Next Article in Journal
Microstructural Evolution of Intermetallic Compound Formed in Boron Steel Hot-Dipped in Al–7%Ni Alloy
Next Article in Special Issue
Novel Recycling Method for Boron Removal from Silicon by Thermal Plasma Treatment Coupled with Steam and Hydrogen Gases
Previous Article in Journal
Fatigue Damage
Previous Article in Special Issue
Environmental Compatibility of Lightweight Aggregates from Mine Tailings and Industrial Byproducts
Article Menu

Export Article

Metals 2017, 7(10), 395; doi:10.3390/met7100395

Article
The Effects of Incorporated Sn in Resynthesized Ni-Rich Cathode Materials on Their Lithium-Ion Battery Performance
Ga-hee Kang 1,2, Ko-woon Lee 2, Kyungjung Kwon 1,*Orcid and Junho Song 2,*Orcid
1
Department of Energy & Mineral Resources Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea
2
Korea Electronics Technology Institute, 25 Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, Korea
*
Correspondence: Tel.: +82-2-3408-3947 (K.K.)
Received: 29 August 2017 / Accepted: 21 September 2017 / Published: 26 September 2017

Abstract

:
LiNixCoyMnz (NCM), one of the most promising candidates for high-capacity cathode materials in Li-ion batteries (LIBs), is synthesized with various amounts of Sn. Sn-incorporated NCM from the resynthesis of NMC in leach liquor containing Sn from spent LIBs is characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, particle strength tests, and electrochemical tests. Sn-incorporated NCM has a globular form, and the uniform distribution of Sn inside cathode materials is confirmed. As Sn is introduced, the (003) diffraction peak tends to shift to a smaller angle and particle breaking strength increases. It is found that Sn-incorporated cathode active materials have better cycle performance and rate capability than pristine cathode active material although the discharge capacity slightly decreases. Because there is a trade-off between decreased discharge capacity and improved cycling and rate performance, the incorporation of Sn in resynthesized NCM should be carefully designed and conducted.
Keywords:
lithium-ion battery; cathode; recycling; Sn

1. Introduction

Li-ion batteries (LIBs) are the most popular type of rechargeable batteries, as they have high energy, high power density, low memory effect, and low self-discharge rate [1]. The usage of LIBs has remarkably extended to electrical appliances, portable electronics, electric vehicles, and power grids [2]. Accordingly, a large number of spent LIBs have surely been generated due to their limited life spans and the rapid rate at which electronic products are updated [3].
In general, an LIB is composed of an anode (e.g., graphite, tin, and silicon), a cathode (e.g., LiCoO2, LiMn2O4, and LiNixCoyMnzO2 (NCM)), current collectors, an organic electrolyte with Li-containing salts, and a separator [4,5]. When spent LIBs are disposed of in a landfill or burned, heavy metals seep into groundwater, and a large volume of poisonous gas is generated. This situation could result in long-term environmental and public health problems [6]. Moreover, spent LIBs contain valuable metals such as cobalt, nickel, manganese, and lithium. Therefore, the recycling of spent LIBs could bring economic profits as well as environmental benefits [7]. Various techniques for recycling spent LIBs have been suggested in several papers [8,9,10]. Above all, the hydrometallurgical process is the most well-established technology for recycling valuable metals from LIBs and has many benefits, such as the complete recovery of metals with high purity, low energy consumption, and low gas emission [11,12,13]. Metal species of spent LIBs are typically leached by HCl, HNO3, or H2SO4, with hydrogen peroxide used as a reducing agent in many cases [14,15,16,17]. Most metal species are expected to dissolve with acidic leaching reagents. Tin from anodes also dissolves with cathode metal species during the leaching process.
Cathode active materials such as NCM can be resynthesized from the leach liquor of spent LIBs by the co-precipitation method. The effect of impurities in resynthesized LIB cathode active materials on their electrochemical performance needs to be studied. The effect of Mg or Al impurities in leach liquor from spent LIBs on the electrochemical performance of resynthesized cathode active materials has been investigated [18,19]. However, there has been no study on the effect of Sn impurity on the LIB performance of resynthesized Ni-rich NCM, which has been highlighted as the most promising candidate for high-capacity cathode materials in LIBs due to their high energy density [20,21]. In this paper, we synthesized NCM with various amounts of Sn, simulating the resynthesis of NMC in leach liquor containing Sn from spent LIBs, and the effect of Sn on the LIB performance of NCM was investigated.

