Sodium-ion battery electrolyte and sodium-ion battery thereof

Abstract

The application discloses a sodium ion battery electrolyte and a sodium ion battery thereof, and belongs to the field of electrochemical energy storage. The electrode liquid contains an additive, and the additive has a structure shown in formula I or formula II: R1, R2 are independently selected from H or C 1‑3 alkyl. The addition of the additive in the commonly used sodium ion battery electrolyte can improve the battery capacity and coulomb efficiency, widen the temperature window of the battery, and expand the use range of the battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage, and specifically relates to sodium-ion battery electrolyte and sodium-ion batteries. Technical Background

[0002] In recent years, the rapid development of the social economy has created an urgent demand for the application of renewable energy. Clean energy sources such as wind and solar power have developed rapidly, but they also suffer from problems such as large amounts of wind and solar power curtailment, discontinuity, and instability. Furthermore, large-scale grid connection can cause safety issues. Energy storage technology can enable the continuous and stable output of renewable energy into the power system. Among various large-scale energy storage technologies, sodium-ion batteries, due to their abundant sodium resources, low cost, and similar energy storage principles and processes as lithium-ion batteries, have gradually become a hot topic in energy storage.

[0003] Among the factors limiting the high and low temperature performance of sodium-ion batteries, the electrolyte is the key factor. At low temperatures, the viscosity of traditional electrolytes increases, leading to poorer compatibility with electrode materials and separators, resulting in decreased ionic conductivity, increased charge transfer resistance, and ultimately, a decline in battery performance. During high-temperature cycling, rapid capacity decay occurs, mainly due to the poor electrochemical stability and low cathode decomposition voltage of traditional electrolytes. Therefore, developing novel electrolytes suitable for a wide temperature range is of great significance for improving the high and low temperature performance of sodium-ion batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention aims to provide an additive for sodium-ion battery electrolytes and a wide-temperature-range electrolyte.

[0005] This invention provides a sodium-ion battery electrolyte, wherein the electrode solution contains an additive having a structure shown in Formula I or Formula II:

[0006]

[0007]

[0008] R1 and R2 are independently selected from H or C. 1-3 alkyl.

[0009] Optionally, the additive is a C5 or C7 cyclic lactone having an acyloxy group;

[0010] The C5 or C7 cyclic lactone is selected from at least one of ε-caprolactone, γ-butyrolactone, or γ-valerolactone.

[0011] Optionally, the additive accounts for 10% to 50% of the total volume percentage of the sodium-ion battery electrolyte, preferably 10% to 20%. The lower limit of the additive's percentage of the total volume percentage of the sodium-ion battery electrolyte is optionally selected from 10% and 20%, and the upper limit is optionally selected from 20% and 50%.

[0012] Optionally, when there are two types of additives, the ratio of the two additives is 0.1 to 1; when there are two types of additives, the ratio of the two additives is 0.5 to 0.7.

[0013] Optionally, the electrolyte comprises a solute and a solvent; the solute is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, and sodium trifluoromethanesulfonate; the solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl acetate, and ethyl acrylate.

[0014] Optionally, the concentration of the solute in the electrolyte is 0.3–1.5 mol / L. -1 Preferably 1 mol L -1 .

[0015] Optionally, the concentration of the solute in the electrolyte is 1–1.5 mol / L. -1 .

[0016] The present invention also provides a sodium-ion battery, wherein the sodium-ion battery uses any of the sodium-ion battery electrolytes described above.

[0017] Preferably, the sodium-ion battery operates at a temperature of -20°C to 55°C.

[0018] The solute is selected from at least one of NaPF6 (sodium hexafluorophosphate), NaClO4 (sodium perchlorate), NaTFSI (sodium bis(trifluoromethanesulfonyl)imide), NaFSI (sodium bis(fluorosulfonyl)imide), and NaOTf (sodium trifluoromethanesulfonate);

[0019] The solvent is selected from one or more of EC (ethylene carbonate), PC (propylene carbonate), DEC (diethyl carbonate), MA (methyl acetate), and EA (ethyl acrylate), and the additive is a cyclic acyloxy lactone, such as at least one of ε-caprolactone, γ-butyrolactone, or γ-valerolactone.

