CN113991054B - Lithium-free negative plate for lithium battery and lithium battery - Google Patents

Abstract

The invention relates to a lithium-free negative electrode sheet for a lithium battery and the lithium battery, and belongs to the technical field of lithium batteries. The lithium-free negative plate for the lithium battery comprises a negative current collector, wherein one or two sides of the negative current collector are sequentially provided with a lithium deposition induction layer and an inorganic electronic insulating layer in a direction away from the negative current collector; the lithium deposition inducing layer includes a negative active material capable of forming an alloy with lithium or forming a compound with lithium. According to the lithium-free negative electrode sheet, the lithium deposition induction layers are arranged on one or two sides of the negative electrode current collector in the direction away from the negative electrode current collector, so that lithium can be induced to be uniformly deposited, the growth of lithium dendrites on the surface of the negative electrode current collector is inhibited, the inorganic electronic insulation layer can prevent the lithium layer with large specific surface area and large porosity from being formed after lithium deposition, and further, a large amount of electrochemical corrosion occurs on a solid-liquid interface to reduce coulomb efficiency, so that the safety and the cycle performance of a lithium battery are greatly improved.

Description

Lithium-free negative electrode sheet and lithium battery for lithium battery

Technical field

The invention relates to a lithium-free negative electrode sheet and lithium battery for lithium batteries, and belongs to the technical field of lithium batteries.

Background technique

At present, lithium battery technology has been widely accepted and used in power, energy storage, and mobile power supplies. However, with the continuous progress of lithium battery research, humans have placed higher expectations on the energy density of lithium batteries, and a large amount of scientific research work has been carried out. Researchers focus on increasing the gram capacity of the cathode material to increase the energy density of lithium batteries. The actual gram capacity of the 811 high-nickel material that has been commercialized and maturely applied is 185mAh/g (1C), which has a certain improvement in the battery energy density. In addition, in the battery design, by reducing the thickness of the current collector and separator, and reducing the mass of the battery's mechanical structural parts, the current mass energy density of the battery has reached 240WH/kg, which still cannot meet the expected goals.

In view of this, lithium metal batteries are sought after by researchers. However, on the one hand, the volume energy density of lithium metal batteries is low due to the excessive use of lithium metal in the negative electrode. On the other hand, the production process of lithium metal requires more stringent environmental control. The production cost is reduced, and lithium-free negative electrode batteries reduce the total mass of the battery because the negative electrode does not have graphite or lithium metal, becoming one of the development paths for high-energy-density lithium batteries. The negative electrode of the lithium-free negative electrode battery is actually just a current collector. There is no need to introduce negative electrodes such as graphite or lithium metal. All the lithium in the full battery comes from the positive electrode lithium metal oxide; this design can not only greatly improve the theoretical specific capacity of the battery, but also The use of Li sheets can be avoided in the assembly process of practical applications, which brings great convenience; copper foil is the most widely used heterogeneous substrate for negative-electrode lithium-ion batteries due to its high conductivity and good mechanical properties; currently The core of the research on anode-free technology is how to ensure the uniform deposition of metallic lithium on the copper current collector. Since lithium and copper cannot form an alloy, the overpotential of lithium deposition on the copper foil is high, resulting in low battery deposition efficiency and uneven deposition, making the lithium Irregular lithium dendrites will be formed during the deposition and extraction process. In the prior art, the Chinese patent document with application publication number CN111969212A discloses a lithium battery without negative electrode copper current collector. This current collector is plated with an induction metal plating layer on the surface of the existing current collector, which can form an alloy with lithium. The induction layer is The lithium layer has a low overpotential, inducing uniform deposition of lithium, effectively inhibiting the growth of lithium dendrites, and improving the cycle stability and service life of the battery. Although setting a lithium deposition induction layer on the copper current collector to induce lithium deposition can reduce the generation of lithium dendrites, since a large amount of lithium deposition layer is directly exposed at the solid-liquid interface after charging, the exposed lithium has a large specific surface area and a poor deposition state. Instead of being balanced, lithium is in a sub-equilibrium state and is prone to irreversible electrochemical corrosion reactions with the electrolyte, resulting in a decrease in cycle performance.

Contents of the invention

The purpose of the present invention is to provide a lithium-free negative electrode sheet for lithium batteries, which can improve the cycle performance of lithium-free negative electrode batteries.

The invention also provides a lithium battery using the lithium-free negative electrode sheet.

In order to achieve the above objectives, the technical solution adopted by the present invention for the lithium-free negative electrode sheet for lithium batteries is:

A lithium-free negative electrode sheet for lithium batteries, including a negative electrode current collector; one or both sides of the negative electrode current collector are sequentially provided with a lithium deposition induction layer and an inorganic electronic insulation layer in a direction away from the current collector; the lithium deposition The induction layer includes a negative active material capable of forming an alloy with lithium or a compound with lithium.

