CN111900495A - Water-based electrolyte and application thereof - Google Patents
Water-based electrolyte and application thereof Download PDFInfo
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H—ELECTRICITY
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- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/54—Electrolytes
- H01G11/58—Liquid electrolytes
- H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract
The application discloses a water-based electrolyte and application thereof. The water-based electrolyte is a mixed solvent composed of water or water and an organic solvent, and contains lithium bis (fluorosulfonyl) imide with the mass molar concentration not less than 10 mol/kg. According to the water-based electrolyte, due to the addition of the high-concentration lithium bis (fluorosulfonyl) imide salt, almost all solvent molecules participate in hydration of anions and cations of the lithium bis (fluorosulfonyl) imide salt, a stable ion sheath layer is formed, the activity of water molecules is reduced, and the decomposition of the water molecules on the surface of an electrode is inhibited; in addition, the high-concentration lithium bis (fluorosulfonyl) imide salt is easy to form an inert layer containing fluoride on the negative electrode, can improve the electrochemical window of the water-based electrolyte, improve the working voltage of the water-based energy storage device, improve the energy density and prolong the service life, has important significance for the research and application of the water-based energy storage device, and lays a foundation for preparing the high-quality water-based energy storage device.
Description
Technical Field
The application relates to the field of electrochemical energy storage electrolyte, in particular to water-based electrolyte and application thereof.
Background
The electrochemical energy storage device of the organic system can provide higher working voltage and energy density, and currently, commercial lithium ion batteries and super capacitors mainly adopt organic electrolyte. However, organic electrolytes have inherent disadvantages of poor safety (flammability), toxicity, environmental pollution, and high cost. In recent years, accidents of explosion and ignition of lithium ion batteries, such as mobile phone explosion, auto-ignition of automobiles and the like, occur frequently, which greatly limits further wide application of electrochemical energy storage devices. Compared with the organic electrolyte, the water system electrolyte has great advantages and application potentials in the aspects of cost, safety, resource storage and the like. However, since the electrochemical stability window of water is narrow, only about 1.23V, and is limited by the hydrogen and oxygen evolution reactions, the cell voltage of conventional aqueous electrolytes is typically less than 1.6V, which severely limits their applications.
In recent years, the electrochemical window of aqueous electrolytes has been expanded to 3.0V by increasing the concentration of the solution. For example, the catalyst is prepared from concentrated salt LiTFSI and NaClO4And KAc, etc., in which almost all water molecules undergo strong coordination with lithium ions to form stable hydrated complexes, thereby widening the electrochemical window of the electrolyte. However, the electrochemical window of these "water-in-salt" electrolytes is currently about 3.0V, which is still much lower than that of conventional organic electrolytes.
Therefore, how to improve the electrochemical window of the water-based electrolyte is still the focus and difficulty of the research of the water-based electrolyte.
Disclosure of Invention
It is an object of the present application to provide an improved water-based electrolyte and its use.
The following technical scheme is adopted in the application:
the first aspect of the application discloses a water-based electrolyte, the solvent of the water-based electrolyte is water or a mixed solvent composed of water and an organic solvent, and the water-based electrolyte contains lithium bis (fluorosulfonyl) imide with the mass molar concentration of not less than 10 mol/kg.
It is noted that the water-based electrolyte of the present application has a high concentration of dissolved thereinLithium bis (fluorosulfonyl) imide salt (F)2NO4S2Li, LiFSI), i.e. the molarity is not less than 10 mol/kg; the high-concentration lithium bis (fluorosulfonyl) imide salt enables almost all solvent molecules to be hydrated with lithium ions, and the strong solvation action reduces the activity of water molecules and inhibits the decomposition of the water molecules on the surface of an electrode; and the high-concentration LiFSI electrolyte can easily form an inert layer containing fluoride on the cathode, can further improve the electrochemical window of the water-based electrolyte, can improve the working voltage of the water-based energy storage device when being applied to the water-based energy storage device, improves the energy density of the device, improves the service life of the device, and has important practical significance for the research and application in the water-based energy storage field.
