High coulombic efficiency organic electrolyte for secondary zinc ion battery and preparation method therefor, and secondary zinc ion battery

Abstract

An organic electrolyte for a secondary zinc ion battery comprises a zinc salt, a sulfone co-solvent, and a main solvent. By using a co-solvent to adjust the solvation structure of zinc ions, the deposition of zinc ions can be more uniform and denser, and a dense deposition structure of (002) crystal planes is presented, thereby inhibiting the growth of zinc dendrites and achieving high coulombic efficiency of the secondary zinc ion battery.

Description

High coulombic efficiency organic electrolyte for secondary zinc-ion batteries and its preparation method; secondary zinc-ion batteries Technical Field

[0001] This invention belongs to the field of rechargeable zinc-ion battery electrolyte technology, and relates to a high coulombic efficiency organic electrolyte for secondary zinc-ion batteries and its preparation method. Background Technology

[0002] The theoretical capacity of zinc is 820 mAh g. -1 Or 5850mAh cm -3 With an electrode potential of -0.76V (vs. standard hydrogen electrode), rechargeable zinc-ion batteries (ZIBs) are among the most popular multivalent rechargeable batteries. Besides the zinc anode, ZIBs typically use materials such as MnO2, V2O5, and VS2 as the cathode, and an aqueous solution as the electrolyte. ZIBs offer advantages such as high safety, affordability, and environmental friendliness, making them more suitable for large-scale storage and commercial applications compared to lithium-ion and lead-acid batteries. Furthermore, proven zinc reserves are abundant, and developing zinc-ion rechargeable batteries will address the high cost of lithium-ion batteries in the energy storage field.

[0003] Current research on zinc-ion batteries focuses on aqueous zinc-ion batteries, which offer advantages such as low cost, intrinsically non-flammable electrolyte, and high specific capacity. However, the thermodynamic instability of the zinc anode with water remains a major concern for aqueous zinc-ion batteries. This leads to problems such as hydrogen evolution, passivation, and corrosion of the zinc anode in aqueous electrolytes. These issues result in short battery life, low coulombic efficiency, and safety concerns related to hydrogen production.

[0004] Many methods have been proposed to address the thermodynamic instability of aqueous electrolytes with zinc anodes, but these methods all aim to establish a "quasi" thermodynamically stable interface between the zinc anode and the aqueous electrolyte. However, with cycling, the collapse of the interfacial layer structure and electrolyte consumption eventually break this "quasi" thermodynamic stability. For pure organic solvents, the intrinsic thermodynamic stability of organic electrolytes with zinc anodes can avoid problems such as hydrogen evolution, passivation, and corrosion commonly found in aqueous zinc-ion batteries. However, organic electrolytes also face greater challenges; their higher viscosity and lower conductivity compared to aqueous electrolytes lead to more severe dendrite growth. Furthermore, for commercial zinc-ion batteries, energy density is a crucial performance indicator. To achieve higher energy density, the anode must achieve the highest possible coulombic efficiency to reduce the N / P ratio. Therefore, achieving commercially viable coulombic efficiency for the anode is a current research focus. This invention is based on this premise. Summary of the Invention

[0005] The purpose of this invention is to provide a high coulombic efficiency organic electrolyte for secondary zinc-ion batteries and its preparation method, so as to improve the zinc anode interface and achieve high coulombic efficiency under high current conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a high coulombic efficiency organic electrolyte for secondary zinc-ion batteries, which is composed of zinc salt, sulfone co-solvent and main solvent with a boiling point exceeding 100°C.

[0008] Furthermore, the zinc salt is one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc tetrafluoroborate, zinc perchlorate, zinc trifluoromethanesulfonate, zinc trifluoroacetate, zinc bis(trifluoromethanesulfonate)imide, and zinc bis(fluorosulfonyl)imide.

[0009] Furthermore, the concentration of the zinc salt is 0.25–2.5 mol / L.

[0010] Furthermore, the organic electrolyte also contains metal ion additives.

[0011] Furthermore, the metal ion additive is selected from metal halides such as calcium fluoride (CaF2), antimony fluoride (SbF3), lead fluoride (PbF2), tin fluoride (SnF2), magnesium fluoride (MgF2), chromium fluoride (CrF3), antimony chloride (SbCl3), tin chloride (SnCl2), and chromium chloride (CrCl3).

[0012] Furthermore, the concentration of the metal ion additive is 0.001–0.25 mol / L.

