Batteries - A look at future technologies
Batteries are an indispensable part of electromobility. But these energy storage devices also raise many questions, especially about performance and climate friendliness. We set out to find some answers.
Electromobility is the future. Legal arrangements and automakers’ announcements have put this beyond doubt. In most applications, the electric motor is indisputably superior to the internal combustion engine in technical, ecological, and economic terms. However, there is a lack of clarity concerning the actual heart of an electric powertrain: the battery. It’s not always easy to assess a battery’s performance or its impact on the climate. This often leads to uncertainty and sometimes to heated discussions.
To put it simply, the two main factors determining an electric vehicle’s range both have to do with its battery: the power density and the capacity. Today’s most widely used lithium NMC and lithium NCA batteries currently have a volumetric energy density of about 400 watt-hours (Wh) per liter of volume. Taking as an example a car with around 75 kWh battery capacity, this leads to real-world ranges of 300 to 400 kilometers. Experts believe that volumetric energy density will increase by another 50 percent in the next ten years, making it possible to achieve ranges of 600 kilometers. Lithium iron phosphate (LFP) batteries, which will also be increasingly used in electric trucks in the future, offer new possibilities here as well.
Another decisive aspect for the possible applications of battery-electric cars and trucks is charging time. This is mainly driven by the maximum permissible charge and the discharge current. The greater the ratio between charging current and battery capacity for a given battery size (known as the C-rate), the shorter the charging time, at least at a state of charge (SOC) between 10 and 80 percent. For the final 20 percent, to get the battery completely full, the charging time then increases significantly. The car in the example would need about 35 minutes at a 125 kW quick charging station at normal outside temperature to “refuel” 55 kWh of energy, or 280 kilometers of range, and return to an 80 percent state of charge.
There is also some uncertainty surrounding the question of how great an effect frequent quick charging has on battery life. What is clear is that slow charging is essentially good for batteries. Manufacturers define battery service life primarily in terms of a guaranteed number of charging cycles. For example, a car battery that is guaranteed to last for 1,000 cycles will provide a total mileage of around 160,000 kilometers over its lifetime. In the fine print, however, manufacturers sometimes point out that the electric car should if possible operate within a state-of-charge range of 20–80 percent and should be fully charged only during planned long-distance trips, as this is the only way to achieve the guaranteed battery life. A bunch of conditions, then, that certainly don’t make it easy for the average user to reliably determine charging time, range, total mileage, and thus vehicle lifetime.
Climate friendliness guaranteed?
However, vehicle lifetime is central to assessing a battery’s climate benefit. Given how energy-intensive battery production is, batteries carry quite a CO2 burden even at zero mileage. This means that the greater the total mileage achieved, the more this CO2 burden is distributed over the kilometers driven, and the more climate-friendly the electric vehicle is compared to one with a combustion engine. Assuming the car in the example recharges using only renewable electricity and only green electricity was used to produce its battery, then its greenhouse gas emissions over the manufacturer’s guaranteed total mileage will be around 90 percent lower than those of a modern diesel vehicle. For trucks, the figure is even better—over 95 percent—thanks to their higher mileage. This is the result of recent calculations by DACHSER´s Corporate Research & Development division.
Even if battery production uses not green electricity but rather today’s electricity mix and production conditions in the European Union or China, then an electric powertrain will still achieve CO2 reductions of at least 90 percent (Europe) and 85 percent (China) for trucks, and at least 80 percent and 65 percent respectively for cars. This shows that the CO2 burden of battery production doesn’t play such a large role for trucks. In the case of passenger cars, though, battery production should be converted to state-of-the-art standards and 100 percent renewable electricity as quickly as possible in order to leverage the full climate protection potential of battery-electric powertrains.
Besides greenhouse gas emissions, however, other environmental and social impacts must also be considered. These can arise primarily from the extraction of the raw materials required for the powertrain batteries. Depending on the chemical elements and processes involved, practices in certain countries and regions in this regard need to be critically monitored and dealt with primarily through regulatory measures.
Switching to all-electric cars and trucks requires drivers and fleet operators to rethink and, above all, be open to these new arrangements. The journey ahead will sometimes be tough, especially in the first years of the upcoming transformation. But there is no alternative because, based on the current state of automotive technology and its economics, no other technological option is in a position to achieve the targeted climate protection effect of near zero emissions. What’s needed is for automotive manufacturers to push the performance and sustainability of battery technology further and to turn a technology that is still complex today into an easy-to-use innovation that people will be keen to take up.