Abstract: To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber. The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

Abstract: A conduction path in an all-solid-state secondary battery is difficult to keep with a volume change in an active material due to charging and discharging in some cases. A positive electrode active material with a small volume change between the charged state and the discharged state is used for an all-solid-state secondary battery. For example, a positive electrode active material that has a layered rock-salt crystal structure in the discharged state and a crystal structure similar to the cadmium chloride type crystal structure in the charged state with a depth of charge of approximately 0.8 changes less in its volume and crystal structure between charging and discharging than known positive electrode active materials.

Abstract: A storage battery includes positive and negative electrodes and an electrolytic solution. The negative electrode includes a first element and carbon. The first element is any of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium. The negative electrode includes an active material and a first layer in contact with a surface of the active material. The first layer has a thickness of 10 nm to 1000 nm inclusive. The electrolytic solution contains first and second cations. The first cation is one or more of a lithium ion, a sodium ion, a calcium ion, and a magnesium ion. The second cation is an imidazolium cation or a tertiary sulfonium cation.

Abstract: According to one embodiment of the present invention, a positive electrode active material with high charge and discharge capacity is provided. Alternatively, a positive electrode active material with high charge and discharge voltage is provided. Alternatively, a positive electrode active material with little deterioration is provided. To improve the reliability of the positive electrode active material, the surface of the positive electrode active material is prevented from reacting with an electrolyte solution and being reduced. The provision of a projection on part of the positive electrode active material surface decreases the reduction of the positive electrode active material surface from reacting with the electrolyte solution, thereby improving the cycle performance.

Abstract: A battery module with high impact resistance is provided. A battery module using an elastic body such as rubber for its exterior body covering a battery is provided. A bendable battery module is provided. As the exterior body covering a battery, an elastic body such as rubber is used, and the exterior body is molded in two steps. First, a first portion provided with a depression in which a battery is stored is molded using a first mold. Next, a battery is inserted into the first portion. Subsequently, second molding is performed using a second mold so as to fill an opening of the depression in the first portion, so that a second portion is formed. The second portion serves as a cover for closing the opening of the depression in the first portion. The second portion is formed in contact with part of the electrodes in the battery and part of an end portion of the second exterior body in the battery.

Abstract: A method for manufacturing a positive electrode active material with high charge and discharge capacity is provided. Alternatively, a method for manufacturing a positive electrode active material with high charge and discharge voltage is provided. Alternatively, a method for manufacturing a power storage device with little deterioration is provided. Alternatively, a method for manufacturing a highly safe power storage device is provided. Alternatively, a method for manufacturing a novel power storage device is provided. A method for manufacturing a secondary battery including a positive electrode active material is provided.

Abstract: A battery module with high impact resistance is provided. A battery module using an elastic body such as rubber for its exterior body covering a battery is provided. A bendable battery module is provided. As the exterior body covering a battery, an elastic body such as rubber is used, and the exterior body is molded in two steps. First, a first portion provided with a depression in which a battery is stored is molded using a first mold. Next, a battery is inserted into the first portion. Subsequently, second molding is performed using a second mold so as to fill an opening of the depression in the first portion, so that a second portion is formed. The second portion serves as a cover for closing the opening of the depression in the first portion. The second portion is formed in contact with part of the electrodes in the battery and part of an end portion of the second exterior body in the battery.

Abstract: A method for manufacturing a novel electrode is provided. The method includes the steps of applying, to a current collector, a mixture comprising an active material, a conductive additive comprising a graphene compound, a binder, and a dispersion medium; performing a drying treatment on the mixture; performing a heat treatment on the mixture at a temperature higher than a temperature of the drying treatment; reducing the graphene compound in the mixture by a chemical reaction using a reducing agent; and performing a thermal reduction treatment on the mixture at a temperature higher than the temperature of the heat treatment.

Abstract: A positive electrode active material that has high capacity and excellent charge and discharge cycle performance for a secondary battery is provided. The positive electrode active material includes a group of particles including a first group of particles and a second group of particles. The group of particles includes lithium, cobalt, nickel, aluminum, magnesium, oxygen, and fluorine. When the number of cobalt atoms included in the group of particles is taken as 100, the number of nickel atoms is greater than or equal to 0.05 and less than or equal to 2, the number of aluminum atoms is greater than or equal to 0.05 and less than or equal to 2, and the number of magnesium atoms is greater than or equal to 0.1 and less than or equal to 6.

Abstract: A positive electrode active material for a lithium-ion secondary battery and with high capacity and excellent charging and discharging cycle performance is provided. The positive electrode active material contains lithium, cobalt, nickel, aluminum, and oxygen, and the spin density attributed to one or more of a divalent nickel ion, a trivalent nickel ion, a divalent cobalt ion, and a tetravalent cobalt ion is within a predetermined range. It is preferable that the positive electrode active material further contain magnesium. An appropriate magnesium concentration is represented by a concentration with respect to cobalt. It is preferable that the positive electrode active material further contain fluorine.

