Method and electrolyte for forming solid electrolyte interface film with gas additive

Abstract

The present invention relates to a method and electrolyte for forming a solid electrolyte interface film with the aid of gas additives. The method comprises: dissolving electrolyte AB in water at a certain concentration to obtain a first solution; wherein A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ Or one or more of the ionic liquid-based cations; B is a fluorine-containing anion; one or more of the gases containing carbon, fluorine, oxygen, and nitrogen elements are introduced into the first solution as a gas additive, and through the induction of the fluorine-containing anions in the first solution, the one or more of the carbon, fluorine, oxygen, and nitrogen elements and the fluorine-containing anions in the first solution interact with each other through charge so that the gas is enriched in the first solution to obtain a second solution; the second solution is used as an electrolyte for an aqueous battery to assemble a battery, and a bias voltage is applied to the battery, the bias voltage is ‑3.05 to 5V vs standard hydrogen electrode, and the duration is 5 minutes to 150 hours, and an ion-conducting and electronically insulating solid electrolyte interface film is generated on the electrode surface.

Description

Technical Field

[0001] The invention relates to the field of material technology, and in particular to a method and an electrolyte for forming a solid electrolyte interface film with the assistance of a gas additive. Background Art

[0002] As one of the current mainstream chemical energy storage technologies, lithium-ion batteries are widely used in consumer electronics, new energy electric vehicles and energy storage fields. Compared with other chemical energy storage methods, lithium-ion batteries have the advantages of long life and high energy density, but these advantages are based on a wide chemical window (0~5Vvs Li / Li + ) as support, and the organic electrolyte is easy to reach the flash point or above the ignition point under the condition of thermal runaway, which will eventually cause the battery to burn or even explode, seriously endangering the life safety of the user. Therefore, although organic lithium-ion batteries have excellent performance, their safety issues have been criticized by consumers. The development of aqueous batteries to replace organic battery systems is undoubtedly an effective and fundamental solution. Because water is a good flame retardant, if water can be used instead of organic solvents, the safety performance of the battery will be significantly improved.

[0003] However, limited by the intrinsic thermodynamic decomposition potential of water (1.23V), the stable electrochemical window of aqueous electrolytes is usually less than 1.5V, and a good solid electrolyte interface film cannot be formed on the negative electrode side to inhibit further side reactions, resulting in low energy density of the battery and a short actual working life.

[0004] Recently, the introduction of a new type of high salt concentration (Water-in-Salt, WIS) aqueous electrolyte with a wide potential window has increased the stability window of aqueous electrolytes from 2V to above 3V for the first time, and can form a solid electrolyte interface film on the negative electrode side to inhibit side reactions, thereby successfully developing a high-voltage aqueous lithium-ion battery with an output voltage of more than 2V. Compared with traditional aqueous batteries, its output voltage is increased by 30% to 50%, and its energy density is increased by 30%, exceeding 100Wh / kg. But at the same time, WIS electrolytes require ultra-high salt concentrations, which greatly increases the cost of the electrolyte. At the same time, the high viscosity caused by ultra-high salt concentrations also limits the kinetic performance of the battery. If the wide electrochemical window can be guaranteed while reducing the electrolyte concentration, it will greatly promote the practicality of aqueous batteries. Summary of the invention

[0005] The embodiments of the present invention provide a method and electrolyte for forming a solid electrolyte interface film with the aid of gas additives. The solid electrolyte interface film is formed with the aid of gas additives containing carbon, fluorine, oxygen, and nitrogen elements, which greatly improves the cycle stability of aqueous batteries while also greatly improving the kinetic performance.

