Battery Cell Electrode Manufacturing 345

active materials

AMs. A substance that contributes to the electrochemical reactions that enable a battery to charge and discharge. Active materials for lithium-ion battery cells include lithium metal oxides, graphite, and silicon.

additives

A substance added in small amounts to another substance or material to change its properties. Additives for electrode manufacturing are inactive materials that improve how active materials mix with solvents or bind to electrode current collector foils.

adhesives

A chemical material used to bond two substances or objects together. Adhesives for electrode manufacturing are inactive materials that improve how active materials bind to electrode current collector foils.

advanced manufacturing

The use of innovative technology and processes to improve the manufacturing of products. Advanced manufacturing technologies include robotics, lasers, and smart manufacturing.

air pressure

The force created by air at a specific location and in a specific amount of space. Air pressure can change by compressing air, changing its temperature, or removing it in a vacuum.

aluminum

A common lightweight, silver-white metal that resists corrosion and is a good conductor of electrical and thermal energy. Aluminum is commonly used as the cathode for lithium-ion batteries.

AMs

Active materials. A substance that contributes to the electrochemical reactions that enable a battery to charge and discharge. AMs for lithium-ion battery cells include lithium metal oxides, graphite, and silicon.

anode

The negative electrode in a battery. The anode in a lithium-ion battery is usually made of copper with graphite or silicon active materials.

anode active materials

AAMs. A substance that contributes to the electrochemical reactions of a battery's negative electrode. Anode active materials for lithium-ion battery cells commonly include graphite and silicon.

atomic structure

The organization of atoms in a substance. Atomic structures determine the physical and mechanical characteristics of a substance.

automated assembly lines

An assembly line in which most tasks are performed by automated machines. Automated assembly lines require little or no human interaction.

batches

A specific number of identical parts that move through the production process as a group. Entire batches of electrodes can be ruined by microscopic flaws or contamination.

burrs

A rough, sharp edge remaining on a workpiece after machining. Burrs can degrade the quality of an electrode and cause the coating to tear.

calender

A machine that uses heavy rollers to compress dried electrode coatings to an even thickness. A calender's rollers may also be heated to provide additional curing and further prevent ionic contamination.

calendering

The process of compressing dried electrode coatings with heavy rollers to create an even thickness and improve atomic structure. Calendering is the fifth major step in battery cell electrode manufacturing.

can

A protective metal cover that surrounds some battery cells. A can is typically cylindrical or prismatic and helps prevent cell swelling, bending, and damage.

cathode

The positive electrode in a battery. The cathode in a lithium-ion battery is usually made of aluminum with lithium oxide active materials.

cathode active materials

CAMs. A substance that contributes to the electrochemical reactions of a battery's positive electrode. Cathode active materials for lithium-ion battery cells commonly include lithium metal oxides.

cell

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

cell assembly

The process of preparing and combining battery cell components, which generally includes winding, welding, and enclosing. Cell assembly is the second stage of battery cell manufacturing that comes between electrode manufacturing and cell finishing.

cell chemistries

The chemical composition of materials in a battery cell. The chemistry of a battery cell influences the cell's design and manufacturing processes.

cell finishing

The process of adding electrolytes to an assembled battery cell, which generally includes filling, aging, and testing. Cell finishing is the third stage of battery cell manufacturing and comes after electrode manufacturing and cell assembly.

chemical hazards

Any substance or mixture of substances that is harmful to employees. Chemical hazards in battery electrode manufacturing include active materials and solvents like NMP.

chillers

A refrigeration system that cools the mixing bucket on some industrial mixers. Chillers can be used to control the temperature of electrode slurries during mixing.

chips

A piece of metal that is removed from a workpiece by cutting. Chips are tiny curls, shards, fragments, shavings, or particles of metal.

circuit

A completely enclosed path for electrical current. Electrical circuits usually include a source, path, load, and control.

classes

A number used to categorize ISO cleanrooms. Class 1 cleanrooms must adhere to the strictest contamination prevention standards, while Class 9 cleanrooms have the least strict requirements.

