Encapsulant
What else is in the battery module besides the cells? This is one of the main determinants of the energy density of a battery. Many battery modules rely on the terminal welds along with adhesive to keep the cells from vibrating against each other; this requires a larger gap between the cells. Other modules have a cooling system with either serpentine cooling coils or immersive fluid between the cells, again taking up extra space but not immobilizing the cells. Some modules fill the space with foam which prevents vibration but insulates the heat that is produced in the body of the cells.
EV Drive uses a highly specialized encapsulation material that allows the cells to be as close as possible without touching or vibrating. The material is electrically resistive to isolate any short circuits but heat conductive to direct the generated heat to the terminal cold plates. The encapsulant is fire resistive to prevent a burn-to-the-ground situation in the case of a collision. And it is very hard and strong, making the modules nearly indestructible.