Negative electrode material, preparation method thereof, negative electrode sheet, battery cell, and sodium ion battery

Abstract

The embodiment of the present disclosure provides a negative electrode material and a preparation method thereof, a negative electrode sheet, a battery cell and a sodium ion battery. The ethylene tar is mixed with the hard carbon material, the mixed material of the ethylene tar and the hard carbon material is subjected to impregnation treatment in an impregnation furnace, and the impregnated hard carbon material is subjected to carbonization treatment to obtain a hard carbon negative electrode material. The ethylene tar has good fluidity and certain viscosity at room temperature, and can reduce the requirements of the impregnation process on temperature and pressure. In the impregnation process, the volatile content of the ethylene tar is relatively low and the carbon residue rate is high, and a large number of pores are not easily formed due to impurity volatilization in the heat treatment process. The prepared soft carbon coated and filled hard carbon material has high initial efficiency, high compaction and excellent cycle stability, which is beneficial to large-scale production and manufacturing of the negative electrode material and improves the use feasibility of the hard carbon material in the sodium ion battery.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of secondary batteries, in particular to a negative electrode material and a preparation method thereof, a negative electrode sheet, a battery cell and a sodium-ion battery. BACKGROUND

[0002] A sodium-ion battery is a kind of rechargeable battery, which mainly relies on the movement of sodium ions between the positive electrode and the negative electrode to work

[0003] The current sodium-ion battery includes a battery cell composed of a positive electrode sheet, a negative electrode sheet and a separator between the positive electrode sheet and the negative electrode sheet, and the battery cell is placed in an electrolyte. The sodium-ion battery relies on the movement of sodium ions between the positive electrode and the negative electrode to work.

[0004] Currently, in the sodium-ion battery, hard carbon is used in the negative electrode material. The hard carbon material cannot be graphitized and the carbon layer arrangement regularity is lower than that of soft carbon, so that more micropores are formed between the layers, thereby facilitating the insertion and extraction of ions. Moreover, the hard carbon material has the advantages of high metal storage capacity, low metal storage voltage and cycle stability, and is the current commonly used negative electrode material. SUMMARY

[0005] In view of the shortcomings of the above related technologies, the purpose of the present disclosure is to provide a negative electrode material and a preparation method thereof, a negative electrode sheet, a battery cell and a sodium-ion battery to solve the technical problem of low feasibility of using hard carbon material in the sodium-ion battery in the related art.

[0006] The first aspect of the present disclosure provides a preparation method of a negative electrode material for a sodium-ion battery, comprising:

[0007] mixing ethylene tar and hard carbon material;

[0008] immersing the mixed material of ethylene tar and hard carbon material in an immersion furnace;

[0009] carburizing the immersed hard carbon material to obtain a hard carbon negative electrode material.

[0010] Optionally, the D50 of the hard carbon material is in the range of 4-10pm, and the specific surface area is in the range of 3.0-10.0g / m2.

[0011] Optionally, the mass ratio of ethylene tar to hard carbon material is 5:100-15:100.

[0012] Optionally, immersing the mixed material of ethylene tar and hard carbon material in an immersion furnace comprises:

[0013] placing the mixed material of ethylene tar and hard carbon material in the immersion furnace;

[0014] vacuumizing and heating the immersion furnace;

[0015] The heated impregnation furnace is subjected to pressure impregnation.

[0016] Optionally, the heating temperature range in the impregnation furnace is 100-300℃, the pressure is 0.8-2MPa, and the impregnation time is 2-6h.

[0017] Optionally, the temperature range of the carbonization process is 900-1200℃, and the carbonization time is 3-6h.

[0018] Optionally, the ethylene tar is mixed with the hard carbon material, including:

[0019] The ethylene tar is added to the hard carbon material and stirred to obtain a mixed material of the ethylene tar and the hard carbon material.

[0020] The second aspect of the present disclosure provides a negative electrode material for a sodium ion battery, including:

[0021] A hard carbon negative electrode material prepared using the negative electrode material of any of the above embodiments.

[0022] The third aspect of the present disclosure provides a negative electrode sheet for a sodium ion battery, including:

[0023] A current collector and a negative electrode active material, the negative electrode active material including the above negative electrode material, a conductive agent, and a binder.

