posted on 2022-12-16, 13:43authored byEveline van der Maas, Wenxuan Zhao, Zhu Cheng, Theodosios Famprikis, Michel Thijs, Steven R. Parnell, Swapna Ganapathy, Marnix Wagemaker
Li3YX6 (X = Cl, Br) materials are
Li-ion
conductors that can be used as solid electrolytes in all solid-state
batteries. Solid electrolytes ideally have high ionic conductivity
and (electro)chemical compatibility with the electrodes. It was proven
that introducing Br to Li3YCl6 increases ionic
conductivity but, according to thermodynamic calculations, should
also reduce oxidative stability. In this paper, the trade-off between
ionic conductivity and electrochemical stability in Li3YBrxCl6–x halogen-substituted compounds is investigated. The compositions
of Li3YBr1.5Cl4.5 and Li3YBr4.5Cl1.5 are reported for the first time,
along with a consistent analysis of the whole Li3YBrxCl6–x (x = 0–6) tie-line. The results show that, while Br-rich
materials are more conductive (5.36 × 10–3 S/cm
at 30 °C for x = 4.5), the oxidative stability
is lower (∼3 V compared to ∼3.5 V). Small Br content
(x = 1.5) does not affect oxidative stability but
substantially increases ionic conductivity compared to pristine Li3YCl6 (2.1 compared to 0.049 × 10–3 S/cm at 30 °C). This work highlights that optimization of substitutions
in the anion framework provide prolific and rational avenues for tailoring
the properties of solid electrolytes.