Positive Electrode Slurry Mixing for High-MW Binder Stability
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Solution Overview
Problem
Existing methods for preparing positive electrode slurry in secondary batteries lack versatility and cannot effectively accommodate binders with different weight average molecular weights, leading to poor manufacturing efficiency and increased costs due to issues like high discharge viscosity and gelation.
Innovation Solution
A multi-step stirring process involving first, second, third, and fourth stirrings is employed, with controlled stirring velocities and durations to prepare a positive electrode slurry, allowing for binders with molecular weights ranging from 800,000 to 8 million, thereby reducing discharge viscosity and gelation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a one-step slurry preparation method is used, then the process is simple, but it cannot adapt to binders with different weight average molecular weights and results in poor versatility
Solution Approach 1:
The slurry preparation process is divided into multiple distinct stirring steps (first stirring, second stirring, third stirring, fourth stirring), each with specific velocity ranges and durations. This segmentation allows different binder molecular weights to be accommodated by adjusting the parameters of individual steps, thereby improving versatility while maintaining manageable process complexity.
Solution Approach 2:
The stirring velocity is made dynamic by specifying different velocity ranges for different steps (e.g., first stirring: 50-150 rpm, second stirring: 100-200 rpm, third stirring: 150-300 rpm, fourth stirring: 200-400 rpm). This dynamic approach enables the process to adapt to binders with different molecular weights, achieving high versatility without excessive complexity.
2Reliability
If high molecular weight binders are used, then the binder performance is improved, but the discharge viscosity of the slurry increases
Solution Approach 1:
The process changes multiple parameters including stirring velocity, stirring duration, and additive composition across four distinct steps. By optimizing these parameters specifically for high molecular weight binders, the method maintains binder performance while controlling discharge viscosity through improved mixing efficiency and reduced aggregation.
Solution Approach 2:
The multi-step stirring process acts as an intermediary mechanism between the binder and solvent, progressively breaking down aggregates and ensuring uniform distribution. This intermediary approach allows high molecular weight binders to be effectively incorporated while minimizing viscosity increase.
3Strength
If high molecular weight binders are used, then the binder strength is improved, but gelation phenomenon occurs
Solution Approach 1:
The gelation prevention is achieved by segmenting the mixing process into four steps with progressively increasing stirring velocities. This gradual approach prevents sudden aggregation and gelation while maintaining binder strength, as each step builds upon the previous one to achieve uniform distribution without excessive shear stress.
Solution Approach 2:
The first two stirring steps perform preliminary mixing and dispersion before the final coating step. This preliminary action ensures that binders are properly distributed and activated before application, preventing gelation during the coating process while maintaining binder strength.
4Ease of operation
If the slurry viscosity is reduced, then the coating processability is improved, but the binder distribution uniformity may be compromised
Solution Approach 1:
The method optimizes multiple parameters including stirring velocity, stirring duration, and additive composition to achieve the right balance. By carefully controlling these parameters, the slurry achieves reduced viscosity for good coating processability while maintaining uniform binder distribution through the progressive mixing approach.
Solution Approach 2:
The four-step stirring process ensures continuous and progressive mixing action, preventing binder aggregation while maintaining uniform distribution. This continuous useful action throughout the preparation process ensures both low viscosity for good processability and uniform distribution for manufacturing precision.
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 method enhances the universality of the slurry preparation, improves production efficiency, and broadens the process window for coating, ensuring low discharge viscosity and stability even with high molecular weight binders.
Implementation Method 1
first stirring, a positive electrode active material and a conductive agent are mixed and stirred to prepare a dry mixture; in the second stirring, a binder and a solvent are mixed and stirred to prepare a glue solution; in the third stirring, the dry mixture and the glue solution are mixed and stirred to prepare a primary slurry; and in the fourth stirring, the binder, the solvent and the primary slurry are mixed and stirred to prepare a positive electrode slurry
Data Source
AI summary
A method for preparing a positive electrode slurry includes four sequential stirring steps. A positive electrode active material and a conductive agent are first stirred to form a dry mixture. A binder and a solvent are then stirred to form a glue solution. The dry mixture and glue solution are subsequently stirred to form a primary slurry. Finally, the binder, the solvent, and the primary slurry are stirred to obtain the positive electrode slurry. The binder and solvent used in the second and fourth stirrings are the same. Based on the total mass of binder used in both steps, 50% to 70% is added during the second stirring, and 30% to 50% during the fourth stirring. The application also relates to a positive electrode slurry prepared by this method, a secondary battery including the slurry, a battery pack, and an electrical apparatus comprising the battery.