[0024] The fourth aspect of the present disclosure provides a sodium ion battery cell, including:

[0025] A positive electrode sheet;

[0026] The above negative electrode sheet;

[0027] A separator disposed between the positive electrode sheet and the negative electrode sheet.

[0028] The fifth aspect of the present disclosure provides a sodium ion battery, including:

[0029] A housing;

[0030] The above cell packaged in the housing;

[0031] An electrolyte injected into the housing.

[0032] As described above, the negative electrode material, the preparation method thereof, the negative electrode sheet, the battery cell and the sodium ion battery are provided in the embodiments of the present disclosure. In the present embodiment, ethylene tar is used as a filler and a coating agent. By means of impregnation, the ethylene tar fills the internal pores of the hard carbon material and adheres to the surface of the hard carbon material. Then, by means of carbonization, the soft carbon formed by the ethylene tar can fill the mesopores and macropores in the hard carbon and reduce the surface defects, and the microporous structure of the hard carbon material is not changed. In particular, the ethylene tar has good fluidity at room temperature and has a certain viscosity, which can reduce the requirements of temperature and pressure on the impregnation process. During the impregnation process, the volatile content of the ethylene tar is relatively low and the carbon residue rate is high. In the heat treatment process, a large number of pores are not easily formed due to the volatilization of impurities. The soft carbon coated and filled hard carbon material prepared has high initial efficiency, high compaction and excellent cycle stability, which is conducive to the large-scale production of the negative electrode material and improves the use feasibility of the hard carbon material in the sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A flowchart of a preparation method of a negative electrode material according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0034] The embodiments of the present disclosure are described below by way of specific examples. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the messages disclosed in the present disclosure. The present disclosure can also be implemented or applied in other different specific embodiments or systems, and the details in the present disclosure can be modified or changed in different ways without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0035] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in various different forms, and is not limited to the embodiments described herein.

[0036] In the description of the present disclosure, the expressions of "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples represented in the present disclosure and the features of the different embodiments or examples without contradiction.

[0037] Although not defined differently, the technical terms and scientific terms used herein include the technical terms and scientific terms commonly used in the art to which the present disclosure belongs, and all the terms have the same meaning as generally understood by those skilled in the art to which the present disclosure belongs. The terms defined in the commonly used dictionary are additionally explained to have a meaning consistent with the relevant technical literature and the message currently prompted, and if not defined, should not be interpreted as an ideal or very formal meaning.

[0038] In the research on the related art, it is found that hard carbon material is used as the negative electrode material of sodium ion battery due to its advantages. During the synthesis process, the hard carbon material is overflowed due to the volatilization of impurity components, so that a large number of pores are formed in the interior of the hard carbon particles, thereby causing the specific surface area of the hard carbon to be large and the compaction density to be low. When used as the negative electrode material of the sodium ion battery, the hard carbon material has the problems of low initial efficiency, low volumetric energy density and poor cycle stability. This reduces the use feasibility of the hard carbon material in the sodium ion battery.

[0039] Figure 1 The flowchart of the method for preparing the negative electrode material of the sodium ion battery provided in the embodiments of the present disclosure is shown in FIG. 1, and the preparation method includes but is not limited to the following steps: Figure 1

[0040] Step 110: mixing ethylene tar and hard carbon material;

[0041] Step 120: performing impregnation treatment on the mixed material of ethylene tar and hard carbon material in an impregnation furnace;

[0042] Step 130: performing carbonization treatment on the impregnated hard carbon material to obtain a hard carbon negative electrode material.

[0043] In the embodiments, ethylene tar is used as a filler and a coating agent. Through impregnation, the ethylene tar fills the internal pores of the hard carbon material and adheres to the surface of the hard carbon material. Then, through carbonization, the soft carbon formed by the ethylene tar fills the mesopores and macropores in the interior of the hard carbon and reduces the surface defects, without changing the micropore structure of the hard carbon material, thereby improving the initial efficiency, compaction density and cycle stability of the hard carbon material.

