An electrochemically active composite material, and a method of making and using the same

Abstract

The application provides an electrochemically active composite material and a preparation method and application thereof, and belongs to the technical field of lithium ion battery materials; the electrochemically active composite material is a porous spherical or spherical-like particle; the Dv50 of the electrochemically active composite material is 2.0-10.0 mu m, the specific surface area is 20-200 m 2 / g; the electrochemically active composite material comprises a catalyst and an organic lithium salt loaded on the surface of the catalyst; the catalyst is a heteroatom-doped carbon loaded metal catalyst, which comprises a carbon matrix, carbon nanotubes and nano metal particles. The composite material provided by the application has low decomposition voltage and high charging capacity, and can be used as a lithium supplement for lithium ion batteries; and the preparation method of the electrochemically active composite material is simple, which is beneficial to actual production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and particularly relates to an electrochemically active composite material, its preparation method, and its application. Background Technology

[0002] During the initial charging process of a lithium-ion battery, the formation of an SEI film on the negative electrode surface consumes active lithium, leading to capacity loss in the positive electrode material. Pre-lithiation technology provides additional active lithium to the lithium-ion battery system for SEI film formation on the negative electrode surface, thereby avoiding the consumption of Li in the positive electrode material. + This improves battery capacity and cycle performance.

[0003] Negative electrode pre-lithiation is currently the most commonly used method for battery pre-lithiation. Its principle involves using a potential difference to directly contact a pre-lithiating agent (such as inert lithium powder) with the negative electrode material, causing a chemical reaction and thus pre-intercalating lithium into the negative electrode. Lithium-ion batteries assembled from negative electrodes pre-lithiated using this method can significantly improve their initial coulombic efficiency. However, this method requires an additional pre-lithiation process during battery assembly, and the pre-lithiating agent has high reactivity, posing extremely high requirements for the humidity of the processing environment and potential safety hazards.

[0004] Cathode pre-lithiation involves directly adding lithium-containing compounds during the cathode homogenization process. This method is simple, effective, widely applicable, and compatible with battery manufacturing processes. Currently, commonly used cathode pre-lithiation additives such as Li₂NiO₂, Li₅FeO₄, Li₆CoO₄, and Li₆MnO₄ possess high theoretical specific capacities. However, their high sensitivity to environmental humidity hinders large-scale commercial application, and the presence of residual metal oxides after lithium addition reduces battery energy density. Compared to these inorganic cathode pre-lithiation additives, some organic lithium salts (such as Li₂C₂O₄, Li₂C₄O₄, Li₂C₃O₅, Li₂C₄O₆, and Li₂CO₃) exhibit good air stability and lower humidity requirements, making them more suitable for battery manufacturing processes. Furthermore, these small-molecule organic lithium salts decompose to produce gas during the first charge, which is discharged during battery formation without leaving any impurities, thus not reducing battery energy density. However, the extremely low electrochemical activity and high decomposition potential of these organic lithium salts significantly hinder their application in batteries. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an electrochemically active composite material with excellent electrochemical activity, low decomposition voltage, and large charging capacity, as well as its preparation method and application.

[0006] To achieve the above objectives, in a first aspect, the present invention provides an electrochemically active composite material, wherein the electrochemically active composite material is porous spherical or near-spherical particles; the Dv50 of the electrochemically active composite material is 2.0-10.0 μm, and the specific surface area is 20-200 m². 2 / g;

[0007] The electrochemically active composite material includes a catalyst and an organic lithium salt supported on the catalyst surface. The catalyst is a heteroatom-doped carbon-supported metal catalyst, comprising a carbon matrix, carbon nanotubes, and nano-metal particles.

[0008] The electrochemically active composite material provided by this invention combines an organic lithium salt with a heteroatom-doped carbon-supported metal catalyst to form porous spherical or near-spherical particles. These particles have a small particle size and a large specific surface area. Furthermore, the composite material possesses a rich three-dimensional conductive network structure, with the organic lithium salt in close contact with the catalyst. During charging, this facilitates easier wetting with the electrolyte, significantly shortening the Li- content of the organic lithium salt. + Migration pathway; at the same time, due to the catalytic effect of the catalyst, charge transfer can be enhanced, the decomposition potential of organic lithium salt can be significantly reduced, electrochemical activity can be improved, and a higher charging capacity can be provided; that is, the electrochemically active composite material provided by the present invention has a low decomposition voltage and a high charging capacity, and therefore can be used as a lithium replenishment additive in lithium-ion batteries.

