Upadhyayula V Varadaraju

Lithium perylene-3,4,9,10-tetracarboxylate (Li-PTCA) is synthesized starting from perylene-3,4,9,10-tetracaboxylicacid-dianhydride (PTCDA). In Li-PTCA, the carbonyl group of the carboxylate redox centers exhibits excellent electrochemical reversibility at an average voltage of 1.2 V with respect to Li+/Li. We have improved the rate capability and capacity of Li-PTCA based electrode by in-situ coating of Li-PTCA with conducting acetylene black carbon. We have demonstrated enhanced rate capability, improved capacity and reduced charge transfer resistance in the in-situ carbon coated electrode vis a vis electrode fabricated by conventional method. A capacity of 120 mAh g-1 is observed at the end of the 50 cycles, at 240 mA g-1. Ex-situ XRD studies have revealed that the crystal structure is robust and is stable for reversible insertion of Li. In-situ carbon coated Na-PTCA shows better reversibility and high capacity retention even after 100 cycles when cycled using current densities as high as 500 mA g-1.

In-situ carbon coated carrollite spinel CuCo 2 S 4 nanoparticles were synthesized by a simple low temperature hydrothermal route and studied as anode for lithium battery applications. The electrochemical reaction with lithium involves initial insertion of 3Li/f.u into the lattice upto 1.5 V followed by conversion reaction upto 0.01 V. A reversible capacity of 180 mAh g −1 was obtained for CuCo 2 S 4 after 30 cycles at C/5 rate (137 mA g −1 ). However, in-situ carbon coated CuCo 2 S 4 shows significantly higher capacity of 375 mAh g −1 even after 30 cycles.

Hierarchical spherical porous carbon (HSPC) is synthesized by adopting a single step soft template method and extensively characterized by XRD, BET surface area, Raman spectroscopy, FE-SEM and HR-TEM analysis. The HSPC electrode outperformed the commercial graphite material at higher current rates when tested for Li-ion battery application. It exhibits superior electrochemical performance such as a high reversible specific capacity of 422 mA h g−1 at a current density of 100 mA g−1 and high rate capability of 102 mA h g−1 at a current density of 5000 mA g−1 with good cyclic stability. The notably higher electrochemical performance is attributed to the hierarchical porosity which resulted in lower charge-transfer resistance and superior rate performance. The simple synthesis approach and superior rate performance in the present study makes HSPC an alternative anode candidate for rechargeable lithium-ion battery application.