An efficient dry electrode mixing method for sodium-ion battery hard carbon anode

Abstract

The present application relates to a kind of efficient dry method electrode mixing method for sodium-ion battery hard carbon negative electrode, belong to sodium-ion battery hard carbon negative electrode technical field.The mixing method includes the following steps:S1, hard carbon and conductive carbon black SP are mixed uniformly, PTFE powder is added, mixed uniformly, ensure that mixing temperature is <18 ℃;Temperature is controlled at 45±2 ℃ and is stirred at medium speed;Finally, temperature is controlled at 50±2 ℃, and high-speed stirring is carried out, to obtain hard carbon negative electrode material.The present application uses solvent-free dry mixing process, realizes the synergistic optimization of efficiency, energy consumption, structure and performance in the process of pole piece preparation;Lay the key process foundation for the preparation of high-performance, high-reliability sodium-ion battery hard carbon negative electrode.

Description

Technical Field

[0001] This invention relates to a highly efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries, belonging to the technical field of hard carbon anodes for sodium-ion batteries. Background Technology

[0002] Sodium-ion battery anode materials primarily use hard carbon as the active material. Hard carbon has the characteristics of moderate specific capacity, low sodium intercalation potential, and good cycle stability, and is therefore widely used in sodium-ion battery systems. Conductive agents need to be added to the anode formulation to improve electronic conductivity, and polymer binders are used to bond and shape the electrode sheets.

[0003] Currently, the mainstream process in the industry is the wet slurry preparation process to prepare sodium-ion battery anodes. This wet slurry preparation process typically uses water-based or organic solvents as the dispersion medium. Hard carbon, conductive agents, and binders are added sequentially to a mixing tank, and the system is made uniform through low-speed stirring and high-speed dispersion. Then, the electrode sheet is obtained by coating and drying.

[0004] For example, the invention patent with application number CN 117832489 A discloses a sodium-ion battery negative electrode slurry. The sodium-ion battery negative electrode slurry includes hard carbon, a first conductive agent, a first thickener, a first binder, and a solvent. The ratio of hard carbon to conductive agent to thickener to first binder is (85~97):(0~5):(0.5~3):(1.5~7) by mass.

[0005] The mixing stage of wet slurry processing has the following typical characteristics: 1) Mixing relies on the liquid phase as the mass transfer and dispersion medium, requiring the binder to swell or dissolve first; 2) Shear energy during mixing must be transferred to solid particles through the liquid phase, and energy utilization efficiency is limited by liquid viscosity and solid content; 3) To avoid local overheating, splashing, or agglomeration of the slurry, the stirring speed is usually limited; 4) The mixing time is relatively long, typically requiring 8-12 hours to meet process requirements. Therefore, in wet slurry processing, the mixing stage not only has high energy consumption but also a slow production pace, becoming a significant factor restricting the efficiency of anode material manufacturing. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems, thereby providing a highly efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries.

[0007] The technical solution of the present invention to solve the above problems is as follows:

[0008] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0009] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0010] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0011] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0012] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0013] This invention provides an innovative dry mixing process for preparing hard carbon anode sheets for sodium-ion batteries. This solution is not a simple replacement for the traditional wet slurry process, but rather a highly efficient material composite solution based on a deep understanding of the intrinsic relationship between electrode microstructure and electrochemical performance, the mechanism of polymer binders, and the shortcomings of existing processes. Its fundamental goal is to solve the high energy consumption, low efficiency, and environmental bottlenecks introduced by organic solvents in the wet slurry process, while overcoming the technical difficulties of unstable conductive networks and poor electrode mechanical properties caused by early dry mixing methods, thereby achieving a greener, more efficient, and higher-performance electrode preparation process.

