Abstract: Disclosed is a power storage unit which can safely operate over a wide temperature range. The power storage unit in a power storage device; a heater for heating the power storage device; a temperature sensor for sensing the to of the power storage device; and a control circuit configured to in charge of the power storage device when its temperature is lower than a first temperature or higher than a second temperature. The first temperature is exemplified by a temperature which allows the formation of a dendrite over a negative electrode of the power storage device, whereas the second temperature is exemplified by a temperature which causes decomposition of a passivating film formed over a surface of a negative electrode active material.

Abstract: To provide a highly reliable power storage device, to improve the security of a power storage device, and to suppress deterioration of a power storage device, a power storage device includes, inside an exterior material, a positive electrode, a negative electrode facing the positive electrode, an electrolyte solution between the positive electrode and the negative electrode, and an adsorbent. A separation body which is impermeable to the electrolyte solution and permeable to a gas is provided between the electrolyte solution and the adsorbent.

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering pan of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: Disclosed is a power storage unit which can safely operate over a wide temperature range. The power storage unit includes: a power storage device; a heater for heating the power storage device; a temperature sensor for sensing the temperature of the power storage device; and a control circuit configured to inhibit charge of the power storage device when its temperature is lower than a first temperature or higher than a second temperature. The first temperature is exemplified by a temperature which allows the formation of a dendrite over a negative electrode of the power storage device, whereas the second temperature is exemplified by a temperature which causes decomposition of a passivating film formed over a surface of a negative electrode active material.

Abstract: Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

Abstract: To inhibit degradation of charge and discharge cycle characteristics of a secondary battery. To suppress generation of defects due to expansion and contraction of an active material in a negative electrode. To inhibit deterioration of an electrode due to changes in its form. An electrode member including a current collector, an active material, and a porous body is used. The porous body is in contact with one surface of the current collector and includes a plurality of spaces. The active material is located in the space in the porous body. The space has a larger size than the active material.

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering part of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: To provide a highly reliable power storage device, to improve the security of a power storage device, and to suppress deterioration of a power storage device, a power storage device includes, inside an exterior material, a positive electrode, a negative electrode facing the positive electrode, an electrolyte solution between the positive electrode and the negative electrode, and an adsorbent. A separation body which is impermeable to the electrolyte solution and permeable to a gas is provided between the electrolyte solution and the adsorbent.

Abstract: To improve the reliability of a power storage device. A granular active material including carbon is used, and a net-like structure is formed on part of a surface of the granular active material. In the net-like structure, a carbon atom included in the granular active material is bonded to a silicon atom or a metal atom through an oxygen atom. Formation of the net-like structure suppresses reductive decomposition of an electrolyte solution, leading to a reduction in irreversible capacity. A power storage device using the above active material has high cycle performance and high reliability.

Abstract: To provide a sheet-like power storage device which can be curved or bent in at least one axis direction. A power storage device includes a power storage element including a plurality of flexible sheet-like positive electrodes each having one end portion fixed to a positive electrode tab; a plurality of flexible sheet-like negative electrodes each having one end portion fixed to a negative electrode tab; and a plurality of flexible sheet-like separators. The positive electrodes and the negative electrodes are alternately stacked so as to overlap with each other with the separator interposed therebetween. The power storage element is sealed in a flexible exterior body.

Abstract: An object is to inhibit a decrease in the capacity of a power storage device or to compensate the capacity, by adjusting or rectifying an imbalance between a positive electrode and a negative electrode, which is caused by decomposition of an electrolyte solution at the negative electrode. Provided is a charging method of a power storage device including a positive electrode using an active material that exhibits two-phase reaction, a negative electrode, and an electrolyte solution. The method includes the steps of, after constant current charging, performing constant voltage charging with a voltage that does not cause decomposition of the electrolyte solution until a charging current becomes lower than or equal to a lower current value limit; and after the constant voltage charging, performing additional charging with a voltage that causes decomposition of the electrolyte solution until a resistance of the power storage device reaches a predetermined resistance.

Abstract: To provide a highly reliable power storage device, to improve the security of a power storage device, and to suppress deterioration of a power storage device, a power storage device includes, inside an exterior material, a positive electrode, a negative electrode facing the positive electrode, an electrolyte solution between the positive electrode and the negative electrode, and an adsorbent. A separation body which is impermeable to the electrolyte solution and permeable to a gas is provided between the electrolyte solution and the adsorbent.

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering part of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer over the positive electrode current collector. The positive electrode active material layer includes a plurality of lithium-containing, composite oxides each of which is expressed by LiMPO4 (M is one or more of Fe (II), Mn (II), Co (II), and Ni (II)) that is a general formula. The lithium-containing composite oxide is a flat single crystal particle in which the length in the b-axis direction is shorter than each of the lengths in the a-axis direction and the c-axis direction. The lithium-containing composite oxide is provided over the positive electrode current collector so that the b-axis of the single crystal particle intersects with the surface of the positive electrode current collector.

Abstract: To improve the reliability of a power storage device. A granular active material including carbon is used, and a net-like structure is formed on part of a surface of the granular active material. In the net-like structure, a carbon atom included in the granular active material is bonded to a silicon atom or a metal atom through an oxygen atom. Formation of the net-like structure suppresses reductive decomposition of an electrolyte solution, leading to a reduction in irreversible capacity. A power storage device using the above active material has high cycle performance and high reliability.

Abstract: A power storage system or a power storage device that can restore reduced capacity is provided. The power storage device includes a first exterior body, a first electrode, a second electrode, a first electrolyte solution, and a carrier ion permeable film. The first electrode, the second electrode, and the first electrolyte solution are covered with the first exterior body. The first electrode and the second electrode are in contact with the first electrolyte solution. The first electrolyte solution includes carrier ions. A first opening is provided in the first exterior body. The carrier ion permeable film is provided to be in contact with the first electrolyte solution and so as to block the first opening without any space. The carrier ion permeable film is configured to be impermeable to water and air but permeable to the carrier ions.

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering part of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer over the positive electrode current collector. The positive electrode active material layer includes a plurality of lithium-containing composite oxides each of which is expressed by LiMPO4 (M is one or more of Fe (II), Mn (II), Co (II), and Ni (II)) that is a general formula. The lithium-containing composite oxide is a flat single crystal particle in which the length in the b-axis direction is shorter than each of the lengths in the a-axis direction and the c-axis direction. The lithium-containing composite oxide is provided over the positive electrode current collector so that the b-axis of the single crystal particle intersects with the surface of the positive electrode current collector.

Abstract: Deterioration of a power storage device is reduced. Switches that control the connections of a plurality of power storage devices separately are provided. The switches are controlled with a plurality of control signals, so as to switch between charge and discharge of each of the power storage devices or between serial connection and parallel connection of the plurality of power storage devices. Further, a semiconductor circuit having a function of carrying out arithmetic is provided for the power storage devices, so that a control system of the power storage devices or a power storage system is constructed.

Abstract: A lithium-ion secondary battery with no negative electrode active material is provided. One embodiment of the present invention is a lithium-ion secondary battery including a positive electrode, a negative electrode, an electrolyte solution, and a separator between the positive electrode and the negative electrode. The negative electrode includes a negative electrode current collector which includes a region in direct contact with at least one of the electrolyte solution and the separator. The electrolyte solution contains fluorine. The negative electrode current collector has a function of making a deposit containing lithium to be deposited on a surface in charging. Furthermore, a spacer may be provided between the separator and the negative electrode. The electrolyte solution may contain an organic compound containing fluorine.