Surface modifications of Li-ion battery electrodes with various ultrathin amphoteric oxide coatings for enhanced cycleability

Abstract

Ultrathin ZnO, ZrO2, and Al2O3 surface coatings are deposited via atomic layer deposition (ALD) with high conformality and atomic scale thickness control to enhance the electrochemical performance of LiMn2O4 for applications in lithium ion batteries. Two types of ALD-modified LiMn2O4 electrodes are fabricated: one is ALD-coated LiMn2O4 composite electrode and the other is electrode composed of ALD-coated LiMn2O4 particles and uncoated carbon/polyvinylidenefluoride network. Cycling performance and cyclic voltammetric patterns reveal that ZnO ALD coating is the most effective protective film for improving the electrochemical performance of LiMn2O4 at either 25 or 55 °C, followed by ZrO2 and Al2O3. After 100 electrochemical cycles in 1 C at 55 °C, the electrode consisting of LiMn2O4 particles coated with six ZnO ALD layers (as thin as ~1 nm) delivers the highest final capacity, more than twice that of the bare electrode. It is also found that amphoteric oxide coating on LiMn2O4 particles can enhance the cycleability of LiMn2O4 more effectively than coating on the composite electrode. Furthermore, for ALD coating either on the composite electrode or on LiMn2O4 particles, the effect of oxide ALD modification for improving capacity retention and increasing specific capacity of LiMn2O4 is more phenomenal at elevated temperature than at room temperature.