Electrochemical Properties Of Li1 Research Articles

Modulating electrochemical properties by Fe3+ doping for cobalt-free Li1.2Ni0.26Mn0.54O2 cathode material

The widespread application of Li-rich cathode material is restricted due to capacity attenuation and poor rate capability caused by crystal structure transformation and irreversible lattice oxygen escape during cycling. The Fe3+-doped effects on lattice structures and electrochemical properties of Li1.2Ni0.26−xMn0.54FexO2 (x = 0, 0.03, 0.05 and 0.08) cathode materials fabricated by a sol-gel method are systematically studied in this paper. Doped materials exhibit good electrochemical performance such as high discharge specific capacity and capacity retention at high current density rates. Li1.2 Ni0.21Mn0.54Fe0.05O2 can supply a specific capacity of 190.7 mAh g−1 with 73.6 % capacity retention after 100th cycle at 2 C, and rate capacities of 230.6, 208.5, 193.1, 172.1 and 105.6 mAh g−1 at 0.1, 0.5, 1, 2 and 5 C, respectively. It is attributed to the enhanced structural stability, enlarged Li layer spacing, intensive interaction between transition metals and oxygen, less manganese disproportionation and oxygen release and increased Li+ diffusion coefficient by Fe3+ doping.

Effects of Copper Doping in High‐Rate, Lithium Manganese‐Rich Layered Oxide Cathodes for Lithium‐Ion Batteries

AbstractLithium manganese‐rich layered oxides are promising cathode materials for lithium‐ion batteries due to their high discharge capacity, but they suffer from capacity fading and poor rate performance. Herein we report on the physicochemical and electrochemical properties of Li1.15Mn0.7Ni0.2Co0.1O2 synthesized via a sol gel method, and study the effect of copper doping on the resulting materials. Electrochemical testing at 1 C revealed 1 % Cu doping enhanced capacity retention (from 58 % to 78 %) but also decreased capacity, while in contrast 10 % Cu doping increased capacity by 21 %. Thorough characterization (including x‐ray diffraction, scanning electron microscopy, inductively coupled plasma‐optical emission spectroscopy, and electrochemical analyses such as voltage vs. capacity and dQ/dV plots) was employed to understand these results, which may be attributed to the competition of two different phenomena depending on the copper content. Consequently, this work highlights the importance of targeting bespoke stoichiometries depending on the desired electrochemical characteristics – an important point for the future design of materials for fast charging and high power applications.

Elucidating the Role of Excess Li in the Electrochemical Performance of Li1+x[Ni0.5Mn0.5]1−xO2 Layered Oxides

Layered cathode materials comprising of Ni and Mn can possess comparable theoretical capacities to Ni-rich cathode materials. However, to draw upon this capacity, they need to overcome rate capability issues and operate to higher voltages. Incorporating excess Li during synthesis can allow much of this capacity to be accessed. This work compares the effects of excess Li on electrochemical properties of Li1+x[Ni0.5Mn0.5]1-xO2 layered oxides in the conventional voltage window as well as with higher upper cut-off voltages. Materials with different amounts of excess Li were systematically compared based on specific capacity, first-cycle irreversible loss, cycling stability, and rate capability in the voltage ranges of 3.0 V–4.3 V, 3.0 V–4.5 V, and 3.0 V–4.8 V. In all samples, excess Li improves the rate capability and cycling stability in all these voltage ranges while significant gains in specific capacity can only be attained when operating these materials at higher voltage cut-offs. The improved rate capability performance in presence of excess Li can be attributed to enhanced electronic conductivity and Li+ ion diffusion arising from reduced amounts of Ni in the Li layer.

