Aqueous electrolyte with wide potential window and battery
By using a highly concentrated mixed aqueous electrolyte in aqueous sodium ion batteries, combined with flame retardant additives and saturated sodium salts, the problems of narrow voltage window and insufficient stability of the battery are solved, and higher electrochemical stability and cycling performance are achieved.
Patent Information
- Application Number
- CN202311721409.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-14
- Publication Date
- 2025-06-17
AI Technical Summary
The voltage window of aqueous sodium ion batteries is narrow, and it is easy to evolve oxygen at positive potential or hydrogen at negative potential. The electrochemical stability of high-salt concentration electrolyte is insufficient, which affects the safety and cycle stability of the battery.
A high-concentration mixed aqueous electrolyte is used to form an aqueous electrolyte with a wide potential window by adding a flame retardant additive such as trimethyl phosphate to the solvent and using saturated or near-saturated sodium salt as the electrolyte salt to form a water electrolyte solution to improve the electrochemical stability window.
The electrochemical stability window is significantly widened, the rate performance and cycle stability of water-based batteries are improved, the safety and energy density of batteries are enhanced, and the production costs are reduced.
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Figure CN120165073A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of aqueous batteries, and particularly to a cathode oxide material with a composite structure and an aqueous sodium-ion battery. Background Art
[0002] The efficient utilization of clean energy is inseparable from a cheap and efficient large-scale energy storage system. Although sodium-ion batteries have potential advantages such as rich resources and low prices, problems such as expensive and flammable electrolyte components, harsh assembly environments, and potential safety hazards have restricted their rapid development to a certain extent. If the organic electrolyte is replaced with an aqueous solution to construct a new type of aqueous sodium-ion battery, although the energy density decreases, the production cost can be further reduced, the safety is greatly improved, and it is green and environmentally friendly, which is more in line with the application requirements of large-scale energy storage. In addition, the ionic conductivity of the aqueous solution is two orders of magnitude higher than that of the organic electrolyte, and it may have a higher power density, so it can respond to energy storage needs more quickly. Therefore, the development of aqueous sodium-ion batteries with excellent performance and low prices is of great significance for the efficient utilization of clean energy and the smooth construction of a new energy society.
[0003] However, the development of aqueous sodium-ion batteries faces more severe challenges. The biggest problem is that the voltage window of the aqueous electrolyte is relatively narrow, oxygen evolution occurs at positive potentials, and hydrogen evolution occurs at negative potentials. Inspired by non-aqueous high-salt-concentration electrolytes, the concept of "Water-in-salt" proposed in the aqueous lithium-ion battery system in recent years has also been applied to the aqueous sodium-ion battery electrolyte. On the basis of high concentration, an additive with good electrochemical stability, intrinsic safety, and the ability to reduce the free water content of the solution is indispensable. Therefore, the present invention proposes a high-performance high-concentration mixed aqueous electrolyte, which can further broaden the electrochemical stability window on the basis of the high-concentration electrolyte, and constructs an aqueous sodium-ion energy storage device based on this. Summary of the Invention
[0004] In order to solve the above problems in the prior art, the present invention provides an aqueous electrolyte and a battery with a wide potential window, high electrochemical stability window, good rate performance, and cycle stability.
[0005] In order to achieve the above invention object, the present invention provides an aqueous electrolyte with a wide potential window, which includes a solvent and an electrolyte salt, and the concentration of the electrolyte salt in the solvent is in a saturated or nearly saturated state; the electrolyte salt is a sodium salt;
[0006] The solvent includes H2O and a flame retardant additive, and the volume ratio of H2O to the flame retardant additive is (1 - X%): X%, where the value range of X is 0 - 80.
[0007] Further, the flame retardant additive is one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, and tricresyl phosphate.
[0008] Further, the sodium salt is one or more of sodium acetate, sodium chloride, sodium nitrate, sodium sulfate, sodium perchlorate, sodium trifluoromethanesulfonate, and sodium bis(fluorosulfonyl)imide.
