CN116598429A - Negative electrode metal foil and its preparation method and battery - Google Patents

Abstract

The invention relates to the technical field of batteries, in particular to a negative electrode metal foil, a preparation method thereof and a battery. The invention discloses a preparation method of a negative electrode metal foil, which comprises the following steps: taking a metal foil substrate as a working electrode, taking graphite or a platinum sheet as a counter electrode, placing the counter electrode in electrolyte, and carrying out anodic oxidation under constant voltage to obtain a composite metal foil with an oxide layer on the surface; performing ultrasonic treatment on the composite metal foil, and removing the oxide layer to obtain a negative metal foil; at least one side surface of the negative electrode metal foil is provided with a plurality of concave structures, and the concave structures are distributed in an array. According to the invention, through anodic oxidation and ultrasonic treatment, a nano concave structure array with a function of homogenizing an electric field is prepared on the surface of a metal foil substrate, so that the electric field of lithium deposition is homogenized to improve the cycle stability of a cathode-free lithium ion battery with high energy density, and the cathode-free lithium ion battery with high specific energy and long cycle is developed.

Description

Negative electrode metal foil and its preparation method and battery

technical field

The invention relates to the technical field of batteries, in particular to a negative electrode metal foil, a preparation method thereof, and a battery.

Background technique

In recent years, with the rapid development of new energy vehicles, people have higher and higher requirements for their cruising range and battery life. The total cruising range of electric vehicles is directly related to the energy density and cycle stability of the power battery equipped. How to develop lithium-ion batteries with high energy density and long-term cycle stability has always been a research hotspot.

At present, the specific energy density of lithium-ion batteries can be improved mainly from two levels of chemistry and physics: (1) Improve the energy density of positive and negative electrode materials at the chemical level: For example, the positive electrode material is developing towards a positive electrode such as a high-nickel content ternary, and the negative electrode It is developing toward negative electrodes such as silicon-based and lithium metals that undergo alloying reactions, but high-energy positive and negative electrode materials often mean higher gas production, poorer cycle stability, and safety issues caused by dendrite growth; ( 2) On the physical level, the specific energy density is improved mainly by simplifying the structural parts of the battery cell and reducing the weight of the battery cell, such as simplifying the cover plate, thinning the shell, and thinning the current collector. Among them, J. Neudecker et al. took the lead in proposing the concept of anode-free battery, which uses anode current collector copper foil instead of traditional graphite anode material, thereby reducing battery quality and increasing energy density.

The anode-free lithium battery replaces the traditional graphite anode with metal foil, so during the charging process of the battery, lithium ions come out of the anode, pass through the separator, and deposit on the surface of the anode metal foil to form lithium metal. During the discharge process, these metal lithium re-form lithium Ions are back-intercalated into the cathode, so the properties of the anode metal foil play a crucial role in determining the cycle stability of Li-ion batteries. However, there are often uneven cracks and defects on the surface of the negative metal foil during the manufacturing process, resulting in uneven deposition and peeling of lithium ions, resulting in the growth of dendrites, piercing the separator, causing short circuits, and bringing safety issues .

In view of this, the present invention is proposed.

Contents of the invention

An object of the present invention is to provide a method for preparing negative electrode metal foil. The negative electrode metal foil obtained by the method has a nano-depression structure array, which can induce uniform nucleation of lithium ions, thereby inducing the uniform growth of subsequent lithium ions and increasing the lithium ion density. Cycling stability of ion batteries.

Another object of the present invention is to provide a negative electrode metal foil prepared by the method for preparing the negative electrode metal foil, the surface of the negative electrode metal foil has a concave structure with uniform size and regular arrangement.

Another object of the present invention is to provide a battery.

In order to realize the above-mentioned purpose of the present invention, special adopt following technical scheme:

A method for preparing negative electrode metal foil, comprising the following steps:

The metal foil substrate is used as the working electrode, graphite or platinum sheet is used as the counter electrode, placed in the electrolyte, and anodized at a constant voltage to obtain a composite metal foil with an oxide layer on the surface; the composite metal foil is subjected to ultrasonic treatment, removing the oxide layer to obtain anode metal foil;

At least one side surface of the negative electrode metal foil has a plurality of recessed structures, and the plurality of recessed structures are distributed in an array.

In one embodiment, the metal foil base includes at least one of titanium foil, aluminum foil, copper foil, nickel foil and iron foil.

