CN115000508A - Electrolyte for forming sulfate-based SEI film and preparation and application thereof - Google Patents

Electrolyte for forming sulfate-based SEI film and preparation and application thereof Download PDF

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CN115000508A
CN115000508A CN202111054821.XA CN202111054821A CN115000508A CN 115000508 A CN115000508 A CN 115000508A CN 202111054821 A CN202111054821 A CN 202111054821A CN 115000508 A CN115000508 A CN 115000508A
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electrolyte
sodium
sulfate
ion battery
sei film
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王海燕
唐正
黄源成
孙旦
周思宇
唐有根
吴鹏飞
王红
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Central South University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The invention relates to the technical field of sodium ion battery electrolyte, and discloses electrolyte for forming a sulfate SEI film, and preparation and application thereof. The electrolyte contains fluorine-containing sodium salt and a solvent, and the solvent comprises: a sulfur ester-containing organic substance and a nonaqueous organic solvent containing an ether bond. The mass fraction of the ether bond-containing non-aqueous organic solvent is 80-99.5 wt%, and the mass fraction of the thioester-containing organic substance is 0.1-20 wt%; the non-aqueous organic solvent containing ether bonds is selected from any one or more of cyclic ethers and chain ethers; the sulfur-containing ester organic matter is selected from one or more of vinyl sulfate (DTD) and Propylene Sulfite (PS). The electrolyte capable of forming the sulfate-based novel SEI film can improve the first coulombic efficiency (ICE is improved from 58% to 79%) of the sodium ion battery, and effectively improves the cycling stability of the battery. The combination with high-performance anode materials is helpful for promoting the industrialization process of the sodium-ion battery.

Description

Electrolyte for forming sulfate-based SEI film and preparation and application thereof
Technical Field
The invention belongs to the technical field of sodium ion battery electrolyte, and particularly designs a thioether-containing electrolyte capable of forming a sulfate-based novel SEI film, and a preparation method and application thereof.
Background
In the field of secondary batteries, lithium ion batteries are widely used in the field of energy storage because of their advantages of high energy density, no memory effect, long cycle life, etc., but their further development is limited due to limited lithium storage, non-uniform distribution, high cost, and poor safety. The sodium resource is rich, the distribution is uniform, the price is low, the requirement of large-scale energy storage and low cost is met, a new choice is provided for electrochemical energy storage, and the sodium-lithium ion battery is considered to be one of battery systems which have the most potential to replace the application of the lithium ion battery in the field of large-scale energy storage. The hard carbon material has rich source and low cost, and the disordered structure of the hard carbon material provides a more storage site for sodium ions, so that the hard carbon material is the preferred material for the anode of the sodium ion battery. The negative electrode material is low in coulomb for the first time due to a series of irreversible reactions such as the formation of a Solid Electrolyte Interface (SEI) film on the surface of the negative electrode material of the battery, and is one of the main obstacles influencing the energy density and commercialization of the sodium ion battery at present. The electrolyte is modified, so that the method is simple and easy to implement and can effectively improve the performance of the sodium-ion battery.
In practical application, good electrolyte can be kept stable in the working process of the battery, and can not continuously react with the positive electrode, the negative electrode and the current collector or be directly decomposed to generate gas, and excellent electrolyte can form stable SEI on the interfaces of the positive electrode, the negative electrode and the electrolyte, so that the service life of the battery and the coulombic efficiency are prolonged.
