DOI: 10.1002/cssc.201402440

Environmentally-Friendly Lithium Recycling From a SpentOrganic Li-Ion BatterySt�ven Renault,* Daniel Brandell, and Kristina Edstrçm[a]

Introduction

The need for chemical energy storage devices has been con-stantly increasing in recent years. Especially lithium-ion batter-ies (LIBs) are successfully used for portable or nomadic elec-tronic devices such as laptops, cameras, cellular phones orelectric vehicles (EVs) due to their design flexibility, high volt-age output, high energy density, high specific energy, and longcycle life. Their standard electrode materials are, however,mostly made of inorganic lithium transition-metal oxides orphosphates (e.g. , LiFePO4, LiMn2O4, LiCoO2, Li4Ti5O12). Suchcompounds are prepared from ores, which are non-renewableand finite minerals resources. Moreover, their preparation andextraction require stringent conditions with high energy con-sumption and heavy anthropogenic greenhouse gas (GHG)emissions, which gives LIBs a poor environmental performancein a life-cycle perspective.[1]

In this context, organic electrodes have been proposed asa solution to reduce the environmental impact of LIBs andfavor their recyclability.[1–3] It is expected that a beneficial effecton the environmental footprint of secondary batteries will beobtained primarily if these organic materials are derived frombiomass using green chemistry principles (ecofriendly process-es, minimal energy consumption). Fewer advantages are antici-pated for organic compounds derived from petroleum (a finiteresource). Biomass-derived organic materials would help tocomplete the requirements of the European directive 2006/66/EC which recommend that 50 % or more of the averageweight of a battery should be recycled in the EU.[4]

Using organic electrode materials is not a new concept forLIBs; one example was reported as far back as the late 1960sfor a primary battery application.[5] However, their limited per-formances (at that time) compared to inorganic electrodes ma-terials have restricted their popularity until they recently ree-merged. Noticeable improvements have been reported latelythanks to the general flexibility of organic chemistry synthesis,and organic materials functioning at both higher[6] and lowerpotentials[7] have been described. Interestingly, these com-pounds might have properties with little or no equivalence ininorganic materials, such as the sacrificial self-recharge for lim-ited time in the presence of oxygen observed for dilithium(2,5-dilithium-oxy)-terephthalate Li4C8H2O6.[8] This material hasalso been used in a symmetrical all-organic full cell with anaverage operation voltage of 1.8 V,[9] thereby improving thepreviously reported 1 V performance for Li4C6O6.[10]

Organic electrode materials for LIBs can be classified intofive different categories based on their elementary reversibleredox functions: conducting polymers, organodisulfides, thio-ethers, nitroxyl radical polymers, and conjugated carbonylcompounds.[11, 12] Considering the abundance of carbonylatedmolecules in nature, specific attention has been made to linkconjugated carbonyl compounds to biomass.[3, 8, 13] This class ofmaterials can be subdivided in categories such as qui-nones,[8, 10, 14–18] imidates,[17, 19–22] anhydrides,[23, 24] or lithium car-boxylates,[7, 9, 25–30] the latter being the most appropriate fornegative electrode materials due to the relatively low averagepotential.

We have previously reported preliminary results on dilithiumtrans–trans benzenediacrylate (BDALi2), an organic material forlithium-ion batteries.[28, 29] With an average potential of 1.2 Vand practical capacity of ca. 200 mA h g�1, it cannot match theperformance of the standard graphite LIB anode material, butcould be considered as a possible alternative for anodes devel-oped for improved safety, such as Li4Ti5O12, if improvements

A simple and straightforward method using non-polluting sol-vents and a single thermal treatment step at moderate tem-perature was investigated as an environmentally-friendly pro-cess to recycle lithium from organic electrode materials for sec-ondary lithium batteries. This method, highly dependent onthe choice of electrolyte, gives up to 99 % of sustained capaci-ty for the recycled materials used in a second life-cycle batterywhen compared with the original. The best results were ob-

tained using a dimethyl carbonate/lithium bis(trifluoromethanesulfonyl) imide electrolyte that does not decompose in pres-ence of water. The process implies a thermal decompositionstep at a moderate temperature of the extracted organic mate-rial into lithium carbonate, which is then used as a lithiationagent for the preparation of fresh electrode material withoutloss of lithium.

