Recycling lithium-ion batteries containing LiNixCoyMnzO2 cathode materials

Proizvodnja i potrošnja litijum-jonskih baterija iz godine u godinu raste, pa samim tim i potreba za njihovom reciklažom. Predmet istraživanja ove doktorske disertacije je bio da se utvrdi koji deo baterije se može reciklirati kao i mogućnost resinteze istrošenog katodnog materijala i njegova ponovna primena. Utvđeno je da 62% baterije čine košuljica, Al, Cu kolektori i katodni materijal. U cilju što efikasnijeg odvajanja katodnog materijala LiNixCoyMnzO2 od Al kolektora, ispitivana su tri načina odvajanja posle manualnog rastavljanja baterije: žarenjem na 700 oC, rastvaranjem organskog veziva u N-metil pirolidonu i alkalnim rastvaranjem u NaOH. Najveći prinos je postignut alkalnim rastvaranjem, pa je nakon odvajanja katodnog materijala procesom alkalnog rastvaranja i prevođenja u stanje rastvora nitratne kiseline, katodni materijal resintetisan različitim postupcima sinteze. Ispitivana su tri različita postupka resinteze katodnog materijala: sol-gel postupak, metod kopecipitacije i reakcija u čvrstom stanju. Sastav resintetisanih prahova određen je atomskom apsorpcionom spektrometrijom dok su strukturne i morfološke osobine dobijenih prahova karakterisane rendgesnkom difrakcijom na prahu, ramanskom spektroskopijom i skenirajućom i transmisionom elektronskom mikroskopijom. Elektrohemijsko ponašanje materijala u vodenim i organskim elektrolitičkim rastvorima ispitano je cikličnom voltametrijom i galvanostatskom metodom. Pošto komercijalne litijum jonske baterije sadrže zapaljiv i toksičan elektrolit, sve je više istraživanja usmereno ka ispitivanju litijum jonskih baterija sa vodenim elektrolitom. Sa aspekta životne sredine, ali i ekonomskog, mogućnost korišćenja resintetisanog katodnom materijala u litijum jonskim, ali i u natrijum jonskim baterijma sa vodenim elektrolitom bi bila značajna. Svi resintetisani materijali su pokazali elektrohemijsku aktivnost u vodenim rastvorima soli LiNO3 i NaNO3. Najveći početni kapacitet od oko 64 mAhg-1 (meren potenciodinamički na vrlo visokim brzinama polarizacije od 20 mVs-1 ili ~ 40 C), kao i najmanji pad kapaciteta tokom cikliranja, u vodenom rastvoru LiNO3 je dobijen u slučaju LiNi0,15Mn0,435Co0,415O2 (re-NMC244kop) koji je resintetisan metodom ko-precipitacije pri kontrolisanim uslovima pH. Po prvi put je ispitana sposobnost reverzibilne interkalacije jona natrijuma iz vodenog rastvora u natrijumsku formu materijala NaNixCoyMnzO2. Kapaciteti skladištenja natrijumovih jona su znatno manji od odgovarajućih kapaciteta skladištenja litijuma, ali je zato dobijena znatno bolja stabilnost interkalatnog kapaciteta natrijuma. Materijal resintetisan metodom ko-precipitacije pri kontrolisanim uslovima pH pokazao je znatno manji početni interkalatni kapacitet natrijuma u vodenom elektrolitu (oko 30 mAh g-1pri brzini polarizacije od 20 mV s-1 ) od odgovarajućeg interkalatnog kapaciteta litijuma, ali i znatno bolju stabilnost kapaciteta tokom višestrukog cikliranja tačnije tokom 50 ciklusa punjenja/pražnjenja praktično nije zapažen pad kapaciteta. Galvanostatskom metodom je pokazano da re-NaNMC244kop materijal može da skladišti i veće količine natrijuma (~93 mAhg-1), ali pri manjim gustinama struje od 0,8 C mA g-1 (1C=120 mAg-1). Imajući u vidu da su kapaciteti vrlo bliski teorijskom kapacitetu NaCo1/3Mn1/3Ni1/3O2 koji iznosi 120 mAhg-1, a da je kapacitet stabilan tokom višestrukog punjenja i pražnjenja, resintetisani materijal ima potencijala da se koristi kao katodni materijal u vodenim natrijum-jonskim baterijama...The production, usage, and disposal of spent Li-ion batteries has been on the rise over the last decade; thus, the need for their proper and efficient recycling has also grown in necessity. The research subject of this doctoral dissertation has therefore been to better define which distinct battery parts may be recycled, as well as to investigate the feasibility of resynthesizing spent cathode material and its functionalization. Therein, it has been found that 62% of a battery is composed of its crust, Al, Cu current collectors, and cathode material. In terms of an efficient LiNixCoyMnzO2 cathode material separation from the Al current collector, three distinct methods of its separation have been here examined after having manually dismantled the batteries’ components: 1. the dissolution of the Al collector in an alkali medium; 2. peeling with N-methylpyrrolidone; and 3. thermal decomposition of the adhesive at 600oC. The highest yield was achieved by the alkali melting method, therefore this method was used for obtaining the cathode material. After its dissolution in nitric acid, the cathode material was resynthesized using different methods. Three re-synthesis methods of the cathode material were carried out: 1. the sol-gel method, 2. the co-precipitation method, and 3. solid state reaction. The chemical content of the resynthesized materials was determined by atomic absorption spectrometry. The structure and morphological properties of the materials were then examined by XRD, Raman spectrometry, scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of the materials in aqueous and organic electrolytic solutions was examined by cyclic voltametry and the galvanostatic method. Since commercial Li-ion batteries contain flammable and toxic electrolytes, the research has been focused on Li-ion batteries containing aqueous electrolytes. In terms of better protecting the environment and from an economic aspect, the potential of using the resynthesized cathode material in Li-ion batteries and in Na-ion batteries containing aqueous electrolyte is crucial. All resynthesized materials showed electrochemical activity in aqueous solutions of LiNO3 and NaNO3 salts. The highest initial capacity of approximately 64 mAhg-1(measured potentiodinamically at a high polarization speed of 20 mVs-1 or 40C) and the lowest capacity fade during cycling in a LiNO3 aqueous solution was obtained for LiNi0,15Mn0,435Co0,415O2 (re-NMC244kop) which was resynthesized by the co-precipitation method under controlled pH conditions. The capability of the reversible intercalation of Na ions in the sodium material of NaNixCoyMnzO2 has also here been researched for the first time. It has been found that while sodium storage capacities are considerably lower than corresponding lithium storage capacities, a better intercalate sodium capacity stability is obtainable. The material resynthesized by the co-precipitation method under controlled pH conditions showed a noticeably smaller initial sodium intercalate capacity in the aqueous solution electrolyte (approximately 30 mAhg-1 at a polarization velocity 20 mVs-1) than the corresponding intercalate lithium capacity, but did show a better capacity stability during multiple cycling. In practical terms, it is not a pronounced capacity fade of the sodium from the layered oxide over 50 charging/discharging cycles. As per the galvanostatic method, it was shown that re-NaNMC244kop material is able to store higher amounts of sodium (~93 mAg-1) at a lower current density of 0.8 C mAg-1 (1C=120 mAg-1). Taking into account that the capacities are close to the NaCo1/3Mn1/3Ni1/3O2 theoretical capacity which amounts 0.8 C mA g-1 (1C = 120 mAhg-1), as well as that the capacity is stable over multiply charging and discharging, the resynthesized material has the potential to be used as a cathode material in aqueous sodium-ion batteries..