[0009] Specifically, in the first aspect, the electrochemically active composite material provided by this invention uses a catalyst as a framework, with organic lithium salts distributed on the catalyst. The content of organic lithium salts gradually decreases from the outside to the inside, forming spherical or near-spherical particles with a three-dimensional porous structure. This design of decreasing organic lithium salt content from the outside to the inside is beneficial for the rapid reaction of organic lithium on the particle surface, accelerating the lithium salt decomposition efficiency and avoiding incomplete lithium salt decomposition due to excessive internal organic lithium at high rates. In the second aspect, the catalyst in the electrochemically active composite material provided by this invention is a heteroatom-doped carbon-supported metal catalyst. The introduction of heteroatoms gives the catalyst excellent conductivity, allowing it to bind tightly with organic lithium salts and providing a conductive site for charge transfer during the organic lithium salt charging reaction, reducing the activation energy of the organic lithium salt decomposition reaction, and thus reducing the decomposition potential of the organic lithium salt charging process. Thirdly, the catalyst in the electrochemically active composite material provided by the present invention uses a carbon matrix with a high specific surface area as the matrix. Through reaction, carbon nanotubes with a one-dimensional structure are generated in situ on the surface of the carbon matrix and wrapped around the surface of the carbon matrix, so that the catalyst has excellent adsorption and conductivity, can better combine with the catalyst, and provides a conductive network for electron transport, thus exhibiting excellent catalytic performance. Furthermore, nano-metal particles are attached to the top of the carbon nanotubes to form a three-dimensional conductive network, thereby reducing the decomposition voltage and increasing the charging capacity.

[0010] In one embodiment, the powder resistivity of the electrochemically active composite material is <100 Ω·cm.

[0011] In one embodiment, at least one of the following (a)-(d) is satisfied:

[0012] (a) The organic lithium salt includes at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, and Li2CO3;

[0013] (b) The heteroatom includes N, and also includes at least one of B, P, S, and F;

[0014] (c) The nano-metal particles include at least one of Fe, Co, Ni, Mn, Cu, Mo, Ti, and V;

[0015] (d) The carbon matrix includes at least one of acetylene black, Super P, Ketjen black, carbon nanotubes, graphene, activated carbon, and ordered mesoporous carbon.

[0016] The present invention has found that by selecting the above-mentioned types of raw materials, electrochemically active composite materials with better overall performance can be obtained.

[0017] The aforementioned lithium salt types not only have good air stability and lower requirements for the usage environment, but also decompose to generate gas during the first charge. The generated gas can be discharged during the battery formation process without any impurity residue, thus not reducing the energy density of the battery. Furthermore, when combined with the catalyst provided by this invention to form an electrochemically active composite material, the problems of low electrochemical activity and high decomposition potential can be effectively solved, and the resulting electrochemically active composite material has excellent comprehensive performance.

[0018] The introduction of heteroatoms can improve the conductivity of the product. In particular, when carbon is doped with two or more heteroatoms (one of which is N) according to the present invention, a good p-π conjugated system can be formed, which makes the catalyst have excellent conductivity. It can be tightly bound to the organic lithium salt, providing a conductive site for charge transfer during the charging reaction of the organic lithium salt, reducing the activation energy of the decomposition reaction of the organic lithium salt, and thus reducing the decomposition potential of the organic lithium salt charging process.

[0019] The aforementioned nano-metal particles can be effectively bonded to the top of carbon nanotubes. The selected nano-metal particles are all transition metals, which not only have good electrical conductivity, but also catalyze the formation of carbon nanotubes and promote the entanglement of carbon nanotubes on the carbon matrix, thereby helping to form a three-dimensional conductive network of electrochemically active composite materials and improving the overall performance of the product.

[0020] The carbon matrix of the above types has a high specific surface area, and selecting the above types of carbon matrix can help achieve good overall performance of the product.

[0021] In one embodiment, the catalyst comprises 1%-30% by mass, based on the mass of the electrochemically active composite material.

[0022] This invention has found that the mass percentage range of catalyst and organic lithium salt in electrochemically active composite materials also affects the overall performance of the product. When the mass percentage of catalyst is further selected to be 1%-30%, the resulting product has a lower decomposition voltage and a higher charging capacity.

[0023] In a second aspect, the present invention provides a method for preparing the electrochemically active composite material, the method comprising the following steps:

[0024] (1) The carbon matrix, transition metal compound, dopant and dispersant are added to the solvent and dispersed, and then a solvothermal reaction is carried out to obtain the first slurry;

[0025] (2) Add organic lithium salt to the first slurry, adjust the solid content and then wet mix to obtain the second slurry;

[0026] (3) After spray drying the second slurry, the first powder is obtained. The first powder is then washed and dried to obtain an electrochemically active composite material.

[0027] In the preparation method of the electrochemically active composite material provided by this invention, a carbon matrix is ​​used as the matrix material. Transition metal compounds and dopant are introduced, and carbon nanotubes are generated in situ on the carbon matrix surface via a solvothermal reaction. Nanoscale metal particles are attached to the tips of the carbon nanotubes, thereby forming a heteroatom-doped carbon-supported metal catalyst with a three-dimensional conductive network. Furthermore, an organolithium salt is introduced in the slurry stage through wet mixing, allowing the organolithium salt to be uniformly dispersed on the catalyst. Then, the organolithium salt is rapidly recrystallized through spray drying, causing the carbon nanotubes in the catalyst to re-entwine the organolithium salt, resulting in a tighter bond between the catalyst and the organolithium salt. This creates a state where the content of organolithium salt decreases from the outside to the inside, further accelerating the decomposition efficiency of the lithium salt, reducing the activation energy of the organolithium salt decomposition reaction, and thus reducing the decomposition potential during the charging process of the organolithium salt. This also increases the charging capacity, giving the composite material higher electrochemical activity. Finally, the material is washed to create pores and remove dispersants, increasing the specific surface area of ​​the material and helping to achieve a smaller particle size, thereby improving the wettability of the composite material with the electrolyte and increasing the decomposition efficiency.