It is understood that the key to the present application is the addition of high concentrations of lithium bis-fluorosulfonylimide based on existing water-based electrolytes. As for the solvent of the specific water-based electrolyte, water or a mixed solvent of water and an organic solvent which has been conventionally used at present may be mentioned. As for the electrolyte of the water-based electrolyte, lithium bis (fluorosulfonyl) imide can be used as an electrolyte material, and therefore, the water-based electrolyte of the present application may not contain other electrolytes; of course, other conventionally used electrolytes may be added as a supporting electrolyte used in combination as needed, for example, a sulfate, a nitrate, an acetate, a perchlorate, a trifluoromethanesulfonate or a chloride of at least one of an alkali metal and zinc; specifically, the electrolyte may be used according to the application of the specific electrolyte, for example, when used in different batteries or water-based electrochemical supercapacitors, the supporting electrolyte is used for the anode and cathode, and is not limited specifically herein. However, in order to ensure the performance and effect of the hydrolysis electrolyte, the solvent and the supporting electrolyte are defined in the preferred embodiments of the present invention, and the details are described in the following embodiments.
Preferably, in the water-based electrolyte of the present application, the organic solvent is at least one of dimethyl carbonate (DMC), Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC), and Tetrahydrofuran (THF).
Preferably, when the water-based electrolyte adopts a mixed solvent, the organic solvent accounts for less than 75% of the total mass of the mixed solvent.
In the water-based electrolyte of the present application, although an organic solvent may be added; however, the amount of organic solvent used is less than 75%. The reason is mainly that, firstly, the salt precipitation can be caused by too large amount of organic solvent, and the high-concentration lithium bis (fluorosulfonyl) imide salt in the application can not be realized; second, too large an amount of the organic solvent affects the safety of the water-based electrolyte.
A second aspect of the present application discloses the use of the water-based electrolyte of the present application in an electrochemical energy storage device.
A third aspect of the present application discloses an electrochemical energy storage device employing the water-based electrolyte of the present application.
The electrochemical energy storage device can reduce the activity of water molecules and inhibit the water molecules from decomposing on the surface of an electrode due to the adoption of the water-based electrolyte; and an inert layer containing fluoride is easily formed on the negative electrode, so that the electrochemical window of the water-based electrolyte is further improved, the working voltage of the electrochemical energy storage device can be improved, the energy density is improved, and the service life is prolonged.
Preferably, the electrochemical energy storage device of the present application is a water-based secondary battery or a water-based electrochemical supercapacitor, or a combination of both.
It is understood that the key point of the present application is to use the water-based electrolyte of the present application, and the specific structural configuration of the electrochemical energy storage device can refer to the existing electrochemical energy storage device, such as a water-based secondary battery or a water-based electrochemical super capacitor, or a combination of the two. As to how both the specific water-based secondary battery and the water-based electrochemical supercapacitor are organically combined, reference may be made to the prior art solutions, which are not specifically limited herein.
Preferably, the electrochemical energy storage device of the present application is specifically a water-based lithium ion battery composed of an organic lithium ion battery anode and sodium titanium phosphate or lithium titanate or titanium dioxide, or a water-based battery capacitor composed of an organic lithium ion battery anode and activated carbon, or a symmetrical water-based supercapacitor composed of carbon-based materials.
It is understood that the specific electrochemical energy storage devices listed above are only those electrochemical energy storage devices specifically employed in one implementation of the present application, and may be other types of water-based secondary batteries or water-based electrochemical supercapacitors or a combination of both, within the inventive concepts of the present application.
The beneficial effect of this application lies in:
according to the water-based electrolyte, due to the addition of the high-concentration lithium bis (fluorosulfonyl) imide salt, almost all solvent molecules are hydrated with lithium ions, so that the activity of water molecules is reduced, and the decomposition of the water molecules on the surface of an electrode is inhibited; in addition, the high-concentration lithium bis (fluorosulfonyl) imide salt is easy to form an inert layer containing fluoride on the negative electrode, can improve the electrochemical window of the water-based electrolyte, improve the working voltage of the water-based energy storage device, improve the energy density and prolong the service life, has important significance for the research and application of the water-based energy storage device, and lays a foundation for preparing the high-quality water-based energy storage device.
