CN114497744A - Sodium ion electrolyte and application thereof, sodium ion battery and preparation method thereof - Google Patents

Sodium ion electrolyte and application thereof, sodium ion battery and preparation method thereof Download PDF

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CN114497744A
CN114497744A CN202210214690.5A CN202210214690A CN114497744A CN 114497744 A CN114497744 A CN 114497744A CN 202210214690 A CN202210214690 A CN 202210214690A CN 114497744 A CN114497744 A CN 114497744A
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sodium
electrolyte
sodium ion
battery
carbonate
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陈祥兰
董晶
高秀玲
马华
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Tianjin EV Energies Co Ltd
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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
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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

Abstract

The invention discloses a sodium ion electrolyte and application thereof, a sodium ion battery and a preparation method thereof. When the electrolyte is applied to a battery, the sodium tetrafluoro oxalate phosphate can form a low-impedance, compact and thermally stable SEI film on the surface of the negative electrode of the battery, the SEI film has the characteristic of low impedance, and the transmission resistance of sodium ions is small even under an ultralow-temperature environment, so that the low-temperature output capacity and the low-temperature cycle life of the battery are improved. Meanwhile, the SEI film has excellent thermal stability, and can improve the cycle life of a battery at an ultra-high temperature.

Description

Sodium ion electrolyte and application thereof, sodium ion battery and preparation method thereof
Technical Field
The embodiment of the invention relates to the technical field of batteries, in particular to a sodium ion electrolyte and application thereof, a sodium ion battery and a preparation method thereof.
Background
The sodium ion battery comprises sodium ion electrolyte, has the advantages of rich resources, low manufacturing cost, good rate capability, long cycle life, environmental friendliness and the like, and is widely applied to the fields of power and energy storage.
However, sodium ion batteries are energy providers, and the use environment seriously affects the performance of the batteries. In a low-temperature environment, the impedance of the sodium ion battery increases, the output capacity decreases, and the cycle life also decreases. In addition, in a high-temperature environment, a Solid Electrolyte Interface (SEI) formed by the sodium ion battery is prone to cracking, which leads to a reduction in the cycle life of the battery.
Disclosure of Invention
The invention provides a sodium ion electrolyte and application thereof, a sodium ion battery and a preparation method thereof, and aims to improve the capacity and the cycle life of the battery in a low-temperature environment and the cycle life of the battery in a high-temperature environment.
In a first aspect, embodiments of the present invention provide a sodium ion electrolyte, including an additive, a non-aqueous solvent, and a sodium salt dissolved in the non-aqueous solvent, where the additive includes sodium tetrafluoro oxalate.
Optionally, the mass of the sodium tetrafluoro oxalate phosphate is 0.1-5% of the total mass of the electrolyte.
Optionally, the sodium salt comprises at least one of sodium hexafluorophosphate, sodium chloride, sodium fluoride, sodium sulfate, sodium carbonate, sodium phosphate, sodium nitrate, sodium tetrafluoroborate, sodium difluorooxalate, and sodium bisoxalato.
Optionally, the mass of the sodium salt is 10% -25% of the total mass of the electrolyte.
Optionally, the non-aqueous solvent comprises at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propionate, or propyl propionate.
Optionally, the electrolyte further comprises an auxiliary film-forming additive, wherein the auxiliary film-forming additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, sodium difluorophosphate and sodium bisoxalateborate.
In a second aspect, the embodiment of the present invention provides an application of any one of the sodium ion electrolytes described above in preparation of portable electronic devices, power batteries, and energy storage sodium power systems.
In a third aspect, an embodiment of the present invention further provides a sodium ion battery, including any one of the sodium ion electrolytes described above.
