In Situ Construction a Stable Protective Layer in Polymer Electrolyte for Ultralong Lifespan Solid‐State Lithium Metal Batteries

/Li SLMBs exhibit an impressive ultra-long cycle lifespan over 1300 cycles at 1 C, as well as 1600 cycles at 0.5 C with a capacity retention ratio over 80%. This work offers an effective strategy for the construction of the stable electrolyte/Li interface, paving the way for the rapid development of long lifespan SLMBs.