Low-Enthalpy and High-Entropy Polymer Electrolytes for Li-Metal Battery

lonic-conductive solid-state polymer electrolytes are promising for the development of advanced lithium batteries yet a deeper understanding of their underlying ion-transfer mechanism is needed to improve performance.Here we demonstrate the low-enthalpy and high-entropy(LEHE)electrolytes can intrinsically generate remarkably free ions and high mobility,enabling them to efficiently drive lithium-ion storage.The LEHE electrolytes are constructed on the basis of introducing CsPbl_(3)perovskite quantum dots(PQDs)to strengthen PEO@LiTFSI complexes.An extremely stable cycling>1000 h at 0.3 mA cm^(-2)can be delivered by LEHE electrolytes.Also,the as-developed Li|LEHE|LiFePO_(4)cell retains 92.3%of the initial capacity(160.7 mAh g^(-1))after 200 cycles.This cycling stability is ascribed to the suppressed charge concentration gradient leading to free lithium dendrites.It is realized by a dramatic increment in lithium-ion transference number(0.57 vs 0.19)and a significant decline in ion-transfer activation energy(0.14 eV vs 0.22 eV)for LEHE electrolytes comparing with PEO@LiTFSI counterpart.The CsPbl_(3)PQDs promote highly structural disorder by inhibiting crystallization and hence endow polymer electrolytes with low melting enthalpy and high structural entropy,which in turn facilitate long-term cycling stability and excellent rate-capability of lithium-metal batteries.