In a fourth aspect, an embodiment of the present invention further provides a method for preparing a sodium ion battery, including obtaining a positive plate after a first current collector coated with a battery positive electrode mixture is subjected to a set process;
after the second current collector coated with the battery negative electrode mixture is subjected to the setting process, a negative plate is obtained;
and packaging the positive plate and the negative plate in a shell, and injecting an electrolyte into the shell, wherein the electrolyte comprises an additive, and the additive comprises sodium tetrafluoro oxalate phosphate.
Optionally, the battery positive electrode mixture comprises a positive electrode active material, a conductive agent and a binder, and the battery negative electrode mixture comprises a negative electrode active material, the conductive agent and the binder;
the positive active material comprises at least one of layered transition metal oxide, polyanion compound and Prussian blue compound;
the negative active material includes at least one of hard carbon, soft carbon, expanded graphite, carbon nanotubes, and graphene.
The embodiment of the invention provides a sodium ion electrolyte and application thereof, a sodium ion battery and a preparation method thereof. When the electrolyte is applied to a battery, the sodium tetrafluoro oxalate phosphate can form a low-impedance, compact and thermally stable SEI film on the surface of the negative electrode of the battery, the SEI film has the characteristic of low impedance, and the transmission resistance of sodium ions is small even under an ultralow-temperature environment, so that the low-temperature output capacity and the low-temperature cycle life of the battery are improved. Meanwhile, the SEI film also has excellent thermal stability, and can prolong the cycle life of the battery at ultrahigh temperature.
Drawings
Fig. 1 is a flowchart of a method for manufacturing a sodium-ion battery according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The embodiment of the invention provides a sodium ion electrolyte, which comprises an additive, a non-aqueous solvent and a sodium salt dissolved in the non-aqueous solvent, wherein the additive comprises sodium tetrafluoro oxalate phosphate.
Sodium tetrafluoro oxalate phosphate is a novel additive, the additive can form a low-impedance, compact and thermally stable Solid Electrolyte Interface (SEI) film on a negative electrode interface, and the SEI film can protect the negative electrode of the battery, so that the material of the negative electrode is not easily damaged, and the cycle life of the electrode material is prolonged. The sodium tetrafluoro oxalate phosphate has low film forming impedance, and can effectively reduce the transmission resistance of sodium ions in a low-temperature environment, thereby improving the output capacity of the battery at low temperature and prolonging the cycle life of the battery at low temperature. In addition, sodium tetrafluoro oxalate phosphate is added into the sodium ion electrolyte, so that the deterioration of an SEI film in the circulating process at high temperature can be reduced, and the circulating life of the battery at high temperature is prolonged. Moreover, the sodium ion electrolyte provided by the embodiment of the invention has wide application prospects in the fields of preparation of portable electronic equipment, power batteries, energy storage sodium-electricity systems and the like.
Optionally, the mass of the sodium tetrafluoro oxalate phosphate is 0.1-5% of the total mass of the electrolyte.
The mass of the sodium tetrafluoro oxalate phosphate is too small, which is not beneficial to improving the cycle life of the battery at low temperature and at high temperature, when the mass of the sodium tetrafluorooxalate phosphate is increased to a certain value, the effect of improving the cycle life of the battery at low temperature and high temperature is best, and even if the mass of the sodium tetrafluorooxalate phosphate is increased, the cycle life of the battery at low temperature and high temperature can not be increased, so the content of the sodium tetrafluorooxalate phosphate in a sodium ion electrolyte needs to be controlled within a certain range. Preferably, the mass of the sodium tetrafluoro oxalate phosphate is 0.1-2% of the total mass of the electrolyte. The mass of the sodium tetrafluoro oxalate phosphate is 0.1-5% of the total mass of the electrolyte, so that the battery has longer cycle life at low temperature and high temperature, the waste of the sodium tetrafluorooxalate phosphate is avoided, and the cost is saved.
Optionally, the sodium salt comprises at least one of sodium hexafluorophosphate, sodium chloride, sodium fluoride, sodium sulfate, sodium carbonate, sodium phosphate, sodium nitrate, sodium tetrafluoroborate, sodium difluorooxalate, sodium bisoxalato.
