Pulsed laser deposition of thin films of TiO2 for Li-ion batteries

Microbatteries produced by physical deposition methods are expected to play a pivotal role in many different micro-electronic applications such as stand-alone sensors, implantable or wearable medical devices, radio frequency identification-based systems and smart-cards. In this study pulsed laser deposition (PLD) using a femtosecond-pulsed laser has been applied to TiO2 target materials to produce thin films of anatase-based nanoparticles on aluminium substrates suitable for application as negative electrode in Li-ion MBs. Different post-deposition treatments have been evaluated: films morphology and composition have been investigated with a multi-technique approach and the corresponding performance and electrochemical properties in Li-ion MBs have been analysed by cyclic voltammetry and galvanostatic techniques. Compact and dense TiO2 films composed by nanoparticles were obtained by PLD with co-crystallization of both anatase and rutile phases. Post-deposition annealing at temperature of 500°C promote the rutile to anatase phase transition. As deposited TiO2 films are electrochemically almost inactive in lithium half cells, whereas post deposition annealing (either in Ar or Air) boosts the electrochemical activity: air annealing outperforms Ar annealing. The additional deposition of a outer carbon layer by PLD on the TiO2 films further improves the Li+ transport properties, the reversibility of the electrochemical intercalation/de-intercalation reaction as well as the battery performance in terms of capacity retention upon cycling and rate response.