2. Materials and Methods

2.1. Synthesis of Materials

Precursors (Ni0.82Co0.12Mn0.06(OH)2) were synthesized by the hydroxide co-precipitation method, which is widely used to produce homogeneous compounds. A mixture of chelating agent (NH4OH), NaOH solution, and aqueous solutions of transition metal salts was pumped into a continuously stirred tank reactor. The resultant precursor slurry was filtered and washed multiple times, and then dried in an oven at 80 °C. Tin was incorporated by mixing dried precursors (Ni0.82Co0.12Mn0.06(OH)2, 10 g) and tin(II) ethoxide (0.05 g, 0.1 g, 0.15 g, and 0.3 g) in isopropyl alcohol (100 mL) at 60 °C. The final Ni-rich cathode active materials (Li[Ni0.82Co0.12Mn0.06]1−xSnxO2 (x = 0, 0.004, 0.008, 0.012, 0.024)) were prepared by calcinating a mixture of Sn-incorporated precursors and the stoichiometric amount of LiOH at 800 °C (heating rate: 3 °C min−1) in an O2 atmosphere for 24 h. Hereinafter, we denote the cathode active materials by their Sn wt %. Namely, we refer to Li[Ni0.82Co0.12Mn0.06]1−xSnxO2 (x = 0, 0.004, 0.008, 0.012, 0.024) as pristine, Sn 0.5 wt %, Sn 1.0 wt %, Sn 1.5 wt %, and Sn 3.0 wt %, respectively. The synthesis procedure is summarized in Scheme 1.

2.2. Physicochemical and Electrochemical Characterizations

The crystal structure of samples was obtained by X-ray diffraction (XRD, Panalytical Emprean, Eindhoven, The Netherlands). The particle morphology of samples was observed using a scanning electron microscope (SEM, JSM-6380, JEOL Ltd., Tokyo, Japan) and energy dispersive X-ray spectroscopy (EDS, JEM 2300, Oxford Ltd., Abingdon, UK). The combined bond state of samples was obtained using X-ray photoelectron spectra (XPS, K-alpha, Thermo, Waltham, MA, USA). The particle hardness of samples was measured using a particle compression tester (PCT, MCT-W500-EGA, Shimadzu, Kyoto, Japan).
Charge–discharge tests were performed using CR2032-type coin cells. Cathodes were prepared by mixing the cathode active materials, carbon black (Super-P), and polyvinylidene fluoride (KF1100) binder in a mass ratio of 95:2:3 respectively. Cells were assembled with the prepared cathodes, lithium metal as an anode, polyethylene film as a separator, and 1 M LiPF6 in a mixture of ethylene carbonate and ethyl methyl carbonate (1:2, volume ratio) as an electrolyte. The cells were cycled from 3.0 to 4.3, 4.4, or 4.5 V (vs. Li/Li+) at different C-rates at room temperature or at a high temperature (60 °C). Unless stated otherwise, potential values are based on Li/Li+ potential.