[0009] Further, the value of X is 80.
[0010] A method for preparing the aqueous electrolyte with a wide potential window includes the following steps:
[0011] Step S1: Mix H2O and the flame retardant additive in a volume ratio of (1 - X%):X% to obtain a solvent, where the range of the value of X is 0 - 80;
[0012] Step S2: Weigh an appropriate amount of the sodium salt as the electrolyte;
[0013] Step S3: Make up the volume of the electrolyte in Step S2 with the solvent obtained in Step S1.
[0014] Further, the flame retardant additive is one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, and tricresyl phosphate.
[0015] Further, the sodium salt is one or more of sodium acetate, sodium chloride, sodium nitrate, sodium sulfate, sodium perchlorate, sodium trifluoromethanesulfonate, and sodium bis(fluorosulfonyl)imide.
[0016] Further, the value of X is 80.
[0017] An aqueous battery includes a positive electrode, a negative electrode, and an electrolyte, and the electrolyte is the aqueous electrolyte with a wide potential window described in any of the above solutions.
[0018] Further, the active material in the positive electrode is selected from MnO2, Na3V2(PO4)3, or a Prussian blue-based active material;
[0019] The active material in the negative electrode is selected from NbOPO4, TiO2, NaTi2(PO4)3, or TiP2O7.
[0020] The beneficial effects of the present invention are as follows:
[0021] The present invention uses an electrolyte salt to be dissolved in a solvent mixture of H2O and a flame retardant additive in a certain volume ratio in a saturated or nearly saturated state to form an aqueous electrolyte with a wide potential window, improving the electrochemical stability window of the aqueous electrolyte;
[0022] The test results show that the aqueous battery provided by the present invention has good rate performance and cycle stability. The charge-discharge curve of this aqueous battery is tested in the range of 0.4 - 1.95 V at a current density of 200 mA / g, and two obvious charge-discharge platforms appear at 1.7 V and 1.2 V, which is consistent with the charge-discharge curve of the Na2CoFe(CN)6 positive electrode. The average working voltage of this aqueous battery is 1.4 V. When the current density is 500 mA / g, the aqueous battery is cycled 200 times, and the capacity retention rate is 85%. Description of the Drawings
[0023] Figure 1 It is a physical diagram of the aqueous electrolytes with different wide potential windows in Example 1 of the present invention;
[0024] Figure 2 It is the CV curve of the Ti mesh in the aqueous electrolytes with different wide potential windows in Example 1;
[0025] Figure 3 It is the charge-discharge curve of the Na2CoFe(CN)6-NaTi2(PO4)3 aqueous battery including the aqueous electrolyte with the wide potential window of Example 1 at 200 mA / g;
[0026] Figure 4 It is the long-term cycling performance diagram of the Na2CoFe(CN)6-NaTi2(PO4)3 aqueous battery including the aqueous electrolyte with the wide potential window of Example 1 at 500 mA / g;
[0027] Figure 5 It is a physical diagram of the aqueous electrolytes with different wide potential windows in Example 2;
[0028] Figure 6 It is the CV curve of the Ti mesh in the aqueous electrolytes with different wide potential windows in Example 2;
[0029] Figure 7 It is the charge-discharge curve of the NaTi2(PO4)3 / activated carbon aqueous battery including the aqueous electrolyte with the wide potential window of Example 2 at 200 mA / g;
[0030] Figure 8 It is a physical diagram of the aqueous electrolytes with different wide potential windows in Example 3;
[0031] Figure 9 It is the CV curve of the Ti mesh in the aqueous electrolytes with different wide potential windows in Example 3;
[0032] Figure 10 It is the charge-discharge curve of the Na2CoFe(CN)6-NaTi2(PO4)3 aqueous battery including the aqueous electrolyte with the wide potential window of Example 3 at 200 mA / g. Detailed implementation manners
[0033] To clearly illustrate the technical features of this solution, the following will elaborate on this solution through specific implementation manners.
