Poly(vinylidene fluoride)‐based polymer electrolytes are being intensely investigated for solid‐state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom‐to‐up strategy is employed to design single‐phase and densified polymer electrolytes via incorporating quasi‐ionic liquid with poly(vinylidene fluoride‐co‐hexafluoropropylene). Due to strong ion/dipole–dipole interaction, the optimized polymer electrolyte delivers high room‐temperature ionic conductivity of 1.55 × 10−3 S cm−1, superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm−3 as well as desirable self‐extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm−2. In particular, lithium metal battery Li||LiNi0.6Co0.2Mn0.2O2 exhibits a room‐temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid‐flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi‐ionic liquid/polymer electrolytes in safe lithium metal batteries.

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The doped garnet-type solid electrolytes are attracting great interest due to high ionic conductivity and excellent electrochemical stability against Li metal. However, the thick electrolyte layer and rigid nature as well as poor interfacial contact are huge obstacles for its application in all-solid-state lithium batteries. Herein, an ultrathin flexible Li6.4La3Zr1.4Ta0.6O12- (LLZTO-) based solid electrolyte with 90 wt% LLZTO content is realized through solvent-free procedure. The resultant 20 μm-thick LLZTO-based film exhibits ultrahigh ionic conductance of 41.21 mS at 30°C, excellent oxidation stability of 4.6 V, superior thermal stability and nonflammability. Moreover, the corresponding Li||Li symmetric cell can stable cycle for more than 2000 h with low overpotential at 0.1 mA cm-2 under 60°C. The assembled Li||LiFePO4 pouch cell with integrated electrolyte/cathode interface exhibits excellent rate performances and cycle performances with a capacity retention of 71.4% from 153 mAh g-1 to 109.2 mAh g-1 at 0.1 C over 500 cycles under 60°C. This work provides a promising strategy towards realizing ultrathin flexible solid electrolyte for high-performance all-solid-state lithium batteries.

Lithium metal anodes hold great promise for enabling high-energy density devices compared with the commercialized graphite electrode. However, huge pressure changes during cycling will lead to the pulverization of the 2D lithium anode, thus deteriorating the battery life due to its poor mechanical strength. Herein we report a 3D lithium−boron (LiB) fibrous framework with great compressive strength through electrochemical delithiation. The LiB alloy fibers with a 3D stable structure play the role of an expansion-tolerant substrate, which could effectively hold the Li metal and reduce the internal pressure changes, showing only a 53.7% pressure change compared with the 2D Li/Cuanode-based pouch cell. A quasi-ionic-liquid-based polymer electrolyte layer is introduced by a scalable tape-casting method, generating a LiF-rich layer inside the 3D Li anode through the reaction between the polymer electrolyte and the internal free Li, which can guide the uniform nucleation and growth of Li metal. As a result, the asymmetric Li−Li cell can sustain 5 mAh cm −2 Li plating/ stripping for 1000 h. A 2.1 Ah pouch cell coupling to a LiF-rich interface-protected 3D Li/LiB anode and a Ni-rich cathode of 30 mg cm −2 exhibits an ultrahigh energy density of 403 Wh kg −1 and a stable cycle life of 100 cycles.

A three-step strategy was employed to prepare a self-lubricating and anti-wear graphene oxide/nano-MoS2 (GO/nano-MoS2, abbreviated GMS) hybrid by chemical compounding as a novel multidimensional assembly.

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