[0006] In a first aspect, an embodiment of the present invention provides a method for forming a solid electrolyte interface film with the aid of a gas additive, comprising:

[0007] The electrolyte AB is dissolved in water at a certain concentration to obtain a first solution; wherein A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ or one or more of the cations in the ionic liquid base; B is a fluorine-containing anion;

[0008] Introducing a gas containing one or more of carbon, fluorine, oxygen, and nitrogen as a gas additive into the first solution, and through the induction of fluorine-containing anions in the first solution, there is a charge interaction between the one or more of carbon, fluorine, oxygen, and nitrogen elements and the fluorine-containing anions in the first solution, so that the gas is enriched in the first solution to obtain a second solution;

[0009] The second solution is used as the electrolyte of the aqueous battery to assemble the battery, and a bias is applied to the battery. The bias voltage is -3.05 to 5V vs standard hydrogen electrode (SHE) for 5 minutes to 150 hours, and a solid electrolyte interface film with ion conduction and electronic insulation is generated on the electrode surface of the battery.

[0010] Preferably, the ionic liquid-based cations include: 1-butyl-3-methylimidazole, 1-ethyl-3-methylimidazole, 1-propyl-3-methylimidazole, 1-hexyl-3-methylimidazole, 1-decyl-3-methylimidazole, 1-octyl-3-methylimidazole, 1-benzyl-3-methylimidazole, 1-hexadecyl-3-methylimidazole, 1-carboxymethyl-3-methylimidazole, 1-carboxymethyl-4-methylimidazole, 1-hydroxyethyl-3-methylimidazole, 1-ethyl methyl-3-methylimidazole, 1-ethyl-2,3-dimethylimidazole, 1-butyl -2,3-dimethylimidazole, 1-hexyl-2,3-dimethylimidazole, 1-octyl-2,3-dimethylimidazole, 1-decyl-2,3-dimethylimidazole, 1-allyl-3-methylimidazole, 1-dodecyl-3-methylimidazole, 1-hexadecyl-2,3-dimethylimidazole, N-ethylpyridine, N-butylpyridine, N-hexylpyridine, N-methyl, propylpiperidine, N-methyl, butylpyrrolidine, tetraethylammonium, tetrabutylammonium, 4-(3-methyl-1-imidazole)-1-butanesulfonic acid, trimethylhydroxyethylammonium;

[0011] The B is a compound containing -F and / or -CF x The anion of the group, 1≤x≤3; the B specifically includes: AsF6 - PF6 - 、BF4 - 、SO3F- 、[N(SO2F)2] - 、SO3CF3 - 、CO2CF3 - 、[N(SO2CF3)2] - 、[N(SO2C2F5)2] - 、[C(SO2CF3)3] - One or more of them.

[0012] Further preferably, a CF bond is formed between the carbon element and the anion in the first solution;

[0013] The oxygen element forms an OF bond with the anion in the first solution;

[0014] The fluorine element forms a CF bond with an anion containing a -CFx group in the first solution;

[0015] The nitrogen element forms NF bonds with the anions in the first solution.

[0016] Preferably, the concentration of the first solution is 0.01 mol / kg-100 mol / kg;

[0017] In the second solution, the amount of the gas additive introduced is 0.1 mmol / L-10 mol / L.

[0018] Preferably, the gas additive specifically includes: one or more of carbon dioxide, oxygen, air, ozone, carbon monoxide, fluorine, nitric oxide, nitrogen dioxide, nitrogen, ammonia, methane, ethane, propane, ethylene, acetylene, carbon tetrafluoride, trifluoromethane, difluoromethane or monofluoromethane;

[0019] The gas additives may be introduced by dissolving the gas inherently in the solution, introducing the gas from the outside, or generating the gas in situ through a chemical reaction.

[0020] Preferably, the introduction of gas from the outside is specifically: introducing gas from the outside using a gas cylinder and a catheter, the gas flow rate is 0.5mL / min-500mL / min, the temperature of the solution is -100°C to 100°C, the pressure at the output end of the gas cylinder is 0.01Mpa-10Mpa, and the ventilation time is 5 minutes to 20 hours.

[0021] In a second aspect, an embodiment of the present invention provides an electrolyte for an aqueous battery, wherein the electrolyte for the aqueous battery is prepared by dissolving an electrolyte AB in water at a certain concentration and then introducing a gas additive, wherein through the induction of fluorine-containing anions in a first solution, there is a charge interaction between one or more of the carbon, fluorine, oxygen, and nitrogen elements and the fluorine-containing anions in the first solution, so that the gas is enriched in the aqueous solution of the electrolyte AB;

[0022] The gas additive is a gas containing one or more of carbon, fluorine, oxygen and nitrogen elements;

[0023] In the electrolyte AB, A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ Or one or more of the ionic liquid-based cations; B is a fluorine-containing anion.

