A composite electrode material, its preparation method and application

Abstract

This invention discloses a composite electrode material, its preparation method, and its application, belonging to the field of battery technology. The composite electrode material provided by this invention comprises at least two active materials. Each active material is combined with a conductive agent and a fibrillated binder to construct a structural unit. The structural unit is a three-dimensional network composite particle formed by the fibrillated binder encapsulating and entangled the active material and the conductive agent. The particle size of the structural unit is 10-500 μm. Multiple structural units are uniformly distributed within the electrode composite coating, and the structural units are intertwined through binder fibers at the interfaces of each structural unit, forming a continuous three-dimensional network structure. This improves structural stability and electronic conductivity, resulting in high rate performance and long cycle life.

Description

Technical Field

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

[0002] Dry electrode technology has become a key technology direction for next-generation battery manufacturing due to its advantages such as no solvent required, environmentally friendly process, low energy consumption, and high electrode density. However, when the electrode needs to be composed of two or more active materials with large differences in physical properties (such as particle size, density, and specific surface area), the traditional dry mixing process faces severe challenges.

[0003] For example, in the cathode, it may be necessary to mix high-specific-surface-area ternary materials (NMC) with low-specific-surface-area lithium iron phosphate (LFP) to balance energy density and safety; in the anode, it may be necessary to mix high-specific-surface-area silicon-carbon materials with low-specific-surface-area graphite to improve capacity. Similar needs exist in sodium-ion batteries, such as mixing layered oxides, Prussian blue compounds, polyanionic compounds, or hard / soft carbon materials with different specific surface areas. When directly mixed, high-specific-surface-area materials preferentially and extensively adsorb conductive agents and binders, leading to insufficient adsorption of low-specific-surface-area materials. This causes a series of problems such as uneven mixing, discontinuous conductive networks, and poor structural stability, ultimately impairing the battery's rate performance and cycle life.

[0004] Patent application CN119236757A proposed the concepts of premixing and secondary mixing, but it mainly focuses on the process combination of conductive agent premixing and binder separate fibrosis, without proposing a specific solution to the core problem of uneven component distribution caused by differences in the physical properties of multiple main materials. Therefore, developing a method that can effectively solve the problem of uniformity in dry mixing of multiple main materials is crucial for promoting the application of dry electrode technology in high-end batteries. Summary of the Invention

[0005] To address the technical problem that the composite electrode structure in the prior art affects the rate performance and cycle life of batteries, this invention provides a composite electrode material that can achieve high structural stability, improved tensile strength and elongation at break after mixing at least two active materials, and has the advantages of high rate performance and long cycle life.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A composite electrode material includes at least two active substances, each of which is combined with a conductive agent and a fibrillated binder to form a structural unit. The structural unit is a three-dimensional network composite particle formed by the fibrillated binder encapsulating and wrapping the active substance and the conductive agent. The particle size of the structural unit is 10-500 μm. Multiple structural units are uniformly distributed within the electrode composite coating, and the structural units are intertwined with each other through binder fibers at the interfaces of each structural unit to form a continuous three-dimensional network structure.

[0007] The core of the composite electrode material prepared by this invention lies in a unique "multi-scale, multi-phase fiber interwoven structure". This structure is not homogeneous, but exhibits specific non-uniform composite characteristics at the macroscopic, mesoscopic and microscopic scales.

[0008] 1. Mesoscale: Identifiable primary structural units and their dimensions At the mesoscopic scale (e.g., 10 μm - 500 μm), the electrode sheet is composed of two or more "primary structural units" interlocked and entangled. These "primary structural units" are fibrous structural units independently constructed for each active material. After hot pressing, they do not dissolve or disperse uniformly, but retain their basic morphology as independent aggregates, which can be regarded as separately kneaded "fiber-reinforced dough".

[0009] These primary structural units can be identified through large-field scanning electron microscopy (SEM) image analysis of the electrodes. Their particle size is mainly distributed between 10 μm and 500 μm, preferably between 20 μm and 200 μm, and more preferably between 20 and 100 μm. This size range is designed to achieve macroscopic uniformity without completely destroying their independent network framework.

