Ionic conducting lanthanide oxides

Unlocking Li superionic conductivity in face-centred cubic oxides via face-sharing configurations

Oxides with a face-centred cubic (fcc) anion sublattice are generally not considered as solid-state electrolytes as the structural framework is thought to be unfavourable for lithium (Li) superionic conduction. Here we demonstrate Li superionic conductivity in fcc-type oxides in which face-sharing Li configurations have been created through cation over-stoichiometry in rocksalt-type lattices via excess Li. We find that the face-sharing Li configurations create a novel spinel with unconventional stoichiometry and raise the energy of Li, thereby promoting fast Li-ion conduction. The over-stoichiometric Li-In-Sn-O compound exhibits a total Li superionic conductivity of 3.38 × 10-4 S cm-1 at room temperature with a low migration barrier of 255 meV. Our work unlocks the potential of designing Li superionic conductors in a prototypical structural framework with vast chemical flexibility, providing fertile ground for discovering new solid-state electrolytes.

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.

Defect Strategy in Solid-State Lithium Batteries

Solid-state lithium batteries (SSLBs) have great development prospects in high-security new energy fields, but face major challenges such as poor charge transfer kinetics, high interface impedance, and unsatisfactory cycle stability. Defect engineering is an effective method to regulate the composition and structure of electrodes and electrolytes, which plays a crucial role in dominating physical and electrochemical performance. It is necessary to summarize the recent advances regarding defect engineering in SSLBs and analyze the mechanism, thus inspiring future work. This review systematically summarizes the role of defects in providing storage sites/active sites, promoting ion diffusion and charge transport of electrodes, and improving structural stability and ionic conductivity of solid-state electrolytes. The defects greatly affect the electronic structure, chemical bond strength and charge transport process of the electrodes and solid-state electrolytes to determine their electrochemical performance and stability. Then, this review presents common defect fabrication methods and the specific role mechanism of defects in electrodes and solid-state electrolytes. At last, challenges and perspectives of defect strategies in high-performance SSLBs are proposed to guide future research.

Review of the Developments and Difficulties in Inorganic Solid-State Electrolytes

All-solid-state lithium-ion batteries (ASSLIBs), with their exceptional attributes, have captured the attention of researchers. They offer a viable solution to the inherent flaws of traditional lithium-ion batteries. The crux of an ASSLB lies in its solid-state electrolyte (SSE) which shows higher stability and safety compared to liquid electrolyte. Additionally, it holds the promise of being compatible with Li metal anode, thereby realizing higher capacity. Inorganic SSEs have undergone tremendous developments in the last few decades; however, their practical applications still face difficulties such as the electrode-electrolyte interface, air stability, and so on. The structural composition of inorganic electrolytes is inherently linked to the advantages and difficulties they present. This article provides a comprehensive explanation of the development, structure, and Li-ion transport mechanism of representative inorganic SSEs. Moreover, corresponding difficulties such as interface issues and air stability as well as possible solutions are also discussed.

Interface Issues and Challenges in All-Solid-State Batteries: Lithium, Sodium, and Beyond

Owing to the promise of high safety and energy density, all-solid-state batteries are attracting incremental interest as one of the most promising next-generation energy storage systems. However, their widespread applications are inhibited by many technical challenges, including low-conductivity electrolytes, dendrite growth, and poor cycle/rate properties. Particularly, the interfacial dynamics between the solid electrolyte and the electrode is considered as a crucial factor in determining solid-state battery performance. In recent years, intensive research efforts have been devoted to understanding the interfacial behavior and strategies to overcome these challenges for all-solid-state batteries. Here, the interfacial principle and engineering in a variety of solid-state batteries, including solid-state lithium/sodium batteries and emerging batteries (lithium-sulfur, lithium-air, etc.), are discussed. Specific attention is paid to interface physics (contact and wettability) and interface chemistry (passivation layer, ionic transport, dendrite growth), as well as the strategies to address the above concerns. The purpose here is to outline the current interface issues and challenges, allowing for target-oriented research for solid-state electrochemical energy storage. Current trends and future perspectives in interfacial engineering are also presented.

