Abstract: According to one embodiment, provided is a secondary battery including an aqueous electrolyte, a positive electrode, and a negative electrode. A compound containing an element A is present on at least a part of the surface of the negative electrode. The element A is at least one selected from the group consisting of Hg, Pb, Zn, and Bi. According to scanning electron microscopy, a region where the compound containing the element A is present accounts for 50% of more of the surface of the negative electrode.

Abstract: According to one embodiment, a secondary battery is provided. The secondary battery includes a negative electrode, a positive electrode, a first aqueous electrolyte, a second aqueous electrolyte, and a partition having a first surface and a second surface opposite to the first surface. The partition is positioned between the negative electrode and the positive electrode. The first aqueous electrolyte is in contact with the first surface of the partition and the negative electrode. The second aqueous electrolyte is in contact with the second surface of the partition and the positive electrode. The partition contains a solid electrolyte having alkali metal ion conductivity. The first aqueous electrolyte includes an organic compound.

Abstract: According to one embodiment, a secondary battery including a positive electrode, a negative electrode, a separator, a first electrolyte, and a second electrolyte is provided. The separator is provided at least between the positive electrode and the negative electrode. The separator includes an alkali metal ion conductive solid electrolyte. The first electrolyte is contained in at least the positive electrode. The first electrolyte includes a first alkali metal salt and a first aqueous solvent. The second electrolyte is contained in at least the negative electrode. The second electrolyte includes a second alkali metal salt and a second aqueous solvent.

Abstract: According to one embodiment, a secondary battery includes a positive electrode, a negative electrode, a separator, a first electrolyte and a second electrolyte. The separator is arranged at least between the positive electrode and the negative electrode. The first electrolyte is contained at least in the positive electrode. The first electrolyte includes a lithium salt and an aqueous solvent. The second electrolyte is contained at least in the negative electrode. The second electrolyte includes a bis(fluorosulfonyl)imide salt and an aqueous solvent.

Abstract: According to one embodiment, provided is a secondary battery including an aqueous electrolyte, a positive electrode, and a negative electrode, where the negative electrode includes a negative electrode active material containing a Ti-containing composite oxide. At least one element A selected from the group consisting of Hg, Pb, Zn, and Bi is present on a surface of the negative electrode. An average of molar ratios (A/(A+Ti)) of the element A is more than or equal to 5% and less than or equal to 40%. Each of the molar ratios is a molar amount of the element A to a sum between the molar amount of the element A and a molar amount of Ti on the surface of the negative electrode, according to scanning electron microscopy-energy dispersive X-ray spectroscopy.

Abstract: According to one embodiment, there is provided a secondary battery including a positive electrode, a negative electrode, and an aqueous electrolyte. The negative electrode contains a titanium-containing oxide. The aqueous electrolyte contains a solvent and alkali metal ions or alkaline earth metal ions, the solvent containing water and a water-soluble organic solvent. An interfacial tension of the aqueous electrolyte is 37 mN/m or less.

Abstract: According to one embodiment, provided is a secondary battery including an aqueous electrolyte, a positive electrode, and a negative electrode. A compound containing an element A is present on at least a part of the surface of the negative electrode. The element A is at least one selected from the group consisting of Hg, Pb, Zn, and Bi.

Abstract: According to one embodiment, a secondary battery is provided. The secondary battery includes a negative electrode, a positive electrode, a first aqueous electrolyte, a second aqueous electrolyte, and a partition having a first surface and a second surface opposite to the first surface. The partition is positioned between the negative electrode and the positive electrode. The first aqueous electrolyte is in contact with the first surface of the partition and the negative electrode. The second aqueous electrolyte is in contact with the second surface of the partition and the positive electrode. The partition contains a solid electrolyte having alkali metal ion conductivity. The first aqueous electrolyte includes an organic compound.

Abstract: According to one embodiment, a secondary battery is provided. The secondary battery includes a positive electrode, a negative electrode, and an aqueous electrolyte containing alkali metal ions. The aqueous electrolyte contains an organic compound containing a carboxyl group or carboxylate group and a hydroxyl group. The pH of the aqueous electrolyte is 0 or less. The ratio of the weight of the organic compound to the weight of the aqueous electrolyte is within a range of 0.01% by weight to 6.5% by weight. The number of carbon atoms in the organic compound is 5 or more.

Abstract: According to one embodiment, a secondary battery including a positive electrode, a negative electrode, a separator, a first electrolyte, and a second electrolyte is provided. The separator is provided at least between the positive electrode and the negative electrode. The separator includes an alkali metal ion conductive solid electrolyte. The first electrolyte is contained in at least the positive electrode. The first electrolyte includes a first alkali metal salt and a first aqueous solvent. The second electrolyte is contained in at least the negative electrode. The second electrolyte includes a second alkali metal salt and a second aqueous solvent.

Abstract: According to one embodiment, a secondary battery includes a positive electrode, a negative electrode, a separator, a first electrolyte and a second electrolyte. The separator is arranged at least between the positive electrode and the negative electrode. The first electrolyte is contained at least in the positive electrode. The first electrolyte includes a lithium salt and an aqueous solvent. The second electrolyte is contained at least in the negative electrode. The second electrolyte includes a bis(fluorosulfonyl)imide salt and an aqueous solvent.

Abstract: In one embodiment, a secondary battery is provided, which includes an electrolytic solution, and a positive electrode and a negative electrode which are immersed in the electrolytic solution. The electrolytic solution contains water, an electrolyte salt, and at least one kind of an organic solvent with a relative permittivity of not more than 42. The relative permittivity of the electrolytic solution when converted according to a volume fraction is not more than 78.5.

Abstract: In one embodiment, a secondary battery is provided, which includes an electrolytic solution, and a positive electrode and a negative electrode which are immersed in the electrolytic solution. The electrolytic solution contains water, an electrolyte salt, and at least one kind of an organic solvent with a relative permittivity of not more than 42. The relative permittivity of the electrolytic solution fractionated when converted according to a volume fraction is not more than 78.50.