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No design rules have yet been established for producing solid electrolytes with a lithium-ion conductivity high enough to replace liquid electrolytes and expand the performance and battery configuration limits of current lithium ion batteries. Taking advantage of the properties of high-entropy materials, we have designed a highly ion-conductive solid electrolyte by increasing the compositional complexity of a known lithium superionic conductor to eliminate ion migration barriers while maintaining the structural framework for superionic conduction. The synthesized phase with a compositional complexity showed an improved ion conductivity. We showed that the highly conductive solid electrolyte enables charge and discharge of a thick lithium-ion battery cathode at room temperature and thus has potential to change conventional battery configurations. [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]

Hydrated materials contain crystal water within their crystal frameworks and can exhibit extraordinary properties as a result. However, a detailed understanding of the mechanism involved in the hydration process is largely lacking, because the overall synthesis process is very difficult to monitor. Here, we elucidate how the insertion of crystal water mediates an anomalous spinel-to-Birnessite phase transition during electrochemical cycling in aqueous media. We find that, at the initial stage of the phase transition, crystal water is inserted into the interlayer space between MnO6 layers in the form of a hydronium ion (H3O+). The H3O+ insertion is chemically driven in the reverse (reducing) direction to the applied anodic (oxidizing) electric field, stabilizing the structure and recovering the charge balance following the deinsertion of Mn2+. A comparative investigation using various electrolyte solutions revealed that the H3O+ insertion competes with the insertion of other ionic charge carriers (Li+, Na+, and Mg2+), and the overall efficiency of the phase transition is determined by this competition. This understanding of crystal water insertion offers an insight into strategies to synthesize hydrated materials. [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]

A variety of proton (H+)-conducting oxides are known, including those used in electrochemical devices such as fuel cells. In contrast, pure H- conduction, not mixed with electron conduction, has not been demonstrated for oxide-based materials. Considering that hydride ions have an ionic size appropriate for fast transport and also a strong reducing ability suitable for high-energy storage and conversion devices, we prepared a series of K2NiF4-type oxyhydrides, La2-x-ySrx+yLiH1-x+yO3-y, in the hope of observing such H- conductors. The performance of an all-solid-state TiH2/o-La2LiHO3 (x = y = 0, o: orthorhombic)/Ti cell provided conclusive evidence of pure H- conduction. [ABSTRACT FROM AUTHOR]

The effect of Li3PO4 coating was investigated for LiNi0.5Mn1.5O4 epitaxial thin film electrodes synthesized on SrTiO3 substrates by pulsed laser deposition (PLD). Amorphous Li3PO4 with a thickness of 1-4 nm was coated at room temperature onto 30 nm thick epitaxial LiNi0.5Mn1.5O4 thin films with (111), (110) and (100) lattice orientations. Electrodes with the surface coating exhibit high charge-discharge capacities and small capacity degradation during cycling experiments in the high voltage region. X-ray absorption near edge structure (XANES) and hard X-ray photoelectron spectroscopy (HAXPES) analyses indicate a higher manganese valence for the electrode surface of the Li3PO4 stacked LiNi0.5Mn1.5O4 film than that for the surface of a pristine LiNi0.5Mn1.5O4 film. Thus, surface coating affects the manganese valence near the electrode surface and improves the cycling characteristics. [ABSTRACT FROM AUTHOR]

To investigate the microscopic magnetic nature of phospho-olivines, we have measured positive muon-spin rotation and relaxation (μ+SR) spectra for NaxFePO4 and FePO4, using powder samples in the temperature range between 2 and 200 K. For Na0.7FePO4, μ+SR measurements under zero external field (ZF) showed the appearance of static magnetic order below TN ~ 61 K, at which the susceptibility Χ(T) exhibits a sharp maximum due to an antiferromagnetic (AF) transition. The wide distribution found for the internal magnetic field (Hint) was reasonably explained by the formation of AF order with the spread in Hint due to a random distribution of Na vacancies. On the other hand, the ZF spectra for FePO4 suggested the formation of the canted AF order below TN = 113 K, as proposed by neutron diffraction (ND), but the ratio between the y and x components of the ordered moment (My/Mx) was determined as 0.6 by μ+SR, whereas 0.22 was measured by ND, probably indicating anisotropic spin fluctuations in FePO4. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of the lithium ionic conductor Li0.17La0.61TiO3 have been successfully synthesized on Al2O3(0001) and Nb:SrTiO3(001) substrates at working temperatures below 750°C using pulsed laser deposition. The application of high laser fluence in conjunction with low oxygen pressure was identified as the key to obtaining highly crystalline Li0.17La0.61TiO3 films. The use of low temperatures prevents the loss of lithium during the deposition process and generates films with no compositional deviation from the target, as confirmed by chemical analyses. The Li0.17La0.61TiO3 film deposited on Al2O3(0001) exhibits a high total ionic conductivity of 3.76 × 10-4 S cm-1 at room temperature, which is comparable to the bulk ionic conductivity of polycrystalline Li0.18La0.16TiO3. The low temperature synthetic process described herein should allow the use of new configurations to fabricate electrode-electrolyte interfaces for use in high power all solid-state batteries incorporating Li0.17La0.16TiO3 as the solid electrolyte. [ABSTRACT FROM AUTHOR]

Epitaxial Li4Ti5O12thin-films were successfully synthesized on SrTiO3single-crystal substrates with (111), (110), and (100) lattice plane orientations using pulsed laser deposition (PLD). Thin-film X-ray diffraction (XRD) revealed that the Li4Ti5O12films had the same orientation as the SrTiO3substrates: Li4Ti5O12(111) on SrTiO3(111), Li4Ti5O12(110) on SrTiO3(110), and Li4Ti5O12(100) on SrTiO3(100). These epitaxial films contained island structures, and the morphology of the (111), (110), and (100) films, observed by field emission scanning electron microscopy (FE-SEM), exhibited angular, needle-like, and circular shapes, respectively. The electrochemical properties of 20 nm thick Li4Ti5O12(111) and (110) films were investigated by cyclic voltammetry. Reversible intercalation proceeded through both lattice planes due to the three-dimensional diffusion pathway of lithium in the spinel framework. Reduction peaks in the first cathodic scan appeared at different positions from those in subsequent scans, suggesting a surface reconstruction at the Li4Ti5O12surface due to interfacial reactions. [ABSTRACT FROM AUTHOR]