Bio-based gel electrolyte with high interfacial compatibility and application of bio-based gel electrolyte in solid-state hybrid capacitor

Abstract

The invention discloses a bio-based gel electrolyte with high interfacial compatibility and an application thereof in a solid-state hybrid capacitor, NH4 < + > and SO4 < 2-> are introduced, a hydration layer of gelatin is destroyed, the solubility of the gelatin is reduced, a gelatin triple helix polymer is induced to aggregate, and strong hydrogen-bond interaction is generated, so that in-situ precipitation is performed to form crystals, and the solid-state hybrid capacitor with high interfacial compatibility is obtained. Further forming a gelatin crystal domain; zn < 2 + > is introduced and forms metal coordination with sodium alginate to form a polymer domain; meanwhile, the two phases are crosslinked under the hydrogen bond action of tannin, so that the bio-based gel electrolyte with a hierarchical heterostructure is constructed; in a gelatin-tannin-sodium alginate gel matrix, stress is transmitted through a sodium alginate polymer domain, and energy is dissipated and cracks are pinned through a gelatin crystal domain, so that the gel electrolyte has high toughness. The solid-state zinc ion hybrid capacitor assembled on the basis of the constructed bio-based gel electrolyte shows excellent charge / discharge stability in the long-term cycle process.

Description

Technical Field

[0001] The present invention belongs to the field of gel electrolytes, and particularly relates to a bio-based gel electrolyte with high interfacial compatibility and its application in solid-state hybrid capacitors. Background Art

[0002] As an emerging energy storage technology, solid-state zinc-ion hybrid capacitors have attracted extensive attention in recent years by combining the high energy density of zinc-ion batteries and the high power density characteristics of supercapacitors. In this context, the development of a suitable solid-state electrolyte system has become a key research direction. Gel electrolytes, with their intrinsic flexibility, environmental friendliness, and high ionic conductivity, have gradually become ideal candidate materials for the design of solid-state electrolytes, especially suitable for flexible electronic fields such as wearable devices.

[0003] Due to the poor cohesive force within the current mainstream gel electrolytes and the interfacial interaction force between the electrode and the electrolyte, the interfacial compatibility between the gel electrolyte and the zinc metal anode is weak. The weak interfacial compatibility usually leads to non-uniform deposition of zinc ions, which in turn promotes the growth of zinc dendrites and induces problems such as device short circuits, severely restricting the cycle stability and safety of the device.

[0004] To address the problem of weak interfacial compatibility between the gel electrolyte and the zinc metal anode, a large number of studies have been carried out by scientific researchers. However, most of them focus on constructing an artificial interface layer between the zinc anode and the electrolyte through non-in-situ modification methods, so as to improve the matching degree of the electrochemical performance and mechanical properties between the zinc anode and the electrolyte, and thus improve the interfacial compatibility. However, the construction of the artificial interface layer may bring new interface problems, including increased internal resistance, anode corrosion, etc., resulting in attenuated electrochemical performance and limited cycle life. At the same time, the traditional gel electrolyte system mainly relies on petroleum-based raw materials, and generally has problems such as complex synthesis processes, poor biocompatibility, non-renewability, and non-degradability. With the promotion of the global sustainable development strategy, the development of environmentally friendly gel electrolytes using renewable biomass resources has become one of the important development directions of emerging energy storage technologies. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of a bio-based gel electrolyte with high interfacial compatibility through in-situ modification.

[0008] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of a bio-based gel electrolyte with high interfacial compatibility, comprising,

[0009] Dissolve gelatin, sodium alginate and tannin in deionized water and stir evenly under heating conditions to obtain a pre-polymer solution;

[0010] Pour the pre-polymer solution into a customized mold and refrigerate it. At low temperature, the gelatin chains entangle and form a triple helix entanglement region to obtain a pre-gel;

[0011] Soak the pre-gel in ammonium sulfate solution. Through the "salting-out" effect of NH4 + and SO4 2- , the solubility of gelatin is reduced and the hydration layer of gelatin is destroyed, making the triple helix entanglement region of gelatin more aggregated and orderly arranged, so as to in-situ precipitate and form crystals, and then form a gelatin crystal domain;

[0012] Soak the obtained gel in zinc acetate solution. Under the action of Zn 2+ , sodium alginate forms a polymer phase through metal coordination to obtain a bio-based gel electrolyte with a hierarchical heterogeneous structure in which gelatin is used as the crystal phase, sodium alginate is used as the polymer phase, and tannin connects the two phases.

