Electric vehicle (EV) sales have been slowing around the world. EV makers have even been cutting prices in China, the world's largest EV market, to spur sales. But Nio (NIO -7.95%) just surprised investors with a strong month in April, and the stock is spiking as a result.

Nio American depositary shares (ADS) were trading higher by 13.2% as of 3:32 p.m. ET after the report. That move has added to a strong rally seen in the shares over the last several weeks.

Nio EV deliveries shine

One reason for the strong reaction from investors was how Nio fared relative to its competition last month. Nio reported deliveries of 15,620 EVs in April. That was an increase of 135% compared to last year. Competitors XPeng and Li Auto didn't see nearly that large an increase. They reported year-over-year April shipment growth of just 33% and 0.4%, respectively.

Nio also just started deliveries of its upgraded 2024 ET7 luxury sedan on April 30. That model is meant to attract executive level users. The company says it features "major enhancements in interior and exterior design and digital cockpit."

The enhanced ET7 could be another catalyst to continue sales growth in the coming months. Nio also began a new partnership in late April with global luxury EV maker Lotus Technology to share its charging and swapping services.

Even after a nearly 40% jump over the last two weeks, Nio shares remain lower by about 40% year to date. After a third straight month of increasing deliveries, and new possible catalysts at hand, investors who see EV growth continuing in the coming months and years might want to take a small position in Nio now.