Heterostructured Gel Polymer Electrolyte Enabling Long-Cycle Quasi-Solid-State Lithium Metal Batteries

For rechargeable lithium–metal batteries (RLBs), gel polymer electrolytes (GPEs) are a very competitive and pragmatic option because the special composite structure could restrain the uncontrolled lithium dendrite in a liquid electrolyte and avoid the poor interface contact for a solid-state electrolyte. However, the difficulty lies in finding a delicate balance between ion transport and interface stability. Herein, a heterostructured GPE, in which a metal–organic framework layer and an ultrathin Al2O3 deposition are coated on the same side of a polymer matrix, is fabricated to homogenize lithium ion transport and stabilize the lithium anode interface. With the heterostructured GPE, the Li+ transference number is improved to 0.74, and the lithium metal electrode displays an enhanced cycle stability over 1000 h. Moreover, Li-rich Mn-based layered oxides, the high-capacity cathode material, are matched for the first time with a lithium–metal anode to assemble a quasi-solid-state RLB, which delivers an initial discharge capacity of 257.5 mAh g–1 with a long-cycle capacity retention of 84.6% after 500 cycles at a rate of 0.2C.