过渡金属氧化物纳米颗粒催化SnO2锂离子电池负极材料不可逆反应的机理研究

SnO2 is deemed as one of the possible candidates as the anode materials for next generation high performance lithium ion batteries (LIBs). However, its theoretical irreversible reaction of Sn to SnO2 during the 1st delithiation process is the main reason for the capacity loss and a low initial coulombic efficiency (<50%). It was found that SnO2 electrochemical performance can be improved greatly with the transition metal oxide nanoparticles. However, there is no solid evidence to prove the exactly reason for this phenomenon. In order to tackle this issue and based on the previous studies, we propose that the transition metal oxide nanoparticles act as the catalyst to promote the conversion of Sn to SnO2 during the 1st delithiation process which is an irreversible reaction. In the other words, catalysts are employed to convert the irreversible reaction into reversible reaction, leading to an enhanced electrochemical performance of SnO2. In this project, we propose to use in-situ TEM, XRD and Raman to investigate the reaction mechanism. The working principle of the catalytic effect of the catalyst can provide a clue to design the new catalysts to further enhance the electrochemical performance of SnO2. We plan to synthesize SnO2/metal-oxides/rGO hybrid functional nanocomposites by hydrothermal and/or ball milling methods to study the reaction mechanism and employed as high performance anode material of LIBs. The investigated mechanism and result provide a new route to enhance the electrochemical performance of SnO2, especially the 1st coulombic efficiency, specific capacity and rate capability, as well as the type of conversion with alloying-dealloying anode material to beyond its theoretical capacity.

研究证实SnO2作为一种新型高性能锂离子电池负极材料在脱锂过程中由于理论不可逆不可以从Sn生成SnO2从而造成不可逆容量的损失，导致了低于50%的首次库仑效率和有限的容量，限制了其进一步发展应用。前期发现，SnO2与金属氧化物纳米颗粒复合可以提高其电化学性能，但没有确切的证据和理论解释性能提高的机理。根据前期研究工作，我们提出金属氧化物颗粒作为催化剂催化Sn生成SnO2的科学假设。换句话说，利用催化剂使不可逆过程变为可逆来提高其电化学性能。本课题拟采用原位TEM、XRD、拉曼光谱寻找其催化反应证据、阐明工作机制、揭示反应机理。我们拟采用水热合成和球磨方法制备金属氧化物纳米颗粒催化剂和SnO2以及石墨烯的复合纳米功能材料作为高性能负极材料。本课题的研究成果为SnO2作为锂离子电池负极材料性能的提高特别是首次库伦、效率容量和倍率性能开辟新的途径，以及提升类SnO2等负极材料的性能提供新的思路。

作为一种新型高性能锂离子电池负极材料，SnO2在脱锂过程中由于理论不可逆不可以从Sn生成SnO2从而造成不可逆容量的损失，导致了低的首次库仑效率和有限的容量，限制了其进一步发展应用。本项目提出金属氧化物（Co3O4等）颗粒作为催化剂催化Sn生成SnO2的科学假设。在本项目的支持下，我们利用水热合成制备SnO2/Co3O4/rGO纳米复合材料并作为高性能负极材料。首次库仑效率从60%提高到了67%，100 mA/g电流下可以达到1038 mAh/g的电容量（远远高出SnO2的理论容量值）以及2000 mA/g大电流下可以达到524 mAh/g的电容量，在1000 mA/g的大电流下循环900次依然可以保持641 mAh/g的电容量，证明了SnO2/Co3O4/rGO的纳米复合材料作为锂离子电池负极材料的潜在应用。我们通过电化学测量以及非原位TEM寻找Co3O4作为催化剂在退锂过程中促进Li2O的分解，使Sn氧化成SnO2，进一步的提出其工作原理。为类SnO2等负极材料的性能提供新的思路。在此基础之上，我们一直致力于提高储能器件（锂/钠离子）电池的能量密度和降低造价。作为本项目的扩展研究，我们制备并研究了NGQDs-WS2/3DCF，FeP@C/rGO钠离子电池负极材料，Li@VG/CC锂金属负极初步工作以及钠金属研究的调研工作。

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