Search

Cross-nanoflower CoS 2 on rGO nanosheets has been synthesized by simply controlling the pre-reaction step during hydrothermal route. Three-dimensional CoS 2 cross-nanoflowers of 150–200 nm in diameter are formed in-situ through self-assembling with rGO nanosheets reduced from GO (shorten as CoS 2 –NF/rGO-NS). From XRD, SEM, XPS and TEM analysis, these CoS 2 nanoflowers are composed of single crystal nano-slices of 20–30 nm in thickness and evenly distributed in the networks of flexible/conductive rGO nanosheets. Owing to both capacitive-controlled and diffusion-controlled mechanisms existing in the discharging/charging processes, CoS 2 –NF/rGO-NS composites show excellent rate performance and cycling stability as anode materials. According to DFT calculations/simulations, the corresponding diffusion barrier (E bar) is derived to be 0.47 eV along ⟨100⟩ diffusion direction for CoS 2 cross-nanoflower, indicating an effective lithium ion diffusion channel. Their enhanced electrochemical properties are therefore attributed to synergistic effects of two components: highly active/stable nanoflower-like CoS 2 –NF structure and flexible/conductive reduced graphene nanosheets (rGO-NS). Image 1 • 150–200 nm CoS 2 cross-nanoflower in-situ self-assembled on rGO nanosheet. • CoS 2 nanoflower composited of 20–30 nm single crystal nanochips in thickness. • CoS 2 nanochips provide a good Li+ diffusion channel along ⟨100⟩ by DFT calculations. • Advanced performance owing to highly active CoS 2 and pseudocapacitive effect by rGO. [ABSTRACT FROM AUTHOR]

• The changes in the surface properties of N-MXene have been studied in detail. • The wrinkled/flexible N-MXene is firstly introduced to enhance NCM811 cathode. • More extra capacity is provided for NCM811 by wrinkled/flexible/layered N-MXene. • Irreversible Mn/Co/Ni migration is prohibited by N-MXene from DFT simulation. In this work, the wrinkled, flexible, and layered nitrogen-doped Ti 3 C 2 T x (shorten as N-MXene) is synthesized by using cyanamide as N-dopants. The changeable (002) plane spacing and the attached functional groups of N-MXene are detected by XRD and XPS analyses in details, respectively. The microscopic morphology of N-MXene is characterized by SEM and TEM, which demonstrates its wrinkled and flexible characteristics. When the wrinkled N-MXene being added into the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) as conductive additive, the attained electrodes obtain enhanced electrochemical performances at the appropriate weight ratio (namely 2.5-N-MXene with 2.5 wt.%). The 2.5-N-MXene delivers "extra" capacity of 226.9 mAh/g at 0.1 C (20 mA/g) current density. The "extra" capacity is assigned to Li ions intercalation/extraction from the wrinkled/flexible/layered N-MXene. Moreover, based on the analyses of CV and dQ/dV curves, the wrinkled/flexible N-MXene additive could effectively inhibit the phase transition of M↔H2 of NCM811 and alleviate the volume change of the particles in the circulation. From DFT simulation, the N-MXene is more capable of preventing Ni/Co/Mn from dissolving and migrating to the negative electrode to form dendrites through adsorption. Therefore, the N-MXene should be a very competitive conductive agent to improve the mechanical and electrochemical properties of high nickel cathode materials. [Display omitted] [ABSTRACT FROM AUTHOR]