MXene/TiO₂ Heterostructure-Decorated Hard Carbon with Stable Ti–O–C Bonding for Enhanced Sodium-Ion Storage

Abstract

Hard carbon (HC) has attracted considerable attention in the application of sodium-ion battery (SIB) anodes, but the poor realistic capacity and low rate performance severely hinder their practical application. Herein we report a solvent mechanochemical protocol for the in situ fabrication of the HC-MXene/TiO 2 electrode by functionalizing MXene to improve the electrochemical performance of the batteries. MXene (Ti 3 C 2 T x ) with abundant oxygen-containing functional groups reacts with HC particles in the ball milling process to form a Ti−O−C covalent cross-linked HC-MXene composite, in which the edge of the MXene nanosheets is in situ oxidized by air to form TiO 2 nanorods, forming a regular 1D/2D MXene/TiO 2 heterojunction structure. Ti− O−C covalent bonding can protect the heterojunction structures from pulverization and detachment from the current collector during charge/discharge cycles due to sodium-ion intercalation/detachment, thus improving the stability of the electrode structure. Meanwhile, the MXene/TiO 2 heterojunction can form a 3D conductive network and provide more active sites. The resulting HC-MXene/TiO 2 electrode exhibits superior electrode capacity (660 mAh g −1 ), making it a promising anode material for SIBs. This simple and efficient method for preparing MXene/TiO 2 heterojunction-decorated HC provides a new perspective on the structural design of MXene and carbon material composites for SIBs. KEYWORDS: hard carbon, Ti 3 C 2 T x , TiO 2 nanorods, ball milling, sodium-ion batteries

In situ preparation of an anatase/rutile-TiO2/Ti3C2Tx hybrid electrode for durable sodium ion batteries

“…Incorporation of TiO 2 with different phases into MXene would further reinforce this effect, leading to increased specific surface area. 39,40 Apparently, the N 2 adsorption capacities of the samples follow the order of Ti 3 C 2 T x < A-TiO 2 /Ti 3 C 2 T x < A/R-TiO 2 /Ti 3 C 2 T x . The formation of TiO 2 nanocrystals on MXene provides more adsorption sites for Na ions.…”

MXene in core–shell structures: research progress and future prospects

“…Aside from electrostatic forces and hydrogen bonding, MXene contains metal constituents that can also provide possible bonding formation. Transition metals within MXene, for example, Ti, can share chemical bonds with other materials which can provide stronger and better contact, such as Ti bonding in Ti-O-P, 142 and Ti-O-C. 143 For instance, the structural formation and encapsulation of SnO 2 within a 3D crumpled MXene are shown in Fig. 10a.…”

Interlayer-Expanded MoS2 Nanoflowers Vertically Aligned on MXene@Dual-Phased TiO2 as High-Performance Anode for Sodium-Ion Batteries

“…Herein, we report 3D cross-linked MoS 2 nanosheets with expanding interplanar spacing by the role of CTAB aligned vertically on highly conductive Ti 3 C 2 T x MXene nanosheets with partially oxidized rutile and anatase dual-phased TiO 2 (MoS 2 @MXene@D-TiO 2 ) through a one-step hydrothermal method as anode materials without further annealing for SIBs. In this unique structure, MoS 2 nanoflowers, grown in situ on MXene@D-TiO 2 formed into a 3D cross-linked hierarchically porous structure, bring many advantages: expanded MoS 2 layer spacing is suitable to the transmission of Na + , and the heterogeneous nanoarchitecture between MoS 2 nanoflowers, MXene, and MXene derived dual-phase TiO 2 is more conducive to electronic diffusion, improves the electrode contact surface area with electrolyte, prevents aggregation between MoS 2 nanoflowers, buffers volume expansion of the bulk, and reduces structural crumble caused by Na + intercalation . Thence, compared to pure MoS 2 , the as-constructed 3D MoS 2 @MXene@D-TiO 2 heterostructure not only guarantees the desirable high-rate ability (571.6 mAh g –1 for 50 mA g –1 and 328 mAh g –1 for 5 A g –1 at room temperature) but also significantly improves cycle performance (396.3 mAh g –1 for 100 mA g –1 at 150 cycles after rate performance, initial capacity of 2 A g –1 is 490.8 mAh g –1 and 570 mAh g –1 after 100 cycles) and delivers an admirable capacity of 171.5 mAh g –1 for 50 mA g –1 after 100 cycles at low temperature of −30 °C and superior electrochemical performance in Na + full batteries coupled with Na 3 V 2 (PO 4 ) 3 cathode.…”