Negative current collector and preparation method and application thereof

Abstract

The invention provides a negative electrode current collector and a preparation method and application thereof, and relates to the technical field of batteries. The negative electrode current collector provided by the invention comprises a metal net and slurry layers coated on two surfaces of the metal net, the slurry layer is mainly composed of a conductive carbon material, metal particles, a sodium-based fast ion conductor or a lithium-based fast ion conductor and a binder; the conductive carbon material is mainly composed of a point type carbon material, a linear carbon material and a surface type carbon material; and the porosity of the slurry layer is 30%-40%. The negative electrode current collector is low in cost, has a porous structure, has sufficient sodium metal or lithium metal deposition space, can enable sodium metal or lithium metal to grow in the negative electrode current collector when being used for a negative-electrode-free electrode, is small in volume change of a battery, and reduces the occurrence of sodium dendrites or lithium dendrites.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative current collector, a preparation method thereof, and an application thereof. Background Art

[0002] The sodium-free anode battery uses layered oxide (such as nickel-iron-manganese oxide and copper-iron-manganese oxide) materials, Prussian blue analogues (such as iron-based Prussian white, etc.) materials, and polyanions (such as sodium iron sulfate, sodium iron phosphate, etc.) as the positive electrode, and an aluminum foil current collector acts as the negative electrode. It mainly uses ethers as solvents, adds Na + metal salts (such as sodium fluoride salt, sodium borate salt, and sodium perchlorate salt, etc.) electrolytes, and various additives (such as film-forming, flame-retardant, and overcharge protection types, etc.) to form an electrolyte. Although the sodium-free anode battery has advantages such as good low-temperature performance, low cost, and high energy density, its battery volume changes significantly (significant expansion and contraction), gas generation, and sodium dendrites are serious, which seriously hinder the application of sodium-ion batteries. As a key component in the battery, the most common modification of the current collector is only to coat a conductive agent on the surface of the aluminum foil. Such a current collector is too traditional and has many problems. For example, the space for sodium metal to deposit on the aluminum foil is limited and can only deposit on the surface, which will lead to a large volume change of the battery and easy generation of sodium dendrites, greatly reducing the cycle life of the battery. Similarly, such current collectors also have similar problems in sodium-free lithium-ion batteries.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The first object of the present invention is to provide a negative current collector to solve the above technical problems.

[0005] The second object of the present invention is to provide a preparation method of the above negative current collector.

[0006] The third object of the present invention is to provide an application of the above negative current collector in a sodium-free battery.

[0007] In order to achieve the above objects, the following technical solutions are specifically adopted:

[0008] In a first aspect, the present invention provides a negative current collector, including a metal mesh and a slurry layer coated on both sides of the metal mesh;

[0009] The slurry layer is mainly composed of a conductive carbon material, metal particles, a sodium-based fast ion conductor or a lithium-based fast ion conductor, and a binder. The mass ratio of the conductive carbon material, metal particles, lithium-based fast ion conductor or sodium-based fast ion conductor, and binder is (5-10):(75-85):(5-10):5;

[0010] The conductive carbon material mainly consists of dot-shaped carbon material, linear carbon material and planar carbon material;

[0011] The porosity of the slurry layer is 30% - 40%.

[0012] As a further technical solution, the metal mesh includes an aluminum mesh or a copper mesh;

[0013] The mesh number of the metal mesh is 5 - 50 meshes.

[0014] As a further technical solution, the dot-shaped carbon material includes carbon black, acetylene black or activated carbon;

[0015] The linear carbon material includes carbon fiber;

[0016] The planar carbon material includes graphite;

[0017] The mass ratio of the dot-shaped carbon material, linear carbon material and planar carbon material is (1 - 2):(2 - 3):(5 - 7).

[0018] As a further technical solution, the metal particles include aluminum particles, aluminum alloy particles, copper particles or copper alloy particles;

[0019] The particle size of the metal particles is 20 - 300 microns.

[0020] As a further technical solution, the sodium-based fast ion conductor includes sodium titanium phosphate or sodium fluoroaluminate.

[0021] The lithium-based fast ion conductor includes lithium titanium aluminum phosphate or lithium lanthanum zirconium oxide.

[0022] As a further technical solution, the binder includes BSR.

