Dendrite-tolerant all-solid-state sodium batteries and an important mechanism of metal self-diffusion

Abstract Inhibition of dendrite growth in all-solid-state lithium batteries (ASSLBs) has long been a challenge to the field. In the present study, the conditions for dendrite growth for a similar but less mature technology, all-solid-state sodium batteries (ASSNBs), are investigated. By simply sticking sodium metal to Na3.4Zr2(SiO4)2.4(PO4)0.6 (NZSP) ceramic pellets and without applying external pressure during operation, the critical current density of Na/NZSP/Na symmetric ASSNBs reaches 9 mA cm−2 at 25 °C. The cells can be stably operated at an areal capacity of 5 mAh cm−2 (per half cycle, with 1.0 mA cm−2) at 25 °C for 300 h in a galvanostatic cycling measurement without any dendrite formation. The results outperform the existing ASSLBs and ASSNBs, and also go beyond satisfying the requirements for practical applications. The influence of the high metal self-diffusion coefficient on the dendritic plating/stripping is regarded as the most likely reason for the high dendrite tolerance of ASSNBs. A mathematical model based on Fick's second law was applied as a first approximation to illustrate this influence. Full ASSNBs were fabricated with infiltrated Na3V2(PO4)3 (NVP) as the cathode and can be stably operated with a capacity of 0.60 mAh cm−2 at high rate of 0.5 mA cm−2 at room temperature.