Modeling, Preparation, and Elemental Doping of Li7La3Zr2O12 Garnet-Type Solid Electrolytes: A Review

Abstract

Recently, all-solid-state batteries (ASSBs) have attracted increasing interest owing to their higher energy density and safety. As the core material of ASSBs, the characteristics of the solid electrolyte largely determine the performance of the battery. Thus far, a variety of inorganic solid electrolytes have been studied, including the NASICON-type, LISICON-type, perovskite-type, garnet-type, glassy solid electrolyte, and so on. The garnet Li 7 La 3 Zr 2 O 1 2 (LLZO) solid electrolyte is one of the most promising candidates because of its excellent comprehensively electrochemical performance. Both, experiments and theoretical calculations, show that cubic LLZO has high room-temperature ionic conductivity and good chemical stability while contacting with the lithium anode and most of the cathode materials. In this paper, the crystal structure, Li-ion transport mechanism, preparation method, and element doping of LLZO are introduced in detail based on the research progress in recent years. Then, the development prospects and challenges of LLZO as applied to ASSBs are discussed.

The Role of Interlayer Chemistry in Li‐Metal Growth through a Garnet‐Type Solid Electrolyte

“…In this regard, excellent solid electrolytes have been extensively sought after over the past few decades, leading to the discovery of new systems that include sulfides, NASICONs, LiSICONs, perovskites, and garnet‐type solid electrolytes that rival conventional liquid electrolytes 1–7. Among them, the garnet‐type solid electrolyte, which is based on the Li 7 La 3 Zr 2 O 12 (LLZO) nominal formula, is considered to be a promising candidate 8,9. LLZO is chemically stable against lithium metal and also benefits from relatively high ionic conductivity at room temperature (≈1 mS cm −1 ), with a lithium‐ion transference number close to unity 10–17.…”

All-Solid-State Lithium-Ion Batteries with Oxide/Sulfide Composite Electrolytes

“…The high-frequency semicircle can be divided into two semicircles that correspond to the bulk and grain-boundary resistances [5,22]. In some cases, a depressed semicircle can also be observed [6,23], depending on the density (porosity) or grain size of the sintered electrolyte sample or the measuring temperature. Figure 4 shows the AC impedance spectra of symmetrical cells consisting of an LLZO-LPSC composite electrolyte and two stainless-steel blocking electrodes measured at 25 • C. For comparison, the AC impedance spectra of the LLZO and LPSC pellets are shown.…”

“…Garnet-structured Li 7 La 3 Zr 2 O 12 (LLZO) is a promising solid electrolyte material because it exhibits higher ionic conductivity (in the order of 10 −4 to 10 −3 S•cm −1 ) and higher electrochemical stability against lithium metal [4][5][6]. However, LLZO requires hightemperature sintering to achieve high relative density (>95%).…”

Crystal Structure and Preparation of Li7La3Zr2O12 (LLZO) Solid-State Electrolyte and Doping Impacts on the Conductivity: An Overview

“…Electrochem 2021, 2, FOR PEER REVIEW 6 The crystal structure shown in Figure 6 reported by Cao et al reveals that both tetrahedral and cubic phase LLZO have the same structural framework except in Li distribution [49]. Bernstein et al reported that tetragonal phase LLZO presents good stability due to its ordered geometry.…”