[0013] As a preferred embodiment of the present invention, wherein: the mass fractions of gelatin, sodium alginate and tannin in the pre-polymer solution are 30 wt%, 2 wt% and 0.7 wt% respectively;

[0014] As a preferred embodiment of the present invention, wherein: the pH value of the pre-polymer solution is 5-7.

[0015] As a preferred embodiment of the present invention, wherein: pour the pre-polymer solution into a customized mold and refrigerate it, wherein the refrigeration temperature is 4°C and the gel time is 1 h.

[0016] As a preferred embodiment of the present invention, wherein: soak the pre-gel in ammonium sulfate solution, wherein the concentration of ammonium sulfate is 30 wt% and the soaking time is 12 h.

[0017] As a preferred embodiment of the present invention, wherein: soak the obtained gel in zinc acetate solution, wherein the concentration of zinc acetate is 20 wt% and the soaking time is 24 h.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide a biobased gel electrolyte with high interfacial compatibility.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a biobased gel electrolyte with high interfacial compatibility in a solid-state hybrid capacitor.

[0020] Advantages of the present invention:

[0021] (1) The present invention provides a preparation method of a biobased gel electrolyte with high interfacial compatibility. By introducing NH4 + and SO4 2- , the hydration layer of gelatin is destroyed and the solubility of gelatin is reduced, inducing the aggregation of gelatin triple helix polymers and generating strong hydrogen bond interactions, thereby in-situ precipitating to form crystals and further forming gelatin crystal domains; by introducing Zn 2+ , metal coordination is formed with sodium alginate to form polymer domains; at the same time, the two phases are crosslinked under the hydrogen bond action of tannin, thereby constructing a biobased gel electrolyte with a hierarchical heterogeneous structure; in the gelatin-tannin-sodium alginate gel matrix, stress is transmitted through the sodium alginate polymer domains, and energy is dissipated and cracks are pinned through the gelatin crystal domains, so that the gel electrolyte has high toughness; at the same time, the gelatin-tannin-sodium alginate gel electrolyte can form strong interfacial interactions through non-covalent interactions such as metal coordination, cation-π, and electrostatic interactions between a large number of functional groups such as catechol, carboxyl, and amino groups and zinc metal, thereby ensuring a strong interfacial interaction between the gel electrolyte and zinc metal; in addition, because the carboxyl groups in the sodium alginate polymer phase can form specific transport paths through ionic coordination with Zn 2+ , it helps the directional transition of Zn 2+ , and then realizes high ionic conductivity and high zinc ion transference number.

[0022] (2) The present invention constructs a biobased gel electrolyte with a hierarchical heterogeneous structure, which has the characteristics of high toughness and strong adhesion at the same time. The high toughness of the constructed gelatin-tannin-sodium alginate gel electrolyte ensures that the gel electrolyte can adapt to the volume change of the zinc metal anode during the charge / discharge cycle and can suppress the deposition of Zn during the cycle, thereby limiting the possibility of dendrite formation; the strong adhesion performance enables the gel electrolyte to maintain good contact with the zinc anode during long-term cycling, helps the effective migration of Zn 2+ at the interface, and prevents Zn 2+Irregular diffusion occurs on the surface of the zinc anode, resulting in dendrite-free Zn growth; precisely under the synergistic effect of the two, a compatible interface between the gel electrolyte and the zinc anode is obtained. Benefiting from this, the solid-state zinc-ion hybrid capacitor assembled based on the constructed bio-based gel electrolyte exhibits excellent charge / discharge stability during long-term charge / discharge cycling.

