Engineered Electronic Contacts for Composite Electrodes in Li Batteries Using Thiophene-Based Molecular Junctions

Fourier transform infrared spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy experiments indicate that molecular junctions can be achieved between non-carbon-coated LiFePO4 (LFP) and multiwall carbon nanotubes (MWCNT) using a thiophene-based conjugated system which was designed to selectively functionalize these two different types of surfaces. The strategy enables the architecturing of the cathode electrode of lithium batteries, leading to a vast improvement in the component intermixing, which results in the individual MWCNT being nanocontacted at the surface of LFP grains. This advancement leads to much higher specific capacity, especially at high charge/discharge rates, for undensified electrodes of 2 mA h cm–2, for which the electronic wiring of the electroactive material is a critical issue. Furthermore, thanks to molecular junctions, better capacity retention comparable to that of carbon-coated LiFePO4 electrodes could be achieved. These results are expected to trigger the development of novel electron transport engineering methods, of special interest for industry-relevant thick battery electrodes.