[a] Dr. S. Renault, Dr. D. Brandell, Prof. K. EdstrçmDepartment of Chemistry—�ngstrçm LaboratoryUppsala UniversityBox 538, 751 21 Uppsala (Sweden)E-mail : steven.renault@kemi.uu.se

Supporting Information for this article is available on the WWW underhttp://dx.doi.org/10.1002/cssc.201402440.

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are made to decrease the conductive additive content and in-crease the long-term cyclability.

Moreover, BDALi2 can be produced from natural compounds.For instance, dilithium trans-trans benzenediacrylate 1 couldbe synthesized through a Doebner modification of the Knoeve-nagel condensation from malonic acid 2 and terephthalalde-hyde 3 (Scheme 1).[31] Malonic acid 2 is a natural but toxic com-pound that can be found in fermented fruits or fruit vine-gars,[32] but it is especially abundant in alfalfa,[33] one of themost cultivated forage legumes in the world. Terephthalalde-hyde 3 can be prepared through a reduction reaction from ter-ephthalic acid,[34] an important monomer for thermoplasticpolymers. Many strategies for a lower environmental impactsynthesis of terephthalic acid have recently been considered.[35]

For instance, terephthalic acid can be produced from naturalterpenes such as limonene,[36] a or b-pinene[37, 38] via a para-cymene intermediate.

Our preliminary work on this material took advantage of itsability to be solubilized in an aqueous medium, enablingcarbon-coating in the liquid state and/or freeze-drying prepa-ration.[28, 29] Its electrochemical performances were then clearlyimproved while its insolubility in common organic electrolytesensured good cyclability. However, it is our belief than manyother properties of this class of material could be improved bytaking advantage of this solubil-ity. We have therefore decidedto extend the possibilities of-fered by the combination of sol-ubility in water and insolubilityin organic solvents not only toelectrode formulation (upstreambattery usage) but also to ex-traction from a spent batteryand recycling of the organicelectrode materials (down-stream battery usage). Solubili-zation of dilithium benzenedia-crylate in an aqueous solutionwould, in theory, allow a separa-tion from insoluble materials ina spent battery (such as theconductive additives) usinga simple filtration step. Further-more, insolubility in organic sol-vents like ethanol would allowseparation of the active materialfrom electrolyte residues (sol-

vent and lithium salt) with a regular washing step. This repre-sents a significant improvement in the overall environmentalsustainability for an electrode material recycling process ascompared to those currently used for standard inorganic elec-trode materials, usually involving leaching with strong acids,(HCl, HNO3, H2SO4) and solvent extraction using phosphonateextractants such as Cyanex 272, PC-88A, P-507 or D2EHPA.[39–45]

Considering that both synthesis and electrode formulationfor this material only require water and ethanol, it is possibleto conceive an idealized environmentally-friendly lithium recy-cling process with minimal energy consumption and wasteproduced (Figure 1). With the exception of the battery utiliza-tion, which generally requires carbonate-based organic electro-lytes, all other steps could thus be performed using water andethanol only, two of the most non-polluting existing solvents.

In this current study, we aim to—for the first time—explorethe performance of recycled materials from a spent organicLIB, using dilithium benzenediacrylate as a model compound.By using extraction in environmentally benign and non-toxicsolvents in combination with combustion at moderate temper-atures, directions for an eco-friendly recycling process aremapped out, thereby closing the loop for a “sustainable” sec-ondary battery produced from biomaterials.

Scheme 1. Possible “all-natural” retrosynthetic pathway for dilithium trans-trans benzenediacrylate 1.

Figure 1. Idealized lithium recycling process of spent batteries made of organic electrode materials obtained fromrenewables.

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Results and Discussion

First life-cycle battery tests

Considering that a secondary battery is a chemically complexsystem, in which cycling adds further complexity, galvanosaticcycling with powder in Swagelok cells was chosen so as not tocontaminate the electrodes. This system allows for measure-ments without the use of the binders conventionally used ina composite electrode, and therefore limits its possible interfer-ence and decomposition in the procedure. Further develop-ments could be considered in the future, however, for examplewith the addition of water-soluble binders such as carboxy-methyl cellulose (CMC), in order to utilize similar recyclingstrategies also for different cell types.

