Electric Double Layer Capacitor Asymmetric Electrode Area Ratio
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Solution Overview
Problem
Electric double layer capacitors connected in series suffer from insufficient life due to variations in holding voltage between cells, leading to degradation during charge and discharge cycles, despite efforts to improve power supply capabilities.
Innovation Solution
The capacitors are designed with electrode bodies having active materials with specific pore diameters for counteranions and cations, and area ratios between positive and negative electrodes are controlled to ensure uniform ion adsorption and voltage distribution, thereby maintaining capacity and extending life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a plurality of cells are connected in series to improve working voltage, then power supply capability is improved, but variations in holding voltage between cells cause degradation and reduce device life
Solution Approach 1:
The patent applies local quality by creating asymmetry in the electrode design: the positive electrode has a larger active material layer area than the negative electrode. This local modification compensates for the inherent differences in leakage current between positive and negative electrodes, balancing the holding voltage across series-connected cells and preventing premature degradation while maintaining high power capability
2Reliability
If the active material layer area of the positive electrode is made larger than that of the negative electrode, then holding voltage variations are suppressed, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by specifically controlling the area ratio between positive and negative electrode active material layers. By setting the positive electrode area to be larger (specifically 1.05 to 1.3 times the negative electrode area), the design systematically adjusts a key geometric parameter to compensate for leakage current differences, thereby stabilizing holding voltage without requiring complex control systems or additional components
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 design achieves both higher power and longer life by ensuring uniform capacity and suppressing voltage variations across electrode bodies, enhancing the overall performance and durability of the electric double layer capacitors.
Implementation Method 1
the positive electrode and the negative electrode comprise an active material having pores, the electrolyte solution comprises an electrolyte having a cation and a counteranion of the cation
Implementation Method 2
the counteranions moving to the positive electrode side enter the pores of the active material of the positive electrode and are adsorbed on the inner walls of the pores. The cations moving to the negative electrode side enter the pores of the active material of the negative electrode and are adsorbed on the inner walls of the pores
Implementation Method 3
the electrolyte solution comprises an electrolyte having a cation and a counteranion of the cation
Data Source
AI summary
An electric double layer capacitor comprising a plurality of electrode bodies comprising a positive electrode and a negative electrode laminated via a separator and being impregnated with an electrolyte solution, wherein the plurality of electrode bodies are electrically connected in series, the positive electrode and the negative electrode comprise an active material having pores, the electrolyte solution comprises an electrolyte having a cation and a counteranion of the cation, a ratio of an average pore diameter of the active material of the positive electrode to an ion diameter of the counteranion is in the range of 2.5 to 2.8, and a ratio of an average pore diameter of the active material of the negative electrode to an ion diameter of the cation is in the range of 1.65 to 1.85.