New Structure Model for Lithium Nickel Batteries
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NEW STRUCTURE MODEL FOR LITHIUM NICKEL BATTERIES M.A. MONGE*, E. GUTIERREZ-PUEBLA*, I. RASINES*, J.A. CAMPA** *Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid, Spain. rasinesicmnm.csic.es ** Facultad de Ciencias Geol6gicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain. ABSTRACT After growing black colored single crystals of Li×NilxO (x = 0.27) and solving its crystal structure, a model is proposed as an alternative to the structural type admitted for Li5Ni1 _5 O. The new rhombohedral cell consists of a cubic close packing of oxygens in which the alternation of two kind of mixed layers containing Li and Ni in different ratios can be detected along the c direction. This model implies a Li order incompatible with the alternation of Ni layers, one of them pure and the other containing some Li. The results of magnetization measurements look consistent with the new structural type, and reveal that LiNil 5 O behaves as mictomagnetic. INTRODUCTION Li5Ni 1_,O shows a practical interest since it could replace more expensive lithium cobalt oxide as a cathode material for long-life 4V rechargeable lithium batteries, and for intermediate temperature fuel cells. A recent electrochemical test [1] of a LixNil_,O half cell has shown a high initial discharge capacity, 158 mAhg-t, but very fast fading just after several tens of charge/discharge cycles. When used as a cathode material, LixNi1 _,O exhibits higher electrical conductivity and better H02/2 fuel cell performance than cobalt lithium oxide [2], although its thermal stability at intermediate temperatures is relatively poorer than that of the later. In LiNi1 -O x can vary [3] between xrO and x
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