A facile strategy to construct composites of amorphous FePO4 (a-FePO4) nanoparticles and carbon additives with high dispersion and tap density was developed in this work, in which the a-FePO4·2H2O nanoparticles were handled without drying until being mixed with carbon nanomaterials in water to assure high dispersion of a-FePO4·2H2O nanoparticles and carbon nanomaterials; the controlled sedimentation was exploited by rapid adjustment of the pH value via a micromixer to obtain the composites that are easy to manipulate; the composites were endowed with high tap density after simple ball-milling. Using this strategy, hybrid carbon additives were uniformly introduced into the a-FePO4 cathode to form a hierarchical 3D conductive network. Through proper distribution of these components to provide both long- and short-range electron pathways, the reversible discharge capacity could reach 175.6 mA h g-1 at 0.1 C and 139.1 mA h g-1 at 5 C. The composites of a-FePO4, carbon black, and carbon nanotubes (CNT) exhibited the distinct advantages of low cost and excellent rate capacity over the composites of a-FePO4 and CNT, indicating the importance of optimizing the hierarchical structure of cathode composites. The high effectiveness of this construction strategy to build a hierarchical conductive network is also promisingly used for the development of other functional nanocomposites.
Keywords: amorphous FePO4; carbon materials; cathode construction; hybrid carbon additives; lithium-ion battery.