Water-processable, sprayable LiFePO4/graphene hybrid cathodes for high-power lithium ion batteries

Abstract

Here, we demonstrate facile water-processable and sprayable electrode fabrication methods for LiFePO4/graphene hybrid cathodes in LIBs, without using an organic solvent. The multi-functionality of graphene oxide (GO), as a dispersant, binder, and precursor for the conductive graphene, was exploited in this fabrication process. Additional polymeric binders or conductive carbons were unnecessary. At high current rates, this water-processed LiFePO4/reduced graphene oxide (LFP/rGO) can store a larger amount of charges than conventional LFP cathodes produced by the previously formulated organic slurry-based blade coating method. The LFP/rGO electrode consisting of 80wt.% LFP and 20wt.% rGO showed capacity of 37mAhg−1 at a very high current rate (2040mAg−1). In contrast, the conventional LFP–based electrodes fabricated with poly(vinylidene fluoride), and carbon black in an organic solvent, exhibited negligible capacity (<1mAhg−1) at such a high current rate. The cycling stability of the sprayed LFP/rGO electrode was also significantly higher than that of the conventional LFP–based electrodes under harsh electrochemical conditions. After 1000 cycles at 3400mAg−1 from 1.5 to 4.5V (vs. Li/Li+), the sprayed LFP/rGO and conventional LFP/PVdF/carbon electrode exhibited capacity retention levels of 88% and 38%, respectively.