Flexible robust binder-free carbon nanotube membranes for solid state and microcapacitor application

Area of Science:

• Materials Science
• Nanotechnology
• Electrochemistry

Background:

• Carbon nanotubes (CNTs) offer unique properties but require effective assembly methods.
• Developing binder-free electrodes is crucial for enhancing energy storage device performance.

Purpose of the Study:

• To develop a liquid-phase self-assembly protocol for creating macroscopic, binder-free CNT membranes.
• To investigate the structural and mechanical properties of these CNT membranes.
• To evaluate the performance of CNT membranes as electrodes in solid-state capacitors.

Main Methods:

• Utilized charge transfer engineering for spontaneous CNT dispersion in a liquid medium.
• Developed a post-synthesis self-assembly protocol to form macroscopic CNT membranes.
• Fabricated and tested single/stacked solid-state capacitors and interdigitated microcapacitors using CNT membranes as electrodes.

Main Results:

• Successfully transformed CNT powder into densely packed, flexible, and robust binder-free macroscopic membranes with hierarchical pores.
• Observed a transition in flexural properties from flexibility to brittleness with increasing membrane thickness.
• Achieved a bulk mass density of ~1.11 g cm⁻³ for the CNT membranes.
• Demonstrated stable capacitor performance over 10,000 cycles with a time constant of ~32 ms.
• Capacitors exhibited good temperature stability up to 90 °C, with specific capacitance reaching 100 F g⁻¹ at 70 °C.
• Reported a low leakage current of ~100 nA cm⁻² at 2.5 V for bipolar stacked solid-state capacitors.

Conclusions:

• The developed liquid-phase protocol effectively produces high-quality, binder-free CNT membranes with tunable properties.
• These CNT membranes are promising electrode materials for high-performance, durable solid-state energy storage devices.
• The processing method preserves the intrinsic properties of CNTs while enabling macroscopic assembly.