Renault ZOE: lithium-ion batteries for more power and range
Since 2012, Groupe Renault electric vehicles have been powered by lithium-ion batteries. Over the years, these safe and reliable batteries have become the benchmark in the electric vehicle world. But how they work may still seem mystifying.
How are electric vehicle batteries made?
They come in the form of interconnected cells controlled by an electronic circuit (the Battery Management System or BMS). The number and size of cells, and the way they are arranged, determine the amount of power that the battery can hold. In other words they determine the battery capacity of electric vehicles, as expressed in kilowatt hours (kWh).
But not all batteries use the same technology. The most common at present, and the one used in the ZOE, is the lithium-ion battery.
While the lithium-ion battery is now the automotive world’s go-to technology, it is different from other types of electric vehicle batteries. One of these, the rechargeable metal hydride battery (Ni-MH) was the most economical technology in the early 2000s and for a long time dominated the hybrid vehicle market. But the technology has several drawbacks, such as poor charge performance (lower than that of a lithium battery).
The lithium-ion battery is the modern choice for the electric car, as its main advantages are a longer lifespan and a power density that outperforms all competing technologies.
ZOE’s Ni-NMC battery
The lithium-ion battery is a family of several technologies. The one powering the ZOE is known generically as Li-NMC (Lithium-Nickel-Manganese-Cobalt). The name comes from the metals used at the negative pole of the battery, the cathode. As in all rechargeable batteries, it has an anode, a cathode and an electrolyte liquid through which ions move from one electrode to the other.
Doubled capacity for better range
In just eight years, Renault Engineering has more than doubled the capacity of ZOE batteries, from 23.3 kWh to 41 kWh and then to 52 kWh.
How? By optimising the design of the electrodes and the power management, and in particular by improving the chemistry of the electrodes to help them store more power. All without increasing the size of the battery.
This has led to a dramatic improvement in the ZOE’s range: 150 real kilometres in 2012, 300 km WLTP in 2016 (Z.E. 40 battery) and 395 km WLTP today (Z.E. 50 battery). The ZOE is thus the benchmark multipurpose electric city car for the market. And this key selling point contributes to its commercial success.
Second life of ZOE batteries
While the performance of these batteries will drop over time, that does not mean they have reached the end of their life. So how are the ZOE’s lithium-ion batteries re-purposed at the end of their average 8 to 10 years of faithful service?
There are various possible second-life scenarios, of which stationary energy storage proves the most suitable. Thus, when their level of performance is no longer sufficient for automotive use, the batteries can power equipment in a house, a district or on an industrial site.
Groupe Renault has already developed several stationary energy storage trials using ZOE batteries, at Porto Santo and Belle-Ile-En-Mer. And the manufacturer is implementing this concept on a very large scale with the Advanced Battery Storage project, which aims to build the biggest stationary electricity storage facility based on electric vehicle batteries ever seen in Europe. These batteries can also power other engines, such as Seine Alliance’s Black Swan electric boats.
Copyrights : Jean-Brice Lemal (Planimonteur), Pagecran
