Nec Corporation

Nec Tokin Corporation

Nec Energy Devices, Ltd.

Ryuichi Kasahara

Jiro Iriyama

Tatsuji Numata

Koji Sakata

Tetsuya Kajita

Yutaka Nakazawa

Takashi Saito

Daisuke Kawasaki

Hiroo Takahashi

Shin Serizawa

Kazuhiko Inoue

Yasutaka Kono

Yukari Kibi

Emiko Fujii

Yutaka Bannai

The object of an exemplary embodiment of the invention is to provide a lithium ion secondary battery having an excellent charge and discharge cycle property. An exemplary embodiment of the invention is a lithium ion secondary battery, comprising a battery assembly in which a positive electrode and a negative electrode are stacked through a separator and a package in which the battery assembly and an electrolyte are placed; wherein the negative electrode comprises a negative electrode collector which is composed of a metal and a negative electrode active material layer which is formed on the negative electrode collector and which comprises a negative electrode active material and a binder; wherein the negative electrode collector and the negative electrode active material layer have a crack which is formed so as to be communicated with each of them; and wherein the crack reaches an outer peripheral edge from an inside of the negative electrode.

Lithium ion secondary battery

A control system for a lithium secondary battery measures a voltage V of a negative electrode that uses silicon oxide as a negative electrode active material, with respect to a lithium reference electrode and a discharge capacity Q of the lithium secondary battery during discharge of the lithium secondary battery; generates a V&#x2212;dQ/dV curve representing a relationship between dQ/dV, which is a proportion of an amount of change dQ in the discharge capacity Q to an amount of change dV in the voltage V, and the voltage V; calculates an intensity ratio of two peaks appearing on the V&#x2212;dQ/dV curve for two voltage values in the voltage V; and senses a state of the negative electrode utilizing the intensity ratio.

System and method for detecting a state of a lithium secondary battery by measuring a voltage of a negative electrode with respect to a reference electrode

There is provided a negative electrode for a nonaqueous electrolyte secondary battery in which when a battery is formed, the energy density is high, and moreover, the decrease in charge and discharge capacity is small even if charge and discharge are repeated. By using silicon oxide particles having a particle diameter in a particular range as a starting raw material, and heating these particles in the range of 850&#xb0; C. to 1050&#xb0; C., Si microcrystals are deposited on the surfaces of the particles. Then, by performing doping of Li, a structure comprising a plurality of protrusions having height and cross-sectional area in a particular range is formed on the surfaces. The average value of the height of the above protrusions is 2% to 19% of the average particle diameter of the above lithium-containing silicon oxide particles. By using the lithium-containing silicon oxide particles obtained by the above means as a negative electrode active material, a negative electrode for a nonaqueous electrolyte secondary battery is fabricated.

Negative electrode for nanaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery using the same, and method for manufacturing negative electrode for nonaqueous electrolyte secondary battery

In a lithium ion secondary battery including a positive electrode, a separator, and a negative electrode opposed to the positive electrode with an intervention of the separator, the negative electrode includes a negative electrode active material including a silicon compound, and a negative electrode binder including a particular polyimide, and lithium is occluded in both the negative electrode active material and the negative electrode binder even during discharge.

A secondary battery according to the present exemplary embodiment is a secondary battery including a laminated electrode body provided with at least one pair of positive and negative electrodes and an outer enclosure that accommodates the laminated electrode body, wherein the outer enclosure includes one or more concave portions, inside a border corresponding to an outer edge of an electrode surface of an outermost layer of the laminated electrode body, on a surface facing the electrode surface, and wherein, when a band-shaped outer circumferential region having an area that is a half of an area inside the border is set inside the border, at least one of the concave portions is located inside the outer circumferential region.

