Composite electrode material and preparation method thereof, lithium battery and electronic equipment

Abstract

The present application discloses a composite electrode material and a preparation method thereof, a lithium battery and an electronic device. The composite electrode material comprises an electrode material core and a coated organic fiber skeleton. The ‑CO‑NH‑ or ‑C=N‑ contained in the organic fiber can form abundant hydrogen bonds with the ‑OH on the surface of the electrode material core, so that the organic fibers are mutually entangled and composited on the surface of the electrode material core, thereby forming a strong organic fiber skeleton on the surface of the electrode material core. The high strength characteristics and small tensile strain of the organic fiber skeleton can limit the volume expansion of the electrode material while ensuring that it is not prone to plastic deformation. Furthermore, it can improve the battery cycle stability, reduce the proportion of the battery in the internal cavity of the electronic device, increase the available cavity space of key components such as chips and circuit boards in the electronic device, avoid problems such as battery bulging and back cover warping after long cycles, and improve the life and safety of electronic products.

Description

Technical Field

[0001] The present application relates to the technical field of electrode materials, and in particular to a composite electrode material and a preparation method thereof, a lithium battery and an electronic device. Background Art

[0002] Secondary batteries and alkali metal batteries, particularly lithium-ion batteries, have become the mainstream battery technology in consumer electronics, electric vehicles, electric boats, power tools, and shared battery swapping markets due to their high energy efficiency, environmental friendliness, and high energy density. Battery swelling is a common safety failure mode in lithium-ion batteries. The primary cause of this swelling is the gradual expansion of the electrode thickness during cycling. This expansion is caused by crystal expansion during lithium insertion and extraction in the positive and negative electrode materials, surface SEI instability caused by this expansion, and repeated film formation. Consequently, some electrode materials with high capacity characteristics have been hindered from widespread application due to their high expansion rates. For example, silicon, with a theoretical capacity of up to 4200 mAh / g, is a highly anticipated next-generation anode material in the field. However, silicon-based anode materials can expand by as much as 300%. Therefore, the degradation of battery cycling performance and swelling caused by this expansion are major challenges to the widespread application of silicon batteries.

[0003] To address the issue of electrode material crystal expansion, many people skilled in the art have limited the crystal expansion of electrode materials by coating the surface of electrode material crystal particles with carbonaceous materials or ceramic materials. However, for carbonaceous materials, excessive coating will affect the efficiency of reversible lithium insertion and extraction, and due to their insufficient structural strength, the improvement effect on electrode material crystal expansion is relatively small. As for ceramic materials, although their structural strength is more effective in improving crystal expansion, they are very prone to plastic deformation. Therefore, when the crystal expansion force or expansion degree is large, the ceramic material layer on the crystal surface will break and lose its effect. Summary of the Invention

[0004] The present application provides a composite electrode material and a preparation method thereof, a lithium battery and an electronic device to solve the problem of electrode volume expansion.

[0005] In a first aspect, the present application provides a composite electrode material comprising an electrode material core and an organic fiber coating having a skeletal structure, the organic fiber coating being bonded to the surface of the electrode material core; the organic fiber contains at least one of -CO-NH- and -C=N-, as well as a benzene ring structure. The -CO-NH- or -C=N- contained in the organic fiber can form abundant hydrogen bonds with the -OH groups on the surface of the electrode material core, allowing the organic fibers to intertwine and bond to the surface of the electrode material core, thereby forming a strong coating with a skeletal structure on the surface of the electrode material core. The high strength and low tensile strain of the organic fiber coating can limit the volume expansion of the electrode material while ensuring that the coating itself is not susceptible to plastic deformation.

[0006] In an optional implementation of the first aspect, the organic fiber further comprises -COOH and / or -NH2. Based on the -COOH and / or -NH2, the organic fiber can form abundant hydrogen bonds with the -OH groups on the surface of the electrode material core, thereby firmly bonding the organic fiber to the core surface and stably reducing the volume expansion of the electrode.

[0007] In an optional implementation of the first aspect, the mass proportion of organic fibers in the composite electrode material is 0.05%-1%. This composite ratio allows the organic fibers to form a coherent and uniform skeleton structure on the surface of the electrode material, ensuring the coating effect. In addition, this composite ratio does not cause changes in the crystal structure and phase characteristics of the electrode material crystal particles, thereby ensuring the stability of the electrochemical properties of the electrode material while limiting the volume expansion of the electrode material. In other words, this composite ratio can take into account both the expansion-limiting effect of the organic fiber skeleton on the electrode material and the charge conduction ability of the material surface.

[0008] In an optional implementation of the first aspect, the benzene ring structure is located in the macromolecular chain of the organic fiber, thereby forming a stronger intermolecular conjugation effect, and such organic fiber has higher stability.

[0009] In an optional implementation of the first aspect, the breaking strength of the organic fiber is greater than 3 cN·dtex -1 , the initial modulus of the above organic fiber is greater than 50cN·dtex -1 , thereby ensuring the structural strength of the organic fiber and its binding effect on the electrode material.

[0010] In an optional implementation of the first aspect, the thickness of the organic fiber coating layer is 10 nm-200 nm.

[0011] In an optional implementation of the first aspect, the diameter of the organic fiber is 5 nm-60 nm, and the length is 200 nm-20 μm. This aspect ratio can form an optimal winding and coating effect with a smaller composite amount.

[0012] In an optional implementation of the first aspect, the organic fiber is aramid fiber, polyaromatic oxadiazole fiber or aromatic sulfone fiber.

[0013] In an optional implementation of the first aspect, the aramid chain segment content in the aramid fiber is greater than 85%, the diameter of the aramid fiber is 5nm-40nm, and the length is 2μm-20μm. This aspect ratio can form the best winding and coating effect with a smaller composite amount.

[0014] In an optional implementation of the first aspect, the composite electrode material includes composite particles and / or polymer particles, the composite particles include an electrode material core and an organic fiber coating layer composited on the surface of the electrode material core by bonding, and the polymer particles are formed by polymerization of the composite particles.

[0015] Optionally, the composite particles include primary composite particles and secondary composite particles, wherein the core of the primary composite particles is the core of the electrode material, and the core of the secondary composite particles is a polymer particle formed by the polymerization of the primary composite particles. In other words, the particles constituting the composite electrode material may be one or more of primary composite particles, secondary composite particles, and polymer particles of primary composite particles and / or secondary composite particles. Since the particle structure and particle size of the primary composite particles, secondary composite particles, and polymer particles thereof are different, when the composite electrode material contains multiple particles, the multiple particles complement each other in performance, and the particle size distribution of the composite electrode material can be adjusted by adjusting the content of each particle, thereby adjusting the compaction density of the composite electrode material.

[0016] In an optional implementation of the first aspect, the composite electrode material further includes a conductive agent and / or an ion conductor. The addition of the conductive agent and / or ion conductor can compensate for the reduced electrical conductivity of the composite electrode material caused by the non-conductive organic fibers, thereby ensuring the surface charge conductivity of the composite electrode material.

