Energy Storage

Battery Cell Contamination Prevention 260

This class summarizes the most common types of lithium-ion battery cell contamination, sources of contamination, and contamination prevention procedures. While any rechargeable battery may experience contamination, lithium-ion batteries are especially susceptible. Certain processes and environmental conditions must be met to reduce contamination. While some contamination is inevitable, proper detection and monitoring can reduce safety concerns and battery performance issues caused by contamination.

After taking this class, learners will understand ionic and particulate contamination, causes of contamination, and prevention methods, such as controlled environments, cleaning techniques, and detection and monitoring. Creating reliable and safe lithium-ion batteries can help increase consumer satisfaction and improve battery safety and quality.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 9

  • Language English


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Course Outline
  • Cell Contamination
  • Contamination Sources
  • Particulate Contamination
  • Ionic Contamination
  • Cell Contamination Review
  • Controlled Production Environments
  • Contact and Noncontact Cleaning
  • Contamination Monitoring and Detection
  • Contamination Prevention and Detection Review
  • Describe the impact of contamination on lithium-ion battery cells.
  • Identify common sources of battery cell contamination.
  • Describe particulate contamination.
  • Describe ionic contamination.
  • Describe controlled production environments.
  • Identify cleaning methods for contamination prevention.
  • Describe contamination monitoring and detection methods.
Vocabulary Term

adhesive elastomer rollers

A contact cleaning device made of static-resistant material, usually silicon or urethane, that is rolled across the surface of a material to remove contaminants. Adhesive elastomer rollers help prevent particulate contamination in smaller lithium-ion battery production processes.


A substance used to join two or more materials. Adhesives are used for various lithium-ion battery manufacturing processes like cleaning and assembly.

air shower

A self-contained air recirculation system at the entrance of a cleanroom that blows air over employees or equipment to remove contaminants. An air shower helps prevent contaminants from entering cleanrooms and dry rooms.


A highly conductive, lightweight, silvery metal. Aluminum particles can alter the flow of current in a lithium-ion battery cell.


The negative electrode in a battery. The anode in a lithium-ion battery is usually made of graphite.

antistatic mats

A mat made of a material that conducts current away from a person or object and into the ground. Antistatic mats can prevent electrostatic discharge that could start a fire or damage sensitive electrical components.

antistatic wrist-straps

A safety device worn around the wrist that conducts electricity away from the wearer and into the ground through a grounding cord attached to a grounded workstation. Antistatic wrist-straps protect the technician and electrical components from electrostatic discharge.


A colorless, odorless, inert gas. Argon is sometimes used for cleaning a variety of surfaces.


Any system, machine, tool, or device that does not require human intervention to operate. Automated processes can reduce contamination generated by humans.

battery cell contamination

The infiltration of particles or moisture into a battery cell. Battery cell contamination includes any particles or moisture in components like the electrode coating or electrolyte.

battery swelling

A buildup of heat and gas in a battery cell that can result from overcharging, cell contamination, or damage to the battery. Battery swelling is dangerous because it can cause fires.


A rough edge on a metal part created as a result of cutting or machining. Burrs can release particles into the air and lead to cell contamination.


The amount of energy that can be extracted from a battery under specific conditions. The capacity of a battery decreases if there is cell contamination.


The positive electrode in a battery. The cathode in a lithium-ion battery is made from a lithium compound.


A single unit of battery. A cell contains a cathode, an anode, and an electrolyte solution.

charge transfer

The movement of electrons between molecules or ions. Charge transfer is disrupted by particulate contamination.


A piece of metal that is removed from a workpiece during cutting or grinding. Chips are particles of metal that can cause cell contamination.


A room in which temperature, humidity, and air pressure are controlled and maintained. Cleanrooms are important for preventing the contamination of sensitive electronics.


The chemical makeup of an object, liquid, or other substance. Composition affects the mechanical and physical properties of a substance.

computed tomography

CT. An X-ray imaging procedure that generates cross-sectional images. Computed tomography scans can identify inhomogeneities, or contamination, in lithium-ion batteries.


