If you have been unable to recondition the cell to a state where the RAID card will accept it, the cell will need to be replaced. (It is also possible the RAID card is faulty, but it's much more likely to be the battery)

Purchase a "606168" Rechargeable Lithium cell from your supplier of choice. If you can get one with offset terminals like the original cell then it'll make replacement a lot easier, but most have symmetrical terminals.

Unless you have a battery tab welder, you'll need to solder the new battery in place. Don't dwell for too long or the cell will heat up. The new cell should come already charged, so follow Step 7 to reinstall the battery.