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Ni-rich layered cathode materials for lithium-ion batteries have received widespread attention due to their large capacity and low cost; however, the structural stability of the material needs to be improved. Herein, F-doped and undoped cathode materials prepared with an advanced co-precipitation method were used to measure the effect of F doping on the material. Compared to the undoped sample, the F-doped cathode materials exhibited an improved rate performance, because the porous structure of F-doped cathode materials is favorable for the infiltration of the electrolyte and the material, and the F-doped cathode material has a larger (003) crystal plane and a smaller Li+ migration barrier energy. This simple F-doping treatment strategy provides a promising way to improve the performance of Ni-rich layered cathode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

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]

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]

Understanding how the morphology and microstructure of secondary particles are affected by pH is essential to design spherical and dense hydroxide aggregates as precursors of high-performance cathode materials for lithium-ion batteries. To investigate the interplay between thermodynamic reaction conditions and the physicochemical properties of precursors, a chemical equilibrium model is used to describe the evolution of metal ammonia complexes. Furthermore, the formation and growth of aggregates are studied by monitoring the changes in surface morphologies and crystal structures of precursors at different reaction times. As the pH value varied, two notable phenomena occurred during crystal growth: the fast growth of grains in the early stage as the pH decreased and the layered growth of grains in the later stage with increased pH values. Such findings could be explained from the following two perspectives. First, the decrease in pH causes a significant increase in the complex ion concentration, thereby facilitating the growth of crystals along the [010] direction. Second, an increase in pH generally accelerates deprotonation of the crystal surface, thus strengthening the adsorption of complex ions on the crystal surface and promoting layer-by-layer growth of primary grains along the [001] direction. [Display omitted] • The effect of pH on crystal growth is investigated by modeling and experimental. • The weak hydrogen bonding dominates the adsorption of complexes on (001) facet. • The deprotonation strengthens the adsorption of complexes on crystal surface. [ABSTRACT FROM AUTHOR]

Layered high-nickel LiNi 0.8 Co 0.1 Mn 0.1 O 2 is a promising candidate of the next generation cathode materials for lithium-ion batteries. However, severe cycling instability and fast capacity drop induced by anisotropic structured change restrict its wide application. To address these defects, the structure design of cathodes is conducted. Herein, a hierarchical layered LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode consisting of orderly stacking hexagonal nanosheets with exposed active {104} facets is successfully synthesized by an improved co-precipitation process and followed with a high temperature lithiation reaction. Benefiting from this unique texture, exposed active {104} facets with lower surface energy supply 3D barrier-free Li+ ion diffusion channels, significantly improving the efficiency of the Li+ diffusion. Moreover, the consistent arrangement of nanosheets in the manner of the {001} facets close attachment is beneficial to alleviate the stress caused by the anisotropic structured change. Thus, this cathode material presents both superior reversible capability (203.8 mAh g−1 at 0.1C, 184.5 mAh g−1 at 1 C, 173.0 mAh g−1 at 5 C and 161.3 mAh g−1 at 10 C) and stable cycling performance (capacity retention of 89.3% after 100 cycles at 1 C, 55.3% after 300 cycles at 5 C and 59.6% after 300 cycles at 10 C). Schematic of single crystal shape evolution of the cathode materials and the corresponding cycle performance of the NCM-3 sample at different rates. [Display omitted] • A hierarchical cathode material consisting of orderly stacking nanosheets with exposed active {104} facets was successfully synthesized. • The exposed active {104} facets with lower surface energy could supply barrier-free Li+ ion diffusion channels. • The consistent arrangement of nanosheets is beneficial to alleviate the stress and inhibit the pulverization of secondary particles. • The hierarchical cathode material presents both superior reversible capability and stable cycling performance. [ABSTRACT FROM AUTHOR]