In the lithium-free negative electrode sheet for lithium batteries of the present invention, the lithium deposition induction layer provided on one or both sides of the negative electrode current collector in a direction away from the negative electrode current collector can induce uniform deposition of lithium, thereby inhibiting lithium dendrites from forming on the negative electrode current collector. The growth of the surface, and the inorganic electronic insulating layer can avoid the formation of a lithium layer with a large specific surface area and large porosity after lithium deposition, and then a large amount of electrochemical corrosion occurs at the solid-liquid interface, resulting in a reduction in Coulombic efficiency, thus greatly improving Safety and cycle performance of lithium batteries.

Preferably, the lithium deposition induction layer can easily form an alloy with lithium metal, and the formation of the alloy is beneficial to the uniform deposition of lithium on the surface of the negative electrode. Further preferably, the main components of the lithium deposition induction layer are graphene, silicon carbide, aluminum, magnesium, indium, beryllium, calcium, barium, titanium, zirconium, vanadium, niobium, chromium, manganese, nickel, cobalt, technetium, One or any combination of rhenium, silver, gold, zinc, cadmium, boron and germanium. The lithium deposition induction layer can be prepared and formed by evaporation, electroplating, magnetron sputtering or coating. For example, the lithium deposition induction layer is composed of silicon carbide, LA133 water-based binder and carboxymethyl cellulose. The mass ratio of silicon carbide, LA133 water-based binder and carboxymethylcellulose is preferably 96.2:0.8:3. In another example, the lithium deposition induction layer is formed by coating with an oily graphene dispersion and then drying.

Preferably, the inorganic electronic insulation layer is mainly composed of an inorganic electronic insulation material and a binder, and the mass ratio of the inorganic electronic insulation material to the binder is ≥70:30. For example, the mass ratio of the inorganic electronic insulating material to the binder is 0.1:99.9-30:70. Further preferably, the mass ratio of the inorganic electronic insulating material to the binder is 90-99:1-10. The adhesive is one or more of a water-soluble adhesive, a hot melt adhesive, an organic solvent adhesive, and an emulsion adhesive. Preferably, the inorganic electronic insulating layer is formed by coating a coating mixture mainly composed of an inorganic electronic insulating material and a binder. Coating can be carried out by gravure, spraying, extrusion, screen printing and other methods.

The coating mixture uses a liquid dispersant as a carrier, and the liquid dispersant is water or an organic solvent. The inorganic electronic insulating material and binder are evenly dispersed in the liquid dispersant to form a coating mixture in the form of paste or paste. The coating mixture is then coated on the current collector, and finally the liquid dispersant is completely volatilized to form an inorganic electronic insulating layer. The mass proportion of the liquid dispersant in the coating mixture is 50%-99.9%. The mass proportion of inorganic electronic insulating materials and binders in the coating mixture is 0.1%-50%. Preferably, the solid content of the coating mixture is 8-35%, for example, the solid content is 12-35%.

The organic solvent-based adhesive is polyvinylidene fluoride.

Preferably, the inorganic electronic insulating material is selected from one or any combination of metal oxides, carbonates, sulfates, fluorides, molybdenum disulfide, diatomite, silica, and boehmite.

Preferably, the metal oxide is selected from one or any combination of aluminum oxide, magnesium oxide, titanium dioxide, calcium oxide, and zinc oxide. The carbonate is selected from one or any combination of magnesium carbonate, calcium carbonate, and lithium carbonate. The fluoride is selected from aluminum fluoride, lithium fluoride, copper fluoride, zinc fluoride, magnesium fluoride, cobalt fluoride, iron fluoride, carbon fluoride, silver fluoride, titanium trifluoride, manganese fluoride one or any combination of them.

Preferably, the _D50 of the inorganic electronic insulating material is 0.05-5 μm, preferably 0.05-1.5 μm.

The negative electrode current collector is copper foil or copper-plated composite foil. The thickness of the negative electrode current collector is preferably 1 μm-30 μm, more preferably 3-15 μm, for example, 8 μm.

Preferably, the lithium deposition induction layer is provided on the negative electrode current collector; and the inorganic electronic insulation layer is provided on the lithium deposition induction layer.

The thickness of the lithium deposition induction layer is preferably 0.005-10 μm, more preferably 5-50 nm, and even more preferably 6-10 nm.

The thickness of the inorganic electronic insulating layer is preferably 0.1-20 μm, more preferably 0.5-10 μm, for example, 3 μm.

