Challenges in making of thin films for LixMnyO4 rechargeable lithium batteries for MEMS

Microelectromechanical systems also known as MEMS are used in various small-scale sensor applications. A new trend is witnessed in the MEMS industry called “system on a chip”. The goal is to develop a chip with a sensor, an actuator and power source and power storage device all on one chip. LiMn2O4 thin films show great promise as providers of power to these sensors and actuators on a silicon chip. These batteries are required to have high power density, high charge and discharge rate capability, long cycle life and reduced capacity fading. To demonstrate these features pulsed laser deposition (PLD) and the laser spark atomization (LSA) techniques were used to deposit LiMn2O4 films on various substrate materials. The thin (<0.2 μm) films grown by PLD were highly crystalline and textured along either (1 1 1) or (0 0 1) direction depending on the substrate type. Films grown by LSA were much thicker (>1 μm) and exhibited a porous structure consisting of a mixture of randomly oriented nanocrystals embedded in an amorphous matrix. The effect of these two different microstructures on the electrochemical properties of the LiMn2O4 thin films has been investigated. The results obtained indicate that differences in film structure and particle morphology have a significant impact upon electrochemical kinetics of Li ion intercalation and de-intercalation.