[0028] In one embodiment, in step (1), the temperature of the solvothermal reaction is 150-300°C and the time is 1-12h.

[0029] This invention has found that the temperature and time of the solvothermal reaction affect the quality of in-situ carbon nanotubes generated on the carbon matrix surface by the doped raw materials, which in turn affects the catalyst and ultimately the decomposition voltage and charge-discharge performance of the product. When the temperature and time of the solvothermal reaction are further selected within the range given in this invention, the overall performance of the obtained product is better.

[0030] In one embodiment, in step (2), adjusting the solid content means adjusting the solid content to 1%-20%.

[0031] The present invention found that the adjustment of solid content in step (2) has a certain impact on the particle size, distribution uniformity and specific surface area of ​​the product. When the solid content is further selected to be 1%-20%, the decomposition voltage of the product is lower and the charging capacity is higher.

[0032] In one embodiment, in step (3), the washing is performed using anhydrous ethanol.

[0033] In one embodiment, during the washing process, the material-to-alcohol ratio is 1g:(1-10)g.

[0034] This invention has found that washing with anhydrous ethanol after spray drying can effectively remove dispersants and achieve pore-forming effects. When the material-to-ethanol ratio is further selected within the range given in this invention, the specific surface area of ​​the product can be further increased, thereby improving the wettability of the composite material with the electrolyte and increasing the decomposition efficiency.

[0035] In one embodiment, the doping material includes a nitrogen source, and also includes at least one of a boron source, a phosphorus source, a sulfur source, and a fluorine source.

[0036] For example, the nitrogen source includes at least one of urea, melamine, dicyandiamide, g-C3N4, o-phenanthroline, and dimethylimidazole. The boron source includes at least one of boric acid and boron oxide; the phosphorus source includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; the sulfur source includes at least one of ammonium sulfide and ammonium hydrogen sulfide; and the fluorine source includes ammonium fluoride.

[0037] This invention has discovered that the introduction of two or more doping materials (one of which is a nitrogen source) can enable the heteroatoms in the catalyst to include N, as well as at least one of B, P, S, and F; thereby forming a good con-p-π conjugated system, giving the catalyst excellent conductivity, allowing it to bind tightly with organic lithium salts, providing a conductive site for charge transfer during the charging reaction of organic lithium salts, reducing the activation energy of the decomposition reaction of organic lithium salts, and thus reducing the decomposition potential of the charging process of organic lithium salts.

[0038] In one embodiment, the transition metal compound includes at least one of oxides, hydroxides, carbonates, acetates, oxalates, nitrates, chlorides, and sulfates of Fe, Co, Ni, Mn, Cu, Mo, Ti, or V.

[0039] This invention has found that when the transition metal compound is selected as a compound of the type described above, after a solvothermal reaction, the transition metal ions therein can attach to the top of the carbon nanotubes formed by the doped raw materials, thereby helping to realize the three-dimensional conductive network structure of the product.

[0040] In one embodiment, the mass ratio of the carbon matrix, transition metal compound and dopant is (1-5):(0.1-1):(5-20).

[0041] This invention has discovered that the mass ratio of carbon matrix, transition metal compound, and dopant material affects the overall performance of the product. When the mass ratio of the three is further selected within the range given in this invention, the overall performance of the obtained product is better.

[0042] In one embodiment, the solvent includes at least one selected from water, anhydrous ethanol, ethylene glycol, N-methylpyrrolidone (NMP), and N,N-dimethylacetamide (DMF).

[0043] In one embodiment, the dispersant includes at least one of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and carboxymethyl cellulose (CMC).

[0044] The present invention has found that when the selected dispersant is of the type described above, the addition of the dispersant can not only help to form a good dispersion effect between substances in the early stage, but also effectively remove the dispersant in the subsequent washing and pore-forming process, further increasing the specific surface area of ​​the product, thereby improving the wettability of the electrochemically active composite material with the electrolyte, improving the decomposition efficiency, reducing the decomposition voltage, and increasing the charging capacity.

[0045] In one embodiment, the dispersant comprises 0.1%-20% by mass, based on the total mass of the carbon matrix, transition metal compound, dopant, and dispersant.

[0046] The present invention has found that when the amount of dispersant added is within the above range, a good dispersion effect can be formed in the early stage, and it can be effectively washed by anhydrous ethanol to form pores, thereby increasing the specific surface area of ​​the product and improving the overall performance of the product.

[0047] In one embodiment, in step (2), the rotation speed of wet mixing is 1000-3000 rpm, and the wet mixing time is 10-60 min.

