High-Shear Mixing Screw for Polymer Fibrillation Without Overload
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Solution Overview
Problem
Conventional high shear mixing methods for fabricating dry electrodes in secondary batteries cause equipment overload and damage due to the fibrillization of polymers, making large-scale production difficult.
Innovation Solution
A high shear mixing unit with a specific design comprising a mixing screw and housing, featuring a rotating shaft with tapered portions and spiral blades, which efficiently micro-fibrillates polymers without causing overload, using a mixing screw with a rotating shaft having a first tapered portion, a kneading portion, and a second tapered portion, along with distinct spiral blades to manage shearing forces effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional planetary mixers or twin-screw extruders are used for high shear mixing, then the fibrillizable polymer can be micro-fibrillated, but the equipment experiences large loads and damage occurs
Solution Approach 1:
The mixing screw is segmented into multiple portions (first tapered portion, first kneading portion, second kneading portion, second tapered portion) with different blade configurations. Each segment handles a specific stage of the mixing and micro-fibrillation process, distributing the mechanical load across different sections rather than concentrating it in one area, thereby preventing equipment overload while achieving effective polymer fibrillation.
Solution Approach 2:
Different sections of the mixing screw have locally optimized properties: the tapered portions create high shear zones for intensive mixing, while the kneading portions provide gentler mixing zones. The blade pitches and angles are locally adjusted to match the specific requirements of each mixing stage, allowing efficient micro-fibrillation without excessive mechanical stress on the equipment.
2Reliability
If shearing force is reduced to prevent equipment damage, then the polymer is not well fibrillized
Solution Approach 1:
The mixing screw design creates dynamic mixing conditions where the polymer material experiences varying shear forces as it progresses through different sections. The tapered portions generate high shear forces for intensive fibrillation, while the kneading portions provide lower shear forces for gentle mixing, creating a dynamic balance that achieves good fibrillation quality without sustained high loads on the equipment.
Solution Approach 2:
The design changes physical parameters (blade pitch, blade angle, screw diameter) along the length of the mixing screw. The pitch and angle are optimized in each section to provide the appropriate shear force level for that stage of processing, enabling effective fibrillation in high-shear zones while using lower-shear zones for gentle mixing, thus preventing equipment overload.
3Productivity
If high shear mixing is applied to fabricate dry electrodes, then mixing efficiency is improved, but equipment overload occurs
Solution Approach 1:
The mixing process is segmented into multiple stages with different intensity levels. The tapered portions handle intensive high-shear mixing for rapid homogenization, while the kneading portions handle gentler mixing for thorough blending. This segmentation allows the system to achieve high overall mixing efficiency without any single section experiencing sustained overload conditions.
Solution Approach 2:
The mixing screw design ensures continuous useful action throughout the entire length of the screw. Material continuously progresses through high-shear zones and kneading zones in sequence, maintaining efficient mixing action throughout the process without interruption or stagnation, thereby achieving high productivity without equipment overload.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The unit efficiently mixes materials without overload, minimizing equipment damage and enabling large-scale production of dry electrodes by effectively micro-fibrillating polymers, enhancing mixing efficiency and reducing stagnation.
Implementation Method 1
high shear mixing methods described above use binders called 'fibrillizable binders' or 'fibril-forming binders,' which, when subjected to high shear mixing in a mixture containing such binders, micro-fibrillate and bind the active and conductive materials
Data Source
AI summary
A high shear mixing unit includes a mixing screw and a housing receiving the mixing screw; wherein the housing includes a nozzle provided at a distal end and a hopper in communication therewith, and wherein the mixing screw includes a rotating shaft and blades provided on an outer surface of the rotating shaft, wherein the rotating shaft has a first tapered portion having a gradually increasing outer diameter in a direction toward the nozzle, a kneading portion having a uniform outer diameter or a gradually increasing outer diameter in a direction toward the nozzle, and a second tapered portion having a gradually decreasing outer diameter in a direction toward the nozzle, in this order, and the blades comprise first spiral blades disposed on an outer surface of the first tapered portion, second spiral blades disposed on an outer surface of the kneading portion, and third spiral blades disposed on an outer surface of the second tapered portion, thereby providing a high shear mixing unit.