[0014] Specifically, at the first rotation speed, hard carbon and SP are mixed at a low speed to achieve initial dispersion and deagglomeration of the two; at the second rotation speed, PTFE powder is introduced and mixed with the hard carbon / SP system to ensure uniform distribution of PTFE without fiberization; at the third rotation speed, the shear strength is increased and the system temperature is raised to cause PTFE to begin to fiberize and form a preliminary fiber network skeleton; at the fourth rotation speed, the shear strength and system temperature are further increased to fully fiberize PTFE and form a continuous and stable three-dimensional network structure, which firmly locks the hard carbon active particles and SP conductive agent within it.

[0015] Background technology has clearly pointed out that the fundamental drawback of wet process is that the energy consumption in the mixing stage is high and the production pace is slow; in addition, there are concerns about structural stability: the introduction of solvent may change the surface properties of some materials, and the evaporation of solvent during the drying process may cause secondary agglomeration of conductive agent, affecting the continuity of the final conductive network.

[0016] The dry mixing process of this invention is a systematic change aimed at addressing the aforementioned contradictions. It transforms electrode preparation from a "wet chemical process" into a "dry physical reconstruction process".

[0017] Firstly, the construction and efficiency improvement of the solvent-free system. This solution completely eliminates solvents, employing a pure solid-phase high-speed shearing physical method to directly act on the powder system. The technical logic lies in achieving mixing and dispersion by directly applying mechanical energy to the van der Waals forces and mechanical meshing points between particles. This fundamentally eliminates all time-consuming steps such as binder dissolution, fine-tuning of slurry viscosity, lengthy stirring, and solvent evaporation and drying. The direct technical effect is a reduction in mixing time from the traditional 8-12 hours to approximately 0.5 hours, increasing efficiency by about 22 times. Simultaneously, it eliminates all high-energy-consuming steps related to solvents, significantly reducing energy consumption per unit output, and completely avoids the complex processes of solvent recovery and waste gas treatment, achieving ultimate simplification and environmental friendliness in the process flow.

[0018] Secondly, the invention employs graded shearing and programmed construction of the conductive network. To avoid powder splashing, secondary agglomeration, or excessive fiberization of the PTFE binder caused by high-speed shearing in a single step, this invention creatively designs a gradient of rotational speeds from low to high (first speed < second speed < third speed < fourth speed). The technical logic is to decompose the complex mixing and fiberization process into four progressive stages: "preliminary mixing → deagglomeration → PTFE fiberization → structural locking." In the low-speed stage, the focus is on achieving sufficient deagglomeration of hard carbon and SP, providing a uniform "powder matrix" for the subsequent construction of the conductive network. The subsequently introduced PTFE is uniformly attached to the powder surface in an unactivated state. Only in the subsequent medium-to-high-speed stages, under precise temperature control, is the PTFE fiberization process initiated and advanced in an orderly manner. The ingenuity of this programmed design lies in ensuring that the SP conductive agent is fully dispersed before the PTFE fiber skeleton is formed, and is captured and fixed on the nodes of the fiber network instantly and uniformly during the fiberization process, thereby minimizing the probability of subsequent agglomeration and ultimately forming a continuous, stable and efficient conductive network, laying a solid structural foundation for improving the cycling stability of the electrode.

[0019] Thirdly, the controlled fibrillation of PTFE under temperature control. The fibrillation behavior of PTFE is extremely sensitive to its molecular weight, shear force, and ambient temperature. This invention achieves precise control over the untangling, orientation, and degree of fibrillation of PTFE molecular chains by setting strict staged temperature control (S1 / S2 stage <18℃, S3 stage 45±2℃, S4 stage 50±2℃). The technical logic lies in controlling the shear temperature near the glass transition temperature of PTFE. At low temperatures, even when shear force is applied, PTFE only undergoes physical displacement and mixing, without triggering slippage and fibrillation of its molecular chains, thus avoiding the premature formation of inhomogeneous, weakly connected structures. When the temperature rises to its activation range, strong shearing is applied, allowing the PTFE molecular chains to smoothly untangle, stretch, and intertwine, forming an ideal three-dimensional fiber network with sufficient toughness and strength. The effect of this temperature control synergistic strategy is to achieve "controllable and full fiberization" of PTFE, which not only ensures that the electrode has sufficient mechanical strength to resist volume deformation during charging and discharging, but also avoids the risk of PTFE degradation or hard carbon structure damage due to excessive temperature, or fiber breakage due to excessive shear, thus obtaining an electrode with stable structure and reliable performance.

