Coaxially MXene-confined solid-state electrolyte for flexible high-rate lithium metal battery

Solid-state polymer electrolytes (SPEs) possess conspicuous merits of facile manufacturing, superior mechanical toughness, and favorable chemical stability with Li anodes, but the intrinsically low room temperature ionic conductivity (~10−8−10−6 S cm−1) and negligible Lithium-ion transfer number (0.1~0.2) badly inhibited its commercial application in lithium metal batteries (LMBs). Herein, we design the three-dimensionally and coaxially MXene-confined solid-state polymer electrolyte (C-MX SPE) for the directional acceleration movement of Li+ ion by introducing MXene nanosheets into the polyacrylonitrile (PAN) fiber. Benefiting from the confinement effect, the homogeneously and coaxially MXene-confined SPE possess an impressive Li+ ion transference number of 0.72 and ionic conductivity of 3.07×10−3 S cm−1 at room temperature, which are 3 and 20 times of magnitude higher than the randomly MXene-dispersed (R-MX) SPE (0.22 and 1.61×10−4 S cm−1), respectively. Also, the Lithium/SPE/Lithium symmetric cell exhibits a flat galvanostatic charge/discharge under 1 mA cm−2 for 2000 h without dendrites, revealing its 3D skeleton structure could mechanically suppress Li dendrite growth. Based on it, the assembled flexible solid-state lithium metal batteries (SSLMBs) possess a rate-capability of 101 mAh g−1 @ 10 C, a capacity retention of 85.18% after 500 cycles @1 C at room temperature and a stability of bending-needling-cutting performance. Evidently, this three-dimensionally and coaxially MXene-confined SPE may represent a promising strategy to address the random distribution and agglomeration of inorganic fillers in SPE and guide a direction for the development of high-performance, secure, and flexible SSLMBs.