NIO's flagship new ET7 saloon has 621 miles of range, 644bhp and a Power Swap battery pack 

NIO recently took the covers off its all-new flagship saloon car, the ET7, at its annual NIO Day event in Chengdu. To go with it, the Chinese electric vehicle company is also developing a revolutionary solid-state battery pack that will see the top-of-the-line model max out with a 621-mile range.

NIO's first saloon car, and its first autonomous driving model, the ET7, is due to go on sale in China in 2022, expanding its all-electric range of vehicles which includes the EP9 hypercar and the ES6 SUV.

The headline news is the car's astounding autonomy, with the range-topper coming in at some 621 miles (1,000km) using China's NEDC testing protocol from a 150kWh solid-state battery pack which would perch NIO atop the pile in terms of overall range and battery capacity from a consumer EV. There's also a 70kWh and 100kWh variant with 310 and 435 miles of range respectively.

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All three variants will be compatible with NIO's unique network of Power Swap stations which allow owners to hot-swap their battery packs on the go, for a full-charged replacement, in just a few minutes - removing the need for charging on a journey entirely. There are currently 123 stations throughout China and NIO says it's increasing its network to more than 500 by the end of 2021.

The car is based on a lightweight steel and aluminium chassis - 5098mm long, 1987mm wide, 1505mm high, with a wheelbase of 3060mm - is driven by a pair of electric motors and has an ultra-slippery body with a drag coefficient of 0.23Cd - helping maximise the range on offer from whichever silicon carbide battery pack variant the customer chooses.

A permanent magnet motor at the front produces 241bhp, whilst an induction motor powering the rear wheels offers 402bhp for a combined total of 644bhp (480kW) and a mighty 627Nm of torque - launching the ET7 from 0-62mph (0-100km/h) in just 3.9 seconds.

The hump above the windscreen houses an array of 33 high performance sensing units - including LIDAR - which produce up to eight gigabytes of data per second. These combine to enable the ET7's full stack autonomous driving technology for a "safe, effortless point-to-point autonomous driving experience across urban, expressway, parking and battery-swapping scenarios". There are 19 driver assistance systems in all, with many coming as standard but the most cutting-edge features may require a monthly subscription fee.

Its minimalist interior uses Karuun sustainable rattan and looks extremely zen, with frameless windows, a panoramic roof and a cushy living room feel. Of course, there's a touchscreen - a 12.8-inch AMOLED centre display with high resolution and strong contrast and a 23-speaker 1,000W sound system.

The ET7 is due for launch in China in early 2022, with a starting price of around £51,000 - although a battery subscription service will reduce that base price for those that opt in.