Preparation method and application of high specific energy and long service life composite negative electrode material

Abstract

The application relates to a preparation method and application of a high-specific-energy and long-service-life composite negative electrode material in the technical field of new energy power and energy storage batteries, and belongs to the technical field of new energy power and energy storage batteries. The preparation method comprises the following steps: step one, dispersing a carbon-based material and an amorphous carbon negative electrode material in an aqueous solution with a dopant to obtain a dispersion A, dispersing a granulating plasticizing agent in the dispersion A to prepare a slurry B, and granulating the slurry B by using a spray drying mode to obtain a spherical material; step two, high-temperature sintering the spherical material under the protection of an inert atmosphere to obtain a doped carbon source; step three, introducing a phosphorus-based negative electrode material into the doped carbon source to form a uniform phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material; and step four, coating a conductive polymer layer on the surface of the phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material to obtain a composite negative electrode material. The prepared sodium ion secondary battery has better electric field distribution, reduces local polarization, effectively slows down the attenuation of the service life of the battery, and improves the cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy power and energy storage batteries, and particularly relates to a preparation method and application of a high-specific-energy and long-service-life composite negative electrode material. BACKGROUND

[0002] Sodium is 400 times more abundant than lithium, and the development of sodium batteries can to a large extent alleviate the supply chain security problems caused by the shortage of lithium resources and the fluctuation of material prices, and is helpful to the sustainable development of the new energy industry, so it has received great attention in recent period. Sodium ion batteries usually use amorphous carbon such as hard carbon / soft carbon as negative electrode material, which can exhibit excellent fast charging and low temperature performance, but due to the capacity of amorphous carbon is generally around 300 mAh / g, combined with the comprehensive index of sodium ion battery, the energy density is lower than that of lithium ion battery, which has certain short board, limiting the use scene of sodium ion battery.

[0003] In order to further improve the energy density, the mainstream solution in the industry is to use amorphous carbon mixed with a certain proportion of new high-specific-energy negative electrode material, among which the most representative is phosphorus-based negative electrode material. Phosphorus is abundant in reserves and low in price, and has a very high specific capacity (Na3P, theoretical capacity > 2500 mAh / g), but due to the huge volume change in the process of forming sodium-phosphorus alloy, the cycle stability of the battery is affected, which limits the direct use of phosphorus as negative electrode material in sodium ion secondary battery. In order to solve the above problems, the current main research direction is to composite phosphorus-based and carbon-based materials to form a phosphorus-carbon composite negative electrode material.

[0004] The use of phosphorus-carbon negative electrode and amorphous carbon negative electrode can effectively improve the energy density of sodium ion secondary battery. The current common compounding method is basically physical mixing in the homogenization section process, but due to the difference in physical properties of the two, the uniformity of the mixture is difficult to guarantee, and the prepared sodium ion secondary battery has uneven electric field distribution in the process of charging and discharging, and there is a phenomenon of local polarization. In addition, there are some side reactions between the intermediate products of phosphorus-carbon negative electrode alloying reaction and electrolyte, which leads to shuttle effect and affects the cycle life of the battery, accelerating the attenuation of the battery. SUMMARY

[0005] The present application aims at the limitations of the above-mentioned phosphorus-carbon negative electrode and amorphous carbon negative electrode in physical mixing, and provides a preparation method and application of a high-specific-energy and long-service-life composite negative electrode material. A carbon-based material with high adsorption and a dopant is selected, granulation is performed on the carbon-based material and the amorphous carbon negative electrode material by a spray drying method through a granulation plasticizing agent, high-temperature sintering is performed to form a doped carbon source, a phosphorus-based negative electrode material with high specific capacity is introduced into the carbon source by an evaporation condensation method, a mixed material with uniform mixing is formed, and a conductive polymer layer is coated on the outer surface of the mixed material. The prepared sodium ion secondary battery avoids the problem of uneven electric field distribution, effectively isolates the contact between the intermediate product of the alloying reaction and the electrolyte, improves the conductivity of the phosphorus-based negative electrode, reduces the impedance, and improves the cycle life of the battery.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A preparation method of a high-specific-energy and long-service-life composite negative electrode material, comprising the following steps:

[0008] Step one, dispersing the carbon-based material and the amorphous carbon negative electrode material in an aqueous solution with a dopant to obtain a dispersion A, dispersing a granulation plasticizing agent in the dispersion A to prepare a slurry B, and performing granulation on the slurry B by a spray drying method to obtain a spherical material;

[0009] Step two, high-temperature sintering the spherical material under the protection of an inert atmosphere to obtain a doped carbon source;

[0010] Step three, introducing a phosphorus-based negative electrode material into the doped carbon source by an evaporation condensation method to form a mixed material of the phosphorus-carbon negative electrode and the amorphous carbon negative electrode;

[0011] Step four, coating a conductive polymer layer on the surface of the mixed material of the phosphorus-carbon negative electrode and the amorphous carbon negative electrode by a liquid-phase in-situ polymerization method to obtain a high-specific-energy and long-service-life composite negative electrode material.

