As the global electric vehicle (EV) industry continues to evolve, a major key to success has always focused on the ongoing advancement of battery technologies. Batteries are arguably the most important element in every EV, accounting for the lion’s share of total cost and weight, while also being the key to delivering higher driving range, which is a primary competitive factor.
In recent years, the rise of Cell-to-Pack (CTP) and Cell-to-Chassis (CTC) approaches have focused on eliminating intermediate modules that traditionally were grouped together to form battery packs. These CTP and CTC configurations can effectively reduce battery weight and cost while increasing energy density and efficiency.
This article focuses on how the use of pouch cells can provide advantages for delivering higher energy density and details how advanced cell contacting system (CCS) technologies are key to configuring large arrays of pouch cells for CTP and CTC applications.
Why Pouch Cells vs. Cylindrical or Prismatic?
Pouch cells, cylindrical cells, and prismatic cells are three common types of lithium-ion batteries used in EVs and many other applications. Each has its own characteristics, advantages and challenges. They differ primarily in their shape, packaging and performance.
Cylindrical Cells: Cylindrical cells are round, typically resembling the shape of a soda can. The most common size for cylindrical lithium-ion cells is the 18650 (18 mm diameter, 65 mm height), though other sizes like 21700 are also common. They are rigid, and their cylindrical shape is a standard design used in many consumer electronics and some EV applications.
Prismatic Cells: Prismatic cells have a rectangular shape, similar to pouch cells, but they are housed in a hard, rigid metal casing (typically aluminum or steel). These cells are sometimes used in larger battery packs for EVs and stationary storage systems due to their rigid and space-efficient design.
Pouch Cells: Pouch cells have a flexible, flat, and rectangular shape. They are typically sealed in a multi-layer aluminum laminate pouch, which is soft and lightweight. The pouch cells’ flexible design allows them to be customized in terms of size and shape to fit a variety of applications and battery array configurations.
Because the pouch cell’s internal components, including anode material, cathode material, separator, and electrolyte, are wrapped in a flexible outer packaging of aluminum-laminated film, the cost, weight and size of rigid packaging is eliminated. This is key to providing higher energy density as well as offering flexibility for custom cell sizes and shapes.
The assembly process for pouch cells involves the careful preparation of each component, the precise stacking or winding of electrodes and separators, and the final sealing of the pouch. After initial testing and aging, the cells undergo rigorous safety and performance tests to ensure they are ready for use in electric vehicles or other applications. The flexibility of the pouch design makes it ideal for various configurations such as CTP and CTC but also requires meticulous handling to avoid issues with mechanical integrity and performance.
Summary Comparison of Cell Types:
| Feature | Pouch Cells | Cylindrical Cells | Prismatic Cells |
| Shape | Flexible, flat, rectangular | Round (e.g., 18650, 21700) | Rectangular, rigid casing |
| Energy Density | High | Moderate to High | Moderate to High |
| Mechanical Durability | Less durable, flexible | Very durable (rigid casing) | Durable, rigid casing |
| Thermal Management | Requires careful management | Better heat dissipation | Requires thermal management |
| Manufacturing Cost | Lower, but requires special handling | Lower (mass production) | Higher (rigid design) |
| Applications | EVs, CTP, CTC, portable electronics | EVs, consumer electronics, power tools | EVs, large battery systems |
Why Cell Contacting Systems are Important
Regardless of the type of individual cells being used, the Cell Contacting System (CCS) is a critical element for bringing cells together in a battery module or pack.
Electrical Connection: The primary function of a CCS is to establish an efficient and reliable electrical connection between the individual cells in a battery pack. This ensures that the electrical current flows properly between the cells when charging and discharging. The CCS typically involves metal tabs or conductive straps that connect the anode and cathode terminals of each cell to the external connections of the module or pack.
Cell Balancing: The CCS plays a role in cell balancing, which ensures that all cells in a battery pack charge and discharge uniformly. Without proper balancing, some cells may become overcharged or over-discharged, leading to decreased performance, reduced lifespan, or potential safety issues. Balancing can be achieved using passive or active balancing methods, both of which may involve the CCS to manage voltage levels and current flow among cells.
Thermal Management: In addition to its electrical function, the CCS often provides mechanical support for the cells, ensuring they are securely held in place within the battery pack or module. This helps prevent shifting, vibrations, or damage to the cells during operation, such as while the EV is in motion.
Safety and Monitoring: The CCS may also integrate with the Battery Management System (BMS) to monitor the health and status of individual cells. It helps with safety features such as detecting short circuits, preventing overcharging/over-discharging, and monitoring temperature to avoid thermal runaway.
CCS Design & Manufacturing are Keys to Success for Pouch Cells in Large Arrays
The CCS plays a central role in optimizing the performance, safety, and longevity of lithium-ion battery systems in EVs and other energy storage applications.
For EV battery configurations using pouch cells, the CCS capabilities become even more important because of minimal structural strength in the individual cells and the goal of achieving high energy density with closely packed cells in large battery configurations.
In contrast to conventional CCS designs that use bulky plastic trays, ENNOVI-Cell Connect-Pouch uses advanced lamination technology to create thin and lightweight solutions that enhance electrical and thermal performance at a lower manufacturing cost.
Precision pre-cut materials with good electrical insulation properties are used to provide good temperature stability. The pre-cut pathways on the lamination layers provide protection against battery thermal runaway by enabling fast exhaust release.
ENNOVI’s FDC is integrated on one end of the lamination, eliminating two layers of insulation material. Low voltage signals are integrated to streamline the amount of material used and create a thinner solution.
Our advanced lamination technology ensures structural integrity and durability. ENNOVI’s proprietary lamination processes for ENNOVI-CellConnect-Pouch can deliver comparable stability to conventional CCS glass fiber designs, while also effectively balancing the gap between the current collector and traces.
Summary
The ENNOVI-CellConnect-Pouch prioritizes cost effectiveness, faster manufacturing cycle time and protection against thermal runaway with advanced lamination and FDC technology.
Our proven technology, knowledge in CCS, vertically integrated production and precision processes help lower costs, simplify logistics and reduce development time.
As with all ENNOVI components, ENNOVI-CellConnect-Pouch is suitable for a range of EV applications. It integrates seamlessly into any organized system and can be customized to each unique manufacturer’s specifications.