[0020] The concentration of the solute in the electrolyte is 0.3–1.5 mol / L. -1 Preferably 1–1.5 mol L -1 .

[0021] When there are two solvents, the volume ratio of the two solvents is 0 to 0.5, preferably 0.2 to 0.4.

[0022] Sodium-ion batteries consist of a carbon-based negative electrode, a separator, and a polyanionic compound positive electrode. The polyanionic compound is one or more of NaFePO4, Na2FeP2O, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, Na3NiZr(PO4)3, Na3V2(PO4)2F3, Na2FePO4F, and Na2FeSiO4, with Na3V2(PO4)3 being preferred. The carbon-based material is one or more of graphene, hard carbon, and soft carbon, with hard carbon being preferred. The membrane material is one or more of glass fiber membrane and Celgard membrane, with Celgard being preferred.

[0023] The electrolyte of this invention can improve battery capacity and coulombic efficiency, broaden the battery's temperature window, and expand its application range.

[0024] This invention adds appropriate additives to commonly used sodium-ion battery electrolytes, which can meet the requirements of long life and high performance operation of batteries under high and low temperature conditions over a wide temperature range. Attached Figure Description

[0025] Figure 1 Room temperature cycling performance of Test Example 1-3 and Comparative Test Example 1-2;

[0026] Figure 2 Cyclic performance of Test Example 1-3 and Comparative Test Example 1-2 at -20℃;

[0027] Figure 3 Cyclic performance of Test Example 1-3 and Comparative Test Example 1-2 at 55°C;

[0028] Figure 4 Test Example 1-3 and Comparative Test Example 1-2: Room temperature first-cycle charge-discharge curves and coulombic efficiency. Detailed Implementation

[0029] Example 1

[0030] A mixed solution was prepared with NaPF6 as the solute, ε-caprolactone (CL) as the additive, and EC and DEC as the solvent, wherein the volume ratio of EC and DEC was 1:1, the concentration of NaPF6 in the mixed solution was 1 mol / L, and the volume concentration of CL in the mixed solution was 10%, to obtain electrolyte 1#.

[0031] Test Example 1

[0032] To characterize the performance of the novel wide-temperature-range electrolyte, a sodium-ion full cell was assembled as the test object. The positive electrode was an NVP electrode (active material was NVP, current collector was aluminum foil); the negative electrode was a hard carbon electrode (active material was hard carbon, current collector was copper foil); and the separator was a Celgard membrane.

[0033] The electrolyte used was electrolyte #1 from Example 1. The test rate was 1C, and the test temperatures were room temperature, -20℃, and 55℃. The test results are shown below. Figure 1 , Figure 2 and Figure 3 .

[0034] Example 2

[0035] A mixed solution was prepared with NaPF6 as the solute, γ-butyrolactone (GBL) as the additive, and EC and DEC as the solvent, wherein the volume ratio of EC and DEC was 1:1, the concentration of NaPF6 in the mixed solution was 1 mol / L, and the volume concentration of GBL in the mixed solution was 10%, to obtain electrolyte 2#.

[0036] Test Example 2

[0037] Following the method in Test Example 1, electrolyte #2 was tested at a testing rate of 1C, and the test temperatures were room temperature, -20℃, and 55℃. The test results are shown below. Figure 1 , Figure 2 and Figure 3 .

[0038] Example 3

[0039] A mixed solution was prepared with NaPF6 as the solute, γ-butyrolactone (GVL) as the additive, and EC and DEC as the solvent, wherein the volume ratio of EC and DEC was 1:1, the concentration of NaPF6 in the mixed solution was 1 mol / L, and the volume concentration of GVL in the mixed solution was 10%, to obtain electrolyte 3#.

[0040] Test Example 3

[0041] Following the method in Test Example 1, electrolyte #3 was tested at a testing rate of 1C, and the test temperatures were room temperature, -20℃, and 55℃. The test results are shown below. Figure 1 , Figure 2 and Figure 3 .

