The electric vehicles powered by renewable energy They have the potential to change the world. One of the biggest barriers to the adoption of electric vehicles and to replace cars with internal combustion engines is the battery: its production costs, the autonomy it offers and the speed at which it recharges are three great challenges to overcome. In order for most drivers to prefer an electric car to a combustion car in general, the user experience should be similar in both cases. This is achieved by equalizing or reducing both cost and performance:
- The sale price of electric vehicles must be equal to or less than that of combustion vehicles.
- increase the energy capacity of batteries to definitively eliminate autonomy anxiety.
- implant a extensive charging network functional, reliable and interoperable.
- reduce the recharge time to bring them closer to the time it takes to refill a fuel tank.
These four challenges require battery innovations and improvements. Today the vast majority of electric vehicles depend on lithium-ion batteries, always with the permission of lithium ferrophosphate (LFP) batteries, which are gaining prominence in recent times. This technology provides a series of characteristics that make up a minimum envelope so that they can be used with guarantees in electric vehicles.– Long life cycle, modest size and weight, fast and efficient charging, functionality in a wide variety of environments, and economically viable.
Building a better battery is based on work in different areas of improvement: materials science, cell design and manufacturing process.
Batteries are simple systems in terms of their composition, with four main components, but complex in terms of their operation, since they do not stop depending on chemical reactions subject to different circumstances. A battery is made up of a positive electrode (cathode), a negative electrode (anode), a separator that prevents them from touching and a electrolyte by which ions move to travel from one electrode to another.
Each of these components can be improved by modifying the materials of which they are made. Thus, in the anode, the use of silicon instead of graphite is considered to build its microstructure or, in the cathode, the use of other materials different from the usual ones to achieve, in both cases, a higher energy density. Also working on the electrolyte to go from the usual liquid systems to a safer and more efficient solid electrolyte or the use of graphene as a conductive binder. There is much research in this regard and some advances already stand out as promising to achieve an important advance in this aspect.
The interior of the batteries is organized into cells, which are the individual units, each of them made up of the four components mentioned above. connected to each other, the number of cells depends on the application of each battery. But the format and the way to connect them is the same whether it is a small electronic device, a mobile phone, a laptop or the battery of an electric car.
In this sense, two types of cells are distinguished: stacked and rolled. the cells stacked they are flat batteries in which the components are placed in horizontal layers one above the other. This is the form actor of batteries which is the type of battery found in laptops, cameras, watches or mobile phones. It is a format that adapts to the final shape of the device and that is why it is also the most widely used even in electric vehicles, although in these the use of cylindrical cells is beginning to prevail. In this case, the stacking of the layers is done by hand or automated through the use of robots in mechanized processes.
The coiled cells They are cylindrical batteries in which, as their name suggests, the layers are wound around each other. The manufacturing process allows the use of machines, which makes it considerably faster and therefore more cost-effective than stacked cells.
Both formats allow the creation of batteries of different sizes. Regardless of cell form factor type. In any case, it is necessary to add sensors for temperature control and air or liquid ventilation systems to cool all the cells. The battery’s thermal management system is responsible for dissipating the heat generated in it, maintaining its operating temperature in an optimal range to ensure safety and performance. On the one hand avoid it gets too hot when it is feeding the traction system or when it is recharging, especially at fast charging stations. This prevents the occurrence of so-called thermal runaway, a security issue key in hybrid and electric vehicles, since it can cause fires that threaten people, buildings and the environment.
Achieving the perfect combination of materials and efficient cell design is not enough. The manufacturing process must be capable of produce all units with precision, speed and quality. An example of a production error was Samsung’s with the Galaxy Note 7 battery (recalled after finding that many units were overheating and even catching fire) was that as production was rapidly ramped up to To satisfy the urgent demand, a welding defect was introduced which was later repeated on a scale.
Advances in materials science, cell design, and the manufacturing process can improve any type of battery. In the case of electric vehicle batteries, it is also possible to optimize the configuration of the batteries. Currently it is not feasible to have a single large battery in an electric vehicle. The current design is to create packs of cells, called modules. The general trend points to elimination of this intermediate division to create a complete battery made up of cells, which allows the elimination of connectors and wiring. Thus, the space occupied by these components is replaced by active material, optimizing the packaging to make it more efficient and effective.
The way the battery pack is designed and arranged has an impact on both the performance and the physical design of the vehicle. This process requires answering various technical and design-related questions and coming up with the best possible answer. How is the temperature of the batteries controlled? How much power can be obtained when the driver demands it? How long can you drive without recharging? How long will it take to fully charge? How do the rest of the vehicle components fit around it?
We are at a relatively early stage in the life of electric vehicles so no one has the definitive answer in this area. As batteries improve, cell packaging will change and improve to accommodate new possibilities and requirements.
Safety and sustainability
Creating a safe, high-energy battery is a holy grail for car battery manufacturers. Teams of researchers from around the world in the academic and private spheres are working on this type of solution.
Current lithium ion batteries are potentially dangerous. Inside, a series of chemical reactions take place between the liquid electrolyte and the electrodes to create energy. The more power the battery has, the more likely it is to catch fire if not managed properly. Thus, for example, pure lithium metal electrodes, which can provide high amounts of energy, can react with liquid electrolytes generating dangerous amounts of heat.
The old lead acid batteries used in cars were extremely poisonous. The smelting and mining process to create lead was terrible for the environment, as well as potentially poisoning workers. Sulfuric acid is also highly corrosive and dangerous to handle.
On the contrary, components of lithium-ion batteries are abundant and non-toxic, but there is no established system to recycle batteries. Its useful life can be the same as that of the vehicle. When they no longer have enough power for use in the vehicle, they can be reused in storage facilities. In this second life, those batteries may still have 70 to 80 percent of their useful life left.