Intrinsic rapid Na+ intercalation observed in NaxCoO2 thin film

Electrochemical properties are investigated for thin film electrode of NaxCoO2, which was fabricated by pulsed laser deposition. A high rate of 400 C was realized in the film together with a fine cyclability where its capacity after 1000 cycles remains 84.4% of the initial one. The NaxCoO(2) thin film exhibits a clear sign of the structural phase transition induced by Na+ intercalation even at the high rate of 200 C. This observation indicates bulk nature of the rapid and highly-reversible Na+ intercalation in NaxCoO(2). Copyright 2013 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4794719]