Negative electrode composite material, and preparation method therefor and application thereof

Abstract

The present invention provides a negative electrode composite material, and a preparation method therefor and an application thereof. The negative electrode composite material comprises a core substrate and an ion-transport-type artificial SEI film disposed on the surface of the core substrate, wherein the ion-transport-type artificial SEI film is obtained by a quasi-atomic layer deposition method. The present invention employs a quasi-atomic layer deposition-based surface modification technique to form a high-rate ion-transport-type artificial SEI film on the surface of the core substrate, thereby enabling the negative electrode composite material to have better kinetic performance, higher initial coulombic efficiency, and excellent cycle performance. The preparation method involves simple operations, low cost, and easy scale-up, and has broad application prospects.

Description

A negative electrode composite material, its preparation method and application Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a negative electrode composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles, portable electronic devices, artificial intelligence, and energy storage systems, the demand for lithium-ion batteries with long cycle life is increasing. Lithium-ion batteries are mainly assembled from a positive electrode, a negative electrode, a separator, and an electrolyte. As one of the key components, the performance of the negative electrode material is crucial to the performance of the lithium-ion battery.

[0003] Carbon anodes are currently the dominant anode materials. After more than 20 years of development, the performance indicators of carbon anode materials, represented by artificial graphite and natural graphite, have become increasingly mature. At present, graphite can achieve an initial efficiency of over 94% and a delithiation capacity of over 350 mAh / g, but its kinetic performance cannot yet fully meet market demands. High-performance carbon anodes with capacities above 4C still need to be developed.

[0004] The key to improving the kinetics of carbon anodes lies in improving their surface chemical structure. Currently, the conventional approach to enhancing kinetic performance is to coat the surface of carbon anodes such as graphite with carbon. A porous carbon coating increases surface ion transport channels and enhances electrolyte wetting of the anode surface through physical adsorption, reducing lithium intercalation resistance. For example, CN108598479A discloses a modified natural graphite lithium-ion battery anode material, comprising the following components: graphite powder, coating agent, surface-active additives, and solvent; wherein the graphite powder is selected from any one of natural flake graphite, amorphous graphite, and sheet graphite with a fixed carbon content of over 95%; the coating layer uses petroleum asphalt, coal tar pitch, or phenolic resin; and the solvent is toluene. By heating in a rotary furnace, the graphite powder is purified and surface-coated, resulting in modified graphite with high particle size uniformity and stable electrochemical performance. CN112456482A discloses a method for coating and modifying lithium-ion battery anode materials, comprising the following steps: dissolving phenolic resin in an organic solvent to obtain coating agent 1, mixing coating agent 1 with graphite uniformly, and carbonizing under a nitrogen atmosphere to obtain primary coated graphite; dissolving asphalt in an organic solvent to obtain asphalt mixture, then mixing graphene conductive slurry with the asphalt mixture uniformly to obtain coating agent 2, mixing coating agent 2 with primary coated graphite uniformly, and carbonizing under a nitrogen atmosphere to obtain secondary protected graphite; the graphite anode material prepared by this method has high compaction density, rate performance, and cycle performance.

[0005] In general, there are two main methods for carbon coating in the industry: solid-phase coating and liquid-phase coating; the coating materials mainly include asphalt and phenolic resin. Although carbon coating can improve the kinetic performance of graphite, surface carbon coating increases electrolyte decomposition at the interface, reduces the initial efficiency of graphite, deteriorates its high-temperature performance, and reduces its cycle life. Therefore, surface carbon coating is not an ideal solution for improving the kinetics of carbon anodes. Thus, achieving both high initial efficiency and excellent cycle performance while improving the kinetics of carbon anodes is a problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a negative electrode composite material, its preparation method, and its application. The preparation method employs atomic layer deposition (ALD) surface modification technology to modify a uniform and dense ion-transporting artificial SEI film on the surface of a core substrate, thereby enabling the negative electrode composite material to possess better kinetic performance, higher initial efficiency, better high-temperature storage performance, and excellent cycling performance. The preparation method is simple to operate, low in cost, easy to scale up, and has broad application prospects.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a negative electrode composite material, the negative electrode composite material comprising a core substrate and an ion-transporting artificial SEI film disposed on the surface of the core substrate; the ion-transporting artificial SEI film is obtained by an atomic layer deposition method.

[0009] Preferably, the preparation method (atomic layer deposition-like method) includes the following steps:

[0010] A blend is provided, the blend comprising a combination of a core substrate, an ion transport medium precursor, a dispersant, and a solvent;

[0011] The blend is subjected to a first shear dispersion to obtain a dispersion;

[0012] The dispersion was dried under second shear dispersion and heat flow conditions to obtain a powder.

[0013] The powder is subjected to dynamic heat treatment to obtain the negative electrode composite material.

[0014] This invention reveals that inorganic ion transport media possess characteristics such as high ion transport rates and good electrolyte wettability. Modifying the surface of carbon anode materials with ion transport media helps promote the desolvation of lithium ions, providing a fast channel for lithium ion transport, facilitating lithium ion embedding on the carbon anode surface, and improving the kinetic performance of the carbon anode. When these inorganic ion transport media are uniformly modified on the surface of the carbon anode, a high-speed ion transport type artificial SEI film is formed. This high-speed ion transport type artificial SEI film improves the kinetic performance of the carbon anode without aggravating the electrolyte reaction on its surface. Compared to existing carbon anodes with surface carbon coating modification, the carbon anode modified with the high-speed ion transport type artificial SEI film exhibits higher initial efficiency, better kinetic performance, and superior cycle performance.

