A kind of nanowire and nanoparticle carbon material and its preparation method, lithium ion battery

Abstract

The present application relates to a kind of nanowires and nano-particle carbon material and its preparation method, lithium ion battery.It is prepared by heating, coprecipitation method and gas deposition method combination with nanowires and nano-particle carbon material;The carbon material prepared simultaneously has nanowires and nano-particle structure, is favorable to material dispersion, can form continuous conductive network as negative electrode material in electrode, has larger surface area, enhances the conduction ability of electron;The structural specificity of carbon material, large surface area;The carbon material prepared makes the electrochemical performance of lithium ion battery have been significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular, to a preparation method of a lithium ion power battery with nanowire and nanoparticle carbon materials. BACKGROUND

[0002] Carbon materials are mainly used as electrodes in lithium ion battery anodes. Carbon materials have low potential, high specific surface area, good electrochemical reaction activity and chemical stability. Among carbon materials, there are several forms, such as natural graphite, artificial graphite, amorphous carbon, nanotubular carbon, graphene, etc. Among them, natural graphite is the most commonly used anode carbon material because of its very regular molecular structure and good electrical conductivity and chemical stability. However, natural graphite has some drawbacks, such as small specific surface area and obvious volume effect, so it is difficult to meet the needs of the development of electric vehicles. In order to overcome the problems of natural graphite, researchers have begun to explore other types of carbon materials. For example, nanotubular carbon and graphene have very high specific surface area and electrical conductivity, so they can improve the capacitance and electrochemical reaction rate. In addition, amorphous carbon can better accommodate lithium ions due to its irregular molecular structure, reducing the volume effect. However, to meet the needs of the rapidly developing electric vehicle market, researchers need to find more advanced materials. Currently, some new carbon materials, such as silicon carbide and fluorinated carbon, are gradually being applied to the research of lithium ion battery anode materials. New lithium ion battery anode carbon materials have the following advantages and disadvantages compared to traditional graphite materials: the advantages are that compared to traditional carbon materials, new carbon materials have higher theoretical specific capacity and specific energy, which can greatly improve the energy density of the battery. Some new carbon materials, such as silicon carbide and fluorinated carbon, have higher ion diffusion rates, which can improve the charge and discharge rate and cycle life of the battery. In addition, some new carbon materials are easier to control in preparation, have higher production efficiency and lower processing cost. The disadvantage is that the stability of some new carbon materials is not enough, which can easily lose activity and affect the life of the battery, and the research of new materials requires higher research and development costs and time.

[0003] There are various existing technologies for preparing carbon materials, and traditional preparation methods can have environmental pollution problems. For example, the preparation of carbon materials using chemical reduction methods or thermal reaction methods generally requires the use of chemical reagents containing harmful substances, which can be harmful to the environment and human health during production. The control of materials during the preparation process is difficult. Due to the high complexity of the topological structure and electrochemical properties of carbon materials, the properties of the materials during the preparation process are not easy to control and are difficult to accurately evaluate, and the production cost is relatively high. Modern science and technology pursue delicacy and efficiency, and the method for preparing negative electrode carbon materials also requires more and more complex and high-end equipment and technical means, so the production cost is relatively high, and large-scale production has not yet been realized. Although researchers have developed various new methods for preparing carbon materials, more research and practice are needed to promote these methods to the scale of industrial production.

[0004] It can be seen that carbon materials play a crucial role in the application of lithium ion batteries. However, the existing negative electrode carbon materials for lithium ion batteries can have the following four shortcomings and limitations during the preparation process: first, the low specific energy and low energy density of lithium ion batteries: compared to high-energy-density positive electrode materials, the energy density of negative electrode materials is relatively low, resulting in a decrease in the energy density of the entire battery. Second, the negative electrode material of the lithium ion battery is prone to volume diffusion and dissolution reaction, which can cause deactivation and peeling with an increase in the number of charge and discharge cycles, reducing the cycle life of the battery. In addition, during high-rate charging and discharging, the electrochemical reaction rate of the negative electrode material of the lithium ion battery cannot meet the needs, resulting in a decrease in the current output capability of the battery. Finally, the production of negative electrode materials for lithium ion batteries requires a large amount of energy and resources, and a large amount of harmful substances and waste are generated during production and use, which can have an impact on the environment.