Investigating the Factors Affecting the Ionic Conduction in Nanoconfined NaBH4

Nanoconfinement is an effective strategy to tune the properties of the metal hydrides. It has been extensively employed to modify the ionic conductivity of LiBH4 as an electrolyte for Li-ion batteries. However, the approach does not seem to be applicable to other borohydrides such as NaBH4, which is found to reach a limited improvement in ionic conductivity of 10−7 S cm−1 at 115 °C upon nanoconfinement in Mobil Composition of Matter No. 41 (MCM-41) instead of 10−8 S cm−1. In comparison, introducing large cage anions in the form of Na2B12H12 naturally formed upon the nanoconfinement of NaBH4 was found to be more effective in leading to higher ionic conductivities of 10−4 S cm−1 at 110 °C.

Rare earth elements based oxide ion conductors

Rare-earth-elements-based oxide ion conductors with various structures and their structure-property relationships were systematically presented and summarized, which can provide new insight and guidance for the development of new oxide ion conductors.

Behind the Candelabra: A Facile Flame Vapor Deposition Method for Interfacial Engineering of Garnet Electrolyte To Enable Ultralong Cycling Solid-State Li-FeF3 Conversion Batteries

The frustrating interfacial issue between Li metal anode and solid electrolyte is the main obstacle that restricts the commercial promotion of solid-state batteries. The garnet-type ceramic electrolyte with high stability against metallic Li has drawn much attention, but it also suffers from huge interfacial resistance and Li dendrite penetration due to the unavoidable formation of the carbonate passivation layer and limited interface contact. Herein, we propose a facile and effective method of flame vapor deposition to spray candle soot (CS) coating on the garnet surface. It enables the reduction of the carbonate layer and the conversion to a highly lithiophilic interlayer especially when in contact with molten Li. The lithiophilicity is rooted in the enrichment of graphitic polycrystalline domains in CS, which can be chemically or electrochemically lithiated to form the ionic/electronic dual-conductive network containing LiC₆ moieties. The CS interlayer binds the Li metal with the garnet electrolyte tightly with gradual transition of Li-ion conductivity, leading to a significant reduction of the area-specific resistance to 50 Ω cm² at 60 °C with high cycling and current endurance. Garnet-based symmetric cells and solid-state full cells conducting this strategy exhibit impressive electrochemical reversibility and durability under the preservation of the compact interface and smooth Li plating/stripping. The modified Li/garnet/FeF₃ batteries exhibit a discharge capacity as high as 500 mA h g^-1 and long-term cyclability for at least 1500 cycles (with capacity preserved at 281.7 and 201 mA h g^-1 at 100 and 200 μA cm^-2, respectively). This candle combustion strategy can be extended to more ceramic electrolytes compatible with high-temperature pretreatment.

Li2CO3-affiliative mechanism for air-accessible interface engineering of garnet electrolyte via facile liquid metal painting

Garnet based solid-state batteries have the advantages of wide electrochemical window and good chemical stability. However, at Li-garnet interface, the poor interfacial wettability due to Li₂CO₃ passivation usually causes large resistance and unstable contact. Here, a Li₂CO₃-affiliative mechanism is proposed for air-accessible interface engineering of garnet electrolyte via facile liquid metal (LM) painting. The natural LM oxide skin enables a superior wettability of LM interlayer towards ceramic electrolyte and Li anode. Therein the removal of Li₂CO₃ passivation network is not necessary, in view of its delamination and fragmentation by LM penetration. This dissipation effect allows the lithiated LM nanodomains to serve as alternative Li-ion flux carriers at Li-garnet interface. This mechanism leads to an interfacial resistance as small as 5 Ω cm² even after exposing garnet in air for several days. The ultrastable Li plating and stripping across LM painted garnet can last for 9930 h with a small overpotential.

At Li-garnet interface, the poor interfacial wettability due to Li₂CO₃ passivation causes large resistance and unstable contact. Here the authors propose a Li₂CO₃-affiliative mechanism for air-accessible interface engineering of garnet electrolyte with superior wettability via facile liquid metal painting.