[0023] (3) The preparation process of the present invention is simple, using three natural components, gelatin, sodium alginate, and tannin, as raw materials. Compared with the preparation of traditional petroleum-based gel electrolytes, it has the characteristics of easy availability of raw materials, simple preparation, environmental friendliness, good biocompatibility, etc., and has potential application prospects in solid-state energy storage systems and flexible wearable materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0025] Figure 1 It is the microscopic morphology diagram of the gel electrolyte prepared in the present invention; among them, a is the microscopic morphology diagram of Example 1, b is the microscopic morphology diagram of Comparative Example 1, c is the microscopic morphology diagram of Comparative Example 2, and d is the microscopic morphology diagram of Comparative Example 3.

[0026] Figure 2 It is the two-dimensional wide-angle diagram of the gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 of the present invention.

[0027] Figure 3 It is the atomic force microscope diagram of the gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 of the present invention; among them, a is the phase diagram and b is the bitmap.

[0028] Figure 4 It is the mechanical property diagram of the gel electrolyte prepared in the present invention; among them, a is the stress-strain curve diagram of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, and b is the columnar diagram of the fracture stress, Young's modulus, and tearing energy of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0029] Figure 5 It is the adhesion property diagram of the gel electrolyte prepared in the present invention; among them, a is the shear strength-displacement curve between Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and the zinc sheet, and b is the adhesion physical diagram between Example 1 and different substrates.

[0030] Figure 6This is the microscopic morphology diagram of the zinc anode after 50 cycles of the symmetrical battery assembled with the gel electrolyte prepared in the present invention; among them, a is the longitudinal section microscopic morphology diagram of the zinc anode after 50 cycles of the symmetrical battery assembled with Examples 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, and b is the cross-sectional microscopic morphology diagram of the zinc anode after 50 cycles of the symmetrical battery assembled with Examples 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0031] Figure 7 This is the long cycle curve of the symmetrical battery assembled with the gel electrolyte prepared in the present invention at a current density of 1 mA cm -2 and an areal capacity of 1 mAh cm -2 under the conditions.

[0032] Figure 8 This is the in-situ optical microscope photograph during the deposition process of the symmetrical battery assembled with the gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 of the present invention at a current density of 5 mA cm -2 of the present invention.

[0033] Figure 9 This is the performance test diagram of the solid-state zinc-ion hybrid capacitor assembled with the gel electrolyte prepared in Example 1 of the present invention; among them, a is the cyclic voltammetry curve of the solid-state zinc-ion hybrid capacitor at different scan rates, b is the charge / discharge curve of the solid-state zinc-ion hybrid capacitor at different current densities, and c is the change in capacity and Coulomb efficiency of the solid-state zinc-ion hybrid capacitor during 10,000 cycles at a current density of 1 A g -1 of the present invention. Detailed Embodiments

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0035] In the embodiments of the present invention, gelatin, sodium alginate, tannin, ammonium sulfate, and zinc acetate were purchased from Aladdin Company; activated carbon, carbon black conductive agent, and styrene-butadiene rubber binder were purchased from Kejing Company, all of which are ordinary commercially available products.

[0036] Example 1

[0037] Preparation of gelatin-tannin-sodium alginate gel:

[0038] (1) Add 30 g of gelatin, 2 g of sodium alginate, and 0.7 g of tannin to 100 g of deionized water, place it in a water bath at 60 °C, and heat and stir for 2 h to obtain a prepolymer solution.

[0039] (2) Transfer the obtained prepolymer solution to a customized mold and store it at 4 °C for 1 h to obtain a pre-gel.

[0040] (3) Immerse the obtained pre-gel in a 30 wt% ammonium sulfate solution for 12 h to cause "salting out" of the pre-gel under the action of NH4 + and SO4 2- .

[0041] (4) Immerse the "salted out" gel in a 20 wt% zinc acetate solution for 24 h to cause cross-linking of the gel under the action of Zn 2+ , and finally obtain a gelatin-tannin-sodium alginate gel electrolyte.

