HIGH LITHIUM CONTENT OF LIXNI1-XO (0-LESS -THAN-X-LESS-THAN-0.5) FOR MOLTEN-CARBONATE FUEL-CELL CATHODE

The dissolution of lithiated nickel oxide and the deposition of dissol ved nickel ions in molten carbonates electrolyte under cell operating conditions is considered to be one of the most important problems conc erning molten carbonate fuel cell (MCFC) development. Lithiated nickel oxide (LixNi1-xO, 0<x<0.5) has a hexagonal phase over a wide range of lithium concentrations 1). LixNi1-xO which is in-situ oxidized and li thiated from the raw materials under a cathodic condition is stabilize d between 0.02 and 0.04 of the x value. Therefore, LixNi1-xO with low lithium contents (0.02<x<0.04) is ordinarily used as the MCFC cathode material. LixNi1-xO with high lithium contents (0.1<x<0.5) as an impro ved cathode material for MCFC was studied for solubility restraint, It was found that LixNi1-xO with high lithium contents had a relatively lower rate of solubility than LixNi1-xO with low lithium contents and the changes in the lithium content of LixNi1-xO were very slow in molt en carbonates. The amount of deposited nickel in the electrolyte using LixNi1-xO with high lithium contents as the cathode material was also measured after the single cell operation. The retarding effect on the nickel deposition by using LixNi1-xO with high lithium contents was c onfirmed, Typical results for the amount of deposited nickel in the Li /K(62/38 mol%) carbonate Electrolyte after cell operation was as follo ws : 3.8 mg/cm(2) using Li0.28Ni0.72O after 3637 h and 8.3 mg/cm(2) us ing Li0.02Ni0.98O after 4570 h.