Abstract: A positive electrode active material, which has higher capacity and excellent charge and discharge cycle performance, for a lithium-ion secondary battery is provided. The positive electrode active material includes lithium, cobalt, magnesium, oxygen, and fluorine; when a pattern obtained by powder X ray diffraction using a CuK?1 ray is subjected to Rietveld analysis, the positive electrode active material has a crystal structure having a space group R-3m, a lattice constant of an a-axis is greater than 2.814×10(?10th power) m and less than 2.817×10(?10th power) m, and a lattice constant of a c-axis is greater than 14.05×10(?10th power) m and less than 14.07×10(?10th power) m; and in analysis by X-ray photoelectron spectroscopy, a relative value of a magnesium concentration is higher than or equal to 1.6 and lower than or equal to 6.0 with the cobalt concentration regarded as 1.

Abstract: Positive electrode active material particles that inhibit a decrease in capacity due to charge and discharge cycles are provided. A high-capacity secondary battery, a secondary battery with excellent charge and discharge characteristics, or a highly-safe or highly-reliable secondary battery is provided. A novel material, active material particles, and a storage device are provided. The positive electrode active material particle includes a first region and a second region in contact with the outside of the first region. The first region contains lithium, oxygen, and an element M that is one or more elements selected from cobalt, manganese, and nickel. The second region contains the element M, oxygen, magnesium, and fluorine. The atomic ratio of lithium to the element M (Li/M) measured by X-ray photoelectron spectroscopy is 0.5 or more and 0.85 or less. The atomic ratio of magnesium to the element M (Mg/M) is 0.2 or more and 0.5 or less.

Abstract: Provided is a positive electrode active material which suppresses a reduction in capacity due to charge and discharge cycles when used in a lithium ion secondary battery. A covering layer is formed by segregation on a superficial portion of the positive electrode active material. The positive electrode active material includes a first region and a second region. The first region exists in an inner portion of the positive electrode active material. The second region exists in a superficial portion of the positive electrode active material and part of the inner portion thereof. The first region includes lithium, a transition metal, and oxygen. The second region includes magnesium, fluorine, and oxygen.

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: A positive electrode active material with high capacity and excellent charge and discharge cycle performance, a positive electrode active material with high productivity, a positive electrode active material that suppresses a decrease in capacity, or the like is provided. Alternatively, a high-capacity secondary battery, a secondary battery with excellent charge and discharge characteristics, a highly safe or reliable secondary battery, or the like is provided. The positive electrode active material is obtained by a first heating step of heating a mixture of a first material, a second material, and a third material and a second heating step of heating a mixture which is a mixture of the mixture, a fourth material, and a fifth material and has a total amount of 15 g or more.

Abstract: A method for forming a positive electrode active material of a lithium ion secondary battery is provided. In the method for forming a positive electrode active material, a first container that includes a mixture of lithium oxide, fluoride, and a magnesium compound and fluoride that is outside the first container are provided in a heating furnace, and the heating furnace is heated at a temperature higher than or equal to a temperature at which the fluoride is volatilized or sublimated. It is further preferable that the fluoride be lithium fluoride and the magnesium compound be magnesium fluoride.

Abstract: A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed.

Abstract: A method of estimating the state of charge of a secondary battery that has high estimation accuracy even when degradation of the secondary battery progresses is provided. Furthermore, a capacity measurement system of a secondary battery that estimates an SOC with high estimation accuracy in a short time at low cost is provided. When the capacity of a secondary battery can be estimated with high accuracy, an anomaly can also be detected in accordance with the value. A novel method of detecting an anomaly of a secondary battery is provided. In the CCCV charging method, the CC time and the CV time are used as learning parameters to construct a learning model. With this learning model, an estimated capacity value with high accuracy can be obtained with use of two data, which are the CC time and the CV time, or three data, which are the CC time, the CV time, and a charge inception voltage value as the minimum input data.

Abstract: Provided is a positive electrode active material that achieves improvement in load resistance such as rate performance and output resistance when used as a positive electrode active material in a lithium-ion secondary battery, achieves improvement in powder properties, has a short manufacturing cycle time, and is low in cost. The positive electrode active material is manufactured by a first step of forming a first mixture by separately pulverizing a compound containing one or more elements selected from magnesium, calcium, zirconium, lanthanum, and barium; a compound containing halogen and an alkali metal; and a fluoride containing one or more metals selected from nickel, aluminum, manganese, titanium, vanadium, iron, and chromium, and then mixing them with metal oxide powder; and a second step of performing heating at a temperature higher than or equal to 700° C. and lower than or equal to 950° C.