[0015] Based on this, the present invention provides a preparation method based on atomic layer deposition (ALD) surface modification technology. The method involves uniformly dispersing the ion transport medium precursor and the core substrate using high shear force, followed by instantaneous drying to uniformly coat and modify the ion transport medium onto the surface of the core substrate, forming a high-speed ion transport type artificial SEI film. The ion transport medium can reduce the energy barrier for lithium ion transport on the surface of the negative electrode material (e.g., graphite), significantly improving the kinetic performance of the negative electrode composite material while exhibiting high initial efficiency, excellent high-temperature storage performance, and excellent cycle performance. This, in turn, enhances the rate performance, high-temperature performance, and cycle performance of the lithium-ion battery containing the composite material, and reduces internal resistance. The preparation method is simple to operate, low in cost, easy to scale up, and has broad application prospects.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0017] Preferably, the core substrate comprises a negative electrode carbon material, and more preferably any one or a combination of at least two of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0018] Preferably, based on the mass of the nuclear substrate as 100%, the mass of the ion transport medium precursor is 0.01%-10%, for example, it can be 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8% or 9%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0019] Preferably, the ion transport medium precursor includes any one or a combination of two of the following: ion-conducting materials and conductive materials.

[0020] The ion-conducting material includes inorganic substances with excellent ion-conducting ability; preferably, the ion-conducting material includes any one or a combination of at least two of lithium salts, lithium oxides, transition metal oxides, transition metal phosphides, transition metal sulfides, half-metal oxides, elemental phosphorus, elemental sulfur, and other solid electrolytes.

[0021] As a preferred embodiment of the present invention, the lithium salt and / or lithium oxide serve as ion-conducting materials, providing excellent ion-conducting capabilities on the one hand, and lithium replenishment on the other.

[0022] More preferably, the ion-conducting material includes any one or a combination of at least two of the following: lithium carbonate, lithium silicate, lithium metasilicate, lithium phosphate, lithium metaphosphate, lithium hypophosphite, lithium borate, lithium titanate, lithium oxide, lithium fluoride, lithium aluminate, lithium phosphide, lithium sulfide, lithium nickelate, calcium oxide, zinc oxide, aluminum oxide, zirconium oxide, zirconium nitride, zirconium phosphide, molybdenum oxide, molybdenum nitride, molybdenum phosphide, molybdenum sulfide, molybdenum borate, silicon suboxide, silicon dioxide, titanium dioxide, elemental phosphorus, elemental sulfur, (other) oxide solid electrolytes, (other) sulfide solid electrolytes, (other) halide solid electrolytes, and polymer electrolytes.

[0023] Preferably, the average particle size of the ion-conducting material is 1-1000 nm, for example, it can be 2 nm, 5 nm, 8 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or 900 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0024] Preferably, the conductive material includes any one or a combination of at least two of graphene, carbon nanotubes, conductive carbon black, amorphous carbon, soft carbon, and hard carbon.

[0025] Preferably, the ion transport medium precursor comprises a combination of an ion-conducting material and a conductive material, wherein the mass ratio of the ion-conducting material to the conductive material is 1:(0.1-10), for example, it can be 1:0.2, 1:0.4, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9, etc.

[0026] Preferably, the solvent includes water.

[0027] As a preferred technical solution of the present invention, the solvent is water, which not only has the characteristics of being environmentally friendly and low cost, but also has suitable solubility and / or dispersibility for ion-conducting materials, which is more conducive to the uniform deposition and coating of ion-conducting materials on the surface of the core substrate, so that the obtained ion-transporting artificial SEI film and negative electrode composite material have excellent ion transport performance.

[0028] Preferably, with the mass of the core substrate as 100%, the mass of the solvent is 50%-500%, for example, it can be 80%, 100%, 150%, 200%, 250%, 300%, 350%, 400% or 450%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, based on the mass of the core substrate as 100%, the mass of the dispersant is 0.01%-5%, for example, it can be 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0030] As a preferred embodiment of the present invention, the dispersant has excellent solubility in water and excellent film-forming properties on the surface of the core substrate. Preferably, its 1% aqueous solution has a pH of 5-10, such as 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 or 9.5, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0031] Preferably, the dispersant comprises any one or a combination of at least two of carboxymethyl cellulose salt, alginate, (meth)acrylic acid homopolymer salt, and (meth)acrylic acid copolymer salt.

[0032] In this invention, the term (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0033] Preferably, the cations in the carboxymethyl cellulose salt, alginate, (meth)acrylic acid homopolymer salt, and (meth)acrylic acid copolymer salt each independently include any one or a combination of at least two of lithium ions, sodium ions, potassium ions, calcium ions, and zinc ions.

[0034] In this invention, an ion-transporting artificial SEI membrane is prepared in an aqueous system with the assistance of a dispersant. The shear force of the first shear dispersion ensures that the core substrate and the ion transport medium precursor are fully dispersed in the solution, preventing aggregation. The aqueous system used in this invention is environmentally friendly, non-corrosive to equipment, and has low production costs, making it suitable for mass production. The dispersant can improve the surface tension of water and promote the dispersion of the core substrate in water through electrostatic interaction, ensuring its uniform distribution in the aqueous system. This enhances the stability of the ion-transporting artificial SEI membrane coating and makes the ion-transporting artificial SEI membrane more uniformly distributed on the surface of the negative electrode composite material.

