Dispersion-Assembly Approach to Synthesize Three-Dimensional Graphene/Polymer Composite Aerogel as a Powerful Organic Cathode for Rechargeable Li and Na Batteries.

Abstract

Polymer cathode materials are promising alternatives to inorganic counterparts for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to their high theoretical capacity, adjustable molecular structure, and strong adaptability to different counterions in batteries, etc. However, they suffer from poor practical capacity and low rate capability because of their intrinsically poor conductivity. Herein, we report the synthesis of self-assembled graphene/poly(anthraquinonyl sufide) (PAQS) composite aerogel (GPA) with efficient integration of a three-dimensional (3D) graphene framework with electroactive PAQS particles via a novel dispersion-assembly strategy which can be used as a free-standing flexible cathode upon mechanical pressing. The entire GPA cathode can deliver the highest capacity of 156 mAh g-1 at 0.1 C (1 C = 225 mAh g-1) with an ultrahigh utilization (94.9%) of PAQS and exhibits an excellent rate performance with 102 mAh g-1 at 20 C in LIBs. Furthermore, the flexible GPA film was also tested as cathode for SIBs and demonstrated a high-rate capability with 72 mAh g-1 at 5 C and an ultralong cycling stability (71.4% capacity retention after 1000 cycles at 0.5 C) which has rarely been achieved before. Such excellent electrochemical performance of GPA as cathode for both LIBs and SIBs could be ascribed to the fast redox kinetics and electron transportation within GPA, resulting from the interconnected conductive framework of graphene and the intimate interaction between graphene and PAQS through an efficient wrapping structure. This approach opens a universal way to develop cathode materials for powerful batteries with different metal-based counter electrodes.