CN115763722A - Multidimensional and multiscale carbon-coated lithium-ion battery cathode material and preparation method thereof - Google Patents

Abstract

The invention provides a multidimensional multi-scale carbon-coated lithium ion battery anode material and a preparation method thereof. The product of the invention has good conductivity and stability, improves the capacity, the cycle performance, the multiplying power and other performances of the battery, and can meet the requirements of the fields of energy storage batteries, power batteries and the like on new materials.

Description

Multidimensional and multiscale carbon-coated lithium-ion battery cathode material and preparation method thereof

technical field

The invention relates to a multi-dimensional and multi-scale carbon-coated lithium-ion battery cathode material and a preparation method thereof, belonging to the technical field of lithium-ion battery cathode materials.

Background technique

At present, the positive electrode materials of lithium-ion batteries include: nickel-cobalt lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary oxides, and inorganic substances.

The layered lithium nickel cobalt manganese oxide (LiNi _x Co _{y Mnz} O ₂ , x+y+z=1, Li-NCM) cathode material combines the advantages of LiCoO ₂ , LiNiO ₂ , and LiMnO ₂ . With the advantages of high specific capacity, good cycle performance, good thermal stability, stable structure and low cost, it has become the most promising ternary cathode material at present. However, the main disadvantage of Li-NCM materials is low electrical conductivity and tap density. During the preparation process, due to the similar radius between nickel ions and lithium ions, part of the nickel ions will occupy the lithium sites and lithium-nickel mixing occurs, resulting in a decrease in the reversible discharge specific capacity of the Li-NCM material and poor cycle performance. This restricts the application of Li-NCM materials in high-power lithium-ion batteries.

However, when lithium iron phosphate (LiFePO ₄ ) is used as the positive electrode material, due to the extremely low electronic conductivity (only 10 ^-9 -10 ^-10 S/cm) and ion diffusion efficiency, the resistance polarization in the reaction becomes larger, making its The rate performance is poor, and these shortcomings greatly limit the wide application of lithium iron phosphate in practice.

In view of this, it is necessary to propose a multi-dimensional and multi-scale carbon-coated lithium-ion battery cathode material and its preparation method to solve the above problems.

Contents of the invention

The purpose of the present invention is to provide a multi-dimensional and multi-scale carbon-coated lithium-ion battery positive electrode material and its preparation method, which has good conductivity and stability, improves the battery capacity, cycle performance, rate performance and other performances, and can meet the requirements of energy storage. Demand for new materials in fields such as batteries and power batteries.

In order to achieve the above object, the present invention provides a method for preparing a multidimensional and multiscale carbon-coated lithium-ion battery cathode material, which mainly includes the following steps:

Step 1. Add 1-5wt% graphite auxiliary material to 95-99wt% resin, and stir and mix it in a water bath at 40-70°C for 5-30min to obtain mixture A;

Step 2, the mixture A obtained in step 1 is peeled off by a three-roll differential speed grinder, and after repeated peeling cycles, the mixture B is collected from the discharge roller;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 50-200vol% to the mixture B obtained from the stripping, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat step 3 and Continue to wash with alcohol, and finally centrifuge to obtain substance C;

Step 4, using the miscellaneous liquid removed after the last ethanol cleaning resin centrifugation in step 3 as a solvent, measuring the miscellaneous liquid which is equal to the volume of the substance C obtained by centrifugation, and dissolving 0.01-0.5wt% of the nitric acid compound raw material, Then mix and stir with substance C for 1-10min to obtain mixture D;

Step 5, adding mixture D to the lithium compound and stirring and mixing for 5-10 minutes to obtain mixture E, the amount of mixture D added accounts for 3-12wt% of the mass fraction of mixture E;

Step 6, the mixture E is further fully stripped and mixed through a three-roll differential speed grinder, and after being recycled and stripped several times, the mixture F is collected from the discharge roller;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at minus 50- minus 30°C to obtain mixture G;

Step 8. Put the freeze-dried mixture G in a tube furnace for heat treatment under argon, from room temperature to 500-850°C at a heating rate of 2-10°C·min ^-1 , keep it warm for 1-5h, and then naturally After cooling down to room temperature, a multi-dimensional and multi-scale carbon-coated lithium-ion battery positive electrode material is obtained.

As a further improvement of the present invention, in step 2, the three-roll differential speed grinder includes a discharge roll N1, a center roll N2 and a feed roll N3, wherein the feed roll N3, the center roll N2 and the The rotation speed ratio of the discharge roller N1 is 1:3:9, and during the cyclic peeling process, the gap between the center roller N2 and the feed roller N3 is always larger than the gap between the discharge roller N1 and the center roller N1. The gap between the rollers N2, the number of cycle stripping is 15-17 times.

As a further improvement of the present invention, during the 1st to 4th cycles of stripping, the gap between the central roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the central roll N2 are equal Located between 40-200μm.

As a further improvement of the present invention, during the 5th to 8th cycles of stripping, the gap between the center roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the center roll N2 are equal. Located between 10-40μm.

As a further improvement of the present invention, during the 9th to 12th cycles of stripping, the gap between the center roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the center roll N2 are equal Located between 2.5-10μm.

As a further improvement of the present invention, after the thirteenth cycle of stripping, the gap between the central roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the central roll N2 are all located at 0.5 Between -2.5μm.

As a further improvement of the present invention, in step 4, the raw material of the nitrate compound is aluminum nitrate or nickel nitrate.

As a further improvement of the present invention, in step 5, the lithium compound is lithium nickel cobalt manganate or lithium iron phosphate.

As a further improvement of the present invention, in step 6, the number of cyclic stripping is 2-3 times. After the cyclic stripping is completed, the gap between the center roll N2 and the feed roll N3 and the discharge roll N1 and the gap between the The gaps between the center rolls N2 are all located between 0.5-5 μm.

In order to achieve the above purpose, the present invention also provides a multidimensional and multiscale carbon-coated lithium ion battery positive electrode material, which is prepared by the above-mentioned preparation method of multidimensional and multiscale carbon coated lithium ion battery positive electrode material.

The beneficial effects of the present invention are: the present invention adopts the three-roll grinder grinding and stripping technology to overcome the interlayer van der Waals force through the shear force generated by the three-roll differential speed, the high-viscosity resin and the phosphorus flake graphite/expanded graphite. , so as to achieve the preparation of a large number of graphene-like nanosheets by peeling off the layered materials with a thickness of micron scale, and their crystal layer spacing becomes larger after peeling off. The graphene-like nanosheets prepared by this method are better than those prepared by traditional techniques Graphene preparation is more efficient and lower cost.

Description of drawings

Fig. 1 is the schematic diagram that the present invention uses graphite as raw material to obtain graphene-like nanosheet material through three-roll mill exfoliation in resin.

Figure 2 is a TEM image of graphene-like nanosheets, carbon nanotubes and amorphous carbon composite modified materials obtained after three-roll grinding and peeling, alcohol cleaning, freeze-drying, and heat treatment.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Here, it should be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and/or processing steps closely related to the solution of the present invention are shown in the drawings, and the steps related to the present invention are omitted. Other details that don't really matter.

Additionally, it should be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also Other elements not expressly listed, or inherent to the process, method, article, or apparatus are also included.