At present, the electrolyte of the commonly used sodium ion battery mainly comprises an ester-based electrolyte and an ether-based electrolyte. The viscosity of the cyclic ester-based electrolyte is high, and Na is limited to a certain extent + Diffusion at the electrolyte and interface. In addition, in the charging and discharging processes, an SEI film with uniform and thick distribution of components is formed on the surface of the negative electrode by the ester-based electrolyte, so that the sodium ion loss is increased, the first coulombic efficiency of the battery is influenced, and the first coulombic efficiency is lowerThe coulombic efficiency will significantly reduce the energy density of the sodium ion full cell, and most of the carbon-based materials reported at present have the first coulombic efficiency of less than 70% based on sulfides (such as molybdenum sulfide, tin sulfide and the like) and phosphides (such as phosphorus, tin phosphide and the like) of the conversion reaction. Titanium-based compounds (e.g. TiO) 2 ) Even below 60% for the first time. Compared to ester-based electrolytes, ether-based electrolytes have better compatibility with hard carbon anodes, such as better wetting, formation of thinner, longer-lasting SEI films, higher ionic conductivity, and higher ionic diffusion coefficient. It is generally considered that Na + The process of entering the main structure of the electrode material from the electrolyte is divided into several key steps of migration desolvation interface reaction and bulk phase diffusion. Hong et al have adopted ether electrolytes to achieve excellent rate performance of carbon materials, and research finds that the excellent rate performance comes from a lower desolvation potential barrier. Therefore, the electrolyte capable of optimizing the electrode-electrolyte interface is developed, the first coulombic efficiency of the sodium ion battery can be improved, and the energy density of the sodium ion full battery can be improved.
Disclosure of Invention
In view of the defects of the prior art, the present invention provides a thioether-containing electrolyte capable of forming a sulfate-based novel SEI film, which can effectively improve the first coulombic efficiency of a sodium ion battery, so as to solve the problems of large first irreversible capacity loss and low energy density of the existing sodium ion battery. The method has the characteristics of simple process, low cost and the like, and has great significance for promoting the improvement of the first coulombic efficiency and stability of the sodium-ion battery and commercialization.
The purpose of the invention is realized by the following technical scheme:
an electrolyte forming a sulfate-based SEI film, the electrolyte containing a fluorine-containing sodium salt and a solvent, the solvent comprising: a sulfur ester-containing organic substance and a nonaqueous organic solvent containing an ether bond.
The electrolyte contains 80-99.5 wt% of nonaqueous organic solvent containing ether bonds, preferably 99%, and 0.1-20 wt% of organic sulfur-containing esters; preferably 0.5-2%.
The electrolyte is characterized in that the sulfur-containing ester organic matter is one or more of ethylene sulfate (DTD), Propylene Sulfite (PS) and ethylene sulfite (DTO).
The nonaqueous organic solvent containing ether bonds comprises any one or more of cyclic ethers and chain ethers; preferably, the cyclic ethers include one or more of Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me-THF), 1, 3-Dioxolane (DOL), 4-methyl-1, 3-dioxolane (4Me-1,3DL), 2-methyl-1, 3-dioxolane (2Me-1,3 DL); the chain ethers include one or more of 1, 2-Dimethoxypropane (DMP), Dimethoxymethane (DMM), and ethylene glycol dimethyl ether (DME) diethylene glycol dimethyl ether (DG).
The electrolyte, the fluorine-containing sodium salt comprises sodium hexafluorophosphate (NaPF) 6 ) Sodium difluorooxalato borate (NaDFOB), sodium triflate (NaCF) 3 SO 3 ) Sodium bis (trifluoromethanesulfonylimide) (NaTFSI), and sodium bis (fluorosulfonylimide) (NaFSI).
The molar concentration of the sodium salt in the electrolyte in a non-aqueous organic solvent is 1-4 mol/L.
The second object of the present invention is to provide a simple method for preparing a sulfate-based SEI film-forming electrolyte by mixing and dissolving the above-mentioned fluorine-containing sodium salt and solvent components.
A third object of the present invention is to provide a sodium ion battery forming a sulfate-based SEI film, the sodium ion battery including the above electrolyte.
A fourth object of the present invention is to provide use of an electrolyte forming a sulfate-based SEI film for manufacturing a sodium ion battery.
The invention has the following beneficial effects:
(1) the invention provides a thioether-containing electrolyte capable of forming a novel sulfate-based SEI film, which has the characteristics of stable property, remarkable effect and high utilization rate, and can effectively reduce sodium loss caused by irreversible reactions such as SEI film formation and the like by only adding a small amount of a thioether-containing organic matter, improve the first coulombic efficiency of a sodium ion battery and improve the energy density of the sodium ion battery.
(2) The invention provides the thioether-containing electrolyte capable of forming the novel sulfate-based SEI film, which has the advantages of simple preparation process, readily available raw materials and low cost. The sodium ion battery is matched with a high-capacity positive electrode material, so that the actual energy density, the cycle life and the safety of the sodium ion battery can be improved, and the industrialization process of the sodium ion battery is promoted.
