Maybe you’ve heard people talking about this. Elon Musk’s Tesla has been saying for weeks that it would soon hold an event called “Battery Day” at which the company would make a big announcement about new advances in battery technology. Originally this was scheduled to take place in late May but that date slipped. The company is still planning to hold two events, one in person an one online, but an exact date isn’t available yet.

So what is this all about and will it really be a big deal for electric car technology? One reason that Battery Day didn’t happen last month may be that Reuters published a detailed story in mid-May which spelled out what Tesla was expected to announce. The big headline is a new million-mile battery:

The new “million mile” battery at the center of Tesla’s strategy was jointly developed with China’s Contemporary Amperex Technology Ltd (CATL) and deploys technology developed by Tesla in collaboration with a team of academic battery experts recruited by Musk, three people familiar with the effort said…

A number of the technical advances made by Tesla and CATL in battery chemistry and design originated at a small research lab at Dalhousie University in Halifax, Nova Scotia. The lab has been run since 1996 by Jeff Dahn, a pioneer in the development of lithium-ion batteries for electric vehicles and grid storage.

Dahn and his team began an exclusive five-year research partnership with Tesla in mid-2016, but the relationship dates back at least to 2012.

Among the critical contributions from Dahn’s lab: Chemical additives and nano-engineered materials to make lithium-ion batteries tougher and more resistant to bruising from stress such as rapid charging, thus extending their life.

The reference to a million mile battery has to do with how many cycles of charging and discharging a battery can take before it begins to fail. Currently, the battery pack in the Tesla Model 3 is expected to last around 1,500 cycles. At that point the lithium crystals inside the battery begin to crumble from the stress of being charged and discharged and the efficiency declines sharply.

But Tesla has filed a patent for a “single crystal cathode” which uses a new process to create a lithium battery which can be charged and discharged at least twice as many times as current cells. In addition, there are some coatings which can be used to further increase the life of the lithium in the battery, meaning Tesla could soon have cars with batteries that don’t have to be replaced for the lifetime of the car. There’s a deep-dive video on the lithium cathode patent here if you’re so inclined.

Tesla may also announce some other changes including a new battery design that doesn’t use cobalt. Cobalt is the most expensive metal used in current batteries. Eliminating it could mean significant cost savings. Additional changes to the size and number of battery cells in each battery pack will simplify the production of the battery packs which could also make producing them significantly cheaper.

The goal of all of this is to bring the cost of the batteries and eventually the packs themselves below the threshold of $100 per kWh. That’s the figure at which it is generally believed the cost of an electric car is roughly equivalent to the cost of a gas-powered vehicle. At present, the excess cost of electric cars has to be offset by state and federal rebates. But once the cost of the batteries drops that shouldn’t be necessary anymore. Elon Musk has said that he believes the cost of the packs will be below that level within two years.

The technology used in these auto batteries is applicable to other things like Tesla’s Powerwall, which is designed as a home battery solution for solar power generation. So to answer the question about whether or not this is a big deal, it probably is if it means the cost of electric cars will drop and make them much more competitive in the market.

As mentioned above, the researcher behind a lot of this new technology is Jeff Dahn. Here’s a brief history of Dahn’s work on lithium ion batteries including his work with Tesla.