CN112670516B - Three-dimensional composite current collector and preparation method thereof - Google Patents

Abstract

The invention provides a three-dimensional composite current collector and a preparation method thereof. The three-dimensional composite current collector provided by the invention includes a copper foil base layer and a lithium battery negative electrode lithophile material coating coated on the copper foil base layer; the lithium battery negative electrode lithophile material coating contains several micron-sized three-dimensional spherical structures. . The lithium-philic material of the lithium battery negative electrode is composed of carbon material, lithium-philic metal oxide, binder, and lithium salt. The invention first prepares a lithium battery negative electrode lithophile material slurry, and then coats the slurry on the copper foil base layer to form a lithium battery negative electrode lithophile material coating, and prepares a lithium battery negative electrode three-dimensional composite current collector. The lithium-philic material of the lithium battery negative electrode is coated on the copper foil to form a composite coating with a micron-sized three-dimensional spherical structure, which can effectively reduce the current density of the lithium metal negative electrode, thereby effectively alleviating and reducing the generation of lithium dendrites, and improving lithium metal Battery cycle performance and safety performance.

Description

Three-dimensional composite current collector and preparation method thereof

Technical field

The present invention relates to the field of battery materials, and in particular to a three-dimensional current collector and a preparation method thereof.

Background technique

Lithium-ion batteries, which have been successfully commercialized at present, have the characteristics of high operating voltage, long cycle life, and no memory effect, and have been widely used in electric vehicles, mobile electronic equipment and other fields. However, economic development and technological progress have increasingly placed higher requirements on the energy density of lithium-ion batteries. Traditional lithium-ion batteries mostly use graphite as negative electrode materials, and their theoretical capacity is limited. Today's commercial lithium-ion batteries are getting closer and closer to their theoretical specific capacity. Therefore, there is a need to seek and develop lithium batteries with higher energy density. The theoretical energy density of metallic lithium anode materials can be about ten times that of graphite anodes, and it has a higher specific capacity and lower potential than graphite. It has become a hot spot in the field of lithium battery anode materials.

Lithium-oxygen batteries and lithium-sulfur batteries with higher energy density use metallic lithium as the negative electrode. However, as the negative electrode of batteries, metallic lithium has always had three problems during the charging and discharging process: the problem of lithium dendrites produced when lithium ions are reduced during the charging process of lithium batteries; the extremely high chemical reactivity of metallic lithium and organic solvents. The low Coulombic efficiency; the volume change caused by the deposition and dissolution process of metallic lithium. These problems limit the industrial application development of metal lithium batteries. At this stage, the main solutions to the stability problem of high specific energy lithium anodes include: improving the electrolyte, constructing a metallic lithium protective layer, designing lithium compound anodes, and constructing a three-dimensional structure current collector.

Improving the electrolyte Although the current dual-salt LiTFSI/LiFSI system has certain improvements in batteries, the process is not completely stable. During long-term high-current charge and discharge processes, the surface of the lithium anode will also turn black, the surface SEI will crack, and the performance will deteriorate. . To construct a protective layer of metallic lithium, most of the current literature reports are to directly grow the protective layer on the surface of metallic lithium in situ. However, due to the strong reactivity of metallic lithium, in-situ growth is difficult and the reaction conditions are strict, which also limits the application of this method. actual use. Lithium-carbon composite electrodes are generally prepared by uniformly coating lithium powder on the carbon electrode. This method introduces great safety risks due to the high reactivity of lithium powder and is difficult to industrialize.

The surface structure and material composition of the current collector have an important impact on the performance of lithium-ion batteries. The currently used negative electrode copper foil current collector has low surface roughness and low bonding strength with the active negative electrode slurry, which greatly limits the use of lithium batteries. The electrochemical performance of the battery. Constructing a three-dimensional structure current collector can effectively reduce the actual current density of the electrode, uniformly distribute the electric field on the electrode surface, induce uniform deposition of metallic lithium and alleviate volume expansion, and can effectively inhibit the growth of lithium dendrites. However, most of the currently reported current collectors with three-dimensional lithiophilic characteristics require complex preparation processes or expensive raw materials, and the surface modification layer often has weak binding force.