[0023] As a further technical solution, the metal mesh is an aluminum mesh;

[0024] The slurry layer is composed of an electrocarbon material, aluminum particles or aluminum alloy particles, a sodium-based fast ion conductor and a binder.

[0025] As a further technical solution, the metal mesh is a copper mesh;

[0026] The slurry layer is composed of an electrocarbon material, copper particles or copper alloy particles, a lithium-based fast ion conductor and a binder.

[0027] In a second aspect, the present invention provides a method for preparing the above-mentioned negative electrode current collector, including the following steps:

[0028] Mix the conductive carbon material, metal particles, sodium-based fast ion conductor or lithium-based fast ion conductor, binder and water to obtain a slurry, and then coat the slurry on both sides of the metal mesh, and prepare the negative electrode current collector after drying.

[0029] In a third aspect, the present invention provides an application of the above-mentioned negative electrode current collector in a non-negative electrode battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The negative electrode current collector provided by the present invention includes a metal mesh and a slurry layer. The metal mesh is the skeleton of the negative electrode current collector, and the slurry layer is coated on both sides of the skeleton. The negative electrode current collector has a low cost, a porous structure, and sufficient deposition space for sodium metal or lithium metal. When used in a non-negative electrode, it can enable sodium metal or lithium metal to grow inside the negative electrode current collector, with small volume change of the battery and reduced appearance of sodium dendrites or lithium dendrites. Detailed implementation manners

[0032] The following will describe the implementation schemes of the present invention in detail in combination with implementation manners and examples. However, those skilled in the art will understand that the following implementation manners and examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. Those not specifying specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0033] In a first aspect, the present invention provides a negative electrode current collector, including a metal mesh and a slurry layer coated on both sides of the metal mesh;

[0034] The slurry layer is mainly composed of a conductive carbon material, metal particles, a sodium-based fast ion conductor or a lithium-based fast ion conductor, and a binder. The mass ratio of the conductive carbon material, metal particles, lithium-based fast ion conductor or sodium-based fast ion conductor, and binder is (5 - 10):(75 - 85):(5 - 10):5;

[0035] The conductive carbon material is mainly composed of dot-shaped carbon materials, linear carbon materials, and planar carbon materials;

[0036] The porosity of the slurry layer is 30% - 40%.

[0037] In the present invention, the metal mesh is the skeleton of the negative electrode current collector; the metal particles are the main fillers of the negative electrode current collector, increasing the void space inside the negative electrode current collector; the metal particles cooperate with the conductive carbon material to increase the conductivity inside the negative electrode current collector; the sodium-based fast ion conductor or the lithium-based fast ion conductor provides uniform deposition sites for sodium metal or lithium metal.

[0038] The negative electrode current collector provided by the present invention uses a metal mesh as the main skeleton and a conductive carbon material in a point-line-plane configuration as an auxiliary carbon skeleton, filled with metal powder particles to form a three-dimensional structure. For a non-negative electrode, it enables sodium metal or lithium metal to grow inside the negative electrode current collector, resulting in a small volume change of the battery and reducing the occurrence of sodium dendrites or lithium dendrites.

[0039] In some alternative embodiments, the metal mesh includes, but is not limited to, an aluminum mesh or a copper mesh, and its metal type can be selected according to the non-negative electrode battery to which the negative electrode current collector is to be applied;

[0040] The mesh number of the metal mesh can be, for example, but not limited to, 5 mesh, 30 mesh, or 50 mesh.

[0041] In some alternative embodiments, the thickness of the metal mesh is 50 - 150 microns, and the thickness of the current collector is 150 - 200 microns.

[0042] In some alternative embodiments, the point-type carbon material includes, but is not limited to, carbon black, acetylene black, or activated carbon;

[0043] The line-type carbon material includes, but is not limited to, carbon fiber;

[0044] The plane-type carbon material includes, but is not limited to, graphite;

[0045] The mass ratio of the point-type carbon material, line-type carbon material, and plane-type carbon material is 1:2:7, 2:3:5, or 1.5:2.5:6.5.

[0046] In some alternative embodiments, the metal particles include, but are not limited to, aluminum particles, aluminum alloy particles, copper particles, or copper alloy particles;

[0047] The particle size of the metal particles is 20 - 300 microns.