[0044] In particular, ethylene tar has good fluidity at room temperature and has a certain viscosity, which can reduce the requirements for temperature and pressure in the impregnation process. In the impregnation process, the volatile component of ethylene tar is relatively low and the carbon residue rate is high. In the heat treatment process, it is not easy to form a large number of pores due to the volatilization of impurities. The soft carbon coated and filled hard carbon material prepared has high initial efficiency, high compaction and excellent cycle stability, which is conducive to the large-scale production of the negative electrode material and improves the use feasibility of the hard carbon material in the sodium ion battery.

[0045] In the embodiments of the present disclosure, the mixing of ethylene tar and hard carbon material includes:

[0046] ​The ethylene tar is added to the hard carbon material and stirred to obtain a mixed material of ethylene tar and hard carbon material.

[0047] The mixing of the ethylene tar and the hard carbon material is made more uniform through stirring, so that the density of the final hard carbon negative electrode material tends to be balanced. The stirring can be performed using low-speed mechanical stirring, and the stirring speed can be adjusted as needed.

[0048] In the embodiments of the present disclosure, the D50 of the hard carbon material is in the range of 4-10 μm, and the specific surface area is in the range of 3.0-10.0 g / m 2 . The D50 refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample, and the specific surface area (SSA) refers to the total surface area possessed by a solid per unit mass. The D50 and the specific surface area are used to characterize the adsorption and storage capacity of active metal ions, and within the range of the embodiments, the hard carbon material can more fully adsorb and store active metals, so that the sodium ion battery has better cycle performance.

[0049] In the corresponding application, the amount of ethylene tar is too high, which can fill the micropores of the hard carbon material, and the amount of ethylene tar is too low, which can affect the filling capacity of the macropores or mesopores. Therefore, in the corresponding application, the mass ratio of ethylene tar to hard carbon material can be adjusted according to experiments.

[0050] In the embodiments of the present disclosure, the mass ratio of ethylene tar to hard carbon material is 5:100-15:100. Within this range, the ethylene tar can better fill the macropores or mesopores of the hard carbon material, and at the same time, the micropore structure will not be changed, so that the hard carbon material can better exert its advantages, thereby making the sodium ion battery have better cycle performance.

[0051] In the embodiments of the present disclosure, the mixed material of ethylene tar and hard carbon material is subjected to impregnation treatment in an impregnation furnace, including:

[0052] The mixed material of ethylene tar and hard carbon material is placed in the impregnation furnace;

[0053] The impregnation furnace is vacuumed and heated;

[0054] The heated impregnation furnace is subjected to pressure impregnation.

[0055] In the embodiments, the impregnation is to make the hard carbon material impregnate in the ethylene tar, so as to coat and fill the hard carbon material. Specifically, the mixed material of ethylene tar and hard carbon material is placed in the impregnation furnace, and impregnation is performed through heating and pressurization.

[0056] The vacuum heating increases the flowability of the ethylene tar, so that the ethylene tar can be fully adhered to the hard carbon material. The pressurization can be performed in a protective gas, such as nitrogen or other inert gas environment. The pressurization allows the ethylene tar to enter the interior of the hard carbon particles.

[0057] In the embodiment of the present disclosure, the heating temperature in the impregnation furnace ranges from 100 to 300℃, the pressure ranges from 0.8 to 2MPa, and the impregnation time ranges from 2 to 6h. The heating temperature and the pressurization pressure affect the filling and coating effects of the ethylene tar on the hard carbon material. The above-mentioned temperature and pressure range in the embodiment does not belong to high temperature and high pressure, and the filling and coating effects can be achieved.

[0058] The above-mentioned temperature, pressure and time range in the embodiment can achieve better filling and coating effects. In corresponding applications, the corresponding parameters can be adjusted within the above-mentioned range. In another embodiment, the effects can be discounted when the parameters exceed the above-mentioned range, but the parameters can also exceed the above-mentioned range without affecting the feasibility of the scheme.

[0059] In the embodiment of the present disclosure, the ethylene tar forms soft carbon through carbonization, and the soft carbon can coat and fill the hard carbon material. The hard carbon material after carbonization has more graphite regions and larger graphite sheet size, and smaller specific surface area, so that the electrochemical performance thereof can be improved.

