Technology Finance Corporation (proprietary) Limited

South African Inventions Development Corporation

Csir

Lilliwyte Societe Anonyme

Technology Finance Corporation (prop.) Ltd

Michael M Thackeray

Rosalind J Gummow

Ernest E Ferg

Johan Coetzer

Margaretha H Rossouw

Peter Barrow

John B Goodenough

Arnold Van Zyl

Annemare De Kock

Graham K Duncan

An electrochemical cell comprises as an anode, a lithium transition metal oxide or sulphide compound which has a [B]Xspinel-type framework structure of an A[B]Xspinel wherein A and B are metal cations selected from Li, Ti, V, Mn, Fe and Co, X is oxygen or sulphur, and n&#x2212; refers to the overall charge of the structural unit [B]Xof the framework structure. The transition metal cation in the fully discharged state has a mean oxidation state greater than +3 for Ti, +3 for V, +3.5 for Mn, +2 for Fe and +2 for Co. The cell includes as a cathode, a lithium metal oxide or sulphide compound. An electrically insulative lithium containing liquid or polymeric electronically conductive electrolyte is provided between the anode and the cathode.

Electrochemical cell

An electrochemical cell comprises as an anode, a lithium transition metal oxide or sulphide compound which has a [B]Xspinel-type framework structure of an A[B]Xspinel wherein A and B are metal cations selected from Li, Ti, V, Mn, Fe and Co, X is oxygen or sulphur, and n&#x2212; refers to the overall charge of the structural unit [B]Xof the framework structure. The transition metal cation in the fully discharged state has a mean oxidation state greater than +3 for Ti, +3 for V, +3,5 for Mn, +2 for Fe and +2 for Co. The cell includes as a cathode, a lithium metal oxide or sulphide compound. An electrically insulative lithium containing liquid or polymeric electronically conductive electrolyte is provided between the anode and the cathode.

An electrochemical cell comprises as an anode, a lithium transition metal oxide or sulphide compound which as a [B]Xspinel-type framework structure of an A[B]Sspinel wherein A and B are metal cations selected from Li, Ti, V, Mn, Fe and Co, X is oxygen or sulphur, and n&#x2212; refers to the overall charge of the structural unit [B]Xof the framework structure. The transition metal cation in the fully discharged state has a mean oxidation state greater than +3 for Ti, +3 for V, +3.5 for Mn, +2 for Fe and +2 for Co. The cell includes as a cathode, a lithium metal oxide or sulphide compound. An electrically insulative lithium containing liquid or polymeric electronically conductive electrolyte is provided between the anode and the cathode.

The invention provides a manganese dioxide-based material which is highly crystalline and chemically prepared. The material has a predominantly ramsdellite structure, and has a powder X-ray diffraction pattern (CuK.sub..alpha. radiation) in which the ratio of a [110] peak height to a [201] peak height is at least 0,6:1,0. The material can be used as an electrode material in an electrochemical cell 10.

Manganese dioxide-based material

An electrochemical cell comprises a cell housing, and a cathode located in the cell housing. The cathode comprises at least one electrochemically active compound of lithium, manganese and oxygen. The compound has a spinel-type structure and has the general formula

An electrochemical cell precursor and method of making it are provided; and a method of making an electrochemical cell and electrodes therefor. The cell precursor comprises a housing having an anode terminal exposed to its interior. An electrolyte is in the housing for electrochemically coupling the terminal to a cathode in the housing, a cathode precursor being in the housing. The cell precursor is made by loading the electrolyte and cathode precursor into the housing, such that the anode is electrochemically coupled by the electrolyte to the cathode precursor, being electrochemically insulated therefrom. The cell and its electrodes are made by subjecting the cell precursor to a charging potential whereby the cathode precursor acts as a cathode. The cathode precursor comprises at least one compound of lithium, manganese and oxygen, which falls in a defined area of an isothermal slice of the Li-Mn-O phase diagram at 20.degree. C.

The invention provides a hydrogen manganese oxide compound. It has manganese cations and oxygen anions arranged in a framework having a hollandite-type structure and defining channels. Cations in the channels are confined to manganse, hydrogen and/or lithium cations. The ionic ratios of lithium:manganese cations and of hydrogen:manganese cations are respectively at most 0.05:1 and at least 0.01:1.00. The invention also provides a method of making said compound; a lithium manganese oxide compound derived from said hydrogen manganese oxide compound and a method of synthesising it therefrom; and electrochemical cells employing said hydrogen manganese oxide and lithium manganese oxide compounds as active cathode materials.

Manganese oxide compounds

The invention provides an essentially layered lithium transition metal oxide compound and a method of making it. It comprises lithium cations, transition metal cations T and oxygen anions, the transition metal cations T having an average valency of from +3 to +4. It has its O anions arranged in layers in a substantially cubic-close-packed arrangement, with its Li cations being arranged in layers and its T cations occupying octahedral sites and being arranged in layers. Each layer of the Li cations is sandwiched between two layers of the O anions and each said layer of O anions is sandwiched between a said layer of Li cations and a layer of the T cations. 75%-99.8% of the T cations in the compound are located in the layers of T cations, and the remainder of the T cations are located in the layers of Li cations, the T cations being selected from Co cations and mixtures of Co and Ni cations.

Lithium transition metal oxide

The invention provides a novel lithium manganese oxide compound in which oxygen anions, lithium cations and manganese cations are arranged in layers, each layer of lithium cations being sandwiched between two layers of oxygen anions, each layer of manganese cations being sandwiched between two layers of oxygen anions and each layer of oxygen anions being sandwiched between a layer of lithium cations and a layer of manganese cations. The invention also provides a method of making the compound; and an electrochemical cell employing the compound as its cathode.

Lithium manganese oxide compound

A method of synthesizing a lithium manganese oxide in accordance with the formula Li.sub.1-x Mn.sub.2 O.sub.4 in which 0.ltoreq.x&lt;1 and having a spinel-type crystal structure includes forming a mixture in finely divided solid form of at least one lithium salt such as Li.sub.2 CO.sub.3 which decomposes when heated in air to form an oxide of lithium, and at least one manganese salt such as MnCO.sub.3 which decomposes when heated in air to form an oxide of manganese. The mixture is heated in an oxidizing atmosphere to a temperature in the range 200.degree.-600.degree. C. to decompose the salts and to obtain the Li.sub.1-x Mn.sub.2 O.sub.4 having a spinel-type crystal structure.

Method of synthesizing a lithium manganese oxide

The invention provides a method of making .beta.'-alumina by heating aluminium oxide in the presence of Na.sub.2 O. A metal oxide dopant in the form of Li.sub.2 O, MgO, ZnO, CoO, NiO, FeO or mixtures thereof, or a precursor of the dopant, is dispersed in a cubic-close packed aluminium oxide or a precursor thereof to form a starting mixture which is calcined by heating to 250.degree.-1100.degree. C. in an oxygen-containing atmosphere. Na.sub.2 O is then dispersed in the calcined starting mixture to form a final mixture, and the final mixture is heated in an oxygen-containing atmosphere to above 1100.degree. C. to produce .beta.'-alumina.

Growing community of inventors

Pretoria, South Africa

Michael M Thackeray