A secondary battery comprising a positive electrode , a negative electrode including a negative electrode current collector, and a negative electrode active material layer carried on one or both surfaces of the negative electrode current collector, the negative electrode active material layer comprising at least one selected from the group consisting of titanium oxide, lithium titanium oxide, niobium titanium oxide, and sodium niobium titanium oxide, and an aqueous electrolyte, wherein the aqueous electrolyte includes a first aqueous electrolyte and a second aqueous electrolyte , the first aqueous electrolyte is in contact with at least part of the positive electrode and contains lithium ions, the second aqueous electrolyte is in contact with at least part of the negative electrode and contains lithium ions, a concentration of the lithium ions contained in the second aqueous electrolyte is higher than the concentration of the lithium ions contained in the first aqueous electrolyte , and a ratio C2/C1 of a concentration C2 of the lithium ions contained in the second aqueous electrolyte to a concentration C1 of the lithium ions contained in the first aqueous electrolyte falls within a range of 2 to 11, the concentration C1 falls within a range from 1 mol/L to less than 5 mol/L, and the concentration C2 falls within a range from 5 mol/L to 12 mol/L, a relationship representing that the concentration of lithium ions contained in the second aqueous electrolyte is higher than the concentration of lithium ions contained in the first aqueous electrolyte does not change even if the secondary battery is charged or discharged. a positive electrode , a negative electrode including a negative electrode current collector, and a negative electrode active material layer carried on one or both surfaces of the negative electrode current collector, the negative electrode active material layer comprising at least one selected from the group consisting of titanium oxide, lithium titanium oxide, niobium titanium oxide, and sodium niobium titanium oxide, and an aqueous electrolyte, wherein the aqueous electrolyte includes a first aqueous electrolyte and a second aqueous electrolyte , the first aqueous electrolyte is in contact with at least part of the positive electrode and contains lithium ions, the second aqueous electrolyte is in contact with at least part of the negative electrode and contains lithium ions, a concentration of the lithium ions contained in the second aqueous electrolyte is higher than the concentration of the lithium ions contained in the first aqueous electrolyte , and a ratio C2/C1 of a concentration C2 of the lithium ions contained in the second aqueous electrolyte to a concentration C1 of the lithium ions contained in the first aqueous electrolyte falls within a range of 2 to 11, the concentration C1 falls within a range from 1 mol/L to less than 5 mol/L, and the concentration C2 falls within a range from 5 mol/L to 12 mol/L, a relationship representing that the concentration of lithium ions contained in the second aqueous electrolyte is higher than the concentration of lithium ions contained in the first aqueous electrolyte does not change even if the secondary battery is charged or discharged. <EOS>