What is a density in a battery?

In a battery, density typically refers to energy density, which measures the amount of energy stored per unit volume or weight. High energy density indicates that a battery can store more energy in a smaller or lighter form, making it more efficient for applications like electric vehicles and portable electronics. Additionally, there is power density, which relates to the rate at which energy can be delivered, affecting the battery's performance during discharge. Both types of density are critical for optimizing battery design and usability.