WO2018103129A1

WO2018103129A1 - Graphene-based sodium ion battery

Info

Publication number: WO2018103129A1
Application number: PCT/CN2016/109899
Authority: WO
Inventors: 杨全红; 张俊; 吕伟; 张思伟; 郑德群; 游从辉; 康飞宇
Original assignee: 清华大学深圳研究生院
Priority date: 2016-12-09
Filing date: 2016-12-14
Publication date: 2018-06-14
Also published as: CN106785008A

Abstract

A graphene-based sodium ion battery, pertaining to the technical field of batteries. The battery comprises a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, the negative electrode sheet comprising a negative electrode current collector and a negative electrode coating disposed on the negative electrode current collector, and the negative electrode coating comprising a negative electrode active material; the electrolyte comprising a non-aqueous solvent and a sodium salt dissolved in the non-aqueous solvent, and the non-aqueous solvent comprising at least one ether compound of general formula (1) or general formula (2): R1-O-R2 (1); R1-O-(R3-O)_n-R2 (2); and the negative electrode active material comprising a graphene powder material. Compared with the prior art, in the sodium ion battery, an ether compound is used as a non-aqueous solvent for the electrolyte, and graphene is used as a negative electrode, which can significantly improve the first charge-discharge coulombic efficiency, charge-discharge specific capacity, and the cycling stability and rate of the graphene-based sodium ion battery.

Description

Graphene-based sodium ion battery

Technical field

The invention relates to the technical field of batteries, in particular to a graphene-based sodium ion battery.

Background technique

In recent years, with the rapid development of electronic equipment, power tools, and small-power electric vehicles, researching energy-efficient materials and devices with high efficiency, abundant resources, and environmental friendliness is a necessary condition for human society to achieve sustainable development. At present, the main energy storage devices are lithium-ion batteries. With the rapid expansion of lithium-ion battery applications from portable electronic devices to electric vehicles and large-scale energy storage devices, the demand for lithium will increase dramatically, but limited lithium resources. And higher prices limit its use in large-scale energy storage systems such as smart grids and renewable energy.

Sodium is one of the more abundant elements on the earth and is similar in chemical properties to lithium. Therefore, sodium ion batteries are similar to lithium ion batteries and are also a promising battery material. Compared with lithium-ion batteries, sodium-ion batteries have outstanding advantages such as low cost and good safety performance, so they are expected to be widely used in place of lithium-ion batteries in the future. Graphene has a rich surface active site and a high theoretical specific capacity, which has the potential to be a practical and commercial negative electrode for sodium ion batteries. However, when a lithium-based commercial ester solvent is used, the reductive decomposition of the solvent is severe, and irreversible reaction with a large number of defects on the surface of the graphene causes severe consumption of sodium ions during the first discharge. Heavy, and the Solid Electrolyte Interphase (SEI) generated by the reaction is also unstable, so the first cycle Coulomb efficiency is extremely low and the cycle stability is not good, which directly hinders the commercial application of the sodium ion battery.

In summary, it is necessary to provide a graphene-based sodium ion battery which can solve the strong irreversible reaction between the electrolyte and the graphene-based powder material and optimize the Coulomb efficiency, reversible specific capacity and rate performance of the first ring.

Summary of the invention

It is an object of the present invention to provide a sodium ion battery capable of effectively reducing the irreversible reaction between an electrolyte and a graphene-based powder material and further optimizing the overall electrochemical performance in view of the deficiencies of the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

A graphene-based sodium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, the negative electrode sheet including a negative electrode current collector and a negative electrode current collector a negative electrode coating on the fluid, the negative electrode coating comprising a negative active material;

The electrolyte solution includes a nonaqueous solvent and a sodium salt dissolved in the nonaqueous solvent, and the nonaqueous solvent includes at least one ether compound of the formula (1) or the formula (2):

R1-O-R2(1);

R1-O-(R3-O) _n -R2(2);

In the general formula (1) and the general formula (2), R1 and R2 are each independently a linear or branched C1 to C6 alkyl group and a linear or branched C1 to C6 hydroxyalkyl group, and R3 is straight. a chain or branched C1-C5 alkylene group, and n is an integer from 1 to 4;

The negative active material includes a graphene-based powder material.

As a modification of the graphene-based sodium ion battery of the present invention, the non-aqueous solvent is dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. At least one or a mixture of one or several.

