T2 and O2 Li[sub 2/3][Co[sub x]Ni[sub 1/3−x/2]Mn[sub 2/3−x/2]]O[sub 2] Electrode Materials

The structure and the electrochemical properties of P 2 ­ Na 2 / 3 [ Co x Ni 1 / 3 − x / 2 Mn 2 / 3 − x / 2 ] O 2 and Li 2 / 3 [ Co x Ni 1 / 3 − x / 2 Mn 2 / 3 − x / 2 ] O 2 ( 0 ⩽ x ⩽ 2 / 3 ) are investigated by X-ray and neutron diffraction as well as by electrochemical techniques. Li 2 / 3 [ Co x Ni 1 / 3 − x / 2 Mn 2 / 3 − x / 2 ] O 2 ( 0 ⩽ x ⩽ 2 / 3 ) can be considered a solid solution between Li 2 / 3 1 + [ Ni 1 / 3 2 + Mn 2 / 3 4 + ] O 2 2 − and Li 2 / 3 1 + [ Co 2 / 3 3 + Mn 1 / 3 4 + ] O 2 2 − . Samples with x near 0 and with x near 2/3 adopt the T2 structure, while those with intermediate x show a stacking faulted O2 structure. This paper demonstrates that T 2 ­ Li 2 / 3 [ Co 2 / 3 Mn 1 / 3 ] O 2 is quite different from T 2 ­ Li 2 / 3 [ Ni 1 / 3 Mn 2 / 3 ] O 2 in its properties. First, neutron diffraction studies indicate that there is no superlattice ordering of Co and Mn in the transition metal layers of P 2 ­ Na 2 / 3 [ Co 2 / 3 Mn 1 / 3 ] O 2 or T 2 ­ Li 2 / 3 [ Co 2 / 3 Mn 1 / 3 ] O 2 , as there is in P 2 ­ Na 2 / 3 [ Ni 1 / 3 Mn 2 / 3 ] O 2 and T 2 ­ Li 2 / 3 [ Ni 1 / 3 Mn 2 / 3 ] O 2 . Second, the electrochemical results show that all the lithium can be extracted from T 2 ­ Li 2 / 3 [ Co 2 / 3 Mn 1 / 3 ] O 2 , unlike T 2 ­ Li 2 / 3 [ Ni 1 / 3 Mn 2 / 3 ] O 2 , from which only one half the available lithium can be extracted.