[0005] In order to solve the above-mentioned problems of negative electrode carbon materials and further improve the performance of lithium ion batteries, the advantages of negative electrode carbon materials can be fully utilized. The present application prepares carbon materials with nanowires and nanoparticles by combining hydrothermal synthesis, co-precipitation, and gas deposition methods. Such carbon materials have both nanowire and nanoparticle structures, which are beneficial for material dispersion and can form a continuous conductive network in the electrode as negative electrode materials, enhancing the electron conduction ability and improving the performance of lithium ion batteries. Through experiments, it is found that this negative electrode carbon material has a nanowire and nanoparticle structure with a large surface area; it can significantly reduce the internal resistance of the lithium ion battery and improve the rate performance and cycle stability of the lithium ion battery. SUMMARY

[0006] The traditional negative electrode carbon material and the new type of carbon material need to be improved in the structure, stability and electrical properties of the material. Based on this, the carbon material with nanowire and nanoparticle structure is prepared by combining the hydrothermal synthesis method, the coprecipitation method and the vapor deposition method. The prepared carbon material has nanowire and nanoparticle structure, which is beneficial to the dispersion of the material and can form a continuous conductive network in the electrode as a negative electrode material, thereby enhancing the electron conduction ability. The carbon material has a special structure and a large surface area, and has excellent electrochemical performance when applied in a lithium ion battery.

[0007] The present application first prepares nickel hydroxide with nanowire structure by the hydrothermal synthesis method, then generates cobalt hydroxide with nanoparticle structure on the nanowire by the coprecipitation method, and finally deposits carbon material on the metal by the vapor deposition method, and removes the metal elements by acid to obtain the carbon material with nanowire and nanoparticle structure.

[0008] The present application relates to a kind of carbon material with nanowire and nanoparticle structure, which is prepared by the following method:

[0009] (1) weigh nickel source, urea in deionized solution, stir to make it fully dissolved;

[0010] (2) the above solution is heated to react, the obtained nanowire nickel hydroxide is washed with deionized water, and dried for standby;

[0011] (3) weigh cobalt source in deionized solution, stir to make it fully dissolved, to obtain the aqueous solution of cobalt source;

[0012] (4) mix the nanowire nickel hydroxide and the aqueous solution of cobalt source uniformly, slowly add sodium hydroxide thereto; After the reaction is completed, the granular cobalt hydroxide is deposited on the nanowire nickel hydroxide, washed with deionized water, and dried for standby;

[0013] (5) by vapor deposition reaction, using ethane as carbon source, so that carbon material is deposited;

[0014] (6) remove the metal elements by acid washing, washing and drying to obtain the carbon material with nanowire and nanoparticle structure.

[0015] In the above method, the nickel source can be one of nickel sulfate, nickel chloride and nickel nitrate; Preferably, the nickel source is nickel chloride; The cobalt source can be one of cobalt sulfate, cobalt chloride and cobalt nitrate; Preferably, the nickel source is nickel chloride; In the above method, the heating method for generating nanowire nickel hydroxide can use one of hydrothermal synthesis method, microwave heating method and solvothermal method; The vapor deposition method can be one of arc method, magnetron sputtering method and rapid pulse high temperature heating.

[0016] For example, specifically, the preparation steps of the carbon material with nanowire and nanoparticle structure can be as follows:

[0017] (1) take 1-3mmol nickel chloride, 1-3mmol urea in 40-60mL deionized solution, stirring 10-30min to make it fully dissolved;

[0018] (2) the above solution is hydrothermal synthesis reaction, the reaction temperature is set to 100-150 DEG C, the reaction time is 2-4h;The obtained nanowire nickel hydroxide is washed with deionized water, and dried for standby;

[0019] (3) take 1-3mmol cobalt chloride in 20-30mL deionized solution, stirring 10-30min to make it fully dissolved, to get the aqueous solution of cobalt chloride;

[0020] (4) the nanowire nickel hydroxide and the aqueous solution of cobalt chloride are mixed evenly, 0.5-2mol / L sodium hydroxide 4-10mL is slowly added to it;After the reaction is completed, the granular cobalt hydroxide is deposited on the nanowire nickel hydroxide, washed with deionized water, and dried for standby;

[0021] (5) through the gas deposition reaction, taking ethane as the carbon source, the reaction temperature is set to 800-1000 DEG C, the reaction time is 1-2h, so that the carbon material is deposited;

[0022] (6) by 1-3mol / L HCl solution 20-50mL wash to remove metal elements, washing and drying can obtain nanowire and granular carbon material.

[0023] The carbon material prepared by the application has significantly improved the electrochemical performance of lithium ion batteries;The nanowire and nanometer granular carbon material has a special structure that can form a conductive network in lithium ion batteries, has a large surface area;The nanowire and granular structure can enhance the electron conduction ability and improve the electrochemical performance of lithium ion batteries.