The technical solution adopted by the lithium battery of the present invention is:

A lithium battery using the above-mentioned lithium-free negative electrode sheet for lithium batteries.

The lithium battery of the present invention adopts the above-mentioned lithium-free negative electrode sheet for lithium batteries, so that it has higher safety and mass specific capacity.

Preferably, the lithium battery is a solid electrolyte lithium battery, a solid-liquid mixed electrolyte lithium battery or a liquid electrolyte lithium battery.

Description of drawings

Figure 1 is a schematic structural diagram of a lithium-free negative electrode sheet for lithium batteries according to Embodiment 1;

Figure 2 is a graph showing the changing trend of the discharge capacity in grams of the positive electrode of the button-type lithium battery tested in Example 9 during the cycle;

Figure 3 is a graph showing the changing trend of the discharge capacity in grams during the cycle of the positive electrode of the single-chip lithium battery tested in Example 10;

Figure 4 is a graph showing the changing trend of the discharge gram capacity of the positive electrode of the single-chip lithium battery tested in Example 11 during the cycle;

Figure 5 is a graph showing the change trend of the discharge capacity in grams of the positive electrode of the single-chip lithium battery tested in Example 12 during the cycle.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with specific implementation modes.

Example 1

The lithium-free negative electrode sheet for lithium batteries of this embodiment, as shown in Figure 1, includes a negative electrode current collector 1, a lithium deposition induction layer 2 and an inorganic electronic insulation layer 3. The lithium deposition induction layer 2 is provided on the negative electrode current collector 1 On one side, the inorganic electronic insulating layer 3 is set on the lithium deposition induction layer 2; the negative electrode current collector 1 is a copper foil with a thickness of 8 μm; the lithium deposition induction layer is an aluminum metal layer with a thickness of 10 nm; the inorganic electronic insulation layer has a thickness of 3 μm and is made of nano-SiO ₂ and polyvinylidene fluoride, the mass ratio of nano-SiO ₂ and polyvinylidene fluoride is 93:7, and the D50 particle size of nano-SiO ₂ is 50nm;

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) Use 8 μm copper foil as the negative electrode current collector, and plate a 10 nm aluminum metal layer on one side of the copper foil through evaporation;

2) Use NN dimethylpyrrolidone as the solvent, first add nano-SiO ₂ to the NN dimethylpyrrolidone and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes, then stir slowly for 30 minutes to defoaming, and get Coating liquid; in the coating liquid, the mass ratio of nano-SiO ₂ and polyvinylidene fluoride is 93:7, and the solid content of the coating liquid is 12%;

3) Use a wire rod to apply the coating liquid obtained in step 2) on the aluminum metal layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the aluminum metal layer to obtain a lithium deposition induction layer and an inorganic insulating layer. Lithium-free negative electrode sheet with electronic insulation layer.

Example 2

The only difference between the lithium-free negative electrode sheet for lithium batteries of this embodiment and the lithium-free negative electrode sheet of Example 1 is that the inorganic electronic insulating layer is composed of boehmite and polyvinylidene fluoride. The mass ratio is 96:4.

The preparation method of the lithium-free negative electrode sheet used in this embodiment for lithium batteries includes the following steps:

1) Use 8 μm copper foil as the negative electrode current collector, and plate a 10 nm aluminum metal layer on one side of the copper foil through evaporation;

2) Using NN dimethylpyrrolidone as the solvent, first add boehmite (D ₅₀ is 125nm) to the solvent and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes. Stir slowly for 30 minutes to eliminate Soak the coating liquid to obtain the coating liquid, which is ready for use; in the coating liquid, the mass ratio of boehmite to polyvinylidene fluoride is 96:4, and the solid content of the coating liquid is 35%;

3) Use a wire rod to apply the prepared coating liquid on the aluminum metal layer on the copper foil. After drying, an inorganic electronic insulation layer is formed on the aluminum metal layer, that is, a lithium deposition induction layer and an inorganic electronic insulation layer are obtained. Lithium-free negative electrode.

Example 3

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer of the lithium-free negative electrode sheet in this embodiment is a silver metal layer with a thickness of 6 nm, inorganic The electronic insulation layer is composed of Li ₂ CO ₃ (D ₅₀ is 1.5 μm) and polyvinylidene fluoride. The mass ratio of Li ₂ CO ₃ to polyvinylidene fluoride is 96:4.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) Use 8 μm copper foil as the negative electrode current collector, and plate a 6 nm silver metal layer on one side of the copper foil through electroplating;

2) Using NN dimethylpyrrolidone as the solvent, first add Li ₂ CO ₃ powder to the solvent and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes. Stir slowly for 30 minutes to defoaming and obtain the coating. The coating liquid is ready for use; the mass ratio of Li ₂ CO ₃ and polyvinylidene fluoride in the coating liquid is 96:4, and the solid content of the coating liquid is 30%;

3) Use a wire rod to apply the coating liquid on the silver metal layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the silver metal layer, thereby obtaining a lithium-free negative electrode with a lithium deposition induction layer and an inorganic electronic insulating layer. piece.

