# Constructing Enhanced Composite Solid-State Electrolytes with Sb/Nb Co-Doped LLZO and PVDF-HFP
## 4 Conclusions  
In this study, co-doped garnet-type LLZSNO solid electrolytes were successfully prepared by the high-temperature solid-phase method. The effects of different Nb contents on the structural properties and electrochemical performance and the performance of the composite solid electrolytes PVDF-HFP/LLZSNO were investigated. The co-doped LLZSNO shows the maximum ionic conductivities of 2.08 \(\times\) 10\({}^{-4}\) S/cm at room temperature and high relative densities of 88.7%. The results suggest that Sb/Nb dual substitution increases the Li vacancy concentration and transport channel. Due to the addition of LLZSNO  
Figure 6: (**a**) LSV curve of PL-x electrolyte; (**b**) rate performance of PVDF-HFP and CSE; (**c**) constant current cycle test of lithium symmetric battery with PL-0.05; and (**d**) different states of pouch batteries light up small bulbs.  
increasing the disorder of the polymer chain segments, the ionic conductivity, and thermal stability of CSEs, the prepared composite solid-state electrolyte PL-0.05 shows an ionic conductivity of 1.76 \(\times\) 10\({}^{-4}\) S/cm, an electrochemical stability window of 5.2 V, and a lithium-ion transfer number of 0.32. The Li/PL-0.05/Li symmetric battery could cycle for more than 1500 h at a current density of 0.10 mA/cm\({}^{2}\), and the Li/PL-0.05/LiFePO\({}_{4}\) battery exhibits excellent cycle and rate performance. The results show that the co-doped LLZSNO solid electrolyte has a potential application in composite solid electrolytes for higher energy density Li-ion batteries.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app14073115/s1](https://www.mdpi.com/article/10.3390/app14073115/s1)]([https://www.mdpi.com/article/10.3390/app14073115/s1](https://www.mdpi.com/article/10.3390/app14073115/s1)): Figure S1: SEM and EDS mapping of LLZSNO powders; Figure S2: TG-DSC synchronous thermal analysis of solid electrolyte (a) PVDF-HFP, (b) PVDF-HFP/LLZSNO; Figure S3: SEM images comparison of surface morphology between (a) PVDF-HFP, and (b) PVDF-HFP/LLZSNO; Figure S4: Flexibility of (a) Polymer SSE membrane, and (b) CSE membrane; Figure S5: (a-e) EIS, and (f) Arrhenius plot of PVDF-HFP and PL-x solid electrolytes; Figure S6: EIS and DC polarization curves of (a) PVDF-HFP, and (b) PL-0.05; Table S1: Ionic Conductivity and Activation Energy of SSEs at Room Temperature.  
Conceptualization, J.C.; methodology, Y.T.; software, W.C.; validation, J.C. and Y.L.; formal analysis, J.C.; investigation, Y.L.; resources, J.W.; data curation, T.W.; writing--original draft preparation, J.C.; writing--review and editing, C.L.; visualization, Y.L.; supervision, C.L.; project administration, C.L.; funding acquisition, C.L. All authors have read and agreed to the published version of the manuscript.  
This work is financially supported by the Science and Technology Commission of Shanghai Municipality (21 ZR1424900, 19 DZ2271100).  
The data presented in this study are available upon request from the corresponding author due to detailed data involving some privacy.  
The authors declare no conflicts of interest.