XRD Measurement during Charge/Discharge Using All-Solid-State Batteries

Introduction

All-solid-state Na ion batteries are next-generation batteries that are expected to be less expensive than Li ion batteries and have faster charge/discharge performance. When operating all-solid-state batteries, it is necessary to continue applying pressure to make it easier for the ions to move within the solid. With this measurement, using cells that can be charged/discharged while applying pressure to an all-solid-state battery, the behavior of an all-solid-state Na ion battery was verified.

Phase transition analysis

• Analysis: Whole battery
• Analysis method: Operando measurement
• Use: Improving battery performance 
• Analyzed materials: All-solid-state Na ion batteries (Cathode TiS₂, solid-state electrolyte Na₃PS₄, anodes)
• Instrument: SmartLab, all-solid-state battery cells

Figure 1: Elapsed time vs 2θ and charge/discharge profile (inside image)

Figure 2: Representation of solid-state battery pellet and pressure conditions

Cathode TiS₂ exhibited the following changes during charging/discharging.

Phase transition from TiS₂  → Na₀.₅₅TiS₂

(i) Change in lattice constant from Na₀.₅₅TiS₂ → NaTiS₂
(ii) Change in lattice constant from NaTiS₂ →   Na_xTiS₂ (x < 0.55)
(iii) Change in lattice constant from Na_xTiS₂  → NaTiS₂
(iv) Unreacted TiS₂ was partially present

Conclusion

It is possible to measure changes in the crystal phase and lattice constant during charging/discharging in an all-solid-state battery.