Morphology and electrochemical performance of Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode materials prepared with different metal sources (original) (raw)
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Journal of New Materials for Electrochemical Systems, 2014
In the present work, layered lithium rich Li(Li0.05Ni0.4Co0.3Mn0.25)O2 cathode materials were synthesized and its structural and electrical studies were analyzed. Layered Li(Li0.05Ni0.4Co0.3Mn0.25)O2 cathode material was prepared by sol-gel technique using citric acid as chelating agent. The prepared sample was characterized by X-ray diffraction, SEM-EDS studies. The crystallite size of the Li(Li0.05Ni0.4Co0.3Mn0.25)O2 cathode material was about 57 nm in which the diffusion path of lithium ion is effectively possible. The complexation behavior of prepared cathode material was analyzed by FT-IR spectroscopy. The electrical properties of the prepared Li(Li0.05Ni0.4Co0.3Mn0.25)O2 cathode material was studied by impedance and dielectric spectral analyzes. The maximum ionic conductivity of LiLi0.05Ni0.4Co0.3Mn0.25)O2 was found to be in the order of 10-3.4 S/cm. The dielectric analysis of cathode material confirms the non-Debye type behavior.
2006
The uniform layered Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 cathode material for lithium ion batteries was prepared by using (Ni 1/3 Co 1/3 Mn 1/3)(OH) 2 synthesized by a liquid phase co-precipitation method as precursor. The effects of calcination temperature and time on the structural and electrochemical properties of the Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 were systemically studied. XRD results revealed that the optimal prepared conditions of the layered Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 were 850 • C for 18 h. Electrochemical measurement showed that the sample prepared under the above conditions has the highest initial discharge capacity of 162.1 mAh g −1 and the smallest irreversible capacity loss of 9.2% as well as stable cycling performance at a constant current density of 16 mA g −1 between 3 and 4.3 V versus Li at room temperature.
Solid State Ionics, 2013
Layered Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 cathode materials have been prepared by sol-gel and co-precipitation methods. The structural, morphological and electrochemical properties of the materials were compared. The XRD patterns show that both the sol-gel and the co-precipitation method formed single phase materials with good layered characteristics. Rietveld refinement reveals some differences in cation disorder between the two materials, where the sample synthesized by the sol-gel method shows lower Li/Ni cation disorder. SEM and BET measurements show that the sol-gel sample consists of relatively less aggregated particles giving larger BET surface area compared to the co-precipitation sample. Electrochemical tests indicate that the material prepared by the sol-gel method has slightly better electrochemical properties, with an initial discharge capacity of 200 mAh·g −1 and capacity retention of 82.2% after 50 cycles at a cycling rate of 0.5 C, as well as better capability at 5 C. The improved performances of the sol-gel synthesized material may be attributed to the low Li/Ni disorder combined with high surface area, the latter increasing the interfacial contact area between the electrolyte and the active material. Effects of calcination conditions on the structure and electrochemical performance of the materials were also investigated. The electrochemical performance was improved by either increasing the O 2 concentration in the calcination atmosphere, or by increasing the flow rate of air, showing the potential of developing low-cost synthesis routes for high-quality cathode materials.
Transactions of Nonferrous Metals Society of China, 2011
The layered Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni 1/3 Co 1/3 Mn 1/3 ] 3 O 4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 structure, morphology and the electrochemical characteristics. The Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni 1/3 Co 1/3 Mn 1/3 ] 3 O 4 , and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA•h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA•h/g at a current density of 1 000 mA/g.
Journal of Power Sources, 2012
a b s t r a c t Microscale Li[Li 0.19 Ni 0.16 Co 0.08 Mn 0.57 ]O 2 powders with a high tap density were synthesized using [Ni 0.2 Co 0.1 Mn 0.7 ]O x precursor with a unique microstructure via coprecipitation in flowing air. The synthesized Li[Li 0.19 Ni 0.16 Co 0.08 Mn 0.57 ]O 2 powders were composed of spherical nanosized primary particles, which results in a high tap density due to the high packing of the spherical primary particles. When used as electrode in a lithium cell, Li[Li 0.19 Ni 0.16 Co 0.08 Mn 0.57 ]O 2 exhibits a very high gravimetric capacity of 263 mAh g −1 and a volumetric capacity of 956 mAh cm −3 , as well as an excellent rate capability delivering a discharge capacity of 202 mAh g −1 at a 2 C-rate. TEM analysis together with SEM observations show that the electrochemical performance of the Li[Li 0.19 Ni 0.16 Co 0.08 Mn 0.57 ]O 2 electrode is primarily governed by its microstructure.
