Developing reversible lithium metal anodes with high rate capability is one of the central aims of current battery research. Lithium metal anodes are not only required for the development of innova...

Physicochemical Concepts of the Lithium Metal Anode in Solid-State Batteries.

Halide solid-state electrolytes (SSEs) with high room-temperature ionic conductivity (>10−3 S cm−1), wide electrochemical windows, and good compatibility toward oxide cathode materials have achieved impressive progress and attracted significant attention for application in all-solid-state lithium batteries (ASSLBs). This review presents an overview of halide SSEs, including their development, structure, ionic conductivity, chemical stability, and current limitations. Firstly, we give a brief overview of the historical development of halide-based SSEs, followed by an introduction to the different types of halide SSEs. From a practical point of view, the synthesis methods, especially scalable liquid-phase synthesis, are intensively discussed. Then, the associated stability issues involving basic structure stability, air/humidity stability, and electrochemical stability (electrolyte/SSE interface and electrochemical stability window) are also discussed in detail. Comprehensive coverage and thorough understanding of the properties of halide SSEs are provided and it is expected to help guide the development of future SSEs towards ASSLBs for energy storage applications.

Progress and perspectives on halide lithium conductors for all-solid-state lithium batteries

The enabling of high energy density of all-solid-state lithium batteries (ASSLBs) requires the development of highly Li+-conductive solid-state electrolytes (SSEs) with good chemical and electrochemical stability. Recently, halide SSEs based on different material design principles have opened new opportunities for ASSLBs. Here, we discovered a series of LixScCl3+x SSEs (x = 2.5, 3, 3.5, and 4) based on the cubic close-packed anion sublattice with room-temperature ionic conductivities up to 3 × 10-3 S cm-1. Owing to the low eutectic temperature between LiCl and ScCl3, LixScCl3+x SSEs can be synthesized by a simple co-melting strategy. Preferred orientation is observed for all the samples. The influence of the value of x in LixScCl3+x on the structure and Li+ diffusivity were systematically explored. With increasing x value, higher Li+, lower vacancy concentration, and less blocking effects from Sc ions are achieved, enabling the ability to tune the Li+ migration. The electrochemical performance shows that Li3ScCl6 possesses a wide electrochemical window of 0.9-4.3 V vs Li+/Li, stable electrochemical plating/stripping of Li for over 2500 h, as well as good compatibility with LiCoO2. LiCoO2/Li3ScCl6/In ASSLB exhibits a reversible capacity of 104.5 mAh g-1 with good cycle life retention for 160 cycles. The observed changes in the ionic conductivity and tuning of the site occupations provide an additional approach toward the design of better SSEs.

Site-Occupation-Tuned Superionic LixScCl3+xHalide Solid Electrolytes for All-Solid-State Batteries.

Energy storage materials are finding increasing applications in our daily lives, for devices such as mobile phones and electric vehicles. Current commercial batteries use flammable liquid electrolytes, which are unsafe, toxic, and environmentally unfriendly with low chemical stability. Recently, solid electrolytes have been extensively studied as alternative electrolytes to address these shortcomings. Herein, we report the early history, synthesis and characterization, mechanical properties, and Li+ ion transport mechanisms of inorganic sulfide and oxide electrolytes. Furthermore, we highlight the importance of the fabrication technology and experimental conditions, such as the effects of pressure and operating parameters, on the electrochemical performance of all-solid-state Li batteries. In particular, we emphasize promising electrolyte systems based on sulfides and argyrodites, such as LiPS5Cl and β-Li3PS4, oxide electrolytes, bare and doped Li7La3Zr2O12 garnet, NASICON-type structures, and perovskite electrolyte materials. Moreover, we discuss the present and future challenges that all-solid-state batteries face for large-scale industrial applications.

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

https://onlinelibrary.wiley.com/doi/epdf/10.1002/aenm.201903719

Mechanochemical Synthesis: A Tool to Tune Cation Site Disorder and Ionic Transport Properties of Li3MCl6 (M = Y, Er) Superionic Conductors

Lithium argyrodite superionic conductors are currently being investigated as solid electrolytes for all-solid-state batteries. Recently, in the lithium argyrodite Li6PS5X (X = Cl, Br, and I), a sit...

Rapid Crystallization and Kinetic Freezing of Site-Disorder in the Lithium Superionic Argyrodite Li6PS5Br

Mechanochemical Synthesis: A Tool to Tune Cation Site Disorder and Ionic Transport Properties of Li3MCl6(M = Y, Er) Superionic Conductors

Over the last decade, some studies with laboratory pair distribution function (PDF) data emerged. Yet, limited Qmax or instrumental resolution impeded in-depth structural refinements. With more advanced detector technologies, the question arose how to design novel PDF equipment for laboratories that will allow decent PDF refinements over r = 1–70 A. It is crucial to reflect the essential requirements, namely, monochromatic X-rays, suppression of air scattering, instrumental resolution, and overall measurement times. The result is a novel PDF setup based on a STOE STADI P powder diffractometer in transmission-/Debye-Scherrer geometry with monochromatic Ag Kα1 radiation, featuring a MYTHEN2 4K detector covering a Q range of 0.3–20.5 A−1. PDF data are collected in a moving PDF mode within 6 h. Structural signatures of liquids can be satisfactorily resolved in the PDF as shown for the ionic liquid hmimPF6. The high instrumental resolution is mirrored in low qdamp values determined from LaB6 measurements. PDF data from a powder sample of ca. 7 nm TiO2 nanoparticles were successfully refined over up to 70 A with goodness-of-fit values Rw < 0.22 (respectively Rw = 0.18 over 30 A), thanks to the low background and high instrumental resolution, hereby enlarging the accessible r range by several tens of Angstroms compared to previous laboratory PDF studies.

Pushing data quality for laboratory pair distribution function experiments.

Thermal decomposition of metal–organic framework (MOF) precursors is a recent method to create well-dispersed metal centers within active catalyst materials with enhanced stability, as required for dynamic operation conditions in light of challenges caused by the renewable energy supply. Here, we use a hard X-ray-based toolbox of pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) analysis combined with X-ray diffraction and catalytic activity tests to investigate structure–activity correlations of methanation catalysts obtained by thermal decomposition of a Ni(BDC)(PNO) MOF precursor. Increasing the decomposition temperature from 350 to 500 °C resulted in Nifcc nanoparticles with increasing particle sizes, alongside a decrease in Ni2+ species and strain-induced peak broadening. For lower temperatures and inert atmosphere, Ni3C and NiO phases co-existed. A graphitic shell stabilized the Ni particles. Compared to an inert atmosphere, reducing conditions led to larger particles and a faster decomposition of the MOF precursor. Catalytic studies revealed that the decomposition at an intermediate temperature of 375 °C in 5% H2/He is the best set of parameters to obtain high specific surface areas while maintaining particle sizes that feature many active Ni centers for the formation of CH4.

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Nils Prinz

Papers

Mechanochemical Synthesis: A Tool to Tune Cation Site Disorder and Ionic Transport Properties of Li3MCl6 (M = Y, Er) Superionic Conductors

Rapid Crystallization and Kinetic Freezing of Site-Disorder in the Lithium Superionic Argyrodite Li6PS5Br

Mechanochemical Synthesis: A Tool to Tune Cation Site Disorder and Ionic Transport Properties of Li3MCl6(M = Y, Er) Superionic Conductors

Pushing data quality for laboratory pair distribution function experiments.

Hard X-ray-based techniques for structural investigations of CO2 methanation catalysts prepared by MOF decomposition