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Low ionic conductivity limits the development of NASICON-type LiZr2(PO4)3 (LZP) for solid-state batteries. Here, we present the possible factors that may affect the conductivity and further establish the relationships among conductivity, crystal structure, relative density, grain size, chemical composition, and elemental distribution. The conditions for the existence of the four phases of LZP (α, α', β, and β') and the phase transition processes among them are systematically clarified. With secondary ion mass spectrometry, the spatial distribution of elements within the grains and grain boundaries is clearly presented. On the basis of our results, proper elemental doping, high sintering temperature, and especially fast cool down rate are all indispensable to stabilize the high-conductivity (α) phase at room temperature. Finally, we demonstrate the feasibility of lithium-based batteries with this LZP solid electrolyte and commercial cathodes. This work provides insights for preparing LZP with high conductivity and paves the way for the development of solid-state batteries. [ABSTRACT FROM AUTHOR]

Glassy, glass-ceramic, and crystalline lithium thiophosphates have attracted interest in their use as solid electrolytes in all-solid-state batteries. Despite similar structural motifs, including PS43-, P2S64-, and P2S74- polyhedra, these materials exhibit a wide range of possible compositions, crystal structures, and ionic conductivities. Here, we present a combined approach of Bragg diffraction, pair distribution function analysis, Raman spectroscopy, and 31P magic angle spinning nuclear magnetic resonance spectroscopy to study the underlying crystal structure of Li4P2S6. In this work, we show that the material crystallizes in a planar structural arrangement as a glass ceramic composite, explaining the observed relatively low ionic conductivity, depending on the fraction of glass content. Calculations based on density functional theory provide an understanding of occurring diffusion pathways and ionic conductivity of this Li+ ionic conductor. [ABSTRACT FROM AUTHOR]

Inorganic lithium solid electrolytes are critical components in next-generation solid-state batteries, yet the fundamental nature of the cation-anion interactions and their relevance for ionic conductivity in these materials remain enigmatic. Here, we employ first-principles molecular dynamics simulations to explore the interplay among chemistry, structure, and functionality of a highly conductive Li+ solid electrolyte, Li3InBr6. Using local-orbital projections to dynamically track the evolution of the electronic charge density, the simulations reveal rapid, correlated fluctuations between cation-anion interactions with different degrees of directional covalent character. These chemical bond dynamics are shown to correlate with Li+ mobility and are enabled thermally by intrinsic frustration between the preferred geometries of chemical bonding and lattice symmetry. We suggest that the fluctuating chemical environment from the polarizable anions functions like a solvent, contributing to the superionic behavior of Li3InBr6 by temporarily stabilizing configurations favorable for migrating Li+. The generality of these conclusions for understanding solid electrolytes and key factors governing the superionic phase transition is discussed. [ABSTRACT FROM AUTHOR]

Solid-state ion conductors based on organic ionic plastic crystals (OIPCs) are a promising alternative to conventional liquid electrolytes in lithium battery applications. The OIPC-based electrolytes are safe (nonflammable) and flexible in terms of design and operating conditions. Magnetic resonance imaging (MRI) is a powerful noninvasive method enabling visualization of various chemical phenomena. Here, we report a first quantitative in situ MRI study of operating solid-state lithium cells. Lithium ion transfer into the OIPC matrix during the ongoing discharge of the anode results in partial liquefaction of the electrolyte at the metal interface. The developed liquid component enhances the ion transport across the interface and overall battery performance. Displacement of the liquefaction front is accompanied by a faster Li transfer through the grain boundaries and depletion at the cathode. The demonstrated solid-liquid hybrid properties, inherent in many OIPCs, combine benefits of highly conductive ionic liquids with safety and flexibility of solids. [ABSTRACT FROM AUTHOR]

Herein we present a new class of ionogel electrolyte for lithium-ion batteries, which can be prepared in either "liquid-in-solid" or "solid-in-liquid" form. The electrolytes are prepared by a nonaqueous self-assembly sol-gel process, in which ionic liquid electrolyte is immobilized within an inorganic gel. These electrolytes were found to exhibit high ionic conductivity, low electronic conductivity, and good thermal and mechanical stability. The inorganic gels weaken the interaction of anions and cations and thereby improve lithium salt dissociation and enhance transport of Li+. Also, the electrolytes are stable: no spontaneous phase separation occurs after 1 year of storage. In addition, their synthesis and shaping are very easy and cheap and form a new class of solid electrolytes, which offer exciting opportunities for preparation of in situ solid-state lithium-ion batteries. Cells with LiFePO4 cathodes and ionogel electrolyte attained a capacity of 150 mAh/g for more than 300 cycles, and even at the 2C rate, the capacity still stayed over 98 mAh/g. There are no prior reports of solid-state batteries employing ionogel electrolyte that exhibit high capacity. [ABSTRACT FROM AUTHOR]