3. Results and Discussion

3.1. Physicochemical Characterizations of Sn-Incorporated Ni-Rich Cathode Active Materials

The SEM images in Figure 1 show the morphology of the Sn-incorporated precursors and the cathode active materials. The secondary particles of the precursors seem to have a quasi-spherical shape, and each secondary particle is an agglomerate of fine acicular primary particles. Similarly, the secondary particles of the cathode active materials have a quasi-spherical shape, and each secondary particle is an agglomerate of granular primary particles, which are thicker than those of the precursors. The average secondary particle sizes of the precursors and the cathode active materials are similar at around 9 μm. There is no distinct correlation between the secondary particle size and the Sn content. Incidentally, Figure S1 represents the cross section of the cathode active materials indicating that the Sn content would not affect the compactness of particles. The distribution of elements in the cathode active materials was looked into by using EDS mapping. Figure 2, which shows the results of the EDS mapping for Sn 3.0 wt %, is a representative result indicating the homogeneous distribution of Ni, Co, Mn, and Sn. The EDS cross-section mapping of the pristine, Sn 0.5 wt %, Sn 1.0 wt %, and Sn 1.5 wt % samples is displayed in Figure S2.
The crystal structures of the cathode active materials were characterized using XRD as shown in Figure 3a. Two representative peak splitting doublets, (006)/(102) and (108)/(110), were clearly observed, which indicates that a well-ordered layered structure was constructed during the calcination process [22]. In addition, no peaks other than Li[Ni0.82Co0.12Mn0.06]O2 were observed even when no less than 3.0 wt % Sn was introduced to the pristine sample, which would mean that all Sn atoms were incorporated into the crystal structure of Li[Ni0.82Co0.12Mn0.06]O2 without forming secondary phases. Figure 3b shows the magnified (003) peak region in the 2θ around 19°. The peak tends to shift toward lower angles with the Sn content, suggesting an expanded d-spacing according to Bragg’s law. This peak shift is in line with increases in lattice parameters in a- and c-directions with increasing the Sn content, as shown in Table 1. These structural characteristics can be explained by a larger ionic radius of Sn4+ (0.71 Å) than that of Co3+ (0.62 Å), Ni2+ (0.69 Å), Ni3+ (0.56 Å), and Mn4+ (0.53 Å) [23]. Incidentally, the peak shift and the corresponding lattice expansion are not proportional to the Sn content beyond 1.0 wt %, the origin of which is not clear at this stage. There is a possibility of SnO2 formation in adding Sn higher than 1.5 wt % to Li[Ni0.82Co0.12Mn0.06]O2 although we did not observe any tangible XRD peak for SnO2 [23]. However, the Sn content in NCM was measured by inductively coupled plasma mass spectrometry, which showed that Li[Ni0.82Co0.12Mn0.06]1−xSnxO2 contains the designed value of Sn up to 3.0 wt %.
In order to investigate the oxidation states of nickel, cobalt, manganese, and tin, an XPS measurement was performed. The wide scan spectrum indicates the presence of Co, Ni, Mn, O, and Sn (Figure S3). Figure 4 shows that the binding energies of Co, Ni, Mn, and Sn belong to Co3+, Ni2+, Ni3+, Mn4+, and Sn4+. The Co 2p spectrum has two main peaks of 2p3/2 at 780 eV and 2p1/2 at 795 eV. For Ni 2p, 2p3/2, and 2p1/2 are located at 854 eV and 872 eV, respectively. While the main peaks of Mn 2p are 2p3/2 at 642 eV and 2p1/2 at 653 eV, the peak position of Sn 3d5/2 and 3d3/2 is 486 eV and 494 eV, which would represent the Sn4+ cations [22,24]. In the O 1s spectra, two peaks are observed characteristic of O2− anions belonging to the crystalline network and weakly absorbed surface species [25].
The breaking strength of cathode active material particles depending on the Sn content was measured as in Table 2. When an indenter of particle compression tester applies force to a particle in the vertical direction, the breaking strength is calculated at breaking point using two parameters as follows:
σ t = 2 . 8 P π D 2
where σt is the breaking strength, P is the force at breaking point, and D is the diameter of the particle. The breaking strength of the Sn-incorporated samples in Table 2 is higher than the pristine sample, and the highest breaking strength was observed at Sn 1.0 wt %. Cathode active material particles that have high breaking strength are expected to show excellent cycleability because high breaking strength restrains structural deformation, particularly at a high voltage and high C-rate [26,27].