[0024] Preferably, the ionic liquid-based cations include: 1-butyl-3-methylimidazole, 1-ethyl-3-methylimidazole, 1-propyl-3-methylimidazole, 1-hexyl-3-methylimidazole, 1-decyl-3-methylimidazole, 1-octyl-3-methylimidazole, 1-benzyl-3-methylimidazole, 1-hexadecyl-3-methylimidazole, 1-carboxymethyl-3-methylimidazole, 1-carboxymethyl-4-methylimidazole, 1-hydroxyethyl-3-methylimidazole, 1-ethyl methyl-3-methylimidazole, 1-ethyl-2,3-dimethylimidazole, 1-butyl -2,3-dimethylimidazole, 1-hexyl-2,3-dimethylimidazole, 1-octyl-2,3-dimethylimidazole, 1-decyl-2,3-dimethylimidazole, 1-allyl-3-methylimidazole, 1-dodecyl-3-methylimidazole, 1-hexadecyl-2,3-dimethylimidazole, N-ethylpyridine, N-butylpyridine, N-hexylpyridine, N-methyl, propylpiperidine, N-methyl, butylpyrrolidine, tetraethylammonium, tetrabutylammonium, 4-(3-methyl-1-imidazole)-1-butanesulfonic acid, trimethylhydroxyethylammonium;

[0025] The B is a compound containing -F and / or -CF x The anion of the group, 1≤x≤3; the B specifically includes: AsF6 - PF6 - 、BF4 - 、SO3F - 、[N(SO2F)2] - 、SO3CF3 - 、CO2CF3 - 、[N(SO2CF3)2] - 、[N(SO2C2F5)2] - 、[C(SO2CF3)3] - One or more of the following;

[0026] The gas additive specifically includes: one or more of carbon dioxide, oxygen, air, ozone, carbon monoxide, fluorine, nitric oxide, nitrogen dioxide, nitrogen, ammonia, methane, ethane, propane, ethylene, acetylene, carbon tetrafluoride, trifluoromethane, difluoromethane or monofluoromethane. Preferably, the carbon element forms a CF bond with the anions in the first solution;

[0027] The oxygen element forms an OF bond with the anion in the first solution;

[0028] The fluorine element forms a CF bond with an anion containing a -CFx group in the first solution;

[0029] The nitrogen element forms NF bonds with the anions in the first solution.

[0030] Preferably, the concentration of the first solution is 0.01 mol / kg-100 mol / kg;

[0031] In the second solution, the amount of the gas additive introduced is 0.1 mmol / L-10 mol / L.

[0032] The method for forming a solid electrolyte interface film with the aid of a gas additive provided in an embodiment of the present invention is to introduce a gas containing one or more of carbon, fluorine, oxygen, and nitrogen elements as a gas additive into an electrolyte, and through the induction of fluorine-containing anions, one or more of carbon, fluorine, oxygen, and nitrogen elements and fluorine-containing anions in the first solution interact with each other in a charge manner, and finally achieve gas enrichment in the electrolyte to obtain an electrolyte containing a gas additive. By introducing a gas additive, a stronger interaction and more gas content than the original dissolved gas can be achieved, and a solid electrolyte interface film can be generated in situ during the charge and discharge process and attached to the electrode surface. This interface film has the characteristics of ion conduction and electronic insulation, and plays an important role in inhibiting the side reaction of water decomposition in the later stage. By introducing a gas additive, a solid electrolyte interface film can be formed in a lower concentration aqueous electrolyte during the charge and discharge process, avoiding the problems of high cost and high viscosity in a high concentration electrolyte, and improving the kinetic performance while ensuring the battery cycle life. The method is simple and effective, and is conducive to promotion, providing a new method and idea for broadening the window of aqueous electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The technical solution of the embodiment of the present invention is further described in detail below through the drawings and examples.

