Fabrication and characterization of Li–Mn–Ni–O sputtered thin film high voltage cathodes for Li-ion batteries

Li-rich and stoichiometric Li1Mn1.5Ni0.5O4 (LMNO) cathode films have been successfully prepared by magnetron sputtering. Sputtering from a Li stoichiometric target yields Li-rich films composed of spinel, layered and monoclinic phases. Films obtained from a Li deficient target are mostly made of a spinel phase and little layered material. The resulting cathode thin films have good capacity retention and very high rate capability. The reaction mechanism has been investigated by XRD and HRTEM and evidences the reversible formation of a spinel phase, as is generally found for the powder samples. The film geometry enables us to understand the effect of coatings (ZnO or LiPON). Coating high voltage cathodes reduces the coulombic losses, but at the price of rate performance. Nonetheless, these coated sputtered electrode thin films offer a higher rate capability than other LMNO thin films obtained by other physical vapor deposition techniques.

► Sputtering from stoichiometric target creates Li-rich films.
► Sputtering from Li deficient target creates films with the right spinel structure.
►  High capacity retention and rate performance: 85 % at 100 C-rate.
► Coating thin film electrodes (ZnO, LiPON) reduces coulombic losses.