Abstract
To improve the cycle performance of spinel 
as the cathode of 4 V class lithium secondary batteries, the quaternary spinel phases 
(M = Co, Cr, Ni; y = 1/12, 1/9, 1/6, 1/3) were prepared at 750°C in air. X‐ray diffraction and electrochemical studies were carried out using the 
cells. These cathodes were more tolerant to repeated lithium extraction and insertion than a standard 
spinel electrode in spite of a small reduction in the initial capacity. Considering both cycle life and capacity density, 
showed good cycle performance with an energy density of 
at the 300th cycle. The improvement in cycling performance is attributed to the stabilization in the spinel structure by the doped metal cations.