Fabrication of PANI-coated ZnFe2O4 nanofibers with enhanced electrochemical performance for energy storage

Abstract

We successfully combined electrospinning with in situ polymerization methods to synthesize the PANI-coated ZnFe2O4 nanofibers which possess the abundant pore structure. The lithium storage properties of PANI-coated ZnFe2O4 nanofibers as anode materials for lithium-ion batteries have been discussed for the first time. PANI nanoparticles were directly coated on the surface of the ZnFe2O4 nanofibers, increasing the electrical conductivity, and also acting as the protect shell to enhance the mechanical strength of material. The electrochemical performance showed that 15% PANI incorporated ZnFe2O4 composite nanofibers (ZP-15) exhibited the highest reversible capacity of 1142 mAhg−1 after 50 cycles, which was much higher than that of pure ZnFe2O4 nanofibers (628 mAhg−1), 10% PANI incorporated ZnFe2O4 composite nanofibers (ZP-10, 975 mAhg−1), and 20% PANI incorporated ZnFe2O4 composite nanofibers (ZP-20, 536 mAhg−1). Additionally, the ZP-15 composite nanofibers achieved outstanding cycling rate capacity of 852, 738, 609 and 539 mAhg−1 with current densities range from 500 to 5000 mA g−1, and exhibited a specific capacity of 1082 mAhg−1 when the current reverted to 50 mA g−1 from the high rate charge-discharge cycles. The enhanced electrochemical performance of PANI-coated ZnFe2O4 nanofibers can be attributed to the PANI providing a highly electrical conductive medium, which can promote electron transfer and facilitate the Li+ transport in the lithiation/delithiation process, also can reduce self-discharge; moreover, the PANI layer covered on the surface of ZnFe2O4 nanofibers can be as buffer matrix to restrain the stress of volume expansion to get stable structure.