substitution enhances the electrochemical

Subscriber access provided by Nottingham Trent University

Energy, Environmental, and Catalysis Applications

Li-Nb-O coating/substitution enhances the electrochemical performance of LiNi0.8Mn0.1Co0.1O2 (NMC 811) Cathode Fengxia Xin, Hui Zhou, Xiaobo Chen, Mateusz Zuba, Natasha A. Chernova, Guangwen Zhou, and M. Stanley Whittingham ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b09696 • Publication Date (Web): 30 Aug 2019 Downloaded from pubs.acs.org on August 30, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Li-Nb-O coating/substitution enhances the electrochemical performance of LiNi0.8Mn0.1Co0.1O2 (NMC 811) Cathode Fengxia Xin†, Hui Zhou†, Xiaobo Chen‡, Mateusz Zuba§, Natasha Chernova†, Guangwen Zhou‡, M Stanley Whittingham†,* †

Chemistry and Materials, ‡Mechanical Engineering and Materials, §Physics, Applied Physics, and

Astronomy, Binghamton University, Binghamton, New York 13902-6000, United States *Corresponding Author: E-mail: [email protected]

Abstract High-nickel layered oxides, such as NMC 811, are very attractive high energy density cathode materials. However, the high nickel content creates a number of challenges, including high surface reactivity and structural instability. Through a wet chemistry method, a Li-Nb-O coated and substituted NMC 811 was obtained in a single step treatment. This Li-Nb-O treatment not only supplied a protective surface coating but also optimized the electrochemical behavior by Nb5+ incorporation into the bulk structure. As a result, the 1st capacity loss was significantly reduced (13.7 vs. 25.1 mAh/g), contributing at least a 5% increase to the energy density of the full cell. In addition, both the rate (158 vs. 135 mAh/g at 2C) and capacity retention (89.6 vs. 81.6% after 60 cycles) performance were enhanced.

1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Keywords: High-energy-density, lithium-ion battery, LiNi0.8Mn0.1Co0.1O2 cathode, coating/ substitution Li-Nb-O compound, wet chemistry method

2


Page 2 of 24

Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction Layered lithium transition metal oxides with the α-NaFeO2 crystal structure have received most attention for the cathode of rechargeable lithium-based batteries. Conventional LiCoO2 (LCO), which was originally commercialized by SONY Company in 1990s, is still widely used in various technological field, such as mobile phones, cameras, laptops, et al.1 However, the high cost of Co and low capacity (135 mAh/g) prevent their practical application in the automotive industry. Combined with Ni and Mn, layered structured LiNizMnyCo1-z-yO2 (NMC) cathode with Ni content less than 60% are fully commercialized.2 Further, high nickel LiNizMnyCo1-z-yO2 (z ≥ 0.6) cathodes are regarded as the technologically most advanced material option for future EVs due to their higher degree of lithium utilization (discharge capacities exceeding 200 mAh/g)3 and relatively high average operating voltage (3.6V vs. Li/Li+).4 Unfortunately, the implementation of Ni rich NMC still face many challenges: (1) highly reactive Ni4+ formed at delithiated state leads to unfavorable side reactions with the electrolyte, which consumes both electrode and electrolyte. Furthermore, the reduction of Ni4+ can cause the formation of an insulating Ni-O impurity phase and oxygen loss on the surface, which damages the crystal structure, reducing the cycling and thermal stability.5-6 (2) Li/Ni cation mixing always appears in high nickel layered oxide due to the similar radius of Li+ (0.076 nm) and Ni2+ (0.069 nm), which can inhibit lithium diffusion and increase reaction impedance, resulting in a practical capacity loss.7 (3) Anisotropic lattice contraction during cycling causes cracks along the grain boundaries, which brings structural degradation of NMC electrode. 8