[0013] Furthermore, the co-solvent is selected from one or more of sulfones and their derivatives, such as dimethyl sulfoxide (DMSO), sulfolane (SL), methyl ethyl sulfone, and isopropyl ethyl sulfone.

[0014] Furthermore, the volume ratio of the co-solvent in the organic electrolyte is 1%-50%, preferably 5-40%, more preferably 10-30%, and exemplaryly, it can be any value within the above range such as 1%, 10%, 20%, 40%, 50%.

[0015] Furthermore, the main solvent is selected from one or more of the following: trimethyl phosphate (TMP), triethyl phosphate (TEP), N,N-dimethylformamide (DMF), N-methylformamide (NMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), diethylene glycol dimethyl ether (DEGDME), diethylene glycol diethyl ether (DEGDEE), dipropylene glycol dimethyl ether (DPGDME), butyl acetate, ethyl butyrate, butyl butyrate, propylene glycol methyl ether acetate, 3-methoxybutyl acetate, 2-ethoxyethyl acetate, methyl acetoacetate, and ethyl acetoacetate.

[0016] In a second aspect, the present invention provides a method for preparing a high coulombic efficiency organic electrolyte for secondary zinc-ion batteries. A zinc salt is added to a main solvent and completely dissolved. Then, a co-solvent is added to obtain a high-efficiency electrolyte for secondary zinc-ion batteries, which is the target product.

[0017] The designed high-current, long-cycle organic electrolyte for secondary zinc-ion batteries can use pure zinc as the negative electrode, or modified or altered zinc as the negative electrode.

[0018] In a third aspect, the present invention provides a secondary zinc-ion battery, comprising, as described above, a high coulombic efficiency organic electrolyte, a zinc negative electrode, a positive electrode, and a separator. It should be noted that the secondary zinc-ion battery is assembled using conventional methods, which is conventional technology in the field and not considered an innovative point of this invention; therefore, it will not be elaborated further. The main innovative difference of the secondary zinc-ion battery provided by the present invention lies in the use of the aforementioned high coulombic efficiency organic electrolyte. Specifically, a porous polyethylene membrane is used as the separator; the positive electrode can be made of materials such as stainless steel or zinc.

[0019] This invention, through research, reveals that in organic systems, the formation of interfacial films primarily relies on the reductive decomposition of anions. This results in the formation of an interfacial film rich in inorganic components on the zinc anode surface. Based on this, by adding a weak solvating solvent (i.e., a co-solvent), the Zn... 2+ The solvation structure allows anions to participate more in Zn. 2+ In the solvated structure of Zn 2+ During anode deposition, anions decompose on the anode surface and form a denser and more stable interfacial film. With the electrolyte adjusted by solvation, the Zn||SS half-cell achieved a coulombic efficiency of 99.996% within 440 cycles, which is the highest reported coulombic efficiency for a metal anode to date.

[0020] This invention designs the organic electrolyte composition and adjusts the solvation structure of zinc ions to improve the interfacial film composition formed on the zinc anode in situ, achieving ultra-high coulombic efficiency and uniform and stable deposition of the zinc anode under high current and long cycling conditions. This invention uses a co-solvent to alter the solvation structure of zinc ions, allowing more anions to enter the solvation layer, making the SEI formed at the anode interface more stable and improving the coulombic efficiency of the metal anode. Furthermore, the addition of the co-solvent forms a specific deposition morphology on the zinc anode surface, suppressing the formation of zinc dendrites, achieving two goals at once. The addition of the co-solvent enables the zinc anode to achieve dendrite-free, commercially viable, stable, and long-cycle-ready coulombic efficiency under high current and high depth of discharge conditions.

[0021] Compared with existing technologies, this invention solves both the dendrite problem and the coulombic efficiency problem of the zinc anode by introducing a co-solvent, thus significantly improving the stability of the zinc anode in secondary zinc-ion batteries, especially enabling dendrite-free, stable, long-cycle operation under high current. Simultaneously, using an organic solvent with a boiling point exceeding 100℃ (at normal pressure) as the main solvent can greatly improve battery safety. Attached Figure Description

[0022] Figure 1 shows the electrolyte prepared in Example 1.

[0023] Figure 2 shows the ionic conductivity of the electrolyte prepared in Example 2.

[0024] Figure 3 shows the deposition / stripping cycle curves of the zinc symmetric coin cell assembled in Comparative Example 1.

[0025] Figure 4 shows the deposition / stripping cycle curves of the zinc symmetric coin cell assembled in Example 3.

