Characterization of LiMn0.3Co0.3Ni0.3Cr0.1O2 Cathode for an All Solid-State Thin Film Battery

Thin film fabrication is very important especially for device fabrication. For an all solid-state thin film battery, very low dimensional (of the order of sub-micron), high quality thin films are needed and the fabrication technique is a key criteria for producing good quality ultra-thin films. Pulse Laser deposition (PLD) is a suitable method for producing high quality finish of metals and metal oxides. Controlling the PLD deposition parameters can affect the characteristics of thin films such as crystal orientation, thickness and roughness which in turn influence the physical and chemical properties of the thin films. Producing thin film metal oxides with simple stoichiometries such as ZnO, MgO and Al₂O₃, may not be such a problem to fabricate. However, producing thin films of complex metal oxides such as LiCo_0.3Ni_0.3Mn_0.3Cr_0.1O₂ for Li-ion battery cathodes can be a problem. The thin film deposition technique must be appropriate so that the thin film material produced will not suffer a change of phase, stoichiometry or purity. Not all gas phase or plasma based methods are suitable for deposition of this type of material. Reactive type thin film fabrication method may not produce the needed stoichiometry or phase and may produce multiphase samples with impurities. PLD may be the choice method for producing thin films of very complex stoichiometries.

This work explores the thin film method of PLD in the fabrication of thin film LiCo_0.3Ni_0.3Mn_0.3Cr_0.1O₂ material. Characteristics such as phase, stoichiometry, crystal growth orientation, and surface roughness, are studied. For this type of complex metal oxide, it is very important for the thin film to be of the right phase and stoichiometry because this will affect the electrochemical behavior of the energy device that will then be fabricated. It is found that thin films of LiCo_0.3Ni_0.3Mn_0.3Cr_0.1O₂ deposited by PLD have good qualities such as mirror finish, dimensionally thin and of correct stoichiometry and high smoothness. Cyclic voltametry result shows that the cathode film is electrochemically active.