As an improvement of the graphene-based sodium ion battery of the present invention, the electrolyte further includes an additive, and the mass ratio of the additive to the non-aqueous solvent is (0.1-20):100.

As an improvement of the graphene-based sodium ion battery of the present invention, the additives are vinyl sulfite (ES), propylene sulfite (PS), vinylene carbonate (VC) and fluoroethylene carbonate (FEC). At least one of them.

As an improvement of the graphene-based sodium ion battery of the present invention, the molar concentration of the sodium salt in the electrolyte is between 0.2 mol/L and 5 mol/L.

As a modification of the graphene-based sodium ion battery of the present invention, the sodium salt is sodium perchlorate (NaClO ₄ ), sodium hexafluorophosphate (NaPF ₆ ), and sodium trifluoromethanesulfonate (NaCF ₃ SO ₃ ). At least one or a combination of several.

As a modification of the graphene-based sodium ion battery of the present invention, the graphene is pure graphene, reduced graphene oxide or doped graphene (e.g., nitrogen-doped graphene, boron-doped graphene). When reduced graphene oxide is used, some defects are introduced into graphene during the preparation process, and these defects have certain electrochemical activities, so the reversible specific capacity is improved compared with pure graphene. In addition, doping graphene changes the electronic structure of graphene, improves conductivity and provides some additional electrochemical sites to improve overall electrochemical performance.

As an improvement of the graphene-based sodium ion battery of the present invention, after the formation, an SEI film is formed on the surface of the negative electrode coating layer, the SEI film includes an outer layer film and an inner layer film; a dense, uniform organic layer composed of a decomposition product polyether of an ether solvent and a compound (CH ₃ -CH ₂ ) ₂ -O-Na formed by decomposition of a sodium ion in the entire SEI film. The content is between 5-40%; the inner film is a dense and uniformly distributed organic and inorganic mixed layer, including 1-10 wt.% organic matter, 1-15 wt.% NaF, 1-15 wt.%. CF, 1-15 wt.% Na ₂ SO ₃ and 1-5 wt.% RSO ₂ OR, the organics including polyether and (CH ₃ -CH ₂ ) ₂ -O-Na, can promote sodium ion conduction Improve the stability of the loop.

As an improvement of the graphene-based sodium ion battery of the present invention, the graphene-based powder has a specific surface area of 100-3000 m ² /g, and when the specific surface area is not large, an effective electrochemical active site can be appropriately provided to enhance reversibility. Specific capacity; when the specific surface area is too large, it will cause a large amount of irreversible decomposition of the electrolyte, reducing the reversible specific capacity.

As an improvement of the graphene-based sodium ion battery of the present invention, the graphene-based powder contains 0.1-30% by weight of an oxygen-containing functional group, and when the number of oxygen-containing functional groups is small, the reversible specific capacity can be increased; if too much, the conductivity is affected. , reduce the specific capacity.

The sodium ion battery electrolyte provided by the invention adopts an ether compound as a non-aqueous solvent, and can greatly improve the first-loop charge and discharge coulombic efficiency, charge-discharge specific capacity, cycle stability performance and rate performance of the graphene-based sodium ion battery.

When linear ethers are used as a solvent, sodium ions are easily solvated with linear ether molecules due to "chelation", and the binding is very tight. Therefore, when the voltage is lower than 0.6-0.8V, the irreversible reaction caused by solvolysis is small; if it is ester, significant solvolysis occurs, and a great irreversible reaction occurs in the first ring, which is the first time that the Coulomb efficiency is huge. The main reason for the difference. In addition, graphene storage is mainly based on the surface electric double layer and tantalum capacitor mechanism. The solid electrolyte interface formed after the first few cycles of charge and discharge of the electrolyte with ether as a solvent is denser, more uniform, and has better ion conductivity. It is more conducive to the diffusion and reaction of sodium ions, which is the main reason for the significant improvement in cycle stability and rate performance. Finally, the reversible reactivity of ether electrolytes with graphene surface defects is higher, and ester electrolytes are more likely to irreversibly react with surface defects, which is the main reason for the large difference in charge-discharge ratio.

The sodium ion battery electrolyte provided by the invention adopts an ether compound as a non-aqueous solvent, and can greatly improve the coulombic efficiency, charge-discharge specific capacity, cycle stability energy and rate of the first ring charge and discharge of the graphene-based sodium ion battery.

