Lithium-Doped Negative Electrode Structure for High-Output Capacitance
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Solution Overview
Problem
Existing electrochemical devices combining lithium ion secondary battery and electric double layer capacitor principles face limitations in achieving high capacitance and high output characteristics due to the use of negative current collectors with through-holes, which increase resistance and reduce strength, making it difficult to achieve both high capacitance and high output simultaneously.
Innovation Solution
The use of a negative current collector with substantially no through-holes and a negative electrode mixture layer with a specific surface area between 30 m2/g to 60 m2/g, pre-doped with lithium ions, allows for high output and capacitance by maintaining strength and reducing resistance, while the thickness of the negative current collector can be minimized to maximize the thickness of the active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a negative current collector with through-holes is used, then the electrolyte penetration is improved, but the strength and resistance are worsened
Solution Approach 1:
The invention extracts and removes the through-holes from the negative current collector, keeping only the necessary surface area for electrode mixture attachment. This eliminates the structural weakness and resistance issues caused by through-holes while maintaining sufficient electrolyte access through the porous electrode mixture layer itself.
2Strength
If the negative current collector thickness is increased to maintain strength, then the strength is improved, but the active material layer thickness is reduced
Solution Approach 1:
By removing the through-holes that compromised structural integrity, the invention allows the use of thinner current collectors without sacrificing strength. This extracted flaw enables maximization of the active material layer thickness, directly increasing the energy storage capacity of the device.
3Quantity of substance
If the specific surface area of the negative electrode mixture layer is increased to improve capacitance, then the capacitance is improved, but the resistance increases
Solution Approach 1:
The invention applies local quality by creating a porous electrode mixture layer structure where the pore distribution and connectivity are optimized locally. This allows high specific surface area for capacitance while maintaining good electrolyte access and ion transport pathways, preventing excessive resistance even at high surface areas.
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 enables high output and capacitance while preventing breakage during charging and discharging, maintaining cycle characteristics and reducing side reactions, thus achieving a synergistic effect for enhanced performance.
Implementation Method 1
The negative electrode mixture layer contains a negative electrode active material that is reversibly doped with lithium ions
Implementation Method 2
electrochemical devices in which the electricity storage principle of a lithium ion secondary battery and the electricity storage principle of electric double layer capacitor are combined
Data Source
AI summary
An electrochemical device includes: an electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and an electrolyte containing a lithium salt. The negative electrode includes a negative current collector and a negative electrode mixture layer supported on the negative current collector. The negative electrode mixture layer contains a negative electrode active material that is reversibly doped with lithium ions, and the negative current collector has substantially no through-hole. A specific surface area of the negative electrode mixture layer is in a range from 30 m2/g to 60 m2/g, inclusive, and in a discharged state, a potential of the negative electrode is less than or equal to 0.2 V with respect to a Li counter electrode.