A sodium-ion battery slurry, a negative electrode sheet, and a sodium-ion battery

Abstract

The present invention discloses a sodium-ion battery slurry, a negative electrode sheet and a sodium-ion battery. The preparation method of the carbon negative electrode material in the sodium-ion battery slurry comprises the following steps: Step 1, impregnate the carbon negative electrode material to be treated in a fluorine-containing precursor at room temperature, stir, and then dry to obtain the impregnated carbon negative electrode material; Step 2, place the impregnated carbon negative electrode material obtained in Step 1 in a chamber, introduce a protective gas, raise the temperature to the required temperature for heat treatment in a programmed manner, and obtain an intermediate after cooling in a programmed manner; Step 3, wash the intermediate obtained in Step 2 with an alkali solution and dry to obtain a fluorinated carbon negative electrode material. The present invention performs fluorination treatment on the carbon negative electrode material, which can effectively reduce the concentration of oxygen-containing functional groups on the surface of the carbon negative electrode material, substitute part of the fluorine-containing functional groups, and significantly improve the hydrophobic characteristics of the material.

Description

[0001] This invention application is a divisional application of the mother application "A Method for Fluorination Surface Treatment of Carbon Anode Materials". The application number of the mother application is 2024102902422, and the application date is March 14, 2024. Technical Field

[0002] The present invention relates to the technical field of material chemistry, and particularly to a slurry for sodium-ion batteries, a negative electrode sheet, and a sodium-ion battery. Background Art

[0003] There are still certain oxygen-containing functional groups remaining on the surface of traditional carbon anode materials. This is mainly because the temperature experienced during the reaction process is relatively low and no special post-treatment is carried out, resulting in insufficient removal of oxygen-containing functional groups. The remaining functional groups have a certain degree of hydrophilicity, prone to agglomeration during aqueous slurry mixing, and prone to powder shedding and material loss after drying to form electrode sheets, making it impossible to be actually used in the assembly of actual battery cells.

[0004] To optimize the slurry mixing characteristics of carbon anode materials and prepare negative electrode sheets with strong adhesion and stability, most of the existing technologies are processed through the following methods:

[0005] I. Conduct high-temperature post-treatment (>1500°C) on the material to further remove oxygen-containing functional groups. Its advantages are that the process steps are relatively simple and the functional group removal efficiency is relatively high. The disadvantages are that high equipment requirements are needed during mass production, which is difficult to achieve (it is difficult to pass a protective atmosphere, the vacuum degree is difficult to increase, and surface oxidation will inevitably occur during the heat treatment process), and in addition, the energy consumption will increase significantly.

[0006] II. Conduct hydrogen reduction on the material to further remove oxygen-containing functional groups. Hydrogen has extremely strong reducibility and can react violently with oxygen-containing functional groups and remove them at a certain temperature. The advantages are that the reaction is controllable, easy to implement, and the functional group removal efficiency is high. The defect is that hydrogen is flammable and explosive, presenting certain safety hazards in industrial production.

[0007] III. Conduct surface coating treatment on the material to introduce more pure carbon components and reduce the number of oxygen-containing functional groups on the outer surface. Its advantage is that it can significantly reduce the concentration of surface oxygen-containing functional groups. The disadvantage is that it is difficult to control the coating uniformity, and the process is difficult. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for fluorination surface treatment of carbon anode materials in view of the problem that there are residual oxygen-containing functional groups on the surface of carbon anode materials in the prior art and agglomeration is prone to occur during slurry mixing.

[0009] The technical solution adopted to achieve the purpose of the present invention is:

[0010] A method for fluorination surface treatment of carbon anode materials, comprising the following steps:

[0011] Step 1: Immerse the carbon negative electrode material to be processed in a fluorine-containing precursor at room temperature, stir, and then dry to obtain the impregnated carbon negative electrode material. In Step 1, the fluorine-containing precursor enters the pore structure of the carbon negative electrode material under the action of capillary force and diffuses inside.

[0012] Step 2: Place the impregnated carbon negative electrode material obtained in Step 1 in a chamber, introduce a protective gas, and heat-treat it by programmed heating to the required temperature. After programmed cooling, an intermediate is obtained. In Step 2, F in the fluorine-containing precursor replaces C atoms or oxygen-containing functional groups in the carbon ring to form C-F bonds.

