Low-Temperature Performance of a Ferroelectric Glass Electrolyte Rechargeable Cell

An electrochemical cell that powers all-electric road vehicles will likely have an alkali-metal anode and the ability to operate down to −20 °C. The traditional all-solid-state batteries can only perform well at temperatures above room temperature. We have shown elsewhere that an alkali-metal negative electrode can be plated dendrite-free from a ferroelectric amorphous-oxide (glass) Li⁺ or Na⁺ electrolyte having a room-temperature Li⁺ or Na⁺ conductivity σ_i ≈ 2.5 × 10^–2 S cm^–1 which is similar to that of a liquid electrolyte. Here, it is demonstrated that the ionic conductivity of the electrolyte is σ_i ≈ 10^–2 S cm^–1 at −20 °C after optimization, and the dielectric constant is ε′_r ≈ 6 × 10⁵ at −35 °C. Moreover, it is shown that the remanent polarization of the ferroelectric-electrolyte (polarization at zero potential) adds to the capacity of the cell. The electrochemical cycling performances between −35 and 25 °C of the Li⁺-glass electrolyte in gold and lithium symmetric cells and in full cells are presented. Furthermore, it is shown that a coin-cell with the ferroelectric Li-glass electrolyte at −35 °C with output current of 56 μA cm^–2 can light a red LED at 1.5 V. Finally, it is concluded that the Li⁺-glass electrolyte performs very well in symmetric cells and performs reasonably well down to −20 °C in asymmetric cells that also rely on the performance of the cathode and on the electrolyte/cathode interface.