Qing Xue

3D Reticular Li1.2Ni0.2Mn0.6O2 Cathode Material for Lithium-Ion Batteries

In this study, a hard-templating route was developed to synthesize a 3D reticular Li1.2Ni0.2Mn0.6O2 cathode material using ordered mesoporous silica as the hard template. The synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 microparticles consisted of two interlaced 3D nanonetworks and a mesopore channel system. When used as the cathode material in a lithium-ion battery, the as-synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 exhibited remarkably enhanced electrochemical performance, namely, superior rate capability and better cycling stability than those of its bulk counterpart. Specifically, a high discharge capacity of 195.6 mA h g-1 at 1 C with 95.6% capacity retention after 50 cycles was achieved with the 3D reticular Li1.2Ni0.2Mn0.6O2. A high discharge capacity of 135.7 mA h g-1 even at a high current of 1000 mA g-1 was also obtained. This excellent electrochemical performance of the 3D reticular Li1.2Ni0.2Mn0.6O2 is attributed to its designed structure, which provided nanoscale lithium pathways, large specific surface area, good thermal and mechanical stability, and easy access to the material center.

Structure Evolution from Layered to Spinel during Synthetic Control and Cycling Process of Fe-Containing Li-Rich Cathode Materials for Lithium-Ion Batteries

As promising cathode materials for lithium-ion batteries (LIBs), Fe-containing Li-rich compounds of Li1+xFe0.1Ni0.15Mn0.55Oy (0 ≤ x ≤ 0.3 and 1.9 ≤ y ≤ 2.05) have been successfully synthesized by calcining the spherical precursors with appropriate amounts of lithium carbonate. The structures, morphologies, and chemical states of these compounds are characterized to better understand the corresponding electrochemical performances. With an increase of lithium content, Li1+xFe0.1Ni0.15Mn0.55Oy evolves from a complex layered-spinel structure to a layered structure. The lithium content also affects the average size and adhesion of the primary particles. At 0.1 C, sample x = 0.1 shows the highest first charge/discharge specific capacities (338.7 and 254.3 mA h g–1), the highest first Coulombic efficiency (75.1%), the lowest first irreversible capacity loss (84.4 mA h g–1), the highest reversible discharge specific capacity, and good rate capability. Notably, voltage fading can be alleviated through the adjustment of structural features. Such superior electrochemical performances of sample x = 0.1 are ascribed to the hierarchical micro-/nanostructure, the harmonious existence of complex layered-spinel phase, and the low charge-transfer resistance. An integral view of structure evolution from layered to spinel during synthetic control and cycling process is provided to broaden the performance scope of Li–Fe–Ni–Mn–O cathodes for LIBs.