[0024] Correspondingly, a preparation method of a lithium ion battery is described as follows, comprising the following steps:

[0025] S1: prepare lithium ion battery positive and negative electrode slurry respectively, the slurry composition includes positive and negative electrode material, adhesive, thickening agent and conductive agent;

[0026] Among them, the lithium ion battery positive electrode slurry includes solid components and solvents. The solid components include positive electrode material, adhesive and conductive agent;Preferably, the mass percentage is positive electrode material (90-98%), adhesive (1-3%) and conductive agent (1-5%) respectively.

[0027] The lithium ion battery negative electrode slurry comprises solid components and solvents.

[0028] Preferably, in the lithium ion battery positive electrode slurry, the positive electrode material is lithium nickel cobalt manganese oxide ternary positive electrode material; the binder is polyvinylidene fluoride; and the conductive agent is conductive carbon black.

[0029] Preferably, in the lithium ion battery negative electrode slurry, the binder is butadiene rubber; the thickening agent is sodium carboxymethyl cellulose; the conductive agent is conductive carbon black; and the negative electrode material is the above-prepared nanowire and particle-shaped carbon material.

[0030] S2: A lithium ion battery positive electrode and a negative electrode, the positive electrode and the negative electrode slurry are coated on the positive electrode and the negative electrode current collector respectively, and are subjected to rolling, slitting, die cutting and baking to obtain.

[0031] Preferably, the positive electrode current collector is an aluminum foil, and the negative electrode current collector is a copper foil.

[0032] S3: A lithium ion battery, which is obtained by assembling the positive electrode and the negative electrode sheet, the separator, the electrolyte and the shell.

[0033] Preferably, the lithium ion battery comprises a positive electrode, a negative electrode, an electrolyte, a separator and a shell.

[0034] Preferably, the positive electrode and the negative electrode of the lithium ion battery are separated by a separator, and the electrolyte and the separator are located inside the shell.

[0035] Preferably, the shell of the lithium ion battery is a square soft package or a square shell.

[0036] Advantages:

[0037] The present application combines hydrothermal synthesis, coprecipitation and vapor deposition to prepare nanowire and nanocarbon materials. Such carbon materials can enable good contact between various substances in the lithium ion battery and the carbon material. At the same time, the nanowire and nanoparticle structure is beneficial to material dispersion, and can form a continuous conductive network as a negative electrode material in the electrode, enhancing the electron conduction ability and improving the performance of the lithium ion battery. The prepared material has nanowire and nanoparticle structure, has a large surface area, and can exhibit more excellent electrochemical performance; for example, it can significantly reduce the internal resistance of the lithium ion battery and improve the rate performance and cycle stability of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and other accompanying drawings can be obtained by those of ordinary skill in the art without any creative effort based on these accompanying drawings.

[0039] Figure 1 The preparation method flowchart of the carbon material provided for Embodiment 1 of the present application is shown in the figure.

[0040] Figure 2 The transmission electron microscope image of the carbon material prepared for Embodiment 1 is shown in the figure.

[0041] Figure 3 The specific surface area of the carbon material corresponding to Embodiment 1, Comparative Example 1 and Comparative Example 2 is shown in the figure.

[0042] Figure 4 The internal resistance comparison of the lithium ion battery corresponding to Embodiment 1, Comparative Example 1 and Comparative Example 2 is shown in the figure.

[0043] Figure 5 The rate retention rate comparison of the lithium ion battery corresponding to Embodiment 1, Comparative Example 1 and Comparative Example 2 is shown in the figure.

[0044] Figure 6 The cycle performance test comparison of the lithium ion battery corresponding to Embodiment 1, Comparative Example 1 and Comparative Example 2 is shown in the figure. DETAILED DESCRIPTION

[0045] The present application will be further described below in combination with the accompanying drawings and embodiments. It should be noted that the embodiments in the present application and the technical features in the embodiments can be combined with each other without conflict. It should be noted that all the technical and scientific terms used in the present application have the same meaning as that generally understood by the ordinary skilled in the art to which the present application belongs, unless otherwise specified. The "including" or "containing" and similar words used in the present application mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects.

[0046] Embodiment 1

[0047] A lithium ion battery, the main preparation process of which comprises the following steps.