3



Coating and substitution are the most common and effective methods to overcome these problems by modifying the surface and bulk of cathode materials.9-11 A coating layer can act as a physical protection to reduce the unwanted side reaction between the highly reactive Ni4+ and electrolyte in the charged state, help mitigate phase transitions, improve structural stability, and suppress the dissolution of transition metal ions.12 Metal oxides, metal fluorides, metal phosphates, metal oxyfluorides, metal hydroxides have been studied as coating materials.13-18 However, these coating layers frequently have poor ionic and electronic conductivities, which can reduce the capacity of electrode and increase the polarization between the charge and discharge processes. Therefore, it is preferred to introduce lithium containing compounds as coating film with ideally a high Li+ ion conductivity.19-21 For example, Li2ZrO322, LiAlO223, Li2TiO324 etc surface coatings on Ni-rich layered oxide cathode (LiNi0.7Co0.15Mn0.15O2, LiNi0.8Co0.1Mn0.1O2, and LiNi0.8Co0.15 Mn0.05O2) have been reported to improve the long-term cyclability. Substitution can alleviate the structural instability of the electrode by hindering the motion of the transition metals and oxygen loss; Al3+, Mg2+, Zr4+, Cr3+, Ti4+ etc are the most commonly used substitution elements.25-29 Most recently Nb5+ substitution has been shown to enhance the cycling stability of the Li/Mn rich NMC and the elevated temperature stability of the 532 NMC.30-31

A coating mainly supplies a surface protection to the material from outside, while substitution modifies the internal structure of the material. Perhaps by combining them together, the material can be optimized from both outside and inside, more improvements are expected. In fact, at elevated temperature, it is common that coating materials will penetrate into the upper layer or 4


Page 4 of 24

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


even the bulk of the particles, partly substituting the active materials.32 In this work, we studied Li-Nb-O coating on LiNi0.8Co0.1Mn0.1O2 (NMC 811) cathode powder by a wet chemistry approach employing lithium niobium ethoxide as precursor. The post annealing at 500oC allowed some of the Nb ions to diffuse and incorporate into the structure of the parent material beneath the coating layer to give a coating-substitution co-modification to the material, which contributes significantly to improved electrochemical performance.

2. Experimental section

Preparation of Li-Nb-O modified NMC 811. LiNi0.8Mn0.1Co0.1O2 materials were obtained from ECOPRO. Lithium niobium ethoxide solution (5% w/v in ethanol, Alfa Aesar) was used as reaction chemical. Li-Nb-O modified NMC 811 samples were synthesized through a wet chemical method. Further, Li-Nb-O was formed by hydrolysis process of the lithium niobium ethoxide.33-34 Typically, NMC 811 powders were mixed with lithium niobium ethoxide solutions in a flask, and trace water (0.5 %) was added to the mixture. After stirring overnight, the ethanol was evaporated at 80 oC. Then, the sample was calcined in a pure oxygen atmosphere at 500 oC for 3h. 1, 2 and 3 wt. % Li-Nb-O coating on NMC 811 samples were prepared.

Structural Characterization. X-ray powder diffraction (XRD) was performed with a BRUKER diffractometer (D8 Advance) equipped with Cu Kα source (λ = 1.54178 Å) and data was obtained with a step size of 0.02° and dwell time of 1 s in spinning state. TOPAS-Academic V4.2 software was used to analyze the XRD data. The morphology and elemental mapping of samples was 5



determined using a Zeiss Supra 55 VP field emission scanning electron micros-copy (SEM) at an operating voltage of 5 kV with an energy dispersive X-ray spectroscopy (EDS) detector. HighAngle Annular Dark-Field (HAADF) scanning transition electron microscopy (STEM) and EDX images were collected using a FEI Talos F200X (200 KeV) at the Center for Functional Nanomaterials in Brookhaven National Lab. The samples were prepared by dispersing particles into ethanol dropped on ultra-thin amorphous carbon-coated copper grids and drying naturally.