[0042] The scanning electron microscope image of the gelatin-tannin-sodium alginate gel electrolyte is shown in Figure 1 .

[0043] The two-dimensional wide-angle image of the gelatin-tannin-sodium alginate gel electrolyte is shown in Figure 2 . It can be seen that its image presents clear diffraction rings, indicating the presence of crystals in the gel electrolyte matrix. This result further confirms the formation of the gelatin crystallization domain.

[0044] The atomic force microscope image of the gelatin-tannin-sodium alginate gel electrolyte is shown in Figure 3 . Combining the phase diagram and the bitmap, it can be seen that the gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 obviously has a two-phase structure, and the gelatin crystallization domain is embedded in the surface of the sodium alginate polymer phase (dark yellow) in a convex shape (light yellow). This result further confirms that the obtained gel electrolyte has a hierarchical heterogeneous structure.

[0045] Comparative Example 1

[0046] (1) Add 30 g of gelatin and 0.7 g of tannin to 100 g of deionized water, place it in a water bath at 60 °C, heat and stir for 2 h to obtain a pre-polymer solution.

[0047] (2) Transfer the obtained pre-polymer solution to a customized mold and store it at 4 °C for 1 h to obtain a pre-gel.

[0048] (3) Immerse the obtained pre-gel in a 30 wt% ammonium sulfate solution for 12 h to cause "salting out" of the pre-gel under the action of NH4 + and SO4 2- .

[0049] (4) Immerse the "salted out" gel in a 20 wt% zinc acetate solution for 24 h to finally obtain a gelatin-tannin gel electrolyte.

[0050] Comparative Example 2

[0051] (1) Add 2 g of sodium alginate and 0.7 g of tannin to 100 g of deionized water, place it in a water bath at 60 °C, heat and stir for 2 h to obtain a pre-polymer solution.

[0052] (2) Transfer the obtained prepolymer solution to a customized mold and store it at 4 °C for 1 h.

[0053] (3) Immerse the above prepolymer solution in a 30 wt% ammonium sulfate solution for 12 h.

[0054] (4) Immerse the above prepolymer solution in a 20 wt% zinc acetate solution for 24 h to cause cross-linking under the action of Zn 2+ to finally obtain a tannin-sodium alginate gel electrolyte.

[0055] Comparative Example 3

[0056] (1) Add 30 g of gelatin and 2 g of sodium alginate to 100 g of deionized water, place it in a water bath at 60 °C, heat and stir for 2 h to obtain a prepolymer solution.

[0057] (2) Transfer the obtained prepolymer solution to a customized mold and store it at 4 °C for 1 h to obtain a pre-gel.

[0058] (3) Immerse the obtained pre-gel in a 30 wt% ammonium sulfate solution for 12 h to cause "salting out" of the pre-gel under the action of NH4 + , SO4 2- .

[0059] (4) Immerse the "salted out" gel in a 20 wt% zinc acetate solution for 24 h to cause cross-linking of the gel under the action of Zn 2+ to finally obtain a gelatin-sodium alginate gel electrolyte.

[0060] Figure 1 a is the microscopic morphology diagram of Example 1, Figure 1 b is the microscopic morphology diagram of Comparative Example 1, Figure 1 c is the microscopic morphology diagram of Comparative Example 2, Figure 1 d is the microscopic morphology diagram of Comparative Example 3. It can be seen from these microscopic morphology diagrams that Comparative Example 1 shows a highly ordered crystalline domain, indicating that the gelatin macromolecular chains form crystals under the action of "salting out"; Comparative Example 2 shows a tangled structure, indicating that the sodium alginate molecular chains cross-link through metal coordination; both of them show a homogeneous structure. Comparative Example 3 shows a typical heterogeneous structure, where gelatin forms crystals under the action of "salting out" and precipitates in-situ from the cross-linked sodium alginate polymer domain. In contrast, in Example 1, not only does the gelatin crystalline domain precipitate in-situ from the sodium alginate polymer domain, but the two phases are connected by hydrogen bond interactions of tannin, thus forming a hierarchical heterogeneous structure.

