Unlocking higher Li-ion conductivity in Zr-based chlorides without compromising the cost-effectiveness

Identifying solid electrolytes with both high Li-ion conductivity and competitive cost is a grand challenge for the pursuit of commercially viable all-solid-state lithium batteries. Without involving overly expensive raw materials, the cost-effective solid electrolytes reported so far may only achieve ionic conductivities of 0.5−2 mS cm −1 at 25 °C, and further improvement seems challenging. Here, we discover that, compared with the extensively utilized metal cations for solid-electrolyte modification, the barely involved non-metal cations with higher ionic potentials may enable faster Li-ion transport. Following this principle, we modify the cost-effective Zr-based chloride solid electrolytes with the highly abundant Si 4+ , whose ionic potential is around 1.5−5 times those of typical metal cations. The 0.6Li 4 SiO 4 -ZrCl 4 obtained this way reaches an ionic conductivity of 3.2 mS cm −1 at 25 °C, greatly exceeding the aforementioned 0.5−2 mS cm −1 range for the existing cost-effective solid electrolytes. Thanks to such improved ionic conductivity, the all-solid-state cells with the Ni-rich layered cathode achieved reversible areal discharge capacities above 10 mAh cm −2 at 25 °C.