Electrochemical measurement. Pristine NMC 811 and Li-Nb-O coated/substituted samples were separately mixed with acetylene black (Alfa Aesar, 100% compressed, > 99.9%) and polyvinylidene fluoride (PVDF) powders with appropriate amount of 1-methyl-2- pyrrolidinone (NMP) solvent in a weight ratio of 90:5:5 in a mixer for 15 mins to form a slurry. The cathode was prepared by casting the homogeneous slurry on aluminum (Al) foil using doctor blade and drying in vacuum oven at 80 oC for overnight. The average mass loading of the electrode was 15 mg/cm2 and was calendered into 2.5 g/cm3. All of these work was performed in a dry room (Temperature: 20-21 oC; Dew point: < -50) to avoid any exposure to moisture. 2325-type coin cells were used to test the electrochemical performance with Li foil as a counter/reference electrode, a Celgard 3501 separator and 1.0 M LiPF6 dissolved in ethylene carbonate/dimethyl carbonate (EC/DMC, 1:1 in volume) as the electrolyte solution. The cells were cycled in the voltage range of 2.8 ~ 4.6 V. Normally the first three cycles was tested with current density of C/10 (1 C = 200 mA/g), then C/3 for the following cycles. In addition, the rate performance was tested from C/10 to 2C (C/10, C/5, C/2, C, and 2C), where the rate changes for both charge and discharge. The electrochemical data 6


Page 6 of 24

Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


were collected on a multichannel Biologic system.

3. Results and discussion

3.1 Materials characterizations. Figure 1 shows the XRD patterns of pristine NMC 811 and LiNb-O modified NMC 811 materials. All the diffraction peaks could be indexed to the hexagonal NaFeO2 structure with R3̅m space group, in which Li, transition-metal and oxygen ions occupy the 3a, 3b and 6c octahedral sites, respectively. No crystalline Nb-contained phase was detected for the coated samples. The refined lattice parameters of the samples are listed in Table 1. The weighted R-factors Rwp are 3.14%, 4.91%, 4.92% and 3.60% for them, showing the excellent fitting and reliable structural data obtained. Compared to pristine NMC 811 (101.45 Å3), the unit cell volumes became slightly larger (101.53, 101.53, and 101.62 Å3 for 1%, 2% and 3% Li-Nb-O coated NMC 811 samples, respectively). This volume increase suggests that some Nb ions are actually substituted into the crystal structure of NMC 811 because of the larger ionic radii of Nb5+ than those of the NMC ions 30 or repulsing forces. In addition, the similar c/a values (all around 4.94) and clear splitting of the (108)/(110) diffraction peaks for all the samples (Figure 1) show that the highly ordered layered structure was not influenced with this small amount of substitution. Furthermore, the decreased Rwp value (Table S1 and Table S2) indicates that Nb5+ might prefer to occupy the 3a sites (Li layer), but further higher Nb concentration studies will be needed to confirm the preferred site.

7



Page 8 of 24

Table 1. Refined lattice parameters for XRD in Figure 1. a (Å) c (Å) Volume (Å3) Rwp (%) Pristine NMC 811 1%-Li-Nb-O 2%-Li-Nb-O 3%-Li-Nb-O

2.8726 (3) 2.8730 (7) 2.8730 (4) 2.8742 (4)

14.195 (4) 14.203 (7) 14.202 (7) 14.203 (5)

101.446 (4) 101.532 (7) 101.529 (7) 101.619 (7)

3.137 4.912 4.918 3.598

c/a 4.9415 4.9436 4.9433 4.9415

Figure 2 compares the morphology of pristine and niobium modified NMC 811. The NMC 811 shows tens of micron sized spherically shaped particles, which consist of tightly packed nanosized primary particles with the length scale of ~ 500 nm (Figure 2 a and b). This type of “meat-ball” morphology is helpful to get the high tap density for the material in application. Before coating/substitution, the primary particles can be clearly seen and separated. After coating/ substitution, no change to the spherical shape and particle size (Figure 2c, 2e, 2g), but the boundary of the primary particles became blurred, looks like something melted and connected these particles together (Figure 2d, 2f, 2h). The energy dispersive spectrometer (EDS) mapping was performed for the coated samples (Figure S1) to determine the elemental distributions. It clearly demonstrates that existence of Nb in the particles. To verify that the Nb did not just exist as a coating layer on the surface but was also incorporated into the structure as suggested by the XRD analysis, one secondary particle of 1% Li-Nb-O coated/ substituted NMC 811 sample was cross-sectioned and characterized by TEM. Focus ion beam (FIB) technique was used to measure internal morphology and element distribution. As evidenced by the High-Angle Annular Dark-Field (HAADF) scanning transition electron microscopy (STEM) and EDS images shown in Figure 3, there is a nano-sized coating layer surrounding the tightly packed particle. The coating layer was made up of a series of tiny (few nano-sized) primary 8


Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


particles and elemental mapping shows mainly Nb and O elements in contrast to the coexistence of Ni, Mn, Co and O elements for the bulk core. This clearly indicates the formation of nano LiNb-O coating layer on the surface of the sample. However, with the 500°C annealing, some Nb ions may have penetrated into the upper layer of the bulk structure of the parent material, as suggested by the changed lattice parameters from the refined XRD patterns. In order to detect the penetration depth and concentration of Nb ions, point EDS analyses were performed along two lines from the surface to the core of the particle (Figure 4). The places detected for EDS were marked with a “+” and numbers in Figure 4 (a). Figure S2 represents the point spectrum, which demonstrate the presence and intensities of the Ni, Mn, Co and Nb elements. The changes of the Nb content with the distance from the particle surface along that two lines are shown in Figure 4 (b). 1~4 at% Nb existed in the initial tens of nanometers thickness, which mainly due to the LiNb-O coating layer on the surface, as represented in Figure 3. When going deeper towards the core of the particle, the content of Nb was dropped to below 0.5 at%. Finally, the Nb concentration maintained around 0.2 at% for a few hundred nanometers depth until dropping to zero. So not only forming the nano-coating layer (tens of nanometers) on the surface, Nb ions also penetrated into the upper layer of the particle for several hundred nanometers, giving a co-modification of coating and substitution to the parent material. This may explain the small change on lattice volume of LiNb-O modified samples. Figure S3 shows the atomic resolved HAADF images of 1% Li-Nb-O coated/ substituted NMC 811 sample. The clearly observed atoms marked by red circles between layers are heavier atoms which occupy the Li site, either Ni or Nb.

9



Page 10 of 24

3.2 Electrochemical Evaluations. To evaluate the effect of this Li-Nb-O co-modification of the 811 material, a series of electrochemical tests were carried out. Substituted Li-Nb-O materials are good ionic conductors, suggesting that the Li-Nb-O coating will not inhibit the diffusion of Li+ ions.35 Figure 5 displays the 1st charge-discharge voltage profiles of pristine NMC 811 and 1, 2 and 3% Li-Nb-O modified samples cycled in the voltage range of 2.8 ~ 4.6 V with a current rate of 0.1 C (1 C = 200 mA g−1). The discharge capacities increased from 216.9 mAh g−1 (NMC 811) to 226.2, 224.6, 219.1 mAh g−1 (1, 2 and 3% Li-Nb-O coated/substituted NMC 811), as summarized in Table 2. More importantly, the irreversible capacity losses were reduced for all the Nb modified materials, contributing to an improved coulombic efficiency. This helps to obtain a more reversible capacity from this material and can enhance the available energy density for practical application. Our past studies suggest that the large capacity loss in the 1st cycle for NMC materials is in part due to the much-reduced Li+ diffusivity for x >0.7 in LixMO2.36 These results suggest that the Nb ions are in some way modifying the lattice to improve the in-diffusion of the Li+ ions. Considering the different ionic radii and charge of the Nb ion compared to the Ni, Mn and Co ions, a strong distortion field might be introduced, reducing the migration of the Ni and oxygen ions and thereby minimizing phase changes near the surface. Table 2. Summary of charge and discharge capacities, irreversible capacities, coulombic efficiency for the first cycle of pristine NMC811 and 1%, 2% and 3% Li-Nb-O coated/ substituted NMC 811 samples. 1st cycle

