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Nickel-rich ternary material LiNi0.8Co0.1Mn0.1O2 is the promising cathode for lithium ion battery, but it has the disadvantage of structural instability. The common method for modifying its electrochemical performance is element doping, such as sodium, aluminum, magnesium and other elements, because the elements with different types and valences have varied ionic radii and binding energies to oxygen. They are incorporated into the layered nickel-rich ternary material to play the distinct roles. In this work, we investigate the effect of Na and Mg co-doping on Li(Ni0.8Co0.1Mn0.1)O2. Our results suggest that the mixed doping has no effect on the crystal structure and morphology of the material. The Rietveld refinement results demonstrated that cation mixing reduced. The electrochemical test results show that the proper amount of Na and Mg mixed doping improves the cyclic reversibility and reduces the resistance of the material. Na and Mg elements can promote each other to improve the electrochemical performance of the material. At the same time we note that high doping concentrations might mitigate the Li diffusion rates. [ABSTRACT FROM AUTHOR]

Polaron delocalization in layered transition-metal oxides can considerably impact their physical properties and technological applications. Herein, we present the evidence for the influence of polaron delocalization on the electrical transport of layered oxides LiNi0.4+xMn0.4−xCo0.2O2, an active cathode material, by controlling the chemical compositions. We find that the chemical composition at x = 0.3 exhibits a sharp increment in electronic conductivity of four orders of magnitude at room temperature with respect to that at x = 0. We attribute the increased electronic conductivity to a low hopping energy in addition to a weak electron–phonon interaction. The weakened electron–phonon interaction is the source of polaron delocalization in LiNi0.4+xMn0.4−xCo0.2O2, which became improved with increasing x due to the increased polaron sizes. Moreover, it is also suggested that the polaron delocalization may have a relationship with the strong Jahn–Teller distortion induced by Ni3+. The analysis of temperature dependent electrical transport within the framework of the small polaron hopping conduction model enables us to comprehend the influence of polaron delocalization on the electrical transport pertinent to the applications of layered oxide materials. [ABSTRACT FROM AUTHOR]

In this study, a Ni-Co-Mn-Cd-based precursor was synthesized using a solvothermal method and the Li(Ni0.6Co0.2Mn0.2O2)xCd1-xO2 cathode materials were prepared using a high-temperature solid-phase method. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to determine the morphology, structure, elemental composition, and electronic state of the pristine and Cd-doped cathode materials. The electrochemical tests indicated that the Cd-doped samples exhibited better electrochemical performance than the pristine material; specifically, at a doping amount of 0.01 mol, the initial discharge capacity was 186.3 mAh g−1 with a capacity retention of 87.49% after 200 cycles at a current rate of 0.5 C and a capacity retention of 72.43% after 300 cycles at a current rate of 2 C, whereas the pristine material only had an initial capacity of 173.2 mAh g−1 and a capacity retention of 61.25% and 41.09% for the same current rate and cycle number, respectively. In addition, at 8 C, the discharge capacity was 129.8 mAh g−1 for the Cd-doped samples but only 119.6 mAh g−1 for the pristine material. The enhanced electrochemical performance was attributed to the in situ doping modification during the synthesis process of the precursor. This approach effectively stabilized the crystal structure, improved the electronic conductivity of the material, and reduced the impact of the hydrofluoric acid (HF) on the electrode surface due to the generation of CdF2 during the cycle process. [ABSTRACT FROM AUTHOR]

Herein, we present the use of lithium tetrafluoroborate (LiBF4) as an electrolyte salt for wide-temperature electrolytes in lithium-ion batteries. The research focused on the application of blend salts to exhibit their synergistic effect especially in a wide temperature range. In the study, LiCoO2 was employed as the cathode material; LiBF4 and lithium difluoro(oxalate)borate (LiODFB) were added to an electrolyte consisting of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC). The electrochemical performance of the resulting electrolyte was evaluated through various analytical techniques. Analysis of the electrical conductivity showed the relationship among solution conductivity, the electrolyte composition, and temperature. Cyclic voltammetry (CV), charge-discharge cycling, and AC impedance measurements were used to investigate the capacity and cycling stability of the LiCoO2 cathode in different electrolyte systems and at different temperatures. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to analyze the surface properties of the LiCoO2 cathode after cycling. The results indicated that the addition of a small amount of LiODFB into the LiBF4-based electrolyte system (LiBF4/LiODFB of 8:2) may enhance the electrochemical performance of the LiCoO2 cell over a relatively wide temperature range and improve the cyclability of the LiCoO2 cell at 60 °C. [ABSTRACT FROM AUTHOR]

In this work, high-temperature solid-phase techniques have been used to produce both natural and nano ZrO 2 -modified Li-rich manganese-based cathodic materials. Several characterizations were carried out to evaluate the morphology, structure, electrical state, and elemental content of unmodified as well as nano-modified Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 . The results of electrochemical tests showed that cathodic materials modified with 0.02 mol nano ZrO 2 performed extremely well electrochemically, with initial discharge capacity and coulombic efficiency at 0.1 C reaching up to 308.5 mAh g -1 and 95.38%, respectively. After 170 cycles at 0.2 C, a magnitude of 200.2 mAh g -1 for the final discharge capacity was attained, which translates to a capacity retention of 68.68%. Calculations using density functional theory (DFT) show that adding nanoscale ZrO 2 speeds up Li-ion diffusion and increases conductivity by lowering the barrier energy for the migration of Li ions. The structural layout of Li-rich manganese-based cathodic materials may therefore be clarified by the proposed modification technique for nano ZrO 2 .

Li-rich, manganese-based cathode materials are attractive candidates for Li-ion batteries because of their excellent capacity, but poor rate and cycle performance have limited their commercial applications. Herein, Li-rich, manganese-based cathode materials were modified with aluminum isopropoxide as an aluminum source modifier using a sol-gel technique followed by a wet chemical method. To investigate the structure, morphology, electronic state, and elemental composition of both pristine- and surface-modified Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , various characterizations were performed. Based on density functional theory simulations and the results of electrochemical tests, the surface of the modified cathode material was found to contain at least part of the LiAlO 2 phase. This was attributed to the aluminum isopropoxide reacting with a Li 2 CO 3 /LiOH byproduct on the material surface to form LiAlO 2 with a three-dimensional Li-ion channel structure. Electrochemical testing revealed that a 3 wt % aluminum isopropoxide coating of cathode materials exhibited excellent electrochemical performance. Furthermore, the initial Coulombic efficiency and discharge capacity at 0.1 C were up to 88.55% and 272.7 mAh g -1 , respectively. A final discharge capacity of 186.4 mAh g -1 was achieved, corresponding to a capacity retention of 83.55% after 300 cycles at 0.5 C. This was attributed to LiAlO 2 partially accelerating the diffusion of Li ions and Al 2 O 3 aiding the avoidance of side reactions in the mixed coating layer by partially protecting the structure.