Evaluation of solid electrolytes: Development of conventional and interdisciplinary approaches

Abstract

Solid‐state lithium batteries (SSLBs) have received considerable attention due to their advantages in thermal stability, energy density, and safety. Solid electrolyte (SE) is a key component in developing high‐performance SSLBs. An in‐depth understanding of the intrinsic bulk and interfacial properties is imperative to achieve SEs with competitive performance. This review first introduces the traditional electrochemical approaches to evaluating the fundamental parameters of SEs, including the ionic and electronic conductivities, activation barrier, electrochemical stability, and diffusion coefficient. After that, the characterization techniques to evaluate the structural and chemical stability of SEs are reviewed. Further, emerging interdisciplinary visualization techniques for SEs and interfaces are highlighted, including synchrotron X‐ray tomography, ultrasonic scanning imaging, time‐of‐flight secondary‐ion mass spectrometry, and three‐dimensional stress mapping, which improve the understanding of electrochemical performance and failure mechanisms. In addition, the application of machine learning to accelerate the screening and development of novel SEs is introduced. This review article aims to provide an overview of advanced characterization from a broad physical chemistry view, inspiring innovative and interdisciplinary studies in solid‐state batteries.

Review of Ionic Conductivity Properties of NASICON Type Inorganic Solid Electrolyte LATP

“…SEs have been the subject of extensive research in the most recent decades, using theoretical calculations, model predictions, and design experiments to investigate their ion transport mechanisms, electrochemical properties, mechanical properties, and electrode compatibility . Concurrently, researchers have also explored various novel SEs to fulfill the requirements of practical applications and have established several essential criteria that high-performance solid-state electrolytes should satisfy: Optimal ionic conductivity and large lithium-ion transference number to ensure high lithium-ion flux and low concentration polarization during battery operation, preventing the formation of lithium dendrites; High thermal stability and low-temperature performance to ensure that the battery can operate in different temperature ranges; A wide electrochemical window to ensure that the solid electrolyte can match the high-voltage cathode and the lithium metal anode without side reactions, to accommodate the electrode reactions in the charge and discharge process; Good mechanical properties, with some toughness and easy to manufacture and process; High safety features (e.g., nonflammable, not prone to leakage, and not prone to short circuit) to adapt to complex working conditions; Low overall cost, suitable for large-scale production and application; Good environmental compatibility, preparation, use, and post-treatment process that do not cause environmental pollution …”

“…SEs have been the subject of extensive research in the most recent decades, using theoretical calculations, model predictions, and design experiments to investigate their ion transport mechanisms, electrochemical properties, mechanical properties, and electrode compatibility. 36 Concurrently, researchers have also explored various novel SEs to fulfill the requirements of practical applications and have established several essential criteria that high-performance solid-state electrolytes should satisfy:…”

Feature-rich electronic properties of three-dimensional ternary compound: Li7P3S11

“…To validate the theoretical predictions, experimental techniques can be employed. X-ray diffraction (XRD) (Tufail et al ., 2023), transmission electron microscopy (TEM) (Chircov et al ., 2021; Song et al ., 2020) and scanning electron microscopy (SEM) (Wang et al ., 2018; Zheng et al ., 2020; Eatmon et al ., 2023) are suitable for determining the optimal geometry, while optical absorption spectra can shed light on the occupied electronic states and band gap. SEM can provide high-resolution images of the material’s surface, revealing details about its morphology, topography and surface features (Tufail et al ., 2021).…”

Understanding Interfaces at the Positive and Negative Electrodes on Sulfide-Based Solid-State Batteries

“…This technology offers remarkable advantages over conventional lithium-ion batteries with liquid electrolytes, from improved safety with nonflammable electrolyte to higher gravimetric and volumetric energy density enabled using LiM anode along with the multilayered bipolar stacking cell fabrication. The combination of solid electrolyte (SE) mechanical strength, flexibility, and safety against self-ignition allows for optimized battery design to meet the specific requirements. − …”

“…Sulfide-based materials have certain drawbacks related to their poor chemical stability toward ambient atmosphere and narrow electrochemical stability window. ,, For instance, the Li 6 PS 5 Cl (LPSCl) argyrodite phase exhibits thermodynamic stability in the potential range of 1.7–2.3 V vs Li/Li + , resulting in incompatibility between the electrolyte and Li metal anode or high-voltage Li­(Ni,Mn,Co)­O 2 (NMC) cathodes. Although in practice the stability window is generally larger for kinetic reasons or due to the formation of passivating layers, − there are numerous studies highlighting the reactivity at the sulfide/Li − or sulfide/NMC interface. − Additionally, mechanisms of degradation of sulfide-containing SSBs are ascribed to microstructural changes arising from the redox processes during cycling, − especially in the case of large volume changes of the cathode active material upon delithiation, ,, poor percolation within the electron-conductive phase, contact loss between the electrolyte and cathode or anode layers, ,− as well as dendrite propagation. , …”