Abstract
Well-dispersed Li-rich Mn-based 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 nanoparticles with diameter ranging from 50 to 100 nm are synthesized by a hydrothermal method in the presence of N-hexyl pyridinium tetrafluoroborate ionic liquid ([HPy][BF4]). The microstructures and electrochemical performance of the prepared cathode materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The XRD results show that the sample prepared by ionic-liquid-assisted hydrothermal method exhibits a typical Li-rich Mn-based pure phase and lower cation mixing. SEM and TEM images indicate that the extent of particle agglomeration of the ionic-liquid-assisted sample is lower compared to the traditional hydrothermal sample. Electrochemical test results indicate that the materials synthesized by ionic-liquid-assisted hydrothermal method exhibit better rate capability and cyclability. Besides, electrochemical impedance spectroscopy (EIS) results suggest that the charge transfer resistance of 0.5Li2MnO3· 0.5LiNi0.5Mn0.5O2 synthesized by ionic-liquid-assisted hydrothermal method is much lower, which enhances the reaction kinetics.
Highlights
Rechargeable lithium-ion batteries (LIBs) have conquered the electronics field due to its many advantages such as high energy and power density, largest output voltage, long cyclic life, and environmental friendliness, compared to other rechargeable batteries (Zhou et al, 2016; Nie et al, 2020; Shi et al, 2020; Tang et al, 2020)
There are three weight losses that appear at 80–100◦C, 220–350◦C, and 600–640◦C in the TG-differential scanning calorimetry (DSC) patterns, respectively, which correspond to the evaporation of free water, the decomposition of the mixture and a small amount of residual ionic liquids, and the formation of lattice oxides, respectively
X-ray diffraction (XRD) results show that the degree of cation mixing and crystalline structure is improved by the ionic liquid during the synthesis
Summary
Rechargeable lithium-ion batteries (LIBs) have conquered the electronics field due to its many advantages such as high energy and power density, largest output voltage, long cyclic life, and environmental friendliness, compared to other rechargeable batteries (Zhou et al, 2016; Nie et al, 2020; Shi et al, 2020; Tang et al, 2020). Many research groups have recently adopted different synthetic methods to improve the electrochemical performance of Li-rich Mn-based layered cathode materials because of the optimization of suitable morphologies and sizes, such as coprecipitation method, sol–gel, and hydrothermal method (Pimenta et al, 2017). Among these methods, the hydrothermal method is promising since it has many advantages over other methods, such as homogeneous mixing at the atomic or molecular level, high purity, and small particle size. The hydrothermal method has several drawbacks such as uneven distribution and serious agglomeration
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