As shown in Figure 1 and Figure 2, the present invention discloses a multi-dimensional and multi-scale carbon-coated lithium-ion battery cathode material, and a preparation method of the multi-dimensional and multi-scale carbon-coated lithium-ion battery cathode material, the method mainly includes the following steps :

Step 1. Add 1-5wt% graphite auxiliary material to 95-99wt% resin, and stir and mix it in a water bath at 40-70°C for 5-30min to obtain mixture A;

Step 2, the mixture A obtained in step 1 is peeled off by a three-roll differential speed grinder, and after repeated peeling cycles, the mixture B is collected from the discharge roller;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 50-200vol% to the mixture B obtained from the stripping, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat step 3 and Continue to wash with alcohol, and finally centrifuge to obtain substance C;

Step 4, using the miscellaneous liquid removed after the last ethanol cleaning resin centrifugation in step 3 as a solvent, measuring the miscellaneous liquid which is equal to the volume of the substance C obtained by centrifugation, and dissolving 0.01-0.5wt% of the nitric acid compound raw material, Then mix and stir with substance C for 1-10min to obtain mixture D;

Step 5, adding mixture D to the lithium compound and stirring and mixing for 5-10 minutes to obtain mixture E, the amount of mixture D added accounts for 3-12wt% of the mass fraction of mixture E;

Step 6, the mixture E is further fully stripped and mixed through a three-roll differential speed grinder, and after being recycled and stripped several times, the mixture F is collected from the discharge roller;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at minus 50- minus 30°C to obtain mixture G;

Step 8. Put the freeze-dried mixture G in a tube furnace for heat treatment under argon, from room temperature to 500-850°C at a heating rate of 2-10°C·min ^-1 , keep it warm for 1-5h, and then naturally After cooling down to room temperature, a multi-dimensional and multi-scale carbon-coated lithium-ion battery positive electrode material is obtained.

Step 1-Step 8 will be described in detail below.

In step 2, the three-roll differential speed grinder includes a discharge roll N1, a center roll N2 and a feed roll N3, wherein the feed roll N3, the center roll N2 and the discharge roll N1 The rotational speed ratio is 1:3:9, and during the cyclic peeling process, the gap between the central roll N2 and the feed roll N3 is always larger than the gap between the discharge roll N1 and the central roll N2 , the number of times of cyclic stripping is 15-17 times; it should be noted that, in the number of times of different cyclic stripping, the distance between the rollers is different. and the gap between the discharge roller N1 and the central roller N2 are all between 40-200 μm; when the cyclic stripping is performed for the 5th to 8th times, the gap between the central roller N2 and the feed roller N3 The gap between the discharge roller N1 and the central roller N2 is located between 10-40 μm; when the cyclic stripping is performed for the 9th-12th time, the gap between the central roller N2 and the feed roller N3 The gap between the discharge roller N1 and the center roller N2 is between 2.5-10 μm; after the 13th cycle of stripping, the gap between the center roller N2 and the feed roller N3 The gap and the gap between the discharge roller N1 and the center roller N2 are both located between 0.5-2.5 μm.

In step 6, the number of cyclic stripping is 2-3 times. After the cyclic stripping is completed, the gap between the central roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the central roll N2 The gaps are all located between 0.5-5μm.

In the present invention, the positive electrode material of the battery uses nickel-cobalt lithium manganese oxide as a raw material, graphite as an auxiliary material, resin as a grinding medium and coated carbon raw material, and aluminum nitrate as a catalyst and a dopant. Among them, the raw material of nickel cobalt lithium manganate is a commercially available product, the tap density is 1.8-2.6g/cm ³ , the particle size (D50) is 2-16μm, and the resin is polyvinyl alcohol, polyvinylidene fluoride resin, One of epoxy resin, phenolic resin and polyethylene resin. The graphite is one or two of flake graphite and expanded graphite. The length and width of the raw material are 300-2000 μm, and the thickness is 50-500 μm. Moreover, the multi-dimensional and multi-scale carbon-coated lithium-ion battery positive electrode material prepared from nickel-cobalt lithium manganese oxide as a raw material, wherein nickel-cobalt lithium manganese oxide accounts for 93-97.5wt% of the total mass, and graphene-like accounts for 2% of the total mass. -4wt%, the amorphous carbon accounts for 0.4-2wt% of the total mass, and the carbon nanotube accounts for 0.1-1wt% of the total mass. Of course, in other embodiments of the present invention, the battery cathode material can also use lithium iron phosphate as a raw material, nickel nitrate as a catalyst and a dopant, and the bulk density of the lithium iron phosphate raw material is 0.5-0.9g /cm ³ , the median diameter is 0.5-5um, which can be set according to needs, without any limitation here. Moreover, the multi-dimensional and multi-scale carbon-coated lithium-ion battery positive electrode material prepared from lithium iron phosphate as a raw material, wherein lithium iron phosphate accounts for 93-97.4wt% of the total mass, and graphene-like accounts for 2-4wt% of the total mass, The amorphous carbon accounts for 0.4-2wt% of the total mass, and the carbon nanotube accounts for 0.1-1wt% of the total mass.

Below in conjunction with embodiment and comparative example specific explanation, wherein, embodiment 1-3 adopts nickel cobalt lithium manganese oxide as raw material, aluminum nitrate is catalyst and dopant, comparative example 1-6 is the comparative example of embodiment 1-3 .

Embodiment 1, using nickel-cobalt lithium manganate as raw material, flake graphite as auxiliary material, phenolic resin as grinding medium and coated carbon raw material, aluminum nitrate as catalyst and dopant, the tap density of said nickel-cobalt lithium manganate is 2.0g/cm ³ , the particle size (D50) is 4 μm, the length and width of the flake graphite raw material are 150 μm, and the thickness is 12 μm, which specifically includes the following steps:

Step 1. Add 3.5wt% graphite flakes to 96.5wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15 minutes to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 4 times, and finally the substance C is obtained by centrifugation;

Step 4, the miscellaneous liquid removed after the centrifugation of the last alcohol cleaning resin in step 3 is used as a solvent, and the miscellaneous liquid equal to the volume of the material C obtained by centrifugation is measured, and the aluminum nitrate raw material of 0.05wt% is dissolved therein, and then mixed with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm, from The discharge roller collects and obtains the mixture F;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 750°C at a rate of 5°C·min ^-1 , keep it warm for 4h, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material.

Weigh 0.07g of graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) g, after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly spread on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble in an argon atmosphere glove box , with metal lithium sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio of 1:1) as the electrolyte, and Celegard2400 as the separator, assembled into a CR2032 button lithium battery. At 25°C, under the condition of 1C, the voltage window is 2.0-4.3V. The battery assembled with graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery positive electrode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles at 1C is 204.8mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 94%, the initial ohmic internal resistance is 1.65Ω, and the internal ohmic resistance after 200 cycles at 1C Resistance 3.08Ω.

Embodiment 2, using nickel cobalt lithium manganate as raw material, expanded graphite as auxiliary material, epoxy resin as grinding medium and coated carbon raw material, aluminum nitrate as catalyst and dopant, the vibration of nickel cobalt lithium manganate The density is 2.2g/cm ³ , the particle size (D50) is 6 μm, the length and width of the expanded graphite raw material are 1000 μm, and the thickness is 100 μm, which specifically includes the following steps:

Step 1, adding 3.5wt% of expanded graphite to 96.5wt% epoxy resin, and mixing it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roller differential speed grinder, and after 15 cycles of peeling, collect the mixture B from the discharge roller; The gap between N2 and N1 is 200 μm, and the gap between N2 and N1 is 80 μm; the gap between N3 and N2 is 40 μm, and the gap between N2 and N1 is 20 μm when the cyclic stripping is 5-8 times; the cyclic stripping is 9-12 At the second time, the gap between N3 and N2 is 10 μm, and the gap between N2 and N1 is 5 μm; for the 13th-15th cycle stripping, the gap between N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm ;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 3 times, and finally the substance C is obtained by centrifugation;

Step 4, the miscellaneous liquid removed after the centrifugation of the last alcohol cleaning resin in step 3 is used as a solvent, and the miscellaneous liquid equal to the volume of the substance C obtained by centrifugation is measured, and 0.1wt% of the aluminum nitrate raw material is dissolved therein, and then mixed with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain mixture E, the amount of mixture D added accounts for 5wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle the peeling and mixing twice. Set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm. Collect mixture F from the discharge roller;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -40°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 600 °C at a heating rate of 2 °C min ^-1 , keep it warm for 5 hours, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material.