Allowing the easy flow of electricity. Most conductive materials are metal.


A material that is used up during a process and must be replaced. Consumables can be costly, and manufacturers avoid using them when possible.

contact cleaning

A type of cleaning that involves directly contacting a surface or material with a tool, such as an adhesive elastomer roller. Contact cleaning can pick up contaminants from machinery or manufacturing materials in smaller production settings.


A highly conductive, reddish-brown metal. Copper particles can alter the flow of current in a lithium-ion battery cell.


A type of protective clothing that covers the entire body from the wrists to the ankles. Coveralls prevent contamination from clothing fibers.


The flow of electricity. Current strength is called amperage and is measured in amperes (A).

cycle life

The total number of times a secondary cell battery can be discharged and recharged before it must be replaced. Cycle life depends on the battery's design, materials, and operating conditions.


To remove excess moisture from the air. Dehumidifying the air in dry rooms reduces ionic contamination

dew point

The temperature at which moisture in the air can form water droplets and dew. The dew point in dry rooms must be closely monitored to ensure that water droplets do not form.

dry rooms

A type of cleanroom that maintains a lower humidity, usually at or below 1 percent. Dry rooms prevent ionic contamination in lithium-ion battery manufacturing.

drying units

An electrical machine that speeds up the process of drying materials. Drying units can reduce ionic contamination in lithium-ion battery manufacturing.

electric vehicles

EVs. A vehicle that uses full or partial electric motor power to propel itself forward. Electric vehicles commonly use lithium-ion batteries.

electrical resistivity

The measurement of how strongly a material opposes the flow of electrical current. Electrical resistivity is impacted by particulate contamination in a lithium-ion battery.


A device within a circuit that conducts electricity. Electrodes in lithium-ion batteries consist of a graphite anode and a cathode made of a lithium compound.

electrode coating

A liquid mixture composed of different active materials that is layered onto an electrode in a thin film. An electrode coating with particulate contamination can significantly decrease battery performance.


A conductive solution containing an acid, an alkaline, or a salt. The electrolyte in a battery connects the two electrodes.

energy density

The amount of energy that a battery can supply per unit of volume. Energy density is measured in watt-hours per liter (Wh/L) or watt-hours per kilogram (Wh/kg).

face masks

An item of protective clothing that is made from multiple layers of cotton or other tightly woven material and fits snugly over the nose and mouth. Face masks protect materials and products from human contamination during manufacturing.

fiber lasers

A type of solid-state laser that uses thin, flexible strands of glass or plastic as a lasing medium. Fiber lasers, or optical fiber lasers, are used in noncontact battery cell cleaning processes.


A gaseous element that is highly reactive and toxic. Fluorine is present in the salts of a lithium-ion battery cell electrolyte.


An air-like fluid that expands freely to fill any space available, regardless of quantity. Gases are used in some lithium-ion battery cell production processes, like machine cleaning, and can introduce ionic contamination.


A type of tight-fitting eye protection that completely covers the eyes, the sockets, and the surrounding facial area. Goggles offer protection from impact, dust, chips, and splashes.


The action of putting on personal protective equipment, such as coveralls, to enter a cleanroom environment. Gowning minimizes contamination.

heat exchangers

A device that moves heat between a source and two fluids kept at different temperatures. Heat exchangers dehumidify the air.

heating, ventilation, and air conditioning

HVAC. A system that controls climates in spaces like vehicles, buildings, and rooms. Heating, ventilation, and air conditioning systems are vital to controlling the environment for lithium-ion battery manufacturing, especially in dry rooms.

high-efficiency particulate air filters

HEPA filters. A disposable dry filter encased in metal or cardboard. High-efficiency particulate air filters are normally paper and extract different amounts of particles, such as skin cells and dust, from the air depending on the filter grade.

high-energy batteries

A battery that can store large amounts of energy and can be recharged hundreds of times. High-energy batteries include lithium-ion batteries, which are used for electronics and electric vehicles.


