Zinc ion battery electrolyte additive and electrolyte

Abstract

The present invention provides a zinc ion battery electrolyte additive and an electrolyte, belonging to the field of new energy materials and electrochemistry. The specific scheme is as follows: the additive includes sodium N,N-dimethylthioformamide propane sulfonate, and its molecular formula is shown in Formula I:

Description

Technical Field

[0001] The invention belongs to the field of new energy materials and electrochemistry, and specifically relates to a zinc ion battery electrolyte additive and an electrolyte. Background Art

[0002] Lithium-ion batteries have been widely used in mobile phones, electric vehicles and other fields, and are one of the current application hotspots in the energy field. However, the large-scale application of lithium-ion batteries is limited by the shortage of lithium resources on the earth. Recently, the price of lithium carbonate has risen from 42,000 yuan / ton to 520,000 yuan / ton. At the same time, lithium-ion batteries use organic electrolytes, which poses risks such as flammability and explosion. Therefore, the application of lithium-ion batteries in energy storage fields with higher safety and cost requirements is limited. Aqueous zinc-ion batteries use metallic zinc as the negative electrode. Due to zinc's high abundance, high tolerance to water environments, and high theoretical mass specific capacity (820mAh g -1 ) and low redox potential (-0.76V vs. SHE), and are considered to be the preferred alternative battery system for lithium-ion batteries.

[0003] Zinc-ion batteries generally use cheap zinc foil as the negative electrode, and the electrolyte is weakly acidic zinc sulfate plus manganese sulfate. However, zinc dendrites are easily formed at the zinc negative electrode during the cycle. The formation of dendrites causes the local current density to increase, which accelerates the rate of hydrogen evolution in the aqueous battery. The accelerated hydrogen evolution will lead to changes in the local pH, thereby forming a byproduct of basic zinc sulfate. The accumulation of basic zinc sulfate on the surface of the zinc negative electrode aggravates the surface unevenness and increases polarization. The increase in polarization will intensify the growth of zinc dendrites. Therefore, the dendrite problem, hydrogen evolution problem and side reaction problems affect and aggravate each other. This vicious cycle leads to extremely low efficiency of zinc negative electrode deposition / stripping, which is not conducive to its commercialization and wide application. In response to the problem of poor reversibility of zinc negative electrode deposition / stripping process, researchers have proposed measures such as designing three-dimensional metal negative electrodes, artificial SEI membranes and using high-concentration electrolytes, which have effectively improved the cycle reversibility of zinc negative electrodes. However, there are still problems such as high cost, complex processing and unsuitability for commercial promotion. Summary of the invention

[0004] Aiming at the problems of dendrite, hydrogen precipitation and negative product in the zinc negative electrode of the existing zinc ion battery, the present invention does not adopt some expensive measures such as artificial SEI film or high-concentration electrolyte, but uses cheap N, N-dimethylthiocarboxamide propane sulfonate sodium (DPS) as an electrolyte additive, which is directly added to the electrolyte, thereby avoiding the generation of dendrites, hydrogen generation and negative product generation. Zinc foil is used as the negative electrode, and the DPS is directly added to the electrolyte at 1 mA·cm -2 Discharge, the cycle number can be increased from 70 to 2000 cycles.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A zinc ion battery electrolyte additive, the additive comprising sodium N,N-dimethylthioformamide propane sulfonate, the molecular formula of which is shown in Formula I:

[0007]

[0008] Furthermore, the concentration of sodium N,N-dimethylthiocarboxamide propane sulfonate in the electrolyte is 2.0×10 -4 g·L -1 -2.0×10 -1 g·L -1 .

[0009] A zinc ion battery electrolyte and the electrolyte additive.

[0010] Furthermore, the electrolyte also includes ZnSO4 and MnSO4.

[0011] Furthermore, the concentration of ZnSO4 is 2M, and the concentration of MnSO4 is 0.5M.

[0012] The steps for assembling a battery using the above electrolyte are as follows:

[0013] Step 1: preparing manganese dioxide positive electrode material;

[0014] Step 2: preparing the negative electrode sheet;

[0015] Step 3: Prepare an electrolyte solution based on 2M ZnSO4+0.5M MnSO4, add an electrolyte additive, sodium N,N-dimethylthioformamide propane sulfonate, and stir;

[0016] Step 4: Assemble in the order of positive electrode shell, positive electrode sheet, diaphragm, electrolyte, negative electrode sheet, gasket, spring, and negative electrode shell, compact the battery with a tablet press, and conduct subsequent testing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The raw materials of the present invention are cheap and pollution-free.

