Researchers on the hunt for the battery of the century

This is reported by the IT portal Golem.de in an analysis on the topic of battery life. Reference is made to research by battery pioneer Jeff Dahn, who has been researching the subject since the late 1970s and advising electric car pioneer Tesla, among others. After years of work, Dahn has identified factors that are critical to battery life. These include the materials used, energy density, ambient temperature and payload.

Explanatory video: structure and function of lithium ion batteries

In years of testing, Dahn has examined the stability of various materials. As early as 2019, he tested a material mix called NMC532 (50 percent nickel, 30 percent manganese, 20 percent cobalt), which requires more resources than current lithium iron phosphate (LFP) batteries, which are considered particularly stable, but also more durable. Dahn’s NMC532 battery is less suitable for electric cars or mobile phone batteries due to the high amount of material, but could be used, for example, in stationary energy storage systems.

Less charging voltage, longer life
How long a battery actually lasts depends not only on the materials used, but also on the voltage: the higher the charging voltage, the more lithium is removed from the cathode during charging, which shortens its life. So Dahn and his team experimented with a lower charging voltage of 3.8 instead of the usual 4.2 volts – and got good results. It is hoped that this can now also be achieved with less resource-intensive cathode materials.

The structure of the cathode also determines the life of the battery: NMC cathodes form layers between which the lithium is enclosed. If the charging voltage is too high, the material becomes less stable and the lithium is gradually removed from the holes. Released metal ions can damage the battery, shortening its life. However, the problem can be avoided by keeping the charging voltage low and ensuring that the NMC cathode layers are very stable during fabrication.

Alternative electrolytes, smaller anodes
Dahn has also conducted promising experiments with the other battery components – electrolyte and anode. This means that smaller anodes are possible with a lower charging capacity and also the amount of electrolyte can be reduced – and this reduces the risk of unwanted chemical side reactions in the battery, which would affect its life. As a test, the researcher replaced the lithium fluorophosphate normally used as an electrolyte with an alternative lithium substance that can withstand higher temperatures and thus promises a longer life.

In general, the storage and operating temperature is a determining factor: the higher the temperature, the faster the chemical processes in the battery take place. 10 degrees Celsius more means a doubling of the reaction rate, which promotes side reactions and shortens the service life.

According to Dahn’s experiments, lithium iron phosphate batteries allow daily charging and discharging processes under ideal conditions and at an operating temperature of 10 degrees. At a room temperature of 20 degrees, that is only 30 years. With the NMC532 material mix and a low charging voltage of 3.65 volts, a lifespan of 1000 to 10,000 years would even be possible under these conditions, says Dahn.

Charging too fast can generate lithium waste
Charging behavior is also an important factor: If a battery – which is common for smartphones with a fast charger – is charged at a very high speed, lithium waste can be produced, which remains in the battery as insoluble salts without being able to be used to generate electricity. to wake up. Charging too fast should therefore be avoided at all costs if you want to use the battery for as long as possible.

Dahn’s research is interesting not only for extending the life of batteries under ideal conditions, but also when the electricity suppliers are used under extreme conditions: a battery operated at temperatures of 50 degrees Celsius can become eligible within a few months. replacement. However, with the right optimisations, the service life can also be extended to more than ten years.

But the research is taking a long time: Dahn is now testing whether the lifespan of his new materials is not due to the cathode itself. It may also be related to previously untapped side reactions in the anode, allowing it to be combined with less resource-intensive materials. Whether this is the case will probably not be known for a few years – battery life tests, of course, take years to complete.