Fabrication of Resorcinol-Formaldehyde Xerogel Based High Aspect Ratio 3-D Hierarchical C-MEMS Structures

Abstract

We demonstrate a novel method to fabricate arrays of resorcinolformaldehyde xerogel (RFX) based high aspect ratio (HAR) threedimensional (3-D) hierarchical C-MEMS structures. Starting from a master pattern of HAR 3-D posts fabricated in SU-8 negative photoresist by photolithography, a negative PDMS stamp with arrays of holes was prepared by micromolding. The PDMS stamp was then used to fabricate HAR 3-D RFX posts by replica molding. The 3-D RFX posts thus fabricated were electrosprayed with SU-8 or an RF sol in the form of submicron or nano sized droplets and followed by pyrolysis to yield HAR 3-D hierarchical carbon posts. To characterize their use in C-MEMS based batteries, galvanostatic (charge and discharge) experiments on RFX derived carbon showed that it can be reversibly intercalated with Li ions and possesses superior intercalation properties as compared to SU-8 derived carbon which is a widely used material in C-MEMS. 10.1149/06107.0045ecst ©The Electrochemical Society ECS Transactions, 61 (7) 45-54 (2014) 45 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 218.248.6.153 Downloaded on 2015-03-17 to IP

State of the Art and Future Research Needs for Multiscale Analysis of Li-Ion Cells

“…RF xerogel in the form of monoliths and powder form exhibits lower specific capacity besides large irreversible capacity [15,16,24]. RF xerogel derived carbon thin films have also exhibited only moderate reversible capacity [25]. To address this, many strategies have been suggested such as activation or nanostructuring in recent past [26,27].…”

Resorcinol-formaldehyde derived carbon xerogels: A promising anode material for lithium-ion battery

“…In the other way, carbon xerogel thin films were prepared on substrate with and without stretchable (PMMA) polymer and tested as anode material for LIB and scaffold for neural cells (cells of nervous system). 49,54 Thin films on the substrate have an additional advantage compared to bulk carbon thin films produced from RF gels for electrochemical applications as these films do not need a binder and toxic solvent for electrode slurry preparation. Carbon thin films on conductive substrate can be directly used as anode material for LIBs, whereas free standing flexible carbon thin films are highly suitable for electrode materials in flexible electronics.…”

“…Sharma et al, produced fractal 3D electrodes by electrospraying of RF sol particles on to 3D RF gel structure followed by pyrolysis. 54…”

“…However, this can be attributed to additional resistance provided by Si substrate rather than thin film structure. 52,54 Further, various forms of nanostructured carbon xerogels were prepared to see the effect of morphology on electrochemical performance. Carbon xerogel microspheres containing Si and Sn were prepared using inverse emulsification process.…”

Effect of Disorder Induced by Ball Milling on the Electrochemical Performance of Catalytically Graphitized Carbon Xerogel as Anode for Lithium Ion Batteries

“…Resorcinol formaldehyde xerogel is an organic gel obtained by sub critical drying of resorcinol formaldehyde sol (13). RFCX is an example of hard carbon which is being explored as anode material for Li ion battery in recent times (14,15) due to its several merits such as easily tunable physiochemical properties, higher carbon yield. However unlike other hard carbon materials, Li ion intercalation capacity values for different forms of RFCX as reported in literature are not promising.…”