In one embodiment, the metal foil substrate has been subjected to ultrasonic cleaning treatment in advance; the detergent used in the ultrasonic cleaning treatment includes acetone and ethanol.

In one embodiment, the metal foil substrate has a thickness of 6-200 μm.

In one embodiment, the electrolyte includes ammonium fluoride, ethylene glycol and water; in the electrolyte, the mass fraction of ammonium fluoride is 0.05% to 0.8%, and the mass fraction of ethylene glycol is 0.5% to 5%.

In one embodiment, the range of the constant voltage is 30-120V.

In one embodiment, the power of the ultrasonic treatment is 500-5000W, and the time of the ultrasonic treatment is 30-600s.

In one embodiment, the shape of the concave structure includes a bowl shape.

In one embodiment, the opening diameter of the recessed structure is 50-500 nm.

In one embodiment, the depth of the recessed structure is 25-250 nm.

In one embodiment, on the one side surface of the negative electrode metal foil, the total opening area of the concave structure accounts for 50%-99.9% of the one side surface area of the negative electrode metal foil.

The negative electrode metal foil prepared by the above-mentioned method for preparing the negative electrode metal foil.

A battery, comprising at least one positive electrode sheet, at least one separator, and at least one negative electrode metal foil, the negative electrode metal foil is the negative electrode metal foil prepared by the above-mentioned method for preparing the negative electrode metal foil or the above-mentioned negative electrode metal foil The positive electrode sheet and the negative electrode metal foil are alternately stacked, and the separator is arranged between the adjacent positive electrode sheet and the negative electrode metal foil; the positive electrode sheet includes a positive electrode current collector and is arranged on the positive electrode A cathode material layer on at least one side surface of the current collector.

In one embodiment, in the lamination direction of the positive electrode sheet, separator and negative electrode metal foil, the projection of the separator forms a first area, the projection of the positive electrode sheet forms a second area, and the projection of the negative electrode metal foil The projection forms a third area, the third area is within the first area, and the second area is within the third area.

In one embodiment, the positive electrode material layer includes a positive electrode active material; the positive electrode active material includes lithium ferrous phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickelate, lithium cobaltate, ternary materials and At least one of the cobalt cathode materials.

In one embodiment, the diaphragm includes at least one of a PP film, a PE film, and a composite diaphragm; the composite diaphragm includes a PP base film and/or a PE base film, and the surface of the base film contains ceramics and PVDF .

In one embodiment, the thickness of the separator is 3-50 μm.

In one embodiment, the thickness of the positive electrode collector is 5-50 μm.

In one embodiment, the thickness of the positive and material layer is 5-500 μm.

In one embodiment, the positive electrode sheet, separator, and negative electrode metal foil are all rectangular; the length of the separator is 2-10 mm longer than the length of the negative electrode metal foil, and the width of the separator is larger than that of the negative electrode metal foil. The width of the negative electrode metal foil is 2-10mm larger; the length of the negative electrode metal foil is 2-10mm larger than the length of the positive electrode sheet, and the width of the negative electrode metal foil is 2-10mm larger than the width of the positive electrode sheet.

Compared with prior art, the beneficial effect of the present invention is:

(1) The present invention prepares a nano-recessed structure array with a homogenizing electric field function on the surface of the metal foil substrate through anodic oxidation and ultrasonic treatment, so as to homogenize the electric field of lithium deposition to improve the non-negative electrode with high energy density The cycle stability of lithium-ion batteries, the development of anode-free lithium-ion batteries with both high specific energy and long cycle.

(2) The negative electrode metal foil obtained by the method of the present invention has a uniform and regular nano-depression structure array on its surface, forming a more uniform electric field, which is conducive to the uniform deposition-stripping of lithium ions, and each depression structure is equivalent to A lithium-ion rivet induces the uniform nucleation of lithium ions, thereby inducing the uniform growth of subsequent lithium ions to improve the cycle stability of lithium-ion batteries.

