Microwave Solvothermal Synthesis Of The Electrode Materials For Lithium-ion Batteries

Lithium ion batteries have attracted great attention due to high specific energy, high working voltage, long cycling life, safety and pollution-free. It is a new type of green energy, which is widely applied in the field of the national economy and people's life. The electrode materials are key to influence lithium battery performance, and it affects the stand or fall of lithium ion battery performance directly. In this paper, the cathode materials (Co₃O₄) and positive materials (LiFePO₄) of lithium ion battery are studied, and the main contents are summarized as follow:In this paper, an efficient microwave-assiste homogeneous approach by urea hydrolysis has been used to synthesize cobalt-basic-carbonate compounds. The dimension and morphology of the synthesized precursor compounds were tailored by the change of the incorporated anions (CO₃^2- and OH^-) under different conditions of microwave irradiation temperature and time. The wire-like cobalt-basic-carbonate compound self-assembled into one-dimensional porous arrays of Co₃O₄ nanowires constructed by interconnected Co₃O₄ nanocrystals along the [110] axis after thermal decomposition at 350℃. The textural characteristics of Co₃O₄ products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous nanowire Co₃O₄ array exhibits the excellent capacity retention and rate capability at higher current rates, and its reversible capacity of 600 mAh g^-1 can be maintained after 100 cycles at a high current rate of 400 mA g^-1.In this paper, we have reported a simple and rapid approach for the large-scale synthesis ofβ-Co(OH)₂ nanoplatelets via the microwave microwave solvothermal process using potassium hydroxide as mineralizer at 140℃for 3 h. Calcining theβ-Co(OH)₂ nanoplatelets at 350℃for 2h, porous Co₃O₄ nanoplatelets with a 3D quasi-single-crystal framework were obtained. The process of converting theβ-Co(OH)₂ nanoplatelets into the Co₃O₄ nanoplatelets is a self-supported topotactic transformation, which is easily controlled by varying the calcining temperature. The textural characteristics of Co₃O₄ products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous Co₃O₄ nanoplatelets exhibit a low initial irreversible loss (18.1%), ultrahigh capacity, and excellent cyclability. For example, a reversible capacity of 900 mA h g^-1 can be maintained after 100 cycles.Co₃O₄ and MWNTs/Co₃O₄ was synthesized by microwave solvothermal method using Co(NO₃)₂·6H₂O as raw materials, urea as precipitating agent, and doping MWNTs. The phase, structure, morphology and capacitance performance of the products were characterized and tested. The results show that: the Co₃O₄ nanowires are composed of 10-20nm crystal grains. After doping MWNTs, Co₃O₄ nanowires changes thinly, and the electrochemistry capacitance performance enhances greatly. Especially, when n(Co₃O₄):n(MWNTs)=2:1, the sample have the excellent electrochemical capacitance with the highest capacitance of 369.5 F·g^-1. It has a good stability and cyclic performance, and has the good condensance characteristic.LiFePO₄ was synthesized by microwave solvothermal method, using inorganic salts as raw materials, and PEG-4000 as the surfactant. The results show that LiFePO₄ powders with various morphologies were prepared by microwave hydrothermal method, and it is very important to synthesize the LiFePO₄ powders with well-defined shape and size controlling experimental conditions, such as the solution pH and surfactant. The modified preparation of LiFePO₄ was built. The coating carbon on LiFePO₄ powders as a core-shell structure was carried out by annealing in 3%H₂/97%N₂ at 700℃for 2 h. As a result, the diffusion coefficient of lithium ions can be increased, and the reversibility of lithium intercalation and deintercalation can be improved markedly. In addition, LiMn_xFe_1-xPO₄ powders were synthesized, which were observed in an ordered olivine structure, but great changes occurred in morphology. Doping Mn²⁺ does not destroy the lattice structure and enlarge the lattice volume. Consequently, the conductivity can be enhanced, and the lithium ion diffusion coefficient can be boosted. The microwave assisted hydrothermal approach presented here opens a potential avenue to explore the synthesis of LiFePO₄ powders.