Positive Electrode Active Material With Outer Crystallite Orientation Control
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving excellent capacity and service life characteristics due to variations in the physical properties of positive electrode active materials, which are influenced by the orientation and structure of crystallites within the particles, making it difficult to maintain consistent performance.
Innovation Solution
A positive electrode active material is developed with a specific proportion of crystallites in the outer region having high long-axis and c-axis orientation degrees, minimizing lithium ion movement distance and reducing particle contraction and expansion, thereby enhancing capacity and service life characteristics. This is achieved by controlling the crystallite structure using scanning ion microscope and EBSD analysis to optimize the orientation of crystallites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the orientation and structure of crystallites within positive electrode active material particles are not controlled, then manufacturing is simpler, but capacity and service life characteristics vary and cannot be maintained consistently
Solution Approach 1:
The patent applies local quality by specifying different crystallite orientation requirements for different regions of the particle. The outer region (from R/2 to surface) requires high long-axis orientation (DoA ≥ 0.5) and high c-axis orientation (cross product ≥ 0.5) to minimize lithium ion transport distance and reduce particle contraction/expansion, while the inner region (from center to R/2) has less stringent requirements. This regional differentiation ensures consistent capacity and service life characteristics without requiring uniform control throughout the entire particle.
2Productivity
If lithium ion movement distance is minimized through optimized crystallite orientation, then capacity characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The patent employs parameter changes by defining specific quantitative thresholds for crystallite orientation parameters: long-axis orientation degree DoA ≥ 0.5 and c-axis orientation degree (cross product of Rc and P') ≥ 0.5 in the outer region. These parameter specifications provide clear manufacturing targets that optimize lithium ion mobility while maintaining manufacturability, as the thresholds are based on fundamental crystallographic orientations rather than requiring complex microstructural engineering.
3Duration of action of stationary object
If particle contraction and expansion is reduced through crystallite orientation control, then service life characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by concentrating the crystallite orientation control requirements specifically in the outer region of the particle (from R/2 to surface), where lithium ion insertion and extraction occur. By requiring high long-axis orientation (DoA ≥ 0.5) and high c-axis orientation (cross product ≥ 0.5) only in this outer region, the patent minimizes particle contraction and expansion during electrochemical cycling, thereby extending service life without requiring uniform precision control throughout the entire particle structure.
Data Source
AI summary
Provided is a positive electrode active material which includes an inner region that is a region from the center of the positive electrode active material particle to R/2; and an outer region that is a region from R/2 to the surface of the positive electrode active material particle, wherein R is a distance from the center of the positive electrode active material particle to the surface thereof. The positive electrode active material further includes 30% to 80% of crystallites A with respect to a total number of crystallites in the outer region of the positive electrode active material, the crystallites A having high crystallite long-axis orientation degree and crystallite c-axis orientation degree. Thus, the positive electrode active material can achieve excellent capacity characteristics and service life characteristics.