(3) In the battery of the present invention, the negative electrode metal foil is used as the negative electrode sheet, and the metal negative electrode foil with a concave structure has more reserved space for storing lithium metal, thereby reducing the weight of the battery as a whole and improving the specific energy of the battery as a whole Density; the battery of the present invention has a more excellent capacity retention rate.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the schematic diagram of the preparation of negative electrode metal foil of the present invention;

2 is a scanning electron microscope image of a surface with a concave structure of the negative electrode metal foil of Example 1 of the present invention;

Fig. 3 is the electric field simulation figure of negative electrode metal foil of the present invention;

4 is a schematic diagram of the deposition of lithium ions of the present invention on the surface of the negative electrode metal foil;

Fig. 5 is the structural representation of the lithium ion battery of monolayer structure of the present invention;

FIG. 6 is a schematic structural view of a lithium-ion battery with a multilayer structure according to the present invention.

Reference signs:

1-negative electrode metal foil, 101-recessed structure, 2-diaphragm, 3-positive electrode current collector, 4-positive electrode material layer.

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be regarded as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.

According to one aspect of the present invention, the present invention relates to a preparation method of negative electrode metal foil, comprising the following steps:

The metal foil substrate is used as the working electrode, graphite or platinum sheet is used as the counter electrode, placed in the electrolyte, and anodized at a constant voltage to obtain a composite metal foil with an oxide layer on the surface; the composite metal foil is subjected to ultrasonic treatment, removing the oxide layer to obtain anode metal foil;

At least one side surface of the negative electrode metal foil has a plurality of recessed structures, and the plurality of recessed structures are distributed in an array.

The present invention prepares a nano-recessed structure array with the function of homogenizing the electric field on the metal foil substrate by the above method, so as to homogenize the electric field of lithium deposition, thereby improving the cycle stability of the negative electrode lithium-ion battery which itself has high energy density , to develop anode-free lithium-ion batteries with high specific energy and long cycle.

In one embodiment, the metal foil includes at least one of titanium foil, aluminum foil, copper foil, nickel foil and iron foil.

In one embodiment, the metal foil substrate has been subjected to ultrasonic cleaning treatment in advance; the detergent used in the ultrasonic cleaning treatment includes acetone and ethanol. In one embodiment, acetone and ethanol are used to wash 2 to 4 times respectively, so as to remove impurities on the surface of the metal foil substrate.

In one embodiment, the metal foil substrate has a thickness of 6-200 μm, such as 10 μm, 20 μm, 30 μm, 50 μm, 100 μm and the like.

In one embodiment, the electrolyte includes ammonium fluoride, ethylene glycol and water; in the electrolyte, the mass fraction of ammonium fluoride is 0.05% to 0.8%, such as 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, etc., the mass fraction of ethylene glycol is 0.5%-5%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

In one embodiment, the range of the constant voltage is 30-120V, such as 30V, 50V, 60V, 70V, 90V, 100V, 120V and so on.

In one embodiment, the present invention can adjust the diameter and depth of the bowl shape of the concave structure by adjusting the concentration of the electrolyte and the magnitude of the constant voltage.

In one embodiment, the power of the ultrasonic treatment is 500-5000W, such as 500W, 1000W, 1500W, 2000W, 2500W, 3000W, 4000W, 5000W, etc. The time of the ultrasonic treatment is 30-600s, such as 30s, 50s, 60s, 100s, 200s, 300s, 500s, 600s and so on. The invention adopts ultrasonic treatment to effectively remove the oxide layer and form a bowl-shaped concave structure.

In one embodiment, the recessed structure comprises a bowl shape.

In one embodiment, the opening diameter of the recessed structure is 50-500 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 350 nm, 400 nm, 500 nm and so on.

In one embodiment, the depth of the recessed structure is 25-250nm, such as 25nm, 30nm, 50nm, 100nm, 150nm, 200nm, 250nm, etc.;

In one embodiment, on the surface of one side of the negative electrode metal foil, the total area of the openings of the recessed structure accounts for 50% to 99.9% of the surface area of one side of the negative electrode metal foil, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

According to another aspect of the present invention, the present invention also relates to the negative electrode metal foil prepared by the above-mentioned method for preparing the negative electrode metal foil.

According to another aspect of the present invention, the present invention also relates to a battery, comprising at least one positive electrode sheet, at least one separator and at least one negative electrode metal foil, the negative electrode metal foil is prepared by the method for preparing the negative electrode metal foil Negative electrode metal foil or the negative electrode metal foil; the positive electrode sheets and the negative electrode metal foils are alternately stacked, and the separator is arranged between the adjacent positive electrode sheets and the negative electrode metal foils;

The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one side surface of the positive electrode current collector.

