Electrochemical behavior of a laser microstructured fluorine doped tin oxide anode layer with a plasma pretreatment for 3D battery systems

Fluorine-doped tin oxide (FTO) films with a thickness of about 3 micrometers were prepared by electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) under 800 W of microwave power, with tetra-methyl tin (TMT) as a tin precursor. The dome-shaped micro-patterned FTO layer was prepared on a copper current collector using a KrF excimer laser micromachining system for application as an anode for 3D lithium-ion batteries. Mild ECR plasma treatment at 600 W was carried out on the surface of the microstructured FTO anode, and the electrochemical characteristics were investigated with regard to the plasma treatment effects. The results show that physical properties such as the smooth and dense surface morphology and reduced surface oxygen functional groups of the plasma-treated samples enhanced the specific capacity, rate capability, and capacity fading. This was probably due to the reduction of side reactions, which may be closely related to the plasma treatment of the microstructured FTO layer. The ECR plasma treatment plays an important role in reducing the charging transfer resistance. In the experimental range studied, a higher specific capacity of 1425 mA h g(-1) at a current density of 117 mA g(-1) was observed, with capacity fading of 37.8% after 100 cycles for the plasma-treated microstructured FTO anode.