Due to the scarcity and high cost of cobalt resources, the development of cobalt free batteries is considered to be the next stage of power battery research. Layered LiNi 0.9 Mn 0.1 O 2 has higher energy density and better magnification performance with good prospects. However, its fragile structural stability and surface interface problems result in inferior cycle performance and rate capability compared to cobalt-containing cathode materials with the same Ni content. In this study, low magnetic resistance Al3+ is used as a doping element to enhance the structure of the material and inhibit Li/Ni disordering. As expected, The Ni-rich, Co-free cathode material doped with 2 mol% Al3+ showed the best structure and interface stability, exhibiting a capacity of 166.1 mAh·g−1 at a rate of 1 C after 180 cycles in the voltage range of 2.7–4.3 V, which was higher than that of untreated LiNi 0.9 Mn 0.1 O 2 and other materials with Al3+ doping. Al3+ doping enhanced the material's rate and cycle performance. Cycling at an ultra-high rate of 5 C, the capacity retention rate reaches 86.4% after 100 cycles. The effectiveness of the modified method has been demonstrated in this study, providing a theoretical basis for the commercialization of the material to some extent. ● Al3+ enhances the structural stability of the material and reduces Li/Ni disordering. ● Significantly improved electrochemical properties of Co-free Ni-rich materials after doping with 2 mol% Al3+. Capacity retention is 86.4% after 100 cycles at 5c. ● The suppressions of the secondary particle cracking and the surface side reactions ensure the electrochemical performance of Al3+ doped Co-free Ni-rich cathode materials.. [ABSTRACT FROM AUTHOR]

Abstract In this study, we have successfully coated the CeO 2 nanoparticles (CeONPs) layer onto the surface of the Ni-rich layered LiNi 0.7 Co 0.2 Mn 0.1 O 2 cathode materials by a wet chemical method, which can effectively improve the structural stability of electrode. The X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) are used to determine the structure, morphology, elemental composition and electronic state of pristine and surface modified LiNi 0.7 Co 0.2 Mn 0.1 O 2. The electrochemical testing indicates that the 0.3 mol% CeO 2 -coated LiNi 0.7 Co 0.2 Mn 0.1 O 2 demonstrates excellent cycling capability and rate performance, the discharge specific capacity is 161.7 mA h g−1 with the capacity retention of 86.42% after 100 cycles at a current rate of 0.5 C, compared to 135.7 mA h g−1 and 70.64% for bare LiNi 0.7 Co 0.2 Mn 0.1 O 2 , respectively. Even at 5 C, the discharge specific capacity is still up to 137.1 mA h g−1 with the capacity retention of 69.0%, while the NCM only delivers 95.5 mA h g−1 with the capacity retention of 46.6%. The outstanding electrochemical performance is assigned to the excellent oxidation capacity of CeO 2 which can oxidize Ni2+ to Ni3+ and Mn3+ to Mn4+ with the result that suppress the occurrence of Li+/Ni2+ mixing and phase transmission. Furthermore, CeO 2 coating layer can protect the structure to avoid the occurrence of side reaction. The CeO 2 -coated composite with enhanced structural stability, cycling capability and rate performance is a promising cathode material candidate for lithium-ion battery. [ABSTRACT FROM AUTHOR]

In this study, Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 cathode materials for lithium-ion battery have been successfully synthesized by triethanolamine(TEA) and ethylene glycol solution assisted co-precipitation technology and solid-state sintering method. Relevant tests (XRD, ICP, SEM) were used to determine the structure, composition and morphology of the Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 cathode materials. The electrochemical tests were performed to evaluate the electrochemical performance of the materials. The results show that the initial discharge capacity is 263.8 mAh g −1 at 0.1C rate in a half battery. Furthermore, this cathode material retains a final capacity of 186 mAh g −1 at 0.5C after 200 cycles and displays an outstanding capacity retention of 98.5%. And all tests prove that the Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 lithium-rich materials synthesized with TEA and ethylene glycol solution assisted co-precipitation method have excellent electrochemical properties. [ABSTRACT FROM AUTHOR]

Schematic illustration of growth mechanism of spherical particles for precursors. [Display omitted] • The crystal growth for precursors is investigated by modeling and experiment. • The key mechanism for the formation of hierarchical precursor particles is revealed. • The cathode with discharge capacity over 190 mAh g−1 at 1C is successfully prepared. Hierarchical structure Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 agglomerates were formed by coprecipitation method in the presence of aqueous ammonia in a continuous stirred tank reactor (CSTR). The resultant spherical secondary particles are comprised of highly anisotropic primary grains as building blocks, which retain a distinct hexagonal flake morphology with six {0 1 0} equivalent crystal facets and two other {0 0 1} facets. The formation of hierarchical agglomerates typically undergoes three steps: (i) the formation of grain nuclei (homogeneous nucleation), (ii) anisotropic growth of grains and formation of hexagonal nanosheets, (iii) agglomeration of single crystal grains and formation and growth of spherical agglomerates. This unique hierarchical structures of Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 point to its promising applications in preparation of high-performance cathode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]