Secondary battery

There is provided a control system for a lithium secondary battery that can quantitatively sense a deterioration state inherent in a lithium secondary battery using silicon oxide as a negative electrode active material, that is, the nonuniform reaction state of a negative electrode. A control system for a lithium secondary battery including a positive electrode, a negative electrode using silicon oxide as a negative electrode active material, and a lithium reference electrode having a reference potential with respect to the negative electrode includes measurement means for measuring a voltage V of the negative electrode with respect to the lithium reference electrode and a discharge capacity Q of the lithium secondary battery during discharge of the lithium secondary battery; generation means for generating a V-dQ/dV curve representing a relationship between dQ/dV, which is a proportion of an amount of change dQ in the discharge capacity Q to an amount of change dV in the voltage V, and the voltage V; calculation means for calculating an intensity ratio of two peaks appearing on the V-dQ/dV curve for two voltage values in the voltage V; and sensing means for sensing a state of the negative electrode utilizing the intensity ratio.

Lithium secondary battery and control system therefor, and method for detecting state of lithium secondary battery

In a lithium ion secondary battery including a positive electrode, a separator, a negative electrode, and a package body, the negative electrode includes simple substance silicon as a negative electrode active material, and a negative electrode binder, and is doped with lithium, and the following formulas (1) and (2) are satisfied:1.2&#x2266;&#x2266;1.9&#x2003;&#x2003;(1)1.0&#x3c;/()&#x3c;1.6&#x2003;&#x2003;(2)wherein an amount of lithium inserted into the negative electrode until the negative electrode reaches a potential of 0.02 V with respect to metal lithium is M(a number of atoms), an amount of lithium released from the positive electrode until the positive electrode reaches a potential of 4.3 V with respect to metal lithium is M(a number of atoms), and an amount of lithium with which the negative electrode is doped is M(a number of atoms).

Lithium ion secondary battery and method for manufacturing the same

The invention provides a lithium ion secondary battery comprising a positive electrode, a negative electrode and an electrolysis solution containing an aprotic solvent having an electrolyte dissolved in it, wherein the negative electrodes uses an amorphous carbon material as a negative electrode active material. The amorphous carbon material has (A) an average particle diameter (median size) of 7 &#x3bc;m to 20 &#x3bc;m inclusive as measured by a laser diffraction scattering method and (B) a particle size distribution as measured by a laser diffraction scattering method, in which distribution the ratio of particles of less than 3 &#x3bc;m in diameter is 1% by mass to 10% mass inclusive, and is free of an electrical conducting material.

An electric double layer capacitor is disclosed which is capable of preventing transmission of an electrolytic solution vaporized in a basic cell through current collectors and capable of improving a yield. A method for preparing the electric double layer capacitor is also disclosed. The electric double layer capacitor comprises a basic cell prepared by the steps of: applying a current collector onto a surface of a substrate; disposing an electrically insulating gasket element on the surface the substrate in such a manner that the current collector laterally abuts on the gasket element to define a concavity; placing a polarizable electrode impregnated with an electrolytic solution on the surface of the current collector; oppositely disposing two intermediate products prepared through the foregoing steps on a separator in such a manner that the gasket elements abut on surfaces of a peripheral portion of the separator; fusion-bonding the gasket elements together to laterally cover the separator with the resulting unified gasket; and removing the substrates from the current collectors and the gasket. The substrate has a vapor transmission rate of a predetermined one or lower with respect to the electrolytic solution vaporized at a temperature of the fusion-bonding.

Electric double layer capacitor and method for preparing the same

An electric double layer capacitor is disclosed which is capable of preventing transmission of an electrolytic solution vaporized in a basic cell through current collectors and capable of improving a yield. A method for preparing the electric double layer capacitor is also disclosed. The electric double layer capacitor includes a basic cell prepared by the steps of: applying a current collector onto a surface of a substrate; disposing an electrically insulating gasket element on the surface the substrate in such a manner that the current collector laterally abuts on the gasket element to define a concavity; placing a polarizable electrode impregnated with an electrolytic solution on the surface of the current collector; oppositely disposing two intermediate products prepared through the foregoing steps on a separator in such a manner that the gasket elements abut on surfaces of a peripheral portion of the separator; fusion-bonding the gasket elements together to laterally cover the separator with the resulting unified gasket; and removing the substrates from the current collectors and the gasket. The substrate has a vapor transmission rate of a predetermined one or lower with respect to the electrolytic solution vaporized at a temperature of the fusion-bonding.