[0048] (1) First, 2mmol of nickel chloride and 2mmol of urea were weighed into 50mL of deionized solution and stirred for 20min to fully dissolve; the above solution was subjected to hydrothermal synthesis reaction, the reaction temperature was set to 125℃, and the reaction time was 3h; the obtained nanowire-shaped nickel hydroxide was washed with deionized water and dried for use; secondly, 2mmol of cobalt chloride was weighed into 25mL of deionized solution and stirred for 20min to fully dissolve to obtain an aqueous solution of cobalt chloride; the nanometer-shaped hydroxide and the aqueous solution of cobalt chloride were mixed evenly, 7mL of 1.5mol / L sodium hydroxide was slowly added thereto; after the reaction was completed, the granular cobalt hydroxide was deposited on the nanowire-shaped nickel hydroxide, which was washed with deionized water and dried for use; then, through a gas phase deposition reaction, ethane was used as a carbon source, the reaction temperature was set to 900℃, and the reaction time was 1.5h, so that the carbon material was deposited; finally, the metal elements were removed by washing with 35mL of 2mol / L HCl solution, and the nanowire and granular carbon material were obtained after washing and drying. Figure 1 as shown in Figure 2 ).

[0049] (2) 45g of polyvinylidene fluoride (PVDF) was dissolved in N-methyl pyrrolidone (NMP) solvent, and then lithium nickel cobalt manganese oxide (NCM) ternary positive electrode material and conductive agent were added and mixed evenly. Among them, the lithium ion battery positive electrode slurry was according to weight percentage, positive electrode material NCM (93%), adhesive PVDF (3%) and conductive agent carbon black (4%). 45g of sodium carboxymethyl cellulose (CMC) was dissolved in deionized water, and then negative electrode material nanowire and nanometer particle-shaped carbon material, conductive agent carbon black and styrene butadiene rubber (SBR) were added and mixed evenly. Among them, the lithium ion battery negative electrode slurry was according to weight percentage, negative electrode material (93%), adhesive SBR (2%), thickening agent CMC (2%) and conductive agent carbon black (3%).

[0050] (3) The obtained lithium ion battery positive electrode slurry was coated on an aluminum foil current collector, and the negative electrode slurry was coated on a copper foil current collector. Finally, the positive and negative electrode sheets were subjected to rolling, slitting, die cutting and baking.

[0051] (4) The positive and negative electrode sheets in step (3) were assembled into a lithium ion battery together with a separator, an electrolyte and a shell.

[0052] Comparative Example 1

[0053] The main preparation process of the lithium ion battery includes the following steps.

[0054] This example provides a lithium ion battery preparation method: the steps are the same as in Example 1, only the negative electrode carbon material is changed, and the negative electrode carbon material used is silicon carbide.

[0055] Comparative Example 2

[0056] A lithium ion battery was prepared according to the following steps.

[0057] A lithium ion battery was prepared according to the following steps. The steps were the same as in Example 1, except that the negative carbon material was changed. The negative carbon material used was graphite.

[0058] The specific surface area, internal resistance, rate discharge retention rate, and cycle performance retention rate of the carbon materials of Example 1, Comparative Example 1, and Comparative Example 2 were measured and are shown in Table 1:

[0059] Table 1

[0060] Test items Example 1 Comparative Example 2 Comparative Example 2 Specific surface area (m2 / g) 82 55 15 Lithium ion battery internal resistance (mΩ) 0.5 1.1 1.6 Rate discharge retention rate (%) 98 92 88 Cycle performance retention rate (%) 97.2 95.3 93.8

[0061] From the above comparison of the specific surface area of the carbon materials of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that the carbon materials prepared in the form of lines and particles have a high specific surface area. This is attributed to the specific structure of the carbon material of Example 1, in which the nano-wire and nano-particle structures increase the specific surface area of the carbon material. Second, the carbon material prepared in Example 1 was applied to a lithium ion battery, and it can be seen from the comparison that the internal resistance of the lithium ion battery of Example 1 is better than that of Comparative Examples 1 and 2. The nano-wire and nano-particle structures can form a continuous conductive network, enhancing the electron conduction ability, thereby improving the rate discharge retention rate and cycle performance retention rate of the lithium ion battery. As can be seen from Table 1, the rate discharge retention rate of Example 1 is 98%, which is better than that of silicon carbide and graphite carbon materials. Moreover, after 500 cycles, the retention rate of the carbon material with nano-wire and nano-particle structures is 97.2%, which is higher than that of Comparative Examples 1 and 2. The specific results of the comparison are also shown in Table 1. Figures 3-6

[0062] The above merely describes certain exemplary embodiments of the present application by way of illustration, and it is needless to say that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present application. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of the claims of the present application.​

Claims

1. A carbon material having nanowires and nanoparticles, characterized by, Prepared by the following method: (1) take the nickel source, urea in deionized solution, stirring to make it fully dissolved; (2) the above solution is heated to react, the nanowire nickel hydroxide obtained by washing with deionized water, drying for future use; (3) take the cobalt source in deionized solution, stirring to make it fully dissolved, to obtain the aqueous solution of cobalt source; (4) the nanowire nickel hydroxide and cobalt source aqueous solution is mixed evenly, to it slowly add sodium hydroxide; after the reaction is complete, the granular cobalt hydroxide is deposited on the nanowire nickel hydroxide, washing with deionized water, drying for future use; (5) by gas deposition reaction, with ethane as carbon source, so that carbon material deposition; (6) by acid washing to remove metal elements, washing and drying can obtain nanowire and granular carbon material.