The battery of the present invention contains the above-mentioned negative electrode metal foil, and each nano-depressed structure is equivalent to a rivet of a lithium ion, which induces the uniform nucleation of lithium ions, thereby inducing the uniform growth of subsequent lithium ions, and improving the cycle stability of the lithium-ion battery ; Compared with the metal negative electrode without nano-depression structure, the negative electrode metal foil of the present invention has more reserved space for storing lithium metal, thereby reducing the overall weight of the battery and increasing the energy density of the battery.

In one embodiment, the battery of the present invention includes an alkali metal ion battery such as a lithium ion battery, a sodium ion battery, a potassium ion battery, a zinc ion battery, a magnesium ion battery, a calcium ion battery, or a liquid metal battery.

In one embodiment, the assembling method of the battery of the present invention includes lamination, winding and the like. The shapes of batteries include soft packs, square shells, and cylinders.

In one embodiment, the positive electrode sheet, the separator and the negative electrode metal foil in the battery are respectively one, as shown in FIG. One side of the concave structure is connected with the diaphragm.

In one embodiment, there are multiple positive electrode sheets, separators and negative electrode metal foils in the battery, as shown in FIG. 6 , at this time, positive electrode material layers are provided on both sides of the positive electrode sheet.

In one embodiment, in the lamination direction of the positive electrode sheet, separator and negative electrode metal foil, the projection of the separator forms a first area, the projection of the positive electrode sheet forms a second area, and the projection of the negative electrode metal foil The projection forms a third area, the third area is within the first area, and the second area is within the third area. That is, the area of the diaphragm is larger than the area of the metal foil of the negative electrode, and the area of the metal foil of the negative electrode is larger than that of the positive electrode sheet. In one embodiment, the center points of any positive electrode sheet, separator and negative electrode metal foil are located on the same straight line.

In one embodiment, the positive electrode material layer includes a positive electrode active material; the positive electrode active material includes lithium ferrous phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickelate, lithium cobaltate, ternary materials and At least one of the cobalt cathode materials. In one embodiment, the positive and material layer has a thickness of 5-500 μm, such as 5 μm, 10 μm, 20 μm, 25 μm, 30 μm, 50 μm, 70 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 450 μm or 500 μm.

In one embodiment, the positive electrode current collector includes aluminum foil. The thickness of the positive current collector is 5-50 μm;

In one embodiment, the diaphragm includes at least one of PP film, PE film and composite diaphragm; the composite diaphragm includes PP base film and/or PE base film, and the surface of the base film contains ceramic and poly Vinylidene fluoride (PVDF). In one embodiment, the separator has a thickness of 3-50 μm (eg, 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.).

In one embodiment, the positive electrode sheet, the separator and the negative electrode metal foil are all rectangular; the length of the separator is 2 to 10 mm longer than the length of the negative electrode metal foil (such as 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, etc. ) The width of the separator is 2-10mm larger than the width of the negative electrode metal foil (such as 2mm, 4mm, 6mm, 8mm, 10mm, etc.); the length of the negative electrode metal foil is 2-10mm larger than the length of the positive electrode sheet (such as 2mm, 4mm, 6mm, 8mm, 10mm, etc.), the width of the negative electrode metal foil is 2-10mm larger than the width of the positive electrode sheet (such as 2mm, 4mm, 6mm, 8mm, 10mm, etc.). The above-mentioned structure of the present invention is more conducive to ensuring that the battery has excellent electrochemical performance.

In one embodiment, the battery also includes an electrolyte; the electrolyte is an organic solvent electrolyte containing lithium salts and additives, the lithium salt is one or more of LiPF ₆ , LiTFSI and LiFSI, and the organic The solvent is one or more mixtures of EC, EMC, DMC, DEC, DOL, FEC and DME, and the additive is one or more of LiNO ₃ , KNO ₃ and KPF ₆ .

In one embodiment, the battery further includes a positive tab and a negative tab.

Further explanation will be given below in conjunction with specific embodiments, comparative examples and accompanying drawings.

The schematic diagram of the preparation of the negative electrode metal foil in Examples 1-3 of the present invention is shown in FIG. 1 .