A series of 14 different electrolytes were selected for thisstudy for comparison of the solvent and/or lithium salt effect;see Table 1. It is well-known that organic electrode materialsare especially sensitive to the electrolyte formulation. All elec-trolytes were tested in three batteries each in order to obtainenough material for the different analyses. A rather high load-ing of 30 mg of dilithium benzenediacrylate was used in thebatteries (i.e. , 45 mg of the mixture BDALi2/carbon SP 2/1 weight ratio) in order to achieve enough material during theextraction process. This resulted in a somewhat higher resist-ance in the cells, and a slightly extended cut-off voltage wasconsequently used to maintain similar capacities as in previouswork (i.e. , 0.8–2 V instead of 0.9–2 V).[28] All batteries werecycled in similar conditions at a rate of one lithium exchangedin 1 h (corresponding to C/2 for the dilithiated compound) for20 cycles, which can be considered a high rate for organicelectrode materials. The risk of side reactions and active mate-rial decomposition is usually higher when cycling is performedusing high currents, and this procedure should therefore gen-erate similar products as during long-term usage; thus, it canbe ascertained whether a significant quantity of material is lostin the process.

After the first series of galvanostatic cycling, 5 electrolyteswere considered to give batteries having too poor a capacityto be of general interest: 0.8 m lithium 2-trifluoromethyl-4,5-di-cyanoimidazole (LiTDI) in dimethyl carbonate (DMC), 1 m LiBF4

in DMC, 1 m lithium bis(trifluoromethane sulfonyl) imide(LiTFSI) in diethyl carbonate (DEC), 1 m LiTFSI in tetraethyleneglycol dimethyl ether (TEGDME), and 1 m LiTDI in propylenecarbonate (PC). However, these samples were kept for analysisof the possible recovery of high quality BDALi2 during thismodus operandi recycling, irrespective of electrochemical per-formance. The performances of the 9 batteries using otherelectrolytes are depicted in Figure 2. As can be seen, the bestresults were obtained from 1 m LiFSI in DMC, 1 m LiPF6 in DMCand 1 m LiTFSI in DMC electrolytes, while the poorest result isobtained from 1 m LiClO4 in DMC.

Extraction of BDALi2 from a spent battery

The strategy outlined here for an environmentally-friendly re-cycling of BDALi2 relies on 3 categories of solubilization prop-erties for the different compounds involved:

· Hydrophobic and non-water-soluble materials.

· Neutral hydrophilic or mono-ionic water-soluble materialssoluble in polar organic sol-vents.

· Polyanionic water-solublematerials insoluble in organicsolvents.

These different categories caneasily be separated from eachother with solubilization/filtra-tion/washing steps using onlywater and ethanol. It can be as-sumed that, in the chemistry ofbattery currently investigated,BDALi2 is the major compound

Table 1. Comparison of battery performances and quality of recycled dilithium trans-trans benzenediacrylatefrom spent batteries with different electrolytes. ND = not determined.

Electrolyte Battery 1 Extraction/Purification Battery 2 Sustained capacity [%][a]

DMC, 1 M LiTFSI + + + + + + + + 97DMC, 0.8 M LiTDI � + + + ND NDDMC, 1 M LiFSI + + + + � 9DMC, 1 M LiClO4 + + + + + 99DMC, 1 M LiPF6 + + + � � 14DMC, 1 M LiBF4 � ND ND NDDEC, 1 M LiTFSI � ND ND NDTEGDME, 1 M LiTFSI � ND ND NDPC, 1 M LiTFSi + + + � 19PC, 1 M LiTDI � ND ND NDDMC/EC (1:1), 1 M LiTFSI + + + + + 56DEC/EC (1:1), 1 M LiTFSI + + + + + + 99DMC/EC (1:1), 1 M LiPF6 (LP30) + + � � 20DEC/EC (1:1), 1 M LiPF6 (LP40) + + � � 19

[a] Calculated as: (sum of capacities for battery 2)/(sum of capacities for battery 1). + + + : Best performance.�: Worst performance or complete failure.

Figure 2. Capacity retention curve of a Li half-cell using dilithium benzene-diacrylate cycled galvanostatically between 0.8 and 2 V at a rate of 1 Li+/1 hin different electrolytes.