[0034] Figure 1 A flow chart of a method for forming a solid electrolyte interface film with the aid of a gas additive provided by an embodiment of the present invention;

[0035] Figure 2The first week discharge curve of the aqueous lithium battery electrolyte introduced with the carbon dioxide gas additive provided in Example 1 of the present invention;

[0036] Figure 3 A scanning electron microscope (SEM) image of the surface of the cycle electrode provided in Example 1 of the present invention;

[0037] Figure 4 The X-ray photoelectron spectroscopy (XPS) diagram of the circulating electrode surface after the introduction of the carbon dioxide gas additive provided in Example 2 of the present invention;

[0038] Figure 5 A transmission electron microscope (TEM) image of the surface of the cycle electrode provided in Example 3 of the present invention;

[0039] Figure 6 Comparison of nuclear magnetic resonance (NMR) fluorine spectra of the electrolyte before and after the introduction of the carbon dioxide gas additive provided in Example 4 of the present invention;

[0040] Figure 7 A 0.5C constant current charge and discharge cycle diagram of a lithium ion battery provided in Example 7 of the present invention, containing an aqueous lithium battery electrolyte before and after the introduction of a carbon dioxide gas additive;

[0041] Figure 8 A rate performance diagram of an aqueous lithium-ion battery at different current densities provided by Example 7 of the present invention;

[0042] Fig. 9 The first week discharge curve of the aqueous lithium battery electrolyte introduced with the oxygen gas additive provided in Example 8 of the present invention;

[0043] Fig.10 The X-ray photoelectron spectroscopy (XPS) diagram of the surface of the cycle electrode provided in Example 9 of the present invention;

[0044] Fig.11 This is a constant current charge and discharge cycle diagram of an aqueous lithium-ion battery provided in Example 9 of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0046] The method of forming a solid electrolyte interface film with the aid of a gas additive of the present invention mainly comprises the following steps: Figure 1 As shown, including:

[0047] Step 110, dissolving electrolyte AB in water at a certain concentration to obtain a first solution;

[0048] Where A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ Or one or more of the ionic liquid-based cations; wherein the ionic liquid-based cations include 1-butyl-3-methylimidazole, 1-ethyl-3-methylimidazole, 1-propyl-3-methylimidazole, 1-hexyl-3-methylimidazole, 1-decyl-3-methylimidazole, 1-octyl-3-methylimidazole, 1-benzyl-3-methylimidazole, 1-hexadecyl-3-methylimidazole, 1-carboxymethyl-3-methylimidazole, 1-carboxymethyl-4-methylimidazole, 1-hydroxyethyl-3-methylimidazole, 1-ethyl ester methyl-3-methylimidazole, 1-ethyl-2,3-dimethylimidazole, 1- One or more of ionic liquid-based large cations such as butyl-2,3-dimethylimidazole, 1-hexyl-2,3-dimethylimidazole, 1-octyl-2,3-dimethylimidazole, 1-decyl-2,3-dimethylimidazole, 1-allyl-3-methylimidazole, 1-dodecyl-3-methylimidazole, 1-hexadecyl-2,3-dimethylimidazole, N-ethylpyridine, N-butylpyridine, N-hexylpyridine, N-methyl, propylpiperidine, N-methyl, butylpyrrolidine, tetraethylammonium, tetrabutylammonium, 4-(3-methyl-1-imidazole)-1-butanesulfonic acid, trimethylhydroxyethylammonium, etc.;

[0049] B is a fluorine-containing anion; specifically, it contains -F and / or -CF x Anions of the group, 1≤x≤3; more specifically, including: AsF6 - PF6 - 、BF4 - 、SO3F - 、[N(SO2F)2] - 、SO3CF3 - 、CO2CF3 - 、[N(SO2CF3)2] - 、[N(SO2C2F5)2] - 、[C(SO2CF3)3] - One or more of

[0050] The concentration of the obtained first solution is 0.01 mol / kg-100 mol / kg, wherein mol / kg means that 1 kg of solvent dissolves 1 mol of solute.