Example 1

A method for preparing negative electrode metal foil 1, comprising the following steps:

(a) The metal foil substrate is subjected to ultrasonic cleaning treatment in advance; the detergent used in the ultrasonic cleaning treatment includes acetone and ethanol, which are treated three times respectively;

(b) the metal foil matrix after washing is used as the working electrode, and the graphite is used as the counter electrode, placed in the electrolyte, and anodized at a constant voltage to obtain a composite metal foil with an oxide layer on the surface; Ultrasonic treatment to remove the oxide layer to obtain a negative electrode metal foil 1; the surface of the negative electrode metal foil 1 has a plurality of bowl-shaped recessed structures 101, and the plurality of recessed structures 101 are distributed in an array;

The metal foil substrate is titanium foil;

The electrolyte includes ammonium fluoride, ethylene glycol and water; in the electrolyte, the mass fraction of ammonium fluoride is 0.4%, and the mass fraction of ethylene glycol is 2.5%;

The constant voltage is 75V;

The power of the ultrasonic treatment is 3000W, and the time of the ultrasonic treatment is 300s;

The opening diameter of the recessed structure 101 is 250nm;

The depth of the recessed structure 101 is 125nm;

On one side surface of the negative electrode metal foil 1 , the total opening area of the recessed structure 101 accounts for 80% of the one side surface area of the negative electrode metal foil 1 .

The scanning electron microscope image of the surface of the negative electrode metal foil 1 with the concave structure 101 in this embodiment is shown in FIG. 2 .

Example 2

A method for preparing negative electrode metal foil 1, comprising the following steps:

(a) The metal foil substrate is subjected to ultrasonic cleaning treatment in advance; the detergent used in the ultrasonic cleaning treatment includes acetone and ethanol, which are treated three times respectively;

(b) the metal foil substrate after washing is used as the working electrode, and the graphite is used as the counter electrode, placed in the electrolyte, and anodized under constant pressure to obtain a composite metal foil with an oxide layer on the surface; Ultrasonic treatment to remove the oxide layer to obtain a negative electrode metal foil 1; the surface of the negative electrode metal foil 1 has a plurality of bowl-shaped recessed structures 101, and the plurality of recessed structures 101 are distributed in an array;

The metal foil substrate is titanium foil;

The electrolyte includes ammonium fluoride, ethylene glycol and water; in the electrolyte, the mass fraction of ammonium fluoride is 0.05%, and the mass fraction of ethylene glycol is 0.5%;

The constant pressure is 30V;

The power of the ultrasonic treatment is 500W, and the time of the ultrasonic treatment is 30s;

The opening diameter of the recessed structure 101 is 50nm;

The depth of the recessed structure 101 is 50nm;

On one side surface of the negative electrode metal foil 1 , the total opening area of the recessed structure 101 accounts for 50% of the one side surface area of the negative electrode metal foil 1 .

Example 3

A method for preparing negative electrode metal foil 1, comprising the following steps:

(a) The metal foil substrate is subjected to ultrasonic cleaning treatment in advance; the detergent used in the ultrasonic cleaning treatment includes acetone and ethanol, which are treated three times respectively;

(b) the metal foil substrate after washing is used as the working electrode, and the graphite is used as the counter electrode, placed in the electrolyte, and anodized under constant pressure to obtain a composite metal foil with an oxide layer on the surface; Ultrasonic treatment to remove the oxide layer to obtain a negative electrode metal foil 1; the surface of the negative electrode metal foil 1 has a plurality of bowl-shaped recessed structures 101, and the plurality of recessed structures 101 are distributed in an array;

The metal foil substrate is titanium foil;

The electrolyte includes ammonium fluoride, ethylene glycol and water; in the electrolyte, the mass fraction of ammonium fluoride is 0.8%, and the mass fraction of ethylene glycol is 5%;

The constant pressure is 120V;

The power of the ultrasonic treatment is 5000W, and the time of the ultrasonic treatment is 600s;

The opening diameter of the recessed structure 101 is 500nm;

The depth of the recessed structure 101 is 250nm;

On one side surface of the negative electrode metal foil 1 , the total opening area of the recessed structure 101 accounts for 99% of the one side surface area of the negative electrode metal foil 1 .

