To promote the development of solid-state batteries, polymer-, oxide-, and sulfide-based solid-state electrolytes (SSEs) have been extensively investigated. However,t he disadvantages of these SSEs,s uch as high-temperature sintering of oxides,a ir instability of sulfides,a nd narrowe lectrochemical windows of polymers electrolytes,significantly hinder their practical application. Therefore,d eveloping SSEs that have ah igh ionic conductivity (> 10 À3 Scm À1 ), good air stability,w ide electrochemical window,e xcellent electrode interface stability,l ow-cost mass production is required. Herein we report ahalide Li + superionic conductor,Li 3 InCl 6 , that can be synthesized in water.M ost importantly,t he assynthesized Li 3 InCl 6 shows ahigh ionic conductivity of 2.04 10 À3 Scm À1 at 25 8 8C. Furthermore,the ionic conductivity can be recovered after dissolution in water.C ombined with aL iNi 0.8 Co 0.1 Mn 0.1 O 2 cathode,t he solid-state Li battery shows good cycling stability.All-solid-state lithium batteries (ASSLBs) using solid-state electrolytes (SSEs) are considered as promising next-generation energy-storage systems with improved safety through the elimination of the flammable liquid electrolyte in convention lithium-ion batteries (LIBs). [1] Among the various types of electrolytes,oxide-based and sulfide-based SSEs are considered to be the most promising candidates for use in ASSLBs because of their high ionic conductivity of over

Solid‐state Li–S and Li–Se batteries are promising devices that can address the safety and electrochemical stability issues that arise from liquid‐based systems. However, solid‐state Li–Se/S batteries usually present poor cycling stability due to the high resistance interfaces and decomposition of solid electrolytes caused by their narrow electrochemical stability windows. Here, an integrated solid‐state Li–Se battery based on a halide Li3HoCl6 solid electrolyte with high ionic conductivity is presented. The intrinsic wide electrochemical stability window of the Li3HoCl6 and its stability toward Se and the lithiated species effectively inhibit degeneration of the electrolyte and the Se cathode by suppressing side reactions. The inherent thermodynamic mechanism of the lithiation/delithiation process of the Se cathode in solid is also revealed and confirmed by theoretical calculations. The battery achieves a reversible capacity of 402 mAh g−1 after 750 cycles. The electrochemical performance, thermodynamic lithiation/delithiation mechanism, and stability of metal‐halide‐based Li–Se batteries confer theoretical study and practical applicability that extends to other energy‐storage systems.

Understanding the relationship between structure, ionic conductivity, and synthesis is the key to the development of superionic conductors. Here, a series of Li3‐3xM1+xCl6 (−0.14 < x ≤ 0.5, M = Tb, Dy, Ho, Y, Er, Tm) solid electrolytes with orthorhombic and trigonal structures are reported. The orthorhombic phase of Li–M–Cl shows an approximately one order of magnitude increase in ionic conductivities when compared to their trigonal phase. Using the Li–Ho–Cl components as an example, their structures, phase transition, ionic conductivity, and electrochemical stability are studied. Molecular dynamics simulations reveal the facile diffusion in the z‐direction in the orthorhombic structure, rationalizing the improved ionic conductivities. All‐solid‐state batteries of NMC811/Li2.73Ho1.09Cl6/In demonstrate excellent electrochemical performance at both 25 and −10 °C. As relevant to the vast number of isostructural halide electrolytes, the present structure control strategy guides the design of halide superionic conductors.

Inorganic solid-state electrolytes (SSEs) have gained significant attention for their potential use in high-energy solid-state batteries. However, there is a lack of understanding of the underlying mechanisms of fast ion conduction in SSEs. Here, we clarify the critical parameters that influence ion conductivity in SSEs through a combined analysis approach that examines several representative SSEs (Li3YCl6, Li3HoCl6, and Li6PS5Cl), which are further verified in the xLiCl-InCl3 system. The scaling analysis on conductivity spectra allowed the decoupled influences of mobile carrier concentration and hopping rate on ionic conductivity. Although the carrier concentration varied with temperature, the change alone cannot lead to the several orders of magnitude difference in conductivity. Instead, the hopping rate and the ionic conductivity present the same trend with the temperature change. Migration entropy, which arises from lattice vibrations of the jumping atoms from the initial sites to the saddle sites, is also proven to play a significant role in fast Li+ migration. The findings suggest that the multiple dependent variables such as the Li+ hopping frequency and migration energy are also responsible for the ionic conduction behavior within SSEs.