A double-stage rotary vane vacuum pump is the go-to choice when you need a significantly deeper vacuum (10^{-3} to 10^{-4} mbar) and higher pumping speeds at a lower cost. In battery research, these are typically used for large-scale vacuum drying ovens or backing glovebox purification systems rather than the sealing machine itself, due to the risk of oil back-streaming.

A rotary vane pump uses centrifugal force to move vanes within a cylindrical housing, trapping and compressing air. A "Double Stage" pump essentially connects two of these mechanisms in series. Stage 1 (High Vacuum Stage): Takes in the gas from the inlet at low pressure and compresses it. Stage 2 (Low Vacuum Stage): Takes the exhaust from the first stage and compresses it further to atmospheric pressure for discharge.

The key features of a double-stage rotary vane vacuum pump are show below: (1) Ultimate Vacuum: It can reach pressures as low as 10^{-3} mbar. This is orders of magnitude deeper than a standard diaphragm pump, which is essential for removing deep-seated moisture in electrode materials. (2) Gas Ballast: The gas ballast can leak a small amount of dry air/nitrogen into the second stage to prevent vapors (like water or electrolyte) from condensing into the pump oil. (3) Anti-Suckback Valve: A critical safety feature. If the power fails, this internal valve prevents the pump oil from being sucked back into your vacuum chamber or pouch cell sealer.