According to one embodiment, a secondary battery is provided. The secondary battery includes a negative electrode. The negative electrode includes an active material composite. The active material composite includes active material particles and a layer covering at least a portion of surfaces of the active material particles. The active material particles include titanium-containing oxide particles. The layer contains N and Si. The layer includes a first surface facing the at least the portion of surfaces of the active material particles and a second surface defining a layer thickness from the first surface. An N concentration in the layer decreases from the first surface to the second surface. A Si concentration in the layer increases from the first surface to the second surface.