Meng Cheng,Tao Qu,Jie Zi,Yaochun Yao,Feng Liang,Wenhui Ma,Bin Yang,Yongnian Dai,Yong Lei
A ceramic in polymer hybrid solid electrolyte (HSE) based on a poly vinylidene fluoride-hexafluoropropylene (PVDF-HFP) polymer comprising Na3Zr2Si2PO12 (NASICON) ceramic particles was prepared by a simple solution casting method followed by activation in a liquid electrolyte. The prepared HSE exhibits good flexibility, high ionic conductivity of 2.25 × 10−3 S cm−1 at room temperature (RT), and good interface stability. The carbon coated sodium vanadium phosphate (Na3V2(PO4)3/C) cathode was synthesized by the sol-gel method and assembled into batteries with different electrolytes. The batteries based on HSE exhibit better electrochemical performance than that of NASICON ceramic solid electrolytes, which delivers a reversible capacity of 98 mAh · g−1 at 0.2 C and exhibits good capacity retention of 85% after 175 cycles at 0.5 C. Not only does the HSE inherit great flexibility, but also exhibits good interfacial contact with electrodes. The schematic diagram of Na-ion conductivity in ceramic, polymer and HSE was illustrated to demonstrate the sodium ion transport mechanism. The HSE with high ionic conductivity and good flexibility for interfacial contact with electrodes shall provide a designing strategy for different solid-state batteries.
Liu Limin,Liang Dongshi,Zhou Xiaoliang,Liu Yujian,Su Jiawen,Xu Yao,Peng Jinsong
NASICON-type material Na 1+ x Zr 2 Si x P 3− x O 12 (0 ≤ x ≤ 3) is considered to be one of the most promising solid-state electrolytes that can be applied in all-solid-state sodium batteries (SSNBs). However, further increasing the ionic conductivity of Na 1+ x Zr 2 Si x P 3− x O 12 (0 ≤ x ≤ 3) to obtain higher performance electrolyte materials is still a challenge for its practical application. Herein, the Na 3.4 Zr 2 Si 2.4 P 0.6 O 12 (NZSP) powder is prepared by the solution-assisted solid-state reaction (SA-SSR), and solid-state electrolytes with excellent electrochemical properties are obtained by doping with NaF as a sintering aid. With the increase of NaF doping, the crystal structure of NZSP is changed as well as a slight excess of Na + may increase the bottleneck size of the crystal, so that it enhances the migration ability of Na + in the crystal. Also, NaF as a sintering aid lowers the sintering temperature, increases the densities and improves the effective contact between crystals, which reduces the grain boundary impedance of NZSP. However, the excessive NaF dopant leads to the generation of microcracks decreasing the Na + conducting and mechanical properties of solid-state electrolytes. Using this simple and low-cost strategy of NaF doping, NZSP-0.3NaF achieves an excellent conductivity of 4.98 mS cm −1 with unexpectedly low activation energy of 0.227 eV. Therefore, this composition is one of the few electrolytes with high conductivity reported so far and is a competitive option for solid-state sodium batteries.
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