[0010] It should be noted that the term "particle size" used in this invention to describe structural units refers to the major axis diameter (maximum Feret diameter) of the structural unit on a two-dimensional image plane as measured by scanning electron microscopy (SEM).

[0011] The particle size of the primary structural unit should be controlled within the range of 10-500 μm. If the size is too small (e.g., <10 μm), it loses the significance of independent functional partitioning and tends to be homogeneous, failing to realize the advantage of customized networks for different active materials. If the size is too large (e.g., >500 μm), it will lead to uneven macroscopic distribution of electrode components, affecting the uniformity of ion / electron transport, thereby causing local polarization and reducing battery performance.

[0012] It is worth noting that, regardless of the original particle size of the various active substances used, the characteristic size distribution ranges of the various primary structural units that are ultimately formed basically overlap or are on the same order of magnitude.

[0013] 2. Microscale: Multilevel fiber network structure At the microscale (e.g., 100 nm–10 μm), multi-layered fiber networks can be observed: Primary network: Within each "primary structural unit," a separate and continuous three-dimensional network is formed by fibrillated binder fibers (such as PTFE), active materials, and conductive agent particles. This network provides a dedicated conductive and bonding framework for the active material.

[0014] Secondary composite network: At the interfaces of different "primary structural units," PTFE fibers from different units extend, entangle, interweave, and mechanically interlock, forming a three-dimensional network that spans the entire electrode across the interfaces. This "secondary composite network" stitches the various primary structural units together like "needle and thread," providing the overall mechanical integrity of the electrode.

[0015] Specifically, the active substance is a combination of a first active substance with a high specific surface area and a second active substance with a low specific surface area; wherein the difference in specific surface area between the first and second active substances is not less than twice the specific surface area of ​​the second active substance with the lower specific surface area. The specific surface area is determined according to the method in standard GB / T19587-2017.

[0016] Preferably, the combination of the first active material and the second active material is selected from at least one of sodium iron pyrophosphate-Prussian blue compounds, sodium iron sulfate-layered oxides, lithium iron phosphate-NCM, and graphite-silicon carbon.

[0017] Preferably, the mass ratio of the first active material to the second active material is (2-8):(2-8); preferably, the mass ratio of the first active material to the second active material is ≤1; more preferably, the mass ratio is (3-5):(5-7). When the active material of the present invention is mainly composed of active materials with low specific surface area, its overall performance is superior. By using a large proportion of low specific surface area active materials to ensure electrode compaction density, structural stability, and long-cycle performance, and by combining a small proportion of high specific surface area active materials to improve ion diffusion kinetics, the battery's rate charge / discharge capability is improved, achieving a synergistic balance between high rate and long cycle life.

[0018] Preferably, the D of the first active substance and the second active substance 50 The particle size is 0.1-20μm.

[0019] Preferably, the specific surface area of ​​the first active substance and the second active substance is 0.1-20 m². 2 / g.

[0020] Specifically, the conductive agent is selected from at least one of conductive carbon black, CNT, Ketjen black, acetylene black, graphene, carbon nanofibers, and Super P.

[0021] Specifically, the adhesive is selected from polytetrafluoroethylene (PTFE).

[0022] Preferably, the mass ratio of conductive agent between different fibrous structural units is (1-4):(1-4).

[0023] Preferably, the mass ratio of conductive agent to binder in a fibrous structural unit is (0.5-2):1.

[0024] The preparation method of the above-mentioned composite electrode material includes the following steps: Different active substances are mixed with conductive agents and binders at 1000-2000 rpm for 5-30 minutes, and then fiberized at 3000-8000 rpm for 1-10 minutes to form corresponding fiberized structural units for each active substance. At least two types of fibrous structural units are mixed at 100-800 rpm for 10-60 minutes to obtain a composite electrode material.

