According to a report today from CNBC, Tesla is working on research and development of battery cells in a lab near its manufacturing facility in Fremont, California. Five anonymous current and former employees said the R&D is focused on "designing and prototyping advanced lithium-ion battery cells," as well as systems that could help the company produce cells at high volume.

Currently, Tesla has a partnership with Panasonic to make the battery cells it uses in its cars and stationary batteries. That relationship extends out to Tesla's Buffalo, New York-based solar panel factory, which Tesla also co-owns with Panasonic. But recently, the fraternity between the two companies seems to be wearing thin.

In September of last year, a Panasonic executive said that the bottleneck for Model 3 production had been the speed at which Panasonic could manufacture battery cells. In October 2018, Panasonic reported that it lost $65 million to the part of its business that makes battery cells for Tesla's vehicles. In April 2019, the Nikkei Asian Review reported that Panasonic would not make additional investments into Tesla's Gigafactory beyond what it had already committed to. Tesla's recent purchase of Maxwell Technologies, which makes automotive- and utility-grade battery components, may also have driven a wedge between the companies.

Ars contacted Tesla for comment, but we have not received a response.

Tesla is currently building out a factory in Shanghai, and it has not partnered with Panasonic exclusively to supply battery cells to that location, though Panasonic or another major manufacturer of battery cells will, in all likelihood, supply the Shanghai factory in the near term. At a recent shareholders' meeting, Tesla CEO Elon Musk said investors ought to look out for two things in the coming year: battery availability and advancements in full self-driving. JB Straubel, Tesla's CTO, commented at the meeting, "It's more obvious now than I think it ever was, we need a large-scale solution to cell production."

Musk said investors would be invited to a battery and powertrain day hosted by the company before the end of 2019.