Silicon is attracting enormous attention due to its theoretical capacity of 4200 mAh g−1 as an anode for Li‐ion batteries (LIBs). It is of fundamental importance and challenge to develop low‐temperature reaction route to controllably synthesize Si/Ti3C2 MXene LIBs anodes. Herein, a novel and efficient strategy integrating in situ orthosilicate hydrolysis and a low‐temperature reduction process to synthesize Si/Ti3C2 MXene composites is reported. The hydrolysis of tetraethyl orthosilicate leads to homogenous nucleation and growth of SiO2 nanoparticles on the surface of Ti3C2 MXene. Subsequently, SiO2 nanoparticles are reduced to Si via a low‐temperature (200 °C) reduction route. Importantly, Ti3C2 MXene not only provides fast transfer channels for Li+ and electrons, but also relieves volume expansion of Si during cycling. Moreover, the characteristics of excellent pseudocapacitive performance and high conductivity of Ti3C2 MXene can synergistically contribute to the enhancement of energy storage performance. As expected, Ti3C2/Si anode exhibits an outstanding specific capacity of 1849 mAh g−1 at 100 mA g−1, even retaining 956 mAh g−1 at 1 A g−1. The low‐temperature synthetic route to Si/Ti3C2 MXene electrodes and involved battery‐capacitive dual‐model energy storage mechanism has potential in the design of novel high‐performance electrodes for energy storage devices.

The novel PDDA-NPCNs/Ti3C2 hybrids via an electrostatic attraction self-assembly approach effectively accelerate reaction kinetics and improve electrochemical performance as PIBs anodes.

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MXenes have attracted increasing attention due to their unique advantages, excellent electronic conductivity, tunable layer structure, and controllable interfacial chemistry. However, the practical applications of MXenes in energy storage devices are severely limited by the issues of torpid reaction kinetics, limited active sites, and poor material utilization efficiency. Herein, the most-up-to date advances in the rational microstructure design to enhance electrochemical reaction kinetics and energy storage performance of MXene-based materials are comprehensively summarized. This review begins with the preparation and properties of MXenes, classified into fluorine-containing acid etching and fluoride-free etching approaches. Afterwards, the interlayer structure design and interfacial functionalization of MXenes with respect to interlayer spacing and porous structure, terminal groups, and surface defects are summarized. Then the focus turns to the construction of advanced MXene-based heterojunctions based on in situ derivation and surface self-assembly. Based on these microstructure modulating strategies, the state-of-the-art progress of MXene-based applications with respect to supercapacitors, alkali metal-ion batteries, metal-sulfur batteries, and photo/electrocatalysis are highlighted. Finally, the critical challenges and perspectives for the future research of 2D MXene-based nanostructures are highlighted, aiming to present a comprehensive reference for the design of MXene-based electrodes for electrochemical energy storage.

Rechargeable Li-O 2 batteries are promising due to their superior high energy density but subject to sluggish oxygen reduction/evolution kinetics. Developing highly efficient catalysts to improve catalytic activity and alleviate oxidation-reduction overpotential of Li-O 2 batteries is of great challenge and importance. Herein, a CO 2 -assisted thermal-reaction strategy is developed to fabricate isolated semi-metallic selenium single-atom-doped Ti 3 C 2 MXene catalyst (SASe-Ti 3 C 2 ) as cathodes for high-performance Li-O 2 batteries. The isolated moieties of single Se atom catalysis centers can function as active catalytic centers to drastically enhance the intrinsic LiO 2 -absorption ability and thus fundamentally modulate the formation/decomposition mechanism of lithium peroxide (Li 2 O 2 ) discharge product, thus demonstrating greatly enhanced redox kinetics and efficiently ameliorated overpotentials. Theoretical simulations reveal that the interaction between Se-involved moieties and Ti 3 C 2 substrate greatly enhances the intrinsic LiO 2 -absorption ability and fundamentally promotes the charge transfer between electrode and Li 2 O 2 product, deeply ameliorating the round-trip overpotential. The well-designed SASe-Ti 3 C 2 electrode exhibits decreased charge/discharge polarization (1.10 V vs Li/Li + ), ultrahigh discharge capacity (17 260 mAh g −1 at 100 mA g −1 ), and superior durability (170 cycles at 200 mA g −1 ) as cathode for Li-O 2 batteries. The promising results will shed light on the design of highly efficient catalysts for oxygen-involved systems of future investigation.