© VON ARDENNE Corporate Archive

Poly­Safe: Mak­ing lithi­um-ion bat­ter­ies safer

The aim of Poly­Safe is to increase the spe­cif­ic ener­gy and safe­ty of lithi­um-ion bat­ter­ies by using nov­el cur­rent col­lec­tors. The focus here is on met­al-poly­mer com­pos­ite cur­rent col­lec­tors, which make the ther­mal run­away of bat­tery cells much more dif­fi­cult and thus reduce the risk of fire. In addi­tion to the Bat­tery Lab­Fac­to­ry Braun­schweig of the Tech­ni­cal Uni­ver­si­ty of Braun­schweig, part­ners from research and indus­try are involved in the project, which is fund­ed with almost four mil­lion euros.

In addi­tion to the weight advan­tage over pure met­al cur­rent col­lec­tors used today, the met­al-poly­mer cur­rent col­lec­tors allow the cir­cuit to be inter­rupt­ed when a crit­i­cal tem­per­a­ture is reached. When this tem­per­a­ture is reached, the cur­rent col­lec­tor melts, inter­rupt­ing the cur­rent flow and thus the short cir­cuit. Cur­rent col­lec­tors are thin met­al foils that con­duct elec­tric­i­ty well. The active mate­r­i­al respon­si­ble for ener­gy stor­age in bat­ter­ies is applied to them.

The fea­si­bil­i­ty of man­u­fac­tur­ing the met­al-poly­mer elec­tric­i­ty col­lec­tors has already been demon­strat­ed joint­ly by VON ARDENNE GmbH and Fraun­hofer FEP as part of the Sax­on research project Poly­Col­lect. The phys­i­cal vapor depo­si­tion process was able to pro­duce alu­minum lay­ers up to 1 micron thick on poly­mer sub­strates with thick­ness­es up to 8 microns. How­ev­er, there are too few data from pro­to­type cells with this mate­r­i­al so far, which is why the appli­ca­tion-ori­ent­ed eval­u­a­tion of this tech­nol­o­gy is still pend­ing. This is now to be done with­in the frame­work of Poly­Safe. The aim of the research project is to qual­i­fy a process chain adapt­ed to the met­al-poly­mer cur­rent col­lec­tors for the pro­duc­tion of bat­tery cells in dif­fer­ent for­mats (round cell, pouch cell) and to inves­ti­gate the safe­ty advan­tage in dif­fer­ent cell designs and chemistries in an appli­ca­tion-ori­ent­ed manner.

In addi­tion to the inte­gra­tion of the man­u­fac­tured met­al-poly­mer cur­rent col­lec­tors in bat­tery cells, the project part­ners want to adapt and opti­mise alu­mini­um or cop­per-poly­mer cur­rent col­lec­tors in a ded­i­cat­ed man­ner to the require­ments of the respec­tive cell design. The chal­lenge is to design the poly­mer sub­strates and the coat­ing process in such a way that a thick­ness com­pa­ra­ble to cur­rent met­al foils as well as an opti­mal elec­tri­cal con­duc­tiv­i­ty of the met­al lay­er is guar­an­teed. At the same time, the pro­duc­tion costs of elec­tric­i­ty col­lec­tors are to be brought to a com­pet­i­tive level.

The Bat­tery Lab­Fac­to­ry Braun­schweig (BLB) of the TU Braun­schweig con­tributes its exper­tise in the pro­duc­tion process and char­ac­ter­i­za­tion of elec­trodes and pouch cells for lithi­um-ion bat­ter­ies. The met­al-poly­mer cur­rent col­lec­tors will be inves­ti­gat­ed with regard to their suit­abil­i­ty for inte­gra­tion into the pro­duc­tion process­es of lithi­um-ion bat­ter­ies and — if nec­es­sary — the pro­duc­tion process­es will be specif­i­cal­ly adapted.

About the Bat­tery Lab­Fac­to­ry Braun­schweig (BLB)
As a trans­dis­ci­pli­nary cen­tre, the BLB of the TU Braun­schweig net­works 14 insti­tutes for the holis­tic research and devel­op­ment of bat­tery elec­tric stor­age tech­nolo­gies and cov­ers the entire val­ue-added cycle from mate­r­i­al pro­duc­tion to cell man­u­fac­tur­ing to recy­cling to close the mate­r­i­al cycle. In a “Joint Pilot Facil­i­ty”, elec­trode and cell pro­duc­tion as well as cell con­di­tion­ing will be mapped in tech­ni­cal, auto­mat­ed process­es on a pilot to pilot scale (bat­tery tech­nol­o­gy plat­form 1000 square meters, includ­ing 200 square meters of dry­ing room, plus 700 square meters of tech­ni­cal rooms for ana­lyt­ics and post-mortem analy­sis), so that defined cells can be pro­duced on a large scale for bat­tery demonstrators.