3.2. Electrochemical Characterizations of Sn-Incorporated Ni-Rich Cathode Active Materials

Figure 5 shows the first charge–discharge profiles of the cathode active materials at a constant current density of 0.1 C between 3.0 and 4.3 V at room temperature. As shown in Table 3, the discharge capacity of the Sn-incorporated cathode active materials is slightly decreased compared to the pristine cathode active material because Sn4+ is inactive during the charge–discharge process.
To evaluate rate performance, the cathode active materials were tested at various C-rates between 3.0 and 4.3 V, and their discharge capacities are presented in Figure 6. The Sn-incorporated cathode active materials have higher discharge capacities (Sn 0.5 wt %: 126.65 mAh g−1, Sn 1.0 wt %: 148.98 mAh g−1, Sn 1.5 wt %: 147.90 mAh g−1, and Sn 3.0 wt %: 147.61 mAh g−1) than the pristine cathode active material (116.80 mAh g−1) at 5 C. It is noticeable that the Sn-incorporated cathode active materials have low overpotential compared to the pristine cathode active material at 5 C (Figure 7). Incorporated Sn could reduce polarization at the interface between the cathode and electrolyte [25]. As previously mentioned, incorporated Sn4+ ions that have a larger ionic radius than other ions allow lattice volume expansion, which enhances Li+ intercalation/deintercalation.
As mentioned previously in Table 2, the cycleability of the Sn-incorporated samples is expected to be superior to that of the pristine sample. Accordingly, the cycleability of the cathode active materials under various conditions was investigated in Figure 8 (to 4.3/4.4/4.5 V at room temperature) and Figure 9 (to 4.3 V at 60 °C). Under the mild charge–discharge condition (to 4.3 V at room temperature) in Figure 8a, the discharge capacities of the Sn-incorporated samples are maintained from the 2nd to 50th cycle, whereas that of the pristine sample continues to decrease slowly. Meanwhile, the discharge capacities of the Sn-incorporated samples also start to decrease at higher charge cutoff voltages, but the degree of capacity decrease of the pristine sample is much higher in Figure 8b,c. Increasing charge cutoff voltage for high capacity would incur structural instability owing to excessive Li-ion extraction [28]. Because the incorporation of Sn strengthens the cathode active material particles as evidenced by the higher breaking strength value, the Sn-incorporated samples can maintain the stability of the crystal structure and have enhanced cycling performance over the pristine sample. Regarding the effect of operating temperature, a high temperature causes the degradation of cycle performance because of electrolyte side reactions [29]. While the discharge capacities of the Sn-incorporated samples at room temperature are maintained (Figure 8a), the high temperature charge–discharge indeed aggravates the cycling performance as shown in Figure 9. However, a trend that the Sn-incorporated samples have improved cycling performance relative to the pristine sample was again observed at high temperatures, which can be attributed to the high breaking strength of the Sn-incorporated samples.

4. Conclusions

The physicochemical characterizations of Sn-incorporated NCM were conducted using SEM, EDS mapping, XRD, XPS, and the breaking strength of particles. The XRD results demonstrated that the (003) peak tends to shift toward lower angles with increases in Sn content, which is in line with a larger ionic radius of Sn4+ (0.71 Å) rather than that of Co3+ (0.62 Å), Ni2+ (0.69 Å), Ni3+ (0.56 Å), and Mn4+ (0.53 Å). The breaking strength of the Sn-incorporated samples is higher than the pristine sample with the highest breaking strength observed at Sn 1.0 wt %. While the discharge capacity of the Sn-incorporated samples is slightly decreased compared to the pristine sample, the Sn-incorporated samples have low overpotential compared to the pristine cathode active material at high C-rates. A trend that the Sn-incorporated samples have improved cycling performance relative to the pristine sample was observed, which can be attributed to the high breaking strength of the Sn-incorporated samples.

Supplementary Materials

The following are available online at http://www.mdpi.com/2075-4701/7/10/395/s1, Figure S1: SEM cross-section images of the cathode active materials; Figure S2: EDS cross-section mapping of the cathode active materials: (a) pristine, (b) Sn 0.5 wt %, (c) Sn 1.0 wt %, and (d) Sn 1.5 wt %; Figure S3: Wide XPS of the cathode active materials.

Acknowledgments

This study was supported by the R&D Center for Valuable Recycling (Global-Top R&BD Program) of the Ministry of Environment. Junho Song was supported by a grant from the Fundamental R&D Program for Technology of World Premier Materials funded by the Ministry of Knowledge Economy, Republic of Korea (Project number: 10037921).

Author Contributions

Ga-hee Kang and Junho Song conceived and designed the experiments; Ga-hee Kang performed the experiments and analyzed the data; Ko-woon Lee provided technical support; Ga-hee Kang and Kyungjung Kwon co-wrote the paper.