Weigh 0.07g of graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) g, after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly spread on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble in an argon atmosphere glove box , with metal lithium sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio of 1:1) as the electrolyte, and Celegard2400 as the separator, assembled into a CR2032 button lithium battery. At 25°C, under the condition of 1C, the voltage window is 2.0-4.3V. The battery assembled with graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery positive electrode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles at 1C is 188.5mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 90%, the initial ohmic internal resistance is 3.22Ω, and the internal ohmic resistance after 200 cycles at 1C Resistance 6.16Ω.

Example 3, using nickel-cobalt lithium manganate as raw material, flake graphite as auxiliary material, water-soluble acrylic resin as grinding medium and coated carbon raw material, aluminum nitrate as catalyst and dopant, the vibration of nickel-cobalt lithium manganate The solid density is 2.4g/cm ³ , the particle size (D50) is 10 μm, the length and width of the flake graphite raw material are 150 μm, and the thickness is 12 μm, which specifically includes the following steps:

Step 1. Add 3.5wt% graphite flakes to 96.5wt% water-soluble acrylic resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roller differential speed grinder, and after 15 cycles of peeling, collect the mixture B from the discharge roller; The gap between N2 and N1 is 200 μm, and the gap between N2 and N1 is 80 μm; the gap between N3 and N2 is 40 μm, and the gap between N2 and N1 is 20 μm when the cyclic stripping is 5-8 times; the cyclic stripping is 9-12 At the second time, the gap between N3 and N2 is 10 μm, and the gap between N2 and N1 is 5 μm; for the 13th-15th cycle stripping, the gap between N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm ;

Step 3. Remove part of the water-soluble acrylic resin by dissolving in deionized water/tap water/distilled water, add water with a volume fraction of 100vol% to the mixture B obtained from the stripping, and stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove Miscellaneous liquid, repeat this step to control the number of alcohol washes to 3 times, and finally centrifuge to obtain substance C;

Step 4, use the miscellaneous liquid removed after the centrifugation of the last water cleaning resin in step 3 as a solvent, measure wherein the miscellaneous liquid equal to the volume of the substance C obtained by centrifugation, dissolve 0.1wt% of the aluminum nitrate raw material wherein, and then mix with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain mixture E, the amount of mixture D added accounts for 5wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle the peeling and mixing twice. Set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm. Collect mixture F from the discharge roller;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -40°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 600 °C at a heating rate of 2 °C min ^-1 , keep it warm for 5 hours, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material.

Weigh 0.07g of graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) g, after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly spread on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble in an argon atmosphere glove box , with metal lithium sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio of 1:1) as the electrolyte, and Celegard2400 as the separator, assembled into a CR2032 button lithium battery. At 25°C, under the condition of 1C, the voltage window is 2.0-4.3V. The battery assembled with graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery positive electrode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles at 1C is 178.3mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 88%, the initial ohmic internal resistance is 3.91Ω, and the internal ohmic resistance after 200 cycles at 1C Resistance 8.12Ω.

Comparative Example 1, compared with Example 1, the difference between this preparation method is that there is no three-roll mill peeling, no phenolic resin, and no aluminum nitrate. As a result, there is no carbon nanotube and amorphous carbon coating, Instead, nickel-cobalt-lithium-manganese-oxide raw material is directly used for battery assembly, which is a commercially available product with a tap density of 2.0 g/cm ³ and a particle size (D50) of 4 μm.

Weigh 0.07g of nickel-cobalt lithium manganate raw material, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) in this comparative example, add 0.4mL of NMP to disperse and mix after fully grinding, and then evenly coat After vacuum drying at 120°C for 10 h on aluminum foil, cut into discs with a diameter of 12 mm, and assemble them in a glove box with argon atmosphere, with a metal lithium sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC : DEC volume ratio is 1:1) as the electrolyte, with Celegard2400 as the diaphragm, assembled into a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery material assembled with the positive electrode material of nickel cobalt lithium manganese oxide raw material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles under the condition of 1C is 101.5 mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 75%, the initial ohmic internal resistance is 18.89Ω, and the ohmic internal resistance after 200 cycles at 1C is 40.58Ω.

Comparative example 2, the preparation method is compared with Example 1, the difference is that there is no flake graphite for three-roll mill peeling, but there is phenolic resin, no aluminum nitrate, there is amorphous carbon coating after heat treatment, but there is no carbon Nanotubes, let alone graphene-like nanosheets, only form amorphous carbon-coated nickel-cobalt lithium manganese oxide. Its concrete preparation steps are as follows:

The preparation method of the amorphous carbon-coated nickel-cobalt lithium manganate battery cathode material of this comparative example adopts nickel-cobalt lithium manganese oxide as raw material, and phenolic resin is the coated carbon raw material, and the described nickel-cobalt lithium manganate raw material is commercially available. The product for sale has a tap density of 2.0g/cm ³ and a particle size (D50) of 4μm; the specific steps are as follows:

Step 1, adding the phenolic resin to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain a mixture A, the amount of the phenolic resin added accounts for 6wt% of the mass fraction of the mixture A;

Step 2. Pass the mixture A through a three-roller differential speed grinder for further thorough mixing, recycle and mix 3 times, set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm. Roll collection to obtain mixture B;

Step 3. Place the mixture B in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture C;

Step 4, heat-treat the freeze-dried mixture C in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Shaped carbon-coated nickel-cobalt-lithium manganese oxide battery cathode material.

Weigh 0.07g of amorphous carbon-coated nickel-cobalt lithium manganese oxide battery positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and add 0.4mL of NMP was dispersed and mixed, then uniformly coated on aluminum foil, after vacuum drying at 120 °C for 10 h, cut into discs with a diameter of 12 mm, assembled in a glove box with an argon atmosphere, and a lithium metal sheet as a counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with amorphous carbon-coated nickel-cobalt lithium manganese oxide cathode material is subjected to constant current charge and discharge tests. The discharge ratio after 200 cycles under 1C conditions The capacity is 130.5mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 82%, the initial ohmic internal resistance is 15.07Ω, and the ohmic internal resistance after 200 cycles at 1C is 33.80Ω.

