Dense CoO/graphene stacks via self-assembly for improved reversibility as high performance anode in lithium ion batteries

Abstract

Here, we propose a novel strategy to prepare dense stacks composed of alternating CoO and graphene layers for an anode in lithium ion batteries (LIBs), which contributes to enhanced stability and relatively large reversible capacity. This is accomplished by spontaneously pre-aligning negatively charged CoO-anchored graphene oxide (CG) and positively charged amine-functionalized graphene (GN) in an acidic medium, followed by thermal reduction. The performance of this product is contrasted with that of CG prepared under the identical conditions without the addition of GN, in which CoO nanoparticles are sandwiched between relatively loose and randomly oriented graphene stacks. For example, the composite delivers a capacity greater than 800 mAh g−1 with a fading rate of 0.04 mAh g−1 cycle−1 during 1000 charge/discharge (C/D) cycles at 1.0 A g−1, in contrast to ca. 400 mAh g−1 and 0.24 mAh g−1 cycle−1 for thermally reduced CG without the addition of GN. The origin of the superior electrochemical performance in the dense stacks is ascribed to the enhanced reversibility of a conversion reaction, which in turn contributes to a persistent formation/dissolution of gel-like polymer films (i.e., stable pseudo-capacitance). Experimental evidences that substantiate the aforementioned behaviors (improved reversibility for both processes) are presented.