The invention patent with application number CN201910524383.5 discloses a three-dimensional current collector for secondary lithium-ion battery negative electrodes and a preparation method thereof. This method mainly involves placing the heat-treated copper foil into an electrolytic cell in a sodium sulfate solution for surface treatment to obtain a three-dimensional current collector for the negative electrode of secondary lithium ion batteries. This method can efficiently prepare a large number of three-dimensional current collectors. However, the disadvantage of this method is that it is processed directly on copper foil, which has a complicated process, high cost, and heavy unit weight, which is not conducive to the tab welding of battery core production. and large-scale production.

The invention patent with application number CN201711449563.9 discloses the application of iron phosphate and iron phosphate composite materials as negative electrodes in dual-ion batteries. The structure of the iron phosphate and iron phosphate doped materials disclosed in this method is a porous spherical shape with a micro-nano structure; the iron phosphate and iron phosphate composite materials are evenly mixed with carbon black and binder, and then coated on the current collector. After vacuum drying and slicing, the iron phosphate and iron phosphate composite negative electrodes are obtained. This composite material has the advantages of high potential and no dendrites produced during repeated charge and discharge processes. However, the disadvantage of this method is that the connection performance between the composite material and metallic lithium is not improved, causing the metallic lithium on the negative electrode to easily fall off. .

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a lithium-philic material for the negative electrode of a lithium battery, a three-dimensional composite current collector and a preparation method thereof. The three-dimensional composite current collector can significantly improve the cycle performance of lithium metal batteries, and the manufacturing method is simple to operate and can meet industrial mass production and use.

In order to achieve the above-mentioned object of the invention, the present invention provides a three-dimensional composite current collector, including a copper foil base layer and a lithium battery negative electrode lithiophilic material coating coated on the copper foil base layer; the lithium battery negative electrode lithiophilic material coating The layers contain several micron-sized three-dimensional spherical structures.

Preferably, the lithium-philic material coating of the lithium battery negative electrode is composed of carbon materials, lithium-philic metal oxides, binders, and lithium salts;

In terms of mass fraction, the mass ratio of the carbon material, the lithiophilic metal oxide, the binder, and the lithium salt is 5% to 35%: 75% to 45%: 15% to 5%: 5%~15%. .

In order to achieve the above-mentioned object of the invention, the present invention also provides a preparation method for the above-mentioned three-dimensional composite current collector, which includes the following steps:

S1. Weigh a predetermined amount of carbon material, lithiophilic metal oxide and lithium salt, mix and stir for 0.5 to 4 hours; add solvent and stir for 0.5 to 2 hours until completely dissolved; then add a predetermined amount of binder, stir for 4 to 10 hours, and prepare Obtain lithium-philic material slurry for lithium battery negative electrode;

S2. Select a copper foil with a thickness of 6 to 20 μm as the base layer, apply the slurry described in step S1 on the copper foil at a coating speed of 10 to 30 m/min, and then dry it in a blast drying oven at 70 to 80°C. 4 to 8 hours, and then dried in a vacuum oven at 110 to 130°C for 8 to 12 hours to prepare a three-dimensional composite current collector.

Preferably, the lithiophilic metal oxide includes but is not limited to one or a mixture of three cobalt tetraoxides, zinc oxide, and copper oxide.

Preferably, the carbon material includes but is not limited to one of carbon nanotubes, carbon fibers, acetylene black, and graphene.

Preferably, the lithium salt includes but is not limited to one of lithium carbonate, lithium fluoride, lithium nitride, and lithium nitrate.

Preferably, the adhesive is one of styrene-butadiene rubber, acrylic resin, acrylonitrile, and polyvinylidene fluoride.

Preferably, the solvent is one of water and N-methylpyrrolidone.

Preferably, in step S1, the mass ratio of the carbon material, the lithiophilic metal oxide, the binder, and the lithium salt is 5%~35%: 75%~45%: 15%~ 5%: 5%~15%.

Compared with the prior art, the beneficial effects of the present invention are:

1. The lithium battery negative electrode lithiophilic material provided by the present invention forms a micron-sized three-dimensional spherical structure on the surface of the copper foil base layer, thereby constructing a composite current collector with a three-dimensional interconnected spherical structure, which has a high specific surface area and can effectively Reducing the actual current density is conducive to providing more Li ⁺ deintercalation sites, thereby achieving uniform deposition; the three-dimensional structure can also buffer the volume changes caused by metallic lithium deposition, alleviate the volume expansion during charge and discharge, and is conducive to buffering the electrode electrode. chemical reaction, thereby improving its electrochemical performance. In addition, during the charge and discharge process, the three-dimensional interconnected spherical structure provides a network that can be easily penetrated by the electrolyte, providing a shorter transport distance for lithium ions and electrons, shortening the Li ⁺ diffusion path, thereby making the lithium battery negative electrode lithiophilic material It has more stable electrochemical performance and rate performance.

