Solid-state redox reactions of LiNi[sub 1/2]Co[sub 1/2]O[sub 2] (R[bar 3]m) for 4 volt secondary lithium cells

Journal Article · Mon Aug 01 04:00:00 EDT 1994 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2055051· OSTI ID:7188557

Ueda, Atsushi; Ohzuku, Tsutomu ^[1]

---

1. Osaka City Univ. (Japan). Electrochemistry and Inorganic Chemistry Lab.

LiNi[sub 1/2]Co[sub 1/2]O[sub 2] (R[bar 3]m; a = 2.84 [angstrom], c = 14.1 [angstrom] in hexagonal setting) whose parent structure was a solid solution of LiNiO[sub 2] and LiCoO[sub 2] was prepared and examined in a nonaqueous lithium cell. The oxidation of LiNi[sub 1/2]Co[sub 1/2]O[sub 2] and reduction of [open square]Ni[sub 1/2]Co[sub 1/2]O[sub 2] proceeded reversibly in the voltage range above 3.5 V. X-ray diffractional examinations indicated the reaction proceeded in a topotactic manner. During the oxidation of LiNi[sub 1/2]Co[sub 1/2]O[sub 2], the c-axis dimension elongated from 14.1 to 14.5 [angstrom] and the a-axis shortened from 2.84 to 2.80 [angstrom] almost linearly as a function of x in Li[sub 1[minus]x]Ni[sub 1/2]Co[sub 1/2]O[sub 2] until x reached about 0.5. Consequently, the lattice volume remained almost invariable at 98.5 A[sup 3]. Further oxidation resulted in the shrinkage of the c-axis dimension and the elongation of the a-axis. Detained open-circuit voltage measurements also were carried out. The open-circuit voltages varied as a function of x in Li[sub 1[minus]x]Ni[sub 1/2]Co[sub 1/2]O[sub 2] following a hyperbolic tangent curve, not an S-shaped Nernstian curve. The composition-dependent open-circuit voltage curve together with the XRD observations indicated that the reaction proceeded in a homogeneous phase. Differences and similarities of the solid-state redox reactions among LiNiO[sub 2], LiNi[sub 1/2]Co[sub 1/2]O[sub 2], and LiCoO[sub 2] were discussed.

• OSTI ID: 7188557
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 141:8; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
250903* -- Energy Storage-- Batteries-- Materials
Components
& Auxiliaries
ALKALI METAL COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
COBALT COMPOUNDS
COBALT OXIDES
CRYSTAL STRUCTURE
ELECTRIC BATTERIES
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELECTROCHEMISTRY
ELECTRODES
FABRICATION
LITHIUM COMPOUNDS
LITHIUM OXIDES
MORPHOLOGICAL CHANGES
NICKEL COMPOUNDS
NICKEL OXIDES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REDOX REACTIONS
TRANSITION ELEMENT COMPOUNDS