Positive Electrode Mixture Conductive Network Design
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Solution Overview
Problem
Lithium secondary batteries face challenges with non-uniform dispersion of positive electrode active materials and conductive agents, leading to reduced battery performance and life characteristics due to low miscibility with solvents and agglomeration of fine conductive agent particles, resulting in inadequate conductivity and adhesion issues.
Innovation Solution
A positive electrode material mixture comprising a combination of particulate, fibrous, and plate-shaped conductive agents, along with crystalline and amorphous binders, is used to create a uniform dispersion and conductive network, enhancing lithium ion conductivity and reducing resistance, thereby improving low-temperature output and high-temperature storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fine conductive agent particles are dispersed in the solvent, then conductivity improvement effect is enhanced, but agglomeration of particles occurs easily due to strong cohesion
Solution Approach 1:
The patent introduces a binder as an intermediary substance between the conductive agent particles and the solvent. The binder wraps around the fine conductive agent particles, preventing direct particle-to-particle contact that causes agglomeration, while still allowing the particles to maintain their conductive function. This mediator approach resolves the contradiction by enabling particle dispersion without sacrificing conductivity.
Solution Approach 2:
The patent creates a composite structure where the binder and conductive agent form a combined material system. The composite consists of conductive agent particles embedded within or coated by the binder matrix, allowing the system to simultaneously exhibit both the conductive properties of the conductive agent and the dispersibility/stability provided by the binder.
2Ease of manufacture
If positive electrode active material and conductive agent are collectively mixed with solvent, then coating process is simplified, but non-uniform dispersion occurs due to low miscibility
Solution Approach 1:
The binder serves as a intermediary that facilitates uniform distribution of both the positive electrode active material and conductive agent throughout the solvent. By acting as a common binding medium for all components, it ensures that each particle type disperses uniformly without segregating, thereby achieving both process simplicity and coating uniformity.
Solution Approach 2:
The patent achieves homogeneity in the positive electrode slurry by using the binder to create a uniform matrix in which all solid components (active material and conductive agent) are evenly distributed. This homogeneous mixture ensures consistent coating thickness and composition across the entire electrode surface.
3Strength
If binder is non-uniformly dispersed in the positive electrode slurry, then adhesive strength becomes non-uniform, but positive electrode active material layer separates from collector
Solution Approach 1:
The binder's uniform dispersion throughout the positive electrode slurry ensures that adhesive strength is consistently distributed across the entire positive electrode active material layer. This homogeneous adhesion prevents localized weak points that could lead to separation or exfoliation during battery operation, thereby maintaining both strength and reliability.
Solution Approach 2:
The binder acts as a intermediary layer between the positive electrode active material layer and the positive electrode collector, providing uniform mechanical bonding. This intermediate binding layer distributes stress evenly and prevents direct contact-induced separation, ensuring both adequate adhesive strength and long-term structural reliability.
Data Source
AI summary
Provided are a positive electrode material mixture, in which, the positive electrode material mixture includes a positive electrode active material, a conductive agent, and a binder, wherein the conductive agent includes a particulate conductive agent, a fibrous conductive agent, and a plate-shaped conductive agent, and the binder includes a crystalline binder having a weight-average molecular weight (Mw) of 500,000 g/mol to 900,000 g/mol and an amorphous binder having a weight-average molecular weight (Mw) of 200,000 g/mol to 400,000 g/mol.