Drawings
FIG. 1 is a plot of cyclic voltammetry scans of two water-based electrolytes of lithium bis (fluorosulfonyl) imide salts at different concentrations in one example of the present application;
FIG. 2 is a plot of cyclic voltammetric scans of a water-based electrolyte according to example two of the present application.
Detailed Description
The present application will be described in further detail with reference to specific examples. The following examples are intended to be illustrative of the present application only and should not be construed as limiting the present application.
Example one
The solvent of the water-based electrolyte is water, the electrolyte salt is lithium bis (fluorosulfonyl) imide, and the preparation method is as follows: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in water to prepare a solution with the mass molar concentration of 32mol/kg, thereby obtaining the water-based electrolyte with the high voltage window.
In addition, a water-based electrolyte with low LiFSI concentration is prepared for comparison, and particularly, LiFSI salt is dissolved in solvent water to prepare the water-based electrolyte with the mass molar concentration of 1mol/kg for comparison.
The electrochemical window test is respectively carried out on the water-based electrolyte with high LiFSI concentration and the water-based electrolyte with low LiFSI concentration prepared by the embodiment by adopting a three-electrode linear voltammetry scanning method, wherein a working electrode in positive scanning is a titanium electrode, a working electrode in negative scanning is an aluminum electrode, a counter electrode is a platinum electrode, a reference electrode is a saturated calomel electrode, the scanning voltage is-2-2.5V (vs. SCE), and the scanning speed is 10 mv/s.
The test results are shown in FIG. 1, in which the solid line represents the result of LiFSI test at a high concentration of 32mol/kg, and the dotted line represents the result of LiFSI test at a low concentration of 1 mol/kg. The results of fig. 2 show that the high LiFSI concentration water-based electrolyte begins to evolve hydrogen at-1.6V and oxygen at 1.8V, indicating that the electrochemical window of the high LiFSI concentration water-based electrolyte is 3.4V; while the water-based electrolyte with low LiFSI concentration has obvious hydrogen evolution and oxygen evolution reactions at-1.2V and 1.1V, and the electrochemical window is only 2.3V.
The results of fig. 1 demonstrate that water-based electrolytes with high LiFSI concentrations have a higher voltage window; moreover, from the aspects of hydrogen evolution and oxygen evolution, in the water-based electrolyte with high LiFSI concentration, water molecules are more difficult to decompose on the surface of the electrode, and the analysis is probably because the high-concentration LiFSI enables almost all solvent molecules to be hydrated with lithium ions, so that the activity of the water molecules is reduced, and the decomposition of the water molecules on the surface of the electrode is inhibited. In addition, a large amount of fluorine contained in the high-concentration lithium bis (fluorosulfonyl) imide salt is easy to form an inert layer containing fluoride on a negative electrode, so that the electrochemical window of a water-based electrolyte is improved, and the working voltage of a water-based energy storage device is improved.
The water-based electrolyte with high LiFSI concentration and the water-based electrolyte with low LiFSI concentration of the embodiment are respectively used in a water-based lithium ion battery, and the anode is commercially used spinel LiMn2O4The negative electrode is TiO2Mixing the positive electrode and the negative electrode according to the weight ratio of active material/acetylene black/PTFE (Polytetrafluoroethylene) 80/10/10 to prepare slurry, coating the slurry on a stainless steel foil, and drying to prepare the electrode. And then assembled into a button cell, wherein the diaphragm is the diaphragm of a commercial nickel-hydrogen battery, namely the electrolyteThe water-based electrolyte of (1).
Measuring the capacity retention rate of the lithium ion battery adopting the water-based electrolyte with high LiFSI concentration and the water-based electrolyte with low LiFSI concentration respectively; specifically, the battery is charged and discharged under a voltage range of 1.0-2.5V, the current density is 200mA/g, and the capacity retention rate of the battery is tested after 1000 cycles.
