Surface modification of vertically aligned graphene nanosheets by microwave assisted etching for application as anode of lithium ion battery

Vertically aligned graphene nanosheets (VAGNS) are grown by plasma enhanced chemical vapor deposition (PECVD) using electron cyclotron resonance (ECR) plasma system for application as an anode material in lithium ion battery (LIB). Microwave assisted etching, in presence and absence of substrate bias, is carried out on as grown VAGNS films to modify the morphology of the film. Scanning electron microscopy (SEM) is used for characterizing the surface features of the VAGNS films. The VAGNS sample which is microwave plasma treated (power 400 W) with substrate bias of 100 V, showed an initial charging specific capacity of 223 μAh·cm−2·μm−1, while as deposited VAGNS showed specific capacity of 124.4 μAh·cm−2·μm−1. After 5 cycles, while the former showed a specific capacity of 68.1 μAh·cm−2·μm−1 (760.7 mAh g−1), while the later showed a specific capacity of 43.9 μAh·cm−2·μm−1(458.7 mAh·g−1). During discharge initially while surface modified VAGNS showed a capacity of 100.1 μAh·cm−2·μm−1, the as deposited VAGNS showed a capacity of 38.2 μAh·cm−2·μm−1. The specific capacity after five cycles, during discharge for modified VAGNS is 68 μAh·cm−2·μm−1 (725.9 mAh g−1), and for as deposited VAGNS it is 34 μAh·cm−2·μm−1(380.6 mAh·g−1). The specific capacity remains fairly constant after this initial capacity loss up to 50 cycles. The results indicate that surface modification of VAGNS improves the performance of the material as anode for lithium ion battery.