Insulating system for a battery system and method for controlling such an insulating system

A vehicle comprising:

• a traction battery having a plurality of battery cells disposed within a housing;
• a battery insulation system disposed between the plurality of battery cells and the housing and including inner and outer walls defining a cavity containing microporous silica;
• a vacuum pump coupled to a first port of the cavity;
• a valve coupled to a second port of the cavity;
• a coolant pump coupled to inlet and outlet ports of the housing, the inlet and outlet ports extending through the cavity to route heat exchanging fluid around the plurality of battery cells;
• and
• a controller communicating with the vacuum pump and the valve, the controller programmed to control the vacuum pump and the valve to lower pressure within the cavity responsive to a temperature difference between ambient temperature and temperature of the traction battery exceeding a threshold to decrease thermal conductivity of the insulation system, and to control the valve to increase pressure within the cavity responsive to the temperature difference not exceeding the threshold.