cleanrooms

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

coating

The process of depositing slurry onto electrode current collectors in a thin, even film. Coating is the third major step in battery cell electrode manufacturing.

computer numerical control

CNC. A programmable system of software and hardware that directs the operation of a machine. Computer numerical control systems use mathematical data to direct machine movements.

conductivity

A material's ability to transfer electricity. The conductivity of a battery cell electrode can be altered by any microscopic flaws or contamination.

conductors

A material that allows free movement of electrons and, therefore, allows electricity to flow easily. Conductors are typically metals like aluminum and copper.

contamination

The presence of undesired particles or substances in a battery cell or electrode. Contamination can alter the conductivity of a battery cell.

convection drying

A noncontact electrode drying method that blows hot air to evaporate liquids. Convection drying uses large amounts of energy and requires electrode sheets to move continuously through long or slalom ovens until they are dry.

copper

A highly conductive, reddish-brown metal. Copper is commonly used as the anode for lithium-ion batteries.

coveralls

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

cures

To cause a material to bond and solidify by permanently cross-linking its molecules through heat, light, time, or chemical means. The drying process cures active materials and binders to the current collector.

current collector foils

An exceedingly thin sheet of metal used to provide structure and conductivity to a battery cell electrode. Current collectors for lithium-ion battery cells are usually copper or aluminum.

cutting

An electrode cutting process that forms daughter rolls into the correct size and shape for cell assembly. Cutting, like slitting and notching, can be performed by laser cutting or mechanical cutting methods.

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.

daughter rolls

A smaller, more manageable sheet of electrode foil. Daughter rolls are produced when a mother roll is cut during slitting.

density

The amount of mass within a given volume of a substance. The density of the slurry is one of the most important factors to consider when selecting or setting up a slot-die extruder for electrode coating.

die

A contact tool that shapes parts by compressing a workpiece in a punch. A die shapes large electrode sheets into individual electrodes during punching.

doctor blade

A long, thin metal bar that controls the flow of slurry during doctor blade coating. A doctor blade offers less precise and less accurate control of coating thickness than slot-die extrusion methods.

doctor blade coating

A contact electrode coating method that uses gravity and the motion of the foil through the coating machinery to deposit slurry and controls its thickness with a specially designed doctor blade. Doctor blade coating is less accurate than slot-die coating.

dosing

Automatically adding ingredients in extremely precise, controlled quantities. Dosing in electrode mixing generally produces a smaller amount of higher-quality slurry than other methods of adding ingredients.

dry powder slurries

A mixture of powdered active materials and inactive materials that does not contain a liquid solvent. Dry powder slurries are less common than semi-liquid slurries but eliminate the need to remove some liquid during later manufacturing steps.

dry rooms

A type of cleanroom that maintains lower humidity levels, typically below 1 percent. Dry rooms prevent ionic contamination in battery cell manufacturing.

drying

The process of evaporating any liquid slurry ingredients or water from the electrode coating. Drying is the fourth major step in battery cell electrode manufacturing and cures active materials and binders to the current collector.

electric vehicles

EVs. A vehicle that is fully or partially propelled by an electric motor that draws its power from a battery. Electric vehicles, including hybrid electric vehicles, require high-energy, lightweight, rechargeable batteries.

electrode manufacturing

The process of fabricating electrodes for battery cells, which generally includes pre-manufacturing, mixing, coating, drying, calendering, and slitting, cutting, and notching. Electrode manufacturing is the first stage of battery cell manufacturing and comes before cell assembly and cell finishing.

electrodes

A component within a circuit that conducts electricity. Electrodes have a positive or negative charge.

electrolyte

A conductive liquid, gel, ceramic, or other solid containing an acid, an alkaline, or a salt. The electrolyte in a battery connects the two electrodes.

electromagnetic wave drying

A noncontact electrode drying method that uses infrared light, lasers, or microwaves to evaporate liquids. Electromagnetic wave drying is fast but expensive.

