Synthesis And Application Of High-capacity Anode For Lithium Ion Batteries

In the period of continuous economic development and energy crisis,the development of clean and efficient energy storage equipment has become a hot topic for researchers.Lithium ion batteries（LIBs）has a good application prospect in the field of energy storage due to its advantages of high energy density,long cycling lifespan,faint self-discharge and no pollution to the environment.With the continuous development of mobile electronic equipment and electric vehicles,the commercial graphite anode can no longer adapt to the energy storage equipment contribute to the low theoretical specific capacity(372 m Ah g^-1).Although the oxide anode has a high theoretical specific capacity,it has a large volume expansion in the process of charging and discharging,resulting in a rapid fading of capacity.At present,the most effective solution is using carbon-coated method to improve its poor conductivity and volume expansion during charging and discharging.In this study,the carbon-coated oxide composite with unique morphology was designed and synthesis.The influence of the coating method on electrochemical performance of the materials and the lithium storage performance of the carbon-coated oxide hybrid were studied.The details are as follows:（1）MnO/C hybrid with three-dimensional（3D）network structure was prepared by using renewable biomass kelp as the swelling adsorption matrix.Using the excellent swelling property of kelp in high concentration solution,the pre-treated dried kelp were soaked in high concentration Mn Cl₂ solution to absorb Mn²⁺.The hydroxyl and carboxyl groups in kelp can coordinated with metal ions and immobilize them in kelp cells.The MnO/C hybrid can be manufactured after ammonia and heat treatment.At the same time,the synergistic effect between highly dispersed MnO nanoparticles and kelp carbon matrix is conducive to the formation of 3D network structure.The electrochemical properties of MnO/C composite were tested and found that the reversible capacity of MnO/C hybrid could reach 978 m Ah g^-1 at a current density of 0.2 Ag^-1.Even at the current density of 2 Ag^-1,the reversible specific capacity can reach 554 m Ah g^-1 after 500 cycles.（2）The Zn₂SiO₄ precursor with different morphologies were designed and synthesized.The surface of Zn₂SiO₄ precursor were modified by Poly dimethyl diallyl ammonium chloride（PDDA）and sodium polystyrenesulfonate（PSS）which were coated by solid or liquid 2-Methyli Midazole zinc salt（ZIF-8）generating method.SiO₂/C composites were manufactured after the heat treatment under argon atmosphere.The effect of the carbon-coated thickness and the microstructure of composite on electrochemical performance of the assembled batteries were studied.The reversible specific capacity of SiO₂/C hybrid can reach 1058.3 m Ah g^-1 after 100 cycles at the current density of 0.2 Ag^-1,showing an excellent electrochemical performance.