Novel quasi-solid-state composite electrolytes boost interfacial Li+ transport for long-cycling and dendrite-free lithium metal batteries

Solid-state composite electrolytes (SCEs) have received wide attention due to their advantages of both solid-state polymer electrolytes and inorganic ceramic electrolytes. However, poor interfacial compatibility in SCEs still limits their practical applications in lithium metal batteries. Herein, a lotus pod-inspired flexible PC-g-PMT/LL-g-PMT20 membrane composed of zero-dimensional LLZTO-g-PVIM+TFSI− (denoted as LL-g-PMT) hairy nanoparticle, one-dimensional PVDF-CTFE-g-PVIM+TFSI− (denoted as PC-g-PMT) comb polymer, and lithium salt LiTFSI (LLZTO = Li6.4La3Zr1.4Ta0.6O12; PVDF-CTFE = poly(vinylidene fluoride-co-chlorotrifluoroethylene); PVIM+TFSI− = poly(1-butyl-3-vinylimidazolium bis(trifluoromethylsulphonyl)imide); LiTFSI = lithium bis(trifluoromethylsulphonyl)imide) is designed and prepared. Our PC-g-PMT/LL-g-PMT20 membrane facilitates molecular-level homogeneous lithium ion (Li+) flux, provides fast transmission pathways for Li+ by the three-dimensional well-developed porous framework, and improves interfacial stability via molecular engineering. The quasi-solid-state composite electrolytes (QSCEs) can be further obtained facilely via introducing plasticizer into PC-g-PMT/LL-g-PMT20 membrane. The as-obtained QSCEs (e.g., PC-g-PMT/LL-g-PMT20/P) integrate features of LLZTO-enhanced Li+ conducting and mechanical properties, PVDF-CTFE backbone-induced flexibility, and PVIM+TFSI− side-chain-strengthened interfacial compatibility. As a result, our PC-g-PMT/LL-g-PMT20/P has a membrane thickness as low as 22 µm, but still delivers an ionic conductivity as high as 6.03 × 10−4 S cm−1 at room temperature. Furthermore, Li/LFP full cell with PC-g-PMT/LL-g-PMT20/P exhibits excellent rate and cycling performance.