Preferred Orientation of Polycrystalline LiCoO[sub 2] Films

Abstract

Polycrystalline films of LiCoO 2 deposited by radio frequency magnetron sputtering exhibited a strong preferred orientation or texturing after annealing at 700ЊC. For films thicker than about 1 m, more than 90% of the grains were oriented with their (101) and (104) planes parallel to the substrate and less than 10% with their (003) planes parallel to the substrate. As the film thickness decreased below 1 m, the percentage of (003)-oriented grains increased until at a thickness of about 0.05 m, 100% of the grains were (003) oriented. These extremes in texturing were caused by the tendency to minimize volume strain energy for the thicker films or the surface energy for the very thin films. Films were deposited using different process gas mixtures and pressures, deposition rates, substrate temperatures, and substrate bias. Of these variables, only changes in substrate temperature could cause large changes in texturing of thick films from predominately ( 101)-( 104) to (003). Although lithium ion diffusion should be much faster through cathodes with a high percentage of (101)-and (104)-oriented grains than through cathodes with predominately (003)-oriented grains, it was not possible to verify this expectation because the resistance of most cells was dominated by the electrolyte and electrolyte-cathode interface. Nonetheless, cells with cathodes thicker than about 2 m could deliver more than 50% of their maximum energies at discharge rates of 5 mA/cm 2 or higher.

All‐Solid‐State Lithium‐Ion Microbatteries: A Review of Various Three‐Dimensional Concepts

“…However, the formation of HT-LiCoO 2 has also been reported by the application of relatively low temperature wet-chemical processes. [ 25 ] The same two polymorphs of LiCoO 2 are also observed when depositing solid-state thinfi lms which can, amongst other methods, be achieved by RF sputtering, [26][27][28][29] sol-gel deposition, [ 27 , 30-32 ] chemical vapor deposition [ 33 , 34 ] and pulsed laser deposition. [ 29 ] HT-LiCoO 2 is well-known for its layered hexagonal structure.…”

Dual Cation- and Anion-Based Redox Process in Lithium Titanium Oxysulfide Thin Film Cathodes for All-Solid-State Lithium-Ion Batteries

“…They are close to the capacity reported for LiCoO 2 thin films. 13 As only this initial charge capacity can be actually used in a Li-ion system, additional electrochemical characterizations in solid state microbatteries were only performed on thin films having the highest capacities (i.e. R1 and R3 thin films).…”

Metal-organic chemical vapor deposition enabling all-solid-state Li-ion microbatteries: A short review

“…In general, LiCoO 2 have two crystal structures: the spinel, low temperature, phase (LT-LiCoO 2 ) and the high temperature layered hexagonal structure (HT-LiCoO 2 ). Various methods have been described to deposit electrochemically active LiCoO 2 thin films, including sol-gel methods [54,55], radio frequency (RF)-magnetron sputtering [55][56][57], and pulsed laser deposition [57].…”