Double reflux mixer: technological innovation and industry application practice of efficient mixing of lithium battery materials

Technical pain points andindustry demands of lithium battery material mixing process

The mixing process of lithium battery positive electrode materials (such as NCM/NCA high nickel ternary, lithium iron phosphate), negative electrode materials (graphite) and electrolyte slurry has strict requirements on material uniformity, particle size distribution consistency and batch stability. The traditional horizontal ribbon mixer is limited by a single stirring mode and has three major technical bottlenecks: first, the mixing motion is single, and it is difficult to achieve shear and permeation mixing of micron-level powders, resulting in uneven dispersion of active substances and conductive agents, affecting the battery charging and discharging performance; second, the continuous production capacity is insufficient, and intermittent operation is difficult to match the beat requirements of lithium battery large-scale production lines; third, the filtration system is easy to clog and cannot effectively cope with the dust removal requirements of ultrafine powders such as lithium carbonate and lithium cobalt oxide, thereby affecting the purity of the material.

As the energy density of power batteries breaks through to more than 300Wh/kg, new systems such as high nickel (NCM811 and above) and silicon-based negative electrodes have put forward higher requirements for mixing equipment. For example, in the preparation of high-nickel ternary materials, the mixing uniformity of LiNi0.8Co0.1Mn0.1O2 and LiOH must reach more than 99%, otherwise it will cause lithium-nickel mixing defects and affect the battery cycle life. The mixing uniformity of traditional equipment can usually only reach 95%-97%, which can no longer meet the process requirements of the new generation of materials.

Technical architecture and innovative breakthroughs of double-reflow mixer

Double-reflow drum structure: synergistic strengthening of radial shear and horizontal spiral

The double-reflow mixer adopts a horizontal drum with double-drum interconnected structure design. Through the composite movement of special spiral direction blades, a three-dimensional mixing field of “radial shear + horizontal spiral” is constructed. When the drum rotates at a maximum speed of 10rpm, the material forms a convection cycle between the inner and outer drums, and is simultaneously affected by the horizontal displacement and radial throwing effect of the propeller spiral thrust. Taking the JSLH-10m³ model as an example, its Φ2000mm drum diameter and 10m³ volume form an ideal aspect ratio. Combined with a loading factor of <0.6, it not only avoids dead corners of material accumulation, but also strengthens the collision and shear between particles through the centrifugal force generated by the rotation of the drum, so that the mixing uniformity reaches ≥99%, which is 2-4 percentage points higher than that of traditional equipment.