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The "Big Three" lithium stocks -- Albemarle Corp. (ALB) , FMC Corp. (FMC) and Sociedad Quimica y Minera de Chile (SQM) -- have all popped higher in recent days, but have never featured in my client portfolios. I'm just not interested in commodity plays.

These three stocks had been falling for most of 2018, but bottomed out around March 1 and have rebounded strongly over the past week. SQM is up 10.6% since closing at $46.73 on March 1, while Albemarle has added 7.1% since March 2 and FMC has gained 6.5% since Feb. 28.

These stocks saw a major inflection point in January, when SQM announced that it had gained approval to expand Chilean production. Chile's stable democracy makes its briny salt flats a relatively safe place for mining companies to invest capital. That leads me to believe that scarcity won't be an issue for lithium, even as demand increases over the next few years as automakers produce more electric cars that run on lithium-ion batteries.

In fact, Morgan Stanley's chemicals team recently predicted that lithium prices will fall 45% by 2021. Lithium investors have been heavily debating that call since it came out, but as an only casual observer of the sector, that's another reason for me to stay away.

Instead, I'm searching for emerging companies with "killer apps" to smooth the global auto industry's transition from gas engines to electric powertrains.

One name that I like is Applied Minerals (AMNL) , an $18 million microcap that's currently testing its Dragonite halloysite clay as a potential material for solid-state lithium-ion batteries. Some in the scientific community believe solid-state batteries could have greater storage capacity and longer useful lives than current liquid- and gel-based versions -- in other words, a potential killer app.

AMNL is a tiny company (and thus a risky stock), but I think that the upside is there. After all, I've been following the auto sector for nearly 26 years, but lately, keeping up with industry trends seems like a lecture in chemistry class.

Toyota has come up with a way to replace some of the expensive rare-earth metal neodymium in its batteries with more abundant lanthanum and cerium. Cobalt is another important raw material for electric-vehicle batteries, but political instability in the Democratic Republic of the Congo (which supplies 60% of the world's cobalt) is a big worry for global auto OEMs.

Every global automaker is scrambling to improve on technology for battery-powered electric vehicles. There will be a flurry of new electric-car introductions over the next few years, but for the most part, those vehicles will use current battery technology.

If someone like AMNL can come up with a "killer app" in battery technology, that company will have a truly valuable product.