[0013] Step 3: Wash the intermediate obtained in Step 2 with an alkali solution and dry to obtain the fluorinated carbon negative electrode material. In Step 3, after neutralizing the fluorine-containing precursor that has not participated in the substitution reaction in the carbon negative electrode material with an alkali solution, it is dried.

[0014] In the above technical solution, in Step 1, the fluorine-containing precursor is one or more of a high molecular polymer prepared by polymerizing fluorine-containing monomers, fluorine-containing organic compounds, and fluorine-containing inorganic compounds; the mass ratio of the carbon negative electrode material to the fluorine-containing precursor is 1:1 - 20:1.

[0015] In the above technical solution, the high molecular polymer is polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), fluorinated ethylene propylene (FEP), or polyvinylidene fluoride (PVDF); the fluorine-containing inorganic compound is hydrofluoric acid (HF), triethylamine trihydrofluoride, sodium fluoride, potassium fluoride, or aluminum fluoride; the fluorine-containing organic compound is polyfluorobenzene, perfluorobenzene, or perfluorocarboxylic acid.

[0016] In the above technical solution, in Step 1, the stirring time is 6 - 12 h, and the stirring speed is 100 - 1000 rmp / min. When the stirring impregnation time is too short, the polymer cannot fully infiltrate the carbon material. When the stirring impregnation time is too long, it will cause over-impregnation, resulting in too high a fluorine content in the final product.

[0017] In the above technical solution, in Step 2, the protective gas is nitrogen or argon, the programmed heating rate is 2 - 5 °C / min, the required temperature is 800 - 1300 °C, the heat treatment time is 2 - 5 h, and the programmed cooling rate is 2 - 5 °C / min.

[0018] In the above technical solution, in Step 3, the alkali solution is a NaCO3 solution with a concentration of 0.1 - 10 mol / L, the drying time is 6 - 24 h, and the drying temperature is 80 - 120 °C.

[0019] In the above technical solution, in step 3, the fluorine content in the fluorinated carbon anode material is 0.5-2 wt%, preferably 1.3-1.8 wt%. The fluorine content is determined by the mass ratio and impregnation time in step 1, the heat treatment time and temperature in step 2, and the lye impregnation ratio and impregnation time in step 3. When the fluorine content is too low, the best modification effect cannot be achieved. When the fluorine content continues to increase, the hydrophobic effect of the carbon material reaches saturation, and at this time, the carbon material will also agglomerate because it cannot be well dispersed in water. At the same time, too high an F doping degree will lead to a decrease in the content of semi-ionic C-F bonds and an increase in fully fluorinated groups, resulting in a decrease in the conductivity of the material, an increase in ohmic polarization, and poor electrochemical performance. After doping the carbon material with an appropriate proportion of F and using it as the anode material for sodium-ion batteries, the first-cycle reversible capacity and first efficiency can be effectively improved.

[0020] In the above technical solution, the carbon anode material is a carbon material with pore shape modification. The carbon material is one or a mixture of petroleum-based carbon and biomass carbon. The petroleum-based carbon is carbon formed by carbonizing petroleum coke, needle coke, or pitch coke. The biomass carbon is carbon formed by carbonizing walnut shells, coconut shells, peanut shells, poplar wood, pine wood, rice husks, plant straws, glucose, or cellulose.

[0021] In the above technical solution, the carbon anode material is a carbon material with parallel slit pores. The pore belly diameter of the parallel slit pores is less than 1 nm, and the pore mouth diameter of the parallel slit pores is less than 0.364 nm. The specific surface area of the carbon material with parallel slit pores obtained by nitrogen adsorption-desorption test cannot be measured, indicating that its pore mouth diameter is less than the diameter of nitrogen molecules, which is 0.364 nm. The preparation method of the carbon material with parallel slit pores includes the following steps:

[0022] Step 1, carbonize poplar wood, pine wood, rice husks, plant straws, or walnut shells at 400-600 °C to form a carbon precursor;

