Preparations And Electrochemical Properties Of Layered Double Hydroxide-Based Transition Metal Compound Of Lithium-Ion Battery Anode Material

Energy issues and environmental problems are two types of major issues of global common concern. Efficient and clean Li-ion batteries have successfully played a key role in many applications, such as portable electronics and electric vehicles. In recent years, increasingly broadening range of applications makes lithium-ion batteries endowed with high-capacity, high-rate and long-cycle stabilities. Transition metal compounds as anode nanomaterials for lithium-ion batteries (LIBs) possess higher theoretical capacity than the commercial carbon anode material, but the further application process are hampered by the common problems of the charge/discharge process large deformation and poor electrical conductivity. Layered double hydroxides (LDHs), well-kown as a large family of two-dimensional (2D) anionic clay materials, have been of increasing scientific and technologic interest in a wide variety of fields, including catalysts, adsorption materials, drug/gene deliveries, and photochemistry, as well as electrochemistry. Utilization of thermal decomposition of LDHs can be an effective way to prepare uniformly distributed bi-metal oxide composite. We herein have demonstrated the facile preparations of two types of transition metal compounds (MgFe2O4/ZnFe2O4 and Co9S8/Al2O3/C) derived from LDH precursors. The obtained nanocomposites are able to exhibit highly enhanced electrochemical performances when used as anode materials for LIBs. The main results and innovations are given as follows.(1) MgFe2O4/ZnFe2O4 nanocomposites are obtained by decomposition of MgZnFe-LDHs precursors prepared by a scalable method of separate nucleation and aging process. Results of XRD, TEM, and XPS clarify that the nanocomposites have the uniform distribution of bi-active MgFe2O4 and ZnFe2O4. The nanocomposite as anode nanomaterial exhibit highly enhanced electrochemical properties in comparison with the physically mixed MgFe2O4/ZnFe2O4 composite. The possibilities of the enhancement could be attributed to the following features:(â…°) mesoporous nanostructures, facilitating improving the electrode/electrolyte contact area; (â…±) good distribution of MgFe2O4/ZnFe2O4 at the atomic scale, thereby buffering the volume changes.(2) Co9S8/Al2O3/C nanocomposite is obtained fancily by calcining the precursor of sodium dodecyl sulfate (SDS) intercalated Co2+ Co3+Al-LDH. The main advantage of this method is to utilize dual roles of the guest molecule as clever sulfur and carbonaceous sources during the efficient and environmentally friendly preparation process. Electrochemical tests showed that the nanocomposite can deliver a specific capacity of 970.3 mA h g-1 under a current density of 100 mA g-1 and a capacity capacity retention of 88% upon up to 200 times. The enhancements can be attributed to the integrated features:(i) carbon to increase the conductivity and prevent the polysulfide intermediates generated during the lithiation process react with or dissolve into the organic electrolyte, (ii) non-active Al2O3 to buffer volume changes during the charge-discharge processes.