Hazards

Lithium-ion batteries may present several safety and health hazards during manufacturing, use, transportation, emergency response, disposal, and recycling. These hazards can include chemical hazards, stored electrical energy, and thermal runaway, which can result in fire, explosions, and the release of chemical byproducts.

Chemical Hazards

Lithium-ion batteries contain various components that present different chemical hazards to workers, such as flammability, toxicity, corrosivity, and reactivity hazards. These chemicals may come into the workplace as raw materials or recycled materials. As processes change, any new chemicals must be thoroughly assessed for potential safety and health impacts to the workplace and workers.

A lithium-ion battery cathode is made of a lithium metal oxide material. The choice of cathode material depends on the desired characteristic of the battery. These materials can include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel manganese cobalt oxide (LiNiMnCoO2), lithium nickel cobalt aluminum oxide (LiNiCoAlO2), or lithium iron phosphate (LiFePO4).

Common materials for lithium-ion battery anodes include carbon-based materials such as graphite, graphene, nanofibers, carbon nanotubes, and titanium-based materials such as lithium titanate and titanium dioxide.

Lithium-ion batteries contain electrolytes that are a combination of solvents with an electrolytic salt. Lithium hexafluorophosphate (LiPF6), the most common salt used in lithium-ion cells, can react with water to form hydrogen fluoride (HF). The most common solvents used in lithium-ion batteries include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Some of these electrolytes are flammable liquids and requirements under OSHA's Process Safety Management standard, 29 CFR 1910.119, may apply to quantities exceeding 10,000 lbs.

Many of the chemicals used in lithium-ion battery manufacturing have been introduced relatively recently. Consequently, there may be limited toxicological information and few established OSHA permissible exposure limits (PELs). Additionally, because some of OSHA's PELs may be outdated and inadequate for ensuring protection of worker health, it is important for employers to consider alternative occupational exposure limits (OELs) developed by technical, professional, industrial and/or government organizations to ensure worker protection. For chemicals without occupational exposure limits, Occupational Exposure Banding and Control Banding can be used in conjunction with the Hierarchy of Controls to manage risks and prevent exposure to hazardous chemicals. See the NIOSH Control Banding webpage and the OSHA Permissible Exposure Limits – Annotated Tables for additional information and explanation.

Additionally, when a lithium-ion battery or cell does not meet the exemption under OSHA's Hazard Communication Standard (HCS), 29 CFR 1910.1200, as an "article," the manufacturer or importer is required to classify the chemical hazards and provide the hazard information to downstream users. For additional information, see OSHA's Letters of Interpretation, including Coverage of lithium-ion batteries under the Hazard Communications Standard (6/23/2021) and Applicability of the HCS to Lithium-ion Batteries (12/1/2022).

Safety Hazards

In addition to electrical hazards, lithium-ion batteries can also present hazards resulting from thermal runaway. Because lithium-ion batteries combine a flammable electrolyte with a significant amount of stored energy, thermal runaway reactions are possible. Thermal runaway is a chain reaction where the heat released from the failure of one cell damages nearby cells. This can be initiated by internal short-circuiting due to defects during manufacturing, mechanical damage to the battery, exposure to excessive heat or cold, and improper charging.

Thermal runaway can be identified by several indicators including a rise in battery temperature, the presence of fire, or venting of gas, vapor, or smoke from the battery. Fires caused by thermal runaway can produce additional chemical hazards that may include hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen cyanide (HCN), phosphoryl fluoride (POF3), carbon monoxide (CO), carbon dioxide (CO2), black carbon, and other potentially hazardous chemicals and particulates.

For additional information see OSHA's Safety and Health Information Bulletin on Preventing Fire and/or Explosion Injury from Small and Wearable Lithium Battery Powered Devices.