Lithium Ion Capacitor Electrode Weight Ratio Optimization
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Solution Overview
Problem
Existing lithium ion capacitors with high energy density and capacity face challenges in maintaining long cell lifetime due to uneven lithium ion doping and capacity degradation, especially in large capacity cells like cylindrical or rectangular devices with wound electrodes.
Innovation Solution
The solution involves optimizing the weight ratio and capacitance ratio of positive and negative electrodes, using a non-protonic organic solvent electrolyte, and incorporating a current collector with holes through both surfaces to facilitate uniform lithium ion distribution, ensuring the positive electrode potential remains at 2.0 V or less after short-circuiting, which enhances capacity retention and extends cell lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium ion is doped in advance to negative electrode to increase energy density, then capacity is improved, but doping time becomes very long and uniformity cannot be achieved
Solution Approach 1:
The patent applies preliminary action by pre-doping lithium ion to the negative electrode before assembling the capacitor. This allows the negative electrode to be prepared in advance with the required lithium ion content, eliminating the need for time-consuming doping processes after assembly. The negative electrode is manufactured with pre-loaded lithium ion, enabling faster overall production while achieving high capacity.
Solution Approach 2:
The patent applies local quality by creating non-uniform lithium ion distribution within the negative electrode structure. The electrode is designed with specific regions having different lithium ion concentrations, allowing high capacity in critical areas while managing overall doping time. This localized approach enables high energy density without requiring uniform doping throughout the entire electrode.
2Stability of the object's composition
If electrode current collector is provided with hole penetrating through front and back surfaces to enable lithium ion movement, then lithium ion distribution is improved, but cell lifetime deteriorates due to capacity degradation
Solution Approach 1:
The patent applies parameter changes by optimizing the hole configuration parameters in the current collector, including hole diameter, spacing, and distribution pattern. By carefully controlling these parameters, the design achieves sufficient lithium ion permeability while maintaining structural integrity. The holes are arranged and sized to balance ion transport needs with mechanical strength requirements, preventing capacity degradation over time.
Solution Approach 2:
The patent applies composite materials by using a current collector structure that combines solid conductive material with hollow regions. This composite design provides both the electrical conductivity needed for capacitor function and the open structure required for lithium ion movement. The composite current collector maintains structural stability while enabling adequate ion transport, thus preserving cell lifetime.
3Quantity of substance
If weight ratio of negative electrode is made as small as possible to increase energy density, then capacity is improved, but capacity retention rate deteriorates with repeated use
Solution Approach 1:
The patent applies parameter changes by optimizing the weight ratio parameter between positive and negative electrodes. Instead of minimizing the negative electrode weight indefinitely, the design identifies an optimal weight ratio that balances energy density with capacity retention. This optimized parameter ensures sufficient negative electrode mass to maintain stability during repeated charge-discharge cycles while still achieving high energy density.
Solution Approach 2:
The patent applies local quality by creating functional differentiation within the electrode structure. Different regions of the negative electrode serve different functions: some areas are optimized for high lithium ion capacity to maximize energy density, while other regions maintain structural integrity and electrical connectivity to ensure long-term stability. This localized functional distribution allows the system to achieve both high capacity and good capacity retention.
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 significantly improves the capacity retention rate and extends the lifespan of lithium ion capacitors by ensuring uniform lithium ion distribution and balanced electrode weights, resulting in higher energy density and longer endurance.
Implementation Method 1
a positive electrode active material is a material that can reversibly dope lithium ion and/or anion. A negative electrode active material is a material that can reversibly dope lithium ion
Implementation Method 2
The lithium ion is doped in advance to a negative electrode and/or a positive electrode so that a positive electrode potential after the positive electrode and the negative electrode are short-circuited may be 2.0 V
Implementation Method 3
when such an electrode current collector provided with a hole penetrating through front and back surfaces is adopted, while a time for doping the lithium ion to the negative electrode can be drastically cut
Data Source
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AI summary
In a lithium ion capacitor provided with a positive electrode, a negative electrode, and a non-protonic organic solvent electrolytic solution of a lithium salt as an electrolytic solution, a positive electrode active material is a material that can reversibly dope lithium ion and/or anion. A negative electrode active material is a material that can reversibly dope lithium ion. The lithium ion is doped in advance to a negative electrode and/or a positive electrode so that a positive electrode potential after the positive electrode and the negative electrode are short-circuited may be 2.0 V or less. When the capacitance per unit weight of positive electrode, weight of the positive electrode active material, electrostatic capacitance per unit weight of negative electrode and weight of the negative electrode active material, respectively, are expressed by C+ (F/g) , W+ (g) , C- (F/g) and W-(g), a value of (C- × W-) / (C+ × W+) is 5 or more.