Construction of Inorganic/Polymer Tandem Layer on Li Metal with Long‐Term Stability by LiNO₃ Concentration Gradient Electrolyte

Abstract Metal electrode with long cycle life is decisive for the actual use of metal rechargeable batteries, while the dendrite growth and side reaction limit their cyclic stability. Herein, the construction of polymer and inorganic‐rich SEI tandem layer structure on Li metal can be used for extraordinarily extending its cycle life is reported, which is generated by an in situ PVDF/LiF/LiNO₃ (PLL) gel layer on the surface of Li metal with a chemically compatible ether solvent. The cycle life of Li//Li cells with the tandem layer structure is over 6000 h, six times longer than those with LiNO₃ homogeneous electrolyte. It highlights the importance of LiNO₃ concentration gradient electrolyte formed by the in situ PLL gel layer, in which highly concentrated LiNO₃ is confined on the surface of Li metal to generate the uniform and inorganic‐rich LiF/Li₂O/Li₃N layer on the bottom of PVDF/LiF with good mechanical strength, resulting in the dendrite free anode in cell cycling. The assembled Li//LiFePO₄ and Li//NMC811 batteries show the capacity retention rate of 80.9% after 800 cycles and 82.3% after 500 cycles, respectively, much higher than those of references.