Preparation of 0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂ with tunable morphologies via polyacrylonitrile as a template and applications in lithium‐ion batteries

Abstract

Samples of 0.4Li 2 MnO 3 Á0.6LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LMO) with tunable morphologies were synthesized via polyacrylonitrile (PAN) as a template. The starting PAN/N,N-dimethylformamide (DMF) ratios, including 1:9, 1:10, 1:12, and 1:14, were optimized for the fiber morphologies and electrochemical performance. Through electrospinning, metal salts were well dispersed in the PAN fibers. The crystal structure and morphologies of the PAN/LMO fibers were characterized by X-ray diffraction, scanning electron microscopy, and thermal analysis. Along with the decrease in the concentration of PAN in the precursor, the diameters of the PAN/LMO fibers decreased. On the other hand, at the highest and lowest concentrations, 1:9 and 1:14, of PAN with DMF, micrometer PAN fibers were electrospun, whereas ratios of PAN to DMF of 1:10 and 1:12 resulted in the electrospinning of millimeter-long fibers of PAN. In the interface of PAN and metal salts, LMOs were grown and accompanied the decomposition of PAN, and the crystal morphologies of LMO quite depended on the diameter and length of the PAN/LMO nanofibers. During heat treatment, the morphologies of the PAN fibers controlled the removal of small molecules and the crystal morphologies of LMOs. The charge/discharge results indicate that LMO with a tubular structure delivered a capacity of 262.3 mAh/g at a cutoff voltage of 2.5-4.8 V at a 0.1 C rate. Benefitting from a unique hollow and nanocrystalline architecture, it also exhibited good rate and cycling performances. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43022.

Morphology and Interconnected Microstructure-Driven High-Rate Capability of Li-Rich Layered Oxide Cathodes

“…The pie chart clearly shows that ES-LLO has one of the highest capacities of all the studies reported. Few similar or slightly higher capacity results are reported in the literature (see refs ,, for the pie chart given in the Supporting Information section); however, it is worth noting that the Co content in our data is the lowest compared to all the reported work on the fibrous compound. Reference which highlights the highest capacity of 300 mA hg –1 is the value measured at 0.05 C-rate.…”

“…Cathodes form an important active material in LIBs. Energy and power density of the cathode materials are critical parameters for ascertaining the electrochemical performance of the LIB for specific application. , Currently, commercial LIBs are made using layered LiCoO 2 -type cathodes because of stable initial specific capacity (140 mA h g –1 ) and stable electrochemical cycling. However, because of the high cost and toxicity, these conventional cathode materials cannot be extended to large-scale applications including electric vehicles. , Furthermore, batteries operating at high charging–discharging rates are required for wider commercialization.…”

“…Electrospinning is a relatively new technique, and morphologically of well-connected particles obtained from this process are yet to be explored in detail. The ES method to synthesize uniform long wires can bring in benefits from several fronts including highly interconnected particles improving the electrical conductivity, mesoporous nature improving the rate-capability, and highly homogeneous materials resulting from the uniform mixing of metallic elements in the polymer solution. , Moreover, obtaining a continuous long strand of material is of great importance because of the high surface to volume ratio. Such a microstructure results in shortening the diffusion pathways, and good connection among the particles improves the effective conductivity. , …”

Orientation of Electrospun Magnetic Nanofibers Near Conductive Areas

“…It should be mentioned that this electrospinning technology is not well-suited to prepare very long nanofibers in the range of several millimeters, as it is possible with the needle-based process [39][40][41]. Due to the usually isotropic arrangement and the interconnections formed between the fibers, length estimation of fibers spun by a wire-based technology is difficult and, to the best of our knowledge, not yet reported in the literature.…”

High rate capability and cyclic stability of Ni‐rich layered oxide LiNi0.83Co0.12Mn0.05−xAlxO2 cathodes: Nanofiber versus nanoparticle morphology

“…While there are few studies that address the methods to improve the electrochemical properties of cathode materials, such as Li-rich layered oxide, studies on nanofibrous Ni-rich layered oxides processed by the ES technique are scarce. 15,16 In this manuscript, we explore enhancing the cyclic performance of nanofibrous Ni-rich layered oxide cathodes by optimizing the process parameters during synthesis and the annealing condition. ES of polymer solution is a novel and efficient technique to prepare 1D solid, hollow, and porous NFs.…”