Abstract: A method for forming a positive electrode active material of a lithium ion secondary battery is provided. The method for forming a positive electrode active material includes a first step of placing a first container in which a mixture of a lithium oxide, a fluoride, and a magnesium compound are put, in a heating furnace, a second step of providing an atmosphere including oxygen in an inside of the heating furnace, and a third step of heating the inside of the heating furnace. The third step is performed after the first step and the second step are performed. Preferably, an atmosphere including oxygen is provided in the heating furnace before the inside of the heating furnace is heated. More preferably, the fluoride is lithium fluoride and the magnesium compound is magnesium fluoride.

Abstract: An analysis method of a lithium composite oxide is provided. The method is to analyze substitution positions of a Ni atom and a Mg atom in a compound represented by a chemical formula Li(1?x?y)Co(1?a?b)Ni(x+a)Mg(y+b)O2. The analysis method includes a first calculation step of calculating stabilization energy when a Ni atom and a Mg atom each substitute for a Li atom and/or a Co atom contained in a LiCoO2 crystal. The analysis method includes a second calculation step of calculating stabilization energy of the compound represented by the chemical formula when cation occupancy of Li sites is changed. The analysis method includes a first measurement step of measuring charge-discharge efficiency in the first cycle and charge-discharge efficiency in the n-th cycle of the compound represented by the chemical formula. Note that n means an integer greater than or equal to 2.

Abstract: The present invention relates to a secondary battery and an electronic device. The secondary battery includes a positive electrode active material which exhibits a broad peak at around 4.55 V in a dQ/dVvsV curve obtained when the charge depth is increased. The secondary battery includes a positive electrode active material which, even when the charge voltage is greater than or equal to 4.6 V and less than or equal to 4.8 V and the charge depth is greater than or equal to 0.8 and less than 0.9, does not have the H1-3 type structure and can maintain a crystal structure where a shift in CoO2 layers is inhibited. The broad peak at around 4.55 V in the dQ/dVvsV curve indicates that a change in the energy necessary for extraction of lithium at around the voltage is small and a change in the crystal structure is small. Accordingly, the positive electrode active material hardly suffers a shift in CoO2 layers and a volume change and is relatively stable even when the charge depth is large.

Abstract: A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed.

Abstract: The present invention relates to a method for manufacturing a secondary battery and a secondary battery. A method for manufacturing a positive electrode active material with high charge and discharge capacity is provided. A method for manufacturing a positive electrode active material with high charging and discharging voltages is provided. A method for manufacturing a positive electrode active material with little deterioration is provided. The positive electrode active material is manufactured through a step of forming a composite oxide that contains lithium, nickel, manganese, cobalt, and oxygen; and a step of mixing the composite oxide and a calcium compound, and then heating the mixture at a temperature higher than or equal to 500° C. and lower than or equal to 1100° C. for 2 hours to 20 hours. By the heating, calcium is distributed at a preferred concentration in a surface portion of the positive electrode active material.

Abstract: A positive electrode material for a lithium-ion secondary battery which has high capacity and excellent charge and discharge cycle performance, and a manufacturing method thereof are provided, or a method of manufacturing a positive electrode material with high productivity is provided. The positive electrode material for a lithium-ion secondary battery includes a crystal represented by a crystal structure with a space group R-3m, a first region, and a second region, which is in contact with at least part of an outer side of the first region and whose outer edge corresponds to a surface of the first particle. The ratio of manganese atoms to cobalt atoms in the first region is lower than the ratio of manganese atoms to cobalt atoms in the second region. The ratio of fluorine atoms to oxygen atoms in the first region is lower than the ratio of fluorine atoms to oxygen atoms in the second region.

Abstract: A semiconductor device that detects deterioration of a secondary battery is provided. The semiconductor device includes a power gauge, an anomalous current detection circuit, and a control circuit. The power gauge includes a current divider circuit and an integrator circuit. The anomalous current detection circuit includes a first memory, a second memory, and a first comparator. The integrator circuit can convert a detection current detected at the current divider circuit into a detection voltage by integrating the detection current. The anomalous current detection circuit is supplied with the detection voltage, a first signal at a first time, and a second signal at a second time. The first signal can make the detection voltage at the first time be stored in the first memory and the second signal can make the detection voltage at the second time be stored in the second memory.

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: A positive electrode active material with high capacity and excellent charging and discharging cycle performance for a lithium-ion secondary battery is provided. The positive electrode active material contains lithium, cobalt, and oxygen, and the spin density attributed to a bivalent 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 as a concentration with respect to cobalt. It is also preferable that the positive electrode active material further contain fluorine.