Fluorine-doped argyrodite sulfide electrolyte enables commercial LiCoO2 use for 4.6 V high-voltage all-solid-state batteries

Sulfide solid-state electrolytes (SSEs) are promising candidates for next-generation high-safety all-solid-state lithium batteries (ASSLBs). However, they still face challenges such as low anodic stability limits and poor interfacial compatibility with high-voltage cathode active materials. Here, we present a series of fluorine-doped argyrodite sulfide SSEs, Li_5.5PS_4.5Cl_1.5-xF_x (LPSCl_1.5-xF_x) (0 < x ≤ 1.5), toward high-voltage LiCoO₂ (LCO)-based ASSLBs, via the <i>in situ</i> formation of a stable fluorine-containing passivating interphase on the cathode active materials surface. Notably, fluorine incorporation significantly raises the practical oxidation limit of LPSCl_1.5 from 2.4 to 3.5 V for LPSClF_0.5, while maintaining a high room-temperature ionic conductivity of 3.3 mS cm^-1. This enhancement is attributed to increased lithium-ion disorder and fluorine's high electronegativity. The ASSLBs, fabricated by directly assembling an LPSClF_0.5 SSE with an uncoated commercial LCO cathode, demonstrate stable cycling with low polarization voltage at 4.3 V (vs. Li⁺/Li), achieving 92.1% capacity retention after 700 cycles at 0.2 C. Remarkably, even under a 4.6 V high-voltage condition, our battery maintains 96.2% capacity retention over 300 cycles, attributed to the <i>in situ</i> formation of a stable fluorine-containing cathode-electrolyte interphase on the LCO surface. When coupled with a lithium metal anode, Li|LPSClF_0.5|LCO ASSLB achieved stable cycling at 4.6 V and delivered 137 mAh g^-1 after 100 cycles at 0.5 C. Significantly, the Si|LPSCl_1.5|LPSClF_0.5|LCO ASSLB, cycled at an ultra-high mass loading LCO of 203.8 mg cm^-2, exhibits an exceptional areal capacity of 25.7 mAh cm^-2, demonstrating immense potential of LPSClF_0.5 SSE for practical high-energy ASSLBs.