Example 4

A kind of lithium ion battery, is 3Ah, comprises positive electrode sheet, diaphragm 2, negative electrode metal foil 1 and electrolyte solution in embodiment 1; Described positive electrode sheet and described negative electrode metal foil 1 are stacked alternately and arranged, and adjacent described The separator 2 is arranged between the positive electrode sheet and the negative electrode metal foil 1; the positive electrode sheet includes a positive electrode current collector 3 and a positive electrode material layer 4 arranged on the surface of the positive electrode collector;

In the stacking direction of the positive electrode sheet, separator 2 and negative electrode metal foil 1, the projection of the separator 2 forms a first area, the projection of the positive electrode sheet forms a second area, and the projection of the negative electrode metal foil 1 forms a second area. Three areas, the third area is located in the center of the first area, the second area is located in the center of the third area; the positive electrode sheet, separator 2 and negative electrode metal foil 1 are all rectangular, The length of the separator 2 is 6 mm larger than the length of the negative metal foil 1, and the width of the separator 2 is 6 mm larger than the width of the negative metal foil 1; the length of the negative metal foil 1 is longer than that of the positive sheet. The length is 6 mm larger, and the width of the negative electrode metal foil 1 is 6 mm larger than the width of the positive electrode sheet.

The positive electrode material layer 4 includes positive electrode active material NCM811, conductive carbon black (SP): carbon nanotube (CNT): polyvinylidene fluoride (PVDF), and the mass ratio of NCM811, SP, CNT and PVDF is 96.5:0.5:1 :2;

The positive current collector 3 is aluminum foil;

The diaphragm 2 is a PP film;

The electrolyte is a carbonate-based electrolyte containing LiPF6.

Example 5

A kind of lithium ion battery, except that battery is 5Ah, other conditions are the same as embodiment 4.

Example 6

A lithium ion battery, except that the battery is 7Ah, other conditions are the same as in embodiment 4.

Example 7

A lithium ion battery, except that the negative electrode metal foil 1 in embodiment 2 is used, other conditions are the same as embodiment 6.

Example 8

A lithium ion battery, except that the negative electrode metal foil 1 in embodiment 3 is used, other conditions are the same as in embodiment 6.

Comparative example 1

A lithium ion battery, except that the negative electrode metal foil is a light titanium foil without surface treatment, and other conditions are the same as in Example 4.

Comparative example 2

A lithium ion battery, except that the negative electrode metal foil is a light titanium foil without surface treatment, and other conditions are the same as in Example 5.

Comparative example 3

A lithium ion battery, except that the negative electrode metal foil is a light titanium foil without surface treatment, and other conditions are the same as in Example 6.

Experimental example

1. The present invention takes the concave size of the negative electrode metal foil in Example 1 as a parameter, and uses Ansys software to perform electric field simulation. Since the nanobowl is centrally symmetric, two-dimensional finite element analysis is used to conduct quantitative simulations on it, and the potential distribution diagram on the surface of the metal foil is obtained. As shown in Figure 3, the potential at the bottom of the concave structure is smaller than the potential at the edge of the top opening, and more Conducive to the uniform deposition of lithium. Based on the lower potential has a strong inductive force for the deposition of lithium ions, draw a schematic diagram of the deposition of lithium ions on the surface of the negative electrode metal foil with a concave structure, as shown in Figure 4, in the nano-array, each nano-structure It is equivalent to a lithium ion rivet, which induces the uniform nucleation of lithium ions, thereby inducing the uniform growth of subsequent lithium ions, and improving the cycle stability of lithium ion batteries.

2. Perform performance tests on the batteries of Examples 4-8 and Comparative Examples 1-3, and observe the capacity retention rate of each battery after 500 cycles under the same cycle conditions. The results are shown in Table 1.

Table 1 Capacity retention test results

Example 1 Capacity/Ah Capacity retention/% Example 4 3 93.1 Example 5 5 92.7 Example 6 7 92.3 Example 7 7 86.6 Example 8 7 84.8 Comparative example 1 3 85.3 Comparative example 2 5 83.9 Comparative example 3 7 83.7

It can be seen from Table 1 that the battery prepared by the negative electrode metal foil with a specific concave structure array obtained by a specific method in the present invention has a higher capacity retention rate. In Comparative Examples 1 to 3, the bare titanium foil without surface treatment was used as the negative electrode, and the capacity retention rate of the obtained batteries was lower than that of the battery prepared by using the specific negative electrode metal foil of the present invention.

