Weld­ing of fuel cells

Bipo­lar plates

The heart of the fuel cell

In fuel cell tech­nol­o­gy, the bipo­lar plate plays a key role and can jus­ti­fi­ably be called the heart of the fuel cell. This seem­ing­ly sim­ple, but cru­cial com­po­nent not only links the indi­vid­ual cells, but also orches­trates the har­mo­nious flow of hydro­gen and oxy­gen to gen­er­ate elec­tri­cal ener­gy. In the man­u­fac­tur­ing of the fuel cells, laser weld­ing enables pre­cise small-sized weld seams, which is par­tic­u­lar­ly impor­tant, as fuel cells often have com­plex and fine structures.
Loss of material in the weld seam due to overheating
Loss of mate­r­i­al in the weld seam due to overheating
Increasing gap (from left to right)
Increas­ing gap (from left to right)
Jammed sheet metal due to a positioning error
Jammed sheet met­al due to a posi­tion­ing error
The laser weld­ing of bipo­lar plates holds par­tic­u­lar chal­lenges. Insuf­fi­cient mon­i­tor­ing of the weld­ing process can lead to errors, which can impact on the struc­ture and func­tion­al­i­ty of the fuel cell. This includes for exam­ple incom­plete weld seams, pores or gaps which affect tight­ness of the cell or result in leaks. There­fore, togeth­er with the Fraun­hofer Insti­tute for Laser Tech­nol­o­gy ILT in Aachen, we have ana­lyzed how and to what extent the 4D.watch­er can be used for auto­mat­ic mon­i­tor­ing dur­ing welding. 

Bipo­lar plates

The heart of the fuel cell

In fuel cell tech­nol­o­gy, the bipo­lar plate plays a key role and can jus­ti­fi­ably be called the heart of the fuel cell. This seem­ing­ly sim­ple, but cru­cial com­po­nent not only links the indi­vid­ual cells, but also orches­trates the har­mo­nious flow of hydro­gen and oxy­gen to gen­er­ate elec­tri­cal energy.
 

Over­all, the bipo­lar plate plays a cru­cial role in the per­for­mance and reli­a­bil­i­ty of fuel cells, which are used in dif­fer­ent appli­ca­tions, from vehi­cles up to sta­tion­ary ener­gy systems.

The bipo­lar plate has sev­er­al impor­tant func­tions in the oper­a­tion of a fuel cell:

Elec­tri­cal connection

The bipo­lar plate is respon­si­ble for estab­lish­ing the elec­tri­cal con­nec­tion between the indi­vid­ual cells in a fuel cell. It con­ducts the elec­tri­cal cur­rent from one cell to the next, which gen­er­ates the total current.

Gas con­nec­tion

In a fuel cell, hydro­gen is used as fuel, and oxy­gen is used as oxi­diz­ing agent. The bipo­lar plate enables the con­trolled inflow and out­flow of these gas­es to the elec­trodes, where the actu­al elec­tro­chem­i­cal reac­tions take place.

Cool­ing

Fuel cells gen­er­ate heat dur­ing oper­a­tion. The bipo­lar plate often serves as heat con­duc­tion plate and enables effi­cient con­duc­tion of the gen­er­at­ed heat. This is cru­cial to keep the fuel cell with­in opti­mum oper­at­ing temperatures.

Struc­ture and strength

The bipo­lar plate con­tributes to the struc­tur­al integri­ty of the fuel cell. It sup­ports indi­vid­ual cells and ensures a robust over­all con­struc­tion. Mate­ri­als such as graphite or stain­less steel are often used due to their elec­tric con­duc­tiv­i­ty and cor­ro­sion resis­tance for manufacturing.

Flu­id handling

The plate can have a spe­cial struc­ture, which ensures opti­mum dis­tri­b­u­tion of gas­es and coolant in the fuel cell. An even gas flow is ensured through chan­nels or open­ings, which improves effi­cien­cy of the fuel cell.

Elec­tri­cal connection

The bipo­lar plate is respon­si­ble for estab­lish­ing the elec­tri­cal con­nec­tion between the indi­vid­ual cells in a fuel cell. It con­ducts the elec­tri­cal cur­rent from one cell to the next, which gen­er­ates the total current.

