3O2âV2O5 Cathode

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Sustainable preparation of LiNi1/3Co1/3Mn1/3O2V2O5 cathode materials by recycling waste materials of spent lithium-ion battery and vanadium-bearing slag Xiangqi Meng, Hongbin Cao, Jie Hao, Pengge Ning, Gaojie Xu, and Zhi H.I. Sun ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03880 • Publication Date (Web): 19 Mar 2018 Downloaded from http://pubs.acs.org on March 19, 2018

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ACS Sustainable Chemistry & Engineering

Sustainable preparation of LiNi1/3Co1/3Mn1/3O2-V2O5 cathode materials by recycling waste materials of spent lithium-ion battery and vanadium-bearing slag Xiangqi Menga,b, Hongbin Caoa,b, Jie Haob, Pengge Ningb,*, Gaojie Xub, Zhi Sunb,* a

School of Chemical Engineering and Technology, Tianjin University, 135 Yaguan Road, Haihe Education Park, Jinnan District,Tianjin 300350, PR China

b

Beijing Engineering Research Centre of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, No. 1, Beier Street, Zhongguancun, Haidian District, Beijing 100190, China

Corresponding author:

Zhi Sun ([email protected]) Tel: +86 10 82544844 Fax: +86 10 82544845 Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Tel: +86 10 82544844 Fax: +86 10 82544845 No. 1 Beierjie, Zhongguancun, Beijing, China

ABSTRACT Waste streams containing heavy metals are always of concerns from both environmental and resource depleting points of view. The challenges are in most cases related to the effectiveness for high-added value materials recovery from such waste, with which the environmental impacts during recycling shall be low. In this research, two typical heavy metals containing waste streams, i.e. spent lithium ion battery and vanadium-bearing slag were simultaneously treated, and it enables regeneration of the LiNi1/3Co1/3Mn1/3O2 cathode materials which was considered difficult due to the 1

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dislocation of nickel and lithium ions during electrochemical performance. By using the intermediate product during vanadium-bearing slag treatment, vanadium embedded cathode material can be prepared which delivers excellent electrochemical performances with a specific capacity of 156.3mAhg-1 after 100 cycles at 0.1C with the capacity retention of 90.6%, even the additive amount is only 5%. A thin layer of vanadium oxide is found to be effective to promote electrochemical performance of the cathode material. Using the principles of green chemistry, this process enables high performance cathode materials regeneration without introducing extraction chemicals and with much lower environmental impacts comparing traditional metallurgical technologies. Key

words:

LiNi1/3Co1/3Mn1/3O2-V2O5;

Cathode

materials;

Sustainable

preparation; Spent lithium-ion batteries

INTRODUCTION With the development of energy storage technology, lithium-ion batteries (LIBs) have been widely applied in smart phones, laptops, and electric vehicles because of its high energy density, high capacity and good electrochemical performance.1-6 Cathode material is an essential part of lithium-ion batteries.7,

8

Because of the excellent

electrochemical performance and relatively low cost, LiNi1−x−yCoxMnyO2 (NCM) has been commercialized as one of the cathode materials for LIBs in electric vehicles.9-17 As the demand of lithium-ion battery increases, a significant amount of spent cathode materials that contain valuable metals (Li, Ni, Co, Mn) have been produced.18-24 Considering both features of environmental impacts and high contents of critical metals, the recycling of spent LIBs has attracted worldwide attentions.25-29 Usually, they can be recycled through a metallurgical treatment.30-37 For instance, a full hydrometallurgical process to selectively recover metals (Ni, Co and Li) from the cathode scraps of spent lithium-ion batteries can be achieved by using ammonia-ammonium sulphate as the leaching solution and sodium sulphite as the reductant, and the total selectivity of Ni, Co and Li is above 98.6% in the first 2