[0017] In an optional implementation of the first aspect, the conductive agent and / or ion conductor is coated on the surface of the composite particles and / or polymer particles, or is mixed between the composite particles and / or polymer particles.

[0018] In an optional implementation of the first aspect, the conductive agent includes a combination of one or more of amorphous carbon, soft carbon, hard carbon, graphite, carbon nanotubes, graphene, and metal particles.

[0019] In an optional implementation of the first aspect, the electrode material includes a ternary positive electrode material, a silicon-based, tin-based, sulfur-based, and metallic lithium negative electrode material.

[0020] In a second aspect, the present application also provides a method for preparing a composite electrode material, comprising: preparing an organic fiber solution, the organic fiber containing at least one of -CO-NH- and -C=N-, and a benzene ring structure; adding an electrode material to the organic fiber solution according to a predetermined compounding ratio and stirring until uniformly dispersed; and drying the mixture of the electrode material and the organic fiber to obtain a composite electrode material. The composite electrode material comprises an electrode material core and an organic fiber coating having a skeletal structure, the organic fiber coating being bonded to the surface of the electrode material core. The -CO-NH- or -C=N- contained in the organic fiber can form abundant hydrogen bonds with the -OH groups on the surface of the electrode material core, allowing the organic fibers to intertwine and bond to the surface of the electrode material core, thereby forming a strong, skeletal coating on the surface of the electrode material core. The high strength and low tensile strain of the organic fiber coating can limit the volume expansion of the electrode material while ensuring that the coating itself is not susceptible to plastic deformation.

[0021] In a third aspect, the present application further provides a composite electrode material, which is prepared using the preparation method described in the second aspect.

[0022] In a fourth aspect, the present application also provides an application of a composite electrode material in the field of preparing lithium batteries.

[0023] In a fifth aspect, the present application also provides a lithium battery comprising a positive electrode material, an electrolyte, a separator and a negative electrode material, wherein the positive electrode material or the negative electrode material adopts the composite electrode material described in any implementation manner in the first aspect.

[0024] In a sixth aspect, the present application also provides an electronic device, comprising a charging and discharging circuit and electrical components, and also comprising the lithium battery described in the fifth aspect, wherein the lithium battery is connected to the charging and discharging circuit and is charged through the charging and discharging circuit or supplies power to the electrical components.

[0025] By using the composite electrode material and its preparation method provided in the embodiments of the present application, a lithium battery including the composite electrode material and an electronic device including the lithium battery can be obtained. The composite electrode material includes an electrode material core and an organic fiber coating layer with a skeleton structure, and the organic fiber coating layer is composited on the surface of the electrode material core through a bonding action. Among them, the -CO-NH- or -C=N- contained in the organic fiber can form abundant hydrogen bonds with the -OH on the surface of the electrode material core, so that the organic fibers are intertwined and composited on the surface of the electrode material core, thereby forming a strong and skeleton-structured coating layer on the surface of the electrode material core. The high strength characteristics and small tensile strain of the organic fiber coating layer can limit the volume expansion of the electrode material, while ensuring that the coating layer itself is not prone to plastic deformation. Furthermore, it can improve the battery cycle stability, reduce the proportion of the battery in the internal cavity of the electronic device, increase the available cavity space for key components such as chips and circuit boards in the electronic device, avoid problems such as battery bulging and back cover warping after long cycles, and improve the life and safety of electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 This is a schematic diagram of the lithium-ion battery structure exemplified in this application;

[0028] Figure 2 A schematic diagram of the structure of a lithium-ion battery composite electrode material provided in an embodiment of the present application;

[0029] Figure 3 A schematic diagram of the structure of a lithium-ion battery composite electrode material provided in an embodiment of the present application;

[0030] Figure 4 A schematic diagram of the structure of a lithium-ion battery composite electrode material provided in an embodiment of the present application;

[0031] Figure 5 A schematic diagram of the structure of a lithium-ion battery composite electrode material provided in an embodiment of the present application;

[0032] Figure 6 The stress-strain curves of aramid, aramid sulfone, polyoxadiazole, styrene-butadiene rubber, and polyacrylic acid provided in the examples of this application;

[0033] Figure 7 A flow chart of the method for preparing a composite electrode material provided in an embodiment of the present application;

[0034] Figure 8 This is an electron microscope image of the aramid nanofiber composite silicon oxide prepared in Example 2;

[0035] Figure 9 This is an electron microscope image of the secondary composite particles of arylsulfone nanofibers and silicon oxide prepared in Example 5. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0037] Figure 1 This is a schematic diagram of the lithium-ion battery structure exemplified in this application. The lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, a separator, and corresponding circuits. The positive and negative electrode materials can intercalate and deintercalate lithium ions to achieve energy storage and release. The electrolyte is a carrier for lithium ions to be transferred between the positive and negative electrodes. The non-conductive separator is permeable to lithium ions but separates the positive and negative electrodes to prevent short circuits. The positive and negative electrode materials are the main components that perform the energy storage function and are the most direct embodiment of the energy density, cycle performance, and safety performance of the battery cell.

[0038] In one implementation, in the lithium-ion battery, the positive electrode may include an aluminum electrode plate and a positive electrode material, wherein the positive electrode material includes, for example, a ternary positive electrode material lithium nickel cobalt manganese oxide LiNixCoyMnzO2, wherein the ratio of nickel, cobalt and manganese (x:y:z) can be adjusted according to actual needs.

[0039] In one implementation, in the lithium-ion battery, the negative electrode may include a copper electrode plate and a negative electrode material, and the negative electrode material includes a carbon material, a silicon-based material, a tin-based material, a sulfur-based material, a metallic lithium material, and the like.

[0040] For example, when a lithium-ion battery is charging, lithium ions are extracted from the lattice of the positive electrode material, then embedded in the negative electrode material after passing through the electrolyte, making the negative electrode lithium-rich and the positive electrode lithium-poor. When a lithium-ion battery is discharging, lithium ions are extracted from the negative electrode material, then embedded in the lattice of the positive electrode material after passing through the electrolyte, making the positive electrode lithium-rich and the negative electrode lithium-poor. The difference in potential between the positive and negative electrode materials relative to metallic lithium during the insertion and extraction of lithium ions is the operating voltage of the battery.

[0041] For ease of explanation, in the following embodiments, positive electrode materials and negative electrode materials are collectively referred to as electrode materials. That is, unless otherwise specified, the electrode materials in the following embodiments refer to positive electrode materials and / or negative electrode materials, and composite electrode materials refer to composite positive electrode materials and / or composite negative electrode materials.

[0042] As electronic products increasingly demand higher energy density and faster charging capabilities, lithium-ion battery safety incidents are becoming more frequent, causing widespread concern in the market and among users. Bulging of soft-pack lithium-ion batteries is a common safety failure mode in certain electronic products. This is often caused by the increased thickness of the electrode sheets, which results from the volume expansion of electrode material crystal particles during cyclic charge and discharge.