Editorial Expression of Concern: Electrochemical properties of Li1−z(Ni1−yFey)1+zO2 synthesized by the combustion method in an air atmosphere

Editorial Expression of Concern: Electrochemical properties of Li1−z(Ni1−yFey)1+zO2 synthesized by the combustion method in an air atmosphere

Electrochemical behavior of Sn-doped Li1.2V3O8 cathode materials for Lithium-ion batteries

The discharge capacity of Li1.2V3O8 is obviously decreased, and the diffusion coefficient of lithium ion is relatively low. In order to improve the electrochemical performances of Li1.2V3O8, the study of Sn4+ doped Li1.2V3O8 is performed. The initial discharge capacity of Li1.2V2.97Sn0.03O8 is lower than that of Li1.2V3O8. However, the discharge capacity of Li1.2V2.97Sn0.03O8 is higher than that of Li1.2V3O8 from the second cycle, and the discharge capacity of Li1.2V2.97Sn0.03O8 are significantly improved at high current density. At 50, 100 and 200 mA g−1, the discharge capacities of Li1.2V2.97Sn0.03O8 are 271.8, 268 and 257.2 mAh g−1, respectively. The discharge capacity is maintained at 264.7, 259.6 and 238.3 mAh g−1, after 50 cycles at room temperature. Furthermore, the electrochemical reactivity of vanadium in Li1.2V3O8 electrodes could be improved by Sn4+ doping. Thus, the electrochemical reaction kinetics and the electrochemical properties of Li1.2V2.97Sn0.03O8 are improved.

Enhanced structural and electrochemical properties of Li1.2Ni0.13Co0.13Mn0.54O2 cathode with polyaniline polymer for lithium-ion batteries

Enhanced structural and electrochemical properties of Li1.2Ni0.13Co0.13Mn0.54O2 cathode with polyaniline polymer for lithium-ion batteries

Synthesis and electrochemical properties of high power Li1+xV3O8 cathode materials for lithium-ion batteries

Monoclinic Li1+xV3O8 cathode materials were synthesized by sol-gel method. The structure, morphology and electrochemical performance of Li1+xV3O8 are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. Moreover, the effects of content of lithium on the physical and electrochemical properties of Li1+xV3O8 cathode materials are studied. The results show that the Li1.2V3O8 cathode material prepared by sol-gel method has good electrochemical properties, which has an initial discharge and charge specific capacities of 279.7 and 305 mAh g−1 at the current of 50 ​mA ​g−1 between 1.5 and 4.0 ​V, respectively, and a good cycle performance. In addition, the Li1.2V3O8 cathode material also has a good rate performance.

Superior electrochemical properties of Zirconium and Fluorine co‐doped Li1.20[Mn0.54Ni0.13Co0.13]O2 as cathode material for lithium ion batteries

In the paper, the Zr4+ and F− co-doping was employed to expectedly improve the rate performance and structure stability of Li1.20[Mn0.54Ni0.13Co0.13]O2. The effects of Zr4+ doping and F− doping on the micro-structure, cathode morphology and element chemical state were investigated by XRD, Rietveld refined XRD, SEM, TEM, and XPS. It indicated the Zr4+ and F− were inserted into the cathode crystal structure with ideally designed. Besides, the electrochemical characterization confirmed that the cathode after the Zr4+ or/and F− doping delivered the superior electrochemical properties when compared to the pristine one. Firstly, the Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 could express a high discharge capacity of 132.6 mAhg−1 at 5C rate, which was 40.1 mAhg−1 larger than that of the pristine one (92.5 mAhg−1). In addition, the Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 remained a capacity retention of 90.7% after 100 cycles at 2C rate and with the 148.2 mAh g−1 left. While the bare cathode delivered an initial discharge capacity of 134.1 mAhg−1 at 2C rate, then dramatically attenuated to 108.7 mAhg−1 after 100 cycles with the capacity retention of 81.1%. The enhanced electrochemical properties of Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 was mainly put down to the suppression of charge transfer resistance increase by the Zr4+ and F− doping modification along with cycles.