DRAWINGS

1 is a graph showing charging and discharging curves of a first ring and a second ring of a sodium ion battery according to Example 1 and Comparative Example 1 of the present invention;

2 is a graph showing the charge and discharge cycle performance of the sodium ion battery of Example 1 of the present invention and Comparative Example 1;

Fig. 3 is a graph showing the performance of a sodium ion battery of Example 1 of the present invention and Comparative Example 1.

detailed description

The present invention provides a graphene-based sodium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, the negative electrode sheet including a negative electrode current collector and disposed on The negative electrode coating layer on the negative electrode current collector, the negative electrode coating layer includes a negative electrode active material; the separator is not particularly limited, and it may be a separator used in a conventional lithium ion battery.

R1-O-R2 (1);

R1-O-(R3-O) _n -R2 (2);

The negative electrode active material is a graphene-based powder material.

Preferably, each of R1 and R2 is independently selected from the group consisting of CH ₃ -, CH ₃ CH ₂ -, CH ₃ CH ₂ CH ₂ -, CH ₃ (CH) ₃ -, -CH ₂ OH, -CH ₂ CH ₂ OH, and (CH ₃ ) ₂ CH- consisting of an alkyl group or a hydroxyalkyl group.

Specifically, the linear ethers may be dimethyl ether (DME), diethylene glycol dimethyl ether (Diglyme), triethylene glycol dimethyl ether (Tiglyme), and tetraethylene glycol dimethyl ether (Tetraglyme). Wait. The non-aqueous solvent may be one or a mixture of the above-mentioned linear ethers, which is not limited in the present invention.

The solute is a sodium salt including sodium salts which can be conventionally used, such as sodium perchlorate (NaClO ₄ ), sodium hexafluorophosphate (NaPF ₆ ) and sodium trifluoromethanesulfonate (NaCF ₃ SO). ₃ ) and the like, the sodium salt may be a sodium salt or a combination of a plurality of sodium salts, which is not limited in the present invention. The sodium salt is dissolved in the non-aqueous solvent to prepare a non-aqueous electrolyte solution. In the present invention, the nonaqueous electrolytic solution has a sodium ion molar concentration of from 0.2 to 5 mol/L.

The additive may be a conventional electrolyte in the art, and the additive may be vinyl sulfite (ES), propylene sulfite (PS), vinylene carbonate (VC), fluoroethylene carbonate (FEC), etc. . In the present invention, the mass ratio of the additive to the sodium ion battery electrolyte is between 0.1% and 20%.

The preparation process of the sodium ion battery electrolyte is as follows:

First, the sodium salt should be dried, specifically dried in a vacuum oven at 110 ° C for 12 h to ensure The sodium salt is fully dried. The dried sodium salt was then transferred to a glove box, and the operation of disposing the electrolyte was all under normal temperature conditions and was completed in a glove box (water content of the glove box of less than 0.5 ppm and oxygen content of less than 0.5 ppm). Weighing, dissolving and stirring the conductive salt in the glove box and further removing water by using molecular sieve (if the water content is still high, it is treated by distillation), and finally ensuring the prepared sodium ion battery electrolyte water The content does not exceed 10 ppm. Of course, it is not limited to the preparation process in the glove box, and the preparation of the sodium ion battery electrolyte can also be performed in other oxygen-free water-free environments, which is not limited in the present invention. Table 1 lists the composition of the 45 sodium ion battery electrolytes and the ratio data of each component.

Table 1 Composition of 45 sodium ion battery electrolytes and ratio data of each component

The preparation process of the positive electrode sheet and the negative electrode sheet and the preparation process of the sodium ion battery are as follows.

The preparation process of the positive electrode sheet is as follows:

The positive active mixture includes a positive electrode material, a conductive agent, and a binder. The positive electrode material, the conductive agent, and the binder are mixed at a mass ratio of 80:10:10. Of course, the ratio can be adjusted according to actual conditions, which is not limited in the present invention. Then, an appropriate amount of N-methylpyrrolidone (NMP) was added and stirred for 6 hours to prepare a positive electrode slurry. The positive electrode slurry is then applied to the opposite faces of the positive electrode current collector, and the positive electrode current collector coated with the positive electrode slurry is placed in a vacuum drying apparatus at 110 ° C for drying, and then rolled to prepare and form. The positive electrode sheet.