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leaching process.38 Chen et al. combined the leaching process with the resynthesis of cathode material. They resynthesized Li1.2Co0.13Ni0.13Mn0.54O2 from spent lithium-ion batteries by using oxalic acid co-precipitation, hydrothermal and calcination, which the capacity retention can be 87% after 50 cycles.39 Various cathode materials were recycled by using metallurgical based methods, including pyrometallurgical and hydrometallurgical methods.40 However, heavy metal-containing residue and waste water could be produced during metallurgical process, which causes secondary pollution.41 Solid-state sintering to regenerate spent cathode materials is another approach in order to minimize potential secondary pollution and improve the recycling effectiveness. Zhang et al regenerated LiFePO4 cathode material from spent lithium-ion batteries by sintering the samples at 650 oC.41 The discharge capacity of this regenerated LiFePO4 cathode material could reach 140.4 mAh/g and the capacity retention is 95.32% after 100 cycles. Nie et al also regenerated LiCoO2 from spent lithium-ion batteries, which was calcined at high temperature for long time (900°C, 12h), and this regenerated LiCoO2 cathode material has a discharge capacity of 150 mAh/g after 80 cycles, inevitably causing energy waste. Direct regeneration method could improve the electrochemical performance of cathode materials and decrease the secondary pollution during the regeneration process.42 It may need to be mixed with other cathode materials in order to achieve acceptable electrochemical performance after regeneration. Meanwhile, this direct regeneration by solid-state sintering has not been applied in NCM cathode materials. The main reasons may be the loss of lithium, which caused by the formation of solid electrolyte interphase (SEI) layer during the cycling process.43, 44 This SEI layer results in the decrease of reversible capacity after multiple cycles. In addition, dislocation of Ni and cationic disordering (namely mixing of Li+ with Ni2+) were adverse to stabilize layered structure (Fig. S1), which demonstrated as another obstacle to regenerate NCM cathode materials directly.45 In this research, a method with thin layer of foreign elements during regeneration of spent NCM is demonstrated. The additive was obtained by recycling of a vanadium-bearing slag. By further incorporating with effective spray drying, it was found that spent NCM cathode material could be successfully regenerated in a much 3



lower regeneration temperature and shorter sintering time than traditional solid-state sintering approaches. This sustainable preparation of LiNi1/3Co1/3Mn1/3O2-V2O5 (NCM-V2O5) cathode materials shows several advantages: i). It enables high performance cathode materials preparation without introducing extraction chemicals and with much lower environmental impacts comparing traditional metallurgical technologies. ii). Compared with the tedious procedures in metallurgical based approach (leaching, co-precipitation, sintering), a shortened process was applied to regenerate cathode materials. iii). Low-energy consumption was another advantage of this preparation process, which was performed at low temperature. Therefore, this work agrees with the concept of green and sustainable chemistry, which provides a new insight to utilize the solid waste in the industrial production.

EXPERIMENTAL Preparation of NCM-V2O5 Spent lithium-ion batteries were provided by Brunp Recycling Co. Ltd. (China). These batteries were discharged and dismantled in the argon-filled glove box with both moisture and oxygen content below 0.1 ppm. Subsequently, cathode scraps were separated, and spent NCM powder could be obtained from cathode scraps by means of calcination. PVDF and acetylene black were removed in this calcination process. NH4VO3 was recovered from the vanadium-bearing slag (Fig. S2), which is provided by CITIC Jinzhou Vanadium Industry Co., Ltd. (China). The regeneration process of spent NCM cathode material was shown in Fig. 1. NH4VO3 was dissolved in the deionized water, and spent NCM cathode powder was dispersed in the solution of NH4VO3. Different ratios of V2O5 (3 wt%, 5 wt%, 8 wt%, 10 wt%) were investigated to obtain the NCM-V2O5 cathode materials with optimal electrochemical performance. Specified amount of NH4VO3 was dissolved in the deionized water to assure that the proportions of V2O5 are 3 wt%, 5 wt%, 8 wt%, and 10 wt%, respectively. Subsequently, spent NCM cathode powder was dispersed in the 4


