National Institute of Advanced Industrial Science and Technology

Secretary, Agency of Industrial Science and Technology

Nat'l Institute of Advanced Industrial Science . . .

Hikari Sakaebe

Tomonari Takeuchi

Kuniaki Tatsumi

Hiroyuki Kageyama

Atsushi Sakuda

Tetsuo Sakai

Hiroshi Senoh

Mitsuharu Tabuchi

Masahiro Shikano

Hikaru Sano

Titus Nyamwaro Masese

Kazuaki Ado

Hironori Kobayashi

Noboru Taguchi

By using a potassium ion secondary battery positive electrode active material comprising a potassium compound represented by general formula (1): KMO, wherein M is copper or iron, n is 0.5 to 3.5, and m is 1.5 to 2.5, provided is a potassium ion secondary battery positive electrode active material having higher theoretical discharge capacity and higher effective capacity than a potassium secondary battery using Prussian blue as a positive electrode active material.

Positive electrode active material for potassium ion secondary cell

Provided is a material that can be used as a potassium secondary battery positive electrode active material (particularly a potassium ion secondary battery positive electrode active material), other than Prussian blue, by using a potassium compound and a potassium ion secondary battery positive electrode active material comprising the potassium compound, the potassium compound being represented by general formula (1):KABO,wherein A is a positive divalent element in groups 7 to 11 of the periodic table; B is positive tetravalent silicon, germanium, titanium or manganese, excluding a case in which A is manganese and B is titanium, and a case in which A is cobalt and B is silicon; n is 1.5 to 2.5; and m is 3.5 to 4.5.

Potassium compound and positive electrode active material for potassium ion secondary batteries containing same

A composite containing phosphorus, lithium, iron, sulfur, and carbon as constituent elements wherein lithium sulfide (LiS) is present in an amount of 90 mol % or more, and wherein the crystallite size calculated from the half-width of a diffraction peak based on the (111) plane of LiS as determined by X-ray powder diffraction measurement is 80 nm or less. The composite exhibits a high capacity (in particular, a high discharge capacity) useful as an electrode active material for a lithium-ion secondary battery (in particular, a cathode active material for a lithium-ion secondary battery), without the need for stepwise pre-cycling treatment.

Lithium-iron-phosphorus-sulfur-carbon composite and method for producing same

The main object is to provide a novel material with excellent charge and discharge characteristics, such as a high utilization rate of a positive electrode, a high capacity, and good cycle characteristic, in which the material is a compound containing as the major component lithium sulfide useful as a cathode active material for lithium secondary batteries. The invention provides a lithium sulfide-iron-carbon composite containing lithium, iron, sulfur and carbon as constituent elements, with lithium sulfide (LiS), as the main phase, having a crystallite size of 50 nm or less as calculated from the half width of the diffraction peak based on the (111) plane of LiS as determined by X-ray powder diffraction.

Lithium sulfide-iron-carbon complex

The sulfide of the present invention comprises an amorphous (lithium) niobium sulfide having an average composition represented by formula (1): LiNbS(wherein 0&#x2264;k1&#x2264;5; 3&#x2264;n1&#x2264;10; and when n1&#x2265;3.5, k1&#x2264;0.5), or an amorphous (lithium) titanium niobium sulfide having an average composition represented by formula (2): LiTiNbS(wherein 0&#x2264;k2&#x2264;5; 0&#x3c;m2&#x3c;1; 2&#x2264;n2&#x2264;10; and when n2&#x2265;3.5, k2&#x2264;1.5). The sulfide of the present invention is a material that is useful as a cathode active material for lithium batteries, such as lithium primary batteries, lithium secondary batteries, and lithium ion secondary batteries, and has a high charge-discharge capacity, high electrical conductivity, and excellent charge-discharge performance.