[0060] In the embodiment of the present disclosure, the temperature range of the carbonization process ranges from 900 to 1200℃, and the carbonization time ranges from 3 to 6h. Within the above-mentioned parameter range, the ethylene tar can be fully carbonized to become soft carbon. In another embodiment, the effects can be discounted when the parameters exceed the above-mentioned range, but the parameters can also exceed the above-mentioned range without affecting the feasibility of the scheme.

[0061] The embodiment of the present disclosure also provides a negative electrode material for a sodium ion battery, which is prepared by using the negative electrode material shown in the above-mentioned embodiment. Figure 1 The embodiment of the present disclosure also provides a hard carbon negative electrode material prepared by using the negative electrode material shown in the above-mentioned embodiment.

[0062] The embodiment of the present disclosure also provides a negative electrode sheet for a sodium ion battery, which comprises:

[0063] The negative electrode sheet comprises a current collector and a negative electrode active material, and the negative electrode active material comprises the above-mentioned negative electrode material, a conductive agent and a binder.

[0064] The embodiment of the present disclosure also provides a sodium ion battery cell, which comprises:

[0065] A positive electrode sheet;

[0066] The above-mentioned negative electrode sheet;

[0067] A separator arranged between the positive electrode sheet and the negative electrode sheet.

[0068] The embodiment of the present disclosure also provides a sodium ion battery, which comprises:

[0069] a shell;

[0070] the above-mentioned battery cell packaged in the shell;

[0071] an electrolyte injected into the shell.

[0072] The embodiment of the present disclosure also provides experimental data to illustrate the beneficial effects of the embodiment.

[0073] Embodiment one:

[0074] A hard carbon material with a particle size D50 = 5.0 μm and a specific surface area = 6.0 g / m 2 The ethylene tar and the hard carbon material are mechanically stirred and uniformly mixed according to a mass ratio of 7:100 to obtain an ethylene tar-hard carbon mixed material, and then the ethylene tar-hard carbon mixed material is placed in an impregnation furnace at 150 DEG C and a pressure of 1.5 MPa for impregnation for 3 h to obtain an impregnated hard carbon material. Finally, the impregnated hard carbon material is carbonized at 1000 DEG C for 5 h to obtain a soft carbon coated and filled hard carbon material. The soft carbon coated hard carbon material, SP (super pll, i.e., conductive carbon black), (Ceramic Matrix Composite, i.e., ceramic matrix composite), SBR (Polymerized Styrene Butadiene Rubber, i.e., styrene butadiene rubber) are uniformly mixed according to a mass ratio of 94.0:3.0:1.0:2.0, and then subjected to coating, drying, rolling and other processes to obtain a negative electrode sheet, which is then assembled into a 2 soft package battery together with a positive electrode sheet, an electrolyte and other materials.

[0075] Embodiment two:

[0076] Compared with embodiment one, the difference between embodiment two and embodiment one is that a hard carbon material with a particle size D50 = 6.5 μm and a specific surface area = 5.0 g / m 2 , and other steps and parameters can be referred to embodiment one.

[0077] Embodiment three:

[0078] Compared with embodiment one, the difference between embodiment two and embodiment one is that the ethylene tar and the hard carbon negative material are mechanically stirred and uniformly mixed according to a mass ratio of 9:100 to obtain an ethylene tar-hard carbon mixed material, and other steps and parameters can be referred to embodiment one.

[0079] Embodiment four:

[0080] Compared with embodiment one, the difference between embodiment two and embodiment one is that the impregnated hard carbon material is carbonized at 1100 DEG C for 5 h to obtain a soft carbon coated and filled hard carbon material, and other steps and parameters can be referred to embodiment one.