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solution of NH4VO3, and the mixture was stirred for 4h at room temperature. After spray drying and sintering, the NCM-V2O5 cathode materials with different proportions of V2O5 can be attained, which are denoted as V-3, V-5, V-8 and V-10, respectively. Meanwhile, three different drying methods were also investigated to obtain NCM-V2O5 cathode materials with improved performance, including rotary evaporation, ball milling coupled with rotary evaporation, and spray drying. In order to prepare NCM-V2O5 cathode materials, the dried samples were sintered at 350 oC for 4h in the tube furnace with a heating rate of 1oC/min. Electrochemical tests and characterization would be carried out for these cathode materials. Electrochemical tests Electrochemical tests were carried out by using CR2025-type coin cells at room temperature. The spent NCM cathode material and NCM-V2O5 cathode materials were prepared by mixing with 80 wt% active material, 10 wt% PVDF, and 10 wt% acetylene black. Coin cells used lithium foil as anode and 1.0 mol/L LiPF6 dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC) in the volume ratio of 1:1 as electrolyte. Meantime, these cells were assembled in the argon-filled glove box with both moisture and oxygen content below 0.1 ppm. Cyclic voltammetry (CV) was performed on an Autolab electrochemical workstation (PGSTAT302N, Metrohm) with the voltage range from 2.8 to 4.6V and the scan rate of 0.1 mV s-1. Electrochemical impedance spectroscopy (EIS) was also carried out on an Autolab electrochemical workstation with a frequency range from 100 kHz to 0.01 Hz. Galvanostatic cycling tests were performed on a LAND CT2001A battery tester with the voltage between 2.5 and 4.3V (versus Li+/Li) at the current density of 0.1C (1C=278 mA g-1). Rate performance was carried out at the current density of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C. Characterizations Crystal phase was characterized by X-ray Diffraction (XRD) (Empyrean, PANalytical B.V.) with a Cu Kα irradiation. Particle morphology was observed by scanning 5



electron microscope (SEM) (SU8020, HITACHI) and transmission electron microscope (TEM) (JEM-2100F, JEOL). The size distribution of cathode powder was tested by Mastersizer 2000 (Malvern Instruments Ltd.). The thermogravimetric analysis of sample was performed with a Thermo Gravimetric Analyzer (EXSTAR6000, SEIKO). The contents of metals were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) (iCAP 6300, Thermo Scientific, USA). X-ray photoelectron spectroscopy (XPS) measurements were carried out by an ESCALAB 250Xi spectrometer (ThermoFisher Scientific). Raman measurements were performed on a LabRAM HR800 spectrometer (Horiba Jobin Yvon). RESULTS AND DISCUSSION Regeneration of spent NCM cathode materials Spent NCM cathode powder was separated from scraps and NH4VO3 was recovered from vanadium-bearing slag. Characterizations of these two recovered materials were shown in more details in the Supporting Information. We dissolved NH4VO3 in the deionized water, and dispersed spent NCM cathode powder in the solution of NH4VO3. Then, the deionized water should be removed from the mixture. Compared with other methods, spray drying is an effective way to prepare cathode materials with coating layer.46, 47 After spray dried, the sample would be sintered to make NH4VO3 convert into V2O5. Based on the result of TG/DTG for the recovered NH4VO3 (Fig. S9), the sintering temperature was determined as 350 oC, which is conductive to decrease energy consumption. Without sacrificing specific capacity, the energy consumption would be reduced because of the addition of V2O5. Based on the characterization results, NCM-V2O5 cathode material with the coating layer was expected to be prepared by using spray drying and sintering. It is known that cation mixing could bring adverse effects to the structural stability of nickel-containing layered cathode materials. In the XRD patterns of these layered cathode materials, the value of I003/I104 (R) is directly associated with the content of 6


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cation mixing.48 The content of cation mixing decreases with the increasing value of R, and cation mixing was proved to be relatively minor when R is above 1.2.48, 49 XRD patterns of SD were presented in Fig. 2a. The value of R for SD (1.58) is higher than 1.2, indicating that cation mixing is relatively minor in the layered structure of SD. SEM images of SD and the spent NCM cathode material were shown in Fig. 2b and 2d. To combine with the size distribution curves of SD (Fig. 2c) and S (Fig. 2e), it can be seen that the spherical particles of SD have been restored relatively perfectly. Based on the element mapping results of the spent NCM cathode material (Fig. 3a) and SD (Fig. 3b and 3c), it can be found that V2O5 has been composited with NCM cathode materials. As shown in Fig. 3d, V2O5 has been coated on the surface of NCM particles and this coating layer may benefit for increasing the capacity retention of cathode material. Subsequently, different factors affecting the electrochemical performance of NCM-V2O5 cathode material were investigated. Effects of different factors on the performance Effect of the content of addictive Different ratios of V2O5 (3 wt%, 5 wt%, 8 wt%, 10 wt%) were investigated to obtain the NCM-V2O5 cathode materials with optimal electrochemical performance, which are denoted as V-3, V-5, V-8 and V-10, respectively. The cycling performance of V-3, V-5, V-8 and V-10 were performed at 0.1C (1C=278 mAh/g). The discharge capacities of these samples were shown in Fig. 4a. It can be clearly seen that the discharge capacity of V-5 was the highest among these samples, and the discharge capacity of V-5 retains at 156.3 mAh/g after 100 cycles with the capacity retention of 90.7%. The rate performance of V-3, V-5, V-8 and V-10 were carried out at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C. (1C=278 mAh/g). The results of rate performance were shown in Fig. 4b. The advantage of V-5 on rate performance was further demonstrated. The discharge capacity of V-5 was higher than that of other samples at different rates. On the basis of these results, the spent

