Tesla Motors (TSLA -3.40%) is no stranger to speculative press. However, the latest theory that tech giant Apple (AAPL 0.51%) might acquire the electric-car maker are both outdated and wildly overblown. The buyout rumor resurfaced after the San Francisco Chronicle broke news over this past weekend about Tesla CEO Elon Musk meeting with Apple's chief of mergers and acquisitions -- a meeting that took place last spring.

As a result, the Web is abuzz this week with headlines such as "Could Apple Drive Away With Tesla?" and "Tesla Motors Closes at Record After Apple Merger Rumor Surfaces." Both stocks moved higher on this news. Shares of Tesla even accelerated to a fresh high of $205.72 on Tuesday. However, it's unlikely that Apple would acquire Tesla outright. While Apple certainly has the cash reserves to do so, a strategic partnership between the two companies makes more sense.

Here's why.

Finding common ground
Forget an outright merger with Apple -- Musk is smarter than that. Not to mention, with a market cap north of $23 billion today, Tesla is expensive, even by Apple's standards. Nevertheless, there are plenty of reasons why these companies should work together. Think about it. What's one thing that both Apple and Tesla have in common? The answer is an unwavering need for lithium-ion-battery cells. That's why a Tesla-Apple "giga factory" could be the play here.

With Tesla preparing its all-electric crossover, the Model X, for delivery later this year and developing its mass-market third-generation car slated for a 2016 launch, lithium supply is the biggest challenge facing the automaker in coming years. That's because, in lieu of gas, lithium-ion batteries power Tesla's cars.

During the company's third-quarter-earnings call in November, Musk said, "If we are to produce 500,000 vehicles per year we need cell capacity commensurate with that, which is bigger than all lithium-ion production today, or at least on par with it."

That's why Musk plans to build a massive "giga factory" in the not-so-distant future. Not only would this factory be environmentally friendly, but it would be capable of producing lithium-ion-battery packs at a scale comparable to all lithium-ion production in the world today. Given the sheer size of such a facility, Tesla would certainly benefit from Apple's resources.

Joining forces to build a giga factory also makes sense for Apple because all of its products use lithium batteries. Moreover, don't overlook the fact that Apple has been flooding resources into green U.S. factories lately, including its Mesa, Ariz., Sapphire venture, as 9to5Mac reported.

The solar solution
Aside from Apple, it's likely that Tesla will also work with SolarCity (SCTY.DL) on this future lithium plant. Musk has already said the factory would be green and self-sustainable to some extent, so what better partner than the solar energy company run by his cousin? "It's going to have essentially zero emissions and there are no toxic elements that are going to come out of this factory and we will build recycling capability right into the factory," Musk told analysts during Tesla's third-quarter-earnings call. 

Tesla is already collaborating with SolarCity on other ventures, including a new energy storage system and Tesla's Supercharger network. SolarCity provides the solar panels used to power supercharging stations that Tesla is installing throughout the United States, Canada, and Europe today. And like Apple and Tesla, SolarCity's business relies on lithium-ion cells to a certain degree.

Source: Tesla Motors.

SolarCity, which installs and helps customers finance solar panels, uses Tesla's lithium-ion batteries in its new solar-powered storage systems. Therefore, the potential benefits of a factory to produce such batteries at scale are significant for not only for Tesla and Apple, but for SolarCity as well.

Given the opportunity here, it's more likely that Apple would pursue a joint venture on a giga factory with Tesla than an outright buyout. Tesla is set to report earnings after the bell today, so investors will likely get more color on the company's plans for a giga factory during the conference call with analysts this afternoon.