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Halide solid electrolytes (SEs) have been highlighted for their high-voltage stability. Among the halide SEs, the ionic conductivity has been improved by aliovalent metal substitutions or choosing a ccp-like anion-arranged monoclinic structure ( C 2/ m ) over hcp- or bcc-like anion-arranged structures. Here, we present a new approach, hard-base substitution, and its underlying mechanism to increase the ionic conductivity of halide SEs. The oxygen substitution to Li 2 ZrCl 6 (trigonal, hcp) increased the ionic conductivity from 0.33 to 1.3 mS cm -1 at Li 3.1 ZrCl 4.9 O 1.1 (monoclinic, ccp), while the sulfur and fluorine substitutions were not effective. A systematic comparison study revealed that the energetic stabilization of interstitial sites for Li migration plays a key role in improving the ionic conductivity, and the ccp-like anion sublattice is not sufficient to achieve high ionic conductivity. We further examined the feasibility of the oxyhalide SE for practical and all-solid-state battery applications.

This study validates the beneficial role of residual Li compounds on the surface of Ni-rich cathode materials (LiNi x Co y Mn z O 2 , NCM). Residual Li compounds on Ni-rich NCM are naturally formed during the synthesis procedure, which degrades the initial Coulombic efficiency and generates slurry gelation during electrode fabrication in Li-ion batteries (LIBs) using liquid electrolytes. To solve this problem, washing pretreatment is usually introduced to remove residual Li compounds on the NCM surface. In contrast to LIBs, we found that residual Li compounds can serve as a functional layer that suppresses the interfacial side reactions of the NCM in all-solid-state batteries (ASSBs). The formation of resistive phosphate-based compounds from the undesirable side reaction during the initial charging step is suppressed by the residual Li compounds on the surface of the NCM, thereby reducing polarization growth in ASSBs and enhancing rate performances. The advantageous effects of the intrinsic residual Li compounds on the NCM surface suggest that the essential washing process of the NCM for the liquid-based LIB system should be reconsidered for ASSB systems.

The wet-chemical processability of sulfide solid electrolytes (SEs) provides intriguing opportunities for all-solid-state batteries. Thus far, sulfide SEs are wet-prepared either from solid precursors suspended in solvents (suspension synthesis) or from homogeneous solutions using SEs (solution process) with restricted composition spaces. Here, a universal solution synthesis method for preparing sulfide SEs from precursors, not only Li 2 S, P 2 S 5 , LiCl, and Na 2 S, but also metal sulfides (e.g., GeS 2 and SnS 2 ), fully dissolved in an alkahest: a mixture solvent of 1,2-ethylenediamine (EDA) and 1,2-ethanedithiol (EDT) (or ethanethiol). Raman spectroscopy and theoretical calculations reveal that the exceptional dissolving power of EDA-EDT toward GeS 2 is due to the nucleophilicity of the thiolate anions that is strong enough to dissociate the GeS bonds. Solution-synthesized Li 10 GeP 2 S 12 , Li 6 PS 5 Cl, and Na 11 Sn 2 PS 12 exhibit high ionic conductivities (0.74, 1.3, and 0.10 mS cm -1 at 30 °C, respectively), and their application for all-solid-state batteries is successfully demonstrated., (© 2022 Wiley-VCH GmbH.)

Developing high-performance all-solid-state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide-rich solid solution phases in the argyrodite Li 6 PS 5 Cl family, Li 6-x PS 5-x Cl 1+x , and combine electrochemical impedance spectroscopy, neutron diffraction, and 7 Li NMR MAS and PFG spectroscopy to show that increasing the Cl - /S 2- ratio has a systematic, and remarkable impact on Li-ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li 5.5 PS 4.5 Cl 1.5 , exhibits a cold-pressed conductivity of 9.4±0.1 mS cm -1 at 298 K (and 12.0±0.2 mS cm -1 on sintering)-almost four-fold greater than Li 6 PS 5 Cl under identical processing conditions and comparable to metastable superionic Li 7 P 3 S 11 . Weakened interactions between the mobile Li-ions and surrounding framework anions incurred by substitution of divalent S 2- for monovalent Cl - play a major role in enhancing Li + -ion diffusivity, along with increased site disorder and a higher lithium vacancy population., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrode materials exploiting multielectron-transfer processes are essential components for large-scale energy storage systems. Organic-based electrode materials undergoing distinct molecular redox transformations can intrinsically circumvent the structural instability issue of conventional inorganic-based host materials associated with lattice volume expansion and pulverization. Yet, the fundamental mechanistic understanding of metal-organic coordination polymers toward the reversible electrochemical processes is still lacking. Herein, we demonstrate that metal-dependent spatial proximity and binding affinity play a critical role in the reversible redox processes, as verified by combined 13 C solid-state NMR, X-ray absorption spectroscopy, and transmission electron microscopy. During the electrochemical lithiation, in situ generated metallic nanoparticles dispersed in the organic matrix generate electrically conductive paths, synergistically aiding subsequent multielectron transfer to π-conjugated ligands. Comprehensive screening on 3d-metal-organic coordination polymers leads to a high-capacity electrode material, cobalt-2,5-thiophenedicarboxylate, which delivers a stable specific capacity of ∼1100 mA h g -1 after 100 cycles.