The test result shows that after 1000 cycles, the capacity retention rate of the water-based electrolyte with high LiFSI concentration is 86%, and the capacity retention rate of the water-based electrolyte with low LiFSI concentration is 58%, which indicates that the water-based electrolyte with high LiFSI concentration can provide higher working voltage, can effectively improve the cycle stability of the water-based lithium ion battery, improve the energy density and improve the service life of the battery.
Example two
The solvent of the water-based electrolyte in the embodiment is water, dimethyl carbonate and ethylene carbonate, the electrolyte salt is lithium bis (fluorosulfonyl) imide, and the preparation method is as follows: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in a mixed solvent of water and dimethyl carbonate (DMC) and Ethylene Carbonate (EC), wherein the volume ratio of the organic component EC to DMC is 1:1, and the total weight of the organic component EC to DMC accounts for 2/3 of the total weight of the solvent, and preparing the LiFSI into a solution with the mass molar concentration of 35mol/kg, namely obtaining the high-voltage window water-based electrolyte.
The water-based electrolyte of this example was subjected to electrochemical window testing using the same method and conditions as in example one.
As shown in FIG. 2, the anodic oxygen evolution potential was 2.7V (vs. SCE), the cathodic hydrogen evolution potential was-2.9V (vs. SCE), and the voltage window reached 5.6V.
The water-based electrolyte of the embodiment is used in a water-based super capacitor, the positive electrode and the negative electrode are activated carbon used commercially, the positive electrode and the negative electrode are mixed according to the weight ratio of active material/acetylene black/PTFE (Polytetrafluoroethylene) 80/10/10 to prepare slurry, and the slurry is coated on a stainless steel foil and dried to prepare an electrode. And then assembled into a button cell, wherein the diaphragm is the diaphragm of a commercial nickel-metal hydride battery, and the electrolyte is the water-based electrolyte in the embodiment.
The capacity retention rate of the super capacitor adopting the water-based electrolyte of the embodiment is measured, specifically, the super capacitor is charged and discharged under the voltage range of 0-2.5V, the current density is 1000mA/g, and the capacity retention rate of 10000 cycles is tested.
The test result shows that the capacity retention rate exceeds 90% after 10000 cycles, which indicates that the water-based supercapacitor adopting the water-based electrolyte of the embodiment has high working voltage and long cycle life.
EXAMPLE III
The solvent of the water-based electrolyte in the embodiment is water and diethyl carbonate, the electrolyte salt is lithium bis (fluorosulfonyl) imide, and the preparation method is as follows: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in water and diethyl carbonate (DEC), wherein the weight ratio of DEC to total solvent is 20%, and preparing LiFSI into a solution with a molar concentration of 28mol/kg, namely obtaining the high-voltage window water-based electrolyte.
The water-based electrolyte of this example was subjected to electrochemical window testing using the same method and conditions as in example one. The results show that the anodic oxygen evolution potential is 1.8V (vs. SCE), the cathodic hydrogen evolution potential is-1.7V (vs. SCE), and the voltage window reaches 4.5V.
The water-based electrolyte of the example is used in a water-based lithium ion hybrid supercapacitor, and the positive electrode is commercially available spinel LiMn2O4The negative active material is active carbon, the positive and negative electrodes are mixed according to the weight ratio of the active material/super-P/PVDF (85/8/7) to prepare slurry, and the slurry is coated on a stainless steel net and dried to prepare the electrode. Then, a lithium ion hybrid supercapacitor was assembled using a separator of a commercial nickel-metal hydride battery, and the electrolyte was the water-based electrolyte of this example.
The capacity retention rate of the lithium ion hybrid supercapacitor adopting the embodiment is measured, specifically, the lithium ion hybrid supercapacitor is charged and discharged under the voltage range of 0-2.1V, the current density is 1000mA/g, and the capacity retention rate of 20000 cycles is tested.
The results show that the capacity retention rate hardly decayed after 20000 cycles. Analysis shows that the lithium ion hybrid supercapacitor of the embodiment can still maintain excellent cycle stability under the working voltage of 2.1V, and the electrochemical stability window of the water-based electrolyte of the embodiment is up to 4.5V; therefore, the cycle stability can be maintained even at an operating voltage of 2.1V.