Wherein the cathode current collector is an aluminum foil or a carbon coated aluminum foil. The positive electrode material may comprise any one or a combination of several suitable reversible intercalation and deintercalation of sodium ions in the art. For example, sodium cobaltate, sodium manganate, sodium vanadate, sodium iron phosphate, sodium vanadium phosphate, sodium vanadium fluorophosphate, and the like. The conductive agent may be artificial graphite, acetylene black, ketjen black, carbon fiber, graphite conductive agent, graphene or the like. The binder is a conventional binder in the art, such as polyvinylidene fluoride (PVDF).

The preparation process of the negative electrode sheet is as follows:

The negative active material mixture includes a negative electrode material, a conductive agent, and a binder. The anode material, the conductive agent, and the binder are mixed at a mass ratio of 70:10:20. Of course, the ratio can be adjusted according to actual conditions, which is not limited in the present invention. Then, an appropriate amount of NMP was added and thoroughly stirred to prepare a negative electrode slurry. Then, the negative electrode slurry is applied to the opposite faces of the negative electrode current collector, and the negative electrode current collector coated with the negative electrode slurry is dried and rolled to prepare the negative electrode sheet.

Wherein the anode current collector is a copper foil or a carbon coated copper foil.

The positive electrode sheet, the separator and the negative electrode sheet are stacked one on another, and then the three are wound into a roll-shaped battery core by a winder, and the obtained electric core is placed in a housing that is open at one end, and injected. Non-provided by the present invention The aqueous electrolyte is sealed and made into a sodium ion battery.

The electrolyte provided in the present invention is an electrolyte of an ether compound, and can be combined with a positive electrode material and a negative electrode material which are common in the art to form a plurality of sodium ion batteries of different specifications, which will not be enumerated here.

Example

In order to make the invention more obvious and obvious, the following detailed description of the preferred embodiments of the present invention is not limited by the following examples. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Example 1

In the present invention, the electrochemical test of the electrolyte is carried out using a sodium ion simulation battery of a two-electrode system, and the assembly process of the sodium ion simulation battery is as follows:

First, the negative electrode material reduction graphene oxide, conductive carbon black and polyvinylidene fluoride are dried in a vacuum oven at 60 ° C, and then thoroughly ground and mixed according to a mass ratio of 7:1:2, and then transferred to a stirring bottle by magnetic stirring. Further, it is uniformly mixed in a dry state. Then, an appropriate amount of NMP was added dropwise thereto to form a viscous slurry. The slurry was thoroughly stirred for 6 hours and then applied to a carbon coated aluminum foil current collector. Then, the above negative electrode sheet was sufficiently dried in a vacuum oven at 110 ° C for 12 hours, and then punched into a circular negative electrode sheet having a punch diameter of 14 mm, weighed and then dried again in a vacuum oven at 110 ° C.

The reduced graphene oxide has a specific surface area of 400 m ² /g, and the reduced graphene oxide contains 15 wt% of an oxygen-containing functional group.

The sodium salt of the electrolyte was selected to be NaCF ₃ SO ₃ as a solute, and Diglyme was used as a solvent (i.e., the eleventh electrolyte in Table 1), wherein the molar concentration of the sodium salt NaCF ₃ SO ₃ was 1 mol/L.

A metal sodium plate of the same diameter was used as a counter electrode. The atmosphere in the glove box in the glove box was maintained at a moisture content of less than 0.5 ppm and an oxygen content of less than 0.5 ppm.

The negative electrode sheets were taken out of the oven and quickly transferred to a glove box, and the GF/D was used as a separator, and a sodium ion analog battery was assembled in the glove box. The glove box in the glove box is an argon atmosphere with a moisture content of less than 0.5 ppm and an oxygen content of less than 0.5 ppm.

Forming a battery, after forming, an SEI film is formed on the surface of the negative electrode coating layer, the SEI film includes an outer layer film and an inner layer film; the outer layer film is a dense and uniform organic layer, and the composition is a polyether decomposition product polyether and a compound (CH ₃ -CH ₂ ) ₂ -O-Na formed by decomposing a product with sodium ions, the outer film having a content of 5-40% in the entire SEI film; The inner film is a dense, uniformly distributed organic and inorganic mixed layer comprising 1-10 wt.% of organic matter, 1-15 wt.% of NaF, 1-15 wt.% of CF, and 1-15 wt.% of Na ₂ SO ₃ and 1-5 wt.% of RSO ₂ OR, the organics include Polyether and (CH ₃ -CH ₂ ) ₂ -O-Na.

