Enhanced Cycling and Rate Capability by Epitaxially Matched Conductive Cubic TiO Coating on LiCoO₂ Cathode Films

Abstract

Layered lithium transition-metal oxides, such as LiCoO 2 and its doped and lithium-rich analogues, have become the most attractive cathode material for current lithium-ion batteries due to their excellent power and energy densities. However, parasitic reactions at the cathode–electrolyte interface, such as metal-ion dissolution and electrolyte degradation, instigate major safety and performance issues. Although metal oxide coatings can enhance the chemical and structural stability, their insulating nature and lattice mismatch with the adjacent cathode material can act as a physical barrier for ion transport, which increases the charge-transfer resistance across the interface and impedes cell performance at high rates. Here, epitaxial engineering is applied to stabilize a cubic (100)-oriented TiO layer on top of single (104)-oriented LiCoO 2 thin films to study the effect of a conductive coating on the electrochemical performance. Lattice matching between the (104) LiCoO 2 surface facets and the (100) TiO plane enables the formation of the titanium mono-oxide phase, which dramatically enhances the cycling stability as well as the rate capability of LiCoO 2 . This cubic TiO coating enhances the preservation of the phase and structural stability across the (104) LiCoO 2 surface. The results suggest a more stable Co 3+ oxidation state, which not only limits the cobalt-ion dissolution into the electrolyte but also suppresses the catalytic degradation of the liquid electrolyte. Furthermore, the high c-rate performance combined with high Columbic efficiency indicates that interstitial sites in the cubic TiO lattice offer facile pathways for fast lithium-ion transport.

Effect of TiOx Surface Modification on the Electrochemical Performances of Ni-Rich (NMC-622) Cathode Material for Lithium-Ion Batteries

“…43 It is worth noting to point out the recent literature, which advises that regardless of the crystalline or amorphous nature of the TiO x , it acts as an excellent electronically conducting material. 61,62 In addition, the surface modification could perhaps enhance the electronic conductivity/electronic percolation of active (both cathode and anode) materials at the electrode and material level. 62 Furthermore, the electronic conductivity measurements further confirm this on both powder and electrode levels.…”

“…61,62 In addition, the surface modification could perhaps enhance the electronic conductivity/electronic percolation of active (both cathode and anode) materials at the electrode and material level. 62 Furthermore, the electronic conductivity measurements further confirm this on both powder and electrode levels.…”

Enhanced Interfacial Kinetics and High Rate Performance of LiCoO2 Thin-Film Electrodes by Al Doping and In Situ Al2O3 Coating

“…An additional small peak observed at approximately 1180 cm –1 indicates the presence of a trace amount of Co 3 O 4 impurity phase, which may be due to the loss of lithium during magnetron sputtering. 26 …”

“…(5) Electrode surface interface treatment. 26 − 29 The electrode–electrolyte interface is stabilized by depositing a coating layer on the electrode surface to reduce the interface impedance. 30 It was reported that Al 2 O 3 coating can significantly improve the electrochemical performance of LCO films.…”

Interface Behavior of Electrolyte/Quinone Organic Active Material in Battery Operation by Operando Surface-Enhanced Raman Spectroscopy

“…In the graphite–LMO system, the cathode often controls the cell capacity. One of the most conventional LMO materials is LiCoO 2 (LCO). − LCO possesses a layered crystal structure. In addition, it is the material that generates capacity by insertion/desorption of lithium cations between layers with cobalt redox reaction, presenting a theoretical maximum capacity of ∼270 mA h g –1 .…”