Battery assembly, battery module, battery pack and power equipment

The invention discloses a battery assembly, a battery module, a battery pack and power equipment, the battery assembly comprises a first battery and a second battery, the first battery is provided with a first shell, and the first shell is used as a positive electrode or a negative electrode of the first battery; the second battery is provided with a second shell, and the second shell serves as a negative electrode or a positive electrode of the second battery; the first shell and the second shell are arranged in an attached mode, and the polarity of the first shell is opposite to that of the second shell. According to the battery assembly provided by the invention, the first battery and the second battery are configured to have opposite polarities of the first shell and the second shell, and the first battery and the second battery are connected in series while the first shell and the second shell are arranged in an attached manner, so that the energy density of the battery assembly is improved.