Cathode Active Material Composition for Low-Impurity Battery Cycling
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving a balance between cost reduction and maintaining high electrochemical performance, particularly when using low-cost raw materials that introduce impurities affecting capacity and stability.
Innovation Solution
A positive electrode active material comprising secondary particles and single-crystal or quasi-single-crystal particles, with controlled impurity contents and particle size ratios, is used to improve kinetic and cycle stability, along with a separator to prevent transition metal ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-cost raw materials (recycled by-products) are used to reduce costs, then manufacturing cost decreases, but impurity content increases reducing capacity
Solution Approach 1:
The positive electrode active material is segmented into two distinct particle types: secondary particles containing M1 element (transition metal other than iron) and single-crystal or quasi-single-crystal particles containing Ma element. This segmentation allows each particle type to serve different functions - secondary particles provide cost-effectiveness while single-crystal particles maintain structural stability and reduce impurity dissolution, thereby resolving the contradiction between using low-cost materials and maintaining battery capacity
Solution Approach 2:
The invention creates a composite material system where secondary particles and single-crystal particles coexist in a specific mass ratio (30:70 to 70:30). The composite structure combines the advantages of both particle types: the cost benefits of recycled materials in secondary particles with the high stability and low impurity content of single-crystal particles, achieving both cost reduction and capacity maintenance
2Ease of manufacture
If secondary particles with high impurity content are used to reduce costs, then manufacturing cost decreases, but transition metal dissolution increases causing self-discharging
Solution Approach 1:
The single-crystal or quasi-single-crystal particles act as an intermediary between the secondary particles and the electrolyte/negative electrode. These particles have lower M1 element content and higher structural stability, serving as a buffer that reduces the dissolution and migration of transition metals from the high-impurity secondary particles, thereby mitigating the self-discharging phenomenon while allowing the use of cost-effective secondary particles
Solution Approach 2:
The invention converts the harmful effect of impurities in recycled materials into a beneficial structure. By intentionally incorporating controlled amounts of M1 element (transition metal impurities) into the secondary particles and balancing them with pure single-crystal particles, the impurities are contained and managed rather than eliminated, reducing overall material costs while maintaining performance through the synergistic particle composition
3Productivity
If small particle size is used to improve kinetic performance, then capacity level increases, but grain boundary quantity increases promoting impurity migration
Solution Approach 1:
The invention applies local quality by creating particles with different internal structures: secondary particles with aggregated primary particles (providing short diffusion paths for kinetic performance) and single-crystal particles (providing structural stability). The local composition varies within and between particle types, allowing small particle sizes for good kinetics while the single-crystal regions provide barriers to impurity migration
Data Source
AI summary
A positive electrode active material, a positive electrode plate, a secondary battery, and a power consuming apparatus are provided. The positive electrode active material includes (i) secondary particles and (ii) single-crystal or quasi-single-crystal particles. The secondary particles are mainly formed by aggregating primary particles and the secondary particles further include an M1 element. The M1 element includes a transition metal element other than iron. A mass content of the M1 element is X1 based on a total mass of the secondary particles, where 500 ppm≤X1≤5000 ppm, and optionally, 800 ppm≤X1≤2000 ppm. The single-crystal or quasi-single-crystal particles include an Ma element. The Ma element includes a transition metal element other than iron. A mass content of the Ma element is X2 based on a total mass of the single-crystal or quasi-single-crystal particles, where X2 is less than X1.