[en] A simple and an efficient synthesis route, solvent mediated milling of NaH and Al with 2 mol% of the dopant precursor, Ti(OBu)₄ followed by hydrogenation, has been developed and employed to synthesize Ti-doped NaAlH₄. The long-term hydrogenation and dehydrogenation, up to 100 cycles were carried out systematically. Reversibility of about 3.4 wt.% hydrogen release was obtained during the first dehydrogenation (160 deg. C) run after the initial hydrogenation of Ti-doped (NaH+Al) at 150 deg. C; ∼11.4 MPa H₂ for 12 h. In the subsequent cycles, the storage capacity increased, reaching an optimum of 4.0 wt.%. This capacity was retained for 40 cycles with the dehydrogenation kinetic curves showing remarkable reproducibility. Comparison of the X-ray diffraction profiles of Ti-doped (NaH+Al) from initial and final stages of the cycling study reveals a growing resistance to the hydrogenation of Na₃AlH₆ to NaAlH₄

[en] The practical application of Li-metal anode in high-energy rechargeable Li batteries is still hindered by the uncontrollable formation of Li dendrites. Here, a facile way is reported to stabilize Li-metal anode by building dendrite-like Li${}_3$Mg${}_7$ alloys enriched with Li-containing polymers as the physical protecting layer and LiH as the Li-ion conductor. This unique dendritic structure effectively reduces local current density and accommodates volume change during the repeated Li plating/stripping process. More importantly, lithiophilic Li${}_3$Mg${}_7$ alloys not only guide the uniform Li deposition down into the below Li metal upon Li deposition, but also thermodynamically promote the extraction of Li during the reverse Li stripping process, which suppresses the parasitic reactions occurring on the surface of Li metal and hence inhibits the formation of Li dendrites. Moreover, the facile diffusion of Mg from Li${}_3$Mg${}_7$ alloys toward Li metal below is thermodynamically permitted, which leads to a uniform distribution of LiMg alloys inside the whole electrode and thus benefits long-term deep cycling stability. As a result, the protected Li-metal anode delivers stable and dendrite-free cycling performance at 10 mA h cm${}^{-<!--\; ???\; -->2}$ for over 900 h. When coupling this anode with LiFePO${}_4$ and S cathodes, the thus-assembled full cells exhibit superior cycling stability. (© 2021 Wiley-VCH GmbH)

[en] Highlights: •The electrochemical regeneration of NaAlH₄ directly from Na and Al is observed. •The mechanisms for the regeneration processes of NaAlH₄ anode are clarified. •A new cycle degradation mechanism is revealed. •The cyclic performance of the NaAlH₄ anode has be realized. -- Abstract: NaAlH₄ is a promising anode material for lithium-ion batteries due to its high theoretical capacity of 1985 mAh g⁻¹. However, the practical application of NaAlH₄ anode is hindered by its low charge reversibility and poor cycle performance. To improve the Li-storage performance of NaAlH₄ anode, the regeneration and degradation mechanism of NaAlH₄ have been revealed in this work. Firstly, the results show that decreasing the crystalline size would result in the direct regeneration of NaAlH₄ from Na and Al without any intermediate phases (such as LiNa₂AlH₆), which dramatically enhances the reversibility of NaAlH₄ anode. Secondly, a new cycle degradation mechanism is demonstrated that NaAlH₄ would decompose above 1.42 V during the charge process, which leads to a rapid degradation of cycle capacity. Therefore, the reversible capacity of NaAlH₄ anode after 20 cycles could be significantly increased from 89 mAh g⁻¹ to 456 mAh g⁻¹ by decreasing the cut-off voltage from 3 V to 1 V, showing an improved cycle stability.

[en] A nanowire array of metal-organic complex copper-tetracyanoquinodimethane (CuTCNQ) was obtained by depositing a layer of copper in the bottom of anodic alumina template channels during a vapor-induced reaction method. SEM observation showed that the channel diameters of anodic alumina membranes prepared under 40 V and 200 V are about 60 nm and 200 nm, respectively, and CuTCNQ nanowire arrays were synthesized in these channels. Nanodevice prototypes with electrical switching characteristics based on a CuTCNQ nanowire array were fabricated, whose reproducible electrical switching and memory effects were observed. The on-off ratio for switching reaches 10⁴. The potential applications in information storage devices are also discussed

[en] 2LiBH${}_4$ - MgH${}_2$ (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 S${}^{2-<!--\; ???\; -->}$ bridges the reversible conversion between Li${}_2$S 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 MgB${}_2$, 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. (© 2024 Wiley‐VCH GmbH)