7



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NCM cathode material mixed with V2O5 at the ratio of 95:5 would show the optimal electrochemical performance. As shown in Fig. 3d, the thickness of V2O5 coating layer for NCM-5%V2O5 is 45.9nm. Based on the thickness of coating layer for NCM-5%V2O5, those of NCM-3%V2O5, NCM-8%V2O5, NCM-10%V2O5 can be estimated (Fig. 3e). With the increasing of V2O5 content, the capacity retention of NCM-V2O5 cathode material increased firstly and then decreased. V2O5 exhibits a high discharge capacity, which helps to increase the capacity of NCM-V2O5 cathode material.50 Consequently, NCM-5%V2O5 cathode material shows the higher capacity retention than NCM-3%V2O5. When the V2O5 content of NCM-V2O5 cathode material exceeds 5%, the capacity fade increases with increasing thickness of the V2O5 coating layer, which is detrimental for lithium ion to diffuse in the cathode materials.50 In addition, electrochemical impedance spectroscopy (EIS) and calculation of lithium ion diffusion coefficient were performed to further understand the difference of the electrochemical performance for NCM-V2O5 cathode materials with different content of V2O5. EIS has been carried out to clarify the effect of the content of addictive (V2O5) on the electrochemical process, which is performed on an Autolab electrochemical workstation (PGSTAT302N, Metrohm) with a frequency range from 100 kHz to 0.01 Hz. The EIS curves of LiNi1/3Co1/3Mn1/3O2-V2O5 cathode materials (including NCM-3%V2O5, NCM-5%V2O5, NCM-8%V2O5, NCM-10%V2O5) are presented in Fig. S18. NCM-5%V2O5 shows the smaller Rct (163.1 Ω) than NCM-3%V2O5 (347.0 Ω), NCM-8%V2O5 (376.2 Ω), NCM-10%V2O5 (567.2 Ω), indicating that the spent NCM cathode material coated by 5%V2O5 using spray drying and sintering could promote the electrochemical process. Furthermore, the inclined line in the lower frequency represents for the Warburg impedance,

which

is

associated

with

lithium-ion

diffusion

in

the

LiNi1/3Co1/3Mn1/3O2-V2O5.51 Therefore, we calculated the lithium ion diffusion coefficient (D), which can be obtained from the formula as following:52 8


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D=

R2 T 2

(1)

2A2 n4 F4 C2 σ2

where A is the surface area of the electrode (7.85×10−6m2), n stands for the number of the electrons per molecule attending the electronic transfer reaction (1.0), F represents for the Faraday constant (96500 C mol−1), C is the concentration of lithium ion in the cathode (1.5×104 mol m−3) that can be obtained from the density and the molecular weight of the regenerated cathode materials, R represents for the gas constant (8.314 J K−1 mol−1), T is the room temperature in this research (298 K), σ stands for the slope of the line Z’~ω−1/2, which can be calculated from Fig. S18, respectively. After calculations, the lithium diffusion coefficient of NCM-5%V2O5 is 1.43×10−13 cm2 s−1, which is higher than that of NCM-3%V2O5 (0.55×10−13 cm2 s−1), NCM-8%V2O5 (0.54×10−13 cm2 s−1), NCM-10%V2O5 (0.62×10−13 cm2 s−1). Based on these results above, it is analyzed that NCM-5%V2O5 show the comparatively better electrochemical process and the diffusion of lithium ion. Because the optimal content of V2O5 can benefit for reducing the side reactions between NCM cathode materials with electrolyte. Effect of drying methods Three different drying methods were investigated to obtain NCM-V2O5 cathode materials with improved performance, including rotary evaporation (RE), ball milling coupled