[0051] Step 120, introducing a gas containing one or more of carbon, fluorine, oxygen, and nitrogen as a gas additive into the first solution, and through the induction of fluorine-containing anions in the first solution, there is a charge interaction between one or more of carbon, fluorine, oxygen, and nitrogen and the fluorine-containing anions in the first solution, so that the gas is enriched in the first solution, thereby obtaining a second solution;

[0052] Wherein, a CF bond is formed between the carbon element and the anion in the first solution;

[0053] An OF bond is formed between the oxygen element and the anion in the first solution;

[0054] The fluorine element forms a CF bond with the anion containing a -CFx group in the first solution;

[0055] NF bonds are formed between the nitrogen element and the anions in the first solution.

[0056] In the second solution, the amount of the gas additive introduced is 0.1 mmol / L-10 mol / L, wherein mmol / L and mol / L refer to the content of dissolved gas per liter of solution.

[0057] The gas additives specifically include: one or more of carbon dioxide, oxygen, air, ozone, carbon monoxide, fluorine, nitric oxide, nitrogen dioxide, nitrogen, ammonia, methane, ethane, propane, ethylene, acetylene, carbon tetrafluoride, trifluoromethane, difluoromethane or monofluoromethane;

[0058] The introduction of gas additives includes: inherently dissolved gas in the solution, introducing gas from the outside, or generating gas in situ through chemical reaction.

[0059] Specifically, the introduction of gas from the outside includes: using a gas cylinder and a conduit to introduce gas from the outside, the gas flow rate is 0.5mL / min-500mL / min, the temperature of the solution is -100°C to 100°C, the pressure at the output end of the gas cylinder is 0.01Mpa-10Mpa, and the ventilation time is 5 minutes to 20 hours. Under the induction of fluorine-containing anions, the charge interaction between the gas introduced from the outside and the fluorine-containing anions is stronger than the charge interaction between the inherent dissolved gas in the solution and the fluorine-containing anions, and the gas content is higher.

[0060] The inherent dissolved gas in the solution refers to the gas that has a certain solubility in water at 20°C and standard atmospheric pressure. When untreated water is used as the solvent, the resulting first solution contains a certain amount of the corresponding gas.

[0061] The in-situ generation of gas through chemical reaction is specifically as follows: under the conditions of heating / strong alkali / pressurization / strong acid, the first solution undergoes a chemical reaction to generate gas, and the gas dissolves into the first solution to form a second solution.

[0062] Step 130, assemble the battery using the second solution as the electrolyte of the aqueous battery, apply a bias voltage to the battery, the bias voltage is -3.05 to 5V vs standard hydrogen electrode (SHE), and the bias voltage is applied for 5 minutes to 150 hours, so as to generate an ion-conducting and electronically insulating solid electrolyte interface film on the electrode surface of the battery.

[0063] The introduction of gas additives can achieve stronger interactions and more gas content than the original dissolved gas, and can generate a solid electrolyte interface film in situ during the charge and discharge process and attach to the electrode surface. This interface film has the characteristics of ion conduction and electronic insulation, and plays an important role in inhibiting the side reaction of water decomposition in the later stage. By introducing gas additives, a solid electrolyte interface film can be formed in a lower concentration aqueous electrolyte during the charge and discharge process, avoiding the problems of high cost and high viscosity in high concentration electrolytes, and improving the kinetic performance while ensuring the battery cycle life.

[0064] In order to better understand the technical solution provided by the present invention, the following uses a number of specific examples to illustrate the use of several methods provided in the above embodiments of the present invention to prepare the electrolyte of the aqueous battery, as well as the method of applying it to secondary batteries and the battery characteristics.

[0065] Example 1

[0066] This embodiment introduces a carbon dioxide gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0067] Step (1) 11.4 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0068] Step (2) Take 6 mL of the solution of step (1), and introduce carbon dioxide from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 0.5 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.01 MPa, and the treatment time is 1 hour.