[0061] (1) Test on the tensile properties of the gelatin-tannin-sodium alginate gel electrolyte:

[0062] The tensile properties of the gelatin-tannin-sodium alginate gel electrolyte were tested using an electronic universal testing machine.

[0063] The gel electrolytes prepared in Example 1 and Comparative Examples 1-3 above were cut into dumbbell-shaped samples with a length of 5 cm, a width of 4 mm, and a thickness of 1 mm.

[0064] Then it was fixed between the tensile fixtures and uniaxially stretched in the vertical direction at a stretching rate of 100 mm / min to obtain the tensile stress-strain curve of the gelatin-tannin-sodium alginate hydrogel. The fracture stress and fracture elongation were recorded, and the Young's modulus was calculated based on the stress-strain of the first 5%. The results are shown in Figure 4 .

[0065] (2) Test of the tearing energy of the gelatin-tannin-sodium alginate gel electrolyte:

[0066] The tearing energy of the gelatin-tannin-sodium alginate gel electrolyte was tested using an electronic universal testing machine.

[0067] The gel electrolytes prepared in Example 1 and Comparative Examples 1-3 above were cut into dumbbell-shaped samples with a length of 5 cm, a width of 4 mm, and a thickness of 1 mm, and a 2-mm notch was cut in the middle of the sample.

[0068] Then it was fixed between the tensile fixtures and uniaxially stretched in the vertical direction at a stretching rate of 100 mm / min to obtain the tensile stress-strain curve of the gelatin-sodium alginate gel. The coating area was determined based on the tensile force of the unnotched sample and the displacement at which the notch crack began to expand, and the tearing energy was calculated. The results are shown in Figure 4 .

[0069] Figure 4 a is the stress-strain curve diagram of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Figure 4 b is the bar chart of the fracture stress, Young's modulus, and tearing energy of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. By comparison, it was found that the fracture stress, fracture elongation, Young's modulus, and tearing energy of Example 1 were the highest among the four, reaching 3.5 MPa, 748.9%, 1.29 MPa, and 14.83 kJ m -2 . Through analysis, Example 1 benefited from the unique multi-scale stress dispersion mechanism of its hierarchical heterogeneous structure. When subjected to external stress, the elastic sodium alginate polymer chains transferred the stress to the entire gel network, while the rigid gelatin crystals were responsible for bearing the stress and pinning the cracks, delaying the crack propagation and deflecting the cracks, thus delaying the fracture.

[0070] (3) Test of the adhesion performance between the gelatin-tannin-sodium alginate gel electrolyte and zinc metal:

[0071] The bonding performance between the gelatin-tannin-sodium alginate gel electrolyte and zinc metal was tested using an electronic universal testing machine.

[0072] The electrolytes prepared in Example 1 and Comparative Examples 1-3 above were cut into block samples with a length of 2 cm, a width of 2 cm, and a thickness of 1 mm, and lap shear tests were performed with zinc sheets, and their shear strengths were measured. The obtained results are shown in Figure 5 .

[0073] Figure 5 a is the shear strength-displacement curve between Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and the zinc sheet, Figure 5 b is the bonding physical diagram between Example 1 and different substrates; through comparison, it is found that the shear strength of Example 1 is the highest among the four, reaching 540.7 kPa. This is because the gelatin-tannin-sodium alginate gel electrolyte forms non-covalent interactions such as metal coordination, cation-π, and electrostatic interactions with zinc metal through a large number of functional groups such as catechol, carboxyl, and amino groups, thus ensuring strong interfacial force with the interface and achieving strong bonding performance.

[0074] Example 2

[0075] Measurement of the conductivity of the gelatin-tannin-sodium alginate gel electrolyte:

[0076] The conductivity of the gelatin-tannin-sodium alginate gel electrolyte was measured using an electrochemical workstation CHI 760e.

