Multiple-functional LiTi2(PO4)3 modification improving long-term performances of Li-rich Mn-based cathode material for advanced lithium-ion batteries
Li-rich layered oxides with high energy densities have become one kind of promising cathode for advanced lithium-ion batteries, however some issues are severely hindering their practical applications. To address these challenges, fast ion conductive LiTi 2 (PO 4 ) 3 (LTPO) is employed to modify the typical Li-rich cathode Li 1 · 2 Mn 0 · 56 Ni 0 · 17 Co 0 · 07 O 2 (LMNCO) via a sol-gel process combined with a two-step annealing treatment in this work. Serving as a physical separator, LTPO coating effectively depresses the side reactions at cathode-electrolyte interface and the transition-metal dissolution from LMNCO active material under harsh electrochemical environment. Meanwhile, LTPO layer with high ion conductivity could facilitate the interfacial Li + diffusion during charge/discharge process. In addition, partial Ti 4+ ions doped into LMNCO effectively elevate the oxygen electronegativity and restrain the excessive oxidization of lattice oxygen, thus stabilizing the crystal structure and alleviating the stress-strain propagation upon cycling. Electrochemical characterization results demonstrate that the LTPO-modified LMNCO cathode exhibits a superior capacity retention of 86.5 % after 400 cycles at room temperature and that of 73.7 % even under an elevated temperature of 45 °C after 250 cycles under 1C. This study provides a facile strategy for the surface modification of Li-rich layered-structure oxides, which also sheds light in enhancing electrochemical performances for various cathode materials .
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