Electrolyte and energy storage device

Abstract

The present invention discloses an electrolyte and an energy storage device. The solute of the electrolyte comprises a zinc salt and an alkaline modifier, the mass concentration of the alkaline modifier is 0.1% to 1%, and the alkaline modifier is an amine or an amine derivative with less than 10 carbon atoms. The "alkalinity" of the alkaline modifier is the ability to combine with protons during the electrochemical cycle. During its movement towards the negative electrode interface, it reduces the concentration of protons at the negative electrode interface. On the other hand, the reduction of the interfacial proton concentration can shift the hydrogen evolution onset potential of the electrolyte in the negative direction, broaden the electrochemical window of the electrolyte and the energy storage device, and shift the hydrogen evolution onset potential in the negative direction, thereby achieving the effect of suppressing hydrogen evolution at the negative electrode. When this electrolyte is applied to an energy storage device, it can inhibit hydrogen evolution at the negative electrode of the energy storage device, thereby improving the long-cycle stable cycling performance of the energy storage device.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical energy storage, and particularly to an electrolyte and an energy storage device. Background Art

[0002] In response to the problems of global warming and overuse of fossil fuels, China has put forward the goals of "carbon neutrality" and "carbon peak". Under the guidance of the "dual carbon" background, clean and renewable energy represented by photovoltaic and wind power has seen a huge upsurge in installed capacity. However, such renewable energy generally has problems such as unstable power generation, which brings pressure to the power grid frequency modulation and peak shaving. Therefore, energy storage facilities are needed to support the large-scale application of clean energy.

[0003] Compared with lithium-ion batteries using flammable and toxic organic electrolytes, aqueous secondary batteries are a new type of energy storage system with low cost, high safety, and high cost performance, and are expected to replace the existing organic system energy storage technology. In recent years, they have received extensive and in-depth research. Among them, aqueous zinc-based energy storage devices are a type of solution widely concerned in the field of aqueous energy storage. Zinc has a higher relative abundance than lithium and has a high theoretical specific capacity. It can perform high-capacity and high-rate discharge simultaneously and has excellent electrochemical performance. In addition, metallic zinc has good stability in aqueous solution, so it can be directly used as the negative electrode, greatly reducing the cost of the battery system.

[0004] However, aqueous energy storage devices including aqueous zinc-ion batteries generally have the problem of hydrogen evolution reaction (HER) at the negative electrode. The reason is that in aqueous solution, the redox potential of zinc is near the hydrogen evolution potential, so in the electrochemical reaction process, the metal negative electrode is prone to react with the electrolyte to generate hydrogen. Hydrogen evolution at the negative electrode will cause the consumption of the metal negative electrode and even the swelling and breakage of the battery, resulting in poor long-cycle stable cycling performance of the aqueous energy storage device. Summary of the Invention

[0005] Based on this, it is necessary to provide an electrolyte that can solve the above hydrogen evolution problem.

[0006] In addition, it is also necessary to provide an energy storage device including the above electrolyte.

[0007] An electrolyte, wherein the solute of the electrolyte includes a zinc salt and an alkaline modifier, the mass concentration of the alkaline modifier is 0.1% to 1%, and the alkaline modifier is an amine or amine derivative with less than 10 carbon atoms.

[0008] In one embodiment, the alkaline modifier contains an amino group.

[0009] In one embodiment, the alkaline modifier further contains at least one of an aromatic ring, a hydroxyl group, a sulfonyl group, and a carbonyl group.

[0010] In one embodiment, the basic modifier is selected from at least one of aniline, sulfanilamide, and sulfonamide.

[0011] In one embodiment, the solvent of the electrolyte is water.

[0012] In one embodiment, the concentration of the zinc salt is 0.5 mol / kg to 3 mol / kg.

[0013] In one embodiment, the zinc salt is selected from at least one of ZnSO4, Zn(CF3SO3)2, and Zn(ClO4)2.

[0014] An energy storage device includes the above-mentioned electrolyte.

[0015] In one embodiment, the energy storage device is an aqueous secondary battery or an aqueous supercapacitor.

[0016] In one embodiment, the aqueous secondary battery is an aqueous zinc-ion secondary battery or an aqueous alkali metal-ion secondary battery.

[0017] The solute of this kind of electrolyte includes a basic modifier which is an amine or an amine derivative with less than 10 carbon atoms. The "basicity" of the basic modifier is the ability to combine with protons during the electrochemical cycle. During its movement towards the negative electrode interface, it reduces the concentration of protons at the negative electrode interface. On the other hand, the reduction of the interfacial proton concentration can shift the hydrogen evolution onset potential of the electrolyte in the negative direction, broaden the electrochemical window of the electrolyte and the energy storage device, and shift the hydrogen evolution onset potential in the negative direction, thus achieving the effect of inhibiting hydrogen evolution at the negative electrode.