The substances are common, and at least one of the substances can be selected as sodium salt to generate sodium ions, so that the implementation is easy.
Optionally, the mass of the sodium salt is 10-25% of the total mass of the electrolyte.
If the mass of the sodium salt is too low relative to the electrolyte, the carriers contained in the sodium ion electrolyte are too few, so that the sodium ion battery has obvious concentration polarization caused by untimely diffusion and migration in charge-discharge cycles, and the cycle performance of the sodium ion battery is influenced. The sodium salt has too high quality relative to the electrolyte, the quantity of anions contained in the sodium ion electrolyte is large, the anions are seriously decomposed at high temperature (>30 ℃), and the decomposition products can damage an electrode-electrolyte interface layer, so that the cycling stability of the sodium ion battery is reduced. Therefore, the content of the sodium salt needs to be controlled within a reasonable range, and the sodium salt accounts for 10-25% of the total mass of the electrolyte, so that the stable cycle performance of the sodium-ion battery can be ensured.
Optionally, the non-aqueous solvent comprises at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propionate, or propyl propionate. The mass of the nonaqueous solvent may be 50% to 90% of the total mass of the electrolyte.
The high quality of the non-aqueous solvent relative to the electrolyte can result in low conductivity of the sodium ion electrolyte, and thus poor conductivity of the sodium ion battery. The mass of the non-aqueous solvent relative to the electrolyte is too low, so that the viscosity of the sodium ion electrolyte is too high, the ion movement is greatly resisted, the diffusion capacity is reduced, and the capacity of the sodium ion battery is reduced. Therefore, the content of the non-aqueous solvent needs to be controlled within a reasonable range, the mass of the non-aqueous solvent is 50% -90% of the total mass of the electrolyte, the sodium ion electrolyte can be ensured to have better conductivity, and the viscosity of the electrolyte is not too high.
Optionally, the electrolyte further comprises an auxiliary film-forming additive, wherein the auxiliary film-forming additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, sodium difluorophosphate and sodium bisoxalate.
The mass of the auxiliary film-forming additive is less than or equal to 10% of the total mass of the electrolyte. The addition of the auxiliary film forming additive can assist the electrode to form a film, further improve the structure of the formed film and form a high-elastic structure with a good interface structure, compact stability and good ionic conductivity.
The embodiment of the invention also provides a sodium ion battery which comprises the sodium ion electrolyte in any embodiment. The beneficial effects of the sodium ion battery are the same as those of the sodium ion electrolyte, and the description of this embodiment is omitted here.
The present invention provides 9 examples and 4 comparative examples to illustrate the beneficial effects of a sodium ion electrolyte or a sodium ion battery. The first table shows the composition of the sodium ion electrolytes of examples 1 to 9 and comparative examples 1 to 4, and the percentages in table 1 are mass percentages.
TABLE 1 compositions of sodium ion electrolytes of examples 1 to 9 and comparative examples 1 to 4
Figure BDA0003533932230000061
Example 1
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 1% of sodium tetrafluorooxalate, 14% of sodium hexafluorophosphate, 34% of Propylene Carbonate (PC), 34% of Ethyl Methyl Carbonate (EMC) and 17% of diethyl carbonate (DEC) by mass percentage respectively based on the total mass of the sodium ion electrolyte as 100%.
Example 2
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 0.1% of sodium tetrafluorooxalate phosphate, 14% of sodium hexafluorophosphate, 34.36% of Propylene Carbonate (PC), 34.36% of Ethyl Methyl Carbonate (EMC) and 17.18% of diethyl carbonate (DEC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
Example 3
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 1.5% of sodium tetrafluorooxalate phosphate, 14% of sodium hexafluorophosphate, 33.8% of Propylene Carbonate (PC), 33.8% of Ethyl Methyl Carbonate (EMC) and 16.9% of diethyl carbonate (DEC) in percentage by mass, wherein the total mass of the sodium ion electrolyte is 100%.
