POROUS TIN FOIL ANODE, A METHOD FOR PREPARING THE SAME AND A SODIUM ION SECONDARY BATTERY

Abstract

A porous tin foil anode includes a porous tin foil. A plurality of holes are uniformly formed on the porous tin foil. A triangular area formed by lines connecting centers of three adjacent holes is used as a smallest unit. The proportion of the area of the holes in each smallest unit is 1%-89%. The distance between the edge of the porous tin foil and the hole is 0.1 mm-10 mm. The porous tin foil anode can be applied to a sodium ion battery system that uses tin foil as both a current collector and an anode active material, which effectively solves the problem of battery expansion and alleviates the problem of decomposition of the solid electrolyte membrane during the charge and discharge process of the battery. The short circuiting that occurs because of burrs on the tin foil puncturing the separator is also eliminated.

Claims

1. A porous tin foil anode, comprising a porous tin foil; wherein a plurality of holes are uniformly formed on the porous tin foil; a triangular area formed by lines connecting centers of three adjacent holes of the plurality of holes is used as a first smallest unit; a proportion of an area of the three adjacent holes in each first smallest unit is 1%-89%; a distance between an edge of the porous tin foil and an outermost hole of the plurality of holes is 0.1 mm-10 mm.

2. The porous tin foil anode according to claim 1, wherein, an isosceles triangular area formed by lines connecting centers of three adjacent holes in two adjacent horizontal rows in the plurality of holes is used as a second smallest unit, and each second smallest unit has an equal proportion of an area of the three adjacent holes in the two adjacent horizontal rows.

3. The porous tin foil anode according to claim 2, wherein, two adjacent holes of the plurality of holes in a horizontal direction have an equal distance, and two adjacent holes of the plurality of holes in a vertical direction have an equal distance.

4. The porous tin foil anode according to claim 3, wherein, a distance between the two adjacent holes in the horizontal direction is equal to a distance between the two adjacent holes in the vertical direction.

5. The porous tin foil anode according to claim 3, wherein, a distance between the two adjacent holes in the horizontal direction is equal to a distance between the two adjacent horizontal rows.

6. The porous tin foil anode according to claim 1, wherein, the plurality of holes have an equal size.

7. The porous tin foil anode according to claim 1, wherein, the proportion of the area of the three adjacent holes in the each first smallest unit is 25%-60%.

8. The porous tin foil anode according to claim 1, wherein, the distance between the edge of the porous tin foil and the outermost hole is 2 mm-5 mm.

9. The porous tin foil anode according to claim 1, wherein, a size of each hole of the plurality of holes is 20 nm-2 mm; and a shape of the each hole is one selected from the group consisting of a circle, an oval, a square, a rectangle, a rhombus, a triangle, a polygon, a pentagram, and a quincunx.

10. The porous tin foil anode according to claim 1, wherein, a surface of the porous tin foil is provided with a carbon material layer, and a thickness of the carbon material layer is 2 nm-5 μm.

11. The porous tin foil anode according to claim 10, wherein, a material of the carbon material layer is at least one selected from the group consisting of a hard carbon, a soft carbon, a conductive carbon black, a graphene, a graphite flake and a carbon nanotube.

12. A method for preparing a porous tin foil anode, comprising the following steps: preparing a porous tin foil by performing mechanical molding on a tin foil with a thickness of 20 μm, according to parameters; wherein a plurality of holes are uniformly formed on the porous tin foil; a triangular area formed by lines connecting centers of three adjacent holes of the plurality of holes is used as a smallest unit; a proportion of an area of the three adjacent holes in each smallest unit is 1%-89%; and a distance between an edge of the porous tin foil and an outermost hole of the plurality of holes is 0.1 mm-10 mm; the parameters are designed by the proportion of the area of the three adjacent holes in each smallest unit, a size of each hole of the plurality of holes, a shape of the each hole and the distance between the edge of the porous tin foil and the outermost hole of the plurality of holes; and coating an aqueous solution containing 1 wt % acetylene black on the porous tin foil, and drying the porous tin foil at a constant temperature of 100° C. for 4 hours to obtain the porous tin foil anode.

13. The method for preparing the porous tin foil anode according to claim 12, wherein, a carbon material layer is prepared on the porous tin foil by the following steps: coating a solution containing a carbon material on a surface of the porous tin foil, and drying the porous tin foil to obtain the porous tin foil anode.