[0018] When this kind of electrolyte is applied to an energy storage device, it can inhibit hydrogen evolution at the negative electrode of the energy storage device, thereby improving the long-term stable cycling performance of the energy storage device.

[0019] In addition, the dosage of the basic modifier is small. When it is added to the electrolyte, its modification effect is achieved. The modification method is simple and easy to implement without environmental pollution. Therefore, this kind of electrolyte is particularly suitable for large-scale and mass preparation of energy storage devices such as aqueous secondary batteries. When applied to an aqueous secondary battery, it exhibits characteristics such as ultra-long cycle life and high stability, and is a very promising electrolyte modification scheme for zinc-based energy storage devices.

[0020] Particularly, when this kind of electrolyte is applied to an aqueous zinc-ion secondary battery, the hydrogen evolution problem of the zinc-ion battery can be greatly alleviated, which helps to significantly improve the cycle life of the device. It is simple, convenient, and easy to industrialize, with low production cost and less pollution, and has advantages such as environmental friendliness. It can endow the aqueous zinc-ion secondary battery using this electrolyte with low-cost advantages and high-stability advantages, and has broad application prospects in large-scale energy storage. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying 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 accompanying drawings can be obtained based on these drawings.

[0022] Among them:

[0023] Figure 1 It is a schematic diagram of the electrochemical window of the electrolyte prepared in Example 1.

[0024] Figure 2 It is a long-term cycle performance graph of the symmetric battery containing aniline additive in Example 5.

[0025] Figure 3 It is a long-term cycle performance graph of the Zn / KMF battery containing aniline additive in Example 7.

[0026] Figure 4 It is a long-term cycle performance graph of the Zn / KMF battery without aniline additive in Example 7. Specific Embodiments

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] The present invention discloses an electrolyte in an embodiment. The solute of the electrolyte includes a zinc salt and a basic modifier. The mass concentration of the basic modifier is 0.1% to 1%, and the basic modifier is an amine or amine derivative with less than 10 carbon atoms.

[0029] Considering that when the number of carbon atoms is too large, the solubility of the basic modifier is poor. In this embodiment, the number of carbon atoms of the basic modifier is limited to less than 10.

[0030] It should be noted that in this embodiment, the number of carbon atoms of the basic modifier is limited to less than 10, and it also includes the case where the number of carbon atoms of the basic modifier is 0 (some amine derivatives).

[0031] It should be noted that the basicity of the basic modifier in the present invention refers to that the aqueous solution of the basic modifier shows alkalinity or weak alkalinity.

[0032] The solute of this electrolyte includes a basic modifier which is an amine or amine derivative with less than 10 carbon atoms. The "basicity" of the basic modifier is the ability to combine with protons during the electrochemical cycle. During its movement towards the negative electrode interface, it reduces the proton concentration at the negative electrode interface. On the other hand, the reduction of the interfacial proton concentration can shift the hydrogen evolution onset potential of the electrolyte towards the negative direction, broaden the electrochemical window of the electrolyte and the energy storage device, and shift the hydrogen evolution onset potential towards the negative direction, thus achieving the effect of suppressing hydrogen evolution at the negative electrode.

[0033] When this electrolyte is applied to an energy storage device, it can inhibit hydrogen evolution at the negative electrode of the energy storage device, thereby improving the long-cycle stable cycling performance of the energy storage device.

[0034] In addition, the dosage of the basic modifier is small. When it is added to the electrolyte, its modification effect is achieved. The modification method is simple and easy to implement without environmental pollution. Therefore, this electrolyte is particularly suitable for large-scale and mass preparation of energy storage devices such as aqueous secondary batteries. When applied to an aqueous secondary battery, it exhibits characteristics such as ultra-long cycle life and high stability, and is a very promising electrolyte modification scheme for zinc-based energy storage devices.

[0035] Particularly, when this electrolyte is applied to an aqueous zinc-ion secondary battery, the hydrogen evolution problem of the zinc-ion battery can be greatly alleviated, which helps to significantly improve the cycle life of the device. It is simple, convenient, and easy to industrialize, with low production cost and less pollution, and has advantages such as environmental friendliness. The aqueous zinc-ion secondary battery using this electrolyte can have the advantages of low cost and high stability, and has broad application prospects in large-scale energy storage.

[0036] Preferably, in this embodiment, the basic modifier contains an amino group.

