07/02/2019
The future of battery technology for electric vehicles.
We will tell you on the example of eczo.bike, how battery technology has improved over the past couple of years and what awaits us in the near future.
In the first version of eczobike battery, we used Li-ion 18650 cells, which were used in electric cars (Model S/X). We designed a 1000Wh battery, a weight of 4 kg, specific energy is about 250 Wh/kg (the first pic).
Some time passed and Tesla has developed the 21700 cell size, which is currently used for Tesla Model 3 and replaced the previous cells 18650. The difference between these cells can be seen in pic 2. In short, the standard cell 18650 has 18 mm in diameter and 65 in length - hence the name, the cylinder volume grows exponentially with an increase in radius, therefore even with a slight increase in diameter (21 mm vs 18 mm) and length (70 mm vs 65 mm) batteries, its capacity becomes 33-35% more.
What does this give in practice?
The size of the battery decreases, but the battery capacity increases. Our new battery for eczobike has a capacity of 1200 Wh, while in the old case about 10% of additional space was freed, which makes it possible to reduce the size of the case with increasing energy capacity (pic 3).
What will happen next?
Now Tesla buys Maxwell Technologies company, which is engaged in the production of batteries, supercapacitors, and other battery components. Maxwell has developed a new dry electrode technology for Li-ion batteries, with which an energy density of 300 Wh/kg has already been achieved (this is better than industry records now - 257 Wh/kg from Tesla), with a possible improvement up to 500 Wh/kg. That technology gives a 10-20% reduction in the cost of production and a 2-fold increase in battery life.
Future of battery technology. Approx calc.
With specific energy of 500 Wh/kg, the 75 kWh battery of Tesla Model 3 will weigh only 239 kg, instead 478 kg now. This is either 2 times lighter battery, or 2 times more mileage while maintaining the current weight (while the battery capacity increases to 145 kWh). Tesla Model 3 RWD with a 75 kWh battery has a 558 km mileage (EPA cycle, city). So in the future, Model 3 will be able to can overcome the distance 1000 km on a single charge.
Maybe this is the breakthrough that has been waiting for?