Conflicts of Interest

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Tarascon, J.M.; Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature 2010, 414, 359–367. [Google Scholar] [CrossRef] [PubMed]
  2. Chen, X.P.; Zhou, T.; Kong, J.R.; Fang, H.X.; Chen, Y.B. Separation and recovery of metal values from leach liquor of waste lithium nickel cobalt manganese oxide based cathodes. Sep. Purif. Technol. 2015, 141, 76–83. [Google Scholar] [CrossRef]
  3. Cai, G.Q.; Fung, K.Y.; Ng, K.M.; Wibowo, C. Process development for the recycle of spent lithium ion batteries by chemical precipitation. Ind. Eng. Chem. Res. 2014, 53, 18245–18259. [Google Scholar] [CrossRef]
  4. Zou, H.Y.; Gratz, E.; Apelian, D.; Wang, Y. A novel method to recycle mixed cathode materials for lithium ion batteries. Green Chem. 2013, 15, 1183–1191. [Google Scholar] [CrossRef]
  5. Park, C.M.; Kim, J.H.; Kim, H.S.; Sohn, H.J. Li-alloy based anode materials for Li secondary batteries. Chem. Soc. Rev. 2010, 39, 3115–3141. [Google Scholar] [CrossRef] [PubMed]
  6. Chagnes, A.; Pospiech, B. A brief review on hydrometallurgical technologies for recycling spent lithium-ion batteris. J. Chem. Technol. Biotechnol. 2013, 88, 1191–1199. [Google Scholar] [CrossRef]
  7. Kang, J.; Senanayake, G.; Sohn, J.; Shin, S.M. Recovery of cobalt sulfate from spent lithium ion batteries by reductive leaching and solvent extraction with Cyanex 272. Hydrometallurgy 2010, 100, 168–171. [Google Scholar] [CrossRef]
  8. Meshram, P.; Pandey, B.D.; Mabkhand, T.R. Extraction of lithium from primary and secondary sources by pre-treatment, leaching and separation: A comprehensive review. Hydrometallurgy 2014, 150, 192–208. [Google Scholar] [CrossRef]
  9. Ordones, J.; Gago, E.J.; Girard, A. Processes and technologies for the recycling and recovery of spent lithium-ion batteries. Energy Rev. 2016, 60, 195–205. [Google Scholar]
  10. Zeng, X.; Li, J.; Singh, N. Recycling of spent lithium-ion battery: A critical review. Environ. Sci. Technol. 2014, 44, 1129–1165. [Google Scholar] [CrossRef]
  11. Huang, K.; Li, J.; Xu, Z. A novel process for recovering valuable metals from waste nickel-cadmium batteries. Environ. Sci. Technol. 2009, 43, 8974–8978. [Google Scholar] [CrossRef] [PubMed]
  12. Pietrelli, L.; Bellomo, B.; Fontana, D.; Montereali, M. Characterization and leaching of NiCd and NiMH spent batteries for the recovery of metals. Waste Manag. 2005, 25, 221–226. [Google Scholar] [CrossRef] [PubMed]
  13. Ku, H.; Jung, Y.; Jo, M.; Park, S.; Kim, S.; Yang, D.; Rhee, K.; An, E.-M.; Sohn, J.; Kwon, K. Recycling of spent lithium-ion battery cathode materials by ammoniacal leaching. J. Hazard. Mater. 2016, 313, 138–146. [Google Scholar] [CrossRef] [PubMed]
  14. Jha, M.K.; Kumari, A.; Jha, A.K.; Kumar, V.; Hait, J.; Pandey, B.D. Recovery of lithium and cobalt from waste lithium ion batteries of mobile phone. Waste Manag. 2013, 33, 1890–1897. [Google Scholar] [CrossRef] [PubMed]
  15. Lee, C.K.; Rhee, K.I. Reductive leaching of cathodic active materials from lithium ion battery wastes. Hydrometallurgy 2003, 68, 5–10. [Google Scholar] [CrossRef]
  16. Nan, J.M.; Han, D.M.; Yang, M.J.; Cui, M.; Hou, X.L. Recovery of metal values from a mixture of spent lithium-ion batteries and nickel-metal hydride batteries. Hydrometallurgy 2006, 84, 75–80. [Google Scholar] [CrossRef]