[0026] Figure 5 shows the morphological characterization of the electrode after cycling of the pure zinc symmetric cell in Comparative Example 2.

[0027] Figure 6 shows the morphological characterization of the electrode after cycling in the pure zinc symmetric battery of Example 4.

[0028] Figure 7 shows the coulombic efficiency curve of the zinc anode in the zinc-stainless steel half-cell of Comparative Example 3.

[0029] Figure 8 shows the coulombic efficiency curve of the zinc anode in Example 5.

[0030] Figure 9 shows the coulombic efficiency curve of the zinc anode in Example 6.

[0031] Figure 10 shows the F1s spectrum of the zinc anode surface in Comparative Example 4 during X-ray photoelectron spectroscopy testing.

[0032] Figure 11 is the F1s spectrum of the zinc anode surface in Example 7, obtained from X-ray photoelectron spectroscopy.

[0033] Figure 12 shows the Raman spectra of the electrolyte and solid Zn(CF3SO3)2 salt in Example 8.

[0034] Figure 13 shows the infrared spectrum curves of the electrolyte and solid Zn(CF3SO3)2 salt in Example 9, obtained by Fourier transform infrared spectroscopy. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0037] Example 1

[0038] A certain amount of zinc trifluoromethanesulfonate was weighed and dissolved in N,N-dimethylformamide (DMF) to a concentration of 0.5 mol / L. -1 Sulfolane (SL) at a volume ratio of 20% was added to the solution to obtain a 0.5M Zn(CF3SO3)2 / DMF / SL electrolyte (i.e., the concentration of Zn(CF3SO3)2 in the electrolyte is 0.5 mol / L). -1 Electrolytes containing 0.01M SbF3 + 10% SL, 0.05M SbF3 + 20% SL, 0.05M SnF3 + 20% SL, and 0.25M SbCl3 + 50% SL were prepared using the same method and photographed, as shown in Figure 1. As can be seen from the figure, all electrolytes are very homogeneous.

[0039] Here, 20%SL means that the volume percentage of SL added during the preparation process is 20%, and the same applies to other values ​​such as 10% and 50%.

[0040] Example 2

[0041] A certain amount of zinc trifluoromethanesulfonate was weighed and dissolved in N,N-dimethylformamide (DMF) to a concentration of 0.5 mol / L. -1 Sulfolane (SL) was added to the solution at volume ratios of 0%, 10%, 20%, 30%, and 50%, respectively, to obtain 0.5 M Zn(CF3SO3)2 / DMF / SL electrolytes (i.e., the concentration of Zn(CF3SO3)2 in the electrolyte was 0.5 mol / L). -1 The test results are shown in Figure 2.

[0042] As can be seen from the figure, the ionic conductivity of the electrolyte gradually decreases as the volume ratio of sulfolane increases. This indicates that the degree of dissociation of Zn(CF3SO3)2 in the electrolyte gradually decreases, meaning that the anions are more likely to enter the solvation structure of zinc ions.

[0043] Comparative Example 1

[0044] A zinc symmetrical button cell was assembled using 0.5M Zn(CF3SO3)2 / DMF as the electrolyte, a 20-micron-thick porous polyethylene membrane as the separator, and pure zinc discs with a diameter of 12mm as both the positive and negative electrodes.

[0045] Deposition / stripping cycles were performed at 25°C with a current density of 5 mA and an areal capacity of 5 mAh. As shown in Figure 3, the symmetric cell short-circuited after 260 hours, indicating that the DMF-based electrolyte has poor compatibility with the unmodified zinc metal anode.

[0046] Example 3

[0047] A zinc symmetrical button cell was assembled using a 0.5M Zn(CF3SO3)2 / 0.01M SbF / DMF / SL solution containing 20% ​​sulfolane as the electrolyte, a 20-micrometer-thick porous polyethylene membrane as the separator, and pure zinc discs with a diameter of 12 mm as both positive and negative electrodes.

[0048] Deposition / stripping cycles were performed at 25°C with a current density of 5 mA and an areal capacity of 5 mAh, as shown in Figure 4. The symmetric cell can meet the requirement of maintaining a stable voltage curve for 2600 hours, indicating that the electrolyte with added co-solvent can effectively improve the zinc anode interface and achieve stable long-term cycling of the zinc anode.

[0049] Comparative Example 2

[0050] The morphology of the electrode after cycling in a pure zinc symmetric cell with 0.5 M Zn(CF3SO3)2 / DMF electrolyte was characterized by scanning electron microscopy. Deposition / stripping cycles were performed at 25 °C with a current density of 5 mA and an areal capacity of 5 mAh. The zinc deposition morphology was observed, as shown in Figure 5.

