High compatible double surface-modification SB-PVDF/SB-Li7La3Zr2O12 composite solid electrolytes

Inorganic/organic composite solid electrolytes are receiving the ever-increasing attention due to high safety and flexibility, however, inferior organic/inorganic interface compatibility also leads to the serious agglomeration of ceramic particles and severe blockage of Li+ transport. Grafting amphoteric sulfonate betaine (SB) onto the surfaces of inorganic/organic components could act as the “wielding flux” and the ion-conductive interface layer, thus resulting in a homogeneous dispersion of the inorganic components, high interface compatibility and ionic conductivity. Herein, a series of composite solid electrolytes were prepared by scraping method, in which SB-modified PVDF (SB-PVDF) acted as the ion-conductive polymer matrix and combined with SB-modified Li7La3Zr2O12 (SB-LLZO) with the different contents (0%, 10%, 20%, 30% and 40%) and 20% bis(trifluoromethane) sulphonyl lithium (LiTFSI). The resultant composites were marked as 0 % SB-LLZO/SB-PVDF/LiTFSI, 10 %SB-LLZO/SB-PVDF/LiTFSI, 20 %SB-LLZO/SB-PVDF/LiTFSI, 30 %SB-LLZO/SB-PVDF/LiTFSI and 40 %SB-LLZO/SB-PVDF/LiTFSI, respectively. Desirably, 30 %SB-LLZO/SB-PVDF/LiTFSI exhibited high ionic conductivity of 1.95 × 10-4 S/cm, high Li+ transference number (tLi+) of 0.71 and wide electrochemical stability window of 5.31 V. Furthermore, the corresponding Li//30 %SB-LLZO/SB-PVDF/LiTFSI//LiFePO4 cell delivered the reversible discharge capacity of 136.9 mAh/g and capacity retention of 95.1% after 200 cycles at 1.0 C. Seemingly, such a double-surface-modification structural design of the composite solid electrolyte showed the promising potential for solid state lithium ion batteries.