  17. Shin, S.M.; Kim, N.H.; Sohn, J.S.; Yang, D.H.; Kim, Y.H. Development of a metal recovery process from Li-ion battery wastes. Hydrometallurgy 2005, 79, 172–181. [Google Scholar] [CrossRef]
  18. Krüger, S.; Hanisch, C.; Kwade, A.; Winter, M.; Nowak, S. Effect of impurities caused by a recycling process on the electrochemical performance of Li[Ni0.33Co0.33Mn0.33]O2. J. Electroanal. Chem. 2014, 726, 91–96. [Google Scholar]
  19. Weng, Y.; Xu, S.; Huang, G.; Jiang, C. Synthesis and performance of Li[(Ni1/3Co1/3Mn1/3)1−xMgx]O2 prepared from spent lithium ion batteries. J. Hazard. Mater. 2013, 246, 163–172. [Google Scholar] [CrossRef] [PubMed]
  20. Lim, J.M.; Hwang, T.; Kim, D.; Park, M.S.; Cho, K.; Cho, M. Intrinsic origins of crack generation in Ni-rich LiNi0.8Co0.1Mn0.1O2 layered oxide cathode material. Sci. Rep. 2017, 8, 39669. [Google Scholar] [CrossRef] [PubMed]
  21. Shu, J.; Ma, R.; Shao, L.Y.; Shui, M.; Wu, K.G.; Lao, M.M.; Wang, D.J.; Long, N.B.; Ren, Y.L. In-situ X-ray diffraction study on the structural evolutions of LiNi0.5Co0.3Mn0.2O2 in different working potential windows. J. Power Sources 2014, 245, 7–18. [Google Scholar] [CrossRef]
  22. Chen, Z.; Wang, J.; Chao, D.L.; Baikie, T.; Bai, L.Y.; Chen, S.; Zhao, Y.L.; Sum, T.C.; Lin, J.Y.; Shen, Z.X. Hierarchical porous LiNi1/3Co1/3Mn1/3O2 nano-/micro spherical cathode material: Minimized cation mixing and improved Li+ mobility for enhanced electrochemical performance. Sci. Rep. 2016, 6, 25771. [Google Scholar] [CrossRef] [PubMed]
  23. Ma, X.L.; Wang, C.W.; Cheng, J.G.; Sun, J.T. Effects of Sn doping on the structural and electrochemical properties of LiNi0.8Co0.2O2 cathode materials. Solid State Ion. 2007, 178, 125–129. [Google Scholar] [CrossRef]
  24. Ren, H.B.; Mu, X.M.; Huang, Y.H.; Li, Z.J.; Wang, Y.H.; Cai, P.; Peng, Z.H.; Zhou, Y.H. Effects of Sn doping on electrochemical characterizations of Li[Ni1/3Co1/3Mn1/3]O2 cathode material. Ionics 2010, 16, 497–502. [Google Scholar] [CrossRef]
  25. Zhao, Y.J.; Xia, M.H.; Hu, X.S.; Zhao, Z.K.; Wang, Y.; Lv, Z. Effects of Sn doping on the structural and electrochemical properties of Li1.2Ni0.2Mn0.8O2 Li-rich cathode materials. Electrochim. Acta 2015, 174, 1167–1174. [Google Scholar] [CrossRef]
  26. Jonsen, P.; Haggblad, H.A.; Sommer, K. Tensile strength and fracture energy of pressed metal powder by diametral compression test. Powder Technol. 2007, 176, 148–155. [Google Scholar] [CrossRef]
  27. Araki, K.; Taguchi, N.; Sakaebe, H.; Tatsumi, K.; Ogumi, Z. Electrochemical properties of Li Ni1/3Co1/3Mn1/3O2 cathode material modified by coating with Al2O3 nanoparticles. J. Power Sources 2014, 269, 236–243. [Google Scholar] [CrossRef]
  28. Zhang, X.H.; Yu, C.; Huang, X.D.; Zheng, J.; Guan, X.F.; Luo, D.; Li, L.P. Novel composites Li[LixNi0.34−xMn0.47Co0.19]O2 (0.18 ≤ x ≤ 0.21): Synthesis and application as high-voltage cathode with improved electrochemical performance for lithium ion batteries. J. Mater. Chem. 2012, 81, 233–238. [Google Scholar] [CrossRef]
  29. Darma, M.S.D.; Lang, M.; Kleiner, K.; Mereacre, L.; Liebau, V.; Fauth, F.; Bergfeldt, T.; Ehrenberg, H. The influence of cycling temperature and cycling rate on the phase specific degradation of a positive electrode in lithium ion batteries: A post mortem analysis. J. Power Sources 2016, 327, 714–725. [Google Scholar] [CrossRef]
Scheme 1. The synthesis procedure of the cathode active materials.
Scheme 1. The synthesis procedure of the cathode active materials.
Metals 07 00395 sch001
