Vehicle heat pump system and method utilizing intermediate gas recompression

A heat pump system for use in a vehicle having a battery and a passenger compartment, the heat pump system comprising:

• a heating circuit configured to circulate refrigerant in a first operating mode, to heat the passenger compartment and cool the battery;
• a cooling circuit configured to circulate refrigerant in a second operating mode, to condition air received by the passenger compartment and cool the battery;
• a compressor having a first inlet and a second inlet, incorporated into each of the heating circuit and the cooling circuit, the compressor configured to compress refrigerant;
• a vapor-liquid separator within each of the cooling circuit and the heating circuit configured to separate refrigerant in a gaseous state flowing therethrough from refrigerant in a liquid state flowing therethrough;
• a first expansion device within each of the heating circuit and cooling circuit upstream of the vapor-liquid separator configured to supply the vapor-liquid separator with refrigerant in a gaseous state and refrigerant in a liquid state;
• and wherein the vapor-liquid separator is configured to transmit and inject refrigerant in a gaseous state into the compressor at the second inlet to increase the mass flow rate of the refrigerant entering the compressor.