[0051] The zinc metal anode using 0.5M Zn(CF3SO3)2 / DMF electrolyte without surface modification exhibits a loose dendritic zinc deposition morphology. This dendritic zinc can easily puncture the porous polyethylene membrane separator, which is only 20 micrometers thick, leading to a short circuit in the battery. This is also the main reason why the pure zinc symmetric battery using 0.5M Zn(CF3SO3)2 / DMF electrolyte has a cycle life of only 260 hours under the conditions of a current density of 5mA and an areal capacity of 5mAh.

[0052] Example 4

[0053] The morphology of the electrode after cycling with a pure zinc symmetric cell containing 20% ​​sulfolane in 0.5 M Zn(CF3SO3)2 / 0.05 M SnF3 / DMF / SL electrolyte was characterized by scanning electron microscopy. Deposition / stripping cycling was performed at 25 °C under the following conditions: current density: 5 mA, areal capacity: 5 mAh. The zinc deposition morphology was observed, as shown in Figure 6.

[0054] Using a 0.5M Zn(CF3SO3)2 / DMF / SL electrolyte, a smooth and uniform hexagonal zinc deposition morphology was observed, with no dendrite formation. This uniform zinc deposition is the main reason for the battery's 2600-hour lifespan.

[0055] Comparative Example 3

[0056] A zinc-stainless steel half-cell was assembled using a 0.5M Zn(CF3SO3)2 / DMF solution as the electrolyte, a 20-micron-thick porous polyethylene membrane as the separator, a 12-mm diameter pure zinc disc as the negative electrode, and a 12-mm diameter stainless steel gasket as the positive electrode. The coulombic efficiency of the zinc negative electrode was measured.

[0057] The coulombic efficiency of zinc was tested at 25°C with a current density of 0.5 mA and an areal capacity of 0.5 mAh. As shown in Figure 7, the zinc-stainless steel half-cell short-circuited due to dendrite formation after only 160 hours of cycling. The average coulombic efficiency of the zinc-stainless steel half-cell was 98.91%. This indicates that although an electrolyte system that is thermodynamically stable with zinc was used, the inability to form a dense SEI on the zinc anode still reduces the coulombic efficiency of the zinc anode.

[0058] Example 5

[0059] A zinc-stainless steel half-cell was assembled using a 0.5M Zn(CF3SO3)2 / DMF / SL solution containing 20% ​​sulfolane as the electrolyte, a 20-micrometer-thick porous polyethylene membrane as the separator, a 12-mm diameter pure zinc disc as the negative electrode, and a 12-mm diameter stainless steel gasket as the positive electrode. The coulombic efficiency of the zinc negative electrode was measured.

[0060] The coulombic efficiency of zinc was tested at 25℃ with a current density of 0.5 mA and an areal capacity of 0.5 mAh, as shown in Figure 8. The zinc-stainless steel half-cell maintained a stable voltage curve over 1000 hours, with an average coulombic efficiency of 99.96%. This indicates that the presence of sulfolane improves the interfacial stability of the zinc anode, suppresses the continuous influence of side reactions, and achieves stable long-term cycling of a zinc anode with high coulombic efficiency.

[0061] Example 6

[0062] A zinc-stainless steel half-cell was assembled using a 0.5M Zn(CF3SO3)2 / 0.05M SbF3 / DMF / SL solution containing 20% ​​sulfolane as the electrolyte, a 20-micron-thick porous polyethylene membrane as the separator, a 12-mm diameter zinc disc as the negative electrode, and a 12-mm diameter stainless steel gasket as the positive electrode. The coulombic efficiency of the zinc negative electrode was measured.

[0063] The coulombic efficiency of zinc was tested at 25℃ with a current density of 2 mA and an areal capacity of 1 mAh, as shown in Figure 9. The zinc-stainless steel half-cell maintained a stable voltage curve over 440 hours, with an average coulombic efficiency of 99.996%. This indicates that the co-solvent sulfolane, when used in conjunction with metal ion additives, can further improve the coulombic efficiency of the zinc anode. This is also the first time that a metal anode has achieved a coulombic efficiency exceeding 99.99%. This demonstrates the significant application potential of sulfone solvents as co-solvents. The presence of sulfolane improves the interfacial stability of the zinc anode, suppresses the continuous influence of side reactions, and enables stable long-term cycling of a zinc anode with high coulombic efficiency under high current and high areal capacity.