Drawings
FIG. 1 shows that the electrolyte prepared in comparative example 1 has a current density of 20mA · g at 30 ℃ in a sodium ion half cell -1 First charge and discharge curves below.
FIG. 2 shows that the electrolyte prepared in example 1 has a current density of 20mA g at 30 ℃ in a sodium ion half-cell -1 First charge-discharge curve below.
FIG. 3 shows that the electrolyte prepared in example 2 has a current density of 20 mA-g at 30 ℃ in a sodium-ion half-cell -1 First charge-discharge curve below.
FIG. 4 shows that the electrolyte prepared in example 2 has a current density of 20 mA-g at 30 ℃ in a sodium-ion half-cell -1 C1s spectrum of XPS chart of carbon negative electrode with voltage of 2V after next cycle.
FIG. 5 shows that the electrolyte prepared in example 2 has a current density of 20 mA-g at 30 ℃ in a sodium-ion half-cell -1 O1s spectrum of XPS chart of carbon negative electrode with voltage of 2V after next cycle.
FIG. 6 shows that the electrolyte prepared in example 2 has a current density of 20mA g at 30 ℃ in a sodium ion half-cell -1 S2p spectrum of XPS chart of carbon negative electrode with voltage of 2V after next cycle.
FIG. 7 shows that the electrolyte prepared in example 3 has a current density of 20 mA-g at 30 ℃ in a sodium ion half-cell -1 First charge-discharge curve below.
FIG. 8 shows that the electrolyte prepared in comparative example 4 has a current density of 20mA · g at 30 ℃ in a sodium ion half cell -1 First charge-discharge curve below.
FIG. 9 shows that the electrolyte prepared in comparative example 5 has a current density of 20mA · g at 30 ℃ in a sodium ion half cell -1 First charge and discharge curves below.
FIG. 10 shows that the electrolyte prepared in comparative example 6 has a current density of 20mA · g at 30 ℃ in a sodium ion half cell -1 First charge-discharge curve below.
FIG. 11 shows that the electrolyte prepared in example 4 has a current density of 20mA g at 30 ℃ in a sodium ion half-cell -1 First charge and discharge curves below.
FIG. 12 shows that the electrolyte prepared in example 5 has a current density of 20mA g at 30 ℃ in a sodium ion half-cell -1 First charge-discharge curve below.
Fig. 13 is a rate profile of the electrolyte prepared in example 2 at 30 c for a sodium ion half cell.
FIG. 14 shows 500mA · g of the electrolyte prepared in example 2 at 30 ℃ for a sodium ion half cell -1 Large current cycling profile of (a).
Detailed Description
The invention is further illustrated, but not limited, by the following figures.
Comparative example 1
1.0mol/L NaPF of common ether solution 6 The preparation method of the sodium ion battery with DME as electrolyte comprises the following steps:
step (1): and preparing a negative electrode. 160mg of commercial hard carbon (Japanese Wuhui chemical Carbotron P), 20mg of conductive carbon black and PVDF20mg are weighed according to the mass ratio of 8:1:1 respectively, uniformly stirred in a mortar of agate, then a proper amount of N-methyl pyrrolidone (NMP) is dripped into the mortar for stirring for 6 to 8 hours to uniform slurry, the slurry is uniformly coated on the surface of copper (Cu) foil by a scraper with the diameter of 100 mu m, the copper foil with the active material is placed in a vacuum drying oven for standing for 12 hours at the temperature of 80 ℃, and then the Cu foil is cut into a disk-shaped negative pole piece.
