It’s not quite that simple. The OP is the original owner of a 2013 Volt, currently around 65K miles, mostly electric, charged every day, but his guess is about 40-50K miles "on the battery and the rest on ICE" (i.e., about 15-25 K miles "on ICE"). The battery is now failing and he wishes he could just "use it like an ICE." Seems to me when he says, "if I could use it as a gas car..." it suggests he views his Volt as an ordinary plug-in hybrid. If "ICE" driving is "driving on engine power without using battery power," then he’s already put nearly one-third of the miles on the odometer by "driving on gas" after depleting the battery. So, if the battery now no longer works well, why he can’t extend the life of the car by driving "on gas," using only the engine? Another participant in the thread (post #6) says he bought a 2015 Volt "to drive solely off of the gas generator, sort of like a plain hybrid of sorts..."
My point is the Gen 1 Volt does NOT become a "plain" gas hybrid car when it runs out of power to run on battery only and the engine kicks on. At that point, unlike the other plug-in hybrids out there, it continues to be a battery-powered car, but now with a second source of power, a gas-powered generator. The 111 kW electric motor continues to be able to provide the car with full performance, and now the 55 kW generator power can be used to supplement the power remaining in the battery (and to keep it charged to a programmed level). You may think of extended range driving as "driving on gas," but that’s because you hear the sound of the 63 kW engine as you drive. You continue to use the 111 kW electric motor for propulsion. "Driving on gas" is a fuel accounting issue, not a propulsion source issue.