[0048] In some alternative embodiments, the metal particles and the metal mesh are pre-treated metal particles and metal mesh;

[0049] The pre-treatment includes the following steps:

[0050] Removing the metal oxide layer on the surfaces of the metal particles and the metal mesh; then oxidizing the metal particles and the metal mesh in an oxygen atmosphere to obtain metal particles and a metal mesh with a uniform surface oxide layer. In some alternative embodiments, the temperature of the oxidation treatment is 200 - 500 °C, and the time of the oxidation treatment is 0.1 h - 1 h.

[0051] In some alternative embodiments, the sodium-based fast ion conductor includes, but is not limited to, sodium titanium phosphate or sodium hexafluoroaluminate.

[0052] The lithium-based fast ion conductor includes, but is not limited to, lithium titanium aluminum phosphate or lithium lanthanum zirconium oxide.

[0053] In some alternative embodiments, the binder includes, but is not limited to, BSR, and other binders well-known to those skilled in the art can also be used.

[0054] In some alternative embodiments, the metal mesh is an aluminum mesh;

[0055] The slurry layer is composed of an electrocarbon material, aluminum particles or aluminum alloy particles, a sodium-based fast ion conductor, and a binder.

[0056] Through research by the inventor, it is found that the negative electrode current collector of the above materials is more suitable for a non-negative electrode sodium ion battery.

[0057] In some alternative embodiments, the metal mesh is a copper mesh;

[0058] The slurry layer is composed of an electrocarbon material, copper particles or copper alloy particles, a lithium-based fast ion conductor, and a binder.

[0059] Through research by the inventor, it is found that the negative electrode current collector of the above materials is more suitable for a non-negative electrode lithium ion battery.

[0060] In some alternative embodiments, the slurry layer further includes other metal particles besides copper and aluminum, and the other metal particles include titanium particles.

[0061] By adding other metal ions, corresponding functions are imparted to the current collector, such as improving conductivity, etc.

[0062] In some alternative embodiments, the slurry layer further includes a dispersant;

[0063] The dispersant includes CMC.

[0064] By adding a dispersant, the dispersibility of each component in the slurry layer is improved, and aggregation is avoided.

[0065] In a second aspect, the present invention provides a method for preparing the above negative electrode current collector, including the following steps:

[0066] Mix a conductive carbon material, metal particles, a sodium-based fast ion conductor or a lithium-based fast ion conductor, a binder, and water to obtain a slurry, and then coat the slurry on both sides of the metal mesh and dry it to prepare the negative electrode current collector.

[0067] This preparation method is simple, convenient, and low-cost, and the prepared negative electrode current collector can be used for the preparation of a non-negative electrode battery.

[0068] In a third aspect, the present invention provides the application of the above negative electrode current collector in a non-negative electrode battery.

[0069] The negative electrode current collector provided by the present invention has a low cost, a porous structure, sufficient deposition space for sodium metal or lithium metal, and can be used for the preparation of a non-negative electrode battery. When used for a non-negative electrode, it enables sodium metal or lithium metal to grow inside the negative electrode current collector, resulting in a small volume change of the battery and a reduction in the occurrence of sodium dendrites.

[0070] The present invention will be further described below through specific examples and comparative examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any way.

[0071] In the following examples and comparative examples, metal particles with a particle size of 20 to 300 microns are used.

[0072] Example 1

[0073] A negative electrode current collector (with a thickness of 200 microns) includes a metal mesh (aluminum mesh, with a thickness of 100 microns) and a slurry layer coated on both sides of the metal mesh;

[0074] The slurry layer includes a conductive carbon material, metal particles (pure aluminum), a sodium-based fast ion conductor (sodium titanium phosphate), a binder (SBR), and a dispersant (CMC). The mass ratio of the conductive carbon material, metal particles, sodium-based fast ion conductor, binder, and dispersant is 7.5:80:7.5:5:5;

[0075] The conductive carbon material is composed of a dot-shaped carbon material (acetylene black), a linear carbon material (carbon fiber), and a planar carbon material (graphite). The mass ratio of the dot-shaped carbon material, linear carbon material, and planar carbon material is 1:2:7;

[0076] The porosity of the slurry layer is 40%.

[0077] The preparation method is as follows:

[0078] Remove the surface impurities of the metal particles and the metal mesh with acetone and pure water, and then remove the original uneven oxide layer on the surface of the metal powder and the metal mesh with dilute hydrochloric acid, and wash it with pure water multiple times.