[0069] Step (3) The solution containing carbon dioxide in step (2) is used as the electrolyte of the lithium secondary battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0070] Figure 2 The first week discharge curve of a lithium secondary battery containing an aqueous lithium battery electrolyte containing a carbon dioxide gas additive at 0.5C. It can be seen that at 2.58V vs Li / Li + There is an obvious platform for carbon dioxide to be reduced to lithium carbonate. Figure 3This is a scanning electron microscope (SEM) image of the electrode surface after the reaction, in which a dense solid electrolyte interface film can be clearly seen.

[0071] Example 2

[0072] This embodiment introduces a carbon dioxide gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0073] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0074] Step (2) Take 6 mL of the solution of step (1), and introduce carbon dioxide from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 10 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.1 MPa, and the treatment time is 1 hour.

[0075] Step (3) uses the solution containing carbon dioxide in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0076] Figure 4 The X-ray photoelectron spectroscopy (XPS) diagram of the cycle electrode surface after the introduction of carbon dioxide additive shows the presence of an obvious film layer containing lithium carbonate.

[0077] Example 3

[0078] This embodiment introduces an oxygen gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0079] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0080] Step (2) Take 6 mL of the solution of step (1), introduce oxygen from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 5 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.01 MPa, and the treatment time is 1 hour.

[0081] Step (3) uses the solution containing oxygen in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0082] Figure 5 The transmission electron microscopy (TEM) image of the cycled electrode surface after the introduction of oxygen additives shows the formation of a lithium peroxide passivation film.

[0083] Example 4

[0084] This embodiment introduces a carbon dioxide gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0085] Step (1) 11.4 g of LiTFSI was dissolved in 8 mL of deionized water to obtain a solution with a concentration of 5 mol / kg.

[0086] Step (2) Take 3 mL of the solution of step (1), and introduce carbon dioxide from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 5 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.01 MPa, and the treatment time is 1 hour.

[0087] Step (3) uses the solution containing carbon dioxide in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0088] Figure 6 The nuclear magnetic resonance (NMR) fluorine spectrum of 5m LiTFSI solution before and after the introduction of carbon dioxide additive shows that the chemical shift of the fluorine spectrum shifts significantly to a lower wavenumber after the introduction of carbon dioxide, indicating that there is a carbon-fluorine interaction between the gas and anions in the solution, which changes the electron cloud density around fluorine. This indicates that the interaction between the externally introduced gas and the fluorine-containing anions is stronger than the interaction between the dissolved gas and the fluorine-containing anions in the original solution.

[0089] Example 5

[0090] This embodiment introduces an oxygen gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0091] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0092] Step (2) Take 3 mL of the solution of step (1), and introduce oxygen from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 0.5 mL / min, the solution temperature is -100°C, the pressure at the output end of the gas cylinder is 0.01 MPa, and the treatment time is 5 minutes.

[0093] Step (3) The solution containing the oxygen additive in step (2) is used as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -3.05 V vs SHE, and the pressurization time is 5 minutes.

[0094] Example 6

[0095] This embodiment introduces air gas additives to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0096] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0097] Step (2) Take 3 mL of the solution of step (1), introduce air from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 500 mL / min, the solution temperature is 100° C., the pressure at the output end of the gas cylinder is 10 MPa, and the treatment time is 20 hours.

[0098] Step (3) uses the air-containing solution in step (2) as an electrolyte for an aqueous lithium-ion battery, with a bias voltage of 5 V vs SHE and a pressurization time of 150 hours.

[0099] Example 7

[0100] This embodiment introduces a carbon dioxide gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0101] Step (1) 11.4 g of LiTFSI was dissolved in 8 mL of deionized water to obtain a solution with a concentration of 5 mol / kg.

[0102] Step (2) Take 3 mL of the solution of step (1), and introduce carbon dioxide from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 15 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.1 MPa, and the treatment time is 1 hour.

[0103] Step (3) uses the solution containing carbon dioxide in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05V vs SHE, and the pressurization time is 20 hours.

[0104] Figure 7 The 0.5C constant current charge and discharge cycle diagrams of lithium-ion batteries with aqueous lithium-ion battery electrolytes before and after the introduction of carbon dioxide gas additives. It can be seen that the battery's cycle performance is significantly improved after the introduction of carbon dioxide; Figure 8 The figure shows the rate performance at different current densities. It can be seen that the battery's kinetic performance has also been significantly improved.