The assembled battery was subjected to constant current charge and discharge at a current density of 100 mA/g and 500 mA/g, and subjected to a magnification test at different current densities (0.05, 0.1, 0.2, 0.5, 1, 2, 5, 0.1 A/ g).

Example 2

Different from the first embodiment, in the present embodiment, the sodium salt of the electrolyte is selected from NaPF ₆ as a solute, and DME/Diglyme (1:1) is used as a solvent, wherein the molar concentration of the sodium salt NaPF ₆ is 1 mol/ L (ie, the 13th electrolyte in Table 1). The reduced graphene oxide has a specific surface area of 2000 m ² /g, and the reduced graphene oxide contains 20 wt% of an oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 3

The difference from Example 1 is that the electrolyte solution in this example is the 26th electrolyte solution in Table 1, the specific surface area of the reduced graphene oxide is 1000 m ² /g, and the reduced graphene oxide contains 12 wt% of the oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 4

The difference from the first embodiment is that the electrolyte in the present embodiment is the 26th electrolyte in Table 1, the graphene powder is pure graphene powder, and the specific surface area of pure graphene is 2200 m ² /g, pure. Graphene contains 8 wt% of an oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 5

The difference from Example 1 is that the electrolyte in this embodiment is the 32nd electrolyte in Table 1, the graphene powder is nitrogen-doped graphene, and the nitrogen-doped graphene has a specific surface area of 1300 m ² /g. The nitrogen-doped graphene contains 14% by weight of an oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 6

The difference from Example 1 is that the electrolyte in this embodiment is the 40th electrolyte in Table 1, the graphene powder is boron-doped graphene, and the boron-doped graphene has a specific surface area of 1100 m ² /g. The boron-doped graphene contains 16% by weight of an oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 7

The difference from Example 1 is that the electrolyte solution in the present embodiment is the fifth electrolyte solution in Table 1, the specific surface area of the reduced graphene oxide is 500 m ² /g, and the reduced graphene oxide contains 5 wt% of the oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 8

The difference from Example 1 is that the electrolyte solution in the present embodiment is the seventh electrolyte solution in Table 1, the specific surface area of the reduced graphene oxide is 300 m ² /g, and the reduced graphene oxide contains 3 wt% of the oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 9

The difference from Example 1 is that the electrolyte solution in the present embodiment is the fifteenth electrolyte solution in Table 1, the specific surface area of the reduced graphene oxide is 600 m ² /g, and the reduced graphene oxide contains 7 wt% of the oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Example 10

The difference from Example 1 is that the electrolyte solution in the present embodiment is the 22nd electrolyte solution in Table 1, the specific surface area of the reduced graphene oxide is 700 m ² /g, and the reduced graphene oxide contains 8 wt% of the oxygen-containing functional group. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

Comparative example 1

In the present comparative example, the sodium ion battery electrolyte was selected to have a volume ratio of 1:1 EC/DEC as a solvent, NaCF ₃ SO _{3 was selected} as a solute, and the molar concentration of NaCF ₃ SO ₃ in the electrolyte was 1 mol/L. Other conditions A sodium ion analog battery was fabricated and tested in the same manner as in Example 1.

The electrochemical performance of the sodium ion battery prepared in this example and the sodium ion battery prepared in Example 1 was compared. Please refer to FIG. 1 to FIG. 3 at the same time, wherein FIG. 1 is a graph showing charging and discharging of the first ring of the sodium ion battery of Example 1 and Comparative Example 1 of the present invention. It can be clearly seen from Fig. 1 that the sodium ion battery electrolyte using the solute of NaCF ₃ SO ₃ and Diglyme as the solvent has a Coulomb efficiency of the first cycle compared to the sodium ion simulation battery of the solvent EC/DEC. There is a big improvement, as shown in Table 2, which is from 34.5% to 74.6%. In addition, the reversible charging capacity was also increased from 408 mAh/g of EC/DEC as a solvent to 556 mAh/g of Diglyme as a solvent. 2 is a graph showing the 100-time charge and discharge cycle performance of the sodium ion battery of Inventive Example 1 and Comparative Example 1. After circulating 100 cycles at a current density of 100 mA/g, the reversible charging specific capacity of the sodium ion battery of Diglyme as a solvent is almost It is twice the sodium ion battery of EC/DEC as a solvent. See Table 2 for details. The reversible charge specific capacity is increased from 262 mAh/g to 509 mAh/g. 3 is a graph showing the rate performance of the sodium ion battery of Inventive Example 1 and Comparative Example 1. The magnification test is performed at different current densities, especially at a large current density, and the sodium ion battery of Diglyme as a solvent is used as a solvent compared to EC/DEC. The sodium ion battery still has a huge advantage.