[0020] As a preferred embodiment of the above technical solution, in steps S3 and S4, hot water is introduced into the jacket of the high-temperature mixer to maintain the required temperature for each step.

[0021] Compared to other heating methods, the heat medium water circulation system has excellent temperature uniformity and precise controllability, which can ensure that the temperature of the key fiberization stages S3 and S4 is stable at the set value (45±2℃ and 50±2℃), thereby achieving controllable process and uniform results of PTFE fiberization, effectively avoiding degradation caused by local overheating or insufficient fiberization caused by insufficient temperature.

[0022] As a preferred embodiment of the above technical solution, the first rotational speed < the second rotational speed < the third rotational speed < the fourth rotational speed.

[0023] By using a speed gradient from low to high, the powder undergoes a gradual process from initial mixing to deagglomeration, PTFE fiberization, and structural locking. This avoids powder splashing, agglomeration, or excessive PTFE fiberization caused by a single high-speed shearing step, ensuring uniform mixing and structural stability.

[0024] As a preferred embodiment of the above technical solution, the linear velocity range of the first rotation speed is 3~8 m / s, and the stirring time at the first rotation speed is 8~12 min.

[0025] At lower speeds and longer durations, the hard carbon and SP are preferentially mixed and deagglomerated, providing a uniform powder matrix free of secondary agglomeration for subsequent PTFE fiberization, thus ensuring the uniformity of the conductive network from the source.

[0026] As a preferred embodiment of the above technical solution, the linear velocity range of the second rotation speed is 8~15 m / s, and the stirring time at the second rotation speed is 6~10 min.

[0027] At low to medium speeds, the PTFE powder is fully mixed with the uniformly dispersed hard carbon / SP system to ensure that the binder is uniformly coated on the powder surface. At the same time, it avoids local frictional heat generation that could cause premature fiberization or agglomeration of PTFE, thus creating an ideal initial homogeneous state for subsequent high-speed shearing.

[0028] As a preferred embodiment of the above technical solution, the linear velocity range of the third rotation speed is 15~25 m / s, and the stirring time at the third rotation speed is 4~6 min.

[0029] Under medium-to-high-speed shear and PTFE activation temperature, PTFE begins to undergo mild fibrosis, forming a preliminary fibrous network that initially wraps around and fixes hard carbon and SP. This stage is a key transition for building a stable conductive network.

[0030] As a preferred embodiment of the above technical solution, the linear velocity range of the fourth rotation speed is 35~45 m / s, and the stirring time at the fourth rotation speed is 2~4 min.

[0031] Under high-speed shearing and fully activated temperatures, PTFE completes full fiberization, forming a continuous and dense three-dimensional network structure. This firmly locks the hard carbon active particles and SP conductive agent within the fiber skeleton, completing the ultimate reconstruction of the electrode structure and ensuring the optimal match between its mechanical strength and conductivity.

[0032] As a preferred embodiment of the above technical solution, in steps S1 and S2, the mass of hard carbon is m1, the mass of SP is m2, and the mass of PTFE is m3; wherein m1+m2 accounts for 95~98% of the total mass; and m2 accounts for 2~5% of the total mass.

[0033] The high content of active materials (95-98%) maximizes the theoretical specific capacity of the electrode; an appropriate amount of SP (2-5%) is sufficient to form a continuous conductive path in the PTFE fiber network; and trace amounts of PTFE (1-3%) act as "molecular glue" to build a stable framework. This formulation achieves the optimal balance between electrochemical performance (high capacity) and structural stability (high strength, high conductivity).