14. A sodium ion secondary battery, comprising: a cathode, an electrolyte, a separator, and an anode; wherein the anode is a porous tin foil anode; the porous tin foil anode comprises a porous tin foil; a plurality of holes are uniformly formed on the porous tin foil; a triangular area formed by lines connecting centers of three adjacent holes of the plurality of holes is used as a first smallest unit; a proportion of an area of the three adjacent holes in each first smallest unit is 1%-89%; a distance between an edge of the porous tin foil and an outermost hole of the plurality of holes is 0.1 mm-10 mm; and the porous tin foil of the porous tin foil anode acts as both a current collector and an anode active material.

15. The sodium ion secondary battery according to claim 14, wherein, an isosceles triangular area formed by lines connecting centers of three adjacent holes in two adjacent horizontal rows in the plurality of holes is used as a second smallest unit, and each second smallest unit has an equal proportion of an area of the three adjacent holes in the two adjacent horizontal rows.

16. The sodium ion secondary battery according to claim 15, wherein, two adjacent holes of the plurality of holes in a horizontal direction have an equal distance, and two adjacent holes of the plurality of holes in a vertical direction have an equal distance; a distance between the two adjacent holes in the horizontal direction is equal to a distance between the two adjacent holes in the vertical direction; and the distance between the two adjacent holes in the horizontal direction is equal to a distance between the two adjacent horizontal rows.

17. (canceled)

18. (canceled)

19. The sodium ion secondary battery according to claim 14, wherein, the plurality of holes have an equal size.

20. The sodium ion secondary battery according to claim 14, wherein, a size of each hole of the plurality of holes is 20 nm-2 mm; and a shape of the each hole is one selected from the group consisting of a circle, an oval, a square, a rectangle, a rhombus, a triangle, a polygon, a pentagram, and a quincunx.

21. The sodium ion secondary battery according to claim 14, wherein, a surface of the porous tin foil is provided with a carbon material layer, and a thickness of the carbon material layer is 2 nm-5 μm.

22. The sodium ion secondary battery according to claim 14, wherein, a proportion of an area of the porous tin foil acting as the current collector in the each first smallest unit is 10%-70%, and a proportion of an area of the porous tin foil acting as the anode active material in the each first smallest unit is 1%-51%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 is a schematic diagram showing the structure of the porous tin foil according to embodiment 1 of the present invention.

[0044] FIG. 2 is a schematic diagram showing the structure of the porous tin foil according to embodiment 2 of the present invention.

[0045] FIG. 3 is a schematic diagram showing the structure of the porous tin foil according to embodiment 26 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The preferred embodiments of the present invention are described hereinafter. It should be noted that those having ordinary skill in the art can make several improvements and modifications without departing from the principles of the embodiments of the present invention, and these improvements and modifications shall fall within the scope of protection of the embodiments of the present invention.

[0047] The embodiments of the present invention are further described hereinafter, but not limited to the following specific embodiments. The present invention can be appropriately modified and implemented without changing the scope of the main claims of the present invention.

Embodiment 1

[0048] A method for preparing the porous tin foil anode includes the following steps.

[0049] (1) The porous tin foil is prepared by performing mechanical molding on a tin foil with a thickness of 20 μm according to the design parameters that a proportion of the area of the holes in each smallest unit is 25%, the size is 1 mm, the shape of the hole is a circle, and the distance between the edge of the outermost hole and the edge of the tin foil is 2 mm. Any resulting burrs are purged and removed with compressed air.

[0050] (2) An aqueous solution containing 1 wt % acetylene black is coated on the prepared porous tin foil mentioned above, and then the porous tin foil is dried at a constant temperature of 100° C. for 4 hours to obtain the porous tin foil anode.

[0051] FIG. 1 is a schematic diagram showing the structure of the porous tin foil according to embodiment 1 of the present invention; wherein d represents the distance (4 mm) from the edge of the outermost hole to the edge of the tin foil, and r represents the radius of the circular hole. An isosceles triangular area formed by lines connecting the centers of three adjacent holes is used as the smallest unit. In the smallest unit, the proportion of the area (πr.sup.2)/2 of the holes in the total area (h*L)/2 of the triangular area is 25%.