[0025] The preparation method of this invention controls specific mixing speed, fiberization speed, and time to improve the degree of fiberization of the binder and the uniformity of particle dispersion. If the speed is too low or the time is too short, the binder cannot be fully fiberized, resulting in insufficient electrode strength and easy powder shedding; if the speed is too high or the time is too long, it is easy to cause the active particles to break and the specific surface area to increase abnormally, which is not conducive to the initial coulombic efficiency and cycle stability.

[0026] A composite electrode sheet includes a current collector and a composite electrode material hot-pressed onto the current collector.

[0027] The method for preparing the composite electrode sheet includes the following steps: hot pressing the composite electrode material onto a current collector to obtain the composite electrode sheet.

[0028] Specifically, the hot pressing temperature is 120~200℃, and the pressure is 10~50MPa. By controlling the hot pressing temperature and pressure, the degree of electrode densification and interfacial bonding strength are optimized.

[0029] A composite battery includes the aforementioned composite electrode sheet.

[0030] The above-mentioned composite batteries are used in power batteries for new energy vehicles, large-scale energy storage systems, consumer electronics and wearable devices, or special equipment.

[0031] Compared with the prior art, the present invention has the following beneficial effects: The composite electrode material provided by this invention comprises at least two active materials with differentiated physical properties. Each active material is combined with a conductive agent and a fibrillated binder to form a structural unit. The structural unit comprises an active material, a conductive agent, and a fibrillated binder. The fibers of the binder encapsulate the active material and the conductive agent into independent aggregates with a characteristic size of 10-500 micrometers through adhesion and entanglement. The independent fibrillated structural units are connected through the adhesion and entanglement of the fibers, thereby improving structural stability and electronic conduction, increasing tensile strength and elongation at break, and exhibiting advantages such as high rate performance and long cycle life. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the composite electrode material.

[0033] Figure 2 The images show the SEM image and EDS distribution diagram of the composite positive electrode sheet prepared in Example 1.

[0034] Figure 3 This is a SEM image of the surface of the composite positive electrode sheet prepared in Example 1.

[0035] Figure 4 This is a SEM image of the cross-section of the composite positive electrode sheet prepared in Example 1.

[0036] Figure 5 The EDS distribution diagram of P element in the composite positive electrode sheet prepared for Comparative Example 1.

[0037] Figure 6 SEM image of the surface of the composite positive electrode sheet prepared in Comparative Example 1.

[0038] Figure 7 The image shows a cross-section of the positive electrode sheet prepared in Comparative Example 1. Detailed Implementation

[0039] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0040] The reagents used in the various embodiments and comparative examples of this invention are described below: Sodium iron pyrophosphate (NFPP): derived from Shenzhen Jia Na, D 50 =5.3μm, specific surface area 9.31m² 2 / g.

[0041] Prussian blue compounds (PBA): derived from Huzhou Chaona, CNC-PBT1, D 50 =6.63μm, specific surface area 4.53m² 2 / g.

[0042] Polytetrafluoroethylene (PTFE): sourced from Daikin, grade F106C.

[0043] Ternary material (NMC811): sourced from Jiangsu Dangsheng, D 50 =9.9μm, specific surface area 0.43 m² 2 / g.

[0044] Lithium iron phosphate (LFP): sourced from Hunan Yuneng, D 50 =0.7μm, specific surface area 12.0 m² 2 / g.

[0045] Graphite: sourced from Hunan Chenyu Fuji, D 50 =14.8μm, specific surface area 1.83 m² 2 / g.

[0046] Silicon-carbon: derived from Lanxi Zhide, D 50 =9.26μm, specific surface area 0.69 m² 2 / g.

[0047] Sodium ferric sulfate: derived from Jiangsu Zhongna, D 50 =2.0μm, specific surface area 14 m² 2 / g.

[0048] Layered oxides: derived from sodium-based new materials, D 50 =6.5μm, specific surface area 1.2m² 2 / g.

[0049] Conductive carbon black (SP): derived from TIMCAL, model Super-P.

