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High specific capacity and long cycling life of anode materials still remain major challenges in the development of sodium-ion batteries (SIBs). Nowadays, transition metal phosphides have been reckoned as promising anodes in view of their high theoretical specific capacities, low potential for sodium storage, and superior conductivity. Herein, molybdenum phosphide (MoP) nanorods wrapped with thin carbon layer have been prepared and applied as an anode for SIBs. By utilizing in situ X-ray diffraction technology, a conversion-type mechanism of MoP anode has been disclosed. This kind of MoP electrode exhibits extraordinary electrochemical properties, including excellent cycling performance with a discharge capacity of 398.4 mA h g–1at a current density of 100 mA g–1after 800 cycles, and remarkable rate capabilities, which remain 104.5 mA g–1at 1600 mA h g–1even after 10 000 loops. The distinguished performances stem from synergetic merits of the morphology, structure, and mechanism of MoP. It is expected that MoP will be a promising anode material for SIBs and this work would provide theoretical basis for the scalable research and applications of MoP-based anode materials for SIBs.

The class of two-dimensional metal carbides and nitrides known as MXenes offer a distinct manner of property tailoring for a wide range of applications. The ability to tune the surface chemistry for expanding the property space of MXenes is thus an important topic, although experimental exploration of surface terminals remains a challenge. Here, we synthesized Ti3C2MXene with unitary, binary, and ternary halogen terminals, e.g., −Cl, −Br, −I, −BrI, and −ClBrI, to investigate the effect of surface chemistry on the properties of MXenes. The electrochemical activity of Br and I elements results in the extraordinary electrochemical performance of the MXenes as cathodes for aqueous zinc ion batteries. The −Br- and −I-containing MXenes, e.g., Ti3C2Br2and Ti3C2I2, exhibit distinct discharge platforms with considerable capacities of 97.6 and 135 mAh·g–1. Ti3C2(BrI) and Ti3C2(ClBrI) exhibit dual discharge platforms with capacities of 117.2 and 106.7 mAh·g–1. In contrast, the previously discovered MXenes Ti3C2Cl2and Ti3C2(OF) exhibit no discharge platforms and only ∼50% of capacities and energy densities of Ti3C2Br2. These results emphasize the effectiveness of the Lewis-acidic-melt etching route for tuning the surface chemistry of MXenes and also show promise for expanding the MXene family toward various applications.

MXene-based catalysts exhibit extraordinary advantages for many catalysis reactions, such as the hydrogen evolution and oxygen reduction reactions. However, MXenes exhibit inadequate catalytic activity for the electrochemical nitrogen reduction reaction (NRR) because they are typically terminated with inactive functional groups, F* and OH*, which mask the active metal sites for N2binding. Here we modified the surface termination of MXene (Ti3C2Tx) nanosheets to achieve high surface catalytic reactivity for the NRR by ironing out inactive F*/OH* terminals to expose more active sites and by introducing Fe to greatly reduce the surface work function. The optimally performing catalyst (MXene/TiFeOx-700) achieved excellent Faradaic efficiency of 25.44% and an NH3yield rate of 2.19 μg/cm2·h (21.9 μg/mgcat·h), outperforming all reported MXene-based NRR catalysts. Our work provides a feasible strategy for rationally improving the surface reactivity of MXene-based catalysts for efficient electrochemical conversion of N2to NH3.

Nonbattery behavior related phase transition of electrodes is usually not favorable for any batteries because it results in performance degradation at all times. Here, we demonstrate a zinc hybrid-ion battery (ZHIB) with an unusual capacity enhancement even within 18 000 cycles by employing V2CTXMXene as the cathode, enormously differing from all reported counterparts with capacity degradation initiated within hundreds of cycles. The dominated mechanisms are determined to be MXene delamination and an unexpected phase transition during cycling. Both the original cathode and secondary derivative contribute to capacity simultaneously, resulting in the unusual capacity enhancement. Consequently, the specific capacity of 508 mAh g–1(highest for all reported aqueous zinc-ion batteries) and high energy density of 386.2 Wh kg–1are realized. Also, the quasi-solid-state batteries fabricated can output stably at −20 °C and in bending, twisting, stabbing, and cutting conditions. Our work brings an effective approach, that is, utilizing “unstable” electrode materials, which should usually be avoided, to achieve continuously enhanced performance of a battery. The idea to use both original and secondary materials for energy storage may be developed to be a general method to achieve extraordinary cycling stability of batteries.

Degradable energy storage systems (ESSs) have been proposed to tackle increasing e-wastes such as heavy metals and toxic organic electrolytes. However, currently reported degradable ESSs are scarce because it is very difficult to make all of the electrochemical components degradable as they must be stable for energy storage. Here, we designed an all-component degradable and rechargeable Zn–MXene capacitor with outstanding anti-self-discharge function using zinc nanosheets and Ti3C2MXene as electrodes. The whole capacitor can retain ca. 82.5% of the capacitance after 1000 cycles and be totally degraded within 7.25 days, comprehensively surpassing the current degradable supercapacitors (120 days, 400 cycles) and batteries (19 days, 0–20 cycles). In addition, while supercapacitors are notorious for intensive self-discharge, the Zn–MXene capacitor demonstrated the lowest self-discharge rate of 6.4 mV h–1, better than all the previous supercapacitors with specifically designed anti-self-discharge components including electrodes (>300 mV h–1), electrolytes (12–50 mV h–1), and separators (20–400 mV h–1). This is illustrated by the as-proposed “static electricity-immune mechanism” which refers to breaking the electrostatic adsorption. This Zn–MXene capacitor represents a great advance in degradable rechargeable ESSs and provides a strategy to fundamentally overcome the self-discharge problem encountered by supercapacitors.

Chalcogens, especially tellurium (Te), as conversion-type cathodes possess promising prospects for zinc batteries (ZBs) with potential rich valence supply and high energy density. However, the conversion reaction of Te is normally restricted to the Te2–/Te0redox with a low voltage plateau at ∼0.59 V (vs Zn2+/Zn) rather than the expected positive valence conversion of Te0to Ten+, inhibiting the development of Te-based batteries toward high output voltage and energy density. Herein, the desired reversible Te2–/Te0/Te2+/Te4+redox behavior with up to six-electron transfer was successfully activated by employing a highly concentrated Cl–-containing electrolyte (Cl–as strong nucleophile) for the first time. Three flat discharge plateaus located at 1.24, 0.77, and 0.51 V, respectively, are attained with a total capacity of 802.7 mAh g–1. Furthermore, to improve the stability of Ten+products and enhance the cycling stability, a modified ionic liquid (IL)-based electrolyte was fabricated, leading to a high-performance Zn∥Te battery with high areal capacity (7.13 mAh cm–2), high energy density (542 Wh kgTe–1or 227 Wh Lcathdoe+anode–1), excellent cycling performance, and a low self-discharge rate based on 400 mAh-level pouch cell. The results enhance the understanding of tellurium chemistry in batteries, substantially promising a remarkable route for advanced ZBs.