Y.Q. Zhang

Metal hydroxide – a new stabilizer for the construction of sulfur/carbon composites as high-performance cathode materials for lithium–sulfur batteries

Rational design and fabrication of advanced sulfur cathodes is highly desirable for the development of high performance lithium–sulfur (Li–S) batteries. Herein, we report Co(OH)2 as a new stabilizer for the sulfur cathode by constructing a cobalt hydroxide-covered sulfur/conductive carbon black (CCB) electrode with the help of thermal and hydrothermal treatments. In this composite, (Co(OH)2@S/CCB), the sublimed sulfur is anchored in the CCB, followed by a uniform coating of Co(OH)2 nanosheets. As cathode materials of lithium–sulfur batteries, the as-prepared Co(OH)2@S/CCB electrode exhibits remarkable electrochemical performances with a high capacity of 1026 mA h g−1 at 0.1C (1C = 1675 mA g−1) and 829 mA h g−1 at 1C. Moreover, it maintains high coulombic efficiencies above 97% after 200 cycles at 1C, much higher than those of the S/CCB counterpart electrode (85%). After 200 cycles at 1C, a high capacity retention of 71.2% is obtained, better than that of the S/CCB electrode (20.2%). The enhanced performance is mainly due to the Co(OH)2 layer which helps to inhibit the shuttle diffusion of polysulfides, resulting in improved capacity retention and cycling life.

A peanut-like hierarchical micro/nano-Li1.2Mn0.54Ni0.18Co0.08O2 cathode material for lithium-ion batteries with enhanced electrochemical performance

A novel peanut-like hierarchical micro/nano-lithium-rich cathode material Li1.2Mn0.54Ni0.18Co0.08O2 has been successfully synthesized via a facile solvothermal method combined with a calcination process. XRD patterns show that the as-prepared sample has high crystallinity and a well-formed layered structure. As a cathode material for Li-ion batteries, this oxide exhibits high capacity, good cyclic stability and superior rate capability. It delivers a discharge capacity of 229.9 mA h g−1 at a current density of 200 mA g−1 between 2.0 and 4.8 V with a high capacity retention of 94.2% after 100 cycles. High reversible discharge capacities of 198.3, 167.5 and 145 mA h g−1 are obtained at 400, 1000 and 2000 mA g−1, respectively. This excellent electrochemical performance is attributed to the hierarchical micro/nanostructure.

Synthesis and electrochemical performance of xLiV3O8·yLi3V2(PO4)3/rGO composite cathode materials for lithium ion batteries

A series of xLiV3O8·yLi3V2(PO4)3/rGO (x : y = 2 : 1, 3 : 1, 1 : 1, 1 : 2, and 1 : 3) composites are synthesized by simple mechanical mixing of LiV3O8 and Li3V2(PO4)/rGO, which are prepared by the hydrothermal method and the sol–gel route, respectively. From scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs, the composites are found to be a mixture of rod-like LiV3O8 particles and flower-shaped Li3V2(PO4)/rGO. Among these composites, the 2LiV3O8·Li3V2(PO4)/rGO electrode delivers an initial discharge capacity of 197 mA h g−1 at a current density of 100 mA g−1 between 2.0 V and 4.3 V, and shows the best comprehensive electrochemical property. The diffusion coefficients of Li ions in the 2LiV3O8·Li3V2(PO4)/rGO electrode are in the range of 10−11.5 to 10−9.5 cm2 s−1 obtained using the galvanostatic intermittent titration technique (GITT).