Surface Modification Of LiNi0 Research Articles

Improvement of electrochemical performance by surface modification of LiNi0.65Co0.15Mn0.2O2 cathode materials with SnO2

LiNi0.65Co0.15Mn0.2O2 batteries have attracted more and more attention due to their high energy density. However, LiNi0.65Co0.15Mn0.2O2 possesses adverse factors such as severe Li-Ni mixing and side reactions between active substance and electrolyte, which limits its electrochemical performance. Hence, we employed the SnO2 surface coating method to enhance its performance. SnO2 coating inhibits the direct contact between LiNi0.65Co0.15Mn0.2O2 and the electrolyte, which reduces the lithium-nickel mixing, enlarges the lithium layer spacing, and contributes to the improvement of the specific capacity of discharge and the cycling performance. The electrochemical results indicate the optimal SnO2-coated LiNi0.65Co0.15Mn0.2O2 show excellent cycling performance (85.0 % capacity retention for 100 cycles at 0.1 C) and multiplicative performance (124.1 mA·h·g−1 discharge specific capacity at 2 C). The paper highlights the SnO2 cladding technology which provides an excellent research idea to improve lithium-ion batteries.

Enhancing the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 by surface modification with homemade high-purity hexagonal phase tungsten oxide nanoparticles

Nickel-rich layered oxides with high energy density and acceptable cost are considered as one of the most ideal cathode materials for power batteries. However, its large-scale production and application still face the challenge in terms of rapid capacity fading and poor structural stability, which has prompted research into surface coating materials/technologies within both academic and industrial fields. In this work, A feasible and environmental friendly fabrication method of high-purity hexagonal phase tungsten oxide (h-WO3) nanoparticles as surface modification of LiNi0.8Co0.1Mn0.1O2(NCM) is proposed.The results indicate that NCM modified with h-WO3 has lower Li+/Ni2+ mixing rate, superior rate performance, and better cycling stability than the pristine NCM. Although tungsten oxide is widely used as surface modification due to its excellent physical and chemical properties, but its crystal type has not been considered, and there is little research on the theoretical explanation of h-WO3 modification.This work reveals the working mechanism of h-WO3 from the perspective of interface and crystal type, which can provide meaningful reference for obtaining nickel-rich layered oxides with excellent electrochemical properties.

Surface Modification of LiNi0.8 Co0.15 Al0.05 O2 Particles via Li3 PO4 Coating to Enable Aqueous Electrode Processing.

The successful implementation of an aqueous‐based electrode manufacturing process for nickel‐rich cathode active materials is challenging due to their high water sensitivity. In this work, the surface of LiNi0.8Co0.15Al0.05O2 (NCA) was modified with a lithium phosphate coating to investigate its ability to protect the active material during electrode production. The results illustrate that the coating amount is crucial and a compromise has to be made between protection during electrode processing and sufficient electronic conductivity through the particle surface. Cells with water‐based electrodes containing NCA with an optimized amount of lithium phosphate had a slightly lower specific discharge capacity than cells with conventional N‐methyl‐2‐pyrrolidone‐based electrodes. Nonetheless, the cells with optimized water‐based electrodes could compete in terms of cycle life.

Surface modification of LiNi0.8Co0.1Mn0.1O2 by WO3 as a cathode material for LIB

WO3 modified LiNi0.8Co0.1Mn0.1O2 materials were got by a wet method. Structure parameters, micromorphology, element distribution of the modified and bare NCM materials were compared by different detection methods, such as XRD, SEM, EDS and TEM. The results reveal that there was no significant change in morphology before and after modification, and the distribution of tungsten was relatively uniform. In addition, tungsten oxide surface modification layer does exist by TEM, FFT and XPS analysis, and affects the distribution and valence states of surface elements. Furthermore, it is found that the micro amount of tungsten oxide modified NCM material is beneficial to the improvement of rate performance and cycle stability, especially at high cutoff voltage. Then the effect of modification on the electrochemical properties was conducted by CV, EIS and SEM detection after cycle. It is displayed that the particles after modification have no cracks, and the polarization and impedance decrease to varying degrees. This simple and feasible method has a good prospect for improving the cyclic stability of Ni-rich materials.