A type of protective clothing that covers the head and has either a face opening or a hole only for the eyes. Hoods prevent hair and skin cells from contaminating sensitive manufacturing materials.


The amount of water vapor in the air. Humidity control is important for lithium-ion battery manufacturing.

hydrogen fluoride

HF. A colorless gas that is extremely toxic and potentially fatal. Hydrogen fluoride gas is produced when a lithium-ion battery combusts or when ionic contamination causes water to interact with fluorine in the battery cell.


IR. Invisible light energy emitted by heated objects. Infrared light can be used to detect contamination in a lithium-ion battery, especially the separator.

infrared thermography

IRT. The process of using a thermal camera to capture and create an image based on infrared radiation. Infrared thermography is used to sense temperature differences between particles and surrounding areas in a battery cell, especially in the separator.

in-line inspection

The examination of a part during the production process. In-line inspection is an efficient way to monitor batteries for contamination.

internal short circuit

ISC. An undesirable high current that occurs when two electrodes unintentionally connect. Internal short circuits can lead to thermal runaway because high current causes increased temperatures.

International Organization for Standardization

ISO. A nongovernmental institution that establishes documented standards, rules, and guidelines to ensure that products, processes, and services are fit for their purpose. The International Organization for Standardization is responsible for standards across many different industries.

ionic contamination

A type of battery cell contamination that results from unwanted moisture in the battery. Ionic contamination can cause a battery to generate hydrogen fluoride gas, which is dangerous to humans and the environment.

ionic residue

A small amount of positively or negatively charged atoms or molecules left behind after a process. Ionic residue may contaminate a lithium-ion battery cell.

ionized gas

A gas that carries an electrical charge. Ionized gas is also referred to as plasma and may be used to remove impurities and contaminants from surfaces.


A device that uses high voltage to electrically charge air molecules into a neutral state. Ionizers are used in cleanrooms to prevent electrostatic discharge and electrostatic attraction.


A silver-white, metallic element that is highly magnetic. Iron particles can alter the flow of current in a lithium-ion battery cell.


Internal short circuit. An undesirable high current that occurs when two electrodes unintentionally connect. ISCs can lead to thermal runaway because high current causes increased temperatures.

ISO 14644

An International Organization for Standardization standard that provides specifications on designing, constructing, validating, and operating a cleanroom. ISO 14644 applies to numerous industries.

laser cleaning

A type of noncontact cleaning that uses a fiber laser to remove contaminants from metallic surfaces. Laser cleaning reduces particulate contamination.

latex gloves

A protective hand covering made from latex, a synthetic or natural rubber. Latex gloves help protect against chemical absorption, contamination, and electrostatic discharge.

Li-ion battery

Lithium-ion battery. A type of secondary cell battery that uses a lithium compound as a cathode and, usually, graphite as an anode. Li-ion batteries are widely used in portable electronics and electric vehicles.


A lightweight, silver-white metal that is highly reactive. Lithium is often used in batteries because it is extremely energy-dense.

lithium-ion battery

Li-ion battery. A type of secondary cell battery that uses a lithium compound as a cathode and, usually, graphite as an anode. Lithium-ion batteries are widely used in portable electronics and electric vehicles.


A metallic object or substance that possesses a force that attracts or repels other metals. Magnets can be used to remove some metallic particulate contamination.


A material made from metal. Metallic particles can impact the flow of current in a lithium-ion battery cell.

nickel-metal hydride batteries

NiMH batteries. A type of secondary cell battery that uses nickel hydroxide as a cathode and a hydrogen alloy as an anode. Nickel-metal hydride batteries are cheaper than lithium-ion batteries and are used in some hybrid electric vehicles.

noncontact cleaning

A type of cleaning that uses automated or indirect systems to that do not touch surfaces or materials to remove contaminants. Noncontact cleaning methods include laser cleaning and plasma cleaning.

nondestructive testing

A category of inspection processes that evaluate a part's properties and performance using methods that do not damage or permanently alter the part. Nondestructive testing in lithium-ion battery manufacturing includes using photo-optical systems, X-rays, CT scans, infrared light, and ultrasonic testing.


