Positive Electrode Particle Resistance Balancing for Cycle Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium ion secondary batteries face challenges in improving battery characteristics such as cycle characteristics due to variations in spreading resistance within the positive electrode active material, particularly for particles with different sizes.
Innovation Solution
The positive electrode incorporates a mixture of first particles with larger diameters and second particles with smaller diameters, ensuring a resistance ratio (log R2/log R1) of 1.25 or less, with uniform attachment of conductive aids to suppress resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If particles with different sizes are used in the positive electrode active material, then the battery capacity can be improved, but the resistance variation among particles increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment and properties of particles based on their size. Small particles (≤8 μm) and large particles (>8 μm) are separately controlled for conductive aid attachment, with each size group receiving optimized treatment to achieve uniform resistance characteristics within each group while maintaining the benefits of size distribution for overall capacity.
Solution Approach 2:
The patent changes the parameter of conductive aid attachment quantity based on particle size. By adjusting the amount of conductive aid attached to small versus large particles, the invention optimizes the resistance characteristics for each particle size group, thereby reducing overall resistance variation while maintaining high battery capacity.
2Reliability
If the conductive aid is uniformly attached to all particles, then the resistance variation is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the particle population into two distinct size groups (small particles ≤8 μm and large particles >8 μm) and applies separate conductive aid attachment processes to each group. This segmentation enables targeted optimization of resistance characteristics for each size group while maintaining a manageable manufacturing process through clear classification and separate treatment.
Data Source
AI summary
A positive electrode includes a positive electrode active material containing a plurality of first particles and a plurality of second particles having an average particle diameter smaller than an average particle diameter of the plurality of first particles, and letting a resistance of the plurality of first particles be R1 and a resistance of the plurality of second particles be R2 as measured using a scanning spreading resistance microscope, a ratio (log R2/log R1) of logarithms of the resistance (R1) of the plurality of first particles and the resistance (R2) of the plurality of second particles is 1.25 or less.