Example 4

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer in this embodiment is a titanium metal layer with a thickness of 10 nm, and the inorganic electronic insulating layer is made of lithium fluoride and Composed of polyvinylidene fluoride, the mass ratio of lithium fluoride and polyvinylidene fluoride is 96:4.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) Using 8 μm copper foil as the negative electrode current collector, a 10 nm titanium metal layer is compounded on one side of the copper foil through magnetron sputtering;

2) Using NN dimethylpyrrolidone as the solvent, first add lithium fluoride powder (D ₅₀ is 800nm) to the solvent and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes, then stir slowly for 30 minutes. Defoaming to obtain a coating liquid; in the coating liquid, the mass ratio of lithium fluoride and polyvinylidene fluoride is 96:4, and the solid content of the coating liquid is 20%;

3) Use a wire rod to apply the coating liquid on the titanium metal layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the titanium metal layer, thereby obtaining a lithium-free negative electrode with a lithium deposition induction layer and an inorganic electronic insulating layer. piece.

Example 5

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer of the lithium-free negative electrode sheet in this embodiment is a germanium metal layer with a thickness of 6 nm, and the inorganic electronic insulating layer It is composed of magnesium oxide and polyvinylidene fluoride, and the mass ratio of magnesium oxide and polyvinylidene fluoride is 90:10.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) An 8 μm copper foil is used as the negative electrode current collector, and a 6 nm germanium metal layer is compounded on one side of the copper foil through magnetron sputtering;

2) Using NN dimethylpyrrolidone as the solvent, first add magnesium oxide powder (D ₅₀ is 150nm) to the solvent and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes. Stir slowly for 30 minutes to eliminate bubble to obtain a coating liquid; in the coating liquid, the mass ratio of magnesium oxide and polyvinylidene fluoride is 90:10, and the solid content of the coating liquid is 25%;

3) Use a wire rod to apply the coating liquid on the germanium metal layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the germanium metal layer, thereby obtaining a lithium-free negative electrode with a lithium deposition induction layer and an inorganic electronic insulating layer. piece.

Example 6

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer of the lithium-free negative electrode sheet in this embodiment is a graphene layer with a thickness of 2 μm.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) An 8 μm copper foil is used as the negative electrode current collector. The purchased oily graphene with a solid content of 5% is compounded on one side of the copper foil by coating with a wire rod. After drying, a graphene layer is formed on the copper foil.

2) Use NN dimethylpyrrolidone as the solvent, first add nano-SiO ₂ to the NN dimethylpyrrolidone and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes, then stir slowly for 30 minutes to defoaming, and get Coating liquid; in the coating liquid, the mass ratio of nano-SiO ₂ (D ₅₀ is 50 nm) and polyvinylidene fluoride is 93:7, and the solid content of the coating liquid is 12%;

3) Use a wire rod to apply the coating liquid obtained in step 2) on the graphene layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the graphene layer to obtain a lithium deposition induction layer and an inorganic insulating layer. Lithium-free negative electrode sheet with electronic insulation layer.

Example 7

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer of the lithium-free negative electrode sheet in this embodiment is a silicon carbide layer with a thickness of 3 μm, and the inorganic electronic insulating layer It is composed of MgSO ₄ and polyvinylidene fluoride, and the mass ratio of MgSO ₄ and polyvinylidene fluoride is 90:10.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) 8μm copper foil is used as the negative electrode current collector. Use a wire rod to coat the silicon carbide mixture on one side of the copper foil, and then dry it thoroughly to form a silicon carbide layer on the surface of the copper foil; the silicon carbide mixture used will Water is mixed with silicon carbide, LA133 water-based binder, and carboxymethyl cellulose (CMC). The mass ratio of silicon carbide: LA133 water-based binder: CMC is 96.2:0.8:3.0; water is used as the solvent. The silicon carbide mixed liquid is a slurry with a solid content of 30%.

2) Using NN dimethylpyrrolidone as the solvent, first add MgSO ₄ powder (D ₅₀ is 130nm) to the solvent and stir thoroughly for 30 minutes, then add the binder polyvinylidene fluoride and stir thoroughly for 30 minutes. Stir slowly for 30 minutes to eliminate bubble to obtain a coating liquid; in the coating liquid, the mass ratio of MgSO ₄ and polyvinylidene fluoride is 90:10, and the solid content of the coating liquid is 25%;

3) Use a wire rod to apply the coating liquid on the silicon carbide layer on the copper foil. After drying, an inorganic electronic insulating layer is formed on the silicon carbide layer. After drying, a lithium deposition induction layer and an inorganic electronic insulating layer are obtained. Lithium-free negative electrode.