[0048] This invention has found that when the rotation speed and time of wet mixing are within the above-mentioned range, good dispersion results can be obtained, thus improving the overall performance of the product.

[0049] In one embodiment, in step (3), the inlet air temperature of the spray dryer is 200-280°C and the outlet air temperature is 90-110°C.

[0050] In one embodiment, in step (3), the drying is performed by forced air drying or vacuum drying, the drying temperature is 100-250℃, and the drying time is 2-20h.

[0051] In a third aspect, the present invention provides the application of the electrochemically active composite material as a lithium replenishing agent in lithium iron phosphate batteries.

[0052] The electrochemically active composite material provided by this invention has a low decomposition voltage and a high charging capacity, and has the advantages of small particle size and large specific surface area, which is conducive to the extraction of lithium ions from organic lithium salts and fully utilizes the charging capacity. Therefore, it can be used as a lithium replenishing agent in lithium iron phosphate batteries, thereby effectively improving the energy density and cycle life of lithium iron phosphate batteries.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] (1) The electrochemically active composite material provided by the present invention combines an organic lithium salt with a heteroatom-doped carbon-supported metal catalyst. The composite material uses the catalyst as a framework, with the organic lithium salt distributed on the catalyst. The organic lithium salt content gradually decreases from the outside to the inside, forming spherical or near-spherical particles with a three-dimensional porous structure. The design of increasing organic lithium salt content from the inside to the outside is conducive to the rapid reaction of organic lithium on the particle surface, accelerating the lithium salt decomposition efficiency and avoiding incomplete lithium salt decomposition due to excessive organic lithium inside at high rates. At the same time, the catalyst is doped with two or more heteroatom-doped carbons, which can form a good p-π conjugated system, giving the catalyst excellent conductivity. It can be tightly combined with the organic lithium salt, providing a conductive site for charge transfer during the organic lithium salt charging reaction, reducing the activation energy of the organic lithium salt decomposition reaction, and thus reducing the decomposition potential of the organic lithium salt charging process.

[0055] (2) In the preparation method of the electrochemically active composite material provided by the present invention, on the one hand, a carbon nanotube-wrapped heteroatom-doped carbon-supported metal catalyst is synthesized in situ through a solvothermal reaction. Compared with physically mixed catalysts, it has higher conductivity and catalytic ability, and can effectively catalyze the decomposition of organic lithium salts by interacting with them. On the other hand, the organic lithium salt is dissolved and fully contacted with the catalyst by a wet mixing method, and then the organic lithium salt is rapidly recrystallized by spray drying. The carbon nanotubes in the catalyst are wrapped around the organic lithium salt again, so that the catalyst and the organic lithium salt are tightly combined, and the composite material has higher electrochemical activity. Finally, the material is pore-forming and the dispersant is removed by alcohol washing, which increases the specific surface area of ​​the material, thereby improving the wettability of the composite material with the electrolyte and improving the decomposition efficiency.

[0056] (3) The composite material prepared by the preparation method provided by the present invention has a porous spherical or near-spherical morphology. The organic lithium salt has a small primary particle size and uniform particle size distribution, which is conducive to the extraction of lithium ions from the organic lithium salt and fully utilizes the charging capacity.

[0057] (4) The electrochemically active composite material provided by the present invention can be effectively used as a lithium supplement in the preparation of lithium iron phosphate batteries, thereby improving the energy density and cycle life of lithium iron phosphate batteries. Attached Figure Description

[0058] Figure 1 Here is a schematic diagram of the structure of the electrochemically active composite material of the present invention:

[0059] 10-Organic lithium salt, 20-catalyst, 21-carbon matrix, 22-nano-metal particles, 23-carbon nanotubes;

[0060] Figure 2 The image shows a SEM image of the catalyst prepared in Example 1.

[0061] Figure 3 SEM image of the electrochemically active composite material prepared in Example 1;

[0062] Figure 4 The image shows a SEM image of the catalyst prepared in Comparative Example 3.

[0063] Figure 5 SEM image of the electrochemically active composite material prepared in Comparative Example 3;

[0064] Figure 6 The charging curves are shown for the electrochemically active composite materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0065] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0066] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in the field.

[0067] Example 1

[0068] This invention provides an electrochemically active composite material, the preparation method of which includes the following steps:

[0069] (1) Add 20g of carbon matrix (Super P), 5g of transition metal compound (cobalt tetroxide), and 200g of dopant (150g of urea and 50g of boric acid) to 500mL of solvent (pure water), and then add 10g of dispersant (polyethylene glycol). After stirring and ultrasonically dispersing the slurry, transfer it to a hydrothermal reactor and heat it to 250℃ for solvothermal reaction for 4h to obtain the first slurry.

[0070] (2) Add 70g of organic lithium salt (Li2C2O4) to the first slurry, add 500mL of pure water to adjust the solid content to 9.09%, and grind and mix the materials by sand mill (3000rpm, 15min) to obtain the second slurry;

[0071] (3) Spray dry the second slurry, adjust the inlet air temperature to 250°C and the outlet air temperature to 110°C to obtain the first powder;

[0072] (4) The first powder is added to anhydrous ethanol solvent and washed with alcohol at a mass ratio of 1:10. The mixture is then filtered, the filter residue is collected and dried at 120°C for 8 hours to obtain the composite material.

