LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) is considered as a promising cathode for high-energy-density solid-sate Li metal battery for its high theoretical capacity. However, the high oxidizability and structural instability during charge limit its practical applications. In this work, 1% (in mass) of nanosized Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) was coated on NCM811 to enhance its electrochemical stability with a ceramic/polymer composite electrolyte. A robust, ultrathin (11 μm) composite electrolyte film was prepared by combining poly(vinylidene fluoride) (PVDF) with polyethylene oxide (PEO)-Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO). An in-situ polymerization process was used to enhance the interface between the PVDF/PEO-LLZTO (PPL) composite electrolyte and the LATP-coated NCM811 (LATP-NCM811). Coin-type Li|LATP-NCM811 cell with the PPL electrolyte exhibits stable cycling with an 81% capacity retention after 100 cycles at 0.5 C. Pouch-type cell was also fabricated, which can be stably cycled for 70 cycles at 0.5 C/1.0 C (80% retention), and withstand abuse tests of bending, cutting and nail penetration. This work provides an applicable method to fabricate solid-state Li metal batteries with high performance.

Na–CO₂ batteries recently are emerging as promising energy-storage devices due to the abundance of Na in the earth’s crust and the clean utilization of greenhouse gas CO₂. However, similar to metallic Li, metallic Na also suffers from a serious issue of dendrite growth upon repeated cycling, while a facile method to solve this issue is still lacking. In this work, we report an effective, environmentally friendly method to inhibit Na dendrite growth by in situ constructing a stable, NaF-rich solid electrolyte interface (SEI) layer on metallic Na via adding a small amount (~3 wt%) of fluorinated graphene (FG) in bulk Na. Inspired by the forging processing, a uniform Na/FG composite was obtained by melting and repetitive FG-adsorbing/hammering processes. The Na/FG–Na/FG half cell exhibits a low voltage hysteresis of 110–140 mV over 700 h at a current density up to 5 mA cm⁻² with an areal capacity as high as 5 mAh cm⁻². Na–CO₂ full cell with the Na/FG anode is able to sustain a stable cycling of 391 cycles at a limited capacity of 1000 mAh g⁻¹. Long cycle life of the cell can be attributed to the protecting effect of the in situ fabricated NaF-rich SEI layer on metallic Na. Both experiments and density functional theory (DFT) calculations confirm the formation of the NaF-rich SEI layer. The inhibition effect of the NaF-rich SEI layer for Na dendrites is verified by in situ optical microscopy observations.

Lithium metal batteries are regarded as promising alternatives to lithium ion batteries due to their high specific capacity. However, lithium dendrite growth during cycling causes safety problem and rapid capacity loss. Here, we report a composite Li anode composed (LYF) of metallic Li and trace amounts (1–2 wt%) of two-dimensional YF_δ. The lithiophilic nature of YF_δ enables its homogeneous dispersion in metallic lithium. The LYF electrode exhibits lower resistance, higher chemical and mechanical stability, and longer cycle life compared to bare Li electrode due to uniform Li stripping and plating with YF_δ incorporation, which was confirmed by in-situ optical microscope observation. X-ray photoelectron spectroscopy reveals that LiF can in-situ form on the LYF electrode with reactions between Li and YF_δ during cycling. The spontaneous reactions are clarified by density functional theory calculations. A quasi-solid-state cell with LYF anode, LiFePO₄ cathode and cathode-supported solid electrolyte layer has been constructed with a soft interface constructed between Li anode and solid electrolyte by in-situ thermal polymerization. The cell shows a high initial discharge capacity of 147 mAh g⁻¹ at 0.5 C at 60 ℃ and sustains a stable cycling over 50 cycles with the in-situ formed LiF-rich layer and soft interface.