A zinc ion eutectic salt electrolyte, a battery using the same, and a preparation method thereof

Abstract

The present application provides a zinc-ion eutectic salt electrolyte, a battery using the same, and a preparation method thereof. The zinc-ion eutectic salt electrolyte composition of the present application includes: Component A: a zinc salt, the zinc salt including zinc chloride; Component B: cellulose and / or a high-hydroxy-content derivative of cellulose; and Component C: water. Wherein, the molar ratio of Component A to Component C is less than or equal to 1:5, the concentration of the zinc salt is greater than or equal to 10 mol / kg, and the weight ratio of Component A to Component B is 1:0.001 to 1:10. This electrolyte composition has a new coordination structure, in which stable coordination is formed between zinc ions and the hydroxyl groups on the cellulose polymer, reducing the coordination between zinc ions and water molecules, and having a high zinc concentration. As a result, the zinc-ion eutectic salt electrolyte composition exhibits high stability at a high charge-discharge current density in the electrochemical window, reducing the occurrence of side reactions such as hydrogen evolution and zinc dendrite growth.

Description

Technical Field

[0001] The present invention relates to a zinc-ion eutectic salt electrolyte, a battery using the same, and a preparation method thereof. In the present invention, a zinc-ion eutectic salt electrolyte added with cellulose and zinc chloride is adopted. Background Art

[0002] With the transformation of the energy structure and the proposal of the dual-carbon commitment, new rechargeable batteries play an important role in large-scale energy storage devices and portable electronic devices. Aqueous zinc-ion batteries have become rechargeable batteries that are intensively studied in the post-lithium era due to their low cost, environmental friendliness, and high safety. The design of zinc-ion batteries is based on the reversible dissolution-deposition of zinc on the negative electrode. However, side reactions occurring on the surface of the zinc negative electrode (such as zinc dendrite growth, hydrogen evolution on the negative electrode surface, and growth of the solid electrolyte interface (SEI)) severely restrict the development of zinc-ion batteries. Among them, electrolyte optimization is one of the important means for preparing a highly reversible zinc negative electrode. The electrochemical window of conventional aqueous electrolytes is relatively narrow (~1.23V), and hydrogen evolution reaction is likely to occur on the zinc negative electrode. High-concentration salt electrolytes or new eutectic salts can significantly reduce the content of free water, thereby broadening the electrochemical window and suppressing the occurrence of hydrogen evolution reaction. However, high-concentration salts or eutectic salts often use high-fluorine components, which not only greatly increase the cost but also bring new burdens to the environment and recycling. And at high currents, there is still much room for improvement in the zinc dissolution-deposition stability of the electrolyte of the new zinc-ion battery.

[0003] To improve the performance of electrolytes, electrolyte additives are often used as an effective means, and their types mainly include inorganic salts and organic small molecules. Chinese Patent CN113206283A discloses a zinc-ion battery electrolyte based on eutectic salt electrolyte, using organic small molecules such as acetamide, succinonitrile or dimethyl sulfoxide as additives in the eutectic salt to improve the battery cycle performance. However, the salt concentration in the electrolyte is low and the water content is high (the water content in the zinc salt reaches 6 times that of zinc), and this system is actually not conducive to suppressing side reactions caused by water, and the test current of the battery is not clearly stated in this literature. Chinese Patent Document CN102683756B discloses a polymer rechargeable zinc-ion battery. The polymer gel electrolyte prepared using polyacrylamide, methylcellulose or ethylcellulose, and zinc salts solves some problems of aqueous solutions. However, the polymer electrolyte still contains about 50% mass fraction of water, which is difficult to avoid side reactions that may occur on the zinc negative electrode and may affect the improvement of the energy density of the whole battery (in this literature, zinc nitrate or zinc sulfate is used as the zinc salt, and a eutectic salt electrolyte is not formed; the maximum mass fraction of zinc salt in the electrolyte is 40%, which is equivalent to the ratio of zinc salt to water being 1:13 to 1:16. At this ratio, the coordination structure of zinc ions by zinc chloride salt changes little and the performance improvement is not obvious; the added cellulose substances (methylcellulose or ethylcellulose) belong to cellulose ethers and do not contain a large number of hydroxyl groups). Chinese Patent Document CN111740172A discloses a gel electrolyte for zinc-ion batteries and its preparation method. The gel electrolyte is prepared by using cellulose, divalent zinc salt, antifreeze and silicate through steps of cleaning, dissolving, stirring, ultrasonic treatment and cooling, and the electrochemical window is broadened. However, the electrolyte preparation process is complex, the types of chemical products used are many, and fluorine-containing components may be used, which has a greater impact on the environment. In this literature, a relatively large ratio of zinc salt to water is adopted, and all examples adopt a water content of more than 1:10, and zinc sulfate is used as the only zinc salt. This scheme is an aqueous gel electrolyte and is completely unsuitable for preparing molten salt electrolytes. Chinese Patent Document CN111211360A discloses an additive-modified aqueous zinc-ion colloidal electrolyte and its preparation method. A gelling agent, a structure optimizer and a surfactant are added to a mixed solution prepared from zinc salt and other metal salts to optimize problems such as electrolyte leakage and zinc negative electrode corrosion. However, due to the low zinc salt concentration and high water content in the electrolyte, the improvement of the energy density of the whole battery is limited, and the electrolyte preparation process is complex and the battery cycle life is short, which further limits the application of the electrolyte in actual situations. In addition, regarding high charge-discharge current densities, none of the existing technologies has adopted up to 10 mA·cm -2The charge-discharge current density. Taking CN 113206283A as an example, in the English literature [Adv. Funct. Mater. 2021, 31, 2102035] by Shi Jinqiang and Tao Zhanliang, the performance of this electrolyte (zinc chloride - acetamide - water (1:3:1)) was tested in a zinc / phenazine (PNZ) full cell. The active material loading of the positive electrode material was 0.25 mg / cm 2 , the capacity was 72.3 mAh / g, and the areal capacity was 0.25 mg / cm 2 *72.3 mAh / g * 1 / 1000 g / mg = 0.018 mAh / cm 2 . 10C means charging is completed in 0.1 hour, so the actual measured charge-discharge current density was 0.18 mA / cm 2 . If a current density of 10 mA / cm 2 is to be achieved at the 10C rate, the active material loading of the positive electrode material needs to reach 13.9 mg / cm 2 . SUMMARY OF THE INVENTION