Example four
The solvent of the water-based electrolyte in the embodiment is water and propylene carbonate, the electrolyte salt is lithium bifluorosulfonyl imide, and the preparation method is as follows: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in water and Propylene Carbonate (PC), wherein the weight ratio of the PC to the total solvent is 50%, and preparing the LiFSI salt to obtain the high-voltage window water-based electrolyte with the mass molar concentration of 35 mol/kg.
The water-based electrolyte of this example was subjected to electrochemical window testing using the same method and conditions as in example one. The results show that the anodic oxygen evolution potential is 2.5V (vs. SCE), the cathodic hydrogen evolution potential is-2.2V (vs. SCE), and the voltage window reaches 4.7V.
The water-based electrolyte of the embodiment is used in a water-based super capacitor, the positive electrode and the negative electrode are activated carbon used commercially, the positive electrode and the negative electrode are mixed according to the weight ratio of active material/acetylene black/PTFE (Polytetrafluoroethylene) 80/10/10 to prepare slurry, and the slurry is coated on a stainless steel foil and dried to prepare an electrode. And then assembled into a button cell, wherein the diaphragm is a whatman glass fiber diaphragm, and the electrolyte is the water-based electrolyte in the embodiment.
The capacity retention rate of the super capacitor adopting the water-based electrolyte of the embodiment is measured, specifically, the super capacitor is charged and discharged under the voltage range of 0-2.4V, the current density is 1000mA/g, and the capacity retention rate of 10000 cycles of the super capacitor is tested.
The result shows that the capacity retention rate is 92% after 10000 cycles, which indicates that the water-based high-voltage super capacitor adopting the water-based electrolyte of the embodiment has long cycle life.
EXAMPLE five
The solvent of the water-based electrolyte is water, the electrolyte salt is lithium bifluorosulfonyl imide, and the supporting electrolyte is zinc trifluoromethanesulfonate, and the preparation method is as follows: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) and zinc trifluoromethanesulfonate in water, and preparing the LiFSI salt to have a mass molar concentration of 30mol/k and the zinc trifluoromethanesulfonate to have a mass molar concentration of 1mol/kg, thereby obtaining the high-voltage window water-based electrolyte of the embodiment.
The water-based electrolyte of this example was subjected to electrochemical window testing using the same method and conditions as in example one. The results show that the anodic oxygen evolution potential is 1.7V (vs. SCE), the cathodic hydrogen evolution potential is-1.5V (vs. SCE), and the voltage window reaches 4.2V.
The water-based electrolyte of the embodiment is used in a water-based lithium-zinc ion battery, and the anode is commercial lithium iron phosphate LiFePO4The negative electrode is zinc foil, the positive electrode is mixed according to the weight ratio of active material/acetylene black/PVDF (polyvinylidene fluoride) 90/5/5 to prepare slurry, and the slurry is coated on stainless steel foil and dried to prepare the electrode. And then the cathode and zinc foil are assembled into a button cell, and the used diaphragm is a whatman glass fiber diaphragm, namely the electrolyte is the water-based electrolyte in the embodiment.
The capacity retention rate of the lithium-zinc ion battery adopting the water-based electrolyte of the embodiment is measured, specifically, the lithium-zinc ion battery is charged and discharged under the voltage range of 0.5-1.7V, the current density is 500mA/g, and the capacity retention rate of the lithium-zinc ion battery is tested after 1000 cycles. The results showed that the capacity retention was 89% after 1000 cycles.
EXAMPLE six
The solvent of the water-based electrolyte is water, the electrolyte salt is lithium bifluorosulfonyl imide, the supporting electrolyte is potassium sulfate, and the preparation method comprises the following steps: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) and potassium sulfate in water, and preparing LiFSI salt to have a molar mass concentration of 30mol/k and potassium sulfate to have a molar mass concentration of 0.5mol/kg, thereby obtaining the high-voltage window water-based electrolyte.
