General Motors announced that it will invest $449 million to upgrade manufacturing processes at Detroit-Hamtramck Assembly and Brownstown Battery Assembly plants in preparation for the next generation of electric vehicles and advanced battery technologies.

Despite sluggish sales for its Chevrolet Volt plug-in hybrid, General Motors appears to be making an even bigger bet on the future of electric vehicles as it prepares to invest $449 million in a key battery-car assembly plant and the factory that produces the lithium-ion packs that will be used there.

Though GM did not provide specific details, the major investment plan is expected to help it upgrade the Volt and possibly add one or more additional battery-based vehicles at the Detroit-Hamtramck assembly plant. But the program is likely to include one or more non-electric model, such as a large sedan being developed by the Cadillac brand.

“Today’s news will ensure that the next generation Chevy Volt continues and solidifies that position of leadership,” Gerald Johnson, GM’s vice president of North America manufacturing, said at an Automotive Press Association luncheon. “We want our customers to benefit from our investments in technology and to keep coming back to General Motors for their purchases.”

The Detroit-Hamtramck factory, generally known as the Poletown plant, has been producing the Chevy Volt since its splashy launch more than three years ago. But sales of the plug-in have been suffering despite a $5,000 price cut last year.

Volume in 2013 slipped to just 23,094, barely half what GM had been hoping for. And sales are down another 15% this year, to just 3,606 for the first three months of 2014.

Steady fuel prices have certainly not helped GM – or its competitors – make the case for battery-electric propulsion, but Nissan and others have been able to gain some ground even as Volt slides.

Industry analysts suggest a variety of factors are behind that, including the vehicle’s still significant cost, design issues, and the limits of the current battery pack.

GM officials have promised they will improve the performance of the lithium-ion technology used in Volt over the coming years – a plan that appears to be backed up by the fact that the Brownstown Township battery plant will benefit from some of the new investment, about $65 million.

(New car buyers name Honda best overall brand again. For more, Click Here.)

A critical goal for GM and others in the battery-car business is to improve the range and performance of lithium-ion technology while lowering both weight and cost. GM has already made some modest improvements with the battery that is going into the new Cadillac ELR plug-in hybrid.

(Click Here to get details on Toyota recalling 6.4 million vehicles worldwide.)

But an updated Volt may also see changes to both its interior and exterior design – and could get a better “range-extender” gasoline engine used to keep the vehicle going when its battery is drained. The current four-cylinder engine in the plug-in is considered one of the vehicle’s biggest weaknesses.

(To have a look at Ford’s 2015 Focus sedan, Click Here.)

GM officials, notably the maker’s recently retired CEO Dan Akerson, have suggested there are more battery-based vehicles to come, and that could be part of the plan for the Poletown plant.

But sources say the factory will likely get one or more conventionally powered vehicles as part of the big investment program. That could include either the Buick LaCrosse or a new Cadillac sedan – or perhaps both. Cadillac has been working up plans to add a larger luxury sedan to its line-up that would serve as a sort of halo vehicle. Production, sources said, could start by late 2015.