Lanzhou Institute of Lithium-air battery electrode materials made a series of research

Lanzhou Institute of Lithium-air battery electrode materials made a series of research

Discharge mechanism and morphology changes of CMF-G-Co/CoO and CMF-G electrodes

A lithium-air battery is a battery that uses metallic lithium as an anode and oxygen in the air as a cathode reactant. In the battery system, the air electrode can continuously extract oxygen from the surrounding environment, the theoretical energy density of up to 11140Wh/kg, far beyond the current lithium-ion battery energy density (<300Wh/kg), in the field of electric vehicles Shows great application prospects. However, lithium-air batteries have a series of problems such as complex electrochemical reaction processes, large overpotentials, and short lifetimes.

Researcher of the Clean Energy Chemistry and Materials Laboratory of the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, and the research team of Yan Xingbin teamed up with researchers from the State Key Laboratory of Oxo Synthesis and Selective Oxidation to design a series of high performance air electrode catalysts and systematically study different catalyst conditions. The discharge process and mechanism of action.

Researchers prepared carbon nanotubes (CFs) as sacrificial templating agents with low specific surface area tubular manganese dioxide (δ-MnO2) and high specific surface area CFs/MnO2 coaxial fibers. The results show that the introduction of δ-MnO2 catalyst can promote the transition of the discharge product (Li2O2) from the ring structure to the lamellar structure. At the same time, the catalyst itself does not adhere to Li2O2. This feature enables the continuous operation of the catalyst and the continuous generation of Li2O2. Improve the electrochemical performance of lithium-air batteries. The researchers further developed an air electrode by combining high specific surface area CFs/MnO2 with low specific surface area carbon black. It was found that under this electrode, Li2O2 was transformed from a highly crystalline ring structure of a pure carbon electrode to an assembly of nearly amorphous Li2O2 nanorods, and these aggregates were randomly scattered on the surface of the electrode, demonstrating that Li2O2 is present under the electrode. It is mainly produced via the liquid phase. This finding further confirmed the mechanism of action of δ-MnO2 and elucidated the growth history of Li2O2 during discharge. In addition, the catalyst significantly reduces the overpotential of the air electrode, thereby greatly improving the electrochemical performance of the lithium air battery. Related work has been published in ChemSusChem. (2015, 8, 1972) and J. Materials Chemistry A (2015, 3, 10811).

Based on the above work, the researchers prepared a carbonized melamine sponge-graphene-core-shell cobalt/cobalt (Co/CoO) three-dimensional composite air electrode in one step. In this design, the melamine sponge carbon skeleton gives the electrode high elasticity and self-supporting characteristics, and provides a support frame for the graphene nanosheets; the planar two-dimensional structure of the graphene nanosheets facilitates uniform loading and discharging of the Co/CoO. Follow-up observation of the product; the introduction of cobalt precursor can increase the degree of reduction of graphene and reduce the adsorption energy of graphene to LiO2 (Li2O2 intermediate). At the same time, Co/CoO as a high LiO2 adsorption energy material can induce the growth of Li2O2 mainly on the surface of Co/CoO particles, which reduces the contact area between graphene and Li2O2, reduces the side reactions occurring on the surface of Li2O2/C, and significantly improves The electrochemical performance of lithium-air batteries. This design provides new ideas and methods for the construction and development of lithium air battery positive electrodes, and provides a new design scheme for the preparation of multifunctional electrodes. This work was recently published online at Advanced Functional Materials (DOI: 10.1002/adfm201503907).

The above work was supported and supported by the National Natural Science Foundation of China and Lanzhou Institute of Chemical Industry “One-Three-Five” key cultivation project.

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