8/23/2023 0 Comments Xps lialo2 coating on nmc cathodeThis is the first time that coatings on NMCs are reviewed based on their functionalities and mechanisms through which the electrochemical properties and performance of NMCs have been improved. This article focuses on review of the recent advancements in coatings of NMCs from the mechanism viewpoint. Coatings provide an effective solution to these problems. However, widespread market penetration of NMCs as cathodes for Li-ion batteries (LIBs) is impeded by their poor capacity retention and low rate capability. Layered lithium nickel manganese cobalt oxides, Li(NixMn圜oz)O2 where x + y + z = 1 (NMCs), have been studied extensively due to their higher capacity, less toxicity and lower cost compared to LiCoO2. It is expected by utilizing the proposed cathode and anode materials in full-cell set up, a high performance battery with fast charge ability is obtained. The electrodes performed very well in half-cell configuration. This technique resulted in the formation of thin lithium phosphate coating around the particle. To enhance their electrochemical properties and rate capabilities, a facile surface modification using phosphoric acid was employed. As for the cathode side, two different members of NMC family materials (NMC333 and NMC532) have been tested. The silicon anodes have been tested successfully in the half-cell coin cells. They have the potential of being commercialized and they do not need expensive equipment. Both of these designs can be synthesized easily without complicated synthesis steps and harmful chemicals. The first approach is the core/shell design and the second one is the silicon/graphite nanocomposite with tailored structure and engineered voids. Here in this thesis, two different approaches are introduced to harness the problems associated with silicon anodes. Lithium nickel manganese cobalt oxide (NMC) cathode family materials are introduced following this idea. Therefore, substitution of cobalt with other elements such as manganese and nickel is necessary. Furthermore, cobalt is known as toxic element. The resources for cobalt element is very limited while the price of cobalt increasing. From the cathode viewpoint, the need for materials with less cobalt content is necessary. However, this material suffers from huge volume expansion during cycling in addition to its intrinsic low conductivity. Silicon with the theoretical capacity of about 10 times higher than graphite is a promising anode. Although graphite can deliver ~ 370 mA h g-1 capacity without significant capacity decay for several cycles, however it is not enough to fulfill the requirements for many applications. Currently, graphite is used as anode, while lithium cobalt oxide serves as cathode dominantly. All mentioned characteristics are directly related to the choice of anode and cathode electrodes. Lithium-ion batteries (LIBs) have revolutionized the portable electronic devices and electric vehicles (EV) and because of this huge demand, it is important to meet high power, high specific energy, and long cycle life. These results demonstrate that the H3PO4 treatment is a facile and general method to improve the electrochemical properties of NMCs with different compositions and can be utilized for practical applications. Similar improvements have also been achieved with NMC333. The rate capability has also been improved significantly with Li3PO4-coated NMC532 exhibiting ∼150 mA h g−1 capacity at 6C while pristine NMC532 showing zero capacity. The final specific capacity of Li3PO4-coated NMC532 is 187 mA h g−1 after 100 cycles at 1C, whereas the corresponding value of pristine NMC532 is only 50 mA h g−1. The specific capacity of the first discharge for NMC532 has been increased drastically from ∼160 mA h g−1 for pristine NMC532 to ∼250 mA h g−1 for Li3PO4-coated counterpart at 0.1C and such a large capacity enhancement is retained throughout the subsequent cycles at 1C. The Li3PO4 coating formed is found to be very potent in enhancing the specific capacity of the first discharge as well as the rate capability and capacity retention in the subsequent charge/discharge cycles for both NMC333 and NMC532. In this study, Li(Ni1/3Mn1/3Co1/3)O2 (NMC333) and Li(Ni0.5Mn0.3Co0.2)O2 (NMC532) have been subjected to a phosphoric acid (H3PO4) solution treatment to form a thin Li3PO4 coating on their surfaces.
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