Has anyone heard of or seen anything that Angels can be redeemed? Has anyone heard of or seen anything that Angels can be redeemed as My boyfriend prayed that he could save the angel and offered to give himself to the lake of fire.
Can someone please help?
First, I agree with DJClayworth's comment:

Because this is a real situation with real consequences, I strongly recommend that you consult a Christian leader or a physician personally about this. There are issues here that are far beyond the question of whether angels can be redeemed. Your boyfriend's physical and spiritual health may be at stake.

Now for a short explanation, which I answer from mainstream Christian traditions (Catholic, Protestants, and Eastern Orthodox).  You are asking:

Whether angels can be redeemed (I assume this is referring to fallen angels)
If #1 is a yes, whether humans can help with the redemption, and
If #2 is a yes, whether the way a human person can help with the redemption is by vicarious substitution offering to take the place of a fallen's angel destiny (lake of fire).

The answers are:

We don't know for sure since God didn't reveal it to us in the Bible.  From the little that the Bible implies, and from medieval theology (as in Aquinas), fallen angels made their decision before humans were created and it's a done deal, irreversible.

No, because the scope of redemption that Jesus provided as revealed in the Bible is limited to human beings.  Jesus may have done more to save the fallen angels, but we are not told in the Bible.

No, since nowhere in the Bible a human person can even sacrifice one's destiny to save another person, let alone an angel!  The only way a human person can assist in another person's redemption is through prayer, NOT through sacrifice.  Only Jesus saves human beings through sacrifice on the cross !!  Remember that the sacrifice has to be acceptable to God, and the Bible is explicit in saying that only Jesus's sacrifice is acceptable, and that the Old Testament offerings (which involved killing a clean animal) has been superseded after Jesus.