[0037] More preferably, the basic modifier further contains at least one of an aromatic ring, a hydroxyl group, a sulfonyl group, and a carbonyl group.

[0038] Since amines, especially aromatic amines, have certain basicity but weaker basicity than ammonia water, etc., they have a certain ability to combine with protons during the electrochemical cycle, thereby reducing the proton concentration in the system and inhibiting hydrogen evolution. In addition, some amines can move to the negative electrode under the action of an electric field to complete adsorption after combining with protons, playing a role of isolating protons at the interface and inhibiting interfacial hydrogen evolution.

[0039] Particularly preferably, the basic modifier is selected from at least one of aniline, sulfanilamide, and sulfonamide.

[0040] In this embodiment, the solvent of the electrolyte is water.

[0041] Generally, in the electrolyte, the concentration of zinc salt is 0.5 mol / kg to 3 mol / kg. In other embodiments, the concentration of zinc salt can also be set according to actual situations.

[0042] In this embodiment, the zinc salt is selected from at least one of ZnSO4, Zn(CF3SO3)2, and Zn(ClO4)2. In other embodiments, specific zinc salts can also be selected according to actual situations.

[0043] The above-mentioned electrolyte can be applied to the field of electrochemical energy storage.

[0044] Specifically, the present invention also discloses an energy storage device according to an embodiment, including the above-mentioned electrolyte.

[0045] Preferably, the energy storage device is an aqueous secondary battery or an aqueous supercapacitor.

[0046] More preferably, the aqueous secondary battery is an aqueous zinc ion secondary battery or an aqueous alkali metal ion secondary battery.

[0047] The following are specific examples.

[0048] In the following examples, the present invention will investigate the hydrogen evolution inhibition effect of the additives involved in the present invention from (1) basic electrochemical properties, including the change of electrochemical window and interfacial corrosion current, etc., through a three-electrode system and an electrochemical workstation; (2) long-cycle performance test of a symmetric battery based on the modified electrolyte to investigate the improvement of the stability of the modified electrolyte, through a Neware battery test system; (3) long-cycle performance test of a full battery system based on the modified electrolyte to investigate the improvement of the long-cycle stability performance of the energy storage device, through a Neware battery test system. All data are repeatedly verified to ensure reliability and effectiveness.

[0049] Example 1 Hydrogen evolution slow-release effect of aniline on Zn(CF3SO3)2 electrolyte

[0050] 0.5 wt% of aniline was added to 1 mol / kg Zn(CF3SO3)2 electrolyte to obtain a modified electrolyte. The stable electrochemical window of the electrolyte was measured by linear sweep voltammetry (LSV) to obtain Figure 1 .

[0051] Combined with Figure 1 , it can be seen that compared with the control group, the electrochemical window of the electrolyte containing aniline is significantly broadened.

[0052] The characterization results show that the addition of aniline effectively plays a role in broadening the electrochemical window. The hydrogen evolution onset potential is -1.23 V. In contrast, the hydrogen evolution onset potential of 1 m Zn(CF3SO3)2 electrolyte is -1.10 V, which is broadened by 130 mV in the negative direction.

[0053] This indicates that the introduction of aniline effectively inhibits the occurrence of hydrogen evolution reaction during the electrochemical cycling process. In addition, Tafel analysis shows that the interfacial corrosion current of the electrolyte containing aniline decreases from [value] to [value], reducing by one order of magnitude, which verifies the hydrogen evolution slow-release effect of aniline on the electrolyte.

[0054] Example 2: Hydrogen evolution slow-release effect of sulfanilamide on Zn(CF3SO3)2 electrolyte

[0055] 1 wt% of sulfanilamide was added to 1 mol / kg Zn(CF3SO3)2 electrolyte to obtain a modified electrolyte, and the stable electrochemical window of the electrolyte was measured by linear sweep voltammetry (LSV).

[0056] The characterization results show that the addition of sulfanilamide effectively plays a role in broadening the electrochemical window. The hydrogen evolution onset potential is -1.29 V. In contrast, the hydrogen evolution onset potential of 1 m Zn(CF3SO3)2 electrolyte is -1.10 V, which is broadened by 190 mV in the negative direction.

[0057] This indicates that the introduction of sulfanilamide effectively inhibits the occurrence of hydrogen evolution reaction during the electrochemical cycling process.

[0058] Example 3: Hydrogen evolution slow-release effect of sulfonamide on Zn(CF3SO3)2 electrolyte

[0059] 0.1 wt% of sulfonamide was added to 1 mol / kg Zn(CF3SO3)2 electrolyte to obtain a modified electrolyte, and the stable electrochemical window of the electrolyte was measured by linear sweep voltammetry (LSV).