energy density

The amount of energy that a battery can supply per unit of volume. Energy density is often measured in kilowatt-hours per liter (kWh/L).

evaporating

The process of turning a liquid into a vapor. Evaporating liquid slurry materials and water from the electrode coating during drying reduces ionic contamination.

eye protection

Personal protective equipment that covers the eyes. Eye protection such as safety glasses, goggles, or face shields must be worn in cleanrooms and dry rooms and when working with hazardous materials.

foil enclosure

A battery cell container made from an exceedingly thin sheet of metal. A foil enclosure encases a pouch cell battery.

graphite

A soft, black form of carbon that conducts electricity. Graphite is a common anode active material for lithium-ion battery cell electrodes.

hardness testing

A destructive testing method that determines how a material responds to external forces that attempt to scratch, penetrate, or indent it. Hardness testing usually involves indenting a material sample and determining its hardness based on the size of the indentation.

heterogenous

Not uniform in composition and properties. Heterogenous, or non-homogenous, slurries do not spread active materials out or dry evenly because the uneven mixture will create areas with too much or too little conductive material.

homogenous

Uniform in composition and properties. Homogenous slurries ensure that active materials spread out and dry evenly on the electrode foil.

humidity

The amount of water vapor in the air. Humidity present during electrode manufacturing can cause ionic contamination.

inactive materials

A substance that is used in battery electrode manufacturing to improve how active materials mix or bind to the electrode current collector foils. Inactive materials include adhesives, solvents, and other additives.

infrared

IR. A wavelength of light that is beyond, or longer than, red on the visible light spectrum. Infrared light can be used to dry electrodes during electromagnetic wave drying.

internal short circuits

ISCs. The unwanted flow of current between electrodes in a cell that occurs when they unintentionally connect. Internal short circuits can lead to increased temperatures and thermal runaway.

International Organization for Standardization

ISO. A non-governmental 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

The presence of unwanted moisture in battery cell components. Ionic contamination can cause a battery to generate hydrogen fluoride gas, which is dangerous to humans and the environment.

ISCs

Internal short circuits. The unwanted flow of current between electrodes in a cell that occurs when they unintentionally connect. ISCs can lead to increased temperatures and thermal runaway.

ISO 14644

An International Organization for Standardization standard that provides specifications for designing, constructing, validating, and operating cleanrooms. ISO 14644 also establishes nine classes for cleanroom cleanliness.

joule heating

A contact electrode drying method that applies an electric current to the current collector to evaporate liquids. Joule heating can cause uneven drying if there are variations in the electric current.

laser cutters

A tool that uses a laser beam to remove material from a workpiece. Laser cutters are high-precision, noncontact cutting tools that can be used in electrode slitting, cutting, and notching.

lasers

A device that generates an intense beam of coherent, collimated, monochromatic light that can be precisely aimed and controlled. Lasers are used for many battery cell and electrode manufacturing processes, including cleaning, welding, and cutting.

lead-acid

A type of rechargeable battery that uses lead dioxide as a cathode and lead as an anode. Lead-acid batteries are very cheap to produce and, therefore, widely used despite their lower specific energy and energy density.

Li-ion

Lithium-ion. A type of rechargeable battery cell that uses a lithium compound in the cathode and, usually, carbon in the form of graphite in the anode. Li-ion battery cells are widely used in portable electronics and electric vehicles.

lithium metal oxides

A chemical compound formed by oxygen, lithium, and another metal, such as cobalt, nickel, or manganese. Lithium metal oxides are used as cathode active materials in lithium-ion battery cells.

lithium-ion

Li-ion. A type of rechargeable battery cell that uses a lithium compound in the cathode and, usually, carbon in the form of graphite in the anode. Lithium-ion battery cells are widely used in portable electronics and electric vehicles.

mechanical cutting

A process that uses a contact tool to remove metal from a workpiece. Mechanical cutting methods include milling, turning, and drilling.

