Porous FeP@C frameworks as anode materials for high performance lithium ion capacitors

Abstract

Porous FeP@C networks are realized via a one-step calcination process, using ferric nitrate and phytic acid as the precursors of FeP along with thiourea and melamine as N, S precursors. Benefited from the cooperative hydrogen bonding of melamine and phytic acid, two dimensional (2D) frameworks embedded with FeP can be formed. This porous architecture largely favors the penetration of electrolyte and shortens the transfer length of Li+ ions. Moreover, the conductive carbon on FeP can significantly alleviate the volume change upon cycling and boost the electronic conductivity. Owing to their unique build, the FeP@C networks exhibit competitive rate performance and cycling stability with a large reversible capacity of 293.0 mAh g−1 at 4 A g−1 after 1000 cycles. Even at the ultrahigh current density of 6 A g−1, there is still a large reversible capacity of 218.3 mAh g−1. Therefore, the lithium ion capacitors (LICs) are devised by selecting the conductive FeP@C networks as anode materials and porous carbon as cathode materials. As expected, the LIC indicates a high energy density of 91.4 Wh kg−1 at the power density of 390 W kg−1.