[0079] Put the treated metal particles and the metal mesh into a tube furnace, introduce pure O 2 , at a temperature of 500 °C, pre-oxidize for 0.1 h, and the surface of the metal powder is uniformly oxidized in an environment of pure O 2 , and a thin and uniform oxide layer is formed on the surface.

[0080] Mix the conductive carbon material, the treated metal particles, the sodium-based fast ion conductor, the binder, and the dispersant with water, and homogenize with a homogenizer for 2 h to obtain a uniform slurry.

[0081] The prepared slurry is coated on the treated metal mesh. The metal particles and the conductive material will fill the inside and surface of the metal mesh. Then, it is placed in a freezer at -10°C for 6 hours and freeze-dried in a freeze-drying device to obtain the aluminum powder@metal mesh three-dimensional current collector.

[0082] Example 2

[0083] A negative electrode current collector (with a thickness of 200 microns) includes a metal mesh (aluminum mesh, with a thickness of 100 microns) and a slurry layer coated on both sides of the metal mesh;

[0084] The slurry layer includes a conductive carbon material, metal particles (pure aluminum), a sodium-based fast ion conductor (sodium hexafluoroaluminate), a binder (SBR), and a dispersant (CMC). The mass ratio of the conductive carbon material, metal particles, sodium-based fast ion conductor, binder, and dispersant is 5:85:5:5:5;

[0085] The conductive carbon material is composed of a dot-shaped carbon material (carbon black), a linear carbon material (carbon fiber), and a planar carbon material (graphite). The mass ratio of the dot-shaped carbon material, linear carbon material, and planar carbon material is 1.5:2.5:6.5;

[0086] The porosity of the slurry layer is 35%.

[0087] The preparation method is as follows:

[0088] The surface impurities of the metal particles and the metal mesh are removed with acetone and pure water, and then the original uneven oxide layer on the surface of the metal powder and the metal mesh is removed with dilute hydrochloric acid and washed with pure water multiple times.

[0089] The treated metal particles and the metal mesh are placed in a tube furnace, and pure O 2 is introduced. The temperature is 200°C, and pre-oxidation is carried out for 1 hour. The surface of the metal powder is uniformly oxidized in an environment of pure O 2 , and a thin and uniform oxide layer is formed on the surface.

[0090] The conductive carbon material, the treated metal particles, the sodium-based fast ion conductor, the binder, and the dispersant are mixed with water and homogenized with a homogenizer for 2 hours to obtain a uniform slurry.

[0091] The prepared slurry is coated on the treated metal mesh. The metal particles and the conductive material will fill the inside and surface of the metal mesh. Then, it is placed in a freezer at -10°C for 6 hours and freeze-dried in a freeze-drying device to obtain the aluminum powder@metal mesh three-dimensional current collector.

[0092] Example 3

[0093] A negative electrode current collector (with a thickness of 200 microns) includes a metal mesh (aluminum mesh, with a thickness of 100 microns) and a slurry layer coated on both sides of the metal mesh;

[0094] The slurry layer includes a conductive carbon material, metal particles (pure aluminum), a sodium-based fast ion conductor (sodium titanium phosphate), a binder (SBR), and a dispersant (CMC). The mass ratio of the conductive carbon material, metal particles, sodium-based fast ion conductor, binder, and dispersant is 10:75:10:5:5;

[0095] The conductive carbon material consists of a dot-shaped carbon material (acetylene black), a linear carbon material (carbon fiber), and a planar carbon material (graphite). The mass ratio of the dot-shaped carbon material, linear carbon material, and planar carbon material is 2:3:5;

[0096] The porosity of the slurry layer is 30%.

[0097] The preparation method is as follows:

[0098] Remove the surface impurities of the metal particles and metal mesh with acetone and pure water, and then remove the original uneven oxide layer on the surface of the metal powder and metal mesh with dilute hydrochloric acid, and wash it with pure water multiple times.

[0099] Put the treated metal particles and metal mesh into a tubular furnace, introduce pure O 2 , at a temperature of 400 °C, pre-oxidize for 0.5 h, and the surface of the metal powder is uniformly oxidized in an environment of pure O 2 , and a thin and uniform oxide layer is formed on the surface.