Pristine NMC 811

Charge

Discharge

Irrev. Cap

242.0

216.9

25.1

10


Coul. Effic. 89.6%

Page 11 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1% Li-Nb-O

241.9

226.2

15.7

93.5%

2% Li-Nb-O

239.0

224.6

14.4

94.0%

3% Li-Nb-O

232.8

219.1

13.7

94.1%

It is these changes that perhaps lead to the improved capacity retention observed on extended cycling, shown in Figure 6 (a). The discharge capacities after 60 cycles at C/3 for pristine NMC 811 and 1, 2 and 3% Li-Nb-O modified samples are respectively 169.3, 175.7, 179.0 and 189.1 mAh g-1, with capacity retentions compared to the initial capacities of 81.6, 82.6, 84.2 and 89.6%. This improved cyclability could result from 1) protection from the surface Li-Nb-O coating layer, which reduces side reactions from the electrolyte. At the same time, it is expected to suppress the dissolution of transition metal ions during the cycling; and 2) the enhanced structural stability from Nb-substitution. Due to the much higher dissociation energy of Nb−O (753 kJ mol−1) compared to M-O (ΔHƒ298 (Ni-O) = 391.6 kJ mol-1, ΔHƒ298 (Co-O) = 368 kJ mol-1 and ΔHƒ298 (Mn-O) = 402 kJ mol-1)30-31, with Nb ions incorporated into the bulk structure, the bonding is enhanced, which will stabilize the structure against phase changes. Further, differential capacity (dQ/dV) curves (Figure S4) for these four electrodes verified this point. Compared with NMC 811, the retention of oxidation and reduction peaks was gradually improved in 1, 2 and 3% Li-Nb-O modified samples, demonstrating better structural stability after coating/substitution. Figure 6 (b) shows the rate capability of the various 811 materials. The Nb modified materials show enhanced capacity at all rates over the pristine material, with the 1% having the highest capacity at low rates and the 3% the highest capacity at high rates. Table S3 summarizes the weight ratio, mass loading, voltage range, electrochemical performance of different coating layer or doping element modified NMC

11



811, including Al2O3, ZrO2, Li3PO4+PPy, Li2TiO3, Ca doped or Cr, Mg substituted NMC 811. The Li-Nb-O modified NMC 811 gives the highest discharge capacity and coulombic efficiency for the first cycle of any of these reported materials for high cutoff voltage 4.6V. It is critical for commercialization, which will increase the energy density in full cells. In addition, the mass loading and the amount of binder/carbon is also a key parameter in the practical application. In this paper, the average mass loading of the electrode is 15 mg/cm2, the weight ratio of active material : binder : carbon is 90 : 5 : 5. Therefore, the high mass loading, high first cycle discharge capacity and high coulombic efficiency, better cycling and rate performance makes Li-Nb-O coated and substituted NMC 811 a highly promising candidate for a high energy density cathode in lithium ion battery. Conclusion NMC 811 was treated through a wet chemical method with lithium niobium ethoxide solution. With post annealing, besides a thin (tens of nanometers) Li-Nb-O layer coated on the particles, some Nb5+ ions diffused and penetrated into the bulk structure for a few hundred nanometers, which was verified by the lattice parameter changes in the XRD and further confirmed through EDS line scan on the cross section of particle. This reduced the 1st cycle capacity loss and improved the rate capability and capacity retention. Supporting Information Supporting Information is available free of charge on the ACS Publications website.

12


Page 12 of 24

Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Further refined lattice parameters of 3% Li-Nb-O modified NMC 811when Nb occupied in 3a sites (Li layer) or 3b sites (TM layer); Element mapping of 1%, 2% and 3% Li-Nb-O coated/substituted NMC 811; Representative EDS spectrum for points 1, 5, 6, and 7 in Figure 4(a); dQ/dV vs V plots of pristine NMC 811, 1%, 2% and 3% Li-Nb-O coated/ substituted NMC 811; Comparison of the weight ratio, mass loading, and electrochemical performance of different coating layer or doping element modified NMC 811. Author information ORCID Fengxia Xin: 0000-0003-4038-6334 Hui Zhou: 0000-0001-8739-963X Xiaobo Chen: 0000-0003-2943-2926 Mateusz Zuba: 0000-0002-3209-7922 Natalya Chernova: 0000-0002-4855-3224 Guangwen Zhou: 0000-0002-9243-293X M Stanley Whittingham: 0000-0002-5039-9334

Notes The authors declare no competing financial interest.

Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, through the Advanced Battery Materials Research Program (Battery500 Consortium). References 13



(1) Whittingham, M. S. Lithium Batteries and Cathode Materials. Chem. Rev. 2004, 104, 4271-4301. (2) Kim, J.; Lee, H.; Cha, H.; Yoon, M.; Park, M.; Cho, J. Prospect and Reality of Ni-Rich Cathode for Commercialization. Adv. Energy Mater. 2018, 8, 1702028. (3) Shi, J. L.; Xiao, D. D.; Ge, M.; Yu, X.; Chu, Y.; Huang, X.; Zhang, X. D.; Yin, Y. X.; Yang, X. Q.; Guo, Y. G. High-Capacity Cathode Material with High Voltage for Li-Ion Batteries. Adv. Mater. 2018, 30, 1705575. (4) Xu, J.; Hu, E.; Nordlund, D.; Mehta, A.; Ehrlich, S. N.; Yang, X. Q.; Tong, W. Understanding the Degradation Mechanism of Lithium Nickel Oxide Cathodes for Li-Ion Batteries. ACS Appl. Mat. Interfaces 2016, 8, 31677-31683. (5) Sun, Y. K.; Myung, S. T.; Park, B. C.; Prakash, J.; Belharouak, I.; Amine, K. High-Energy Cathode Material for Long-Life and Safe Lithium Batteries. Nat. Mater. 2009, 8, 320-324. (6) Shi, J.-L.; Qi, R.; Zhang, X.-D.; Wang, P.-F.; Fu, W.-G.; Yin, Y.-X.; Xu, J.; Wan, L.-J.; Guo, Y.-G. HighThermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries. ACS Appl. Mat. Interfaces 2017, 9, 42829-42835. (7) Kim, H.; Kim, M. G.; Jeong, H. Y.; Nam, H.; Cho, J. A New Coating Method for Alleviating Surface Degradation of LiNi0.6Co0.2Mn0.2O2 Cathode Material: Nanoscale Surface Treatment of Primary Particles. Nano Lett. 2015, 15, 2111-2119. (8) Schipper, F.; Erickson, E. M.; Erk, C.; Shin, J.-Y.; Chesneau, F. F.; Aurbach, D. Review-Recent Advances and Remaining Challenges for Lithium Ion Battery Cathodes. J. Electrochem. Soc. 2016, 164, A6220-A6228. (9) Dou, S. Review and Prospect of Layered Lithium Nickel Manganese Oxide as Cathode Materials for Li-ion Batteries. J. Solid State Electrochem. 2013, 17, 911-926. (10) Yi, T.-F.; Xie, Y.; Zhu, Y.-R.; Zhu, R.-S.; Ye, M.-F. High rate micron-sized niobium-doped LiMn1.5Ni0.5O4 as ultra high power positive-electrode material for lithium-ion batteries. J. Power Sources 2012, 211, 59-65. (11) Zhang, X. D.; Shi, J. L.; Liang, J. Y.; Yin, Y. X.; Zhang, J. N.; Yu, X. Q.; Guo, Y. G. Suppressing Surface Lattice Oxygen Release of Li-Rich Cathode Materials via Heterostructured Spinel Li4Mn5O12