[0052] In the present embodiment, the plurality of holes are arranged in a rectangular array with an equal distance between any two adjacent holes in the horizontal direction and an equal distance between any two adjacent holes in the vertical direction, and the distance between any two adjacent holes in the horizontal direction is equal to the distance between any two adjacent holes in the horizontal direction. Each horizontal row has an equal number of holes, and each vertical row has an equal number of holes. The holes are aligned and have an equal size.

[0053] Preparation of the Tin-Graphite Dual-Ion Battery

[0054] A graphite cathode material with a specific capacity of 100 mAh/g, polyvinylidene difluoride (PVDF) and conductive carbon black in a mass ratio of 95:3:2 are coated on the tin foil to form the cathode. The processing technology and process control of the cathode adopt the current industrial process technology. Finally, the porous tin foil anode prepared in the embodiment of the present invention, the cathode, an electrolyte and a separator are encapsulated in a glove box filled with argon to obtain the entire battery and battery sample C10, wherein the electrolyte is 4 mol/L NaPF.sub.6 in a mixed solution of EC, dimethyl carbonate (DMC) and EMC (in a volume ratio of 1:1:1) and the separator is a celgard2400 polypropylene porous membrane.

[0055] Preparation of the Conventional Sodium Ion Battery

[0056] Na.sub.2Fe.sub.2(SO.sub.4).sub.3 cathode material with a specific capacity of 100 mAh/g, PVDF, conductive carbon black in a mass ratio of 95:3:2 are coated on the aluminum foil to form the cathode. The processing technology and process control of the cathode adopt the current industrial process technology. Finally, the porous tin foil anode prepared in the embodiment of the present invention, the cathode, an electrolyte, and a separator are encapsulated in a glove box filled with argon to obtain the entire battery and battery sample C20, wherein the electrolyte is 4 mol/L NaPF.sub.6 in a mixed solution of EC, DMC and EMC (in a volume ratio of 1:1:1), and the separator is a celgard2400 polypropylene porous membrane.

[0057] Comparative Embodiment 1 (Tin-Graphite Dual-Ion Battery)

[0058] The tin foil with a thickness of 20 μm is used as the anode. The graphite cathode material with a specific capacity of 100 mAh/g, PVDF and conductive carbon black in a mass ratio of 95:3:2 are coated on the tin foil to form the cathode. Then, the cathode, the tin foil anode, an electrolyte, and a separator are encapsulated in a glove box filled with argon to obtain the entire battery and battery sample C00, wherein the electrolyte is 4 mol/L LiPF6 in a mixed solution of EC, DMC and EMC (in a volume ratio of 1:1:1), and the separator is a celgard2400 polypropylene porous membrane.

Embodiments 2-25

[0059] With reference to the specific steps of embodiment 1, the related parameters can be adjusted to obtain different embodiments 2-25. The parameters of the specific embodiments and test results are shown in Table 1:

