Wenqiang Hu,Jiahe Zang,Qisen Wang,Siyuan Xiao,Jichao Zhang,Fang Fang,Zhongliang Ma,Dalin Sun,Yun Song
Magnesium hydride (MgH 2 ) 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 Li 3 VO 4 , 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 MgH 2 , but also maintains the high activity of P doped Li 3 VO 4 , thereby ensuring the hydrogen capacity of MgH 2 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.
Peng Ge,Shaohui Yuan,Wenqing Zhao,Limin Zhang,Yue Yang,Lingling Xie,Limin Zhu,Xiaoyu Cao
Due to its high theoretical capacity (∼280 mA h g−1), lithium vanadium oxide (LiV3O8) is considered a promising electrode material for meeting the demands for a longer battery life. However, it still suffers from an inferior cycling stability and rate properties. Benefitting from the unique traits of rare earth metal La, La-doping was introduced to V-sites, leading to an expansion of the lattice volume and reduced particle size, and bringing about more oxygen defects for fast ion redox reactions. The considerable discharge capacity of optimized La-doped LiV3O8 could reach up to 308 mA h g−1, and the capacity could be kept at 252 mA h g−1 after numerous loops. Supported by a detailed analysis of the capacity curves, an improved redox activity of V5+ was strongly demonstrated. Moreover, compared to the basic materials, an increasing rate capacity located in the low potential range was detected, ascribed to the existence of an oxygen vacancy, enabling a reduction in the energy barrier and a broadening of the energy distribution. Interestingly, La-doping could ultimately improve the capacity and is thus worth further exploration, particularly for the design of advanced cathodic materials.
Sicong Shen,Bing Sun,Xiaomeng Bai,Song Yang,Dongmei Zhang,Cunyuan Pei,Pengju Li,Shibing Ni
Disordered rock-salt (DRS) LiVO2 has attracted enormous attention for use as a fast-charging anode due to its high Li+ diffusion efficiency. However, sluggish interfacial kinetics hinder the electrochemical performance despite LiVO2 having rapid bulk-phase transport dynamics. Herein, we design flower-like N-doped carbon-confined LiVO2 with a sandwich structure (LiVO2/NC NFs) through an in situ grafting approach using polyacrylonitrile (PAN) as a template. Part of the cyano groups of PAN was hydrolyzed into carboxylate ions, promoting strong adhesion between the PAN and LiVO2 precursors due to electrostatic interactions, thus ensuring the DRS structure and a continuous charge-transfer pathway for the LiVO2/NC NF electrode. The obtained LiVO2/NC heterointerface provides abundant active sites and enhances the interfacial transport kinetics of the ions. As a result, the LiVO2/NC NFs electrode exhibits excellent electrochemical performances (including an average discharge capacity of 415 mA h g−1 at 8.0 A g−1 after 4 periodic rate tests over 250 cycles, and a discharge capacity of 223 mA h g−1 at a high discharge current of 10.0 A g−1 after 5000 cycles), outperforming other LiVO2-based anodes. It is hoped that the design strategy of LiVO2/NC NFs will provide impetus for further development of fast-charging electrodes.
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