Michael Makepeace Thackeray

Spinel Electrodes from the Li‐Mn‐O System for Rechargeable Lithium Battery Applications

The electrochemical and structural properties of spinel phases in the Li-Mn-O system are discussed as insertion electrodes for rechargeable lithium batteries. In this paper the performance of button-type cells containing electrodes from the Li{sub 2}O yMnO{sub 2} system, e.g., the stoichiometric spinel Li{sub 4}Mn{sup 5}O{sub 12}(y = 2.5) and the defect spinel Li{sub 2}Mn{sub 4}O{sub 9}(y = 4.0), is highlighted and compared with a cell containing a standard LiMn{sub 2}O{sub 4} spinel electrode.

Structure and electrochemistry of lithium cobalt oxide synthesised at 400°C

A novel LiCoO2 compound has been prepared by the reaction of Li2CO3 and CoCO3 at 400°C. Unlike the well-known LiCoO2 structure that is synthesised at higher temperature (900°C) and contains Li+ and Co3+ ions in discrete layers between planes of close-packed oxygen ions, the structure of LiCoO2 (400°C) has approximately 6% cobalt within the lithium layers. The electrochemical properties of LiCoO2 (400°C) differ significantly from LiCoO2 (900°C). Whereas electrochemical extraction from LixCoO2 (900°C) in room-temperature lithium cells takes place as a single-phase reaction above 3.9V for x≤0.9, electrochemical extraction from LixCoO2 (400°C) occurs as a two-phase reaction at an open-circuit voltage of 3.61V for 0.1<x<0.95. Because LixCoO2 (400°C) is a less oxidizing material than its high-temperature analogue, it is expected to be more stable in many of the organic-based electrolytes that are currently employed in lithium cells.

Structural aspects of lithium-manganese-oxide electrodes for rechargeable lithium batteries

The structural characteristics of “LixMnOy” electrodes, prepared by reacting manganese oxides with lithium salts at 400°C–900°C, for ambient temperature, rechargeable lithium cells have been determined by powder X-ray and neutron diffraction studies. The identification of structure types and cyclic voltammetry data show that the rechargeability of the “LixMnOy” electrodes in Li“LixMnOy” cells can be attributed predominantly to a spinel component of the system LixMn2−zO4 (0≤x≤1.33 and 0≤z≤0.33) which includes the spinel phases LiMn2O4, Li2Mn4O9 and Li4Mn5O12.

Alpha manganese dioxide for lithium batteries: A structural and electrochemical study

Abstract A highly crystalline α-MnO 2 phase has been synthesised by acid treatment of Li 2 MnO 3 . A neutron-diffraction study has shown that the stoichiometry of this phase is A 0.36 Mn 0.91 O 2 (or MnO 2 ·0.2A 2 O) where A refers predominantly to H + ions and a very minor concentration of Li + ions. Heat-treatment at 300°C leaves a virtually anhydrous α-MnO 2 product. The absence of any foreign cation such as K + , Na + or Rb + within the channels of the structure has raised the possibility of utilizing the α-MnO 2 framework as a high performance electrode for secondary lithium cells. Preliminary electrochemical data indicate that capacities in excess of 200 mAh/g are achievable from these α-MnO 2 electrodes in room-temperature lithium cells. Cyclic voltammograms show that lithium is inserted into α-MnO 2 in a two-step process and that this process is reversible.

Structural characterization of Li1+xV3O8 insertion electrodes by single-crystal X-ray diffraction

Abstract The crystal structures of Li1.2V3O8 and a lithiated product Li4.0V3O8 have been determined by single-crystal X-ray diffraction methods. The structure refinement of Li1.2V3O8 confirms that of Li1+xV3O8 (x ≈ 0) reported by Wadsley thirty-six years ago. However, unlike Wadsleys data, the refinement of Li1.2V3O8 demonstrates that the lithium ions are distributed over two independent crystallographic sites. One lithium ion, Li(1), is octahedrally coordinated; the other, Li(2), has tetrahedral coordination. Lithiation of Li1.2V3O8 with n-butyllithium at room temperature displaces Li(1) through an octahedral face into a neighbouring octahedral site, whereas Li(2) shifts its position very slightly to adopt octahedral coordination. During lithiation, the packing of the oxygen-ion array is adjusted slightly to adopt an arrangement that approaches cubic-close-packing. The lithiated product Li4V3O8 has a defect rock salt structure. The structural data provide a greater insight into the discharge mechanism that occurs in Li/Li1+xV3O8 electrochemical cells.