[0050] Example 1 A composite positive electrode sheet includes a current collector and a composite electrode material hot-pressed onto the current collector; The current collector is aluminum foil.

[0051] The composite electrode material includes active materials, namely active material A and active material B. Active material A and active material B respectively form structural units with conductive agent and fibrillated binder. The structural units are three-dimensional network composite particles formed by fibrillated binder wrapping and entanglement of active material and conductive agent. Multiple structural units are uniformly distributed in the electrode composite coating, and the structural units are intertwined with each other through binder fibers at the interface of each structural unit to form a continuous three-dimensional network structure.

[0052] like Figure 1 As shown, it is more like a composite structure formed by two separately kneaded "fiber-reinforced doughs" after uniform kneading. In this structure, the fiber network (primary network) structural units of the two premixes are relatively preserved, while at their interfaces, through the entanglement, interpenetration, and locking of binder fibers (such as PTFE fibers), a stable "secondary composite network" is formed. This structural unit ensures the macroscopic uniformity and microscopic functional partitioning of the electrode, which cannot be achieved by traditional wet processes.

[0053] Specifically, the composite electrode material comprises: 94 wt% active material, 3 wt% conductive carbon black (SP) conductive agent, and 3 wt% PTFE powder binder.

[0054] The active substances include active substance A and active substance B. Active substance A is sodium iron pyrophosphate (NFPP) with a high specific surface area, accounting for 40% of the total mass of active substances; active substance B is Prussian blue compound (PBA) with a low specific surface area, accounting for 60% of the total mass of active substances.

[0055] The method for preparing the composite positive electrode sheet includes the following steps: S1: First mixing and fiberization: Material weighing and mixing: The NFPP was mixed with a portion of SP (40 wt% of the total SP mass) and a portion of PTFE (40 wt% of the total PTFE mass) in a high-speed mixer at 1000 rpm for 30 minutes to obtain a first premix. The PBA was mixed with the remaining SP (60 wt% of the total SP mass) and PTFE (60 wt% of the total PTFE mass) in another high-speed mixer with the same parameters to obtain a second premix.

[0056] Fiberization: The two initial mixtures are sheared in a high-speed disperser at 4000 rpm for 5 minutes to fully fiberize the PTFE, forming flocculent / clump-like fibrous structural units.

[0057] S2: Second mixing: Add the first premix and the second premix together into a low-speed mixer and mix slowly at 300 rpm for 20 minutes to obtain the composite electrode material.

[0058] S3: Hot pressing: The fiberized composite electrode material is rolled onto an aluminum foil current collector at 120°C and 40MPa using a double-roller hot press to obtain a composite positive electrode sheet.

[0059] Example 2 A composite positive electrode sheet includes a current collector and a composite electrode material hot-pressed onto the current collector; The current collector is aluminum foil.

[0060] The composite electrode material includes active materials, namely active material A and active material B. Active material A and active material B respectively form structural units with conductive agent and fibrillated binder. The structural units are three-dimensional network composite particles formed by fibrillated binder wrapping and entanglement of active material and conductive agent. Multiple structural units are uniformly distributed in the electrode composite coating, and the structural units are intertwined with each other through binder fibers at the interface of each structural unit to form a continuous three-dimensional network structure.

[0061] Specifically, the composite electrode material comprises: 94 wt% active material, 3 wt% conductive carbon black (SP) conductive agent, and 3 wt% PTFE powder binder.

[0062] The active materials include active material A and active material B. Active material A is high specific surface area lithium iron phosphate (LFP), accounting for 30% of the total mass of active materials; active material B is low specific surface area ternary material (NMC811), accounting for 70% of the total mass of active materials; the conductive agent is conductive carbon black (SP); and the binder is PTFE powder.

