Yushun Intelligent Double Planetary Mixer: Innovating the Preparation Technology of Lithium Battery Cathode Slurry

Today, as the battery power industry is accelerating its progress towards the TWh era, the energy density, cycle life and safety performance of lithium batteries have already become the key indicators of a company's core competitiveness. And all these performance aspects are rooted in the quality of the lithium battery positive electrode slurry preparation - as the "first line of defense" in the production of lithium battery positive electrode sheets, the uniformity, stability and dispersion of the positive electrode slurry directly determine the effectiveness of subsequent coating, rolling and other processes, and even influence the overall performance of the final battery product. Under such industry demands, Yushun Intelligent Double Planetary Mixer Machine, relying on its technical accumulation and innovative breakthroughs in the field of lithium battery equipment, precisely solves the core problems of positive electrode slurry preparation, and becomes a key equipment that helps enterprises reduce costs, increase efficiency and enhance product competitiveness.

Lithium battery cathode paste is not merely a simple mixture of materials, but rather a complex colloidal system composed of multiple components in precise proportions. It can be regarded as the "nutrient solution" of lithium batteries and serves as the core link connecting the raw materials of the cathode and the finished battery cells. Its main components include four key ingredients: cathode active materials (such as NCM523, NCM811, lithium iron phosphate, etc.), conductive agents (such as conductive carbon black, carbon nanotubes, etc.), binders (such as polyacrylonitrile, PVDF, etc.), and organic solvents (such as N,N-dimethylacetamide, N-methylpyrrolidone, etc.). Some formulations may also add a small amount of inorganic fillers and grinding agents to optimize performance.

These four components each have their own functions and are indispensable: The active materials are the core for energy storage and release, directly determining the energy density and voltage platform of the battery; The conductive agents are responsible for constructing an efficient electron transmission network, reducing the ohmic resistance of the electrode, and avoiding poor contact between active material particles; The binder acts like "glue", firmly fixing the active materials and conductive agents on the aluminum foil current collector, maintaining the integrity of the electrode structure, and ensuring a firm adhesion between the coating and the current collector; The organic solvents serve as the dispersion medium, dissolving the binders and wetting the surface of the solid particles, providing a guarantee for the uniform mixing of all components.

Ideally, the cathode slurry should achieve the effects of "no agglomeration, no bubbles, high uniformity, and high stability", allowing the conductive agent to uniformly cover the surface of the active material and the binder to form effective connections between the particles without blocking the pores. This microscopic-level uniform distribution is the prerequisite for lithium batteries to achieve high cycle life, high rate performance, and high safety, and it is also the core pursuit goal of the slurry preparation process. According to industry statistics, approximately 15% of lithium battery performance failures are attributed to slurry mixing process defects, which clearly demonstrates the importance of cathode slurry preparation.

At present, the slurry homogenization process for lithium battery cathode pastes mainly consists of four routes: wet method, semi-dry method, dry method, and wet method without binder (one-step method). Although each of these routes has its own focus, they all face a series of common and individual challenges, which have become the key bottlenecks restricting the production efficiency and product quality of enterprises. These can be summarized into four core problems:

The problem of uneven dispersion and agglomeration is prominent

The active materials and conductive agents in the cathode slurry are mostly nano-sized powders, which have a large specific surface area and high surface energy. They are prone to agglomeration. The traditional equipment has a single stirring method, which is difficult to form a comprehensive and high-intensity shear force, resulting in the powder particles not being fully dispersed, forming "hard agglomerated" particles - these agglomerated particles will block the electron transmission channels, reducing the battery energy density, and may also cause the separator to crack and capacity to decline. Especially in the dry method process, the uniformity of powder mixing is extremely high (the deviation value needs to be <3%), and traditional equipment is difficult to meet this strict standard. At the same time, it also faces the bottleneck of low powder wetting efficiency, and has extremely high requirements for the equipment stirring trajectory and dispersion disc line speed (≥17m/s).

Bubble retention and insufficient stability

Whether in the wet process for preparing PVDF gel solution or in the "one-step" production method without gel preparation, air is prone to be entrained during the stirring process, resulting in the formation of bubbles. The vacuum control capacity of traditional equipment is limited, and it is unable to effectively remove the tiny bubbles in the slurry. These bubbles will cause pinholes and material shortage defects during the electrode coating process, not only affecting the appearance quality of the electrode but also potentially causing internal short circuits in the battery, seriously threatening the safety of use. At the same time, traditional equipment has difficulty in precisely controlling the slurry temperature and viscosity, leading to stratification and precipitation of the slurry during storage and use, poor batch consistency, and affecting the stability of subsequent production - in the wet process, traditional equipment often faces problems such as bubble retention in the gel solution, insufficient material penetration, and poor batch stability; in the wet non-gel preparation process, the equipment is required to simultaneously achieve high-speed dispersion (1350 r/min) and precise vacuum control (-80 kPa), but traditional equipment is unable to balance dispersion efficiency and slurry stability.