Step (2): and (3) preparing an electrolyte. 1.0mol/L NaPF of common ether-based electrolyte is used 6 /DME。
And (3): and (6) assembling the half cell. CR2016 button cell assembled in an Ar-filled MIKROUNA glove box using the prepared hard carbon electrode as the negative electrode and 1.0mol/L NaPF of commercial electrolyte 6 The 2016 button cell was assembled with DME as electrolyte and Na metal sheet as counter electrode.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, same below), and a charge/discharge test was performed. The results of the electrochemical tests are shown in Table 1 and FIG. 1. from the first charge/discharge curve of FIG. 1, it can be seen that the charge/discharge rate is 1.0mol/L NaPF 6 Half cell with DME as electrolyte at 20 mA.g -1 The first coulombic efficiency under the current density of (1) is low and is only 58.86%, and the specific discharge capacity of the hard carbon negative electrode in the electrolyte in the first circle is 463.62 mAh.g -1 The charging specific capacity of the first circle is 272.92mAh g -1 The specific discharge capacity of the second ring is 314.76mAh g -1 The specific discharge capacity after 50 cycles is 291.69mAh g -1 The capacity retention rate after 50 cycles was 92.67%.
Comparative example 2
1.0mol/L NaPF of common ether-based electrolyte 6 The preparation method of the sodium ion battery with/DME +0.5 wt% FEC (fluoroethylene carbonate) as electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.025g of FEC was dissolved in 5g of 1.0mol/L NaPF in a MIKROUNA glove box filled with Ar 6 In DME (1:1), electrolyte containing 0.5 wt% of FEC is obtained after complete mixing of FEC and DME electrolyte.
And (3): and (6) assembling the half cell. And (3) assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, wherein the prepared hard carbon electrode is used as a negative electrode, the electrolyte is the electrolyte prepared in the step (2), and the Na metal sheet is used as a counter electrode, so that the 2016 button cell is assembled.
Laying aside the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, same below), and a charge/discharge test was performed. The results of the electrochemical tests are shown in Table 1, with 0.5 wt% FEC +1.0mol/L NaPF 6 Half cell with DME as electrolyte at 20 mA.g -1 The first coulombic efficiency under the current density of the electrolyte is 59.36 percent, and the first-circle specific discharge capacity of the hard carbon cathode in the electrolyte is 466.83 mAh.g -1 First loop chargingSpecific capacity of 277.11mAh g -1 The specific discharge capacity of the second ring is 273.16mAh g -1 The specific discharge capacity after 50 cycles is 245.22mAh g -1 The capacity retention rate after 50 cycles was 89.77%.
Comparative example 3
The preparation method of the sodium ion battery with 1.0mol/L NaPF6/DME +1 wt% TMSB (trimethylsilylborate) of common ether electrolyte as the electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.05g of TMSB solid is weighed in an MIKROUNA glove box filled with Ar atmosphere and dissolved in 5g of 1.0mol/L NaPF6/DME (1:1), and after the TMSB solid is completely dissolved, an electrolyte containing 1 wt% of TMSB is obtained.
And (3): and (6) assembling the half cell. And (3) assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, wherein the prepared hard carbon electrode is used as a negative electrode, the electrolyte is the electrolyte prepared in the step (2), and the Na metal sheet is used as a counter electrode, so that the 2016 button cell is assembled.
And (3) placing the assembled button cell for 4-6h, placing the button cell in a 30 ℃ constant temperature test system, and carrying out charge and discharge tests on the button cell in a voltage interval of 0.01-2.0V (vs. Na +/Na, the same applies below). Electrochemical test results are shown in table 1, the first coulombic efficiency of a half-cell taking 1 wt% of TMSB +1.0mol/L NaPF6/DME as electrolyte is 60.38% under the current density of 20 mA.g < -1 >, the first circle discharge specific capacity of a hard carbon cathode in the electrolyte is 393.525 mAh.g < -1 >, the first circle charge specific capacity is 237.61 mAh.g < -1 >, the second circle discharge specific capacity is 295.6 mAh.g < -1 >, the discharge specific capacity is 266.57 mAh.g < -1 > after 50 circles of circulation, and the capacity retention rate is 90.18% after 50 circles of circulation. In view of the first coulombic efficiency (58.86%) obtained in comparative example 1, the first coulombic efficiency did not increase significantly when the electrolyte containing 1 wt% of the TMSB additive was used in the hard carbon negative electrode.
Comparative example 4
The preparation method of the sodium ion battery with 1.0mol/L NaPF6/DME +1 wt% VEC (ethylene carbonate) of common ether-based electrolyte as the electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.05g of VEC solid is weighed in an MIKROUNA glove box filled with Ar atmosphere and dissolved in 5g of 1.0mol/L NaPF6/DME (1:1), and after TMSB solid is completely dissolved, electrolyte containing 1 wt% of VEC is obtained.