2. The nanowire and nanometer granular carbon material of claim 1, further characterized in that the nickel source is one of nickel sulfate, nickel chloride, nickel nitrate; the cobalt source is one of cobalt sulfate, cobalt chloride, cobalt nitrate.

3. The nanowire and nanometer granular carbon material of claim 1, further characterized in that the heating method for generating nanowire nickel hydroxide in the above method is one of hydrothermal synthesis method, microwave heating method, solvothermal method.

4. The nanowire and nanometer granular carbon material of any one of claims 1-3, further characterized in that the preparation steps are as follows: (1) take 1-3 mmol of nickel chloride, 1-3 mmol of urea in 40-60 mL of deionized solution, stirring for 10-30 min to make it fully dissolved; (2) the above solution is hydrothermal synthesis reaction, the reaction temperature is set to 100-150 DEG C, the reaction time is 2-4 h; the nanowire nickel hydroxide obtained by washing with deionized water, drying for future use; (3) take 1-3 mmol of cobalt chloride in 20-30 mL of deionized solution, stirring for 10-30 min to make it fully dissolved, to obtain the aqueous solution of cobalt chloride; (4) the nanowire nickel hydroxide and cobalt chloride aqueous solution is mixed evenly, to it slowly add 0.5-2 mol / L of sodium hydroxide 4-10 mL; after the reaction is complete, the granular cobalt hydroxide is deposited on the nanowire nickel hydroxide, washing with deionized water, drying for future use; (5) by gas deposition reaction, with ethane as carbon source, the reaction temperature is set to 800-1000 DEG C, the reaction time is 1-2 h, so that carbon material deposition; (6) by 1-3 mol / L of HCl solution 20-50 mL to remove metal elements, washing and drying can obtain nanowire and granular carbon material.

5. A lithium ion battery prepared using the nanowire and nanometer granular carbon material of any one of claims 1-4.

6. The lithium-ion battery of claim 5, wherein the lithium-ion battery is a lithium-ion battery. The preparation method comprises the following steps: S1: respectively prepare lithium ion battery positive and negative electrode slurry, slurry composition includes positive and negative electrode material, adhesive, thickening agent and conductive agent; the negative electrode material is the nanowire and granular carbon material prepared above; S2: A lithium ion battery positive and negative electrode, the positive and negative electrode slurry is coated on the positive and negative electrode current collector, respectively, through rolling, slitting, die cutting and baking to obtain; S3: A lithium ion battery, which is obtained by assembling the positive and negative electrode sheets with the separator, electrolyte and shell.

7. A lithium-ion battery as in claim 6, further characterized by, In S1, the lithium ion battery positive electrode slurry includes solid components and solvents; the solid components include positive electrode materials, adhesives and conductive agents; the positive electrode material is a lithium nickel cobalt manganese ternary positive electrode material; the adhesive is polyvinylidene fluoride, and the conductive agent is carbon black, with mass percentages of positive electrode material (90-98%), adhesive (1-3%) and conductive agent (1-5%) respectively; The lithium ion battery negative electrode slurry includes solid components and solvents; the solid components include negative electrode materials, adhesives, thickening agents and conductive agents; the adhesive is butadiene rubber, the thickening agent is sodium carboxymethyl cellulose, and the conductive agent is carbon black, and the negative electrode material is the above-mentioned nano-wire and granular carbon material; The mass percentages of negative electrode material, adhesive, thickening agent and conductive agent are 90-96%, 1-2%, 1-2% and 1-3% respectively.

8. The lithium ion battery of claim 6, further characterized in that in S2, the positive electrode current collector is an aluminum foil, and the negative electrode current collector is a copper foil.

9. The lithium ion battery of claim 6, further characterized in that in S3, the lithium ion battery positive and negative electrodes are separated by a separator; the electrolyte separator and the lithium ion battery positive and negative electrodes are located inside the shell; and the lithium ion battery shell is a square soft package or a square shell.

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