CN111987356A - Long-term circulating sodium-carbon fluoride secondary battery and preparation method thereof - Google Patents

Abstract

The invention discloses a long-term circulating sodium fluorocarbon secondary battery and a preparation method thereof, wherein the battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is a sodium ion solid electrolyte, and the sodium ion solid electrolyte is prepared from polyvinylidene fluoride, a sodium ion conductor and sodium salt; the active material of the positive electrode is carbon fluoride, and the negative electrode is metal sodium. The sodium ion solid electrolyte membrane prepared by the invention belongs to a flexible membrane, adopts polyvinylidene fluoride as a matrix, has good chemical compatibility with a metal sodium cathode, and can be used without adding an isolation layer. The sodium ion solid electrolyte is used for replacing liquid electrolyte, so that the safety of the sodium-carbon fluoride secondary battery can be effectively improved, and the circulation stability is improved. The preparation method is simple and energy-saving.

Description

Long-term circulating sodium-carbon fluoride secondary battery and preparation method thereof

Technical Field

The invention relates to a secondary battery, in particular to a sodium-fluorinated carbon secondary battery adopting long-acting circulation of solid electrolyte.

Background

The carbon fluoride anode material has excellent characteristics of high specific capacity, stable electrochemistry, stable discharge platform and the like, and is widely applied to the lithium primary battery. In recent years, fluorinated Carbon positive electrode materials have attracted attention in room temperature sodium secondary batteries (w.liu, h.li, j. -y.xie, z. -w.fu, ACS appl.mater.interfaces 2014,6, 2209; w.liu, z.shape, Carbon,93,2015,523; y.shao, h.yue, chem.mater.2016,28,1026), magnesium primary batteries (x.miao, j.yang, w.pan, h.yuan, y.nuli, s.i.hirano, electrochim.acta 2016). But at present Na/CF_xThe liquid electrolyte used by the system has potential safety hazard; in addition, in the liquid electrolyte, the loss of active materials is easily caused, and the poor cycle performance is caused.

Disclosure of Invention

The invention aims to overcome the defect of poor circulation performance of liquid electrolyte in the prior art, and the sodium ion solid electrolyte is used for replacing the liquid electrolyte, and polyvinylidene fluoride is selected as a matrix as an electrolyte material, so that the polyvinylidene fluoride has good chemical compatibility with a metal sodium electrode. In addition, the conventional method for preparing the sodium ion solid electrolyte needs high temperature, long-time sintering, ball milling and other processes, the preparation process is complicated, the energy consumption is high, and the invention also provides a simple and energy-saving method for preparing the sodium ion solid electrolyte.

In order to achieve the purpose, the invention provides a long-acting circulating sodium-carbon fluoride secondary battery, which comprises a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is a sodium ion solid electrolyte prepared from polyvinylidene fluoride, a sodium ion conductor and a sodium salt; the active material of the positive electrode is carbon fluoride, and the negative electrode is metal sodium.

Preferably, the sodium salt is NaTFSI and NaPF₆、NaSO₂CF₃、NaClO₄And NaFSI.

Preferably, the sodium ion conductor material is Al₂O₃、Na₃PS₄、Na₄SiS₄、Na₃PSe₄、NaM₁M₂(PO₄)₃One or more of; the NaM₁M₂(PO₄)₃In, M₁、M₂Are respectively selected from Zn²⁺,Cd²⁺,Ni²⁺,Mn²⁺,Co²⁺,Fe³⁺,Sc³⁺,Ti³⁺,V³⁺,Cr³⁺,Al³⁺,In³⁺,Ga³⁺,Y³⁺,Lu³⁺,Ti⁴⁺,Zr⁴⁺,Hf⁴⁺,Sn⁴⁺,Si⁴⁺,Ge⁴⁺,V⁵⁺,Nb⁵⁺,Ta⁵⁺,Sb⁵⁺Or As⁵⁺Any one of the ions.