2009
Li[Mn 0.5−x Cr 2x Ni 0.5−x ]O 2 (0 < 2x <0.2) (Mn/Ni = 1) cathode materials have been synthesized by a solution method. X-ray diffraction patterns of the as-prepared materials were fitted based on a hexagonal unit cell (␣-NaFeO 2 layer structure). The extent of Li/Ni intermixing decreased, and layering of the structure increased, with increasing Cr content. Electrochemical cycling of the oxides, at 30 • C in the 3-4.3 V range vs. Li/Li + , showed that the first charge capacity increased with increasing Cr content. However, maximum discharge capacity (∼143 mAh g −1 ) was observed for 2x = 0.05. X-ray absorption near edge spectroscopic (XANES) measurements on the K-edges of transition metals were carried out on pristine and delithiated oxides to elucidate the charge compensation mechanism during electrochemical charging. The XANES data revealed simultaneous oxidation of both Ni and Cr ions, whereas manganese remains as Mn 4+ throughout, and does not participate in charge compensation during oxide delithiation.
Effects of Lithium Source and Content on the Properties of Li-Rich Layered Oxide Cathode Materials
ChemEngineering
Lithium-rich layered oxide (LLO) are considered high-capacity cathode materials for next-generation lithium-ion batteries. In this study, LLO cathode materials were synthesized via the hydroxide coprecipitation method followed by a two-step lithiation process using different lithium contents and lithium sources. The effects of lithium content and lithium source on structure and electrochemical performance were investigated. This study demonstrated the clear impact of Li/TM ratio on electrochemical performance. Lower Li/TM ratio reduced the irreversible capacity loss in the first cycle and provided better cycling stability among all samples. The best results exhibited an initial discharge capacity of 279.65 mAh g−1 and reached a discharge capacity of 231.9 mAh g−1 (82.9% capacity retention) after 30 cycles. The sample using Li2CO3 as lithium source exhibits better electrochemical performance than the sample using LiOH as lithium source. Therefore, it is important to choose the approp...
Ionics, 2017
The enriched lithium ion containing layered oxide cathode materials Li(Li 0.05 Ni 0.7 -x Mn 0.25 Co x )O 2 have been prepared by using facile sol-gel technique. The phase purity and crystalline nature of the layered oxide cathodes have determined by X-ray diffraction analysis. Surface morphology and elemental analysis have been carried out using scanning electron microscopy with energy dispersive analysis by X-rays and HR-TEM. Cyclic voltammetry analysis of the lithium-enriched cathode material shows a well redox performance at electrode-electrolytic interface. The Li(Li 0.05 Ni 0.7 -x Mn 0.25 Co x )O 2 cathode shows the most promising electrochemical properties under different conditions in which an appropriate rising of discharge capacity (i.e., 167 mAh g -1 at 0.5 C) and cycling stability (i.e., capacity retention: 83% at 1 C after 20 cycles, cutoff voltage 2.8-4.5 V) at ambient temperature. These unique properties allow the effective use of these cathode materials as positive electrodes for the development of rechargeable lithium ion batteries.
Layered cathode materials Rate capability and cycle life a b s t r a c t The structure of the layered Li(Ni x Mn y Co 1ÀxÀy)O 2 in different amounts of x and y ranging between 0.2 and 0.6, have been synthesized and investigated by powder X-ray diffraction and electron microscopy techniques. In the current work spray pyrolysis was used to obtain spherical fine-sized morphology followed by heat treatment to obtain better elec-trochemical activity. The precursor powders were prepared using aqueous solution via spray pyrolysis. Synthesized samples were then heat treated at 850 C. X-Ray Diffraction patterns of synthesized cathode materials showed well defined splitting of [006]/[102] and [108]/[110] diffraction peaks indicating layered structure and good hexagonal ordering. In this study, Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 (111), Li(Ni 0.2 Mn 0.2 Co 0.6)O 2 (226), Li(Ni 0.6 Mn 0.2 Co 0.2)O 2 (622) and Li(Ni 0.2 Mn 0.6 Co 0.2)O 2 (262) were synthesized. The morphology of cathode materials was investigated by scanning electron microscopy and average crystallite size was measured to be between 0.2 mm and 0.6 mm. Moreover, particle sizes were verified by particle size measurement and transmission electron microscopy techniques. The electrochemical cells were cycled at 0.1C and 0.3C rate (1C ¼ 170 mAhg À1) and it was found that fast charging and discharging behavior were not sufficient. However, capacity retention after 32 cycles were determined to be 85.3% and 90%, for (111) and (262) samples, respectively.
ACS Applied Materials & Interfaces, 2020
Morphology dependent electrochemical performance of Li-rich layered oxide (LLO) cathode with the composition Li1.23Mn0.538Ni0.117Co0.114O2 in three different microstructural forms namely, randomly shaped particles, platelets and nanofibers are synthesized through solid-state reaction (SSR-LLO), hydrothermal method (HT-LLO) and electrospinning process (ES-LLO), respectively. Even though the cathodes possess different morphology, structurally they are identical. The elemental dispersion studies using energy dispersive X-ray spectroscopy (EDS) mapping in scanning transmission electron microscopy show uniform distribution of elements. However, SSR-LLO and ES-LLO nanofibers show slight Co rich regions. The electrochemical studies of LLO cathodes are evaluated in terms of charging/discharging, Crate capability and