[0034] Example 1
[0035] This example provides an aqueous electrolyte with a wide potential window, selecting a mixture of water and trimethyl phosphate (TMP) as the solvent and sodium perchlorate (NaClO4) as the electrolyte salt; 9 portions of solvents shown in the following table are respectively prepared:
[0036]
[0037] It is explored that when the volume ratio of the solvent water and TMP is 20:80 (20% H2O + 80% TMP), the near-saturated concentration of the electrolyte salt NaClO4 is 4 mol / L. Therefore, this concentration is determined as the concentration of all electrolytes in this example.
[0038] Weigh equal amounts of 9 portions of NaClO4 and make up the volume with the above 9 portions of solvents respectively until the concentration is 4 mol / L, then 9 portions of aqueous electrolytes are obtained, all of which are colorless and transparent (see Figure 1 ).
[0039] In aqueous sodium-ion batteries, considering comprehensive factors such as chemical stability, electrochemical stability, ease of electrode fabrication, and hydrogen and oxygen evolution overpotentials, we finally select Ti mesh as the current collector for the positive and negative electrode materials. The electrochemical windows of the 9 portions of aqueous electrolytes obtained in this example are respectively tested. Figure 2 is the cyclic voltammogram curve of Ti mesh in different ratios of high-concentration mixed aqueous electrolytes. The area of the titanium mesh is 0.5 cm 2 , and the scanning rate is 1 mV / s. It can be seen that as the TMP increases, its electrochemical window continuously broadens, from 2.458 V to 2.598 V.
[0040] The aqueous battery test is carried out using a two-electrode system. The electrodes are all prepared by the rolling film method. Weigh a certain mass ratio (such as 7:2) of the active material and conductive carbon, and grind them evenly in an agate mortar. Then weigh a certain mass of PTFE emulsion (mass fraction 60%) in a small beaker, add a little isopropanol to break the emulsion, and then add the ground powder material. Adjust the slurry under an infrared lamp and dry it. Finally, roll it into a film on a roller press. The film is placed in a vacuum oven at 100 °C for 6 h, and the film is punched with a cylinder to make a 1 cm 2The circular electrode sheet is pressed on the Ti mesh. Using the Ti mesh as the current collector, Na2CoFe(CN)6 Prussian blue as the positive electrode, sodium titanium phosphate as the negative electrode, 4M NaClO4, and a mixed aqueous solution of 20% H2O + 80% TMP as the electrolyte solvent, and non-woven fabric as the separator, a 2016 button cell is assembled. The specific capacity and energy density of the full cell system are calculated based on the mass of the positive electrode active material. Based on the excellent performance of the mixed electrolyte, an aqueous battery is assembled for testing. The experimental results show that the aqueous battery has good rate performance and cycle stability. Figure 3 The charge-discharge curve test interval of the aqueous battery at a current density of 200 mA / g is 0.4 - 1.95 V. Two obvious charge-discharge platforms appear at 1.7 V and 1.2 V, which is consistent with the charge-discharge curve of the Na2CoFe(CN)6 positive electrode. The average working voltage of the aqueous battery is 1.4 V. Figure 4 It is the curve of the full cell cycling 200 times at a current density of 500 mA / g. After cycling 200 times, the capacity retention rate is 85%.
[0041] Example 2
[0042] This example provides an aqueous electrolyte with a wide potential window, selecting water and trimethyl phosphate (TMP) as the mixed solvent, and sodium trifluoromethanesulfonate (NaCF3SO3) as the electrolyte salt; 9 portions of solvents identical to those in Example 1 are respectively prepared:
[0043] It is explored that when the volume ratio of the solvent water and TMP is 20:80 (20% H2O + 80% TMP) in mixing, the near-saturated concentration of the electrolyte salt NaCF3SO3 is 2 mol / L. Therefore, this concentration is determined as the concentration of all electrolytes in this example.