[0004] At present, biomass materials have the advantages of wide sources, environmental friendliness, low price and safety, etc., but they are rarely used as electrolyte additives in zinc-ion batteries, and the current preparation process of cellulose applied to zinc-ion batteries is complex and the optimization effect is not obvious. Due to the presence of a large amount of free water in the current aqueous zinc-ion electrolytes, it is easy to cause positive electrode dissolution and serious side reactions, thus limiting the electrolyte voltage window (~1.23 V). Eutectic salt electrolytes have a high cost, serious side reactions occur during the charge-discharge process at high current density, the growth of zinc dendrites will lead to a decrease in Coulomb efficiency, capacity attenuation, and even short circuit; the hydrogen evolution reaction on the one hand causes gas generation inside the battery, increasing the internal pressure of the battery, directly leading to the swelling and destruction of the battery, and on the other hand, it will consume the electrolyte, cause the local pH value to increase, and can cause the growth of the SEI interface. The above factors make it difficult for the zinc negative electrode to achieve a high-stability and highly reversible dissolution-deposition cycle. There is a continuous need in the art for an environmentally friendly zinc-ion electrolyte composition that can exhibit high stability at high charge-discharge current densities such as (10 mA·cm -2 ), improve the utilization rate of the zinc negative electrode, and at the same time effectively inhibit the side reactions of the zinc negative electrode, so as to fundamentally solve the challenges of the zinc negative electrode and promote the practical application of zinc-ion batteries. The inventors of the present application unexpectedly found that by reducing the water content, not using fluorides in the zinc-ion electrolyte composition, and using cellulose or its derivatives containing a large number of hydroxyl groups as part of the electrolyte composition to form a coordination structure with zinc ions, the above requirements can be met, and a zinc-ion eutectic salt electrolyte composition with a novel coordination structure can be obtained.

[0005] The present invention includes the following:[[]]END]]

[0006] A zinc ion eutectic salt electrolyte composition, comprising:

[0007] Component A: a zinc salt, the zinc salt comprising zinc chloride,

[0008] Component B: cellulose and / or high-hydroxyl-content derivatives of cellulose

[0009] Component C: water,

[0010] wherein, the molar ratio of component A to component C is less than or equal to 1:5,

[0011] the concentration of zinc is greater than or equal to 10 mol / kg, calculated based on the mass of water,

[0012] the weight ratio of component A to component B is 1:0.001 to 1:10. The electrolyte composition does not contain fluorides, that is, fluoride-containing compounds are not deliberately added.

[0013] Further, according to the electrolyte composition described above, wherein

[0014] the molar ratio of component A to component C is 1:2 to 1:4, or 1:2.1 to 1:3.8, or 1:2.1 to 1:3.7, or 1:2.2 to 1:3.6.

[0015] Further, according to the electrolyte composition described above, wherein

[0016] Calculated based on the total weight of component A, the content of zinc chloride in component A is more than 70 wt%; optionally calculated based on the total weight of the composition, the mass percentage of component A is more than 67 wt%. Component A may further include any one or more of zinc salts selected from zinc sulfate, zinc acetate, etc.