Figure 1. SEM images of the Sn-incorporated precursors ((a) pristine, (b) Sn 0.5 wt %, (c) Sn 1.0 wt %, (d) Sn 1.5 wt %, and (e) Sn 3.0 wt %) and the cathode active materials ((f) pristine, (g) Sn 0.5 wt %, (h) Sn 1.0 wt %, (i) Sn 1.5 wt %, and (j) Sn 3.0 wt %).
Figure 1. SEM images of the Sn-incorporated precursors ((a) pristine, (b) Sn 0.5 wt %, (c) Sn 1.0 wt %, (d) Sn 1.5 wt %, and (e) Sn 3.0 wt %) and the cathode active materials ((f) pristine, (g) Sn 0.5 wt %, (h) Sn 1.0 wt %, (i) Sn 1.5 wt %, and (j) Sn 3.0 wt %).
Metals 07 00395 g001
Figure 2. EDS (energy dispersive X-ray spectroscopy) cross-section mapping of the Sn 3.0 wt % cathode active materials.
Figure 2. EDS (energy dispersive X-ray spectroscopy) cross-section mapping of the Sn 3.0 wt % cathode active materials.
Metals 07 00395 g002
Figure 3. XRD patterns of the cathode active materials: (a) full spectrum and (b) expanded view around (003).
Figure 3. XRD patterns of the cathode active materials: (a) full spectrum and (b) expanded view around (003).
Metals 07 00395 g003
Figure 4. XPS of the cathode active materials.
Figure 4. XPS of the cathode active materials.
Metals 07 00395 g004
Figure 5. Initial charge–discharge profiles of the cathode active materials.
Figure 5. Initial charge–discharge profiles of the cathode active materials.
Metals 07 00395 g005
Figure 6. Discharge capacity of the cathode active materials at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and 5 C.
Figure 6. Discharge capacity of the cathode active materials at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and 5 C.
Metals 07 00395 g006
Figure 7. Discharge profile of the cathode active materials at 5 C.
Figure 7. Discharge profile of the cathode active materials at 5 C.
Metals 07 00395 g007
Figure 8. Cycling performance of the cathode active materials at room temperature from 3.0 to (a) 4.3, (b) 4.4, or (c) 4.5 V (0.1 C for the 1st cycle and 0.5 C from the 2nd cycle).
Figure 8. Cycling performance of the cathode active materials at room temperature from 3.0 to (a) 4.3, (b) 4.4, or (c) 4.5 V (0.1 C for the 1st cycle and 0.5 C from the 2nd cycle).
Metals 07 00395 g008aMetals 07 00395 g008b
Figure 9. Cycling performance of the cathode active materials at high temperature (60 °C) and 0.5 C (0.1 C for the 1st cycle and 0.5 C from the 2nd cycle).
Figure 9. Cycling performance of the cathode active materials at high temperature (60 °C) and 0.5 C (0.1 C for the 1st cycle and 0.5 C from the 2nd cycle).
Metals 07 00395 g009
Table 1. Lattice parameters of the cathode active materials.
Table 1. Lattice parameters of the cathode active materials.
Lattice ParameterPristineSn 0.5 wt %Sn 1.0 wt %Sn 1.5 wt %Sn 3.0 wt %
a [Å]2.867692.867942.870312.870072.86819
c [Å]14.1371614.1440514.1961214.1766714.14698
Table 2. Breaking strength of the cathode active material particles.
Table 2. Breaking strength of the cathode active material particles.
SampleForce P (mN)Diameter D (µm)σt (MPa)
Pristine8.299.3983.86
Sn 0.5 wt %12.129.87110.98
Sn 1.0 wt %12.348.91138.49
Sn 1.5 wt %13.7511.4793.16
Sn 3.0 wt %10.5210.2489.43
Table 3. Initial charge–discharge capacity of the cathode active materials.
Table 3. Initial charge–discharge capacity of the cathode active materials.
SampleCharge (mAh g−1)Discharge (mAh g−1)
Pristine225.98199.92
Sn 0.5 wt %224.03193.38
Sn 1.0 wt %221.39187.39
Sn 1.5 wt %217.43190.38
Sn 3.0 wt %216.80189.74
Metals EISSN 2075-4701 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top