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

Highly conductive glass-ceramic electrolytes are successfully prepared in the system Li2S-P2S5 with 70 and 80 mol% Li2S. The conductivities of these electrolytes are respectively 3.2 x 10(-3) and 1.0 x 10(-3) S cm(-1) at room temperature. The precipitated crystals upon heat treatment of the glass are new superionic phase Li7P3S11 and thio-LISICON II analog Li3+5xP1-xS4, respectively. The crystal structure of the new phase Li7P3S11 is analyzed and found to have a triclinic unit cell with space group of P - 1 and to contain PS43- and P2S74- ions. All-solid-state batteries using the Li2S-P2S5 glass-ceramics are fabricated in order to evaluate the cell performance as a lithium secondary battery. The cells In/80Li(2)S.20P(2)S(5) (mol%) glass-ceramic/LiCoO2 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 LiCoO2 particles were used as an active material.