[0063] The method for preparing the composite positive electrode sheet includes the following steps: S1: First mixing and fiberization: Material weighing and mixing: The NMC811 was mixed with a portion of SP (70 wt% of the total SP mass) and a portion of PTFE (70 wt% of the total PTFE mass) in a high-speed mixer at 1000 rpm for 30 minutes to obtain a first premix. The LFP was mixed with the remaining SP (30 wt% of the total SP mass) and PTFE (30 wt% of the total PTFE mass) in another high-speed mixer with the same parameters to obtain a second premix.

[0064] Fiberization: The two initial mixtures are sheared in a high-speed disperser at 3000 rpm for 10 minutes to fully fiberize the PTFE, forming flocculent / clump-like fibrous structural units.

[0065] S2: Second mixing: Add the first premix and the second premix together into a low-speed mixer and mix slowly at 200 rpm for 30 minutes to obtain the composite electrode material.

[0066] S3: Hot pressing: The fiberized material is rolled onto an aluminum foil current collector at 120℃ and 50MPa using a double-roller hot press to obtain a composite positive electrode sheet.

[0067] Example 3 A composite negative electrode sheet includes a current collector and a composite electrode material hot-pressed onto the current collector; The current collector is aluminum foil.

[0068] The composite electrode material includes active materials, namely active material A and active material B. Active material A and active material B respectively form structural units with conductive agent and fibrillated binder. The structural units are three-dimensional network composite particles formed by fibrillated binder wrapping and entanglement of active material and conductive agent. Multiple structural units are uniformly distributed in the electrode composite coating, and the structural units are intertwined with each other through binder fibers at the interface of each structural unit to form a continuous three-dimensional network structure.

[0069] Specifically, the composite electrode material comprises: 94 wt% active material, 3 wt% conductive carbon black (SP) conductive agent, and 3 wt% PTFE powder binder.

[0070] The active materials include active material A and active material B. Active material A is a low specific surface area silicon-carbon material, accounting for 20% of the total mass of active materials; active material B is a high specific surface area graphite, accounting for 80% of the total mass of active materials; the conductive agent is conductive carbon black (SP); and the binder is PTFE powder.

[0071] The method for preparing the composite negative electrode sheet includes the following steps: S1: First mixing and fiberization: Material weighing and mixing: Silicon carbide material was mixed with a portion of SP (20 wt% of total SP mass) and a portion of PTFE (20 wt% of total PTFE mass) in a high-speed mixer at 1000 rpm for 30 minutes to obtain the first premix. Graphite was mixed with the remaining SP (80 wt% of total SP mass) and PTFE (80 wt% of total PTFE mass) in another high-speed mixer with the same parameters to obtain the second premix.

[0072] Fiberization: The two initial mixtures are sheared in a high-speed disperser at 4000 rpm for 10 minutes to fully fiberize the PTFE, forming flocculent / clump-like fibrous structural units.

[0073] S2: Second mixing: Add the first premix and the second premix together into a low-speed mixer and mix slowly at 400 rpm for 40 minutes to obtain the composite electrode material.

[0074] S3: Hot pressing: The fibrous material is rolled onto the copper foil current collector by a double-roller hot press at 130℃ and 50MPa to obtain a composite negative electrode sheet.

[0075] Example 4 A composite negative electrode sheet differs from Example 1 in that the active material in this example includes active material A and active material B. Active material A is sodium ferric sulfate, accounting for 40% of the total mass of the active material; active material B is a layered oxide, accounting for 60% of the total mass of the active material.

[0076] Example 5 A composite negative electrode sheet differs from Example 1 in that the ratio of active material A to active material B is 4:1.

[0077] Example 6 A composite negative electrode sheet differs from Example 1 in that the ratio of active material A to active material B is 1:1.

[0078] Comparative Example 1 A composite positive electrode sheet, differing from Example 1, is prepared using a traditional one-step mixing method, the specific steps of which are as follows: In Example 1, NFPP, PBA, all SP and all PTFE were added to a mixer at once and mixed at 1000 rpm for 30 minutes. Then, the mixture was sheared at 4000 rpm for 5 minutes in a high-speed disperser, and then slowly mixed at 300 rpm for 30 minutes in a low-speed mixer. Finally, the mixture was rolled onto an aluminum foil current collector at 120°C and 40 MPa using a two-roll hot press to obtain a composite positive electrode sheet.