Example 8

The lithium battery of this embodiment is a liquid button lithium battery, including a positive electrode sheet, a separator and a negative electrode sheet. The negative electrode is the lithium-free negative electrode sheet used for lithium batteries in Example 1, cut into a disc with a radius of 8 mm; the positive electrode is The LiNi _0.5 Co _0.2 Mn _0.3 O ₂ active material, PVDF binder, and SP conductive agent are mixed in a mass ratio of 94:3:3, and then coated, dried, rolled, and cut into pieces. A disc with a radius of 7 mm.

Assembly of the liquid button lithium battery in this embodiment: dry the cut positive and negative electrode sheets at 120°C (positive) and 100°C (negative) for 8 hours respectively in a vacuum environment, and place the electrode pieces in a dew point controlled environment. The button battery is assembled in the battery. The lithium salt of the electrolyte selected is LiPF ₆ , the solvent is a conventional electrolyte of carbonate type, and the separator is a 20 μm PP base film. After sealing, the assembly process of buckling battery is completed.

After the liquid button-type lithium battery of this embodiment was left standing for 24 hours, the battery was subjected to a 0.1C charge/0.2C discharge cycle in the voltage range of 2.8-4.45V. The positive first efficiency of the test was 90.1%. After 50 cycles The capacity retention rate is 83.9%.

Example 9

The lithium battery in this embodiment is a liquid button lithium battery, including a positive electrode sheet, a negative electrode sheet and a separator. The positive electrode sheet is the same as that used in Example 8, and the negative electrode sheet is the lithium-free negative electrode used for lithium batteries in Example 2. Cut out the negative electrode piece with a radius of 8mm and the positive electrode piece with a radius of 7mm.

Assembly of the liquid button-type lithium battery in this embodiment: dry the cut positive and negative electrode sheets at 120°C (positive) and 100°C (negative) for 8 hours respectively in a vacuum environment, and place the electrode pieces in a dew point controlled environment. The button battery is assembled in the battery; the lithium salt of the electrolyte selected is LiPF ₆ , the solvent is a conventional carbonate electrolyte, and the separator is a 20 μm PP base film. After sealing, the assembly process of the button battery is completed.

After the liquid button-type lithium battery of this embodiment was left to stand for 24 hours, the battery was subjected to a 0.1C charge/0.2C discharge cycle at 25°C between 2.8-4.45V. The tested positive electrode gram capacity changed trend during the cycle. See the data in Group A in Figure 2. The first effect of the positive electrode is 89.3%, and the capacity retention rate after 50 cycles is 75.7%.

For comparison, after there is a 10nm aluminum plating layer on the 8 μm thick copper foil, after replacing the negative electrode sheet of this embodiment, the same assembly method is used to assemble the button lithium battery, and the same testing method as in this embodiment is used to test the button type lithium battery. The changing trend of the discharge capacity of the positive electrode of the lithium battery during the cycle is shown in the data of Group B in Figure 2. The first efficiency of the positive electrode is 91.3%, and the capacity retention rate after 50 cycles is 35.1%.

Example 10

The lithium battery of this embodiment is a liquid single-chip lithium battery, including a positive electrode sheet, a separator and a negative electrode sheet, in which the negative electrode sheet is the lithium-free negative electrode sheet used for lithium batteries in Example 3 (cut with tabs using a mold), The positive electrode sheet is made by mixing LiNi _0.5 Co _0.2 Mn _0.3 O ₂ active material, PVDF binder, and SP conductive agent in a mass ratio of 94:3:3, and then after coating, drying, rolling, and cutting piece (a pole piece with tabs that matches the negative pole piece).

The assembly of the liquid monolithic battery in this embodiment: a single-sided ceramic-coated PE separator is used. After lamination, tab welding, primary packaging, drying, liquid injection, and secondary packaging, the assembly of the monolithic battery is completed. The selected The lithium salt of the electrolyte is LiPF ₆ , and the solvent is a conventional carbonate electrolyte. The liquid injection and secondary packaging of the battery after drying need to control the dew point of the operating environment.

After the single-chip battery of this embodiment was left to stand for 24 hours, a splint was used to apply pressure to the single-chip battery. The battery was subjected to a 0.1C charge/0.2C discharge cycle in the voltage range of 2.8-4.45V at 25°C, and the positive electrode was discharged for the first time. The gram capacity is 190.3mAh/g, and the first charge and discharge efficiency is 90.5%. After 50 cycles, the capacity retention rate is 90.7%. The gram capacity changes with the cycle process as shown in Figure 3, C.