[0043] For this reason, some electrode materials with high capacity characteristics have been hindered from widespread application due to their high expansion rate. For example, silicon-based anode materials, with a theoretical capacity of up to 4200 mAh / g, are highly anticipated as next-generation anode materials in this field. However, during charging, crystalline silicon undergoes Si-Si bond rupture, forming a lithium-silicon alloy. This process is accompanied by significant volume expansion. Within the material itself, this volume expansion generates significant shear stress, causing silicon particles to fracture, increasing internal resistance and hindering direct electron transport across the electrode. Within the electrode as a whole, the stress induced by volume expansion can damage the electrode structure, including shedding of active material and delamination from the binder and conductive network, leading to capacity decay. Furthermore, volume expansion can cause the SEI on the silicon surface to destabilize, leading to repeated rupture and the continuous generation of a new SEI film with the electrolyte. This consumes a large amount of lithium ions, resulting in a gradual thickening of the SEI, hindering electron transfer and lithium ion diffusion, and increasing impedance and polarization. Furthermore, volume expansion can cause previously dispersed silicon particles to fuse after lithium insertion, resulting in localized increases in particle size, which is detrimental to later cycling and stress release. It can be seen that the battery cycle performance degradation and battery swelling caused by the volume expansion of silicon-based negative electrode materials have become the biggest challenges to the widespread application of silicon-based materials.

[0044] To address the issue of volume expansion in electrode materials, embodiments of the present application provide a composite electrode material and a method for preparing the same. The composite electrode material is an active material for lithium-ion batteries and is used to make electrodes. This composite electrode material uses the electrode material as its core material and, through an organic fiber skeleton structure coated on the outer layer of the core material, effectively limits the volume expansion of the core material.

[0045] Figures 2 to 5 This is a schematic diagram of the structure of the lithium-ion battery composite electrode material provided in the embodiments of the present application.

[0046] See Figure 2In certain embodiments, the composite electrode material comprises an electrode material core 201 and an organic fiber coating 202 having a skeleton structure. The organic fiber coating 202 is composed of organic fibers bonded to the surface of the electrode material core 201. In other words, the organic fibers adhere to and entangle with each other while coating the surface of the electrode material core 201, forming an organic fiber skeleton on the surface of the electrode material core 201. The high strength and low tensile strain of the organic fiber skeleton can limit the volume expansion of the electrode material while ensuring that the organic fiber skeleton itself is not easily deformed.

[0047] It should be noted that the so-called bonding effect between the organic fiber and the electrode material core in this application is not limited to referring to chemical bonds such as metal bonds, ionic bonds and covalent bonds, but also refers to hydrogen bonds. Among them, the molecular structure of the organic fiber contains at least one of -CO-NH- and -C=N-, as well as a benzene ring structure. Among them, the benzene ring structure is located in the macromolecular chain of the organic fiber, thereby forming a strong intermolecular conjugation effect, which provides a force for the mutual adhesion and entanglement between the organic fibers, thereby ensuring the structural strength and stability of the skeleton structure. -CO-NH- or -C=N- can form abundant hydrogen bonds with -OH on the surface of the electrode material core, and hydrogen bonds provide binding force between the organic fiber and the electrode material core, so that the organic fiber is firmly compounded on the surface of the electrode material core.

[0048] In some embodiments, the organic fiber may further contain -COOH and / or -NH2. Based on -COOH and / or -NH2, the organic fiber can form abundant hydrogen bonds with -OH groups on the surface of the core material, so that the organic fiber is firmly bonded to the surface of the core material, thereby playing a role in stably reducing the volume expansion of the core material.

[0049] It should be noted that the organic fiber coating is not limited to being bonded to the surface of the electrode material via hydrogen bonding. For example, in certain embodiments, a specific chemical treatment method can be used to graft groups that can form stable chemical bonds with the electrode material onto the chain structure of the organic fiber, thereby allowing the organic fiber to be bonded to the surface of the electrode material core via chemical bonding.

[0050] It is worth noting that the mass proportion of organic fibers in the composite electrode material is a key factor affecting the strength of the skeleton structure and the coating effect, and thus is also a key factor affecting the effect of limiting the volume expansion of the core material. Specifically, when the composite ratio is too low, the skeleton structure formed by the organic fibers is not coherent enough, the gaps are too large, and it is impossible to form a coherent coating effect on the surface of the core material, and the ability to limit the expansion of the core material is insufficient; when the composite ratio is too high, the poor conductivity of the organic fibers will lead to a decrease in the surface charge conduction ability of the core material, affecting the rate performance.

[0051] In some embodiments, the mass proportion of organic fibers in the composite electrode material is 0.05%-1%. This composite ratio allows the organic fibers to form a coherent and uniform skeleton structure on the surface of the core material, ensuring the coating effect. In addition, this composite ratio will not cause changes in the crystal structure and phase characteristics of the core material crystal particles, thereby ensuring the stability of the electrochemical properties of the electrode material while limiting the volume expansion of the electrode material. In other words, this composite ratio can take into account both the expansion-limiting effect of the organic fiber skeleton on the core material and the charge conduction ability of the material surface.

[0052] In some embodiments, the breaking strength of the organic fiber is greater than 3 cN·dtex -1 , the initial modulus of the above organic fiber is greater than 50cN·dtex -1 , thereby ensuring the structural strength of the organic fiber and its binding effect on the electrode material.

[0053] In some embodiments, the organic fibers have a diameter of 5 nm to 60 nm and a length of 200 nm to 1 μm and 1 μm to 20 μm. In other words, the organic fibers have an aspect ratio greater than 30. A suitable aspect ratio can achieve optimal winding and coating effects with a relatively small composite weight.

[0054] In certain embodiments, the thickness of the organic fiber coating layer is 10 nm-200 nm.

[0055] As an example, the organic fiber skeleton is composed of aramid fiber. Aramid fiber is an aromatic polyamide fiber, mainly including poly-p-phenylene diamine terephthalamide fiber (PPTA), hereinafter referred to as para-aramid fiber, and poly-metaphenylene isophthalamides (MPIA), hereinafter referred to as meta-aramid fiber. The molecular structure of meta-aramid fiber is as follows (1), and the molecular structure of para-aramid fiber is as follows (2):

[0056]

[0057] In some implementations, the diameter of the aramid fiber is 5 nm to 40 nm, and the length is 2 μm to 20 μm. Using aramid fiber with an appropriate aspect ratio can form the best winding and coating effect with a smaller composite amount.

[0058] As an example, the organic fiber skeleton is composed of aromatic polyoxadiazole fiber. Polyaromatic polyoxadiazole fiber (POD) has a molecular structure in which the main chain contains benzene rings and oxadiazole rings, the chain segments contain aromatic groups, and the macromolecular chain is a rigid rod-like structure. Its molecular structure is as follows (3):

[0059]

[0060] As an example, the organic fiber skeleton is composed of aromatic sulfone fiber. Aromatic sulfone, also known as polysulfonamide fiber (PSA), is an aromatic polyamide fiber containing a sulfone group (-SO2-) on the polymer backbone. Its chemical name is terephthaloyl-3,3-4,4-diaminodiphenylsulfone fiber. The fiber-forming polymer polysulfoneamide is formed by the condensation of terephthaloyl chloride, 4,4'-diaminodiphenylsulfone (4,4'-DDS), and 3,3'-diaminodiphenylsulfone (3,3'-DDS). It is a linear macromolecule composed of para- and meta-phenyl groups connected by amide and sulfone groups. Its molecular structure is shown in the following formula (4).