[0012] Further, in step one, the carbon-based material includes one or a combination of carbon nanotubes, porous carbon, and activated carbon; and the amorphous carbon negative electrode material includes one or a combination of hard carbon and soft carbon.

[0013] Further, in step one, the dopant includes one or a combination of ammonium dihydrogen phosphate and ammonium sulfate; and the granulation plasticizing agent includes one or a combination of CMC, guar gum, polyethylene glycol, and sodium alginate.

[0014] Further, in step one, the mass ratio of the carbon-based material to the amorphous carbon negative electrode material is 1:3-200; the ratio of the weight of the granulating plasticizing agent to the sum of the weights of the carbon-based material and the amorphous carbon negative electrode material is 1:4-10, and the concentration of the dopant in the aqueous solution with the dopant is 0.1-1M.

[0015] Further, in step one, the solid content of the slurry B is in the range of 20%-50%.

[0016] Further, in step two, the high-temperature sintering is performed at a temperature of 500-800°C, preferably 550-650°C, for 6-18h, preferably 8-12h.

[0017] Further, in step three, the specific steps of the evaporation-condensation method are as follows: the phosphorus-based negative electrode material powder and the carbon-doped source are placed in a sealed container, the phosphorus-based negative electrode material powder and the carbon-doped source are separately placed, the sealed container is vacuumized and placed in a high-temperature furnace for heating, so that the phosphorus-based negative electrode material powder sublimates, and in the heating process, the phosphorus-based negative electrode material vapor is slowly adsorbed by the carbon-based material, and then cooled to room temperature, thereby obtaining a phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material. Preferably, the phosphorus-based negative electrode material is red phosphorus.

[0018] Further, in step three, the weight ratio of the carbon-doped source to the phosphorus-based negative electrode material is 1:0.01-0.25.

[0019] Further, in step four, the conductive polymer includes one or more combinations of polypyrrole, polythiophene, and polyaniline.

[0020] Further, the D50 particle size of the prepared high-specific-energy and long-life composite negative electrode material is in the range of 3-15μm, preferably 5-10μm.

[0021] A sodium-ion secondary battery, wherein the negative electrode material of the sodium-ion secondary battery comprises the composite negative electrode material prepared by the preparation method.

[0022] An electric device comprising the sodium-ion secondary battery.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The application realizes uniform mixing of carbon-based material and amorphous carbon negative material by granulation means, and forms element doping, improves the bonding ability of carbon atoms, enhances the adsorption of phosphorus-based negative material, introduces phosphorus-based negative material into carbon-based material, and performs conductive polymer coating, so that the cycle life is significantly improved while high specific energy is obtained. The composite negative material prepared by the application has the following advantages: the process of spray drying is adopted to uniformly mix the carbon-based material and the amorphous carbon negative material and form spherical particles, realize uniform distribution of the phosphorus-carbon negative electrode and the amorphous carbon negative electrode, compared with the physical mixing of the two in the homogenate, the composite negative material prepared by the application has better electric field distribution in the prepared sodium ion secondary battery, reduces the local polarization phenomenon, the outer layer is coated with a conductive polymer layer, improves the conductivity, alleviates the side reaction of active material and electrolyte, effectively slows down the attenuation of battery life, and improves the cycle stability.

[0025] In the granulation process, an aqueous solution of diammonium hydrogen phosphate or ammonium sulfate is used for dispersion, and in the process of spray drying, the water in the solution is quickly evaporated, the dopant is precipitated and attached to the carbon-based material and amorphous carbon, and the spherical material obtained by granulation is sintered at high temperature, so that nitrogen element, phosphorus element or sulfur element doping is introduced, the adsorption capacity of carbon-based material to phosphorus-based negative electrode is effectively improved, so that high energy density is realized. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the spherical granulation structure of the composite negative material prepared by the application;

[0027] Figure 2 is a scanning electron microscope image of the composite negative material prepared by the application;

[0028] Figure 3 is a particle size distribution diagram of the composite negative material prepared by the application;

[0029] Figure 4 is a schematic diagram of the structure of a sodium ion secondary battery containing the composite negative material;

[0030] Figure 5 is a schematic diagram of the structure of a power utilization equipment containing a sodium ion secondary battery using the composite negative material;

