© ZSW

ZSW recy­cles raw mate­ri­als from lithi­um ion batteries

Wide­spread recy­cling of lithi­um-ion bat­ter­ies, espe­cial­ly from elec­tric cars, will sus­tain­ably ensure the sup­ply of crit­i­cal raw mate­ri­als in the future. Today’s recy­cling process­es recov­er only some met­als, lithi­um is par­tial­ly lost, graphite even com­plete­ly. A new process could now change this: In the Recy­cleMat project, the Cen­ter for Solar Ener­gy and Hydro­gen Research Baden- Würt­tem­berg (ZSW) has devel­oped a recy­cling process by which active mate­ri­als from used lithi­um-ion bat­ter­ies can be reprocessed and used direct­ly in new bat­ter­ies. This is done in rel­a­tive­ly sim­ple chem­i­cal process­es. Mate­r­i­al pow­ders reac­ti­vat­ed with the new process reach 95 per­cent of their ini­tial capac­i­ty. This is true both for the met­al oxides in the pos­i­tive pole of the bat­ter­ies and, sur­pris­ing­ly, for the graphite of the neg­a­tive pole. The researchers have already pro­duced new bat­tery cells from such recy­cled mate­r­i­al and mea­sured them electrochemically.

In the devel­op­ment project “Cath­ode and anode mate­ri­als from recy­cled lithi­um-ion bat­ter­ies (Recy­cleMat)”, which has been fund­ed by the Baden-Würt­tem­berg Min­istry of Eco­nom­ics, Labor and Tourism with 870,000 euros since August 2020, ZSW has devel­oped a resource-sav­ing process to mechan­i­cal­ly sep­a­rate the active mate­ri­als from the cath­ode, the pos­i­tive pole of the bat­tery, and the anode, the neg­a­tive pole, from used or defec­tive bat­tery elec­trodes, clean them and process them into as-new pow­ders via heat treatment.

“The new recy­cling process makes it pos­si­ble to reac­ti­vate dis­card­ed bat­tery elec­trodes with a cath­ode struc­ture made of the lithi­um-nick­el-man­ganese-cobalt oxides com­mon­ly used today and an anode made of graphite, and then use them direct­ly in new cells,” explains Dr. Mar­ile­na Manci­ni, sci­en­tif­ic direc­tor of the project. “Unlike con­ven­tion­al process­es, the new process pre­serves the active mate­ri­als as such and reuses them direct­ly in new bat­ter­ies after restor­ing their orig­i­nal func­tion­al­i­ty. This approach avoids the cur­rent­ly com­mon and ener­gy-inten­sive dis­so­lu­tion and recov­ery of the metal­lic com­po­nents with simul­ta­ne­ous loss of the graphite.”

“Recy­cling bat­ter­ies is not only desir­able, but absolute­ly nec­es­sary. The tran­si­tion to a cli­mate-neu­tral econ­o­my requires a com­pre­hen­sive expan­sion of the cir­cu­lar econ­o­my — espe­cial­ly for bat­ter­ies, which con­tain var­i­ous crit­i­cal raw mate­ri­als. With high-qual­i­ty recy­cling, how­ev­er, we not only help the envi­ron­ment, but also reduce our depen­dence on raw mate­r­i­al imports in the long term. In view of the cur­rent chal­lenges posed by dis­rupt­ed sup­ply chains, we are thus increas­ing the resilience and com­pet­i­tive­ness of Baden-Würt­tem­berg as a busi­ness loca­tion. The research results of the ZSW make an impor­tant con­tri­bu­tion to achiev­ing these ambi­tious goals and show how recy­cling is fea­si­ble in an effi­cient and resource-sav­ing way,” says Eco­nom­ics Min­is­ter Dr. Nicole Hoffmeister-Kraut.

Recy­cling of cath­ode and anode masses

As part of the project, new approach­es and process­es had to be devel­oped in par­tic­u­lar for recy­cling the graphite from the neg­a­tive ter­mi­nal of the bat­tery, since graphite is not typ­i­cal­ly recy­cled today but is usu­al­ly sim­ply incin­er­at­ed. The solu­tion to the prob­lem was a com­plex tem­per­a­ture treat­ment that both frees the sur­face of the par­ti­cles from impu­ri­ties and restores the crys­talline mate­r­i­al struc­ture. The graphite pow­der treat­ed in this way has 95 per­cent of the spe­cif­ic ener­gy con­tent of the orig­i­nal mate­r­i­al and can be used direct­ly in new batteries.

The mate­ri­als with the high­est val­ue con­tent in the bat­tery are the cath­ode mass­es in the pos­i­tive pole of the bat­tery, as they con­tain expen­sive met­als such as nick­el, man­ganese, cobalt (NMC) and lithi­um, among oth­ers. Cur­rent recy­cling process­es there­fore focus on these cath­ode mate­ri­als by dis­solv­ing them com­plete­ly in acid dur­ing the process and then con­vert­ing them back into bat­tery raw mate­ri­als step by step. How­ev­er, these recy­cling process­es con­sume a lot of ener­gy and ide­al­ly require prox­im­i­ty to a chem­i­cal site.

The ZSW process for recy­cling cath­ode mate­ri­als is essen­tial­ly the same as for graphite and thus avoids pre­cise­ly these ener­gy-inten­sive chem­i­cal steps. After only two rel­a­tive­ly sim­ple process steps, the cath­ode mate­ri­als can be direct­ly reused in new bat­ter­ies and also show sig­nif­i­cant­ly more than 90% of their orig­i­nal capacity.

Recov­er­ing met­als pays off

Over the past decade, sci­en­tif­ic and indus­tri­al devel­op­ment of lithi­um-ion bat­ter­ies has focused on increas­ing ener­gy den­si­ty while reduc­ing costs. With the increas­ing suc­cess of elec­tro­mo­bil­i­ty and the mass pro­duc­tion of bat­ter­ies, the end-of-life dis­cus­sion — recy­cling — is now also com­ing to the fore. On the one hand, this dis­cus­sion is dri­ven by legal frame­work con­di­tions that, depend­ing on the respec­tive region or coun­try, require a recy­cling rate of up to 80 per­cent for the scrap­ping of elec­tric cars. On the oth­er hand, there are cal­cu­la­tions accord­ing to which large quan­ti­ties of recy­cled met­als will be nec­es­sary in order to be able to build suf­fi­cient bat­ter­ies for elec­tric vehi­cles at all in the future.

Although lithi­um-ion bat­ter­ies do not con­tain pre­cious met­als, the mate­ri­als used are far too valu­able not to be recy­cled: It is the large quan­ti­ties of met­als such as cop­per, nick­el, cobalt, alu­minum and the lithi­um that already make bat­tery recy­cling eco­nom­i­cal and lucra­tive due to their met­al val­ues: For exam­ple, one ton of nick­el-bear­ing rock from a nick­el mine con­tains only about 20 kilo­grams of nickel.

How­ev­er, a bat­tery of the type need­ed for a mid-size car already con­tains 60 kilo­grams of nick­el. With a bat­tery weight of 500 kilo­grams, this cor­re­sponds to a five­fold enrich­ment of this met­al com­pared to the mine. In the case of lithi­um, this fac­tor is much high­er: six kilo­grams of lithi­um in a bat­tery save the pro­cess­ing of sev­er­al thou­sand cubic meters of lithi­um-con­tain­ing salt solu­tion when suc­cess­ful­ly recycled.