[0035] Preferably, the first shearing and dispersing device includes any one or a combination of at least two of a disperser, a mixer, a homogenizer, and a rotor homogenizing circulation pump, and more preferably a combination of a disperser and a rotor homogenizing circulation pump.

[0036] Unlike traditional ball milling / sand milling processes, the method of this invention employs a gentle shearing process in an aqueous system with the assistance of a dispersant. This results in low shearing force and minimal impact force during dispersion, preventing damage to the structure and surface morphology of the components in the slurry and avoiding irreversible damage to the material. This enables high-speed dispersion without destroying the structure.

[0037] As a preferred embodiment of the present invention, the first shear dispersion device includes a rotor homogenizing circulation pump; the blend is dispersed as it flows under driving force and passes through a slit. The characteristic of this process is that the slurry (blended material) forms a high-speed flow under external force, generating pressure; the pressure drives the fluid to rapidly pass through the slit, and all substances in the slurry are uniformly dispersed under the action of pressure and the slit. This method of dispersion is highly efficient and effective.

[0038] Preferably, the first shear dispersion time is 0.1-5h, for example, it can be 0.2h, 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h, 2h, 2.5h, 3h, 3.5h, 4h or 4.5h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0039] In this invention, the second shear dispersion occurs during the drying process. The dispersion liquid forms microdroplets under shear force, and these droplets are instantly dried upon contact with the hot airflow to obtain powder. The function of the second shear dispersion is to uniformly disperse the core substrate and ion transport medium precursor in numerous microdroplets, achieving instantaneous drying. On the one hand, the microdroplets ensure that the ion transport medium precursor and core substrate are uniformly dispersed in each droplet, increasing coating uniformity; on the other hand, the microdroplets significantly increase the drying rate, shorten the drying time, achieve instantaneous drying, and improve coating uniformity. If the drying time is too long, the ion transport medium will move on the surface of the core substrate with the evaporation of water, accumulating at defects and reducing coating uniformity.

[0040] Preferably, the dispersion of the liquid into microdroplets is achieved by any one or a combination of at least two of the following: vibration, centrifugation, rotating impeller, and hot airflow impact.

[0041] Preferably, the dispersion is rapidly and uniformly dried into microdroplets under the second shear dispersion and heat flow conditions, comprising any one or a combination of at least two of the following methods 1)-3):

[0042] 1) Drying gas at a certain temperature passes through the dispersion liquid material layer at a controlled speed. With the assistance of vibration, the material is impacted by the hot gas. The impact shear force causes the material to form micro-droplets and reach a fluidized state. The micro-droplets are dried instantly to obtain powder.

[0043] 2) The dispersed liquid is atomized into small droplets through a high-speed centrifugal disc or atomized into small droplets under the drive of compressed gas. The small droplets then come into contact with hot air in the drying chamber, where the moisture evaporates and particles are formed. The small particles are carried away from the drying chamber with the hot air.

[0044] 3) The dispersion is fed into a compact drying chamber, where it comes into contact with hot air and a rotating impeller. The shear force caused by the rotation drive and thermal shock breaks the dispersion into small droplets. The small droplets are dried instantly to form a powdered product, which is then carried out of the drying chamber along with the hot air.

[0045] Preferably, the drying apparatus includes any one or a combination of at least two of the following: fluidized bed, flash dryer, spray dryer, rotary kiln, blast drying box, tube furnace, and roller kiln.

[0046] Preferably, the flash dryer includes an airflow flash dryer and / or a rotary flash dryer.

[0047] Preferably, the spray dryer includes a centrifugal spray dryer and / or a two-fluid spray dryer.

[0048] Preferably, the drying temperature is 50-400℃, for example, it can be 60℃, 80℃, 100℃, 120℃, 150℃, 180℃, 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, 350℃ or 380℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0049] In this invention, the dynamic heat treatment involves subjecting the dried powder to high-temperature treatment under dynamic conditions. During the treatment, the dispersant is completely carbonized / volatilized, and an ion transport medium coating layer is formed in situ on the surface of the core substrate, thus forming a high-speed ion transport type artificial SEI film. During the dynamic heat treatment, collisions and friction occur between the materials. The resulting frictional force prevents the aggregation and nucleation of the nanoscale ion transport medium, ensuring the integrity and uniformity of the ion transport medium coating the core substrate.

[0050] Preferably, the dynamic heat treatment apparatus includes any one or a combination of at least two of the following: rotary kiln, blast drying oven, sintering furnace, tube furnace, roller kiln, VC mixer, and fusion coating machine.

[0051] More preferably, the apparatus for the dynamic heat treatment includes a rotary kiln and / or a sintering furnace.

[0052] Preferably, the dynamic heat treatment is carried out in an inert atmosphere.

[0053] Preferably, the inert atmosphere includes nitrogen and / or argon.

[0054] Preferably, the rotational speed of the dynamic heat treatment is 1-20 r / min, for example, it can be 2 r / min, 4 r / min, 5 r / min, 6 r / min, 8 r / min, 10 r / min, 12 r / min, 15 r / min or 18 r / min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0055] Preferably, the temperature of the dynamic heat treatment is 100-1500℃, for example, it can be 200℃, 400℃, 500℃, 600℃, 800℃, 1000℃, 1200℃ or 1400℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0056] Preferably, the dynamic heat treatment time is 0.5-10h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h or 9h, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0057] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0058] A blend is provided, the blend comprising a combination of a core substrate, an ion transport medium precursor, water, and a dispersant;

[0059] Based on the mass of the nuclear substrate being 100%, the mass of the ion transport medium precursor is 0.01%-10%, the mass of the dispersant is 0.01%-5%, and the mass of the water is 50%-500%.