Example 4
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 2 mass percent of sodium tetrafluorooxalate phosphate, 14 mass percent of sodium hexafluorophosphate, 33.6 mass percent of Propylene Carbonate (PC), 33.6 mass percent of Ethyl Methyl Carbonate (EMC) and 16.8 mass percent of diethyl carbonate (DEC) respectively, wherein the total mass of the sodium ion electrolyte is 100 percent.
Example 5
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 5 mass percent of sodium tetrafluorooxalate phosphate, 14 mass percent of sodium hexafluorophosphate, 32.4 mass percent of Propylene Carbonate (PC), 32.4 mass percent of Ethyl Methyl Carbonate (EMC) and 16.2 mass percent of diethyl carbonate (DEC) respectively, wherein the total mass of the sodium ion electrolyte is 100 percent.
Example 6
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, the non-aqueous solvent comprises Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and the sodium ion electrolyte also comprises an auxiliary film-forming additive which comprises Vinylene Carbonate (VC). The sodium ion electrolyte comprises 1% of sodium tetrafluoro oxalate, 1% of Vinylene Carbonate (VC), 14% of sodium hexafluorophosphate, 33.6% of Propylene Carbonate (PC) and 50.4% of Ethyl Methyl Carbonate (EMC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
Example 7
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, the non-aqueous solvent comprises Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and the sodium ion electrolyte also comprises an auxiliary film-forming additive which comprises fluoroethylene carbonate (FEC). The sodium ion electrolyte comprises 2 mass percent of sodium tetrafluorooxalate phosphate, 1 mass percent of fluoroethylene carbonate (FEC), 14 mass percent of sodium hexafluorophosphate, 33.2 mass percent of Propylene Carbonate (PC) and 49.8 mass percent of Ethyl Methyl Carbonate (EMC) respectively, wherein the total mass of the sodium ion electrolyte is 100 percent.
Example 8
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, the non-aqueous solvent comprises Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and the sodium ion electrolyte also comprises an auxiliary film-forming additive which comprises Vinylene Carbonate (VC). The sodium ion electrolyte comprises 1.5% of sodium tetrafluoro oxalate phosphate, 1% of Vinylene Carbonate (VC), 25% of sodium hexafluorophosphate, 29% of Propylene Carbonate (PC) and 43.5% of Ethyl Methyl Carbonate (EMC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
Example 9
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, the non-aqueous solvent comprises Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and the sodium ion electrolyte also comprises an auxiliary film-forming additive which comprises fluoroethylene carbonate (FEC). The sodium ion electrolyte comprises 3% of sodium tetrafluorooxalate, 2% of fluoroethylene carbonate (FEC), 10% of sodium hexafluorophosphate, 34% of Propylene Carbonate (PC) and 51% of Ethyl Methyl Carbonate (EMC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
Comparative example 1
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 10 mass percent of sodium tetrafluorooxalate phosphate, 14 mass percent of sodium hexafluorophosphate, 30.4 mass percent of Propylene Carbonate (PC), 30.4 mass percent of Ethyl Methyl Carbonate (EMC) and 15.2 mass percent of diethyl carbonate (DEC) respectively, wherein the total mass of the sodium ion electrolyte is 100 percent.
Comparative example 2
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, and the non-aqueous solvent comprises Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC). The sodium ion electrolyte comprises 14 mass percent of sodium hexafluorophosphate, 34.4 mass percent of Propylene Carbonate (PC), 34.4 mass percent of Ethyl Methyl Carbonate (EMC) and 17.2 mass percent of diethyl carbonate (DEC) respectively, wherein the total mass of the sodium ion electrolyte is 100 percent.