[0060] The characterization results show that the addition of sulfonamide effectively plays a role in broadening the electrochemical window. The hydrogen evolution onset potential is -1.20 V. In contrast, the hydrogen evolution onset potential of 1 m Zn(CF3SO3)2 electrolyte is -1.10 V, which is broadened by 100 mV in the negative direction.

[0061] This indicates that the introduction of sulfonamide effectively inhibits the occurrence of hydrogen evolution reaction during the electrochemical cycling process.

[0062] Example 4: Hydrogen evolution slow-release effect of aniline on ZnSO4 electrolyte

[0063] A modified electrolyte was obtained by adding 0.5 wt% aniline to 1 mol / kg ZnSO4 electrolyte, and the stable electrochemical window of the electrolyte was measured by linear sweep voltammetry (LSV).

[0064] The characterization results showed that the addition of aniline effectively widened the electrochemical window. The initial hydrogen evolution potential was -1.09 V. In contrast, the initial hydrogen evolution potential of 1 m Zn(CF3SO3)2 electrolyte was -0.98 V, which was widened by 110 mV in the negative direction.

[0065] This indicated that the introduction of aniline effectively inhibited the occurrence of hydrogen evolution reaction during the electrochemical cycling process.

[0066] Example 5 Stable cycling performance of aniline-modified Zn(CF3SO3)2 electrolyte

[0067] Fabrication of symmetric cell: Smooth zinc sheets were prepared into 15-mm-diameter circular wafers by a tablet press as the two electrodes of the symmetric cell, and they were assembled in the order of negative electrode shell, negative electrode, separator, positive electrode, positive electrode sheet, gasket, spring sheet, and positive electrode shell. Among them, 100 μL of the electrolyte based on Example 1 was injected after covering the separator, and the separator was a glass fiber separator. The above cell was sealed to obtain a symmetric cell.

[0068] Performance test: Charge-discharge current density was 1 mA cm -2 , the charge-discharge cycle time was fixed at 1 h, the upper limit of the protection voltage was 1.0 V, and the symmetric cells prepared above using the electrolyte with / without aniline additive were subjected to long-term cycling performance test to obtain Figure 2 .

[0069] Combined with Figure 2 , it can be seen that the long-term cycling performance of the symmetric cell with aniline additive was significantly better than that of the control group.

[0070] The results showed that the symmetric cell using the electrolyte without aniline additive showed abnormal polarization curves within 100 h, showing an irregular deposition / stripping voltage curve. This can be attributed to the formation of zinc dendrites and hydrogen evolution reaction (HER). On the contrary, the cycle life of the symmetric cell using the electrolyte with aniline additive was greatly improved, exceeding 1000 h, and the overpotential was 120 mV. After such a long cycle, the cell did not rupture, indicating that gas generation reactions such as HER could be effectively reduced.

[0071] Example 6 Stable cycling performance of sulfanilamide-modified Zn(CF3SO3)2 electrolyte

[0072] Fabrication of symmetric battery: Smooth zinc sheets were processed into 15-mm-diameter wafers by a tablet press to serve as the two electrodes of the symmetric battery, which were assembled in the order of negative electrode case, negative electrode, separator, positive electrode, positive electrode sheet, gasket, shrapnel, and positive electrode case. Among them, 100 μL of the electrolyte based on Example 2 was injected after covering the separator, and a glass fiber separator was selected. The above battery was sealed to obtain the symmetric battery.

[0073] The performance test was as follows: the charge-discharge current density was 1 mA cm -2 , the charge-discharge cycle time was fixed at 1 h, and the upper limit of the protection voltage was 1.0 V.

[0074] The results showed that the symmetric battery using the electrolyte without sulfanilamide exhibited abnormal polarization curves within 100 h, showing an irregular deposition / stripping voltage curve. The cycle life of the battery using the electrolyte containing sulfanilamide additive was significantly improved, exceeding 1500 h. After such a long period, the battery did not rupture, indicating that the gas generation reactions such as HER could be effectively reduced.

[0075] Repeating the above tests by changing the current density and the deposition amount per unit area, similar results could be obtained. When the current density was 2 mA cm -2 and the deposition amount was 2 mAh cm -2 , the life of the symmetric battery using 1 m Zn(CF3SO3)2 electrolyte was 100 h, while that of the battery containing sulfanilamide additive reached 1000 h; when the current density was 5 mA cm -2 and the deposition amount was 5 mAh cm -2 , the life of the symmetric battery using 1 m Zn(CF3SO3)2 electrolyte was 84 h, while it reached 800 h after adding sulfanilamide.

