In lithium-ion battery manufacturing, the uniform mixing of cathode materials (NCM, LFP), anode materials (graphite, silicon-carbon), conductive agents, and binders is a core process determining battery energy density, cycle life, and safety performance. The stability and uniformity of the mixed system directly affect the lithium-ion transport efficiency and structural integrity within the electrode, becoming a crucial link between material research and development and battery mass production.
The mixing of cathode materials needs to balance complementary properties with balanced dispersion. NCM materials have the advantage of high energy density, while LFP materials are more competitive in terms of safety and cost control. Mixing the two in a specific ratio can achieve synergistic performance. During the mixing process, precise control of rotation speed and time is required to ensure thorough interweaving of the two types of particles. Simultaneously, conductive agents are added to build a continuous conductive network, and binders are used to enhance interparticle adhesion, avoiding polarization caused by excessively high local concentrations. Research shows that mixing a small amount of LFP with NCM can improve electrode density, but the mixing ratio needs to be strictly controlled to balance energy density and rate performance.
The core of anode material mixing is solving the volume expansion problem of silicon-carbon. Graphite materials exhibit excellent cycle stability, but their energy density is a bottleneck. Silicon-carbon materials, while possessing high energy density, are prone to volume deformation during charge and discharge. When mixing these two materials, the silicon powder must first undergo sand milling pretreatment to reduce particle size and remove impurities before being mixed with graphite at a mass ratio of 5%-15%. Ball milling ensures the silicon-carbon particles are uniformly dispersed within the graphite matrix, forming an elastic network with the aid of a binder. This buffers the structural damage caused by volume expansion and ensures uniform distribution of the conductive agent in the mixture, maintaining electron transport efficiency.
The compatibility between the conductive agent and the binder directly affects the quality of the mixture. The conductive agent must uniformly cover the surfaces of the positive and negative electrode active materials to construct a three-dimensional conductive pathway; its proportion is typically controlled at 5%-10%. The binder must be selected based on the material properties, balancing viscosity and flexibility, and its dosage must be precisely controlled to avoid affecting ion transport. During the mixing process, a step-by-step feeding strategy is required. The active materials and conductive agent are pre-mixed first, then the binder solution is added and dispersed at high speed, while simultaneously controlling ambient humidity and temperature to prevent slurry agglomeration or stratification.
Optimizing the uniform mixing process is key to breakthroughs in battery performance. From ball mill speed and mixing ratio to slurry viscosity control, every parameter adjustment directly affects electrode performance. In the future, with the precision upgrade of mixing equipment, the microscopic uniformity of material mixing will be further achieved, laying the foundation for the large-scale production of high-performance lithium-ion batteries.