The invention also provides a preparation method of the long-term circulating sodium fluorocarbon secondary battery, which comprises the following steps:

s1, preparing a sodium ion solid electrolyte;

s2, preparing a positive plate;

and S3, assembling the positive plate prepared in the step S2 into the long-acting circulating sodium-carbon fluoride secondary battery by taking metal sodium as a negative electrode and taking the sodium ion solid electrolyte prepared in the step S1 as a diaphragm and an electrolyte under the condition of dry air or inert atmosphere.

Preferably, step S1 includes the steps of:

s1.1, dissolving polyvinylidene fluoride in a solvent to prepare a solution;

s1.2, adding sodium salt into the solution, fully stirring, adding a sodium ion conductor material, and stirring overnight;

and S1.3, preparing the solution into a membrane to obtain the sodium ion solid electrolyte.

Preferably, in S1.1, the concentration of the polyvinylidene fluoride is 10-50 mg/ml; the solvent is one of dimethylformamide, acetonitrile, dimethyl carbonate and tetrahydrofuran.

Preferably, in S1.2, the sodium salt is NaTFSI or NaPF₆、NaSO₂CF₃、NaClO₄One or more of NaFSI, the content is 5-15 mg/ml; the sodium ion conductor material is Al₂O₃、Na₃PS₄、Na₄SiS₄、Na₃PSe₄、NaM₁M₂(PO₄)₃One or more of the above (1), the content is 2-15 mg/ml; the NaM₁M₂(PO₄)₃In, M₁、M₂Are respectively selected from Zn²⁺,Cd^{2 +},Ni²⁺,Mn²⁺,Co²⁺,Fe³⁺,Sc³⁺,Ti³⁺,V³⁺,Cr³⁺,Al³⁺,In³⁺,Ga³⁺,Y³⁺,Lu³⁺,Ti⁴⁺,Zr⁴⁺,Hf⁴⁺,Sn⁴⁺,Si^{4 +},Ge⁴⁺,V⁵⁺,Nb⁵⁺,Ta⁵⁺,Sb⁵⁺Or As⁵⁺Any one of the ions.

Preferably, the film forming method described in S1.3 is a casting method.

Preferably, step S2 includes the steps of:

s2.1, dispersing the lamellar carbon material in water under the action of a surfactant to form lamellar carbon dispersion liquid; the lamellar carbon material is selected from any one or more than two of graphene, graphene oxide, nitrogen-doped graphene, sulfur-doped graphene or phosphorus-sulfur-doped graphene;

s2.2, adding a positive active substance and a conductive agent into the lamellar carbon dispersion liquid to prepare a positive active substance dispersion liquid; the material of the positive electrode active substance is a carbon fluoride material, and the carbon fluoride material is any one or more than two of graphite fluoride, carbon fluoride nanotubes, graphene fluoride, carbon fluoride fibers, carbon fluoride nano discs and fluorinated coke; the conductive agent is one or more of superconductive carbon black, acetylene black, conductive graphite, conductive carbon fiber, carbon nano tube and the like;

and S2.3, filtering the positive active substance dispersion liquid, forming a film, drying and removing to obtain the carbon fluoride positive pole piece.

Preferably, step S2 includes the steps of:

s2.1, dissolving the adhesive to prepare a uniform solution; the adhesive is one of polyvinylidene fluoride and LA132/133, and the mass ratio is 5% -15%;

s2.2, adding the positive active substance and the conductive agent into the solution to prepare carbon fluoride positive active substance slurry; the anode active substance is made of carbon fluoride materials, the carbon fluoride materials are selected from one or more of graphite fluoride, carbon fluoride nanotubes, fluorinated graphene, carbon fluoride fibers, carbon fluoride nano disks and fluorinated coke, the conductive agent is one or more of superconducting carbon black, acetylene black, conductive graphite, conductive carbon fibers, carbon nanotubes and graphene, and the mass ratio of the conductive agent to the conductive agent is 10-40%;

s2.3, coating the carbon fluoride anode active substance slurry on the surface of the current collector, and drying to obtain a carbon fluoride anode material; the current collector is made of one of aluminum foil, carbon-coated aluminum foil and corrosion aluminum foil, and the drying temperature is 80-100 ℃.

The beneficial effects of the invention include:

(1) the sodium ion solid electrolyte membrane prepared by the invention belongs to a flexible membrane, adopts polyvinylidene fluoride as a matrix, has good chemical compatibility with a metal sodium cathode, and can be used without adding an isolation layer.

(2) The sodium ion solid electrolyte is used for replacing liquid electrolyte, so that the safety of the sodium-carbon fluoride secondary battery can be effectively improved, and the circulation stability is improved.

(3) The preparation method is simple and energy-saving.

Drawings

Fig. 1 is a microscopic morphology view of a sodium ion solid electrolyte prepared in example 1 of the present invention.

Fig. 2 is a graph showing the results of voltage stability tests of the sodium ion solid electrolyte prepared in example 1 of the present invention.

Fig. 3 is a charge-discharge graph of a long-cycling sodiumfluoride secondary battery prepared in example 1 of the present invention.

Fig. 4 is a graph showing the results of cycle stability tests for a long-cycling sodiumfluoride secondary battery prepared in example 1 of the present invention.

Fig. 5 is a microscopic morphology view of a sodium ion solid electrolyte prepared in example 2 of the present invention.

Fig. 6 is a graph showing the results of cycle stability tests for a long-cycling sodiumfluoride secondary battery prepared in example 2 of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

When the sodium ion solid electrolyte is prepared, the crystallinity of a polymer matrix is reduced by adding the sodium salt, the chain scission movement of the polyvinylidene fluoride is improved, the sodium ion conduction capability is improved, and the impedance of a battery is reduced. By adding the sodium ion conductor, the electrochemical window is expanded, the working temperature range of the battery is improved, the internal resistance of the battery is reduced, and the ionic conductivity, the electrochemical stability and the mechanical strength of the solid electrolyte are improved.

Example 1

Preparing a sodium ion solid electrolyte: 0.3g of polyvinylidene fluoride was dissolved in 15mL of dimethylformamide. After the polyvinylidene fluoride is completely dissolved, 0.1g of NaTFSI is added, and after the mixture is fully stirred for 4 hours, 0.09g of alumina is added, and the mixture is stirred overnight. The film is formed by adopting a tape casting method, and the specific implementation mode is as follows: pouring the solution into a mold, and heating the solution in vacuum at 60 ℃ to form a film, wherein the vacuum degree is-0.1 MPa. The micro-topography is shown in fig. 1. The voltage stability test results are shown in fig. 2, and the electrolyte is in a stable state when the voltage is lower than 4.7V. Therefore, when the voltage of the positive electrode is lower than 4.7V, the sodium ion solid electrolyte prepared by the method is suitable for a sodium fluorocarbon secondary system and has better electrochemical stability.

Preparing a positive plate: and dispersing 5mg of graphene oxide in 50ml of deionized water, performing ultrasonic treatment to form a uniform solution, sequentially adding 5mg of superconducting carbon black conductive agent and 15mg of graphite fluoride material, and performing ultrasonic treatment for 3 hours to obtain the modified carbon fluoride anode dispersion solution. After suction filtration, the anode is taken off and dried at 85 ℃.

Assembling a sodium-carbon fluoride secondary battery: and (3) punching and cutting the prepared graphite fluoride anode into a round pole piece with phi of 14mm, and drying for 24 hours in a vacuum drying oven at 85 ℃. Under the condition of dry air or inert atmosphere, a metal sodium sheet is taken as a negative electrode, and the prepared sodium ion solid electrolyte is taken as a diaphragm and an electrolyte to assemble the CR2016 button cell.

The cell was discharged to 1.0V at a current density of 50mA/g and then charged to 4.3V. The charge and discharge curves are shown in fig. 3. As shown in fig. 4, the capacity retention rate was 75.6% after 50 cycles. At present, the longest cycle life reported at home and abroad is 65 times, and the capacity retention rate is 52.2% (chem.Commun., 2018, 54, 2341), and according to the data in the text, the capacity retention rate of the battery is less than 60% when the battery is cycled for 50 times. Therefore, the sodium-fluorinated carbon secondary battery prepared by the invention has good cycling stability.

Example 2

Preparing a sodium ion solid electrolyte: 0.3g of polyvinylidene fluoride was dissolved in 15mL of dimethylformamide. After the polyvinylidene fluoride is completely dissolved, 0.1g of NaTFSI is added, the mixture is fully stirred for 4 hours, and 0.09g of Na is added₃Zr₂Si₂PO₁₂And stirred overnight. The film is formed by adopting a tape casting method, and the specific implementation mode is as follows: pouring the solution into a mold, and heating the solution in vacuum at 60 ℃ to form a film, wherein the vacuum degree is-0.1 MPa. The micro-topography is shown in fig. 5.

Preparing a positive plate: 100mg of polyvinylidene fluoride was dissolved in 3ml of N-methylpyrrolidone (NMP) and stirred to form a uniform solution. Adding 800mg of carbon fluoride intermediate phase carbon microspheres and 100mg of superconducting carbon black conductive agent into the solution, and stirring for 8 hours to obtain carbon fluoride anode active substance slurry. And coating the carbon fluoride anode active substance slurry on the surface of the carbon aluminum foil, and drying at 100 ℃ to obtain the carbon fluoride anode material.

Assembling a sodium-carbon fluoride secondary battery: and (3) punching and cutting the prepared graphite fluoride anode into a round pole piece with phi of 14mm, and drying for 24 hours in a vacuum drying oven at 85 ℃. Under the condition of dry air or inert atmosphere, a metal sodium sheet is taken as a negative electrode, and the prepared sodium ion solid electrolyte is taken as a diaphragm and an electrolyte to assemble the CR2016 button cell.

The cell was discharged to 1.0V at a current density of 50mA/g and then charged to 4.3V. As shown in fig. 6, the capacity retention rate of the battery was 70.2% after 50 cycles.

In conclusion, the invention provides a sodium-carbon fluoride secondary battery with long-term circulation, which adopts a sodium ion solid electrolyte membrane to replace a conventional liquid electrolyte, can effectively improve the safety of the sodium-carbon fluoride secondary battery, and simultaneously improves the circulation stability. The prepared sodium ion solid electrolyte belongs to a flexible membrane, adopts polyvinylidene fluoride as a matrix, has good chemical compatibility with a metal sodium cathode, and can be used without adding an isolation layer. The preparation method is simple and energy-saving.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.

Claims (10)

1. The long-acting circulating sodium-carbon fluoride secondary battery is characterized by comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is a sodium ion solid electrolyte prepared from polyvinylidene fluoride, a sodium ion conductor and sodium salt; the active material of the positive electrode is carbon fluoride, and the negative electrode is metal sodium.

2. The long-term circulating sodium fluorinated carbon secondary cell of claim 1 wherein the sodium salt is NaTFSI, NaPF₆、NaSO₂CF₃、NaClO₄And NaFSI.

3. The long-term circulating sodium fluorinated carbon secondary cell of claim 1 wherein the sodium ion conductor material is Al₂O₃、Na₃PS₄、Na₄SiS₄、Na₃PSe₄、NaM₁M₂(PO₄)₃One or more of; the NaM₁M₂(PO₄)₃In, M₁、M₂Are respectively selected from Zn²⁺,Cd²⁺,Ni²⁺,Mn²⁺,Co²⁺,Fe³⁺,Sc³⁺,Ti³⁺,V³⁺,Cr³⁺,Al³⁺,In³⁺,Ga³⁺,Y³⁺,Lu^{3 +},Ti⁴⁺,Zr⁴⁺,Hf⁴⁺,Sn⁴⁺,Si⁴⁺,Ge⁴⁺,V⁵⁺,Nb⁵⁺,Ta⁵⁺,Sb⁵⁺Or As⁵⁺Any one of the ions.

4. A method of making a long-cycle sodiumfluorocarbon secondary battery as claimed in claim 1, comprising the steps of:

s1, preparing a sodium ion solid electrolyte;

s2, preparing a positive plate;

and S3, assembling the positive plate prepared in the step S2 into the long-acting circulating sodium-carbon fluoride secondary battery by taking metal sodium as a negative electrode and taking the sodium ion solid electrolyte prepared in the step S1 as a diaphragm and an electrolyte under the condition of dry air or inert atmosphere.