For comparison, after replacing the negative electrode sheet of this embodiment with 8 μm thick copper foil, the same assembly method is used to assemble a single-chip lithium battery, and the same testing method as in this embodiment is used to test the positive electrode of the button lithium battery during the cycle. The changing trend of mid-discharge gram capacity is shown in group D data in Figure 3. The first efficiency of the positive electrode is 90.8%, and the capacity retention rate after 50 cycles is 8.7%.

For comparison, after compounding a 6nm-thick silver metal layer on an 8-μm-thick copper foil, and replacing the negative electrode sheet in this example, the same assembly method was used to assemble a single-chip lithium battery, and the same testing method in this example was used. Test the changing trend of the discharge capacity of the positive electrode of the button-type lithium battery during the cycle. See the data in Group E of Figure 3. The first efficiency of the positive electrode is 89.9%, and the capacity retention rate after 50 cycles is 57.7%.

Example 11

The lithium battery of this embodiment is a liquid monolithic lithium battery, including a positive electrode sheet, a separator and a negative electrode sheet. The negative electrode sheet is the lithium-free negative electrode sheet used in lithium batteries in Example 4, and the positive electrode sheet is made of LiNi _0.5 Co _0.2 Mn _0.3 The _O2 active material, PVDF binder, and SP conductive agent are mixed in a mass ratio of 94:3:3, and then coated on aluminum foil, dried, rolled, and cut into pieces (with an electrode that matches the negative electrode sheet pole piece of ear).

The assembly of the liquid monolithic lithium battery in this embodiment: the separator is a PE separator coated with ceramics on one side. After lamination, tab welding, primary packaging, drying, liquid injection, and secondary packaging, the assembly of the monolithic battery is completed. The lithium salt of the electrolyte selected is LiPF ₆ , and the solvent is a conventional carbonate electrolyte. The dew point of the operating environment needs to be controlled for the liquid injection and secondary packaging of the battery after drying.

After the single-chip liquid monolithic lithium battery of this embodiment is left to stand for 24 hours, a splint is used to apply pressure to the single-chip battery, and the battery is subjected to a 0.1C charge/0.2C discharge cycle at 25°C in the voltage range of 2.8-4.45V. , the first positive electrode discharge gram capacity is 189.9mAh/g, the first charge and discharge efficiency is 90.1%, after 50 cycles, the capacity retention rate is 95.1%, the gram capacity changes with the cycle process, Figure 4 Group F data.

For comparison, a 10nm titanium metal layer was composited on an 8μm thick copper foil and the negative electrode sheet of this embodiment was replaced. The same assembly method was used to assemble a single-chip lithium battery. The same testing method as in this embodiment was used. The test unit The changing trend of the discharge capacity of the positive electrode of the lithium-ion battery during the cycle is shown in the data of group G in Figure 4. The first efficiency of the positive electrode is 90.5%, and the capacity retention rate after 50 cycles is 52.7%.

Example 12

The lithium battery of this embodiment is a liquid single-chip battery, including a positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet is the lithium-free negative electrode sheet used for lithium batteries in Example 5, and the positive electrode sheet is made of LiNi _0.5 Co _0.2 Mn _0.3 O. _2. The active material, PVDF binder, and SP conductive agent are mixed in a mass ratio of 94:3:3, and then undergo coating, drying, rolling, and cutting (electrode with tabs matching the negative electrode sheet) piece).

The assembly of the liquid monolithic lithium battery in this embodiment: the separator is a PE separator coated with ceramics on one side. After lamination, tab welding, primary packaging, drying, liquid injection, and secondary packaging, the assembly of the monolithic battery is completed. The lithium salt of the electrolyte selected is LiPF ₆ , and the solvent is a conventional carbonate electrolyte. The dew point of the operating environment needs to be controlled for the liquid injection and secondary packaging of the battery after drying.

After the liquid monolithic lithium battery of this embodiment is left to stand for 24 hours, a splint is used to apply pressure to the single chip, and the battery is subjected to a 0.1C charge/0.2C discharge cycle at 25°C in the voltage range of 2.8-4.45V. The first discharge gram capacity of the positive electrode is 185.9mAh/g, and the first charge and discharge efficiency is 86.5%. After 50 cycles, the capacity retention rate is 91%. The gram capacity changes with the cycle process, as shown in Figure 5, group H data.