14


Page 14 of 24

Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Coating. Adv. Mater. 2018, 30, 1801751. (12) Chen, Z.; Qin, Y.; Amine, K.; Sun, Y. K. Role of Surface Coating on Cathode Materials for Lithiumion Batteries. J. Mater. Chem. 2010, 20, 7606-7612. (13) Kim, S.; Cho, W.; Zhang, X.; Oshima, Y.; Choi, J. W. A Stable Lithium-rich Surface Structure for Lithium-rich Layered Cathode Materials. Nat. Commun. 2016, 7, 13598. (14) Li, C.; Zhang, H. P.; Fu, L. J.; Liu, H.; Wu, Y. P.; Rahm, E.; Holze, R.; Wu, H. Q. Cathode Materials Modified by Surface Coating for Lithium Ion Batteries. Electrochim. Acta 2006, 51, 3872-3883. (15) Cho, D.-h.; Yashiro, H.; Sun, Y.-K.; Myung, S.-T. Electrochemical Properties of Polyaniline-Coated Li-Rich Nickel Manganese Oxide and Role of Polyaniline Coating Layer. J. Electrochem. Soc. 2013, 161, A142-A148. (16) Chen, J.; Herricks, T.; Xia, Y. Polyol Synthesis of Platinum Nanostructures: Control of Morphology through the Manipulation of Reduction Kinetics. Angew. Chem. Int. Ed. 2005, 44, 2589-2592. (17) Liu, W.; Wang, M.; Gao, X. l.; Zhang, W.; Chen, J.; Zhou, H.; Zhang, X. Improvement of the Hightemperature, High-voltage Cycling Performance of LiNi0.5Co0.2Mn0.3O2 Cathode with TiO2 Coating. J. Alloys Compd. 2012, 543, 181-188. (18) Sun, Y. K.; Lee, M. J.; Yoon, C. S.; Hassoun, J.; Amine, K.; Scrosati, B. The Role of AlF3 Coatings in Improving Electrochemical Cycling of Li-enriched Nickel-manganese Oxide Electrodes for Li-ion Batteries. Adv. Mater. 2012, 24, 1192-1196. (19) Kim, H.; Byun, D.; Chang, W.; Jung, H.-G.; Choi, W. A Nano-LiNbO3 coating Layer and Diffusioninduced Surface Control towards High-performance 5 V Spinel Cathodes for Rechargeable Batteries. J. Mater. Chem. A 2017, 5, 25077-25089. (20) Jo, C.-H.; Cho, D.-H.; Noh, H.-J.; Yashiro, H.; Sun, Y.-K.; Myung, S. T. An Effective Method to Reduce Residual Lithium Compounds on Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 Active Material using a Phosphoric Acid Derived Li3PO4 Nanolayer. Nano Res. 2014, 8, 1464-1479. (21) Zhang, B.; Dong, P.; Tong, H.; Yao, Y.; Zheng, J.; Yu, W.; Zhang, J.; Chu, D. Enhanced Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 with Lithium-Reactive Li3VO4 Coating. J. Alloys Compd. 2017, 706, 198-204.

15



(22) Song, B.; Li, W.; Oh, S. M.; Manthiram, A. Long-Life Nickel-Rich Layered Oxide Cathodes with a Uniform Li2ZrO3 Surface Coating for Lithium-Ion Batteries. ACS Appl. Mat. Interfaces 2017, 9, 9718-9725. (23) Srur-Lavi, O.; Miikkulainen, V.; Markovsky, B.; Grinblat, J.; Talianker, M.; Fleger, Y.; Cohen-Taguri, G.; Mor, A.; Tal-Yosef, Y.; Aurbach, D. Studies of the Electrochemical Behavior of LiNi0.80Co0.15Al0.05O2 Electrodes Coated with LiAlO2. J. Electrochem. Soc. 2017, 164, A3266-A3275. (24) Meng, K.; Wang, Z.; Guo, H.; Li, X.; Wang, D. Improving the Cycling Performance of LiNi0.8Co0.1Mn0.1O2 by Surface Coating with Li2TiO3. Electrochim. Acta 2016, 211, 822-831. (25) Zhang, B.; Li, L.; Zheng, J. Characterization of Multiple Metals (Cr, Mg) Substituted LiNi0.8Co0.1Mn0.1O2 Cathode Materials for Lithium Ion Battery. J. Alloys Compd. 2012, 520, 190-194. (26) Chen, M.; Zhao, E.; Chen, D.; Wu, M.; Han, S.; Huang, Q.; Yang, L.; Xiao, X.; Hu, Z. Decreasing Li/Ni Disorder and Improving the Electrochemical Performances of Ni-Rich LiNi0.8Co0.1Mn0.1O2 by Ca Doping. Inorg. Chem. 2017, 56, 8355-8362. (27) Kim, U.-H.; Myung, S.-T.; Yoon, C. S.; Sun, Y.-K. Extending the Battery Life Using an Al-Doped Li[Ni0.76Co0.09Mn0.15]O2 Cathode with Concentration Gradients for Lithium Ion Batteries. ACS Energy Lett. 2017, 2, 1848-1854. (28) Schipper, F.; Dixit, M.; Kovacheva, D.; Talianker, M.; Haik, O.; Grinblat, J.; Erickson, E. M.; Ghanty, C.; Major, D. T.; Markovsky, B.; Aurbach, D. Stabilizing Nickel-Rich Layered Cathode Materials by a High-Charge Cation Doping Strategy: Zirconium-Doped LiNi0.6Co0.2Mn0.2O2. J. Mater. Chem. A 2016, 4, 16073-16084. (29) Weigel, T.; Schipper, F.; Erickson, E. M.; Susai, F. A.; Markovsky, B.; Aurbach, D. Structural and Electrochemical Aspects of LiNi0.8Co0.1Mn0.1O2 Cathode Materials Doped by Various Cations. ACS Energy Lett. 2019, 4, 508-516. (30) Zubair, M.; Li, G.; Wang, B.; Wang, L.; Yu, H. Electrochemical Kinetics and Cycle Stability Improvement with Nb Doping for Lithium-Rich Layered Oxides. ACS Appl. Energy Mater. 2018, 2, 503512. (31) Yang, Z.; Xiang, W.; Wu, Z.; He, F.; Zhang, J.; Xiao, Y.; Zhong, B.; Guo, X. Effect of Niobium Doping on the Structure and Electrochemical Performance of LiNi0.5Co0.2Mn0.3O2 Cathode Materials for Lithium

