A. de Kock

Improved capacity retention in rechargeable 4 V lithium/lithium-manganese oxide (spinel) cells

The rechargeable capacity of 4 V LixMn2O4 spinel cathodes (0<x⩽1) has been improved by modifying the composition of the spinel electrode. Stable rechargeable capacities in excess of 100 mAh/g in flooded-electrolyte lithium cells can be achieved if LiMn2O4 is doped with mono- or multivalent cations (e.g. Li+, Mg2+, Zn2+) or, alternatively, with additional oxygen to increase the average manganese-ion oxidation state marginally above 3.5.

Spinel Anodes for Lithium‐Ion Batteries

Anodes of Li4MnsO12, Li4Ti5012, and Li2Mn409 with a spinel-type structure have been evaluated in room-temperature lithium cells. The cathodes that were selected for this study were the stabilized spinels, Li1.03Mnl.g704 and LiZnoo25Mn1.9504, and layered LiCoO2. The electrochemical data demonstrated that Li + ions will shuttle between two transition-metal host structures (anode and cathode) at a reasonably high voltage with a concomitant change in the oxidation state of the transition metal cations so that the Li § ions do not reduce to the metallic state at the anode during charge. These cells reduce the safety hazards associated with cells containing metallic-lithium, lithium-alloy, and lithium-carbon anodes.

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.

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.

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system

Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structures of two defect-spinel compounds synthesised by the reaction of MnCO3 and Li2CO3 at 400°C are reported. The cation distributions in the structures were determined by neutron-diffraction to be {Li.85□.15}8a[Mn1.74Li.26]16dO4 and {Li.87□.13}8a[Mn1.71Li.29]16dO4, where 8a and 16d refer to the tetrahedral and octahedral sites of the prototypic spinel space group Fd3m, respectively. The structures are discussed in relation to the spinel system Li2O·MnO2 (y≥2.5).

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.

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  Fe, Co, Mn) that have like A- and B-type cations, the lithium spinels Li[M 2 ]O 4 (M  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.

The versatility of MnO2 for lithium battery applications

Manganese dioxide has for many years found widespread use as a cathode material in aqueous Leclanche, zinc chloride and alkaline cells and, more recently, in nonaqueous lithium cells. However, despite the large number of polymorphic structures that exist in the manganese dioxide family, the battery industry has used y-MnOz exclusively as the positive electrode in these cells. With the advent of rechargeable lithium battery technology, research efforts have demonstrated that other MnO, structures, when processed in the correct way, provide attractive electrochemical properties for lithium cells. In this paper, some recent advances that have been made in MnOz materials technology are discussed, for example, in the development of cr-MnOz, layered-MnO,, spine]-related L&O -yMnO* 01.2.5) and ramsdellite-MnO, materials. An attempt has been made to clarify issues relating to the structural features of ‘CDMO’-type materials that are prepared by the reaction of r_MnO, with LiNOB (or LiOH) at 300400 “C.

The effect of multivalent cation dopants on lithium manganese spinel cathodes

The cycling stability of 4 V Li ,Mn,O, electrodes in lithium. flooded electrolyte glass cells has been improved by the addition of multivalent cation dopants (Mg’+. Zn’+ and Al’+ ). Optimal dopant levelx to achieve maximum capacity and the greatest stability with repeated cycling have been determined. The effect of doping the oxygen-rich spine1 Li,Mn,O, was also determined and shown to make