Comparative example 3
The sodium salt in the sodium ion electrolyte comprises sodium hexafluorophosphate, the non-aqueous solvent comprises Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and the sodium ion electrolyte also comprises an auxiliary film-forming additive which comprises Vinylene Carbonate (VC). The sodium ion electrolyte comprises 1% of Vinylene Carbonate (VC), 14% of sodium hexafluorophosphate, 34% of Propylene Carbonate (PC) and 51% of Ethyl Methyl Carbonate (EMC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
Comparative example 4
The sodium ion electrolyte comprises sodium hexafluorophosphate as a sodium salt, a nonaqueous solvent comprising Propylene Carbonate (PC) and Ethyl Methyl Carbonate (EMC), and an auxiliary film-forming additive comprising fluoroethylene carbonate (FEC). The sodium ion electrolyte comprises 1% of fluoroethylene carbonate (FEC), 14% of sodium hexafluorophosphate, 34% of Propylene Carbonate (PC) and 51% of Ethyl Methyl Carbonate (EMC) by mass percentage respectively, wherein the total mass of the sodium ion electrolyte is 100%.
After the sodium ion electrolyte solution of the above examples 1 to 9 and comparative examples 1 to 4 was used for preparing a sodium ion battery, a Direct Current Resistance (DCR) test was performed, a low temperature discharge test at-40 ℃, a cycle performance test at-20 ℃, and a cycle performance test at 55 ℃.
DCR test:
the sodium ion battery is charged to 3.8V (cutoff current 0.05C) at constant current and constant voltage with the current of 1C (the current of the nominal capacity of the battery), placed for 30min, then discharged to 50% of the SOC value (SOC is the state of charge and is used for reflecting the residual capacity of the battery, and the value is defined as the ratio of the residual capacity to the battery capacity) with the current of 1C, placed for 1h, discharged for 10s with the current of 5C, and discharged till the end. The DCR calculation formula is as follows: DCR ═ (Vt-V0)/I × 1000; wherein, Vt is the voltage of the sodium-ion battery at the pulse discharge end time; v0 is the voltage of the sodium ion battery before pulse discharge; i is the average current of the discharge.
-40 ℃ ultra low temperature discharge test:
charging the sodium ion battery to 3.8V (cutoff current of 0.05C) at constant current and constant voltage at 25 ℃ by using the current of 1C, and then discharging to 1.8V at constant current of 1C to obtain normal-temperature discharge capacity; then the sodium ion battery is charged to 3.8V (cut-off current 0.05C) with constant current and constant voltage by the current of 1C. Then the sodium ion battery is placed in an environment with the temperature of minus 40 ℃ for 10 hours to ensure that the temperature of the battery reaches minus 40 ℃, and then the constant current discharge is carried out to 1.8V at the current of 1C in the environment with the temperature of minus 40 ℃ to obtain the low-temperature discharge capacity with the temperature of minus 40 ℃. The ultralow-temperature discharge capacity retention ratio K1 at-40 ℃, (Q1/Q2) × 100%, where Q1 is the discharge capacity at-40 ℃, and Q2 is the normal-temperature discharge capacity. The discharge capacity can be measured by a specific apparatus.
-20 ℃ low temperature cycling test:
and in an environment of 20 ℃ below zero, charging the sodium ion battery to 3.8V (with the cut-off current of 0.05C) at a constant current and a constant voltage by using the current of 1C, discharging the sodium ion battery to 1.8V at a constant current by using the current of 1C, and performing charge and discharge circulation until the circulation is up to the set test circulation period. The cycle capacity retention ratio M1 is (L1/L2) × 100%, where L1 is the set test cycle discharge capacity and L2 is the average of the previous 3 cycle discharge capacities.
High temperature cycle test at 55 ℃:
and in an environment of 55 ℃, charging the sodium ion battery to 3.8V (with the cutoff current of 0.05C) at a constant current and a constant voltage by using the current of 1C, discharging the sodium ion battery to 1.8V at a constant current by using the current of 1C, and performing charging and discharging circulation until the circulation is up to the set test cycle period. The calculation method of the circulation capacity retention rate is referred to the low-temperature circulation test at-20 ℃, and the details are not repeated.