Table 2: Performance test results of Examples 1 to 10 and Comparative Example 1.

It can be seen from the test results that the sodium ion-simulated battery in Example 1 using the reduced graphene oxide as the anode material and the Diglyme as the solvent and the solute as the electrolyte of NaCF ₃ SO ₃ is the first ring charge and discharge efficiency and charge The discharge specific capacity, cycle stability, or rate performance was greatly improved as compared with the sodium ion analog battery in Comparative Example 1. When linear ethers are used as a solvent, the irreversible reaction caused by solvolysis is small, which is the main reason for the significant increase in the first coulombic efficiency. In addition, the solid electrolyte interface formed after the first few cycles of charge and discharge of the electrolyte with ether as solvent is denser, more uniform and more ionic conductive, which is more conducive to the diffusion and reaction of sodium ions, which is caused by cycle stability. And the main reason for the significant improvement in rate performance. Finally, the reversible reactivity of ether electrolytes with graphene surface defects is higher, and ester electrolytes are more likely to irreversibly react with surface defects, which is the main reason for the large difference in charge-discharge ratio.

Claims

A graphene-based sodium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, the negative electrode sheet including a negative electrode current collector and a negative electrode current collector a negative electrode coating on the fluid, the negative electrode coating comprising a negative active material;

The electrolyte solution includes a nonaqueous solvent and a sodium salt dissolved in the nonaqueous solvent, wherein the nonaqueous solvent includes at least one ether represented by the general formula (1) or the general formula (2). Compound:

R1-O-R2 (1);

R1-O-(R3-O) n -R2 (2);

In the general formula (1) and the general formula (2), R1 and R2 are each independently a linear or branched C1 to C6 alkyl group and a linear or branched C1 to C6 hydroxyalkyl group, and R3 is straight. a chain or branched C1-C5 alkylene group, and n is an integer from 1 to 4;

The negative active material includes a graphene-based powder material.
The graphene-based sodium ion battery according to claim 1, wherein the nonaqueous solvent is dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol a mixture of at least one of one or more of methyl ethers.
The graphene-based sodium ion battery according to claim 1, wherein the electrolyte further comprises an additive, and the mass ratio of the additive to the non-aqueous solvent is (0.1-20):100.
The graphene-based sodium ion battery according to claim 3, wherein the additive is vinyl sulfite (ES), propylene sulfite (PS), vinylene carbonate (VC), and At least one of fluoroethylene carbonate (FEC).
The graphene-based sodium ion battery according to claim 1, wherein the molar concentration of the sodium salt in the electrolytic solution is between 0.2 mol/L and 5 mol/L.
The graphene-based sodium ion battery electrolyte according to claim 5, wherein the sodium salt is sodium perchlorate (NaClO 4 ), sodium hexafluorophosphate (NaPF 6 ), and sodium trifluoromethanesulfonate. At least one or a combination of several of (NaCF 3 SO 3 ).
The graphene-based sodium ion battery according to claim 1, wherein the graphene is pure graphene, reduced graphene oxide or doped graphene.
The graphene-based sodium ion battery according to claim 1, wherein after the formation, an SEI film is formed on a surface of the negative electrode coating layer, the SEI film comprising an outer layer film and an inner layer film; The film is a dense, uniform organic layer composed of a decomposition product polyether of an ether solvent and a compound (CH 3 -CH 2 ) 2 -O-Na formed by decomposition products with sodium ions. The content in the SEI film is between 5-40%; the inner film is a dense, uniformly distributed organic and inorganic mixed layer, including 1-10 wt.% organic matter, 1-15 wt.% NaF, 1 -15 wt.% CF, 1-15 wt.% Na 2 SO 3 and 1-5 wt.% RSO 2 OR, the organics include polyether and (CH 3 -CH 2 ) 2 -O-Na.
The graphene-based sodium ion battery according to claim 1, wherein the graphene-based powder has a specific surface area of from 100 to 3,000 m 2 /g.
The graphene-based sodium ion battery according to claim 1, wherein the graphene-based powder contains 0.1 to 30% by weight of an oxygen-containing functional group.