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Following the ammonia treatment, the pores created by the folds allow for electrolyte storage and facilitate ion transport. The interlayer spacing between MXene nanosheets widens due to the volume increase when water freezes. The generous ion transport paths and redox-active ammonium ions offer higher specific capacity and faster reaction kinetics. [Display omitted] Ti 3 C 2 T x MXene demonstrates excellent potential as an anode material for sodium-ion capacitors. However, the narrow interlayer spacing and self-stacking phenomenon limit its applicability. In this study, we demonstrate an easy two-step method involving freezing and crumpling of MXene nanosheets to improve their Na-ion storage via the addition of ammonium ions (referred to as FCM nanosheets). Flat MXene particles aggregate and undergo folding in an alkaline solution. Ammonium ions can penetrate the gaps between MXene nanosheets, expanding interlayer spaces and inducing the formation of folds. Compared to MXene nanosheets, FCM nanosheets exhibit improved ion transfer kinetics and additional high capacity owing to the intercalated ammonium ions. The manufactured FCM anode exhibits remarkable electrochemical properties, including a high specific capacity of 313 mAh g−1 and stability over 15,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] In this paper, we have developed a simple and efficient sulfur-amine chemistry strategy to prepare a three-dimensional (3D) porous Ti 3 C 2 T x composite with large amounts of N and S terminal groups. The well-designed 3D macroporous architecture presents enlarged interlayer spacing, large specific surface area, and unique porous structure, which successfully solves the re-stacking issue of MXene during storage and electrode fabrication. It is the amount of concentrated hydrochloric acid added to the S-EDA (ethylenediamine)/MXene colloidal suspension that is critical to the formation of 3D morphology. In addition, N and S terminals on MXene could improve the adsorption ability of K+. Owing to the synergistic effect of the structure design and terminal modification, the N, S codoped three-dimensional porous Ti 3 C 2 T x (3D-NSPM) material shows a high surface capacitive contribution and rapid diffusion kinetics for K+ and Na+. As a result, the as-prepared 3D-NSPM delivers high reversible capacity (237 and 273 mAh g−1 at 0.1 A g−1 for PIBs and SIBs, respectively), superb cycling stability (84.9% capacity retention after 10,000 cycles at 1 A g−1 in PIBs and 74.0% capacity retention after 2200 cycles at 1 A g−1 in SIBs), and excellent rate capability (111 and 196 mAh g−1 at 5 A g−1 for PIBs and SIBs, respectively), which are superior to other MXene-based anodes for PIBs and SIBs. Moreover, the described strategy provides a new insight for constructing the 3D porous structure from 2D building blocks beyond MXene. [ABSTRACT FROM AUTHOR]

MoSSe nanosheets anchored carbon tubes (CTs) were prepared with facile hydrothermal method and further selenized carbonization treatment. The hollow tubular carbon skeletons with abundant functional groups can regulate the uniform growth of MoS 2 clusters. In the subsequent step, the selenation treatment can extend the interlayer spacing of MoS 2 and form chemical bond (Mo N C) between the interface of MoSSe and CTs, which can effectively facilitate the transport of electron/ions. As the electrode materials for both SIBs and KIBs, the MoSSe@CTs presented a high and efficient Na+/K+ ions storage capability and good cycling stability. [Display omitted] • The tubular carbon skeletons expose abundant active sites for MoS 2 nanosheets growth. • The selenization treatment can expand the interlayer spacing of MoS 2 nanosheets. • The unique structure can improve rate capability and cycling stability of batteries. The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS 2 ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS 2) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g−1 at 1 A g−1 and retains a stable reversible capacity of 465 mAh g−1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg−1 at 1 A g−1 and a good cycling stability (maintains at 272 mA hg−1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries. [ABSTRACT FROM AUTHOR]

MoSSe nanosheets anchored carbon tubes (CTs) were prepared with facile hydrothermal method and further selenized carbonization treatment. The hollow tubular carbon skeletons with abundant functional groups can regulate the uniform growth of MoS 2 clusters. In the subsequent step, the selenation treatment can extend the interlayer spacing of MoS 2 and form chemical bond (Mo N C) between the interface of MoSSe and CTs, which can effectively facilitate the transport of electron/ions. As the electrode materials for both SIBs and KIBs, the MoSSe@CTs presented a high and efficient Na+/K+ ions storage capability and good cycling stability. [Display omitted] • The tubular carbon skeletons expose abundant active sites for MoS 2 nanosheets growth. • The selenization treatment can expand the interlayer spacing of MoS 2 nanosheets. • The unique structure can improve rate capability and cycling stability of batteries. The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS 2 ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS 2) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g−1 at 1 A g−1 and retains a stable reversible capacity of 465 mAh g−1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg−1 at 1 A g−1 and a good cycling stability (maintains at 272 mA hg−1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries. [ABSTRACT FROM AUTHOR]

Bifunctional catalyst was prepared by one-step pyrolysis of trimetallic ZIF. The obtained catalyst showed excellent charge–discharge stability in rechargeable Zn-air battery. • A facile and effect strategy is proposed for the synthesis of catalyst precursor. • This strategy reduces the adverse effects of the pyrolysis process on the catalyst. • The coexistence of Co NPs and CoFe-N x improves the ORR/OER activity. • The catalyst displays excellent durability as a cathode for Zn-air battery. Searching for high active, low cost and durable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains challenge in developing metal-air battery cathodes. Herein, we proposed a novel bifunctional catalyst derived from the pyrolysis of Co/Fe/Zn trimetallic zeolitic imidazolite framework. The obtained Co@CoFe 0.01 N C catalyst displays desirable activity for both ORR and OER (E 1/2 = 0.844 V, E j=10 = 1.654 V). The Zn-air battery equipped with Co@CoFe 0.01 N C catalyst on the cathode exhibits a high peak power density of 174.1 mW cm−2, which is much superior than that of commercial 20% Pt/C (87.6 mW cm−2). Significantly, the designed Co@CoFe 0.01 N C presents an outstanding stability for over 100 h in rechargeable Zn-air battery. [ABSTRACT FROM AUTHOR]

A three-dimensional free-standing hard carbon (FHC) electrode is synthesized by carbonizing the hemp haulm and employed as anode for sodium-ion batteries directly. A high current charging-discharging process is carried out to reconstruct surface structure of the FHC. Surface reconstructed FHC display a high capacity of 256 mAh/g and enhanced rate ability. With the formation of order surface structure, the plateau capacity increase and more sodium ions can insert into the FHC. This work demonstrates the importance of surface structure for sodium ion diffusion and storage and provide a new strategy to design high-performance anode materials. [ABSTRACT FROM AUTHOR]