[0100] Mix the conductive carbon material, treated metal particles, sodium-based fast ion conductor, binder, and dispersant with water, and homogenize with a homogenizer for 2 h to obtain a uniform slurry.

[0101] Coat the prepared slurry on the treated metal mesh. The metal particles and conductive material will fill the inside and surface of the metal mesh. Then place it in a freezer at -10 °C for 6 h and perform freeze-drying in a freeze-drying equipment to obtain an aluminum powder@metal mesh three-dimensional current collector.

[0102] Example 4

[0103] The difference from Example 1 is that the metal particles and metal mesh are not subjected to deoxidation and re-oxidation treatment.

[0104] Comparative Example 1

[0105] A current collector, the difference from Example 1 is that the conductive carbon material is all dot-shaped carbon material.

[0106] Comparative Example 2

[0107] A current collector, the difference from Example 1 is that the conductive carbon material is all linear carbon material.

[0108] Comparative Example 3

[0109] A current collector, different from that of Example 1 in that all the conductive carbon materials are planar carbon materials.

[0110] Comparative Example 4

[0111] A current collector, different from that of Example 1 in that the metal mesh is replaced with aluminum foil of the same thickness.

[0112] Comparative Example 5

[0113] A current collector, different from that of Example 1 in that no sodium-based fast ion conductor is added.

[0114] Comparative Example 6

[0115] A conventional current collector is carbon-coated aluminum foil (thickness 200 microns).

[0116] Test Example 1

[0117] The current collectors provided in Examples 1 to 3 and Comparative Examples 1 to 6 were used as the negative electrode to prepare a sodium-ion battery without a negative electrode. Among them, the positive electrode sheet was prepared by uniformly mixing sodium iron pyrophosphate phosphate, conductive carbon black, PVDF, and PAA in a ratio of 95:2:2:1 and adding them to a solvent (NMP) to obtain a positive electrode slurry, and then coating the positive electrode slurry on the surface of the carbon-coated aluminum foil to obtain the positive electrode sheet;

[0118] The electrolyte was: containing 1M NaPF 6 in diglyme;

[0119] The separator was: polyethylene separator.

[0120] The sodium-ion laminated battery without a negative electrode was assembled in a glove box under an inert atmosphere according to the same preparation method.

[0121] The performances of the batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were respectively detected (including charge-discharge capacity, initial Coulomb efficiency, 5C capacity retention rate (compared with the normal 0.5C cycle, the percentage of the capacity compared with the 0.5C cycle), capacity retention rate of charge-discharge cycling 100 times at 0.1C / 0.1C, gas generation amount, capacity retention rate of charge-discharge cycling 300 times at 0.5C / 1C), and the results are shown in Table 1.

[0122] Table 1

[0123]

[0124] Example 5

[0125] A negative electrode current collector (thickness 200 microns) includes a metal mesh (copper mesh, thickness 10 microns) and slurry layers coated on both sides of the metal mesh;

[0126] The slurry layer includes a conductive carbon material, metal particles (pure copper), a lithium-based fast ion conductor (lithium aluminum titanium phosphate), a binder (SBR), and a dispersant (CMC). The mass ratio of the conductive carbon material, metal particles, lithium-based fast ion conductor, binder, and dispersant is 7.5:80:7.5:5:5;

[0127] The conductive carbon material consists of a dot-shaped carbon material (acetylene black), a linear carbon material (carbon fiber), and a planar carbon material (graphite). The mass ratio of the dot-shaped carbon material, linear carbon material, and planar carbon material is 1:2:7;

[0128] The porosity of the slurry layer is 40%.

[0129] The preparation method is as follows:

[0130] Remove the surface impurities of the metal particles and metal mesh with acetone and pure water, and then use dilute hydrochloric acid to remove the original uneven oxide layer on the surface of the metal powder and metal mesh, and wash it with pure water multiple times.

[0131] Put the treated metal particles and metal mesh into a tube furnace, introduce pure O 2 , at a temperature of 500 °C, pre-oxidize for 0.1 h, and the surface of the metal powder is uniformly oxidized in an environment of pure O 2 , and a thin and uniform oxide layer is formed on the surface.

[0132] Mix the conductive carbon material, treated metal particles, lithium-based fast ion conductor, binder, and dispersant with water, and homogenize with a homogenizer for 2 h to obtain a uniform slurry.

