A Li-enriched amorphous Zr-based oxychloride solid electrolyte for high-rate and long-cycling all-solid-state ultrahigh-nickel cathodes

The Zr-based chloride solid electrolyte (SE) Li₂ZrCl₆ is well compatible with 4 V-class cathodes and cost-effective, yet its low conductivity (<1 mS cm⁻¹) would restrain the capacity delivery of the electrodes especially at high rates. Herein, we further elevated the room-temperature ionic conductivity of Zr-based lithium oxychloride to 2.11 mS cm⁻¹ in Li_2.15Zr_0.85In_0.15Cl₄O by tuning its Li content through partial substitution of Zr⁴⁺ with In³⁺ in the formula Li_2+xZr_1−xIn_xCl₄O. Cold-pressed Li_2.15Zr_0.85In_0.15Cl₄O presents both a dense morphology arising from its amorphous phase and enhanced ionic conductivity, which is significantly higher than that of Li₂ZrCl₆, facilitating better solid–solid contact and improved reaction kinetics in the composite cathodes. As a result, the all-solid-state cathode coupling Li_2.15Zr_0.85In_0.15Cl₄O and LiNi_0.92Co_0.03Mn_0.05O₂ shows a capacity of 175.3 mAh g⁻¹ at 4C and a retention of 91.44% for 450 cycles when charged to 4.3 V vs. Li⁺/Li. More attractively, as the charge upper limit increases to 4.8 V, Li_2.15Zr_0.85In_0.15Cl₄O also enables ultrahigh-nickel cathodes to cycle for over 250 cycles with a capacity retention of 81.86%.