[0019] 2. The preparation process is simple and feasible. It only needs to add a small amount of sodium N,N-dimethylthioformamide propane sulfonate as an additive into the electrolyte according to the concentration requirement, and then assemble the battery.

[0020] 3. The strong interaction between the sulfonic acid groups and the zinc surface causes chemical adsorption on the zinc surface, changing the surface energy of zinc. The sulfonic acid groups covering the surface of the zinc negative electrode minimize the energy of the protrusion tip, and the uneven morphology can be smoothed.2+ Has a larger binding energy and partially replaces Zn 2+ The water molecules in the solvation shell change the solvent shell structure of the hydrated zinc ions and achieve desolvation. The two work together to achieve the zinc negative electrode without byproduct generation and dendrite generation, and have good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Schematic diagram of the molecular formula of sodium N,N-dimethylthioformamide propane sulfonate;

[0022] Figure 2 : XRD patterns of the negative electrode surface products in different electrolyte systems;

[0023] Figure 3 :SEM images of zinc foil of Zn||Zn symmetric battery after constant current charge and discharge, (a) shows that the concentration of N,N-dimethylthiocarboxamide propane sulfonate (DPS) in the electrolyte system is 2.0×10 -3 g·L -1 , discharge current 4.4mA·cm -2 , SEM image of zinc foil corresponding to 2000 cycles, (b) is the concentration of N,N-dimethylthiocarboxamide propane sulfonate (DPS) in the electrolyte system is 2.0×10 -4 、Discharge current 1.0mA·cm -2 , (c) is the SEM photo of the zinc foil corresponding to 1000 cycles, (d) is the SEM photo of the zinc foil corresponding to 50 cycles without adding sodium N,N-dimethylthiocarboxamide propane sulfonate (DPS) in the electrolyte; (d) is the SEM photo of the original zinc foil;

[0024] Figure 4 :Constant current charge-discharge cycle curves of Zn||Zn symmetric battery, the DPS concentration in the electrolyte is 2×10 -3 g·L -1 , the current density is 4.4 mA cm -2 ;

[0025] Figure 5 :Constant current charge-discharge cycle curves of Zn||Zn symmetric battery; the DPS concentration in the electrolyte is 2×10 -4 g·L -1 , the current density is 1 mA cm -2 ;

[0026] Figure 6 :MnO2|ZnSO4+MnSO4|Zn full battery cycle performance curve, with 1Ag -1 Current density discharge. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] (1) Preparation of positive electrode sheet. Preparation of a-MnO2 nanorods by hydrothermal method: 1.264g KMnO4 was dissolved in 75mL deionized water, 2mL 98% H2SO4 was added, and stirred for 15 minutes. It was transferred to a Teflon reactor (100mL) and kept at 140℃ for 3.5h. After cooling to room temperature, the sample was centrifuged and washed with deionized water 2-3 times. Then, the sample was placed in a 60℃ oven and dried for 24h to obtain a-MnO2. a-MnO2:SuperP:PVDF was mixed in a mass ratio of 7:2:1, and then stirred on a magnetic stirrer for 24h; the mixed positive electrode paste was evenly coated on a carbon paper with a diameter of 10mm and placed in a 60℃ oven and dried for 24h.

[0030] (2) Preparation of negative electrode sheet: The zinc foil was cut into 12 mm thick sheets, and pressed at a pressure of 5 MPa for 5 min. Subsequently, the zinc sheet was polished with 2000-grit sandpaper, placed in an ethanol solution, ultrasonicated for 5 min, and dried naturally in air to obtain a zinc electrode sheet.

[0031] (3) Prepare the electrolyte. Based on 2M ZnSO4+0.5M MnSO4, add the electrolyte additive N,N-dimethylthiocarboxamide propane sulfonate (DPS) at a concentration of 2.0×10 -3 g·L -1 , stir for 30 minutes.

[0032] (4) Assemble a symmetrical battery according to the negative electrode shell, negative electrode gasket, negative electrode, separator, electrolyte, negative electrode, negative electrode gasket and negative electrode shell.

[0033] (5) Assemble the positive electrode shell, positive electrode sheet, diaphragm, electrolyte, negative electrode sheet, gasket, spring, and negative electrode shell in order, and compact the battery using a tablet press.

