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In this work, we reveal the impact of moisture-induced chemical degradation and proton–lithium exchange on the Li-ion dynamics in the bulk and the grain boundaries and at the interface with lithium metal in highly Li-conducting garnet electrolytes. A direct correlation between chemical changes as measured by depth-resolved secondary ion mass spectrometry and the change in transport properties of the electrolyte is provided. In order to probe the intrinsic effect of the exchange on the lithium kinetics within the garnet structure, isolated from secondary corrosion product contributions, controlled-atmosphere processing was first used to produce proton-free Li6.55Ga0.15La3Zr2O12 (Ga0.15-LLZO), followed by degradation steps in a H2O bath at 100 °C, leading to the removal of LiOH secondary phases at the surface. The proton-exchanged region was analyzed by focused ion beam secondary ion mass spectrometry (FIB-SIMS) and found to extend as far as 1.35 μm into the Ga0.15-LLZO garnet pellet after 30 min in H2O. Impedance analysis in symmetrical cells with Li metal electrodes indicated a greater reactivity in grain boundaries than in grains and a significantly detrimental effect on the Li transfer kinetics in the Li metal/garnet interface correlated to a 3-fold decrease in the Li mobility in the protonated garnet. This result indicates that the deterioration of Li charge transfer and diffusion kinetics in proton-containing garnet electrolytes have fundamental implications for the optimization and integration of these systems in commercial battery devices. [ABSTRACT FROM AUTHOR]

Crystalline Li7P3S11 is a promising solid electrolyte for all solid-state lithium/lithium ion batteries. A controllable liquid phase synthesis of Li7P3S11 is more desirable than conventional mechanochemical synthesis, but recent attempts suffer from reduced ionic conductivities. Here we elucidate the mechanism of formation of crystalline Li7P3S11 synthesized in the liquid phase [acetonitrile (ACN)]. We conclude that crystalline Li7P3S11 forms through a two-step reaction: (1) formation of solid Li3PS4·ACN and amorphous "Li2S·P2S5" phases in the liquid phase and (2) solid-state conversion of the two phases. The implication of this two-step reaction mechanism for morphology control and the transport properties of liquid phase synthesized Li7P3S11 is identified and discussed. [ABSTRACT FROM AUTHOR]

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]

Solid solutions of Sn-Si derivatives with an LGPS (Li10GeP2S12)-type structure are synthesized by a solid-state reaction in the Li3PS4-Li4SnS4-Li4SiS4 quasi-ternary system. The monophasic region of the LGPS-type structure deviates from the tie line between Li10SiP2S12 and Li10SnP2S12, and the composition of the solid solution is determined to be -0.1 ≤ δ ≤ 0.5 and 0 ≤ y ≤ 1.0 in Li10+δ[SnySi1-y]1+δP2-δS12 (0.50 ≤ x ≤ 0.7 and 0 ≤ y ≤ 1.0 in Li4-x[SnySi1-y]1-xPxS4). The solid solution is formed by a double substitution that changes the Sn/Si ratio and the M4+ (Sn4+ and Si4+)/P5+ ratio, which adjusts the sizes of the lithium conduction tunnels and the lithium concentration, and contributes to the optimal conductivity value. The highest ionic conductivity value of 1.1 × 10-2 S cm-1 is achieved for the composition of Li10.35[Sn0.27Si1.08]P1.65S12 (Li3.45[Sn0.09Si0.36]P0.55S4) at 298 K, which is close to the value for the original LGPS compound (1.2 × 10-2 S cm-1). The Ge-free solid electrolyte could be suitable for practical applications in all-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]

β-NaMnO2 is a high-capacity Na-ion battery cathode, delivering ca. 190 mAh/g of reversible capacity when cycled at a rate of C/20. Yet, only 70% of the initial reversible capacity is retained after 100 cycles. We carry out a combined solid-state 23Na NMR and first-principles DFT study of the evolution of the structure of β-NaMnO2 upon electrochemical cycling. The as-synthesized structure contains planar defects identified as twin planes between nanodomains of the α and β forms of NaMnO2. GGA+U calculations reveal that the formation energies of the two polymorphs are within 5 meV per formula unit, and a phase mixture is likely in any NaMnO2 sample at room temperature. 23Na NMR indicates that 65.5% of Na is in β-NaMnO2 domains, 2.5% is in α-NaMnO2 domains, and 32% is close to a twin boundary in the as-synthesized material. A two-phase reaction at the beginning of charge and at the end of discharge is observed by NMR, consistent with the constant voltage plateau at 2.6-2.7 V in the electrochemical profile. GGA+U computations of Na deintercalation potentials reveal that Na extraction occurs first in α-like domains, then in β-like domains, and finally close to twin boundaries. 23Na NMR indicates that the proportion of Na in α-NaMnO2-type sites increases to 11% after five cycles, suggesting that structural rearrangements occur, leading to twin boundaries separating larger α-NaMnO2 domains from the major β-NaMnO2 phase. [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]

