CNT Cathode Layer Composition for Dense Li-Ion Battery Pores
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Solution Overview
Problem
Increasing the density of the positive electrode active material layer in nonaqueous electrolyte secondary batteries leads to small pore diameters, making it difficult for the positive electrode film forming agent to penetrate uniformly, resulting in degraded durability and capacity retention, especially in vehicle drive power supplies.
Innovation Solution
Incorporating 80% or more carbon nanotubes as a conductive material in the positive electrode active material layer with a peak pore diameter of 0.50 μm to 0.70 μm, and a content of 0.2% to 1.0% by mass, to enhance impregnating ability and ensure uniform film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of the positive electrode active material layer is increased, then the energy density and power output are improved, but the pore diameter becomes excessively small, making it difficult for the positive electrode film forming agent to permeate uniformly
Solution Approach 1:
The patent applies local quality by introducing carbon nanotubes as a conductive material specifically located within the positive electrode active material layer. These nanotubes create localized conductive pathways and maintain pore structures with peak diameters of 0.50-0.70 μm in critical regions, allowing the film-forming agent to permeate uniformly even when the overall layer density is increased to 3.8-4.0 g/cm³.
Solution Approach 2:
The patent employs composite materials by combining the positive electrode active material with carbon nanotubes as a conductive additive. This composite structure allows the layer to achieve high density while maintaining adequate porosity and conductivity. The carbon nanotubes fill spaces between active material particles, creating a composite that preserves pore architecture necessary for uniform film formation.
2Quantity of substance
If the density of the positive electrode active material layer is increased, then the energy density is improved, but the durability and capacity retention during storage deteriorate
Solution Approach 1:
The patent applies local quality by strategically distributing carbon nanotubes within the dense positive electrode active material layer. These nanotubes maintain localized pore structures with peak diameters of 0.50-0.70 μm, ensuring that the film-forming agent can reach and protect active material particles throughout the layer, thereby maintaining durability and capacity retention despite high overall density.
Solution Approach 2:
The carbon nanotubes act as intermediaries between the film-forming agent and the positive electrode active material particles. They facilitate the penetration and uniform distribution of the film-forming agent throughout the dense layer, mediating the interaction between the electrolyte additive and the active material to ensure adequate protection and long-term stability.
3Quantity of substance
If the pore diameter of the positive electrode active material layer is reduced, then the density is improved, but the initial resistance characteristics worsen
Solution Approach 1:
The patent employs composite materials by combining the positive electrode active material with carbon nanotubes. This composite structure reduces initial resistance despite small pore diameters. The carbon nanotubes form a conductive network that provides alternative pathways for electron transport, compensating for the limited ionic transport through small pores and maintaining low initial resistance.
Solution Approach 2:
The patent applies local quality by introducing carbon nanotubes specifically within the positive electrode active material layer to create localized conductive regions. These nanotubes establish efficient electron pathways at the particle level, ensuring low resistance characteristics even when the overall pore diameter is reduced to maintain high density.
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 configuration improves initial resistance and storage characteristics of the battery, maintaining capacity and reducing resistance increase during long-term storage, even with small pores, making it suitable for vehicle drive power supplies.
Implementation Method 1
The positive electrode active material layer includes a conductive material, wherein a content of the conductive material in the positive electrode active material layer is 0.2% by mass to 1.0% by mass. 80% by mass or more of the conductive material is carbon nanotubes
Implementation Method 2
A technique known to date is to make a nonaqueous electrolyte include an additive for forming a film on a positive electrode (also referred to as a so-called 'positive electrode film forming agent' or a 'positive electrode additive')
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery having excellent initial resistance characteristics and storage characteristics despite small pores of a positive electrode active material layer. The nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode includes a positive electrode current collector, and a positive electrode active material layer supported on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a conductive material. The positive electrode active material layer has a peak pore diameter of 0.50 μm to 0.70 μm. A content of the conductive material in the positive electrode active material layer is 0.2% by mass to 1.0% by mass. 80% by mass or more of the conductive material is carbon nanotubes. The nonaqueous electrolyte includes a nonaqueous solvent, an electrolyte salt, and a positive electrode film forming agent.