Influence of sintering temperatures on microstructure and electrochemical performances of LiNi0.93Co0.04Al0.03O2 cathode for high energy lithium ion batteries.

In this study, we present a method for synthesizing Ni-rich LiNi0.93Co0.04Al0.03O2 (NCA) with a high-energy cathode material by the solid-phase method. The sintering temperature plays a very important role in the electrochemical performance of the LiNi0.93Co0.04Al0.03O2 since it affects the crystallinity and structural stability. Therefore, various sintering temperatures (660 °C/690 °C/720 °C/750 °C/780 °C/810 °C) are studied to get optimum electrochemical performances. The electrochemical performance of LiNi0.93Co0.04Al0.03O2 sintered at 720 °C shows the highest discharge capacity of 217.48 mAh g-1 with excellent Coulombic efficiency of 87.84% at 0.1 C. Moreover, the LiNi0.93Co0.04Al0.03O2 sintered at 720 °C exhibits excellent rate-capability (181.1 mAh g-1 at 2.0 C) as well as superior cycle stability (95.4% after 80 cycles at 0.5 C). This is because optimized sintering temperature leads to good structural stability with low cation disorder and residual lithium content.

Dual function Li-reactive coating from residual lithium on Ni-rich NCM cathode material for Lithium-ion batteries.

In this study, lithium phosphate (Li3PO4) is coated on the surface of Ni-rich LiNi0.91Co0.06Mn0.03O2 cathode material to enhance its cyclability and rate performance. The process is carried-out by achieving dual benefits, reduction of residual lithium compounds by converting them into Li3PO4 coating material. The 0.1 mol.% Li3PO4 (LiP) sample exhibits a capacity retention of 82% while the pristine NCM shows only 68.1% after 100 cycles. In addition, the LiP-0.1 NCM delivers high discharge capacities (161.9 mAh g-1 at 3C, 144.3 mAh g-1 at 4C and 94.6 mAh g-1 at 5C) as compared to the pristine NCM (129.3 mAh g-1 at 3C, 67.4 mAh g-1 at 4C and 33.4 mAh g-1 at 5C) in the voltage range of 3.0-4.3 V. In addition, the irreversible phase transition has also suppressed in the coated sample which is confirmed by cyclic voltammetry. Our study suggests that Li3PO4 coating reduces the polarization and acts as protecting layer between the electrode and electrolyte that results in the superior electrochemical performance.

Use of carbon coating on LiNi0.8Co0.1Mn0.1O2 cathode material for enhanced performances of lithium-ion batteries.

Ni-rich cathode is one of the promising candidate for high-energy lithium-ion batteries. In this work, we prepare the different super-P carbon black amounts [0.1 (SPB 0.1 wt%), 0.3 (SPB 0.3 wt%), 0.5 (SPB 0.5 wt%) and 0.7 wt% (SPB 0.7 wt%)] of carbon coated LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes and their electrochemical performances are investigated. Carbon coating does not change the crystal structure and morphology of NCM811. Among the coated NCM811, the SPB 0.5 wt% NCM811 delivers the excellent cyclability (87.8% after 80 cycles) and rate capability (86.5% at 2 C) compared to those of pristine NCM811. It is ascribed to that the carbon coating not only increase the Li ion and electron transfer as well as protect the NCM811 cathode materials from side reaction at the electrolyte/NCM811 interface. Therefore, we can conclude that the appropriate amount of carbon coating can be regarded as an effective approach for Ni-rich NCM cathode.

Influence of Mo addition on the structural and electrochemical performance of Ni-rich cathode material for lithium-ion batteries.

Molybdenum modified LiNi0.84Co0.11Mn0.05O2 cathode with different doping concentrations (0-5 wt.%) is successfully prepared and its electrochemical performances are investigated. It is demonstrated that molybdenum in LiNi0.84Co0.11Mn0.05O2 has a positive effect on structural stability and extraordinary electrochemical performances, including improved long-term cycling and high-rate capability. Among all samples, the 1 wt. % molybdenum LiNi0.84Co0.11Mn0.05O2 delivers superior initial discharge capacity of 205 mAh g-1 (0.1 C), cycling stability of 89.5% (0.5 C) and rate capability of 165 mAh g-1 (2 C) compared to those of others. Therefore, we can conclude that the 1 wt. % molybdenum is an effective strategy for Ni-rich LiNi0.84Co0.11Mn0.05O2 cathode used in lithium ion batteries.

Superior Performances of B-doped LiNi0.84Co0.10Mn0.06O2 cathode for advanced LIBs.

