Synthesis of nanosized materials for lithium-ion batteries by mechanical activation. Studies of their structure and properties

This short review reports on the synthesis of nanosized electrode materials for lithium-ion batteries by mechanical activation (MA) and studies of their properties. Different structural types of compounds were considered, namely, compounds with a layered (LiNi1 - x - y Co (x) Mn (y) O-2), spinel (LiMn2O4, Li4Ti5O12), and framework (LiFePO4, LiTi2(PO4)(3)) structures. The compounds also differed in electronegativity, which varied from 10(-4) S cm(-1) for LiCoO2 to 10(-9) S cm(-1) for LiFePO4. The preliminary MA of mixtures of reagents in energy intensive mechanoactivators led to the formation of highly reactive precursors, and annealing of the latter formed nanosized products (the mean particle size is 50-200 nm). The local structure of the synthesized compounds and the composition of their surface were studied by spectral methods. An increase in the dispersity and defect concentration, especially in the region of the surface, improved some electrochemical characteristics. It increased the stability during cycling (LiMn2O4, at 3 V) and the regions of the formation of solid solutions during cycling (Li4Ti5O12, LiFePO4), led to growth of surface Li-ion conductivity (LiTi2(PO4)(3)), etc. The mechanochemical approach was also used for the synthesis of core-shell type composite materials (LiFePO4/C, LiCoO2/MeO (x) ) and materials based on two active electrode components (LiCoO2/LiMn2O4).