[0017] Further, according to the electrolyte composition described above, wherein

[0018] more than 80% of the polymerization units in the high-hydroxyl-content derivatives of cellulose have hydroxyl groups (the hydroxyl groups are those carried by the substituents, or the polymerization units are unsubstituted),

[0019] Further, according to the electrolyte composition described above, wherein the high-hydroxyl-content derivatives of cellulose include one or more selected from the following: hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; the source of the cellulose is selected from materials with high cellulose content such as paper, wood, and industrial cellulose.

[0020] Further, according to the electrolyte composition described above, wherein

[0021] the weight ratio of component A to component B is 1:0.3 to 1:5.

[0022] A zinc-ion battery, comprising:

[0023] a positive electrode, a negative electrode, and an electrolyte composition according to any one of Embodiments 1 to 6, the electrolyte composition being disposed between the positive electrode and the negative electrode.

[0024] Furthermore, in the zinc-ion battery according to the above, the negative electrode includes a zinc foil or a zinc plate.

[0025] A method for preparing the electrolyte composition according to any one of the above, comprising:

[0026] Mixing component A, component B, and component C and heating them to form a homogeneous phase to obtain the electrolyte composition.

[0027] Embodiment 10. In the method according to Embodiment 9, the heating is performed at a temperature higher than room temperature and less than or equal to 100 °C.

[0028] This application also includes a zinc-ion eutectic salt electrolyte composition prepared according to the above.

[0029] This application provides a zinc-ion eutectic salt electrolyte composition with a novel coordination structure, where the concentration of the zinc salt is higher than 10 mol / kg, the water content in the system is significantly reduced, and the coordination structure of zinc ions in the electrolyte is changed, thereby optimizing the zinc deposition process. A stable coordination is formed between the zinc ions in this composition and the hydroxyl groups on the cellulose polymer, reducing the coordination between zinc ions and water molecules, further optimizing the zinc deposition process, and reducing the occurrence of side reactions such as hydrogen evolution and zinc dendrite growth. As a result, the electrochemical window of this zinc-ion eutectic salt electrolyte composition is significantly broadened, and it exhibits high stability at a high charge-discharge current density (10 mA·cm -2 ), greatly improving the battery cycle life. The process route of the present invention is simple, easy to operate, environmentally friendly, and low in cost. It is prepared by a one-step method and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present disclosure and do not limit the present disclosure.

[0031] Figure 1 Shows a schematic diagram of the coordination structure of a zinc-ion eutectic salt electrolyte composition according to a specific embodiment of the present application.

[0032] Figure 2 Shows the cycling performance of a zinc-ion eutectic salt electrolyte with added cellulose in a symmetric battery according to a specific embodiment of the present application.

[0033] Figure 3 The cycling of a zinc-ion eutectic salt electrolyte without added cellulose in a symmetric cell is shown.

[0034] Figure 4 The spectral characterization of a zinc-ion eutectic salt electrolyte with added cellulose in a specific embodiment of the present application is shown (and the comparison with the spectral characterizations in other embodiments is also shown), demonstrating the formation of a new coordination structure.

[0035] Figure 5 is Figure 4 The superposition diagram of the spectra between "3800 cm -1 and 2400 cm -1 " can clearly show the formation of the new coordination structure.

[0036] Figure 6 The charge-discharge cycling of a symmetric cell with added DMSO at 10 mA·cm -2 is shown.

[0037] Figure 7 The schematic diagram of the hydrogen bond structure in ordinary cellulose is shown. This figure is mainly used for comparison with Figure 1 to further illustrate the new coordination structure formed in the present application.

[0038] Figure 8 The charge-discharge cycling of the symmetric cell of Comparative Example 6 at 10 mA·cm -2 is shown. Specific Embodiment

[0039] The terms in the present application, unless explicitly stated to the contrary or inconsistent with the context, have the meanings commonly understood by those skilled in the art. The term "zinc-ion eutectic salt electrolyte composition" in the present application refers to a eutectic salt electrolyte composition with a zinc salt content higher than 60%.

[0040] At present, the application of biomass materials as electrolyte additives in zinc-ion batteries is less, and the preparation process is complex and the optimization effect is not obvious. The current eutectic salt electrolytes have a high cost, and there are serious side reactions in aqueous zinc-ion electrolytes, and it is difficult for zinc to achieve a highly stable and highly reversible dissolution-deposition cycle. There is a continuous need in the art for an environmentally friendly zinc-ion electrolyte composition that can exhibit high stability at a high charge-discharge current density such as (10 mA·cm -2 ). The inventors of the present application unexpectedly found that by reducing the water content, not using fluorides in the zinc-ion electrolyte composition, and using cellulose or its derivatives containing a large number of hydroxyl groups as part of the electrolyte composition to form a coordination structure with zinc ions, the above needs can be met, and a zinc-ion eutectic salt electrolyte composition with a new coordination structure can be obtained.

