Optimizing Ion Pathway in Titanium Carbide MXene for Practical High‐Rate Supercapacitor

Abstract

MXene for supercapacitor application which shows outstanding proton-induced pseudocapacitance in acidic aqueous electrolytes. [14,15] High electronic conductivity (up to 15 000 S cm −1), high packing density (up to 4 g cm −3), along with high pseudocapacitance endow Ti 3 C 2 T x ultrahigh volumetric capacitance (≈1500 F cm −3), which gives Ti 3 C 2 T x incomparable advantages over other electrode materials for supercapacitors. [16] However, Ti 3 C 2 T x electrodes suffer from long ion transport pathways due to the stacking nature of 2D materials, leading to ultra-low rate performance in a thick electrode. When used as a power supply for electronic devices where high areal energy densities at high rates are required, MXene electrodes need to be thick enough to ensure high charge storage capability. In this context, the ion transport issue becomes more critical because the low rate performance will deteriorate with the increase of film thickness. [17] Numerous efforts have been made to alleviate the restacking issue of Ti 3 C 2 T x film electrodes. Typical strategies include interlayer insertion of graphene, carbon nanotube or other nanomaterials, pillared structure design, template sacrifice method, vertical alignment, and etching holes. [17-27] However, by most of the reported approaches, the rate performances are increased at the expense of volumetric capacitance because of the introduction of inactive materials, excess spacing, or active materials with lower volumetric capacitance. For example, ≈15% decrease

An Organic Solvent-Assisted Intercalation and Collection (OAIC) for Ti3C2Tx MXene with Controllable Sizes and Improved Yield

“…As shown in Fig. S14, the gravimetric capacitance of S-Ti 3 C 2 T x is ~ 300 F g −1 , which similarly with prsitine Ti 3 C 2 T x of previous reports [ 12 , 18 , 28 , 42 – 45 ]. The gravimetric capacitances and rate performance of O-Ti 3 C 2 T x film electrodes were compared with pristine Ti 3 C 2 T x of previous reports and summarized in Table S3, which clearly demonstrate that O-Ti 3 C 2 T x products show outstanding capacitive performance.…”

“…The size-dependent electrochemical properties of Ti 3 C 2 T x have a compromise between the electrical conductivity and ion pathways of electrolyte. Specifically, although the larger Ti 3 C 2 T x flakes have higher electrical conductivity which heighten the charge transfer thereby boosting the capacitive performance [ 28 ], the film electrodes prepared by larger Ti 3 C 2 T x flakes suffer from long ion transport pathways resulting the poor rate performance [ 42 ]. Therefore, the O-Ti 3 C 2 T x -3 with median flakes area finds a balance between the good electrical conductivity and the less hinder of ion transport of electrolyte.…”

“…Ti 3 C 2 T x of previous reports[12,18,28,[42][43][44][45]. The gravimetric capacitances and rate performance of O-Ti 3 C 2 T x film electrodes were compared with pristine Ti 3 C 2 T x of previous reports and summarized in TableS3, which clearly demon-…”

A comprehensive review of MXenes as catalyst supports for the oxygen reduction reaction in fuel cells

“…Therefore, it is vital to develop a good strategy to prevent MXene restacking, such as introducing space vectors between the layers using CNTs 211 or by using the concentrated acid etching method. 212 Although achievements in the research and development of these materials have greatly progressed, there are still some challenges in their ORR activity and stability. In most active PGM-free catalysts, the catalytic activity is still below the DOE 2020 target of 44 mA/cm 2 .…”

Coating Porous MXene Films with Tunable Porosity for High‐Performance Solid‐State Supercapacitors

“…Very recently, Tang et al. reported a facile method based on oxidation with sulfuric acid to create favorable ion diffusion pathways in MXene freestanding films, however, the usage of concentrated sulfuric acid pose extra potential risk during the synthesis of materials [27] . Hence, for cost‐effective production of porous MXene films and their potential applications in energy storage devices, novel, industrially‐scalable techniques with low (no) environmental/safety concerns should be developed.…”