Electrochemical performance as cathode of lithium iron silicate, borate and phosphate glasses with different Fe2+ fractions

Abstract Lithium iron silicate glasses with different fractions of Fe 2 + ions of 40Li 2 O–10Fe 2 O 3 –50SiO 2 (mol%) are prepared by conventional melt-quenching method and reducing heat treatment technique, and their electrochemical properties as cathode materials for Li + ion secondary batteries (LIBs: lithium ion batteries) are examined. It is demonstrated for the first time that Li 2 O–Fe 2 O 3 –SiO 2 glasses work as cathode in LIBs, e.g., the discharge capacity at 100/C in the first cycle is 54.6 mAh g − 1 . The heat treatment at 350 °C in 5% H 2 /Ar induces not only the increase in the fraction of Fe 2 + ions but also the increase in the packing density and the decrease in the electrical conductivity. It is clarified that the discharge capacity of the glasses is largely improved due to the increase in the fraction of Fe 2 + ions. The data on thermal, physical, and discharge properties obtained in 40Li 2 O–10Fe 2 O 3 –50SiO 2 glasses are compared with those in borate and phosphate glasses of 40Li 2 O–10Fe 2 O 3 –50(B 2 O 3 , P 2 O 5 ).