A Novel Strategy of In Situ Trimerization of Cyano Groups Between the Ti3C2Tx(MXene) Interlayers for High-Energy and High-Power Sodium-Ion Capacitors

摘要

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 Ti3C2Tx 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 Ti3C2 Tx nanosheets and simultaneously form sodium tricyanomelaminate(Na3TCM)by the catalyst-free trimerization.The as-prepared Ti3C2Tx/Na3TCM exhibits a high N-doping of 5.6 at.%in the form of strong Ti-N bonding and stabilized triazine ring structure.Consequently,coupling Ti3C2Tx/Na3 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).