A material that is not made from metal. Nonmetallic materials include plastic, ceramic, and organic materials like skin cells and pollen that come from humans or the environment.

particle counter

A device that measures particles by passing air through a laser chamber that counts the number and size of particles in the chamber. Particle counters can help identify contamination trends and reduce contamination.


A relatively small portion of matter. Particles that may contaminate lithium-ion batteries include metallic and nonmetallic debris from cell production.

particulate contamination

A type of battery cell contamination that results from nonmetallic or metallic particles in the electrode coating or electrolyte. Particulate contamination is the most common type of contamination.

personal protective equipment

PPE. Any clothing or device that employees wear or use to minimize exposure to hazards, prevent injury, or protect sensitive products like battery cells from contamination. Personal protective equipment includes safety glasses, gloves, masks, gowns, and earplugs.

photo-optical systems

A system used for imaging, such as a camera with sensors. Photo-optical systems can detect contamination by passing components through a beam of light.

plasma cleaning

A type of noncontact cleaning that disperses ionized gas onto a metal surface to remove contaminants. Plasma cleaning can remove contaminants from machine surfaces or material surfaces.


An opening or void in a material. Pores in the separator film of a battery cell can be blocked by particulate contamination.


Having many openings or voids. Electrodes are porous, making them susceptible to moisture.


A collection of small, uniform, separate particles of a solid material. Powders are used in the lithium-ion battery manufacturing process.


Personal protective equipment. Any clothing or device that employees wear or use to minimize exposure to hazards, prevent injury, or protect sensitive products like battery cells from contamination. PPE includes safety glasses, gloves, masks, gowns, and earplugs.

raw materials

An untreated or minimally treated material used in the manufacturing of a product. Raw materials that are critical for manufacturing lithium-ion batteries include lithium, graphite, cobalt, and manganese.


A breathing device worn to prevent inhalation of hazardous substances. Respirators filter out chemicals and particulate matter and also prevent employees from contaminating sensitive materials.


A chemical compound with a crystalline structure. Salts are used in the electrolyte of a lithium-ion battery cell.

scrap rates

The number of manufactured components discarded as waste or recycled due to defects. Scrap rates can be decreased by using contamination prevention measures.

self-discharge rate

The amount of energy a battery loses over a specific amount of time when it is not connected to a circuit. Self-discharge rates increase when batteries have defects.


A device that detects a change in a physical stimulus and turns it into a signal that can be measured and recorded. Sensors may be connected to a machine or system in order to collect operational data that is later analyzed.


A battery component that provides a barrier between the anode and cathode. Separators can perforate from contamination and cause an internal short circuit.


A chemical used to dissolve another material. Solvents are used in electrode coatings to ensure that they are properly mixed.

static electricity

An electrical charge caused by the buildup of friction in a person or object. Static electricity can be controlled by using antistatic safety accessories.

thermal runaway

The process of a defective or damaged battery cell overheating and damaging nearby cells, causing them to also overheat. Thermal runaway can cause fires or explosions if not detected and stopped.


A general change in variables that can help predict future behavior. Identifying data trends in lithium-ion battery manufacturing can help identify sources of contamination.

ultrasonic testing

UT. A nondestructive testing method that uses high-frequency sound waves to detect internal part discontinuities and defects. During ultrasonic testing, reflected sound waves are converted into electrical signals, which technicians can evaluate.


A joining process that uses heat, friction, or a combination of methods to fuse two materials together permanently. Welding is used in the manufacturing of lithium-ion batteries.


A type of electromagnetic wave with a high frequency and short wavelength. X-rays are used to view the interior of solid objects during computed tomography.