Lithium-Doped Negative Electrode for High-Voltage Electrochemical Capacitors
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Solution Overview
Problem
Conventional electrochemical capacitors experience a reduction in energy density due to the increase in electric potential of the negative electrode during charge and discharge cycles, which affects the potential difference between the positive and negative electrodes.
Innovation Solution
The capacitor design includes a negative electrode with a current collector and an electrode layer where the ratio of anion decomposition compound peak value to electrolyte peak value, as measured by X-ray photoelectron spectroscopy, is between 0.5 and 2.55, suppressing the increase in electric potential and enhancing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium ions are pre-doped into carbon material of the negative electrode to increase voltage, then energy density is improved, but electric potential of the negative electrode increases during charge and discharge cycles, reducing the potential difference and energy density
Solution Approach 1:
The patent applies preliminary action by pre-doping lithium ions into the carbon material of the negative electrode before the capacitor enters service. This preliminary doping establishes a stable baseline electric potential, allowing the capacitor to operate at higher voltages while maintaining stability during subsequent charge-discharge cycles. The pre-doped lithium ions create a buffer that prevents excessive potential increases during operation.
Solution Approach 2:
The patent changes the chemical composition parameter of the negative electrode by incorporating lithium-doped carbon material. This parameter change increases the voltage range of the capacitor while the controlled doping level maintains electric potential stability. The specific lithium content is optimized to achieve the desired balance between energy density improvement and potential stability.
2Power
If conventional capacitors are used with standard electrode configurations, then manufacturing is simple, but energy density is limited due to smaller capacitance and voltage compared to secondary batteries
Solution Approach 1:
The patent applies local quality by modifying only the negative electrode's carbon material with lithium doping, while keeping the positive electrode and overall capacitor structure conventional. This localized modification increases voltage and energy density without requiring complex changes to the entire device architecture. The lithium-doped carbon material is applied specifically where needed to achieve the voltage increase.
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 effectively maintains and improves energy density by controlling the electric potential of the negative electrode, ensuring a higher energy storage capacity even after repeated charge and discharge cycles.
Implementation Method 1
lithium ions are previously stored (pre-doped) into carbon material of the negative electrode
Implementation Method 2
a ratio Ia/Ib is 0.5 or more and less than 2.55 in a spectrum of an atom forming the anion as measured by X-ray photoelectron spectroscopy method
Data Source
AI summary
A negative electrode for an electrochemical capacitor includes a current collector having electric conductivity, and an electrode layer formed on a surface of the current collector and having cations stored therein. In at least a part of the electrode layer, a value of ratio Ia/Ib of peak value Ia indicating a presence of an anion decomposition compound and peak value Ib indicating a presence of an electrolyte in a spectrum of an atom forming the anion is 0.45 or more and less than 2.55 as measured using X-ray photoelectron spectroscopy.