[0073] Example 2

[0074] This invention provides an electrochemically active composite material, the preparation method of which includes the following steps:

[0075] (1) 15g of carbon matrix (acetylene black), 5g of transition metal compound (nickel acetate), and 45g of dopant (30g of melamine and 15g of diamine hydrogen phosphate) were added to 1000mL of solvent (anhydrous ethanol), and then 5g of dispersant (polyethylene glycol) were added. After the slurry was stirred and ultrasonically dispersed, it was transferred to a hydrothermal reactor and heated to 230℃ for solvothermal reaction for 6h to obtain the first slurry.

[0076] (2) Add 80g of organic lithium salt (Li2C4O4) to the first slurry, add 1000mL of pure water to adjust the solid content to 4.8%, and grind and mix by sand mill (speed 2500rpm, time 30min) to obtain the second slurry;

[0077] (3) Spray dry the second slurry, adjust the inlet air temperature to 230°C and the outlet air temperature to 100°C to obtain the first powder;

[0078] (4) The first powder was added to anhydrous ethanol solvent and washed with alcohol at a mass ratio of 1:6. The residue was collected by vacuum filtration and dried at 120°C for 8 hours to obtain the composite material.

[0079] Example 3

[0080] This invention provides an electrochemically active composite material, the preparation method of which includes the following steps:

[0081] (1) Add 5g of carbon matrix (Ketjen black), 5g of transition metal compound (ferric nitrate), and 100g of dopant (75g of dicyandiamide and 25g of ammonium dihydrogen phosphate) to 2000mL of solvent (ethylene glycol), and then add 2g of dispersant (polyethylene glycol). After stirring and ultrasonically dispersing, the slurry is transferred to a hydrothermal reactor and heated to 210℃ for solvothermal reaction for 8h to obtain the first slurry.

[0082] (2) Add 90g of organic lithium salt (Li2C3O5) to the first slurry, add 3000mL of pure water to adjust the solid content to 2.0%, and grind and mix by sand mill (speed 2000rpm, time 45min) to obtain the second slurry;

[0083] (3) Spray dry the second slurry, adjust the inlet air temperature to 210°C and the outlet air temperature to 90°C to obtain the first powder;

[0084] (4) The first powder is added to anhydrous ethanol solvent and washed with alcohol at a mass ratio of 1:3. The mixture is then filtered, the filter residue is collected and dried at 120°C for 8 hours to obtain the composite material.

[0085] Example 4

[0086] This invention provides an electrochemically active composite material, the preparation method of which includes the following steps:

[0087] (1) Add 4g of carbon matrix (activated carbon), 1g of transition metal compound (manganese dioxide), and 10g of dopant (8g of o-phenanthroline and 2g of ammonium sulfide) to 500mL of solvent (N-methylpyrrolidone), and then add 2g of dispersant (polyethylene glycol). After stirring and ultrasonically dispersing, the slurry is transferred to a hydrothermal reactor and heated to 190℃ for solvothermal reaction for 10h to obtain the first slurry.

[0088] (2) Add 95g of organic lithium salt (Li2C4O6) to the first slurry, add 500mL of pure water to adjust the solid content to 9.0%, and grind and mix by sand mill (speed 1500rpm, time 60min) to obtain the second slurry;

[0089] (3) Spray dry the second slurry, adjust the inlet air temperature to 210°C and the outlet air temperature to 90°C to obtain the first powder;

[0090] (4) The first powder is added to anhydrous ethanol solvent and washed with alcohol at a mass ratio of 1:1. The mixture is then filtered, the filter residue is collected and dried at 120°C for 8 hours to obtain the composite material.

[0091] Example 5

[0092] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is the raw materials in step (1). The raw materials in step (1) of this embodiment are: the carbon matrix is ​​ordered mesoporous carbon CMK-3, the transition metal compound is cobalt acetate, the doping raw materials are 150g dimethylimidazole and 50g boric acid, and the solvent is N,N-dimethylacetamide.

[0093] Example 6

[0094] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is the raw material in step (1). In this embodiment, the raw material in step (1) is: the carbon matrix is ​​graphene and the transition metal compound is titanium dioxide.

[0095] Example 7

[0096] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is the raw material in step (1). The raw material in step (1) of this embodiment is: carbon nanotubes as the carbon matrix and molybdenum dioxide as the transition metal compound.

[0097] Example 8

[0098] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the temperature of the solvothermal reaction is 180°C.

[0099] Example 9

[0100] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the solvothermal reaction time is 10 hours.

[0101] Example 10

[0102] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the amount of dispersant added is 2g.

[0103] Example 11

[0104] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the amount of organic lithium salt added is 270g.

[0105] Example 12

[0106] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the amount of organic lithium salt added is 35g.

[0107] Example 13

[0108] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the total mass of the carbon matrix, transition metal compound and dopant remains unchanged, and the mass ratio of the carbon matrix, transition metal compound and dopant is changed to 5:1:5.