[0023] Step 2: Dry-mix the carbon precursor obtained in Step 1 with the solid base in a certain proportion. The mass ratio of the solid base to the carbon precursor is greater than 0.4 and less than or equal to 1 (only within this proportion range can a large number of parallel fissure pores with a size below 1 nm be created. If the proportion increases, the pore shape will change to wedge-shaped pores or cylindrical pores with an increased curvature of the pore wall, which are not beneficial for enhancing the plateau potential. If the proportion is too small, the number of parallel fissure pores is too small and the capacity of the carbon material is too low). Then, under the protection of a protective gas, perform activation pore formation at 800 - 900 °C. When the temperature is too high, the etching degree will be severe, forming wedge-shaped pores or cylindrical pores with a pore belly diameter greater than 1 nm. When the temperature is too low, the etching degree is low, the number of parallel slit pores is not abundant, resulting in a smaller plateau capacity. The pore formation time is 120 - 240 min. If the time is too long, the activation degree will be high, forming wedge-shaped pores or cylindrical pores with a pore belly diameter greater than 1 nm. If the time is too short, the activation is insufficient and the number of pores is small. After the reaction ends, perform pickling and drying to obtain porous carbon;

[0024] Step 3: Place the porous carbon into a tube furnace, introduce a protective gas at a flow rate of 10 - 100 ml / min, then heat up to 700 - 1100 °C, and then introduce a carbon source gas at a flow rate of 10 - 100 ml / min. After the deposition reaction ends, close the carbon source gas and cool down to room temperature to obtain a carbon negative electrode material with parallel fissure pores.

[0025] In the above technical solution, the carbon negative electrode material is sieve-type carbon, and the preparation method of the sieve-type carbon includes the following steps:

[0026] Step 1: Rapidly reduce the pore opening to a diameter of 0.33 - 0.364 nm by the first chemical vapor deposition: Place walnut shell-based porous carbon, bamboo-based activated carbon, coconut shell-based porous carbon, peanut shell-based porous carbon, petroleum coke-based porous carbon, needle coke-based porous carbon, or activated carbon fiber in a chemical vapor deposition device, introduce a protective gas at a predetermined flow rate, heat up to 1100 - 1300 °C, and then introduce a carbon source gas at a rate of 10 - 500 ml / min (if the flow rate of the carbon source gas is too small, the pore opening size left during the first chemical vapor deposition is large, which will cause a large amount of deposited carbon to enter the pores during the second step of pore mouth refinement; if the flow rate of the carbon source gas is too large, it will overly block the pores and generate a large amount of ineffective deposited carbon at the pore mouth, resulting in too low initial Coulombic efficiency during sodium storage). Keep the temperature for 0 - 30 min and not 0 (the purpose of the first chemical vapor deposition is to rapidly reduce the pore opening and prevent deposited carbon from entering the pores. If the heat preservation time is too long, it will cause excessive deposition and affect the initial Coulombic efficiency of sodium storage);

[0027] Step 2, the second chemical vapor deposition is used to refine the pore opening to a diameter less than 0.33 nm: After the first heat preservation is completed, the source gas is cut off, and the temperature is lowered to 600 - 800 °C. Then, a carbon source gas is introduced at a rate greater than or equal to 10 ml / min (if the flow rate of the carbon source gas is too small, it will take a long time to refine the pore opening), and heat preservation is carried out. The heat preservation time is greater than or equal to 3 h (since the deposition temperature is controlled within a lower range in the second stage of deposition, the deposition only occurs selectively at the pore opening at this time. After the pore opening is refined, the deposition will not occur. If the deposition time is < 3 h, it will not be able to achieve the effect of refining the pore opening, resulting in a lower initial Coulombic efficiency and a lower sodium storage capacity. In Step 2, the reaction temperature is controlled at a lower level, and the pyrolytic deposition of the carbon source gas must occur at a position with a low energy barrier. For porous carbon, the sites with a low energy barrier are the pore openings rich in defects. When the pore opening positions are all occupied by the deposited carbon, there are no sites available for the pyrolytic deposition of the carbon source gas, so the deposition will not occur even if the time is extended).

[0028] Step 3, turn off the carbon source gas, and cool down to room temperature at a predetermined cooling rate to obtain the carbon negative electrode material described above.

[0029] In the above technical solution, the carbon source gas is methane, benzene vapor, toluene vapor, xylene vapor, ethane, propane or acetylene.

[0030] On the other hand, the present invention also includes a preparation method of a sodium ion battery slurry, which includes the following steps:

[0031] Step 1, prepare a CMC aqueous dispersion with a mass fraction of 1 - 4 wt%; an SBR aqueous dispersion with a mass fraction of 20 - 50%.

[0032] Step 2, stir and mix the fluorinated carbon negative electrode material, the CMC glue solution obtained in Step 1, the conductive agent, the SBR solution obtained in Step 1, and deionized water in proportion to obtain a slurry with a viscosity of 5000 - 7000 mPa·s.

