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[en] Highlights: • Alkalized Ti3C2 MXene nanoribbons (a-Ti3C2) with expanded interlayer spacing is synthesized by shaking treatment of Ti3C2 MXene in KOH solution. • a-Ti3C2 shows narrow widths of nanoribbons (6–22 nm) as well as 3D interconnected porous frameworks. • a-Ti3C2 displays high capacities and superior cycling stability over 500 cycles for sodium/ potassium storage. As post-lithium ion batteries, both sodium ion batteries (SIBs) and potassium ion batteries (PIBs) possess great potential for large scale energy storage. However, the improvements of both SIBs and PIBs for practical applications are facing great challenges in the development of high-performance electrode materials. Here, we demonstrate the fabrication of alkalized Ti3C2 (a-Ti3C2) MXene nanoribbons attained by continuous shaking treatment of pristine Ti3C2 MXene in aqueous KOH solution. Benefited from the expanded interlayer spacing of a-Ti3C2, narrow widths of nanoribbons as well as three-dimensional interconnected porous frameworks for enhanced ion reaction kinetics and improved structure stability, the resulting a-Ti3C2 anodes showed excellent sodium/potassium storage performance, for example, high reversible capacities of 168 and 136 mA h g−1 at 20 mA g−1 and 84 and 78 mA h g−1 at 200 mA g−1 were obtained for SIBs and PIBs, respectively. Notably, a-Ti3C2 possessed outstanding long-term cyclability at high current density of 200 mA g−1, delivering a capacity of ~ 50 mA h g−1 for SIBs and ~ 42 mA h g−1 for PIBs after 500 cycles, which outperformed most of reported MXene based anodes for SIBs and PIBs. Moreover, this alkalization strategy could be extended as a universal approach for fabricating various alkalized MXene-based frameworks derived from a large family of MAX phases for numerous applications, such as catalysis, energy storage and conversion.
[en] Guiding the lithium ion (Li-ion) transport for homogeneous, dispersive distribution is crucial for dendrite-free Li anodes with high current density and long-term cyclability, but remains challenging for the unavailable well-designed nanostructures. Herein, we propose a two-dimensional (2D) heterostructure composed of defective graphene oxide (GO) clipped on mesoporous polypyrrole (mPPy) as a dual-functional Li-ion redistributor to regulate the stepwise Li-ion distribution and Li deposition for extremely stable, dendrite-free Li anodes. Owing to the synergy between the Li-ion transport nanochannels of mPPy and the Li-ion nanosieves of defective GO, the 2D mPPy-GO heterostructure achieves ultralong cycling stability (1000 cycles), even tests at 0 and 50 °C, and an ultralow overpotential of 70 mV at a high current density of 10.0 mA cm, outperforming most reported Li anodes. Furthermore, mPPy-GO-Li/LiCoO full batteries demonstrate remarkably enhanced performance with a capacity retention of >90 % after 450 cycles. Therefore, this work opens many opportunities for creating 2D heterostructures for high-energy-density Li metal batteries. (© 2020 Wiley‐VCH Verlag GmbH and Co. KGaA, Weinheim)