ALL-SOLID-STATE LITHIUM SECONDARY, BATTERIES USING SULFIDE-BASED GLASS CERAMIC ELECTROLYTES

Highly conductive glass-ceramic electrolytes are successfully prepared in the system Li ₂ S - P ₂ S ₅ with 70 and 80 mol% Li ₂ S . The conductivities of these electrolytes are respectively 3.2 × 10^-3 and 1.0 × 10^-3 S cm ^-1 at room temperature. The precipitated crystals upon heat treatment of the glass are new superionic phase Li ₇ P ₃ S ₁₁ and thio-LISICON II analog Li _3+5x P _1-x S ₄, respectively. The crystal structure of the new phase Li ₇ P ₃ S ₁₁ is analyzed and found to have a triclinic unit cell with space group of P-1 and to contain [Formula: see text] and [Formula: see text] ions. All-solid-state batteries using the Li ₂ S - P ₂ S ₅ glass-ceramics are fabricated in order to evaluate the cell performance as a lithium secondary battery. The cells In /80 Li ₂ S ·20 P ₂ S ₅ (mol%) glass-ceramic/ LiCoO ₂ exhibit excellent cycling performance of over 500 times with no decrease in the discharge capacity (100 mAh g^-1) at limited current densities. They also worked under very high current densities of 10 mA cm^-2 when oxide- or sulfide-coated LiCoO ₂ particles were used as an active material.