[0133] Coat the prepared slurry on the treated metal mesh. The metal particles and conductive material will fill the inside and surface of the metal mesh. Then, place it in a freezer at -10 °C for 6 h and perform freeze-drying in a freeze-drying device to obtain a copper powder@metal mesh three-dimensional current collector.

[0134] Comparative Example 7

[0135] A current collector is a pure copper foil (thickness 200 microns).

[0136] Test Example 2

[0137] Use the current collectors provided in Example 5 and Comparative Example 7 as the negative electrode to prepare a non-aqueous negative electrode lithium-ion battery. Among them, the positive electrode sheet is: Mix NCM811, conductive carbon black, PVDF, and PAA in a ratio of 95:2:2:1 and add them uniformly to a solvent (NMP) to obtain a positive electrode slurry, and coat the positive electrode slurry on the surface of a carbon-coated aluminum foil to prepare a positive electrode sheet;

[0138] The electrolyte is: ethylene glycol dimethyl ether containing 1 M LiFSI;

[0139] The separator is: a polyethylene separator.

[0140] Assemble into a lithium-ion laminated battery without a negative electrode in a glove box under an inert atmosphere according to the same preparation method.

[0141] Detect the performance of the batteries prepared in Example 5 and Comparative Example 7 respectively (including charge-discharge capacity, initial Coulomb efficiency, 5C capacity retention rate (compared with the normal 0.5C cycle, the percentage of the capacity compared with the 0.5C cycle), capacity retention rate of charge-discharge cycling 100 times at 0.1C / 0.1C, gas generation amount, capacity retention rate of charge-discharge cycling 300 times at 0.5C / 1C), and the results are shown in Table 2.

[0142] Table 2

[0143]

[0144] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode current collector, characterized in that: It includes a metal mesh and slurry layers coated on both sides of the metal mesh; The slurry layer is mainly composed of a conductive carbon material, metal particles, a lithium-based fast ion conductor or a sodium-based fast ion conductor, and a binder, and the mass ratio of the conductive carbon material, the metal particles, the lithium-based fast ion conductor or the sodium-based fast ion conductor and the binder is (5-10):(75-85):(5-10):5; The conductive carbon material is mainly composed of point-type carbon material, line-type carbon material and surface-type carbon material; The porosity of the slurry layer is 30% to 40%.

2. The negative electrode current collector according to claim 1, characterized in that: The metal mesh includes an aluminum mesh or a copper mesh; The mesh number of the metal mesh is 5 to 50 meshes.

3. The negative electrode current collector according to claim 1, characterized in that: The point-type carbon material includes carbon black, acetylene black or activated carbon; The linear carbon material includes carbon fiber; The surface-shaped carbon material includes graphite; The mass ratio of the point-type carbon material, the line-type carbon material and the surface-type carbon material is (1-2): (2-3): (5-7).

4. The negative electrode current collector according to claim 1, characterized in that: The metal particles include aluminum particles, aluminum alloy particles, copper particles or copper alloy particles; The particle size of the metal particles is 20 to 300 microns.

5. The negative electrode current collector according to claim 1, characterized in that: The sodium-based fast ion conductor includes sodium titanium phosphate or sodium fluoroaluminate; The lithium-based fast ion conductor includes lithium aluminum titanium phosphate or lithium lanthanum zirconium oxide.

6. The negative electrode current collector according to claim 1, characterized in that: The binder includes BSR.

7. The negative electrode current collector according to claim 1, characterized in that: The metal mesh is an aluminum mesh; The slurry layer consists of electrocarbon material, aluminum particles or aluminum alloy particles, sodium-based fast ion conductor and binder.

8. The negative electrode current collector according to claim 1, characterized in that: The metal mesh is a copper mesh; The slurry layer consists of electric carbon material, copper particles or copper alloy particles, lithium-based fast ion conductor and binder.

9. The method for preparing a negative electrode current collector according to any one of claims 1 to 8, characterized in that: The following steps are involved: Conductive carbon material, metal particles, lithium-based fast ion conductor or sodium-based fast ion conductor, binder and water are mixed to obtain slurry, and then the slurry is coated on both sides of the metal mesh and dried to prepare the negative electrode current collector.

10. Use of the negative electrode current collector according to any one of claims 1 to 8 in a negative electrode-free battery.

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