Abstract: To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber. The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

Abstract: To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber. The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

Abstract: A positive electrode active material that has high capacity and excellent charge and discharge cycle performance for a secondary battery is provided. A positive electrode active material that inhibits a decrease in capacity in charge and discharge cycles is provided. A high-capacity secondary battery is provided. A secondary battery with excellent charge and discharge characteristics is provided. A highly safe or reliable secondary battery is provided. A positive electrode active material contains lithium, cobalt, oxygen, and aluminum and has a crystal structure belonging to a space group R-3m when Rietveld analysis is performed on a pattern obtained by powder X-ray diffraction. In analysis by X-ray photoelectron spectroscopy, the number of aluminum atoms is less than or equal to 0.2 times the number of cobalt atoms.

Abstract: An object is to provide a method for manufacturing a positive electrode active material that achieves high powder properties and high load resistance (e.g., rate performance and output resistance) when used in a lithium-ion secondary battery, within a short manufacturing cycle time and at low cost. To perform heat treatment at temperatures lower than the melting point of magnesium fluorine, lithium fluoride is mixed to melt magnesium fluorine and modify the surface of lithium cobalt oxide powder. By mixing lithium fluoride, magnesium fluorine can be melted at a temperature lower than its melting point, and a positive electrode active material is formed utilizing this eutectic phenomenon.

Abstract: A positive electrode active material for a lithium ion secondary battery which has a large capacity and a good charge-and-discharge cycle performance is provided. The positive electrode active material includes lithium, cobalt, oxygen, and magnesium, and has a compound represented by a layered rock-salt crystal structure. A space group of the compound is represented by R-3m. The compound is a composite oxide in which magnesium is substituted for a lithium position and a cobalt position. The compound is a particle. The magnesium substituted for a lithium position and a cobalt position exists more in the region from the surface to 5 nm than in the region deeper than 10 nm from the surface. More magnesium is substituted for a lithium position than for a cobalt position.

Abstract: Provided is a power storage device whose charging and discharging characteristics are unlikely to be degraded by heat treatment or a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body. The separator is positioned between the positive electrode and the negative electrode and includes polyphenylene sulfide or cellulosic fiber. The electrolyte includes propylene carbonate, ethylene carbonate, and vinylene carbonate, lithium hexafluorophosphate, and lithium bis(pentafluoroethanesulfonyl)amide. A concentration of lithium hexafluorophosphate with respect to the electrolyte is more than or equal to 0.01 wt % and less than or equal to 1.9 wt % in a weight ratio.

Abstract: A conduction path in an all-solid-state secondary battery is difficult to keep with a volume change in an active material due to charging and discharging in some cases. A positive electrode active material with a small volume change between the charged state and the discharged state is used for an all-solid-state secondary battery. For example, a positive electrode active material that has a layered rock-salt crystal structure in the discharged state and a crystal structure similar to the cadmium chloride type crystal structure in the charged state with a depth of charge of approximately 0.8 changes less in its volume and crystal structure between charging and discharging than known positive electrode active materials.

Abstract: Provided is a power storage device whose charging and discharging characteristics are unlikely to be degraded by heat treatment or a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body. The separator is positioned between the positive electrode and the negative electrode and includes polyphenylene sulfide or cellulosic fiber. The electrolyte includes propylene carbonate, ethylene carbonate, and vinylene carbonate, lithium hexafluorophosphate, and lithium bis(pentafluoroethanesulfonyl)amide. A concentration of lithium hexafluorophosphate with respect to the electrolyte is more than or equal to 0.01 wt % and less than or equal to 1.9 wt % in a weight ratio.

Abstract: A battery module with high impact resistance is provided. A battery module using an elastic body such as rubber for its exterior body covering a battery is provided. A bendable battery module is provided. As the exterior body covering a battery, an elastic body such as rubber is used, and the exterior body is molded in two steps. First, a first portion provided with a depression in which a battery is stored is molded using a first mold. Next, a battery is inserted into the first portion. Subsequently, second molding is performed using a second mold so as to fill an opening of the depression in the first portion, so that a second portion is formed. The second portion serves as a cover for closing the opening of the depression in the first portion. The second portion is formed in contact with part of the electrodes in the battery and part of an end portion of the second exterior body in the battery.

Abstract: A method for manufacturing a lithium-ion secondary battery more safely at a lower cost is provided. A method for manufacturing a positive electrode for a secondary battery includes a step of forming slurry by mixing graphene oxide, a binder, and a positive electrode active material in a solvent containing water; a step of applying the slurry on a positive electrode current collector; and a step of reducing graphene oxide by at least one of chemical reduction and thermal reduction. As a reducing agent for the chemical reduction, ascorbic acid can be used.