Enabling all-solid-state Li-ion batteries requires solid electrolytes with high Li ionic conductivity and good electrochemical stability.F ollowing recent experimental reports of Li 3 YCl 6 and Li 3 YBr 6 as promising new solid electrolytes,weused first principles computation to investigate the Li-ion diffusion, electrochemical stability,a nd interface stability of chloride and bromide materials and elucidated the origin of their high ionic conductivities and good electrochemical stabilities.Chloride and bromide chemistries intrinsically exhibit lowmigration energy barriers,wide electrochemical windows,a nd are not constrained to previous design principles for sulfide and oxide Li-ion conductors,allowing for muchg reater freedom in structure,c hemistry,c omposition, and Li sublattice for developing fast Li-ion conductors.O ur study highlights chloride and bromide chemistries as apromising new researchdirection for solid electrolytes with high ionic conductivity and good stability.All-solid-state lithium-ion batteries (ASBs) with inorganic lithium solid electrolytes (SEs) are regarded as promising next-generation energy storage devices.ASBs solve the safety issue caused by the flammability of organic liquid electrolyte and potentially provide higher energy density with Li metal anode and high-voltage cathode materials. [1] However,i th as been ag reat challenge to develop solid-state Li-ion conductors with high Li + conductivity at room temperature comparable to that of liquid electrolytes and with good electrochemical stability for Li-ion batteries with avoltage of > 4V .C urrent research efforts on solid-state Li-ion conductors focus mostly on oxides and sulfides. [1a,b,2] Unfortunately, oxide and sulfide chemistries have an undesirable trade-off between ionic conductivity and stability.S ulfide-based solidstate Li-ion conductors such as Li 10 GeP 2 S 12 (LGPS) andSupportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Figure 3. Calculated thermodynamics intrinsic electrochemical windows of Li-M-X ternary fluorides, chlorides, bromides, iodides, oxides, and sulfides. Mi sametal cation at its highest commonv alence state.

Solid-state batteries with desirable advantages, including high-energy density, wide temperature tolerance, and fewer safety-concerns, have been considered as a promising energy storage technology to replace organic liquid electrolyte-dominated Li-ion batteries. Solid-state electrolytes (SSEs) as the most critical component in solid-state batteries largely lead the future battery development. Among different types of solid-state electrolytes, garnet-type Li7La3Zr2O12 (LLZO) solid-state electrolytes have particularly high ionic conductivity (10–3 to 10–4 S/cm) and good chemical stability against Li metal, offering a great opportunity for solid-state Li-metal batteries. Since the discovery of garnet-type LLZO in 2007, there has been an increasing interest in the development of garnet-type solid-state electrolytes and all solid-state batteries. Garnet-type electrolyte has been considered one of the most promising and important solid-state electrolytes for batteries with potential benefits in energy density, electrochemical stability, high temperature stability, and safety. In this Review, we will survey recent development of garnet-type LLZO electrolytes with discussions of experimental studies and theoretical results in parallel, LLZO electrolyte synthesis strategies and modifications, stability of garnet solid electrolytes/electrodes, emerging nanostructure designs, degradation mechanisms and mitigations, and battery architectures and integrations. We will also provide a target-oriented research overview of garnet-type LLZO electrolyte and its application in various types of solid-state battery concepts (e.g., Li-ion, Li–S, and Li–air), and we will show opportunities and perspectives as guides for future development of solid electrolytes and solid-state batteries.

The all-solid-state lithium-ion battery is a promising next-generation battery technology. However, the realization of all-solid-state batteries is impeded by limited understanding of solid electrolyte materials and solid electrolyte-electrode interfaces. In this review, we present an overview of recently developed computation techniques and their applications in understanding and advancing materials and interfaces in all-solid-state batteries. We review the role of ab initio molecular dynamics simulations in studying fast ion conductors and discuss the capabilities of thermodynamic calculations powered by materials databases for identifying the chemical and electrochemical stability of solid electrolyte materials and solid electrolyte-electrode interfaces. We highlight the computational studies in the design and discovery of new solid electrolyte materials and outline design guidelines for solid electrolytes and their interfaces. We conclude with discussion of future directions in computation techniques, materials development, and interface engineering for all-solid-state lithium-ion batteries.

This study quantifies the thermal stability of oxide SEs with Li metal and observes thermal runaway behaviors of common SEs with Li metal. Theoretic calculations and experiments indicate that the oxygen generation from the SEs at elevated temperatures triggers a highly exothermic reaction with molten metallic Li, leading to thermal runaway. As an alert to the community, our results highlight the urgency to systematically investigate and deepen the understanding of safety issues in ASSBs.