[0060] The blend is subjected to a first shear dispersion for 0.1-5 hours to obtain a dispersion.

[0061] The dispersion forms microdroplets under second shear dispersion and heat flow conditions, and is dried at 50-400℃ to obtain powder;

[0062] The powder is subjected to dynamic heat treatment in an inert atmosphere at a temperature of 100-1500℃, a rotation speed of 1-20 r / min, and a time of 0.5-10 h to obtain the negative electrode composite material.

[0063] Secondly, the present invention provides an apparatus for preparing a negative electrode composite material, the apparatus comprising a first dispersion device, a second dispersion and drying device, and a dynamic heat treatment device connected in sequence.

[0064] Preferably, the preparation method as described in the first aspect is carried out in the preparation apparatus.

[0065] Preferably, the first dispersing device includes any one or a combination of at least two of the following: a disperser, a mixer, a homogenizer, and a rotary homogenizing circulating pump.

[0066] Preferably, the second dispersion drying device includes any one or a combination of at least two of the following: fluidized bed, flash dryer, spray dryer, rotary kiln, blast drying box, tube furnace, and roller kiln.

[0067] Preferably, the flash dryer includes an airflow flash dryer and / or a rotary flash dryer.

[0068] Preferably, the spray dryer includes a centrifugal spray dryer and / or a two-fluid spray dryer.

[0069] Preferably, the dynamic heat treatment device includes any one or a combination of at least two of the following: rotary kiln, blast drying box, sintering furnace, tube furnace, roller kiln, VC mixer, and fusion coating machine.

[0070] More preferably, the dynamic heat treatment apparatus includes a rotary kiln and / or a sintering furnace.

[0071] Thirdly, the present invention provides a negative electrode composite material, the negative electrode composite material comprising a core substrate and an ion transport type artificial SEI film disposed on the surface of the core substrate; the negative electrode composite material is prepared by the preparation method described in the first aspect.

[0072] In this invention, a high-speed ion-transport type artificial SEI film is formed on the surface of the core substrate. This ion-transport type artificial SEI film can reduce the lithium-ion desolvation and intercalation energy barrier, improve the rate performance of the core substrate (carbon material), and protect the surface of the core substrate, reducing electrolyte decomposition on the core substrate surface. The negative electrode composite material has excellent kinetic performance, cycle life, and high initial efficiency, which can significantly improve the rate performance, high-temperature performance, and cycle performance of lithium-ion batteries containing it, and reduce internal resistance.

[0073] Preferably, the core substrate comprises a negative electrode carbon material, the specific types and parameters of which are as described in the first aspect, and for the sake of brevity, will not be repeated.

[0074] Preferably, the ion-transporting artificial SEI membrane comprises any one or a combination of at least two of ion-conducting materials, conductive materials, and lithium-supplementing materials, and more preferably ion-conducting materials and / or conductive materials.

[0075] The types and parameters of the ion-conducting and conductive materials are as described in the first aspect, and for the sake of brevity, they will not be repeated here.

[0076] Preferably, the ion-transporting artificial SEI membrane comprises a combination of ion-conducting and conductive materials, and the ion-transporting artificial SEI membrane has at least one of the following structures: A-D.

[0077] Structure A: The ion-conducting material is coated on the surface of the conductive material;

[0078] Structure B: The conductive material is coated on the surface of the ion-conducting material;

[0079] Structure C: The conductive material is distributed within the ion-conducting material;

[0080] Structure D: The ion-conducting material is distributed within the conductive material.

[0081] Fourthly, the present invention provides a negative electrode material composition comprising a combination of an active material, a binder, and a conductive material, wherein the active material comprises a negative electrode composite material as described in the third aspect.

[0082] Preferably, the mass percentage of active material in the negative electrode material composition is 80-98%, for example, it can be 82%, 85%, 88%, 90%, 92%, 95% or 97%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0083] Preferably, the adhesive comprises any one or a combination of at least two of acrylic polymers, acrylate polymers, polyacrylonitrile, styrene-based copolymers, and sodium carboxymethyl cellulose (CMC).

[0084] Preferably, the styrene-based copolymer includes styrene-butadiene rubber (SBR).

[0085] Preferably, the mass percentage of the binder in the negative electrode material composition is 0.1-12%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or 11%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0086] Preferably, the conductive material includes any one or a combination of at least two of carbon black, graphite, and carbon fiber.

[0087] Preferably, the mass percentage of conductive material in the negative electrode material composition is 0.1-10%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0088] Fifthly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a current collector and a coating disposed on the current collector, the material of the coating comprising the negative electrode material composition as described in the fourth aspect.

[0089] Preferably, the method for preparing the negative electrode sheet includes: mixing the negative electrode material composition with a solvent to obtain a negative electrode slurry; coating the negative electrode slurry onto a current collector and drying it to obtain the negative electrode sheet.

[0090] Preferably, the drying process further includes a rolling step.

[0091] In a sixth aspect, the present invention provides an electrochemical energy storage device, the electrochemical energy storage device comprising at least one of the negative electrode composite material as described in the third aspect, the negative electrode material composition as described in the fourth aspect, and the negative electrode sheet as described in the fifth aspect.

[0092] Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, supercapacitors, and solid-state batteries, with lithium-ion batteries being more preferred.

