Hydrothermal synthesis of reduced graphene oxide-LiNi0.5Mn1.5O4 composites as 5 V cathode materials for Li-ion batteries

Abstract

Composite materials consisting of reduced graphene oxide and LiNi0.5Mn1.5O4 were in-situ prepared by a simple one-step hydrothermal-treating method. The physical property and electrochemical performance of the composite materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), charge/discharge testing and electrochemical impedance spectroscopy (EIS). The results demonstrate that the graphene oxide is partially reduced and uniformly in-situ anchored on the surface of LiNi0.5Mn1.5O4. As a result, the specific surface area of the composite material dramatically increases from 0.2488 m 2 •g-1 to 8.71 m 2 •g-1 and the initial specific discharge capacity improves from 125.8 mAh•g-1 to 140.2 mAh•g-1 , respectively. Furthermore, the capacity retention maintains 95.8 % after 100 cycles and the electrode polarization has significantly been lessened. At rates of 1 C, 2 C and 5 C, the composite material with 5 % reduced graphene oxide can deliver much higher capacities than the pristine LiNi0.5Mn1.5O4. Moreover, AC impedance test results show that the interfacial charge transfer impedance obviously reduced. It's confirmed that the introduction of reduced graphene oxide through hydrothermal treating is effective to enhance the electrochemical performance of the composite material.

Effect of Single-Walled Carbon Nanotube Sub-carbon Additives and Graphene Oxide Coating for Enhancing the 5 V LiNi0.5Mn1.5O4 Cathode Material Performance in Lithium-Ion Batteries

“…The two bands at 495 and 403 cm −1 were related to the Ni 2+ −O stretching (E g ) mode. 6,30 The strong peak splitting at 580−630 cm −1 was related mainly to the ordered crystal structure with the P4 3 32 space group. 48 Although the spectrum of P-LNMO did not feature any noticeable strong peak splitting in the range 580−630 cm −1 , the intensities of the peaks mentioned above were weakened for the GO-coated LNMO samples (Figure S5).…”

“…These two-dimensional (2D) GO nanosheets would presumably form a strong and thin protective layer on the LNMO surface, stabilized through electrostatic or hydrogen bonding interactions. 30,47 Figure 1C,D presents SEM images of the pristine LNMO and 0.1%SWCNT-LNMO electrodes. The former contained only the LNMO material and Super P; the latter also featured the SWCNT sub-carbon additive.…”

“…Nevertheless, those metal oxides, fluorides, and phosphates have been able to control only the effects of Mn dissolution and electrolyte species attack but have not been able to increase the electronic conductivity of the cathode materials. 30 Furthermore, most of these coatings have been obtained after post-annealing at high temperature, resulting in non-uniform coating layers and the reduction of Mn 4+ to Mn 3+ species. 23,31 In contrast, conductive polymer and carbon coatings have been able to increase the electronic/ionic conductivities of LNMO cathodes, thereby boosting their high-rate and reversible capacities.…”

Influence of Graphene Wrapped-Cerium Oxide Coating on Spherical Lini0.5mn1.5o4 Particles as Cathode in High-Voltage Lithium-Ion Batteries

“…However, the coating methods employed for accomplishing the ceria coating provide difficulty in controlling the homogeneity of the coating layer [40,41]. Moreover, metal oxide coatings lend extra resistance to the mobility of ions and electrons and lower the rate capability of LNMO [42]. Hence, due to graphene's exceptional electrical characteristics, stable chemical properties, and large surface area, it has been keenly investigated for energy storage applications [43].…”

“…Hence, Graphene oxide is often utilized as a coating precursor as it attaches easily to the cathode surface owing to the oxygen-containing groups that it possesses [51]. However, the electronic conductivity of graphene oxide is lower compared to graphene, so a calcination process is often utilized that reduces the graphene oxide into graphene sheets and enables efficient coverage of the cathode material [42,52].…”