Gas con­nec­tion

In a fuel cell, hydro­gen is used as fuel, and oxy­gen is used as oxi­diz­ing agent. The bipo­lar plate enables the con­trolled inflow and out­flow of these gas­es to the elec­trodes, where the actu­al elec­tro­chem­i­cal reac­tions take place.

Cool­ing

Fuel cells gen­er­ate heat dur­ing oper­a­tion. The bipo­lar plate often serves as heat con­duc­tion plate and enables effi­cient con­duc­tion of the gen­er­at­ed heat. This is cru­cial to keep the fuel cell with­in opti­mum oper­at­ing temperatures.

Struc­ture and strength

The bipo­lar plate con­tributes to the struc­tur­al integri­ty of the fuel cell. It sup­ports indi­vid­ual cells and ensures a robust over­all con­struc­tion. Mate­ri­als such as graphite or stain­less steel are often used due to their elec­tric con­duc­tiv­i­ty and cor­ro­sion resis­tance for manufacturing.

Flu­id handling

The plate can have a spe­cial struc­ture, which ensures opti­mum dis­tri­b­u­tion of gas­es and coolant in the fuel cell. An even gas flow is ensured through chan­nels or open­ings, which improves effi­cien­cy of the fuel cell.

Vari­ants

Graphite and metal­lic bipo­lar plates

Both types of bipo­lar plates play a key role in the opti­miza­tion of per­for­mance and dura­bil­i­ty of fuel cells. The choice of graphite and metal­lic plates depends on dif­fer­ent fac­tors, includ­ing costs, appli­ca­tion require­ments and envi­ron­men­tal con­di­tions. In many cas­es, they are also used in com­bi­na­tion, to use the advan­tages of both materials.

Graphite bipo­lar plates
Metal­lic bipo­lar plates

Graphite bipo­lar plates main­ly con­sist of expand­ed graphite, which is pro­duced through heat treat­ment. These plates pro­vide excel­lent elec­tric con­duc­tiv­i­ty and are cor­ro­sion-resis­tant. The porous struc­ture enables an improved dis­tri­b­u­tion of the reac­tion gas­es, which improves the effi­cien­cy of the fuel cell.

In com­par­i­son, metal­lic bipo­lar plates con­sist of met­al alloys such as stain­less steel or tita­ni­um. These plates offer high mechan­i­cal strength and are thus resis­tant to pres­sure and stress­es. The smooth sur­face facil­i­tates seal­ing and pre­vents gas leaks.

Graphite bipo­lar plates

Graphite bipo­lar plates main­ly con­sist of expand­ed graphite, which is pro­duced through heat treat­ment. These plates pro­vide excel­lent elec­tric con­duc­tiv­i­ty and are cor­ro­sion-resis­tant. The porous struc­ture enables an improved dis­tri­b­u­tion of the reac­tion gas­es, which improves the effi­cien­cy of the fuel cell.

Metal­lic bipo­lar plates

In com­par­i­son, metal­lic bipo­lar plates con­sist of met­al alloys such as stain­less steel or tita­ni­um. These plates offer high mechan­i­cal strength and are thus resis­tant to pres­sure and stress­es. The smooth sur­face facil­i­tates seal­ing and pre­vents gas leaks.

Pre­ci­sion and efficiency

Fuel cell and laser technology

The weld­ing of fuel cells with laser tech­nol­o­gy is an advanced method which is used in the man­u­fac­tur­ing of fuel cells. This tech­nol­o­gy pro­vides accu­rate and effi­cient join­ing options for the dif­fer­ent com­po­nents of a fuel cell.

Dur­ing laser weld­ing, high­ly inten­sive laser radi­a­tion is focused on the mate­r­i­al to be joined. The laser beam melts the mate­r­i­al on the weld seam, and a firm con­nec­tion is formed once cooled. This method enables a very pre­cise intro­duc­tion of heat and min­i­mizes ther­mal strains in adja­cent areas.

Advan­tages

Laser weld­ing for fuel cells

Pre­ci­sion

Laser weld­ing enables pre­cise small-sized weld seams, which is par­tic­u­lar­ly impor­tant, as fuel cells often have com­plex and fine structures.

Heat intro­duc­tion

The tar­get­ed heat intro­duc­tion reduces the risk of defor­ma­tions and ther­mal­ly induced dam­age to sen­si­tive com­po­nents, such as bipo­lar plates.