The water-based electrolyte of this example was subjected to electrochemical window testing using the same method and conditions as in example one. The results show that the anodic oxygen evolution potential is 1.7V (vs. SCE), the cathodic hydrogen evolution potential is-1.6V (vs. SCE), and the voltage window reaches 4.3V.
The water-based electrolyte of the example is used in a water-based lithium-potassium ion battery, and the Prussian blue analogue K is used as the positive electrode2MnFe(CN)6The negative electrode is NaTi2(PO4)3The positive and negative electrodes are mixed uniformly according to the weight ratio of active material/acetylene black/PTFE (80/10/10) to prepare a film, and the film is pressed on a titanium net and dried to prepare the electrode. Then the anode and the cathode zinc foil are assembled into a button cell, the used diaphragm is a whatman glass fiber diaphragm, and the electrolyte is the electrolyte of the embodimentA water-based electrolyte.
The capacity retention rate of the lithium-potassium ion battery using the water-based electrolyte of the embodiment is measured, specifically, the lithium-potassium ion battery is charged and discharged under the voltage range of 0.5-2.0V, the current density is 500mA/g, and the capacity retention rate of the lithium-potassium ion battery after 1000 cycles is tested. The results showed that the capacity retention was 89% after 1000 cycles.
EXAMPLE seven
The solvent of the water-based electrolyte is water, the electrolyte salt is lithium bis (fluorosulfonyl) imide, the supporting electrolyte is sodium sulfate, and the preparation method comprises the following steps: dissolving lithium bis (fluorosulfonyl) imide (LiFSI) and sodium sulfate in water, and preparing LiFSI salt to have a molar mass concentration of 30mol/k and sodium sulfate to have a molar mass concentration of 1mol/kg, thereby obtaining the high-voltage window water-based electrolyte.
Electrochemical window tests were carried out on the water-based electrolyte of this example using the same method and conditions as in the example, and the results showed that the anodic oxygen evolution potential was 1.7V (vs. sce), the cathodic hydrogen evolution potential was-1.6V (vs. sce), and the voltage window reached 4.3V.
The water-based electrolyte of the embodiment is used in a water-based lithium-sodium ion battery, and the positive electrode is spinel LiMn2O4The negative electrode is NaTi2(PO4)3The positive and negative electrodes are mixed uniformly according to the weight ratio of active material/acetylene black/PTFE (80/10/10) to prepare a film, and the film is pressed on a titanium net and dried to prepare the electrode. And then the cathode and the anode are assembled into a button cell, and the used diaphragm is a whatman glass fiber diaphragm, namely the electrolyte is the water-based electrolyte in the embodiment.
The capacity retention rate of the lithium-sodium ion battery adopting the water-based electrolyte of the embodiment is measured, specifically, the lithium-sodium ion battery is charged and discharged under the voltage range of 1.0-1.9V, the current density is 1000mA/g, and the capacity retention rate of the lithium-sodium ion battery after 1000 cycles is tested. The results showed that the capacity retention was 95% after 1000 cycles.
Example eight
In this example, on the basis of the first example, the concentration of lithium bis (fluorosulfonyl) imide (LiFSI) is adjusted, the solvent is also water, and in this example, water-based electrolytes with different LiFSI concentrations are prepared, and the rest is the same as the first example. The water-based electrolytes of various concentrations in this example are shown in table 1.
The electrochemical window test was performed on the water-based electrolyte of this example in the same manner as in example 1, and the test results are shown in Table 1.
The capacity retention rates of 1000 cycles of lithium ion batteries using water-based electrolytes with different LiFSI concentrations were measured by the same method as in example one, and the test results are shown in table 1.