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belonging to the third category in a spent battery, possiblyalong with minor decomposition compounds such as thoseformed in the solid electrolyte interphases (SEI) layer. The con-ductive carbon additive belongs to the first category, while theelectrolyte (both the solvent and lithium salt) belongs to thesecond.

The recycling route can thus proceed as follows:

· Post-mortem opening of the battery and careful removal ofthe lithium foil, avoiding any contact with water.

· Solubilization in deionized water of the electrode materials.· Filtration in order to remove the conductive additive in sus-

pension.· Drying of the filtrate.· Washing the filtrate with ethanol in order to remove traces

of electrolyte.· Final drying.

A more detailed protocol is provided in Section 2.3. Fromthis extraction route, it is clear that stability in water of the dif-ferent compounds is an important factor in the success of thisprocess.

It should be kept in mind, however, that LiPF6 salts areknown to react with water according to the following reactionformula:

LiPF6 þ H2O! 2 HFþ LiFþ POF3 ð1Þ

POF3 þ 3 H2O! H3PO4 þ 3 HF ð2Þ

It was also observed during the recycling processfor the three samples originating from a LiPF6 elec-trolyte battery (1 m LiPF6 in DMC, 1 m LiPF6 in DMC/EC (1:1, LP30) and 1 m LiPF6 in DEC/EC (1:1, LP40)that very small quantities of material were recoveredas compared to the other samples, and the glass-ware containing these samples showed clear indica-tions of glass corrosion. This is a common phenom-enon when glass is in contact with HF, and confirmsthe decomposition of LiPF6 and the associated con-tamination of any recycled organic material.

The 9 different collected recycled materials wereanalyzed with 1H NMR (Figure 3), IR (Figure 4 a), ele-mental analyses and inductively coupled plasmaatomic emission spectroscopy (ICP-AES) (Table 2) andcompared with pure BDALi2. From the 1H NMR spec-tra, it is clear that no BDALi2 was recovered from theLiPF6 electrolyte battery. As stated above, this can beexplained by the presence of the highly acidic HFduring the extraction process which might well havereacted with BDALi2 according to:

R-CO2Liþ HF! R-CO2Hþ LiF ð3Þ

Since the resulting benzenediacrylic acid is poorlywater-soluble and highly soluble in ethanol, it can beenvisioned that the compound has been completelyeliminated during the extraction process, which ex-

plains why no aromatic signals are seen with 1H NMR spectros-copy. Moreover, the signals seen in the IR spectra for the sam-

Figure 3. 1H NMR spectra of different samples of recycled dilithium trans–trans benzenediacrylate from spent batteries with different electrolytes inD2O.

Figure 4. Infrared spectra recorded in transmission mode of different recycled dilithiumtrans–trans benzenediacrylate samples from spent batteries (left) and of their respectivethermal decomposition product (right).

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ples obtained from batteries containing LiPF6 do not matchwith LiPF6, POF3,[48] or H3PO4. 31P NMR spectroscopy performedin D2O on the LP30 sample revealed multiple peaks at 1–2 ppm in the phosphate O = P(OR)3 area and a single minorpeak at 20 ppm in the phosphonate O = PR(OR’)2 area. This in-dicates that LiPF6/POF3 are not present and underwent furtherevolution to water-stable phosphate/phosphonate derivatives.In addition, 1H NMR spectra of the samples of LiPF6 in DMC/ECand of LiPF6 in DEC/EC revealed the presence of an organiccontaminant with peaks in the 3.5–4.5 ppm area (Figure 5).Such signals correspond to unsymmetrical ethylene glycol de-rivatives (R-O-CH2-CH2-O-R’), which presumably originate fromethylene carbonate decomposition. These signals are not seenfor the LiPF6 in DMC sample, which does not contain EC. Fur-

thermore, the absence of EC de-composition products in thesamples originating from theLiTFSI/DMC/EC and LiTFSI/DEC/EC batteries indicates that thesolvent decomposition is relat-ed to the presence of LiPF6.[49]

In conclusion, the combined de-composition of LiPF6 in water,the associated decompositionof EC and the HF release makeLiPF6 a poor choice in any recy-cling procedure carried out inwater for a lithium carboxylateelectrode material. LiPF6 is usu-ally considered as one of thebest salts in terms of ionic con-ductivity in LiBs, but it is alsoknown for its inferior safety and

toxicological issues.[50] To this, we can now add its poor influ-ence on recyclability when water is involved in the process.Nevertheless, the powder collected from the LiPF6 electrolytebatteries contains 7–9 weight % of lithium as seen in the ICP-AES measurements (see Table 2 and discussion below).

