All-solid-state batteries (ASSBs) have attracted enormous attention as one of the critical future technologies for safe and high energy batteries. With the emergence of several highly conductive solid electrolytes in recent years, the bottleneck is no longer Li-ion diffusion within the electrolyte. Instead, many ASSBs are limited by their low Coulombic efficiency, poor power performance, and short cycling life due to the high resistance at the interfaces within ASSBs. Because of the diverse chemical/physical/mechanical properties of various solid components in ASSBs as well as the nature of solid−solid contact, many types of interfaces are present in ASSBs. These include loose physical contact, grain boundaries, and chemical and electrochemical reactions to name a few. All of these contribute to increasing resistance at the interface. Here, we present the distinctive features of the typical interfaces and interphases in ASSBs and summarize the recent work on identifying, probing, understanding, and engineering them. We highlight the complicated, but important, characteristics of interphases, namely the composition, distribution, and electronic and ionic properties of the cathode−electrolyte and electrolyte−anode interfaces; understanding these properties is the key to designing a stable interface. In addition, conformal coatings to prevent side reactions and their selection criteria are reviewed. We emphasize the significant role of the mechanical behavior of the interfaces as well as the mechanical properties of all ASSB components, especially when the soft Li metal anode is used under constant stack pressure. Finally, we provide full-scale (energy, spatial, and temporal) characterization methods to explore, diagnose, and understand the dynamic and buried interfaces and interphases. Thorough and in-depth understanding on the complex interfaces and interphases is essential to make a practical high-energy ASSB.
Functional microporous conducting carbon with a high surface area of about 1230 m 2 g À1 is synthesized by single-step pyrolysis of dead plant leaves (dry waste, ground powder) without any activation and studied for supercapacitor application. We suggest that the activation is provided by the natural constituents in the leaves composed of soft organics and metals. Although the detailed study performed and reported here is on dead Neem leaves (Azadirachta indica), the process is clearly generic and applicable to most forms of dead leaves. Indeed we have examined the case of dead Ashoka leaves as well. The comparison between the Neem and Ashoka leaves brings out the importance of the constitution and composition of the bio-source in the nature of carbon formed and its properties. We also discuss and compare the cases of pyrolysis of green leaves as well as un-ground dead leaves with that of ground dead leaf powder studied in full detail. The concurrent high conductivity and microporosity realized in our carbonaceous materials are key to the high energy supercapacitor application. Indeed, our synthesized functional carbon exhibits a very high specific capacitance of 400 F g À1 and an energy density of 55 W h kg À1 at a current density of 0.5 A g À1 in aqueous 1 M H 2 SO 4 . The areal capacitance value of the carbon derived from dead (Neem) plant leaves (CDDPL) is also significantly high (32 mF cm À2 ). In an organic electrolyte the material shows a specific capacitance of 88 F g À1 at a current density of 2 A g À1 . Broader contextWaste management has always been a big problem in big cities. Most such waste is a rich source of carbon but may contain other elements in different proportions. Usually the waste from natural sources is just burnt producing ash and hazardous gaseous pollution products. If instead it is harnessed to synthesize electronically active carbon, one could use it for value-added products such as materials for supercapacitor electrodes. Supercapacitors have been attracting signicant interest due to their applications in electrical vehicles, digital devices, pulsing techniques etc. In this work we demonstrate the synthesis of high surface area microporous conducting carbon by one-step pyrolysis of dead plant leaves (abundant waste material) without any chemical or physical activation and have examined its properties for supercapacitor application. Although the detailed study performed and reported here is on dead Neem leaves (Azadirachta indica), the process is clearly generic and applicable to most forms of dead leaves. Indeed we have examined the case of dead Ashoka leaves too. With dead Neem leaves we have achieved a high specic capacitance of 400 F g À1 and a energy density of 55 W h kg À1 at 0.5 A g À1 . Moreover, in an organic electrolyte the material shows a specic capacitance of 88 F g À1 at 2 A g À1 .
All-solid-state batteries are expected to enable batteries with high energy density with the use of lithium metal anodes. Although solid electrolytes are believed to be mechanically strong enough to prevent lithium dendrites from propagating, various reports today still show cell failure due to lithium dendritic growth at room temperature. While cell parameters such as current density, electrolyte porosity and interfacial properties have been investigated, mechanical properties of lithium metal and the role of applied stack pressure on the shorting behavior is still poorly understood. Here, we investigated failure mechanisms of lithium metal in all-solid-state batteries as a function of stack pressure, and conducted in situ characterization of the interfacial and morphological properties of the buried lithium in solid electrolytes. We found that a low stack pressure of 5 MPa allows reliable plating and stripping in a lithium symmetric cell for more than 1000 hours, and a Li | Li6PS5Cl | LiNi0.80Co0.15Al0.05O2 full cell, plating more than 4 µm of lithium per charge, is able to cycle over 200 cycles at room temperature. These results suggest the possibility of enabling the lithium metal anode in all-solid-state batteries at reasonable stack pressures.
Sulfide-based solid electrolytes are promising candidates for all solid-state batteries (ASSBs) due to their high ionic conductivity and ease of processability. However, their narrow electrochemical stability window causes undesirable electrolyte decomposition. Existing literature on Li-ion ASSBs report an irreversible nature of such decompositions, while Li–S ASSBs show evidence of some reversibility. Here, we explain these observations by investigating the redox mechanism of argyrodite Li6PS5Cl at various chemical potentials. We found that Li–In | Li6PS5Cl | Li6PS5Cl–C half-cells can be cycled reversibly, delivering capacities of 965 mAh g–1 for the electrolyte itself. During charging, Li6PS5Cl forms oxidized products of sulfur (S) and phosphorus pentasulfide (P2S5), while during discharge, these products are first reduced to a Li3PS4 intermediate before forming lithium sulfide (Li2S) and lithium phosphide (Li3P). Finally, we quantified the relative contributions of the products toward cell impedance and proposed a strategy to reduce electrolyte decomposition and increase cell Coulombic efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.