LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} spinels (0.1 {le} x {le} 0.5): A new class of 5 V cathode materials for Li batteries. 1: Electrochemical, structural, and spectroscopic studies
- Covalent Associates, Inc., Woburn, MA (United States)
- Brookhaven National Labs., Upton, NY (United States)
- Argonne National Lab., IL (United States)
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 spinels are nearly identical in structure to cubic LiMn{sub 2}O{sub 4} and successfully undergo reversible Li intercalation. The electrochemical data 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). The data also 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+}. 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 X-ray absorption near-edge spectroscopy 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. The substitution of manganese by copper enhances the reactivity of the spinel structure toward hydrogen: the compounds are more easily reduced at moderate temperature ({approximately} 200 C) than LiMn{sub 2}O{sub 4}.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- Department of the Army, Washington, DC (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38; AC02-76CH00016
- OSTI ID:
- 624304
- Journal Information:
- Journal of the Electrochemical Society, Vol. 145, Issue 4; Other Information: PBD: Apr 1998
- Country of Publication:
- United States
- Language:
- English
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