[0077] The electrolyte samples prepared in Example 1 and Comparative Examples above were respectively cut into cylindrical samples with a diameter of 12 mm and a height of 10 mm. Assembled into a symmetric cell in the manner of platinum sheet|gel electrolyte|platinum sheet, and an AC impedance test was performed on the assembled device at a polarization voltage of 5 mV in the frequency range of 10 5 ~0.01 Hz, and then its conductivity was calculated. The obtained results are shown in Table 1.

[0078] Table 1

[0079] <![CDATA[Conductivity (mScm -1 )]]> Example 1 46.14 Comparative Example 1 7.78 Comparative Example 2 30.04 Comparative Example 3 33.67

[0080] By comparison, the conductivity of Example 1 is the highest, followed by Comparative Examples 2 and 3, and Comparative Example 1 is the lowest. These results indicate that the sodium alginate polymer domain forms a Zn 2+ transport channel through metal coordination, promoting the directional transition of Zn 2+ , thus making the gel electrolyte have high conductivity.

[0081] Example 3

[0082] Measurement of the zinc ion transference number of the gelatin-tannin-sodium alginate gel electrolyte:

[0083] The zinc ion transference number of the gelatin-tannin-sodium alginate gel electrolyte was tested using an electrochemical workstation CHI 760e.

[0084] The gel electrolyte samples prepared in Example 1 and the comparative examples above were cut into block samples with a length of 2 cm, a width of 2 cm, and a thickness of 1 mm.

[0085] Zinc sheets were used as the electrode materials, and the devices were assembled in the form of zinc sheet|gel electrolyte|zinc sheet. In the frequency range of 10 5 ~0.01 Hz, with a polarization voltage of 10 mV, the assembled devices were subjected to AC impedance tests before and after polarization, and then their zinc ion transference numbers were calculated. The obtained results are shown in Table 2.

[0086] Table 2

[0087] <![CDATA[Transport number of zinc ion (t + )]]> Example 1 0.77 Comparative Example 1 0.08 Comparative Example 2 0.44 Comparative Example 3 0.59

[0088] A high zinc ion transference number means that the ion transport path in the sodium alginate polymer phase ensures the directional transition of solvated Zn 2+ so that it can achieve a directional transition, thus realizing the rapid desolvation of Zn 2+ .

[0089] Example 4

[0090] Test on the interfacial compatibility between the gelatin-tannin-sodium alginate gel electrolyte and the zinc metal anode:

[0091] The interfacial compatibility of the gelatin-tannin-sodium alginate gel electrolyte was tested using an electrochemical workstation CHI 760e and a scanning electron microscope.

[0092] The gel electrolyte samples prepared in Example 1 and the comparative examples above were cut into block samples with a length of 2 cm, a width of 2 cm, and a thickness of 1 mm.

[0093] Zinc sheets were used as the electrode materials, and the devices were assembled in the form of zinc sheet|gel electrolyte|zinc sheet. Under the conditions of a current of 1 mA cm -2 and a areal capacity of 1 mAh cm -2 , the devices were cycled 50 times, and then the cycled zinc anodes were disassembled and taken out. The deposition morphology of the zinc anodes was studied using a scanning electron microscope. The obtained results are shown in Figure 6 .

[0094] Figure 6 Figure a shows the longitudinal cross-sectional micrographs of the zinc anodes after 50 cycles of the symmetric cells assembled using Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Figure 6b is the cross-sectional microscopic morphology diagram of the zinc anode after 50 cycles of the symmetric battery assembled using Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3; by comparison, only the symmetric battery assembled using Example 1 has a regular zinc anode surface and no obvious protrusions on the side after 50 cycles. This is because the high toughness of the gelatin-tannin-sodium alginate gel electrolyte can suppress zinc deposition during the charge-discharge cycle and adapt to the volume change of the zinc anode; the strong adhesion helps to keep close contact with the zinc anode during the cycle, inducing Zn 2+ to diffuse more orderly at the interface, forming a uniform and dense zinc deposit. The synergistic effect of the two realizes dendrite-free zinc deposition.