[0061]

[0062] In some embodiments, the organic fiber polymer used to prepare the composite electrode material has a film-forming tensile stress greater than 5 MPa and a tensile strain less than 50%, so as to ensure that the organic fiber skeleton formed on the surface of the core material has high strength characteristics and low tensile strain characteristics, thereby effectively limiting the volume expansion of the electrode material while ensuring that it itself is not prone to plastic deformation.

[0063] For example, the organic polymers that can be used to prepare composite electrode materials can be selected by testing the film-forming tensile stress and tensile strain of various organic polymers. For example, the film-forming performance tests are carried out on aramid, sulfone and polyoxadiazole, styrene-butadiene rubber and polyacrylic acid. Specifically, first, aramid slurry, sulfone and polyoxadiazole slurry, styrene-butadiene rubber slurry and polyacrylic acid slurry are prepared respectively; then, according to the predetermined solid content, appropriate amounts of the above slurries are injected into the polytetrafluoroethylene mold frame, and air-dried at room temperature to form a film; the film is cut into 30mm×3mm strips, and the DMA-800 instrument of TA Company is used to test the tensile properties of the sample. The test conditions specifically include: test mode: controlled force mode (DMA Controlled force), test target: stress-strain (Stress-Strain), fixture: tensile film (Tensile Film), preload force: 0.1N, constant temperature: 25℃, standing time: 1min, lifting rate: 1N / min; after testing, the following results are obtained: Figure 6The stress-strain curves shown are as follows. A is the stress-strain curve of styrene-butadiene rubber film, B is the stress-strain curve of polyacrylic acid film, C is the stress-strain curve of arylsulfone film, D is the stress-strain curve of aramid film, and E is the stress-strain curve of polyoxadiazole film.

[0064] It can be seen that the film-forming tensile stress of aramid, arylsulfone and polyoxadiazole is greater than 5MPa, and the tensile strain is less than 50%. The film-forming tensile stress of styrene-butadiene rubber is less than 5MPa, and the tensile strain is greater than 500%. The film-forming tensile stress of polyacrylic acid is greater than 5MPa, and the tensile strain is greater than 300%.

[0065] It should be noted that, in the present application, the organic fiber skeleton compounded on the surface of the core material is formed by high-strength nanofibers entwined with each other. Based on the high-strength characteristics of the organic fiber skeleton, the volume expansion of the electrode material can be effectively limited. It is worth noting that some schemes that use organic polymers for coating to limit expansion utilize the elasticity and toughness of the polymer coating layer without considering the strength of the polymer coating layer. Different from the rigid limiting effect of the organic fiber skeleton described in the present application, the effect of this type of polymer coating layer is similar to that of "gummy candy". In addition, since the structure of this type of polymer coating layer is different from the structure of the organic fiber skeleton in the present application, the principles and effects of the two limiting the expansion of the core material are also different.

[0066] In certain embodiments, the main particles of the composite electrode material include composite particles and / or polymer particles. Composite particles refer to particles based on a core body with an organic fiber coating layer on the surface of the core body. It should be understood that the particle structures of composite particles based on different core bodies are different. For details, see Figures 2 to 5 Aggregate particles refer to composite particle clusters formed by the aggregation of one or more types of composite particles.

[0067] Figure 2 An example of composite particles is shown schematically. Figure 2 As shown, the composite particle 200 may include an electrode material core 201 and an organic fiber skeleton 202 composited on the surface of the electrode material core 201. Figure 2 The composite particles shown in the figure, which have electrode material crystal particles as the core and are covered with an organic fiber skeleton, are called primary composite particles.

[0068] Figure 3 Another example of composite particles is shown. Figure 3 As shown, the composite particle 300 may include a core group 301 formed by agglomerating a plurality of electrode material cores 201 and an organic fiber skeleton 302 composited on the outer surface of the core group 301 .

[0069] It should be understood that the composite particles may also include composite particle clusters formed by agglomerating multiple primary composite particles and an organic fiber skeleton composited on the outer surface of the composite particle clusters. For ease of explanation, the composite particles having a core cluster and / or composite particle clusters as the core and coated with an organic fiber skeleton may be referred to as secondary composite particles.

[0070] Figure 4 An example of polymer particles is shown schematically. Figure 4 As shown, the polymer particles 400 are formed by agglomerating the primary composite particles 200 .

[0071] Figure 5 An example of polymer particles is shown schematically. Figure 5 As shown, the polymer particles 500 are formed by agglomerating the secondary composite particles 300 .

[0072] It should be noted that the structures of the polymer particles provided in this application include but are not limited to the above Figure 4 and Figure 5 For example, the polymer particles can also be formed by polymerizing primary composite particles and secondary composite particles.

[0073] In other words, the main particles comprising the composite electrode material can be one or more of primary composite particles, secondary composite particles, and aggregated particles of primary and / or secondary composite particles. Because the primary composite particles, secondary composite particles, and aggregated particles thereof all have different particle structures and particle sizes, when the composite electrode material comprises multiple types of particles, the various particles complement each other in terms of performance. The particle size distribution of the composite electrode material can also be adjusted by adjusting the content of each type of particle, thereby adjusting the compaction density of the composite electrode material.

[0074] It should be understood that secondary composite particles and polymer particles can be obtained by granulation. Among them, the core cluster mentioned above can be obtained by bonding multiple cores. In other words, the core cluster can be formed by the aggregation of multiple cores, and the particle cluster can refer to the particle cluster obtained by bonding particles with an organic fiber skeleton. Exemplary, the method of obtaining secondary composite particles and polymer particles can be, for example: by controlling the temperature of the core material particles or composite particles, so that the core material particles and the composite particles form core clusters or particle clusters through the adhesion of their own materials; or, by adding a binder, the core material particles and the composite particles have adhesion, thereby forming core clusters or particle clusters. Among them, the method of obtaining secondary particles by granulation is not limited to this, and this application is not limited to this.

[0075] In some embodiments, the composite electrode material further includes a conductive agent. The addition of the conductive agent can compensate for the problem of weakened conductivity of the composite electrode material caused by the non-conductive organic fibers, thereby ensuring the surface charge conduction ability of the composite electrode material. The conductive agent includes, but is not limited to, one or a combination of amorphous carbon, soft carbon, hard carbon, graphite, carbon nanotubes, graphene, metal particles, etc.

[0076] In some embodiments, the composite electrode material further includes an ion conductor. The addition of the ion conductor can improve the lithium ion diffusion ability of the composite electrode material. The ion conductor includes, but is not limited to, solid electrolytes such as oxides and sulfides, and materials with multi-dimensional lithium ion channels.