2. In the lithiophilic material for the lithium battery negative electrode provided by the present invention, the carbon material, the lithiophilic metal oxide and the lithium salt are mixed together to prepare a lithiophilic transition metal oxide/carbon material/lithium ion composite material. 1) The role of carbon materials is: the coating of carbon materials can alleviate the volume expansion of lithiophilic metal oxides; enhance their conductive properties; and can make the structure of composite materials more stable. 2) The role of lithium-loving metal oxides is: on the one hand, it can make up for the shortcomings of low specific capacity of carbon materials; on the other hand, lithium-philic metal oxides can react with metallic lithium to anchor lithium on the copper foil, and then chemically combine The force and external pressure work together to firmly contact the metal lithium with the copper foil and reduce the contact resistance. 3) The role of lithium salt is: a small proportion of lithium salt mainly plays a role in stabilizing metal lithium. When the metal lithium is exhausted, turns into lithium powder or thermally runs out of control, lithium salt can stabilize the safety performance of the battery, especially carbonic acid. The decomposition of lithium and lithium nitride and the side reactions of lithium fluoride, etc., the gas production can disconnect the active material from the current collector. In addition, lithium salts are mostly non-conductive materials, which can delay the active reaction of lithium to a certain extent during the charge and discharge process, and play a role in stabilizing the metallic lithium negative electrode. Therefore, the present invention mixes lithium-philic metal oxides, carbon materials and lithium salts. In addition to improving the electrochemical performance of the lithium-philic material for the negative electrode of lithium batteries, it also achieves the goal of anchoring metallic lithium and increasing conductivity. The role of stable and stable metallic lithium. Moreover, mixing the three under the action of a binder can only be used as a coating between copper foil and metallic lithium. The mixed material of the three can not be used as the negative electrode of a lithium battery when used alone. Therefore, all three are indispensable, otherwise there will be a certain loss in the performance of metallic lithium.

3. In the three-dimensional composite current collector provided by the present invention, the lithium battery negative electrode lithiophilic material is coated on the copper foil to form a micron-sized three-dimensional spherical structure. The formation mechanism is that the tubular or fibrous carbon material is wound and agglomerated after high-speed stirring. Form microspheres together, add lithiophilic metal oxides, fill them under stirring, and then apply and dry to form micron-sized spheres.

4. In the three-dimensional composite current collector provided by the present invention, the micron-sized three-dimensional spherical structure formed by coating the lithium-philic material of the lithium battery negative electrode on the copper foil can effectively reduce the current density of the lithium metal negative electrode, thereby effectively alleviating and reducing lithium dendrites. The production of lithium metal batteries improves the cycle performance and safety performance of lithium metal batteries. At the same time, the micro-nano three-dimensional structure can provide space for the expansion of the lithium metal anode and alleviate the rupture of the SEI film on the surface of the lithium metal anode, thereby improving the Coulombic efficiency of the lithium metal battery.

5. In the three-dimensional negative electrode current collector provided by the present invention, the Gibbs free energy ΔG of the lithiophilic metal oxide and metallic lithium is <0, indicating that the lithiophilic metal oxide can spontaneously react with metallic lithium, thereby making the copper foil The lithium-philic material of the negative electrode of lithium battery is closely connected with the metallic lithium, which improves the binding force between the copper foil and the lithium ribbon and reduces the chance of metallic lithium falling off.

6. The three-dimensional negative electrode current collector provided by the present invention significantly improves the cycle performance of lithium metal batteries, has a simple manufacturing process, can meet industrial mass production and use, and has excellent development prospects in the field of lithium battery applications.

Description of the drawings

Figure 1 is a physical diagram of the three-dimensional composite current collector prepared in Example 1 of the present invention.

Figure 2 is an electron microscope image of the three-dimensional spherical structure of the three-dimensional composite current collector prepared in Example 1 of the present invention. The scale bar is 5 μm.

Figure 3 is an electron microscope image of the three-dimensional spherical structure of the three-dimensional composite current collector prepared in Example 1 of the present invention. The scale bar is 20 μm.

