Inorganic solid electrolytes (SEs) possess substantial safety and electrochemical stability, which make them as key components of safe rechargeable solid-state Li batteries with high energy density. However, complicated integrally molding process and poor wettability between SEs and active materials are the most challenging barriers for the application of SEs. In this regard, we explore composite SEs of the active ceramic LiAlGe(PO) (LAGP) as the main medium for ion conduction and the polymer P(VDF-HFP) as a matrix. Meanwhile, for the first time, we choice high chemical, thermal, and electrochemical stability of ionic liquid swelled in polymer, which significantly ameliorate the interface in the cell. In addition, a reduced crystallinity degree of the polymer in the electrolyte can also be achieved. All of these lead to good ionic conductivity of the composite electrolyte (LPELCE), at the same time, good compatibility with the lithium electrode. Especially, high mechanical strength and stable solid electrolyte interphase which suppressed the growth of lithium dendrites and high thermal safety stability can also be observed. For further illustration, the solid-state lithium battery of LiFePO/LPELCE/Li shows relatively satisfactory performance, indicating the promising potentials of using this type of electrolyte to develop high safety and high energy density solid-state lithium batteries.
Rationally
constructing inexpensive sulfur hosts that have high
electronic conductivity, large void space for sulfur, strong chemisorption,
and rapid redox kinetics to polysulfides is critically important for
their practical use in lithium–sulfur (Li–S) batteries.
Herein, we have designed a multifunctional sulfur host based on yolk–shelled
Fe2N@C nanoboxes (Fe2N@C NBs) through a strategy
of etching combined with nitridation for high-rate and ultralong Li–S
batteries. The highly conductive carbon shell physically confines
the active material and provides efficient pathways for fast electron/ion
transport. Meanwhile, the polar Fe2N core provides strong
chemical bonding and effective catalytic activity for polysulfides,
which is proved by density functional theory calculations and electrochemical
analysis techniques. Benefiting from these merits, the S/Fe2N@C NBs electrode with a high sulfur content manifests a high specific
capacity, superior rate capability, and long-term cycling stability.
Specifically, even after 600 cycles at 1 C, a capacity of 881 mAh
g–1 with an average fading rate of only 0.036% can
be retained, which is among the best cycling performances reported.
The strategy in this study provides an approach to the design and
construction of yolk–shelled iron-based compounds@carbon nanoarchitectures
as inexpensive and efficient sulfur hosts for realizing practically
usable Li–S batteries.
Despite their high theoretical energy density, lithium-sulfur (Li-S) batteries are hindered by practical challenges including sluggish conversion kinetics and shuttle effect of polysulfides. Here, a nitrogen-doped continuous porous carbon (CPC) host anchoring monodispersed sub-10 nm FeS 2 nanoclusters (CPC@FeS 2 ) is reported as an efficient catalytic matrix for sulfur cathode. This host shows strong adsorption of polysulfides, promising the inhibition of polysulfide shuttle and the promoted initial stage of catalytic conversion process. Moreover, fast lithium ion (Li-ion) diffusion and accelerated solid-solid conversion kinetics of Li 2 S 2 to Li 2 S on CPC@FeS 2 host guarantee boosted electrochemical kinetics for conversion process of sulfur species in Li-S cell, which gives a high utilization of sulfur under practical conditions of high loading and low electrolyte/sulfur (E/S) ratio. Therefore, the surfur cathode (S/CPC@FeS 2 ) delivers a high specific capacity of 1459 mAh g −1 at 0.1 C, a stable cycling over 900 cycles with ultralow fading rate of 0.043% per cycle, and an enhanced rate capability compared with cathode only using carbon host. Further demonstration of this cathode in Li-S pouch cell shows a practical energy density of 372 Wh kg −1 with a sulfur loading of 7.1 mg cm −2 and an E/S ratio of 4 µL mg −1 .
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