Recently, the research group of Qin Xiaoying, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei Institute of Physical Science has made progress in the research of negative electrode materials for lithium ion batteries. The related research results are published in Journal of Materials Chemistry A (2015, 18, 9682-9688).
The negative electrode material is an important part of lithium ion battery. The current theoretical low capacity (372 mAh / g) of commercial graphite materials seriously restricts the development of high energy density power battery. Therefore, the development of a new high charge-discharge capacity, safe and economical anode material, is one of the key areas of battery materials research.
As a negative electrode material of lithium ion, Fe2O3 has attracted a lot of attentions due to its high theoretical capacity (~ 1000 mAh / g), low cost and good environmental compatibility. However, the Fe2O3 itself has poor conductivity, large volume change during charging and discharging, and is easily pulverized, seriously impairing its electrochemical performance. The research team led by Qin Xiaoying used γ-Fe2O3 @ C ​​nanoparticles with core-shell structure and their composites with multi-walled carbon nanotubes (MWNTs) by vacuum carbonization of metal-organic complexes. Its electrochemical properties and electrode activation process. The capacity of the γ-Fe2O3 @ C ​​/ MWNT electrode stabilized at 1139 mAh / g after 60 cycles at a current density of 100 mA / g, which is higher than the theoretical capacity of the Fe2O3 material. The study also found that at different current densities, the capacity showed a slowly increasing trend, corresponding to the slow activation of the electrode. Through the cyclic voltammetry and microstructural characterization of the electrodes in different stages, it was found that the γ-Fe2O3 particles gradually became porous vesicular structure during the cycle, forming a large number of interfaces with defects, increasing the capacity through the interface lithium storage, At the same time, the porous structure also promoted the rapid transport of Li +. On the other hand, the surface carbon shell effectively protected the Fe2O3 particles, inhibited the pulverization and maintained the stability of the electrode structure. This work provides an important reference for the structural design of the new anode material.
(a) Cyclic behavior and microstructure evolution of γ-Fe2O3 @ C ​​/ MWNT electrode; (b) CV curve of γ-Fe2O3 @ C ​​/ MWNT electrode after different cycles.
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