Garnet-type solid-state electrolytes have attracted extensive attention due to their high ionic conductivity, approaching 1 mS cm, excellent environmental stability, and wide electrochemical stability window, from lithium metal to ∼6 V. However, to date, there has been little success in the development of high-performance solid-state batteries using these exceptional materials, the major challenge being the high solid-solid interfacial impedance between the garnet electrolyte and electrode materials. In this work, we effectively address the large interfacial impedance between a lithium metal anode and the garnet electrolyte using ultrathin aluminium oxide (AlO) by atomic layer deposition. LiLaCaZrNbO (LLCZN) is the garnet composition of choice in this work due to its reduced sintering temperature and increased lithium ion conductivity. A significant decrease of interfacial impedance, from 1,710 Ω cm to 1 Ω cm, was observed at room temperature, effectively negating the lithium metal/garnet interfacial impedance. Experimental and computational results reveal that the oxide coating enables wetting of metallic lithium in contact with the garnet electrolyte surface and the lithiated-alumina interface allows effective lithium ion transport between the lithium metal anode and garnet electrolyte. We also demonstrate a working cell with a lithium metal anode, garnet electrolyte and a high-voltage cathode by applying the newly developed interface chemistry.

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.

A solid electrolyte framework with porous and dense layers for high-energy and safe Li-metal batteries.

No abstract

Solid-state batteries have many enticing advantages in terms of safety and stability, but the solid electrolytes upon which these batteries are based typically lead to high cell resistance. Both components of the resistance (interfacial, due to poor contact with electrolytes, and bulk, due to a thick electrolyte) are a result of the rudimentary manufacturing capabilities that exist for solid-state electrolytes. In general, solid electrolytes are studied as flat pellets with planar interfaces, which minimizes interfacial contact area. Here, multiple ink formulations are developed that enable 3D printing of unique solid electrolyte microstructures with varying properties. These inks are used to 3D-print a variety of patterns, which are then sintered to reveal thin, nonplanar, intricate architectures composed only of Li La Zr O solid electrolyte. Using these 3D-printing ink formulations to further study and optimize electrolyte structure could lead to solid-state batteries with dramatically lower full cell resistance and higher energy and power density. In addition, the reported ink compositions could be used as a model recipe for other solid electrolyte or ceramic inks, perhaps enabling 3D printing in related fields.

Doping the zirconium site in NASICON (Na 3 Zr 2 Si 2 PO 12 ) with lower valent cations enhanced the ionic transport of the material. exhibited a higher bulk conductivity than undoped Na 3 Zr 2 Si 2 PO 12 at room temperature. A decrease in the low temperature activation energy for all doped NASICON was observed, which helped contribute to the higher room temperature conductivity. The lower activation energy and enhanced conductivity of doped materials were a result of alterations in the NASICON structure. The charge imbalance created by aliovalent substitution increased the sodium in the lattice resulting in more charge carriers with better mobility. Furthermore, the conductivity was optimized by the ionic radius of the species in the zirconium site. Ultimately, NASICON doped with a +2 oxidation state cation having an ionic radius of approximately 0.73 Å (Zn and Co) attained a maximum in conductivity. Zn-doped NASICON displayed the greatest room temperature bulk conductivity of 3.75×10 −3 S/cm, while Co-doped NASICON demonstrated the greatest total conductivity of 1.55×10 −3 S/cm.

No abstract

The development of high-performance cathodes for sodium-ion batteries remains a great challenge, while low-cost, high-capacity Na2/3Fe1/2Mn1/2O2 is an attractive electrode material candidate comprised of earth-abundant elements. In this work, we designed and fabricated a free-standing, binder-free Na2/3Fe1/2Mn1/2O2@graphene composite via a filtration process. The porous composite led to excellent electrochemical performance due to the facile transport for electrons and ions that was characterized by electrochemical impedance spectroscopy at different temperatures. The electrode delivered a reversible capacity of 156 mAh/g with high Coulombic efficiency. The importance of a fluorinated electrolyte additive with respect to the performance of this high-voltage cathode in Na-ion batteries was also investigated.