[0077] In an alternative implementation, the conductive agent and / or the ion conductor is coated on the surface of the composite particles and / or the polymer particles, or mixed between the composite particles and / or the polymer particles.

[0078] In some embodiments, the electrode material for preparing the above composite electrode material, that is, the core material, can be a positive electrode material or a negative electrode material. Among them, the positive electrode material can be a ternary material. The negative electrode material can be materials such as silicon-based, tin-based, sulfur-based, metallic lithium, etc., such as silicon, nano-silicon, micro-silicon, silicon oxide, silicon monoxide (SiOx, 0 < x < 2), silicon carbide (Si / C), porous silicon, thin film silicon, tin, tin dioxide, silicon-tin alloy, lithium-silicon alloy, lithium-phosphorus alloy, lithium titanate, etc.

[0079] It should be understood that the above-listed negative electrode materials and positive electrode materials of the lithium ion battery are only exemplary examples, and it can also include many other materials, which are not limited in the embodiments of the present application.

[0080] The preparation method of the composite electrode material provided by the embodiments of the present application is introduced below. Figure 7 The flowchart of the preparation method of the composite electrode material provided by the embodiments of the present application is shown. As Figure 7 shown, it can include the following steps:

[0081] S701, prepare an organic fiber solution, the molecular structure of the organic fiber contains at least one of -CO-NH- and -C=N-, and a benzene ring structure.

[0082] In some embodiments, a nano-scale organic fiber solution is prepared through S701. For the convenience of description, it is hereinafter referred to as a nanofiber solution.

[0083] Among them, the organic nanofiber solution can be prepared using the precursor of the organic fiber molecule as the initial raw material. The precursor here refers to the premise that the organic fiber molecule is the target product. In other words, the precursor of the organic fiber molecule is the form of existence before the organic fiber molecule is obtained. Taking aramid fiber as an example, in the embodiment of using p-phenylenediamine and terephthaloyl chloride to prepare aramid fiber, p-phenylenediamine and terephthaloyl chloride are precursors. The nanofiber solution can also be prepared using a fiber-forming polymer as the initial raw material. The fiber-forming polymer here is the original fibril fiber, which refers to a large-sized fiber relative to nanofibers. For example, large-sized aramid fibers can be used to prepare aramid nanofibers.

[0084] Specifically, the methods for preparing the nanofiber solution include, but are not limited to: polymerization-induced self-assembly, electrospinning, mechanical disintegration, and deprotonation.

[0085] Polymerization-induced self-assembly refers to a method of directly preparing polymer nanofibers by monomer polymerization. Taking aramid fibers as an example, in the traditional polymerization process, PPTA molecular chains aggregate as the chains grow and form high molecular weight aramid fibers. In order to obtain aramid nanofibers instead of large-sized aramid fibers, an inducer, such as methoxypolyethylene glycol or polyethylene glycol dimethyl ether, needs to be added during the synthesis process. The role of the inducer is to adjust the direction of the chain by forming hydrogen bonds with the aramid nanofiber monomers, inhibit the irregular aggregation of the aramid nanofiber monomer molecular chains caused by the free assembly of hydrogen bonds, and promote the formation of a stable aramid nanofiber solution. However, it should be noted that it is difficult to control the degree of polymerization in the self-assembly method, and it is often necessary to introduce some inert groups to control the reaction speed and degree, so it is difficult to control the size of the final nanofiber.

[0086] During the electrospinning process to produce fibers, a strong acid or base is first used to dissolve the fibers to obtain an electrospinning solution. The resulting solution is then spray-spun in a strong electric field. Under the action of the electric field, the droplet at the needle changes from a spherical shape to a conical shape (the "Taylor cone"), and fiber filaments extend from the tip of the cone. Because strong acids or bases are needed to dissolve the fibers, the conductivity of the electrospinning solution is too high, or the solution viscosity is mismatched, making it more difficult to produce fibers.

[0087] The mechanical disintegration method is based on the fact that the fiber's molecular chains have strong atomic bonds along the axial direction and weak molecular bonds along the radial direction, giving the fiber significant strength anisotropy. This allows the fiber's epidermis to easily peel along the fiber axis under mechanical fibrillation. The fiber molecules can be pre-treated with hydrolysis using acid or alkaline solutions to assist in mechanical disintegration. This is combined with alkane hydrolysis to change the ionic charge on the fiber surface, ultimately producing a nanofiber solution.

[0088] The deprotonation method works by placing the fibers in a strongly alkaline DMSO solution. Negative charges gradually accumulate on the fiber chains, generating electrostatic repulsion, which breaks the top fibers into PPTA microfibers averaging 1-2 μm. As the deprotonation increases, the electrostatic repulsion between the polymer chains becomes stronger, providing the energy required to break the hydrogen bonds between them, ultimately yielding nanofibers with a high aspect ratio. A balance between electrostatic repulsion, van der Waals forces, and π-π stacking allows the nanofibers to be stably dispersed.

[0089] S702, adding the core material into the organic fiber solution and dispersing it evenly.

[0090] Core materials, i.e., untreated electrode materials, can be either positive or negative electrode materials. Positive electrode materials include, but are not limited to, ternary materials such as NCM811. Negative electrode materials include, but are not limited to, silicon-based, tin-based, sulfur-based, and metallic lithium. It is understood that the core material used is generally an electrode material that exhibits significant volume expansion.

[0091] S703, drying the mixture of the core material and the organic fiber to obtain a composite electrode material.

[0092] Among them, the mixture of the core material and the organic fiber can be dried by freeze drying, spray drying, or hot air drying, and the drying parameters can be adjusted according to needs.

[0093] It is noteworthy that during the drying process, no inert gas atmosphere is required and no heat treatment (semi-carbonization) is required, thereby ensuring the strength of the coating layer.

[0094] The following describes the preparation method of the composite electrode material through specific examples, and uses the composite electrode material samples prepared in the examples to prepare lithium-ion batteries, and tests the performance of the lithium-ion batteries and the expansion of the electrode sheets.

[0095] Example 1

[0096] Aramid nanofiber (ANFs) composite ternary cathode material (NCM811) was prepared with a composite ratio of 0.05%, hereinafter referred to as "ANFs-NCM811-0.05", and the specific implementation steps are as follows.

[0097] S110, preparing an aramid nanofiber solution. Specifically comprising:

[0098] S111, add 100 mL of N-methylpyrrolidone into the reaction vessel, and heat to 100° C. under a nitrogen atmosphere.

[0099] S112, stirring at 100°C for 5 minutes.

[0100] S113, add CaCl2 and dimethyl ether, and stir and dissolve at 100°C for 30 minutes.

[0101] S114, cool to 0°C, add p-phenylenediamine, and stir until p-phenylenediamine is completely dissolved.

[0102] In the above steps, the stirring speed can be controlled at 400 rpm.

