LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} spinels -- 5 V cathode materials
A series of electroactive spinel compounds, LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} (0.1 {le} x {le} 0.5) has been studied by crystallographic, spectroscopic and electrochemical methods and by electron-microscopy. These LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} spinels are nearly identical in structure to cubic LiMn{sub 2}O{sub 4} and successfully undergo reversible Li intercalation. The electrochemical data show slight shifts to higher voltage for the delithiation reaction that normally occurs at 4.1 V in standard Li{sub 1{minus}x}Mn{sub 2}O{sub 4} electrodes (1 {ge} x {ge} 0) corresponding to the oxidation of Mn{sup 3+} to Mn{sup 4+}. The data also show a remarkable reversible electrochemical process at 4.9 V which is attributed to the oxidation of Cu{sup 2+} to Cu{sup 3+}. The inclusion of Cu in the spinel structure enhances the electrochemical stability of these materials upon cycling. The initial capacity of LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} spinels decreases with increasing x from 130 mAh/g in LiMn{sub 2}O{sub 4} (x = 0) to 70 mAh/g in LiMn{sub 1.5}Cu{sub 0.5}O{sub 4} (x = 0.5). Although the powder X-ray diffraction pattern of LiMn{sub 1.5}Cu{sub 0.5}O{sub 4} shows a single-phase spinel product, neutron diffraction data show a small, but significant quantity of an impurity phase, the composition and structure of which could not be identified. X-ray absorption spectroscopy was used to gather information about the oxidation states of the manganese and copper ions. The composition of the spinel component in the LiMn{sub 1.5}Cu{sub 0.5}O{sub 4} was determined from X-ray diffraction and XANES data to be Li{sub 1.01}Mn{sub 1.67}Cu{sub 0.32}O{sub 4} suggesting, to a best approximation, that the impurity in the sample was a lithium-copper-oxide phase.
- Research Organization:
- Covalent Associates, Inc., Woburn, MA (US)
- Sponsoring Organization:
- US Department of the Army; USDOE
- DOE Contract Number:
- W-31109-ENG-38; AC02-76CH00016
- OSTI ID:
- 20019158
- Resource Relation:
- Conference: 1997 Materials Research Society Fall Meeting, Boston, MA (US), 12/01/1997--12/05/1997; Other Information: PBD: 1998; Related Information: In: Materials for electrochemical energy storage and conversion II -- Batteries, capacitors and fuel cells. Materials Research Society symposium proceedings, Volume 496, by Ginley, D.S.; Doughty, D.H.; Scrosati, B.; Takamura, T.; Zhang, Z.J. [eds.], 702 pages.
- Country of Publication:
- United States
- Language:
- English
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