Constructing host-guest recognition electrolytes promotes the Li⁺ kinetics in solid-state batteries

Owing to their good interfacial contact with electrodes, solid polymer electrolytes (SPEs) are believed to be a promising candidate for solid-state batteries. However, the inferior kinetics of SPEs, which are caused by their lower Li+ conductivity and narrower electrochemical window, have severely hindered their applications. Here, a novel host-guest recognition gel polymer electrolyte (GPE) strategy is proposed and further combined with in situ polymerization technology to construct a MOFs-GPE system. Innovatively, Ti-MOFs with synergetic various sites serve as a "host" platform for the GPE to tune the electrolyte properties; they not only act as a highly effective accelerator for Li+ ion conduction, but also afford favorable properties in terms of mechanical strength and withstanding high voltage. The MOFs-GPE system enables the stable operation of state-of-the-art cathodes LiFePO4 and high-voltage LiNi0.9Co0.05Mn0.05O2. The as-assembled LiNi0.9Co0.05Mn0.05O2|G@MOFs (Ti)|graphite full battery demonstrates a good cycling stability with 71.4% capacity retention after 250 cycles at room temperature. In situ measurements and DFT calculations reveal that the transport kinetics of the Li+ ions in the composite electrolyte can be accelerated by the introduced MOF host. This work provides significant guidance for improving ion transport in host-guest recognition SPEs and an understanding of the potential Li+ kinetics mechanisms.