Controlling Sodium Dendrite Growth via Grain Boundaries in Na3Zr2Si2PO12 Electrolyte

Abstract Na 3 Zr 2 Si 2 PO 12 (NZSP)‐based NASICON solid‐state electrolytes (SSEs) show not only competitive ionic conductivity but also high chemical stability in air, holding a great promise for enabling the use of sodium metal anode in solid‐state sodium batteries. However, sodium (Na) metal dendrite growth inside SSE always leads to undesirable short‐circuiting in battery even no obvious changes in interfacial contact loss and interfacial decomposition during cycling. How to control Na metal dendrite growth and in situ observe the effect of SSE/Na interface change on dendrite growth is quite challenging. Herein, an in situ synchrotron‐based X‐ray imaging method is developed to systematically investigate the dendrite origin in NZSP‐based SSEs. It is find that the dendrite growth intrinsically depends on the grain boundaries (GBs) in NZSP and the NZSP/Na interfacial properties. It is confirmed that Na dendrite infiltration kinetic evolution in NZSP is strongly associated with Na ion/electron conductivity and Young's modulus of GBs. Moreover, the electro‐chemo‐mechanical phase‐field model evaluation demonstrates that the basic reason for Na metal dendrite intrusion into the GBs of SSE is a combination of local polarization potential and the presence of stress formed at GBs.