Rechargeable solid-state lithium ion batteries (SSLB) require fast ion conducting solid electrolytes (SEs) to enable high charge and discharge rates. Li7P3S11 is a particularly promising lithium solid electrolyte, exhibiting very high room temperature conductivities of up to 17 mS·cm-1 and high ductility, allowing fast ion transport through the bulk and intimate contact to high surface electrodes. Here we present a novel hot-press setup that facilitates the synthesis of solid electrolytes by combining in situ electrochemical impedance spectroscopy (EIS) with simultaneous temperature- and pressure-monitoring. While a high room temperature conductivity in the order of 10 mS·cm-1 is readily achieved for phase pure Li7P3S11 with this design, it further enables monitoring of the different steps of crystallization from an amorphous Li2S-P2S5 glass to triclinic Li7P3S11. Nucleation, crystallization and at temperatures exceeding 280 °C decomposition of the material are analyzed in real time, enabling process optimization. The results are supported ex situ by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Raman spectroscopy. Proof-of-principle experiments show the promising cycling- and rate capability of Li0.3In0.7/Li7P3S11/S-composite all-solid-state batteries. It is furthermore presented that discharging below a limit of 1.2 V results in decomposition of the SE/cathode interface. [ABSTRACT FROM AUTHOR]

Magnesium substituted P2-structure Na0.67Ni0.3Mn0.7O2 materials have been prepared by a facile solid-state method and investigated as cathodes in sodium-ion batteries. The Mg-doped materials described here were characterized by X-ray diffraction (XRD), 23Na solid-state nuclear magnetic resonance (SS-NMR), and scanning electron microscopy (SEM). The electrochemical performance of the samples was tested in half cells vs Na metal at room temperature. The Mg-doped materials operate at a high average voltage of ca. 3.3 V vs Na/Na+ delivering specific capacities of -120 mAh g-1, which remain stable up to 50 cycles. Mg doping suppresses the well-known P2-O2 phase transition observed in the undoped composition by stabilizing the reversible OP4 phase during charging (during Na removal). GITT measurements showed that the Na-ion mobility is improved by 2 orders of magnitude with respect to the parent P2-Na0.67Ni0.3Mn0.7O2 material. The fast Na-ion mobility may be the cause of the enhanced rate performance. [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]

All solid-state batteries are of key importance in the development of next-generation energy storage devices with high energy density. Herein, we report the fabrication and operation of bulk-type 5 V-class all solid-state batteries consisting of LiNi0.5Mn1.5O4 cathode, Li10GeP2S12 solid-electrolyte, and Li metal anode. The 1st discharge capacity is about 80 mAh g-1 with an average voltage of 4.3 V. The discharge capacity gradually decreases during the subsequent cycles. X-ray diffraction and electrochemical impedance spectroscopy measurements reveal that the capacity fading results from the growth of a resistive interfacial layer on the cathode composite. The development of suitable conductive additive and sulfide solid electrolyte materials is essential for the development of high-voltage all solid-state batteries. [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]

In this study, we assembled a bulk-type all-solid-state battery comprised of a TiS2 positive electrode, LiBH4 electrolyte, and Li negative electrode. Our battery retained high capacity over 300 dischargeâ€"charge cycles when operated at 393 K and 0.2 C. The second discharge capacity was as high as 205 mAh gâ€"1, corresponding to a TiS2 utilization ratio of 85%. The 300th discharge capacity remained as high as 180 mAh gâ€"1 with nearly 100% Coulombic efficiency from the second cycle. Negligible impact of the exposure of LiBH4 to atmospheric-pressure oxygen on battery cycle life was also confirmed. To investigate the origin of the cycle durability for this bulk-type all-solid-state TiS2/Li battery, electrochemical measurements, thermogravimetry coupled with gas composition analysis, powder X-ray diffraction measurements, and first-principles molecular dynamics simulations were carried out. Chemical and/or electrochemical oxidation of LiBH4 occurred at the TiS2 surface at the battery operating temperature of 393 K and/or during the initial charge. During this oxidation reaction of LiBH4 with hydrogen (H2) release just beneath the TiS2 surface, a third phase, likely including Li2B12H12, precipitated at the interface between LiBH4 and TiS2. Li2B12H12 has a lithium ionic conductivity of log(σ/S cmâ€"1) = â'4.4, charge transfer reactivity with Li electrodes, and superior oxidative stability to LiBH4, and thereby can act as a stable interface that enables numerous dischargeâ€"charge cycles. Our results strongly suggest that the creation of such a stable interfacial layer is due to the propensity of forming highly stable, hydrogen-deficient polyhydro-closo-polyborates such as Li2B12H12, which are thermodynamically available in the ternary Liâ€"Bâ€"H system. [ABSTRACT FROM AUTHOR]