100 mL of deionized water with continuous stirring until completely dissolved as a pre-liquid.

[0062] 2) 6M NaOH was prepared and slowly added to the pre-liquid to adjust the pH to 10, and continue to stir for 15 min.

[0063] 3) Then 0.675 μL of GMA (glycidyl methacrylate) was added to the pre-liquid, and stirred at 60℃ for 24 h to obtain the reacted solution; the reacted solution was precipitated by adding an appropriate amount of ethanol, and the white product was obtained by vacuum filtration, and washed with ethanol for 2-3 times, and then freeze-dried to obtain the modified sodium alginate white product, i.e. the modified sodium alginate.

[0064] The micro infrared spectra of the modified sodium alginate and the unmodified sodium alginate and GMA (glycidyl methacrylate) are shown in Figure 1 .

[0065] Figure 1 There are three curves in the figure, which are the infrared spectra of the modified sodium alginate, the unmodified sodium alginate and GMA (glycidyl methacrylate), respectively. The arrow in the figure indicates the characteristic peak of the double bond of the modified sodium alginate. It can be concluded from Figure 1 that the sodium alginate has been successfully modified to obtain a double bond structure.

[0066] Example 2, a modified sodium alginate cross-linked hydrogel electrolyte and a method for preparing the same

[0067] The present example provides a method for preparing a modified sodium alginate cross-linked hydrogel electrolyte, comprising the following steps:

[0068] S1, 2 g of monomer acrylamide was dissolved in 20 mL of deionized water, 30 mg of ammonium persulfate and 50 mg of sodium bisulfate were added, and the solution was stirred at 60℃ for 2 h to obtain a polymerization initiator solution.

[0069] The modified sodium alginate prepared in Example 1 was used as an initiator and a cross-linking agent, respectively, and after the solute was fully dissolved, 200 μL of acrylic acid was added to adjust the solution pH to weakly acidic (pH 3-5 to prevent zinc salt precipitation in alkaline environment), to obtain a pre-polymerization solution.

[0070] S2, degassing the prepolymer solution, adding into a sealed mold, polymerizing at 60°C for two hours to obtain a hydrogel (the thickness of the hydrogel is 1-2 mm).

[0071] S3, preparing a 2M ZnSO4 solution as an electrolyte, soaking the hydrogel prepared in step S2 in the electrolyte for 24 hours, taking out the hydrogel, cutting the hydrogel into a circular piece with a diameter of 16 mm and a thickness of 1 mm, as an electrolyte (modified sodium alginate cross-linked hydrogel electrolyte) and a separator of a zinc ion battery.

[0072] The actual picture of the modified sodium alginate cross-linked hydrogel electrolyte prepared in Example 2 is as shown in Figure 2 .

[0073] It can be seen from Figure 2 that the surface of the modified sodium alginate cross-linked hydrogel is smooth and flat, has good expandability, and has the potential for large-scale production.

[0074] Example 3, a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method thereof

[0075] Compared with Example 2, the difference is that 30 mg of the modified sodium alginate prepared in Example 1, i.e., 1.5% of the monomer acrylamide content, is added in Example 3, and the remaining steps are the same as those in Example 2.

[0076] Example 4, a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method thereof

[0077] Compared with Example 2, the difference is that 40 mg of the modified sodium alginate prepared in Example 1, i.e., 2% of the monomer acrylamide content, is added in Example 3, and the remaining steps are the same as those in Example 2.

[0078] Example 5, a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method thereof

[0079] Compared with Example 2, the difference is that 60 mg of the modified sodium alginate prepared in Example 1, i.e., 3% of the monomer acrylamide content, is added in Example 3, and the remaining steps are the same as those in Example 2.

[0080] Example 6, a modified sodium alginate cross-linked hydrogel electrolyte and a preparation method thereof

[0081] The difference between Example 6 and Example 2 is only that the hydrogel is not cut into a circular piece after treatment, the hydrogel is cut into a 8 cm x 10 cm sheet, zinc foil is used as a negative electrode, and manganese dioxide electrode piece is used as a positive electrode, and a flexible application test is carried out by connecting an electronic watch.