Poor process compatibility and high energy consumption

Different cathode materials (such as ternary materials and lithium iron phosphate) and different homogenization process routes have significantly different requirements for parameters such as the rotational speed, torque, temperature control, and blade structure of the mixing equipment. For example, in the LFP system, due to its higher density (2.6g/cm³ vs NCM 2.0g/cm³), a higher rotational speed is needed to overcome the particle sedimentation resistance, while in the NCM system, an excessively high rotational speed will cause the PVDF molecular chains to break; in the semi-dry process, the "mixing-dispersion" dual-stage requires the equipment to have strong torque output and intelligent temperature control capabilities. Conventional equipment is prone to problems such as material jamming in the shaft, high energy consumption, and incomplete dispersion when using it. Traditional equipment is mostly of a fixed structure, unable to flexibly adapt to different process requirements. When changing the process, it is necessary to replace the equipment or make significant adjustments to the parameters, which is cumbersome and results in low equipment utilization and high energy consumption, increasing the production cost of the enterprise.

Low production efficiency and poor batch consistency

The stirring cycle of traditional homogenization equipment is long. For example, the conventional production cycle of the wet process requires more than 12 hours. Among them, the preparation of PVDF gel requires 4-6 hours of stirring + 12 hours of standing, the main material infiltration requires 5 hours, and the high-speed dispersion requires a continuous speed of 1300 r/min for 5 hours. This severely restricts the production efficiency. At the same time, the equipment lacks intelligent control capabilities and cannot monitor and adjust the stirring parameters in real time, resulting in large fluctuations in viscosity, dispersion degree and other indicators of the slurry from different batches (exceeding the national standard ±5% requirement), affecting the consistency of battery products, and increasing the workload and cost of subsequent sorting and testing.

In response to the four core pain points of the homogenization process, the R&D team of Yushun Intelligent Equipment spent three years conducting technical research and development. By integrating fluid mechanics, materials science and intelligent control technology, they have created a new generation of intelligent dual-planet mixing system. With five core advantages, it precisely solves the problems in the preparation of cathode pastes and becomes the preferred equipment for lithium battery enterprises - choosing Yushun intelligent double planetary mixer essentially means choosing an efficient, stable and energy-saving production solution, and also choosing to enhance product competitiveness.

Dual-planet compound mixing, solving the problem of uneven dispersion

The equipment adopts a dual-movement system of "planet frame revolution + dispersion disk rotation", combined with a rotary scraper design, to achieve 360° no-corner mixing and turbulent convection of the materials, completely saying goodbye to mixing dead zones and material residues. The bottom scraping design of the mixing paddle, combined with the high roundness (less than 0.2mm) of the barrel interior and the reasonable paddle-material gap, ensures that the materials on the barrel wall and bottom can be fully mixed. At the same time, the line speed of the dispersion disk can reach 25m/s, far exceeding the industry's conventional standards, which can generate high-intensity shear force, effectively break the powder agglomeration, and control the particle size of the paste at an extremely low level. The actual measurement data shows that compared with traditional equipment, the uniformity of the processed materials has improved by 40%, the batch consistency reaches 99.3%, perfectly meeting the strict requirements of the dry process for the uniformity of powder mixing, and significantly improving the powder wetting efficiency, suitable for the dispersion needs of various cathode materials such as ternary and lithium iron phosphate.

Upercritical vacuum technology eliminates the risk of residual bubbles

Yushun Intelligent has innovatively developed a multi-stage vacuum gradient control system, which can achieve an ultra-high vacuum level of -98 kPa, far exceeding the vacuum level of conventional equipment in the industry. At the same time, it adopts two sets of mechanical seals and a soft-hard composite seal design, as well as a fully sealed structure for the planetary transmission box, ensuring that the vacuum pressure remains above -0.092 for 24 hours without any oil leakage or gas leakage. This efficient vacuum system can quickly remove tiny bubbles from the slurry, increasing the defoaming efficiency by 60%, reducing the residual bubble content to less than 0.01%. This eliminates defects such as electrode holes and material shortages at their root, ensuring the safety performance of the battery. Moreover, the vacuum environment can effectively prevent solvent evaporation and slurry oxidation, further enhancing the stability of the slurry, and meeting the strict vacuum requirements of the wet non-curing process "one-step method"