Fluorinated Phosphazene Electrolyte for High-Voltage Supercapacitors
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Solution Overview
Problem
Existing supercapacitors face limitations in energy storage capacity and stability due to the constraints of conventional electrolytes, particularly aqueous and organic electrolytes, which restrict voltage range and temperature performance, necessitating complex arrangements and limited cycle life.
Innovation Solution
A supercapacitor composition comprising a specific combination of nitrile solvent, lithium, sodium, or potassium salt, and a phosphazene additive with fluorine atoms, enhancing ionic conductivity and stability, thereby improving energy storage and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional aqueous or organic electrolytes are used in supercapacitors, then the device can operate with basic ionic conductivity, but the voltage range is limited and temperature performance is restricted, requiring complex arrangements to achieve conventional voltages
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated phosphazene additives with specific molecular structures (formula I and II) into non-aqueous electrolytic solutions. This chemical parameter modification enables the electrolyte to maintain stability and ionic conductivity across a broader temperature range (-40°C to +85°C) and higher voltage ranges (up to 2.8V), eliminating the need for complex series arrangements of multiple units to achieve conventional voltages.
2Power
If the nominal voltage of supercapacitor terminals is increased to improve energy storage and power delivery, then performance is greatly improved, but the electrolyte must remain stable in the electrochemical window while maintaining good ionic conductivity, high temperature range, and low viscosity
Solution Approach 1:
The patent creates a composite electrolyte system by combining non-aqueous electrolytic solution base components (such as cyclic carbonates, chain carbonates, or cyclic carboxylic acid esters) with fluorinated phosphazene additives. This composite formulation synergistically provides both the stability required to withstand high electrochemical potentials (enabling nominal voltages up to 2.8V) and the ionic conductivity necessary for high power delivery, while maintaining appropriate viscosity and temperature range.
3Stability of the object's composition
If aqueous electrolytes are used in supercapacitors, then the applicable nominal voltage range is limited to approximately 1V due to water decomposition, but complex arrangements of several supercapacitor units are required to achieve conventional voltages
Solution Approach 1:
The patent changes the fundamental chemical composition parameter from aqueous to non-aqueous electrolytic solution, thereby expanding the electrochemical stability window from approximately 1V to 2.8V or higher. The fluorinated phosphazene additives further enhance this stability while maintaining ionic conductivity, allowing single supercapacitor units to achieve conventional voltages without complex series arrangements.
4Temperature
If organic electrolytes are used to achieve larger electrochemical stability window, then voltage range is improved, but temperature performance and cycle life stability are limited
Solution Approach 1:
The fluorinated phosphazene compounds act as intermediary additives in the non-aqueous electrolytic solution, mediating between the electrode surfaces and the bulk electrolyte. These intermediaries form stable interfacial layers that enhance both the electrochemical stability window (enabling operation from -40°C to +85°C) and the cycle life stability (maintaining capacity after 10,000+ charge-discharge cycles), while preserving the voltage range benefits of organic electrolytes.
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 composition achieves improved discharge capacity and safety, with enhanced performance after 10,000 cycles and reduced flammability, demonstrating a 12% increase in cyclic voltammetry capacity and 3% increase in galvanostatic cycling capacity, while ensuring non-flammability.
Implementation Method 1
the addition of a phosphazene compound to a non-aqueous electrolytic solution... the decomposition of the electrolyte is reduced
Implementation Method 2
good ionic conductivity; a high temperature range; and a relatively low viscosity so as to allow good ion mobility
Data Source
AI summary
The invention relates to a supercapacitor comprising at least one cell formed of two electrodes of opposite polarity. The cell is formed from a positive electrode and a negative electrode made of activated carbon, between which an electrolyte composition is arranged comprising at least one nitrile solvent, at least one salt and also comprising at least one additive from the family of phosphazenes having at least one fluorine atom. One of the compositions comprises acetonitrile, a tetramethylammonium tetrafluoroborate salt and an additive, hexafluorocyclotriphosphazene at a concentration of 1 to 10%.