Figure 4 is a schematic diagram of the formation of a three-dimensional spherical structure in the three-dimensional composite current collector provided by the present invention.

Figure 5 is a schematic structural diagram of the three-dimensional composite current collector prepared in Example 1 of the present invention.

Figure 6 is a graph showing the charge-discharge cycle and specific capacity of the three-dimensional composite current collector prepared in Example 1 and Comparative Example 1 of the present invention.

Figure 7 is a charge-discharge curve diagram of the three-dimensional composite current collector prepared in Example 1 and Comparative Example 3 of the present invention.

Figure 8 is a peeling test chart of Example 2 and Comparative Example 5 of the present invention.

Figure 9 is a graph showing the cycle retention rate of the lithium-philic material coating and lithium on the negative electrode of the charge-discharge lithium battery of the three-dimensional composite current collector prepared in Example 3 of the present invention.

Reference signs:

1. Lithium metal layer; 2. Lithiophilic material coating of lithium battery negative electrode; 3. Copper foil base layer.

Detailed ways

The technical solutions of various embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present invention.

The invention provides a preparation method for a three-dimensional composite current collector, which includes the following steps:

S1. Weigh a predetermined amount of carbon material, lithiophilic metal oxide and lithium salt, mix and stir for 0.5 to 4 hours; add solvent and stir for 0.5 to 2 hours until completely dissolved; then add a predetermined amount of binder, stir for 4 to 10 hours, and prepare Obtain lithium-philic material slurry for lithium battery negative electrode;

S2. Select a copper foil with a thickness of 6 to 20 μm as the base layer, apply the slurry on the copper foil at a coating speed of 10 to 30 m/min, and then dry it in a blast drying oven at 70 to 80°C for 4 to 8 hours, and then dried in a vacuum oven at 110-130°C for 8-12 hours to prepare a three-dimensional composite current collector.

Further, the solvent is one of water and N-methylpyrrolidone.

Further, in step S1, the mass ratio of the carbon material, the lithiophilic metal oxide, the binder, and the lithium salt is 5%~35%: 75%~45%: 15%~ 5%: 5%~15%.

Further, the lithiophilic metal oxide includes but is not limited to one or a mixture of three cobalt tetroxide, zinc oxide, and copper oxide.

Further, the carbon material includes but is not limited to one of carbon nanotubes, carbon fibers, acetylene black, and graphene.

Further, the lithium salt includes but is not limited to one of lithium carbonate, lithium fluoride, lithium nitride, and lithium nitrate.

Further, the adhesive is one of styrene-butadiene rubber, acrylic resin, acrylonitrile, and polyvinylidene fluoride.

The preparation method of the three-dimensional composite current collector provided by the present invention will be further described in detail below through Examples 1-17 and Comparative Examples 1-5 and in conjunction with Figures 1-9.

Example 1

Preparation method of three-dimensional composite current collector:

S1. Weigh 30g carbon nanotubes and 55g copper oxide particles and place them in a stirring tank and stir for 2 hours; then add 10g of lithium carbonate into the stirring tank and stir for 2 hours, then add an appropriate amount of N-methylpyrrolidone and stir for 2 hours until completely dissolved; then Add 5g of polyvinylidene fluoride into a mixing tank and stir for 10 hours to prepare a lithium battery negative electrode lithiophilic material slurry;

S2. Select a copper foil with a thickness of 8 μm and no impurities on the surface as the base layer. Coat the slurry on the copper foil with a coating machine at a coating speed of 10 m/min, and then place it in a blast dryer. Bake in a box at 75°C for 4 hours, and finally bake in a vacuum oven at 120°C for 12 hours to prepare a three-dimensional composite current collector.

Please refer to Figures 1-5 to describe the three-dimensional composite current collector prepared in Example 1. As shown in Figure 1, the three-dimensional composite current collector prepared in Example 1 of the present invention appears black.

As shown in Figure 2, the three-dimensional composite current collector prepared in this embodiment exhibits a micron-sized three-dimensional spherical structure, which is composed of interconnected particles of micron and nano-sized particles, and the surface of the spherical particles exhibits a dense porous structure. This three-dimensional porous spherical structure can alleviate to a certain extent the volume expansion problem of lithium-philic materials in the negative electrode of lithium batteries during cycling. It can also store the infiltration of electrolyte, shorten the round-trip path of lithium ions, and improve the lithium-philic materials in the negative electrode of lithium batteries. Rate performance and long-term cycling stability. The mesoporous structure generated by micron-sized spheres provides a network that is relatively easy to be penetrated by electrolytes, and its porosity combined with micro- and nano-sized structural units significantly improves electrochemical performance.