[0093] Compared with the prior art, the present invention has the following beneficial effects:

[0094] (1) In the preparation method provided by this invention, an atomic layer deposition (ALD)-based surface modification technology is used to uniformly disperse the ion transport medium precursor and the core substrate, and uniformly coat and modify the ion transport medium on the surface of the core substrate to form a high-speed ion transport type artificial SEI film. The ion transport medium can reduce the energy barrier for lithium ion transport on the surface of the negative electrode material, enabling the negative electrode composite material to have better kinetic performance, higher first-pass efficiency, better high-temperature storage performance, and excellent cycle performance. The preparation method is simple to operate, low in cost, easy to scale up, and has broad application prospects.

[0095] (2) In the negative electrode composite material provided by the present invention, a uniform and tightly coated ion-transporting artificial SEI film is formed on the surface of the core substrate. The ion-transporting artificial SEI film can reduce the lithium-ion desolvation and intercalation energy barrier, improve the rate performance of the core substrate, and at the same time protect the surface of the core substrate and reduce the decomposition of the electrolyte on the surface of the core substrate. The negative electrode composite material has excellent kinetic performance, cycle life and high initial efficiency, and can significantly improve the initial efficiency, rate performance, high temperature performance and cycle performance of lithium-ion batteries containing it, and reduce internal resistance. Detailed Implementation

[0096] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0097] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0098] "Optionally", "maybe", "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event may occur and the possibility that the event may not occur.

[0099] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0100] The terms "one embodiment," "some embodiments," "exemplary," "specific example," or "some examples," etc., used in this invention refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this document, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example.

[0101] Furthermore, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0102] The following will use several embodiments as examples to describe in detail the specific components and preparation methods of the negative electrode composite material, the negative electrode sheet, and the lithium-ion battery containing the same, but the negative electrode composite material, the negative electrode sheet, and the lithium-ion battery containing the same are not limited to these embodiments.

[0103] In the following specific embodiments, the core substrate (artificial graphite, natural graphite), ion-conducting materials, conductive materials, and dispersants used are all commercially available chemicals. Specifically, sodium alginate was purchased from Maclean's S817374; sodium carboxymethyl cellulose was purchased from Maclean's C6332; and polyacrylate (sodium polyacrylate) was purchased from Maclean's 767418. The materials used to prepare the negative electrode, positive electrode, and electrolyte are all commercially available chemicals.

[0104] Example 1

[0105] Negative electrode composite materials and their preparation:

[0106] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium alginate, and 1g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is dispersed into microdroplets by a spray dryer and dried under a hot flow condition at 200℃, and the powder is collected. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0107] Negative electrode sheet and its preparation:

[0108] Using the negative electrode composite material provided in this embodiment as the active material, it was mixed with conductive carbon black SP, sodium carboxymethyl cellulose CMC, and styrene-butadiene rubber SBR at a mass ratio of 96:1:1.2:1.8 to obtain a negative electrode material composition. The negative electrode material composition was then thoroughly mixed and dispersed with deionized water to obtain a negative electrode slurry with a solid content of 52.3%. The negative electrode slurry was then uniformly coated onto a current collector (copper foil), dried, and rolled to obtain a negative electrode sheet with a double-sided coating surface density of 161 g / m². 2 The compacted density is 1.6 g / cm³. 3 .

[0109] Positive electrode sheet and its preparation:

[0110] The positive electrode active material (nickel-cobalt-manganese ternary material, NCM811), conductive carbon black SP, carbon nanotubes CNT, and polyvinylidene fluoride (PVDF5130) were mixed in a mass ratio of 96.2:1.5:1:1.3. N-methylpyrrolidone (NMP) was added and mixed thoroughly and evenly to obtain a positive electrode slurry with a solid content of 70.4%. The positive electrode slurry was uniformly coated onto an Al current collector, dried, and rolled to obtain a positive electrode sheet with a double-sided coating areal density of 375 g / m². 2 The compacted density is 3.4 g / cm³. 3 .

[0111] Lithium-ion batteries and their preparation:

[0112] Using the above-mentioned positive and negative electrode sheets, and Celegard 2400 separator, an electrolyte of 1.1M LiPF6 is injected. The solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), and also includes additives such as vinylene carbonate (VC), ethylene sulfate (DTD), and 1,3-propanesulfonate lactone (PS). The ratio of EC:EMC:DEC:VC:DTD:PS is 30:50:20:1:1:1 (mass ratio). A 2Ah pouch cell is assembled.

[0113] Example 2

[0114] A negative electrode composite material is prepared as follows: 100g of natural graphite, 1.5g of sodium alginate, and 0.5g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is then dispersed into microdroplets through a fluidized bed and dried under a hot flow condition at 100℃, and the powder is collected. The powder is placed in a sintering furnace and heated to 300℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 10h. After holding, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0115] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0116] Example 3

[0117] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.2g of sodium alginate, and 0.4g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank; 400g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 1h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a rotary flash dryer, dried under a heat flow condition at 200℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 1000℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 15r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0118] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0119] Example 4

[0120] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 3g of sodium alginate, and 0.2g of titanium dioxide nanoparticles (particle size 50nm) are weighed and added to a 500mL dispersion tank; 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by an airflow flash dryer, dried under a 100℃ heat flow condition, and the powder is collected; the powder is placed in a rotary kiln, heated to 1500℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 1h at a rotary kiln speed of 20r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0121] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0122] Example 5

