Non-Aqueous Electrolyte Cell Pack for Redox Shuttle Overcharge Balance
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Solution Overview
Problem
Existing non-aqueous electrolyte solutions with redox shuttles struggle to effectively suppress overcharging under realistic conditions, particularly at high current densities, and do not account for individual cell capacity differences, leading to imbalances and instability in cell packs.
Innovation Solution
A cell pack configuration with non-aqueous secondary cells connected in series or parallel, using a non-aqueous electrolyte solution containing a redox shuttle with specific substituents and a ratio of maximum to minimum cell capacity between 1.00<B/A<2.00, along with a non-aqueous solvent comprising acetonitrile and a linear carbonate, enhances stability and balances cell capacities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redox shuttle is added to a non-aqueous electrolyte solution to suppress overcharging, then overcharge suppression function is improved, but diffusion rate within electrode layer becomes insufficient at high current density
Solution Approach 1:
The patent changes the chemical parameters of the redox shuttle by introducing specific substituents (alkyl groups, alkoxy groups, fluorine-substituted alkyl groups, or aromatic hydrocarbon groups) with defined carbon atom counts. These parameter modifications optimize the diffusion rate and electrochemical reactivity of the redox shuttle, enabling it to function effectively at high current densities while maintaining overcharge suppression capability.
Solution Approach 2:
The patent applies local quality by specifying that the substituents on the aromatic ring should have particular properties (electron-donating or electron-withdrawing characteristics) to create localized electronic environments that facilitate faster diffusion and redox reactions at the electrode interface, thereby resolving the diffusion rate limitation.
2Ease of manufacture
If individual cell capacity differences are not addressed, then manufacturing simplicity is maintained, but cell imbalance occurs leading to reduced productivity
Solution Approach 1:
The patent implements self-service by enabling the redox shuttle system to automatically detect and compensate for individual cell capacity differences through its electrochemical reactions. The redox shuttle naturally distributes charge more evenly across cells with different capacities, eliminating the need for external screening or matching processes while maintaining high productivity.
3Reliability
If electronic circuit methods are used for overcharge suppression, then overcharge protection is achieved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/electronic circuit-based overcharge suppression system with a chemical-based redox shuttle system. The redox shuttle uses electrochemical reactions to suppress overcharging, eliminating the need for complex electronic circuits, sensors, and control systems while maintaining reliable overcharge protection.
4Reliability
If redox shuttle diffusion is optimized for low current density, then overcharge suppression is effective, but performance deteriorates at high current density
Solution Approach 1:
The patent modifies the physical and chemical parameters of the redox shuttle molecule by introducing specific substituent groups with controlled sizes and electronic properties. These parameter changes reduce steric hindrance and enhance electrochemical reactivity, allowing the redox shuttle to maintain fast diffusion rates and effective overcharge suppression across a wide current density range from low to high.
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 solution eliminates cell imbalances and ensures stable charge/discharge cycling even at high current densities and varying temperatures, improving cell pack performance and yield.
Implementation Method 1
a method of adding a redox reagent having a redox potential corresponding to an overcharge potential to a non-aqueous electrolyte solution has been considered. According to this method, when the reversible reactivity of the redox reagent is good, a suppression mechanism by which reciprocation between positive and negative electrodes consumes an overcharge current is formed.
Implementation Method 2
However, diffusion is the rate-determining factor for the function of the redox shuttle in PTL 1 and 2, whereas diffusion within the electrode layer does not reach a practical level in a conventional non-aqueous electrolyte solution.
Data Source
AI summary
Provided is a high-capacity cell pack in which cell imbalance is eliminated, precipitation of a poorly soluble redox shuttle can be prevented, deterioration due to overcharging is suppressed, cell yield is improved, and charge/discharge cycling is stable. The cell pack according to the present invention is a cell pack comprising non-aqueous secondary cells each comprising a non-aqueous electrolyte solution containing an electrolyte salt and a non-aqueous solvent, a positive electrode, and a negative electrode, wherein the cell pack is configured with a module in which two or more of the non-aqueous secondary cells are connected in series or with two or more of the modules in parallel, or the cell pack is configured with a module in which two or more of the non-aqueous secondary cells are connected in parallel or with two or more of the modules in series.