And (3): and (5) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
And (3) placing the assembled button cell for 4-6h, placing the button cell in a constant temperature test system at 30 ℃, and carrying out charge and discharge tests on the button cell in a voltage interval of 0.01-2.0V (vs. Na +/Na, the same below). The electrochemical test results are shown in Table 1 and FIG. 8, and it can be seen from FIG. 8 that the first coulombic efficiency of the half-cell using 1 wt% VEC +1.0mol/L NaPF6/DME as the electrolyte is 60.18% at the current density of 20mA · g-1, and the first-turn specific discharge capacity of the hard carbon negative electrode in the electrolyte is 338.24mAh · g -1 The charging specific capacity of the first circle is 203.55mAh g -1 The specific discharge capacity of the second coil is 216.29mAh g -1 And the specific discharge capacity after 50 cycles is 147.6mAh g -1 The capacity retention after 50 cycles was 67.99%. In view of the first coulombic efficiency (58.86%) obtained in comparative example 1, there was no significant increase in the first coulombic efficiency when the electrolyte containing 1 wt% of the VEC additive was used in the hard carbon negative electrode.
Comparative example 5
Using ether solution 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with DME as electrolyte comprises the following steps:
step (1): and preparing a negative electrode. Weighing 160mg of commercial soft carbon, 20mg of conductive carbon black, 20mg of PVDF20mg and agate according to a mass ratio of 8:1:1, stirring uniformly, then dropping a proper amount of N-methylpyrrolidone (NMP) for stirring, stirring for 6-8h to uniform slurry, uniformly coating the slurry on the surface of a copper (Cu) foil by using a 100 scraper, placing the copper foil in a vacuum drying oven, standing for 12 h at 80 ℃, and cutting the Cu foil with an active material into a disk-shaped negative electrode piece.
Step (2): the electrolyte was prepared as in comparative example 1. An ether based electrolyte of 1.0mol/LNaPF6/DME was used.
And (3): and (6) assembling the half cell. CR2016 button cells were assembled in an Ar-filled MIKROUNA glove box using the prepared soft carbon electrode as the negative electrode, commercial electrolyte 1.0mol/L NaPF6/DME as the electrolyte, Na metal sheet as the counter electrode, to assemble 2016 button cells.
Laying aside the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. The results of the electrochemical measurements are shown in Table 1 and FIG. 9, and it can be seen from the first charge and discharge curve of FIG. 9 that 1.0mol/L NaPF is used 6 Half cell with DME as electrolyte at 20 mA.g -1 The first coulombic efficiency under the current density is low and is only 56.79%, and the specific discharge capacity of the first circle of the soft carbon negative electrode in the electrolyte is 234.78 mAh.g as can be seen from table 1 -1 The first-circle charging specific capacity is 133.33 mAh.g -1 The specific discharge capacity of the second ring is 137.68mAh g -1 And the discharge specific capacity after 50 cycles of circulation is 126.7mAh g -1 And the capacity retention rate after 50 cycles is 92.2%.
Comparative example 6
Common ether-based electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +1 wt% DTD as electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 5
Step (2): and (4) preparing an electrolyte. 0.05g of DTD solid is weighed in an MIKROUNA glove box filled with Ar atmosphere and dissolved in 5g of 1.0mol/L NaPF6/DME (1:1), and an electrolyte containing 1 wt% of DTD is obtained after the DTD solid is completely dissolved.
And (3): and (5) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared soft carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies below) ofAnd in the voltage interval, carrying out charge and discharge tests on the voltage interval. The electrochemical test results are shown in Table 1 and FIG. 10, and it can be seen from the first charge and discharge curve of FIG. 10 that the half cell of the electrolyte prepared in comparative example 4 was operated at 20mA g -1 The first coulombic efficiency under the current density of (1) is 55.21%, and the specific discharge capacity of the first circle of the soft carbon negative electrode in the electrolyte is 176.16mAh g from the table 1 and the figure 10 -1 The charging specific capacity of the first circle is 96.24mAh g -1 The specific discharge capacity of the second ring is 97.46 mAh.g -1 And the specific discharge capacity after 50 cycles of circulation is 90.7mAh g -1 And the capacity retention rate after 50 cycles is 93.06%. In view of the first coulombic efficiency (56.79%) obtained in comparative example 5, the first coulombic efficiency was not improved when the electrolyte containing 1 wt% of the DTD additive was used in the soft carbon anode.
