Nanoimprinted Carbon Structures As High Performance Lithium Ion Battery Anodes

We demonstrated the synthesis of carbon thin film with ordered nanostructure via nanoimprint lithography starting from thermal plastic polymer polyvinylpyrrolidone (PVP). After the pattern is completely transferred onto PVP thin film during the nanoimprinting process, a three-step thermal treatment is performed to convert the polymer into patterned carbon thin film. Feature size of the pattern ranges between 250 nm up to 2 um with various shapes including 1D line, 2D hole and pillar. Characterized with Raman spectroscopy, the carbon thin film shows a high degree of disorder with a small in-plane graphitic crystallite size of about 1.346 nm calculated using the peak intensity of D band and G band of sp²carbon. Those patterned carbon thin film exhibits good electrical conductivity. When used as anode of lithium ion battery, it shows an enhanced cyclic performance compared to those unpatterned carbon thin films and also graphite. Further study with Electrochemical Strain Microscope (ESM) helps to understand the enhanced Li ion storage capacity locally on the nanoscale.

Figure 1. (A) Atomic force microscopy topography scan of imprinted carbon thin film, (B) cyclic charge/discharge performance of imprinted and unpatterned carbon.