SK On Increases Emphasis on Prismatic Battery Production with New Trial Facility
Unidirectional vs Bidirectional Prismatic Battery Cells: Implications for Electric Vehicles and Energy Storage Systems
Unidirectional and bidirectional prismatic battery cells are two key types of battery technology that are making waves in the electric vehicle (EV) and energy storage system (ESS) industries. These cells differ significantly in their electrical current flow capability and structural design, each with unique advantages and implications.
Unidirectional Prismatic Cells
Unidirectional prismatic cells allow current flow primarily in one direction during charging and discharging. Their internal design and electrolyte flow paths are optimized for this single-direction operation. This simplicity makes them suitable for fixed, predictable energy flow applications, such as stationary energy storage systems.
Bidirectional Prismatic Cells
In contrast, bidirectional prismatic cells enable electrical current flow in both directions efficiently, supporting more flexible charging and discharging cycles. This capability can improve system integration by allowing faster response times, enhanced energy recovery, and dynamic load balancing. Bidirectional cells are better suited for applications requiring frequent bidirectional flows, such as EVs and grid storage systems with variable input/output.
Implications for Electric Vehicles and Energy Storage Systems
The table below summarizes the key differences between unidirectional and bidirectional prismatic cells in terms of current flow, efficiency, thermal management, control complexity, system flexibility, cycle life, and degradation:
| Aspect | Unidirectional Prismatic Cells | Bidirectional Prismatic Cells | |-------------------------|--------------------------------------------------------------|----------------------------------------------------------------| | Current flow | Single direction (charge → discharge) | Both directions, supports more dynamic charging/discharging | | Efficiency | Optimized for conventional charge/discharge patterns | Higher efficiency in regenerative braking and energy recovery | | Thermal management | Simpler management due to predictable current paths | More complex, as current reverses and thermal profiles vary | | Control complexity | More straightforward battery management system (BMS) | Requires advanced BMS to handle bidirectional currents | | System flexibility | Suitable for fixed, predictable energy flow applications | Better suited for applications requiring frequent bidirectional flows such as EVs and grid storage systems with variable input/output | | Cycle life and degradation | Potentially longer cycle life due to simpler operation | Can experience different aging patterns due to bidirectional current stress |
Practical Considerations
In EVs, bidirectional prismatic cells enhance regenerative braking efficiency, allowing vehicles to recover kinetic energy and store it effectively. They also support vehicle-to-grid (V2G) technologies where EV batteries can feed energy back to the grid. In energy storage systems, bidirectional cells enable smoother integration with renewable energy sources by efficiently managing charge/discharge cycles with variable inputs like solar or wind, improving grid stability.
Recent developments in the battery industry include Samsung SDI's seven-year deal with Hyundai Motor to supply batteries for its European EV lineup between 2026 and 2032, and SK On's unveiling of its unidirectional and bidirectional prismatic prototypes at the InterBattery 2025 exhibition in Seoul in March. As the global prismatic battery market is expected to grow from approximately $25 billion in 2028 to $40 billion by 2033, it is clear that prismatic battery cells are gaining popularity due to their high energy density, enhanced safety, and packaging efficiency.
Industry experts suggest that SK On's expansion into unidirectional designs could help it build a more diversified customer base and better compete with Chinese firms such as CATL and CALB. Automakers like Hyundai Motor Group, GM, Volkswagen, and Ford are adopting prismatic designs for next-generation EVs and hybrid vehicles.
In conclusion, the choice between unidirectional and bidirectional prismatic battery cells depends on the specific application requirements. While unidirectional cells offer simpler design and potentially longer cycle life, bidirectional cells provide greater system flexibility, efficiency, and dynamic response capabilities, making them ideal for EVs and energy storage systems with variable input/output.
- In the context of electric vehicles (EVs), bidirectional prismatic cells improve regenerative braking efficiency, allowing for more effective energy recovery, and facilitate vehicle-to-grid (V2G) technologies.
- As the global prismatic battery market witnesses growth, driven by factors such as high energy density, enhanced safety, and packaging efficiency, industry experts observe that companies like SK On, with its unidirectional and bidirectional prismatic prototypes, can expand their customer base and compete effectively in the industry, particularly against Chinese firms such as CATL and CALB.