Example 1
1.0mol/L NaPF of common ether-based electrolyte 6 The preparation method of the sodium ion battery with/DME +0.25 wt% DTD as electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.025g of DTD solid was dissolved in 10g of 1.0mol/L NaPF in a MIKROUNA glove box filled with Ar 6 In DME (1:1), an electrolyte containing 0.25 wt% of DTD is obtained after the DTD solid is completely dissolved.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. The results of the electrochemical measurements are shown in Table 1 and FIG. 2, and it can be seen from the first charge-discharge curve of FIG. 2 that the DTD is 0.25 wt% and 1.0mol/LNaPF 6 Half cell with DME as electrolyte at 20 mA.g -1 The first coulombic efficiency under the current density of 73.61 percent, and the specific discharge capacity of the second circle of the hard carbon cathode in the electrolyte296.08mAh·g -1 The specific discharge capacity after 50 cycles is 270.56mAh g -1 The capacity retention rate after 50 cycles was 91.38%.
Example 2
1.0mol/L NaPF of common ether-based electrolyte 6 The preparation method of the sodium ion battery with/DME +0.5 wt% DTD as electrolyte comprises the following steps:
step (1): the negative electrode was prepared as in comparative example 1.
Step (2): and (3) preparing an electrolyte. 0.05g of DTD solid is weighed in a MIKROUNA glove box filled with Ar atmosphere and dissolved in 10g of 1.0mol/L NaPF6/DME (1:1), and an electrolyte containing 0.5 wt% of DTD is obtained after the DTD solid is completely dissolved.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. The electrochemical test results are shown in Table 1, FIG. 3, FIG. 13 and FIG. 14, and it can be seen from the rate performance curve of FIG. 13 that the current density increases with 1.0mol/L NaPF 6 The discharge specific capacity of the half-cell taking/DME +0.5 wt% DTD as the electrolyte is obviously attenuated. As shown in FIG. 13, the current densities were 50mA · g, respectively -1 ，100mA·g -1 ，200mA·g -1 ，500mA·g -1 ，1000mA·g -1 ，100mAg -1 The specific capacity of the battery is 325mAh g -1 ，293mAh·g -1 ，276mAh·g -1 ，254mAh·g -1 ，212mAh·g -1 ，285mAh·g -1 . Under the condition of large current of 1000mA g -1 Can still return to the original capacity (100 mAg) after circulation -1 285mAhg still remained -1 Specific capacity of). Large current (500mA · g) from FIG. 14 -1 ) The cycling curves can also see the capacity fade of the half cells. As can be seen from the first charge-discharge curve of FIG. 3, the preparation using example 2The half cell of the electrolyte solution (2) is at 20 mA.g -1 The first coulombic efficiency of the sodium ion battery is obviously improved from 58.86% of a half battery prepared from the electrolyte without DTD to 79.89%. From the information in table 1, in the sodium ion half-cell prepared by adding the electrolyte with different mass concentration of DTD, the electrolyte with 0.5 wt% of DTD has the best effect of improving the first coulombic efficiency, and the first coulombic efficiency is at 20mA · g -1 The discharge specific capacity of the hard carbon cathode in the electrolyte in the second circle is 285.72mAh g -1 The specific discharge capacity after 50 cycles is 271.44mAh g -1 And the capacity retention rate is 95%, so that the half-cell prepared by adding the electrolyte with 0.5 wt% of DTD has good rate capability and cycle performance. As can be seen from the spectrum of C1S in FIG. 4, the spectrum of O1S in FIG. 5, and the spectrum of S2p in FIG. 6, the C-S structure corresponding to the characteristic peak at 286.3eV in the spectrum of C1S, the S-O structure corresponding to the characteristic peak at 533.1eV in the spectrum of O1S, the S-O structure corresponding to the characteristic peak at 167.1eV in the spectrum of S2p, and the C-Sox-C structure corresponding to the characteristic peaks at 169.2eV and 171.6eV in the spectra of S1S, O1S, and S2p in XPS of carbon cathode, it can be well demonstrated that SO exists in carbon cathode 4 2- The existence of (b) can further explain that the SEI film component contains sulfate.