[0034] After assembling the symmetrical battery in this embodiment, the -2 After 2000 cycles, Figure 2 The XRD pattern of the product on the negative electrode surface is shown, and no basic zinc sulfate by-product is generated. Figure 3(a) is a SEM photo of the negative electrode surface of the symmetrical battery assembled in this embodiment after 2000 cycles. No dendrites are generated on the surface. This shows that the addition of sodium N,N-dimethylthioformamide propane sulfonate inhibits the formation of dendrites. Figure 3 (c) is a SEM photo of the zinc foil after battery cycling when no additives were added to the electrolyte. Figure 3 (d) is the original zinc foil. The SEM photo shows that the surface morphology of the zinc foil is rough and uneven, which is significantly different from when the DPS additive is added. Figure 4 It is a symmetrical battery at 4.4mA.cm -2 The discharge cycle performance diagram shows that the stability is greatly improved after adding sodium N,N-dimethylthiocarboxamide propane sulfonate (DPS). Figure 6 The MnO2|ZnSO4+MnSO4|Zn battery assembled for this embodiment is 1A·g -1 Cyclic performance curve of current density discharge. The battery cycled stably for 2000 times and the capacity remained at 168mAh g -1 , Coulombic efficiency is greater than 98%.

[0035] Example 2

[0036] (1) Preparation of negative electrode sheet: The zinc foil was cut into 12 mm thick sheets, and pressed at a pressure of 5 MPa for 5 min. Subsequently, the zinc sheet was polished with 2000-grit sandpaper, placed in an ethanol solution, ultrasonicated for 5 min, and dried naturally in air to obtain a zinc electrode sheet.

[0037] (2) Prepare the electrolyte. Based on 2M ZnSO4+0.5M MnSO4, add the electrolyte additive N,N-dimethylthiocarboxamide propane sulfonate (DPS) at a concentration of 2.0×10 -4 g·L -1 .

[0038] (3) Assemble a symmetrical battery according to the negative electrode shell, negative electrode gasket, negative electrode, separator, electrolyte, negative electrode, negative electrode gasket and negative electrode shell.

[0039] The symmetrical battery assembled in this embodiment is 1mA.cm -2 After 1000 cycles, Figure 2 The XRD pattern of the product on the negative electrode surface is shown, and no basic zinc sulfate by-product is generated. Figure 3 (b) is a surface SEM photograph of the symmetrical battery assembled in this embodiment after 1000 cycles, and no serious dendrites are generated on the surface. Figure 5 It is a symmetrical battery at 1.0mA.cm -2 The discharge cycle performance diagram shows that the stable cycle reaches 1000 cycles.

[0040] Example 3

[0041] (1) Preparation of negative electrode sheet: The zinc foil was cut into 12 mm thick sheets, and pressed at a pressure of 5 MPa for 5 min. Subsequently, the zinc sheet was polished with 2000-grit sandpaper, placed in an ethanol solution, ultrasonicated for 5 min, and dried naturally in air to obtain a zinc electrode sheet.

[0042] (2) Prepare the electrolyte 2M ZnSO4+0.5M MnSO4.

[0043] (3) Assemble a symmetrical battery according to the negative electrode shell, negative electrode gasket, negative electrode, separator, electrolyte, negative electrode, negative electrode gasket and negative electrode shell.

[0044] The symmetrical battery assembled in this embodiment is 1mA.cm -2 After 50 cycles, Figure 2 The XRD diagram of the product on the negative electrode surface is shown. The diffraction peak of the Zn (002) plane has a high diffraction intensity, which makes it easier to generate dendrites. Figure 3 (c) is a SEM photograph of the negative electrode surface of the symmetrical battery assembled in this embodiment after cycling. The surface has dendrites and is uneven.

[0045] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A zinc ion battery electrolyte, characterized in that: The electrolyte includes sodium N,N-dimethylthioformamide propane sulfonate, and its molecular formula is shown in Formula I: The concentration of sodium N,N-dimethylthiocarboxamide propane sulfonate in the electrolyte is 2.0×10 -4 g·L -1 -2.0×10 -1 g·L -1 .

2. A zinc ion battery electrolyte according to claim 1, characterized in that: The electrolyte also includes ZnSO4 and MnSO4.

3. A zinc ion battery electrolyte according to claim 2, characterized in that: The concentration of the ZnSO4 is 2M, and the concentration of the MnSO4 is 0.5M.

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