In addition, in the lithium-philic material coating of the lithium battery negative electrode, carbon nanotubes were successfully coated on the outside of copper oxide. The outer layer of carbon material can not only enhance the conductivity of the lithium-philic metal oxide, but also serve as a protective layer to improve the mechanical properties of the lithium-philic metal oxide and extend the cycle performance and service life of the lithium-philic metal oxide.

As shown in Figure 4, the formation process of the three-dimensional spherical structure in the three-dimensional composite current collector is mainly as follows: tubular or fibrous carbon materials are entangled through high-speed stirring, agglomerated to form micro-spherical shapes, and lithiophilic metal oxides are added. Filling it, then coating and drying can form micron-sized spheres.

As shown in Figure 5, in the three-dimensional composite current collector provided by the present invention, the lithium-philic material of the lithium battery negative electrode is compounded on the copper foil base layer in a coating manner to construct a micro-nano-sized three-dimensional spherical structure composite current collector. Among them, the Gibbs free energy ΔG of the lithiophilic metal oxide and metallic lithium in the lithium-philic material of the lithium battery negative electrode is <0, indicating that the lithiophilic metal oxide can react spontaneously with metallic lithium, thereby making the lithium-philic metal oxide composite on the copper foil The lithium-philic material film of the negative electrode of the lithium battery is closely connected with the metallic lithium layer, which improves the binding force between the copper foil and the lithium ribbon and reduces the chance of metallic lithium falling off.

Therefore, the present invention mixes the lithium-philic metal oxide, the carbon material and the lithium salt. In addition to improving the electrochemical performance of the lithium-philic material in the negative electrode of the lithium battery, it also achieves the function of anchoring metal lithium and conducting electricity. The role of stabilizing metal lithium. Moreover, the mixture of the three under the action of the binder is only used as a coating between the copper foil and the metallic lithium. The mixed material of the three is used alone and is not used as the negative electrode of the lithium battery. Therefore, all three are indispensable, otherwise there will be a certain loss in the performance of metallic lithium.

Comparative example 1

The difference from Example 1 is that the lithium battery negative electrode lithiophilic material is not coated on the copper foil base layer to prepare a battery with the negative electrode being a pure lithium sheet.

Referring to Figure 6, the experiment found that as the number of cycles increases, the capacity retention rate of the lithium battery using the three-dimensional composite current collector prepared in Example 1 is 97%@350cycle, while the pure lithium battery prepared using Comparative Example 1 The capacity retention rate of the lithium-ion battery gradually decreases as the number of cycles increases. It can be seen that the battery cycle performance of the lithium battery with a three-dimensional composite current collector prepared in Example 1 of the present invention is far better than that of the pure lithium sheet battery prepared in Comparative Example 1, indicating that coating lithium battery negative electrode lithiophilic materials can significantly improve lithium metal batteries cycle performance.

Comparative example 2

The difference from Example 1 is that no carbon material (carbon nanotubes) is added in the preparation of the lithium-philic material slurry for the lithium battery negative electrode to prepare the composite current collector.

After charging and discharging cycle tests, it can be seen that the battery cycle performance and stability performance of the battery assembled by using the composite current collector prepared in Comparative Example 2 as the negative electrode current collector of the lithium battery are not as good as those in Example 1. This is mainly due to the fact that although the specific capacity of lithiophilic metal oxide anode materials is higher than that of carbon materials, their cycle stability is not as good as that of carbon materials, and their rate performance is low. Lithiophilic metal oxide copper oxide that is not coated with carbon materials will repeatedly react with metallic lithium, resulting in large volume changes. Therefore, the negative electrode material itself is prone to powdering, and the point contact between the current collector and the active material is gradually lost, resulting in Gradually lose the ability of electrochemical energy storage reaction, resulting in rapid capacity fading.