with

rotary

evaporation

(BM-RE),

and

spray

drying

(SD).The

charge-discharge curves and cycling performance of the spent NCM cathode material and RE, BM-RE, SD were shown in Fig. S19, S20, S21, and S22. It can be clearly seen that the discharge capacities of these three NCM-V2O5 cathode materials are higher than that of the spent NCM cathode material (76.0 mAh/g) in the first cycle, and the discharge capacity of SD (172.4 mAh/g) is greater than that of RE (132.3 mAh/g) and BM-RE (121.4 mAh/g). As shown in Fig. 5a, the cycling performance of NCM-V2O5 cathode materials by using different drying methods were carried out at 0.1C (1C=278 mAh/g). Fig. 5b further displayed the comparison of rate performance 9



for the samples prepared by different drying methods. The advantage of NCM-V2O5 cathode material prepared by spray drying (NCM-V2O5-SD) on the cycling and rate performance could be demonstrated, indicating that spray drying may be a better way to prepare NCM-V2O5 cathode material. The Raman spectra of NCM-V2O5-SD is plotted in Fig. S24, and the spectrum of the spent NCM cathode material is presented for comparison. For NCM-V2O5-SD, the peak centered at around 589 cm-1 can be observed, which is contributed by metal-oxygen (M-O) vibrations.53 These three peaks show more sharply than that of BM-RE, indicating the destruction of M-O for BM-RE. The destruction of M-O would affect the layered structure of NCM and decrease the electrochemical performance of the cathode material, and it is consistent with the results of electrochemical tests. Comprehensive tests were performed to attain more detailed electrochemical properties of NCM-V2O5-SD. The cycling performance of NCM-V2O5-SD was compared with the spent NCM cathode material in Fig. 5c, and it could be clearly found that the discharge capacity of NCM-V2O5-SD retains at 156.3 mAh/g after 100 cycles with the capacity retention of 90.6%, which is significantly higher than that of the spent NCM cathode material, indicating that NCM-V2O5 cathode material prepared by using spray drying has great cycling performance. Fig. 5d further demonstrates the advantage of NCM-V2O5-SD on the rate performance. As shown, NCM-V2O5-SD could deliver the highest reversible capacities at different rates, especially delivered a capacity of 179.6mAh/g at 0.1C. With V2O5 coated, the cycling and rate performance of cathode material are improved, which meet the requirement of the practical application. Cyclic voltammetry (CV) tests of NCM-V2O5-SD and the spent NCM cathode material were performed at 0.1mV/s from 2.8 to 4.6V during the first cycle. Fig. 5e displays the CV curves of these two samples, and the cathodic peaks of NCM-V2O5-SD at 3.6V and anodic peaks at around 3.9V can be observed, which are obviously sharp than that of the spent NCM cathode material. This means that the process of reversible redox reaction can be conducted in NCM-V2O5 cathode materials more completely than that of the spent NCM cathode material, indicating the high electronic conductivities and reversible capacities of NCM-V2O5-SD, which 10


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is consistent with the results of cycling and rate performance tests. Electrochemical

impedances

of

the

spent

NCM

cathode

material

and

NCM-V2O5-SD were also measured. As shown in Fig. 5f, ohmic resistance (Rs) is similar for these cells, which means the contacts of cells and the resistances of electrolyte are approximately equal. But they have different charge transfer resistance (Rct), and it is indicated that the different electrochemical processes were taking place inside different cells. It can be seen from the fitted results that the Rct of NCM-V2O5-SD (163.1Ω) is obviously lower than that of the spent NCM cathode material (311.1Ω), which reveals that the intercalation/deintercalation process of lithium ion can take place more easily in NCM-V2O5-SD than in spent NCM cathode material. It is consistent with the results of cycling performance and rate performance, which indicates that NCM-V2O5 prepared by spray drying shows the great electrochemical performance. XRD patterns of cathode materials were displayed in Fig. 6, including spent NCM cathode material, NCM-NH4VO3, and NCM-V2O5 prepared by spray drying. The splitting peaks of (006)/(012) and (108/110) splitting peak of NCM-V2O5 is obviously strong than the spent NCM cathode material and NCM-NH4VO3, indicating NCM-V2O5 has better layered structure. This means that the restoration of layered structure can be performed by using spray drying and sintering. In order to compare the oxidation states of the metals for NCM-V2O5 and the spent NCM cathode material, XPS spectra was carried out and Fig. S25 presents XPS results of Ni, Co, Mn, and V. It can be seen that the binding energies of Ni, Co, Mn, and V are around 855.0, 780.3, 642.5 eV, and 517.2 eV, which are consistent with binding energies of Ni2+, Co3+, Mn4+, and V5+. For the spent NCM cathode material, the intensity of Ni is slightly lower than that of NCM-V2O5, indicating the restoration of Ni-O during the preparation process. It is known that Ni-O of the layered structure is important for the capacity and stability of NCM-based cathode materials. For NCM cathodes, it seems that the effect of Li/Ni mixing is linked to the deterioration of electrochemical performance.54 The disordered distribution of Li+ and Ni2+ in 3a and 3b sites can 11