It should be noted that at last: above each embodiment is only in order to illustrate technical scheme of the present invention, and is not intended to limit; Although the present invention has been described in detail with reference to foregoing each embodiment, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for 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 technical solutions of the various embodiments of the present invention. range.

Claims (10)

1. a preparation method of negative electrode metal foil, is characterized in that, comprises the following steps: The metal foil substrate is used as the working electrode, graphite or platinum sheet is used as the counter electrode, placed in the electrolyte, and anodized at a constant voltage to obtain a composite metal foil with an oxide layer on the surface; the composite metal foil is subjected to ultrasonic treatment, removing the oxide layer to obtain anode metal foil; At least one side surface of the negative electrode metal foil has a plurality of recessed structures, and the plurality of recessed structures are distributed in an array. 2. The preparation method of negative electrode metal foil according to claim 1, characterized in that, comprising at least one of the following features (1) to (3): (1) The metal foil substrate includes at least one of titanium foil, aluminum foil, copper foil, nickel foil and iron foil; (2) The metal foil substrate has been subjected to ultrasonic cleaning in advance; the detergent used in the ultrasonic cleaning includes acetone and ethanol; (3) The thickness of the metal foil substrate is 6-200 μm. 3. the preparation method of negative electrode metal foil according to claim 1 is characterized in that, described electrolytic solution comprises ammonium fluoride, ethylene glycol and water; In the electrolyte, the mass fraction of ammonium fluoride is 0.05%-0.8%, and the mass fraction of ethylene glycol is 0.5%-5%. 4 . The method for preparing negative electrode metal foil according to claim 1 , wherein the range of the constant voltage is 30-120V. 5 . The method for preparing negative electrode metal foil according to claim 1 , characterized in that, the power of the ultrasonic treatment is 500-5000 W, and the time of the ultrasonic treatment is 30-600 s. 6. The method for preparing negative electrode metal foil according to claim 1, characterized in that it comprises at least one of the following features (1) to (4): (1) The shape of the concave structure includes a bowl shape; (2) The opening diameter of the concave structure is 50-500 nm; (3) The depth of the concave structure is 25-250nm; (4) On the surface of one side of the negative electrode metal foil, the total area of the openings of the concave structure accounts for 50% to 99.9% of the surface area of one side of the negative electrode metal foil. 7. The negative electrode metal foil prepared by the method for preparing the negative electrode metal foil according to any one of claims 1 to 6. 8. A battery, characterized in that it comprises at least one positive electrode sheet, at least one diaphragm and at least one negative electrode metal foil, and the negative electrode metal foil is the method for preparing the negative electrode metal foil according to any one of claims 1 to 6 The prepared negative electrode metal foil or the negative electrode metal foil according to claim 7; the positive electrode sheets and the negative electrode metal foils are alternately stacked, and the adjacent positive electrode sheets and the negative electrode metal foils are provided with the diaphragm; The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one side surface of the positive electrode current collector. 9. The battery according to claim 8, characterized in that it comprises at least one of the following features (1) to (6): (1) In the lamination direction of the positive electrode sheet, separator and negative electrode metal foil, the projection of the separator forms a first area, the projection of the positive electrode sheet forms a second area, and the projection of the negative electrode metal foil forms a third area. an area, the third area is within the first area, and the second area is within the third area; (2) The positive electrode material layer includes a positive electrode active material; the positive electrode active material includes lithium ferrous phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickelate, lithium cobaltate, ternary materials, and cobalt-free positive electrode materials at least one of (3) the diaphragm includes at least one of a PP film, a PE film and a composite diaphragm; the composite diaphragm includes a PP base film and/or a PE base film, and the surface of the base film contains ceramics and PVDF; (4) The thickness of the diaphragm is 3-50 μm; (5) The thickness of the positive current collector is 5-50 μm; (6) The thickness of the positive and material layer is 5-500 μm. 10. The battery according to claim 9, characterized in that, the positive electrode sheet, separator and negative electrode metal foil are all rectangular; the length of the separator is 2 to 10 mm longer than the length of the negative electrode metal foil, and the length of the separator is The width of the negative electrode metal foil is 2 to 10 mm larger than the width of the negative electrode metal foil; the length of the negative electrode metal foil is 2 to 10 mm larger than the length of the positive electrode sheet, and the width of the negative electrode metal foil is 2 to 10 mm larger than the width of the positive electrode sheet ~10mm.