By any measure, Chinese electric-vehicle maker NIO (NYSE:NIO) had a good year in 2020. After beginning the year short of cash amid the COVID-19 pandemic, NIO recovered to finish strong with a successful new-model launch and a record sales total. 

How will it follow that? We'll get an idea on Jan. 9, this coming Saturday, when the company holds its annual NIO Day -- a party for its investors, customers, and fans that includes previews of upcoming products and technologies.

The highlight of NIO Day: A new electric sedan

While NIO typically keeps a surprise or two up its sleeve, it has told us that the highlight of this year's NIO Day will be the debut of its first sedan model, shown (sort of) in the "teaser" photo below.

The outline of a sedan, the words "Ready for Tomorrow," and Saturday's date.

NIO released this teaser photo ahead of its annual NIO Day event. Image source: NIO.

Analysts expect the sedan to be a production version of the ET Preview, a concept vehicle that the company showed in 2019. As shown back then, the ET Preview was a dual-motor all-wheel-drive design, with estimated range of over 450 kilometers (about 280 miles) and a zero-to-100 kilometers-per-hour (0 to 62 miles per hour) time of 4.7 seconds. 

I say "as shown back then" because it's likely that the production version will have better range and acceleration numbers thanks to a new 150 kilowatt-hour (kWh) battery pack that NIO also plans to unveil on Saturday. It will also have "the latest autonomous driving technologies," NIO promises. We'll have to wait until Saturday to find out exactly what that means.

The NIO ET Preview show car, a sleek white electric sedan.

The new sedan will probably look a lot like NIO's ET Preview show car from 2019. Image source: NIO.

Mindful of Tesla, NIO is moving quickly to give its customers more range

That new battery pack is something of a surprise. Auto investors who follow NIO will recall that just two months ago, the company introduced a 100 kWh battery pack -- its largest up to that point -- that can be swapped into any of its models to increase range. 

That 100 kWh pack, developed jointly by NIO and battery giant Contemporary Amperex Technologies (or CATL), has a claimed 37% higher energy density than NIO's earlier packs, is cheaper to build, and incorporates heat-management technologies intended to extend its service life. 

Not only does NIO offer the 100 kWh battery pack as an upgrade on all of its models, but it also offers the pack to existing NIO owners via its batteries-as-a-service subscription program. Customers who subscribe can use NIO's automated battery swap stations to "recharge" via a battery swap in about 3 minutes. Those who subscribe when they purchase a new NIO can buy the car without a battery at a lower up-front price.

A blue NIO ES8, an upscale electric SUV, is shown existing a gray battery-swap station.

NIO has over 150 automated battery-swap stations operating in China now. It's expected to show a new station design that is cheaper to build at NIO Day on Saturday. Image source: NIO.

It's not yet clear whether NIO will make the new 150 kWh battery pack available via the battery subscription program, but with Tesla (NASDAQ:TSLA) ramping up local production of its Model Y -- a direct competitor to NIO's ES6 and EC6 -- it seems likely that it will. 

NIO is also doubling down on batteries-as-a-service

Last but not least, NIO also plans to show an improved version of its battery swap station on Saturday. The new stations will contain more battery packs than the current design, and NIO said they can be built at lower cost, which will allow it to accelerate deployment. The company had about 150 stations in operation as of its most recent update last fall. It expects to add "nearly one new station per day" in the coming year.  

The subscription plan is only a few months old, but it's already popular. NIO said last weekend that over 40% of customers who bought a NIO in December opted for the battery subscription option. 

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