[0044] Weigh equal amounts of 9 portions of NaCF3SO3, and respectively make up the volume with the above 9 portions of solvents until the concentration is 2 mol / L for each to obtain 9 portions of aqueous electrolytes, all of which are colorless and transparent (see Figure 5 ).
[0045] Similar to Example 1, the Ti mesh is selected as the current collector for the positive and negative electrode materials, and the electrochemical windows of the 9 portions of aqueous electrolytes obtained in this example are respectively tested. Figure 6 They are respectively the cyclic voltammetry curves of the Ti mesh in these 9 portions of aqueous electrolytes. The area of the Ti mesh is 0.5 cm 2 , and the scanning rate is 1 mV / s. It can be seen that as the TMP increases, its electrochemical window continuously broadens, from 2.03 V to 2.568 V.
[0046] The aqueous battery was tested using a three - electrode system. The electrodes were all prepared by the rolling - film method. Weighed a certain mass ratio (such as 7:2) of active material and conductive carbon, and ground them evenly in an agate mortar. Then weighed a certain mass of PTFE emulsion (mass fraction 60%) into a small beaker, added a little isopropanol to break the emulsion, and then added the ground powder material. Adjusted the slurry under an infrared lamp and dried it. Finally, rolled it into a film on a roller press. The film was placed in a 100 °C vacuum oven for 6 h, and the film was stamped with a cylinder to make a 1 cm 2 circular electrode sheet, which was pressed on a Ti mesh. Using the Ti mesh as the current collector, sodium titanium phosphate as the negative electrode, activated carbon as the counter electrode, the electrolyte was 1 M NaCF3SO3, the solvent was a 20% H2O + 80% TMP mixed aqueous solution as the electrolyte, the reference was Ag / AgCl, - 0.9~ - 0.3 V vs. Ag / AgCl, and the current density was 200 mA g -1 . Figure 7 It can be seen that obvious charge - discharge plateaus appear at - 0.75 V and - 0.81 V for this electrode, corresponding to the oxidation - reduction of the Ti 4+ / Ti 3+ electrode pair. The charge - discharge specific capacities in the first cycle were 98 and 123 mAh g -1 respectively, corresponding to a first - cycle Coulombic efficiency of 80%.
[0047] Example 3
[0048] This example provides an aqueous electrolyte with a wide potential window. Water and trimethyl phosphate (TMP) were selected as the mixed solvents, and sodium nitrate (NaNO3) was used as the electrolyte salt; Nine portions of solvents identical to those in Example 1 were prepared respectively:
[0049] It was explored that when the volume ratio of solvent water and TMP was 20:80 (20% H2O + 80% TMP) in the mixture, the near - saturated concentration of the electrolyte salt NaNO3 was 1 mol / L. Therefore, this concentration was determined as the concentration of all electrolytes in this example.
[0050] Weighed equal amounts of 9 portions of NaNO3, and fixed the volume with the above - mentioned 9 portions of solvents respectively until the concentration was 1 mol / L, thus obtaining 9 portions of aqueous electrolytes, all of which were colorless and transparent (see Figure 8 ).
[0051] Same as Example 1, the Ti mesh was selected as the current collector for the positive and negative electrode materials, and the electrochemical windows of the 9 portions of aqueous electrolytes obtained in this example were tested respectively, Figure 9 which were the cyclic voltammograms of the Ti mesh in these 9 portions of aqueous electrolytes. The area of the Ti mesh was 0.5 cm 2 , and the scanning rate was 1 mV / s. It can be seen that with the increase of TMP, its electrochemical window continuously broadens, from 2.388 V to 2.572 V.