[0079] Comparative Example 2 A composite positive electrode sheet, differing from Example 2 in that it is prepared using a traditional one-step mixing method, the specific steps of which are as follows: In Example 2, NMC811, LFP, all SP and all PTFE were added to a mixer at once and mixed at 1000 rpm for 30 minutes. Then, the mixture was sheared at 3000 rpm for 10 minutes in a high-speed disperser, and then slowly mixed at 200 rpm for 30 minutes in a low-speed mixer. Finally, the mixture was rolled onto an aluminum foil current collector at 120°C and 50 MPa using a two-roll hot press to obtain a composite positive electrode sheet.

[0080] Comparative Example 3 A composite negative electrode sheet, differing from Example 3 in that it is prepared using a traditional one-step mixing method, the specific steps of which are as follows: In Example 3, graphite, silicon carbide, all SP and all PTFE were added to a mixer at once and mixed at 1000 rpm for 30 minutes. Then, the mixture was sheared at 4000 rpm for 10 minutes in a high-speed disperser, and then slowly mixed at 200 rpm for 30 minutes in a low-speed mixer. Finally, the mixture was rolled onto an aluminum foil current collector by a two-roll hot press at 130°C and 50 MPa to obtain a composite negative electrode sheet.

[0081] 1. Microscopic morphological characterization The composite positive electrode sheets prepared in Example 1 and Comparative Example 1 were characterized by SEM and EDS, and their structures are as follows: Figure 2-7 As shown.

[0082] like Figure 2 The SEM image of the composite positive electrode sheet prepared in Example 1 and the corresponding EDS distribution map of P element are shown. The P element is derived only from NFPP, indicating that NFPP and PBA "dough" are distributed independently.

[0083] like Figure 3 The SEM image of the composite positive electrode prepared in Example 1 shows that each component region of NFPP and PBA maintains a recognizable independent network. The particle size of the first structural unit composed of NFPP, conductive agent, and fibrillated binder is 34 μm, and the particle size of the second structural unit composed of PBA, conductive agent, and fibrillated binder is 80 μm.

[0084] like Figure 4 The SEM image of the cross-section of the composite positive electrode sheet prepared in Example 1 shows that the PTFE is fully fiberized, with the fibers penetrating the electrode sheet and intertwining with each other to connect the various active materials.

[0085] like Figure 5 The EDS distribution diagram of P element in the composite positive electrode sheet prepared in Comparative Example 1 is shown. The P element is uniformly distributed without regional aggregation, and the size is significantly smaller than that in Example 1.

[0086] like Figure 6The SEM images of the composite positive electrode prepared in Comparative Example 1 show that the cubic-shaped particles are PBA, and the broken and irregularly shaped particles are NFPP. It can be seen that both materials are randomly distributed, with a relatively uniform and disordered structure, no enriched regions, and no identifiable independent units.

[0087] like Figure 7 The image shown is a SEM image of the cross-section of the positive electrode sheet prepared in Comparative Example 1. It can be seen that the conductive agent and binder exhibit agglomeration, the PTFE filaments are unevenly distributed, and the fiberization is insufficient.

[0088] 2. Mechanical property testing The composite electrode materials from step S2 of the preparation methods in Examples 1-3 and Comparative Examples 1-3 were laminated into a single self-supporting thin film. As a comparative example, the fibrous structural units prepared using a one-time mixing process were also laminated into a self-supporting thin film.

