Synthesis and Li-storage behavior of CrN nanoparticles

Abstract

Bulk CrN nanoparticles are prepared by the thermal decomposition of a Cr–urea complex in a flowing NH₃ + N₂ atmosphere and characterized by X-ray diffraction (XRD) and high resolution-transmission electron microscopy (HR-TEM) along with selective area electron diffraction (SAED) techniques. The Li-cycling performance of bulk CrN is evaluated by galvanostatic cycling and cyclic voltammetry on the cells with Li metal as counter electrode in the voltage range of 0.005–3.0 (3.5) V at ambient temperature. When cycled at 60 mA g⁻¹ (0.1 C) up to 3.0 V, the composition 55 : 30 : 15 (active material : carbon : binder) showed a first-cycle reversible capacity of 635 (±10) mA h g⁻¹ (1.6 moles of Li). The reversible capacity of 500 (±10) mA h g⁻¹ (1.23 moles of Li) is stable between 10 and 80 cycles. At 0.5 C, it showed a stable capacity of 350 (±10) mA h g⁻¹ for 40 cycles and the original capacity is regained when cycled at 0.1 C rate after 160 cycles. The coulombic efficiency is found to be >96% in the range of 20–80 cycles. The low impedance at the discharge potential <1.3 V and high impedance at charge potential 3.0 V evaluated from the impedance spectra (EIS) showed the decomposition and formation of CrN during the 1st cycle. The apparent D_Li+ obtained from EIS is in the range, 0.73–3.6 (±0.1) × 10⁻¹⁴ cm² s⁻¹ during the first-cycle.