Positive Electrode Active Material with Oriented Crystallites
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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 material particles, which are influenced by the orientation and shape of primary particles, making it difficult to represent the properties of entire particles using TEM analysis.
Innovation Solution
A positive electrode active material is developed with a specific proportion of crystallites having a long-axis orientation degree of 0.5 to 1 and c-axis orientation degree of 0.5 to 1, calculated using scanning ion microscope and EBSD analysis, to improve the capacity and service life characteristics of lithium secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TEM analysis is used to analyze the shape and orientation of primary particles, then the shape and orientation information can be obtained, but it is difficult to represent the properties of the entire positive electrode active material particles because only partial region information is obtained
Solution Approach 1:
The invention transitions from two-dimensional TEM surface analysis to three-dimensional X-ray tomography analysis, enabling comprehensive observation of the entire particle interior and exterior structure, thus obtaining complete shape and orientation information of all primary particles within secondary particles
2Reliability
If the particle structure is controlled to improve performance, then capacity characteristics can be improved, but the complexity of characterizing and controlling crystallite orientation increases
Solution Approach 1:
The invention introduces X-ray tomography as an intermediary characterization technique that bridges the gap between microscopic crystallite orientation and macroscopic particle morphology, enabling non-destructive three-dimensional visualization and quantitative analysis of crystallite distribution and orientation within entire secondary particles
Data Source
AI summary
Provided is a positive electrode active material including a plurality of crystallites A, wherein the plurality of crystallites A has a crystallite long-axis orientation degree DoA represented by Equation 1 below is 0.5 to 1, and a crystallite c-axis orientation degree represented by a cross product value of a c-axis rotation vector Rc of a crystal lattice of a crystallite obtained by electron backscatter diffraction (EBSD) analysis and a position unit vector P′ of the crystallite is 0.5 to 1. A proportion of the plurality of crystallites A is 25% to 80% with respect to a total number of crystallites in a cross-section of a positive electrode active material. Further provided is a positive electrode and a lithium secondary battery including the positive electrode active material.