Specif­i­cal­ly brought into the project i) the process and prod­uct com­pe­tence in elec­trode pro­duc­tion estab­lished since 2007, (ii) com­pe­tence in man­u­fac­tur­ing, join­ing and han­dling tech­nol­o­gy in the field of cell assem­bly, pack­ag­ing, con­tact­ing (iii) method­olog­i­cal com­pe­tence for ener­gy-ori­ent­ed mod­el­ling and life cycle assess­ment; and (iv) elab­o­rate pro­ce­dures for for­ma­tion and cycling for cell con­di­tion­ing and diag­nos­tic methods.

Respon­si­bil­i­ties of the partners
VON ARDENNE GmbH is respon­si­ble for the coor­di­na­tion of the Poly­Safe research project. In addi­tion, based on the results of the tech­no­log­i­cal devel­op­ment at Fraun­hofer FEP, the Dres­den-based com­pa­ny will con­tribute its know-how to the tech­ni­cal design of a pro­duc­tion plant for the depo­si­tion of the met­al lay­ers, which meets both the tech­no­log­i­cal and the eco­nom­ic require­ments for the pro­duc­tion of met­al-poly­mer elec­tric­i­ty collectors.

Brück­n­er Maschi­nen­bau GmbH & Co.KG is work­ing on the devel­op­ment of poly­mer films which are adapt­ed to the require­ments of met­al­liza­tion as well as to the appli­ca­tion in bat­ter­ies. The aim is to devel­op inno­v­a­tive poly­mer sub­strates and sur­face treat­ments and scale them up to roll scale. The most promis­ing mate­ri­als will be made avail­able as sub­strates for metallization.

The sci­en­tists at Fraun­hofer FEP are devel­op­ing a suit­able tech­no­log­i­cal process con­trol for the depo­si­tion of the alu­minum and cop­per lay­ers in a roll-to-roll process. The aim is to under­stand the influ­ence of para­me­ters of the strip run, the sub­strate pre-treat­ment as well as the met­al evap­o­ra­tion in a holis­tic way and to devel­op opti­mal process set­tings to achieve the tech­no­log­i­cal and eco­nom­ic requirements.

The Fraun­hofer IST is research­ing the suit­abil­i­ty of met­al-poly­mer cur­rent col­lec­tors for nov­el bat­tery cell gen­er­a­tions, with a par­tic­u­lar focus on lithi­um-met­al anodes. Spe­cial empha­sis will be placed on the man­u­fac­tur­ing steps of the lithi­um met­al anodes and the result­ing cells.

VARTA Micro­bat­tery takes care of the inte­gra­tion of the new elec­trodes with met­al-poly­mer cur­rent col­lec­tors in full cells and the stan­dard-com­pli­ant safe­ty test­ing. In par­tic­u­lar, the pro­cess­ing and safe­ty of round cells with met­al-poly­mer cur­rent col­lec­tors will be inves­ti­gat­ed and com­pared with pure met­al foils.

Project Data:
Poly­Safe is a research project to increase the safe­ty of lithi­um-ion bat­ter­ies by means of met­al-poly­mer com­pos­ite cur­rent col­lec­tors and is fund­ed by the Fed­er­al Min­istry of Edu­ca­tion and Research (BMBF) with around four mil­lion euros (fund­ing code 03XP0408E). The project start­ed in August 2021 and will run for three years. In addi­tion to the TU Braun­schweig, the fol­low­ing com­pa­nies are involved: VON ARDENNE GmbH (coor­di­na­tion), Brück­n­er Maschi­nen­bau GmbH & Co. KG, Fraun­hofer Insti­tute for Organ­ic Elec­tron­ics, Elec­tron Beam and Plas­ma Tech­nol­o­gy FEP, Fraun­hofer Insti­tute for Sur­face Engi­neer­ing and Thin Films IST and Var­ta Micro­bat­tery GmbH.