Table 2 is a table of test results of the sodium-ion battery provided in this embodiment after DCR test, -40 ℃ ultra-low temperature discharge test, -20 ℃ low temperature cycle test, and 55 ℃ high temperature cycle test.
Table 2 performance test results of sodium ion battery
Figure BDA0003533932230000111
Figure BDA0003533932230000121
As can be seen from the data in Table 2, the sodium ion electrolyte in comparative example 2 does not contain sodium tetrafluorooxalate, and the capacity retention rate of the sodium ion electrolyte in cycles of-20 ℃ for 500 weeks is 75.4%, while the sodium tetrafluorooxalate is added to the sodium ion electrolytes in examples 1 to 5, and the capacity retention rates of the sodium ion electrolyte in cycles of-20 ℃ for 500 weeks are 85.6%, 82.4%, 86.7%, 87.6% and 88.2% in sequence, so that the cycle capacity retention rate of the sodium ion electrolyte in cycles of-20 ℃ is improved after the sodium tetrafluorooxalate is added, and the sodium tetrafluorooxalate additive in the sodium ion electrolyte can effectively improve the ultralow temperature cycle performance of the sodium ion battery. Compared with the comparative example 2, the DCR of the sodium-ion battery is reduced in the examples 3 and 4, the temperature application range of the sodium-ion battery is widened, the DCR is reduced by 28-32%, and the retention rate of the circulation capacity of the sodium-ion battery after circulation for 500 weeks at-20 ℃ is improved by 11-12%. Therefore, the sodium tetrafluoro oxalate phosphate can form a low-impedance SEI film on the surface of the cathode material of the sodium ion battery, the DCR of the battery is reduced, the transmission rate of sodium ions of the sodium ion battery in an ultralow-temperature environment is improved, and the low-temperature output capacity and the low-temperature cycle life of the sodium ion battery are further improved.
The sodium ion electrolyte in comparative example 2 does not contain sodium tetrafluorooxalate phosphate, and the capacity retention rate after 1500 weeks at 55 ℃ is 70.8%, while the sodium tetrafluorooxalate phosphate is added to the sodium ion electrolytes in examples 1 to 5, and the capacity retention rates after 1500 weeks at 55 ℃ are 80.4%, 75.5%, 83.4%, 85.5% and 86.3% in this order. Therefore, after the sodium tetrafluorooxalate is added, the circulating capacity retention rate of the sodium ion electrolyte at 55 ℃ is improved, the sodium tetrafluorooxalate additive in the sodium ion electrolyte can improve the ultralow-temperature circulating performance of the sodium ion battery and the ultrahigh-temperature circulating performance, and the sodium tetrafluorooxalate is controlled within the range of 0.1-2% by mass, so that the excellent circulating performance can be obtained, and the sodium ion electrolyte can be used within a wider temperature range. Compared with the comparative example 2, the DCR of the sodium-ion battery is reduced in the examples 3 and 4, the temperature application range is widened, and the cycle capacity retention rate of the battery subjected to 55 ℃ cycling for 1500 weeks is improved by 12-14%.
In comparative example 1, 10% of sodium tetrafluorooxalate was added, and the DCR was higher than that obtained in example 2 without adding sodium tetrafluorooxalate, indicating that the effect of reducing the DCR of the battery was not good due to the excessively high amount of sodium tetrafluorooxalate added. And the retention rate of the circulation capacity of the electrolyte of the embodiment 1, which is circulated at-20 ℃ for 500 weeks, and the retention rate of the circulation capacity of the electrolyte of the embodiment 4, which is circulated at 55 ℃ for 1500 weeks, are close to the retention rate of the electrolyte to which 2% of sodium tetrafluorooxalate phosphate is added, so that it is not necessary to add excessive sodium tetrafluorooxalate phosphate.
