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

Abstract

HIGHLIGHTS • A novel N-doped strategy of C 2 N 3 − in situ trimerization between the 2D MXene interlayers was first proposed. • The ultra-fast pseudocapacitive behavior of Ti 3 C 2 T x /Na 3 TCM anode was managed and verified. • The as-fabricated sodium-ion capacitor delivers excellent electrochemical performance by anode/cathode mass matching. 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 TiN 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).

Strongly Coupled 2D Transition Metal Chalcogenide-MXene-Carbonaceous Nanoribbon Heterostructures with Ultrafast Ion Transport for Boosting Sodium/Potassium Ions Storage

“…Particularly, after pyrolysis, the -OH in chitin were well retained, guaranteeing the high affinity between MXenes and fungus by providing adequate active sites for hydrogen bonds generation [ 19 , 20 ]. Furthermore, the adsorption peaks at around 1651 and 1708 cm −1 can be classified as the bond of C=O in both Ti 3 C 2 O 2 and biofungi, which is favorable for boosting electrochemical storages performance [ 21 ]. From the Raman spectra variation in Fig.…”

“…Meanwhile, the Se 3d spectra in Fig. S10b could be classified to three specific signals centered at about 54.1, 55.2, and 59.6 eV, assigning to the electronic orbits of 3d 5/2 and 3d 3/2 of Se 2− , as well as the Se-Se or Se-O bonds resulting from the selenylation procedure [ 21 ]. As for NiSe 2 -MXene-CNRib and CoSe 2 -MXene-CNRib aerogels, the corresponding high-resolution Ni 2p and Co 2p spectra are explicitly displayed in Fig.…”

“…The D K values for the potassiation process varied in range of 10 –10 to 10 –11 cm 2 s −1 and were 10 –8 ~ 10 –10 cm 2 s −1 for the depotassation process. The high K + diffusion coefficients confirmed that the ternary Cu 1.75 Se-MXene-CNRib anode allows rapid K + migration and storage at a more efficient kinetic behavior, and it can be a competitive anode for PIBs [ 21 , 36 – 39 ].…”

“…Compared to pristine Ti 3 C 2 T x , the appearance of Ti-O in Ti 2p spectra of ternary nanohybrids demonstrates the partial oxidation process for surficial Ti atoms during hybridization. Furthermore, a noticeable peak located at about 456.9 eV can be ascribed to the Ti-N resulted by the adsorption of MXene and N-rich carbonaceous fibers, suggesting the effective bio-adsorption between the Aspergillus niger fibers and the MXene nanosheets as well as the chalcogenide decorations [23].…”

Sodium‐Ion Capacitors: Recent Development in Electrode Materials

“…Recently, a new group of 2D transition metal carbides, carbonitrides, and nitrides, labeled as MXene, has attracted wide attention [74,75] . Generally, the MXene family can be expressed as M n +1 X n T x , where M refers to a transition metal (Ti, Nb, Mn, Mo, Cr, etc.…”