Abstract:
A simple, scalable, and cost-effective CO2 laser direct-write process is introduced to produce adherent, high-quality micro-gradient-patterned carbon coating on multiple substrates under ambient conditions for application as anode-free battery electrodes. It involves laser pyrolysis of low-temperature-polymerized coating of a bio-waste-derived furfuryl alcohol liquid precursor and generates submicron-scale modulations of graphene-like carbon (GLC) and disordered carbon forms emanating from the direct laser-beam-exposed region and the region between the laser scan lines. The functionality and highly adherent nature of the coating result from the process- and precursor-borne functionalization of GLC. We demonstrate the applicability of such coating implemented on copper foil for anode-free Li–metal battery application. In the case of micro-gradient coating, the nucleation of lithium occurs with significantly lower (almost by a factor of 5) activation energy as compared to bare Cu, resulting in 4 times higher plating (0.5 mA cm–2)/stripping (1.5 mA cm–2). The defects produced on graphene and the natural incorporation of electronegative oxygen atoms by the laser pyrolysis process provide the lithiophilic centers leading to homogeneous lithium nucleation and deposition. The carbon nanostructures reduce the effective areal current density, and the enhanced adhesion helps with mechanical stability for effective lithium deposition for prolonged cycle life.