[0031] Among them, 1 is amorphous carbon negative material, 2 is phosphorus-carbon negative material, 3 is granulation plasticizer, 4 is conductive polymer, 5 is sodium ion secondary battery. DETAILED DESCRIPTION

[0032] The technical solutions in the present application will be described clearly and completely in connection with the drawings and embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0033] Embodiment 1

[0034] A preparation method of a high specific energy and long life composite negative electrode material, comprising the following steps:

[0035] 1. Preparation of doped carbon source: 10 g of carbon nanotubes and 650 g of hard carbon are dispersed in an aqueous solution of diammonium hydrogen phosphate with a concentration of 0.1 M to obtain dispersion A, then 100 g of CMC is dispersed in dispersion A, and a mixed slurry with a solid content of 40% is prepared by stirring, stirring for 0.5 h, centrifuging at a speed of 15000 r / min, and spray drying and granulating to obtain spherical materials. The spherical materials are placed in a quartz tube and protected by argon, heated to 600℃ in a tube furnace, and kept for 10 h to obtain N, P element doped carbon source.

[0036] 2. 50 g of doped carbon source and 1 g of red phosphorus are added to a quartz tube and placed at intervals. After the quartz tube is vacuumed and sealed, it is placed in a tube furnace and heated at 550℃ for 8 h, and then cooled to room temperature to obtain a phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material.

[0037] 3. 1 g of the phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material and 0.5 mL of pyrrole, 3 mL of 0.2 M hydrochloric acid, and 60 mL of anhydrous ethanol are added to a flask to form a mixed slurry, which is stirred in a cold water bath at 0-4℃ for 12 h. After filtration and washing, it is dried in a vacuum oven at 60℃ for 12 h to obtain a composite negative electrode material with a polypyrrole coating layer. The particle size test D50 value is 5.55 μm.

[0038] The composite negative electrode material is used as a secondary battery negative electrode material to make an electrode, which is applied to a secondary battery for electrochemical performance testing. The electrode is made as follows: 80% by mass of the composite negative electrode material, 10% conductive carbon black, and 10% sodium polyacrylate PAANa are mixed and stirred to obtain a uniform slurry, which is coated on the surface of a copper current collector. After vacuum drying at 90°C for 5h, a secondary battery negative electrode is prepared. A secondary battery is assembled using the above electrode. A metal sodium sheet is used as a counter electrode, Whatman glass fiber filter paper is used as a separator, and 1.0M NaPF6 in EC:DMC=1:1 Vol% is used as an electrolyte. A CR2032 button cell is assembled in an argon-filled glove box, and the button cell is tested for charge and discharge capacity and initial coulombic efficiency in the voltage range of 0.1V-2.0V at a charge and discharge rate of 0.05C / 0.05C. The button cell is tested for cycle life at a charge and discharge rate of 0.2C / 0.2C.

[0039] Example 2

[0040] A method for preparing a high specific energy and long life composite negative electrode material, comprising the following steps:

[0041] 1. Preparation of doped carbon source: 10g of porous carbon and 380g of soft carbon are dispersed in an aqueous solution of 0.1M ammonium sulfate to obtain dispersion A, and 40g of polyethylene glycol is dispersed in dispersion A. After stirring, a mixed slurry with a solid content of 30% is prepared, stirring for 0.5h, centrifugation at a speed of 15000r / min, and spray drying to obtain spherical materials. The spherical materials are placed in a quartz tube and protected by argon, heated to 650°C in a tube furnace for 8h, and N and S element-doped carbon source is obtained.

[0042] 2. In the quartz tube, 30g of doped carbon source and 1g of red phosphorus are placed at intervals. After the quartz tube is vacuumed and sealed, it is placed in a tube furnace and heated to 550°C for 8h. After cooling to room temperature, a phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material is prepared.

[0043] 3. In a flask, 1g of the phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material, 0.2mL of thiophene, 3mL of 0.2M hydrochloric acid, and 60mL of absolute ethanol are added to form a mixed slurry. Stirring is carried out in a cold water bath at 0-4°C for 12h. After filtration and washing, drying is carried out in a vacuum oven at 60°C for 12h to obtain a composite negative electrode material with a polythiophene coating layer. The particle size test D50 value is 7.68μm.

