Abstract: A sealed battery comprises: a bottomed tubular outer can accommodating an electrode body; and a sealing body for sealing an opening of the outer can. The present invention is characterized in that: the sealing body includes a current blocking mechanism that seals the electrode body together with the outer can and is activated in response to gas pressure inside the battery, and a cap that forms a sealed space above the current blocking mechanism; and the cap includes an explosion-proof valve that opens in response to the gas pressure inside the battery.

Abstract: Even after the battery reaches the last stage of the end of life, the use can be continued. A charging system includes battery pack and charger. During the charge of lithium-ion secondary battery, charge control unit calculates the full charge capacity maintaining rate, sets a first charge current value on the basis of the full charge capacity maintaining rate, and charges the battery. When lithium-ion secondary battery reaches the last stage of the end of life, charge control unit sets a second charge current value lower than the first charge current value set based on the full charge capacity maintaining rate, and charges the battery.

Abstract: Even after the battery reaches the last stage of the end of life, the use can be continued. A charging system includes battery pack and charger. During the charge of lithium-ion secondary battery, charge control unit calculates the full charge capacity maintaining rate, sets a first charge current value on the basis of the full charge capacity maintaining rate, and charges the battery. When lithium-ion secondary battery reaches the last stage of the end of life, charge control unit sets a second charge current value lower than the first charge current value set based on the full charge capacity maintaining rate, and charges the battery.

Abstract: A positive electrode includes a positive electrode current collector, and a positive electrode active material layer formed on the surface of the positive electrode current collector. The positive electrode active material layer includes: a lithium-containing nickel oxide represented by the general formula (1): LixNi1?(p+q+r)CopAlqMrO2+y, where M is a transition metal (excluding Ni and Co) or the like, 0.8?x?1.4, and 0<(p+q+r)?0.7); and lithium carbonate. The positive electrode active material layer has a high concentration region of the lithium carbonate and a low concentration region of the lithium carbonate. The high concentration region covers 2 to 80% of the total thickness of the positive electrode active material layer, the range starting from the surface thereof. The low concentration region covers the range remaining on the positive electrode current collector side of the positive electrode active material layer.

Abstract: An object of the present invention is to provide: a positive electrode including a lithium-containing nickel oxide which serves as a positive electrode active material and having excellent input/output characteristics, durability, and reliability; and a lithium ion battery which uses this positive electrode. The positive electrode includes a positive electrode current collector, and a positive electrode active material layer formed on the surface of the positive electrode current collector. The positive electrode active material layer includes: a lithium-containing nickel oxide represented by the general formula (1): LixNi1?(p+q+r)CopAlqMrO2+y, where M is a transition metal (excluding Ni and Co) or the like, 0.8?x?1.4, and 0<(p+q+r)?0.7); and lithium carbonate. The positive electrode active material layer has a high concentration region of the lithium carbonate and a low concentration region of the lithium carbonate.