[0109] Example 14

[0110] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the total mass of the carbon matrix, transition metal compound and dopant remains unchanged, and the mass ratio of the carbon matrix, transition metal compound and dopant is changed to 5:1:20.

[0111] Example 15

[0112] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the doping raw material is 200g of urea.

[0113] Example 16

[0114] This invention provides an electrochemically active composite material. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that the doping raw material is 200g of boric acid.

[0115] Comparative Example 1

[0116] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and Example 1 is that no transition metal compound and doping material are added in step (1).

[0117] Comparative Example 2

[0118] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and Example 1 is that no carbon matrix and doping raw materials are added in step (1).

[0119] Comparative Example 3

[0120] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that no transition metal compound is added in step (1).

[0121] Comparative Example 4

[0122] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that no doping material is added in step (1).

[0123] Comparative Example 5

[0124] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and Example 1 is that the temperature of the solvothermal reaction in step (1) is 120°C.

[0125] Comparative Example 6

[0126] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and Example 1 is that the temperature of the solvothermal reaction in step (1) is 320°C.

[0127] Comparative Example 7

[0128] The present invention provides an electrochemically active composite material in a comparative example. The only difference between the preparation method of the electrochemically active composite material and that of Example 1 is that in step (4), the first powder is not washed with alcohol, but directly dried at 120°C for 8 hours to obtain the composite material.

[0129] Comparative Example 8

[0130] This invention provides an electrochemically active composite material, the preparation method of which includes the following steps:

[0131] (1) Add 20g of carbon matrix (Super P), 5g of transition metal compound (cobalt tetroxide), and 200g of dopant (150g of urea and 50g of boric acid) to 500mL of solvent (pure water), and then add 10g of dispersant (polyethylene glycol). After stirring and ultrasonically dispersing the slurry, transfer it to a hydrothermal reactor and heat it to 250℃ for solvothermal reaction for 4h to obtain the first slurry.

[0132] (2) Filter the first slurry, collect the filter residue and dry it to obtain the catalyst;

[0133] (3) Mix 30g of catalyst and 70g of organic lithium salt (Li2C2O4) by ball milling and grind at 500rpm for 2h to obtain composite material.

[0134] Example of effect 1

[0135] The effects of this invention are investigated by examining the properties of the composite materials prepared in Examples 1-16 and Comparative Examples 1-8:

[0136] 1. A schematic diagram of the composite material provided by this invention is shown below. Figure 1 As shown, the composite material consists of an organolithium salt 10 and a catalyst 20. The catalyst 20 serves as a framework, with the organolithium salt 10 distributed on it. The content of the organolithium salt 10 gradually decreases from the outside to the inside, forming spherical or near-spherical particles with a three-dimensional porous structure. The catalyst 20 includes a carbon matrix 21, nano-metal particles 22, and carbon nanotubes 23. The nano-metal particles 22 are dispersed at the top of the carbon nanotubes 23, and the carbon nanotubes 23 and the carbon matrix form a three-dimensional conductive network through entanglement. The organic combination of the organolithium salt 10 and the catalyst 20 can significantly improve the reactivity of the organolithium salt 10 and reduce the decomposition activation energy.

[0137] 2. The catalyst in Example 1 was prepared as follows: 20g of carbon matrix (Super P), 5g of transition metal compound (cobalt tetroxide), and 200g of dopant (150g of urea and 50g of boric acid) were added to 500mL of solvent (pure water), and then 10g of dispersant (polyethylene glycol) was added. After the slurry was stirred and ultrasonically dispersed, it was transferred to a hydrothermal reactor and heated to 250℃ for a solvothermal reaction for 4 hours to obtain the first slurry. The first slurry was spray-dried, and the inlet air temperature was adjusted to 250℃ and the outlet air temperature to 110℃ to obtain the first powder. The first powder was then added to anhydrous ethanol solvent and washed with ethanol at a material-to-ethanol mass ratio of 1:10. The residue was collected by vacuum filtration and dried at 120℃ for 8 hours to obtain the catalyst.

[0138] SEM image of the catalyst in Example 1 is shown below. Figure 2 As shown, from Figure 2As can be seen, the catalyst uses a carbon matrix as the matrix material, with carbon nanotubes wound around the surface of the carbon matrix and metal nanoparticles (high-brightness particles) adsorbed on the carbon nanotubes, together forming a three-dimensional conductive network; the SEM image of the composite material in Example 1 is shown below. Figure 3 As shown, from Figure 3 The microstructure of the composite material can be seen as micron-sized spherical particles. The particle surface is composed of organic lithium salt nanoparticles and is wrapped with carbon nanotubes, exhibiting a porous morphology.

[0139] 3. The only difference between the preparation method of the catalyst in Comparative Example 3 and the preparation method of the catalyst in Example 1 is that no transition metal compound is added;

[0140] The SEM image of the catalyst prepared in Comparative Example 3 is shown below. Figure 4 As shown, the SEM image of the composite material prepared in Comparative Example 3 is as follows. Figure 5 As shown, from Figure 4-5 As can be seen, without the addition of transition metal compounds, the doped raw materials cannot be catalyzed to form carbon nanotubes, and due to the lack of carbon nanotube entanglement, the prepared composite material has a loose morphology.