[0034] In summary, the present invention has the following beneficial effects:

[0035] 1. Significant improvement in process efficiency and economic benefits: Through solvent-free dry process, the mixing time is shortened from several hours to less than half an hour, and the efficiency is improved by more than 20 times; at the same time, high-energy-consuming and high-cost links such as solvent evaporation, recovery and waste gas treatment are eliminated, significantly reducing production energy consumption and operating costs, improving production efficiency, and showing outstanding prospects for industrial application.

[0036] 2. Synergistic enhancement of electrode structure stability and electrochemical performance: Through the synergistic effect of graded shearing and temperature control, the PTFE binder was controlled and fully fibrousized, constructing a continuous and stable three-dimensional conductive network. This not only significantly improved the mechanical strength of the electrode, enabling it to better withstand the volume changes caused by sodium ion insertion / extraction, thereby improving the cycle life and structural stability of the battery, but also optimized the electron conduction path, ensuring the effective performance of the electrode's electrochemical performance.

[0037] 3. Guarantee of green environmental protection and safe production: Completely eliminating organic solvents eliminates the risks of flammability and explosion, toxic waste gas emissions and complex solvent recovery systems from the source, greatly reducing environmental pressure and safety hazards, which meets the country's urgent requirements for energy conservation and emission reduction and green manufacturing in the new energy industry, and helps enterprises achieve sustainable development.

[0038] 4. Simplified process and optimized equipment investment: The dry mixing process has simple steps and does not require large-scale drying, solvent recovery and waste gas treatment equipment, which simplifies the overall production process, reduces the one-time investment in production line construction and the plant space requirements, and provides convenience for enterprises to quickly start production and expand production capacity.

[0039] 5. In summary, the solvent-free dry mixing process of this invention, starting from the intrinsic requirements of electrode microstructure design, achieves synergistic optimization of efficiency, energy consumption, structure, and performance during electrode preparation through a disruptive process route and refined process control. This solution transcends the traditional functional positioning of wet slurry mixing as a "dispersion-coating" pretreatment step, evolving into a highly efficient material processing technology integrating "mixing, dispersion, compounding, and molding." It not only provides an ultimate solution to the high energy consumption and high pollution problems of wet processes but also lays a crucial process foundation for the preparation of high-performance, high-reliability hard carbon anodes for sodium-ion batteries. This has significant engineering practical significance for promoting the industrialization of sodium-ion battery technology and reducing costs and increasing efficiency. Attached Figure Description

[0040] Figure 1 These are the charge-discharge curves of the negative electrode coin cells for the dry method (Example 1) and the wet method (Comparative Example 1). Detailed Implementation

[0041] The present invention will be further explained and described below with reference to the accompanying drawings.

[0042] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. Any changes made by those skilled in the art after reading the specification of the present invention, as long as they are within the scope of the claims, will be protected by patent law.

[0043] Example 1

[0044] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0045] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0046] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0047] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0048] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0049] Specifically, the parameters for Example 1 are as follows:

[0050] Formula: Hard carbon m1 = 95.0 g, SP m2 = 3.0 g, PTFE m3 = 2.0 g, m1 + m2 account for 98% of the total mass, and m2 accounts for 3% of the total mass.

[0051] Process parameters:

[0052] S1: First rotational speed linear velocity 5 m / s, stirring time 10 min, cooling water controlled temperature 15℃;

[0053] S2: Second rotational speed linear velocity 12 m / s, stirring time 8 min, cooling water controlled temperature 16℃;

[0054] S3: Third rotational speed linear velocity 20 m / s, stirring time 5 min, jacket heating medium water control temperature 45℃;

[0055] S4: Fourth rotational speed linear velocity 40 m / s, stirring time 3 min, jacket heating medium water control temperature 50℃;

[0056] Total mixing time: 26 min.

