The electrodes are dried again to remove all solvent content and to reduce free water ppm prior to the final processes before assembling the cell.

The final shape of the electrode including tabs for the electrodes are cut. At this point you will have electrodes that are exactly the correct shape for the final cell assembly.

Challenges
●Avoiding burrs on edges
●Ensuring no loose metallic particles contaminate coatings

In a cylindrical cell, the anode, cathode, and separator are wound into a spiral. In pouch cells, the electrodes are stacked in layers: anode, separator, cathode, separator, and so on. Some prismatic cells have stacked electrodes, while others feature a flat-wound jelly roll design.

Challenges
●Alignment of layers
●Avoid punctures of separator
●Separator folding
●lots of countermeasures applied over time like separator envelope welding not all manufacturers countermeasure in this way

The anodes are connected to the negative terminal and the cathodes to the positive terminal. The quality and strength of this connection are crucial, as welding the cell to the busbars can potentially damage the internal welds.

Challenges
●Trimming of tabs and avoiding any burrs or particles being left behind
●Gathering all the foils and presenting them to the welder
●Aligning gathered electrode foils with tab
●Weld position alignment, whether that is Laser Alignment, spot weld or ultrasonic horn and anvil alignment
●Wear of electrodes / horn / anvil
●Consistent energy burst, energy oscillation, changes in materials or even surfaces
●Ensuring no sputter contaminates cell
●Ensuring good consistent electrical connections

The electrodes, either in the form of a roll or a stack of layered sheets, are carefully inserted into a can (for cylindrical or prismatic cells) or a pouch (for pouch cells). The specific process of enclosing the electrodes will vary depending on the type of cell format being produced. For cylindrical cells, the electrodes are wound into a tight spiral and inserted into a metal can, while for pouch cells, the stack is layered directly into the flexible pouch casing. The process needs to ensure proper alignment, secure sealing, and minimal air exposure to preserve cell integrity.

Challenges
●Ensuring no debris in can
●Ensuring no damage to jelly roll or stack
●Pouch
●Pouch Cup formation – avoid die inclusions
●Stack placement in pouch – alignment
●2nd Pouch (over) cup – avoid die inclusions
●Heat Sealing integrity time, applied energy – avoid heater bar contamination affecting seal integrity
●Open cell seal handling prior to injection
●Pouch Taping – a line of tape applied on inner side of cup corresponding to placement of stack
●Isolation Testing
●HiPot testing or Capacitance tests are done at this stage to establish the integrity of the cell, this should find:
●debris / metallic foreign particles
●folds in the separator
●holes in the separator
●burrs on current collectors

This step involves filling the dry cell with electrolyte, which is crucial for activating the electrochemical process inside the battery. A partial vacuum is first created inside the cell, which allows for efficient distribution and wetting of all internal layers when the electrolyte is introduced. This ensures that the electrolyte thoroughly penetrates the entire cell structure, improving performance.

●Electrolyte Dispensing:
The electrolyte is injected based on a specific, pre-determined volume to ensure accuracy.

●Quality Control:
After the electrolyte is added, the weight of the cell is checked both before and after filling to ensure the correct amount of electrolyte has been added.This process helps ensure consistent performance and quality of the battery, as the correct amount of electrolyte is crucial for proper functioning.

Challenges
●Environment ppm control
●"vacuum" injection pressure integrity
●The electrolyte needs to be in the very low ppb range for H2O.
●Higher levels of H2O create HF not only is a safety hazard, but it also eats the battery from the inside out.
●Mass flow injection (as opposed to vol flow injection)
●Traceability finesse of the injection tanks, purge control, downtime in pipework etc
●Injection and feeder tank residues build up (preventative maintenance control and frequency)
●Temporary seal integrity checks
●Wetting of all layers within the jelly roll or stack with electrolyte
●May require rolling / rotation protocol to enhance wetting

The cell is charged and at this point gases form in the cell. The gases are released before the cell is finally sealed.

Challenges
●Environmental control in charging bays during formation
●Time stamp control of applied protocol
●Degas evacuation pressure level e.g. electrolyte boil off control prior to permanent seal
●Checking cell is sealed securely
●Mass check is often used
●Running formation cycle without damaging the cell

After the cell is fully sealed, the next stage involves charging and discharging cycles. During this step, the cell undergoes repeated charge and discharge processes to ensure it meets performance standards and specifications. This step can also be part of the final conditioning of the battery before it is ready for use.
The charge and discharge cycles help in determining the capacity, efficiency, and overall stability of the battery. It also aids in identifying any potential issues with the cell's performance, such as capacity fade or internal resistance changes.
The duration and number of charge/discharge cycles vary depending on the battery's type and the manufacturer's protocol. This process is crucial to ensure that the battery operates optimally when used in its final application.

Challenges
●Temperature control: Maintaining a stable temperature during charge and discharge to prevent overheating or underperformance.
●Cycle consistency: Ensuring consistent results across multiple cells in a batch.
●Charge rate management: Balancing the speed of charging and discharging without affecting the cell's long-term health.
●Monitoring: Continuous monitoring of voltage, current, and capacity to assess cell behavior.
●Quality control: Testing cells post-cycling to confirm they meet all required performance criteria before proceeding to the next stage.

The heat and cold resistance test measure the performance and safety of battery cells under extreme temperature conditions. The cells are exposed to high and low temperatures to assess their durability, charge/discharge capabilities, and potential for degradation or failure.

Challenges
●Optimize the electrolyte formulation to enhance performance at extreme temperatures, improving both high-temperature safety and low-temperature discharge efficiency.
●Strengthen the cell casing and internal components to reduce the risk of expansion or contraction under thermal stress, maintaining long-term reliability.
●Incorporate advanced thermal management systems to maintain consistent cell performance across a wide range of temperatures, reducing the impact of extreme conditions on battery life.

The nail penetration test is conducted to evaluate the safety of battery cells when subjected to mechanical abuse. A sharp metal nail is driven through the battery cell to simulate an internal short circuit. This test checks for dangerous outcomes such as thermal runaway, fire, or explosion.

Challenges
●Refine the nail penetration angle and speed to simulate more realistic external forces encountered in various environments.
●Enhance the cell structure and materials to improve resistance to internal short circuits, minimizing the risk of thermal runaway during mechanical abuse.
●Implement more sensitive temperature and pressure sensors within the cell to detect early signs of failure during penetration tests.