[0081] Comparative Example

[0082] Preparation of precursor: 100 parts of enzymatic hydrolysis lignin, 16 parts of tetraisocyanate silane were added into 150 parts of benzene, stirred until completely dissolved, heated to 80℃ and kept constant, 0.55 parts of triethylamine was added dropwise, 30 min after dropping, the reaction was carried out under stirring for 5 h, after the reaction was completed, it was naturally cooled to room temperature, filtered, washed with benzene for 3 times to remove unreacted raw materials, vacuum dried at 80℃ for 12 h, ground to 0.3 mm, ready for use;

[0083] Pre-treatment of precursor: the precursor was ball milled in XQM-0.5L planetary ball mill with φ=10 mm agate balls, φ=6 mm agate balls, number ratio of 1:4, total 15, at a rotation speed of 300 r / min, ball-to-material ratio of 7:1 for 26 h, to obtain a ball milled material with a particle size of 12 μm, then the ball milled material was dispersed in 210 parts of 5 wt% phytanic acid solution (solvent benzene) with a frequency of 80 KHZ and a power of 400 W, ultrasonic time was 1 h, benzene was removed by reduced pressure distillation, dried and frozen, φ=6 mm agate balls, φ=6 mm agate balls, φ=6 mm agate balls, number ratio of 1:1:1, total 15, at a rotation speed of 450 r / min, ball-to-material ratio of 10:1 for 36 h, to obtain a powder with a particle size of 2.7 μm, ready for use;

[0084] Carbonization: the pre-treated powder was added into a rotary carbonization furnace, argon was introduced, heated uniformly to 1400℃ at a rate of 10℃ / min and kept constant for 3 h for carbonization, after the carbonization was completed, it was cooled to room temperature, and ground to obtain a hard carbon powder with a particle size of 8 μm;

[0085] Chemical vapor deposition: the hard carbon powder obtained by carbonization was added into a reaction chamber, argon was introduced, heated uniformly to 1000℃ at a rate of 5℃ / min and kept constant, argon and acetylene mixed gas with a volume ratio of 2:1 was introduced, kept constant for 2 h, after the constant temperature was completed, argon was introduced at a rate of 8℃ / min to reduce to room temperature, to obtain a hard carbon material coated on the surface.

[0086] The experimental results are shown in the following table:

[0087]

[0088] From the above table, compared with the comparative example, the particle size and specific surface area of the final hard carbon negative electrode material of each example are relatively small, and the compaction density, initial efficiency and cycle performance are improved.

[0089] Therefore, in the embodiment, ethylene tar is selected as the filler and coating agent, which has high economic value. In addition, the ethylene tar has good flowability at room temperature and certain viscosity, can well penetrate into the mesopores and macropores in the hard carbon particles, and adhere to the surface of the hard carbon to improve the surface defects. The operation process is simple and efficient, and does not affect the microporous structure of the hard carbon material. Finally, the ethylene tar has relatively low volatile matter and high carbon residue rate, and is not easy to form a large number of pores due to impurity volatilization during heat treatment. The soft carbon coated and filled hard carbon material prepared has high initial efficiency, high compaction, and excellent cycle stability.

[0090] The above embodiments only exemplarily illustrate the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present disclosure should be covered by the claims of the present disclosure.

Claims

1. A method for preparing a negative electrode material for a sodium-ion battery, characterized by, The method comprises the following steps: Ethylene tar is mixed with hard carbon material having a D50 in the range of 4-10 pm and a specific surface area in the range of 3-10 g / m 2 2, the mass ratio of ethylene tar to hard carbon material being 5: 100-15: 100; The mixed material of the ethylene tar and the hard carbon material is subjected to impregnation treatment in an impregnation furnace, wherein the impregnation treatment comprises vacuumizing and pressurized impregnation at 100-300 ℃, the pressure in the impregnation furnace is 0.8-2 MPa, and the impregnation time is 2-6 h; The hard carbon material after impregnation is subjected to carbonization treatment to obtain the hard carbon negative electrode material, and the temperature range of the carbonization treatment process is 900-1200 ℃, and the carbonization time is 3-6 h.

2. The method for preparing a negative electrode material for a sodium-ion battery according to claim 1, characterized in that, The mixing of the ethylene tar and the hard carbon material comprises the following steps: The ethylene tar is added to the hard carbon material and stirred to obtain the mixed material of the ethylene tar and the hard carbon material.

3. A negative electrode material for a sodium-ion battery, characterized by, The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2.

4. A negative electrode sheet for a sodium-ion battery, characterized by, The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2.

5. A sodium-ion battery cell, characterized in that, The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2.

6. A sodium-ion battery, characterized in that, The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode material preparation method for a sodium ion battery according to any one of claims 1-2. The hard carbon negative electrode material prepared by using the negative electrode

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