Comparison with Comparative Example 2 also shows that in the lithium battery assembled with the three-dimensional negative electrode current collector prepared in Example 1, during the charge and discharge process, the carbon nanotubes can inhibit the volume expansion of copper oxide and enhance the conduction. ability; on the other hand, the three-dimensional spherical structure formed by the carbon material and the lithiophilic metal oxide increases the specific surface area of the negative electrode current collector. The excellent specific surface area increases the utilization of the negative electrode material and exposes more surface area to the electrolyte. , the load on lithium ions is greatly increased. Therefore, the lithium battery prepared in Example 1 has excellent electrochemical performance and battery cycle performance.

Comparative example 3

The difference from Example 1 is that in the preparation of the lithium-philic material slurry for the lithium battery negative electrode, no lithium salt (lithium carbonate) is added to prepare the composite current collector.

As shown in Figure 7, after charge and discharge cycle testing, the electrochemical performance of the battery assembled using the composite current collector prepared in Comparative Example 3 as the negative electrode current collector of the lithium battery was not as good as that of Example 1. This is mainly because: metallic lithium has the lowest reduction potential and is relatively active. The charge and discharge curve of the battery on the lithium salt-free coating is unstable. The non-conductive property of the dispersed lithium salt can make the current more stable. Therefore, the charge and discharge of Example 1 The curve is more stable.

In the lithium-philic material for the lithium battery negative electrode provided by the present invention, a small proportion of lithium salt mainly plays a role in stabilizing metal lithium. When the metal lithium is exhausted, turns into lithium powder or thermally runs out of control, the lithium salt can stabilize the safety of the battery. Performance, especially the decomposition of lithium carbonate and lithium nitride and the side reactions of lithium fluoride, etc. The gas production can disconnect the active material from the current collector. In addition, lithium salts are mostly non-conductive materials, which can delay the active reaction of lithium to a certain extent during the charge and discharge process, and play a role in stabilizing the metallic lithium negative electrode.

Comparative example 4

The difference from Example 1 is that no lithiophilic metal oxide (copper oxide) is added in the preparation of the lithium-philic material slurry for the lithium battery negative electrode to prepare the composite current collector.

After charge and discharge cycle tests, Comparative Example 4 was used to prepare a composite current collector as a negative electrode current collector for a lithium battery assembly. The battery cycle performance and specific capacity were not as good as Example 1. This is mainly because: as an anode material, the carbon material has a low potential, forms an interface film with the electrolyte, and easily causes lithium precipitation; the ion migration speed is slow, so the charge and discharge rate is low, which affects the electrochemical performance of lithium batteries. Moreover, carbon materials will suffer irreversible capacity losses due to side reactions when they are first charged and discharged. Comparison with Comparative Example 4 also shows that in the lithium battery assembled with the three-dimensional negative electrode current collector prepared in Example 1, during the charge and discharge process, the addition of lithiophilic metal oxides can make up for the shortcomings of the low specific capacity of the carbon material. .

At the same time, the reaction ΔG between the lithium-philic metal oxide and the metallic lithium in the lithium-philic material coating of the lithium battery negative electrode prepared in this example is a spontaneous reaction. Therefore, the lithium-philic metal oxide can react with the metallic lithium to anchor the lithium in the on copper foil. Then, through the combined action of chemical bonding force and external pressure, the metal lithium can be firmly contacted with the copper foil, reducing the contact resistance.

Example 2

Preparation method of three-dimensional composite current collector:

S1. Weigh 30g of carbon nanotubes and 55g of zinc oxide particles and place them in a stirring tank and stir for 2 hours; then add 10g of lithium carbonate into the stirring tank and stir for 2 hours, then add an appropriate amount of N-methylpyrrolidone and stir for 2 hours until completely dissolved; then Add 5g of polyacrylonitrile LA133 into a mixing tank and stir for 10 hours to prepare a lithium battery negative electrode lithiophilic material slurry;

S2. Select a copper foil with a thickness of 8 μm and no impurities on the surface as the base layer. Coat the slurry on the copper foil with a coating machine at a coating speed of 10 m/min, and then place it in a blast dryer. Bake in a box at 75°C for 4 hours, and finally bake in a vacuum oven at 120°C for 12 hours to prepare a three-dimensional composite current collector.

Comparative example 5

The difference from Example 2 is that graphite is coated on the copper foil current collector to prepare a traditional graphite negative electrode.

Figure 8 is a peeling test chart of Example 2 and Comparative Example 5 of the present invention. As shown in Figure 7, the peeling strength of the three-dimensional composite current collector anode of the LA133/ZnO system prepared in Example 2 is equivalent to that of the traditional graphite anode, indicating that the three-dimensional composite current collector prepared in this example improves the bonding force between copper foil and lithium foil. , reducing the chance of metallic lithium falling off, thereby improving the electrochemical performance of lithium batteries to a certain extent.

