A sodium-ion battery, comprising a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector and comprises a positive electrode active material; the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector and comprises a negative electrode active material, and the negative electrode active material is hard carbon; and wherein a ratio of a median particle size A of the positive electrode active material to a median particle size B of the negative electrode active material satisfies 0.1 ≤ A/B ≤ 1, as measured according to the description; and wherein the positive electrode active material comprises one or more of polyanionic compounds and Prussian blue compounds; and wherein the polyanionic compounds comprise A 1 f M 3 g (PO 4) i O j X 1 3- j, wherein A is one or more of H, Li, Na, K and NH 4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 is one or more of F, Cl and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2; and wherein the Prussian blue compounds comprise A u M 6 v [M 7 6] w • x H 2 O, wherein A is one or more of H +, NH 4+, alkali metal cations and alkaline-earth metal cations, M 6 and M 7 are respectively one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ I, 0 < w ≤ I, 0 < x < 6. wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector and comprises a positive electrode active material; the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector and comprises a negative electrode active material, and the negative electrode active material is hard carbon; and wherein a ratio of a median particle size A of the positive electrode active material to a median particle size B of the negative electrode active material satisfies 0.1 ≤ A/B ≤ 1, as measured according to the description; and wherein the positive electrode active material comprises one or more of polyanionic compounds and Prussian blue compounds; and wherein the polyanionic compounds comprise A 1 f M 3 g (PO 4) i O j X 1 3- j, wherein A is one or more of H, Li, Na, K and NH 4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 is one or more of F, Cl and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2; and wherein the Prussian blue compounds comprise A u M 6 v [M 7 6] w • x H 2 O, wherein A is one or more of H +, NH 4+, alkali metal cations and alkaline-earth metal cations, M 6 and M 7 are respectively one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ I, 0 < w ≤ I, 0 < x < 6.