electric vehicles because of their high energy density and long cycle life, etc. However, traditional LIBs are composed of organic liquid electrolytes in which there exists latent danger of fire and even explosion. [1] Thanks to the remarkable mechanical strength and inflammable nature of solid-state electrolytes, solid-state batteries (SSBs) are expected to address the critical safety issues of the traditional LIBs. [2] Simultaneously, the solid-state electrolytes are capable to resist the growth of lithium dendrites enabling possible use of lithium-metal anodes to replace graphite thus markedly improving the energy density.With the discovery of sodium super ion conductor (NASICON) in 1976 by Goodenough et al., [3] numerous research has been focused on oxide ceramic electrolytes (OCEs), including several crystal structures like NASICON-type, perovskite-type, LISICON-type (lithium superionic conductor), and garnet-type, etc. [4] The OCEs have been shown to be very promising for the development of SSBs given their advantages of high ionic conductivity (10 −4 -10 −3 S cm −1 at 25 °C), wide electrochemical High room-temperature ionic conductivities, large Li + -ion transference numbers, and good compatibility with both Li-metal anodes and high-voltage cathodes of the solid electrolytes are the essential requirements for practical solid-state lithium-metal batteries. Herein, a unique "superconcentrated ionogel-in-ceramic" (SIC) electrolyte prepared by an in situ thermally initiated radical polymerization is reported. Solid-state static 7 Li NMR and molecular dynamics simulation reveal the roles of ceramic in Li + local environments and transport in the SIC electrolyte. The SIC electrolyte not only exhibits an ultrahigh ionic conductivity of 1.33 × 10 −3 S cm −1 at 25 °C, but also a Li + -ion transference number as high as 0.89, together with a low electronic conductivity of 3.14 × 10 −10 S cm −1 and a wide electrochemical stability window of 5.5 V versus Li/Li + . Applications of the SIC electrolyte in Li||LiNi 0.5 Co 0.2 Mn 0.3 O 2 and Li||LiFePO 4 batteries further demonstrate the high rate and long cycle life. This study, therefore, provides a promising hybrid electrolyte for safe and high-energy lithium-metal batteries.

To achieve next-generation lithium metal batteries (LMBs) with desirable specific energy and reliability, the electrolyte shown simultaneously high reductive stability toward lithium metal anode and oxidative stability toward highvoltage cathode is of great importance. Here, we report for the first time that high-concentration lithium bis(fluorosulfonyl)imide (LiFSI) initiates ringopening polymerization of 1,3-dioxolane in presence of ethylene carbonate and ethylmethyl carbonate to produce in-situ a novel polymeric concentrated quasi-solid electrolyte (poly-CQSE). The unique poly-CQSE with 10 M LiFSI forms a mixed-lithiophobic-conductive LiF-Li 3 N solid electrolyte interphase on lithium metal anode, and a F-rich conformal cathode electrolyte interphase on LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode simultaneously. As a result, the poly-CQSE not only enables stable Li plating/stripping of metallic Li anode at a sound Coulombic efficiency of 95.3% without dendrite growth, but also enables a stable cycling of the LijjNCM523 quasi-solid-state LMB at a capacity retention of 94% over 100 cycles.

Exploring solid electrolytes with promising electrical properties and desirable compatibility toward electrodes for safe and high-energy sodium metal batteries remains a challenge. In this work, these issues are addressed via an in situ hybrid strategy, viz., highly conductive and thermally stable 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide is immobilized in nanoscale silica skeletons to form ionogel via a non-hydrolytic sol-gel route, followed by hybridizing with polymeric poly(ethylene oxide) and inorganic conductor Na3Zr2Si2PO12. Such hybrid design yields the required solid electrolyte, which shows not only a stable electrochemical stability window of 5.4 V vs Na/Na+ but also an extremely high ionic conductivity of 1.5 × 10−3 S cm−1 at 25 °C, which is demonstrated with the interacted and monolithic structure of the electrolyte by SEM, XRD, thermogravimetric (TG), and XPS. Moreover, the capabilities of suppressing sodium metal dendrite growth and enabling high-voltage cathode Mg-doped P2-type Na0.67Ni0.33Mn0.67O2 are verified. This work demonstrates the potential to explore the required solid electrolytes by hybridizing an in situ ionogel, a polymer, and an inorganic conductor for safe and high-energy solid-state sodium metal batteries.

Lithium metal batteries (LMBs) enabled by quasi-solid electrolytes are under consideration for their prospect of reliable safety and high energy density. The limited oxidative stabilization and inferior chemical compatibility of quasi-solid electrolytes toward high-voltage cathodes are a long-standing challenge. Herein, we report that an additive level (0.05 M) of LiPF6 is introduced to a polymeric concentrated quasi-solid electrolyte (10 M LiFSI in poly-1,3-dioxolane [poly-DOL], ethylene carbonate [EC], and ethyl methyl carbonate [EMC]) to build in situ a fluorine-regulated cathode electrolyte interphase (CEI) on a highly catalytic LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. The CEI with a conformal thickness of ∼7 nm features a fluorine-rich outer layer and manipulative LiF/organofluorine species, which mitigates the detrimental side reactions between the quasi-solid electrolyte and NCM cathode and maintains the structure of cycled NCM, as demonstrated by the characterizations of SEM, TEM, XRD, Raman spectroscopy, AFM, EDS, and XPS. As a result, the LiPF6-contained polymeric concentrated quasi-solid electrolyte not only provides a superior ionic conductivity of 3.1 × 10−4 S cm−1 at 25 °C and a remarkable electrochemical stability window of 5.5 V vs Li/Li+, but also achieves an excellent capacity retention of 74% after 100 cycles for LiǁNCM811 quasi-solid-state LMB, bringing a quasi-solid electrolyte design strategy of engineered CEI chemistry for LMBs.