Positive Electrode Active Material Porous Structure
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Solution Overview
Problem
Existing secondary batteries cannot be effectively evaluated by simply measuring the porosity of the positive electrode mixture layer or the ratio of holes within the active material, as these metrics do not fully capture the battery's performance potential.
Innovation Solution
A novel structure for the positive electrode active material is introduced, featuring secondary particles formed from aggregated primary particles of lithium transition metal oxide with hollow portions and through holes, optimizing the ratios of inner volume to apparent volume and in-particle to out-of-particle porosity to enhance the battery's collecting capability and high-rate, cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porosity of the positive electrode mixture layer is increased to improve electrolyte penetration and ion migration, then the high-rate characteristics are improved, but the structural stability and manufacturing precision deteriorate
Solution Approach 1:
The patent applies porous materials by designing the positive electrode active material with a controlled porous structure having specific porosity (20-40%) and pore size distribution (0.1-3 μm). This porous structure enables improved electrolyte penetration and ion migration paths, enhancing high-rate discharge characteristics while maintaining structural integrity through controlled pore architecture rather than uncontrolled high porosity
Solution Approach 2:
The patent employs parameter changes by precisely controlling multiple parameters including porosity (20-40%), pore volume (10-150 mm³/g), and pore diameter (0.1-3 μm) of the positive electrode mixture layer. By optimizing these parameters within specific ranges, the patent achieves improved high-rate characteristics while maintaining manufacturing precision and structural stability
2Duration of action of stationary object
If the porosity of the positive electrode mixture layer is increased to enhance ion migration, then the cycle characteristics are improved, but the mechanical strength and structural stability worsen
Solution Approach 1:
The patent utilizes porous materials with a carefully engineered pore structure (porosity 20-40%, pore diameter 0.1-3 μm) that provides sufficient pathways for ion migration to improve cycle characteristics while the controlled pore size and distribution maintain the mechanical strength and structural stability of the electrode layer
Solution Approach 2:
The patent applies composite materials by combining the positive electrode active material with a binder and conductive additive to form a composite positive electrode mixture layer. This composite structure provides both the porous pathways needed for ion migration (improving cycle characteristics) and the mechanical framework provided by the binder and conductive network (maintaining structural stability)
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optimized structure improves the battery's high-rate and cycle characteristics by ensuring appropriate porosity and porosity ratios, allowing for better electrolyte penetration and ion migration, thereby enhancing performance and stability.
Implementation Method 1
a hollow portion formed in the secondary particles, and through holes penetrating the secondary particles so as to connect the hollow portion and the outside. A ratio (Vbc/Va) of an inner volume Vbc of holes formed inside the positive electrode mixture layer to an apparent volume Va of the positive electrode mixture layer satisfies 0.25≦(Vbc/Va)
Data Source
AI summary
A secondary battery 100 includes a positive electrode current collector 221 and a positive electrode mixture layer 223 which is coated over the positive electrode current collector 221. The positive electrode mixture layer 223 includes a positive electrode active material 610, an electrically conductive material 620, and a binder 630. In addition, the positive electrode active material 610 has secondary particles 910 formed by an aggregation of a plurality of primary particles of a lithium transition metal oxide, a hollow portion 920 formed in the secondary particle 910, and through holes 930 penetrating the secondary particles 910 so as to connect the hollow portion 920 and the outside. A ratio (Vbc/Va) of an inner volume Vbc of holes formed inside the positive electrode mixture layer 223 to an apparent volume Va of the positive electrode mixture layer 223 satisfies 0.25≦(Vbc/Va). In addition, in a section of the positive electrode mixture layer 223, a ratio (Vb/Vc) of an inner volume Vb of holes B formed inside the positive electrode active material 610 to an inner volume Vc of holes C formed outside the positive electrode active material 610 satisfies 0.05≦(Vb/Vc)≦2.5.