Positive Electrode Composition for High-Density Low-Resistance Batteries
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving both improved energy density and reduced electric resistance.
Innovation Solution
A secondary battery design incorporating a positive electrode with a lithium-cobalt composite oxide, a vinylidene fluoride polymer binder with a melting point of 160-170°C, and carbon black conductor, along with specific weight and volume density ratios, to enhance energy density and reduce electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the positive electrode active material layer contains a high proportion of active material to improve energy density, then the energy density increases, but the electric resistance increases due to insufficient conductor content
Solution Approach 1:
The patent optimizes the weight ratios of components in the positive electrode active material layer, specifically setting the active material at 97.9-98.5 wt%, binder at 0.8-1.4 wt%, and conductor at 0.5-1.1 wt%. This precise parameter control allows high energy density while maintaining low electric resistance through adequate conductor distribution.
Solution Approach 2:
The patent uses a composite structure combining lithium-cobalt composite oxide active material with vinylidene fluoride polymer binder and carbon black conductor. This composite material approach allows simultaneous optimization of energy storage capacity and electrical conductivity by integrating multiple functional materials in specific proportions.
2Use of energy by moving object
If the positive electrode active material layer is compressed to increase volume density for higher energy density, then the energy density improves, but the manufacturing complexity increases
Solution Approach 1:
The patent specifies a volume density range of 4.15-4.30 g/cm³ for the positive electrode active material layer. By controlling this physical parameter during manufacturing, the patent achieves high energy density without requiring overly complex compression processes, as the specified range balances density achievement with manufacturing feasibility.
3Reliability
If the binder content is increased to improve adhesion between electrode and separator, then the adhesion improves, but the energy density decreases due to increased non-active material content
Solution Approach 1:
The patent optimizes the binder content to a specific range of 0.8-1.4 wt% of the total positive electrode active material layer weight. This precise parameter control ensures adequate adhesion between the electrode and separator while minimizing the impact on energy density by keeping the non-active material content as low as possible.
Solution Approach 2:
The patent uses vinylidene fluoride polymer with specific properties (melting point 160-170°C, molecular weight 300,000-700,000) to provide localized adhesion functionality. This allows the binder to perform its adhesion function effectively in the electrode- separator interface region without requiring high overall content, thus preserving energy density.
Data Source
AI summary
A method of manufacturing a secondary battery is provided and including a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductor. The negative electrode includes a negative electrode active material. The positive electrode active material includes a lithium-cobalt composite oxide. The positive electrode binder includes a vinylidene fluoride polymer having a melting point of higher than or equal to 160° C. and lower than or equal to 170° C. The positive electrode conductor includes carbon black having a hollow structure. The negative electrode active material includes a carbon material.