easily occur because of the small differences in the ionic sizes of Ni 2+ (0.69 Å) and Li+ (0.76 Å), which may interfere with lithium diffusion.55, 56 XPS results of Ni 2p3/2 for the spent NCM cathode material and NCM-V2O5 cathode material have been fitted using casaXPS. As shown in Fig. S26 and Table S3, it is analyzed that the content of Ni2+ for the spent NCM cathode material is higher than that of NCM-V2O5 cathode material, indicating the cation mixing can be decreased during the regeneration process. To combine with the results of electrochemical performance (Fig. 5c), the discharge capacity increases with the decrease of the content of Ni2+. With V2O5 coated, the discharge capacity and capacity retention of cathode material are increased to meet the requirement of the practical application. Meanwhile, the V2O5 coated layer’s stability has been investigated by scanning electron microscopy (SEM) after the cycles. CR2025-type coin cells were assembled at room temperature, which used lithium foil as anode and 1.0 mol/L LiPF6 dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC) in the volume ratio of 1:1 as electrolyte. Then, galvanostatic cycling tests were performed on a LAND CT2001A battery tester with the voltage between 2.5 and 4.3V (versus Li+/Li) at the current density of 0.1C (1C=278 mA g-1). The coin cells after 100 cycles were used to investigate the stability of V2O5 coated layer, which were discharged to 0 V and then disassembled. The cathodes were rinsed with DMC to remove residual electrolyte. The SEM and vanadium mapping images of NCM-V2O5 after 100 cycles were shown in Fig. 7. It is shown that the morphologies of the NCM-V2O5 cathode particles could remain stable after 100 cycles (Fig. 7a, b). No significant damage to the NCM-V2O5 cathode particle, such as particle cracking or disconnections between particles, was observed from these SEM results. Based on the vanadium mapping images of the NCM-V2O5 after 100 cycles (Fig. 7c,d), it could be concluded that V2O5 can be well coated on the surface of NCM particles after multiple cycles, indicating the good stability of V2O5 coating layer.

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Development of the regeneration of spent NCM cathode material Based on above results, it can be concluded that NCM-V2O5-SD shows best electrochemical performance. Compared with the resynthesized NCM cathode materials in literature (Table 1), the capacity retention of this NCM-V2O5 cathode material by using spray drying and sintering is higher, which benefits from the coating layer of V2O5.

Table 1 Summary of resynthesized NCM cathode materials from spent LIB in literature and this research

Cathode material

Discharge capacity

Capacity

(mAh/g)

retention

130.2 (0.2C)

82.4% (50 cycles)

20

155.4 (0.1C)

83.0% (30 cycles)

35

139.0 (0.5C)

65.0% (100 cycles)

37

172.4 (0.1C)

90.6% (100 cycles)

This research

Regeneration method

Reference

Leaching-co-precipitation LiNi1/3Co1/3Mn1/3O2 - solid state synthesis LiNi1/3Co1/3Mn1/3O2

