Recent advances on rare earths in solid lithium ion conductors

Halogen chemistry of solid electrolytes in all-solid-state batteries

All-solid-state batteries (ASSBs) using solid-state electrolytes, replacing flammable liquid electrolytes, are considered one of the most promising next-generation electrochemical energy storage devices because of their improved, inherent safety and energy density. A family of solid electrolytes incorporating halogens has attracted attention because of their potentially high ionic conductivity, good deformability and wide electrochemical windows. Although progress has been made for halogen-containing solid electrolytes (HSEs) in ASSBs, challenges in the preparations, characterizations and low-cost industrial scalability remain. In this Review, we focus on the development of halide battery chemistry, the preparation, modification and properties of HSEs, and issues with HSEs in ASSBs. The chemical action of halogen and ion transport mechanisms are discussed. Moreover, the main challenges and future development directions of halide-based ASSBs are discussed to pave the way for practical applications of HSEs for next-generation rechargeable batteries.

Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution

Oxygen evolution reaction (OER) is one of the important half-reactions in energy conversion equipment such as water-spitting devices, rechargeable metal-air batteries, and so on. It is beneficial to develop efficient and low-cost catalysts that understand the reaction mechanism of OER and analyze the reconstruction phenomenon of transition metal sulfide. Interestingly, copper sulfide and cuprous sulfide with the same components possess different reconstruction behaviors due to their different metal ion valence states and different atomic arrangement modes. Because of a unique atomic arrangement sequence and certain cationic defects, the reconstruction phenomenon of CuS nanomaterials are that S2- is firstly oxidized to SO4 2- and then Cux + is converted into CuO via Cu(OH)2 . In addition, the specific "modified hourglass structure" of CuS with excellent conductivity is easier to produce intermediates. Compared with Cu2 S, CuS exhibits excellent OER activity with a lower overpotential of 192 mV at 10 mA cm-2 and remarkable electrochemical stability in 1.0 m KOH for 120 h. Herein, this study elucidates the reconstruction modes of CuS and Cu2 S in the OER process and reveals that CuS has a stronger CuS bond and a faster electronic transmission efficiency due to "modified hourglass structure," resulting in faster reconstruction of CuS than Cu2 S.

Investigation of Structure, Ionic Conductivity, and Electrochemical Stability of Halogen Substitution in Solid-State Ion Conductor Li3YBr x Cl6-x

Li₃YX₆ (X = Cl, Br) materials are Li-ion conductors that can be used as solid electrolytes in all solid-state batteries. Solid electrolytes ideally have high ionic conductivity and (electro)chemical compatibility with the electrodes. It was proven that introducing Br to Li₃YCl₆ increases ionic conductivity but, according to thermodynamic calculations, should also reduce oxidative stability. In this paper, the trade-off between ionic conductivity and electrochemical stability in Li₃YBr _x Cl_6-x halogen-substituted compounds is investigated. The compositions of Li₃YBr_1.5Cl_4.5 and Li₃YBr_4.5Cl_1.5 are reported for the first time, along with a consistent analysis of the whole Li₃YBr _x Cl_6-x (x = 0-6) tie-line. The results show that, while Br-rich materials are more conductive (5.36 × 10^-3 S/cm at 30 °C for x = 4.5), the oxidative stability is lower (∼3 V compared to ∼3.5 V). Small Br content (x = 1.5) does not affect oxidative stability but substantially increases ionic conductivity compared to pristine Li₃YCl₆ (2.1 compared to 0.049 × 10^-3 S/cm at 30 °C). This work highlights that optimization of substitutions in the anion framework provide prolific and rational avenues for tailoring the properties of solid electrolytes.