TABLE-US-00001 TABLE 1 Proportion Proportion Proportion (%) of the (%) of the (%) of the area of the anode active anode current Hole holes in the material in the collector in the Coating Number Cathode type size (mm) smallest unit smallest unit smallest unit material Embodiment 1 graphite 1 25 25 50 1% acetylene black Embodiment 2 graphite 2 30 30 40 1% conductive carbon black Embodiment 3 graphite 1 25 25 50 Embodiment 4 graphite 2 25 32.5 42.5 1% graphite flake Embodiment 5 graphite 2 25 32.5 42.5 1% S-p Embodiment 6 graphite 0.2 32.5 32.5 35 1% hard carbon Embodiment 7 graphite 0.8 25 35 45 2% conductive carbon black Embodiment 8 graphite 0.5 89 1 10 2% soft carbon Embodiment 9 graphite 0.3 79 1 20 2% acetylene black Embodiment 10 graphite 0.5 70 10 20 2% conductive carbon black Embodiment 11 Na Nl Co Mn 1.5 65 15 20 2% graphene Embodiment 12 Na V (PO ) 1.2 60 20 20 2% graphite flake Embodiment 13 Na Fe (SO ) 1.5 55 25 20 2% S-p Embodiment 14 Na CoO 1.2 45 35 20 2% hard carbon Embodiment 15 graphite 0.00002 10 40 50 2% conductive carbon black Embodiment 16 graphite 0.0002 19 51 30 3% soft carbon Embodiment 17 graphite 0.001 15 51 34 3% acetylene black Embodiment 18 graphite 0.005 40 40 20 3% conductive carbon black Embodiment 19 graphite 0.05 50 30 20 3% graphene Embodiment 20 graphite 0.01 15 45 40 3% graphite flake Embodiment 21 graphite 0.00005 10 30 60 3% S-p Embodiment 22 graphite 0.002 20 35 45 3% hard carbon Embodiment 23 graphite 0.001 30 45 25 3% conductive carbon black Embodiment 24 graphite 0.02 40 40 20 3% graphene Embodiment 25 graphite 0.05 10 20 70 3% graphite flake Comparative graphite 0 0 25 75 0 Embodiment 1 500-cycle Distance (mm) Battery battery Tin foil between hole first capacity thickness edge and efficiency retention Number (μm) Hole shape electrode edge (%) rate (%) Embodiment 1 20 circle 4 85 86.5 Embodiment 2 45 pentagram 3 84 85 Embodiment 3 35 rhomboid 3 83.5 84.5 Embodiment 4 25 pentagram 3 85 85 Embodiment 5 20 circle 3 85 85 Embodiment 6 90 pentagram 4 84.5 86 Embodiment 7 80 square 2 86 86 Embodiment 8 25 square 2 84.5 94.5 Embodiment 9 40 square 2 85 95 Embodiment 10 30 regular hexagon 2 86 91 Embodiment 11 40 regular pentagon 2 89 91 Embodiment 12 20 circle 3 89.5 91 Embodiment 13 40 regular pentagon 2 87 90.5 Embodiment 14 20 circle 3 88 90.5 Embodiment 15 70 rhombus 0.1 88.5 88.5 Embodiment 16 25 rhombus 0.5 88 89 Embodiment 17 16 rhombus 1 87.5 87.5 Embodiment 18 40 rhombus 0.5 87 88 Embodiment 19 50 rhombus 0.5 86.5 89 Embodiment 20 100 rhombus 2 88 87 Embodiment 21 60 circle 4 89 88 Embodiment 22 30 circle 2 88.5 88.5 Embodiment 23 75 circle 5 88 87 Embodiment 24 40 circle 3 86.5 86 Embodiment 25 50 circle 1 89 92 Comparative 50 0 65 80 Embodiment 1 indicates data missing or illegible when filed

Embodiment 26

[0060] A Method for Preparing the Porous Tin Foil Anode Includes the Following Steps:

[0061] (1) The porous tin foil is prepared by performing mechanical molding on a tin foil with a thickness of 20 μm according to the design parameters that a proportion of the area of the holes in each smallest unit is 25%, the size is 1 mm, the shape of the hole is a circle and the distance between the edge of the outermost hole and the edge of the tin foil is 2 mm. Any resulting burrs are purged and removed with compressed air.

[0062] (2) An aqueous solution containing 1 wt % acetylene black is coated on the prepared porous tin foil mentioned above, and then, the porous tin foil is dried at a constant temperature of 100° C. for 4 hours to obtain the porous tin foil anode.

[0063] FIG. 3 is a schematic diagram showing the structure of the porous tin foil according to embodiment 26 of the present invention; wherein d represents the distance (2 mm) from the edge of the outermost hole to the edge of the tin foil, and r represents the radius of the circular hole. An isosceles triangular area formed by lines connecting the centers of three adjacent holes in two adjacent rows is used as the smallest unit. In each smallest unit, the proportion of the area (πr.sup.2)/2 of the holes in the total area of the triangular area is 25%. In the present embodiment, any two adjacent holes in the horizontal direction have an equal distance, and any two adjacent holes in the vertical direction have an equal distance. The distance between any two adjacent holes in the horizontal direction is equal to the distance between two adjacent rows. In other embodiments, the distance between any two adjacent holes in the horizontal direction may be not equal to the distance between two adjacent rows. Each odd-numbered horizontal row or vertical row has an equal number of holes, and each even-numbered horizontal row or vertical row has an equal number of holes. The holes of each odd-numbered horizontal row or even-numbered horizontal row are aligned and have an equal size.

[0064] It should be noted that those skilled in the art can make several changes and modifications to the foregoing embodiments of the present invention according to the teachings and description of the above specification. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention shall fall within the scope of protection of the claims of the present invention. In addition, although certain terminologies are used in the specification, these terminologies are only intended to facilitate the description and cannot be construed as any limitation on the present invention.