[0082] Comparative Example 1

[0083] The difference compared with Example 2 is that, in Comparative Example 1, the modified sodium alginate prepared in Example 1 is replaced by MBAA (N, N-methylene bisacrylamide) to prepare a MBAA cross-linked hydrogel, and the remaining steps are the same as in Example 2.

[0084] Test Example I, battery electrochemical test

[0085] 1. When assembling the battery, the zinc foil serves as both the positive electrode and the negative electrode of the battery, and the hydrogel soaked in the electrolyte in Example 2, Example 6 and Comparative Example 1 serves as the electrolyte and the separator, and the symmetric battery electrochemical test is carried out.

[0086] 2. When assembling the full battery, the manganese dioxide electrode serves as the positive electrode, the zinc foil serves as the negative electrode, and the hydrogel soaked in the electrolyte in Example 2, Example 6 and Comparative Example 1 serves as the electrolyte and the separator, and the full battery electrochemical test is carried out.

[0087] Results:

[0088] The electrochemical impedance test of the symmetric battery assembled by the hydrogel prepared in Example 2 is shown in Figure 3 . The test voltage is 0 V, and the test frequency range is 0.1-1000000. As can be seen from Figure 3 , the interface impedance of the hydrogel is small, and the contact resistance is also small.

[0089] The ion conductivity calculation diagram of the hydrogel prepared in Example 2 is shown in Figure 4 . As can be seen from Figure 4 , the ion conductivity of the modified sodium alginate cross-linked hydrogel is higher than that of the MBAA cross-linked hydrogel, indicating that the modified sodium alginate cross-linked hydrogel electrolyte has better ion transmission capacity.

[0090] The cycle performance diagram of the symmetric battery assembled by the hydrogel prepared in Example 2 at a current density of 0.5 mA cm -2 and a surface capacity of 1 mAh cm -2 is shown in Figure 5 . As can be seen from Figure 5 , the modified sodium alginate cross-linked hydrogel battery can be stably cycled for more than 900 h, and has good cycle stability.

[0091] The cycle performance diagram of the symmetric battery assembled by the MBAA cross-linked hydrogel prepared in Comparative Example 1 at a current density of 0.5 mA cm -2 and a surface capacity of 1 mAh cm -2 is shown in Figure 6 . As can be seen from Figure 6 , the battery of the MBAA cross-linked hydrogel does not have long cycle capacity under the same conditions.

[0092] The symmetric cell assembled using the hydrogel prepared in Example 2 achieved a speed of 1.5 mA cm⁻¹. -2 Current density and 1mAh cm -2 Cyclic performance diagram under surface capacity is shown below Figure 7 As shown. From Figure 7 It can be seen that the modified sodium alginate crosslinked hydrogel battery can cycle stably for more than 800 hours, and also has good cycle stability under high current density.

[0093] like Figure 8 As shown, the rate performance of a full cell assembled using the modified sodium alginate crosslinked hydrogel electrolyte prepared in Example 2, with manganese dioxide as the positive electrode, is displayed at different current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C. From... Figure 8 As can be seen, the material is stable under various current density tests, indicating that the hydrogel zinc-ion battery has stable rate performance.

[0094] like Figure 9 The figure shows the cycling performance of a full cell assembled using the modified sodium alginate crosslinked hydrogel electrolyte prepared in Example 2 and manganese dioxide as the positive electrode at a current density of 0.5 A g⁻¹.

[0095] Figure 9 There are two curves: curve No. 1 is the coulombic efficiency curve, and curve No. 2 is the charge / discharge specific capacity curve. From... Figure 9 As can be seen, the zinc-ion battery containing modified sodium alginate can stably cycle 200 times with a remaining capacity of 60 mAh g. -1 This indicates that the zinc-ion battery with modified sodium alginate crosslinked hydrogel electrolyte has stable cycle performance.

[0096] The modified sodium alginate crosslinked hydrogel flexible battery prepared in Example 6 exhibits the following application effects under different conditions: Figure 10 As shown. From Figure 10 As can be seen, the flexible battery of the present invention can still function under different conditions such as stretching, twisting, and folding.

[0097] A schematic diagram of the modified sodium alginate prepared in Example 1 is shown below. Figure 11 As shown.

