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NIO and the solid-state battery

07. May 2021

Up until now electric vehicles have been supplied with electricity by lithium-ion batteries with liquid electrolytes. One has been talking about a new battery technology with solid electrolytes for years, which is supposed to bring certain advantages - including significantly greater ranges. However, its implementation on the market is proving difficult, even if a Chinese start-up is resolutely pushing forward.

solid-state battery

Liquid was yesterday

Whether entertainment electronics or electromobility: Lithium-ion batteries are implemented for all devices that use rechargeable accumulators. These provide a relatively large amount of energy in a small storage medium and don't lose much capacity even when charged many times. This type of battery is however in the meantime reaching its limits, the development potential seems to be exploited. The search for new battery concepts is in full swing.

A promising future technology is the solid-state battery, on which many studies are being carried out worldwide. It essentially differs from the conventional lithium-ion battery because neither the electrodes nor the electrolytes contained in the battery are liquid, they are instead in a solid state. Solid electrolytes can for example be made from plastic polymers or glass and have – just like liquid electrolytes – the task of conducting ions between the cathode and the anode.

More reliable, safer, more durable

The solid electrolyte structures bring several advantages.

On the one hand as a result of less need for cooling and safety devices they are lighter and less bulky, on the other hand much more electric energy can be saved in the same amount of space because the energy density is higher. As such they enable a low-weight, filigree design and take up less space in providing a customary volume of energy. Furthermore, the mode of action of solid electrolytes is allegedly not dependent on temperatures, even if there are contradictory opinions on this point. At the same time, the risk of electric cars catching fire, a theme that has often been covered in the media in the past, is eliminated because solid materials don't catch fire easily. Solid-state batteries are therefore considered to be more reliable and safer than lithium-ion batteries with liquid electrolytes.

No fast process

However promising the solid-state battery may sound, its market entry is proving difficult. There are still some uncertainties that are holding up the chances of fast mass production - above all the hitherto lacking opportunity of testing the batteries sufficiently outside of the laboratory.

According to some experts, it could take up to ten years before the serial production of solid-state batteries is possible. Too many development and production steps on unknown territory have to take place before the classic lithium-ion battery with liquid electrolytes can be replaced.

The price is a further factor that will be decisive regarding the future of the solid-state battery: Since pure lithium has to be used, the volume needed increases. Indeed, 20% more pure lithium is needed for the same capacity compared to a current lithium-ion battery.


In addition to several European and Eastern Asian industry representatives, among others Volkswagen in cooperation with QuantumScape, above all the Chinese start-up NIO is among the solid-state pioneers. The company already produces five serial vehicles with a battery powered electric drive.

After a sports car and three cross-over models, the company is now bringing out the ET7, an upper-class limousine (480 kW/653 hp) which was announced for the year 2022 last year.

According to the NEDC cycle, the range of the ET7 is estimated to be 1,000 kilometres thanks to the integrated solid-state battery – in the words of the ADAC – a clear declaration of war to Tesla. The model is by all accounts additionally going to reach the third stage of autonomous driving as well.

In addition to the new technology, the charging solution of the NIO ET7 also sounds promising.

In order to come closer to the "box stop" of fuel-powered vehicles, NIO has installed a battery changing system. Instead of charging at the charging pump, an automated changing station that looks like a car wash, serves to completely replace the empty battery with a full one so that the car can continue on its journey. The empty battery is recharged on-site and once fully charged can be mounted into the next car that comes by. The entire process only takes a few minutes.

Although NIO is venturing an exciting advance forward with the ET7, it isn't to be assumed that the solid-state battery will revolutionise the electric industry in the immediate future. There are still too many uncertainties and imponderables which will prevent such a fast market entry. However, the technology does have the potential of taking on an important role in the mobility sector long-term. The empirical values obtained by the operation of the NIO ET7 will be of great relevance for the further development of the technology.

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