Comparative Example 3, compared with Example 1, the difference between this preparation method is that there is flake graphite for three-roll mill peeling, but finally all the phenolic resin is washed away, there is no aluminum nitrate, and no heat treatment is required, so there is no carbon Nanotubes and amorphous carbon coating, so only graphene-like nanosheets composite nickel-cobalt-lithium manganese oxide are formed. Its concrete preparation steps are as follows:

The preparation method of the graphene-like composite nickel-cobalt lithium manganese oxide battery cathode material of this comparative example adopts nickel-cobalt lithium manganese oxide as raw material, flake graphite is auxiliary material, and phenolic resin is grinding medium, and described nickel-cobalt lithium manganese oxide raw material , is a commercially available product with a tap density of 2.0g/cm ³ and a particle size (D50) of 4 μm; the length and width of the flake graphite raw material are 150 μm and a thickness of 12 μm; the specific steps are as follows:

Step 1. Add 3.5wt% graphite flakes to 96.5wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15 minutes to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove the resin by alcohol dissolution. Add alcohol with a volume fraction of 100vol% to the stripped mixture B. After stirring and ultrasonic assistance for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid. Repeat this step to control the number of alcohol cleanings 15 times, finally centrifuged to obtain substance C;

Step 4, adding substance C to lithium nickel cobalt manganese oxide and stirring and mixing for 5 minutes to obtain mixture D, the amount of substance C added accounts for 6wt% of the mass fraction of mixture D;

Step 5. Pass the mixture D through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. The gap between N3 and N2 is set to 4 μm, and the gap between N2 and N1 is 2 μm. From The discharge roller is collected to obtain the mixture E;

Step 6. Put the mixture E in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture F;

Step 7, heat-treat the freeze-dried mixture F in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Graphene composite nickel cobalt lithium manganese oxide battery cathode material.

Weigh 0.07g of the graphene-like composite nickel-cobalt lithium manganese oxide positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and add 0.4mL of NMP to disperse after fully grinding Mixed, then uniformly coated on aluminum foil, after vacuum drying at 120 ° C for 10 h, cut into discs with a diameter of 12 mm, assembled in a glove box in an argon atmosphere, with metal lithium sheets as counter electrodes, 1 M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the diaphragm to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery assembled with the graphene-like composite nickel-cobalt lithium manganese oxide cathode material is subjected to constant current charge and discharge tests, and the discharge specific capacity after 200 cycles under the condition of 1C It is 148.0mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 85%, the initial ohmic internal resistance is 11.35Ω, and the ohmic internal resistance after 200 cycles at 1C is 24.48Ω.

Comparative example 4, the preparation method is compared with Example 1, the difference is that there is no flake graphite for three-roll mill peeling, there is phenolic resin, there is aluminum nitrate, and heat treatment is required, so there are carbon nanotubes and amorphous carbon coating , thus forming carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide. Its concrete preparation steps are as follows:

The preparation method of the carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material of this comparative example adopts nickel-cobalt lithium manganese oxide as raw material, phenolic resin as grinding medium and coated carbon raw material, and aluminum nitrate as The catalyst and dopant are commercially available products with a tap density of 2.0g/cm ³ and a particle size (D50) of 4 μm; the specific steps are as follows:

Step 1. Add phenolic resin to nickel-cobalt lithium manganese oxide and mix for 8 minutes to obtain mixture A. The amount of phenolic resin added accounts for 6wt% of the mass fraction of mixture A, and then 0.05wt% aluminum nitrate raw material is dissolved in alcohol and added into mixture A to obtain mixture B.

Step 2. Pass the mixture B through a three-roller differential speed grinder for further thorough mixing, recirculate and mix 3 times, set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm. Roll collection to obtain mixture C;

Step 3. Place the mixture C in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture D;

Step 4. Place the freeze-dried mixture D in a tube furnace for heat treatment under argon, from room temperature to 750 °C at a heating rate of 5 °C·min ⁻¹ , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain carbon Nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide.

Weigh 0.07g of the carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and fully grind Finally, 0.4 mL of NMP was added to disperse and mix, and then uniformly coated on aluminum foil, after vacuum drying at 120 °C for 10 h, cut into discs with a diameter of 12 mm, and assemble them in a glove box with an argon atmosphere, and replace them with lithium metal The sheet is used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio is 1:1) is used as the electrolyte, and Celegard2400 is used as the diaphragm to assemble a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery assembled with carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganate cathode material is subjected to constant current charge and discharge tests. Under the condition of 1C, 200 The specific discharge capacity after one cycle is 168.4mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 88%, the initial ohmic internal resistance is 6.19Ω, and the internal ohmic resistance after 200 cycles at 1C is 11.86Ω.

Comparative example 5, this preparation method is compared with embodiment 1, and the difference is that the drying mode adopted is drying rather than freeze-drying, is the graphene-like carbon nanotube amorphous carbon coated aluminum doped that the drying mode forms Lithium nickel cobalt manganate. Its concrete preparation steps are as follows:

The preparation method of the graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material in this comparative example uses nickel-cobalt lithium manganese oxide as raw material, flake graphite as auxiliary material, and phenolic resin as grinding medium and coated carbon raw materials, aluminum nitrate as a catalyst and a dopant, the nickel cobalt lithium manganese oxide raw material is a commercially available product, the tap density is 2.0g/cm ³ , and the particle size (D50) is 4 μm; The length and width of the described flake graphite raw material are 150 μm, and the thickness is 12 μm; the specific steps are as follows:

Step 1. Add 3.5wt% graphite flakes to 96.5wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15 minutes to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 4 times, and finally the substance C is obtained by centrifugation;

Step 4, the miscellaneous liquid removed after the centrifugation of the last alcohol cleaning resin in step 3 is used as a solvent, and the miscellaneous liquid equal to the volume of the material C obtained by centrifugation is measured, and the aluminum nitrate raw material of 0.05wt% is dissolved therein, and then mixed with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm, from The discharge roller collects and obtains the mixture F;

Step 7. Put the mixture F in an oven and dry it at 50°C to obtain the mixture G;

Step 8, heat-treat the dried mixture G in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide on graphene carbon nanotubes.

Weigh 0.07g of the graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), and 0.015g of PVDF (HSV900, binder) , after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly coat on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble them in an argon atmosphere glove box, A lithium metal sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery assembled with graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide cathode material is subjected to constant current charge and discharge tests. At 1C The discharge specific capacity after 200 cycles under the same conditions is 182.8mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 90%, the initial ohmic internal resistance is 3.46Ω, and the ohmic internal resistance after 200 cycles at 1C 6.82Ω.

Comparative Example 6, compared with Example 1, the preparation method differs in the number of times of cleaning the phenolic resin. Example 1 is cleaned 4 times, and this comparative example is cleaned 1 time. The purpose is to improve the thickness of the carbon coating during subsequent heat treatment. different. Its concrete preparation steps are as follows:

The preparation method of the graphene-like nanosheet carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery positive electrode material of this comparative example adopts nickel-cobalt lithium manganate as raw material, flake graphite is auxiliary material, and phenolic resin is Grinding media and coated carbon raw materials, aluminum nitrate as a catalyst and a dopant, the nickel cobalt lithium manganese oxide raw material is a commercially available product, the tap density is 2.0g/cm ³ , and the particle size (D50) is 4 μm ; The length and width of the flake graphite raw material is 150 μm, and the thickness is 12 μm, and the specific steps are as follows:

Step 1. Add 3.5wt% graphite flakes to 96.5wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15 minutes to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 1, and finally centrifuged to obtain substance C;

Step 4, the miscellaneous liquid removed after the centrifugation of the last alcohol cleaning resin in step 3 is used as a solvent, and the miscellaneous liquid equal to the volume of the material C obtained by centrifugation is measured, and the aluminum nitrate raw material of 0.05wt% is dissolved therein, and then mixed with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to nickel-cobalt lithium manganate and stirring and mixing for 5 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roller differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 4 μm, and the gap between N2 and N1 to 2 μm, from The discharge roller collects and obtains the mixture F;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 750°C at a rate of 5°C·min ^-1 , keep it warm for 4h, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide battery cathode material.