[0044] The composite negative electrode material is used as a secondary battery negative electrode material to make an electrode, which is applied to a secondary battery for electrochemical performance testing. The electrode is made as follows: 80% by mass of the composite negative electrode material, 10% conductive carbon black, and 10% sodium polyacrylate PAANa are mixed and stirred to obtain a uniform slurry, which is coated on the surface of a copper current collector. After vacuum drying at 90°C for 5h, a secondary battery negative electrode is prepared. A secondary battery is assembled using the above electrode. A metal sodium sheet is used as a counter electrode, Whatman glass fiber filter paper is used as a separator, and 1.0M NaPF6 in EC:DMC=1:1 Vol% is used as an electrolyte. A CR2032 button cell is assembled in an argon-filled glove box, and the button cell is tested for charge and discharge capacity and initial coulombic efficiency in the voltage range of 0.1V-2.0V at a charge and discharge rate of 0.05C / 0.05C. The button cell is tested for cycle life at a charge and discharge rate of 0.2C / 0.2C.

[0045] Example 3

[0046] A preparation method of a high specific energy and long life composite negative electrode material, comprising the following steps:

[0047] 1. Prepare a doped carbon source: disperse 10 g of activated carbon and 650 g of hard carbon in an aqueous solution of diammonium hydrogen phosphate with a concentration of 0.1 M to obtain dispersion A, then disperse 80 g of guar gum in dispersion A, fully stir to prepare a mixed slurry with a solid content of 35%, stir for 0.5 h, centrifuge at a speed of 15000 r / min, and spray dry and granulate to obtain spherical materials. The spherical materials are placed in a quartz tube and protected by argon, heated to 550℃ in a tube furnace for 12 h, and a N, P element doped carbon source is obtained.

[0048] 2. Add 50 g of the doped carbon source and 1 g of red phosphorus to the quartz tube, and place them at intervals. After the quartz tube is vacuumed and sealed, it is placed in a tube furnace and heated at 550℃ for 8 h, and then cooled to room temperature to obtain a phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material.

[0049] 3. Add 1 g of the phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material, 0.2 mL of aniline, 3 mL of hydrochloric acid with a concentration of 0.2 M, and 60 mL of anhydrous ethanol to a flask to form a mixed slurry, stir in a cold water bath at 0-4℃ for 12 h, filter and wash, and then dry in a vacuum oven at 60℃ for 12 h to obtain a composite negative electrode material with a polyaniline coating layer. The particle size test D50 value is 5.68 μm.

[0050] The composite negative electrode material is used as a secondary battery negative electrode material to make an electrode, which is applied to a secondary battery for electrochemical performance testing. The electrode manufacturing process and electrochemical performance testing method are the same as in Example 1.

[0051] Example 4

[0052] A preparation method of a high specific energy and long life composite negative electrode material, comprising the following steps:

[0053] 1. Prepare a doped carbon source: disperse 10 g of carbon nanotubes and 380 g of soft carbon in an aqueous solution of ammonium sulfate with a concentration of 0.1 M to obtain solution A, then disperse 80 g of sodium alginate in solution A, fully stir to prepare a mixed slurry with a solid content of 25%, stir for 0.5 h, centrifuge at a speed of 15000 r / min, and spray dry and granulate to obtain spherical materials. The spherical materials are placed in a quartz tube and protected by argon, heated to 600℃ in a tube furnace for 10 h, and a N, S element doped carbon source is obtained.

[0054] 2. In a quartz tube, 30 g of carbon source doped and 1 g of red phosphorus were placed at intervals. The quartz tube was vacuumized and sealed, and then placed in a tube furnace. After heating at 550 °C for 8 h, the quartz tube was cooled to room temperature to obtain a phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material.

[0055] 3. In a flask, 1 g of spherical core material, 0.2 mL of pyrrole, 3 mL of 0.2 M hydrochloric acid, and 60 mL of anhydrous ethanol were added to form a mixed slurry. The mixture was stirred in a cold water bath at 0-5 °C for 12 h. After filtration and washing, the mixture was dried in a vacuum oven at 60 °C for 12 h to obtain a composite negative electrode material with a polypyrrole coating layer. The particle size test D50 value was 8.24 μm.

[0056] The composite negative electrode material was used as a secondary battery negative electrode material to make an electrode, which was applied to a secondary battery for electrochemical performance testing. The electrode preparation process and electrochemical performance testing method were the same as in Example 1.

[0057] Comparative Example 1

[0058] A phosphorus-carbon negative electrode material was prepared. In a quartz tube, 1 g of carbon nanotubes and 1.2 g of red phosphorus were placed at intervals. The quartz tube was vacuumized and sealed, and then placed in a tube furnace. After heating at 550 °C for 8 h, the quartz tube was cooled to room temperature to obtain a phosphorus-carbon negative electrode material.