[0098] The assembled symmetric cell of the MBAA crosslinked hydrogel prepared in Comparative Example 1 at 1.5 mA cm⁻¹ -2 Current density and 1mAhcm -2 Cyclic performance diagram under surface capacity is shown below Figure 12 As shown. From Figure 12 It can be seen that the battery made of MBAA cross-linked hydrogel does not have long cycle life under the same conditions.

[0099] As Figure 13 shown, the MBAA cross-linked hydrogel electrolyte prepared by using Comparative Example 1, and the full cell assembled with manganese dioxide as the positive electrode has a cycle performance graph at a current density of 0.5 A g -1 Figure 13 There are two curves in the graph, curve No. 1 is the coulombic efficiency curve, and curve No. 2 is the specific capacity curve. As Figure 13 can be seen from the graph, the capacity retention rate of the zinc ion battery of the MBAA cross-linked hydrogel is poor.

[0100] Test Example Two, Swelling Rate Test

[0101] The modified sodium alginate cross-linked hydrogels prepared in Examples 2-5 were subjected to a swelling rate test. The initial average mass m0 of the hydrogel was measured, and the mass was measured every 24 hours, and the average value m was taken to perform a swelling rate test to verify whether the modified sodium alginate can be used as a cross-linking agent and the absorption rate of the electrolyte by the hydrogel.

[0102] As Figure 14 shown, the swelling rate curve graphs of the modified sodium alginate cross-linked hydrogels prepared in Examples 2-5 and the control hydrogel (Comparative Example 1) of different concentrations.

[0103] As Figures 14 to 16 can be seen from the graph, the swelling rate of the modified sodium alginate cross-linked hydrogel is better. With the increase of the concentration, the cross-linking degree is improved, and the swelling rate gradually decreases. It is proved that the modified sodium alginate indeed plays a role as a cross-linking agent. As Figures 14 to 16 can be seen from the graph, the addition amount of 50 mg of the modified sodium alginate is the optimal addition amount (Example 2).

[0104] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and do not limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.​

Claims

1. A method for preparing a modified sodium alginate cross-linked hydrogel electrolyte, characterized by, The method comprises the following steps: S1, dissolving monomer acrylamide in deionized water, then adding ammonium persulfate and modified sodium alginate to obtain a mixed solution; S2, adjusting the pH of the mixed solution obtained in step S1 to obtain a pre-polymerization solution; S3, degassing the pre-polymerization solution, sealing, polymerizing to obtain a hydrogel; S4, soaking the hydrogel in an electrolyte to obtain a modified sodium alginate cross-linked hydrogel electrolyte; The double bond structure of glycidyl methacrylate is grafted onto sodium alginate to form modified sodium alginate; The preparation method of the modified sodium alginate comprises the following steps: 1) dissolving sodium alginate in deionized water to obtain a pre-liquid, adjusting the pH of the pre-liquid to be alkaline to obtain a mixed solution; 2) adding glycidyl methacrylate to the mixed solution for mixing and stirring, then precipitating, and then vacuum filtering, washing and freeze-drying to obtain modified sodium alginate; In step S2, the reagent for adjusting the pH of the mixed solution obtained in step S1 includes acrylic acid; In step S4, the electrolyte includes ZnSO4.

2. The method for preparing a modified sodium alginate cross-linked hydrogel electrolyte according to claim 1, wherein, The ratio of sodium alginate to glycidyl methacrylate is 4g:0.675μL.

3. The preparation method of the modified sodium alginate crosslinked hydrogel electrolyte as described in claim 1, characterized in that, The reagent for adjusting the pH of the pre-liquid includes NaOH, and the pH of the pre-liquid is 10-11.

4. The preparation method of the modified sodium alginate crosslinked hydrogel electrolyte as described in claim 1, characterized in that, The mass ratio of ammonium persulfate to modified sodium alginate is 1:(1-2).

5. The preparation method of the modified sodium alginate crosslinked hydrogel electrolyte as described in claim 4, characterized in that, The mass ratio of ammonium persulfate to modified sodium alginate is 3:

5.

6. The modified sodium alginate cross-linked hydrogel electrolyte prepared by the preparation method of the modified sodium alginate cross-linked hydrogel electrolyte according to any one of claims 1-5.

7. The application of the modified sodium alginate cross-linked hydrogel electrolyte according to claim 6 in the preparation of a battery.

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