Structural and Electrochemical Properties of Li1.2Ni0.16Mn0.54Co0.08O2 - Al2O3 Composite Prepared by Atomic Layer Deposition as the Cathode Material for LIBs

Structural and Electrochemical Properties of Li1.2Ni0.16Mn0.54Co0.08O2 - Al2O3 Composite Prepared by Atomic Layer Deposition as the Cathode Material for LIBs

Effect of Na Doping on Electrochemical Properties of Cobalt-Free Li-Rich Mn-Based Cathode Materials

Na doping is introduced to improve the electrochemical properties of Li1.2Mn0.6Ni0.2O2 cathode material, which is synthesized by sol–gel method. The effect of Na doping on the morphological, structural and electrochemical properties was systematically studied and analyzed. These results illustrate that lattice layer spacing is enlarged by Na doping, which is beneficial for the diffusion of Li-ion, and the voltage fading is successfully suppressed. The best electrochemical properties were obtained when Na doping amount is approximately 1%, which is attributed to the stronger structural stability and better reversibility of Li+ during the initial charge and discharge process.

Improving the electrochemical properties of Mn-rich Li1.20[Mn0.54Ni0.13Co0.13]O2 by Nb and F co-doping

The typical sol-gel method was adopted to synthesize the pristine Li1.20[Mn0.54Ni0.13Co0.13]O2 and Li1.20[Mn0.54-xNi0.13Co0.13Nbx]O1.95F0.05 (x = 0, 0.01, 0.02, 0.03). And the effects of Nb5+ and F− substitution on the lattice structures, particles morphologies and electrochemical properties were comprehensively studied by using the X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and galvanostatic charge-discharge tests. The results demonstrated that the Nb5+ and F− doping modification could increase the lattice parameter of a and c, and would not obviously change the morphologies of cathode particles. Besides, the electrochemical properties of Li1.20[Mn0.54Ni0.13Co0.13]O2 were significantly improved after the Nb5+ and F− doping. Among all samples, the Li1.20[Mn0.52Ni0.13Co0.13Nb0.02]O1.95F0.05 delivered the highest discharge capacity of 117.1 mAh g−1 at 5C high rate and the most stable capacity retention of 92.5% at 0.5C rate after 200 cycles. The Electronic Impedance Spectroscopy (EIS) analysis reflected that the Nb5+ and F− doping could relieve the increase of charge transfer resistance and the ohmic resistance of interaction between electrolyte and cathode during cycling.

Effect of Drying Time on Electrochemical Properties of Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

Effect of Drying Time on Electrochemical Properties of Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

In situ formation of LiF decoration on a Li-rich material for long-cycle life and superb low-temperature performance

The electrochemical properties of Li1.2Ni0.13Co0.13Mn0.54O2 (LLO) are improved by LiPF6 coating and subsequent heating.

Fabrication and electrochemical properties of Li1.3Al0.3Ti1.7(PO4)3 solid electrolytes by sol-gel method

Sodium super ionic conductor (NASICON)-type solid electrolytes, Li1.3Al0.3Ti1.7(PO4)3 (LATP), have high lithium ion conductivity and chemical/electrochemical stability. In this study, we proposed a new sol-gel route to synthesize LATP precursor powder. The LATP powder was prepared from lithium nitrate (LiNO3), aluminum phosphate (AlPO4), ammonium phosphate (NH3PO4), and titanium isopropoxide (Ti-(OCH(CH3)2)4). The LATP electrolyte with high relative density (99%) and lithium ion conductivity (4.2 × 10−4 S/cm at 30 °C) could be fabricated by sintering the precursor powder at 1000 °C for 6 h. XRD analysis results revealed that the electrolyte sample sintered at 1000 °C for 6 h was impurity-free single phase LATP. FE-SEM observations showed that the grain size and density increased with increasing sintering temperature. AC impedance spectra and SEM observations suggest that the enhanced lithium ion conductivity was due to an increase in grain size and density of the LATP electrolyte.

