Sulfur-Doped Aluminum-Substituted Manganese Oxide Spinels for Lithium-Ion Battery Applications

Abstract

Spinels with nominal composition Li 1.02 Al 0.25 Mn 1.75 O 3.97 S 0.03 , Li 1.02 Al 0.25 Mn 1.75 O 4 , and Li 1.02 Al 0.15 Mn 1.85 O 3.96 S 0.04 have been evaluated for their suitability as positive electrode materials in rechargeable lithium-ion batteries for electric ͑EV͒ and hybrid electric vehicle ͑HEV͒ applications. 7 Li magic angle spinning, nuclear magnetic resonance, X-ray diffraction, ͑XRD͒ and energydispersive spectroscopy experiments indicate that sulfur is most likely present as a trace impurity on the surface of the spinel particles rather than substituting for oxygen ions in the bulk, so it is unlikely to account for the previously reported enhanced cyclability of this material. Rather, the unusual particle morphology produced during calcination of some samples in the presence of sulfur compounds appears to impede ͑but does not completely prevent͒ conversion to the tetragonal phase that occurs at 3 V vs. Li and ameliorates the capacity fading associated with it. These materials exhibit reduced rate capability and capacity at 4 V, making them unsuitable for high energy density EV, or high power density applications.The synthesis and electrochemical behavior of LiAl 0.25 Mn 1.75 O 3.97 S 0.03 , a novel sulfur-doped spinel, have recently been described. 1,2 In contrast to other manganese oxide spinels, it has been reported to show excellent reversibility even when cycled at 3 V vs. Li or at elevated temperatures. Although power management considerations preclude utilization of capacity on both the 3 and 4 V plateaus in batteries for vehicular applications, stable electrode materials that can withstand overdischarge and other abusive conditions are necessary to obtain the desired long cycle life of the cell stacks. Because of severe cost constraints 3 associated with devices intended for electric vehicles ͑EVs͒ and hybrid electric vehicles ͑HEVs͒, less expensive manganese oxide spinels would make particularly attractive replacements for cobalt and cobalt nickel oxides currently used in lithium-ion batteries, provided that cycling problems can be overcome. Spinels may be particularly well suited for HEV batteries, because high energy density is not required, but high power density is.Capacity fading upon cycling of Li/LiMn 2 O 4 cells has been attributed to irreversible oxidation of electrolyte, 4,5 dissolution of manganese ions in acidic electrolyte solutions, and formation of defect spinel near the end of charge ͑particularly above 55°C͒, 6,7 and disconnection of particles associated with the tetragonal phase conversion that occurs at 3 V vs. Li. 8 The latter may also occur at 4 V during high-rate discharges. 9 Development of new electrolytes, 10 partial substitution of manganese with lithium 11 or other transition metals, 12 and protective coating of particles with lithium carbonate, 13 zinc oxide, 14 or LiCoO 2 15 have substantially improved cyclability in recent years. The severe capacity loss associated with reduction of spinels past an average Mn oxidation state of 3.5 and transformation to a tetr...

Gas-generated thermal oxidation of a coordination cluster for an anion-doped mesoporous metal oxide

“…In particular, incorporation of another anion into metal oxides, i.e. anion doping, provides excellent performance in ion-storage 8 and photocatalytic reaction 9 10 . However, synthesis of porous metal oxides and anion doping have been individually developed.…”

Effect of structure on the storage characteristics of manganese oxide electrode materials

“…For the O3 cathode, there is an initial rise in capacity both at room temperature and 55ºC as the structure converts to spinel, but decreases occur after about 10 cycles. The rapid capacity loss is associated with volume changes induced by the conversion of spinel to a Jahn-Teller distorted tetragonal phase upon deep discharge [24].…”