For comparison, a 10nm germanium metal layer was compounded on an 8μm thick copper foil and the negative electrode sheet of this embodiment was replaced. The same assembly method was used to assemble a single-chip lithium battery. The same testing method as in this embodiment was used. The test unit The changing trend of the discharge capacity of the positive electrode of the lithium-ion battery during the cycle is shown in Group I of Figure 5. The first efficiency of the positive electrode is 90.3%, and the capacity retention rate after 50 cycles is 36.9%.

Example 13

The lithium battery of this embodiment is a liquid button lithium battery, including a positive electrode sheet, a separator and a negative electrode sheet. The negative electrode is the lithium-free negative electrode sheet used for lithium batteries in Example 6, cut into a disc with a radius of 8 mm; the positive electrode is The LiNi _0.5 Co _0.2 Mn _0.3 O ₂ active material, PVDF binder, and SP conductive agent are mixed in a mass ratio of 94:3:3, and then coated, dried, rolled, and cut into pieces. A disc with a radius of 7 mm.

Assembly of the liquid button-type lithium battery in this embodiment: dry the cut positive and negative electrode sheets at 120°C (positive) and 100°C (negative) for 8 hours respectively in a vacuum environment, and buckle them in a dew point controlled environment. For the assembly of the battery, the lithium salt of the electrolyte selected is LiPF ₆ , the solvent is a conventional carbonate electrolyte, and the separator is a 20 μm PP base film. After sealing, the assembly process of buckling is completed.

After the liquid button-type lithium battery of this embodiment was left standing for 24 hours, the battery was subjected to a 0.1C charge/0.2C discharge cycle in the voltage range of 2.8-4.45V. The positive first efficiency of the test was 89.1%. After 20 cycles, The capacity retention rate is 91.1%.

As a comparison, the graphene-coated copper foil obtained in step 1) of the preparation method of the lithium-free negative electrode sheet for lithium batteries in Example 6 was used as the lithium-free negative electrode sheet, and the button-type lithium button was assembled using the assembly method of this embodiment. For the battery (the separator and positive electrode sheet used are the same as in this embodiment), using the same test method as in this embodiment, the first positive electrode efficiency of the tested button lithium battery is only 85%, and the capacity retention rate after 20 cycles is 50.1%.

Example 14

The lithium battery in this embodiment is a liquid button lithium battery, including a positive electrode sheet, a separator and a negative electrode sheet. The negative electrode is the lithium-free negative electrode sheet used for lithium batteries in Example 7, cut into a disc with a radius of 8 mm; the positive electrode is The LiNi _0.5 Co _0.2 Mn _0.3 O ₂ active material, PVDF binder, and SP conductive agent are mixed in a mass ratio of 94:3:3, and then coated, dried, rolled, and cut into pieces. A disc with a radius of 7 mm.

Assembly of the liquid button-type lithium battery in this embodiment: dry the cut positive electrode sheets and negative electrode sheets at 120°C (positive) and 100°C (negative) for 8 hours respectively in a vacuum environment, and button-type the electrode pieces in an inert atmosphere. For the assembly of the battery, the lithium salt of the electrolyte selected is LiPF ₆ , the solvent is a conventional carbonate electrolyte, and the separator is a 20 μm PP base film. After sealing, the assembly process of buckling is completed.

After the liquid button-type lithium battery of this embodiment was left standing for 24 hours, the battery was subjected to a 0.1C charge/0.2C discharge cycle in the voltage range of 2.8-4.45V. The positive first efficiency of the test was 87.5%. After 50 cycles, The capacity retention rate is 81.1%.

As a comparison, the silicon carbide layer-coated copper foil obtained in step 1) of the preparation method of the lithium-free negative electrode sheet for lithium batteries in Example 7 was used as the lithium-free negative electrode sheet, and the button-type assembly was assembled using the assembly method of this embodiment. Lithium battery (the separator and positive electrode sheet used are the same as in this embodiment), using the same test method as in this embodiment, the first positive electrode efficiency of the tested button lithium battery is only 85%, and the capacity retention rate after 50 cycles is 23.1% .

Example 15

The only difference between the lithium-free negative electrode sheet for lithium batteries in this embodiment and the lithium-free negative electrode sheet in Example 1 is that the lithium deposition induction layer of the lithium-free negative electrode sheet in this embodiment is a silver metal layer with a thickness of 2 nm, and the inorganic electronic insulating layer It is composed of silver fluoride and polyethylene oxide, and the mass ratio of nanometer silver fluoride and polyethylene oxide is 70:30.