Designing composite solid-state electrolytes for high performance lithium ion or lithium metal batteries

Solid-state electrolytes (SSEs) are capable of inhibiting the growth of lithium dendrites, demonstrating great potential in next-generation lithium-ion batteries (LIBs). However, poor room temperature ionic conductivity and the unstable interface between SSEs and the electrode block their large-scale applications in LIBs. Composite solid-state electrolytes (CSSEs) formed by mixing different ionic conductors lead to better performance than single SSEs, especially in terms of ionic conductivity and interfacial stability. Herein, we have systematically reviewed recent developments and investigations of CSSEs including inorganic composite and organic-inorganic composite materials, in order to provide a better understanding of designing CSSEs. The comparison of different types of CSSEs relative to their parental materials is deeply discussed in the context of ionic conductivity and interfacial design. Then, the proposed ion transfer pathways and models of lithium dendrite growth in composites are outlined to inspire future development of CSSEs.

Oxide-ion conduction in the Dion-Jacobson phase CsBi2Ti2NbO10-δ

Oxide-ion conductors have found applications in various electrochemical devices, such as solid-oxide fuel cells, gas sensors, and separation membranes. Dion–Jacobson phases are known for their rich magnetic and electrical properties; however, there have been no reports on oxide-ion conduction in this family of materials. Here, for the first time to the best of our knowledge, we show the observation of fast oxygen anionic conducting behavior in CsBi₂Ti₂NbO_10−δ. The bulk ionic conductivity of this Dion–Jacobson phase is 8.9 × 10⁻² S cm⁻¹ at 1073 K, a level that is higher than that of the conventional yttria-stabilized zirconia. The oxygen ion transport is attributable to the large anisotropic thermal motions of oxygen atoms, the presence of oxygen vacancies, and the formation of oxide-ion conducting layers in the crystal structure. The present finding of high oxide-ion conductivity in rare-earth-free CsBi₂Ti₂NbO_10−δ suggests the potential of Dion–Jacobson phases as a platform to identify superior oxide-ion conductors.

Oxide ion conductors are an exciting class of materials with applications in various domains. Here, the authors show that Dion–Jacobson Phases are a structure supporting high O²⁻ mobility. The bulk conductivity of CsBi₂Ti₂NbO_10−δ even exceeds that of YSZ, offering new possibilities in electrolyte discovery.

Probing the Geometric and Electronic Structures of the Monogadolinium Oxide GdO n-1/0 ( n = 1-4) Clusters

The existence of abundant 4f electrons significantly increases the complexity and difficulty in precisely determining the geometric and electronic structures of the lanthanide oxide clusters. Herein, by combining the photoelectron imaging spectroscopy and density functional theory (DFT) calculations, the electronic structure of GdO was investigated. An electron affinity (EA) of 1.16 ± 0.09 eV is obtained, and the measured anisotropy parameter (β) provides direct experimental evidence about the orbital symmetry of the detached electron in GdO^-. DFT calculations have been employed to acquire the optimized geometries of the GdO _n^-1/0 ( n = 2-4) clusters, and multiple activated oxygen species, which are radical, peroxide, superoxide, triradical, and ozonide radical, are found in these oxide clusters. Simulated photoelectron spectra (PES) of the GdO _n^-1/0 ( n = 2-4) clusters are examined, which may stimulate further experimental investigations on the gadolinium oxide clusters. In addition, the valence molecular orbitals (MOs) of these clusters are also discussed to reveal the interaction between the lanthanide metal (Gd) and O atoms.

Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction

This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors.