[0033] Step 3, sieve to obtain the sodium ion battery slurry.

[0034] In the above technical solution, in Step 2, the mass ratio of the carbon negative electrode material, CMC in Step 1, the conductive agent, and the SBR solution obtained in Step 1 is 90:2:5:3 - 95:1:2:2.

[0035] In the above technical solution, the conductive agent in Step 2 is SUPER-P, KS-6, conductive graphite, carbon nanotubes, graphene, carbon fiber VGCF, acetylene black or Ketjen black.

[0036] Another aspect of the present invention further includes a method for preparing a negative electrode sheet of a battery, comprising the following steps: coating the sodium ion battery slurry on a copper foil current collector and then drying to obtain the negative electrode sheet of the battery.

[0037] Another aspect of the present invention further includes the negative electrode sheet of the battery obtained based on the above preparation method.

[0038] Another aspect of the present invention further includes a sodium ion battery, comprising a positive electrode, a negative electrode, a separator, and the negative electrode sheet of the battery described above.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. In the present invention, the carbon negative electrode material is fluorinated, which can effectively reduce the concentration of oxygen-containing functional groups on the surface of the carbon negative electrode material, substitute some fluorine-containing functional groups, and significantly improve the hydrophobic characteristics of the material.

[0041] 2. In the present invention, the surface fluorination is mainly based on a liquid-phase reaction, with high controllability, easy process implementation, and easy equipment scaling. Specifically, the ratio and concentration of surface fluorination can be controlled by the material ratio, the liquid-phase reaction can be controlled by heating temperature and stirring conditions, etc., and the equipment can be scaled up proportionally using a reaction kettle, etc.

[0042] 3. The carbon negative electrode material of the present invention uses a sieve-type carbon or a carbon material with parallel crack pores. The carbon material with parallel crack pores has a large number of parallel crack pores. The pore belly diameter of the parallel crack pores is less than 1 nm, the pore mouth diameter is less than 0.364 nm, and it has a relatively high average working potential of the plateau. The pore mouth diameter of the sieve-type carbon is less than 0.33 nm, and it has a relatively high first Coulomb efficiency. Description of the Drawings

[0043] Figure 1 It is the TEM of the carbon material with parallel crack pores in Example 2.

[0044] Figure 2 It is the TEM of the carbon negative electrode material obtained in Comparative Example 12. Detailed Embodiments

[0045] The following further elaborates on the present invention in detail with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] Example 1

[0047] A sieve-type carbon is prepared by the following method:

[0048] Step 1, rapid reduction of pore openings by the first chemical vapor deposition: Put the porous carbon with a rich pore structure into a tube furnace. The porous carbon is activated carbon fiber, and the specific surface area measured by small-angle scattering is 1420 m 2 / g, and the specific surface area measured by nitrogen adsorption-desorption is 1380 m 2 / g. The large specific surface area of the porous carbon indicates that it has a rich pore number and a large internal space. Therefore, it is a raw material for large pore bellies. Then, introduce the protective gas argon with a flow rate of 90 ml / min, and heat it up to the final temperature of 1200 °C at a heating rate of 10 °C / min. Under the condition of the final temperature of 1200 °C, introduce methane gas with a flow rate of 30 ml / min and continuously react for 25 min to rapidly reduce the pore openings;

[0049] Step 2, precise refinement of pore openings to a diameter less than 0.33 nm by the second chemical vapor deposition: Cut off the methane gas, cool down to 700 °C, introduce methane gas with a flow rate of 10 ml / min, and continuously react for 300 min to further refine the pore openings so that the pore opening diameter is less than 0.33 nm;

[0050] Step 3, turn off the carbon source gas, and cool down to room temperature at a cooling rate of 10 °C / min to obtain the sieve-type carbon described.

[0051] The specific surface area measured by small-angle X-ray scattering of the porous carbon in Step 1 is 1420 m 2 / g, and the specific surface area measured by small-angle X-ray scattering of the sieve-type carbon obtained in Step 3 is 1415 m 2 / g, indicating that the deposited carbon did not enter the interior of the pore bellies during the two chemical vapor depositions, achieving the effect of selectively adjusting the pore openings.

[0052] The specific surface area measured by nitrogen adsorption-desorption of the porous carbon in Step 1 is 1380 m 2 / g. After the first chemical vapor deposition in Step 1, the specific surface area decreased to 30 m 2 / g. After the second chemical vapor deposition in Step 2, the specific surface area decreased to 5 m 2 / g, indicating that after the first chemical vapor deposition, most of the pore opening diameters were less than 0.364 nm (the molecular kinetic diameter of N2), and after the second chemical vapor deposition, the pore opening diameters of all pores were less than 0.364 nm.