[0057] Example 2

[0058] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0059] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0060] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0061] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0062] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0063] Specifically, the parameters for Example 2 are as follows:

[0064] Mixing ratio: Hard carbon m1 = 93.0 g, SP m2 = 5.0 g, PTFE m3 = 2.0 g, m1 + m2 account for 98% of the total mass, and m2 accounts for 5% of the total mass;

[0065] Process parameters:

[0066] S1: First rotational speed linear velocity 3 m / s, stirring time 12 min, cooling water controlled temperature 17℃;

[0067] S2: Second rotational speed linear velocity 8 m / s, stirring time 10 min, cooling water controlled temperature 18℃;

[0068] S3: Third rotational speed linear velocity 15 m / s, stirring time 6 min, jacket heating medium water control temperature 43℃;

[0069] S4: Fourth rotational speed linear velocity 35 m / s, stirring time 4 min, jacket heating medium water control temperature 48℃;

[0070] Total mixing time: 32 min.

[0071] Example 3

[0072] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0073] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0074] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0075] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0076] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0077] Specifically, the parameters for Example 3 are as follows:

[0078] Mixing ratio: Hard carbon m1 = 96.0 g, SP m2 = 2.0 g, PTFE m3 = 2.0 g, m1 + m2 account for 98% of the total mass, and m2 accounts for 2% of the total mass.

[0079] Process parameters:

[0080] S1: First rotational speed linear velocity 8 m / s, stirring time 8 min, cooling water controlled temperature 14℃;

[0081] S2: Second rotational speed linear velocity 15 m / s, stirring time 6 min, cooling water controlled temperature 15℃;

[0082] S3: Third rotational speed linear velocity 25 m / s, stirring time 4 min, jacket heating medium water control temperature 47℃;

[0083] S4: Fourth rotational speed linear velocity 45 m / s, stirring time 2 min, jacket heating medium water control temperature 52℃;

[0084] Total mixing time: 20 min.

[0085] Example 4

[0086] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0087] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0088] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0089] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0090] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0091] Specifically, the parameters for Example 4 are as follows:

[0092] Mixing ratio: Hard carbon m1 = 92.0 g, SP m2 = 3.0 g, PTFE m3 = 5.0 g, m1 + m2 account for 95% of the total mass, and m2 accounts for 3% of the total mass.

[0093] Process parameters:

[0094] S1: First rotational speed linear velocity 4 m / s, stirring time 11 min, cooling water controlled temperature 16℃;

[0095] S2: Second rotational speed linear velocity 10 m / s, stirring time 9 min, cooling water controlled temperature 17℃;

[0096] S3: The third rotational speed linear velocity is 18 m / s, the stirring time is 5 min, and the jacket heating medium water temperature is controlled at 44℃.

[0097] S4: Fourth rotational speed linear velocity 38 m / s, stirring time 3 min, jacket heating medium water control temperature 49℃;

[0098] Total mixing time: 28 min.

[0099] Example 5

[0100] A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries includes the following steps:

[0101] S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃.

[0102] S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃.

[0103] S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃.

[0104] S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

[0105] Specifically, the parameters for Example 2 are as follows:

[0106] Formula: Hard carbon m1 = 96.0 g, SP m2 = 3.0 g, PTFE m3 = 1.0 g, m1 + m2 account for 99% of the total mass, and m2 accounts for 3% of the total mass.

[0107] Process parameters:

[0108] S1: First rotational speed linear velocity 6 m / s, stirring time 9 min, cooling water controlled temperature 15℃;

[0109] S2: Second rotational speed linear velocity 13 m / s, stirring time 7 min, cooling water controlled temperature 16℃;

[0110] S3: Third rotational speed linear velocity 22 m / s, stirring time 4 min, jacket heating medium water control temperature 46℃;

[0111] S4: Fourth rotational speed linear velocity 42 m / s, stirring time 2 min, jacket heating medium water control temperature 51℃;

[0112] Total mixing time: 22 min.