[en] The state of the art of energy storage and conversion is still unfulfilled application for lithium-ion devices, which require high energy density and superior safety. The development of innovative electrode materials with excellent electrochemical performances is supposed to be the only way to satisfy the diversified and extended application of lithium-ion batteries (LIBs). As anode electrode materials, the active materials of classical intercalation reaction (i.e. graphite) and alloying have been investigated for many years. However, the relative low theoretical capacities and capacity fading limit their application in the next-generation LIBs. Recently, the conversion materials, especially metal hydrides, have been demonstrated to be attractive anode materials for LIBs due to their small polarization, high theoretical capacity and suitable working potential. In this review, we provide a critical overview of various metal hydrides ranging from binary hydrides (MgH₂, TiH₂, AlH₃, etc.) to ternary hydrides (B-, Al- and Mg-based ternary hydrides) that are used as anode materials for LIBs, with the employment of organic liquid electrolyte or solid-state electrolyte. The reaction mechanisms, modification methods and electrochemical performances of these various metal hydrides were discussed in detail. We also discussed the remaining challenges and proposed some suggestions to the emerging research of metal hydrides. We hope that this review can stimulate more extensive and insightful studies for the fabrication and design of new metal hydrides with excellent physical and electrochemical performances.

[en] An ethanol gas sensor was fabricated based on Ti doped ZnO nanotetrapods which were prepared by chemical vapor deposition (CVD) of ZnO nanotetrapods followed by co-annealing with TiO₂ powder. X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM) were used to characterize the morphology and structure of the as-obtained sample and the ethanol-sensing characteristics of the device were investigated. ZnO:Ti sensors show higher gas response than ZnO counterparts towards 100 ppm ethanol gas at a temperature of 260 deg. C. The recovery times of the devices are 3.1 min for ZnO:Ti and 10.1 min for ZnO, respectively. The enhancement of sensing properties of ZnO:Ti tetrapods indicates the potential application for fabricating low power and highly sensitive gas sensors.

[en] Solid-state sodium-ion/metal batteries (SSSBs) are highly desirable for next-generation energy storage systems, while very limited Na-ion solid-state electrolytes are explored. The borohydride-based solid electrolytes are expected to achieve the high energy density target, due to their low redox potential, low Young's modulus as well as high stability toward alkali metals. However, the biggest challenge of borohydride-based electrolyte is the low ionic conductivity. In this study, an anti-perovskite solid-state electrolyte (SSE) material rich in vacancy defects is explored, Na${}_2$BH${}_4$NH${}_2$, to solve above problems. Benefitting from rich vacancy defects, a high ionic conductivity of 7.56 × 10${}^{-<!--\; ???\; -->4}$ S cm${}^{-<!--\; ???\; -->1}$ with a low activation energy for Na${}^{+}$ migration of 0.67 eV at 90 °C are achieved. The NaSn|Na${}_2$BH${}_4$NH${}_2$|NaSn symmetric cell cycles at a current density of 0.1 mA cm${}^{-<!--\; ???\; -->2}$ for 500 h. Moreover, the universality of Na${}_2$BH${}_4$NH${}_2$ electrolyte is verified by TiS${}_2$ cathode, indicating that Na${}_2$BH${}_4$NH${}_2$ has good compatibility with electrode material. These outstanding performances suggest that it is a viable strategy to increase the ionic conductivity by forming vacancy defects, leading to the further development of solid electrolytes with superior properties. (© 2023 Wiley-VCH GmbH)

[en] Transition metal chalcogenides represent a class of the most promising alternative electrode materials for high-performance lithium-ion batteries (LIBs) owing to their high theoretical capacities. However, they suffer from large volume expansion, particle agglomeration, and low conductivity during charge/discharge processes, leading to unsatisfactory energy storage performance. In order to address these issues, we rationally designed three-dimensional (3D) hybrid composites consisting of ZnSe nanodots uniformly confined within a N-doped porous carbon network (ZnSe ND@N-PC) obtained via a convenient pyrolysis process. When used as anodes for LIBs, the composites exhibited outstanding electrochemical performance, with a high reversible capacity (1,134 mA·h·g⁻¹ at a current density of 600 mA·g⁻¹ after 500 cycles) and excellent rate capability (696 and 474 mA·h·g⁻¹ at current densities of 6.4 and 12.8 A·g⁻¹, respectively). The significantly improved lithium storage performance can be attributed to the 3D architecture of the hybrid composites, which not only mitigated the internal mechanical stress induced by the volume change and formed a 3D conductive network during cycling, but also provided a large reactive area and reduced the lithium diffusion distance. The strategy reported here may open a new avenue for the design of other multifunctional composites towards high-performance energy storage devices. .

[en] An LaMg₂Ni alloy film was prepared by electron beam evaporation plus annealing. Upon hydrogen loading/unloading, the film shows the reversible conversion from a metallic, reflecting state to a semiconducting, color-neutral transparent one. The contrast ratio of the resistivity between two states is over four orders of magnitude. The lower reflection in the dehydrogenated film is attributed to the rough surface originated from the previous hydrogenation