[0041] On the one hand, the present application provides a zinc ion eutectic salt electrolyte composition, comprising:

[0042] Component A: a zinc salt, the zinc salt comprising zinc chloride,

[0043] Component B: cellulose and / or high hydroxyl content derivatives of cellulose, and

[0044] Component C: water,

[0045] wherein, the molar ratio of component A to component C is less than or equal to 1:5,

[0046] the concentration of the zinc salt is greater than or equal to 10 mol / kg, calculated based on the weight of water,

[0047] the weight ratio of component A to component B is from 1:0.001 to 1:10. The electrolyte composition does not contain fluorides, that is, no fluoride-containing compounds are deliberately added. The expression "the concentration of the zinc salt is greater than or equal to 10 mol / kg" in the present application means that the number of moles of the zinc salt added per kg of water is more than 10 mol. In fact, calculated by "the molar ratio of component A to component C is less than or equal to 1:5", the concentration of the zinc salt is greater than 11.1 mol / kg of water.

[0048] Without being limited by theory, it is considered that due to the low concentration of zinc ions in conventional aqueous zinc ion electrolytes, usually about 2M, it is difficult to achieve stable cycling and hydrogen evolution reaction is likely to occur under high charge-discharge current density (10 mA·cm -2 ); while in the usual zinc ion eutectic salt electrolyte composition, although the concentration of zinc ions is high, side reactions such as zinc dendrite growth are likely to occur. In the zinc ion eutectic salt electrolyte composition of the present application, zinc ions enter the hydrogen bond network of cellulose and form coordination with the hydroxyl groups on the cellulose polymer, and are no longer the Zn(H2O)6 2+ coordination structure, and the number of H2O molecules in the coordination is significantly reduced. Due to the formation of a new coordination structure between cellulose and Zn 2+ the water coordinated with Zn 2+ is reduced, the stability of the electrolyte is increased, and the electrochemical window of the electrolyte is significantly broadened, thereby suppressing the hydrogen evolution reaction, so that the symmetric battery of the electrolyte composition exhibits high stability under high charge-discharge current density (10 mA·cm -2 ). At the same time, since fluoride is not used in the electrolyte composition, environmental pollution is reduced. Figure 1 Shows a schematic diagram of the coordination structure of the zinc ion eutectic salt electrolyte composition according to a specific embodiment of the present application. Figure 7 Shows a schematic diagram of the hydrogen bond structure in ordinary cellulose, Figure 7 for use in comparison with Figure 1A comparison is made to further illustrate the novel coordination structure formed in this application. Figure 4 and Figure 5 The spectral diagrams in [relevant reference] confirm the existence of this new coordination structure.

[0049] There is no particular limitation on the type of cellulose described in this application, and biomass materials from various sources can be used, such as cotton, wood, straw, reed, hemp, mulberry bark, bagasse, coconut shell, and so on.

[0050] In some embodiments, in the electrolyte composition according to this application, the molar ratio of component A to component C is from 1:2 to 1:4, or 1:2.1 to 1:3.8, or 1:2.1 to 1:3.7, or 1:2.2 to 1:3.6. Because in a system with a higher water content, it is easy to form Zn(H2O)6 2+ coordination structure. When the molar ratio of component A to component C is much less than 1:6, this coordination structure can be effectively inhibited, and further promote the formation of an effective coordination structure between zinc ions and cellulose. An appropriate water content can provide a medium for the formation of a new coordination structure and change properties such as the viscosity and conductivity of the electrolyte. The water molecules are incorporated into the hydrogen bond network structure of the eutectic salt, thereby inhibiting irreversible side reactions with zinc ions.

