Search

Magnesium batteries have attracted considerable attention as a promising technology for future energy storage because of their capability to undergo multiple charging reactions. However, most oxide materials utilized as hosts for magnesium batteries do not perform well at room temperature or in nonaqueous electrolytes. Herein, a host material, Na0.04MoO3·(H2O)0.49 is successfully developed through the chemical reduction of alpha‐MoO3, which enables magnesium storage reaction in a 0.5 m Mg(ClO4)2/acetonitrile electrolyte at 25 °C. Electrochemical analysis reveals that the cathode material possesses a discharge capacity of 157.4 mAh g−1 at a 0.2 C rate. The Na0.04MoO3·(H2O)0.49 cathode material also exhibits a capacity retention of 93.4% after 100 cycles compared to the first cycle at a 2 C rate, with an average discharge voltage of −0.474 V versus activated carbon (≈2.16 V estimated discharge voltage vs Mg/Mg2+). The study findings demonstrate, for the first time, the potential of this material as a cathode for magnesium batteries at ambient temperatures and in nonaqueous electrolytes. [ABSTRACT FROM AUTHOR]

Tunnel‐type sodium manganese oxide is a promising cathode material for aqueous/nonaqueous sodium‐ion batteries, however its storage mechanism is not fully understood, in part due to the complicated sodium intercalation process. In addition, low cyclability due to manganese dissolution has limited its practical application in rechargeable batteries. Here, the intricate sodium intercalation mechanism of Na0.44MnO2 is revealed by combination of electrochemical characterization, structure determination from powder X‐ray diffraction data, 3D bond valence difference maps, and barrier‐energy calculations of the sodium diffusion. NaI is proposed as an important electrolyte solution additive. It is shown to form a thin, beneficial, and durable cathode surface film that prevents manganese dissolution. The addition of 0.01 m NaI to electrolyte solutions based on alkyl carbonate solvents and NaClO4 greatly improves the cycling efficiency, raising the capacity retention from 86% to 96% after 600 cycles. This study determines the core aspects of the sodium intercalation mechanism in tunnel‐type sodium manganese oxide and shows how it can serve as a durable cathode material for rechargeable Na batteries. [ABSTRACT FROM AUTHOR]

A new type of ammonium vanadium bronze, (NH 4 ) 2 V 7 O 16 , was synthesized by the hydrothermal method. The triclinic crystal structure ( P 1̅) is successfully identified by the single-crystal X-ray diffraction method. The layered structure is similar to that of other vanadium bronzes but with an unprecedented stoichiometry and crystal structure. The structure is composed of a stack of V 7 O 16 layers along the c axis, and two NH 4 + ions occupy the interlayer space per formula unit. Each ammonium ion is hydrogen-bonded to four lattice oxygen atoms, resulting in a stable structure with a large interlayer space, thus enabling the intercalation of various guest ions. Lithium ions are electrochemically intercalated into (NH 4 ) 2 V 7 O 16 , with an initial discharge capacity of 232 mAh g -1 and an average discharge voltage of 2 V (vs Li/Li + ). Upon the first discharge, lithium ions are inserted, whereas ammonium ions are extracted. Upon charging, a reverse reaction takes place. However, only a fraction of the extracted ammonium ions are reaccommodated. Despite the small quantity, the reinsertion of ammonium ions contributes crucially to the structural stability, improving the electrochemical performance. These results could provide a general understanding of the intercalation mechanism of host materials containing ammonium ions. In addition, (NH 4 ) 2 V 7 O 16 intercalates Na + ions reversibly, implying a potential capability as a host material for other guest ions.

The crystal structure of calcium perchlorate anhydrate was determined from laboratory X-ray powder diffraction data. The title compound was obtained by heating hydrated calcium perchlorate [Ca(ClO 4 ) 2 · x H 2 O] at 623 K in air for 12 h. It crystallizes in the ortho-rhom-bic space group Pbca and is isotypic with Ca(AlD 4 ) 2 . The asymmetric unit contains one Ca, two Cl and eight O sites, all on general sites (Wyckoff position 8 c ). The crystal structure consists of isolated ClO 4 - tetra-hedra and Ca 2+ cations. The Ca 2+ cation is coordinated by eight O atoms of eight symmetry-related ClO 4 - tetra-hedra within a distorted square-anti-prismatic environment.