Speed

The high ener­gy inten­si­ty of the laser beam enables fast weld­ing process­es, which increas­es pro­duc­tion speed.

Ver­sa­til­i­ty

Laser weld­ing can be per­formed with dif­fer­ent mate­ri­als, includ­ing met­als and poly­mers, which enables adap­ta­tion to dif­fer­ent fuel cell constructions.

Automa­tion

Automa­tion of the laser weld­ing process con­tributes to the effi­cien­cy in the mass pro­duc­tion of fuel cells.

Pre­ci­sion
Laser weld­ing enables pre­cise small-sized weld seams, which is par­tic­u­lar­ly impor­tant, as fuel cells often have com­plex and fine structures.
Heat intro­duc­tion
The tar­get­ed heat intro­duc­tion reduces the risk of defor­ma­tions and ther­mal­ly induced dam­age to sen­si­tive com­po­nents, such as bipo­lar plates.
Speed
The high ener­gy inten­si­ty of the laser beam enables fast weld­ing process­es, which increas­es pro­duc­tion speed.
Ver­sa­til­i­ty
Laser weld­ing can be per­formed with dif­fer­ent mate­ri­als, includ­ing met­als and poly­mers, which enables adap­ta­tion to dif­fer­ent fuel cell constructions.
Automa­tion
Automa­tion of the laser weld­ing process con­tributes to the effi­cien­cy in the mass pro­duc­tion of fuel cells.

Chal­lenges

Bal­anc­ing of sev­er­al influences

  • Fast process with high vol­umes: non-detect­ed process devi­a­tions and a high rate of pseu­do errors
  • Mate­r­i­al com­plex­i­ty: Fuel cells con­sist of dif­fer­ent lay­ers of mate­ri­als, which each have spe­cif­ic prop­er­ties; the laser beam must be opti­mal­ly adapt­ed to this range in order to gen­er­ate an effi­cient weld seam with­out dam­ag­ing the sen­si­tive components.
  • Fluc­tu­at­ing mate­r­i­al: Fluc­tu­a­tions in thick­ness, alloys and coat­ings make trou­bleshoot­ing more difficult
  • Ther­mal influ­ence: Laser weld­ing gen­er­ates heat, and the fuel cells often con­tain tem­per­a­ture-sen­si­tive parts; pre­cise con­trol of the ther­mal effect is cru­cial to avoid unwant­ed effects, such as defor­ma­tions or degra­da­tion of the materials
  • Size of the fuel cells: a pre­cise focus of the laser beam onto small, com­plex com­po­nents requires advanced opti­cal sys­tems and high­ly devel­oped weld­ing techniques
  • Automa­tion: the inte­gra­tion of robot­ics and advanced con­trol sys­tems is nec­es­sary to max­i­mize the effi­cien­cy and accu­ra­cy of the weld­ing process

Pre­ci­sion. Effi­cien­cy. Quality.

Process mon­i­tor­ing dur­ing the weld­ing of bipo­lar plates

Dur­ing the laser cut­ting process, advanced mon­i­tor­ing sys­tems are used to ensure that the exact con­tours and struc­tures are achieved in accor­dance with the design spec­i­fi­ca­tions. Cam­eras and sen­sors con­tin­u­ous­ly mon­i­tor the laser beam and posi­tion­ing of the bipo­lar plates, to detect any devi­a­tions in real time.

Our solu­tion

Thanks to Loss­less Tech­nol­o­gy, the high speeds of > 1 m/s can be mon­i­tored reli­ably and seamlessly.

Mehr über den 4D.watcher erfahren

4D.watch­er

Mehr über die Antwort auf (fast) alles erfahren

4D.TWO

Con­tact us!

If you would like to learn more about our prod­ucts and ser­vices, or would like to request a cus­tomized offer, please do not hes­i­tate to con­tact us. You can con­tact us by phone, via email or by using our con­tact form. We look for­ward to receiv­ing your enquiry!

Con­tact
Sched­ule con­sul­ta­tion appointment

Con­tact us!

If you would like to learn more about our prod­ucts and ser­vices, or would like to request a cus­tomized offer, please do not hes­i­tate to con­tact us. You can con­tact us by phone, via email or by using our con­tact form. We look for­ward to receiv­ing your enquiry!

Con­tact
Sched­ule con­sul­ta­tion appointment
Scroll to Top