Lithium-Ion Battery Safety in Manufacturing: A Fire Hazards Overview

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Corey Kinsman, P.E.

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July 9, 2024

Lithium-ion batteries are rechargeable power sources widely used in various applications, from portable electronics to electric vehicles. However, with enormous popularity comes an increasing risk in the manufacturing of these components.  

Before we dive into the specifics of battery manufacturing safety, let’s cover a few basics.

What’s Inside a Lithium-Ion Battery?

Lithium-ion batteries consist of several components, including:

  • Anode: The negative electrode that stores lithium ions during the charging process.
  • Cathode: The positive electrode that discharges lithium ions. This generates an electrical current that powers a connected device.
  • Electrolyte: An electrolyte is typically a mixture of lithium salt that is dissolved in an organic solvent. This mixture facilitates the movement of lithium ions between the anode and cathode during charge cycles.
  • Separator: The thin polymer membrane that separates the anode and cathode. The separator prevents short circuits while allowing lithium ions to pass through.
  • Current Collectors: Current collectors conduct electrons to and from the external circuit.
  • Casing: The outer shell that houses all components, providing structural integrity and safety.

Safety Challenges During Lithium-Ion Battery Manufacturing

Although manufacturing incorporates several safety stages throughout the aging and charging protocol, lithium-ion battery cells are susceptible to fire hazards.

These safety challenges vary depending on the specific manufacturing environment, but common examples include:

Configuration of Lithium-Ion Battery Cells: The placement of cells within enclosures or located where suppression systems are obstructed can significantly increase the risk of a fire hazard. In the event of a fire in rack storage, for instance, ceiling-level sprinklers may be ineffective at applying water to the source of the fire. In addition, enclosures create confined spaces where the flammable gases produced in thermal runaway can be concentrated and create an explosion hazard.

Voltage Range: Each cell chemistry has a safe voltage range, typically between 3.6 and 3.7 V. Discharges or overcharges can degrade the cell’s electrodes, causing battery failure or thermal runaway—a self-perpetuating process of increased temperature and energy release—to occur.

State of Charge (SOC): Higher SOC levels decrease the stability of the cells, and the higher energy density results in more significant impacts when these cells fail.

Hazardous Materials: Various materials and chemicals are used in the manufacturing process, and they have a range of flammable, toxic, and corrosive characteristics that present physical and health hazards.

Process Equipment: The process and material handling equipment used in manufacturing can create complex environments for fire protection and life safety. The long lines of equipment can create egress travel distances in excess of the distances allowed by codes. Also, the dense storage of products and batteries in racks and Automated Storage and Retrieval Systems (ASRS) create challenges to fire protection systems design.

Many manufacturing companies utilize computer fire and egress modeling to develop safe building designs for occupant egress and use engineered designs when codes and standards have yet to provide design guidance.

Fire Hazards in Lithium-Ion Battery Manufacturing 

The manufacturing process for lithium-ion battery cells involves three critical steps, each with specific hazards and risks. 

1. Electrode Manufacturing

During electrode manufacturing, raw materials are mixed and coated onto sheets of foil, which then become the cathode and anode electrodes. Hazards involved in these process steps include: 

  • High-piled storage of combustible commodities.
  • Storage, handling and use of hazardous materials, including flammable and combustible liquids, toxic powders and corrosive liquids.
  • Combustible dust hazards.
  • Heating of combustible liquids and ventilation systems transporting flammable vapors.

2. Cell Assembly

Once the electrodes are created, cathode and anode rolls are cut to specific sizes and assembled with separators and casing. These cells are then filled with liquid electrolytes. 

Hazards involved in these process steps include: 

  • High-piled storage of combustible commodities.
  • Combustible dust hazards.
  • Long egress travel paths.
  • Storage and use of electrolyte (a flammable and corrosive liquid) for injection into the cells.

3. Cell Formation

The sealed cells then undergo an activation process, during which they are subjected to charging and discharging cycles, aging processes and several quality tests. Cell formation stabilizes the cell’s performance, activates the electrode materials and improves its capacity and lifecycle.

Hazards involved in these process steps include: 

  • High-piled storage of charged lithium-ion cells
  • Material handling of charged lithium-ion cells (conveyors, stacker cranes, automated loading/unloading of trays of cells, removal of gas buildup during the Degas stage, Automated Storage and Retrieval Systems).
  • Charging and discharging of lithium-ion cells.
  • Disposal of cells that do not meet quality standards.

Are Lithium-Ion Batteries Dangerous? 

Yes, they can be, especially if not properly handled or controlled. Lithium-ion batteries contain flammable electrolytes and solvents that can rapidly propagate fires. They are also prone to thermal runaway, resulting in rapid temperature increases that can cause fires or explosions. 

Given this potential for severe damage, robust safety measures should be implemented and observed, including working with a fire protection engineer.

Fire protection engineers (FPEs) are trained professionals who proactively mitigate fire hazards, particularly in lithium-ion battery manufacturing. They focus on minimizing risks and enhancing compliance with safety standards in mind.

Conducting a Fire Hazard Analysis

FPEs enhance fire safety by conducting a fire hazard analysis (FHA), a systematic assessment that evaluates potential fire risks within an environment. It begins by identifying sources of ignition, fuel and oxygen that could contribute to a fire. Once hazards are identified, the analysis assesses the likelihood of fires starting and spreading and potential consequences like property damage or injury.

An FPE would assess lithium-ion batteries at various manufacturing process stages. Based on this analysis, the engineer would then provide recommendations for building and system design, including fire resistance ratings, specialized fire suppression systems, smoke and gas detection, and ventilation to mitigate these risks. 

Emergency response plans and training sessions would also be developed to ensure personnel is prepared in the incident of a fire. These measures collectively enhance fire safety design and reduce the likelihood of hazard escalation.

Conclusion

Lithium-ion battery manufacturing is a complex process that faces inherent fire hazards. An FPE's expertise ensures facilities have robust fire prevention systems, including ventilation and fire suppression. Their guidance mitigates the risk from flammable components, safeguards personnel, and ensures safety standards are met throughout the battery lifecycle. 

Performance Based Fire offers fire hazard analysis services to identify, document and classify hazards, recommend safe building and systems design, and ensure compliance with building and fire codes. Contact us today to get started.