[0064] Comparative Example 4

[0065] A zinc symmetrical button cell was assembled using a 0.5M Zn(CF3SO3)2 / DMF solution as the electrolyte, a 20-micron-thick porous polyethylene membrane as the separator, and pure zinc discs with a diameter of 12 mm as both positive and negative electrodes.

[0066] Deposition / stripping cycling was performed at 25°C with a current density of 5 mA and an areal capacity of 5 mAh. After 50 cycles, the battery was removed, and X-ray photoelectron spectroscopy (XPS) was performed on the zinc anode surface. Fluorine (F) signal was measured at different depths (0 nm, 25 nm, 50 nm, 75 nm). The test results are shown in Figure 10.

[0067] After cycling in 0.5M Zn(CF3SO3)2 / DMF / SL electrolyte, the zinc anode surface contains 32.44% ZnF2 and 67.56% CF3.

[0068] Example 7

[0069] A zinc symmetrical button cell was assembled using a 0.5M Zn(CF3SO3)2 / 0.25M PbF3 / DMF / SL solution containing 20% ​​sulfolane as the electrolyte, a 20-micrometer-thick porous polyethylene membrane as the separator, and pure zinc discs with a diameter of 12 mm as both positive and negative electrodes.

[0070] Deposition / stripping cycling was performed at 25°C with a current density of 5 mA and an areal capacity of 5 mAh. After 50 cycles, the battery was removed, and X-ray photoelectron spectroscopy (XPS) was performed on the zinc anode surface. Fluorine (F) signal was measured at different depths (0 nm, 25 nm, 50 nm, 75 nm). The test results are shown in Figure 11.

[0071] The proportion of ZnF2 on the zinc anode surface was significantly increased after cycling in an electrolyte containing 20% ​​sulfolane in 0.5M Zn(CF3SO3)2 / DMF / SL. This indicates that the SEI formed at the zinc anode interface after adding SL contains more inorganic components, which inhibits further side reactions at the zinc anode interface.

[0072] Example 8

[0073] Raman spectroscopy was performed on the electrolyte containing different proportions of sulfolane and solid Zn(CF3SO3)2 salt in Example 1. The partial images of the test results are shown in Figure 12.

[0074] 750-780cm in Figure 12 -1 Raman spectral peaks in the frequency range correspond to OTf - The vibrational peaks of the ions. With the increase of sulfolane, the characteristic peaks shift towards the high-frequency region, indicating that Zn... 2+ With OTf - Enhanced interaction, meaning more anions enter Zn 2+ In the solvation structure.

[0075] Example 9

[0076] Fourier transform infrared spectroscopy was performed on the electrolyte containing different proportions of sulfolane and solid Zn(CF3SO3)2 salt in Example 1. The partial images of the test results are shown in Figure 13.

[0077] In Figure 13, with the addition of SL, OTf - The SO3 stretching vibration peak shifted to a lower frequency region, indicating that the addition of sulfolane promoted the production of more OTf. - Ions participate in Zn 2+ The solvation structure.

[0078] Example 10

[0079] This embodiment is basically the same as Embodiment 3, except that in this embodiment, the co-solvent of the electrolyte is dimethyl sulfoxide.

[0080] Deposition / stripping cycling was performed at 25°C with a current density of 5 mA and an areal capacity of 5 mAh, as shown in Figure 14. The symmetric cell can meet the requirement of stable cycling for about 600 hours, indicating the consistency of uniform zinc deposition and high coulombic efficiency of sulfone electrolyte.

[0081] Meanwhile, based on Examples 3 and 10, it can be seen that different sulfone electrolytes have significantly different effects on improving the stability of the zinc anode.

[0082] Example 11

[0083] This embodiment is basically the same as Embodiment 3, except that in this embodiment, the co-solvent of the electrolyte is isopropyl ethyl sulfone.

[0084] Example 12

[0085] This embodiment is basically the same as embodiment 3, except that in this embodiment, the zinc salt electrolyzed is zinc bis(TFSI)2 (zinc bis(trifluoromethanesulfonate)).

[0086] Example 13

[0087] This embodiment is basically the same as embodiment 3, except that in this embodiment, the zinc salt electrolyzed is zinc trifluoroacetate (Zn(TFA)2).

[0088] Example 14

[0089] This embodiment is basically the same as Embodiment 3, except that in this embodiment, the main solvent of the electrolyte is N-methylformamide (NMF).