Solid state method Leaching-co-precipitation

LiNi1/3Co1/3Mn1/3O2 - solid state synthesis LiNi1/3Co1/3Mn1/3O2-V2O5

Spray drying - sintering

The NCM-V2O5 cathode material prepared by spray drying has great cycling performance and capacity retention, and enables the restoration of Ni-O because of the V2O5 coating layer. In addition, only a shortened process is needed, rather than the tedious procedures (leaching, co-precipitation, sintering) required in metallurgical based approach. Meanwhile, energy consumption during this preparation process is discussed. Unlike conventional regeneration method(Fig. S27), this preparation process is performed at 350 oC for 4h, which is far below that of solid-state method, the detailed results of calculation was presented in the Supporting Information35,57. Therefore, low-energy consumption was demonstrated as an advantage of this preparation process, which is consistent with the concepts of green chemistry. Furthermore, the utilization efficiencies of cobalt, lithium, and vanadium have been 13



improved significantly and a practical method to synthetically utilize different solid wastes has been developed, which is consistent with the concepts of sustainable chemistry. As one of the potential technologies, direct regeneration may be greener than them of chemically extracting the metallic elements from waste materials where secondary waste water and solid waste are inevitably generated. Through this direct regeneration process, NCM-based cathode materials with high performance can be recycled. During the process of battery production, the cathode scraps can be regenerated by using this method, which has the application foreground for large-scale industrial application. CONCLUSIONS To conclude, we developed a method to prepare NCM-V2O5 cathode material with high performance by using spent LIBs and vanadium-bearing slag, which can deliver a specific capacity of 156.3mAhg-1 after 100 cycles at 0.1C with the capacity retention of 90.6%. By incorporating with effective spray drying, it was found that spent NCM cathode material could be successfully regenerated with a thin layer of V2O5 coated on the surface of NCM. Using the principles of green chemistry, this method was demonstrated as a shortened process with low-energy consumption. Moreover, it enables high performance cathode materials preparation without introducing extraction chemicals and with much lower environmental impacts comparing traditional metallurgical technologies. We believe that this method can be applied to regenerate the cathode scraps in the process of practical battery production. ASSOCIATED CONTENT Supporting Information Brief statement in non-sentence format listing the contents of the material supplied as Supporting Information. AUTHOR INFORMATION 14


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Corresponding author: *E-mail: [email protected] (Zhi Sun) ORCID Hongbin Cao: 0000-0001-5968-9357 Zhi Sun: 0000-0001-7183-0587 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS The authors acknowledge the funding support from the National Science Fund for Distinguished Young Scholars of China (Grants No.51425405), 1000 Talents Program of China (Z.S.), Key Program of Chinese Academy of Sciences KFZD-SW-315, National Natural Science Foundation of China (No. 51425405) and Beijing Municipal Science & Technology Commission (Z171100002217028). REFERENCES 1.

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For Table of Contents Use Only

Synopsis This research enables direct regeneration of LiNi1/3Co1/3Mn1/3O2 cathode materials by introducing V2O5 coating layer, which decreases energy consumption and second pollution.

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Fig.1 Schematic plot of the regeneration process of spent NCM cathode material

Fig. 2 XRD patterns of NCM-V2O5 prepared by spray drying and spent NCM (a), SEM images of NCM-V2O5 prepared by spray drying (b), spent NCM (d), size distribution curves of NCM-V2O5 prepared by spray drying (c), spent NCM (e)


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Fig. 3 Mapping images of spent NCM (a), NCM-V2O5 prepared by spray drying (b), vanadium mapping image(c) and TEM image (d) of NCM-V2O5 prepared by spray drying, the thickness of V2O5 coating layer for NCM-3%V2O5, NCM-5%V2O5, NCM-8%V2O5, and NCM-10%V2O5 cathode materials (e)

Fig. 4 Cycling performance (a) and rate performance (b) of NCM-V2O5 with different different ratios of V2O5 (0 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%)



Fig. 5 Cycling performance (a) and rate performance (b) of NCM-V2O5 cathode materials by using different drying methods, cycling performance (c), rate performance (d), cyclic voltammetry (e), electrochemical impedance spectroscopy (f) of spent NCM and NCM-V2O5 prepared by spray drying


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Fig. 6 XRD patterns of cathode materials, along with enlarged 2θ portions, between 37°and 39° (a), between 63°and 66°(b)

Fig. 7 SEM images of fresh NCM-V2O5 (a) and NCM-V2O5 after 100 cycles (b), vanadium mapping images of fresh NCM-V2O5 (c) and NCM-V2O5 after 100 cycles (d)


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