[0076] Stable cycling performance of aniline-modified ZnSO4 electrolyte in Example 7

[0077] Fabrication of symmetric battery: Smooth zinc sheets were processed into 15-mm-diameter wafers by a tablet press to serve as the two electrodes of the symmetric battery, which were assembled in the order of negative electrode case, negative electrode, separator, positive electrode, positive electrode sheet, gasket, shrapnel, and positive electrode case. Among them, 100 μL of the electrolyte based on Example 4 was injected after covering the separator, and a glass fiber separator was selected. The above battery was sealed to obtain the symmetric battery.

[0078] The performance test was as follows: the charge-discharge current density was 1 mA cm -2 , the charge-discharge cycle time was fixed at 1 h, and the upper limit of the protection voltage was 1.0 V. The symmetric battery was tested for the number of cycles, and Figure 3 and Figure 4 .

[0079] Combined with Figure 3 andFigure 4 , it can be seen that the cycling performance of the battery containing aniline additive is greatly improved.

[0080] The results show that the symmetric battery using the electrolyte without aniline addition shows abnormal polarization curves within 150 h, showing an irregular deposition / stripping voltage curve. The cycling life using the electrolyte containing aniline additive is greatly improved, exceeding 900 h. After such a long cycle, the battery does not rupture, indicating that the gas generation reactions such as HER can be effectively reduced.

[0081] Example 8 Performance of Zn / KMF battery based on aniline-modified Zn(CF3SO3)2 electrolyte

[0082] Fabrication of the full cell: First, conductive carbon black, Prussian blue material (KMF) with manganese and potassium as the framework structure, and binder PTFE are made into a slurry in a ratio of 2:7:1. After wet grinding and dry grinding, the material is cut into circular pieces using a tablet press and dried for 12 h to obtain the positive electrode sheet.

[0083] The performance test is as follows: Select 0.2 - 1.8 V as the voltage range for the full cell test. Under the condition of a current density of 1 A g -1 , the long-term cycling performance of the entire battery is evaluated in this chapter.

[0084] After 6000 electrochemical cycles, the full cell using the aniline-modified 1 mol / kg Zn(CF3SO3)2 based on Example 1 maintained a high Coulombic efficiency of 97% and a capacity retention rate of 83%, and the specific capacity was 45 mAh g -1 . For the battery assembled with ordinary Zn(CF3SO3)2 electrolyte, the battery failed within the 100th cycle. Its capacity decreased rapidly, mainly due to poor deposition uniformity and more side reactions.

[0085] Example 9 Performance of Zn / NaVO battery based on sulfanilamide-modified Zn(CF3SO3)2 electrolyte

[0086] Fabrication of the full cell: First, conductive carbon black, sodium-ion doped vanadium pentoxide material (NaVO), and binder PTFE are made into a slurry in a ratio of 2:7:1. After wet grinding and dry grinding, the material is cut into circular pieces using a tablet press and dried for 12 h to obtain the positive electrode sheet.

[0087] The performance test is as follows: Select 0.2 - 1.4 V as the voltage range for the full cell test. Under the condition of a current density of 1 A g -1 , the long-term cycling performance of the entire battery is evaluated in this chapter.

[0088] After 1000 electrochemical cycles, the full cell using the sulfonamide-modified 1 mol / kg Zn(CF3SO3)2 based on Example 2 maintained a high Coulombic efficiency of 98% and a capacity retention rate of 85%, with a specific capacity of 280 mAh g -1 . For the cell assembled with the ordinary Zn(CF3SO3)2 electrolyte, the cell failed within the 200th cycle. Its capacity decreased rapidly, mainly due to poor deposition uniformity and many side reactions.

[0089] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An electrolyte, characterized in that, The electrolyte is an electrolyte for an aqueous energy storage device. The solute of the electrolyte includes a zinc salt and an alkaline modifier, and the mass concentration of the alkaline modifier is 0.1% - 1%; the alkaline modifier is selected from at least one of aniline, sulfanilamide, and sulfonamide.

2. The electrolyte according to claim 1, wherein The concentration of the zinc salt is 0.5 mol / kg - 3 mol / kg.

3. The electrolyte according to claim 2, wherein The zinc salt is selected from at least one of ZnSO4, Zn(CF3SO3)2, and Zn(ClO4)2.

4. A energy storage device, characterized in that, It includes the electrolyte according to any one of claims 1 to 3.

5. The energy storage device according to claim 4, characterized in that, The energy storage device is an aqueous secondary battery or an aqueous supercapacitor.

6. The energy storage device according to claim 5, wherein The aqueous secondary battery is an aqueous zinc ion secondary battery or an aqueous alkali metal ion secondary battery.

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