Dual-channel MOF enabling high-flux Li+ conduction and in situ LiI-rich SEI for high-performance solid-state lithium metal batteries

Abstract

Solid-state lithium metal batteries (SSLMBs) face critical challenges from dendrite growth and unstable interfaces. While composite polymer electrolytes (CPEs) offer promise, poor ionic conductivity (<10⁻⁵ S cm⁻¹), low Li⁺ transference numbers (t_Li+ < 0.5), and inadequate interfacial stability limit practical application. Herein, we design a dual-channel metal-organic framework (MOF)-based CPEs that simultaneously regulate ion transport and construct a high-conductivity interphase. This MOF features two distinct channels. The one imposes spatial confinement (0.57 nm in pore size) to suppress anion migration (TFSI⁻), while the other facilitates immobilizing TFSI⁻ through iodine-mediated nucleophilic substitution. More importantly, the liberated I⁻ reacts with Li⁺ to in situ generate lithium iodide (LiI)-enhanced solid-electrolyte interphase (SEI), replacing insulating LiF-rich counterparts. This LiI-SEI exhibits superior ionic conductivity and homogenizes Li⁺ flux to suppress dendrites. Integrated into a poly(vinylidene fluoride)-cohexafluoropropylene (PVDF-HFP) matrix, the MOF CPE achieves exceptional ionic conductivity (2.13×10⁻⁴ S cm⁻¹) and a high t_Li+ of 0.95 (25 °C). Density functional theory and molecular dynamics calculations verify ion-regulation mechanisms. As a result, LiFePO₄//Li cells retain 94.99% capacity after 800 cycles (1 C), while NCM811//Li cells demonstrate sustained stability over 200 cycles. This work provides valuable insights into the design of multifunctional MOF ionic conductors for high-performance SSLMBs.