Surface Modification Of LiNi0 Research Articles

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.