All-solid-state lithium metal batteries (LMBs) are currently one of the best candidates for realizing the yearning high-energy-density batteries with high safety. However, even polyethylene oxide (PEO), the most popular polymeric solid-state electrolyte (SSE) with the largest ionic conductivity in the category so far, has significant challenges due to the safety issues of lithium dendrites, and the insufficient ionic conductivity. Herein, molecular sieve (MS) is integrated into the PEO as an inert filler with the liquid metal (LM) as a functional module, forming an "LM-MS-PEO" composite as both SSE with enhanced ionic conductivity, and protection layer against lithium dendrites. As demonstrated by theoretical and experimental investigations, LM released from MS can be uniformly and efficiently distributed in PEO, which could avoid agglomeration, enable the effective blocking of lithium dendrites, and regulate the mass transport of Li ions, thus achieving even deposition of lithium during charge/discharge. Moreover, MS could reduce the crystallinity of PEO, improve lithium-ion conductivity, and reduce operating temperature. Benefiting from the introduction of the functional MS/LM, the LM-MS-PEO electrolyte exhibits fourfold higher lithium ionic conductivity than the pristine PEO at 40 °C, while the as-assembled all-solid-state LMBs have four to five times longer stable cycle life.
Keywords: all-solid-state lithium metal batteries; functional protective electrolyte; liquid metal; lithium dendrite; molecular sieve.
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