[0095] Example 5

[0096] Test on the interfacial compatibility between the gelatin-tannin-sodium alginate gel electrolyte and the zinc anode:

[0097] The interfacial compatibility of the gelatin-tannin-sodium alginate gel electrolyte was tested using an electrochemical workstation CHI 760e.

[0098] The gel electrolyte samples prepared in the above Example 1 and Comparative Examples were respectively cut into block samples with a length of 2 cm, a width of 2 cm, and a thickness of 1 mm. The electrode material used was a zinc sheet, and the device was assembled in the manner of zinc sheet|gel electrolyte|zinc sheet. Under the conditions of a current of 1 mA cm -2 and a areal capacity of 1 mAh cm -2 , a long cycle test was carried out. The obtained results are shown in Figure 7 .

[0099] Through Figure 7 comparison, it can be seen that the overpotential of Comparative Example 1 fluctuated violently at 50 h and then the circuit was interrupted; the overpotential of Comparative Example 2 fluctuated at 170 h and then the circuit was interrupted; the overpotential of Comparative Example 3 decreased significantly at 350 h and then a short circuit occurred. However, the overpotential of Example 1 remained stable during the 500-h cycle and did not show large fluctuations, which means that a compatible interface was formed between the gelatin-tannin-sodium alginate gel electrolyte and the zinc anode, thus inducing the zinc deposit to grow orderly and layer by layer, and further realizing stable zinc deposition / stripping behavior.

[0100] Example 6

[0101] Test on the interfacial compatibility between the gelatin-tannin-sodium alginate gel electrolyte and the zinc anode:

[0102] The in-situ tracking during the deposition process of the symmetric battery assembled with the gelatin-tannin-sodium alginate gel electrolyte was carried out using an optical microscope.

[0103] The gelatin-tannin-sodium alginate gel electrolyte sample prepared in Example 1 above was cut into block samples with a length of 2 cm, a width of 2 cm, and a thickness of 1 mm. The electrode material used was a zinc sheet, and a symmetric battery was assembled in the manner of zinc sheet|gel electrolyte|zinc sheet. At a current of 5 mA cm -2 for 60 min, the change of the deposit on the zinc anode during the deposition process was in-situ recorded by an optical microscope. The obtained results are shown in Figure 8 . It can be seen from the figure that as the deposition process proceeds, the Zn deposits always nucleate horizontally along the zinc anode and accumulate layer by layer to form a flat and uniform zinc deposition. This result further confirms that a compatible interface is formed between the gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 and the zinc anode.

[0104] Example 7

[0105] The gelatin-tannin-sodium alginate gel electrolyte prepared in Example 1 was applied to a solid-state zinc-ion hybrid capacitor:

[0106] (1) 3.7 g of activated carbon, 0.1 g of carbon black conductive agent, and 0.2 g of styrene-butadiene rubber binder were stirred evenly in deionized water to form a slurry, which was evenly coated on a titanium sheet with a thickness of 0.05 mm. The coating layer thickness was 0.15 mm. After drying, it was cut into square pieces with a length of 2 cm and a width of 2 cm as the positive electrode plate.

[0107] (2) The zinc sheet was cut into square pieces with a length of 2 cm and a width of 2 cm as the negative electrode plate.

[0108] (3) The activated carbon positive electrode, the gel electrolyte obtained in Example 1, and the zinc metal negative electrode were assembled into a solid-state zinc-ion hybrid capacitor, which was cycled at a current density of 1 A g -1 . The charge-discharge cut-off voltage was 0.3 - 1.8 V. The obtained results are shown in Figure 9 . From Figure 9 a, it can be seen that the curves of the assembled zinc-ion hybrid capacitor show a quasi-rectangle at different scan numbers, indicating that the device has typical capacitive behavior and can withstand a large scan number range and maintain a stable capacitive output; from Figure 9 b, it can be seen that the assembled device can still maintain a satisfactory capacitive output even at a large current density of 10 A g -1 , reaching 111 mAh g -1 . When at a small current density of 0.5 A g -1 , the device can reach the highest capacitive output, which is 260 mAh g -1 ; from Figure 9 c, it can be seen that when the assembled device is at a current density of 1 A g -1 , the first-cycle discharge capacity is 233.6 mAhg-1 , the initial Coulombic efficiency is 99.7%, the capacity retention rate is 97.6% after 10,000 cycles, and the Coulombic efficiency is 98.2%, showing excellent cycle stability.

