LiMn{sub 2-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 : I. electrochemical, structural and spectroscopic studies.
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 a remarkable reversible electrochemical process at 4.9 V which is attributed to the oxidation of Cu{sup 2+} to Cu{sub 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 130mAh/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 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. The substitution of manganese by copper enhances the reactivity of the spinel structure towards 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., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 10990
- Report Number(s):
- ANL/CMT/CP-97391; TRN: AH200127%%598
- Resource Relation:
- Conference: Materials for Electrochemical Energy Storage and Conversion II Batteries, Capacitors and Fuel Cells, Warrendale, PA (US), Conference dates not supplied; Other Information: PBD: 5 Oct 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
LiMn{sub 2{minus}x}Cu{sub x}O{sub 4} spinels -- 5 V cathode materials
Synthesis, characterization and electrochemmistry of lithium battery electrodes : xLi{sub 2}MnO{sub 3}{center_dot}(1-x)LiMn{sub 0.333}Ni{sub 0.333}Co{sub 0.333}O{sub2} (0{le}x{le}0.7).