Differential Amplifier to Scale Down DC Voltage
You've left out a few things for us to answer fully. What is Rload? Is it to power some other part of the circuitry or just to provide a voltage to another IC?
What is powering the op-amp?

So my guess here is that you want to measure the LiPo voltage but the measuring circuit has a maximum input voltage of 3V.
In this case I would check what that circuit's input impedance or input leakage current is.

A simple voltage divider should do the trick. If R-load is too high for reasonably high divider resistors put an op-amp in follower mode between the voltage divider and the measuring pin.

With your chosen resistors (1M and 680k) the current flowing through the divider would be ~2.2uA so if the measuring pin leakage current is much less than 1/20th (100nA or less) of that current the amplifier isn't needed.
If you intend on powering circuitry from the scaled version of the LiPo voltage then the first question is why?

EDIT
Based on the OP's clarifications.

I would not use an op-amp to act as a power source. The other issue with your proposed circuit is the powering of the op-amp from the same voltage as the one you are scaling. This means that the op-amp needs to accept an input voltage up to it's positive supply voltage.

I would simply use a diode in series with the LiPo. This would drop ~0.7V, consumes no current on it's own and at 150mA going through it would dissipate ~73mW in heat.

Alternatively, if you can gain access to the circuit that detects the low battery voltage, break the sense pin out. Then you can use a DC-DC converter to power your device and a resistive divider linked to the broken out pin for the supply detection.