Amorphous (lithium) niobium sulfide or (lithium) titanium niobium sulfide

The present invention provides a novel lithium titanium sulfide, lithium niobium sulfide, or lithium titanium niobium sulfide that contains a sulfide containing lithium, titanium and/or niobium, and sulfur as constituent elements, and that has excellent charge-discharge performance (especially excellent charge-discharge capacity and charge-discharge potential) useful as a cathode active material or the like for lithium batteries, such as metal lithium secondary batteries or lithium-ion secondary batteries. Particularly preferred are, for example, (1) lithium titanium sulfide containing lithium, titanium, and sulfur as constituent elements and having a cubic rock salt crystal structure, (2) lithium niobium sulfide containing lithium, niobium, and sulfur as constituent elements and having a diffraction peak at a specific position in an X-ray diffractogram, and (3) lithium titanium niobium sulfide containing lithium, titanium, niobium, and sulfur as constituent elements and having a diffraction peak at a specific position in an X-ray diffractogram.

Lithium titanium sulfide, lithium niobium sulfide, and lithium titanium niobium sulfide

The present invention provides a process for producing a lithium sulfide-carbon composite, the process comprising placing a mixture of lithium sulfide and a carbon material having a specific surface area of 60 m/g or more in an electrically-conductive mold in a non-oxidizing atmosphere, and applying a pulsed direct current to the mold while pressurizing the mixture in a non-oxidizing atmosphere, thereby subjecting the lithium sulfide and the carbon material to heating reaction; and a lithium sulfide-carbon composite obtained by this process, the composite having a carbon content of 15 to 70 weight %, and a tap density of 0.4 g/cmor more when the carbon content is 30 weight % or more, or a tap density of 0.5 g/cmor more when the carbon content is less than 30 weight %. The present invention can improve the electronic conductivity of lithium sulfide, which is expected to be put into practical use as a high-capacity positive electrode active material, so as to further enhance the performance of lithium sulfide as a positive electrode active material for lithium ion secondary batteries.

Lithium sulfide-carbon complex, process for producing the complex, and lithium ion secondary battery utilizing the complex

The present invention provides a process for producing a composite of metal sulfide and metal oxide obtained by dispersing a metal sulfide, which is nickel sulfide, copper sulfide, iron sulfide or a mixture thereof, in a metal salt-containing aqueous solution, and depositing metal salt on the metal sulfide by drying the aqueous solution; and heat-treating the metal sulfide comprising a metal salt deposited thereon at 400 to 900&#xb0; C. in a sulfur-containing atmosphere. Also disclosed is a composite obtained by the aforementioned process, comprising a metal sulfide having a surface partially covered with a metal oxide. The composite of the present invention has improved cycle characteristics while maintaining a high charge/discharge capacity and excellent electrical conductivity inherently possessed by metal sulfide, which is usable as a material having a high theoretical capacity and excellent electrical conductivity when used as a positive-electrode material for a lithium secondary battery.

Composite of metal sulfide and metal oxide and process for producing the composite

The present invention provides a production process of a metal sulfide, which includes placing a metal component and sulfur in a conductive container, and applying a pulsed direct current to the container in a non-oxidizing atmosphere to cause the metal component to react with sulfur, and also provides a metal sulfide obtained by the process and represented by a composition formula: MS, wherein M is at least one member selected from the group consisting of Ni, Cu, Fe, and Co, and 1&#x3c;x&#x2266;2. The present invention is capable of easily producing a metal sulfide with a high proportion of sulfur atoms, which is expected to exhibit excellent properties as a positive-electrode active material for a high capacity lithium secondary battery.

Process for producing metal sulfide

The present invention provides a single-phase lithium ferrite based oxide which is suitable as a cathode material for a secondary battery, a process for preparing the oxide, and its uses, the oxide having a layered rock salt-type structure and comprising lithium ferrite (LiFeO )&minus;Li MO solid solution wherein M is at least one species selected from the group consisting of Mn, Ti and Sn, 0&lE;x<2, 0&lE;y&lE;1 such that the proportion of iron is &lE;Fe/(Fe&plus;M)&lE;0.9.

Growing community of inventors

Ikeda, Japan

Hikari Sakaebe