Porous Positive Electrode Material for Adhesion and Capacity Balance
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Solution Overview
Problem
The adhesion force between the positive electrode current collector and the positive electrode mixture layer decreases when the positive electrode active material has a large number of pores, requiring more binding material, which can lead to a decrease in battery capacity, while a small number of pores reduces the reactive area, also decreasing battery capacity.
Innovation Solution
A positive electrode active material with specific pore-size distributions, including a peak at ≥30 nm in the adsorption isotherm and ≥twice the pore volume at ≤5 nm in the desorption isotherm, maintains sufficient reactive area and prevents binding material entry, thus maintaining adhesion force and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the positive electrode active material has a large number of pores, then the reactive area increases and battery capacity improves, but the adhesion force between the positive electrode current collector and the positive electrode mixture layer decreases
Solution Approach 1:
The patent applies porous materials with specifically controlled pore size distributions. The positive electrode active material contains pores with a volume ratio of 20-80% in the range of 0.003-0.05 μm and 5-30% in the range of 0.05-0.2 μm. This controlled porosity provides sufficient reactive area for high battery capacity while preventing excessive binding material penetration that would weaken adhesion force.
Solution Approach 2:
The patent changes the physical parameters of the pore structure by specifying precise pore size distributions. By controlling the volume ratios of different pore size ranges (0.003-0.05 μm and 0.05-0.2 μm), the patent optimizes the balance between reactive area and adhesion force, resolving the contradiction between these two parameters.
2Strength
If a larger amount of binding material is used to improve adhesion force, then the adhesion force between the positive electrode current collector and the positive electrode mixture layer increases, but the battery capacity decreases
Solution Approach 1:
The patent uses porous materials with optimized pore size distributions to reduce the need for binding material. The controlled pore structure (20-80% volume in 0.003-0.05 μm range, 5-30% in 0.05-0.2 μm range) provides adequate adhesion without requiring excessive binding material, thus maintaining battery capacity.
Solution Approach 2:
The patent changes the pore size parameters to achieve optimal adhesion with minimal binding material. By specifying the volume ratio distribution of different pore sizes, the patent reduces binding material penetration and requirements, resolving the contradiction between adhesion force and battery capacity.
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
This approach effectively suppresses the decrease in adhesion force and battery capacity by optimizing pore distributions, ensuring high peeling strength and capacity retention.
Implementation Method 1
in a pore-size distribution obtained by BJH analysis of a nitrogen adsorption isotherm
Implementation Method 2
a binding material enters the pores of the positive electrode active material during preparation of a positive electrode
Data Source
Figure 1
AI summary
Provided is a positive electrode active material capable of suppressing decrease in the adhesion force between a positive electrode collector and a positive electrode mixture layer and decrease in a battery capacity. The positive electrode active material having pores is characterized in that: in a pore diameter distribution obtained by analyzing a nitrogen adsorption isotherm by the BJH method, a pore diameter is 30 nm or more and a pore volume has a peak of 0.003 cm3/g or more; and in a pore diameter distribution obtained by analyzing a nitrogen desorption isotherm by the BJH method, the pore volume of a peak in a region having a pore diameter of 5 nm or less is twice or more of the pore volume of a peak in a region having a pore diameter of more than 5 nm in a desorption side pore diameter distribution.