[0089] Tensile strength and elongation at break were tested using a universal testing machine, following the standard GB / T1040.3-2006. The test specimen was a 100mm × 10mm rectangular sample, and the tensile rate was 50mm / min. The results are shown in Table 1. Table 1

[0090] Test results show that the fibrous structural unit film prepared by the method of this invention has higher mechanical strength than that of the traditional one-step mixing method. This proves that the process of this invention achieves full fibrillation of PTFE, forming a stable three-dimensional network structure. This invention, through the composite design of at least two structural units, allows the binder fibers at the interfaces of different structural units to intertwine, forming a continuous and stable three-dimensional network structure, significantly improving the tensile strength and elongation at break of the electrode. Its excellent mechanical properties can effectively buffer the volume change of the active material during charge and discharge, preventing electrode cracking and active material shedding, thereby improving the battery's initial coulombic efficiency, rate performance, and long-cycle capacity retention, while also improving the electrode's processing performance and production yield.

[0091] 3. Electrochemical performance testing The electrode sheets prepared in each embodiment and comparative example were assembled into coin cells for testing. Charge-discharge tests were performed on the assembled coin cells, and the results are shown in Table 2 below. Sodium-ion battery: The materials prepared in Example 1 and Comparative Example 1 were used as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and 1 mol / L NaPF6-PC / EMC (volume ratio 1:1) as the electrolyte, with 4 wt% FEC additive added. Lithium-ion battery: The materials prepared in Example 2 and Comparative Example 2 were used as the positive electrode, lithium metal was used as the negative electrode, PP membrane was used as the separator, 1 mol / L LiPF6-EC / DMC (volume ratio 1:1) was used as the electrolyte, and 4 wt% FEC additive was added.

[0092] The materials prepared in Example 3 and Comparative Example 3 were used as the negative electrode, lithium metal was used as the positive electrode, PP membrane was used as the separator, 1 mol / L LiPF6-EC / DMC (volume ratio 1:1) was used as the electrolyte, and 4 wt% FEC additive was added.

[0093] Table 2

[0094] The results show that the electrodes prepared by the stepwise mixing method of Examples 1-3 of the present invention produce batteries with significantly better capacity, rate performance and cycle stability than the conventional one-step mixing method of Comparative Examples 1-3.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite electrode material, characterized in that, The material includes at least two active materials, each of which is combined with a conductive agent and a fibrillated binder to form a structural unit. The structural unit is a three-dimensional network composite particle formed by the fibrillated binder encapsulating and wrapping the active material and the conductive agent. The particle size of the structural unit is 10-500 μm. Multiple structural units are uniformly distributed in the composite electrode material, and the structural units are intertwined with each other through the binder fibers at the interfaces of each structural unit to form a continuous three-dimensional network structure.

2. The composite electrode material according to claim 1, characterized in that, The combination of active substances is selected from at least one of sodium iron pyrophosphate-Prussian blue compounds, sodium iron sulfate-layered oxides, lithium iron phosphate-NCM, and graphite-silicon carbon.

3. The composite electrode material according to claim 1, characterized in that, The conductive agent is selected from at least one of conductive carbon black, CNT, Ketjen black, acetylene black, graphene, carbon nanofibers, and Super P.

4. The composite electrode material according to claim 1, characterized in that, The adhesive is selected from polytetrafluoroethylene.

5. The composite electrode material according to claim 1, characterized in that, The particle size of the structural unit is 20~200μm.

6. A method for preparing the composite electrode material according to any one of claims 1 to 5, characterized in that, Includes the following steps: Different active substances are mixed with conductive agents and binders at 1000~5000 rpm for 5~30 minutes, and then fiberized at 1000~10000 rpm for 1~20 minutes to form corresponding fiberized structural units for each active substance. At least two types of fibrous structural units are mixed at 100-800 rpm for 10-60 minutes to obtain a composite electrode material.

7. A composite electrode sheet, characterized in that, The composite electrode material according to any one of claims 1 to 5 includes a current collector and a hot-pressed composite on the current collector.

8. The application of the composite electrode sheet of claim 7 in the preparation of a battery.

9. A composite battery, characterized in that, Includes the composite electrode sheet as described in claim 7.

10. The application of the composite battery of claim 9 in new energy vehicle power batteries, large-scale energy storage systems, consumer electronics and wearable devices or special equipment.

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