Weigh 0.07g of the graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), and 0.015g of PVDF (HSV900, binder) , after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly coat on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble them in an argon atmosphere glove box, A lithium metal sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery assembled with graphene-like carbon nanotube amorphous carbon-coated aluminum-doped nickel-cobalt lithium manganese oxide cathode material is subjected to constant current charge and discharge tests. At 1C The discharge specific capacity after 200 cycles under the same conditions is 155.2mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 86%, the initial ohmic internal resistance is 7.78Ω, and the ohmic internal resistance after 200 cycles at 1C 13.75Ω.

As shown in Table 1 below, it is the performance comparison of Examples 1-3 and Comparative Examples 1-6.

The performance contrast of table 1 embodiment 1-3 and comparative example 1-6

Examples 4-6 use lithium iron phosphate as a raw material, nickel nitrate as a catalyst and a dopant, and Comparative Examples 7-12 are comparative examples of Examples 4-6.

Embodiment 4, using lithium iron phosphate as raw material, flake graphite as auxiliary material, phenolic resin as grinding medium and coated carbon raw material, nickel nitrate as catalyst and dopant, the bulk density of described lithium iron phosphate is 0.8g/ cm ³ , the median diameter is 2 μm, the length and width of the flake graphite raw material is 150 μm, and the thickness is 12 μm, which specifically includes the following steps:

Step 1. Add 4wt% flake graphite to 96wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 4 times, and finally the substance C is obtained by centrifugation;

Step 4, with the miscellaneous liquid removed after the centrifugation of the last ethanol cleaning resin in step 3 as solvent, measure wherein and the miscellaneous liquid of the equal volume of material C obtained by centrifugation, wherein the nickel nitrate raw material of 0.05wt% is dissolved wherein, and then with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to lithium iron phosphate and stirring and mixing for 8 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roll differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm , is collected from the discharge roller to obtain the mixture F;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 750°C at a rate of 5°C·min ^-1 , keep it warm for 4h, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material.

Weigh 0.07g of graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) , after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly coat on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble them in an argon atmosphere glove box, A lithium metal sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button lithium battery. At 25°C, under 1C conditions, the voltage window is 2.0-4.3V. The battery assembled with graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. At 1C The discharge specific capacity after 200 cycles under the same conditions is 154.4mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 93%, the initial ohmic internal resistance is 4.25Ω, and the ohmic internal resistance after 200 cycles at 1C 6.60Ω.

Example 5, using lithium iron phosphate as a raw material, expanded graphite as an auxiliary material, epoxy resin as a grinding medium and coated carbon raw material, nickel nitrate as a catalyst and a dopant, and the bulk density of the lithium iron phosphate is 0.6g /cm ³ , the median diameter is 4 μm, the length and width of the flake graphite raw material are 1000 μm, and the thickness is 100 μm, which specifically includes the following steps:

Step 1, adding 2wt% of expanded graphite to 98wt% epoxy resin, and mixing it in a water bath at 40°C for 10 minutes by stirring to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roller differential speed grinder, and after 15 cycles of peeling, collect the mixture B from the discharge roller; The gap between N2 and N1 is 200 μm, and the gap between N2 and N1 is 80 μm; the gap between N3 and N2 is 40 μm, and the gap between N2 and N1 is 20 μm when the cyclic stripping is 5-8 times; the cyclic stripping is 9-12 At the second time, the gap between N3 and N2 is 10 μm, and the gap between N2 and N1 is 5 μm; for the 13th-15th cycle stripping, the gap between N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm ;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 3 times, and finally the substance C is obtained by centrifugation;

Step 4, with the miscellaneous liquid removed after the centrifugation of the last ethanol cleaning resin in step 3 as solvent, measure wherein and the miscellaneous liquid of the equal volume of the material C obtained by centrifugation, dissolve wherein the nickel nitrate raw material of 0.2wt%, and then mix with Substance C was mixed and stirred for 10 minutes to obtain mixture D;

Step 5. Add mixture D to lithium iron phosphate and stir and mix for 5 minutes to obtain mixture E. The amount of mixture D added accounts for 8 wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roll differential speed grinder for further sufficient peeling and mixing, and recirculate the peeling and mixing twice, set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm, the mixture F was collected from the discharge roller;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -40°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 650 °C at a heating rate of 3 °C min ^-1 , keep it warm for 5 hours, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material.

Weigh 0.07g of graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) , after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly coat on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble them in an argon atmosphere glove box, A lithium metal sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button lithium battery. At 25°C, under 1C conditions, the voltage window is 2.0-4.3V. The battery assembled with graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. At 1C The discharge specific capacity after 200 cycles under the same conditions is 138.2mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 88%, the initial ohmic internal resistance is 6.63Ω, and the ohmic internal resistance after 200 cycles at 1C 11.24Ω.

Example 6, using lithium iron phosphate as a raw material, flake graphite as an auxiliary material, polyethylene resin as a grinding medium and coated carbon raw material, nickel nitrate as a catalyst and a dopant, and the bulk density of the lithium iron phosphate is 0.5g /cm ³ , the median diameter is 4.5 μm, the length and width of the flake graphite raw material is 200 μm, and the thickness is 20 μm, which specifically includes the following steps:

Step 1. Add 5wt% graphite flakes to 95wt% polyethylene resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, the mixture A obtained in step 1 is peeled off by a three-roll differential speed grinder, and after 15 cycles of peeling, the mixture B is collected from the discharge roller; the three-roll rate of the three-roll differential speed grinder is The rotation speed ratio is feed roller N3: center roller N2: discharge roller N1 is 1:3:9, and the gap between N3 and N2 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm when the cyclic stripping is 5-8 times; the gap between N3 and N2 is 6 μm when the cyclic stripping is 9-12 times, The gap between N2 and N1 is 3 μm; for the 13th-15th cycles of stripping, the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 0.5 μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 50vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 6 times, and finally the substance C is obtained by centrifugation;

Step 4, with the miscellaneous liquid removed after the centrifugation of the last ethanol cleaning resin in step 3 as solvent, measure wherein and the miscellaneous liquid of the equal volume of material C obtained by centrifugation, wherein the nickel nitrate raw material of 0.05wt% is dissolved wherein, and then with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to lithium iron phosphate and stirring and mixing for 9 minutes to obtain mixture E, the amount of mixture D added accounts for 10wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roll differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm , is collected from the discharge roller to obtain the mixture F;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -40°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 700 °C at a heating rate of 8 °C min ^-1 , keep it warm for 2 hours, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material.

Weigh 0.07g of graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material prepared in this example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder) g, after fully grinding, add 0.4mL of NMP to disperse and mix, then evenly spread on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assemble in an argon atmosphere glove box , with metal lithium sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio of 1:1) as the electrolyte, and Celegard2400 as the separator, assembled into a CR2032 button lithium battery. At 25°C, under 1C conditions, the voltage window is 2.0-4.3V. The battery assembled with graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. At 1C The discharge specific capacity after 200 cycles under the same conditions is 132.7mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 85%, the initial ohmic internal resistance is 8.72Ω, and the ohmic internal resistance after 200 cycles at 1C 15.14Ω.