Improvement of electrochemical performance of nickel-manganese-based lithium-rich layer-structured cathode material by controlling lithium/transition-metal ratio

As a cathode material, Li1.2Ni0.2Mn0.6O2 delivers high discharge capacity at low C-rate but low discharge capacity at high C-rate. Furthermore, a large potential hysteresis occurs during charge and discharge, and the charge-discharge curves change shape during the charge-discharge cycling. Increasing nickel/manganese (Ni/Mn) ratio in Li1.2NiyMn0.8−yO2 improves discharge capacity at high C-rate, but it decreases discharge capacity at low C-rate. To accomplish high discharge capacity at both high and low C-rates, lithium/transition-metal (Li/TM) ratio in high-nickel-content material, namely, Li1.2Ni0.35Mn0.45O2, was adjusted. Cathode materials with varied lithium/transition-metal ratio (x), namely, Li1.2−xNi0.35+(0.35/0.8)xMn0.45+(0.45/0.8)xO2 (x = 0, 0.02, 0.04, 0.06, or 0.08), were prepared, and their electrochemical performances were evaluated. It was found that as x was decreased, discharge capacity first increased then decreased, and Li1.2−xNi0.35+(0.35/0.8)xMn0.45+(0.45/0.8)xO2 (x = 0.04), which can be described as Li1.16Ni0.37Mn0.47O2, was found to exhibit the highest discharge capacity. Accordingly, the electrochemical properties of Li1.16Ni0.37Mn0.47O2 were compared with those of a conventional lithium-rich layer-structured cathode material, namely, Li1.2Ni0.2Mn0.6O2. The rate performance of Li1.16Ni0.37Mn0.47O2 was higher than that of Li1.2Ni0.2Mn0.6O2. Furthermore, potential hysteresis and shape change of the charge-discharge curves for Li1.16Ni0.37Mn0.47O2 were smaller than those for Li1.2Ni0.2Mn0.6O2. It is thus concluded that changing the composition of the cathode material from Li1.2Ni0.2Mn0.6O2 to Li1.16Ni0.37Mn0.47O2 alleviates the drawbacks of lithium-rich layer-structured cathode material, namely, low rate performance, potential hysteresis, and shape change of charge-discharge curves.

Surface modification of Li1.20Mn0.54Ni0.13Co0.13O2 cathode materials with SmF3 and the improved electrochemical properties

The Li1.20Mn0.54Ni0.13Co0.13O2 cathode materials with the different SmF3 coating contents were successfully synthesized through the typical wet chemical method. The X-ray diffractometer, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy and galvanostatic charge–discharge tests were adopted to investigate the influence of SmF3 layer on the crystal structural, morphology and electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2. The results showed that the cathode materials were successfully coated with SmF3 without changing its micro-structure. Besides, the electrochemical tests results demonstrated that electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2 were significantly enhanced after applying the SmF3 coating. The specific discharge capacity of the 2 wt% SmF3 coated Li1.20Mn0.54Ni0.13Co0.13O2 is 30.4 mAh g−1 higher than that of pristine one at 0.5C rate. Meanwhile, the 2 wt% SmF3 coated Li1.20Mn0.54Ni0.13Co0.13O2 delivered an outstanding cycle stability with a high capacity retention of 91.4% after 100 cycles, while the pristine one showed the less discharge capacity and a low capacity retention of 85.2%. The enhanced electrochemical properties could be ascribed to the SmF3 coating layer, which not only stabilizes the cathode structure by restricting the side reaction between cathodes materials with electrolyte, but also relieves the increase of impedance for Li+ migration across the electrode/electrolyte interface during cycling.

