What happened

After tumbling 7.3% in May, investors were a lot more charged up about QuantumScape (QS 5.69%) stock last month. According to data provided by S&P Global Market Intelligence, shares of QuantumScape rose 23.1% in June, outpacing the simultaneous 6.5% rise of the S&P 500.

So what

While solid-state batteries have considerable advantages over the traditional liquid lithium-ion batteries used in electric vehicles (EVs), many are skeptical about the ability to produce them on a large scale. It's unsurprising, therefore, that many investors are both intrigued and cautious about QuantumScape, a leader in solid-state battery technology. But in mid-June, investors received a green flag from Toyota that made QuantumScape seem a lot more alluring.

Reuters reported on June 13 that Toyota had heralded a "technological breakthrough" with regard to solid-state batteries -- a breakthrough that will help the batteries last longer. Additionally, Toyota said it's targeting 2027 to 2028 for commercial production of its solid-state batteries.

Two weeks later, QuantumScape held an investor presentation that rallied investors' spirits. For one, the company celebrated that it has inked commercial agreements with six automotive original equipment manufacturers. Additionally, QuantumScape noted its agreement with Fluence, a leading energy storage company.

On the technological front, QuantumScape stated in its presentation that it believes it can develop a battery capable of charging from 10% to 80% in 15 minutes -- a rate that is notably faster than that of traditional lithium-ion batteries. Should the company succeed in bringing these batteries to market, they would, undoubtedly, be in high demand considering the lengthy charge times that EV drivers currently endure.

Now what

Although the news of Toyota's advancement in solid-state battery technology doesn't directly benefit QuantumScape, it represented a bullish signal to investors. Toyota's "breakthrough" suggests that it may very well be possible to commercially produce solid-state batteries -- something that skeptics have argued is unlikely. Furthermore, this builds on the fact that QuantumScape has achieved several milestones in the past couple of years that suggest the company may be able to meet the technological challenges that have precluded other solid-state battery companies from bringing products to market.

Investors remain charged up about QuantumScape stock, sending it more than 13% higher in July. While it's certainly not too late for growth investors to power their portfolios with it, they should recognize that the company is still in the early innings of its development, and it's still a speculative investment. Therefore, they should allot a position according to their tolerance for risk.