ACTIVE MATERIAL LAYER FOR NEGATIVE ELECTRODE, METHOD FOR PRODUCING SAME, ELECTRODE MIXTURE PASTE FOR POWER STORAGE DEVICE NEGATIVE ELECTRODE, NEGATIVE ELECTRODE FOR POWER STORAGE DEVICE, AND POWER STORAGE DEVICE

This power storage device uses a negative electrode active material layer which contains a negative electrode active material containing silicon-based particles and a polyimide-based binder, wherein the negative electrode active material layer has a porosity of less than 20%. This power storage device has a high charge/discharge capacity and excellent cycle characteristics.