[0123] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 1g of sodium alginate, and 3g of alumina nanoparticles (particle size 5-10nm) are weighed and added to a 500mL dispersion tank; 300g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a heat flow condition at 100℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 500℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0124] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0125] Example 6

[0126] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium carboxymethyl cellulose, and 2g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank; 300g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a hot flow condition at 100℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 1h at a rotary kiln speed of 5r / min; after holding at this temperature, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0127] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0128] Example 7

[0129] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 3g of sodium carboxymethyl cellulose, and 3g of lithium carbonate powder (particle size 5-15nm) are weighed and added to a 500mL dispersion tank; 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a heat flow condition at 400℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 600℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 1h at a rotary kiln speed of 5r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0130] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0131] Example 8

[0132] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 5g of sodium polyacrylate, and 1g of lithium titanate powder (particle size 1-3nm) are weighed and added to a 500mL dispersion tank; 300g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a heat flow condition of 400℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 1000℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 3h at a rotary kiln speed of 5r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0133] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0134] Example 9

[0135] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.3g of sodium carboxymethyl cellulose, and 0.5g of molybdenum oxide powder (particle size 1-3nm) are weighed and added to a 500mL dispersion tank; 500g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser; simultaneously, the slurry is circulated by a rotor homogenizing pump at a rotor speed of 2000r / min and a linear velocity of 14m / s; after dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a hot flow condition at 200℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 1500℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0136] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0137] Example 10

[0138] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium alginate, 1g of titanium dioxide nanoparticles (particle size 3-5nm), and 5g of conductive carbon black are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is dispersed into microdroplets by a spray dryer, dried under a hot flow condition at 200℃, and the powder is collected. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0139] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0140] Example 11

[0141] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium alginate, 1g of titanium dioxide nanoparticles (particle size 3-5nm), and 1g of carbon nanotubes are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is dispersed into microdroplets by a spray dryer and dried under a hot flow condition at 200℃, and the powder is collected. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0142] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0143] Example 12

[0144] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium alginate, and 1g of carbon nanotubes are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is dispersed into microdroplets by a spray dryer and dried under a hot flow condition at 200℃, and the powder is collected. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0145] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0146] Example 13

[0147] A negative electrode composite material is prepared in a manner that differs from that of Example 12 only in that 1g of carbon nanotubes is replaced with 5g of graphene. The types, amounts, and preparation methods of other materials are the same as in Example 12, thus obtaining the negative electrode composite material.

[0148] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0149] Example 14

[0150] A negative electrode composite material is prepared in a manner that differs from that of Example 9 only in that the dispersant is replaced with an equal mass of gum arabic, while the types, amounts, and preparation methods of other materials are the same as in Example 9, thus obtaining the negative electrode composite material.

[0151] Using the negative electrode composite material provided in this embodiment as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0152] Comparative Example 1

[0153] A negative electrode material, namely the artificial graphite in Example 1, was not subjected to any surface treatment.

[0154] Using artificial graphite as the active material in this comparative example, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0155] Comparative Example 2

[0156] A negative electrode composite material is prepared in a manner that differs from that of Example 1 only in that sodium alginate is not added; the types, amounts, and preparation methods of other materials are the same as in Example 1, thus obtaining the negative electrode composite material.

[0157] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0158] Comparative Example 3

[0159] A negative electrode composite material is prepared as follows: 100g of artificial graphite, 0.8g of sodium alginate, and 1g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank; 200g of deionized water is added to the dispersion tank, and the mixture is stirred at 1000r / min for 0.5h under the drive of a high-speed disperser to obtain a dispersion; the dispersion is dispersed into microdroplets by a spray dryer, dried under a heat flow condition at 200℃, and the powder is collected; the powder is placed in a rotary kiln, heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h, with the rotary kiln speed at 5r / min; after the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0160] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0161] Comparative Example 4

[0162] A negative electrode composite material is prepared as follows: 100g of graphite, 0.8g of sodium alginate, and 1g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed, mixed, and pre-milled with high-energy ball mill for 1h. The mixture is then added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is stirred at 1000r / min for 1h under the drive of a high-speed disperser to obtain a dispersion. The dispersion is then dispersed into microdroplets using a spray dryer, dried under a heat flow condition at 200℃, and the powder is collected. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h. The rotary kiln speed is 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0163] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0164] Comparative Example 5

[0165] A negative electrode composite material is prepared as follows: 100g of graphite, 0.8g of sodium alginate, and 1g of titanium dioxide nanoparticles (particle size 3-5nm) are weighed and added to a 500mL dispersion tank. 200g of deionized water is added to the dispersion tank, and the mixture is dispersed at a high speed of 1000r / min for 0.5h under the drive of a high-speed disperser. Simultaneously, a rotor homogenizing circulation pump is used to drive the slurry circulation at a rotor speed of 2000r / min and a linear velocity of 14m / s. After dispersion, the mixture is filtered through a 100-mesh sieve, and the filtrate is collected to obtain a dispersion. The dispersion is dried in a forced-air drying oven at 200℃, and the collected powder is dispersed. The powder is placed in a rotary kiln and heated to 800℃ at a rate of 2℃ / min under nitrogen purging, and held at this temperature for 2h at a rotary kiln speed of 5r / min. After the holding period, the mixture is cooled to room temperature, and the powder is collected to obtain the negative electrode composite material.