cathodes, [10][11][12] silicon-based anodes, [13][14][15][16] and optimizing organic liquid electrolytes. [17,18] However, the safety challenges related to the electrolyte are serious because operation of LIBs is exothermic and organic liquid electrolytes mostly with ester carbonates are highly flammable, generating massive heat. [19,20] Dendritic lithium in LIB represents a further challenge considering internal short circuit would occur if the dendrite punctures the separator. [21,22] Therefore, solutions for safety of LIBs are urgently required.Inorganic ceramic solid-state electrolyte (SSE) provides an ideal alternative to liquid flammable electrolytes for the design of safe ASSBs, since ceramic SSE is nonflammable and it has adequate fracture toughness to prevent internal short circuit from lithium dendrite. [23][24][25] Furthermore, lithium metal anode, the ultimate anode with the highest specific capacity and lowest electrochemical potential has been demonstrated in ASSBs, which exhibited intrinsic safety under rigorous conditions. [26][27][28][29][30] In the search for SSEs, while most of the superionic conductors with conductivity >1 mS cm −1 are based on sulfides, such as Li 10 GeP 2 S 12 , [31,32] Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , [33] and Li 9.6 P 3 S 12 , [34] it has shown that garnet-type oxides are the most stable SSEs with lithium metal anode. [35][36][37][38][39] However, the lithium/garnet interface appeared to have a remarkably large impedance due to the poor interfacial contact. [40] This motivates a variety of studies to turn garnet from lithiophobic to lithiophilic by coating garnet with metal, [41][42][43][44] metal oxides, [45,46] semi-conductors, [47,48] polymer interlayers, [49,50] and graphite. [51] Although these approaches have shown great progress, they mainly addressed the interface issue from garnet side. As a result, ample opportunities remain on lithium metal side.Here we introduce a new strategy to synthesize a ceramic compatible lithium anode by using graphite additives. Our scheme to implement a lithium/garnet interface experiment is sketched in Figure 1. We find that pure lithium is not compatible with garnet, which is consistent with that expected for lithiophobic garnet surface and previous reports (Figure 1a). [52] On the other side, lithium-graphite (Li-C) composite presents lower fluidity and higher viscosity compared to pure Li. So the Li-C composite, like a paste, can be casted onto garnet and exhibits an intimate contact (Figure 1b). As expected, All-solid-state batteries (ASSBs) with ceramic-based solid-state electrolytes (SSEs) enable high safety that is inaccessible with conventional lithium-ion batteries. Lithium metal, the ultimate anode with the highest specific capacity, also becomes available with nonflammable SSEs in ASSBs, which offers promising energy density. The rapid development of ASSBs, however, is significantly hampered by the large interfacial resistance as a matched lithium/ ceramic interface that is not easy to pursue. Here, a lithium-graphite...

Although machine learning has gained great interest in the discovery of functional materials, the advancement of reliable models is impeded by the scarcity of available materials property data. Here we propose and demonstrate a distinctive approach for materials discovery using unsupervised learning, which does not require labeled data and thus alleviates the data scarcity challenge. Using solid-state Li-ion conductors as a model problem, unsupervised materials discovery utilizes a limited quantity of conductivity data to prioritize a candidate list from a wide range of Li-containing materials for further accurate screening. Our unsupervised learning scheme discovers 16 new fast Li-conductors with conductivities of 10−4–10−1 S cm−1 predicted in ab initio molecular dynamics simulations. These compounds have structures and chemistries distinct to known systems, demonstrating the capability of unsupervised learning for discovering materials over a wide materials space with limited property data.

Ion transport in crystalline fast ionic conductors is a complex physical phenomenon. Certain ionic species (e.g., Ag+, Cu+, Li+, F–, O2–, H+) in a solid crystalline framework can move as fast as in liquids. This property, although only observed in a limited number of materials, is a key enabler for a broad range of technologies, including batteries, fuel cells, and sensors. However, the mechanisms of ion transport in the crystal lattice of fast ionic conductors are still not fully understood despite the substantial progress achieved in the last 40 years, partly because of the wide range of length and time scales involved in the complex migration processes of ions in solids. Without a comprehensive understanding of these ion transport mechanisms, the rational design of new fast ionic conductors is not possible. In this review, we cover classical and emerging characterization techniques (both experimental and computational) that can be used to investigate ion transport processes in bulk crystalline inorganic materials which exhibit predominant ion conduction (i.e., negligible electronic conductivity) with a primary focus on literature published after 2000 and critically assess their strengths and limitations. Together with an overview of recent understanding, we highlight the need for a combined experimental and computational approach to study ion transport in solids of desired time and length scales and for precise measurements of physical parameters related to ion transport.

We report integral cross sections (ICSs) for electron impact excitation of the A 3 + u , B 3 g , W 3 u , B 3 − u , a 1 − u , a 1 g , ω 1 u , C 3 u , E 3 + g and a 1 + g electronic states of N 2 . The present data, for each state, were derived at five incident electron energies in the range 15-50 eV, from the earlier crossedbeam differential cross section (DCS) measurements of our group. This was facilitated by using a molecular phase shift analysis technique to extrapolate the measured DCSs to 0 • and 180 • , before performing the integration. A comprehensive comparison of the present ICSs with the results of earlier experimental studies, both crossed beam and electron swarm, and theoretical calculations is provided. This comparison clearly indicates that some of the previous estimates for these excited electronic-state cross sections need to be reassessed. In addition, we have used the present ICSs in a Monte Carlo simulation for modelling the behaviour of an electron swarm in the bulk of a low current N 2 discharge. The macroscopic transport parameters determined from this simulation are compared against those measured from independent swarm-based experiments and the self-consistency of our ICSs evaluated.