[0105] Example 8

[0106] This embodiment introduces an oxygen gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0107] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0108] Step (2) Take 6 mL of the solution of step (1), introduce oxygen from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 15 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.01 MPa, and the treatment time is 1 hour.

[0109] Step (3) uses the solution containing oxygen in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0110] Fig. 9 This is the first week discharge curve of aqueous lithium battery electrolyte after the introduction of oxygen gas additive. It can be seen that at 2.68V vs Li / Li + There is an obvious platform where oxygen is reduced to lithium peroxide.

[0111] Example 9

[0112] This embodiment introduces an oxygen gas additive to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0113] Step (1) 11.4 g of LiTFSI was dissolved in 2 mL of deionized water to obtain a solution with a concentration of 21 mol / kg.

[0114] Step (2) Take 6 mL of the solution of step (1), introduce oxygen from the outside using a gas cylinder and a catheter, wherein the air flow rate in the catheter is 15 mL / min, the solution temperature is 25° C., the pressure at the output end of the gas cylinder is 0.1 MPa, and the treatment time is 1 hour.

[0115] Step (3) uses the solution containing oxygen in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05 V vs SHE, and the pressurization time is 20 hours.

[0116] Fig.10 The X-ray photoelectron spectroscopy (XPS) diagram of the cycle electrode surface after the introduction of oxygen additives shows that a clear lithium peroxide passivation layer is formed. Fig.11 This is the constant current charge and discharge cycle diagram at 0.5C for aqueous lithium-ion batteries. It can be seen that the cycle performance has been significantly improved.

[0117] Example 10

[0118] In this embodiment, the solid electrolyte interface film is assisted in forming in the aqueous lithium-ion battery by using the inherent dissolved carbon dioxide gas additive in the solution.

[0119] Step (1) At 20° C. and standard atmospheric pressure, without any other treatment, the solubility of carbon dioxide in water is 878 mL.

[0120] Step (2) Take 2 mL of water in step (1), wherein the carbon dioxide content is 1.756 mL, and dissolve 11.4 g of LiTFSI therein to obtain a solution with a concentration of 21 mol / kg.

[0121] Step (3) uses the solution containing carbon dioxide in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05V vs SHE, and the pressurization time is 20 hours.

[0122] Embodiment 11

[0123] In this embodiment, a carbon dioxide gas additive is generated in situ by chemical reaction to assist in forming a solid electrolyte interface film in an aqueous lithium-ion battery.

[0124] Step (1) 5.99 g of lithium trifluoroacetate was dissolved in 10 mL of deionized water to obtain a solution with a concentration of 5 mol / kg.

[0125] Step (2) The solution in step (1) is heated at 80° C. for 2 minutes, wherein the carboxylic acid molecules undergo a decarboxylation chemical reaction, generating carbon dioxide gas in situ and dissolving in the solution.

[0126] Step (3) uses the solution containing carbon dioxide in step (2) as the electrolyte of the aqueous lithium-ion battery, the bias voltage is -1.05V vs SHE, and the pressurization time is 20 hours.

[0127] Example 12

[0128] This embodiment provides a comparison of the carbon dioxide content in the lithium ion electrolyte before and after the introduction of carbon dioxide gas and air gas additives.

[0129] In the two comparative experiments, the following steps were followed:

[0130] Step (1) 11.4 g of LiTFSI was dissolved in 8 mL of deionized water to obtain a solution with a concentration of 5 mol / kg.

[0131] Step (2) Take 3 mL of the solution of step (1) and introduce a gas additive (carbon dioxide or air) from the outside using a gas cylinder and a catheter, wherein the gas flow rate in the catheter is 15 mL / min, the solution temperature is 25°C, the pressure at the output end of the gas cylinder is 0.1 MPa, and the treatment time is 1 hour.

[0132] Step (3) takes the solution in step (1) and the solution in step (2) and compares the carbon dioxide content therein.