Comparative Example 7, compared with Example 1, the difference between this preparation method is that there is no three-roll mill peeling, no phenolic resin, and no nickel nitrate, and as a result, there is no carbon nanotube and amorphous carbon coating, Instead, the lithium iron phosphate raw material is directly used for battery assembly, the bulk density of the lithium iron phosphate raw material is 0.8g/cm ³ , and the median diameter is 2um.

Weigh 0.07g of lithium iron phosphate raw material, 0.015g of acetylene black (conductive agent), and 0.015g of PVDF (HSV900, binder) in this comparative example, add 0.4mL of NMP to disperse and mix after fully grinding, and then evenly coat on aluminum foil After vacuum drying at 120°C for 10 h, cut into discs with a diameter of 12 mm, and assemble them in an argon atmosphere glove box, with a lithium metal sheet as the counter electrode, 1M LiPF ₆ solution (solvent EC: DEC The volume ratio is 1:1) as the electrolyte, and Celegard2400 is used as the diaphragm to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under the condition of 1C. The battery material assembled with the lithium iron phosphate raw material positive electrode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles under the condition of 1C is 82mAh g ^{- 1.} The capacity retention rate after 200 cycles at 1C is 70%, the initial ohmic internal resistance is 20.89Ω, and the ohmic internal resistance after 200 cycles at 1C is 50.78Ω.

Comparative Example 8, the preparation method is compared with Example 1, the difference is that there is no flake graphite for three-roll mill peeling, but there is phenolic resin, no nickel nitrate, there is amorphous carbon coating after heat treatment, but there is no carbon Nanotubes, let alone graphene-like nanosheets, only form amorphous carbon-coated lithium iron phosphate. Its concrete preparation steps are as follows:

The preparation method of the amorphous carbon-coated lithium iron phosphate battery positive electrode material of this comparative example adopts lithium iron phosphate as a raw material, and phenolic resin is a coated carbon raw material. The bulk density of the described lithium iron phosphate raw material is 0.8g/cm ³ , the median diameter is 2um; the specific steps are as follows:

Step 1, adding phenolic resin to lithium iron phosphate and stirring and mixing for 8 minutes to obtain mixture A, the amount of phenolic resin added accounts for 6wt% of the mass fraction of mixture A;

Step 2, the mixture A is further fully mixed through a three-roller differential speed grinder, and recirculated and mixed 3 times, and the gap between N3 and N2 is set to 1.5 μm, and the gap between N2 and N1 is 0.5 μm, from The discharge roller is collected to obtain the mixture B;

Step 3. Place the mixture B in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture C;

Step 4, heat-treat the freeze-dried mixture C in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Shaped carbon coated lithium iron phosphate battery cathode material.

Weigh 0.07g of amorphous carbon-coated lithium iron phosphate battery cathode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and add 0.4mL of NMP to disperse after fully grinding Mixed, then uniformly coated on aluminum foil, after vacuum drying at 120 ° C for 10 h, cut into discs with a diameter of 12 mm, assembled in a glove box in an argon atmosphere, with metal lithium sheets as counter electrodes, 1 M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the diaphragm to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with amorphous carbon-coated lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles under 1C conditions is 98.2mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 78%, the initial ohmic internal resistance is 17.42Ω, and the internal ohmic resistance after 200 cycles at 1C is 38.56Ω.

Comparative Example 9, compared with Example 1, the difference between this preparation method is that there is flake graphite for three-roll mill peeling, but finally all the phenolic resin is washed away, there is no nickel nitrate, and no heat treatment is required, so there is no carbon Nanotubes and amorphous carbon coating, so only graphene-like nanosheet composite lithium iron phosphate is formed. Its concrete preparation steps are as follows:

The preparation method of the graphene-like composite lithium iron phosphate battery cathode material of this comparative example adopts lithium iron phosphate as a raw material, flake graphite is an auxiliary material, and phenolic resin is a grinding medium, and the bulk density of the described lithium iron phosphate raw material is 0.8 g/cm ³ , the median diameter is 2um; the length and width of the flake graphite raw material is 150μm, and the thickness is 12μm; the specific steps are as follows:

Step 1. Add 4wt% flake graphite to 96wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove the resin by alcohol dissolution. Add alcohol with a volume fraction of 100vol% to the stripped mixture B. After stirring and ultrasonic assistance for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid. Repeat this step to control the number of alcohol cleanings 15 times, finally centrifuged to obtain substance C;

Step 4. Add substance C to lithium iron phosphate and stir and mix for 8 minutes to obtain mixture D. The amount of substance C added accounts for 6wt% of the mass fraction of mixture D;

Step 5. Pass the mixture D through a three-roll differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm , collect mixture E from the discharge roller;

Step 6. Put the mixture E in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture F;

Step 7, heat-treat the freeze-dried mixture F in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Graphene composite lithium iron phosphate battery cathode material.

Weigh 0.07g of the graphene-like composite lithium iron phosphate cathode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and add 0.4mL of NMP to disperse and mix after fully grinding. Then evenly coated on aluminum foil, after vacuum drying at 120 °C for 10 h, cut into discs with a diameter of 12 mm, and assembled in an argon atmosphere glove box, with a metal lithium sheet as the counter electrode, 1M LiPF ₆ The solution (solvent EC:DEC volume ratio is 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with graphene-like composite lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. The discharge specific capacity after 200 cycles under 1C conditions is 112.5 mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 82%, the initial internal resistance ohm is 15.33Ω, and the ohmic internal resistance after 200 cycles at 1C is 30.62Ω.

Comparative Example 10, compared with Example 1, the difference is that there is no flake graphite for three-roll mill peeling, there is phenolic resin, there is nickel nitrate, and heat treatment is required, so there are carbon nanotubes and amorphous carbon coating , thus forming carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate. Its concrete preparation steps are as follows:

The preparation method of the carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery positive electrode material of this comparative example uses lithium iron phosphate as raw material, phenolic resin as grinding medium and coated carbon raw material, nickel nitrate as catalyst and doped agent, lithium iron phosphate raw material, the bulk density is 0.8g/cm3, the median diameter is 2um; the specific steps are as follows:

Step 1. Add phenolic resin to lithium iron phosphate and stir and mix for 8 minutes to obtain mixture A. The amount of phenolic resin added accounts for 6wt% of the mass fraction of mixture A, and then 0.05wt% nickel nitrate raw material is dissolved in alcohol and added to the mixture In A, mixture B is obtained.

Step 2, the mixture B is further fully mixed through a three-roller differential speed grinder, and recirculated and mixed 3 times, the gap between N3 and N2 is set to 1.5 μm, and the gap between N2 and N1 is 0.5 μm, from The discharge roller is collected to obtain the mixture C;

Step 3. Place the mixture C in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture D;

Step 4. Place the freeze-dried mixture D in a tube furnace for heat treatment under argon, from room temperature to 750 °C at a heating rate of 5 °C·min ⁻¹ , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain carbon Nickel-doped lithium iron phosphate coated with nanotube amorphous carbon.

Weigh 0.07g of the carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate positive electrode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binder), and add 0.4mL of NMP was dispersed and mixed, then uniformly coated on aluminum foil, after vacuum drying at 120°C for 10h, cut into discs with a diameter of 12mm, and assembled in a glove box with an argon atmosphere. As the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio is 1:1) was used as the electrolyte, and Celegard2400 was used as the diaphragm to assemble a CR2032 button lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests, and 200 cycles under 1C conditions. The final discharge specific capacity was 118.7mAh g ^-1 , the capacity retention rate after 200 cycles at 1C was 83%, the initial ohmic internal resistance was 12.57Ω, and the ohmic internal resistance after 200 cycles at 1C was 22.15Ω.