Bulk-type all-solid-state lithium-ion batteries (ASLBs) for large-scale energy-storage applications have emerged as a promising alternative to conventional lithium-ion batteries (LIBs) owing to their superior safety. However, the electrochemical performance of bulk-type ASLBs is critically limited by the low ionic conductivity of solid electrolytes (SEs) and poor ionic contact between the active materials and SEs. Herein, highly conductive (0.14 mS cm -1 ) and dry-air-stable SEs (Li 4 SnS 4 ) are reported, which are prepared using a scalable aqueous-solution process. An active material (LiCoO 2 ) coated by solidified Li 4 SnS 4 from aqueous solutions results in a significant improvement in the electrochemical performance of ASLBs. Side-effects of the exposure of LiCoO 2 to aqueous solutions are minimized by using predissolved Li 4 SnS 4 solution., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bulk-type all-solid-state lithium-ion batteries (ASLBs) have the potential to be superior to conventional lithium-ion batteries (LIBs) in terms of safety and energy density. Sulfide SE materials are key to the development of bulk-type ASLBs because of their high ionic conductivity (max of ∼10 -2 S cm -1 ) and deformability. However, the severe reactivity of sulfide materials toward common polar solvents and the particulate nature of these electrolytes pose serious complications for the wet-slurry process used to fabricate ASLB electrodes, such as the availability of solvent and polymeric binders and the formation of ionic contacts and networks. In this work, we report a new scalable fabrication protocol for ASLB electrodes using conventional composite LIB electrodes and homogeneous SE solutions (Li 6 PS 5 Cl (LPSCl) in ethanol or 0.4LiI-0.6Li 4 SnS 4 in methanol). The liquefied LPSCl is infiltrated into the tortuous porous structures of LIB electrodes and solidified, providing intimate ionic contacts and favorable ionic percolation. The LPSCl-infiltrated LiCoO 2 and graphite electrodes show high reversible capacities (141 and 364 mA h g -1 ) at 0.14 mA cm -2 (0.1 C) and 30 °C, which are not only superior to those for conventional dry-mixed and slurry-mixed ASLB electrodes but also comparable to those for liquid electrolyte cells. Good electrochemical performance of ASLBs employing the LPSCl-infiltrated LiCoO 2 and graphite electrodes at 100 °C is also presented, highlighting the excellent thermal stability and safety of ASLBs.

All-solid-state sodium-ion batteries that operate at room temperature are attractive candidates for use in large-scale energy storage systems. However, materials innovation in solid electrolytes is imperative to fulfill multiple requirements, including high conductivity, functional synthesis protocols for achieving intimate ionic contact with active materials, and air stability. A new, highly conductive (1.1 mS cm(-1) at 25 °C, Ea =0.20 eV) and dry air stable sodium superionic conductor, tetragonal Na3 SbS4 , is described. Importantly, Na3 SbS4 can be prepared by scalable solution processes using methanol or water, and it exhibits high conductivities of 0.1-0.3 mS cm(-1) . The solution-processed, highly conductive solidified Na3 SbS4 electrolyte coated on an active material (NaCrO2 ) demonstrates dramatically improved electrochemical performance in all-solid-state batteries., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new, highly conductive (4.1 × 10(-4) S cm(-1) at 30 °C), highly deformable, and dry-air-stable glass 0.4LiI-0.6Li4 SnS4 is prepared using a homogeneous methanol solution. The solution process enables the wetting of any exposed surface of the active materials with highly conductive solidified electrolytes (0.4LiI-0.6Li4 SnS4), resulting in considerable improvements in the electrochemical performance of these electrodes over conventional mixture electrodes., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)