BOOSTING EV RANGE WITH INNOVATIVE TECHNOLOGY
SEOUL, May 21, 2024 — When it comes to choosing an electric vehicle (EV), one of the top considerations is undoubtedly range per charge, or all-electric range (AER). Hyundai Motor Group (the Group) is doubling down on four key areas to efficiently maximize this capability.
Thermal Management System
Thermal management systems play a crucial role in maintaining the optimal temperature of batteries.
For lithium-ion batteries, the optimal temperature under normal driving conditions is typically between 20 and 35 degrees Celsius. To maintain this temperature range, EVs, like internal combustion engine (ICE) vehicles, use cooling systems that circulate coolants.
Most automakers rely on what are called positive temperature coefficient (PTC) heaters to warm EV cabins, a type of electric heater that converts electrical energy into heat. The Group goes a step further and employs “heat pump” technology that utilizes wasted energy, increasing efficiency by over 10 percent at low temperatures compared to conventional systems.
To enhance heat pump technology, the Group is further conducting research on “gas injection” technology, which increases the refrigerant flow rate at ultra-low temperatures, allowing for greater heat recovery and significant improvement in efficiency.
Battery Energy Density
To increase the range and efficiency of EVs, the Group is also conducting research to improve the energy density of batteries, chiefly focusing on the following four areas.
1. Enlarging Battery Cells for Higher Energy Capacity
One way to increase the driving range per charge is to increase the amount of energy stored within the battery cells, which can be achieved through upscaling the battery cells. While the number of components going into smaller and larger cells remains the same, larger cells tend to have a decreased volume ratio for these components, which results in more space within the battery cell to store energy.
2. Thick Film for High Current Density
The Group is also changing the internal design of batteries by incorporating thick film technology. While conventional battery cells involve stacking thin layers of anode and cathode materials, along with aluminum and copper collectors, the use of thick film technology enables an increase in the thickness of positive and negative electrodes. This helps reduce the need for auxiliary materials like separators, consequently increasing energy density and saving resources such as aluminum and copper required for manufacturing the battery.
3. ‘Two-Stage Cathode Press’ for Cell Thinning
Cathode pressing involves compressing the cathode using a press, which helps to shrink the size of the battery pack while increasing the energy density of the battery. What normally complicates this seemingly simple process is the occurrence of the “spring back” phenomenon — wherein the cathode thickness increases after the pressing process. To tackle this issue, the Group has developed a double-press method, which allows for the creation of battery cells with the desired thickness.
4. ‘Bat Ear’ Volume Reduction
Bat ear volume reduction is a technique used for pouch-type battery cells, which consist of a functional layer that enables adhesion. When heat is applied to both sides, the layer forms a pouch. The Group’s research concentrates on folding any protruding parts — or bat ears — during this process, ultimately reducing the overall volume during stacking. This enables a higher energy capacity within the battery cell.
Battery Materials
Battery material research is not to be overlooked. The Group is conducting research on various material technologies to enhance energy density in battery cells.
With cathode materials, efforts are being made to increase the nickel content and improve the lifespan and stability. What began as a 30 percent or lower nickel content in the early development of lithium-ion batteries has now reached up to 80 to 90 percent. However, high nickel content can have some disadvantages in terms of lifespan and thermal stability, which is why the Group is trying to solve this issue by minimizing chemically induced reactions through various element combinations and surface treatments.
In the case of anode materials, research is primarily conducted in the high-densification of graphite particles, with the Group also working on enhancing energy density through the development of high-capacity silicon technologies. Silicon anode materials are drawing attention as potential replacements for graphite-based anodes due to their unit energy density advantage, which is more than 10 times higher. However, their drawback being natural volume expansion during charge and discharge processes necessitates the development of techniques to control this expansion. The Group, therefore, is studying ways to enhance anode energy density through the appropriate combination of silicon and graphite materials.
Another area of research centers around battery electrolyte volume. While electrolytes do not have a significant impact on cell capacity, reducing their volume can improve cell energy density.
Other subjects of research include optimizing the usage of electrolytes and exploring the use of high-performance additives to improve the lifespan and output of battery cells. The Group is also working to reduce the thickness of the separator, which would reduce the volume it occupies within the battery cell.
Ultra-Fast Charging
To significantly reduce waiting times for EV charging, the Group is studying optimal battery materials and structural designs aimed at minimizing heat generation and lowering resistance, partly by applying new algorithms.
One example is the so-called battery preconditioning feature, which optimizes the battery temperature even before charging begins. With batteries typically having much lower charging efficiency at lower temperatures, this reduces the initial resistance, ultimately quickening the speed of charging.