[0051] In some embodiments, in the electrolyte composition according to this application, calculated based on the total weight of component A, the content of zinc chloride in component A is 70 wt% or more; optionally, calculated based on the total weight of the composition, the mass percentage of component A is 67 wt% or more. Component A may also include any one or several zinc salts selected from zinc salts such as zinc sulfate and zinc acetate. There is no limitation on the type of zinc salt in the electrolyte composition of this application, as long as a stable and homogeneous electrolyte composition can be formed. In a preferred embodiment, the mass percentage of component A is 67 wt% or more, which reduces the water molecule content in the electrolyte, changes the coordination structure of zinc ions, inhibits side reactions of water in the electrolyte on the zinc dissolution - deposition process, and provides support for cellulose dissolution, having a certain effect on optimizing the zinc dissolution - deposition stability at a high current density. In some embodiments, the mass percentage of component A is 80 wt% or more. Without being limited by theory, it is considered that zinc chloride is most suitable for the method of this application. Some zinc salts with low solubility, such as zinc fluoride, are not suitable for the method of this invention. For other zinc salts such as zinc sulfate and zinc acetate, their binding energy is weaker than that of zinc ions and water molecules in the Zn(H2O)6 2+ coordination structure and cannot weaken Zn(H2O)6 2+The amount of the coordination structure, and thus, it is not suitable to be added to the composition of the present application in a large amount. Zinc bromide also cannot be used in a large amount in the electrolyte composition of the present application because the electrolyte composition formed by zinc bromide will have serious polarization after long-term cycling (as shown in Comparative Example 6 of the present application).

[0052] In some embodiments, in the electrolyte composition according to the present application, more than 80% of the polymerization units in the high hydroxyl content derivative of cellulose have hydroxyl groups (the hydroxyl groups are carried by the substituents or the polymerization units are unsubstituted). The main principle of the present application is to dissolve cellulose into a homogeneous liquid phase in the presence of a small amount of water and zinc salt, and the hydroxyl groups on the cellulose macromolecular chain form stable new complexes with zinc ions, thereby providing a high-performance electrolyte composition. It is believed that as long as the hydroxyl content of cellulose is high, it is helpful to form the electrolyte composition. However, in the case of low hydroxyl content, it is relatively difficult to form a homogeneous liquid phase or a stable coordination structure.

[0053] In some embodiments, in the electrolyte composition according to the present application, the high hydroxyl content derivative of cellulose includes one or more selected from the following: carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; the source of the cellulose is selected from materials with high cellulose content such as paper, wood, and industrial cellulose.

[0054] In some embodiments, in the electrolyte composition according to the present application, the weight ratio of component A to component B is 1:0.025 to 1:0.15. However, too much cellulose usually makes it difficult to form a homogeneous liquid phase electrolyte. When the molecular weight of the zinc salt is similar to the molecular weight of each polymerization unit of cellulose, the molar ratio and weight ratio of the zinc salt to cellulose can be approximately equalized.

[0055] The electrolyte composition of the present application can be used in batteries of various structures, and there is no limitation on its specific application scope. Another aspect of the present application provides a zinc ion battery, which includes: a positive electrode, a negative electrode, and the electrolyte composition according to the present application, and the electrolyte composition is disposed between the positive electrode and the negative electrode.

[0056] A battery using the electrolyte composition of the present application. In some embodiments, in the zinc ion battery according to the present application, the negative electrode includes a zinc foil or a zinc plate.

[0057] There is no limitation on the method for preparing the electrolyte composition described in the present application, as long as each component can be uniformly mixed together to form a homogeneous liquid phase. On the other hand, the present application provides a one-step method for producing the electrolyte composition according to the present application. The method for preparing the electrolyte composition of the present application includes: mixing component A, component B, and component C and heating them to form a homogeneous phase, thereby obtaining the electrolyte composition.

[0058] In some embodiments, in the method for preparing the electrolyte composition of the present application, the heating is carried out at a temperature higher than room temperature and less than or equal to 100 °C.

[0059] Therefore, the present application also provides a zinc-ion eutectic salt electrolyte composition prepared by the method for preparing the electrolyte composition according to the present application.

[0060] The present application provides a zinc-ion eutectic salt electrolyte composition with a novel coordination structure. A stable coordination is formed between the zinc ions in this composition and the hydroxyl groups on the cellulose polymer, reducing the coordination between the zinc ions and water molecules. The concentration of zinc is higher than 10 mol / kg, so that the zinc-ion eutectic salt electrolyte composition exhibits high stability at a high charge-discharge current density (10 mA·cm -2 ), reducing the occurrence of side reactions such as hydrogen evolution and zinc dendrite growth. The process route of the present invention is simple, easy to operate, and low in cost, and is prepared by a one-step method.

[0061] The numerical ranges described in the present application can be used alone or in combination.

[0062] Examples

[0063] The raw material sources used in the examples of the present application are shown in Table 1, and other materials not listed in the table are all commercially available products.

[0064] Table 1 Raw material sources

[0065]

[0066] Example 1 (ZnCl2 + cellulose (1:2.2 + 0.6 g))

[0067] This example discloses the zinc-ion eutectic salt electrolyte composition 1 of the present application and its preparation process.

[0068] The components of the zinc-ion eutectic salt electrolyte composition 1 are as follows:

[0069] Component A: 6.815 g of zinc salt ZnCl2;

[0070] Component B: 0.6 g of cellulose powder;

[0071] Component C: 1.98 g of deionized water.