Example 3

Preparation method of three-dimensional composite current collector:

S1. Weigh 30g of carbon nanotubes and 55g of cobalt tetroxide particles and place them in a mixing tank for 2 hours; add 10g of lithium carbonate to the mixing tank and stir for 2 hours; then add an appropriate amount of N-methylpyrrolidone and stir for 2 hours until completely dissolved; then add Add 5g of styrene-butadiene rubber into a mixing tank and stir for 10 hours to prepare a lithium battery negative electrode lithiophilic material slurry;

S2. Select a copper foil with a thickness of 8 μm and no impurities on the surface as the base layer. Coat the slurry on the copper foil with a coating machine at a coating speed of 10 m/min, and then place it in a blast dryer. Bake in a box at 75°C for 4 hours, and finally bake in a vacuum oven at 120°C for 12 hours to prepare a three-dimensional composite current collector.

As shown in Figure 9, as the number of charge and discharge cycles increases, the cycle retention rate of the lithium-philic material coating of the lithium battery negative electrode and lithium remains above 97% until the number of cycles reaches 500, which has excellent electrochemical performance; Then as the number of charge-discharge cycles increases, the retention rate shows a slowly decreasing trend. It can be seen that the use of the lithiophilic coating as the current collector in Example 3 greatly improves the electrochemical performance of the lithium metal negative electrode.

Example 4-10

The difference from Example 1 is that in the preparation of the lithium-philic material slurry for the negative electrode of the lithium battery, the types of carbon materials, lithiophilic metal oxides, binders, and lithium salts are different, as shown in Table 1. Others are the same as those in the implementation. The same as Example 1 and will not be repeated here.

Table 1 shows the types of raw materials in the lithium-philic materials for the negative electrode of lithium batteries in Example 1 and Examples 4-10.

Example carbon material Lithiophilic metal oxides adhesive Lithium salt Example 1 carbon nanotubes Copper oxide Polyvinylidene fluoride Lithium carbonate Example 4 Graphene Copper oxide Styrene-butadiene rubber Lithium fluoride Example 5 Acetylene black Cobalt tetroxide Acrylonitrile Lithium nitride Example 6 carbon fiber Cobalt tetraoxide Acrylic Lithium nitrate Example 7 carbon nanotubes Zinc oxide Polyvinylidene fluoride Lithium carbonate Example 8 Graphene Zinc oxide Styrene-butadiene rubber Lithium fluoride Example 9 Acetylene black Copper oxide Acrylonitrile Lithium nitride Example 10 carbon fiber Zinc oxide Acrylic Lithium nitrate

As shown in Table 1, in the present invention, the different types of carbon materials, lithiophilic metal oxides, binders, and lithium salts used in the preparation of the lithium-philic material slurry for the lithium battery negative electrode will affect the composite current collector and the lithium battery negative electrode. The three-dimensional spherical structure of lithiophilic materials has a certain impact: tubular carbon materials provide the skeleton, powdered carbon materials are compositely accumulated with other materials, and the three-dimensional structure formed by layered carbon materials has a wide range of sizes. Lithiophilic materials, binders, and lithium salt stabilizers are filled and accumulated. The lithium salt that produces gas can improve the stability of electrochemical performance and safety performance, and the lithium salt that does not produce gas can stabilize the electrochemical behavior of the battery.

In Example 4, due to the layered structure of graphene, part of the lithiophilic material coating of the negative electrode of the lithium battery forms irregular three-dimensional structure spheres, and other parts form three-dimensional structures of other shapes.

In Example 5, because acetylene black is in powder form, the lithiophilic material coating on the negative electrode of the lithium battery basically has a three-dimensional random structure, with a small number of irregular three-dimensional structure spheres.

Examples 11-17

The difference from Example 1 is that in the preparation of lithium battery negative electrode lithiophilic material slurry, the quality of carbon materials, lithiophilic metal oxides, binders, and lithium salts is different, as shown in Table 2, and the others are the same as those in the implementation The same as Example 1 and will not be repeated here.

Table 2 shows the quality settings of the raw materials in the lithium-philic materials for the negative electrode of lithium batteries in Example 1 and Examples 11-17.