As seen in Figures 3 and 4 a, the other six samples of “recy-cled” material from the spent batteries contain BDALi2 as themajor constituent. It is interesting to notice that, according to1H NMR data, the visible contaminants possess aromatic pro-tons (peaks at around 6–8 ppm). Considering that dilithiumbenzenediacrylate is the only source of aromatic protons inthe selected half-cell system, these contaminants most likelyoriginate from decomposition of the organic electrode materi-al. Taking into account that extraction from the poor capacitysample (1 m LiClO4 in DMC) gives rather pure BDALi2 and thatextraction from the almost zero-capacity sample (1 m LiTDI inDMC) results in a completely pure BDALi2 (data not shown forthe latter), it can be assumed that the aforementioned decom-position is not related to the extraction process, at least if theelectrolyte is stable in water. Therefore, this decompositionmust be related to a side reaction of dilithium benzenediacry-late during cycling in the lithium-ion battery. This can also ex-plain the capacity fading observed after a few cycles in mostcases for this material (Figure 2). This capacity fading has beenobserved for most of the lithium carboxylates reported todate.[7, 25–30] Since many other organic electrode materials aremore stable, it can be assumed that this side reaction is relatedto an instability of one of the redox forms of a lithium carbox-ylate under battery cycling. This could open up new perspec-tives for further development of long-time cycling of lithiumcarboxylates if appropriate considerations are taken to stabilizethe compounds during their redox process.

The sample that possesses most aromatic contaminations isthe sample obtained from the 1 m LiFSI/DMC battery. Althoughlittle is yet known regarding the reactivity of the LiFSI salt,recent studies suggest that the weak S�F bond is easilybroken with further evolution of the resulting S+ species.[51, 52]

It can be assumed that such specie can react with BDALi2,

Table 2. Comparison of atom content in “recycled” materials from spent batteries with different electrolytes.ND = not determined.

Weight content in recycled BDALi2 [%] Weight contentin ashes [%]

C[a] H[a] N[a] Li[b] Li[b]

Reference (theoretical)[c] 62.6 3.5 0 6.0 18.8Reference (exp.) 60.6[d] 4.0[d] <0.3[d] 5.9[d] 18.1DMC, 1 m LiTFSI 58.1 3.3 <0.3 6.2 17.9DMC, 1 m LiFSI 36.7 2.8 1.1 7.8 11.9DMC, 1 m LiClO4 59.6 3.4 <0.3 5.9 16.7DMC, 1 m LiPF6 ND[e] ND ND 9.0 10.9PC, 1 m LiTFSi 47.5 3.2 <0.3 6.4 15.3DMC/EC (1:1), 1 m LiTFSI 57.8 3.5 <0.3 6.3 17.0DEC/EC (1:1), 1 m LiTFSI 57.3 3.5 <0.3 6.3 16.9DMC/EC (1:1), 1 m LiPF6 ND ND ND 8.9 13.6DEC/EC (1:1), 1 m LiPF6 ND ND ND 7.2 10.8

[a] Determined by elemental analyses. [b] Determined by ICP-AES technique. [c] Anhydrous BDALi2 or Li2CO3

were considered. [d] Measured on a sample containing ca. 1.4 % of water. [e] Not determined.

Figure 5. Detail of 1H NMR spectra of different samples of recycled dilithiumtrans–trans benzenediacrylate from spent batteries with LiPF6-based electro-lytes in D2O.

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even though it is unclear if this will occur during cycling and/or throughout the extraction process.

Results obtained from elemental analyses and ICP-AES meas-urements (Table 2) of the extracted samples agree well withthe afore-mentioned data. The samples giving atomic percent-age values closest to the values for pure dilithium benzenedia-crylate are those obtained using LiClO4 in DMC and LiTFSI inDMC, while the sample obtained using LiFSI in DMC appearsto be highly contaminated.The simultaneous low levels ofcarbon and hydrogen and high level of nitrogen and lithiumindicates an important contamination from the LiFSI deriva-tives (LiFSI being the only source of nitrogen in the system) in-dicating salt decomposition, possibly due to reaction withwater. These results are in good correlation with the expectedhigher stability of fluorine derivatives possessing C�F bonds(LiTFSI) as compared to S�F bonds (LiFSI) or P�F bonds (LiPF6).

