Explain the concept of 'energy density' in the context of EV batteries.

Energy density is a crucial concept in the context of electric vehicle (EV) batteries, as it determines how much energy can be stored in a given weight or volume of the battery. Specifically, energy density is typically expressed in watt-hours per kilogram (Wh/kg) for weight or watt-hours per liter (Wh/L) for volume. High energy density means that a battery can store more energy without significantly increasing its size or weight, which is essential for electric vehicles to maximize driving range and efficiency.

In practical terms, a battery with a higher energy density will enable a vehicle to travel further on a single charge, which is a key selling point for EVs. Manufacturers are constantly seeking advancements in battery technology to improve energy density, as this directly impacts the performance, design, and usability of electric vehicles on the market. Hence, understanding energy density is fundamental for evaluating battery performance and the overall effectiveness of an EV.