Recently, ABO 3-type perovskite oxides have received much attention because of their physical/chemical properties including high electric/ionic conductivity and good structural stability. 21–25 Certain requirements must be met when choosing candidates such as: (1) the coating materials need good electrical conductivity which facilitates the electron transfer rate and (2) an HF scavenger, it should be able to improve the high voltage performance of LIBs by suppressing the interfacial side reactions between electrode and electrolyte. There are a lot of inorganic materials e.g., LiYO 2, SiO 2, WO 3, Li 2MnO 3, Li 3PO 4, CaO, etc., which have been reported to be used as coating materials. 20 Among the various methods, surface modification is considered as the most effective method for improving the electrochemical performances of Ni-rich cathode material. To prevent such degradation, various methods have been adopted including morphology control, surface modification, and substitution of elements. 19ĭEC + LiPF 6 → C 2H 5OCOOPF 4 + C 2H 4 + HF + LiFįrom the above factors, it is important to prevent the side reactions between the cathode electrode material and electrolyte. 18 As shown in eqn (1) and (2), these by-products form a cathode electrolyte interface (CEI) film on the cathode material surface, which leads to decreasing capacity and rate capability because of low ionic and electric conductivities. 16,17 The decomposition of organic electrolytes produces a variety of by-products. Li/Li +), causing oxidation of the electrolyte. In addition, NCM811 cathode materials are charged at high voltage (≥4.5 V vs. 12–15 This structural rearrangement hinders the diffusion of lithium ions and leads to rapid capacity fading. At high voltages, unstable Ni 4+ on the surface of the cathode materials is reduced to Ni 2+ and is accompanied by the formation of a spinel phase or rock salt phase. However, some factors like thermal stability and structural change induce performance degradations in Ni-rich layered oxide NCM811 materials. In particular, NCM811 is one of the most promising Ni-rich cathode materials which have a higher capacity than conventional LiCoO 2 cathode material. Furthermore, the content of cobalt (Co) plays a role in improving the rate capability. 8,9 The high Ni content in NCM helps to result in a high capacity and the content of manganese (Mn) increases the structural stability. 7 Among the various materials used in LIBs, high nickel (Ni) compounds such as LiNi 1− x− 圜o xMn yO 2 (NCM, 1 − x − y ≥0.5) are promising materials for EVs and HEVs. In order to improve the cathode materials, many efforts are being made such as changing the structure or synthesizing materials. 6 Improving the electrode active material is a way to achieve these purposes, especially for cathode active materials. 5 A high capacity retention and high energy density are the main points for making commercialized LIBs in electric vehicles. 1–4 They are also anticipated to provide electrochemical energy storage for solar energy and wind power sources. Introduction Lithium ion batteries (LIBs) with a high energy density and power density have been used for electric vehicles (EVs) and hybrid electric vehicles (HEVs) as renewable energy systems. Li/Li + under high voltage conditions with Ni-rich cathode active materials. Furthermore, the 0.5 wt% LaFeO 3-coated NCM811 delivers excellent rate capability and demonstrates improved structural stability at 4.6 V vs. Even after 80 cycles, 0.5 wt% LaFeO 3-coated NCM811 cathode material shows about 13% higher cycling stability when compared to the bare NCM811 and other ratios of coated materials. The LaFeO 3 coating layer significantly protects the cathode material from corrosion due to the HF formation and restrains the dissolution of other ions into liquid electrolyte during high voltage charge–discharge processes. Herein, we report the surface modification of NCM811 cathodes with a perovskite material, i.e., lanthanum iron oxide (LaFeO 3), which has drawn attention for various research areas due to its non-toxicity, electric conductivity, chemical stability, and low cost and systematically investigate the influence of the LaFeO 3 coating on NCM811. Li/Li + needs to be addressed to enhance the electrochemical performance. However, the severe capacity fading which occurs above 4.2 V vs. Ni-rich LiNi 0.8Co 0.1Mn 0.1O 2 (NCM811) is regarded as a potential cathode material due to its higher capacity.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |