CATHODE MATERIAL PREPARATION METHOD, CATHODE MATERIAL AND LITHIUM-ION BATTERY

Abstract

The present invention is related to the method for producing the cathode material, cathode material and lithium-ion battery. The present invention provides the higher capacity and number of recharge cycles. The lithium battery comprises the metallic lithium anode, electrolyte and a cathode comprising metallic current collector coated with a suspension (concentration 0.1-1 g/mL) of composite material comprising V.sub.2O.sub.5 nanorods in graphene shell, dissolved in acetone.

Claims

1. A method for producing composite cathode material comprising the following steps: synthesis of V.sub.2O.sub.5 hydrogel or xerogel; heating a mixture of vanadia hydrogel (or xerogel) and carbon material in sealed Teflon autoclave at 130-200° C. and pressure 100-600 MPa for 24 hours, to obtain composite material comprising vanadia nanorods in graphene shell; centrifuging of the resulting composite material; washing the composite material; drying the composite material at 50° C.

2. The method for producing composite cathode material in accordance with claim 1, wherein the mixture contains components in the following content, mass. %: Vanadia hydrogel or xerogel—60-95; Carbon material—5-40.

3. The method for producing composite cathode material in accordance with claim 1, wherein the hydrogel or xerogel is obtained as a result of hydrolysis of organic derivatives of vanadic acid or by polycondensation of vanadates in aqueous solution in acidic media, or by decomposition of peroxovanadate compounds formed after dissolution of crystalline V.sub.2O.sub.5 in hydrogen peroxide solution.

4. The method for producing composite cathode material in accordance with claim 1, wherein the carbon material is preliminary treated with the hydrogen peroxide solution in acidic media.

5. The method for producing composite cathode material in accordance with claim 4, wherein the carbon material can be chosen from the group: graphite oxide, reduced graphite oxide, acetylene black, activated carbon.

6. A composite cathode material according to claim 1, comprising the V.sub.2O.sub.5 core and graphene shell.

7. Lithium battery comprising metallic Li anode, electrolyte and a cathode coated with the suspension (concentration 0.1-1 g/mL) of the composite material from the claim 6, dissolved in acetone.

8. The battery from the claim 7, wherein the current collector is plate or mesh.

9. Battery from the claim 8, wherein the coating suspension of the current collector additionally contain hydrophobic polymer binder with content of 0-20 mass. %.

10. The battery from the claim 9, wherein the hydrophobic polymer binder can be chosen from the group: poly(vinyliden fluoride), poly(tetrafluorethylene).

11. The battery from the claim 7, wherein the electrolyte contains salt dissolved in the solvent, where salt is chosen from the group: lithium perchlorate, lithium hexafluoruphosphate, lithium tetrafluoroborate.

12. The battery from the claim 11, wherein the solvent is chosen from the group: propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethylsulfoxide, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis-triflouromethylsulfonilimide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis-triflouromethylsulfonilimide, 1-methyl-1-propylpiperidin hexafluorophosphate, 1-methyl-1-propylpiperidin bis-triflouromethylsulfonilimide and mixture thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1—Galvanostatic discharge curve of the lithium battery comprising the cathode material from the closest analogue in the prior art.

[0027] FIG. 2—Galvanostatic discharge curve of lithium battery comprising the cathode material composed of V.sub.2O.sub.5 nanorods in graphene shell.

[0028] FIG. 3—Galvanostatic discharge curve of lithium battery comprising the cathode material composed of V.sub.2O.sub.5 nanorods in graphene shell, at current 0.1 C after 30 recharge cycles. Black curve represents the 1st discharge cycle, grey curve—30th discharge cycle.

[0029] FIG. 4—Galvanostatic charge curve of lithium battery comprising the cathode material composed of V.sub.2O.sub.5 nanorods in graphene shell, at current 0.1 C after 30 recharge cycles. Black curve represents the 1st charge cycle, grey curve—30th charge cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The method for producing the composite cathode material contains the following steps: [0031] producing V.sub.2O.sub.5 hydrogel or xerogel; [0032] heating a mixture of vanadia hydrogel (or xerogel) and carbon material in sealed Teflon autoclave at 130-200° C. and pressure 100-600 MPa for 24 hours, to obtain composite material comprising vanadia nanorods in graphene shell; [0033] centrifuging of the resulting composite material; [0034] washing the composite material; [0035] drying the composite material at 50° C.

[0036] The mixture comprises the following components with the content, mass. %:

[0037] Vanadia hydrogel or xerogel—60-95;

[0038] Carbon material—5-40.

[0039] The carbon material content less than 5 mass. % causes low electrical conductivity of the cathode material, thus decreasing characteristics of the battery. The carbon content more than 40 mass. % lowers the specific capacity of the cathode material due to the high amount of inactive carbon material in the composite cathode.

[0040] Hydrogel or xerogel can be obtained by the hydrolysis of organic derivatives of vanadic acid or by polycondensation of vanadates in aqueous solution in acidic media, or by decomposition of peroxovanadate compounds formed after dissolution of crystalline V.sub.2O.sub.5 in hydrogen peroxide solution.

[0041] Carbon material is preliminary treated with hydrogen peroxide solution in acidic media.

[0042] Treatment of carbon material with hydrogen peroxide solution provides better adhesion of carbon material to the V.sub.2O.sub.5 surface.

[0043] Carbon material can be chosen from the group: graphite oxide, reduced graphite oxide, acetylene black, activated carbon.

[0044] Composite material comprises the V.sub.2O.sub.5 core and graphene shell.

[0045] Lithium battery contains the housing with the space to place the cathode and the metallic Li anode, that are separated from each other by the liquid electrolyte that is filled into the battery housing, and the cathode comprises metallic current collector coated with the suspension (concentration 0.1-1 g/mL) of composite material dissolved in acetone.

[0046] If concentration of the suspension is less than 0.1 g/mL, the viscosity of the suspension is low, and if the concentration is more than 1 g/mL, the viscosity is too high, that does not allow to coat and fix the composite material on the current collector uniformly.

[0047] Current collector is made of foil or mesh.

[0048] The suspension for coating the current collector can additionaly contain hydrophobic polymer binder with content of 0-20 mass. %. The content of the hydrophobic binder more than 20 mass. % leads to the decrease in electrical conductivity of the cathode material.

[0049] Hydrophobic polymer binder can be chosen from the group: poly(vinyliden fluoride), poly(tetrafluorethylene).

[0050] Electrolyte contains salt that is dissolved in the solvent and can be chosen from the group: lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate.

[0051] The solvent can be chosen from the group: propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethylsulfoxide, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis-triflouromethylsulfonilimide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis-triflouromethylsulfonilimide, 1-methyl-1-propylpiperidin hexafluorophosphate, 1-methyl-1-propylpiperidin bis-triflouromethylsulfonilimide and mixture thereof.

EXAMPLE 1

[0052] V.sub.2O.sub.5 hydrogel is obtained by the hydrolysis of organic derivatives of vanadic acid. Then hydrogel in content of 60 mass. % is mixed with carbon material in content of 40 mass. %, chosen from the group: graphite oxide, reduced graphite oxide, acetylene black, activated carbon. The mixture of hydrogel and carbon material is placed in sealed Teflon autoclave at 200° C. and pressure 100 MPa for 24 hours, to obtain composite material containing V.sub.2O.sub.5 nanorods in graphene shell. After that the composite material is centrifuged to separate it from the solution. Then composite material is washed in distilled water to remove the impurities, e.g. hydrogen ions and vanadate-ions, and dried at 50° C.

EXAMPLE 2

[0053] V.sub.2O.sub.5 hydrogel is obtained by the polycondensation of vanadates in aqueous solution in acidic media. Then V.sub.2O.sub.5 hydrogel in content of 95 mass. % is mixed with carbon material in content 5 mass. % chosen from the group: graphite oxide, reduced graphite oxide, acetylene black, activated carbon. The mixture of hydrogel and carbon material is placed in sealed Teflon autoclave at 130° C. and pressure 600 MPa for 24 hours, to obtain composite material cotaining V.sub.2O.sub.5 nanorods in graphene shell. After that the composite material is centrifuged to separate it from the solution. Then the composite material is washed in distilled water to remove the impurities, e.g. hydrogen ions and vanadate-ions, and dried at 50° C.

Example 3

[0054] The battery comprising metallic lithium anode, cathode comprising metallic current collector coated with the suspension (concentration 0.5 g/mL) of composite material containing V.sub.2O.sub.5 nanorods in graphene shell, dissolved in acetone, and electrolyte containing 1 M LiCIO.sub.4 in a mixture of propylene carbonate and dimethoxyethane in a volume ratio of 7:3, operates as follows. At the battery discharge lithium anode is dissolved in electrolyte forming Li.sup.+ions. As the electrolyte solution contains LiCIO.sub.4 salt, Li.sup.+ions from the electrolyte are intercalated into the cathode material structure forming Li-containing phases. At battery charge Li.sup.+ions are deintercalated from the cathode material structure into electrolyte and uniformly deposited as a metal on the anode surface.

[0055] Experiments showed that, in contrast to the battery described in the closest analogue, for the battery of the present invention comprising the cathode that contains metallic current collector coated with the suspension (concentration 0.1-1 g/mL) of composite material, that was obtained according to the present invention and contains V.sub.2O.sub.5 nanorods in graphene shell, the specific capacity increases for 150 mAh/g (FIG. 1, 2) and capacity fade after 30 cycles is not higher than 3% (FIG. 3, 4).

[0056] Thus, the battery from the present invention provides higher capacity and higher number of recharge cycles.

[0057] Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains, after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.