A facile strategy to construct composites of amorphous FePO 4 (a-FePO 4 ) nanoparticles and carbon additives with high dispersion and tap density was developed in this work, in which the a-FePO 4 •2H 2 O nanoparticles were handled without drying until being mixed with carbon nanomaterials in water to assure high dispersion of a-FePO 4 • 2H 2 O 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-FePO 4 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-FePO 4 , carbon black, and carbon nanotubes (CNT) exhibited the distinct advantages of low cost and excellent rate capacity over the composites of a-FePO 4 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.
In
this article, nanostructured amorphous FePO4 (a-FePO4)–carbon nanotube (CNT) composites, with high purity
of FePO4 and a controllable FePO4/C ratio, were
directly synthesized by a fast nanoprecipitation process in a microreactor,
using Fe(NO3)3 and (NH4)3PO4 as precursors. Oxidized CNTs are well dispersed via
strong electrostatic repulsion in a high pH solution system. Subsequently,
a-FePO4 nanoparticles are adhered onto CNTs just following
the fast nanoprecipitation process; then, the precipitated composites
are compacted by ball-milling, forming a compact conductive network
with well dispersed and highly loaded active materials. As cathode
materials for lithium-ion batteries, the composites exhibit a capacity
of 175.8 mAh g–1 at 0.1 C, close to the theoretical
capacity (178 mAh g–1), and a good cycle performance
with a reversible capacity of 137.0 mAh g–1 after
500 cycles at 5 C. Importantly, the enhanced micromixing enables fast
nanoprecipitation in suspension and opens a shortcut for constructing
nanostructured composites that have potential in functionalization
and are easy to handle.
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