[0141] 4. The specific parameters and performance parameters of the composite materials prepared in Examples 1-16 and Comparative Examples 1-8 include the following aspects:

[0142] (1) Mass percentage of catalyst: Accurately weigh 1g of composite material and add it to 100mL of pure water solvent. Stir for 10min and filter. Dry the filter residue at 100℃ for 120min to obtain catalyst powder. Weigh the powder and record it as m. Calculate the mass percentage of catalyst. The calculation formula is: Mass percentage of catalyst = m / 1 × 100%.

[0143] (2) Dv50: Measured using a dry laser particle size analyzer (Malvin Mastersizer 3000);

[0144] (3) Specific surface area: 2g of composite material was weighed and degassed at 150℃. Nitrogen was used as the adsorbent and helium was used as the carrier gas. The change in nitrogen was measured by a specific surface area and pore size analyzer (BSD-3H-2000A).

[0145] (4) Powder resistivity: The powder resistivity was tested using a four-probe method with a fixed test cell height of 20 mm. 1.2 g of the composite material was weighed and added to the test cell. The material was then compacted under a pressure of 12 MPa. The resistivity was calculated using the following formula:

[0146]

[0147] Where ρ is resistivity, C is probe correction coefficient, G is height correction coefficient, W is powder compaction height, S is probe spacing, d is cavity cross-sectional area, V is test voltage, and I is test current.

[0148] (5) Charging capacity: The composite material was used as the active material and mixed with Super P and PVDF at a mass ratio of 90:5:5. NMP was used as the solvent, and the solid content of the slurry was adjusted to 30%. The mixed slurry was obtained by rapid stirring. The mixed slurry was coated on aluminum foil, transferred to a drying oven for drying, and then cut into small positive electrode discs to prepare coin cells. After assembling the coin cells, charge and discharge tests were performed using a blue electric current tester. The voltage was measured at 4.35 / 4.5V after charging at a current of 40mA.

[0149] (6) The decomposition voltage is the same as the charging capacity test. The charging voltage in the charge-discharge curve is the decomposition voltage.

[0150] The results are shown in Table 1.

[0151] Table 1

[0152]

[0153]

[0154] As can be seen from Table 1, when the technical solution provided by this invention is adopted, the prepared composite material has a small particle size and a large specific surface area. Simultaneously, the prepared composite material has a low powder resistivity, a low decomposition voltage, and a high charging capacity. Specifically, the obtained product has a particle size between 2.15 and 7.29 μm and a specific surface area of ​​32 m². 2 The powder resistivity is below 50.4 Ω·cm, the decomposition voltage is below 4.25V, and the charging capacity is above 420mAh / g.

[0155] Comparative Examples 1 and 2, using carbon matrix and metal oxide as individual catalysts respectively, exhibited limited catalytic activity, resulting in high voltage plateaus and low capacities. Comparative Example 2, in particular, had a charging capacity of only 32 mAh / g. Comparative Example 3, with its catalyst feedstock consisting of carbon matrix and urea without a metal source, could not catalyze the formation of carbon nanotubes from the doped feedstock. Due to the lack of carbon nanotube entanglement, the prepared composite material had a loose morphology and weak composite strength. Comparative Example 4, without any doped feedstock, lacked the nitrogen source necessary for metal catalysis to form carbon nanotubes. Furthermore, the high-temperature carbothermic reduction reaction between the metal and carbon source consumed some of the carbon matrix, leading to reduced catalyst conductivity and a high decomposition potential and low charging capacity in the corresponding composite material. Comparative Example 5, with a solvothermal reaction temperature of 120℃, was too low, resulting in incomplete or no reaction between the catalyst feedstocks, thus hindering the formation of the desired catalyst. Poor chemical reaction capability and low charging capacity of the composite material; the solvothermal reaction temperature of the catalyst in Comparative Example 6 was too high, resulting in a low specific surface area of ​​the prepared composite material, which is not conducive to the composite with organolithium salt, leading to low charging capacity; Comparative Example 7 did not undergo alcohol washing to create pores, and a polymer film formed on the surface of the corresponding material particles, making it difficult for the electrolyte to penetrate into the particle interior. In addition, the electronic insulation of most of the dispersant led to low decomposition reaction efficiency of organolithium salt, indicating that alcohol washing can effectively improve surface porosity and improve the reaction activity and efficiency of the material; Comparative Example 8 directly physically dry-mixed organolithium salt and catalyst, and the decomposition voltage and charging capacity were worse than those of the examples. Physical dry mixing could not completely break down the organolithium salt, resulting in large particle size. Wet mixing and sand milling with aqueous solution can dissolve the organolithium salt and improve the combination of organolithium salt and catalyst, thereby achieving the best composite effect.