The auxiliary film forming additives are added in the examples 6 to 9 and the comparative examples 3 to 4, and compared with the other examples without the auxiliary film forming additives, the sodium tetrafluoro oxalate additive in the sodium ion electrolyte can further improve the cycle performance of the sodium ion battery in the ultra-low temperature environment of-40 ℃ and the ultra-high temperature environment of 55 ℃ and prolong the service life of the sodium ion battery when matched with other auxiliary film forming additives such as Vinylene Carbonate (VC) and fluoroethylene carbonate (FEC).
Compared with examples 1-9, comparative examples 2-4, in which sodium tetrafluorooxalate was not added, had DCR values within 2.5-3.3, higher DCR values, the retention rate of discharge capacity at ultra-low temperature of-40 ℃ was about 50%, and lower retention rate of cycle capacity at-20 ℃ for 500 weeks. Therefore, analysis shows that the sodium tetrafluoro oxalate can form a low-impedance, compact and thermally stable SEI film on the surface of the cathode material of the sodium ion battery, the DCR of the battery is reduced, the transmission rate of sodium ions of the sodium ion battery in an ultralow temperature environment is improved, and the low-temperature output capacity and the low-temperature cycle life of the sodium ion battery are further improved. In addition, sodium tetrafluoro oxalate phosphate is added into the electrolyte, so that the degradation of an SEI (solid electrolyte interface) film of a negative electrode in an ultrahigh-temperature environment can be reduced, and the cycle life of the sodium-ion battery at high temperature is prolonged.
The embodiment of the present invention further provides a method for manufacturing a sodium ion battery, fig. 1 is a flowchart of the method for manufacturing a sodium ion battery according to the embodiment of the present invention, and referring to fig. 1, the method for manufacturing a sodium ion battery includes:
s100: and (4) obtaining the positive plate after the first current collector coated with the battery positive electrode mixture passes through a set process.
Optionally, the battery positive electrode mixture includes a positive electrode active material, a conductive agent and a binder, and the positive electrode active material includes at least one of a layered transition metal oxide, a polyanion compound and a prussian blue compound. In this embodiment, the positive electrode active material may be a layered transition metal oxide (NaNi)0.6Fe0.25Mn0.15O2) The conductive agent can be carbon black, the binder can be polyvinylidene fluoride, the first current collector can be an aluminum foil current collector, and the layered transition metal oxide, the carbon black and the polyvinylidene fluoride are fully and uniformly stirred in a slurry mixing tank according to the ratio of 97:2:1 and then coated on the aluminum foil current collector. The setting process comprises drying, rolling and die cutting. And coating the positive active substance, the conductive agent and the binder on an aluminum foil current collector, and drying, rolling and die cutting to obtain the positive plate.
S200: and (4) after the second current collector coated with the battery negative electrode mixture is subjected to a set process, obtaining a negative plate.
Optionally, the battery negative electrode mixture includes a negative electrode active material, a conductive agent and a binder, and the negative electrode active material includes at least one of hard carbon, soft carbon, expanded graphite, carbon nanotubes and graphene. In this embodiment, hard carbon is used as a negative electrode active material, carbon black is used as a conductive agent, sodium carboxymethyl cellulose and styrene butadiene rubber are used as binders, the second current collector is an aluminum foil current collector, and the hard carbon, the carbon black, the sodium carboxymethyl cellulose and the styrene butadiene rubber are fully and uniformly stirred in a slurry mixing tank according to a ratio of 95.5:1:1.5:2 and then coated on the aluminum foil current collector. And coating the negative active material, the conductive agent and the binder on an aluminum foil current collector, and drying, rolling and die cutting to obtain the negative plate.
S300: and packaging the positive plate and the negative plate in a shell, and injecting an electrolyte into the shell, wherein the electrolyte comprises an additive, and the additive comprises sodium tetrafluoro oxalate phosphate.