[0133] The following Table 1 compares the carbon dioxide content in the lithium ion electrolyte provided in Example 12 of the present invention before and after the introduction of carbon dioxide and air additives.

[0134]

[0135] Table 1

[0136] Table 1 compares the content of carbon dioxide introduced from the outside and inherent in the original solution. It can be found that the amount of carbon dioxide in the solution after treatment with carbon dioxide is the largest, the amount of carbon dioxide in the solution after treatment with air is second, and the amount of carbon dioxide in the original solution is the least, indicating that the gas introduced from the outside can achieve a higher gas content in the solution.

[0137] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for forming a solid electrolyte interface film with the aid of a gas additive, characterized in that: The method comprises: The electrolyte AB is dissolved in water at a certain concentration to obtain a first solution; wherein A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ One or more of; B is a fluorine-containing anion; the concentration of the first solution is 5 mol / kg-21 mol / kg; Introducing a gas containing carbon or oxygen as a gas additive into the first solution, and through the induction of fluorine-containing anions in the first solution, there is a charge interaction between the carbon or oxygen element and the fluorine-containing anions in the first solution, so that the gas is enriched in the first solution to obtain a second solution; the gas additive is carbon dioxide or oxygen; Formation of CF bonds between the carbon element and the anions in the first solution; The oxygen element forms an OF bond with the anion in the first solution; Assembling a battery using the second solution as an electrolyte of an aqueous battery, applying a bias voltage to the battery, wherein the bias voltage is -3.05 to 5 V vs. a standard hydrogen electrode, and the bias voltage is applied for a period of 5 minutes to 150 hours, thereby generating an ion-conducting and electronically insulating solid electrolyte interface film on the electrode surface of the battery; The B is a compound containing -F and / or -CF x The anion of the group, 1≤x≤3; the B specifically includes: AsF6 - PF6 - 、BF4 - 、SO3F - 、[N(SO2F)2] - 、SO3CF3 - 、CO2CF3 - 、[N(SO2CF3)2] - 、[N(SO2C2F5)2] - 、[C(SO2CF3)3] - One or more of the following; The gas additive is introduced by introducing gas from the outside; the introduction of gas from the outside is specifically: introducing gas from the outside using a gas cylinder and a catheter, the gas flow rate is 0.5mL / min-500mL / min, the solution temperature is -100°C to 100°C, the pressure at the output end of the gas cylinder is 0.01Mpa-10Mpa, and the ventilation time is 5 minutes to 20 hours.

2. The method for forming a solid electrolyte interface film with the aid of a gas additive according to claim 1, characterized in that: In the second solution, the amount of the gas additive introduced is 0.1 mmol / L-10 mol / L.

3. An aqueous battery electrolyte obtained by the method according to any one of claims 1 to 2, characterized in that: The electrolyte of the aqueous battery is prepared by dissolving electrolyte AB in water at a certain concentration, and then introducing a gas containing carbon or oxygen as a gas additive. Through the induction of fluorine-containing anions in the first solution, there is a charge interaction between the carbon or oxygen element and the fluorine-containing anions in the first solution, so that the gas is enriched in the aqueous solution of the electrolyte AB; the concentration of the first solution is 5 mol / kg-21 mol / kg; The gas additive is carbon dioxide or oxygen; In the electrolyte AB, A is a cation, including alkali metal ions, alkaline earth metal ions, Zn 2+ 、Al 3+ One or more of, B is a fluorine-containing anion; Formation of CF bonds between the carbon element and the anions in the first solution; The oxygen element forms an OF bond with the anion in the first solution; The B is a compound containing -F and / or -CF x The anion of the group, 1≤x≤3; the B specifically includes: AsF6 - PF6 - 、BF4 - 、SO3F - 、[N(SO2F)2] - 、SO3CF3 - 、CO2CF3 - 、[N(SO2CF3)2] - 、[N(SO2C2F5)2] - 、[C(SO2CF3)3] - One or more of them.

4. The electrolyte according to claim 3, characterized in that In the second solution, the amount of the gas additive introduced is 0.1 mmol / L-10 mol / L.

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