Boron-doped Ni-rich LiNi0.84Co0.10Mn0.06O2 (B-NCM) cathode material is prepared and its electrochemical performances are investigated. The structural properties indicate that the incorporation of boron leads to highly-ordered layered structure and low cation disordering. All samples have high areal loadings of active materials (approximately 14.6 mg/cm2) that meets the requirement for commercialization. Among them, the 1.0 wt% boron-doped NCM (1.0B-NCM) shows the best electrochemical performances. The 1.0B-NCM delivers a discharge capacity of 205. 3 mAh g-1, cyclability of 93.1% after 50 cycles at 0.5 C and rate capability of 87.5% at 2 C. As a result, we can conclude that the 1.0B-NCM cathode can be regarded as a promising candidate for the next-generation lithium ion batteries.

Optimized electrochemical performance of Ni rich LiNi0.91Co0.06Mn0.03O2 cathodes for high-energy lithium ion batteries.

We report high electrochemical performances of LiNi0.91Co0.06Mn0.03O2 cathode material for high-energy lithium ion batteries. LiNi0.91Co0.06Mn0.03O2 is synthesized at various sintering temperatures (640~740 °C). The sintering temperatures affect crystallinity and structural stability, which play an important role in electrochemical performances of LiNi0.91Co0.06Mn0.03O2. The electrochemical performances are improved with increasing sintering temperature up to an optimal sintering temperature. The LiNi0.91Co0.06Mn0.03O2 sintered at 660 °C shows remarkably excellent performances such as initial discharge capacity of 211.5 mAh/g at 0.1 C, cyclability of 85.3% after 70 cycles at 0.5 C and rate capability of 90.6% at 2 C as compared to 0.5 C. These results validate that LiNi0.91Co0.06Mn0.03O2 sintered at 660 °C can be regarded as a next generation cathode.

Improving the electrochemical performances using a V-doped Ni-rich NCM cathode.

Ni-rich layered LiNi0.84Co0.10Mn0.06O2 cathode material was modified by doping with vanadium to enhance the electrochemical performances. The XRD, FESEM and XPS analyses were indicated that the vanadium is successfully doped in the crystal lattice of LiNi0.84Co0.10Mn0.06O2 with high crystallinity. 0.05 mol% vanadium doped LiNi0.84Co0.10Mn0.06O2 exhibits superior initial discharge capacity of 204.4 mAh g-1, cycling retention of 88.1% after 80 cycles and rate capability of 86.2% at 2 C compared to those of pristine sample. It can be inferred that the vanadium doping can stabilize the crystal structure and improve the lithium-ion kinetics of the layered cathode materials.

Electrochemical Performances of Yttrium Doped Li3V(2-X)Y(X)(PO4)3/C Cathode Material for Lithium Secondary Battery.

In this study, the Li3V(2-X)Y(X)(PO4)3 compounds have been synthesized by a simple solid state method. In addition, a polyurethane was added to apply carbon coating on the surface of the Li3V(2-X)Y(X)(PO4)3 particles for enhancement of the electrical conductivity. The crystal structure and morphology of the synthesized Li3V(2-x)Y(x)(PO4)3/C (LVYP/C) was investigated using an X-ray diffraction (XRD) and a scanning electron microscopy (SEM) systematically. The electrochemical performance of synthesized material, such as the initial capacity, rate capability, cycling performance and EIS was evaluated. The sizes of synthesized particle ranged from 1 to 5 µm. The Li3V(2-X)Y(X)(PO4)3/C (x = 0.02) delivered the initial discharge capacity of 171.5 mAh·g(-1) at 0.1C rate. It showed a capacity retention ratio of 73.0% at 1.OC after 100th cycle. The electrochemical impedance spectroscopies (EIS) results revealed that the charge transfer resistance of the material decreases by Y doping.

A Promising Na3V2(PO4)3/Ag + Graphene Composites as Cathode Material for Hybrid Lithium Batteries.

The NASICON (sodium super ionic conductor) based Na3V2(PO4)3/Ag + graphene (NVP/Ag + G) was successfully synthesized through a sol-gel route using a silver nitrate and graphene as a raw material. The effects of the physical and electrochemical properties of the NVP/Ag + G composites have been evaluated with X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical measurements. The graphene and Ag significantly influenced the morphology, structure and electrochemical performance of the Na3V2(PO4)3 material. In the electrochemical measurement, the (NVP/Ag + G) electrode showed the discharge capacity of 102 mAh g(-1) at 0.1 C rate, which was higher than the pristine Na3V2(PO4). At a current rate of 5 C, it still exhibits the discharge capacity of 73 mAh g(-1) and the capacity retention of 71.6%. The results of higher electrochemical performance of the NVP/Ag + G composites are mainly attributed to the synergetic effect of the graphene and the silver particles.