An electric double-layer capacitor includes a cell structure formed by laminating basic cells in series one on another. Each of the basic cells includes a pair of collectors, a separator disposed between said collectors, gaskets disposed at peripheral edges of said pair of collectors and said separator to define a pair of closed spaces, and a pair of polarizable electrodes which are disposed in said closed spaces defined by said collectors, said separator and said gaskets, respectively and which contain an electrolytic solution. The basic cells are laminated one on another with a back of each of said collectors opposed to said polarizable electrode serving as a connection surface. The electric double-layer capacitor further includes a lead terminal/electrode plate assembly having electrode plates bonded to the collectors located at opposite ends of the cell structure through conductive bond layers. At least one of interfaces between the collectors included in said cell structure has a surface shape based on a rugged surface shape of the surface of the polarizable electrode contacting with and opposed to at least one of the two collectors forming such interface. Thus, in the electric double-layer capacitor, a lower ESR can be realized both at an initial stage of the service of the capacitor and after the service of the capacitor for a long period.

Electric double-layer capacitor and method for preparing the same

An electric double-layer capacitor includes a cell structure constituted by laminating basic cells in series with their collectors serving as connections. Each of the basic cells includes a pair of collectors, a separator disposed between the collectors, and a pair of polarizable electrodes which are disposed between the collectors and the separator and in which an electrolytic solution is contained. The capacitor further includes lead terminal/electrode plate assemblies each having an electrode plate electrically connected to the collectors at opposite ends of the cell structure. Each of the collectors includes a matrix made of an elastomer having a hardness Hs in a range of about 55 (inclusive) to lower than about 85 at ambient temperature, and conductive particles dispersed in the matrix. Thus, in the electric double-layer capacitor, a lower ESR can be realized at in initial stage and even after the service for a long period.

Electric double-layer capacitor, and process for producing the same

A component cell of an electric double layer capacitor is fabricated by forming first and second half portions of the cell. In each of the half portions a polarized electrode impregnated with electrolyte is pasted to a collector electrode so that a stepped portion is formed on the periphery of the collector electrode. A gasket is attached to the stepped portion of each half portion, and a center gasket is attached to the periphery of a separator which is placed between the first and second half portions. Pressure is then applied to the first and second half portions of the cell in directions towards each other at an elevated temperature so that all gaskets are thermally joined together. A plurality of such component cells are stacked in a layered structure and sealed in a package.

Electric double layer capacitor of low ESR value and a method of fabricating same with low percent defective

An electric double-layer capacitor (EDLC) has a laminated overcoat encapsulating a stacked body including a plurality of basic cells and a pair of terminals sandwiching therebetween the stacked body. The innermost film of the laminated overcoat is thermally fused onto the exposed surfaces of the terminal plates and the stacked body substantially without a gap. The fusing step is conducted by an equal-pressure pressing using a hot water while the internal of the laminated overcoat is evacuated.

Electric double-layer capacitor having a laminated overcoat

An electric double layer capacitor includes a plurality of basic cells each including a pair of polarizing electrodes sandwiching therebetween a separator and impregnated with an electrolyte. The separator is made of unwoven fabric or porous film including polyolefine or fluorine based resin. The polarizing electrodes and the separator are bonded together in advance before stacking the basic cells to form a stacked cell structure. The bonding is performed by applying a thrust pressure to the polarizing electrodes sandwiching the separator, while heating at a temperature above a softening temperature of the polyolefine or fluorine based resin.

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Tokyo, Japan

Ryuichi Kasahara