[0156] Example 2

[0157] This invention investigates the performance of the composite materials prepared in Example 1 and Comparative Example 1 in lithium-ion batteries. The composite materials prepared in Example 1 and Comparative Example 1 were used as the positive electrode active material. They were mixed with PVDF and conductive carbon black in a 90:5:5 ratio, and NMP solvent was added until the slurry solid content reached 25%. The mixture was stirred to prepare the positive electrode slurry. After coating, drying, rolling, stamping, and vacuum drying, the slurry yielded the positive electrode sheet. The positive electrode sheet, negative electrode sheet, electrolyte, and separator were assembled into a button-type lithium-ion battery. Charge-discharge tests were conducted on the lithium-ion battery with a voltage range of 2.8–4.35V, a constant current of 40mA, and a cutoff current of 20mA to test its electrochemical performance. The test results are as follows: Figure 6 As shown; from Figure 6As can be seen, the total charging capacity of Example 1 is 485 mAh / g, the constant voltage charging capacity is low, the charging voltage plateau is 4.10V, and the voltage plateau is obvious; while the charging capacity of Comparative Example 1 is <350 mAh / g, and the constant voltage charging is significantly higher, the charging voltage plateau is greater than 4.4V, and the voltage window is not obvious. This indicates that the combination of organic lithium salt and NB heteroatom-doped carbon-supported metal catalyst can significantly improve the decomposition efficiency of organic lithium salt and reduce the decomposition potential.

Claims

1. An electrochemically active composite material, characterized in that, The electrochemically active composite material is a porous spherical or near-spherical particle; the Dv50 of the electrochemically active composite material is 2.0-10.0 μm, and the specific surface area is 20-200 m². 2 / g; The electrochemically active composite material includes a catalyst and an organic lithium salt supported on the catalyst surface. The catalyst is a heteroatom-doped carbon-supported metal catalyst, including a carbon matrix, carbon nanotubes, and nano-metal particles. Carbon nanotubes are generated in situ on the surface of a carbon matrix. The carbon nanotubes and the carbon matrix form a three-dimensional conductive network by entanglement. Nano-metal particles are dispersed at the top of the carbon nanotubes, and the content of organic lithium salt gradually decreases from the outside to the inside. The organic lithium salt includes at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, and Li2CO3; The heteroatom includes N, and also includes at least one of B, P, S, and F; The preparation method of the electrochemically active composite material includes the following steps: (1) The carbon matrix, transition metal compound, doped raw material and dispersant are added to the solvent and dispersed, and then a solvothermal reaction is carried out to obtain the first slurry; (2) Add the organic lithium salt to the first slurry, adjust the solid content, and then wet mix to obtain the second slurry; (3) After spray drying the second slurry, the first powder is obtained. The first powder is then washed and dried to obtain an electrochemically active composite material. In step (1), the temperature of the solvothermal reaction is 150-300℃ and the time is 1-12h; In step (2), the solid content is adjusted to 1%-20%. In step (3), the washing is performed using anhydrous ethanol; The doping material includes a nitrogen source, and also includes at least one of a boron source, a phosphorus source, a sulfur source, and a fluorine source.

2. The electrochemically active composite material according to claim 1, characterized in that, Satisfying at least one of the following (a)-(b): (a) The nano-metal particles include at least one of Fe, Co, Ni, Mn, Cu, Mo, Ti, and V; (b) The carbon matrix includes at least one of acetylene black, Super P, Ketjen black, carbon nanotubes, graphene, activated carbon, and ordered mesoporous carbon.

3. The electrochemically active composite material according to claim 1, characterized in that, The catalyst comprises 1%-30% by mass of the electrochemically active composite material.

4. The method for preparing the electrochemically active composite material according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) The carbon matrix, transition metal compound, doped raw material and dispersant are added to the solvent and dispersed, and then a solvothermal reaction is carried out to obtain the first slurry; (2) Add the organic lithium salt to the first slurry, adjust the solid content, and then wet mix to obtain the second slurry; (3) After spray drying the second slurry, the first powder is obtained. The first powder is then washed and dried to obtain an electrochemically active composite material. In step (1), the temperature of the solvothermal reaction is 150-300℃ and the time is 1-12h; In step (2), the solid content is adjusted to 1%-20%. In step (3), the washing is performed using anhydrous ethanol; The doping material includes a nitrogen source, and also includes at least one of a boron source, a phosphorus source, a sulfur source, and a fluorine source.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the carbon matrix, transition metal compound, and dopant is (1-5):(0.1-1):(2-20).

6. The preparation method according to claim 4, characterized in that, The solvent includes at least one of water, anhydrous ethanol, ethylene glycol, N-methylpyrrolidone, and N,N-dimethylacetamide; And / or, the dispersant includes at least one of polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and carboxymethyl cellulose.

7. The preparation method according to claim 4, characterized in that, The mass percentage of the dispersant is 0.1%-20% based on the total mass of the carbon matrix, transition metal compound, dopant, and dispersant.

8. The application of the electrochemically active composite material as described in any one of claims 1-3 as a lithium replenishing agent for lithium iron phosphate batteries.

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