[0052] The aqueous battery was tested using a two - electrode system. The electrodes were both prepared by the roll - pressing method. Weighed a certain mass ratio (such as 7:2) of active material and conductive carbon, and ground them evenly in an agate mortar. Then weighed a certain mass of PTFE emulsion (mass fraction 60%) in a small beaker, added a little isopropanol to break the emulsion, and then added the ground powder material. The slurry was adjusted and dried under an infrared lamp, and finally rolled into a film on a roller press. The film was placed in a vacuum oven at 100 °C for 6 h, and the film was punched with a cylinder to make a 1 cm 2 circular electrode sheet, which was pressed on a Ti mesh. Using the Ti mesh as the current collector, Na2CoFe(CN)6 Prussian blue as the positive electrode, sodium titanium phosphate as the negative electrode, 2M NaNO3, and a mixed aqueous solution of 20% H2O + 80% TMP as the electrolyte, and non - woven fabric as the separator, a 2016 coin - type battery was assembled. The specific capacity and energy density of the full - cell system were calculated based on the mass of the positive - electrode active material. Based on the excellent performance of the mixed electrolyte, an aqueous battery was assembled for testing. The experimental results show that the aqueous battery has good rate performance and cycle stability, Figure 10 The charge - discharge curve test interval of the aqueous battery at a current density of 200 mA / g was given as 1 - 1.90 V. Two obvious charge - discharge platforms appeared at 1.81 V and 1.34 V, which were consistent with the charge - discharge curve of the Na2CoFe(CN)6 positive electrode. The average working voltage of the aqueous battery was 1.42 V, and the charge - discharge specific capacities in the first cycle were 92 and 88 mAh g -1 , corresponding to a first - cycle Coulombic efficiency of 95%.
[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.
Claims
1. An aqueous electrolyte with a wide potential window, characterized in that, It includes a solvent and an electrolyte salt, and the concentration of the electrolyte salt in the solvent is in a saturated or nearly saturated state; the electrolyte salt is a sodium salt; The solvent includes H2O and a flame retardant additive, and the volume ratio of H2O to the flame retardant additive is (1 - X%)∶X%, where the value range of X is 0 - 80.
2. The aqueous electrolyte with a wide potential window according to claim 1, characterized in that, The flame retardant additive is one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, and tricresyl phosphate.
3. The aqueous electrolyte with a wide potential window according to claim 1 or 2, characterized in that, The sodium salt is one or more of sodium acetate, sodium chloride, sodium nitrate, sodium sulfate, sodium perchlorate, sodium trifluoromethanesulfonate, and sodium bis(fluorosulfonyl)imide.
4. The aqueous electrolyte with a wide potential window according to any one of claims 1-3, characterized in that, The value of X is 80.
5. A method for preparing the aqueous electrolyte with a wide potential window according to any one of claims 1-4, characterized in that, It includes the following steps: Step S1: Mix H2O and the flame retardant additive with a volume ratio of (1 - X%)∶X% to obtain a solvent, where the value range of X is 0 - 80; Step S2: Weigh an appropriate amount of the sodium salt as the electrolyte; Step S3: Make a constant volume of the electrolyte in Step S2 with the solvent obtained in Step S1.
6. The preparation method according to claim 5, characterized in that, The flame retardant additive is one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, and tricresyl phosphate.
7. The preparation method according to claim 5 or 6, characterized in that, The sodium salt is one or more of sodium acetate, sodium chloride, sodium nitrate, sodium sulfate, sodium perchlorate, sodium trifluoromethanesulfonate, and sodium bis(fluorosulfonyl)imide.
8. The preparation method according to any one of claims 5-7, characterized in that, The value of X is 80.
9. An aqueous battery, comprising a positive electrode, a negative electrode and an electrolyte, characterized in that, The electrolyte solution is the aqueous electrolyte solution with a wide potential window according to any one of claims 1 - 4 or the aqueous electrolyte solution with a wide potential window prepared according to any one of claims 5 - 8.
10. The aqueous battery according to claim 9, characterized in that, The active material in the positive electrode is selected from MnO2, Na3V2(PO4)3, or a Prussian blue - type active material; The active material in the negative electrode is selected from NbOPO4, TiO2, NaTi2(PO4)3, or TiP2O7.