Composite Carbon Anode Material for Thinner Lithium-Ion Capacitors
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Solution Overview
Problem
The existing negative electrode active material for lithium ion capacitors does not achieve the desired high energy density and initial charge capacity per unit weight, limiting the potential for a high energy density lithium ion capacitor.
Innovation Solution
A composite carbon material is created by kneading carbon black with a carbon precursor, followed by baking and pulverization to achieve a specific particle size and BET specific surface area, optimizing the material's structure for improved charge capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the layer of negative active material is reduced to decrease cell volume, then the energy density per unit volume increases, but the initial charge capacity per unit weight decreases
Solution Approach 1:
The patent employs porous carbon materials with optimized pore structures to increase the surface area available for lithium ion insertion. The porous structure allows more lithium ions to be accommodated within the same volume, thereby maintaining high charge capacity while reducing overall cell volume. The pore size and distribution are controlled to optimize both capacity and energy density.
Solution Approach 2:
The patent uses composite carbon materials combining different carbon forms (amorphous carbon, graphite, carbon nanotubes) to achieve synergistic effects. The composite structure provides both high surface area for charge storage and adequate mechanical integrity, enabling thin layer construction without sacrificing charge capacity.
2Quantity of substance
If the average diameter of carbon black is reduced to increase surface area, then the initial charge capacity increases, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent optimizes the average diameter of carbon black to a specific range (1-20 μm) to achieve the best balance between charge capacity and manufacturing feasibility. This parameter optimization ensures sufficient surface area for lithium ion insertion while maintaining ease of handling, mixing, and electrode fabrication.
Solution Approach 2:
The patent uses a moderate amount of carbon precursor (30-200 parts by weight per 100 parts carbon black) to create porous structures without excessive complexity. This partial action approach achieves the desired porosity and surface area while keeping the manufacturing process simple and cost-effective.
3Quantity of substance
If the BET specific surface area is increased to improve charge capacity, then the initial charge capacity increases, but the bonding strength decreases
Solution Approach 1:
The patent creates composite materials where porous carbon particles are embedded in a carbon precursor matrix. This composite structure provides both high surface area for charge storage and strong bonding between particles and the electrode substrate, resolving the contradiction between capacity and bonding strength.
Solution Approach 2:
The patent creates local porous regions within the carbon material that provide high surface area for charge storage, while the overall structure maintains adequate bonding strength. The porous structures are distributed locally rather than uniformly throughout, allowing different regions to serve different functions.
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 composite carbon material enhances the initial charge capacity per unit weight and energy density of lithium ion capacitors, enabling a higher energy density while reducing the cell volume, with improved workability and bonding characteristics.
Implementation Method 1
kneading a carbon black having an average diameter of 12-300μm measured by the electron microscope method with a carbon precursor
Implementation Method 2
baking the kneaded mixture at a temperature of 800°C-3200°C
Implementation Method 3
baking the kneaded mixture at a temperature of 800°C-3200°C
Implementation Method 4
followed by pulverizing into an average diameter (D 50 ) of 1-20μm
Implementation Method 5
BET specific surface area of the porous carboneous composite material is above 100m2
Data Source
AI summary
This invention provides a negative electrode active material for lithium ion capacitor, which reduces the thickness of a negative-electrode active material layer while maintaining the conventional level of energy density. The negative-electrode active material for a lithium ion capacitor is a composite carbon material manufactured by kneading a carbon black having an average particle diameter of 12 to 300 nm measured by the electron microscopy method with a carbon precursor such as pitch, the resulting mixture is baked or graphitized baking between 800°C to 3200°C, and then pulverized such that the average particle diameter (D50) thereof is 1 to 20 µm and the BET specific surface area is between 100- 350 m2/g. An initial charging capacity is at least 700 mAh/g, and the cell volume is reduced as the thickness of the negative electrode active material layer becomes thinner than the conventional one.