Combustion of BDALi2

The presence of decomposition products of BDALi2 in mostsamples makes their direct introduction in a new battery ques-tionable. These decomposition products can be seen as deadweight as compared to the redox active material, and will au-tomatically result in batteries with lower capacities and energydensities. It could therefore be useful to consider further andmore advanced purification methods to separate these con-taminations from BDALi2.

Alternatively, a simple method capable of rejuvenatingalmost all the capacity from the contaminated samples withoutloss of lithium would be thermal decomposition and novelsynthesis from the ashes. It has been reported that organiclithium salts such as dilithium rhodizonate (Li2C6O6) can bethermally decomposed into lithium carbonate Li2CO3.[10] Con-sidering that lithium carbonate is used as a lithium source forthe synthesis of dilithium benzenediacrylate, this would repre-sent a way to completely close the loop for an environmental-ly-friendly recycling of lithium using organic electrode lithiumsalts.

The thermal stability of pure BDALi2 was consequently inves-tigated under air (Figure 6). After water loss at 130 8C (1.4 % intotal weight), dilithium benzenediacrylate is stable to approxi-mately 340 8C and then starts to decompose with a maximumof weight loss at 380 8C. A white powder is then obtained, cor-responding to 32.1 % of the initial mass. If analyzed with IRspectroscopy and compared with commercial lithium carbon-ate (Figure 7), the result clearly indicates that lithium carbonateis the major thermal decomposition product of BDALi2 underair. Moreover, the comparison between the theoretical weightratio:

Li2CO3/Li2C12H8O4; 73.89:230.07 = 32.1 %

and the experimentally obtained value from thermogravimetricanalyses:

Li2CO3/anhydrous Li2C12H8O4 ; 32.1:98.6 = 32.5 %

shows that no lithium is lost during the process and that littleor no byproducts are present in the resulting ashes. It can be

assumed that if the contaminants from recycled BDALi2 under-go a similar thermal decomposition, pure lithium carbonatecan be obtained from the combustion process. To this end, the9 different recycled samples that contained lithium were sub-mitted to a thermal treatment consisting of a ramp usinga heating rate of 5 8C min�1 up to 450 8C, followed by a 3 h-long isothermal step under air. Due to the small quantities ofmaterial involved, all combustion reactions were performed ina TGA apparatus that allows a parallel weight variation control(Figure 8). As expected, the more pure BDALi2 the initialsample contains (according to NMR and IR spectra, and data inTable 2), the closer the measured remaining weight value is tothe reference sample. For example, 34.6 % and 37.4 % ofweight remains after combustion of the LiClO4/DMC andLiTFSI/DMC samples, respectively. However, the sample ob-tained from the LiFSI/DMC electrolyte shows a different behav-ior, with a decomposition process starting at 200 8C and 44.8 %of remaining weight, thus indicating possible residual contami-nation in correspondence with the discussion on LiFSI above.Also the three samples extracted from LiPF6 electrolyte batterythat did not display any BDALi2 content exhibit rather moder-ate weight loss as compared to the other samples.

The set of nine different ashes were collected and analyzedwith IR spectroscopy (Figure 4 b) and ICP-AES (Table 2). As canbe seen in Figure 4 b, the LiPF6 electrolyte battery samplesclearly do not contain lithium carbonate and exhibit a singlebroad peak centered at 1019 cm�1. Nevertheless, as seen withICP-AES measurements, these samples obviously contain lithi-

Figure 6. Thermal analysis of dilithium trans–trans benzenediacrylate per-formed under air at a heating rate of 5 8C min�1.

Figure 7. Comparison of IR spectra of commercial lithium carbonate (red)and residues from thermal decomposition of dilithium trans–trans benzene-diacrylate (blue).

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um and were therefore used for the rest of study as possiblelithiation agents for benzenediacrylic acid. The IR spectrum ofthe sample originating from the LiFSI/DMC battery reveals thepresence of a significant contamination, seen as an intensepeak at 1119 cm�1. Contaminants are also present at a smallerscale in the samples obtained from LiTFSI/PC, LiTFSI/DMC/EC,and LiTFSI/DEC/EC batteries. As can be seen from the results,ashes obtained from LiClO4/DMC and LiTFSI/DMC samples ap-peared similarly to commercial lithium carbonate, according toIR and ICP-AES.