[0053] The specific surface area measured by carbon dioxide adsorption-desorption of the porous carbon in Step 1 is 1358 m 2 / g. After the first chemical vapor deposition, the specific surface area decreased to 600 m 2 / g. After the second chemical vapor deposition, the specific surface area decreased to 6 m 2 / g, indicating that after the rapid reduction of the orifice size in Step 1, most of the orifice diameters are still larger than 0.330 nm (the molecular dynamic diameter of CO2), and after the refinement of the orifices in Step 2, the orifice diameters of all the pores are less than 0.330 nm.

[0054] Example 2

[0055] A carbon material with parallel fissure pores is prepared by the following method:

[0056] Step 1: Crush poplar wood to 10 - 20 mesh, put it into a tube furnace, carbonize it in a nitrogen atmosphere at 400 °C for 60 min to obtain a carbon precursor;

[0057] Step 2: Mix the carbon precursor obtained in Step 1 with NaOH at a mass ratio of 1:1 to obtain mixture A. Place mixture A in a tube furnace protected by a nitrogen atmosphere, introduce nitrogen at a flow rate of 100 ml / min, heat it to 800 °C at a heating rate of 5 °C / min and hold for 3 h, then cool it down at a cooling rate of 5 °C / min in a programmed manner to obtain mixture B. Immerse the product cooled to near room temperature in an acid solution with a hydrogen ion concentration of 1 mol / L and wash it 5 times, 30 minutes each time. Dry the obtained product under normal pressure at 105 °C, denoted as porous carbon;

[0058] Step 3: Place the porous carbon in a tube furnace. Under the condition of continuously introducing nitrogen with a flow rate of 100 ml / min, heat it to 900 °C at a heating rate of 5 °C / min. After the furnace temperature is stable for 60 min, introduce a mixed gas of a carbon source gas and nitrogen with a molar ratio of 1:2 into it. After introducing for 120 min, cool it down at a cooling rate of 10 °C / min in a programmed manner to obtain a carbon material with parallel fissure pores (the pore belly diameter is less than 1 nm).

[0059] In the carbon material obtained in Step 3 of this example, the graphite microcrystals are all stacked flatly, as Figure 1 shown. The voids between the microcrystals are parallel fissure pores less than 1 nm. In Step 3, the microstructure before and after shrinking the orifices does not change significantly. The pore belly diameter of the parallel fissure pores is less than 1 nm, and shrinking the orifices does not affect the internal structure of the pores, and the pore belly diameter remains unchanged.

[0060] Example 3

[0061] Using the sieve - type carbon obtained in Example 1 or the carbon material with parallel fissure pores obtained in Example 2 as the carbon negative electrode material, perform fluorination surface treatment on the carbon negative electrode material, including the following steps:

[0062] Step 1: Immerse the carbon negative electrode material in the fluorine-containing precursor at room temperature. The mass ratio of the carbon negative electrode material to the fluorine-containing precursor is 1:1. Stir and immerse for 12 h at a stirring speed of 500 rmp / min, and then dry to obtain the impregnated carbon material.

[0063] Step 2: Place the impregnated carbon-containing material in a certain chamber, introduce a protective gas, and heat it to the heat treatment temperature. The heating rate is 5 °C / min, carry out heat preservation heat treatment, and obtain an intermediate after programmed cooling. The cooling rate is the same as the heating rate.

[0064] Step 3: Wash the intermediate with a 1 mol / L NaCO3 solution and dry to obtain the fluorinated carbon negative electrode material.

[0065] Prepare a sodium-ion battery slurry using the fluorinated carbon negative electrode material, including the following steps:

[0066] Step 1: Prepare CMC (2%) colloid: In a planetary stirrer, configure CMC powder into a 2% CMC colloid with deionized water, stir at 3000 rmp / min for 6 h until the colloid is clear, transparent, and bubble-free, and prepare a 30% SBR aqueous dispersion.

[0067] Step 2: Mix the fluorinated carbon negative electrode material, CMC colloidal solution, conductive agent SP, SBR solution, and deionized water in a ratio of 90:2:5:3:50, stir at 3000 rmp / min for 4 h, test the viscosity of the slurry, and keep it at 5000 - 7000 mPa·s.