[0166] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0167] Comparative Example 6

[0168] A negative electrode composite material is prepared in a manner that differs from that of Example 1 only in that the rotary kiln is not rotated during the 800°C treatment process; the types and amounts of materials, as well as other preparation processes and parameters, are the same as in Example 1, thus obtaining the negative electrode composite material.

[0169] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0170] Comparative Example 7

[0171] A negative electrode composite material is prepared as follows: 100g of graphite is added to a VC mixer, and 6.5g of asphalt (15% residual carbon) is added. The mixture is mixed for 2 hours to obtain an asphalt-coated material. After mixing, the asphalt-coated material is added to a roller kiln and heated to 1100℃ at a rate of 2℃ / min under nitrogen purging. The temperature is maintained for 3 hours and then cooled to room temperature. The graphite with carbon coating on the surface is depolymerized to obtain the negative electrode composite material.

[0172] Using the negative electrode composite material provided in this comparative example as the active material, a negative electrode sheet was prepared and a lithium-ion battery was assembled using the same method as in Example 1.

[0173] Performance testing:

[0174] The initial coulombic efficiency of the above-mentioned soft-pack battery was tested, and the specific formation process was set as follows: 0.05C constant current charging for 120 minutes to the upper limit voltage of 3.5V, with a capacity of Q1; rest for 10 minutes; 0.15C constant current charging for 150 minutes to the upper limit voltage of 3.6V, with a capacity of Q2; after formation, it was placed in a high-temperature explosion-proof box at 45±1℃ for 8 hours.

[0175] Specific capacity grading steps are set as follows: 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C, capacity Q3; rest for 10 minutes; 0.33C constant current discharging to the lower limit voltage of 2V; rest for 10 minutes, discharge capacity Q4; 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C; rest for 10 minutes; 0.33C constant current discharging to the lower limit voltage of 2V; rest for 10 minutes; 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C;

[0176] The first effect of the sample is: Q4 / (Q1+Q2+Q3).

[0177] The rate performance of the aforementioned pouch batteries was tested within a charge / discharge voltage range of 2.75-4.2V and a temperature of 25±1.0℃. Charging was performed at 2.0C, followed by discharging at 1.0C, and the capacity retention rate was tested after 500 cycles. Internal resistance (DCR) was tested at 50% SOC under 25℃ conditions. The batteries were then stored at 60℃ for 7 days in a fully charged state, and the capacity retention rate was tested by discharging at 0.5C to 2.75V, followed by charging at 0.5C to 4.2V to test the capacity recovery rate.

[0178] The test data is shown in Table 1:

[0179] Table 1

[0180] As shown in Table 1, the present invention uses an ALD-like coating technology to coat the surface of carbon materials (graphite) with an ion transport medium to form an ion transport type artificial SEI film, which can effectively improve the kinetic performance of carbon-based anode composite materials. While reducing DCR and improving cycle performance, it does not deteriorate high-temperature storage performance, thus comprehensively improving the rate performance, high-temperature performance and cycle performance of lithium-ion batteries using it.

[0181] Furthermore, as can be seen from the comparison of Examples 7-12, ion-transporting artificial SEI films formed by different types of fast ion conductors (ion-conducting materials) can all improve the kinetics of graphite, but the improvement effects vary, and different dispersants also affect the degree of kinetic improvement. The use of conductive carbon black and carbon nanotubes as conductive materials in conjunction with ion-conducting materials to form ion-transporting artificial SEI films can comprehensively improve battery performance and kinetics.

[0182] A comparison of Example 1 and Comparative Examples 1-7 shows that the ALD-like surface coating technology provided by this invention is crucial to the performance of the negative electrode composite material. In Comparative Example 2, no dispersant was added, and in Comparative Example 3, no first-phase shear dispersion in the liquid phase was performed, resulting in uneven coating of the graphite by the ion transport medium, preventing the prepared negative electrode composite material from achieving the expected performance improvement. A comparison of Example 1 and Comparative Example 4 shows that replacing the first-phase shear dispersion with high-speed ball milling significantly reduces graphite performance because the high shear force of ball milling damages the graphite structure. A comparison of Example 1 and Comparative Example 5 shows that the failure to atomize the dispersion into droplets and instantly dry it through second-phase shear dispersion results in limited improvement in graphite performance. A comparison of Example 1 and Comparative Example 6 shows that this invention employs dynamic heat treatment, which allows the ion transport medium to be uniformly coated on the graphite surface through frictional collisions between material particles, effectively improving the material's kinetic properties; Comparative Example 6, lacking dynamic heat treatment, resulted in the ion transport medium tending to agglomerate, limiting the improvement in kinetics.

[0183] A comparison of Example 1, Comparative Example 1, and Comparative Example 7 shows that conventional surface carbon coating modification can reduce battery DCR and improve kinetics, but surface carbon coating will significantly deteriorate high-temperature performance and worsen the cycle performance of the cell. The mechanism is that surface carbon coating will exacerbate the decomposition of electrolyte on the graphite surface and trigger a series of side reactions.

[0184] The applicant declares that the present invention illustrates the negative electrode composite material, its preparation method, and its application through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a negative electrode composite material, characterized in that, The negative electrode composite material includes a core substrate and an ion-transporting artificial SEI film disposed on the surface of the core substrate; the ion-transporting artificial SEI film is obtained by an atomic layer deposition method.

2. The preparation method according to claim 1, characterized in that, The atomic-layer-like deposition method includes the following steps: A blend is provided, the blend comprising a combination of a core substrate, an ion transport medium precursor, a dispersant, and a solvent; The blend is subjected to a first shear dispersion to obtain a dispersion; The dispersion was dried under second shear dispersion and heat flow conditions to obtain a powder. The powder is subjected to dynamic heat treatment to obtain the negative electrode composite material.

