Robust Pitaya-Structured Pyrite as High Energy Density Cathode for High-Rate Lithium Batteries.

To solve the serious problems (the agglomeration of nano-Fe0, dissolution of polysulfide, and low electronic conductivity of Li2S) of earth-abundant pyrite (FeS2) cathodes for lithium batteries, a simple in situ encapsulation and transformation route has been successfully developed to synthesis pitaya-structured porous carbon embedded with FeS2 nanoparticles. Due to such a hierarchical architecture design, this cathode of pitaya-structured FeS2@C can effectively avoid the serious agglomeration and coarsening of small Fe nanoparticles, reduce the dissolution of polysulfide, and provide superior kinetics toward lithium storage, resulting in enhanced reversibility and rate capability. Cycling in the voltage region of 1.0-3.0 V at 0.3 A g-1, the current conversion-based FeS2@C cathode displays a high and stable energy density (about 1100 Wh kg-1), ultrahigh rate capability (a reversible capability of 660, 609, 554, 499, 449, and 400 mA h g-1 at 0.2, 0.5, 1.0, 2.0, 5.0, and 10 A g-1, respectively), and stable cycling performance.