Surface modification of LiNi0.8Co0.1Mn0.1O2 with conducting polypyrrole

A facile method for the surface modification of high-voltage and high-temperature LiNi0.8Co0.1Mn0.1O2 cathode materials is demonstrated. In order to prepare polypyrrole (PPy) coating LiNi0.8Co0.1Mn0.1O2 material, the facile chemical polymerization method uses Fe(III) tosylate as oxidant and ethanol as solvent to avoid the side reaction with solvent. TEM depicts that LiNi0.8Co0.1Mn0.1O2 serves as hard template and the nanoscale PPy layer grows along the surface of LiNi0.8Co0.1Mn0.1O2 during the synthesis process. Because of flocculent and nanofiber coating layer, much improved rate performance, high temperature cycling, as well as high voltage performance are obtained. Cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) results demonstrate that the PPy coating layer effectively alleviates the side reactions between liquid electrolytes and LiNi0.8Co0.1Mn0.1O2 surface that are highly unstable at high temperature and high charge voltage.

Surface modification of LiNi0.5Mn1.5O4 cathodes with ZnAl2O4 by a sol–gel method for lithium ion batteries

The 5V spinel LiNi0.5Mn1.5O4 cathodes have been surface-modified with ZnAl2O4 by a sol–gel method and characterized by X-ray diffraction, high-resolution transmission electron microscopy, and electrochemical measurements. Although the pristine electrode experienced the prominent degradation after the storage test at 60°C in the intervals of cycling test at room temperature, the ZnAl2O4-coated LiNi0.5Mn1.5O4 cathode exhibited the significant capacity retention even after storing at elevated temperatures. The X-ray photoelectron spectroscopy data reveals that the improved electrochemical performances of surface-coated cathode are mostly due to the suppressed side reaction between the cathode and the electrolyte especially at the high-temperature environment. Differential scanning calorimetry showed that the decreased heat evolution could be found with the surface-modified cathode. Our experimental findings suggest a direction to the further development of cathode materials which are endurable to the highly oxidized state and high-temperature environment.

Effect of surface modifiers in improving the electrochemical behavior of LiNi0.4Mn0.4Co0.2O2 cathode

Surface modification of LiNi0.4Mn0.4Co0.2O2 (442) compound with certain metal oxides viz., Al2O3, Bi2O3 and In2O3 has been attempted with a view to improve the structural and cycling stability, especially upon high voltage and high rate cycling conditions. In addition to HF scavenging effect, the protective metal oxide inter-connect layer restricts the number of oxide ion vacancies eliminated during the initial cycling of cathode, resulting in the reduced irreversible capacity loss of the first cycle. Among the surface modified cathodes, Bi2O3 coated LiNi0.4Mn0.4Co0.2O2 cathode exhibits appreciable specific capacity values of 196mAhg−1 (Qdc1) and 175mAhg−1 (Qdc100) with 89% capacity retention, thus evidencing the superiority of Bi2O3 modifier in improving the electrochemical behavior of pristine LiNi0.4Mn0.4Co0.2O2 cathode. Further, suitability of Bi2O3 coated LiNi0.4Mn0.4Co0.2O2 cathode for high voltage (5.0V) and high rate (3C) lithium intercalation and de-intercalation applications has been demonstrated up to 100 cycles. Based on the extent of improvement in electrochemical behavior, the cathodes under investigation could be arranged in the order: Bi2O3 coated>Al2O3 coated>In2O3 coated>uncoated LiNi0.4Mn0.4Co0.2O2 oxide.

Surface modification of LiNi0.5Mn1.5O4 by LiCoO2/Co3O4 composite for lithium-ion batteries

A novel and simple liquid-phase process has been first put forward to surface modify spinel LiNi0.5Mn1.5O4 with LiCoO2/Co3O4 composite. The results show that the LiCoO2/Co3O4 composite has been successfully coated on the surface of LiNi0.5Mn1.5O4 particles, and the electrochemical performance is improved remarkably. Compared with the pure LiNi0.5Mn1.5O4, the initial discharge capacities of the modified LiNi0.5Mn1.5O4 improve 9.1, 9.6, 11.6mAhg−1 at rates of 1C, 3C and 5C, respectively. It also exhibits excellent cycle performance, retaining 97.8% of the maximal attainable discharge capacity (110.1mAhg−1) after 200 cycles at the rate of 5C. These results demonstrate that the surface modification with LiCoO2/Co3O4 composite could be a feasible way to improve the electrochemical performance of spinel LiNi0.5Mn1.5O4 for lithium-ion batteries.