[0059] The prepared 0.05 g of phosphorus-carbon negative electrode material was physically mixed with 1.55 g of hard carbon material as a secondary battery negative electrode material to make an electrode, which was applied to a secondary battery for electrochemical performance testing. The electrode preparation process was as follows: 2.4% of the phosphorus-carbon material, 77.6% of the hard carbon material, 10% of the conductive carbon black, and 10% of the polyacrylic acid sodium PAANa were mixed and stirred to obtain a uniform slurry, which was coated on the surface of a copper current collector. After vacuum drying at 90 °C for 5 h, a secondary battery negative electrode was prepared. A secondary battery was assembled using the above electrode. A metal sodium sheet was used as the counter electrode, Whatman glass fiber filter paper was used as the separator, and 1.0 M NaPF6 in EC:DMC=1:1 Vol% was used as the electrolyte. A CR2032 button cell was assembled in an argon-filled glove box. The button cell was tested for charge and discharge capacity and the first coulombic efficiency in the voltage range of 0.1 V-2.0 V at a charge and discharge rate of 0.05C / 0.05C. The cycle life of the button cell was tested at a charge and discharge rate of 0.2C / 0.2C.

[0060] Table 1. Electrochemical performance results of the button cell

[0061] Serial number Discharge specific capacity (0.05 C) First coulombic efficiency (%) 0.2 C cycle 100 cycle capacity retention Example 1 332 90.4 92.3 Example 2 354 89.6 87.5 Example 3 328 90.8 91.7 Example 4 346 89.9 88.2 Comparative Example 1 336 89.4 85.6

[0062] Figure 1As shown, according to the scheme of the application, the material core is obtained in spherical material through granulation of the plasticizing agent 3, realizing uniform mixing of the amorphous carbon negative electrode 1 and the phosphorus-carbon negative electrode material 2, and the outside is coated with a conductive polymer 4 to improve the conductivity and reduce the side reaction with the electrolyte.

[0063] Figure 2 As shown, the scanning electron microscope picture of the composite negative electrode material can clearly show that the material after granulation is in a spherical shape.

[0064] Figure 3 As shown, the particle size data of Example 1 is D50 5.55 μm, and the particle size distribution interval is narrow.

[0065] The high specific energy, long life composite negative electrode material is applied in a sodium ion secondary battery 5, and the sodium ion secondary battery 5 is applied in the field of electric vehicles.

[0066] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and the person skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that can be understood by the person skilled in the art.

Claims

1. A method for preparing a high specific energy, long life composite negative electrode material, characterized by, The method comprises the following steps: Step one, dispersing the carbon-based material and amorphous carbon negative electrode material in a water solution with a dopant to obtain dispersion A, and then dispersing a granulation plasticizing agent in dispersion A to prepare slurry B, and using a spray drying method to granulate slurry B to obtain spherical materials; the dopant comprises a combination of one or more of ammonium dihydrogen phosphate and ammonium sulfate; the mass ratio of the carbon-based material to the amorphous carbon negative electrode material is 1:3-200; the concentration of the dopant in the water solution with the dopant is 0.1-1M; the carbon-based material comprises a combination of one or more of carbon nanotubes, porous carbon, and activated carbon; the amorphous carbon negative electrode material comprises a combination of one or both of hard carbon and soft carbon; the granulation plasticizing agent comprises a combination of one or more of CMC, guar gum, polyethylene glycol, and sodium alginate; Step two, high-temperature sintering of the spherical materials under the protection of an inert atmosphere to obtain a doped carbon source; the high-temperature sintering temperature is 500-800℃, and the holding time is 6-18h; Step three, introducing a phosphorus-based negative electrode material into the doped carbon source by an evaporation condensation method to form a uniform phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material; Step four, coating a conductive polymer layer on the surface of the phosphorus-carbon negative electrode and amorphous carbon negative electrode mixed material to obtain a high-specific-energy, long-life composite negative electrode material.

2. The method of claim 1, wherein: In step one, the ratio of the weight of the granulation plasticizing agent to the sum of the weights of the carbon-based material and the amorphous carbon negative electrode material is 1:4-10.

3. The method of claim 1, wherein: In step one, the solid content of slurry B is in the range of 20%-50%.

4. The method of claim 1, wherein: In step three, the weight ratio of the doped carbon source to the phosphorus-based negative electrode material is 1:0.01-0.

25.

5. The method of claim 1, wherein: In step four, the conductive polymer comprises a combination of one or more of polypyrrole, polythiophene, and polyaniline.

6. A sodium-ion secondary battery, characterized by: The negative electrode material of the sodium-ion secondary battery comprises the composite negative electrode material prepared by the preparation method of any one of claims 1-5.

7. An electric device comprising the sodium-ion secondary battery of claim 6.

Images