Example 3
Common ether electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +1 wt% DTD as electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.05g of DTD solid is weighed in an MIKROUNA glove box filled with Ar atmosphere and dissolved in 5g of 1.0mol/L NaPF6/DME (1:1), and an electrolyte containing 1 wt% of DTD is obtained after the DTD solid is completely dissolved.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying aside the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. The electrochemical test results are shown in Table 1 and FIG. 7, and it can be seen from the first charge-discharge curve of FIG. 7 that the half cell of the electrolyte prepared in example 3 was at 20mA g -1 The first coulombic efficiency under the current density of the electrolyte is 79.76 percent, and the specific discharge capacity of the second circle of the hard carbon cathode in the electrolyte is 299.33 mAh.g -1 And the discharge specific capacity after circulating for 50 circles is 363.11mAh g -1 And the capacity retention rate after 50 cycles is 92.2%.
Example 4
Common ether-based electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +2 wt% DTD as electrolyte comprises the following steps:
step (1): preparation of negative electrode was the same as in comparative example 1
Step (2): and (4) preparing an electrolyte. 0.1g of DTD solid is weighed in an MIKROUNA glove box filled with Ar atmosphere and dissolved in 5g of 1.0mol/L NaPF6/DME (1:1), and an electrolyte containing 2 wt% of DTD is obtained after the DTD solid is completely dissolved.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
And (3) placing the assembled button cell for 4-6h, placing the button cell in a constant temperature test system at 30 ℃, and carrying out charge and discharge tests on the button cell in a voltage interval of 0.01-2.0V (vs. Na +/Na, the same below). The electrochemical test results are shown in Table 1 and FIG. 11, and it can be seen from the first charge and discharge curve of FIG. 11 that the half cell of the electrolyte prepared in example 4 was at 20mA g -1 The first coulombic efficiency under the current density of the electrolyte is 78.29 percent, and the specific discharge capacity of the second circle of the hard carbon cathode in the electrolyte is 296.79 mAh.g -1 The specific discharge capacity after 50 cycles is 269.72mAh g -1 The capacity retention after 50 cycles was 90.87%.
Example 5
GeneralEther-based electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +5 wt% DTD as electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.25g of DTD solid was dissolved in 5g of 1.0mol/L NaPF in a MIKROUNA glove box filled with Ar 6 In DME, electrolyte containing 5 wt% of DTD is obtained after DTD solid is completely dissolved.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
And (3) placing the assembled button cell for 4-6h, placing the button cell in a 30 ℃ constant temperature test system, and carrying out charge and discharge tests on the button cell in a voltage interval of 0.01-2.0V (vs. Na +/Na, the same applies below). The electrochemical test results are shown in Table 1 and FIG. 12, and it can be seen from the first charge and discharge curve of FIG. 12 that the half cell of the electrolyte prepared in example 5 was operated at 20mA g -1 The first coulombic efficiency under the current density of the electrolyte is 67.79 percent, and the specific discharge capacity of the second circle of the hard carbon cathode in the electrolyte is 316.53 mAh.g -1 And the discharge specific capacity after circulating for 50 circles is 297.16mAh g -1 And the capacity retention rate after 50 cycles is 93.88%.
Example 6
Common ether-based electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +0.5 wt% PS as electrolyte comprises the following steps:
step (1): preparation of negative electrode was the same as in comparative example 1
Step (2): and (4) preparing an electrolyte. 0.025g of PS was weighed into a MIKROUNA glove box filled with Ar gas and 5g of 1.0mol/L NaPF 6 In DME, the electrolyte containing 0.5 wt% of PS is obtained after PS is completely mixed with the electrolyte.
And (3): and (6) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. Electrochemical test results are shown in Table 1, with the electrolyte prepared in example 6 at 20mA g half cell -1 The first coulombic efficiency under the current density of the electrolyte is 74.27 percent, and the specific discharge capacity of the second circle of the hard carbon cathode in the electrolyte is 298.97 mAh.g -1 The specific discharge capacity after 50 cycles is 274.72mAh g -1 The capacity retention rate after 50 cycles was 91.79%.