[0103] S115, adding terephthaloyl chloride, stirring, and starting the reaction. The stirring speed can be controlled at 2000 rpm.

[0104] In the above reaction system, the concentrations of terephthaloyl chloride and p-phenylenediamine are 0.21 and 0.20 mol / L, respectively, and methyl ether accounts for 3 wt% of the total weight of terephthaloyl chloride and p-phenylenediamine.

[0105] S116, after the reaction stops, dilute the reaction product with N-methylpyrrolidone and add a certain amount of deionized water.

[0106] S117, placing the diluted product in a high shear homogenizer for homogenization to obtain an aramid nanofiber solution with a concentration of 0.1%. The speed of the homogenizer is 10000 rpm and the homogenization time is 5 min.

[0107] S120, adding NCM811 material to the above-mentioned aramid nanofiber solution, stirring at a low speed to evenly disperse, wherein the mass ratio of NCM811 material to aramid nanofiber is 0.05:99.95.

[0108] S130, transferring the mixed solution of NCM811 material and aramid nanofibers into a freeze dryer, freeze-drying at about -60°C, and collecting the product, which is the aramid nanofiber (ANFs) composite polycrystalline ternary positive electrode material (NCM811).

[0109] Example 2

[0110] Aramid nanofibers (ANFs) composited with silicon dioxide was prepared with a composite ratio of 0.1%, hereinafter referred to as "ANFs-SiO-0.1", and the specific implementation steps are as follows.

[0111] S210, preparing an aramid nanofiber solution. Specifically comprising:

[0112] S211, adding a mixture of 0.5 g of poly (p-phenylene terephthalamide) and 1.0 g of KOH to 300 mL of dimethyl sulfoxide, and magnetically stirring at room temperature for 7 days to obtain a uniform and transparent ANF / DMSO solution.

[0113] S212, diluting the reaction product with dimethyl sulfoxide to dilute the concentration of ANF to 0.05%.

[0114] S220, adding 500 g of silicon dioxide powder to the ANF / DMSO solution having an ANF concentration of 0.05%, stirring evenly, transferring the solution to a mixer, and shaking the solution at 1200 rpm for 15 minutes.

[0115] S230, placing the mixed solution of silicon dioxide and ANF / DMSO in a freeze dryer and freeze-drying at about -60°C.

[0116] In step S240, the freeze-dried product is added to ethanol containing a trace amount of water. In step S240, the ANF is re-protonated at a slower rate, repairing some of the connections between the nanofibers and ensuring the strength of the aramid nanofibers and their adhesion to the silica particles.

[0117] S250, placing the solution in S240 in a freeze dryer, freeze-drying at a temperature of about -60°C, and collecting the product, which is aramid nanofibers (ANFs) composited with silicon oxide.

[0118] Figure 8 This is an electron microscope image of the aramid nanofiber composite silicon oxide prepared in Example 2.

[0119] Example 3

[0120] Aramid nanofibers (ANFs) composited with silicon oxide was prepared with a composite ratio of 0.5%, hereinafter referred to as "ANFs-SiO-0.5", and the specific implementation steps are as follows.

[0121] S310, preparing an aramid nanofiber solution. Specifically comprising:

[0122] S311, adding a mixture of 0.5 g of poly (p-phenylene terephthalamide) and 1.0 g of KOH to 300 mL of dimethyl sulfoxide, and magnetically stirring at room temperature for 7 days to obtain a uniform and transparent ANF / DMSO solution.

[0123] S312, diluting the reaction product with dimethyl sulfoxide to dilute the concentration of ANF to 0.05%.

[0124] S320, adding 100 g of silicon dioxide powder to the above-mentioned ANF / DMSO solution with an ANF concentration of 0.05%, stirring evenly, transferring the solution to a mixer, and shaking at 1200 rpm for 15 minutes.

[0125] S330, placing the mixed solution of silicon dioxide and ANF / DMSO in a freeze dryer and freeze-drying at about -60°C.

[0126] In step S340, the freeze-dried product is added to ethanol containing a trace amount of water. In step S340, the ANF is re-protonated at a slower rate, repairing some of the connections between the nanofibers and ensuring the strength of the aramid nanofibers and their adhesion to the silica particles.

[0127] S350, placing the solution in S340 in a freeze dryer, freeze-drying at a temperature of about -60°C, and collecting the product, which is the aramid nanofiber composite silicon oxide.

[0128] Example 4

[0129] Aramid nanofibers (ANFs) composited with silicon oxide was prepared with a composite ratio of 1%, hereinafter referred to as "ANFs-SiO-1", and the specific implementation steps are as follows.

[0130] S410, preparing an aramid nanofiber solution. Specifically comprising:

[0131] S411, adding a mixture of 0.5 g of poly (p-phenylene terephthalamide) and 1.0 g of KOH to 300 mL of dimethyl sulfoxide, and magnetically stirring at room temperature for 7 days to obtain a uniform and transparent ANF / DMSO solution.

[0132] S412, diluting the reaction product with dimethyl sulfoxide to dilute the ANF concentration to 0.05%.

[0133] S420, adding 50 g of silicon dioxide powder to the above-mentioned ANF / DMSO solution with an ANF concentration of 0.05%, stirring evenly, transferring to a mixer, and shaking at 1200 rpm for 15 minutes.

[0134] S430, placing the mixed solution of silicon dioxide and ANF / DMSO in a freeze dryer and freeze-drying at about -60°C.

[0135] In step S440, the freeze-dried product is added to ethanol containing a trace amount of water. In step S340, the ANF is re-protonated at a slower rate to repair the connection between some nanofibers, thereby ensuring the strength of the aramid nanofibers and their adhesion to the silica particles.

[0136] S450, placing the solution in S440 in a freeze dryer, freeze-drying at a temperature of about -60°C, and collecting the product, which is the aramid nanofiber composite silicon oxide.

[0137] Example 5

[0138] Preparation of polysulfone nanofiber (PSA) composite silicon dioxide secondary composite particles, the composite ratio is 0.5%, hereinafter referred to as "PSA-SiO-agg-0.5", the specific implementation steps are as follows.

[0139] S510, preparing a polysulfone nanofiber solution. Specifically comprising:

[0140] S511, adding the fibril PSA fiber and KOH in a mass ratio of 1:1 into the N-methylpyrrolidone solution and stirring for 30 minutes.

[0141] S512, placing the stirred solution in an ultrasonic cell disruptor, and performing ultrasonic stripping treatment on the arylsulfone fibers in the solution at 18kHz-21kHz to obtain an arylsulfone nanofiber solution.

[0142] S520, preparing a mixed solution of silicon dioxide and aromatic sulfone nanofibers.

[0143] In step S521, silicon oxide powder having a D50 of 5 μm is added to an ethanol solution to obtain a silicon oxide slurry. The silicon oxide slurry is then sand-milled using zirconia beads with a diameter of 3 mm. The ball-to-material ratio is 10:1, the rotation speed is 3000 rpm, and the sand-milling time is 30 minutes. Sand-milling the silicon oxide powder in step S521 can reduce the D50 of the silicon oxide to below 1 μm and achieve a more uniform particle size distribution.

