Solid-state chemistry and electrochemistry of LiCo1/3Ni1/3Mn1/3O2 for advanced lithium-ion batteries. I. First-principles calculation on the crystal and electronic structures

The first-principles calculation on the crystal and electronic structures of a lithium insertion material of LiCo1/3Ni1/3Mn1/3O2 has been carried out to search new positive-electrode materials for advanced lithium-ion batteries. LiCo1/3Ni1/3Mn1/3O2 having a superlattice based on an alpha-NaFeO2-type structure is suggested to be stable. According to the calculations, formal charges of Co, Ni, and Mn in LiCo1/3Ni1/3Mn1/3O2 (P3112, a = 4.904 A, c = 13.884 A) are, respectively, estimated to be +3, +2, and +4. The solid-state redox reactions of LiCo1/3Ni1/3Mn1/3O2 are investigated under the assumption of a lithium insertion scheme, and the reactions are shown to be formally Ni2+/Ni3+ for 0 *# < x + *# < 1/3 in Li1-xCo1/3Ni1/3Mn1/3O2, Ni3+/Ni4- for 1/3 *# < x *# < 2/3 and Co3+/Co4+ for 2/3 *# < x *# < 1. Manganese ions do not participate for the redox reactions in an entire range. The illustrated maps on the change in electron density for the solid-state redox reactions indicate that the charge balance is due to the loss or gain of electrons on oxygen ions while the redox centers are transition metal ions of Ni or Co. Reversible potentials of Li1-xCo1/3Ni1/3Mn1/3O2 against a lithium electrode are also calculated and the possibility of implementation is discussed with respect to the computational chemistry based on the first-principles calculation.