Cyanobacterial polysaccharide gels with efficient rare-earth-metal sorption

The cyanobacterial polysaccharide sacran, which contains carboxylate and sulfate groups, was extracted from Aphanothece sacrum , and the metal sorption behavior of sacran was investigated. Heterogels, where the sacran chains were trapped by polyvinyl alcohol networks, were prepared and immersed in NdCl3 solutions to shrink and cloud due to Nd binding. These heterogels had the ability to sorb excessive amounts of Nd ions, more than the stoichiometric ratio of 1:3 (sacran anion/Nd). Furthermore, the sacran-containing gels sorbed Nd ions under highly acidic conditions below pH 2 more efficiently than alginate-containing gels. We speculated that the strong Nd condensation effect of the sulfate groups in sacran under the acidic conditions may enhance the Nd sorption to the carboxylate groups.

Architectures of strontium hydroxyapatite microspheres: solvothermal synthesis and luminescence properties

Strontium hydroxyapatite (Sr(5)(PO(4))(3)OH, SrHAp) microspheres with 3D architectures have been successfully prepared through a efficient and facile solvothermal process. The experimental results indicate that the SrHAP microspheres are composed of a large amount of nanosheets, which are assembled in a radial form from the center to the surface of the microspheres. The as-obtained SrHAp samples show an intense and bright blue emission from 350 to 570 nm centered at 427 nm (CIE coordinates: x = 0.153, y = 0.081; lifetime: 9.2 ns; quantum efficiency: 31%) under long-wavelength UV light excitation (344 nm). This blue emission might result from the CO(2)(*-) radical impurities in the crystal lattice. Furthermore, the surfactants CTAB and trisodium citrate have an obvious impact on the morphologies and the luminescence properties of the products, respectively. The possible formation and luminescent mechanisms for Sr(5)(PO(4))(3)OH microspheres have been presented in detail.

Selective removal of lanthanides from natural waters, acidic streams and dialysate

The increased demand for the lanthanides in commercial products result in increased production of lanthanide containing ores, which increases public exposure to the lanthanides, both from various commercial products and from production wastes/effluents. This work investigates lanthanide (La, Ce, Pr, Nd, Eu, Gd and Lu) binding properties of self-assembled monolayers on mesoporous silica supports (SAMMS), that were functionalized with diphosphonic acid (DiPhos), acetamide phosphonic acid (AcPhos), propionamide phosphonic acid (Prop-Phos), and 1-hydroxy-2-pyridinone (1,2-HOPO), from natural waters (river, ground and sea waters), acid solutions (to mimic certain industrial process streams), and dialysate. The affinity, capacity, and kinetics of the lanthanide sorption, as well as regenerability of SAMMS materials were investigated. Going from the acid side over to the alkaline side, the AcPhos- and DiPhos-SAMMS maintain their outstanding affinity for lanthanides, which enable the use of the materials in the systems where the pH may fluctuate. In acid solutions, Prop-Phos- and 1,2-HOPO-SAMMS have differing affinity along the lanthanide series, suggesting their use in chromatographic lanthanide separation. Over 95% of 100 microg/L of Gd in dialysate was removed by the Prop-Phos-SAMMS after 1 min and 99% over 10 min. SAMMS can be regenerated with an acid wash (0.5M HCl) without losing the binding properties. Thus, they have a great potential to be used as in large-scale treatment of lanthanides, lanthanide separation prior to analytical instruments, and in sorbent dialyzers for treatment of acute lanthanide poisoning.

Synthesis and Growth Mechanisms of One-Dimensional Strontium Hydroxyapatite Nanostructures

Strontium hydroxyapatite (SrHAp) nanowires with an aspect ratio of several hundreds were synthesized by controlling the growth conditions during a hydrothermal process. In the strontium phosphate system, it was found that the phase evolution changed with pH and that the aspect ratio of SrHAp was affected by the phases present before heating. Since the conditions for SrHAp nucleation prohibits one-dimensional growth, it was impossible to grow large-scale SrHAp nanowires using routine hydrothermal methods. Through thermodynamic considerations, the mechanisms of nanowire formation appear to involve the rapid release of the stored chemical potential in a metastable phase, which promotes the anisotropic growth of the most stable SrHAp nanostructures. Thereby, the conditions for both the nucleation of the SrHAp phase and the anisotropic growth were determined simultaneously, and considerable quantities of SrHAp nanowires were synthesized.