[0090] Example 15

[0091] This embodiment is basically the same as Embodiment 3, except that in this embodiment, the main solvent of the electrolyte is N'N-dimethylpyrrolidone (NMP).

[0092] Example 16

[0093] This embodiment is basically the same as Embodiment 6, except that in this embodiment, the co-solvent of the electrolyte is dimethyl sulfoxide.

[0094] Example 17

[0095] This embodiment is basically the same as Embodiment 6, except that in this embodiment, the co-solvent of the electrolyte is isopropyl ethyl sulfone.

[0096] Example 18

[0097] This embodiment is basically the same as Embodiment 6, except that in this embodiment, the metal ion additive for the electrolyte is calcium fluoride (CaF2).

[0098] Example 19

[0099] This embodiment is basically the same as Embodiment 6, except that in this embodiment, the metal ion additive for the electrolyte is chromium fluoride (CrF3).

[0100] Example 20

[0101] This embodiment is basically the same as Embodiment 6, except that in this embodiment, the metal ion additive for the electrolyte is chromium chloride (CrCl3).

[0102] Based on the above, it can be seen that by using an organic electrolyte, the present invention avoids the intrinsic thermodynamic instability of the zinc anode and water caused by using an aqueous electrolyte, thus avoiding parasitic reactions (hydrogen evolution, passivation, dendrite formation) of the zinc anode. Secondly, by using a co-solvent to adjust the solvation structure of zinc ions, more anions enter the solvation structure of zinc ions. The anions are reduced in situ on the anode surface to form a layer of inorganic-rich SEI, which significantly improves the cycling performance of the zinc anode. The change in the solvation structure also makes the deposition of zinc ions more uniform and dense, exhibiting a dense deposition of (002) crystal plane structure, inhibiting the growth of zinc dendrites and achieving high coulombic efficiency of the zinc anode during long-term high-current cycling.

[0103] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high coulombic efficiency organic electrolyte for secondary zinc-ion batteries, characterized in that, This includes zinc salts, sulfone cosolvents, and main solvents with boiling points exceeding 100°C.

2. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 1, characterized in that, The zinc salt is one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc tetrafluoroborate, zinc perchlorate, zinc trifluoromethanesulfonate Zn(OTf)2, zinc trifluoroacetate, zinc bis(trifluoromethanesulfonate)imide, and zinc bis(fluorosulfonyl)imide. The concentration of the zinc salt is 0.25–2.5 mol / L.

3. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 1, characterized in that, The organic electrolyte also contains metal ion additives.

4. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 3, characterized in that, The metal ion additive is selected from one or more of calcium fluoride, antimony fluoride, lead fluoride, tin fluoride, magnesium fluoride, chromium fluoride, antimony chloride, tin chloride, and chromium chloride. The concentration of the metal ion additive is 0.001–0.25 mol / L.

5. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 1, characterized in that, The co-solvent is selected from one or more of dimethyl sulfoxide, sulfolane SL, methyl ethyl sulfone, isopropyl ethyl sulfone, and their derivative organic compounds.

6. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 1, characterized in that, The volume ratio of the co-solvent in the organic electrolyte is 1%-50%.

7. The high coulombic efficiency organic electrolyte for secondary zinc-ion batteries according to claim 1, characterized in that, The main solvent with a boiling point exceeding 100°C is selected from one or more of the following: trimethyl phosphate, triethyl phosphate, N,N-dimethylformamide, N-methylformamide, N-methylpyrrolidone, dimethylacetamide, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, butyl acetate, ethyl butyrate, butyl butyrate, propylene glycol methyl ether acetate, 3-methoxybutyl acetate, 2-ethoxyethyl acetate, methyl acetoacetate, and ethyl acetoacetate.

8. A method for preparing a high coulombic efficiency organic electrolyte for a secondary zinc-ion battery as described in any one of claims 1-7, characterized in that, Zinc salt is added to the main solvent and completely dissolved. Then, a co-solvent is added to obtain a high-efficiency electrolyte for secondary zinc-ion batteries, which is the target product.

9. A secondary zinc-ion battery, characterized in that, Includes the high coulombic efficiency organic electrolyte, zinc negative electrode, positive electrode, and separator of the secondary zinc-ion battery as described in any one of claims 1-7.

10. A method for achieving high coulombic efficiency in long-cycle zinc negative maximum current, characterized in that, When constructing a secondary zinc-ion battery, the high coulombic efficiency organic electrolyte for secondary zinc-ion batteries as described in any one of claims 1-7 is used.

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