Lithium manganese oxides from Li2MnO3 for rechargeable lithium battery applications

Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leaching of Li2O from the rock salt phase Li2MnO3 (Li2O.MnO2) with acid at 25°C. Preliminary electrochemical tests have shown that capacities of approximately 200 mAh/g based on the mass of the lithium-manganese oxide electrode can be obtained in room-temperature lithium cells, and that capacities in excess of 140 mAh/g can be achieved on cycling. Although a detailed structure analysis of an extensively delithiated sample has not yet been undertaken, it is believed that it may be a novel layered lithium-manganese oxide compound Li2−xMnO3−x2 (0<x<2) with a cubic-close-packed oxygen anion array in which some of the Li+ ions are ionexchanged with H+ ions.rnrnHeat-treatment of an extensively delithiated Li2MnO3 sample at 300°C in air transforms the product to a γβ−MnO2 type phase, whereas delithiated samples that still contain an appreciable amount of lithium transform on heating to a two-phase product of Li2MnO3 and a compound with a spinel-related structure.

Ramsdellite-MnO2 for lithium batteries: the ramsdellite to spinel transformation

A pure and highly crystalline form of ramsdellite-MnO2 has been synthesized by acid treatment of the spinels LiMn2O4 and Li2Mn4O9 at 95°C. Although the ramsdellite—MnO2 framework remains intact on lithiation at 70°C, the hexagonally-close-packed oxygen array buckles towards a cubic-close-packed structure to accommodate the inserted lithium ions. The reaction is reversible but the instability of the structure on cycling limits the utility of ramsdellite-MnO2 as a rechargeable electrode in lithium cells. The ramsdellite structure can be stabilized by reaction with LiOH or LiNO3 at 300–400°C; this reaction, which displaces manganese ions from the MnO2 framework into interstitial octahedral sites generates spinel-related domains that coexist with the lithiated ramsdellite phase. At 300°C, under vacuum, the lithiated ramsdellite phase Li0.5MnO2 transforms to the spinel LiMn2O4; at 300–400°C, in air, it oxidizes slowly and transforms to a defect spinel LiMn2O4+δ (0 < δ ⩽ 0.5) via an intermediate compound. A mechanism for the ramsdellite—spinel transition is proposed.

Defect spinels in the system Li2O.yMnO2 (y>2.5): A neutron-diffraction study and electrochemical characterization of Li2Mn4O9

Abstract The structure of the defect spinel Li2Mn4O9 which is a component of the system Li2O.yMnO2 (y = 4.0) has been determined by neutron diffraction analysis; it has the spinel notation (Li0.89□0.11) [Mn1.78□0.22]O4. The electrochemical properties of Li2Mn4O9 when used as an insertion electrode in rechargeable room-temperature lithium cells have been evaluated.

Characterization of LT ‐ Li x Co1 − y Ni y O 2 Electrodes for Rechargeable Lithium Cells

LT-LiCo{sub 0.9}Ni{sub 0.1}O{sub 2} prepared at 400 C with a structure that is intermediate between an ideal lithiated spinel and a layered structure has been investigated as an electrode in rechargeable lithium cells; it delivers a voltage vs. pure lithium that is significantly lower than the voltage provided by its high-temperature analogue, HT-LiCo{sub 0.9}Ni{sub 0.1}O{sub 2}, (synthesized at 900 C). The rechargeability of Li/LT-LiCo{sub 0.9}Ni{sub 0.1}O{sub 2} cells can be improved by leaching some lithium and a small amount of cobalt performance is attributed to the formation of a defect spinel phase Li{sub 0.8}[Co{sub 1.6}Ni{sub 0.2}]O{sub 4} in which the lithium ions adopt the tetrahedral A sites and the cobalt and nickel ions the B sites of an A[B{sub 2}]O{sub 4} spinel.

Spinel electrodes for lithium batteries — A review

Abstract This paper briefly reviews recent electrochemical data of several transition-metal oxide and sulphide spinel compounds of general formula A[B 2 ]X 4 that have been employed as cathode materials in both room-temperature and high-temperature (400 °C) lithium cells. Particular attention is given to the performance of the oxide spinels M 3 O 4 (M ue5fb Fe, Co, Mn) that have like A- and B-type cations, the lithium spinels Li[M 2 ]O 4 (M ue5fb Ti, V, Mn) and LiFe 5 O 8 , and the thiospinels CuCo 2 S 4 and CuTi 2 S 4 . Reaction processes and the structural characteristics of the reaction products are highlighted.