Clean Rooms Are Not Dry Rooms
Manufacturing lithium ion batteries is a complicated technical process that has many challenges - not the least of which is the requirement for all processing of the lithium electrodes to be done under very low humidity conditions - typically below 1% RH or lower (- 35°C or -40°C dew point) and must also be a low particulate environment. On the other hand, clean rooms (like those used in the semiconductor industry) are actually designed to leak, so that the positive internal pressure prevents any particle intrusion into the space. These environments are typically controlled at higher humidity levels as cleanliness is the primary concern, not extreme dryness. To better control the humidity in the lithium ion battery processing areas, dry rooms were developed that allowed manufacturing to take place in a dry environment that is hermetically sealed to maintain these very low humidity levels and provides particle filtration for cleanliness.