5. The method of manufacturing a long-term cycling sodium fluorocarbon secondary battery as claimed in claim 4, wherein step S1 includes the steps of:

s1.1, dissolving polyvinylidene fluoride in a solvent to prepare a solution;

s1.2, adding sodium salt into the solution, fully stirring, adding a sodium ion conductor material, and stirring overnight;

and S1.3, preparing the solution into a membrane to obtain the sodium ion solid electrolyte.

6. The method for manufacturing a long-term cycling sodium fluorocarbon secondary battery as claimed in claim 5, wherein in S1.1, the concentration of polyvinylidene fluoride is 10-50 mg/ml; the solvent is one of dimethylformamide, acetonitrile, dimethyl carbonate and tetrahydrofuran.

7. The method of claim 5, wherein in S1.2, the sodium salt is NaTFSI or NaPF₆、NaSO₂CF₃、NaClO₄One or more of NaFSI, the content is 5-15 mg/ml; the sodium ion conductor material is Al₂O₃、Na₃PS₄、Na₄SiS₄、Na₃PSe₄、NaM₁M₂(PO₄)₃One or more of the above (1), the content is 2-15 mg/ml; the NaM₁M₂(PO₄)₃In, M₁、M₂Are respectively selected from Zn²⁺,Cd²⁺,Ni²⁺,Mn²⁺,Co²⁺,Fe³⁺,Sc³⁺,Ti³⁺,V³⁺,Cr³⁺,Al³⁺,In³⁺,Ga³⁺,Y³⁺,Lu³⁺,Ti⁴⁺,Zr⁴⁺,Hf⁴⁺,Sn⁴⁺,Si⁴⁺,Ge⁴⁺,V⁵⁺,Nb⁵⁺,Ta⁵⁺,Sb⁵⁺Or As⁵⁺Any one of the ions.

8. The method of claim 5, wherein the film forming process of S1.3 is a casting process.

9. The method of manufacturing a long-term cycling sodium fluorocarbon secondary battery as claimed in claim 4, wherein step S2 includes the steps of:

s2.1, dispersing the lamellar carbon material in water under the action of a surfactant to form lamellar carbon dispersion liquid; the lamellar carbon material is selected from any one or more than two of graphene, graphene oxide, nitrogen-doped graphene, sulfur-doped graphene or phosphorus-sulfur-doped graphene;

s2.2, adding a positive active substance and a conductive agent into the lamellar carbon dispersion liquid to prepare a positive active substance dispersion liquid; the material of the positive electrode active substance is a carbon fluoride material, and the carbon fluoride material is any one or more than two of graphite fluoride, carbon fluoride nanotubes, graphene fluoride, carbon fluoride fibers, carbon fluoride nano discs and fluorinated coke; the conductive agent is one or more of superconductive carbon black, acetylene black, conductive graphite, conductive carbon fiber, carbon nano tube and the like;

and S2.3, filtering the positive active substance dispersion liquid, forming a film, drying and removing to obtain the carbon fluoride positive pole piece.

10. The method of manufacturing a long-term cycling sodium fluorocarbon secondary battery as claimed in claim 4, wherein step S2 includes the steps of:

s2.1, dissolving the adhesive to prepare a uniform solution; the adhesive is one of polyvinylidene fluoride and LA132/133, and the mass ratio is 5% -15%;

s2.2, adding the positive active substance and the conductive agent into the solution to prepare carbon fluoride positive active substance slurry; the anode active substance is made of carbon fluoride materials, the carbon fluoride materials are selected from one or more of graphite fluoride, carbon fluoride nanotubes, fluorinated graphene, carbon fluoride fibers, carbon fluoride nano disks and fluorinated coke, the conductive agent is one or more of superconducting carbon black, acetylene black, conductive graphite, conductive carbon fibers, carbon nanotubes and graphene, and the mass ratio of the conductive agent to the conductive agent is 10-40%;

s2.3, coating the carbon fluoride anode active substance slurry on the surface of the current collector, and drying to obtain a carbon fluoride anode material; the current collector is made of one of aluminum foil, carbon-coated aluminum foil and corrosion aluminum foil, and the drying temperature is 80-100 ℃.

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