16


Page 16 of 24

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ion Batteries. Ceram. Int. 2017, 43, 3866-3872. (32) Schipper, F.; Bouzaglo, H.; Dixit, M.; Erickson, E. M.; Weigel, T.; Talianker, M.; Grinblat, J.; Burstein, L.; Schmidt, M.; Lampert, J.; Erk, C.; Markovsky, B.; Major, D. T.; Aurbach, D. From Surface ZrO2 Coating to Bulk Zr Doping by High Temperature Annealing of Nickel-Rich Lithiated Oxides and Their Enhanced Electrochemical Performance in Lithium Ion Batteries. Adv. Energy Mater. 2018, 8, 1701682. (33) Özer, N.; Lampert, C. M. Electrochemical Lithium Insertion in Sol-Gel Deposited LiNbO3 Films. Sol. Energy Mater. Sol. Cells 1995, 39, 367-375. (34) Hirano, S.; Kato, K. Formation of LiNbO3 Films by Hydrolysis of Metal Alkoxides. J. Non-Cryst. Solids 1988, 100, 538-541. (35) Glass, A.; Nassau, K.; Negran, T. Ionic Conductivity of Quenched Alkali Niobate and Tantalate Glasses. J. Appl. Phys. 1978, 49, 4808-4811. (36) Li, Z.; Ban, C.; Chernova, N. A.; Wu, Z.; Upreti, S.; Dillon, A.; Whittingham, M. S. Towards Understanding the Rate Capability of Layered Transition Metal Oxides LiNiyMnyCo1−2yO2. J. Power Sources 2014, 268, 106-112.

17



Figure 1. XRD patterns and Rietveld refinement results for (a) pristine NMC 811; (b) 1% Li-Nb-O; (c) 2% Li-Nb-O and (d) 3% Li-Nb-O modified NMC 811 samples.

18


Page 18 of 24

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. SEM images of pristine NMC 811 (a, b); 1% (c, d); 2% (e, f) and 3% (g, h) Li-Nb-O modified NMC 811.

19



Figure 3. (a-c) HAADF STEM images of a cross sectioned 1% Li-Nb-O modified NMC 811 sample by FIB with EDX mapping (d-j).

20


Page 20 of 24

Page 21 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. (a) TEM image showing the areas for point EDS for1% Li-Nb-O modified NMC 811 sample. Two lines (red and black) were crossed from the surface to the core of particle and some points were selected along the lines and marked with white cross-shaped “+” and numbers, which are the places tested for point EDS. (b) The change of Nb content along that two lines from the surface to the core of particle based on the point EDS data.

21



Figure 5. Charge and discharge curves of pristine NMC811, 1%, 2% and 3% Li-Nb-O coated/ substituted NMC 811 for the first cycle in the voltage range of 2.8 ~ 4.6V.

22


Page 22 of 24

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. Compare of (a) cycling and (b) rate performance of pristine NMC 811 and that after 1%, 2% and 3% Li-Nb-O coating/substitution in the voltage range 2.8 - 4.6 V.

23



Table of Content graphic


Page 24 of 24

substitution enhances the electrochemical

Recommend Documents