Mechanistic insights into high lithium storage performance of mesoporous chromium nitride anchored on nitrogen-doped carbon nanotubes

- Unique nanocomposite structure consists of mesoporous CrN with NCNTs homogenously distributed on surface.
- The CrN/0.08%-NCNT electrode retains a high capacity of 1042.9 mAh g−1 at 20 °C.
- The network structure with conductive electron paths enables high rate capability.
- The reversible conversion reaction mechanism of CrN into Cr metal and Li3N is revealed.
- Pyridinic nitrogen has a high influence on the Li storage properties for NCNTs.

Chromium nitride (CrN) synthesized by heating at 550 °C under a continuous stream of ammonia has been investigated as anode material for lithium electrochemistry. Due to its low lithium insertion potential, Cr is an attractive material for lithium-ion battery application, but the usual volume variation effect obstructs its practical use. In this study, different concentrations of carbon nanotubes doped with nitrogen (NCNTs) are combined with CrN to attain high electrochemical performance. The synthesized CrN/0.08%-NCNTs nanocomposite demonstrates network structure with 30-40 nm CrN nanoparticles anchored to specific sites on 40-60 nm diameter NCNTs. Upon electrochemical testing, CrN/0.08%-NCNTs nanocomposite displays a discharge capacity of 1172 mAh g−1 after 200 cycles with high coulombic efficiency (∼100%) and rate capability. The electrode can deliver a reversible capacity of 1042.9 mAh g−1 at 20 C. The n-type concentration, along with the conductive CNTs framework, mesoporous channels, appropriate surface area and buffering capability of CNTs, are together responsible for the excellent electrochemical performance. The electrochemical reaction mechanism of CrN with lithium is explored by investigating the structural changes using ex situ X-ray photoelectron spectroscopy, X-ray diffraction, selected area electron diffraction, and high-resolution transmission electron microscopy. The reversible conversion reaction of CrN into Cr metal and Li3N is revealed.

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