The preparation method of the lithium-free negative electrode sheet for lithium batteries in this embodiment includes the following steps:

1) 8μm copper foil is used as the negative electrode current collector, and a 2nm silver metal layer is compounded on one side of the copper foil through magnetron sputtering;

2) Using NN dimethylpyrrolidone (NMP) as the solvent, first add nanometer silver fluoride powder (D ₅₀ is 210nm) to the solvent and stir thoroughly for 30 minutes, then add the binder polyethylene oxide (the solvent is NMP) and stir thoroughly. After mixing for 30 minutes, stir slowly for 30 minutes to eliminate foam and obtain a coating liquid; in the coating liquid, the mass ratio of silver fluoride and polyvinylidene fluoride is 70:30, and the solid content of the coating liquid is 20%;

3) Use a wire rod to apply the coating liquid on the silver metal layer on the copper foil. After drying, an inorganic electronic insulation layer is formed on the silver metal layer. After drying, a lithium deposition induction layer and an inorganic electronic insulation layer are obtained. Lithium-free negative electrode.

The above-mentioned negative electrode sheet is prepared to form a liquid monolithic battery, including a positive electrode sheet, a separator and a negative electrode sheet. The positive electrode sheet is made of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ active material, PVDF binder and SP conductive agent according to a mass ratio of 94: The slurry is mixed at a ratio of 3:3, and then coated, dried, rolled, and cut into pieces (pole pieces with tabs that match the negative electrode pieces).

The assembly of the liquid monolithic lithium battery in this embodiment: the separator is a PE separator coated with ceramics on one side. After lamination, tab welding, primary packaging, drying, liquid injection, and secondary packaging, the assembly of the monolithic battery is completed. The lithium salt of the electrolyte selected is LiPF ₆ , and the solvent is a conventional carbonate electrolyte. The dew point of the operating environment needs to be controlled for the liquid injection and secondary packaging of the battery after drying.

After the single-chip battery of this embodiment was left standing for 24 hours, a splint was used to apply pressure to the single-chip battery. The battery was subjected to a 0.1C charge/0.2C discharge cycle in the voltage range of 2.8-4.45V. The first positive electrode discharge gram capacity was 186.7 mAh/g, the first charge and discharge efficiency is 89.9%, and the capacity retention rate is 91.3% after 50 cycles.

For comparison, after replacing the negative electrode sheet in this example with silver plating on 8 μm thick copper foil, the same assembly method was used to assemble a single-chip lithium battery. Using the same testing method in this example, the first positive electrode discharge capacity was 185.7mAh. /g, the first charge and discharge efficiency is 88.7%, and after 50 cycles, the capacity retention rate is 60.3%.

Claims (6)

1. A lithium-free negative electrode sheet for lithium batteries, including a negative electrode current collector, characterized in that one or both sides of the negative electrode current collector are sequentially provided with a lithium deposition induction layer and inorganic electrons in a direction away from the negative electrode current collector. Insulating layer; the lithium deposition induction layer includes a negative active material or graphene or silicon carbide that can form an alloy with lithium or a compound with lithium; The components that can form alloys with lithium or form compounds with lithium are aluminum, magnesium, indium, beryllium, calcium, barium, titanium, zirconium, vanadium, niobium, chromium, manganese, nickel, cobalt, technetium, rhenium, silver, gold One or any combination of zinc, cadmium, boron and germanium; The inorganic electronic insulating layer is mainly composed of inorganic electronic insulating material and binder, and the mass ratio of inorganic electronic insulating material and binder is ≥70:30; The inorganic electronic insulating material is selected from one or any combination of metal oxides, carbonates, sulfates, fluorides, molybdenum disulfide, diatomite, silica, and boehmite; The fluoride is selected from aluminum fluoride, lithium fluoride, copper fluoride, zinc fluoride, magnesium fluoride, cobalt fluoride, iron fluoride, carbon fluoride, silver fluoride, titanium trifluoride, manganese fluoride one or any combination of them. 2. The lithium-free negative electrode sheet for lithium batteries according to claim 1, characterized in that: the metal oxide is selected from one or any combination of aluminum oxide, magnesium oxide, titanium dioxide, calcium oxide, and zinc oxide. ; The carbonate is selected from one or any combination of magnesium carbonate, calcium carbonate, and lithium carbonate. 3. The lithium-free negative electrode sheet for lithium batteries according to claim 1, wherein the negative electrode current collector is copper foil or copper-plated composite foil. 4. The lithium-free negative electrode sheet for lithium batteries according to claim 1, characterized in that: the thickness of the lithium deposition induction layer is 0.005-10 μm, and the thickness of the inorganic electronic insulating layer is 0.1-20 μm. 5. A lithium battery using the lithium-free negative electrode sheet for lithium batteries as claimed in claim 1. 6. The lithium battery according to claim 5, characterized in that: the lithium battery is a solid electrolyte lithium battery, a solid-liquid mixed electrolyte lithium battery or a liquid electrolyte lithium battery.