Amorphous Boron Nitride Nanosheet-Based Solid State Electrolytes with High Ionic Conductivity

Amorphous boron nitride nanosheets, with natural electrical insulation, outstanding chemical stability and mechanical properties, are introduced as a matrix to be incorporated with lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) and polymer polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), for constructing a novel composite solid-state electrolyte by a simple solution-casting method. Amorphous boron nitride nanosheets are produced via a combination method of ball milling and pure water exfoliation. The obtained composite solid-state electrolyte containing 40 % (mass fraction) PVDF-HFP shows a high lithium ion conductivity (1.936x10-3 S cm-1) and lithium ion transference number (0.47), and a wide electrochemical stability window (5 V) at room temperature. The LiFePO4/Li based all solid-state battery, consisting of the composite solid electrolyte (40 % PVDF-HFP), delivers a capacity of 128.1 mAh g-1, a Coulombic efficiency of 99.79 % after 500 cycles and a capacity retention rate of 94.5 % at 1.0 C and 25 degrees C. The composite solid electrolyte (40 % PVDF-HFP) can maintain flat and stable stripping/plating plateaus for over 800 hours in symmetrical cells. The amorphous boron nitride nanosheets with high lithium ion conductivity are employed to construct solid-state electrolytes, which is important significant for the development of high energy density, high safety, and long cycle life all-solid-state lithium-ion batteries. Amorphous boron nitride nanosheets are prepared by ball milling combined with pure water exfoliation method. High ceramic content amorphous boron nitride (BN) nanosheets/polymer polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) composite solid electrolyte (CSE) are prepared by solution casting method. When PVDF-HFP accounts for 40 %, the amorphous BN nanosheets/PVDF-HFP-40 % (CSE-40 %) composite electrolyte exhibits excellent electrochemical performance, thermal stability, and mechanical properties. image