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Magnesium hydride (MgH2) is a promising hydrogen storage material for its high hydrogen capacity of 7.6 wt.%. However, the further application is severely hampered by the sluggish reaction kinetics and stable thermodynamics. Introducing catalysts is an effective method to improve the reaction rate, but the catalytic activity tends to decrease with an increasing number of reaction cycles, due to the highly reductive Mg and H species. Herein, the spring effect has been observed in the P doped Li3VO4, in which both V─P and V─V bonds undergo compression and elongation during hydrogen absorption and desorption, respectively. Such a unique self‐regulation spring effect not only improves the reaction kinetics of MgH2, but also maintains the high activity of P doped Li3VO4, thereby ensuring the hydrogen capacity of MgH2 even after 100 loops. This spring effect of chemical bonding, stretched‐recovered‐stretched with the motion between the highly reductive Mg and H species, will provide insight into catalyst design for hydrogen‐related industries. [ABSTRACT FROM AUTHOR]

2LiBH4−MgH2 (Li‐RHC) is a potential hydrogen storage candidate with a capacity of 11.5 wt.%. However, its further application is severely limited by the long nucleation induction period and poor reversibility of end‐product. Unlike the traditional focus on the catalytical role of cation, herein, a new perspective of previously ignored anion tuning has been proposed, in which S2− bridges the reversible conversion between Li2S and MgS during de‐/hydrogenation cycling of Li‐RHC. Such conversion not only enhances the migration of Li+, leading to the rapid destabilization of B─H bonds without obvious nucleation period of MgB2, but also improves the cycling stability of Li‐RHC with capacity retention over 90% even after 50 cycles. The universal of this anion modulation has been verified, along with the matching criteria of the corresponding transition metal cation. The results highlight the contribution of anion, push anion modulation from back to stage and eventually broaden the selection of catalysts for Li‐RHC. [ABSTRACT FROM AUTHOR]

Potassium‐ion batteries (PIBs) have been considered as potential alternatives for lithium‐ion batteries since there is a demand for better anode with superior energy, excellent rate capability, and long cyclability. The high‐capacity zinc selenide (ZnSe) anode, which combines the merits of conversion and alloying reactions, is promising for PIBs but suffers from poor cyclability and low electronic conductivity. To effectively boost electrochemical performance of ZnSe, a "dual‐carbon‐confined" structure is constructed, in which an inner N‐doped microporous carbon (NMC)‐coated ZnSe wrapped by outer‐rGO (ZnSe@i‐NMC@o‐rGO) is synthesized. Combining finite element simulation, dynamic analysis, and density functional theory calculations, the respective roles of inner‐ and outer‐carbon in boosting performance are revealed. The inner‐NMC increased the reactivity of ZnSe with K+ and alleviated the volume expansion of ZnSe, while outer‐rGO further stabilized the structure and promoted the reaction kinetics. Benefiting from the synergistic effect of dual‐carbon, ZnSe@i‐NMC@o‐rGO exhibited a high specific capacity 233.4 mAh g−1 after 1500 cycles at 2.0 A g−1. Coupled with activated carbon, a potassium‐ion hybrid capacitor displayed a high energy density of 176.6 Wh kg−1 at 1800 W kg−1 and a superior capacity retention of 82.51% at 2.0 A g−1 after 11000 cycles. [ABSTRACT FROM AUTHOR]

The pulverization of silicon during lithiation/delithiation due to its huge volume change results in a loss of electrochemical activity. In this work, advantage is taken of the unavoidable pulverization and an innovative strategy of in‐situ self‐adapting electrochemical grinding (ECG) is designed for stable silicon anode. MgH2 is utilized as the grinding aid to electrochemically grind micronsized Si particles. During ECG process, the lithiation processes of MgH2 and Si occur at different potentials and both result in appreciable volume expansion, leading to a strong internal stress inside the electrode. With this strong internal stress, the lithiation products of MgH2, i.e., Mg and LiH, would migrate into the cracked Si particles and gradually transform into a conductive matrix consisting of ionic conductive LiH and electronic conductive via partially reversible lithiation of Mg. After ECG process, micronsized Si particles are spontaneously grinded to an equilibrium size, which can accommodate the volume change and ensure the stable cycling. As prepared Si anode delivers an excellent reversible specific capacity of 3228 mAh g−1 and a capacity retention of 91% after 200 cycles. The proposed in situ self‐adapting ECG strategy offers a unique perspective for the development of Si‐based anode materials for next‐generation lithium ion batteries. [ABSTRACT FROM AUTHOR]

Magnesium hydride has been regarded as a promising hydrogen storage material. However, its further commercialization is severely hampered by its stable thermodynamic and sluggish kinetic performance. Herein, to simultaneously solve above two problems, a bimetallic oxide Ni3(VO4)2 has been synthesized and applied to catalyze the hydrogen storage reaction of MgH2. Benefiting from the formation of the Mg2Ni alloy, as well as kinetic modulation of V, the dehydrogenation temperature decreased to 210 °C, with a promising rehydrogenation capacity of 2.3 wt% near room temperature. X-ray absorption spectroscopy was employed to comprehensively reveal local structures of Ni and V in different states, with the detection of NiV2O4 intermediate active species for the first time. This work not only elucidates the structure evolution of the Ni3(VO4)2 catalyst, but also clarifies the synergistic effect between Ni and V, which sheds light on further rational designs for multi-element metallic catalysts. [ABSTRACT FROM AUTHOR]

Magnesium-based hydrides are promising hydrogen storage materials; however, little progress has been achieved in improving hydrogen storage performance under ambient conditions, consequently impeding further commercial application. Herein, a lithium rich transition metal oxide, Li3VO4 has been employed to catalyze the hydrogen storage reaction of magnesium-based hydrides, enabling a fast and full hydrogenation of Mg at lower temperatures. The structural stability of Li3VO4 upon de/rehydrogenation reactions has been confirmed by neutron diffraction and transmission electron microscope observations. The synergistic catalytic role of Li3VO4 has elucidated that the existence of Li stimulates the catalytic activity of V and simultaneously suppresses the activity of O. V is the key catalytically active site, while O can react with active Mg to generate MgO which is a passivation layer and could prevent the diffusion of H. These findings will give an opportunity for the use of other lithium rich transition metal oxides in the field of catalyzing hydrogen storage systems. [ABSTRACT FROM AUTHOR]