Illustratively, the positive plate, the diaphragm and the negative plate are stacked in a zigzag manner in this order, and the diaphragm is arranged between the positive plate and the negative plate and used for insulating the positive plate and the negative plate. And stacking the positive plate, the diaphragm and the negative plate, packaging the stacked positive plate, the diaphragm and the negative plate in a shell, baking, injecting electrolyte, pre-charging, exhausting, forming and the like to obtain the sodium-ion battery.
The sodium ion batteries of examples 1 to 9 and comparative examples 1 to 4 described above were prepared by the method for preparing the sodium ion battery provided in this example.
In the sodium ion battery prepared by the method in the embodiment, because sodium tetrafluoro oxalate is added to the electrolyte of the battery, a Solid Electrolyte Interface (SEI) film with low impedance, compactness and thermal stability can be formed on the negative electrode interface. The sodium tetrafluoro oxalate phosphate has low film forming impedance, and can effectively reduce the transmission resistance of sodium ions in a low-temperature environment, thereby improving the output capacity of the battery at low temperature and prolonging the cycle life of the battery at low temperature. Sodium tetrafluoro oxalate is added into the sodium ion electrolyte, so that the deterioration of an SEI film in the circulating process at high temperature can be reduced, and the circulating life of the battery at high temperature is prolonged.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements and substitutions will now be apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in some detail by the above embodiments, the invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the invention, and the scope of the invention is determined by the scope of the appended claims.

Claims (10)

1. A sodium ion electrolyte is characterized by comprising an additive, a non-aqueous solvent and a sodium salt dissolved in the non-aqueous solvent, wherein the additive comprises sodium tetrafluoro oxalate.
2. The sodium ion electrolyte of claim 1, wherein the mass of the sodium tetrafluoro oxalate is 0.1-5% of the total mass of the electrolyte.
3. The sodium ion electrolyte of claim 1, wherein the sodium salt comprises at least one of sodium hexafluorophosphate, sodium chloride, sodium fluoride, sodium sulfate, sodium carbonate, sodium phosphate, sodium nitrate, sodium tetrafluoroborate, sodium difluorooxalate, sodium bisoxalato.
4. The sodium ion electrolyte of claim 3, wherein the mass of the sodium salt is 10% to 25% of the total mass of the electrolyte.
5. The sodium ion electrolyte of claim 1, wherein the non-aqueous solvent comprises at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propionate, or propyl propionate.
6. The sodium ion electrolyte of claim 1, further comprising an auxiliary film-forming additive comprising at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, sodium difluorophosphate, and sodium bisoxalato.
7. The sodium ion electrolyte of claim 1, wherein the sodium ion electrolyte is used for preparing portable electronic equipment, power batteries and energy storage sodium power systems.
8. A sodium-ion battery comprising the sodium-ion electrolyte of any one of claims 1 to 6.
9. A method for preparing a sodium-ion battery is characterized by comprising the following steps:
obtaining a positive plate after the first current collector coated with the battery positive electrode mixture is subjected to a set process;
after the second current collector coated with the battery negative electrode mixture is subjected to the setting process, a negative plate is obtained;
and packaging the positive plate and the negative plate in a shell, and injecting an electrolyte into the shell, wherein the electrolyte comprises an additive, and the additive comprises sodium tetrafluoro oxalate phosphate.
10. The method of claim 9, wherein the battery positive electrode mixture comprises a positive electrode active material, a conductive agent, and a binder, and the battery negative electrode mixture comprises a negative electrode active material, the conductive agent, and the binder;
the positive active material comprises at least one of layered transition metal oxide, polyanion compound and Prussian blue compound;
the negative active material includes at least one of hard carbon, soft carbon, expanded graphite, carbon nanotubes, and graphene.
CN202210214690.5A 2022-03-07 2022-03-07 Sodium ion electrolyte and application thereof, sodium ion battery and preparation method thereof Pending CN114497744A (en)

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