3. The preparation method according to claim 2, characterized in that, The core substrate includes a negative electrode carbon material, preferably any one or a combination of at least two of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres; Preferably, the mass of the ion transport medium precursor is 0.01%-10% based on the mass of the nuclear substrate being 100%; Preferably, the ion transport medium precursor includes any one or a combination of two of the following: ion-conducting materials and conductive materials. Preferably, the ion-conducting material includes any one or a combination of at least two of the following: lithium salt, lithium oxide, transition metal oxide, transition metal phosphide, transition metal sulfide, half-metal oxide, elemental phosphorus, elemental sulfur, and other solid electrolytes. Preferably, the ion-conducting material comprises any one or a combination of at least two of the following: lithium carbonate, lithium silicate, lithium metasilicate, lithium phosphate, lithium metaphosphate, lithium hypophosphite, lithium borate, lithium titanate, lithium oxide, lithium fluoride, lithium aluminate, lithium phosphide, lithium sulfide, lithium nickelate, calcium oxide, zinc oxide, aluminum oxide, zirconium oxide, zirconium nitride, zirconium phosphide, molybdenum oxide, molybdenum nitride, molybdenum phosphide, molybdenum sulfide, molybdenum borate, silicon suboxide, silicon dioxide, titanium dioxide, elemental phosphorus, elemental sulfur, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolyte. Preferably, the average particle size of the ion-conducting material is 1-1000 nm; Preferably, the conductive material includes any one or a combination of at least two of graphene, carbon nanotubes, conductive carbon black, amorphous carbon, soft carbon, and hard carbon. Preferably, the ion transport medium precursor comprises a combination of an ion-conducting material and a conductive material, wherein the mass ratio of the ion-conducting material to the conductive material is 1:(0.1-10).

4. The preparation method according to claim 2 or 3, characterized in that, The solvent is water; Preferably, the solvent has a mass of 50%-500% based on 100% of the core substrate. Preferably, the mass of the dispersant is 0.01%-5% based on 100% of the mass of the core substrate; Preferably, the dispersant comprises any one or a combination of at least two of carboxymethyl cellulose salt, alginate, (meth)acrylic acid homopolymer salt, and (meth)acrylic acid copolymer salt.

5. The preparation method according to any one of claims 2-4, characterized in that, The first shear dispersion device includes any one or a combination of at least two of the following: a disperser, a mixer, a homogenizer, and a rotor homogenizing circulation pump; Preferably, the first shear dispersion time is 0.1-5 hours; Preferably, the drying apparatus includes any one or a combination of at least two of the following: fluidized bed, flash dryer, spray dryer, rotary kiln, blast drying box, tube furnace, and roller kiln; Preferably, the flash dryer includes an airflow flash dryer and / or a rotary flash dryer; Preferably, the spray dryer includes a centrifugal spray dryer and / or a two-fluid spray dryer; Preferably, the drying temperature is 50-400℃; Preferably, the apparatus for dynamic heat treatment includes any one or a combination of at least two of the following: rotary kiln, blast drying oven, sintering furnace, tube furnace, roller kiln, VC mixer, and fusion coating machine; Preferably, the apparatus for dynamic heat treatment includes a rotary kiln and / or a sintering furnace; Preferably, the dynamic heat treatment is carried out in an inert atmosphere; Preferably, the rotational speed of the dynamic heat treatment is 1-20 r / min; Preferably, the temperature of the dynamic heat treatment is 100-1500℃; Preferably, the dynamic heat treatment time is 0.5-10 hours.

6. An apparatus for preparing a negative electrode composite material, characterized in that, The preparation apparatus includes a first dispersion device, a second dispersion and drying device, and a dynamic heat treatment device connected in sequence. Preferably, the preparation method according to any one of claims 1-5 is carried out in the preparation apparatus; Preferably, the first dispersing device includes any one or a combination of at least two of a disperser, a mixer, a homogenizer, and a rotary homogenizing circulating pump; Preferably, the second dispersion drying device includes any one or a combination of at least two of the following: fluidized bed, flash dryer, spray dryer, rotary kiln, blast drying box, tube furnace, and roller kiln; Preferably, the flash dryer includes an airflow flash dryer and / or a rotary flash dryer; Preferably, the spray dryer includes a centrifugal spray dryer and / or a two-fluid spray dryer; Preferably, the dynamic heat treatment apparatus includes a rotary kiln and / or a sintering furnace.

7. A negative electrode composite material, characterized in that, The negative electrode composite material includes a core substrate and an ion-transporting artificial SEI membrane disposed on the surface of the core substrate; the negative electrode composite material is prepared by the preparation method according to any one of claims 1-5.

8. A negative electrode material composition, characterized in that, The negative electrode material composition comprises a combination of an active material, a binder, and a conductive material, wherein the active material comprises the negative electrode composite material as described in claim 7.

9. A negative electrode sheet, characterized in that, The negative electrode sheet includes a current collector and a coating disposed on the current collector, wherein the material of the coating includes the negative electrode material composition as described in claim 8.

10. An electrochemical energy storage device, characterized in that, The electrochemical energy storage device includes at least one of the negative electrode composite material as described in claim 7, the negative electrode material composition as described in claim 8, and the negative electrode sheet as described in claim 9; Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, supercapacitors, and solid-state batteries.

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