Physical and electrochemical characterization of 0.3Li2MnO3 x 0.7LiMn0.60Ni0.25Co0.15O2 material for Li secondary battery.

The 0.3Li2MnO3 x 0.7LiMn0.60Ni0.25Co0.15O2 cathode materials were synthesized using a coprecipitation method at a various heat-treatment temperature. From XRD pattern analysis, pure layered structure without impurities was confirmed from all samples and the peak intensity of Li2MnO3 was increased as the heat-treatment temperature increased. The primary particle size increased approximately from 100 nm to 500 nm with increasing heat-treatment temperature. The initial discharge capacity of the materials obtained at 950 degrees C was 235 mA h/g at 0.1 C rate, but then decreased down to 228 mA h/g with further increasing heat-treatment temperature. And, in the voltage range of 2.0-4.6 V, the electrode heat-treated at 900 degrees C showed the highest capacity retention of 68% at 5 C rate against to 0.1 C rate.

Synthesis and electrochemical characterization of LiMn0.6Fe0.4PO4/C cathode material via a modified-solid state reaction method.

LiMn0.6Fe0.4PO4/C cathode material is synthesized via a modified-solid state reaction method. The calcination temperature is adjusted in the range of 500-700 degrees C for 10 h. The crystal structure, morphology, and carbon coating layer of the synthesized LiMn0.6Fe0.4PO4/C are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The electrochemical performance of LiMn0.6Fe0.4PO4/C, such as initial capacity, rate capability, cycling performance and EIS is also evaluated. The synthesized cathode material shows around 100-200 nm of primary particle size with no impurities. The highest initial discharge capacity of 162.1 mA h g(-1) and columbic efficiency of 98.5% are obtained at a heat treatment temperature of 600 degrees C. In addition, LiMn0.6Fe0.4PO4/C active material shows the high capacity retention of 85% at 5 C compared to 0.2 C. It also shows the excellent capacity retention of 97.5% after the 50th charge/discharge.

Electrochemical performance of Li[Ni0.7Co0.1Mn0.2]O2 cathode materials using a co-precipitation method.

The Li[Ni0.7Co0.1Mn0.2]O2 cathode material synthesized using a co-precipitation method was investigated as a function of various pH level in terms of its microstructure and electrochemical properties. From the XRD pattern analysis, the Li[Ni0.7Co0.1Mn0.2]O2 cathode material prepared in this study are found to well coincide with typically hexagonal alpha-NaFeO2 structure. The primary particle size was about 100-300 nm at all compositions while secondary particle size increased as pH level increased from 10.34 microm (pH 10.3) to 14 microm (pH 12.5). The initial discharge capacity increased up to 165 mAh/g (0.1 C) at pH 11, and then decreased down to 144 mAh/g with further increasing pH level. The capacity retention of the cathode (pH 11) showed 90% at 0.2 C and 15% at 5 C respectively compared with the discharge capacity at 0.1 C. The capacity retention of the cathode (pH 10.3) performed 94% of the initial capacity after 22 cycles at 0.5 C charge/discharge test. Therefore, it is thought to be that pH 10.3 is optimized condition of the Li[Ni0.7Co0.1Mn0.2]O2 cathode material in this study because pH 10.3 shows better cycle performance than other conditions.

Synthesis and electrochemical performance of 0.3Li2MnO3 x 0.7LiMO2 (M = Mn, Co, Ni) cathode materials for Li-lon batteries.

The Mn0.720Ni0.175Co0.105(OH)2 precursor was co-precipitated by the Couette-Taylor reactor. The 0.3Li2MnO3 x 0.7LiMn0.60Ni0.25Co0.15O2 of the high capacity cathode material for a Li-ion battery was synthesized according to the amount of lithium excess (5-20 mol.%). X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) were used to characterize the 0.3Li2MnO3 x 0.7Li-Mn0.60Ni0.25Co0.15O2. Based on the XRD patterns and FE-SEM images, the 5 and 10 mol.% lithium excess samples were observed for spinel structure. The 15 and 20 mol.% lithium excess samples were not observed for the structure. We can conclude that the spinel structure was made in 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2, due to a lack of lithium. The discharge specific capacity of 5, 10, 15, and 20 mol.% lithium excess were measured at 216, 246, 262, and 261 mA h g(-1), respectively. Cyclic voltammograms show that the Li2MnO3 has a lower lithium influence than a spinel or layered structure. Based on these experiment results, we can conclude that the best Li source amount of the 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2 synthesis is a 15 mol.% excess.