[0113] Comparative Example 1 (Wet Process)

[0114] Mixing ratio: Hard carbon m1 = 95.0 g, SP m2 = 3.0 g, binder m3 = 2.0 g (using CMC+SBR system), m1+m2 account for 98% of the total mass, and m2 accounts for 3% of the total mass.

[0115] Process parameters:

[0116] Solvent: Deionized water, solid content 45%;

[0117] Slurry mixing process: First, add deionized water and CMC, and stir at low speed for 30 min to fully dissolve CMC; add hard carbon and SP, and stir at low speed for 1 h; add SBR emulsion, and stir at low speed for 30 min; disperse at high speed for 8 h, and control the temperature <40℃;

[0118] Coating: Coating speed 5 m / min, drying temperature 100℃, drying time 10 min;

[0119] Total mixing time: 10 h.

[0120] The negative electrode material of Example 1 was fabricated into a dry-process electrode sheet, and the same as the wet-process electrode sheet prepared in Comparative Example 1 were assembled with the same sodium metal positive electrode to form standard coin cells for testing. Electrochemical tests were then conducted. The results are shown in Table 1.

[0121] Table 1. Performance Comparison of Coin Cells with Dry-Process and Wet-Process Electrodes sample Mixing method Discharge specific capacity mAh / g Charging specific capacity mAh / g First-time efficiency % Example 1 Dry mixing 297.55 326.26 91.21% Comparative Example 1 Wet slurry 296.39 325.51 91.05% .

[0122] like Figure 1 As shown, the negative electrode coin charge-discharge curves for the dry method (Example 1) and the wet method (Comparative Example 1) are displayed.

[0123] From Table 1 and Figure 1 It is clear that the electrical performance of the embodiments of the present invention is not significantly different from that of the control group batteries. However, the dry mixing time is only 0.5 hours, compared to 11 hours for wet slurry mixing, resulting in a 22-fold increase in efficiency.

Claims

1. A high-efficiency dry electrode mixing method for hard carbon anodes in sodium-ion batteries, comprising the following steps: S1. Add hard carbon and conductive carbon black SP to the high speed mixer and stir at the first speed to ensure that the hard carbon and conductive carbon black SP are fully and evenly mixed. During this process, cooling water is circulated to ensure that the mixing temperature is <18℃. S2. Add PTFE powder and stir at the second speed to mix thoroughly and evenly. During this process, cool water is circulated to ensure that the mixing temperature is <18℃. S3. Turn off the cooling water and stir at the third speed. During the stirring process, the temperature is controlled at 45±2℃. S4. Stirring at the fourth rotation speed, with the temperature controlled at 50±2℃ during the stirring process, to obtain the hard carbon anode material for the sodium-ion battery.

2. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 1, characterized in that: In steps S3 and S4, the required temperature for each step is maintained by introducing hot water into the jacket of the high-temperature mixer.

3. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 1, characterized in that: First speed < Second speed < Third speed < Fourth speed.

4. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 3, characterized in that: The linear velocity range of the first rotational speed is 3~8 m / s, and the stirring time at the first rotational speed is 8~12 min.

5. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 3, characterized in that: The linear velocity range of the second rotation speed is 8~15 m / s, and the stirring time at the second rotation speed is 6~10 min.

6. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 3, characterized in that: The linear velocity range of the third rotation speed is 15~25 m / s, and the stirring time at the third rotation speed is 4~6 min.

7. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 3, characterized in that: The linear velocity range of the fourth rotation speed is 35~45 m / s, and the stirring time at the fourth rotation speed is 2~4 min.

8. The efficient dry electrode mixing method for hard carbon anodes in sodium-ion batteries according to claim 1, characterized in that: In steps S1 and S2, the mass of hard carbon is m1, the mass of conductive carbon black SP is m2, and the mass of PTFE is m3; wherein m1+m2 accounts for 95%~98% of the total mass; and m2 accounts for 2%~5% of the total mass.

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