Reactive template synthesis of Li1.2Mn0.54Ni0.13Co0.13O2 nanorod cathode for Li-ion batteries: Influence of temperature over structural and electrochemical properties

Understanding the different effects of 4d-transition metals on the performance of Li-rich cathode Li2MnO3 by first-principles

The poor cycling performance of Li-rich cathode Li₂MnO₃, a promising cathode for next-generation Li-ion batteries, limits its commercial applications. Transition metal (TM) doping is widely applied to optimize the electrochemical performance of Li₂MnO₃, where the d valence electrons of the TM play a crucial role. Nevertheless, the rule of the doping effect of TM with various numbers of d electrons has not been well summarized. In this work, 4d-TMs (Zr, Nb, Mo, Ru and Rh) are selected as dilute doping elements for Li₂MnO₃ to evaluate their effect on the performance of Li₂MnO₃ through first-principles calculations. The calculations indicate that as the number of 4d electrons increases, the doped TM transforms from an electrochemically inert state (Zr and Nb) to an electrochemically active state (Mo, Ru and Rh) in Li₂MnO₃. Meanwhile, the orbital hybridization between the 4d electrons of the TM and the 2p electrons of O becomes stronger from Zr to Rh, which promotes the co-oxidation of the TM and O for charge compensation and alleviates the excessive oxidation of O, thus enhancing the stability of O. Moreover, the oxidation of the doped TM and lattice Mn during charging can trigger a decrease in the initial average delithiation potential. Although the 4d-TMs exhibit slight promoting or inhibiting effects on Li diffusion, no obvious rule related to the number of d electrons has been found. Our work highlights the rule of the doping effect of TMs with different 4d electrons on the electrochemical performance of Li₂MnO₃ and would facilitate a better design of Li₂MnO₃ cathode materials.

Improve the Midpoint Voltage and Structural Stability of Li-Rich Manganese-Based Cathode Material by Increasing the Nickel Content

Lithium-rich manganese is a promising new-generation cathode material for lithium-ion batteries. However, it has the common problems of serious discharge capacity decline, poor rate performance, and faster midpoint voltage decay. In this experiment, a sol-gel method was used to synthesize a high-nickel, lithium-rich layered oxide (1 − x)Li1.2Mn0.54Co0.13Ni0.13O2 − xLiNiO2 (x = 0, 1.0, 2.0, 3.0 and 4.0) that was characterized by XRD, SEM, XPS, TEM, and charge-discharge performance tests. The research results show that increasing Ni content can improve the stability of the material structure and enhance the electrochemical performance of the cathode material. When the LiNiO2 is 0.3, the electrochemical performance is better, the capacity retention rate is 100.3% after 60 cycles at a current density of 0.2 C, and the capacity retention rate for 100 cycles at 0.5 C is 99.0%.

Controllable preparation of one-dimensional Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials for high-performance lithium-ion batteries

Lithium-rich layered oxides are attractive candidates of high-energy-density cathode materials for high-performance lithium ion batteries because of their high specific capacity and low cost. Nevertheless, their unsatisfactory rate capability and poor cycling stability have strongly hindered commercial applications in lithium ion batteries, mainly due to the ineffectiveness of the complicated synthesis techniques to control their morphologies and sizes. In this work, the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials with a one-dimensional rod-like morphology were synthesized via a facile co-precipitation route followed by a post-calcination treatment. By reasonably adding NH₃·H₂O in the co-precipitation reaction, the sizes of the metal oxalate precursors could be rationally varied. The electrochemical measurements displayed that the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ short rods delivered a high capacity of 286 mA h g^-1 at 0.1C and excellent capacity retention of 85% after 100 cycles, which could be contributed to the improvement of the electrolyte contact, Li⁺ diffusion, and structural stability of the one-dimension porous structure.

Simple Glycerol-Assisted and Morphology-Controllable Solvothermal Synthesis of Lithium-Ion Battery-Layered Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Materials

High-performance lithium-rich-layered oxide is regarded as a promising candidate for lithium-ion battery (LIB) cathode materials because of its outstanding high specific capacity. Despite in-depth research over the past decade, there are still a number of serious problems limiting its commercialization. Here, we report a simple morphological design and size-controllable material preparation strategy to enhance the electrochemical performance of LIB cathode materials. We use a simple solvothermal method to obtain a carbonate precursor material with different morphologies by adjusting the solvent ratio of the system, which will be conveniently formed into Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ by calcination. Moreover, further relation between the morphology and electrochemical performance of cathode materials is systematically investigated. The microsphere cathode material with suitable size exhibits superior electrochemical performances among all samples in terms of initial reversible capacity (280.4 mA h g^-1 at 0.1 C) and cycle performance (87.67% retention after 200 cycles at 1 C). Even at 5 C, a high discharge capacity of 150.8 mA h g^-1 can be obtained. In addition, this work provides a feasible and effective approach to controllable synthesis of stable structures and high-performance oxide electrode materials for LIBs.