(665f) Sacrificial Presodiation Additive Toward High-Capacity Sodium All-Solid-State Batteries

Sodium all-solid-state batteries (NaSSBs) are garnering interest due to their sufficient element resources and superior safety features. Using an alloy-type anode in the full cell configuration, such as tin (Sn) and antimony (Sb), can substantially enhance capacity and energy density comparing to state-of-art hard carbon anode. Additionally, due to the high Na+ diffusivity, the alloy and de-alloy process do not require mixing with electrolytes to enhance ionic conductivity, which reduces inactive component in NaSSBs. However, the irreversible loss of Na⁺ at the alloy anode side during the initial cycle results in diminished capacity and stability, impairing the battery's overall performance. This study presents an easy-to-implement cathode presodiation strategy that effectively mitigates Na⁺ loss with an additive in the cathode and improves overall energy density. Na2S was used as the main component in pre-Na agent due to the large theoretical capacity (~700mAh/g) and matched Na+ ion extraction voltage (~1.8V vs. Na/Na+). Other components of Na₃PS₄ (NPS) and acetylene black (AB) were used to activate Na2S by introducing ionic and electronic conductivity. The optimized composition of pre-Na agent (Na2S:NPS:C=2:1:1) delivers a high capacity of 550mAh/g with a 90% utilization of its theoretical capacity,. Material characterization reveals the mechanism of the sodium supplement process: chemical composition and electrochemical changes during charging. The cell performance with NaCrO₂ (NCO), Na_0.55Ni_0.1Fe_0.1Mn_0.8O₂ (NNFM) cathode, and Sn, Sb anode shows good material compatibility, promoted cycling performance and interfacial stability. This work goes beyond previous efforts by first providing a scalable, accessible, and efficient method to enhance the full-cell performance of NaSSBs significantly, advancing the technology of solid-state batteries, and offering a promising avenue for sustainable and efficient energy storage.