Increasing sinterability and ionic conductivity of Na3Zr2Si2PO12 ceramics by high energy ball-milling

Abstract

Na3Zr2Si2PO12 (NZSP) is one of the most promising solid electrolytes for all-solid-state sodium-ion batteries. In this work, NZSP was obtained using the mechanochemically assisted solid-state route. The effect of high-energy ball milling (HEBM) on sintering and conductive properties of as-prepared NZSP was shown. It was mentioned that the polydisperse particle size distribution of HEBM samples has a positive effect on densification during the pressing, which enables using low pressure (10 MPa). High-density ceramics (3.14 g∙cm−3) with high ionic conductivity (2.12∙10−3 S∙cm−1) and low activation energy (0.31 eV) was obtained after 10 min of HEBM. The value of the electronic conductivity obtained from the analysis of DC polarization using blocking Au electrodes is equal to 4.85∙10−9 S∙cm−1. The NZSP ceramics shows stability during the charge-discharge process at a current density of 0.1 mA∙cm−2 for 200 h at room temperature. The transference number of Na+ ions is 0.95 and practically does not change during cycling. The high ionic conductivity, exceeding 10−3 S∙cm−1, is confirmed by measuring ionic conductivity at AC and DC current.