Boosting lithium ion storage of lithium nickel manganese oxide via conformally interfacial nanocoating

Reconsideration of simultaneous bulk doping and interface structures modification of high-voltage spinel LiNi0.5Mn1.5O4 cathode materials using elemental iodine

The insufficient structural stability of high-voltage spinel cobalt-free LiNi0.5Mn1.5O4 (LNMO) throughout the cycling process hinders its widespread application. To address these issues, we incorporate elemental iodine into LNMO during the precursor preparation process using an ethanol-assisted hydrothermal method and successfully modify the bulk and interface coating structure of LNMO-3% I2. The incorporation of iodine not only induces the formation of a cavity and fast lithium-ion transfer pathway within the particles but also facilitates the development of a thin LiI coating layer on the surface of cathode materials. Compared with bared LNMO, LNMO-3% I2 exhibits a capacity retention of 90.31% following 500 cycles at 1C and a capacity retention of 88.74% even following 450cycles at a high-rate of 50C. Furthermore, the cells with LNMO-3% I2 demonstrate an excellent electrochemical performance under both high temperatures of 40 ℃ and low temperatures of -15 ℃. This study offers valuable insights into the simultaneous optimization of internal and external structures in cathode materials, thereby enhancing the long-term cycling performance of high-voltage lithium-ion batteries.

Recent Progress of High Voltage Spinel LiMn1.5Ni0.5O4 Cathode Material for Lithium-Ion Battery: Surface Modification, Doping, Electrolyte, and Oxygen Deficiency

High voltage spinel LiMn1.5Ni0.5O4 (LMNO) is a promising energy storage material for the next generation lithium batteries with high energy densities. However, due to the major controversies in synthesis, structure, and interfacial properties of LMNO, its unsatisfactory performance is still a challenge hindering the technology's practical applications. Herein, this paper provides general characteristics of LiMn1.5Ni0.5O4 such as spinel structure, electrochemical properties, and phase transition. In addition, factors such as electrolyte decomposition and morphology of LMNO that influence the electrochemical performances of LMNO are introduced. The strategies that enhance the electrochemical performances including coating, doping, electrolytes, and oxygen deficiency are comprehensively discussed. Through the discussion of the present research status and presentation of our perspectives on future development, we provide the rational design of LMNO in realizing lithium-ion batteries with improved electrochemical performances.

Rate Performance Modification of a Lithium-Rich Manganese-Based Material through Surface Self-Doping and Coating Strategies

Lithium-rich manganese-based materials are currently considered to be highly promising cathode materials for next-generation lithium-ion batteries due to their high specific capacity (>250 mA h g^-1) and low cost. A key challenge for the commercialization of these lithium-rich manganese-based materials is their poor rate performance, which is caused by the low electronic conductivity and increasing interface charge transfer resistance produced by the side reaction during the cycling procedure. In this work, we try to improve the rate performance of a lithium-rich manganese-based material Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ using a collaborative approach with Co-doping and Na_xCoO₂-coating methods. Cobalt doping can improve the electronic conductivity, and Na_xCoO₂ coating provides a convenient lithium-ion diffusion channel and moderately alleviates the inevitable decrease in cycling stability caused by cobalt doping. Under the synergistic effect of these two modification strategies, the surface and internal dynamics of the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ material are enhanced and its rate performance is considerably improved without decay of the cycle stability.

Improved Electrochemical Performance of 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 Cathode Materials for Lithium Ion Batteries Synthesized by Ionic-Liquid-Assisted Hydrothermal Method

Well-dispersed Li-rich Mn-based 0.5Li₂MnO₃·0.5LiNi0.5Mn_0.5O₂ 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· 0.5LiNi0.5Mn_0.5O₂ synthesized by ionic-liquid-assisted hydrothermal method is much lower, which enhances the reaction kinetics.