[0068] If the viscosity is higher than this range, add deionized water to adjust the viscosity, continue stirring for 2 h, and then continue to measure the viscosity until it meets the requirements.

[0069] Step 3: After passing through a 150-mesh sieve, the product slurry is obtained.

[0070] Prepare a carbon negative electrode sheet using the product slurry, including the following steps:

[0071] Coat the product slurry on a copper foil current collector, place it in a vacuum oven at 100 °C and dry for 12 h to obtain a dried electrode sheet, and cut it into a circular sheet matching the button battery, that is, the carbon negative electrode sheet is obtained.

[0072] Assemble a button half-cell using the carbon negative electrode sheet:

[0073] It includes the sodium-ion battery carbon negative electrode, sodium metal sheet, electrolyte, and separator; among them, the electrolyte is NaClO4 (EC / DEC 1:1), and the separator is GF / A.

[0074] Perform constant current charge and discharge experiments on the LAND battery test system with a voltage range of 0V - 2.5V and a current density of 50 mA / g. The test results are shown in the following table:

[0075]

[0076] Although the initial cycle reversible specific capacity, initial efficiency, and average working potential in the plateau section of Comparative Example 3.2, Comparative Example 3.3, and Comparative Example 3.5 are similar to the performance obtained in Example 3.1, agglomeration occurs during the slurry processing, and the carbon negative electrode sheet peels off.

[0077] Comparative Example 4

[0078] The difference in the preparation process of the carbon negative electrode material from Example 1 is that step 2 is not carried out, and other steps and parameters are the same as those in Example 1.

[0079] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are the same as those in Example 4.1.

[0080] The product slurry has no agglomeration, the initial cycle reversible specific capacity is 280 mAh / g, and the initial efficiency is 80%.

[0081] Comparative Example 5

[0082] The preparation process of the carbon negative electrode material is compared with that of Example 1. The difference is that in Comparative Example 5, the continuous reaction time in step 1 is 1 h, and step 2 is not carried out.

[0083] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are the same as those in Example 4.1.

[0084] The product slurry has no agglomeration, the initial cycle reversible specific capacity is 230 mAh / g, and the initial efficiency is 50%.

[0085] Comparative Example 6

[0086] The preparation process of the carbon negative electrode material is compared with that of Example 1. The difference is that in Comparative Example 6, the continuous reaction time in step 1 is 2 h, and step 2 is not carried out.

[0087] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are the same as those in Example 4.1.

[0088] The product slurry has no agglomeration, the initial cycle reversible specific capacity is 270 mAh / g, and the initial efficiency is 60%.

[0089] Comparative Example 7

[0090] The preparation process of the carbon negative electrode material was compared with that of Example 1. The difference is that in Comparative Example 7, the temperature of the first chemical vapor deposition in Step 1 was 900 °C, and the reaction continued for 25 min. Step 2 was the same as that of Example 1. The temperature of the second chemical vapor deposition was 700 °C, and the reaction continued for 300 min.

[0091] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button half-cell were consistent with those of Example 4.1.

[0092] The product slurry had no agglomeration. The first-cycle reversible specific capacity was 320 mAh / g, and the first efficiency was 85%.

[0093] Comparative Example 8

[0094] The preparation process of the carbon negative electrode material was compared with that of Example 1. The difference is that in Comparative Example 8, the temperature of the first chemical vapor deposition in Step 1 was 1000 °C, and the reaction continued for 25 min. Step 2 was the same as that of Example 1. The temperature of the second chemical vapor deposition was 700 °C, and the reaction continued for 300 min.

[0095] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button half-cell were consistent with those of Example 4.1.

[0096] The product slurry had no agglomeration. The first-cycle reversible specific capacity was 335 mAh / g, and the first efficiency was 88%.

[0097] Comparative Example 9

[0098] The preparation process of the carbon negative electrode material was compared with that of Example 1. The difference is that in Comparative Example 9, the temperature of the second chemical vapor deposition in Step 2 was 700 °C, and the reaction continued for 2 h.

[0099] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button half-cell were consistent with those of Example 4.1.

[0100] The product slurry had no agglomeration. The first-cycle reversible specific capacity was 310 mAh / g, and the first efficiency was 80%.

[0101] Comparative Example 10

[0102] The preparation process of the carbon negative electrode material was compared with that of Example 1. The difference is that in Step 2, the temperature of the second chemical vapor deposition was 900 °C, and the reaction continued for 5 h.