[0072] The preparation method of the zinc ion eutectic salt electrolyte composition 1 is as follows: Pour Component A, Component B, and Component C into a flask, heat and stir at 80 °C for 2 hours to form a homogeneous liquid, and thus obtain the electrolyte composition 1.

[0073] Prepare the electrolyte composition 1 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 , and the measured results are as Figure 2 shown. During the 1000-hour test process, the occurrence of side reactions such as hydrogen evolution reaction and zinc dendrite growth was effectively inhibited, and a highly reversible and highly stable zinc dissolution-deposition cycle was achieved. The test results show that the preparation method of this electrolyte composition is simple and can be prepared by a one-step method; using biomass materials - cellulose and fluoride-free components as the effective components of the electrolyte reduces the cost of the electrolyte and its impact on the environment; it solves the problem of poor zinc dissolution-deposition cycle performance of currently used zinc eutectic salts at high current densities. The results of spectral testing of the obtained electrolyte composition 1 are shown in Figure 4 and Figure 5 , and the results of Figure 4 and Figure 5 show the formation of a new coordination structure.

[0074] Cellulose is insoluble in water but can dissolve in ZnCl2 solution. As shown in Figure 4 , after adding the ZnCl2(1:2.2) electrolyte, the characteristic peaks of cellulose at 1430 cm -1 and 1047 cm -1 decrease significantly, indicating that the C-O bond and C-H bond structures therein are destroyed and cellulose dissolves. For the calibration of the cellulose infrared spectrum peaks, please refer to Table 2. At the same time, Zn 2+ enters the cellulose hydrogen bond network structure, and the coordination structure of Zn(H2O)6 2+ changes. Comparing the comparative composition 1 of Comparative Example 1 and the electrolyte composition 1 of Example 1 ( Figure 4 ), through peak fitting, it is found that the area ratio of the peak around 3200 cm -1 (representing the intermolecular hydrogen bonds of cellulose and the vibration of water molecules connected by hydrogen bonds) increases by about 3%, and at the same time, the area of the peak around 3350 cm -1 (representing the intramolecular hydrogen bonds of cellulose and the vibration of water molecules connected by weak hydrogen bonds) decreases by about 3%. This shows that the added cellulose has participated in the zinc ion coordination structure, forming an electrolyte containing a new coordination structure. In this example, it is further found that similar experimental results can be obtained when the addition amount of cellulose is 0.2 g, 0.6 g, and 1.0 g.

[0075] Table 2. Calibration of Infrared Spectral Peaks

[0076]

[0077] Example 2 (ZnCl2 + Cellulose (1:3.6 + 0.2 g))

[0078] This example discloses the zinc ion eutectic salt electrolyte composition 2 of the present application and its preparation process.

[0079] The components of the zinc ion eutectic salt electrolyte composition 2 are as follows:

[0080] Component A: 6.815 g of zinc salt ZnCl2;

[0081] Component B: 0.2 g of cellulose (conventional toilet paper);

[0082] Component C: 3.24 g of deionized water.

[0083] The preparation method of the zinc ion eutectic salt electrolyte composition 2 is: Pour Component A, Component B and Component C into a flask, heat with 80 °C hot water and stir for 2 hours to form a homogeneous liquid, thus obtaining the electrolyte composition 2.

[0084] Prepare the electrolyte composition 2 into a Zn||Zn symmetric battery, and use a Neware battery test device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 , and the measured results are almost exactly the same as those in Example 1. It is found during the test that this electrolyte can effectively inhibit the occurrence of side reactions such as hydrogen evolution reaction and zinc dendrite growth, and achieve a highly reversible and highly stable zinc dissolution-deposition cycle. It is further found in this example that similar experimental results can be obtained when the addition amount of cellulose is 0.2 g, 0.6 g, and 1.0 g.

[0085] Example 3 (ZnCl2 + Hydroxypropyl Cellulose (1:2.2 + 0.6 g))

[0086] This example discloses the zinc ion eutectic salt electrolyte composition 3 of the present application and its preparation process.

[0087] The components of the zinc ion eutectic salt electrolyte composition 3 are as follows:

[0088] Component A: 6.815 g of zinc salt ZnCl2;

[0089] Component B: 0.6 g of hydroxypropyl cellulose;

[0090] Component C: 1.98 g of deionized water.

[0091] The preparation method of the zinc-ion eutectic salt electrolyte composition 3 is as follows: Pour component A, component B, and component C into a flask, heat with 80°C hot water and stir for 2 hours to form a homogeneous liquid, thus obtaining the electrolyte composition 3.