microns

A metric measurement equal to 0.000001 meter, or approximately 0.000039 inches. Microns, or micrometers, are used to measure electrode thickness.

microwaves

A type of electromagnetic wave with a shorter than standard wavelength. Microwaves can be used to dry electrodes during electromagnetic wave drying.

mining

Extracting raw materials from the earth. Mining includes processes used to obtain raw metal ore used for current collector foils.

mixing

The process of blending active materials, solvents, and other inactive materials to form an electrode slurry. Mixing is the second major step in battery cell electrode manufacturing, after pre-manufacturing.

mother rolls

A large, uncut sheet of electrode foil. Mother rolls are cut into smaller daughter rolls during slitting.

nickel-metal hydride

NiMH. A type of rechargeable 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.

N-methyl-2-pyrrolidone

NMP. A colorless or yellowish organic solvent that is liquid at room temperature. N-methyl-2-pyrrolidone is currently the most common solvent used in lithium-ion electrode manufacturing but is classified as a chemical hazard because it can cause environmental, reproductive, and developmental harm.

NMP

N-methyl-2-pyrrolidone. A colorless or yellowish organic solvent that is liquid at room temperature. NMP is currently the most common solvent used in lithium-ion electrode manufacturing but is classified as a chemical hazard because it can cause environmental, reproductive, and developmental harm.

non-homogenous

Not uniform in composition and properties. Non-homogenous, or heterogenous, slurries do not spread active materials out or dry evenly because the uneven mixture will create areas with too much or too little conductive material.

notching

An electrode cutting process that creates tabs on individual electrodes. Notching leaves a small strip of uncoated current collector foil, which enables electrodes to be welded to each other and to other components in the finished battery.

particulate contamination

The presence of unwanted nonmetallic or metallic particles in battery cell components. Particulate contamination is the most common type of contamination and includes clothing fibers, undesired metal fragments, hair, skin cells, and dust.

personal protective equipment

PPE. Any clothing or device used to minimize exposure to hazards and prevent injury. Personal protective equipment includes safety glasses, gloves, masks, coveralls, and earplugs.

planetary vacuum mixers

A special type of industrial mixer that creates a vacuum seal around slurry ingredients during mixing. Planetary vacuum mixers often include features like chillers, specially designed double beaters, and the ability to rotate in multiple directions to produce even mixtures.

polymer binders

A polymer-based agent that holds or draws other materials together. Polymer binders like polyethylene (PE) and polypropylene (PP) are commonly used as inactive materials in electrode slurries and to pretreat substrate before coating.

pores

An opening or void in a material. Pores between particles of active materials can be eliminated or made smaller and more uniform by calendering electrodes.

porosity

The presence of tiny spaces or voids within a material. Porosity in electrode coatings can be reduced by calendering, which improves the electrode's ability to conduct current.

pre-manufacturing

The process of designing battery cell components and acquiring materials for fabricating battery cell electrodes. Pre-manufacturing is the first step of electrode manufacturing.

pressure

The exertion of a mechanical force upon an object or substance. Pressure from the rollers of a calender compress particles of an electrode's active materials together to improve its ability to conduct current.

punching

A mechanical shearing operation that uses pre-formed tools called dies to separate metal sheets to shape. Punching is an affordable alternative to laser cutting for electrodes but can cause burrs, tears, and chips.

rechargeable batteries

A battery that can be recharged. Rechargeable batteries, or secondary cell batteries, are charged by running electrical current back through them to restore their chemical energy.

refining

The process of purifying raw materials to make them usable in a manufacturing process. Extensive refining is required for most active materials and metals before they can be used in electrode manufacturing.

reservoir

A container used to store large quantities of liquid. Reservoirs are used in slot-die coating and doctor blade systems to hold slurry.

respiratory protection

A form of personal protective equipment that protects the wearer from breathing in hazards present in the air. Respirators are a common type of respiratory protection.