Complex Metal Borohydrides: From Laboratory Oddities to Prime Candidates in Energy Storage Applications

Despite being the lightest element in the periodic table, hydrogen poses many risks regarding its production, storage, and transport, but it is also the one element promising pollution-free energy for the planet, energy reliability, and sustainability. Development of such novel materials conveying a hydrogen source face stringent scrutiny from both a scientific and a safety point of view: they are required to have a high hydrogen wt.% storage capacity, must store hydrogen in a safe manner (i.e., by chemically binding it), and should exhibit controlled, and preferably rapid, absorption–desorption kinetics. Even the most advanced composites today face the difficult task of overcoming the harsh re-hydrogenation conditions (elevated temperature, high hydrogen pressure). Traditionally, the most utilized materials have been RMH (reactive metal hydrides) and complex metal borohydrides M(BH₄)_x (M: main group or transition metal; x: valence of M), often along with metal amides or various additives serving as catalysts (Pd²⁺, Ti⁴⁺ etc.). Through destabilization (kinetic or thermodynamic), M(BH₄)_x can effectively lower their dehydrogenation enthalpy, providing for a faster reaction occurring at a lower temperature onset. The present review summarizes the recent scientific results on various metal borohydrides, aiming to present the current state-of-the-art on such hydrogen storage materials, while trying to analyze the pros and cons of each material regarding its thermodynamic and kinetic behavior in hydrogenation studies.

Gram-Scale Synthesis of Nanosized Li3 HoBr6 Solid Electrolyte for All-Solid-State Li-Se Battery

Rare earth (RE) based halide solid electrolytes (HEs) are recently considered as research hotspots in the field of all-solid-state batteries (ASSBs). The RE-based HEs possess high ionic conductivity, credible deformability, and good stability, which can bring excellent electrochemical performances for ASSBs. However, the conventional synthetic methods of RE HEs are a mechanochemical process and co-melting strategy, both approaches require expensive raw materials and sophisticated equipment. Therefore, a lot of research work is required to promote the preparation methods for these promising SSEs in ASSBs. Thus, a vacuum evaporation-assisted synthesis method is developed for the massive synthesis of HEs. The as-prepared Li₃ HoBr₆ (LHB) has a high lithium-ion conductivity close to the mS cm^-1 level and the LHB-based Li-Se ASSBs can be assembled by cold pressing. Theoretical calculations have revealed that the Li migrations are highly preferred in Li₃ HoBr₆ owing to the low energy cost and high tolerance of stable structure. The tetrahedral and octahedral pathways are responsible for Li migrations in short and long ranges, respectively. The results show that the LHB-based Li-Se battery has good stability and rate performance, indicating that LHB has potential application in the field of ASSBs.

Rare-Earth-Based Metal-Organic Frameworks as Multifunctional Platforms for Catalytic Conversion

The development of catalytic conversion is very important for human society. In the catalytic process, metal-organic frameworks (MOFs) can be utilized to obtain effective catalysts for their porous structures and adjustable properties. In addition, the introduction of rare-earth (RE) elements with unique properties for catalysts can realize good catalytic performances. Thus, the RE-MOF related catalysts for catalytic conversion are summarized. Due to the cooperation of RE elements and porous MOF structures, the RE-based MOFs can be used as promising catalysts or precursors/supports for other catalysts in the areas of energy conversion, environmental governance, and organic synthesis. These aggregated studies highlight the RE-MOFs as promising candidates for catalytic conversion.

Metal Borohydrides beyond Groups I and II: A Review

This review consists of a compilation of synthesis methods and several properties of borohydrides beyond Groups I and II, i.e., transition metals, main group, lanthanides, and actinides. The reported properties include crystal structure, decomposition temperature, ionic conductivity, photoluminescence, etc., when available. The compiled properties reflect the rich chemistry and possible borohydrides’ application in areas such as hydrogen storage, electronic devices that require an ionic conductor, catalysis, or photoluminescence. At the end of the review, two short but essential sections are included: a compilation of the decomposition temperature of all reported borohydrides versus the Pauling electronegativity of the cations, and a brief discussion of the possible reactions occurring during diborane emission, including some strategies to reduce this inconvenience, particularly for hydrogen storage purposes.