[0144] S522, uniformly mixing the sand-milled silicon dioxide slurry and the aromatic sulfone nanofiber solution according to a composite ratio of 0.5%.

[0145] S530, transferring the mixed liquid of silicon dioxide and polysulfone nanofibers to a closed spray drying container, spray drying the mixed liquid under the conditions of a centrifugal atomizing disk speed of 15,000 rpm, an atomizing temperature of 150° C., and a drying medium of N2 to obtain secondary composite particles of polysulfone nanofibers and silicon dioxide.

[0146] Figure 9 This is an electron microscope image of the secondary composite particles of arylsulfone nanofibers and silicon oxide prepared in Example 5.

[0147] Example 6

[0148] Poly (aryl oxadiazole) nanofiber (POD) composite silicon carbon (Si / C) was prepared with a composite ratio of 1%, hereinafter referred to as "POD-Si / C-1", and the specific implementation steps are as follows.

[0149] S610, preparing a poly (aryl oxadiazole) nanofiber solution. Specifically comprising:

[0150] S611, adding the fibril POD fibers and KOH in a mass ratio of 1:1 to 300 ml of N-methylpyrrolidone solution, and stirring for 7 days to obtain a POD / DMSO suspension.

[0151] Because the conjugation between the benzene ring and the heterocyclic ring in POD is strong, only partial deprotonation can be achieved to form nanofibers after stirring in a strong alkaline DMSO environment for 7 days.

[0152] S612, pouring the POD / DMSO suspension into a centrifuge tube, centrifuging at 10,000 rpm for 15 minutes, and taking the upper transparent solution portion to obtain a POD nanofiber / DMSO dispersion.

[0153] S620, adding silicon carbon (Si / C) powder to the POD nanofiber / DMSO dispersion according to the composite ratio, and stirring at a rotation speed of 300 rpm for 6 hours.

[0154] S630, placing the mixture of silicon carbon (Si / C) powder and POD nanofiber in a forced air drying oven, drying it completely at 60° C., collecting the product, and obtaining poly (aryl oxadiazole) nanofiber (POD) composite silicon carbon (Si / C).

[0155] Comparative Example 1

[0156] The silicon oxide material without surface treatment was used as the negative electrode material in Comparative Example 1, hereinafter referred to as "SiO blank".

[0157] Comparative Example 2

[0158] A polyurethane (PUR) composite silicon dioxide negative electrode material was prepared with a composite ratio of 0.1%, hereinafter referred to as "PUR-SiO-0.1".

[0159] The specific preparation steps include: weighing 1g of polyurethane and dissolving it in water, stirring until the polyurethane is completely dissolved; weighing 1000g of SiO2 and adding it to the polyurethane solution, stirring to obtain a mixed slurry; transferring the mixed slurry to a spray dryer, introducing nitrogen, and spray drying at 130°C to obtain a polyurethane (PUR) composite silicon oxide powder.

[0160] Comparative Example 3

[0161] A polyaniline (PANI) composite silicon dioxide negative electrode material was prepared with a composite ratio of 0.5%, hereinafter referred to as "PANI-SiO-0.5".

[0162] The specific preparation steps include: weighing 1g of polyaniline and dissolving it in NMP, stirring until the polyaniline is completely dissolved; weighing 200g of SiO2 and adding it to the polyaniline solution, stirring to obtain a mixed slurry; transferring the mixed slurry to a spray dryer, introducing N2, and spray drying at 200°C to obtain a solid powder.

[0163] Comparative Example 4

[0164] The Si / C material without surface treatment was used as the negative electrode material in Comparative Example 4, hereinafter referred to as “Si / C blank”.

[0165] Comparative Example 5

[0166] Silicon dioxide aggregate particles were prepared, hereinafter referred to as "SiO-agg blanks".

[0167] The specific implementation steps are as follows:

[0168] Silicon oxide powder with a D50 of 5 μm was added to an ethanol solution to produce a silicon oxide slurry. The slurry was then sand-milled using 3 mm diameter zirconium oxide beads. The ball-to-powder ratio was 10:1, the rotation speed was 3000 rpm, and the sand-milling time was 30 minutes. The sand-milled silicon oxide slurry was transferred to a closed spray drying vessel and spray-dried at a centrifugal atomizer speed of 15000 rpm, an atomization temperature of 150°C, and a drying medium of nitrogen to produce silicon oxide polymer particles.

[0169] Material performance testing

[0170] The composite cathode material "ANFs-NCM811-0.05" prepared in Example 1 and the cathode material "NCM811 blank" prepared in Comparative Example 1 were paired with graphite anodes to form two 4Ah pouch cells. The two cells had the same design. Specifically, the anode had an areal density of 12.8 mg / cm² and a compacted density of 1.7 g / cm³. The cathode had an areal density of 20.7 mg / cm² and a compacted density of 3.5 g / cm³, and an N / P ratio of 1.1.

[0171] At a current density of 1C, the two groups of batteries were subjected to cyclic charge and discharge tests. After 1000 cyls, the capacity retention rate was tested, and the positive electrode plates were disassembled and the expansion rate of the positive electrode plates was tested. The test results are shown in Table 1 below:

[0172] Table 1

[0173]

[0174] As shown in Table 1, compared with the "NCM811 blank", the 1000 cycle capacity retention rate of "ANFs-NCM811-0.05" increased by 6%, and at the same time, the expansion rate of the positive electrode sheet improved by 2%. From the above results, it can be seen that the use of aramid nanofiber (ANFs) composite ternary positive electrode material (NCM811) positive electrode material can limit the expansion of the positive electrode sheet and improve the battery electrical performance. This is because when charged to 4.3V, the polycrystalline high-nickel material releases nearly 80% of the lithium, the grains shrink, and the microstress changes dramatically. During discharge, the polycrystalline high-nickel material embeds lithium, and the grain volume expands again. The repeated contraction and expansion of the grains lead to lattice collapse and grain microcracks, which in turn cause irreversible expansion of the pole piece and increase in thickness. At the same time, the particles lose contact, the conductivity decreases, and even the conductive network is lost, and the electrical performance decreases accordingly.

[0175] The "ANFs-SiO-0.1", "ANFs-SiO-0.5", "ANFs-SiO-1", "PSA-SiO-agg-0.5", and "POD-Si / C-1" prepared in Examples 2-6, as well as the "PUR-SiO-0.1", "PANI-SiO-0.5", "Si / C blank", and "SiO-agg blank" prepared in Comparative Examples 1-5, were respectively used to prepare slurries and negative electrode sheets according to the ratio of composite electrode material: conductive agent (SP): binder = 75%:15%:10%, and button batteries were prepared with metal lithium as the positive electrode.

