Li-Rich Layered Oxides

Different from simple coating, we also have to mention here the core-shell materials. The principle consists in preparing a thick and stable shell (micrometer order) completely encapsulating a high-energy but unstable core. S5mergetic (positive) effect of the two materials is expected. Formation process of microscale coreshell structures is tedious, and it requires, at least, three distinct steps (e.g., hydroxide co-precipitation, formation of core-shell 

According to the composite structure notation, the mechanism involved during charge/discharge may be summarized as follows  

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It has been reported that the Li-rich layered oxide material Li2Mn03 LiM02 (M = Co, Ni) exhibits a discharge capacity of >280 mAh/g when operated above 4.7 V, which is about twice that of current commercial positive electrode materials for lithium-ion batteries, making it a promising candidate for a positive electrode material. 

Formation mechanism of SEI layers on cathodes in Li-ion batteries, their thermal and electrochemical stabihty, and their roles in affecting the cycle life and safety characteristics are well documented by many researchers [43 6]. Here we present some recent data on identifying the surface layer generation and their composition on transition metal oxide cathodes like spinel and layered materials by various spectroscopic techniques. The structural changes and the reaction at the surface during the first delithiation process in Li-rich layered material are explained. The effects of additives and coatings on electrode materials to their electrochemical performance are also discussed at the end. 

The main positive electrode materials for lithium-ion batteries, LiCo02, LiNi02, LiMn204, and LiFeP04, were discussed in Chapters 2 through 5. In this chapter, several other important positive electrode materials will be discussed, including Li-rich layered Mn oxides, phosphates, sulfates, silicates, borates, titanates, V2O5, and other oxides [1]. 

DBMS) [ARM 06] nevertheless, the quantity of gas detected was not sufficient to compensate for the total quantity of lithium deintercalated on the plateau . It has been shown that this unusual mechanism arose due to the reversible participation of the oxygen anion in the redox processes. This original mechanism, demonstrated for the first time for layered oxides, is possible due to the particular composition of these Li- and Mn-rich materials the hybridization of transition metals nd levels and anions 2p levels leads to a mixed redox process involving both the cations and the anions [KOG 13a, SAT 13a, SAT 13b]. This mechanism, responsible for the exceptional reversible capacity these materials deliver, is enhanced for transition metals that are highly oxidized and electronegative (Figure 2.13). 

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