[0103] The fluorination surface treatment step of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button half-cell were consistent with those of Example 4.1.

[0104] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 290 mAh / g, and the first efficiency is 78%.

[0105] Comparative Example 11

[0106] This comparative example is compared with Example 1. The procedure of Step 1 is the same as that of Example 1. The difference is that the temperature of the second chemical vapor deposition in Step 2 is 500 °C and the reaction lasts for 5 h.

[0107] The fluorination surface treatment procedure of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are consistent with those in Example 4.1.

[0108] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 290 mAh / g, and the first efficiency is 75%.

[0109] Comparative Example 12

[0110] In the preparation of the carbon negative electrode material compared with Example 2, in this comparative example, poplar wood is replaced by petroleum coke, and petroleum coke is used as the precursor, and the remaining parameter conditions are the same as those in Example 1. The TEM of the carbon negative electrode material is as Figure 2 shown. It can be seen that the mesoporous structure of the prepared porous carbon material D is not only composed of parallel slit pores, but also some wedge-shaped pores of 1-2 nm appear.

[0111] The fluorination surface treatment procedure of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are consistent with those in Example 4.1.

[0112] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 445 mAh / g, the first efficiency is 87%, and the average working potential of the plateau section is 30 mV.

[0113] Comparative Example 13

[0114] In the preparation of the carbon negative electrode material compared with Example 2, in this comparative example, in Step 2, the mass ratio of NaOH to the carbon precursor is 2:1.

[0115] The fluorination surface treatment procedure of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a coin-type half-cell are consistent with those in Example 4.1.

[0116] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 500 mAh / g, the first efficiency is 86%, and the average working potential of the plateau section is 30 mV.

[0117] Comparative Example 14

[0118] In the preparation of the carbon negative electrode material compared with Example 2, the deposition temperature is too low, specifically 600 °C, and the pore mouths are not completely shrunk, resulting in larger pore mouth sizes in the obtained porous carbon material.

[0119] The fluorination surface treatment steps of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button-type half cell are the same as those in Example 4.1.

[0120] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 300 mAh / g, the first efficiency is 75%, and the average working potential in the plateau section is 50 mV.

[0121] Comparative Example 15

[0122] Compared with Example 2 in the preparation of the carbon negative electrode material, in step 2, the activation pore-forming temperature is 700 °C, and the rest is the same as in Example 2. The obtained carbon negative electrode material has a low etching degree and the number of parallel fissure pores is not abundant.

[0123] The fluorination surface treatment steps of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button-type half cell are the same as those in Example 4.1.

[0124] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 350 mAh / g, the first efficiency is 87%, and the average working potential in the plateau section is 70 mV.

[0125] Comparative Example 16

[0126] Compared with Example 2 in the preparation of the carbon negative electrode material, in step 2, the activation pore-forming temperature is 1000 °C, and the rest is the same as in Example 2. The obtained carbon negative electrode material has a large number of wedge-shaped pores or cylindrical pores with a pore belly diameter greater than 1 nm.

[0127] The fluorination surface treatment steps of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button-type half cell are the same as those in Example 4.1.

[0128] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 455 mAh / g, the first efficiency is 86%, and the average working potential in the plateau section is 45 mV.

[0129] Comparative Example 17

[0130] In this comparative example compared with Example 1, in step 2, the mass ratio of NaOH to the precursor is 0.3, and the rest is the same as in Example 1. The obtained carbon material has an insufficient number of parallel fissure pores.

[0131] The fluorination surface treatment steps of the carbon negative electrode material, the product slurry, and the process of assembling the carbon negative electrode sheet into a button-type half cell are the same as those in Example 4.1.

[0132] The product slurry has no agglomeration, the first-cycle reversible specific capacity is 300 mAh / g, the first efficiency is 88%, and the average working potential in the plateau section is 70 mV.

[0133] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a sodium ion battery slurry, characterized in that, It includes the following steps: Step 1, prepare a CMC aqueous dispersion with a mass fraction of 1-4 wt%; an SBR aqueous dispersion with a mass fraction of 20-50%; Step 2, stir and mix the carbon negative electrode material, the CMC colloidal solution obtained in Step 1, the conductive agent, the SBR solution obtained in Step 1, and deionized water in proportion to obtain a slurry with a viscosity of 5000-7000 mPa·s; Step 3, screen to obtain the sodium-ion battery slurry; The carbon negative electrode material in Step 2 is prepared by the following steps: Step s1, immerse the carbon negative electrode material to be treated in a fluorine-containing precursor at room temperature. The fluorine-containing precursor is one or more of a high molecular polymer prepared by polymerization of a fluorine-containing monomer, a fluorine-containing organic compound, and a fluorine-containing inorganic compound; the mass ratio of the carbon negative electrode material to the fluorine-containing precursor is 1:1-20:1; the high molecular polymer is polytetrafluoroethylene, perfluoroalkoxy resin, polyperfluoroethylene-propylene, or polyvinylidene fluoride, the fluorine-containing inorganic compound is hydrofluoric acid, triethylamine trihydrofluoride, sodium fluoride, potassium fluoride, or aluminum fluoride, and the fluorine-containing organic compound is polyfluorobenzene, perfluorobenzene, or perfluorocarboxylic acid. Stir and process for 6-12 h, with a stirring speed of 100-1000 rpm / min, and then dry to obtain the impregnated carbon negative electrode material; Step s2, place the impregnated carbon negative electrode material obtained in Step s1 in a chamber, introduce a protective gas, and raise the temperature to the required temperature for heat treatment at a programmed heating rate. After programmed cooling, an intermediate is obtained; the protective gas is nitrogen or argon, the programmed heating rate is 2-5 °C / min, the required temperature is 800-1300 °C, the heat treatment time is 2-3 h, and the programmed cooling rate is 2-5 °C / min; Step s3, wash the intermediate obtained in Step s2 with an alkali solution and dry to obtain the fluorinated carbon negative electrode material; The carbon negative electrode material to be treated is a sieve-type carbon, and the preparation method of the sieve-type carbon includes the following steps: Step 1, first chemical vapor deposition to quickly reduce the pore orifice to a diameter of 0.33-0.364 nm: place walnut shell-based porous carbon, bamboo-based activated carbon, coconut shell-based porous carbon, peanut shell-based porous carbon, petroleum coke-based porous carbon, needle coke-based porous carbon, or activated carbon fiber in a chemical vapor deposition device, introduce a protective gas with a predetermined flow rate, raise the temperature to 1100-1300 °C, and then introduce a carbon source gas at a rate of 10-500 ml / min, and keep the temperature for 0-30 min and not 0; Step 2, second chemical vapor deposition to refine the pore orifice to a diameter less than 0.33 nm: after the first heat preservation ends, cut off the source gas, cool down to 600-800 °C, introduce a carbon source gas at a rate greater than or equal to 10 ml / min, and carry out heat preservation for a heat preservation time greater than or equal to 3 h; Step 3, close the carbon source gas and cool down to room temperature at a predetermined cooling rate to obtain the carbon negative electrode material.

2. The preparation method of the sodium ion battery slurry according to claim 1, wherein, In Step s3, the alkali solution is a Na2CO3 solution with a concentration of 0.1-10 mol / L, the drying time is 6-24 h, and the drying temperature is 80-120 °C.

3. The preparation method of the sodium ion battery slurry according to claim 1, characterized in that, In the step s3, the impregnation ratio of the intermediate to the lye is 0.1:1 - 1:1, the impregnation time is 2 - 24 h, and the fluorine content in the obtained carbon negative electrode material treated by fluorination is 0.5 - 2 wt%.

4. The preparation method of the sodium ion battery slurry according to claim 1, characterized in that, In the step 2, the mass ratio of the carbon negative electrode material, CMC in the step 1, the conductive agent, and the SBR solution obtained in the step 1 is 90:2:5:3, or the mass ratio of the carbon negative electrode material, CMC in the step 1, the conductive agent, and the SBR solution obtained in the step 1 is 95:1:2:

2.

5. The preparation method of the sodium ion battery slurry according to claim 1, characterized in that, The conductive agent in the step 2 is SUPER-P, KS-6, conductive graphite, carbon nanotubes, graphene, carbon fiber VGCF, acetylene black or Ketjen black.

6. A negative electrode plate of a battery, characterized in that, It is prepared by the following steps: After coating the sodium-ion battery slurry prepared by the preparation method of the sodium-ion battery slurry as described in claim 1 on a copper foil current collector, it is dried to obtain a battery negative electrode sheet.

7. A sodium-ion battery, characterized in that, It includes a positive electrode, the battery negative electrode sheet as described in claim 6, and a separator.

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