A secondary battery includes a metal housing and an electrode assembly arranged inside the metal housing. The electrode assembly includes a negative electrode. The negative electrode includes a negative electrode material layer. The negative electrode material layer includes a binder. The binder includes a first binder and a second binder, where the first binder is selected from styrene-butadiene rubber polymers and the second binder is selected from polyacrylic acid polymers. A weight-average molecular weight of the first binder is 40,000 to 300,000, and a weight-average molecular weight of the second binder is 400,000 to 2,000,000. A mass percentage of the first binder is 10% to 90% based on a mass of the binder.