A Novel Strategy of In Situ Trimerization of Cyano Groups Between the Ti3C2Tx (MXene) Interlayers for High-Energy and High-Power Sodium-Ion Capacitors
Siyang Liu, Fangyuan Hu, Wenlong Shao, Wenshu Zhang, Tianpeng Zhang, Ce Song, Man Yao, Hao Huang, Xigao Jian
Abstract
Abstract 2D MXenes are attractive for energy storage applications because of their high electronic conductivity. However, it is still highly challenging for improving the sluggish sodium (Na)-ion transport kinetics within the MXenes interlayers. Herein, a novel nitrogen-doped Ti 3 C 2 T x MXene was synthesized by introducing the in situ polymeric sodium dicyanamide (Na-dca) to tune the complex terminations and then utilized as intercalation-type pseudocapacitive anode of Na-ion capacitors (NICs). The Na-dca can intercalate into the interlayers of Ti 3 C 2 T x nanosheets and simultaneously form sodium tricyanomelaminate (Na 3 TCM) by the catalyst-free trimerization. The as-prepared Ti 3 C 2 T x /Na 3 TCM exhibits a high N-doping of 5.6 at.% in the form of strong Ti–N bonding and stabilized triazine ring structure. Consequently, coupling Ti 3 C 2 T x /Na 3 TCM anode with different mass of activated carbon cathodes, the asymmetric MXene//carbon NICs are assembled. It is able to deliver high energy density (97.6 Wh kg −1 ), high power output (16.5 kW kg −1 ), and excellent cycling stability (≈ 82.6% capacitance retention after 8000 cycles).