Second life-cycle battery tests

The different ashes were introduced separately in new synthe-sis processes of BDALi2 with fresh benzenediacrylic acid andin situ carbon super porous (SP) and prepared in a similar wayas the initial batch of electrode materials. These were there-after cycled versus Li in a battery using the same conditions asbefore, and using the same electrolyte. Cycling data for thesebatteries are shown in Figure 9, while their sustained capacitiesare listed in Table 1.

The results displayed in Figure 9 show that the LiPF6 electro-lyte batteries have almost no capacity, thereby indicating thatthe lithium-containing ashes did not react with the carboxylicacid to give lithium carboxylate. Although lithium carbonatewas clearly present in ashes obtained from the LiTFSI/PC andLiFSI/DMC samples, their corresponding second life-cycle bat-tery tests also exhibit poor capacity, possibly due to a negativeinfluence of the contamination with by-products found afterextraction. The cycling performance of the LiTFSI/DMC/ECsample decreased significantly in its second-cycle, with only56 % of the original capacity sustained (see Table 1). On theother hand, LiTFSI/DEC/EC, LiClO4/DMC, and LiTFSI/DMC batter-ies exhibit remarkably well-sustained performances with 99, 99,and 97 % of sustained capacity, respectively. Moreover, thequantity of material recovered after a complete battery–extrac-tion–synthesis cycle is also very good in these three cases with74, 80, and 79 % respectively of powder introduced in thesecond life-cycle battery, as compared to the first one. This val-idates our strategy to recycle lithium from organic electrode

materials using non-toxic solvents and a single ther-mal treatment step. In particular, the sample cycledin a LiTFSI in DMC battery exhibited overall goodelectrochemical performances and excellent recyclingabilities, possibly due to the excellent stability ofLiTFSI in water. An overview of the results obtainedduring this study can be seen in Table 1.

Conclusions

In summary, a simple method only utilizing waterand ethanol as solvents for synthesis, electrode for-mulation, extraction, and recycling of lithium out oforganic electrode materials issued from biomass hasbeen described here. In the best cases, up to 99 % ofthe capacity is retained with recycled BDALi2, thus

only a moderate quantity of lithium is lost during the courseof the complete procedure. The success of the recycling is alsohighly dependent on both electrolyte salt and solvent. Notably,the choice of a LiTFSI/DMC electrolyte provides good overallelectrochemical performance, high recovery of the lithium andexcellent sustained capacity.

Considering that the use of water for solubilizing the organicelectrode material is an important step in the extraction pro-cess, the stability in water of the different battery componentsis essential. LiPF6 is responsible for HF release under these con-ditions of an environmentally benign recycling protocol, whichcontributes to its previously reported lack of sustainability.[49]

Finally, although this study was focused on an organic LIBmodel compound, it could well be extended to all water-solu-ble organic electrode materials.[7, 25–30]

Figure 9. Capacity retention curve of a Li half-cell using recycled dilithiumbenzenediacrylate cycled galvanostatically between 0.8 and 2 V at a rate of1 Li+/1 h in different electrolytes.

Figure 8. Thermal decomposition profile of recycled dilithium trans–trans benzenediacry-late from spent batteries with different electrolytes.

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Experimental Section

General Methods

Solvents and reagents were purchased from Aldrich or Alfa Aesarand were used as received. 1H and 31P NMR spectra were recordedat 400 MHz and 162 MHz on a JEOL ECP-400 spectrometer, atroom temperature, respectively. Chemical shifts (d) were expressedin parts per million (ppm) relative to residual D2O or an internalstandard. Infrared spectra were recorded with a PerkinElmer Spec-trum One FT-IR spectrometer in the 650–4000 cm�1 frequencyrange equipped with an attenuated total reflectance probe (ATR).No signicant peaks were observed in the 1800–4000 cm�1 region.Elemental analyses were performed with a Flash EA 1112 fromThermo Finnigan. ICP-AES measurements were performed witha Spectro Cirros CCD ICP-AES, Kleeve, Germany. The quantitativemeasurements were performed by matrix-matched calibrationstandards of known concentrations of the analyte (Li 670.780 nm).The sample was aspirated 45 seconds before a triplicate reading of24 seconds was done, and the average values were used for fur-ther calculations. Thermogravimetric measurements (TG) and com-bustion reactions were investigated under air with a TA Instru-ments Q500 using alumina crucibles. TG analyses were systemati-cally obtained using a heating rate of 5 8C min�1. Drying undervacuum was performed in a B�chi B-580 glass-oven.

