All-solid-state lithium batteries (ASSLBs), which use solid electrolytes instead of liquid ones, have become a hot research topic due to their high energy and power density, ability to solve battery safety issues, and capabilities to fulfill the increasing demand for energy storage in electric vehicles and smart grid applications. Garnet-type solid electrolytes have attracted considerable interest as they meet all the properties of an ideal solid electrolyte for ASSLBs. The garnet-type Li7La3Zr2O12 (LLZO) has excellent environmental stability; experiments and computational analyses showed that this solid electrolyte has a high lithium (Li) ionic conductivity (10−4–10−3 S·cm−1), an electrochemical window as wide as 6 V, stability against Li metal anode, and compatibility with most of the cathode materials. In this review, we present the fundamentals of garnet-type solid electrolytes, preparation methods, air stability, some strategies for improving the conductivity based on experimental and computational results, interfacial issues, and finally applications and challenges for future developments of LLZO solid electrolytes for ASSLBs.

The scalable multifunctional solid electrolyte (MSE) composed of poly(ethylene oxide)-solid oxide lithium-ion conductor Li 7 La 3 Zr 2 O 12 -succinonitrile (PEO 18 -LiTFSI-LLZO-SN) is demonstrated as a promising candidate for high performance all-solidstate batteries. Among these electrolytes, PEO 18 -LiTFSI-7.5%LLZO-10%SN presents a highest ionic conductivity of 1.19 × 10 −4 S • cm −1 at room temperature and a much higher Li + transference number. Moreover, this MSE has a good electrochemical stability of 5.5 V vs. Li/Li + , and exhibits excellent interfacial compatibility against lithium electrode. Owing to the improved interface contact and enhanced Li + transference, the MSE-based ASSLBs present outstanding cycling and rate performance at 60 • C. Notably, the initial discharge capacity at 1 C is 130.2 mAh • g −1 , and after 500 cycles 80.0% capacity is retained. The cell can be operated normally at lower temperatures (30 • C and 45 • C) while still delivering a relatively high specific capacity.

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.

Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for the discrimination, identification, and potential quantification of certain compounds/organisms. However, its real application is challenging due to the multiple interference from the complicated detection matrix. Therefore, selective/specific detection is crucial for the real application of SERS technique. We summarize in this review five selective/specific detection techniques (chemical reaction, antibody, aptamer, molecularly imprinted polymers and microfluidics), which can be applied for the rapid and reliable selective/specific detection when coupled with SERS technique.

No abstract