Example 7
Common ether-based electrolyte 1.0mol/L NaPF 6 The preparation method of the sodium ion battery with/DME +0.5 wt% (DTD: PS ═ 1:1) as the electrolyte comprises the following steps:
step (1): negative electrode preparation same as comparative example 1
Step (2): and (4) preparing an electrolyte. 0.025g of PS and 0.025g of DTD were weighed into 10g of 1.0mol/L NaPF in an MIKROUNA glove box filled with Ar 6 In DME, the electrolyte containing 0.5 wt% (DTD: PS: 1) is obtained after DTD is completely dissolved and completely mixed with PS and the electrolyte.
And (3): and (5) assembling the half cell. Assembling a CR2016 button cell in an MIKROUNA glove box filled with Ar atmosphere, using the prepared hard carbon electrode as a negative electrode, the electrolyte as the electrolyte prepared in the step (2), and a Na metal sheet as a counter electrode, and assembling the 2016 button cell.
Laying the assembled button cell for 4-6h, and placing in a 30 deg.C constant temperature test system at 0.01-2.0V (vs. Na) + Na, the same applies hereinafter) was subjected to a charge-discharge test. Electrochemical test results are shown in Table 1, with the electrolyte prepared in example 7 at 20mA g half cell -1 The first coulombic efficiency under the current density is 74.96 percent, and the specific discharge capacity of the hard carbon cathode in the second circle of the electrolyte is 301.14 mAh.g -1 The specific discharge capacity after 50 cycles is 278.04mAh g -1 The capacity retention rate after 50 cycles was 92.33%.
The above description is only exemplary of the present invention and should not be taken as limiting, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention should be included in the protection scope of the present invention.
TABLE 1 tables of relevant parameters for half-cells assembled according to comparative examples 1-6 and examples 1-7
Figure BDA0003254220320000161
Injecting: the capacity retention rate refers to the retention rate after 50 cycles relative to the second cycle, the first cycle belonging to the formation process.

Claims (9)

1. An electrolyte forming a sulfate-based SEI film, the electrolyte comprising a fluorine-containing sodium salt and a solvent, the solvent comprising: a sulfur ester-containing organic substance and a nonaqueous organic solvent containing an ether bond.
2. The electrolyte according to claim 1, wherein the ether bond-containing non-aqueous organic solvent is 80 to 99.5 wt%, preferably 99 wt%, and the thioester-containing organic substance is 0.1 to 20 wt%; preferably 0.5 to 2% by mass.
3. The electrolyte of claim 1, wherein the sulfur-containing ester organic compound is one or more of vinyl sulfate, propylene sulfite, and ethylene sulfite.
4. The electrolyte according to claim 1, wherein the ether bond-containing non-aqueous organic solvent includes any one or more of cyclic ethers and chain ethers; preferably, the cyclic ethers include one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 2-methyl-1, 3-dioxolane; the chain ethers include one or more of 1, 2-dimethoxypropane, dimethoxymethane and ethylene glycol dimethyl ether diethylene glycol dimethyl ether.
5. The electrolyte of claim 1, wherein the fluorine-containing sodium salt comprises one or more of sodium hexafluorophosphate, sodium difluorooxalate, sodium triflate, sodium bistrifluoromethanesulfonylimide, and sodium bistrifluorosulfonylimide.
6. The electrolyte according to claim 1, wherein the molar concentration of the sodium salt in the non-aqueous organic solvent is 1 to 4 mol/L.
7. A method for preparing an electrolyte for forming a sulfate-based SEI film, comprising mixing and dissolving the fluorine-containing sodium salt according to any one of claims 1 to 6 and a solvent component.
8. A sodium ion battery forming a sulfate-based SEI film, comprising the electrolyte of any one of claims 1 to 6.
9. The application of the electrolyte for forming the sulfate-based SEI film is used for preparing the sodium-ion battery.
CN202111054821.XA 2021-09-09 2021-09-09 Electrolyte for forming sulfate-based SEI film and preparation and application thereof Pending CN115000508A (en)

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