Self-shutdown function and uniform Li-ion flux enabled by a double-layered polymer electrolyte for high-performance Li metal batteries

Polymer electrolytes with high safety and high performance are considered to be one of the most promising candidates to upgrade the traditional organic-solvent-based lithium-ion batteries. However, unlimited thermal runaway and incompatibility between electrolyte and electrode greatly limit the development of advanced polymer electrolytes. In this work, we fabricated bilayer polymer electrolytes (DLMs) with a multilevel heterostructure to achieve high-temperature self-shutdown functionality and uniform Li-ion flux. The double-layer heterostructure consists of a self-shutdown layer in contact with the cathode and an ionic liquid composite polymer layer in contact with the anode, which can achieve effective electrode–electrolyte interface contact, fast self-shutdown, and more than 900 h of stable lithium plating/stripping. In addition, the NCM523/DLM/Li battery exhibits a high reversible capacity of 129.7 mAh g −1 at 0.5 C and maintains high-capacity retention (> 89%) after 200 charge–discharge cycles. This study shows a great advantage in handling thermal abuse and a stable lithium anode, suggesting a promising approach to the high-safety lithium metal batteries.