Abundant Coordinatively Unsaturated Atoms in P-Ni_0.96S with Excellent Intrinsic Dynamic Performance for Li-S Batteries

Theelectrocatalytic mechanism/performance of P-Ni0.96S@C andLi-S batteries as clean energy is conducive to sustainabledevelopment. Heteroatom-dopedtransition metal compounds possess abundant defectsand subtle electron properties, which have broad potential in solvingthe problems that hinder the commercial application of Li-Sbatteries. Here, P-Ni0.96S nanoparticles with coordinativelyunsaturated atoms dotted in the 3D porous carbon (P-Ni0.96S@C/CP) were synthesized by heteroatom doping engineering and appliedto catalyze multistep-multiphase conversion. It is demonstrated thatthe electronic structure of Ni0.96S was drastically changedby P-doping. The intrinsic dynamic performance was tested in a self-madeflowing three electrode system to exclude the effect of diffusionon electron transfer kinetics. The result showed that P-Ni0.96S exhibited excellent dynamics with a low Tafel slope for Li2S6 redox (67.75 and 93.45 mV/dec) and Li2S2 redox (74.96 and 75.87 mV/dec). The corresponding exchangecurrent densities of Li2S6 and Li2S2 redox were 227.26 and 11.05 & mu;A/cm(2). The activation energy (E (a)) test showedthat P-Ni0.96S reduced the reaction energy barrier, particularlyfor the rate-determining step (0.44 eV). Thus, the battery using theS@P-Ni0.96S@C/CP electrode delivered a high specific capacityof 1155.2 mAh g(-1) and stable long cycle performanceat 2 C. Importantly, S@P-Ni0.96S@C/CP exhibited a highareal capacity of 5.6 mA h cm(-2) under a load of6.2 mg cm(-2).