[0042] Comparative Example 1

[0043] Electrolyte A was prepared by mixing NaPF6 as the solute, fluoroethylene carbonate (FEC) as the additive, and EC and DEC as the solvent, wherein the volume ratio of EC and DEC was 1:1, the concentration of NaPF6 in the mixed solution was 1 mol / L, and the volume concentration of FEC in the mixed solution was 10%.

[0044] Comparative Test Case 1

[0045] Following the method in Test Example 1, electrolyte A was tested at a test rate of 1C, and the test temperatures were room temperature, -20℃, and 55℃. The test results are shown below. Figure 1 , Figure 2 and Figure 3 .

[0046] Comparative Example 2

[0047] Electrolyte B was prepared by mixing NaPF6 as the solute, propenyl-1,3-sulfonyl lactone (PST) as the additive, and EC and DEC as the solvent, wherein the volume ratio of EC and DEC was 1:1, the concentration of NaPF6 in the mixed solution was 1 mol / L, and the volume concentration of PST in the mixed solution was 10%.

[0048] Comparative Test Example 2

[0049] Following the method in Test Example 1, electrolyte B was tested at a testing rate of 1C, and the test temperatures were room temperature, -20℃, and 55℃. The test results are shown below. Figure 1 , Figure 2 and Figure 3 .

[0050] Figure 1 The graph shows the cyclic test results of test examples 1-3 and control test example 1-2 at room temperature and 1C rate. Figure 2 The figure in the middle shows the cyclic test results of test examples 1-3 and control test example 1-2 under the conditions of -20℃ and 1C expansion. Figure 3 The figure in the middle shows the cycle test results of the test examples and comparative test examples under the conditions of -50℃ and 1C rate. By comparing the electrochemical cycle performance of the batteries of the example and the comparative examples at 25℃, -20℃, and 55℃ respectively, it can be seen that using CL, GBL, and BVL as additives can enable the batteries to have good and stable cycle performance at room temperature, low temperature, and high temperature. This may be related to the interface formed by CL, GBL, and BVL additives at the positive and negative electrodes of sodium-ion batteries. Figure 4 The charge-discharge curves and coulombic efficiency diagrams of the test cases and control test cases at room temperature and 0.1C rate are shown. To further illustrate the impact of the interface, the first-cycle coulombic efficiency of the test cases and control test cases was compared. It was found that the batteries using CL, GBL, and BVL additives have high first-cycle efficiency, proving that these additives have higher efficiency in forming SEI and better SEI effect in the first cycle.

Claims

1. A sodium-ion battery electrolyte, characterized in that, The electrolyte contains an additive having the structure shown in Formula I and / or Formula II: Equation I; Formula II; R1 and R2 are independently selected from H or C. 1-3 alkyl; The additive accounts for 10% to 50% of the total volume percentage of the sodium-ion battery electrolyte; The sodium-ion battery operates at a temperature of -20℃ to 55℃.

2. The sodium-ion battery electrolyte according to claim 1, characterized in that, The additive is at least one of ε-caprolactone, γ-butyrolactone, or γ-valerolactone.

3. The sodium-ion battery electrolyte according to claim 1, characterized in that, When there are two types of additives, the ratio of the two additives is 0.1 to 1.

4. The sodium-ion battery electrolyte according to claim 3, characterized in that, When there are two additives, the ratio of the two additives is 0.5 to 0.

7.

5. The sodium-ion battery electrolyte according to claim 1, characterized in that, The electrolyte includes a solute and a solvent; The solute is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, and sodium trifluoromethylsulfonate. The solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl acetate, and ethyl acrylate.

6. The sodium-ion battery electrolyte according to claim 5, characterized in that, The concentration of the solute in the electrolyte is 0.3-1.5 mol / L. -1 .

7. The sodium-ion battery electrolyte according to claim 5, characterized in that, The concentration of the solute in the electrolyte is 1-1.5 mol / L. -1 .

8. A sodium-ion battery, characterized in that, The sodium-ion battery uses the sodium-ion battery electrolyte as described in any one of claims 1-7.

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