An active material has a favorable capacity property. The active material is to be used for a fluoride ion battery, the active material including a crystal phase having a perovskite structure, and represented by ABO.sub.3 or a fluoride of the ABO.sub.3, in which the A and the B are different metal elements; the A includes at least one kind of a metal element belonging to Group 2 and Group 3 in the periodic table; and the B includes at least one kind of a transition metal element belonging to Period 4 to Period 6 in the periodic table.

To provide a cathode active material capable of obtaining a lithium ion secondary battery which has a high discharge capacity and of which a decrease of the discharge capacity when a charge and discharge cycle is repeatedly carried out is suppressed, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery. A cathode active material comprising a lithium-containing composite oxide represented by the formula aLi(Li.sub.1/3Mn.sub.2/3)O.sub.2.(1a)LiMO.sub.2 (wherein M is an element containing at least Ni and Mn, and 0<a<1), wherein in an X-ray diffraction pattern, the integral breadth of a peak of (110) plane assigned to a crystal structure with space group C2/m is at most 1.25 deg.

An electrical energy storage device and a method of forming such electrical energy storage device. The electrical energy storage device includes an electrolyte that is arranged to dissipate energy when subjected to external mechanical load applied to the electrical energy storage device. The electrolyte includes a polymer matrix of at least two crosslinked structures, including a first polymeric material and a second polymeric material; and an electrolytic solution retained by the polymer matrix.

An electrolyte for use in an energy storage device, an energy storage device and a method of forming such electrolyte. The electrolyte includes a polymer matrix of at least two crosslinked structures, including a first polymeric material and a second polymeric material; an electrolytic solution retained by the polymer matrix; and a separator retained by the polymer matrix; wherein the electrolyte is arranged to receive at least one connection member penetrating the polymer matrix and a pair of electrodes disposed on opposite sides of the electrolyte for maintaining integrity of the energy storage device.

An electrolyte for use in an energy storage device, an energy storage device and a method of forming such electrolyte. The electrolyte includes a polymer matrix of at least two crosslinked structures, including a first polymeric material and a second polymeric material; an electrolytic solution retained by the polymer matrix; and a separator retained by the polymer matrix; wherein the electrolyte is arranged to receive at least one connection member penetrating the polymer matrix and a pair of electrodes disposed on opposite sides of the electrolyte for maintaining integrity of the energy storage device.

There is provided a method of producing a lithium ion secondary battery. A positive electrode mixture layer is formed on a positive electrode current collector using an aqueous positive electrode mixture paste that includes a positive electrode active material including a lithium manganese composite oxide, and aqueous solvent, and additionally includes Li.sub.5FeO.sub.4 as an additive.

A positive active material for a positive electrode of a battery cell which includes a first component containing Li.sub.2MnO.sub.3. The first component includes a doping with nitrogen ions N.sup.2 which replace a portion of the oxygen ions O.sup.2 of component. A positive electrode of a battery cell which includes a positive material, and a battery cell which includes at least one positive electrode, are also described.

A method for preparing cathode material for a lithium primary battery includes an active cathode material and an active anode material. The active cathode material is manganese dioxide, and the active anode material is either one of lithium metal and lithium alloy. The method includes: a first kneading step in which a boron compound and a thickening agent are kneaded with a diluent to prepare a paste made by dissolving the boron compound in the diluent; a second kneading step in which the paste is kneaded with a conductive additive; and a third kneading step in which the paste obtained in the second kneading step is kneaded with the active cathode material and a binder to prepare the cathode material in slurry form.

Electrochemical cells are provided, wherein a metal ion is adsorbed to a manganese dioxide- or carbon-containing electrode due to the addition of a metal additive to the cell's electrolyte and/or cathode. Methods for preparing such cells are also provided. In particular embodiments, the electrochemical cells are alkaline electrochemical cells, and the electrode contains manganese dioxide.

Electrochemical cells are provided, wherein a metal ion is adsorbed to a manganese dioxide- or carbon-containing electrode due to the addition of a metal additive to the cell's electrolyte and/or cathode. Methods for preparing such cells are also provided. In particular embodiments, the electrochemical cells are alkaline electrochemical cells, and the electrode contains manganese dioxide.