[0092] Prepare the electrolyte composition 3 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 . The measured results are almost exactly the same as those of Example 1. During the testing process, it was found that this electrolyte can effectively inhibit the occurrence of side reactions such as hydrogen evolution reaction and zinc dendrite growth, and achieve a highly reversible and highly stable zinc dissolution-deposition cycle.

[0093] Example 4 (ZnCl2 + zinc sulfate + cellulose (1:3.6 + 0.2 g))

[0094] This example discloses the zinc-ion eutectic salt electrolyte composition 4 of the present application and its preparation process.

[0095] The components of the zinc-ion eutectic salt electrolyte composition 4 are as follows:

[0096] Component A: 5.452 g of zinc chloride ZnCl2 + 1.615 g of zinc sulfate ZnSO4;

[0097] Component B: 0.2 g of cellulose (ordinary toilet paper);

[0098] Component C: 3.24 g of deionized water.

[0099] The preparation method of the zinc-ion eutectic salt electrolyte composition 4 is as follows: Pour component A, component B, and component C into a flask, heat with 80°C hot water and stir for 2 hours to form a homogeneous liquid, thus obtaining the electrolyte composition 4. In this example, it was found that this composition can form a uniform and stable electrolyte with good fluidity.

[0100] Prepare the electrolyte composition 4 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 . The measured results are almost exactly the same as those of Example 1. During the testing process, it was found that this electrolyte can effectively inhibit the occurrence of side reactions such as hydrogen evolution reaction and zinc dendrite growth, and achieve a highly reversible and highly stable zinc dissolution-deposition cycle. In this example, it was further found that similar experimental results can be obtained when the addition amount of cellulose is 0.2 g and 0.6 g.

[0101] Comparative Example 1 (ZnCl2 (1:2.2))

[0102] This example discloses Comparative Composition 1 and its preparation process.

[0103] The components of the Comparative Composition 1 are as follows:

[0104] Component A: 6.815 grams of zinc salt ZnCl2;

[0105] Component C: 1.98 grams of deionized water.

[0106] The preparation method of the Comparative Composition 1 is: Pour Component A and Component C into a flask, heat with 80°C hot water and stir for 10 minutes to form a homogeneous liquid, thus obtaining the Comparative Composition 1.

[0107] Prepare the Comparative Composition 1 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 The measured results are as Figure 3 shown. The test results show that after cycling for about 250 hours, zinc dendrite growth is severe and the polarization of the symmetric battery increases significantly.

[0108] Comparative Example 2 (ZnCl2(1:3.6))

[0109] This example discloses Comparative Composition 2 and its preparation process.

[0110] The components of the Comparative Composition 2 are as follows:

[0111] Component A: 6.815 grams of zinc salt ZnCl2;

[0112] Component C: 3.24 grams of deionized water.

[0113] The preparation method of the Comparative Composition 2 is: Pour Component A and Component C into a flask, heat with 80°C hot water and stir for 10 minutes to form a homogeneous liquid, thus obtaining the Comparative Composition 2.

[0114] Prepare the Comparative Composition 2 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 The measured results are exactly the same as those of Comparative Example 1. The test results show that after cycling for about 250 hours, zinc dendrite growth is severe and the polarization of the symmetric battery increases significantly.

[0115] Comparative Example 3 (ZnCl2-DMSO-H2O(1:3:6))

[0116] This example discloses Comparative Composition 3 and its preparation process, repeating the formulation of CN 113206283A.

[0117] The components of the comparative composition 3 are as follows:

[0118] Component A: 1.36 g of zinc salt ZnCl2;

[0119] Component B: 2.82 g of dimethyl sulfoxide (DMSO);

[0120] Component C: 1.08 g of deionized water.

[0121] The preparation method of the comparative composition 3 is as follows: Pour Component A, Component B and Component C into a flask, heat and stir at 80 °C to form a homogeneous liquid, thus obtaining the comparative composition 3.

[0122] Prepare the comparative composition 3 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 The measured results are as Figure 6 shown. The test results show that after cycling for about 10 hours, severe zinc dendrite growth occurs and the symmetric battery shorts.

[0123] Comparative Example 4 (ZnCl2-H2O (2M, about 1:28))

[0124] This example discloses the comparative composition 4 and its preparation process.

[0125] The components of the comparative composition 4 are as follows:

[0126] Component A: 1.36 g of zinc salt ZnCl2;

[0127] Component C: Add water to make up to a 2M solution.

[0128] The preparation method of the comparative composition 4 is as follows: Pour Component A and Component C into a flask, heat and stir at 80 °C for 10 minutes to form a homogeneous liquid, thus obtaining the comparative composition 4.

[0129] Prepare the comparative composition 4 into a Zn||Zn symmetric battery, and use a Neware battery testing device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 The measured results are similar to those of Comparative Example 3. The test results show that after cycling for about 10 hours, severe zinc dendrite growth occurs and the symmetric battery shorts.