Influences of Gd3+ doping modification on the crystal microstructure and electrochemical performance of Li1.20[Mn0.52Ni0.20Co0.08]O2 as cathode for Lithium-ion batteries

ABSTRACT The Li1.20[Mn0.52-xGdxNi0.20Co0.08]O2 (x = 0, 0.01, 0.02, 0.03) cathode materials have been synthesized by using the combination of co-precipitation with high temperature sintering method. The XRD, SEM, TEM and galvanostatic charge-discharge tests were carried out to study the influence of Gd3+ doping on the crystal structural, morphology and electrochemical properties of Li1.20[Mn0.52Ni0.20Ni0.08]O2. The XRD result revealed the Gd3+ doping modification could decrease the cation mixing degree. The galvanostatic charge-discharge tests results showed the improved electrochemical properties were obtained through the Gd3+ doping modification. With the increase of Gd3+ doping content, the capacity retentions enhanced from 88.1% to 90.3% and then decrease to 87.0% after 100 cycles with x = 0.01, 0.02 and 0.03, respectively, while the un-doped sample delivered the capacity retention of 85.1%. The Li1.20[Mn0.50Gd0.02Ni0.20Co0.08]O2 exhibited a discharge capacity of 115.5 mAh g−1 at 5C rate, much larger than that (85.1 mAh g−1) of the un-doped Li1.20[Mn0.52Ni0.20Co0.08]O2. The cyclic voltammetric analysis has proved that the Gd3+ doping modification can keep the stability of the cathode layer structure and further hold the high working voltage.

Effects of Citric Acid Treatment on the Electrochemical Properties of Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

Effects of Citric Acid Treatment on the Electrochemical Properties of Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

Electrochemical Properties of Li1.3Al0.3Ti1.7(PO4)3-Filled Composite Polymer Gel Electrolytes of Pvdf-HFP and Hydroxypropylcellulose

The composite polymer gel electrolytes (CPGE) for lithium-ion batteries are prepared by combining poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and hydroxypropylcellulose (HPC) as binary polymer components, Li1.3Al0.3Ti1.7(PO4)3 (LATP) as an inorganic filler, and 1 M LiPF6 dissolved in EC:PC:EMC as an electrolyte solution. The PVdF-HFP is included as a linear flexible polymer chain in the electrolyte medium, the rigid rod-like molecules of HPC has the lyotropic property between liquid crystalline and isotropic phases, and the LATP supports mechanical strength and also provides another conduction path in the gel medium [1] to increase ionic conductivity. The synergy among each component is expected to lead highly ionic conductive electrolytes with excellent mechanical strength. In this study, the electrochemical properties of LATP-filled CPGE are investigated and the charge-discharge performance of LiCoO2/graphite lithium-ion battery cell adopting the CPGE is also carried out. Through such the electrochemical investigations, the optimum amount of LATP showing the best performance would be mainly determined. Moreover, the low-temperature performance of the LiCoO2/CPGE/graphite cell would be particularly examined because the LATP(50 wt.)-filled CPGE (polymer 100 wt.) exhibits higher ionic conductivity (e.g., 4x10-3 S/cm) at low temperature (e.g., -10oC), compared with the CPGE without LATP (3.6x10-4 S/cm). In the presentation, how each component and its content contribute to the electrochemical performance of the cell would also be discussed in detail. Figure 1

Ce3+ doping into 0.6Li2MnO3·0.4LiNi0.5Co0.2Mn0.3O2 as cathode material for Li-ion batteries applied in new energy vehicle

The pristine Li1.20[Mn0.52Ni0.20Co0.08]O2 and Ce3+-doped Li1.20[Mn0.50Ni0.20Co0.08Ce0.02]O2 cathode materials have been synthesized by using the typical sol-gel method. The XRD, SEM, ICP-OES and galvanostatic charge-discharge tests were carried out to study the influence of Ce3+ doping on the crystal structural, morphology and electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2. The XRD result revealed the Ce3+ doping modification could decrease the cation mixing degree. The galvanostatic charge-discharge tests results showed that the sample after Ce3+ doping demonstrated the smaller irreversible capacity loss, more stable cyclic performance and better rate capacity than those of the pristine one.