[0109] The present invention uses three biomass resources, namely gelatin, tannin, and sodium alginate, as raw materials. By "salting out", the solubility of the gelatin triple helix polymer is reduced and its aggregation is induced, thereby precipitating to form a gelatin crystalline domain; the cross-linking of the sodium alginate macromolecular chain is promoted through metal coordination to form a sodium alginate polymer phase; tannin connects the two phases through hydrogen bond interactions formed between phenolic hydroxyl groups and amino and carboxyl groups, and then constructs a bio-based gel electrolyte with a hierarchical heterogeneous structure. The high toughness of the obtained bio-based gel electrolyte helps it adapt to the volume change of the zinc anode and suppress the growth of zinc deposits during the charge-discharge cycle; the strong adhesion helps it maintain close contact with the zinc anode during the charge-discharge cycle, which is conducive to the efficient migration of Zn 2+ at the interface and form uniform zinc deposition. The synergistic effect of the two enables the prepared bio-based gel electrolyte to achieve good interfacial compatibility with zinc metal. Due to the interfacial compatibility with zinc metal, the solid-state zinc-ion hybrid capacitor assembled based on the prepared bio-based gel electrolyte exhibits excellent stability during long-term charge-discharge cycles.

[0110] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A method for preparing a bio-based gel electrolyte with high interfacial compatibility, characterized in that: include, Dissolving gelatin, sodium alginate and tannin in deionized water and stirring evenly under heating conditions to obtain a prepolymer solution; The prepolymer solution is poured into a custom mold and refrigerated. At low temperatures, the gelatin macromolecular chains are entangled under the drive of hydrogen bonds to form gelatin triple helical polymers, and cross-linked with tannin molecules under the induction of hydrogen bonds to obtain pregels. The pregel was soaked in ammonium sulfate solution, using NH4 + and SO4 2- The "salting out" effect reduces the solubility of gelatin and destroys the hydration layer of gelatin, inducing the aggregation of gelatin triple helical polymers and generating strong hydrogen bonding, thereby precipitating in situ to form crystals, and then forming gelatin crystal domains; The obtained gel was immersed in zinc acetate solution. 2+ Under the action of metal, polymer domains are formed through metal coordination, thereby obtaining a fully bio-based gel electrolyte with a hierarchical heterogeneous structure; wherein gelatin serves as the crystalline domain and sodium alginate serves as the polymer domain. At the same time, tannin interacts with the amino groups in the gelatin crystalline domain and the carboxyl groups in the sodium alginate polymer domain through phenolic hydroxyl groups to form hydrogen bonds, thereby connecting the crystalline domain and the polymer domain.

2. The preparation method according to claim 1, characterized in that: The mass fractions of gelatin, sodium alginate and tannin in the precursor solution are 30wt%, 2wt% and 0.7wt% respectively.

3. The preparation method according to claim 1, characterized in that: The pH value of the precursor solution is 5-7.

4. The preparation method according to claim 1, characterized in that: The prepolymer solution is poured into a custom mold and refrigerated, wherein the refrigeration temperature is 4° C. and the gel time is 1 hour.

5. The preparation method according to claim 1, characterized in that: The pre-gel is immersed in an ammonium sulfate solution, wherein the concentration of the ammonium sulfate is 30wt% and the immersion time is 12h.

6. The preparation method according to claim 1, characterized in that: The obtained gel is immersed in a zinc acetate solution, wherein the concentration of zinc acetate is 20wt% and the immersion time is 24h.

7. A fully bio-based gel electrolyte with high interfacial compatibility obtained by the preparation method as described in any one of claims 1 to 6.

8. Use of the bio-based gel electrolyte with high interfacial compatibility as claimed in claim 7 in a solid hybrid capacitor.

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