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

Abstract

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 LiNi_0.9Co_0.05Mn_0.05O₂. The as-assembled LiNi_0.9Co_0.05Mn_0.05O₂|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.