robots

A programmable mechanical device used to perform a variety of complex, repetitive tasks. Robots are used in automated assembly lines to enable a higher degree of accuracy and precision than human assemblers.

rollers

A heavy, cylindrical drum that applies pressure to a surface as it rotates. Rollers in a calender compress electrode coatings to a uniform thickness and may be heated to provide additional drying.

roll-to-roll

A manufacturing technique that takes spooled material off one roll, processes it, and re-spools it onto a new roll. Roll-to-roll processes like electrode coating are continuous operations.

secondary cell batteries

A battery that can be recharged. Secondary cell batteries, or rechargeable batteries, are charged by running electrical current back through them to restore their chemical energy.

separator

A film in a battery cell that provides a barrier between the anode and cathode. Separators can be perforated by contamination and cause internal short circuits.

shearing

A basic metal cutting process that separates sheet metal into smaller sections without forming chips. Shearing processes like punching are contact methods for shaping electrodes.

silicon

A lustrous gray, semi-metallic semiconductor material. Silicon is a common anode active material for lithium-ion battery cell electrodes.

slalom

Moving back and forth in a zigzag or wave pattern. Slalom ovens are used in convection drying to increase the time electrode sheets are in the dryer without making the dryer longer.

slitting

An electrode cutting process that separates large rolls of electrode sheets into smaller rolls that are easier to machine and handle. Slitting divides large mother rolls into several smaller daughter rolls.

slot-die coating

A noncontact electrode coating method that uses a precision nozzle to deposit slurry onto current collector foils. Slot-die coating is more accurate than other methods like doctor blade coating.

slot-die extruder

A precision nozzle that dispenses and controls the flow of electrode slurry during slot-die coating. A slot-die extruder uses either gravity or pumps to deposit slurry onto current collector foils and may have an adjustable opening.

slurry

A mixture of liquid and suspended solids. Slurries for electrode manufacturing contain a blend of active materials, inactive materials, and solvents like NMP.

solvents

A chemical used to dissolve other materials and substances. Solvents for battery electrode manufacturing, such as N-methyl-2-pyrrolidone (NMP), are used to improve mixing of active ingredients but present potential respiratory and skin hazards.

substrate

The material onto which a coating or other substance is applied. The current collector may be referred to as the substrate, or web, during some electrode manufacturing steps, such as coating.

supply chains

A complex network of companies and organizations that work together to produce and distribute a product. A supply chain consists of a company, its suppliers, its distributors, and its customers.

tabs

A small strip of uncoated current collector foil that enables electrodes to be welded to each other and to other components in the finished battery. Tabs are formed during notching.

tensiometer

An instrument that measures the surface tension of liquids. Tensiometers can be used to determine if an electrode slurry coating is the correct thickness.

thermal conductivity

A material's ability to act as a medium for conveying heat. Thermal conductivity in battery cells can be improved by reducing the porosity of the electrode coating, which reduces the risk of thermal runaway.

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.

ultrasonication

A method of mixing electrode slurries that uses sound waves to agitate particles. Ultrasonication is an expensive alternative to using industrial mixers or blenders.

vacuum

A space with negative air pressure created by removing air with suction. A vacuum can create a seal that keeps contaminants outside and hazardous materials inside.

vacuum drying

A noncontact electrode drying method that reduces humidity in a vacuum-sealed container to evaporate liquids. Vacuum drying can dry electrodes at lower temperatures and makes it easier to recover evaporated solvents for reuse.

viscosity

A liquid or semi-liquid substance's ability to resist flowing. The viscosity of the slurry is one of the most important factors to consider when selecting or setting up a slot-die extruder for electrode coating.

web

The material onto which a coating or other substance is applied. The current collector may be referred to as the web, or substrate, during some electrode manufacturing steps, such as coating.

welded

Having permanently joined two or more materials with heat, pressure, or friction. Welded connections can be made between electrodes and other battery components via tabs.

wetting

The process of saturating an electrode with an electrolyte. Wetting occurs during cell finishing and can be improved by electrode calendering.