ZrO2 coated Li1.2Ni0.16Mn0.56Co0.08O2 (NMC) materials with improved electrochemcial performance.

No abstract

Lithium-rich layered oxides (LLOs) such as Li1.2Ni0.13Mn0.54Co0.13O2 are suitable cathode materials for future lithium-ion batteries (LIBs). Despite some salient advantages, like low cost, ease of fabrication, high capacity, and higher operating voltage, these materials suffer from low cyclic stability and poor capacity retention. Several different techniques have been proposed to address the limitations associated with LLOs. Herein, we report the surface modification of Li1.2Ni0.13Mn0.54Co0.13O2 by utilizing cheap and readily available silica (SiO2) to improve its electrochemical performance. Towards this direction, Li1.2Ni0.13Mn0.54Co0.13O2 was synthesized utilizing a sol–gel process and coated with SiO2 (SiO2 = 1.0 wt%, 1.5 wt%, and 2.0 wt%) employing dry ball milling technique. XRD, SEM, TEM, elemental mapping and XPS characterization techniques confirm the formation of phase pure materials and presence of SiO2 coating layer on the surface of Li1.2Ni0.13Mn0.54Co0.13O2 particles. The electrochemical measurements indicate that the SiO2-coated Li1.2Ni0.13Mn0.54Co0.13O2 materials show improved electrochemical performance in terms of capacity retention and cyclability when compared to the uncoated material. This improvement in electrochemical performance can be related to the prevention of electrolyte decomposition when in direct contact with the surface of charged Li1.2Ni0.13Mn0.54Co0.13O2 cathode material. The SiO2 coating thus prevents the unwanted side reactions between cathode material and the electrolyte. 1.0 wt% SiO2-coated Li1.2Ni0.13Mn0.54Co0.13O2shows the best electrochemical performance in terms of rate capability and capacity retention.

Lithium rich layered oxides (LLO) are one of the potential candidates for Li-ion batteries. however, LLO materials have serious drawbacks such as poor cyclic stability, poor rate capability and rapid voltage decay upon cycling, which needs to be overcome in order to successfully commercialize them. In this work, SiO2 coating is employed (1.0%, 1.5%, and 2.0 wt. %) to combat these issues. Li1.2Ni0.13Mn0.54Co0.13O2 synthesis was carried out by sol-gel process and SiO2 coating was done using dry ball milling method. XRD analysis confirmed the synthesis of phase pure materials without the presence of any impurity phases. SEM and TEM analysis showed the synthesis of nanometric sized particles. Furthermore, TEM elemental mapping displayed the homogeneous distribution of SiO2 on the cathode particles. XPS was further employed to confirm the SiO2 on the cathode material. The electrochemical analysis showed that 1.0 wt.% SiO2 displayed the best performance in terms of rate capability. Uncoated Li1.2Ni0.13Mn0.54Co0.13O2 displayed a fast capacity fade, especially at higher C-rate. On the other hand, SiO2 coated Li1.2Ni0.13Mn0.54Co0.13O2 materials showed improved rate capability. Coated materials also showed improved cycling performance when compared with bare Li1.2Ni0.13Mn0.54Co0.13O2. The improved electrochemical performance can be attributed to the positive impact of SiO2 coating, which impedes the electrolyte oxidation by preventing the direct contact of cathode active material and electrolyte. Overall, the SiO2 coating had a positive impact on the electrochemical performance of Li1.2Ni0.13Mn0.54Co0.13O2 and can pave the way for commercialization of LLO materials.

Lithium ion batteries (LIBs) are attractive for energy storage application. In this regard, lithium rich layered oxides (LLOs), are considered viable cathodes due to their tempting properties such as lower production cost, faster manufacturing process, excellent reversible capacity, and better electrochemical performance at high voltages. Despite these properties, LLOs lack in cyclic stability and inferior capacity retention. This study proposes a surface modification technique to overcome the above-mentioned limitations in which a layer of silica (SiO2) has been coated on the particles of Li1.2Ni0.13Mn0.54Co0.13O2. The Li1.2Ni0.13Mn0.54Co0.13O2 was synthesized by a sol-gel process and then coated with SiO2 (SiO2=1.0 wt. %, 1.5 wt. %, and 2.0 wt. %). The coatings were undertaken through a dry ball milling technique. Different characterization test such as X-Ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), elemental mapping, and X-ray photoelectron spectroscopy (XPS), were utilized to prove phase pure material formation and identify the SiO2 layer on the surface of Li1.2Ni0.13Mn0.54Co0.13O2. The electrochemical measurements, confirm the improvement in capacity retention and cyclability of SiO2 coated Li1.2Ni0.13Mn0.54Co0.13O2 samples with reference to the uncoated samples. This improvement can be ascribed to the protective and barrier effect of the coated layer on the LLOs particles avoiding any unwanted side reactions when the cathode is exposed to the electrolyte. A small trade-off between electrochemical performances and the coating thickness confirms the best efficiency of 1 wt.% SiO2 coated Li1.2Ni0.13Mn0.54Co0.13O2 when compared to other coated samples.