TABLE 1 electrochemical Window and Capacity Retention test results for Water-based electrolytes of different LiFSI concentrations
| Test number | LiFSI concentration | Anodic oxygen evolution potential | Cathodic hydrogen evolution potential | Voltage window | Capacity |
| Test | |||||
| 1 | 5mol/kg | 1.1V | -1.2V | 2.3V | 60 |
| Test | |||||
| 2 | 9mol/kg | 1.1V | -1.3V | 2.4V | 67 |
| Test | |||||
| 3 | 10mol/kg | 1.6V | -1.4V | 3.0V | 82％ |
| Test 4 | 20mol/kg | 1.7V | -1.5V | 3.2V | 85％ |
| Test 5 | 30mol/kg | 1.7V | -1.6V | 3.3V | 87％ |
The results in Table 1 show that the voltage window is relatively small when the molar mass concentration of lithium bis (fluorosulfonyl) imide is less than 10mol/kg, and the voltage window is greater than 3V when the molar mass concentration is greater than or equal to 10mol/kg, which has a higher voltage window. And when the mass molar concentration of the lithium bis (fluorosulfonyl) imide is greater than or equal to 10mol/kg, the lithium bis (fluorosulfonyl) imide has better cycling stability and energy density, and can better improve the service life of the battery.
Example nine
In this example, different amounts of organic solvent were tested on the basis of example two, which is otherwise the same as example two, e.g. a 1:1 volume ratio of EC to DMC and a 35mol/kg LiFSI concentration, as follows:
test 1: the weight ratio of the water to the mixed organic solvent is 2:1, namely the organic solvent accounts for 33.3 percent of the total weight of the mixed solvent;
test 2: the weight ratio of the water to the mixed organic solvent is 1:1, namely the organic solvent accounts for 50 percent of the total weight of the mixed solvent;
test 3: the weight ratio of the water to the mixed organic solvent is 1:3, namely the organic solvent accounts for 75 percent of the total weight of the mixed solvent;
test 4: the weight ratio of the water to the mixed organic solvent is 1:4, namely the organic solvent accounts for 80 percent of the total weight of the mixed solvent.
A water-based electrolyte of example LiFSI concentration was prepared according to the above four mixed solvents and subjected to the same electrochemical window test. The results show that in test 3 and test 4, when the proportion of the organic solvent reaches or exceeds 75%, LiFSI salt is precipitated, and meanwhile, the ignition test is carried out on the four electrolytes, and the electrolytes in test 3 and test 4 are both found to have a combustion phenomenon, while the electrolytes in test 1 and test 2 cannot be ignited, which indicates that the electrolytes become unstable and flammable when the proportion of the organic solvent reaches or exceeds 75%, and the intrinsic safety of the water-based electrolyte is lost.
The foregoing is a more detailed description of the present application in connection with specific embodiments thereof, and it is not intended that the present application be limited to the specific embodiments thereof. It will be apparent to those skilled in the art from this disclosure that many more simple derivations or substitutions can be made without departing from the spirit of the disclosure.
Claims (7)
1. A water-based electrolyte characterized by: the solvent of the water-based electrolyte is water or a mixed solvent consisting of water and an organic solvent, and the water-based electrolyte contains lithium bis (fluorosulfonyl) imide with the mass molar concentration of not less than 10 mol/kg.
2. The water-based electrolyte as claimed in claim 1, wherein: the organic solvent is at least one of dimethyl carbonate, ethylene carbonate, diethyl carbonate, propylene carbonate and tetrahydrofuran.
3. The water-based electrolyte as claimed in claim 1 or 2, wherein: in the mixed solvent, the organic solvent accounts for less than 75% of the total mass of the mixed solvent.
4. Use of the water-based electrolyte according to any of claims 1-3 in an electrochemical energy storage device.
5. An electrochemical energy storage device employing the water-based electrolyte as claimed in any one of claims 1 to 3.
6. An electrochemical energy storage device as in claim 5, wherein: the electrochemical energy storage device is a water-based secondary battery or a water-based electrochemical supercapacitor, or a combined energy storage capacitor of the two.
7. An electrochemical energy storage device as in claim 5, wherein: the electrochemical energy storage device comprises a water-based lithium ion battery consisting of an organic lithium ion battery anode and sodium titanium phosphate or lithium titanate or titanium dioxide, a water-based battery capacitor consisting of an organic lithium ion battery anode and activated carbon, and a symmetrical water-based supercapacitor consisting of carbon-based materials.
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