[0130] Comparative Example 5 (ZnCl2 + zinc sulfate + cellulose (1:3.6 + 0.2 g))

[0131] This example discloses the comparative composition 5 and its preparation process.

[0132] The components of the comparative composition 5 are as follows:

[0133] Component A: 4.089 g of zinc chloride ZnCl2 + 3.230 g of zinc sulfate ZnSO4;

[0134] Component B: 0.2 g of cellulose (conventional toilet paper);

[0135] Component C: 3.24 g of deionized water.

[0136] The preparation method of the comparative composition 5 is as follows: Pour Component A, Component B, and Component C into a flask, heat with 80°C hot water and stir for 2 hours to form a homogeneous liquid, but the fluidity is poor, so subsequent tests were not continued. When the composition of Component A was changed to "2.726 g of zinc chloride ZnCl2 + 4.845 g of zinc sulfate ZnSO4", it was found that a uniform electrolyte could not be formed and layering occurred.

[0137] Comparative Example 6 (ZnBr2 + cellulose (1:3.6 + 0.2 g))

[0138] This example discloses Comparative Composition 6 and its preparation process.

[0139] The components of this Comparative Composition 6 are as follows:

[0140] Component A: 11.25 g of zinc salt ZnBr2;

[0141] Component B: 0.2 g of cellulose (conventional toilet paper);

[0142] Component C: 3.24 g of deionized water.

[0143] The preparation method of the comparative composition 6 is as follows: Pour Component A, Component B, and Component C into a flask, heat with 80°C hot water and stir for 2 hours to form a homogeneous liquid, that is, the comparative composition 6 is obtained.

[0144] Prepare the comparative composition 6 into a Zn||Zn symmetric battery, and use a Neware battery test device (CT-4008) to test its cycling performance at a high charge-discharge current density of 10 mA·cm -2 It was found that when cycling for 25 h, the battery polarization increased significantly. (See Figure 8 )

[0145] The above is only an exemplary embodiment of the present disclosure, and is not used to limit the protection scope of the present disclosure. The protection scope of the present disclosure is determined by the appended claims.

Claims

1. A zinc ion eutectic salt electrolyte composition, comprising: Component A: a zinc salt, the zinc salt comprising zinc chloride, and calculated based on the total weight of Component A, the content of zinc chloride in Component A is above 70 wt%, Component B: cellulose and / or a high-hydroxyl-content derivative of cellulose, and Component C: water, wherein the molar ratio of Component A to Component C is from 1:2 to 1:4, the concentration of the zinc salt is greater than or equal to 10 mol / kg, calculated based on the weight of water, the weight ratio of Component A to Component B is from 1:0.001 to 1:10, and the electrolyte composition is a homogeneous liquid phase.

2. The electrolyte composition according to claim 1, wherein the molar ratio of Component A to Component C is from 1:2.1 to 1:3.

8.

3. The electrolyte composition according to claim 1, wherein calculated based on the total weight of the composition, the mass percentage of Component A is above 67 wt%.

4. The electrolyte composition according to claim 1, wherein more than 80% of the polymerization units in the high-hydroxyl-content derivative of cellulose have hydroxyl groups, where the hydroxyl groups are carried by the substituents or the polymerization units are unsubstituted.

5. The electrolyte composition according to claim 1, wherein the high-hydroxyl-content derivative of cellulose includes one or more selected from the following: carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; the source of the cellulose is selected from materials with high cellulose content, and the materials are selected from: paper, wood, and industrial cellulose.

6. The electrolyte composition according to claim 1, wherein the weight ratio of Component A to Component B is from 1:0.025 to 1:0.

15.

7. The electrolyte composition according to claim 1, wherein the molar ratio of Component A to Component C is from 1:2.1 to 1:3.

7.

8. The electrolyte composition according to claim 1, wherein the molar ratio of Component A to Component C is from 1:2.2 to 1:3.

6.

9. The electrolyte composition according to claim 3, wherein Component A further includes any one or several selected from zinc sulfate and zinc acetate.

10. A zinc ion battery, comprising: a positive electrode, a negative electrode, and the electrolyte composition according to any one of claims 1 to 6, and the electrolyte composition is disposed between the positive electrode and the negative electrode.

11. The zinc ion battery according to claim 10, wherein the negative electrode comprises a zinc foil or a zinc plate.

12. A method for preparing the zinc ion eutectic salt electrolyte composition according to any one of claims 1 to 9, comprising: mixing Component A, Component B, and Component C and heating them to form a homogeneous phase to obtain the electrolyte composition.

13. The method according to claim 12, wherein the heating is carried out at a temperature higher than room temperature and less than or equal to 100 °C.

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