锂离子电池纳米MoO_2基负极材料的研究

Ultrafine MoO_2-based anode materials for lithium ion batteries

通过水热反应及随后的氮化处理或碳包覆分别制备了MoO_2/N和MoO2/C负极材料,其颗粒尺寸约为10 nm。氮化处理的MoO_2/N中生成了微量的δ-Mo N;碳包覆的MoO_2/C中在MoO2表面包覆了一层无定形碳。电化学测试表明,碳含量为30%的MoO_2/C表现出最佳的循环稳定性能,其可逆比容量可达658.5 m A·h·g^(-1)。MoO_2/N和MoO_2/C的循环容量随着充放电循环的进行呈先上升后下降的趋势。在充放电循环的前期,"插层反应机制"和"转换反应机制"并存。然而,随着循环次数增加,"转换反应机制"逐渐成为主要的脱嵌锂机制。与此同时,电极材料中原位生成了Li_2MoO_4。MoO_2负极材料的脱嵌锂机制由"插层反应机制"向"转换反应机制"的转变与其循环性能的变化相符合。

N2-treated and carbon-coated ultrafine MoO2 particles with size ca.10 nm have been synthesized through hydrothermal route followed by N2 treatments or carbonization process.δ-MoN has been formed in the N2-treated MoO2.Amorphous carbon covers MoO2 particles in the carbon-coated MoO2.The electrochemical performances of the MoO2-based products have been evaluated as anode candidates for lithium ion batteries,among which carbon-coated MoO2 with carbon content of 30%exhibits much improved cyclic capacity and stability with the highest reversible capacity of 658.5 mA·h·g-1.The cyclic capacities of the MoO2-based products increase in the initial cycling,and then decrease with further cycling.Intercalation and conversion mechanisms coexist in the initial lithiation/delithiation cycles of MoO2.However,conversion mechanism gradually becomes predominant with cycling.Meanwhile Li2MoO4 is in situ formed in the electrode,which can act as anode materials through conversion mechanism.The transition from intercalation to conversion mechanism of MoO2 with cycling is consistent with its cyclic performance.