Pre-Intercalated MXene Electrodes for RTIL Supercapacitor Ion Transport
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Solution Overview
Problem
MXenes used in supercapacitors exhibit limited capacitance and rate capability in room-temperature ionic liquids due to the large size of RTIL cations, which hinders their accessibility and transport in porous electrodes, and the limited potential window of RTILs restricts their use in high energy density devices.
Innovation Solution
Intercalating alkylammonium cations into MXene layers to increase the interlayer spacing, allowing for improved transport of larger ions and expanding the voltage window, thereby enhancing specific capacitance and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If MXenes are used in room-temperature ionic liquids, then the voltage window is expanded, but the capacitance and rate capability are limited due to large RTIL cation size
Solution Approach 1:
The patent applies preliminary action by pre-intercalating alkylammonium cations into the MXene layers before introducing RTILs. This pre-expansion of interlayer spacing (from ~1.1 nm to ~2.0 nm) creates channels that facilitate subsequent RTIL cation transport, resolving the contradiction between expanded voltage window and limited capacitance by preparing the structure in advance for optimal ion access.
Solution Approach 2:
The patent applies local quality by creating regions of different interlayer spacing within the MXene structure. The pre-intercalated regions with expanded spacing (~2.0 nm) provide localized pathways for RTIL cation transport, while maintaining the overall layered structure. This local modification enables high capacitance in specific regions without compromising the overall structural integrity and voltage window expansion.
2Speed
If interlayer spacing is increased to improve ion transport, then rate capability is enhanced, but structural stability may be compromised
Solution Approach 1:
The patent uses alkylammonium cations as intermediary substances that fit within the MXene interlayer spacing. These intermediaries act as spacers that maintain a stable expanded distance (~2.0 nm) between layers, preventing both excessive compression and over-expansion. This intermediary approach enables sustained high rate capability while preserving structural stability during cycling.
Solution Approach 2:
The patent applies parameter changes by systematically varying the alkyl chain length of pre-intercalated cations to optimize interlayer spacing. By tuning this parameter to achieve ~2.0 nm spacing, the patent finds the optimal balance between ion transport speed (rate capability) and structural stability, demonstrating that controlled parameter modification can resolve the contradiction between these two properties.
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 intercalated MXene electrodes demonstrate significantly higher specific capacitances and energy densities in RTILs, surpassing previous reports and even carbon-based materials, with excellent cycling stability and power delivery.
Implementation Method 1
Intercalating alkylammonium cations into MXene layers to increase the interlayer spacing, allowing for improved transport of larger ions
Implementation Method 2
The intercalated MXene electrodes demonstrate significantly higher specific capacitances and energy densities in RTILs
Data Source
AI summary
The present disclosure relates generally to a supercapacitor comprising an electrode having an intercalated MXene material, and a room temperature ionic liquid (RTIL), the supercapacitor having superior electrochemical performance.