Borderline Metal Centers on Nonporous Metal‐Organic Framework Nanowire Boost Fast Li‐Ion Interfacial Transport of Composite Polymer Electrolyte
Jianqi Xu, Guixin Ma, Ning Wang, Simin Zhao, Jisheng Zhou
Abstract
Abstract Metal‐organic frameworks (MOFs) fillers are emerging for composite polymer electrolytes (CPEs). Enhancing Lewis acid–base interaction (LABI) among MOFs, polymer and Li‐salt is expected to promote Li + ‐transport. However, it is unclear how to customize a strong LABI interface. The large surface‐area of classical MOFs also interferes with clarifying the LABI influence on Li + ‐transport. Herein, Bi 3+ as metal centers to design colloidal‐dispersed nonporous MOFs (Bi/HMT‐MOFs) nanowire with a surface‐area of only 17.13 m 2 g −1 to prepare polyethylene oxide (PEO)‐based CPEs (BMCPE) is chosen. The nonporous feature can exclude the surface‐area effect on Li + ‐transport. More interestingly, Bi 3+ is a typical borderline acid, which can interact with both hard‐basic PEO and soft‐basic Li‐salt anion. Accordingly, Bi/HMT‐MOFs are uniformly dispersed in the BMCPE to form a strong LABI interface with PEO and Li‐salt, promoting Li‐salt dissociation and providing rapid Li + ‐transport channels. Despite the ultralow surface‐area of Bi/HMT‐MOFs, BMCPE exhibits significantly enhanced ion‐conductivity and Li + transference number, which completely rival traditional MOFs‐filled CPEs. BMCPE also enables symmetric and full cells with excellent high‐rate performance and long‐term cycling stability. In contrast, when Bi 3+ sites are obscured, electrochemical performances are obviously decreased. Therefore, employing borderline metal centers will be an effective strategy to construct a LABI interface for high‐performance MOFs‐filled CPEs.