Comparative example 11, the preparation method is compared with Example 1, the difference is that the drying method adopted is drying instead of freeze-drying, and it is the graphene-like carbon nanotube amorphous carbon coated nickel doped that is formed by the drying method Lithium Iron Phosphate. Its concrete preparation steps are as follows:

The preparation method of the graphene-like carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material in this comparative example uses lithium iron phosphate as a raw material, graphite flakes as an auxiliary material, and phenolic resin as a grinding medium and coated carbon Raw material, nickel nitrate as catalyst and dopant, lithium iron phosphate raw material, bulk density is 0.8g/cm ³ , median diameter is 2um; the length and width of the flake graphite raw material is 150μm, and the thickness is 12μm; the specific steps are as follows :

Step 1. Add 4wt% flake graphite to 96wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 3 times, and finally the substance C is obtained by centrifugation;

Step 4, with the miscellaneous liquid removed after the centrifugation of the last ethanol cleaning resin in step 3 as solvent, measure wherein and the miscellaneous liquid of the equal volume of material C obtained by centrifugation, wherein the nickel nitrate raw material of 0.05wt% is dissolved wherein, and then with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to lithium iron phosphate and stirring and mixing for 8 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roll differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm , is collected from the discharge roller to obtain the mixture F;

Step 7. Put the mixture F in an oven and dry it at 50°C to obtain the mixture G;

Step 8, heat-treat the dried mixture G in a tube furnace under argon, from room temperature to 750 °C at a heating rate of 5 °C min ^-1 , keep it warm for 4 hours, and then naturally cool down to room temperature to obtain Amorphous carbon-coated nickel-doped lithium iron phosphate on graphene carbon nanotubes.

Weigh 0.07g of graphene-like carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binding agent), fully After grinding, 0.4 mL of NMP was added to disperse and mix, and then evenly coated on aluminum foil. After vacuum drying at 120 °C for 10 h, it was cut into discs with a diameter of 12 mm, and assembled in a glove box with an argon atmosphere. A lithium sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with graphene-like carbon nanotubes amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. Under 1C conditions The discharge specific capacity after 200 cycles is 141.0mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 86%, the initial ohmic internal resistance is 6.16Ω, and the ohmic internal resistance after 200 cycles at 1C is 10.28Ω .

Comparative Example 12, compared with Example 1, the preparation method differs in the number of times of cleaning the phenolic resin. Example 1 is cleaned 4 times, and this comparative example is cleaned 1 time. The purpose is to improve the carbon coating thickness during subsequent heat treatment. different. Its concrete preparation steps are as follows:

The preparation method of the graphene-like nanosheet carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material of this comparative example adopts lithium iron phosphate as raw material, flake graphite as auxiliary material, phenolic resin as grinding medium and coating Carbon-coated raw material, nickel nitrate as catalyst and dopant, lithium iron phosphate raw material, bulk density is 0.8g/cm ³ , median diameter is 2um; the length and width of the flake graphite raw material is 150μm, and the thickness is 12μm; Proceed as follows:

Step 1. Add 4wt% flake graphite to 96wt% phenolic resin, and stir and mix it in a water bath at 50°C for 15min to obtain mixture A;

Step 2, then peel the mixture A obtained in step 1 through a three-roll differential speed grinder, and after 16 cycles of peeling, collect the mixture B from the discharge roll; The gap between N2 and N1 is 100 μm, and the gap between N2 and N1 is 50 μm; the gap between N3 and N2 is 25 μm, and the gap between N2 and N1 is 12 μm during the 5th-8th cycle stripping; The gap between N3 and N2 is 6 μm, the gap between N2 and N1 is 3 μm; the gap between N3 and N2 is 1.5 μm, and the gap between N2 and N1 is 13-16 times. 0.5μm;

Step 3. Remove part of the resin by alcohol dissolution, add alcohol with a volume fraction of 100vol% to the stripped mixture B, stir and ultrasonically assist for 10 minutes, put it into a centrifuge tube for centrifugation and remove miscellaneous liquid, repeat this step to control alcohol cleaning The number of times is 1, and finally centrifuged to obtain substance C;

Step 4, with the miscellaneous liquid removed after the centrifugation of the last ethanol cleaning resin in step 3 as solvent, measure wherein and the miscellaneous liquid of the equal volume of material C obtained by centrifugation, wherein the nickel nitrate raw material of 0.05wt% is dissolved wherein, and then with Substance C was mixed and stirred for 5 minutes to obtain mixture D;

Step 5, adding mixture D to lithium iron phosphate and stirring and mixing for 8 minutes to obtain mixture E, the amount of mixture D added accounts for 6wt% of the mass fraction of mixture E;

Step 6. Pass the mixture E through a three-roll differential speed grinder for further sufficient peeling and mixing, and recycle peeling for 3 times. Set the gap between N3 and N2 to 1.5 μm, and the gap between N2 and N1 to 0.5 μm , is collected from the discharge roller to obtain the mixture F;

Step 7. Put the mixture F in a freeze dryer, and freeze-dry it in a vacuum at -45°C to obtain a mixture G;

Step 8, heat-treat the freeze-dried mixture G in a tube furnace under argon, from room temperature to 750°C at a rate of 5°C·min ^-1 , keep it warm for 4h, and then naturally cool down to room temperature to obtain Graphene carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate battery cathode material.

Weigh 0.07g of graphene-like carbon nanotube amorphous carbon-coated nickel-doped lithium iron phosphate cathode material prepared in this comparative example, 0.015g of acetylene black (conductive agent), 0.015g of PVDF (HSV900, binding agent), fully After grinding, 0.4 mL of NMP was added to disperse and mix, and then evenly coated on aluminum foil. After vacuum drying at 120 °C for 10 h, it was cut into discs with a diameter of 12 mm, and assembled in a glove box with an argon atmosphere. A lithium sheet was used as the counter electrode, 1M LiPF ₆ solution (solvent EC:DEC volume ratio 1:1) was used as the electrolyte, and Celegard2400 was used as the separator to assemble a CR2032 button-type lithium battery. At 25°C, the voltage window is 2.0-4.3V under 1C conditions. The battery assembled with graphene-like carbon nanotubes amorphous carbon-coated nickel-doped lithium iron phosphate cathode material is subjected to constant current charge and discharge tests. Under 1C conditions The discharge specific capacity after 200 cycles is 125.2mAh g ^-1 , the capacity retention rate after 200 cycles at 1C is 84%, the initial ohmic internal resistance is 10.14Ω, and the ohmic internal resistance after 200 cycles at 1C is 19.68Ω .

As shown in Table 2 below, it is the performance comparison of Examples 4-6 and Comparative Examples 7-12.

The performance contrast of table 2 embodiment 4-6 and comparative example 7-12

In summary, the present invention adopts the three-roll mill grinding and stripping technology to overcome the interlayer van der Waals force through the shear force generated by the three-roll differential speed, the high-viscosity resin and the phosphorus flake graphite/expanded graphite. A large number of graphene-like nanosheets can be prepared by peeling off layered materials with a thickness of micron scale, and their crystal interlayer spacing becomes larger after peeling off. The graphene-like nanosheets prepared by this method are better than graphite prepared by traditional technology Alkenes are produced more efficiently and at lower cost.