Example carbon nanotubes Copper oxide Polyvinylidene fluoride Lithium carbonate Example 1 30g 55g 5g 10g Example 11 25g 60g 5g 10g Example 12 20g 60g 5g 15g Example 13 15g 65g 10g 10g Example 14 10g 70g 10g 10g Example 15 5g 75g 5g 15g Example 16 15g 75g 5g 5g Example 17 35g 45g 15g 5g

As shown in Table 2, in the present invention, the different qualities of carbon materials, lithiophilic metal oxides, binders, and lithium salts in the preparation of the lithium-philic material slurry for the lithium battery negative electrode will affect the composite current collector and the lithium battery negative electrode. The three-dimensional spherical structure of lithiophilic materials has a certain impact. Among them, the more binder, the greater the adhesion between the lithiophilic coating and the copper foil, but the film resistance increases, and the binder content is at least 5%.

It should be noted that those skilled in the art should understand that in the lithium-philic material for the lithium battery negative electrode provided by the present invention, the lithiophilic metal oxide can also be other types of metal oxides, and the lithium salt can also be Other types of lithium salts.

In summary, the present invention provides a three-dimensional composite current collector and a preparation method thereof. The three-dimensional composite current collector provided by the invention includes a copper foil base layer and a lithium battery negative electrode lithophile material coating coated on the copper foil base layer; the lithium battery negative electrode lithophile material coating contains several micron-sized three-dimensional spherical structures. . The lithium-philic material of the lithium battery negative electrode is composed of carbon material, lithium-philic metal oxide, binder, and lithium salt. The invention first prepares a lithium battery negative electrode lithophile material slurry, and then coats the slurry on the copper foil base layer to prepare a lithium battery negative electrode three-dimensional composite current collector. The lithium-philic material of the lithium battery negative electrode is coated on the copper foil to form a composite coating with a micron-sized three-dimensional spherical structure, which can effectively reduce the current density of the lithium metal negative electrode, thereby effectively alleviating and reducing the generation of lithium dendrites, and improving lithium metal Battery cycle performance and safety performance.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not 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 it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some or all of the technical features; however, these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims (6)

1. A three-dimensional composite current collector, characterized in that: the three-dimensional composite current collector includes a copper foil base layer and a lithium battery negative electrode lithium-philic material coating coated on the copper foil base layer; the lithium battery negative electrode lithium-philic material coating The material coating contains several micron-sized three-dimensional spherical structures; The preparation method of the three-dimensional composite current collector includes the following steps: S1. Weigh a predetermined amount of carbon material, lithiophilic metal oxide and lithium salt, mix and stir for 0.5 to 4 hours; add solvent and stir until completely dissolved; then add a predetermined amount of binder, stir for 4 to 10 hours, and prepare lithium Battery negative electrode lithium-philic material slurry; S2. Select a copper foil with a thickness of 6 to 20 μm as the base layer, and apply the lithium battery negative electrode lithium-philic material slurry obtained in step S1 on the copper foil to form a lithium battery negative electrode lithium-philic material coating. The coating speed is 10~30 m/min, then dried in a blast drying oven at 70~80°C for 4~8 hours, and then dried in a vacuum oven at 110~130°C for 8~12 hours to prepare a three-dimensional composite current collector; The carbon material is one of carbon nanotubes and carbon fibers. 2. The three-dimensional composite current collector according to claim 1, characterized in that: the lithiophilic material coating of the lithium battery negative electrode is composed of carbon materials, lithiophilic metal oxides, binders, and lithium salts; in step S1 , in terms of mass fraction, the mass ratio of the carbon material, the lithiophilic metal oxide, the binder, and the lithium salt is 5%~35%: 75%~45%: 15%~5% :5%~15%. 3. The three-dimensional composite current collector according to claim 1, wherein the lithiophilic metal oxide contains one or a mixture of cobalt tetroxide, zinc oxide, and copper oxide. 4. The three-dimensional composite current collector according to claim 1, wherein the lithium salt contains one of lithium carbonate, lithium fluoride, lithium nitride, and lithium nitrate. 5. The three-dimensional composite current collector according to claim 1, wherein the binder contains one of styrene-butadiene rubber, acrylic resin, acrylonitrile, and polyvinylidene fluoride. 6. The three-dimensional composite current collector according to claim 1, wherein the solvent is one of water and N-methylpyrrolidone.