[0176] The ten groups of button cells prepared above were tested, including reversible gram capacity, initial efficiency, rate performance, 50 cyls cycle capacity retention, and negative electrode expansion. The test results are shown in Table 2 below:

[0177] Table 2

[0178]

[0179] As shown in Table 2, the gram capacity, initial efficiency and rate performance of the composite electrode material remain basically unchanged compared to the electrode material without surface treatment. In other words, the organic fiber coating layer on the surface of the negative electrode core material will not affect the basic electrochemical properties of the core material. It is worth noting that, compared with the negative electrode material without surface treatment, the expansion rate of the composite negative electrode plate is significantly improved after the battery cycles 50cyls. It can be seen that the composite negative electrode material with an organic fiber coating layer on the surface provided in the embodiment of the present application has a significant effect of reducing the expansion of the plate.

[0180] It should be understood that the composite electrode materials provided in the embodiments of the present application are not limited to the several types listed above. Based on the core idea of coating the surface of the core material with an organic fiber coating layer having a skeleton structure, the selection of core materials and organic fibers can also include many other types, which are not limited in the present application.

[0181] As can be seen from the above embodiments, the present application provides a composite electrode material, comprising an electrode material core and an organic fiber coating layer having a skeleton structure, wherein the organic fiber coating layer is composited on the surface of the electrode material core through bonding; the organic fiber contains at least one of -CO-NH- and -C=N-, as well as a benzene ring structure. The -CO-NH- or -C=N- contained in the organic fiber can form abundant hydrogen bonds with the -OH groups on the surface of the electrode material core, so that the organic fibers are intertwined and composited on the surface of the electrode material core, thereby forming a strong coating layer with a skeleton structure on the surface of the electrode material core. The high strength characteristics and small tensile strain of the organic fiber coating layer can limit the volume expansion of the electrode material, while ensuring that the coating layer itself is not easily plastically deformed.

[0182] In addition, an embodiment of the present application also provides a lithium battery, including a positive electrode material, an electrolyte, a separator and a negative electrode material, characterized in that the positive electrode material or the negative electrode material adopts the above-mentioned composite electrode material.

[0183] An embodiment of the present application also provides an electronic device, including a charging and discharging circuit and electrical components, and also including the above-mentioned lithium battery, where the lithium battery is connected to the charging and discharging circuit and is charged by the charging and discharging circuit or supplies power to the electrical components.

[0184] By using the composite electrode material and its preparation method provided in the embodiments of the present application, a lithium battery including the composite electrode material and an electronic device including the lithium battery can be obtained. The composite electrode material includes an electrode material core and an organic fiber coating layer with a skeleton structure, and the organic fiber coating layer is composited on the surface of the electrode material core through a bonding action. Among them, the -CO-NH- or -C=N- contained in the organic fiber can form abundant hydrogen bonds with the -OH on the surface of the electrode material core, so that the organic fibers are intertwined and composited on the surface of the electrode material core, thereby forming a strong and skeleton-structured coating layer on the surface of the electrode material core. The high strength characteristics and small tensile strain of the organic fiber coating layer can limit the volume expansion of the electrode material, while ensuring that the coating layer itself is not prone to plastic deformation. Furthermore, it can improve the battery cycle stability, reduce the proportion of the battery in the internal cavity of the electronic device, increase the available cavity space for key components such as chips and circuit boards in the electronic device, avoid problems such as battery bulging and back cover warping after long cycles, and improve the life and safety of electronic products.

[0185] In this specification, the same or similar parts between the various embodiments can be referred to each other. In particular, for the embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description in the method embodiments.

[0186] The above-described embodiments of the present invention do not limit the protection scope of the present invention.

Claims

1. A composite electrode material, characterized in that It comprises an electrode material core and an organic fiber coating layer, wherein the organic fiber coating layer is composited on the surface of the electrode material core; The organic fiber contains at least one of -CO-NH- and -C=N-, and a benzene ring structure; the mass proportion of the organic fiber in the composite electrode material is 0.05%-1%.

2. The composite electrode material according to claim 1, characterized in that The organic fibers further contain -COOH and / or -NH2.

3. The composite electrode material according to claim 1, characterized in that The benzene ring structure is located in the molecular chain of the organic fiber.

4. The composite electrode material according to claim 3, characterized in that The breaking strength of the organic fiber is greater than 3cN·dtex -1 The initial modulus of the organic fiber is greater than 50 cN·dtex -1 .

5. The composite electrode material according to claim 3, characterized in that The thickness of the organic fiber coating layer is 10nm-200nm.

6. The composite electrode material according to claim 5, characterized in that The organic fiber has a diameter of 5nm-60nm and a length of 200nm-20μm.

7. The composite electrode material according to claim 1, characterized in that The organic fiber is aramid fiber, polyoxadiazole fiber or aromatic sulfone fiber.

8. The composite electrode material according to claim 7, characterized in that The aramid chain segment content in the aramid fiber is greater than 85%, and the diameter of the aramid fiber is 5nm-40nm, and the length is 2μm-20μm.

9. The composite electrode material according to claim 1, characterized in that The composite electrode material includes composite particles and / or polymer particles. The composite particles include the electrode material core and an organic fiber coating layer composited on the surface of the electrode material core by bonding. The polymer particles are formed by polymerizing the composite particles.

10. The composite electrode material according to claim 9, characterized in that The composite particles include primary composite particles and secondary composite particles. The core of the primary composite particles is the electrode material core, and the core of the secondary composite particles is the polymerized particles formed by polymerization of the primary composite particles.

11. The composite electrode material according to claim 9, characterized in that Conductive agents and / or ionic conductors are also included.

12. The composite electrode material according to claim 11, characterized in that The conductive agent and / or ion conductor is coated on the surface of the composite particles and / or polymer particles, or is mixed between the composite particles and / or polymer particles.

13. The composite electrode material according to claim 11, characterized in that The conductive agent includes one or more of amorphous carbon, soft carbon, hard carbon, graphite, carbon nanotubes, graphene, and metal particles.

14. The composite electrode material according to claim 1, characterized in that The electrode materials include ternary positive electrode materials, silicon-based, tin-based, sulfur-based, and metallic lithium negative electrode materials.

15. A method for preparing a composite electrode material, characterized in that: The method comprises: preparing an organic fiber solution, wherein the organic fiber has a molecular structure containing at least one of -CO-NH- and -C=N-, and a benzene ring structure; Adding the electrode material to the organic fiber solution according to a predetermined composite ratio and stirring until the solution is evenly dispersed; The mixed solution of the electrode material and the organic fiber is dried to obtain the composite electrode material as claimed in claim 1.

16. A composite electrode material, characterized in that The method according to claim 15 is used for preparation.

17. Use of the composite electrode material according to claim 1 in the field of preparing lithium batteries.

18. A lithium battery, characterized in that: The invention comprises a positive electrode material, an electrolyte, a separator and a negative electrode material, wherein the positive electrode material or the negative electrode material adopts the composite electrode material according to any one of claims 1 to 14.

19. An electronic device comprising a charging and discharging circuit and an electrical component, characterized in that: It also includes the lithium battery according to claim 18, which is connected to the charging and discharging circuit and is charged by the charging and discharging circuit or supplies power to the electrical components.

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