After the graphite is peeled off by three-roll differential speed grinding, it forms graphene-like nanosheets and continues to mix with nickel-cobalt lithium manganese oxide or lithium iron phosphate on the equipment. After 2-3 times of recycling and peeling, the gap between each roller shaft Adjusting it to 1-5 μm can not only grind and disperse lithium nickel cobalt manganese oxide and forcibly refine it, but also further strengthen the contact and coating of graphene-like nanosheets with lithium nickel cobalt manganese oxide or lithium iron phosphate. Due to the certain viscosity of the resin, the traditionally used drying technology tends to make the mixture F form a paste-like agglomerate. The present invention adopts the freeze-drying technology to process, and can obtain a powder with a very good dispersion effect.

The present invention adopts aluminum nitrate or nickel nitrate as catalyst and dopant, and the aluminum nitrate or nickel nitrate solution is mixed evenly with the resin. During the subsequent heat treatment process at 500-850°C, the aluminum nitrate catalyzes the resin to generate carbon nanotubes in situ. Adding carbon nanotubes has better dispersion and saves costs. Its special tubular structure and intertwined network structure can speed up the transmission rate of Li+ ions. At the same time, aluminum nitrate will be doped to nickel by aluminum ions in the subsequent heat treatment process. In lithium cobalt manganese oxide or lithium iron phosphate, the degree of lithium-nickel mixing caused by nickel ions occupying lithium sites can be reduced, and the electrochemical performance of the positive electrode material can be improved.

The invention prepares graphene-like nanosheets formed by three-roller grinding and peeling of graphite with a thickness of micron in resin, carbon nanotubes formed by heat-treating and catalyzing part of the resin, and amorphous carbon-coated aluminum-doped Al or Ni-doped, composite conductive agent (two-dimensional graphene-like nanosheet, one-dimensional carbon nanotube), and amorphous carbon coating are formed. Technology in one to prepare a low-cost, high-performance lithium-ion battery cathode material. The two-dimensional graphene-like nanosheets obtained by three-roll differential grinding and exfoliation not only have a larger crystal layer spacing, but also allow more foreign reactants to undergo intercalation reactions, and compared with pristine graphite, the specific surface area is greatly improved, which can Greatly improve its conductivity; the interpenetration of one-dimensional carbon nanotubes and zero-dimensional amorphous carbon coating nickel-cobalt lithium manganese oxide or lithium iron phosphate, the three-dimensional network structure of the three carbon forms is conducive to further improving its electronic conduction and ion transmission , which reduces its polarization and impedance during charge and discharge. At the same time, graphene-like nanosheets, carbon nanotubes, and amorphous carbon constitute a "protective barrier" to nickel-cobalt lithium manganese oxide or lithium iron phosphate, inhibiting the electrolyte from The side reaction of nickel-cobalt lithium manganate or lithium iron phosphate greatly increases the structural stability and electrical conductivity of nickel-cobalt lithium manganate or lithium iron phosphate, and greatly improves the electrochemical performance of nickel-cobalt lithium manganate or lithium iron phosphate. Performance to meet the needs of new energy vehicles, electric vehicles, large-scale energy storage, starter power and other fields.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. A preparation method of a multi-dimensional and multi-scale carbon-coated lithium ion battery anode material is characterized by comprising the following steps: the method mainly comprises the following steps:

step 1, adding 1-5wt% of graphite auxiliary material into 95-99wt% of resin, and stirring and mixing the graphite auxiliary material in a water bath at 40-70 ℃ for 5-30min to obtain a mixture A;

step 2, peeling the mixture A obtained in the step 1 through a three-roller differential grinding machine, circularly peeling for multiple times, and collecting a mixture B from a discharging roller;

step 3, removing part of resin through alcohol dissolution, adding 50-200vol% alcohol into the mixture B obtained through stripping, stirring and ultrasonically assisting for 10min, placing the mixture into a centrifugal tube for centrifugation, removing impurity liquid, repeating the step 3, continuously cleaning the mixture with alcohol, and finally centrifuging to obtain a substance C;

step 4, taking the impurity solution removed after the last alcohol cleaning resin in the step 3 is centrifuged as a solvent, measuring the impurity solution with the volume equal to that of the substance C obtained by centrifugation, dissolving 0.01-0.5wt% of nitric compound raw material in the impurity solution, and mixing and stirring the nitric compound raw material and the substance C for 1-10min to obtain a mixture D;

step 5, adding the mixture D into a lithium compound, stirring and mixing for 5-10min to obtain a mixture E, wherein the addition amount of the mixture D accounts for 3-12wt% of the mass fraction of the mixture E;

step 6, further fully stripping and mixing the mixture E through a three-roller differential grinding machine, and collecting the mixture F from a discharge roller after repeated circulation stripping;

step 7, placing the mixture F in a freeze dryer, and carrying out freeze drying in a vacuum environment at the temperature of minus 50-minus 30 ℃ to obtain a mixture G;

step 8, placing the mixture G after freeze drying in a tube furnace for heat treatment under argon, and heating the mixture G at the temperature of 2-10 ℃ for min from room temperature ^-1 The temperature is raised to 500-850 ℃, the temperature is preserved for 1-5h, and then the temperature is naturally lowered to the room temperature, so as to obtain the multidimensional multi-scale carbon-coated lithium ion battery anode material.

2. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery positive electrode material according to claim 1, characterized by comprising the following steps: in step 2, the three-roller differential grinding machine comprises a discharge roller N1, a central roller N2 and a feed roller N3, wherein the rotation speed ratio of the feed roller N3 to the central roller N2 to the discharge roller N1 is 1:3: and 9, in the circulating stripping process, the gap between the central roller N2 and the feeding roller N3 is always larger than the gap between the discharging roller N1 and the central roller N2, and the circulating stripping frequency is 15-17 times.

3. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to claim 2, characterized by comprising the following steps: and when the circulation stripping is carried out for 1-4 times, the clearance between the central roller N2 and the feeding roller N3 and the clearance between the discharging roller N1 and the central roller N2 are both between 40 and 200 mu m.

4. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to claim 2, characterized by comprising the following steps: and when the circulation stripping is carried out for 5-8 times, the gap between the central roller N2 and the feeding roller N3 and the gap between the discharging roller N1 and the central roller N2 are both between 10 and 40 mu m.

5. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to claim 2, characterized by comprising the following steps: and when the circulation stripping is carried out for 9-12 times, the clearance between the central roller N2 and the feeding roller N3 and the clearance between the discharging roller N1 and the central roller N2 are both between 2.5 and 10 mu m.

6. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to claim 2, characterized by comprising the following steps: after 13 th time of the cyclic peeling, the gap between the center roll N2 and the feed roll N3 and the gap between the discharge roll N1 and the center roll N2 were each between 0.5 and 2.5 μm.

7. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to claim 1, characterized by comprising the following steps: in step 4, the raw material of the nitric compound is aluminum nitrate or nickel nitrate.

8. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery positive electrode material according to claim 1, characterized by comprising the following steps: in step 5, the lithium compound is lithium nickel cobalt manganese oxide or lithium iron phosphate.

9. The preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery positive electrode material according to claim 2, characterized by comprising the following steps: in the step 6, the number of times of the cyclic stripping is 2-3, and after the cyclic stripping is finished, the gap between the central roller N2 and the feeding roller N3 and the gap between the discharging roller N1 and the central roller N2 are both between 0.5 and 5 microns.

10. A multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material is characterized in that: the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material is prepared by the preparation method of the multi-dimensional and multi-scale carbon-coated lithium ion battery cathode material according to any one of claims 1 to 9.

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