Synthesis procedures

Original material : A first batch of dilithium benzenediacrylate1 was prepared according to our previously published proce-dure.[28] 1.091 g (5 mmol) of benzenediacrylate acid was stirredwith a stoichiometric equivalent of lithium carbonate (369.5 mg,5 mmol) and 575.1 mg of carbon super porous (SP, 33 % in totalweight of the active matter) at 50 8C for 2 days in a 40 mL solutionof water and ethanol (1:1, v/v). After completion of the reaction,the mixture was then dried in a ventilated oven at 120 8C for 8 h,ball-milled for 1 hour and dried under vacuum at 90 8C for 12 h.

Recycled material : A similar procedure as above was used ona smaller scale. Typically 3–10 mg of ashes were recovered fromthe extraction/combustion method and stirred in a water-ethanolsolution with an adjusted quantity of fresh benzenediacrylate acidand carbon SP, assuming that the ashes comprised 100 % lithiumcarbonate. After 2 days and completion of the reaction, the mix-ture was dried in a ventilated oven at 120 8C for 8 h, ball-milled for1 hour and dried under vacuum at 90 8C for 12 h. The material wasthen used in a second life-cycle battery using the same electrolyte.

Extraction/combustion procedure

Li-ion batteries were opened after 20 charge/discharge cycles withdilithium benzenediacrylate in its oxidized form, thereby renderingit stable in air. The lithium foil was carefully removed. The elec-trode material and the fiberglass separator layer in contact withthe powder were put in a flat-bottom flask with 5 mL of deionizedwater and ultrasonicated for 30 min. The solution was then filtratedthrough glass wool and filter paper held in a funnel, where afterthe insoluble black particles were washed with 10 mL of deionizedwater. The remaining transparent solution was collected and driedin a ventilated oven at 90 8C for 15 h. The resulting white solid wasthen washed with 12 mL of ethanol and dried in order to removesolvent traces before thermal decomposition. Combustion of thewhite solid was performed in presence of air in a TGA apparatus

with a ramp using a heating rate of 5 8C min�1 up to 450 8C, fol-lowed by a 3 h long isothermal step.

Electrochemical study

Electrochemical performances of the organic electrodes weretested vs. lithium in Swagelok-type cells using Li metal discs asnegative electrode and fiberglass separators soaked with electro-lyte. Electrodes were prepared without binder by mixing the or-ganic active material with 33 % carbon SP (in total mass) in theliquid state. No other conductive additive or binder was added tothe mixture dilithium benzenediacrylate/carbon SP. Mechanicalmixing was carried out on a Restch during 1 hour. The powder and2 balls (diameter: 20 mm) were stowed in a milling container(55 mL). Cells were assembled in an argon-filled glove box andcycled in galvanostatic mode using an Arbin BT-2043 or a DigatronBTS-600 system at a typical rate of one lithium exchanged in1 hour (corresponding to C/2 for the dilithiated compound) be-tween 0.8 and 2 V.

Acknowledgements

This work has been supported by the Swedish Foundation forStrategic Research. The authors thank Jean Pettersson for theICP-AES measurements.

Keywords: environmentally-friendly process · li-ion batteries ·lithium recycling · organic electrodes · sustainability

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Received: May 20, 2014

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FULL PAPERS

S. Renault,* D. Brandell, K. Edstrçm

&& –&&

Environmentally-Friendly LithiumRecycling From a Spent Organic Li-IonBattery

Pre-loved lithium: A simple method isinvestigated for recycling lithium fromorganic electrode materials for secon-dary lithium batteries. The method usesnon-polluting solvents and a singlethermal treatment step at moderatetemperature. Up to 99 % of the capacityis retained with the recycled materials.Moreover, only a moderate quantity oflithium is lost during the course of thecomplete procedure.

� 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemSusChem 0000, 00, 1 – 10 &10&

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